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Near-infrared collisional radiative model for Xe plasma electrostatic thrusters: the role of metastable atoms | High-Speed Image Analysis and Filtered Imaging of Nested Hall Thruster Oscillations | Mounting evidence against the role of ICC in neurotransmission to smooth muscle in the gut | eng_Latn | 10,000 |
Transitions between shifted Landau states and photoionization of the hydrogen atom moving in a strong magnetic field | Cold and Ultracold Rydberg Atoms in Strong Magnetic Fields | Transcriptional activation of HIF-1 by a ROS-ERK axis underlies the resistance to photodynamic therapy | eng_Latn | 10,001 |
Radiation, radiation detection and radiation protection are topics in physics and its applications which generate a wide interest in the public. This interest is either generated through medical procedures, applications of nuclear energy or nuclear accidents. The technical nature of these topics usually means that they are not well covered in the normal education stream, opening many opportunities to engage with schools and the general public to showcase the latest developments and their applications. The detection of radiation is at the very heart of understanding radiation, its fascination and associated fears. The outreach group of the nuclear physics group at the University of Glasgow demonstrates a number of successful outreach activities centred around radiation detection and described in this paper, focusing on activities delivered to a variety of audiences and related to applied nuclear physics work within our group. These concentrate on the application of novel sensor technologies for nuclear decommissioning, medical imaging modalities and the monitoring of environmental radioactivity. The paper will provide some necessary background material as well as practical instructions for some of the activities developed. | In this work, we explored the possibility of using Cs2AgBiBr6, a double perovskite crystal, for radiation detection. Cs2AgBiBr6 crystals were grown using the solution growth technique. The resistivity of the as-grown Cs2AgBiBr6 crystal is larger than 1010 Ω cm, which is high enough to ensure low leakage current for fabrication of semiconductor radiation detectors. Using the temperature-dependent resistivity measurements, we estimated that the Fermi level is at 0.788 eV above the valence band and the material is a p-type semiconductor. From the low-temperature cathodoluminescence measurements, two near band gap energies at 1.917 eV and 2.054 eV were revealed. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,002 |
Whenever free electrons collide with atoms and molecules, a wide variety of kinetic processes may take place. Electron collision cross-sections, of interest in plasma processing of VLSI production, carbonization of surfaces and so on, modeling of gas lasers, physics of gaseous dielectrics, analysis of high current discharge switches, applications for space science and radiation physics and chemistry, have been determined from available electron beam and electron swarm data utilizing the Boltzmann analysis. The goal of electron collision studies is to provide absolute values of cross-sections for all processes involved, from elastic to inelastic scattering, as a function of incident electron energy and scattering angle. In spite of many experimental and theoretical studies, electron impact cross-sections for atoms and molecules have not been systematically quantified. | R-matrix calculations are performed for electron collision with CH4 at energies between 0.02 and 15 eV using a series of different ab initio models for both the target and the full scattering system. A target model similar to the standard multi-reference configuration interaction used in electronic structure calculations is found to give the best results. Results are presented for elastic scattering, with particular emphasis on the Ramsauer–Townsend miminum, and for rotational excitation, momentum transfer and electron impact dissociation. Extensive comparisons are made with previous studies. | This new book edited by R Janev covers in 16 chapters almost all important atomic and molecular collision processes of relevance for the modelling and diagnostics of fusion edge plasmas. These processes include excitation, ionization of atoms and molecules by electrons, as well as electron - ion recombination processes and low-energy charge exchange collisions of impurity ions with neutral atoms. In addition, a chapter about the spectroscopic characteristics of plasma edge constituents is included. Each chapter deals with a specific type of collision process and comprises contributions from specialists in the respective fields. The book contains contributions from 27 authors. The primary purpose of the book is to provide the fusion plasma researcher with a source of critically assessed information on atomic and molecular collision processes. Many chapters give a basic introduction to the most commonly applied experimental and theoretical methods of how presented collision data are gained. Physical mechanisms of collision processes are described briefly on a rather fundamental level. Very helpful for a reader who is looking for more detailed information on a specific collision process are the comprehensive lists of references at the end of each chapter. Atomic data, such as cross sections, are represented by figures, tables and often (most helpful for quick and convenient application) by fitting parameters to analytic formulae. This book has to be regarded as an excellent review of the present day status of available data for low-energy collision processes between electrons, ions, atoms and molecules. Although this book is intended mainly for fusion plasma researchers, it might also be of interest for students and scientists working in atomic collision physics who are looking for an overview of this field. | eng_Latn | 10,003 |
Cs 2 LiYCl 6 :Ce 3+ (CLYC) scintillator has gained recent interest because of its ability to perform simultaneous gamma spectroscopy and thermal neutron detection. Discrimination between the two incident particle types owes to the fundamentally unique emission waveforms, a consequence of the interaction and subsequent scintillation mechanisms within the crystal. Due to this dual-mode detector capability, CLYC was selected for the development of an Advanced Radiation Monitoring Device (ARMD), a compact handheld instrument for radioisotope identification and localization. ARMD consists of four 1 in.-right cylindrical CLYC crystals, custom readout electronics including a suitable multi-window application specific integrated circuit (ASIC), battery pack, proprietary software, and Android-based tablet for high-level analysis and display. We herein describe the motivation of the work and engineering design of the unit, and we explain the software embedded in the core module and for radioisotope analysis. We report an operational range of tens of keV to 8.5 MeV with approximately 5.3% gamma energy resolution at 662 keV, thermal neutron detection efficiency of 10%, battery lifetime of up to 10 h, manageable rates of 20 kHz; further, we describe in greater detail time to identify specific gamma source setups. | The design and configuration of a multi-layered imaging system with the ability to detect thermal neutrons, fast neutrons and gamma rays has been developed and its efficacy demonstrated. The work presented here numerically determines the systems efficiency and spatial resolution, using 252Cf and 137Cs as a case study. The novelty of this detection system lies in the use of small form factor detectors in a three-layer design, which utilises neutron elastic scattering and Compton scattering simultaneously. The current configuration consists of 10 mm thick natural lithium glass (GS10) scintillator integrated with a 20 mm thick plastic scintillator (EJ-204) in the first layer, a 15 mm thick lithium glass (GS10) scintillator in the second and a 30 mm thick CsI(Tl) scintillator forming the final layer. Each of these layers is backed with an 8 x 8 silicon photomultiplier diode (SiPM) array. The overall size of the imaging system is 27 mm x 27 mm x 135 mm. MCNPv6.1 and Geant4-10.04 were alternatively used to optimise the overall configuration and to investigate detection modalities. Results show promising performance with high precision source localisation and characterization abilities. Measurements were virtually obtained of two gamma-ray sources within steel enclosures at angles of 15o, 30o and 50o separation in order to test spatial resolution ability of the system. With the current active size of the system and the 8x8 SiPM configuration, the results estimate the spatial resolution to be close to 30o. The ability of the system to characterise and identify sources based on the type and energy of the radiation emitted, has been investigated and results show that for all radiation types the system can identify the source energy within the energy range of typical reported sources in literature. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,004 |
The Linac Coherent Light Source (LCLS) project at SLAC uses a dense 15 GeV electron beam passing through a long undulator to generate extremely bright x-rays at 1.5 angstroms. The project requires electron bunches with a nominal peak current of 3.5 kA and bunch lengths of 0.020 mm (70 fs). The RF stability required by the bunch compressors is tighter than what is currently required to run experiments. Measurements to determine how well the existing linac will meet the new requirements are ongoing. Presented is an update on the measurements and how they pertain to LCLS. | The Linac Coherent Light Source (LCLS) project at SLAC uses a dense 15 GeV electron beam passing through a long undulator to generate extremely bright x-rays at 1.5 angstroms. The project requires electron bunches with a nominal peak current of 3.5kA and bunch lengths of 0.020mm (70fs). The bunch compression techniques used to achieve the high brightness impose challenging tolerances on the accelerator RF phase and amplitude. The results of measurements on the existing SLAC linac RF phase and amplitude stability are summarized and improvements needed to meet the LCLS tolerances are discussed. | The Linac Coherent Light Source (LCLS) project at SLAC uses a dense 15 GeV electron beam passing through a long undulator to generate extremely bright x-rays at 1.5 angstroms. The project requires electron bunches with a nominal peak current of 3.5kA and bunch lengths of 0.020mm (70fs). The bunch compression techniques used to achieve the high brightness impose challenging tolerances on the accelerator RF phase and amplitude. The results of measurements on the existing SLAC linac RF phase and amplitude stability are summarized and improvements needed to meet the LCLS tolerances are discussed. | eng_Latn | 10,005 |
After a two years evaluation and assessment period of the CYClotron of LOuvain la NEuve (CYCLONE) usability for heavy ion SEE testing, the European Space Agency has now initiated the set-up of a permanent beam line dedicated for SEE testing. This paper describes the CYCLONE accelerator, the beam line used so far, presents some experimental results which are compared with data obtained at the Tandem accelerator at Brookhaven National Laboratory (BNL) and details present and future developments. | This paper presents experimental results putting in evidence the potential weaknesses of a state-of-the-art fault tolerance strategy, the Triple Modular Redundancy (TMR), when implemented in SRAM-based FPGAs. HW/SW fault injection campaigns and accelerated radiation ground tests were performed to quantify the number of faults, Single Event Upsets (SEUs) required to obtain such critical failures. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,006 |
The angle- and energy-resolved Larmor radiation from atomic ionization in the focus of ultra-intense laser field is calculated using a semi-classical, trajectory ensemble model of ionization. We find that including the quantum nature of the atomic ionization decreases the radiation yield by an order of magnitude compared to a classical electron calculation due to interference effects in the extended probability of the electron wavefunction and the quantum nature of tunnelling ionization. The evolution of the radiation from non-relativistic to relativistic continuum dynamics is presented as a function of the laser intensity with Larmor radiation not becoming prominent until 1019 W cm−2. For the ionization of Na10+ at a density of 1015 atoms cm−3 and a peak-focused laser intensity of 1020 W cm−2, the radiation is highly directional at an angle of 45° from the laser electric field with photon energies out to 500 eV. | The interaction of high-intensity and ultrashort lasers with matter produces high energy particles and photons. Recent experiments include the generation of high quality GeV electron (Kneip et al., 2009; Leemans et al., 2006) and multi-MeV proton (Clark et al., 2000; Snavely et al., 2000) beams in laser plasma interactions. Different schemes can now be followed to produce ultra-short x-ray radiation. The production of keV x-rays from betatron oscillations of relativistic electrons in plasma channels was demonstrated 5 years ago (Rousse et al., 2004). Femtosecond x-ray beams have also been detected when high energy laser pulses cross relativistic electrons from a conventional linear electron accelerator (LINAC) (Schoenlein et al., 1996). Recently, an ultrashort x-ray pulse has been produced from the scattering of an ultrashort laser pulse off a laser generated relativistic electron beam (Schwoerer et al., 2006). The primary processes of x-ray generation are the ionization of an atom/ion and the subsequent acceleration of photoelectrons to relativistic energies in the intense laser field. A detailed description of radiation from laser-atom interaction is necessary to fully understand the mechanism behind x-ray generation from laser-plasma interactions and there is a growing interest in the physics of the radiation from laser acceleration of photoionization at relativistic intensities (Chowdhury et al., 2005). In this chapter we focus on the generation of x-ray photons by Thomson scattering from atomic ionization in ultra-strong laser fields. When an atom is submitted to an ultra-strong laser field, the laser electric field Elaser suppresses the Coulomb barrier and the outermost electron ionizes as it tunnels through the suppressed barrier. Photoelectrons ionized in an ultra-strong field 1 × 1018 W/cm2 are accelerated to a relativistic speed in a fraction of an optical cycle, the magnetic field of the ionizing laser field becomes significant and the motion of these ionized free electrons is nonlinear. Through its relativistic and non-linear motion, the electron may emit radiation at high harmonics of the drive field frequency in a process known as non-linear Thomson scattering. During tunneling ionization, the ultra-strong laser field leaks out an electron wave packet out of an atom at a finite rate, typically every half cycle of the laser field. For each ionization event, the electron wave packet spreads to a spatial dimension from nm to μm over the interaction time of the laser field. The electron may also radiate as it is relativistically accelerated in the ultra-strong laser field. It becomes natural to ask how this spatially extended relativistically driven electron wave packet may radiate. Different parts of the Source: Advances in Solid-State Lasers: Development and Applications, Book edited by: Mikhail Grishin, ISBN 978-953-7619-80-0, pp. 630, February 2010, INTECH, Croatia, downloaded from SCIYO.COM | We report nearly complete preservation of “spin memory” between optical absorption and photoluminescence under excitation >0.2 eV above the band gap in nanometer GaSe slabs. | eng_Latn | 10,007 |
Nomenclature s a = radius, m t A =area, m tD B = magnetic induction, = nH\ Wb/m = 1 Tesla T( c = speed of light, 3 x 10 m/s T, C = capacitance, F T d = thickness, spacing; m v e = electron charge, 1.6x 10" C E electric field, V/m 8 = electron energy, eV 87 = electron normal energy, eV 80 =m0c/e rest mass, 5.11 x 10 eV /£ = fraction of stored charge which blows off /stop = fraction of electrons captured in a material G = transmitted blowoff current rate of rise, A/s h height, m H = magnetic field, A/m / = current, A j =VT A/ J = current density, A/m e k = wave number co/c, rad/m e0 t,l = length, m 77 L = inductance, H 777 = macroparticle mass, kg X me = electron mass, 9.1 x 10~ kg ju0 n = electron number density, No./m v N = neutral species number density, No./m p P = time rate of change of dipole moment per unit area, o A/m ,, ff. q = macroparticle charge, C co Q = total charge, C r = distance, m R = radius, m; resistance, 0 c Rr = radiative resistance, 12 d P V w x,y,z Y | Time-domain techniques were employed to capture the EMI emission in laboratory simulated spacecraft on-orbit electrostatic discharges. The test setup included custom-built four-channel data acquisition instrumentation anchored by a 15-GHz digital oscilloscope, and a dedicated fiberglass vacuum chamber inside a semi-anechoic shielded room. The test article was designed to simulate a section of a solar cell array and was irradiated with an electron gun. Radiated emission pulse waveforms have been captured and converted to frequency spectra via Fourier transform. This time-domain measurement approach allowed us to capture the entire L-, S-, and C-bands of the ESD pulse radiated emission spectrum instead of the narrow frequency band snapshots obtained using a spectrum analyzer. Latest data and statistical analysis will be presented. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,008 |
Scientific CCDs designed in thick high resistivity silicon (Si) are excellent detectors for astronomy, high energy and nuclear physics, and instrumentation. Many applications can benefit from CCDs ultra low noise readout systems. The present work shows how sub electron noise CCD images can be achieved using digital signal processing techniques. These techniques allow readout bandwidths of up to 10 K pixels per second and keep the full CCD spatial resolution and signal dynamic range. | DECam is a 520 Mpix, 3 square-deg FOV imager being built for the Blanco 4m Telescope at CTIO. This facility instrument will be used for the 'Dark Energy Survey' of the southern galactic cap. DECam has chosen 250 ?m thick CCDs, developed at LBNL, with good QE in the near IR for the focal plane. In this work we present the characterization of these detectors done by the DES team, and compare it to the DECam technical requirements. The results demonstrate that the detectors satisfy the needs for instrument. | Perfect Quantum Cloning Machines (QCM) would allow to use quantum nonlocality for arbitrary fast signaling. However perfect QCM cannot exist. We derive a bound on the fidelity of QCM compatible with the no-signaling constraint. This bound equals the fidelity of the Bu\v{z}ek-Hillery QCM. | eng_Latn | 10,009 |
Recent advances in the detection and the routine measurements of heavy elements by accelerator mass spectrometry (AMS) are reviewed. Particular emphasis will be given to the measurement of low energy (⩽ 15 MeV) and high-Z ions using small (⩽ 3 MV) accelerators. | The suppression of interferences from atomic and molecular isobars is a key requirement for the extension of accelerator mass spectrometry (AMS) to the analysis of new cosmogenic isotopes and for increasing the range of applications for small AMS systems. In earlier work, it was shown that unwanted isobars can be eliminated by anion-gas reactions (Litherland et al. 2007). Recently, a prototype system in which such reactions could be applied to ions from an AMS ion source, the Isobar Separator for Anions (ISA), was described (Eliades et al. 2009). This system decelerates the beam of rare anions from keV to eV energies, guides them through a single radiofrequency quadrupole (RFQ) gas cell, and re-accelerates them for further analysis in a 2.5MV AMS system. Tests of this system with Cl and S anions and NO2 gas showed a suppression of S with respect to Cl of over 6 orders of magnitude, with a transmission of ~30% for the Cl beam. In this work, results of the analysis of a range of standard reference materials are reported; these show the linearity of the system for measuring the 36Cl/35Cl ratio over a span of 2 orders of magnitude. Further tests, using the AMS system as a diagnostic tool, have provided clues about the loss of Cl at higher cell pressure and the nature of the residual low level of S transmission. These lead to the assessment of various gases for cooling the Cl- beam. Suppression measurements for 41K in the analysis of 41Ca, using NO2 as a reaction gas, are also discussed. These preliminary measurements have provided data for the development of a more advanced system with separate cooling and reaction cells. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,010 |
The highest precision in direct mass measurements is obtained with Penning trap mass spectrometry. Most experiments use the interconversion of the magnetron and cyclotron motional modes of the stored ion due to excitation by external radiofrequency-quadrupole fields. In this work a new excitation scheme, Ramsey’s method of time-separated oscillatory fields, has been successfully tested. It has been shown to reduce significantly the uncertainty in the determination of the cyclotron frequency and thus of the ion mass of interest. The theoretical description of the ion motion excited with Ramsey’s method in a Penning trap and subsequently the calculation of the resonance line shapes for different excitation times, pulse structures, and detunings of the quadrupole field has been carried out in a quantum mechanical framework and is discussed in detail in the preceding article in this journal by M. Kretzschmar. Here, the new excitation technique has been applied with the ISOLTRAP mass spectrometer at ISOLDE/CERN for mass measurements on stable as well as short-lived nuclides. The experimental resonances are in agreement with the theoretical predictions and a precision gain more than a factor of three was achieved compared to the use of the conventional excitation technique. | The progress within atomic and nuclear physics relies on refining and adding new observables. One of these is the polarization of the nuclear spin, where there is a manifest interest in accessing a wide variety of polarized beams, e.g. at energies suitable for Coulomb excitation and transfer experiments. In particular, exotic nuclei with half-lives considerably less than one second are difficult to produce, but the issues present in traditional methods could be overcome by using the tilted foils technique. Two setups for measuring the degree of polarization of an ion beam after the REX-ISOLDE linear accelerator at CERN are being evaluated. An approach based on Coulomb excitation has been utilized in an experiment and preliminary results will be presented. Furthermore, a β-NMR setup is currently under construction that will take radioactive beams soon. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,011 |
