- 标题
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Synchrotron Radiation from the Fast Tail of Dynamical Ejecta of Neutron Star Mergers
摘要： We ?nd, using high-resolution numerical relativistic simulations, that the tail of the dynamical ejecta of neutron star mergers extends to mildly relativistic velocities faster than 0.7c. The kinetic energy of this fast tail is ～1047–1049 erg, depending on the neutron star equation of state and on the binary masses. The synchrotron ?are arising from the interaction of this fast tail with the surrounding interstellar medium (ISM) can power the observed nonthermal emission that followed GW170817, provided that the ISM density is ～10?3 cm?3, the two neutron stars had roughly equal masses and the neutron star equation of state is soft (small neutron star radii). One of the generic predictions of this scenario is that the cooling frequency crosses the X-ray band on a timescale of a few months to a year, leading to a cooling break in the X-ray light curve. While the recent observation of the superluminal motion resolved by very long baseline interferometry (VLBI) rules out the dynamical ejecta scenario, the model described in this paper is generic and can be applied for future neutron star merger events.
关键词： gamma-ray burst: individual (GRB 170817A),stars: neutron
更新于2025-09-09 09:28:46
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Computational investigation of arranged scintillating particle composites for fast neutron detection
摘要： Composite materials have the potential to play an important role in enabling high-performance and cost-effective neutron detectors for fundamental science, global security, and dosimetry applications. This study presents neutron and gamma transport simulation results on composites consisting of 6Li-containing GS20 scintillator glass particles arranged in an organic matrix. These composites achieve high sensitivity for neutrons while suppressing signals from gamma rays. The simulations successfully identified optimal composite parameters such as particle size, geometry, and inter-particle pitch. This information is key to the subsequent fabrication and scale-up of the desired GS20-in-acrylic composite. The simulation results presented in this paper demonstrate that arranged composites can provide high neutron detection efficiency with gamma misidentification values of <1 in 106 gamma rays, assuming irradiation with a 252Cf spontaneous fission source.
关键词： Scintillator particle,Fast and thermal neutron detection,Lithium-6,Composite
更新于2025-09-09 09:28:46
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Analysis of the Behavior of Nonequilibrium Semiconductor Structures and Microwave Transistors During and After Pulsed γ- and γ-Neutron Irradiation
摘要： The influence of nonequilibrium processes in semiconductor structures under the effect of radiation on the characteristics of structures and microwave transistors based on them is analyzed. Special attention is paid to the comparison of pilot (experimental) and series-produced structures and transistors based on them before and after γ-neutron irradiation.
关键词： radiation resistance,nonequilibrium processes,γ-neutron irradiation,microwave transistors,semiconductor structures
更新于2025-09-09 09:28:46
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Polarisation analysis on the LET time-of-flight spectrometer
摘要： We present a design for implementing uniaxial polarisation analysis on the LET cold neutron time-of-?ight spectrometer, installed on the second target station at ISIS. The polarised neutron beam is to be produced by a transmission-based supermirror polariser with the polarising mirrors arranged in a “double-V” formation. This will be followed by a Mezei-type precession coil spin ?ipper, selected for its small spatial requirements, as well as a permanent magnet guide ?eld to transport the beam polarisation to the sample position. The sample area will contain a set of holding ?eld coils, whose purpose is to produce a highly homogenous magnetic ?eld for the wide-angle 3He analyser cell. To facilitate fast cell changes and reduce the risk of cell failure, we intend to separate the cell and cryostat from the vacuum of the sample tank by installing both in a vessel at atmospheric pressure. When the instrument upgrade is complete, the performance of LET is expected to be commensurate with existing and planned polarised cold neutron spectrometers at other sources. Finally, we discuss the implications of performing uniaxial polarisation analysis only, and identify quasi-elastic neutron scattering (QENS) on ionic conducting materials as an interesting area to apply the technique.
关键词： cold neutron,polarisation analysis,LET spectrometer,quasi-elastic neutron scattering,supermirror polariser,Mezei-type precession coil,time-of-?ight,3He analyser cell
更新于2025-09-04 15:30:14
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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA, USA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Design of a Photoneutron Convertor for Energy Selective Neutron Imaging
摘要： Neutron imaging plays an essential role in the industrial applications, such as turbine blade manufacturing, fuel cell research, and nuclear fuel quality inspection. As isotopic neutron sources and neutron generators cannot provide high-intensity neutron beams, and neutron beam lines of research reactors or spallation neutron sources are very scarce, a cost-effective neutron source with high neutron yield and long life-span should be researched. The e-LINAC driven photoneutron source, which converts X-rays to photoneutrons, has been proved to be a robust neutron source that can realize neutron yield ranging from 1010 to 1015n/s. Hence it is a promising neutron source to provide neutron beams used for the neutron imaging. Because the e-LINAC works at a pulsed mode and the photoneutrons have a continuous energy spectrum, energy selective neutron imaging can thus be realized with the e-LINAC driven photoneutron source, with the aid of time of flight (TOF) technique. In this research, an e-LINAC driven photoneutron source is researched to strike the compromise between the neutron flux and the energy resolution. With a well-designed heavy water photon-to-neutron convertor, a 10 MeV/ 20 