The electron and gas temperature of non-equilibrium argon plasma torch sustained by a focused 24 GHz microwave beam in the external atmosphere of air was measured by optical emission spectroscopy. The excitation temperature of argon atoms was found about 5000 K, while the vibrational and rotational temperatures of ambient nitrogen molecules were respectively estimated at 3000 K and 2000 K. The effective mixing of the external gas atmosphere into the plasma torch is experimentally demonstrated. The vibrational and rotational temperatures of nitrogen molecules slightly increased with the distance from the nozzle exit. Experimental results demonstrate that microwave discharge at atmospheric pressure may be relevant for the decomposition of highly stable molecules, e.g. carbon dioxide, in non-equilibrium conditions. | Quantities of Spectroscopy.- Spectroscopic Instruments.- Detectors.- Calibration.- Radiative Processes in Plasmas.- Collisional Processes.- Kinetics of the Population of Atomic Levels in Plasmas.- Line Broadening.- Diagnostic Applications. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,012 |
Gabor x-ray holograms of biological specimens and of test objects that display ≤56–nm resolution are presented. This spatial resolution is more than an order of magnitude smaller than what has been achieved previously in x-ray holography. The holograms were recorded on photoresist using 2.57-nm soft x rays from the X–17t undulator at the National Syncrotron Light Source at Brookhaven National Laboratory. The processed photoresists were enlarged with an electron microscope and digitized using a scanning microdensitometer; the digitized holograms were reconstructed numerically. The exposure requirements were in good agreement with simple theory. The method offers promise as a technique for soft-x-ray microscopy. | Photodiodes with x‐ray sensitive photocathodes are commonly used as broadband x‐ray detectors in fusion plasma diagnostics. We have measured the photocathode quantum efficiency between 1–500 A of common photocathode materials including aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. We have also studied the effects of the experimental environment and long‐term cathode aging on the measured quantum efficiencies. In addition, we have measured the x‐ray mass‐absorption coefficients of x‐ray filter windows of Kimfoil, aluminum, polypropylene, and Formvar in energy regions where data were previously unavailable. Measurements between 1–50 A were performed at the Los Alamos Scientific Laboratory’s low‐energy x‐ray calibration facility, while the measurements between 50–500 A were performed at the National Bureau of Standard’s synchrotron ultraviolet radiation facility. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 10,013 |
In the present work, we exhibited the experimental results of the direct current glow discharge electron gun source (DCEG) and their consecutive developments as electron beam energy lower than 5 keV and high intensity beams of tens microamperes to be used in some applications. A new type of direct current glow discharge electron gun was developed and modified for an improved treatment which supplies low –power and high electron-current density applications. This electron source is working on the condition of the abnormal glow discharge. The best working conditions were found to be at discharge pressure in the range of 10-4 mbar and gap distance between the cathode and the anode = 3 mm and a disk of Teflon insulator diameter of 5 mm, finally, the distance between the cathode exit and the extractor (focusing electrode) is equal to 4 mm. Internal and external operational characteristics (discharge and output ion beam currents) have been studied at this optimum distance using hydrogen, nitrogen and air gases. Finally, a glow discharge electron gun was used as a preparation tool of the surface of polyethylene terephthalate PET polymer substrate to be ready for coating or thin film deposition. The pristine PET is transparent and its surface is smooth | Preface. 1 Low-Pressure Discharges for Plasma Electron Sources. 1.1 Hollow-Cathode Discharge. 1.2 Discharges in Crossed Electric and Magnetic Fields. 1.3 Arc Discharges. 1.3.1 Vacuum-Arc Discharge. 1.3.2 Constricted Low-Pressure Arc Discharge. References. 2 Electron Emission from Plasma. 2.1 General Features of Electron Emission from Plasma. 2.1.1 Ion Extraction from Plasma. 2.1.2 Processes Associated with Electron Extraction from Plasma. 2.2 Control of Plasma Electron Emission Current. 2.2.1 Control of Steady-State Electron Current. 2.2.2 Control of Electron Emission in Pulsed Mode. 2.3 Emission Characteristics of the Plasma of a Constricted Arc Discharge with an Extended Anode Section. 2.4 Electron Emission from Plasma at Fore-Vacuum Pressures. 2.5 Special Features of Electron Emission from Nonstationary Plasma. References. 3 Plasma Sources for Axially Symmetric Electron Beams. 3.1 Cylindrical Electron-Beam Sources Based on Hollow-Cathode Discharges. 3.2 Sources of Steady-State Focused Electron Beams. 3.3 Sources of Tubular Electron Beams. References. 4 Generation of Large-Cross-Section Beams in Plasma-Cathode Systems. 4.1 Electron Sources with High Pulsed Energy Density. 4.2 Plasma Cathode Accelerators and Electron Sources with Microsecond Low-Pressure Arc Discharge. 4.3 Sub-Microsecond Pulsed Electron-Beam Sources. 4.4 Plasma-Cathode Large-Cross-Section Electron Sources Based on Hollow-Cathode Glow. 4.5 Pulsed Low-Energy Electron Sources. 4.6 Plasma-Cathode Electron Source for Ribbon Beam Production in the Fore-Vacuum Pressure Range. 4.6.1 Design of the Electron Source. 4.6.2 Characteristics of the Electron Source. 4.6.3 Parameters of the Plasma Sheet Generated by a Ribbon Electron Beam. References. 5 Some Applications of Plasma-Cathode Electron Sources. 5.1 Electron-Beam Welding. 5.2 Electron-Beam Cladding of Wear-Resistant Materials. 5.3 Use of Low-Energy, High-Current Electron Beams for Surface Treatment. 5.4 Production of Carbon Coatings by Plasma Produced by a Ribbon Electron Beam at Fore-Vacuum Pressure. References. Conclusion. Subject Index. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,014 |
The role of ion acoustic turbulence in the formation of high-energy ion tails in the plume of a 100-A LaB6 hollow cathode is experimentally and theoretically examined. At fixed flow rate and varying discharge current, single-point measurements of fluctuation intensity in the cathode plume are taken and compared to ion energy measurements. It is shown that for high discharge current the formation of energetic ions is correlated with the amplitude of the ion acoustic turbulence. Two-dimensional maps of background plasma parameters and wave turbulence are made at the highest discharge current investigated, 140 A. A simple, one-dimensional quasilinear model for the interaction of the ion energy distribution with the ion acoustic turbulence is employed, and it is shown that the energy in the measured wave turbulence is sufficiently large to explain the formation of ion tails in the cathode plume. Mitigation techniques for minimizing the amplitude of the turbulence are discussed. | Several researchers have measured ions leaving ion thruster discharge chambers with energies far greater than measured discharge chamber potentials. Presented in this paper is a new mechanism for the generation of high energy ions and a comparison with measured ion spectra. The source of high energy ions has been a puzzle because they not only have energies in excess of measured steady state potentials, but as reported by Goebel et. al. [1], their flux is independent of the amplitude of time dependent plasma fluctuations. The mechanism relies on the charge exchange neutralization of xenon ions accelerated radially into the potential trough in front of the discharge cathode. Previous researchers [2] have identified the importance of charge exchange in this region as a mechanism for protecting discharge cathode surfaces from ion bombardment. This paper is the first to identify how charge exchange in this region can lead to ion energy enhancement. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,015 |
Laser-driven d(d, n)-3He beam-target fusion neutron production from bulk deuterated plastic (CD) targets is compared with a pitcher-catcher target scheme using an identical laser and detector arrangement. For laser intensities in the range of (1–3) × 1019 W cm−2, it was found that the bulk targets produced a high yield (5 × 104 neutrons per steradian) beamed preferentially in the laser propagation direction. Numerical modeling shows the importance of considering the temperature adjusted stopping powers to correctly model the neutron production. The bulk CD targets have a high background target temperature leading to a reduced stopping power for the deuterons, which increases the probability of generating neutrons by fusion. Neutron production from the pitcher-catcher targets was not as efficient since it does not benefit from the reduced stopping power in the cold catcher target. Also, the inhibition of the deuteron acceleration by a proton rich contamination layer significantly reduces the pitcher-catche... | Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at "table-top" scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (∼104 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (∼0.1 T V/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 μm laser pulses irradiating planar foils up to 250 nm thick at 2-8 × 1020 W/cm2. These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ∼2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. The plans and prospects for further improvements and applications are also discussed. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,016 |
The High-Altitude Water Cherenkov (HAWC) Observatory is used for detecting TeV gamma rays. HAWC is operating at 4,100 meters above level sea on the slope of the Sierra Negra Volcano in the State of Puebla, Mexico, and consists of an array of 300 water Cherenkov detectors (WCDs) covering an area of 22,000 $m^2$. Each WCD is equipped with four photomultiplier tubes (PMTs) to detect Cherenkov emission in the water from secondary particles of extensive air-shower (EAS) that are produced in the interactions of primary particles (gamma rays or charged cosmic rays) in the atmosphere. HAWC is able to reconstruct the EAS in the 0.5 to 100 TeV energy range. In order to improve the core determination for events with high energy ($>10$ TeV) when the events arrive outside of the HAWC array, the Outrigger upgrade project is adding 350 small WCDs around the main array. These outrigger tanks each have one PMT in a 1.5 meter diameter cylindrical polyethylene tank, covering a total area four times larger than that of the HAWC array. In this work we present leak light testing to identify the stability of the detector and an analysis of deposited charges to understand the detector performance. | The Auger Observatory water Cherenkov detectors (WCD) will require that the initial calibration and subsequent monitoring of each of the WCDs be done in a remote way. We present a method to perform these tasks based on the detection of muons decaying inside the detectors and the application of adequate selection cuts. This technique may be complemented with another based on muons crossing the WCDs. Samples of decaying and crossing muon events were obtained with a WCD prototype to demonstrate the viability of the techniques. Three clear peaks of PMT charge distributions were identified. All of them are useful for calibration and monitoring of WCDs: one for stopping muons, one for decay electrons and one for crossing muons. The mean value of the peak found in the decay-electron charge distribution is 0.18 times the corresponding value for vertically crossing muons; likewise, the mean value of the peak in the charge distribution of crossing muons (excluding corner clipping muons) is 6.1 times the value for decay electrons in a tank of our dimensions; finally, the mean value of the peak in the charge distribution of stopping muons is 0.55 times the value for decay electrons. The techniques described can be applied equally well to unsegmented or segmented Auger tanks as each of the three PMTs of an Auger WCD can be self-triggered independently. The experimental data are well reproduced by numerical simulations. | It is proved, by using topological properties, that when a group automorphism of a locally compact totally disconnected group is ergodic under the Haar measure, the group is compact. The result is an answer for Halmos's question that has remained open for the totally disconnected case. | eng_Latn | 10,017 |
We review the time structure of synchrotron radiation and its use for fast time-resolved diffraction experiments in macromolecular photocycles using flash photolysis to initiate the reaction. The source parameters and optics for ID09 at ESRF are presented together with the phase-locked chopper and femtosecond laser. The chopper can set up a 900 Hz pulse train of 100 ps pulses from the hybrid bunch-mode and, in conjunction with a femtosecond laser, it can be used for stroboscopic data collection with both monochromatic and polychromatic beams. Single-pulse Laue data from cutinase, a 22 kD lipolic enzyme, are presented which show that the quality of single-pulse Laue patterns are sufficient to refine the excited state(s) in a reaction pathway from a known ground state. The flash photolysis technique is discussed and an example is given for heme proteins. The radiation damage from a laser pulse in the femto and picosecond range can be reduced by triggering at a wavelength where the interaction is strong. We propose the use of microcrystals in the range 25–50 μm for efficient photolysis with femto and picosecond pulses. The performance of circular storage rings is compared with the predicted performance of an X-ray free electron laser (XFEL). The combination of micro beams, a gain of 10 5 photons per pulse and an ultrashort pulse length of 100 fs is likely to improve pulsed diffraction data very substantially. It may be used to image coherent nuclear motion at atomic resolution in ultrafast uni-molecular reactions. | A novel subpicosecond x-ray streak camera (called PX1) was developed by the INRS group for subpicosecond time resolved spectroscopy in x rays and X-UV range. Using the PX1 camera, we have measured keV x-ray pulses with a 950 fs FWHM and a 850 fs rise time. The camera has also been coupled to ultrafast photoconductive switches and tested in jitter-free mode as a signal averaging detector. This instrument allows to analyze ultrafast changes in short wavelength signals with an unlimited dynamic range. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,018 |
The Lawrence Berkeley National Laboratory (LBNL) is presently designing and building the 2.5 MeV injector for the Spallation Neutron Source (SNS). The design includes various beam intercepting devices such as beam stops and slits. The target power densities can be as high as 500 kW/cm/sup 2/ with a beam stopping range of 25 to 30 microns, producing stresses well above yield in most materials. In order to analyze the induced temperatures and stresses, a finite element model has been developed. The model has been written parametrically to allow the beam characteristics, target material, dimensions, angle of incidence and mesh densities to be easily adjusted. The heat load is applied to the model through the use of a 3-dimensional table containing the calculated volumetric heat rates. The load is based on a bi-gaussian beam shape which is absorbed by the target according to a Bragg peak distribution. The results of several analyses using the SNS Front End beam are presented. | One of the goals of the PXIE at Fermilab is to demonstrate the capability to form an arbitrary bunch pattern from an initially CW 162.5 MHz Hbunch train coming out of an RFQ. The bunch-by-bunch selection will take place in the 2.1 MeV Medium Energy Beam Transport (MEBT) by directing the undesired bunches onto an absorber that needs to withstand a beam power of up to 21 kW, focused onto a spot with a ~2 mm rms radius. A design was developed to respond to the driving requirements: high surface power density of 17W/mm 2 and resistance to ion-induced surface blistering. A 1⁄4 size prototype of the absorber was manufactured, and its thermal properties were tested with an electron beam generating a peak power density similar to the one expected during normal operation of the PXIE beam line. The note describes the absorber concept, the prototype, the testing procedure with the electron beam, and the results of testing. Operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359 with the United States Department of Energy. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,019 |
In confining this review to non-L.T.E. plasmas, it will be clear that the main emphasis, of relevance to beam-foil spectroscopy, is on separation of ion stages and line identification. Only rarely can lifetimes be determined. The majority of line classifications for highly-charged ions, carried out over the last forty years, have used the two-electrode vacuum spark, a source that is still in use today. Low inductance triggered vacuum sparks have produced spectra up to copper XXVIII and have some properties in common with the plasma focus source. Laser-generated plasmas with temperatures of 100 eV or higher offer unique facilities for separating neighbouring stages of ionization. Magnetically confined plasmas are more homogeneous in temperature and often allow ion separation in time, during the ionizing phase. Astrophysical plasmas have a particular interest for forbidden line studies. The forbidden coronal line identifications of nearly thirty years age are now being extended by new observations into the ultraviolet. Other new forbidden lines in the solar soft X-ray spectrum, have changed our understanding of helium-like ion lifetimes. | The interaction of ionising radiation with atoms and ions is a key fundamental process. This report concentrates on studies of photoexcitation/photoionisation using laser-produced plasmas as continuum sources and synchronised laser plasma plumes to provide the absorbing atom or ion species. Examples from studies of the interaction of ionising radiation with atoms and ions ranging from few-electron atomic and ionic systems to the many-electron high atomic number actinides are reviewed and illustrate the advantages and limitations of the Dual Laser Plasma technique. | ●The conditions are officially justified not as punishment for prisoners but as an administrative measure. Prisoners are placed in control units in administrative moves and since there are no rules governing such moves (in contrast to punitive moves), prisoners are denied any due process and prison officials can incarcerate any prisoner in a control unit for as long as they choose, without having to give any reason. | eng_Latn | 10,020 |
The accurate response of a cylindrical NaI(Tl) detector for gamma rays up to 6.13 MeV has been calculated using a Monte Carlo method. The effects of the detector housing and scintillation efficiency of a NaI(Tl) crystal have been investigated. With consideration of these effects, the calculated results of energy spectra, intrinsic total efficiencies and photopeak efficiencies indicate excellent agreement with our experimental data. The variation of spectra, when the position of a gamma source is shifted, has also been studied comparing them with the experimental ones. | The Monte Carlo method was used to calculate the photon detection efficiency and energy resolution curves for a 1.5 00 � 100 NaI(Tl) scintillator detector (crystal þ housing þ photomultiplier tube material equivalent) exposed to gamma rays in the energy range from 20 keV to 662 keV. This work aims to design a precise computational model, based in Monte Carlo simulation, which can be used in practical application. The energy resolution curve was used to improve the response of the mathematical simulation of the detector. The detector was modeled with the MCNP-X code and the results were compared to experimental photopeak efficiency measurements of radiation sources. The results showed good agreement with the experimental data. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,021 |
The present paper reviews fundamentals of optical emission spectroscopy (OES) of plasmas and, in particular, its applications to processing plasmas. Collisional radiative model is described to understand the excitation kinetics and population distributions of excited states in order to examine the electron temperature and density. It is shown that corona equilibrium is often adopted as justifiable assumption of excitation kinetics for general processing plasmas. Two OES methods to understand molecular gas discharge plasmas are also reviewed. One of them is to determine vibrational or rotational temperatures of molecular gas discharge plasmas by OES measurement. The other is the actinometry measurement method to examine neutral radical density. | The vibrational and rotational temperatures in a spark-discharge plasma were measured using optical emission spectroscopy, and the influence of the air flow velocity and ambient pressure on these t... | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,022 |
The Naval Postgraduate School (NPS) Beam Physics Laboratory, Niowave, Inc., and The Boeing Company have completed construction of a superconducting 500 MHz quarter-wave gun and photocathode drive laser system. This prototype gun went from conception to initial operation in just under one calendar year. Such rapid progress is due in part to the decision to develop the gun as a prototype, deliberately omitting some features, such as tuners and a cathode loadlock, desired for a linac beam source. This will enable validation of the basic concept for the gun, including high-charge bunch dynamics, as rapidly as possible, with lessons learned applied to the next generation gun. This paper presents results from initial testing of the gun, technical challenges of the prototype design, and improvements that would enhance capabilities in future versions of this novel design. | The Helium processing technique has been used at CERN to improve the performance of the accelerating RF cavities with respect to field emission. It was extensively used in the vertical bare cavity tests to improve the superconducting cavities for the LEP Project. However this technique was rarely used on fully equipped production modules because of the risk of damaging the power couplers and the ceramic window by a possible glow discharge. First experience with He processing on finished modules equipped with additional vacuum interlocks to protect the power couplers was acquired in the test area in October 1996. He processing was applied to three modules limited by field emission. Their overall performance was increased to about 7 MV/m. One module was then processed in the LEP tunnel just before the shutdown 1996. The results obtained confirmed the feasibility of this method on a module already installed in the LEP tunnel and its efficiency in improving the performances. During the winter shutdown 1996-97, He processing has been done separately on seven modules installed in LEP. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 10,023 |
Delbruck scattering involves the scattering of photons off the Coulomb field of atoms via the creation of virtual electron-positron pairs from the vacuum. The complexity of the cross section is such that calculations in the 1980’s took over one solar year to perform. The next generation of high flux γray sources from laser Compton scattering will make possible much more precise measurement of Delbruck scattering. As a result, accurate numerical calculations are necessary for comparison. We show how to calculate the Delbruck scattering cross section using the LoopTools package of routines designed for calculations of the loop integrals from Feynman diagrams of Delbruck scattering and some preliminary calculations. | A high-contrast high-intensity petawatt-class Ti:sapphire chirped-pulse amplification laser has been developed for research on high field science. A saturable absorber and a low-gain optical parametric chirped-pulse amplification preamplifier in the front-end have improved the temporal contrast in the system to ∼ ::: $2 \times 10^{12}$ ::: on the subnanosecond time scale at the ∼70 TW power level. In addition to the high-contrast broadband high-energy output from the final amplifier has been achieved with a flat-top spatial profile with a filling factor of ∼70%. This is the result of pump beam spatial profile homogenization with diffractive optical elements. The system produces the uncompressed output pulse energy of 29 J, indicating the capability for reaching a peak power of ∼600 TW. We discuss in detail the design, performance, and characterization of the laser including output power, pulse duration, and spatiotemporal beam quality. We also describe the on-going upgrade of the laser system and some applications for the laser in relativistic dominated laser–matter interactions. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,024 |
Forescatter electron imaging is a popular microscopy technique, especially for scanning electron microscopes equipped with an electron backscatter diffraction detector. In principal, this method enables qualitative imaging of microstructure but quantitative assessment can be limited due to limited information about the contrast afforded. In this work, we explore forescatter electron imaging and demonstrate that imaging can be optimised for topographic, phase, and subtle orientation contrast imaging through appropriate sample and detector positioning. We demonstrate the relationship between imaging modes using systematic variation in detector positioning and compare this with pseudo-forescatter electron images, obtained from image analysis of diffraction patterns, to explore and confirm image contrast modes. We demonstrate these contrast mechanisms on a map obtained from a sample of the Gibeon meteorite. | Electron Optics of a Scanning Electron Microscope.- Electron Scattering and Diffusion.- Emission of Backscattered and Secondary Electrons.- Electron Detectors and Spectrometers.- Image Contrast and Signal Processing.- Electron-Beam-Induced Current and Cathodoluminescence.- Special Techniques in SEM.- Crystal Structure Analysis by Diffraction.- Elemental Analysis and Imaging with X-Rays. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,025 |
An activation detector has been developed for measuring the output of pulsed neutron generators. This detector utilizes the 75As(n, n′)75mAs reaction and detection of the 0.3 MeV gamma rays from 75 m As (τ 1 2 =17 ms ) by a plastic scintillator. The efficiency in counts per incident neutron is about 0.25% at 2.5 MeV and 0.35% at 14 MeV. | A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and ::: tested. The detection system is accurate and sensitive to neutrons with energies above 10 MeV; ::: importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It ::: is based upon the use of praesodymium, an element that has a single, naturally occurring isotope (Pr-141), a ::: significant (n,2n) cross section, and decays by positron emission. Neutron fluences are measured by using ::: the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay ::: product. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma ::: Focus Laboratory fusion sources. Comparisons with lead, copper, beryllium and silver activation detectors ::: have been performed. The detection method allows measurement of 14 MeV neutrons with a total error of ::: ± 10%. | A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and ::: tested. The detection system is accurate and sensitive to neutrons with energies above 10 MeV; ::: importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It ::: is based upon the use of praesodymium, an element that has a single, naturally occurring isotope (Pr-141), a ::: significant (n,2n) cross section, and decays by positron emission. Neutron fluences are measured by using ::: the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay ::: product. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma ::: Focus Laboratory fusion sources. Comparisons with lead, copper, beryllium and silver activation detectors ::: have been performed. The detection method allows measurement of 14 MeV neutrons with a total error of ::: ± 10%. | eng_Latn | 10,026 |
Fluxes of energetic ions with energies exceeding 100 keV were observed upstream of the bow shock of comet Halley by the Tunde instrument which was on board the VEGA 1 spacecraft. Downstream of the shock, ion fluxes in the energy range 100 to 800 keV were observed. Cometary ions, such as O+, newly picked up by the solar wind have energies of about 15 keV in the solar wind frame of reference; hence the measured ion fluxes indicate that acceleration processes must have been operating near comet Halley. The measured ion fluxes were transformed into distribution functions in the solar wind frame using a variety of assumptions concerning the energy dependence of the distribution function and the identity of the ion species. The derived distribution function upstream of the shock falls off steeply with energy between 100 and 150 keV, with an effective temperature of about 7 keV or spectral index about −15. The distribution function increases with decreasing cometocentric distance, on average, reaching a maximum at the bow shock. Downstream of the shock, the spectra can be represented in two ways: (1) one population with a single spectral index based on a power law energy dependence or (2) two exponential function populations with different effective temperatures. In the latter case a soft component exists with an effective temperature of about 30 keV for energies less than about 250 keV and a harder component exists for higher energies with an effective temperature of about 100 keV. Downstream of the shock, the ion fluxes decrease with decreasing cometocentric distance. The measured distribution functions are compared with those obtained by similar instruments on Giotto and the International Cometary Explorer as well as with the predictions of several theoretical models that employ different acceleration mechanisms. | A quasi-linear diffusion model including both pitch angle and energy diffusion, adiabatic compression and convective motion with the solar wind flow has been used to investigate the cometary ion pickup process along the Sun-comet line at comet Halley. The total pickup ion densities and magnetic turbulence spectrum levels observed by Giotto were used to constrain the quasi-linear model. Comparisons of the model results were made with energetic ion distributions observed by instruments onboard the Giotto spacecraft. The observed power spectrum index of magnetic turbulence γ is about 2–2.5. However, our simulation shows that when γ was 2, the calculated proton distributions were much more isotropic than the observed ones; hence we have chosen γ = 2.5 in our study. Furthermore, we assumed that only about 5% of the total low frequency wave power propagates away from the comet. The numerical solutions of the quasi-linear diffusion equations show that the isotropization of the pickup ion distribution, particularly at the pickup velocity, is not complete even close to the bow shock (but upstream), which agrees with the observations. The calculated and observed proton distributions are somewhat more isotropic than the water group ion distributions in the region far upstream of the shock, but the opposite is true near the bow shock. We find that given the observed turbulence level, quasi-linear theory gives pickup ion energy distributions that agree with the observed ones quite well and easily produces energetic ions with energies up to hundreds of keV. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,027 |
A semiconductor Compton camera for a balloon borne experiment aiming at observation in high energy astrophysics ::: is developed. The camera is based on the concept of the Si/CdTe semiconductor Compton Camera, ::: which features high-energy and high-angular resolution in the energy range from several tens of keV to a few ::: MeV. It consists of tightly packed double-sided silicon strip detectors (DSSDs) stacked in four layers, and a ::: total of 32 CdTe pixel detectors surrounding them. The Compton reconstruction was successfully performed and ::: gamma-ray images were obtained from 511 keV down to 59.5 keV. The Angular Resolution Measure (ARM) at ::: 511 keV is ~ 2.5 degrees, thanks to the high energy resolution in both the DSSD and CdTe parts. | The development of focusing optics based on wide band Laue lenses operating from ∼60 keV up to several hundreds of keV is particularly challenging. This type of hard X-ray or gamma ray optics requires a high performance focal plane detector in order to exploit to the best its intrinsic capabilities. We describe a three dimensional (3D) position sensitive detector prototype suitable for use as the basic module for a high efficiency Laue lens focal plane detector. This detector configuration is currently under study for use in a balloon payload dedicated to performing a high significance measurement of the polarization status of the Crab nebula/pulsar between 100 and 500 keV. The prototype is made by packing 8 linear modules, each composed of one basic sensitive unit bonded onto a thin supporting ceramic layer. Each unit is a drift strip detector based on a CZT crystal, irradiated transversally to the electric field direction. The anode is segmented into 8 detection cells, each comprising one collecting strip and 8 surrounding drift strips. The drift strips are biased by a voltage divider. The cathode is divided into 4 horizontal strips for the reconstruction of the Z interaction position. The detector readout electronics is based on three RENA-3 ASICs and the data handling system uses custom electronics based on an FPGA to provide the ASIC setting, the event handling logic and the data acquisition. We will describe the components and the status of the ongoing activities for the assembling of the proposed 3D CZT prototype and the result of the first performance tests on the CZT linear modules. | This paper describes a CCD (charge coupled device) camera‐based hyperspectral imaging system designed for both stationary and airborne remote sensing applications. The system consists of a high performance digital CCD camera, an imaging spectrograph, an optional focal plane scanner, and a PC computer equipped with a frame grabbing board and camera utility software. The CCD camera provides 1280(h) × 1024(v) pixel resolution and true 12‐bit dynamic range. The imaging spectrograph is attached to the camera via an adapter to disperse radiation into a range of spectral bands. The effective spectral range resulting from this integration is from 457.2 nm to 921.7 nm. The optional focal plane scanner can be attached to the front of the spectrograph via another adapter for stationary image acquisition. The camera and the frame grabbing board are connected via a double coaxial cable, and the utility software allows for complete camera control and image acquisition. The imaging system captures one line imag... | eng_Latn | 10,028 |
In the 100 MeV H Linac to be constructed at Fermilab, the use of fast ferrite high power phase shifters will allow all of the accelerating RF cavities to be driven by a single 2.5 MW, 325 MHz klystron. This results in substantial cost savings. The shifters are coaxial with aluminum doped Yttrium Iron Garnet (YIG) ferrite. In combination with branch line couplers, they will provide independent phase and amplitude control for each cavity. This is achieved by adjusting the solenoidal magnetic field applied to the ferrite. We report on our results in both low power (timing) and high power tests, for both 3 and 15/8 OD phase shifters. The low power measurements demonstrate that the rate of phase shift is well within the spec of 1 degree/μs. The high power tests were performed at the Advanced Photon Source at Argonne National Lab. We measured phase shifts and the failure point (applied power) for tuners in various configurations. In addition, we performed phase and amplitude measurements for a setup consisting of a 1-5/8 OD phase shifter along with a prototype branch line coupler. | One of the approaches to power distribution system of a superconducting proton linac that is under discussion at Fermilab requires development of a fast-action, megawatt-range phase shifter. Using two phase shifters with a waveguide hybrid junction can allow independent control of phase and amplitude of RF power at the input of each superconducting cavity of the linac. This promises significant saving in number of klystrons and modulators required for the accelerator. A prototype of a waveguide version of a phase shifter that uses Yttrium-Iron Garnet (YIG) blocks was developed and tested. This report presents design concept of the device and main results of simulation and proof-of-principle tests. | One of the approaches to power distribution system of a superconducting proton linac that is under discussion at Fermilab requires development of a fast-action, megawatt-range phase shifter. Using two phase shifters with a waveguide hybrid junction can allow independent control of phase and amplitude of RF power at the input of each superconducting cavity of the linac. This promises significant saving in number of klystrons and modulators required for the accelerator. A prototype of a waveguide version of a phase shifter that uses Yttrium-Iron Garnet (YIG) blocks was developed and tested. This report presents design concept of the device and main results of simulation and proof-of-principle tests. | eng_Latn | 10,029 |
Single crystals of GaAs containing Ga{111}, As{111}, and {110} faces decomposed at rates between 4×10−2 and 1×10−3 times the free evaporation rates were examined microscopically. At these high values, the decomposition rate is observed to be orientation dependent in the order As{111}>Ga{111}, as previously reported. The {110} face decomposes at a rate intermediate between the As{111} and the Ga{111} faces. At our high decomposition rates, the As{111} faces are completely corroded in a noncrystallographic manner, while crystallographic decomposition pits are produced on the Ga{111} face. At low decomposition rates, the degree of decomposition on all three faces appears equal and decomposition pits made up of {111} faces are formed. Surface kinks produced by mechanical damage and chemical etch pitting act as nucleation sites for decomposition pits. Dislocations do not serve as nucleation sites for decomposition pits. A model that accounts for the experimental observation is presented. | Experiments were performed to evaluate production of 72Se, parent radionuclide of the positron emitter 72As, at high energy at the Brookhaven Linac Isotope Producer (BLIP). Excitation functions for 75As(p, xn)72/75Se in the 52-105 MeV energy range were measured by irradiating thin gallium arsenide (GaAs) wafers. Maximum cross section value for the natAs(p, 4n)72Se reaction in the energy range was 103±9 mb at 52±1 MeV. Production size GaAs and arsenic metal (As°) targets were irradiated with 136 μA and 165 μA beam current possessing an initial Linac energy of 117 MeV. A total of 3.77±0.1 GBq (102±3 mCi) of 72Se was produced from a GaAs target at a calculated target entrance energy of 105.4 MeV, and 13.8±0.3 GBq (373±8 mCi) of 72Se from an As° target at a calculated incident energy of 49.5 MeV irradiated for 116.5 h and 68.9 h, respectively. | Blunt trauma abdomen rarely leads to gastrointestinal injury in children and isolated gastric rupture is even rarer presentation. We are reporting a case of isolated gastric rupture after fall from height in a three year old male child. | eng_Latn | 10,030 |
For injection of beams into circular machines with different horizontal and vertical emittance acceptance, the injection efficiency can be increased if these beams are flat, i.e. if they feature unequal transverse emittances. Generation of flat electron beams is well known and has been demonstrated already in beam experiments. It was proposed also for ion beams that were generated in an Electron Cyclotron-Resonance (ECR) source. We introduce an extension of the method to beams that underwent charge state stripping without requiring their generation inside an ECR source. Results from multi-particle simulations are presented to demonstrate the validity of the method. | In 1926, H. Busch formulated a theorem for one single charged particle moving along a region with a longitudinal magnetic field [H. Busch, Berechnung der Bahn von Kathodenstrahlen in axial symmetrischen electromagnetischen Felde, Z. Phys. 81 (5) p. 974, (1926)]. The theorem relates particle angular momentum to the amount of field lines being enclosed by the particle cyclotron motion. This paper extends the theorem to many particles forming a beam without cylindrical symmetry. A quantity being preserved is derived, which represents the sum of difference of eigen-emittances, magnetic flux through the beam area, and beam rms-vorticity multiplied by the magnetic flux. Tracking simulations and analytical calculations using the generalized Courant-Snyder formalism confirm the validity of the extended theorem. The new theorem has been applied for fast modelling of experiments with electron and ion beams on transverse emittance re-partitioning conducted at FERMILAB and at GSI. | Many methods exist to invert airborne imagery from units of either radiance or sensor specific digital counts to units of reflectance. These compensation algorithms remove unwanted atmospheric variability allowing objects on the ground to be analyzed. Low error levels in homogenous atmospheric conditions have been demonstrated. In many cases however, clouds are present in the atmosphere which introduce error into the inversion at unacceptable levels. For example, the relationship that is defined between sensor reaching radiance and ground reflectance in a cloud free scene will not be the same as in an adjacent region with clouds in the surround. A novel method has been developed which utilizes ground based measurements to modify the empirical line method (ELM) approach on a per-pixel basis. A physics based model of the atmosphere is used to generate a spatial correction for the ELM. Creation of this model is accomplished by analyzing whole-sky imagery to produce a cloud mask which drives input parameters to the radiative transfer (RT) code MODTRAN. The RT code is run for several different azimuth and zenith orientations to create a three-dimensional representation of the hemisphere. The model is then used to achieve a per-pixel correction by adjusting the ELM slope spatially. This method is applied to real data acquired over the atmospheric radiation measurement (ARM) site in Lamount, OK. Performance of the method is evaluated with the Hyperspectral Digital Imagery Collection Experiment (HYDICE) instrument. The sensitivity to spectral sampling is also assessed by down-sampling the HYDICE data to the spectral response of the multi-spectral system Wildfire Airborne Sensor Program LITE (WASP Lite). Finally a method to utilize this approach when additional sensors (like a sky camera) are not available is | eng_Latn | 10,031 |
We investigate the effects of electron cyclotron resonant heating on the kinetic evolution and acceleration of the fast solar wind. A previous study has shown that kinetic wave-particle interactions due to ion resonant heating, may account for the bulk acceleration of the solar wind, the preferential heating of the helium ions over the protons, as well as the occasionally observed double-peaked proton velocity distributions. The model followed the evolution of the particle distributions along an inhomogeneous field line under the effects of ion heating, Coulomb collisions, and an ambipolar electric field that was consistent with the distributions themselves. This study extends the model to take into account also the effect of electron cyclotron resonant heating. Our parametric study shows that the electron heating does not change the solar wind qualitative features described above. However, the wave-particle interaction increases the ambipolar electric field, thereby enhancing the solar wind velocity. | this paper. The charge per mass of the ion O 6+ and Fe 9+ are different, a fact which results in different features of the ion-cyclotron resonance with waves. In plasma with protons, drifting alpha particles, and electrons, the dispersion relation of cyclotron waves has two branches. The oxygen ions tend to resonate with the inward propagating waves of the lefthand-polarized (LHP) first branch and the outward propagating waves of the LHP second branch. These resonances may together lead to a velocity distribution with a central velocity higher than the proton (solar wind) bulk velocity by about 50 km/s at 1 AU. The Fe 9+ ions tend to resonate with both the inward and outward propagating waves of the first branch and may thus form a velocity distribution with a central velocity very near the proton bulk velocity. These analytical results are shown to be supported by numerical results from a two-dimensional simulation based on the quasi-linear diffusion equation. The limitations of the present analysis and further work, which should be done to support the ideas proposed here, are also discussed. INDEX TERMS: 2164 Interplanetary Physics: Solar wind plasma; 2159 Interplanetary Physics: Plasma waves and turbulence; 7867 Space Plasma Physics: Wave/ particle interactions; 7871 Space Plasma Physics: Waves and instabilities; KEYWORDS: solar wind ions, ion differential streaming, pitch angle diffusion, ion-drift regulation | Impacts of low energy He+ ions on reflectivity and stability of EUV multilayers is investigated in this work. Combination of X-ray reflectivity, grazing incidence EUV reflectivity near Silicon edge, and theoretical ion irradiation damage analysis can explain the degradation of ML performances. It is found that MLs irradiation of 4 keV helium ions degrades reflectivity performances with much more impact on grazing incidence mirrors. The proposed method can also regain changes in optical properties due to the irradiations of low energy ions. | eng_Latn | 10,032 |
It is shown that “zebra-pattern” in solar continuum events (in type IV bursts) can be formed as a result of interference between direct and reflected rays coming from a source of small size in a stratified atmosphere. The emission is generated by plasma mechanism. Full emission flux is contributed from a great number of narrow-band short-lived sources of small sizes, which are formed by plasma waves captured in density minima of background plasma fluctuations. | In the literature, discussion continues about the nature of the zebra structure (ZS) in type IV radio bursts, and understanding even the most extended mechanism associated with double plasma resonance has been improved in series of works. Moreover, in the recent work (Ben\'a\v{c}hek, Karlick\'y, Yasnov, 2017) its ineffectiveness was shown under the usually adopted conditions in the radio source. In this case in a number of works we demonstrated the possibility of modeling with whistlers to explain many thin components of ZS stripes, taking into account the effects of scattering whistlers on fast particles. This situation stimulates the search for new mechanisms. For example, earlier we showed the importance of explosive instability, at least for large flares with the ejections of protons. In the system a weakly relativistic beam of protons, nonisothermic plasma, the slow beam mode of the space charge possesses negative energy, and in the triplet slow and fast beam modes and ion acoustic wave an explosive cascade of harmonics from ionic sound is excited. Electromagnetic waves in the form of ZS stripes appear as a result of the fast protons scattering on these harmonics. Such a mechanism can also be promising for a ZS in radio emission from the pulsar in the Crab nebula. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,033 |
The elemental composition on planetary surface provides us an essential information to improve geological and geochemical understanding of planets. An active X-ray spectrometer (AXS) was developed and proposed as one of the mission payloads to perform in-situ X-ray fluorescence analysis. The AXS consists of multiple pyroelectric X-ray generators (PXGs) and a silicon drift detector (SDD). Although the PXG is light in weight and low in electric consumption, the limited X-ray intensity and reproducibility hamper obtaining the elemental composition by short time observation. This is attributed mainly to the less known mechanism of X-ray and electron emission by the pyroelectric crystal. In this study, we observed the crystal surface during X-ray emission as a function of the distance between the crystal top and a Cu target. Two types of light emission derived from the electric discharge were observed. The dependence of light emission on the distance was found to be related with the physical mechanism of pyroelectric X-ray emission. The study provides clues to obtain high intensity and reproducible X-rays emission. The experimental results and discussion are presented in this paper. | The phenomenon of pyroelectric electron emission has been employed to develop miniature x-ray sources, such as the Cool-X by Amptek (www.amptek.com/coolx.html). The source strength of a pyroelectric x-ray generator is dependent on the emitted electron energy and current. Similarly, the source strength of a pyroelectric neutron generator will be dependent on the energy and production rate of deuterium ions in the fill gas. This paper summarizes our results in experiments directed toward creating high-energy electrons and positive ions with a pyroelectric source. Single-crystal sources are shown to produce positive ions with energies of up to 98keV and electron energies of up to 143keV. X-ray spectra are presented as proof that a paired-crystal source can increase electron energy to at least 215keV. In addition, we offer independent verification of the “bunched” electron emission effect observed by [Brownridge et al., Appl. Phys. Lett. 78, 1158 (2001)]. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,034 |
The design of the SPEAR 3 injection kicker system is presented. This system will include three kicker magnets and their associated pulsers. The magnet design is based on the DELTA kicker magnets, which present a low RF impedance to the beam, and are relatively straightforward to construct. The pulsers use cascaded IGBT stages that are based on the modulator pulsers developed by a SLAC/LLNL collaboration for the NLC. Design considerations and the results of prototype tests will be discussed. | SPEAR 3 is an upgrade of the 18-cell SPEAR 2 storage ring to 3GeV beam energy, 18nm-radian emittance and up to 500mA circulating current. The existing arrangement of photon beam lines remains largely unchanged, but opportunities arise for additional ID and dipole radiation exit ports. For optimum beam stability, the entire tunnel floor will be excavated and replaced with reinforced concrete. The magnet/vacuum-chamber supports will be mounted on rigid steel rafts (3 per cell). The cable plant and RF drive will be installed ahead of time while the power supplies, tunnel floor and pre-assembled rafts will be installed in a 6-month shutdown beginning April, 2003. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,035 |
This work assesses the performance of a modified two-dimensional gamma scan system in spent fuel pin studies. The techniques for a two-dimensional gamma scan studied have been developed at the Hot Cell of Institute of Nuclear Energy Research (INER). Samples are acquired from the spent fuel pin, TPC-SP-C1, which was irradiated in a commercial reactor core (the first of its kind in Taiwan) for 2 years and then deposited in a cooling pool for 10 years. The spent fuel pin was then transferred into INER for further examination. The gamma scanning system was driven by a step motor which had an accuracy within 0.1 mm in both X-Y directions. Data obtained from this system are presented in both an isotopic distribution and contour plot. Results in this study closely correspond to those in other investigations, thereby confirming the effectiveness of this modified system. | Imaging of nuclear fuel using radiation has been carried out for decades for a variety of reasons. Two important reasons are Physical Inventory Verification (PIV) and Quality Assurance (QA). The work covered in this review focuses on the imaging of nuclear fuel using ionising radiation. The fuels investigated are both fresh and spent, composed of assorted materials, and in various physical forms. The radiations used to characterise the nuclear fuel include γ, α, β, muons, neutrons and X-rays. The research covered in this review, spans the past four decades and show how the technology has developed over that time. The advancement of computing technology has greatly helped with the progression of the images that are produced. The field began with 2D images in black and white showing the density profiles of rays from within an object, culminating in 2013 when a pebble bed fuel element was reproduced in 3D showing each 0.5 mm UO2 globule within it. With the ever increasing computing technology available to the industry, this can only mean an increase in the rate of development of imaging technologies like those covered in this review. | The Archimedes Wave Swing is a system that converts ocean wave energy into electric energy. A pilot plant of this system has been built. The generator system consists of a permanent-magnet linear synchronous generator with a current source inverter (CSI). The correlation between the measured and the calculated parameters of the designed generator is reasonable. The annual energy yield of the pilot plant is calculated from the wave distribution as 1.64 GWh. Using a voltage source inverter instead of a CSI improves the power factor, the current waveforms, the efficiency and the generator force, so that the annual energy yield increases with 18%. | eng_Latn | 10,036 |
Spatial and spectral profiles of O VI emission behind a shock wave on the northern edge of the Cygnus Loop were obtained with the Far Ultraviolet Spectroscopic Explorer. The velocity width of the narrowest O VI profile places a tight constraint on the electron-ion and ion-ion thermal equilibration in this 350 km s-1 collisionless shock. Unlike faster shocks in SN 1006 and in the heliosphere, this shock brings oxygen ions and protons to within a factor of 2.5 of the same temperature. Comparison with other shocks suggests that shock speed, rather than Alfven Mach number, may control the degree of thermal equilibration. We combine the O VI observations with a low-resolution far-UV spectrum from the Hopkins Ultraviolet Telescope, an Hα image, and ROSAT PSPC X-ray data to constrain the preshock density and the structure along the line of sight. As part of this effort, we model the effects of resonance scattering of O VI photons within the shocked gas and compute time-dependent ionization models of the X-ray emissivity. Resonance scattering affects the O VI intensities at the factor of 2 level, and the soft spectrum of the X-ray rim can be mostly attributed to departures from ionization equilibrium. The preshock density is about twice the canonical value for the Cygnus Loop X-ray-emitting shocks. | A modular unit for erosion control due to wave action is disclosed. The system utilizes a series of symmetrical units linked together to dissipate the kinetic energy of incoming waves. Symmetry of building blocks enables the device to work in any orientation. Energy dissipators on each block allow the wave action to be broken up while allowing passage of water through the unit. | We characterize stability under composition, inversion, and solution of ordinary differential equations for ultradifferentiable classes, and prove that all these stability properties are equivalent. | eng_Latn | 10,037 |
Parametric X-radiation can be described as the diffraction of virtual photons associated with the electric field of a relativistic charged particle passing through a crystal. In analogy with Bragg reflection of X-rays, these diffracted photons appear as real photons, with an energy which satisfies Bragg's law for the reflecting crystal planes. We describe the results of experiments performed on the Naval Postgraduate School linac which were designed to explore the basic properties of PXR in order to assess its potential application as a compact tunable X-ray source. Experiments using a mosaic graphite radiator show that this radiator produced multiple order, narrow bandwidth reflections from 5-45 keV. The measured production efficiency is found to exceed that predicted for spectral orders n>1. We demonstrated the tunability of PXR by rotating the crystal in order to change the Bragg angle relative to the incident 90 MeV electron beam.<<ETX>> | We describe our recent experimental study of the production of x rays by an electron beam interacting with a crystal lattice, i.e., parametric x-ray (PX) generation. In this radiation process, the virtual photon field associated with a relativistic electron traveling in a crystal is diffracted by the crystal lattice in the same way that real x rays are diffracted by crystals. The radiation produced satisfies the Bragg conditions associated with the diffraction of the virtual photons which are nearly parallel to the velocity of the electrons. This phenomenon is associated with a more general class of radiation production mechanisms which include transition radiation (TR), diffraction radiation (DR), and Smith-Purcell radiation. In each case, radiation is produced when the particle's fields are altered by interacting with a material whose dielectric constant varies along or near the particle's trajectory. The usual acceleration mechanism for the production of radiation is not involved in these phenomena. In the case of a crystal, the periodic electric susceptibility interacting with the particle's field produces parametric x rays. We will also present a theoretical overview of this phenomenon which can be used to generate monochromatic, linearly polarized, directional x rays. Accelerators with energies ranging from a few MeV to hundreds of MeV may be used as drivers for novel parametric x-ray generators for various applications requiring the unique properties of these sources. | Bayesian approach remained rather unsuccessful in treating nonparametric problems. This is primarily due to the difficulty in finding workable prior distribution on the parameter space , which in nonparametric problems is taken to be a set of probability distributions on a given sample space. Two Desirable Properties of a Prior 1. The support of the prior should be large. 2. Posterior distribution given a sample of observation should be manageable analytically. These properties are antagonistic : One may be obtained at the expense of other. | eng_Latn | 10,038 |
We are developing seeded XFEL pulse with HH for coherent XFEL pulse. Using the monitor of temporal overlap with EO sampling technique, seeded pulse was obtained long time against timing drift. | The 13th harmonic of a Ti:sapphire (Ti:S) laser in the plateau region was injected as a seeding source to a 250-MeV free-electron-laser (FEL) amplifier. When the amplification conditions were fulfilled, strong enhancement of the radiation intensity by a factor of 650 was observed. The random and uncontrollable spikes, which appeared in the spectra of the Self-Amplified Spontaneous Emission (SASE) based FEL radiation without the seeding source, were found to be suppressed drastically to form to a narrow-band, single peak profile at 61.2 nm. The properties of the seeded FEL radiation were well reproduced by numerical simulations. We discuss the future precept of the seeded FEL scheme to the shorter wavelength region. | not available DOI: http://dx.doi.org/10.3329/pulse.v5i2.20263 Pulse Vol.5 July 2011 p.31-40 | eng_Latn | 10,039 |
The Compact Linear Collider (CLIC) is a proposed high-luminosity collider that would collide electrons with their antiparticles, positrons, at energies ranging from a few hundred Giga-electronvolts (GeV) to a few Tera-electronvolts (TeV). By covering a large energy range and by ultimately reaching multi-TeV $e^+e^-$ collisions, scientists at CLIC aim to improve the understanding of nature's fundamental building blocks and to discover new particles or other physics phenomena. CLIC is an international project with institutes world-wide participating in the accelerator, detector and physics studies. First $e^+e^-$ collisions at CLIC are expected around 2035, following the High-Luminosity phase of the Large Hadron Collider at CERN. | Together with the recent CLIC detector model CLICdet a new software suite was introduced for the simulation and reconstruction of events in this detector. This note gives a brief introduction to CLICdet and describes the CLIC experimental conditions at 380 GeV and 3 TeV, including beam-induced backgrounds. The simulation and reconstruction tools are introduced, and the physics performance obtained is described in terms of single particles, particles in jets, jet energy resolution and flavour tagging. The performance of the very forward electromagnetic calorimeters is also discussed. | Together with the recent CLIC detector model CLICdet a new software suite was introduced for the simulation and reconstruction of events in this detector. This note gives a brief introduction to CLICdet and describes the CLIC experimental conditions at 380 GeV and 3 TeV, including beam-induced backgrounds. The simulation and reconstruction tools are introduced, and the physics performance obtained is described in terms of single particles, particles in jets, jet energy resolution and flavour tagging. The performance of the very forward electromagnetic calorimeters is also discussed. | eng_Latn | 10,040 |
The main physics programme of the International Linear Collider (ILC) requires a measurement of the beam energy with a relative precision of 10 4 or better. To achieve this goal a spectrometer using high resolution beam position monitors (BPM) and accurately monitored bending magnets has been proposed. A prototype spectrometer chicane using 4 dipoles is now commissioned in End Station A (ESA) at SLAC, intending to demonstrate the required stability of this method and investigate possible systematic effects and operational issues. In this contribution we will describe the experimental setup for this ESA test experiment (T-474/491), which has been finalised during two runs in 2007, and present results from the BPM commissioning runs in 2006. The design of the International Linear Collider is driven by the broad precision physics programme of electroweak, Higgs, QCD and possible SUSY measurements. The uncertainty on the energy of the colliding electron and positron bunches contributes directly to the systematic error on e.g. top quark W and Higgs masses [2], making a precise energy measurement of the beam of crucial importance. At LEP2, an energy spectrometer was successfully commissioned, achieving an accuracy of 1.9 × 10 4 [3]. Dipoles in the bending sections of the storage ring were used to induce a deflection of the lepton beam. With accurate knowledge of the total integrated field of these bending magnets together with a measurement of the deflection itself, one can derive the energy of the beam. The ILC energy spectrometer has similar design requirements in terms of accuracy, however to limit the emittance growth due to synchrotron radiation in the beam delivery system, the introduced dispersion in the spectrometer chicane has been restricted to 5 mm. Also, at the ILC the measurement has to be done in a single shot. High resolution RF cavity BPM systems are therefore preferred to strip-line or button BPMs as these can achieve resolutions well below a micron [4], needed for a precision energy measurement. As a proof of principle, a test beam experiment (T-474/491) was proposed [5] at ESA at the Stanford Linear Accelerator Center (SLAC), focusing on studying the achievability and | T-474 at SLAC is a prototype BPM-based energy spectrometer for the ILC. We describe magnetic measurements and simulations for the 4-magnet chicane used in T-474. | T-474 at SLAC is a prototype BPM-based energy spectrometer for the ILC. We describe magnetic measurements and simulations for the 4-magnet chicane used in T-474. | eng_Latn | 10,041 |
[1] Coincident particle and optical measurements from the Reimei spacecraft suggest that sheared flows through an inverted-V arc may be unstable to the emission of Alfven waves. The particle measurements reveal time dispersed field-aligned electron bursts typical of low energy electrons accelerated by inertial Alfven waves (IAWs). These Alfven wave accelerated electrons are embedded within multi-keV inverted-V electron structures. The optical measurements at the footprint of the inverted-V structures reveal counter propagating and folded/vortical discrete auroral forms moving with speeds of ∼14–18 km/s. We show that the flow shear inferred from this motion exceeds that required for instability to the emission of Alfven waves on scales of the order of an electron inertial length. The emission of these waves provides a likely means for driving the low energy dispersed electron bursts we observe. | [1] Using a self-consistent drift-kinetic simulation code, we investigate whether electron acceleration owing to shear Alfven waves in the plasma sheet boundary layer is sufficient to cause auroral brightening in the ionosphere. The free parameters used in the simulation code are guided by in situ observations of wave and plasma parameters in the magnetosphere at distances >4 RE from the Earth. For the perpendicular wavelength used in the study, which maps to ∼4 km at 110 km altitude, there is a clear amplitude threshold which determines whether magnetospheric shear Alfven waves above the classical auroral acceleration region can excite sufficient electrons to create the aurora. Previous studies reported wave amplitudes that easily exceed this threshold; hence, the results reported in this paper demonstrate that auroral acceleration owing to shear Alfven waves can occur in the magnetosphere at distances >4 RE from the Earth. | The stationary inertial Alfven (StIA) wave (Knudsen, 1996) was predicted for cold, collisionless plasma. The model was generalized (Finnegan et al., 2008) to include nonzero values of electron and ion collisional resistivity and thermal pressure. Here, the two-fluid model is further generalized to include anisotropic thermal pressure. A bounded range of values of parallel electron drift velocity is found that excludes periodic stationary Alfven wave solutions. This exclusion region depends on the value of the local Alfven speed V A , plasma beta perpendicular to the magnetic field β ⊥ and electron temperature anisotropy. | eng_Latn | 10,042 |
A fibreform nanostructured layer is formed on a tungsten surface by helium plasma bombardment. The helium fluence was of the order of 1026 m−2, and the surface temperature and incident ion energy during helium irradiation were, respectively, 1900 K and 75 eV. By irradiating a laser pulse to the surface in the plasma, a unipolar arc, which many people have tried to verify in well-defined experiments, is promptly initiated and continued for a much longer time than the laser pulse width. The laser pulse width (~0.6 ms) and power (~5 MJ m−2) are similar to the heat load accompanied by type-I edge localized modes (ELMs) in ITER. The unipolar arc is verified from an increase in the floating potential, a moving arc spot detected by a fast camera and arcing traces on the surface. This result suggests that the nanostructure on the tungsten surface formed by the bombardment of helium, which is a fusion product, could significantly change the ignition property of arcing, and ELMs become a trigger of unipolar arcing, which would be a great impurity source in fusion devices. | Characterization of a pulsed plasma formed with a plasma gun device was performed. The averaged electron density was measured with an interferometer system using a Zeeman laser at 633 nm. It was found that the plasma with the density of ~ 1022 m-3 was successfully formed. The temporal evolution of the plasma was observed with a fast framing camera. It was found that the shape of the plasma was significantly varied temporally. From the intensity profile, the vertical emission profile was obtained using Abel inversion. The emission profile had a flat top shape with the radius of ~ 20 mm, and gradually decreased with the radius. The penetration behavior of the gun plasma across the magnetic field was observed. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,043 |
The high-luminosity LHC (HL-LHC) upgrade is setting a new challenge for particle detector technologies. The increase in luminosity will produce a higher particle background with respect to present conditions. In order to study performance and stability of detectors at LHC and future HL-LHC upgrades, a new dedicated facility has been built at CERN: the Gamma Irradiation Facility (GIF++). The GIF++ is a unique place where high energy charged particle beams (mainly muons) are combined with gammas from a 14 TBq 137Cesium source which simulates the background expected at the LHC experiments. Several centralized services and infrastructures are made available to all the LHC detector community for facilitating the different R&D programs. | Operation of large-area muon detectors at the future Large Hadron Collider (LHC) will be characterized by large sustained hit rates over the whole area, reaching the range of kHz cm −2 . We describe a dedicated test zone built at CERN to test the performance and the aging of the muon chambers currently under development. A radioactive source delivers photons causing the sustained rate of random hits, while a narrow beam of high-energy muons is used to directly calibrate the detector performance. A system of remotely controlled lead filters serves to vary the rate of photons over four orders of magnitude, to allow the study of performance as a function of rate. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,044 |
The electron emission yield of materials is an important quantity to be determined in various fields of physics. Among them, dielectric materials have a strong ability to retain charges and remain charged when submitted to electrical field, in particular when irradiated by electron beam. Without the use of specific measurement methodology, experimental investigation of dielectric materials may lead to an inaccurate measurement of the total electron emission yield (TEEY). This paper shows that a particular attention should be paid to the pulse duration of the incident electron beam and to hysteresis effects induced by charge trapping. | Secondary electron emission (SEE) is one of the main parameters controlling spacecraft potential. It also plays an important role in the triggering of the multipactor phenomenon occurring in waveguides (electron avalanche in microwave electric fields). In this paper, we propose an original method adapted to low-energy SEE measurements on dielectrics and conductors (incident electron energy below 20 eV). It is based on Kelvin probe (KP) surface potential measurements after electron irradiation. It is particularly well suited to insulating materials but can also be used on metals by letting the sample potential float. We present results of SEE measurements performed on metals used in waveguides, Kapton, Teflon, and CMX cover glass. In order to avoid any experimental artifact due to the earth magnetic field and conduct accurate low-energy measurements with the KP method, the distance between the electron gun and the sample is chosen to be negligible compared to the Larmor radius. | We construct stationary black holes in SU(2) Einstein-Yang-Mills theory, which carry angular momentum and electric charge. Possessing non-trivial nonabelian magnetic fields outside their regular event horizon, they represent nonperturbative rotating hairy black holes. | eng_Latn | 10,045 |
A dedicated gas-filled magnet with a deflection angle of 135° has been installed for isobaric suppression in AMS. The optimum bending angle of 135° has been calculated with a Monte Carlo code. Among different gases studied, nitrogen showed the best compromise between multiple scattering and charge changing cross sections for superior resolution of isobars. Other components of this system are a time-of-flight measurement with a 250 ps resolution and an ionization chamber with five Δ E measurements, position and angle sensitivity in the horizontal plane and angle sensitivity in the vertical. Test measurements have been performed for 36Cl, 53Mn, 59Ni and 60Fe. The excellent resolution achieved allows for the first time sensitive AMS measurements of 53Mn. The measurement of the 60Fe concentration in the meteorite Tlacotepec registered no events at a sensitivity level of 1.5 × 10−14. | The detection of (41)Ca atoms in tooth enamel using accelerator mass spectrometry is suggested as a method capable of reconstructing thermal neutron exposures from atomic bomb survivors in Hiroshima and Nagasaki. In general, (41)Ca atoms are produced via thermal neutron capture by stable (40)Ca. Thus any (41)Ca atoms present in the tooth enamel of the survivors would be due to neutron exposure from both natural sources and radiation from the bomb. Tooth samples from five survivors in a control group with negligible neutron exposure were used to investigate the natural (41)Ca content in tooth enamel, and 16 tooth samples from 13 survivors were used to estimate bomb-related neutron exposure. The results showed that the mean (41)Ca/Ca isotope ratio was (0.17 +/- 0.05) x 10(-14) in the control samples and increased to 2 x 10(-14) for survivors who were proximally exposed to the bomb. The (41)Ca/Ca ratios showed an inverse correlation with distance from the hypocenter at the time of the bombing, similar to values that have been derived from theoretical free-in-air thermal-neutron transport calculations. Given that gamma-ray doses were determined earlier for the same tooth samples by means of electron spin resonance (ESR, or electron paramagnetic resonance, EPR), these results can serve to validate neutron exposures that were calculated individually for the survivors but that had to incorporate a number of assumptions (e.g. shielding conditions for the survivors). | Solid-state properties such as strain or chemical composition often leave characteristic fingerprints in the angular dependence of electron scattering. Scanning transmission electron microscopy (STEM) is dedicated to probe scattered intensity with atomic resolution, but it drastically lacks angular resolution. Here we report both a setup to exploit the explicit angular dependence of scattered intensity and applications of angle-resolved STEM to semiconductor nanostructures. Our method is applied to measure nitrogen content and specimen thickness in a GaNxAs1-x layer independently at atomic resolution by evaluating two dedicated angular intervals. We demonstrate contrast formation due to strain and composition in a Si- based metal-oxide semiconductor field effect transistor (MOSFET) with GexSi1-x stressors as a function of the angles used for imaging. To shed light on the validity of current theoretical approaches this data is compared with theory, namely the Rutherford approach and contemporary multislice simulations. Inconsistency is found for the Rutherford model in the whole angular range of 16-255 mrad. Contrary, the multislice simulations are applicable for angles larger than 35 mrad whereas a significant mismatch is observed at lower angles. This limitation of established simulations is discussed particularly on the basis of inelastic scattering. | eng_Latn | 10,046 |
Electronic personal dosimeters (EPD) based on solid state detectors have been used for personnel monitoring for radiation protection purpose; their use has been extended to practices with pulsed radiation beams although their performance is not well known. Deficiencies in the EPD response in pulsed radiation fields have been reported; they were not detected before since type tests and calibrations of EPDs were established in terms of continuous X and gamma reference radiations. An ISO working group was formed to elaborate a standard for test conditions and performance requirements of EPDs in pulsed beams; the PTB/Germany implemented a special X-ray facility for generating the reference pulsed radiation beams. In this work, an 800 Plus VMI medical X-ray machine of the Dosimeter Calibration Laboratory of CDTN/CNEN was characterized to verify its feasibility to perform EPD tests. Characterization of the x-ray beam was done in terms of practical peak voltage, half-value layer, mean energy and air kerma rate. Reference dosimeters used for air kerma measurements were verified as far their metrological coherence and a procedure for testing EDPs was established. | Electronic personal dosimeters (EPDs) based on solid state detectors have widely been used but some deficiencies in their response in pulsed radiation beams have been reported. Nowadays, there is not an international standard for pulsed x-ray beams for calibration or type testing of dosimeters. Irradiation conditions for testing the response of EPDs in both the constant potential and pulsed x-ray beams were established in CDTN. Three different types of EPDs were tested in different conditions in similar ISO and IEC x-ray qualities. Results stressed the need of performing additional checks before using EPDs in constant potential or pulsed x-rays. | By using a superluminescent diode as the light source and a depolariser inside the fibre coil, a constant scale factor is achieved without using polarisation control elements. For long-term behaviour an RMS-bias drift of 10 degrees/h is obtained. | eng_Latn | 10,047 |
The RPA-Copernic plasma experiment for the Giotto mission consists of two sensors, the RPA1-EESA spectrometer and the RPA2-PICCA electrostatic mass analyser. RPA1-EESA measures the three-dimensional distributions of electrons between 10 eV and 30 keV. These electron measurements should contribute to the definition of the properties of the cometary plasma and its interaction with the solar wind. This sensor includes an electrostatic symmetric quadrispherical analyser of novel design and provides 4 pi electron measurements with high sensitivity and good energy, angular and time resolution. With a 360 degrees *4 degrees field of view and with 17 fast-counting MCP sectors, a three-dimensional distribution is obtained every 2 s (half a spin of the space probe). The experiment includes three microprocessors. They interface RPA1-EESA with RPA2-PICCA and with the spacecraft, and perform extensive onboard data processing. One of the processors is designed to sort the three-dimensional electron distribution into two-dimensional pitch angle distributions in real time. The symmetry axis of the electron momentum flux tensor is computed on board. This symmetry axis is generally aligned with the magnetic field direction. | A low-energy ion spectrometer (LEIS) for use aboard three-axis stabilized spacecraft has been developed to measure ion energy per charge distribution in three-dimensional space with good energy-, angular- and temporal-resolutions. For the standard top-hat electrostatic analyzer used widely in space plasma detection, three-axis stabilized spacecraft makes it difficult to obtain complete coverage of all possible ion arrival directions. We have designed angular scanning deflectors supplementing to a cylindrically symmetric top-hat electrostatic analyzer to provide a half-space field of view as 360°×90° (–45°–+45°), and fabricated the LEIS flight model for detecting magnetospheric ions in geosynchronous orbit. The performance of this payload has been evaluated in detail by a series of simulation and environmental tests, and the payload has also been calibrated through laboratory experiments using a low-energy ion source. The results show that capabilities of the LEIS payload are in accordance with the requirements of a magnetospheric mission. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,048 |
The vacuum system for a proposed 2.5 GeV, 10/spl mu/A re-circulating linac synchrotron light source is readily achievable with conventional vacuum hardware and established fabrication processes. Some of the difficult technical challenges associated with synchrotron light source storage rings are sidestepped by the relatively low beam current and short beam lifetime requirements of a re-circulating linac. This minimal lifetime requirement leads directly to relatively high limits on the background gas pressure through much of the facility. The 10/spl mu/A average beam current produces very little synchrotron radiation induced gas desorption and thus the need for an "ante-chamber" in the vacuum chamber is eliminated. In the arc bend magnets, and the insertion devices, the vacuum chamber dimensions can be selected to balance the coherent synchrotron radiation and resistive wall wakefield effects, while maintaining the modest limits on the gas pressure and minimal outgassing. | We present an overview of collective effects in a proposed ultrafast X-ray facility, based on a recirculating linac. The facility requires a small vertical emittance of 0.4 mm-mrad and is designed to operate with a "flat bunch" with a large emittance ratio. Emittance control from the electron source at the RF photocathode to the photon production chain of undulators, including understanding and mitigation of collective effects, is critical to successful machine operation. Key aspects of accelerator physics involved in beam break-up, coherent synchrotron radiation, resistive wall impedance and other effects have been addressed and reported here. | A promising way of addressing the issue of growing water scarcity is through wider use of drip irrigation, which delivers water and fertilizer to crops in a slow, targeted manner, and has been shown to increase yields and water use efficiency. Yet, drip irrigation system adoption is low, primarily due to the high capital cost of the pressurized piping network and the pump, and operating energy cost. Lowering the water pressure needed for drip emitters to deliver water can reduce both capital and operating costs of drip systems. Here we present the results from field trials of new pressure-compensating online drip emitters that operate with a minimum compensating inlet pressure of 15 kPa (0.15 bar), in comparison to typical commercial emitters with minimum pressures of 50–100 kPa (0.5–1.0 bar). The field trials were carried out on nine farms in Morocco and Jordan over the course of one irrigation season with freshwater and treated wastewater. Low-pressure emitters are shown to reduce hydraulic energy per unit volume of water delivered by 43% on average compared to commercial emitters, without significantly sacrificing water emission uniformity (low-pressure emitters show uniformities of 81–91%, compared to 87–96% for commercial emitters). This energy reduction could lead to savings of 22–31% in the capital cost of a pump and emitters and the energy cost for a typical drip irrigation system. Thus, the low-pressure online emitters can be used as substitutes to commercial emitters that require higher water pressures, leading to reduced environmental impact and lower system costs. | eng_Latn | 10,049 |
We describe a conceptual proposal to combine the Dielectric Wakefield Accelerator (DWA) with the Emittance Exchanger (EEX) to demonstrate a high-brightness DWA with a gradient of above 100 MV/m and less than 0.1% induced energy spread in the accelerated beam. We currently evaluate the DWA concept as a performance upgrade for the future LANL signature facility MaRIE with the goal of significantly reducing the electron beam energy spread. The preconceptual design for MaRIE is underway at LANL, with the design of the electron linear accelerator being one of the main research goals. Although generally the baseline design needs to be conservative and rely on existing technology, any future upgrade would immediately call for looking into the advanced accelerator concepts capable of boosting the electron beam energy up by a few GeV in a very short distance without degrading the beam's quality. Scoping studies have identified large induced energy spreads as the major cause of beam quality degradation in high-grad... | A multi-meter long collinear dielectric wakefield accelerator is considered, and it is shown that a single bunch breakup instability is a major limiting factor for obtaining highly efficient energy transfer from the drive bunch to the main bunch. Different methods for instability suppression are studied. Numerical simulations using a 6D particle tracking computer code are performed and tolerances to various errors are defined. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,050 |
A new class of two-phase electron emission detectors has been introduced in experimental practice recently. The detectors employ effect of effective extraction of excess electrons from some condensed nonpolar dielectrics into equilibrium gas phase under influence of external electric field. This approach allows combination of massive working media for detection of rare events with gas-discharge or electroluminescence of rarefied media used for amplification of signals originated from a few or even singular electrons. Properties of working media suitable for emission detectors are discussed. Applications of two-phase dielectrics for detection of radiation and exotic particles are reviewed. | Coherent scattering is a flavor-blind, high-rate, as yet undetected neutrino interaction predicted by the Standard Model. We propose to use a compact (kg-scale), two-phase (liquid-gas) argon ionization detector to measure coherent neutrino scattering off nuclei. In our approach, neutrino-induced nuclear recoils in the liquid produce a weak ionization signal, which is transported into a gas under the influence of an electric field, amplified via electroluminescence, and detected by phototubes or avalanche diodes. This paper describes the features of the detector, and estimates signal and background rates for a reactor neutrino source. Relatively compact detectors of this type, capable of detecting coherent scattering, offer a new approach to flavor-blind detection of man-made and astronomical neutrinos, and may allow development of compact neutrino detectors capable of non-intrusive real-time monitoring of fissile material in reactors. | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,051 |
Center-of-mass best values for the normalized Legendre coefficients and the 0° differential cross sections as functions of input energy have been derived from various experimental results for the reactions 7 Li( p , n ) 7 Be and 7 Li (p,n) 7 Be ∗ (431 keV). This information has been used to calculate laboratory differential cross sections as functions of the laboratory proton energy and neutron emission angle which are given in tabular form together with the corresponding neutron energies. | Applications such as the Active Interrogation of shielded nuclear material that require the detection of specific gamma and neutron signatures in a high mixed radiation field background, require detector materials and device fabrications that are not highly susceptible to neutron or photon activation. This paper presents an activation analysis from Active Interrogation experiments where a pulsed-power accelerator was used to deliver 2.5 MeV protons onto a lithium target to produce a spectrum of neutrons up to 1 MeV. The experimental objectives were to characterize the neutron energy spectrum and spatial distribution produced from the ion beam diode utilized with the pulsed accelerator with a view to its utility for the purposes of active detection. A variety of neutron and gamma detectors were used to record the resulting signatures including sodium iodide (NaI), which is the main focus of this paper, and which is also a candidate detector technology to detect fission signatures from active detection systems. A High Purity Germanium (HPGe) detector was used to measure the amount of activation created in the NaI detector. The results showed significant activation of the core detection material, with activation product decay time constants of the order of seconds and minutes. Activation of the detector construction materials was also observed. From this type of analysis, the minimum time between active interrogations can be determined based on the recovery time of the detectors following activation, or alternatively, materials can be sought that are less susceptible to activation. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,052 |
An energetic auroral proton entering the atmosphere will, by charge exchange in collisions with atmospheric constituents, alternate between being a proton H + and a neutral hydrogen atom H. This study provides a procedure to evaluate the auroral Doppler shifted and broadened hydrogen Balmer profile as a function of initial energy, flux, pitch angle and view angle relative to the geomagnetic field. The differential proton energy flux entering the atmosphere is deduced using ground-based measurements of H α and H β from Nordlysstasjonen in Adventdalen, Longyearbyen. The main assumptions are that the geomagnetic field lines are: parallel and vertical, and that the pitch angle of the H/H + -particle is preserved in collisions with atmospheric constituents before being thermalized. This numerical method estimates the fate of the auroral H/H + -particle in the atmosphere, and from measured Doppler profiles the corresponding incoming particle flux can be deduced. Optimization of the method will continue through extensive use of observational data. | We present for the first time a numerical ki- netic/fluid code for the ionosphere coupling proton and elec- tron effects. It solves the fluid transport equations up to the eighth moment, and the kinetic equations for suprathermal particles. Its new feature is that for the latter, both elec- trons and protons are taken into account, while the preceding codes (TRANSCAR) only considered electrons. Thus it is now possible to compute in a single run the electron and ion densities due to proton precipitation. This code is success- fully applied to a multi-instrumental data set recorded on 22 January 2004. We make use of measurements from the fol- lowing set of instruments: the Defence Meteorological Satel- lite Program (DMSP) F-13 measures the precipitating parti- cle fluxes, the EISCAT Svalbard Radar (ESR) measures the ionospheric parameters, the thermospheric oxygen lines are measured by an all-sky camera and the H line is given by an Ebert-Fastie spectrometer located at Ny- ˚ Alesund. We show that the code computes the H spectral line profile with an excellent agreement with observations, providing some com- plementary information on the physical state of the atmo- sphere. We also show the relative effects of protons and elec- trons as to the electron densities. Computed electron den- sities are finally compared to the direct ESR measurements. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,053 |
Highly homogeneous discharges have been obtained in pure Ar gas at high pressures of 10 - 20 atm by using a discharge device in which the surface discharge plasma from a dielectric surface is used as a preionizer and an electrode, the plasma electrode, aiming at an Ar 2 * excimer laser. The plasma electrode consists of a ceramic pipe with a length of 290 mm. The same electrode is used as a cathode and an anode. The electrode separation is 2 mm to generate the main discharge. The fluorescence of Ar 2 * excimer radiation has been investigated at a wavelength of around 126 nm. Time-resolved electron density and gain measurements have been carried out with nanosecond time-resolution. The electron density was over 16th power of ten at 10 atm. The optical gain at 126 nm has been observed at an Ar gas pressure of 15 atm, and the peak gain was 8.6%/cm. | The excimer laser potential of Ar supersonic jets excited by an intense pulsed discharge is studied. Excimer emission is recorded during and after the 100 ns discharge. The time-resolved emission is recorded as a function of plenum gas pressure and distance from the nozzle. A simple mechanism is proposed to account for the luminescence data. Model calculations are compared to the experimental data. > | Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights. | eng_Latn | 10,054 |
Magnetoresistance in a high-mobility two-dimensional electron gas contained in a GaAs quantum well on a cylindrical surface exposed to microwave radiation has been measured. The responses to microwave radiation in the magnetotransport of two-dimensional electron gas are shown to be different on planar and cylindrical surfaces. Qualitative explanations to the latter difference are given. | Sign-alternating magnetic field is of great interest both in terms of magnetotransport of two-dimensional electron gas (2DEG) and microwave response of two-dimensional electron gas. Reasons of such interest are emergence of new trajectories of electron motion and changing the energy spectrum of 2DEG. Magnetic field dependences of resistance of 2DEG in cylindrical shells was investigated with Hall bar being located near region of zero effective magnetic field. | A three-oxide sodium borosilicate glass was irradiated with 2.3 MeV electrons up to 0.15 GGy and 4.6 GGy, and subsequently with 96 MeV Xe ions. The irradiated samples were characterised using Raman spectroscopy, ToF-SIMS, microhardness and surface profilometry. Electron irradiation of the pristine glasses resulted in different structural modifications at the sample surface and in the bulk of the glass, whereas, ion irradiation of either the pristine or bulk of the electron pre-irradiated glasses induced same structural, physical and mechanical property changes. Furthermore, sample surfaces showed a different behaviour than that of the bulk upon subsequent ion irradiation. These results show that the radiation sensitivity of surfaces can significantly vary depending on the type of the irradiation. Therefore, detailed studies aimed at understanding the response of the surfaces to mono and electron-ion double-beam irradiations should be undertaken to address the long-term evolution of the nuclear waste glass matrix surfaces. | eng_Latn | 10,055 |
Some medical compact cyclotrons have self-shielding to reduce neutron fluxes. Thermal neutron fluxes in an 18-MeV unshielded cyclotron room and in a 16.5-MeV self-shielded cyclotron room were evaluated. In addition, the radioactivities in concrete and metals due to thermal neutrons in the cyclotron rooms for 30 years were calculated of operation such that the sum of the ratio of the nuclide concentration to the nuclide clearance level was equal to 1. The thermal neutron flux from the unshielded cyclotron was approximately 10(2) cm(-2) s(-1), whereas that from the self-shielded cyclotron was approximately 10(2) cm(-2) s(-1). The thermal neutron fluxes for concrete, stainless steel, vessel steel, and aluminum that reached their clearance levels were 9.80 × 10(4), 2.17 × 10(3), 1.87 × 10(4), and 2.41 × 10(5) cm(-2) s(-1), respectively. The specific activities in the cyclotron room were found to be sufficiently below the clearance level when the self-shield was employed. | A self-shielded medical cyclotron (11 MeV) was commissioned at our center, to produce positron emitters, namely, 18 F, 15 O, 13 N and 11 C for positron emission tomography (PET) imaging. Presently the cyclotron has been exclusively used for the production of 18 F - for 18 F-FDG imaging. The operational parameters which influence the yield of 18 F - production were monitored. The radiation levels in the cyclotron and radiochemistry laboratory were also monitored to assess the radiation safety status in the facility. The target material, 18 O water, is bombarded with proton beam from the cyclotron to produce 18 F - ion that is used for the synthesis of 18 F-FDG. The operational parameters which influence the yield of 18 F - were observed during 292 production runs out of a total of more than 400 runs. The radiation dose levels were also measured in the facility at various locations during cyclotron production runs and in the radiochemistry laboratory during 18 F-FDG syntheses. It was observed that rinsing the target after delivery increased the number of production runs in a given target, as well as resulted in a better correlation between the duration of bombardment and the end of bombardment 18 F - activity with absolutely clean target after being rebuilt. The radiation levels in the cyclotron and radiochemistry laboratory were observed to be well within prescribed limits with safe work practice. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,056 |
Samples of dielectric materials have been irradiated with low- (1 to 25 keV) and mid-energy (25 to 100 keV) electrons. Charging and discharging characteristics for samples of OSR, mylar, Kapton, perforated Kapton and Alphaquartz are discussed. Results of tests conducted with monoenergetic midenergy electrons indicate that the worst-case peak discharge current, Is, is relatively constant with exposure energy; that dls/dt is relatively constant with exposure energy; and that the predischarge surface potential, Vi, is only a weak function of energy. Results of irradiating samples of OSR, mylar, and Kapton with low-energy and mid-energy electrons indicate that the surface potential may be tailored to low values (Vs <2 kV) and yet still achieve discharges (on OSR and mylar samples), and that for an OSR sample, the frequency content of these discharges is much higher than for discharges observed during exposure to monoenergetic low-energy electrons alone. | Charge buildup, storage, and decay in 25‐μm polyfluoroethylenepropylene (Teflon type A) foils due to irradiation with partially penetrating monoenergetic electron beams in the 10–50‐keV range are investigated. Currents from the irradiated front surface and the nonirradiated rear surface are measured separately by means of 1000‐A evaporated aluminum electrodes. Charge storage due to irradiation and a charge recall effect caused by irradiation of previously charged samples are observed. Discharge currents measured after termination of the irradiation indicate the importance of the delayed component of radiation‐induced conductivity. Measurements of the spatial depth of the charge are also reported. A mathematical model is developed which takes into account the radiation‐induced conductivity and the electrical and geometrical parameters of the sample. It allows for the calculation of current transients during and after irradiation. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,057 |
The first measurements of absolute Total Electron Content (TEC) and L-band amplitude and phase scintillation was made from Thule, Greenland, a polar cap station, in early 1984. These measurements were made using signals transmitted from the Global Positioning System (GPS) satellites. The variability of the TEC, especially during the afternoon to pre-midnight hours, is large, with increases in TEC above the background values of greater than 100% not uncommon. During one disturbed time, quasi-periodic TEC enhancements having periods as short as ten minutes and amplitudes equal to the background TEC were observed for over two hours. The TEC during some of the disturbed periods in the dark Thule ionosphere exceeded mid-latitude daytime values. Amplitude scintillations were small, not exceeding 3 dB peak to peak during the entire observing period, but they were associated with the times of TEC enhancements, with some evidence for stronger scintillation occurring during the negative gradients of the TEC enhancements. Phase scintillations were highest during some of the times of enhanced TEC, and depend critically upon the phase detrend internal used. | Sun-aligned (SA) arcs are a prevalent feature of the polar cap ionosphere during northward interplanetary magnetic field conditions. These arcs are, like the auroral arc, a complex electrodynamic system coupling the ionosphere and magnetosphere. The electron precipitation and convection electric field associated with this system modify the polar cap ionospheric plasma distribution. In the past decade, a wealth of observational information has indicated the complexity of these ionospheric modifications, but only a limited number of model studies have been carried out to elucidate the changes associated with SA arcs. In this investigation, an extensive parametric study has been conducted to identify and order these ionospheric modifications. Specifically, we are interested in modeling the local evolution and decay of ionospheric modification due to a source consisting of an idealized, though representative, SA arc structure. The Utah State University time-dependent ionospheric model (TDIM) has been used to define the ionospheric physics and its dependencies on both solar cycle and season. An SA arc model has been developed. This model enables one to systematically vary the key arc parameters; electric field strength, width, electron precipitation energy flux, and electron precipitation characteristic energy. Our findings indicate that the changes associated with the E and F regions are quite different. F region structures have relatively long lifetimes and are significantly affected by transport. This leads to a significant role for cross-arc convection. The E region is much less affected by transport due to short chemical recombination times and thus, E region modifications are confined to the arc structure itself where precipitation and enhanced electric fields are present. Furthermore, the response of the F region to changes in the arc parameters is not linear, and the largest ionospheric modifications occur for intermediate arc widths and electric field strengths. An important indicator of F region modification is the total electron content (TEC) for flux tubes convecting through SA arc structures. The magnitude and variation of the TEC enhancement with various arc parameters can be an important indicator of real processes which are occurring in the arc structure. In addition to TEC we examine the variation of Te, Ti, Ne, ΣP, and ΣH for various arc parameters. | 1. After traumatic spinal cord injury (SCI), histological and neurological consequences are developing for several days and even weeks. However, little is known about the dynamics of changes in spinal axonal conductivity. The aim of this study was to record and compare repeated spinal cord evoked potentials (SCEP) after SCI in the rat during a 4 weeks’ interval. These recordings were used: (i) for studying the dynamics of functional changes in spinal axons after SCI, and (ii) to define the value of SCEP as an independent outcome parameter in SCI studies. | eng_Latn | 10,058 |
Imaging processes built on the Compton scattering effect have been under continuing investigation since it was first suggested in the 50s. However, despite many innovative contributions, there are still formidable theoretical and technical challenges to overcome. In this paper, we review the state-of-the-art principles of the so-called scattered radiation emission imaging. Basically, it consists of using the cleverly collected scattered radiation from a radiating object to reconstruct its inner structure. Image formation is based on the mathematical concept of compounded conical projection. It entails a Radon transform defined on circular cone surfaces in order to express the scattered radiation flux density on a detecting pixel. We discuss in particular invertible cases of such conical Radon transforms which form a mathematical basis for image reconstruction methods. Numerical simulations performed in two and three space dimensions speak in favor of the viability of this imaging principle and its potential applications in various fields. | Compton scattering is widely used to analyse electron momentum distributions in solid state systems. Perhaps less well-known is its role as the major cause of image contrast in medical and industrial radiography. This article discusses the principles and applications of a technique, known as Compton scatter imaging (CSI), which is based on direct registration of the Compton scatter radiation. Following a historical survey of the major developments in this field, the strengths and weaknesses of transmission radiography and Compton scatter imaging are compared in order to determine those measurement situations to which the latter is best suited. A description is given of several disturbing effects to which CSI is prone and ways in which these may be accounted for to yield quantitative density data are presented. The most important types of imaging system based on Compton scatter are discussed and compared. The ComScan (an acronym for Compton scatter scanner) is a commercially-available backscatter imaging system which is discussed here in some detail. ComScan images taken from applications of topical and historical interest are presented. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,059 |
Simple, two-dimensional Vlasov–Poisson descriptions of thermal equilibrium have been applied to both an unbunched ion beam propagating in a continuous linear focusing channel and an unneutralized, single-species plasma confined in a Penning–Malmberg trap geometry. In scaled variables, these two thermal equilibrium systems result in an identical nonlinear equation that must be solved to describe the radial density and/or potential of the equilibrium. Numerous publications have been based on numerical solutions of the highly nonlinear equilibrium equation. Following a brief review of the thermal equilibrium model, we construct approximate, closed-form analytical solutions to the equilibrium equation that are accurate over a wide range of system parameters. | Self-consistent Vlasov-Poisson simulations of beams with high space-charge intensity often require specification of initial phase-space distributions that reflect properties of a beam that is well adapted to the transport channel--both in terms of low-order rms (envelope) properties as well as the higher-order phase-space structure. Here, we first review broad classes of kinetic distributions commonly in use as initial Vlasov distributions in simulations of unbunched or weakly bunched beams with intense space-charge fields including: the Kapchinskij-Vladimirskij (KV) equilibrium, continuous-focusing equilibria with specific detailed examples, and various non-equilibrium distributions, such as the semi-Gaussian distribution and distributions formed from specified functions of linear-field Courant-Snyder invariants. Important practical details necessary to specify these distributions in terms of usual accelerator inputs are presented in a unified format. Building on this presentation, a new class of approximate initial kinetic distributions are constructed using transformations that preserve linear-focusing single-particle Courant-Snyder invariants to map initial continuous-focusing equilibrium distributions to a form more appropriate for non-continuous focusing channels. Self-consistent particle-in-cell simulations are employed to show that the approximate initial distributions generated in this manner are better adapted to the focusing channels for beams with high space-charge intensity. This improved capability enables simulation applications that more precisely probe intrinsic stabilitymore » properties and machine performance.« less | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,060 |
For the CERN Lead Ion Accelerating Facility (achieved within a collaboration of several outside laboratories and with financial help of some member states) a new dedicated Linac has been built. This Linac has been installed in 1994 and served during two extended physics runs. This paper reviews the main characteristics of this machine and describes the first operational experience. Emphasis is put on new features of this accelerator, its associated equipment and on the peculiarities of heavy ions. | High accelerating gradients are very interesting for future machines, and, in particular, for high-current heavy-ion linac projects like the “Inertial Fusion Driver”. In order to explore the maximum field achievable in an Interdigital-H type structure (IH), an experiment has been carried out at CERN with the Lead Ion Linac (Linac3). After the 1997 run, the RF amplifiers were rearranged in order to allow the feeding of the IH Tank number 2 (1.54 m long, 28 gaps, frequency of 202.56 MHz) with up to 2 MW pulsed RF power. After two weeks of conditioning at pulse lengths varying between 200 μs and 1 ms with a constant pulse repetition rate of 0.8 Hz, the maximum effective accelerating gradient achieved was 10.7 MV/m. This corresponds to a local field maximum of 75 MV/m, and to fields in excess of 50 MV/m (3.5 times the Kilpatrick limit) on large portions of the drift tube surfaces. This paper reports the conditioning procedure used, the measurements of field emission current at different voltages and pulse lengths, the determination of the surface field enhancement factor as well as the calculation of the electric field distribution for the gap with the highest surface fields. | June of 1993 marked the installation of Titan Beta’s first commercially designed LINAC for the exclusive use of the sterilization of new medical products at its contract sterilization facility located in Denver, Colorado. This system, a 10 MeV, 10 kW RF Linac has been operating successfully, since that time, at its planned duty cycle of up to 7,000 hours per year. More recently, Titan commissioned its second sterilization facility, located in San Diego, California, in the past summer of 1995. This facility incorporates a Titan Beta Model TB-10/15 RF Linac, a design based on the Denver machine with upgrades that have addressed marketing requirements and Denver’s operational data. In addition to the San Diego machine, Titan Beta has recently completed the installation and validation of an identical TB-10/15 Linac at the BSE Mediscan facility located in Austria. Both the San Diego and Austrian machines were assembled, tested and installed within 11–12 months after receipt of order, and were fully operational... | eng_Latn | 10,061 |
The High Current Experiment (HCX) is being built to explore heavy-ion beam transport at a scale appropriate to the low-energy end of a driver for fusion energy production. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge dominated heavy-ion beams at high space-charge intensity (line-charge density /spl sim/0.2 /spl mu/C/m) over long pulse durations (3-10 /spl mu/sec). A single beam transport channel will be used to evaluate scientific and technological issues resulting from the transport of an intense beam subject to applied field nonlinearities, envelope mismatch, misalignment-induced centroid excursions, imperfect vacuum, halo, background gas and electron effects resulting from lost beam ions. Emphasis will be on the influence of these effects on beam control and limiting degradations in beam quality (emittance growth). Electrostatic (Phase I) and magnetic (Phase II) quadrupole focusing lattices have been designed and future phases of the experiment may involve acceleration and/or pulse compression. The Phase I lattice is presently under construction and simulations to better predict machine performance are being carried out. Here we overview: the scientific objectives of the overall project, processes that will be explored, and transport lattices developed. | The Heavy Ion Fusion Virtual National Laboratory is building a High Current Experiment (HCX) to explore the transport of a heavy-ion beam at a scale appropriate to the low-energy end of a driver for heavy ion fusion. The HCX is presently being designed and assembled in multiple stages at the Lawrence Berkeley National Laboratory (LBNL). The scientific motivation for the HCX is presented in a related paper. We overview the engineering design of an early phase of the HCX involving the transport of a 1.7 MeV, 0.7 Amp K/sup +/ beam through a lattice of alternating gradient electrostatic quadrupoles (ESQs). Four tanks of 10 quadrupoles each are ultimately planned, corresponding to 20 periods of ESQ transport. Mechanical, high-voltage, and vacuum engineering aspects of the ESQ transport lattice are presented. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,062 |
Laboratory measurements of the interaction of low-energy, bare, and hydrogen-like ions with neutral gases are presented. The measurements demonstrate that charge-exchange-induced cometary K-shell X-ray spectra represent rich spectral diagnostics for determining the speed of the solar wind and the collision dynamics within the coma. We show that the K-shell spectrum observed from low-energy ion-neutral collisions (≤ 50 km s-1) has a distinct high-energy component that is suppressed in high-energy collisions (≥800 km s-1). As a result, the hardness ratio of the K-shell spectrum increases by as much as a factor of 4 as the ions decelerate in the coma. The change in spectral shape can be observed even with low-resolution energy dispersive solid-state detectors, opening the possibility of spatial imaging of the solar wind heavy-ion velocity profile in the coma. Our results clearly show that energy-dependent data are needed to fully describe charge-exchange-induced X-ray production in the heliosphere. | In the interaction of fast ions with dense matter, the collision frequency is high enough to facilitate the simultaneous excitation of several electrons. Such multiply-excited few-electron systems have been exploited variously for plasma diagnostics. Beam-foil spectroscopic techniques, benefiting from the inherent time-resolution offered by the geometry of typical experiments, have proven particularly fruitful for the study of emission patterns and level lifetimes of specific multiply-excited levels, especially those of maximum spin and total angular momentum. Typical cases are recalled to illustrate some general principles. Among many others, earlier beam-foil measurements have targeted the core-excited 2p53s3p 4D7/2 – 2p5 3s3d 4F9/2 transition in several Na-like spectra ranging from S VI to Cu XIX. Data on the six intermediate elements missing at that time are now added. The interest in such atomic systems with multiple excitations and high total angular momentum values is discussed with a variety of examples. | We prove that groups acting geometrically on delta-quasiconvex spaces contain no essential Baumslag-Solitar quotients as subgroups. This implies that they are translation discrete, meaning that the translation numbers of their nontorsion elements are bounded away from zero. | eng_Latn | 10,063 |
The Thomas Jefferson National Accelerator Facility (formerly known as CEBAF) has embarked on the construction of a 1 kW free-electron laser operating initially at 5 microns that is designed for laser-material interaction experiments and to explore the feasibility of scaling the system in power for Navy defense and industrial applications. The accelerator system for this IR Demo includes a 10 MeV photocathode-based injector, a 32 MeV CEBAF-style superconducting radio-frequency linac, and single-pass transport that accelerates the beam from injector to wiggler, followed by energy-recovery deceleration to a dump. The initial optical configuration is a conventional near-concentric resonator with transmissive outcoupling. Following commissioning, the laser output will be extended to an operating range of 3-to-6.6 microns, and distributed to six labs in a user facility built with funds from the Commonwealth of Virginia. A description of the machine and facility and the project status are presented. | We have built a high-DC-voltage photoemission gun and a diagnostic beamline permitting us to measure rms transverse emittance (/spl epsi//spl tilde//sub x/) and rms momentum spread (/spl delta/) of short-duration electron pulses produced by illuminating the cathode with light from a mode-locked, frequency-doubled Nd:YLF laser. The electron gun is a GaAs photocathode source designed to operate at 500 kV. We have measured /spl epsi//spl tilde//sub x/ and /spl delta/ for conditions ranging from emittance-dominated to space-charge-dominated. We report these measurements as functions of microbunch charge for different beam radii, pulse lengths, and voltages/field gradients at the cathode, and compare them with PARMELA calculations. | Single-mode operation at 4.4 THz is obtained from distributed-feedback quantum-cascade lasers with complex-coupling metallic gratings. The emission shows a stable side-mode suppression of more than 20 dB at all injection currents and operating temperatures | eng_Latn | 10,064 |
AC Magnetic Guide for Cold Atoms in an Ioffe Tube | We propose a novel ac magnetic waveguide for cold neutral atoms in an Ioffe tube. The time-averaged magnetic potential and force for the guided atoms in the magnetic guiding tube are calculated, and the results show that it is high enough to collect and guide nearly all of cold atoms from a standard magneto-optical trap with a temperature of ~120μK. We also estimate the atomic losses from background thermal-atom collision, quantum tunneling effect and spin-flip transition in the guiding. Our study shows that a cold and dense atomic beam with a guiding efficiency of ~92% and a beam intensity of about 1011 atoms/cm 2• s can be output from the magnetic guide tube, and the guiding scheme proposed here could be used to manipulate spin polarized cold atoms. | It is shown that the temperature gradients caused by the heating of an angularly accelerated gas due to compression and the converse cooling of the decelerated gas have appreciable effects on isotope separation factors as determined by centrifugation. These effects were found to be greater than would be indicated by the isothermal theory. The influence of these non-uniform temperatures on the performance of flow-through centrifuges is discussed. (C.J.G.) | kor_Hang | 10,065 |
Measurement of the dead time of XRF detection systems using a pulsed beam | A method of measuring the dead time of nuclear detectors using a pulsed beam is described. The application of the method to detectors used in an electron microprobe device is reported and results obtained in this way are presented. The method seems to be suitable for measuring the dead time of any nuclear x-ray counting system which can be operated with a pulsed beam. | A new approach was proposed for the DOA joint estimation of signal,and the algorithms are based on ESPRIT and two or more array data correlation matrix.It estimated simultaneously the DOA of bis/multistatic.The algorithms estimated parameter are auto paired.The CRLB of the DOA stimation was also derived.The simulating results show that the new methods are equally effective. | eng_Latn | 10,066 |
Measurement of Phosphorus in Metals by RNAA | An RNAA procedure has been developed for measurement of low-level phosphorus in metals. Samples are irradiated at a neutron flux of 2.7·1013 n·cm−2·s−1 then mixed with carrier and dissolved in acid. After chemical separation and purification of the phosphorus and gravimetric determination of carrier yield, 32P is determined using a beta proportional counter. The detection limit for a 0.1 g sample irradiated for 30 minutes is 5 μg/kg. The method has been used to determine 6.4±0.6 mg/kg phosphorus in SRM 2175 refractory alloy. | NSRRC has been operating a 1.5 GeV synchrotron light source, the Taiwan Light Source (TLS), for over 15 years and has established a large user community. For the future development of synchrotron radiation research in Taiwan, a feasibility study report to construct a 3.0 GeV low‐emittance storage ring, the Taiwan Photon Source (TPS), was issued in July 2005. The government approval of the TPS project was obtained in December 2007 and the machine will be built at current site of NSRRC. The project has progressed steadily since and reached several major milestones now: the architect firm has finished the site plan and civil design, the accelerator design has been fixed, and purchase of long‐lead items begins its course. The TPS storage ring has a circumference of 518.4 meters with a concentric booster of 496.8 meters. The storage ring adopted a 24‐cell double‐bend structure with a 1.6 nm‐rad natural emittance. There are six 12‐m and eighteen 7‐m ID straights. For user research, five new beamlines have been ... | eng_Latn | 10,067 |
Cross sections for K-shell ionisation in relativistic heavy-ion collisions | For relativistic heavy-ion collisions K-shell ionisation cross sections are calculated in the semiclassical approximation by using a relativistic description of the electronic states. The calculations are compared with measurements with 4.88 GeV protons and 670 MeV amu-1 Ne ions as projectiles. | Abstract The structures observed in recent missing mass experiments 3 He(p, d)X and p( 3 He, d)X are discussed and shown to agree to a high accuracy with a rotational like scheme M = M 0 + M 1 J ( J +1). An explanation is suggested as to why these structures have not been observed in some other experiments. | eng_Latn | 10,068 |
Two components of extracellularly-recorded photoreceptor potentials in the cephalopod retina: Differential effects of Na+, K+ and Ca2+ | The ERG of the isolated, superfused half-eye of the cephalopod Sepiola atlantica, evoked by a brief (10 Μs) light flash, has been studied by recording intraretinal potentials with glass microelectrodes. The intensity-response characteristics of the potentials recorded at an electrode fixed at the surface (V s ) can be fitted by a simple equation derived from an equivalent circuit model based on a sodium conductance increase mechanism. Raising the external potassium level reduces the maximal response (δV m ), but does not alter the half-saturation intensity value (I0). Reducing external sodium does not affect (δV m ), but increases I0. Reducing external calcium also does not affect (δV m ), but decreases I0. These effects are adequately described by the model if it is also assumed (a) that changing the external sodium does not significantly alter the transmembrane sodium gradient, and (b) that sodium and calcium ions compete for the sensitivity control mechanism. | Abstract A simple method of compensating for the kinematic energy spread of the particles from a nuclear reaction detected in a silicon PSD is described. The technique relies on a suitable choice of the series resistor for the reaction of interest and the degree of compensation is shown to be equivalent to the first order correction for the acceptance of a magnetic spectrometer. Experimental results using recoil protons, elastically scattered alpha-particles and carbon ions from a heavy ion induced reaction illustrate the practical application and success of the technique. The limit of the compensation for light ions is set by the resistive noise in the ‘energy x position’ signal while for heavy ions the nuclear scattering spread sets the lower limit. | eng_Latn | 10,069 |
Grain Dust Explosion and Dust Explosion Suppression | Summarize the grain dust explosion theory, explosion properties and some factors which can influence the explosion in this paper, and put forward countermeasure to prevent grain dust explosion through theory and technic aspect. Offer reference data for prevent and reduce the grain dust explosion. | A Geant4 simulation of a Micromegas detector in hadron beams is presented. Very large energy deposits are observed, resulting from the production of highly ionizing particles in nuclear interactions of incoming hadrons with different parts of the detector. Assuming a spark is induced by a local, large energy deposit, we find that the spark rate grows as a power law with the gain of the detector, as observed experimentally. Using measurements with alpha particles, or alternatively the well known Raether limit, our simulation gives a correct estimate of the spark rate observed in hadron beams. A few experimental tests are proposed to check the validity of this simulation. | eng_Latn | 10,070 |
Longitudinal Beam-Shaping Simulation for Enhanced Transformer Ratio in Beam-Driven Accelerators | A beam-driven structure wakefield accelerator (SWFA) is currently under consideration for future multi-user xray free-electron-laser (FEL) light sources. One of the challenges associated with SWFA is the efficient energy transfer from the drive to the main bunch that can be enhanced via a precise control over the drive-bunch current profile. This paper discusses the development and initial beam-dynamics simulation of the drive-bunch longitudinal dynamics using the fast-tracking program TWICE. This code, written in PYTHON, allows for rapid prototyping of the beam shaping process while taking into account the collective effects using simplified models. This paper describes the algorithm implementation and its capabilities of including collective effects into both forward and backward tracking. Initial results of optimizing beam shape with a conventional linac to produce a drive beam with a shape optimized for SFWA are presented. | We calculate the localization lengths for lattice fermions with random gap in two dimensions. This is done by means of the transfer matrix approach. Numerical results are analyzed for finite-size scaling and they exhibit a metal-insulator and a insulator-insulator transition. At these transitions we calculate the critical exponent of the localization length. | eng_Latn | 10,071 |
Spin dependence of pp-->np pi + from 492 to 796 MeV. | Spin correlation parameters {ital A}{sub {ital LL}}, {ital A}{sub {ital SL}},{ital A}{sub {ital NL}}, {ital A}{sub {ital NO}}, {ital A}{sub {ital SO}}, {ital A}{sub {ital LO}}, and{ital A}{sub {ital OL}} have been measured for {ital pp}{r arrow}{ital np}{pi}{sup +} at 492, 576, 643, 729, and 796 MeV over a large part of phase space, using a longitudinally polarized target and a polarized beam. Results rule out broad dibaryons in this mass range in {ital NN} {sup 3}P{sub 2} and {sup 3}F{sub 3}; in {sup 1}D{sub 2} some phase variation is observed, resembling that expected of a strong inelastic threshold. | Plasma-based pattern transfer of lithographically produced nanoscale patterns in advanced photoresist materials is often accompanied by photoresist surface roughening and line edge roughening due to factors which are not well understood. We have studied the evolution of surface roughening in prototypical 193 and 248nm photoresist materials during plasma processing as a function of plasma operating parameters. We used real-time ellipsometry and mass spectrometry, along with atomic force microscopy, x-ray photoemission spectroscopy and time-of-flight secondary ion mass spectrometry in an effort to understand the morphological and chemical changes of the photoresist materials as a function of plasma–surface interactions parameters, e.g., maximum ion energy, total energy flux, and plasma chemistry, and photoresist material. A comparison of 248nm photoresist with 193nm photoresist shows that significantly more surface roughness is introduced in the 193nm photoresist for most plasma processing conditions invest... | eng_Latn | 10,072 |
ICIMACS: the Ohio State Instrument Control and Image Acquisition System | The Ohio State Instrument Control and IMage ACquisition System, ICIMACS, is the computer hardware and software used by all instruments developed by the Imaging Science Laboratory (ISL) to control the detector, pre-process data, record image data on a separate computer system for data reduction and analysis, generate real time data display, control the mechanisms within an instrument, interface with the telescope controller, connect to a user interface, and perform engineering functions such as temperature or pressure logging. ICIMACS has now been used on 12 different instruments and is herein described as applied to 'MOSAIC' the near IR imager/spectrometer in use on the Kitt Peak 2.1 and 4 meter telescopes and on the MDM 2.4 and 1.3 meter telescopes. | This article introduces the construction and mechanics of IOMMU,one of the most important components within Sun SPARC, gives details of the method employed by POST in SPARC's BOOTPROM to test it and points the deficiency out of it.Finially we present a more integral way to test IOMMU and present the procedure. | eng_Latn | 10,073 |
ON THE SPONTANEOUS PION EMISSION BY HEAVY NUCLEI | In this paper a method of detecting the pionic nuckar radio-activity discussed by lon et al. is proposed using in clusive high energy gamma ray measurement. Taking the maximum pion energy given by lon et al, the energy ranges of the gamma rays from the emitted π~θ mesons are calculated. | The Monte Carlo simulation with CORSIKA is ran to simulate EAS events at the high altitude,make certain the selecting criterion to get EAS events with low first interaction height.The hadronic interaction in the forward region from TeV region can be studied by detecting the EAS core of low first interaction height events.It is confirmed that a perfect information of forward region can be gotten by researching the development of cosmic ray with high energy,the hadronic interaction models in the forward region from TeV region can be discussed effectively. | yue_Hant | 10,074 |
Nuclear structure studies close to N = Z = 50 | The level structures in 98,99Rh, and 99Pd nuclei have been investigated through in beam γ-ray spectroscopic techniques following the 75As(28Si, xpyn) fusion-evaporation reaction at Elab = 120 MeV. These investigations were carried out using Indian-National-Gamma-Array (INGA) consisting of Compton-suppressed clover detectors at the Inter-University Accelerator Centre, New Delhi. The level structures observed in 99Pd, and 98,99Rh have been established up to ∼ 11 MeV, 10 MeV and 16 MeV excitation energy and spin ∼ 23ħ, 23ħ, and 28ħ respectively. In the doubly-odd 98Rh nucleus, new band structures and isomeric states have been identified at lower spins and new states below the previously identified 2+ ground state (T1/2 = 8.5 m) are identified. In the present work 99Rh structure have been observed similar to 101Rh which is based on p1/2 and g9/2 orbitals. Various positive and negative parity states in these nuclei are observed to be energetically more favored with respect to the neighboring ones, and are like... | This article reviews Uncertainties in the Estimation of Radiation Risks and Probability of Disease Causation, NCRP Report No. 171. , Bethesda, MD, 2012. 418 pp. Price: $155.00. ISBN: 9780983545019 (hardcover). | eng_Latn | 10,075 |
Comparative study of macrophage migration in different strains of mice: absence of migration in C3H mice. | In the course of studying the susceptibility of mice to Salmonella infection, we discovered that C3H/HeJ mice differ from other strains in both their susceptibility to infection and their response to prior vaccination. Others have noted the absence of the usual B cell stimulation by LPS in these mice. To investigate the status of delayed hypersensitivity in C3H/HeJ mice, we tried to use the technique of macrophage migration. Under conditions of normal migration for other strains, C3H/HeJ peritoneal and splenic macrophages failed to migrate, thus establishing another differentiating immunological trait for this strain. | External injection of an electron bunch in the laser wakefield can result in femtosecond accelerated bunches with relatively low energy spread. In this paper it is shown that the density transition from vacuum to plasma can play an important role in the trapping process. The plasma wavelength in this transition region changes continuously, which means that the injected electrons see an altering wakefield. This can result in strong defocusing of the injected bunch. It is found that the effect becomes stronger for stronger wakefields, longer transition lengths, and lower injection energies. The transition region can be avoided if the bunch is injected into the wakefield at an angle. Injecting the bunch at an angle allows the bunch to be wider and results in more charge being trapped. The dynamics of the bunch in this case are similar to the dynamics of a bunch injected in front of the laser pulse | eng_Latn | 10,076 |
CO/sub 2/ magnetohydrodynamic laser | Two types of powerful, continuous action gas lasers are being most actively developed at the present time: the electrical discharged and the gas dynamic lasers. IVTAN research workers proposed a new method of generating laser beams - a magnetohydrodynamic method. As working fluid an MHDL may utilize a mixture of He + CO/sub 2/ with the addition of easily ionized atoms. The work conducted at IVTAN since 1970 is described. The preprint consists of two portions: the first is dedicated to the theoretical examination of MHDL: calculations of optimum lasing medium compositions, examination of various flow modes, calculations of amplification coefficient, and of MHD laser emission intensity. In the second part the results of the experimental studies of MHDL are discussed. The main result is that the lasing effect was obtained for the first time in an MHD laser. | This paper presents the methodology and the physical models implemented in our computational code to predict the flow field over a Mars Sample Return Orbiter entering a Mars-like atmosphere. Because no validation against flight data or experiments can be done at present, the results obtained here are compared to other computed results for verification purpose. The predicted flow fields show that the chemical species CO and CO2, that are highly radiative species, are present in a large amount and at high temperature in the shock layer and in the wake of the flow past the orbiter. | eng_Latn | 10,077 |
Terahertz Radiation-Enhanced-Emission-of-Fluorescence | Terahertz (THz) wave science and technology have been found countless applications in biomedical imaging, security screening, and non-destructive testing as they approach maturity. However, due to the challenge of high ambient moisture absorption, the development of remote open-air broadband THz spectroscopy technology is lagging behind the compelling need that exists in homeland security, astronomy and environmental monitoring. Furthermore, the underlying physical mechanisms behind the interaction between the THz wave and laserinduced plasma which responds strongly to electromagnetic waves have not been fully understood. | Abstract We report ESR experiments on a LaAl 2 sample doped with 6% Gd. The experiments were performed at 1, 3, 9 and 35 GHz. We find for T ≈ T c essentially a frequency independent shift of H res , but a frequency dependence for the minimum in the linewidth. The results will be discussed in terms of static internal fields and dynamic field fluctuations. | deu_Latn | 10,078 |
Effects of Propagation of Narrow Bipolar Pulses, Generated by Compact Cloud Discharges, over Finitely Conducting Ground | Propagation effects on the narrow bipolar pulses (NBPs) or the radiation fields generated by compact cloud discharges as they propagate over finitely conducting ground are presented. The results were obtained using a sample of NBPs recorded with high time resolution from close thunderstorms in Sri Lanka. The results show that the peak amplitude and the temporal features such as the full width at half maximum (FWHM), zero-crossing time, and the time derivative of NBPs can be significantly distorted by propagation effects. For this reason, the study of peak amplitudes and temporal features of NBPs and the remote sensing of current parameters of compact cloud discharges should be conducted using NBPs recorded under conditions where the propagation effects are minimal. | In this Brief Report we consider a nonlocal Ginzburg-Landau-Higgs model in the presence of a neutralizing uniform background charge. We show that such a system possesses vortices that feature a strong radial electric field. We estimate the basic properties of such an object and characteristic length scales in this model. | eng_Latn | 10,079 |
A Full-View Spherical Image Format | This paper proposes a full-view spherical image format which is based on the geodesic division of a sphere. In comparison with the conventional 3D array representation which consists of five parallelograms, the proposed spherical image format is a simple 2D array representation. The algorithms of finding the neighboring pixels given a pixel of a spherical image and mapping between spherical coordinate and spherical image pixel are given also. | This paper reviews the formalism of maximum entropy beam diagnostic tomography as applied to the Fusion Materials Irradiation Test (FMIT) prototype accelerator. The same formalism has also been used with streak camera data to produce an ultrahigh speed movie of the beam profile of the Experimental Test Accelerator (ETA) at Livermore. | eng_Latn | 10,080 |
Analytic model for surface ground motion with spall induced by underground nuclear tests | This report provides a detailed presentation and critique of a model used to characterize the surface ground motion following a contained, spalling underground nuclear explosion intended for calculation of the resulting atmospheric acoustic pulse. Some examples of its use are included. Some discussion of the general approach of ground motion model parameter extraction, not dependent on the specific model, is also presented. | We study the effects of gluon radiation on top production and decay processes at an $e^+e^-$ collider.The matrix elements are computed without any approximations, using spinor techniques. We use a Monte Carlo event generator which takes into account the infrared singularity due to soft gluons and differences in kinematics associated with radiation in the production versus decay process. The calculation is illustrated for several strategies of top mass reconstruction. | eng_Latn | 10,081 |
Atmospheric production of energetic protons, electrons and positrons observed in near Earth orbit | Substantial fluxes of protons and leptons with energies below the geomagnetic cutoff have been measured by the AMS experiment at altitudes of 350–390 km, in the latitude interval ±51.7� . The production mechanisms of the observed trapped fluxes are investigated in detail by means of the FLUKA Monte Carlo simulation code. All known processes involved in the interaction of the cosmic rays with the atmosphere (detailed descriptions of the magnetic field and the atmospheric density, as well as the electromagnetic and nuclear interaction processes) are included in the simulation. The results are presented and compared with experimental data, indicating good agreement with the observed fluxes. The impact of the secondary proton flux on particle production in atmosphere is briefly discussed. � 2003 Elsevier B.V. All rights reserved. | Abstract We present a convenient analytical parametrization, in both configuration and momentum spaces, of the deuteron wave-function calculated with the Paris potential. | eng_Latn | 10,082 |
A preliminary measurement of {alpha}{sub s} from W and Z + jets events at D0 | A comparison of the relative production rate of weak vector bosons (W and Z) with and without hard QCD radiation is used with NLO QCD calculations to extract the strong coupling constant {alpha}{sub s}. The data sample consists of W and Z boson events detected via the electron decay channel in the D0 detector. | We consider the cross area of the PP_ and PSV_wave window as the best window for joint PP_ and PSV_wave acquisition in VTI media. Within the effective window, the PP_ and PSV_wave's raypathes and phase angles at all reflection points are calculated, and the reflection (or transmission) coefficients' ratios of PSV- to PP_wave solved from Zoeppritz equations are defined as the controlling factor G. Then we use G values as the main controlling parameters of joint PP_ and PSV_wave acquisition design in VTI media, determine the best receiving window of detectors by analyzing G values, and derive the method of optimizing the receiving window for acquisition of multi_component converted seismic data in VTI media. | eng_Latn | 10,083 |
RADIAL WAVE FUNCTIONS FOR THE CESIUM ATOM | This paper presents the radial wave functions for 26 electronic orbitals of the cesium atom. For each orbital the electron is considered to move in a screened Coulomb potential which is taken to be approximately the Thomas-Fermi potential for a singly charged cesium ion. The states obtained here are improvements over those obtained by Russek, Sherman, and Flinchbaugh and extend the scope of that work as well. | THIS PAPER CRITICALLY REVIEWS THE VARIOUS RADIOISOTOPE METHODS USED TO MEASURE THE FLOW OF STREAMS AND RIVERS, PARTICULARLY UNDER AUSTRALIAN CONDITIONS. PROBLEMS SUCH AS SELECTION OF RADIOISOTOPE, MIXING LENGTH, ADSORPTION, EQUIPMENT, CALIBRATION, AND SAFETY ARE DISCUSSED. AN OUTLINE IS GIVEN OF A PROPOSED AUSTRALIAN RESEARCH PROGRAM TO INVESTIGATE THESE METHODS AND PHENOMENA IN DETAIL. /AUTHOR/ | yue_Hant | 10,084 |
The enigma of jets and outflows from young stars | Research in recent decades has seen many important advances in understanding the role of jets and outflows in the star formation process. Al though, many open issues still remain, multi-wavelength high resolution observati ons have provided unprecedented insights into these bizarre phenomena. An overview of some of the current research is given, in which great strides have been made in addressing fundamental questions such as: how are jets generated? what is the jet acceleration mechanism? how are jets collimated? what is the relationship between accretion and ejection? how does mass accretion proceed? do jets somehow extract angular momentum? and finally, is there a universal mechanism for jet generation on all scales from brown dwarfs to AGNs? | Preface Bose-Einstein Condensation in Nonlinear System New Aspects of Relaxation Processes in Cryogenic Solids Induction Transformer Coupled Discharges: Investigation & Application P-Type InGaAs/AlGaAs Quantum Well Structures for Infrared Photodetection A D-3He Spherical Tokamak Reactor with the Plasma Current Ramp-Up by Vertical Field 5-Dimension Space-Time Field Theory & Realization of Matter Chemical Physics of Phonons & Superconductivity: A Heuristic Approach Description of the Ultraslow Light Phenomenon in Atomic Bose Condensates in the Framework of the Microscopic Approach Energy Decay Mechanism of Quantum Grid Turbulence in He II Below 1 K Dark Matter Haloes as Fruits of Merger Trees in a CDM Garden Application of GEANT4 Code in Gamma Irradiation Processing Stochastic Dynamic Systems with Long-Range Correlations: Basic Notions & Applications Index. | eng_Latn | 10,085 |
Resonant production of vector mesons by polarized photons. Special considerations on the ρN decay mode of Δ(1950) and Δ(2420) | The differential cross-section and the vector-meson density-matrix elements for resonant production of vector mesons from nucleons γN→resonance J →VN are given in terms of partial-wave helicity and multipole amplitudes. A large-J approximation of thed J (ϑ) functions turns out to yield a good qualitative picture of the behaviour of the differential cross-section and density-matrix elements forJ ≳ 11/2. Numerical results for the differential cross-section for γN→Δ J →ρN and for the ρ density-matrix elements are presented for the special model of magnetic excitation and decay, which is motivated from quark-model and vector-meson-dominance model considerations. The observability of these resonance formation processes with unpolarized and polarized photons is extensively discussed by taking into account the diffractive background present in ρ0 production from protons. Much of the material of this work may also be used to discuss resonance effects in Compton scattering. | We consider the cross area of the PP_ and PSV_wave window as the best window for joint PP_ and PSV_wave acquisition in VTI media. Within the effective window, the PP_ and PSV_wave's raypathes and phase angles at all reflection points are calculated, and the reflection (or transmission) coefficients' ratios of PSV- to PP_wave solved from Zoeppritz equations are defined as the controlling factor G. Then we use G values as the main controlling parameters of joint PP_ and PSV_wave acquisition design in VTI media, determine the best receiving window of detectors by analyzing G values, and derive the method of optimizing the receiving window for acquisition of multi_component converted seismic data in VTI media. | eng_Latn | 10,086 |
Design and modeling of compact high power fiber lasers | Highly-doped phosphate glasses provide significantly higher gain than regular silica doped glasses. We will discuss a novel design strategy for compact, high gain, double clad and photonic crystal fiber lasers and amplifiers. Modeling tools include higher order finite element-based vector modal solvers for passive and active single and multi-core devices, optical and thermal transport and mechanical stress calculations for high power laser operation. | In this study, the neutron emission rate from neutron sources using prompt gamma rays in hydrogen was determined, and several improvements were applied. Using Monte Carlo calculations, the best positions for the source, moderator and detector relative to each other were selected. For (241)Am-Be and (252)Cf sources, the sizes for polyethylene spheres with the highest efficiency were 12- and 10-inch, respectively. In addition, a new shielding cone was designed to account for scattered neutrons and gamma rays. The newly designed shielding cone, which is 45 cm in length, provided suitable attenuation for the source radiation. | eng_Latn | 10,087 |
Laser-manipulated the multiphoton transitions of a harmonically trapped particle | A single particle magneto-confined in a one-dimensional (1D) quantum wire experiences a harmonic potential, and imposing a sharply focused laser beam on an appropriate site shapes a δ potential. The theoretical investigation has demonstrated that for a sufficiently strong δ pulse the quantum motional stationary state of the particle is one of the eigenstates of the free harmonic oscillator, and it is determined by the site of the laser beam uniquely, namely a quantum state is admissible if and only if the laser site is one of its nodes. The numerical computation shows that all the nodes of the lower energy states with quantum numbers n ≤ 20, except the coordinate origin, are mutually different. So we can manipulate the multiphoton transitions between the quantum states by adjusting the position of the laser δ pulse and realize the transition from an unknown higher excitation state to a required lower energy state. | Abstract The burning history of a spherical diffusion flame element (Lagrangian flamelet) is modeled under three distinctive burning conditions: a quasi-steady burning process, a quasi-periodic burning mode, and a purely transient burning condition. In the quasi-periodic burning mode, the time scale of the oscillations is shown to affect the chemistry by providing an observed extinction reignition process associated with the unsteady fuel flux into the flame sheet. For the purely transient burning process radiation extinction occurs for certain soot loadings, initial fuel element sizes, and environmental temperatures. | eng_Latn | 10,088 |
Interferometrische Messung des Brechungsindex für Röntgenstrahlen | The refractive indexn for X-rays is measured with a single crystal X-ray interferometer. Using CuKα radiation the following values of (1-n) × 106 have been obtained Lucite: 4.135±0.13% Beryllium: 5.296±0.16% LiF: 7.980±0.18% NaF: 8.702±0.12% | Preface to first edition Preface to second edition 1. Plasma diagnostics 2. Magnetic diagnostics 3. Plasma particle flux 4. Refractive-index measurements 5. Electromagnetic emission by free electrons 6. Electromagnetic radiation from bound electrons 7. Scattering of electromagnetic radiation 8. Neutral atom diagnostics 9. Fast ions and fusion products Appendices Glossary. | deu_Latn | 10,089 |
Radiative and other rare ρ, ω, ϕ-decays from VEPP-2M | The review of results on the ρ , ω , and ϕ radiative and rare hadronic decays, measured in SND and CMD-2 experiments at VEPP-2M e + e − -collider is presented. Comparison with KLOE measurements and theoretical models is given. | The objective of the article is to present several original results, obtained through the combined approach of experiments and two-dimensional modeling, which could suggest solutions in order to improve the choice of the operating conditions in an LPCVD (low-pressure chemical vapor deposition) reactor for this kind of deposition | eng_Latn | 10,090 |
The Polarized-gamma p ---> K+ Lambda and polarized-gamma p ---> K+ Sigma0 reactions at forward angles with photon energies from 1.5-GeV to 2.4-GeV | Differential cross sections and photon beam asymmetries for the gamma p rightarrow K+ Lambda and gamma p rightarrow K+ Sigma0 reactions have been measured in the photon energy range from 1.5 GeV to 2.4 GeV and in the angular range from Theta_{cm} = 0 to 60 of the K+ scattering angle in the center of mass system at the SPring-8/LEPS facility. The photon beam asymmetries for both the reactions have been found to be positive and to increase with the photon energy. The measured differential cross sections agree with the data measured by the CLAS collaboration at cosTheta_{cm} 0.9. In the K+Lambda reaction, the resonance-like structure found in the CLAS and SAPHIR data at W=1.96 GeV is confirmed. The differential cross sections at forward angles suggest a strong K-exchange contribution in the t-channel for the K+Lambda reaction, but not for the K+Sigma0 reaction. | The minimization of plasma-induced damage (PID) in plasma etching is important for the precise and smooth removal of a depth of approximately 7 nm of GaN films to fabricate gate-recess GaN-based normally-off power electronic devices. We have systematically studied the photoluminescence (PL) properties and surface morphologies of GaN films exposed to Cl2 plasma at 400 °C, focusing on their dependences on etch time and ion energy. It is noticeable that PL degradation saturated at etch times of more than 2 min, while surface roughness increased continuously with etch time. Variations of surface roughness with bias voltage were negligible. PID was successfully suppressed by reducing bias voltage, leading to the decrease in incident ion energy on the surface, and thus the near-band-edge emission (NBE) intensity as a PL property was increased to 98.8% of the initial value. | eng_Latn | 10,091 |
Compressed xenon gas near its critical point as an ionization medium | The authors report results obtained from a dual gridded ionization chamber filled with highly purified gaseous xenon operating near its critical point where the density, rho /sub c/=1.09 g/cm/sup 3/, approaches that of the liquid phase. The data obtained suggest that xenon near its critical point is an important addition to the presently available high-resolution radiation detector media. Both the ability to drift ionization electrons over large distances without attenuation and stability with time have been demonstrated. The energy resolution of the 976-keV K-conversion electron peak of /sup 207/Bi was measured to be 20 keV FWHM in 1.4 g/cm/sup 3/ (62 atm) of xenon, independent of the distance over which the charge drifts. These findings indicate that attachment to electronegative impurities is not a problem. An additional effect was observed as the density of the xenon gas was lowered from 1.4 to 0.5 g/cm/sup 3/: the energy resolution improved without an increase in the average charge collected. > | Here,the acetic waster water was disposed by pressure bio film method through the principle of Dolton partial pressure law,the experiment results show that increasing air pressure would not harm microoraganism,otherwise,it would be benefit to the bio film oxidation processes.The removal efficiency of COD was increasing 30%-50% at 0.2 MPa and 0.3 MPa atomsphere pressure compared with normal pressure. | eng_Latn | 10,092 |
Reactions induced in 12C by nucleons of energy 120-150 MeV | Measurements are presented of the cross sections for producing individual states of the residual nuclei in the 12C (n, np)11B, 12C (p, pn)11C and 12C (p, 2p)11B reactions. Observation of the decay γ-radiation from these states provides the necessary energy resolution; the γ-radiation is observed in coincidence with protons suitably selected to reject other reactions which could produce γ-radiation. To a first approximation the results provide a measure of the parentage of the ground state of 12C; they are therefore discussed in terms of nuclear models. We find that mirror pairs of states are produced with equal cross sections in the mirror (p, pn) and (n, np) reactions, except for the states at 4.46 MeV in 11B and 4.32 MeV in 11C where the cross sections differ by a factor of 2. The strong production of these J = 5/2- states implies either that the ground state of 12C is not a pure shell-model state or that a two-stage scattering process occurs. | We show <-50 dB AM-to-PM conversion over a wide photocurrent range in MUTC photodiodes. By controlling the AM-to-PM coefficient minimum, we generate 15 dBm microwave power with 60 dB AM rejection onto the microwave phase. | eng_Latn | 10,093 |
Interchannel interaction versus relativistic effects: Xe5pphotoionization revisited | Xenon 5(P) subshell photoionization has been studied in the vicinity of the Xe 4d shape resonance by angle and spin resolved photoelectron spectroscopy. Dipole matrix elements and relative phase shifts derived from these experimental data are compared with calculations with regard to the strength of interchannel and relativistic interactions. The comparison shows strong influence of interchannel interactions on the transition-matrix elements, particularly on the phase shift in the vicinity of the 4d shape resonance, but gives little evidence for relativistic interactions of comparable strength. | Ultra wide band (UWB) impulse radio (IR) technology calls for robust and low-complexity receiver techniques. State-of-the-art proposals are both coherent ML receivers, noncoherent transmitted reference systems, or hybrid choices, all of which are derived from an AWGN model. In this paper we investigate an alternative technique which has been recently proposed, and which is based upon a Gaussian mixture (GM) model for multiple access interference. We show that this technique exhibits superior performance in comparison to AWGN receivers, and can be implemented with low-complexity. | eng_Latn | 10,094 |
Temperature effects in five-dimensional Kaluza-Klein theory | Abstract We examine the combined effectsof thermal and quantum-mechanical fluctuations in a Kaluza-Klein universe with a single compact spatial dimension of length L ¯ 5 . From the one-loop effective potential for L ¯ 5 two types of instability are evident. If initially L ¯ 5 is less than a temperature-dependent critical length, L ¯ 5 will shrink at least down to a length comparable to the Planck length. This instability has been noted by Appelquist and Chodos in the zero-temperature limit. If, on the other hand, L ¯ 5 starts out larger than the critical length, it will tend to increase. This result suggests that temperature effects may play an important role in Kaluza-Klein cosmological models. | Abstract A soft X-ray pulse height analyzer has been designed and installed on the J-TEXT tokamak for measuring the electron temperature and possibly for monitoring the impurity content and concentration. A multi-channel analyzer, a set of amplifiers, and three silicon drift detectors constitute the detection system. An off-line analysis code was developed to analyze the raw data recorded by the system. The system can measure a minimum electron temperature of 400 eV, and its routine operation provides electron temperature measurements at three different positions with a temporal resolution of 60 ms and channel separation of 18 cm. Line radiation from some moderate and high Z impurities are observable by the system. The results show that the intensity of line radiation from heavy impurity ions is inversely proportional to the plasma density under similar discharge conditions. | eng_Latn | 10,095 |
Advanced Ultrasound: Prostate Elastography and Photoacoustic Imaging | Conventional B-mode transrectal ultrasound (TRUS) is used extensively to aid in visualizing the prostate gland and needle during biopsy. However, TRUS has limited sensitivity and specificity for prostate cancer detection (Nelson et al. 2007; Correas et al. 2013), and therefore advanced ultrasonic methods are currently being investigated to improve prostate cancer detection. | Summary form only given, substantially as follows. Reviews fifteen possible model experiments on astrophysics with lasers. When a focused ultra-intense laser irradiates a high-Z material, relativistic high-energy electrons are efficiently produced, and subsequent nuclear and QED (quantum electrodynamics) phenomena are expected to take place inside the target. The relativistic Fokker-Planck equation has been solved numerically for electrons and positrons with parameters used in the experiment. The author clarifies what physics is most important in the experiment and how the energy spectrum of the created positrons are determined. Such studies suggest that relativistic and dense electron-positron plasmas can be made in the laboratory. | eng_Latn | 10,096 |
Whole body MRI: How, When, Why. | Poster: "ECR 2017 / C-1075 / Whole body MRI: How, When, Why. " by: "A. Stecco1, A. Cassara1, F. Buemi1, A. ferrari1, L. Canalis1, G. Leale1, L. SUKHOVEI 1, S. Berardo1, A. Carriero2; 1Novara/IT, 2Novara (NO)/IT" | Abstract We have developed image analysis software to facilitate the analysis of optical-transition radiation (OTR) patterns generated by the electron beam from the Los Alamos free-electron laser facility. The software can be used for beam alignment, beam profile and angular divergence measurements, and the programs run on an IBM AT microcomputer. The programs and their use are described and some results shown. | eng_Latn | 10,097 |
Meson Production Near Threshold | This experimental program focuses on meson production near threshold via the reaction p + d → 3He + X. The incident beam energy and the 3He momentum are matched in such a way that the mesons are produced at rest in the c.m. system. Clear signals can be observed at the ω,ή, K \(\bar K\) and φ thresholds. | We argue that in the measured $p_T$ domain of RHIC, collisional rather than the radiative energy loss is the dominant mechanism for jet quenching. Accordingly we calculate nuclear suppression factor for light hadrons by taking only the elastic energy loss in sharp contrast with the previous calculations where only the radiative loss are considered. | eng_Latn | 10,098 |
Laser acupuncture induced specific cerebral cortical and subcortical activations in humans | As recent studies demonstrated, acupuncture can elicit activity in specific brain areas. This study aims to explore further the central effect using laser acupuncture. We investigated the cerebral effects of laser acupuncture at both acupoints GB43 with functional magnetic resonance imaging (fMRI). As a control condition the laser was mounted at the same acupoints but without application of laser stimulation. The group results showed significant brain activations within the thalamus, nucleus subthalamicus, nucleus ruber, the brainstem, and the Brodmann areas 40 and 22 for the acupuncture condition. No significant brain activations were observed within the placebo condition. The activations we observed were laser acupuncture-specific and predominantly ipsilateral. This supports the assumption that acupuncture is mediated by meridians, since meridians do not cross to the other side. Furthermore, we could show that laser acupuncture allows one to design a pure placebo condition. | To satisfy the requirements of surface and atomic physics study in the field of low energy multiple charge state ion incident experiments, a low energy (10eV∕q–20keV∕q) ion beam platform is under design at IMP. A simple test bench has been set up to test the ion beam deceleration systems. Considering virtues such as structure simplicity, easy handling, compactness, cost saving, etc., an all-permanent magnet ECRIS LAPECR1 [Lanzhou all-permanent magnet electron cyclotron resonance (ECR) ion source No. 1] working at 14.5GHz has been adopted to produce intense medium and low charge state ion beams. LAPECR1 source has already been ignited. Some intense low charge state ion beams have been produced on it, but the first test also reveals that many problems are existing on the ion beam transmission line. The ion beam transmission mismatches result in the depressed performance of LAPECR1, which will be discussed in this paper. To obtain ultralow energy ion beam, after being analyzed by a double-focusing analyzer m... | eng_Latn | 10,099 |
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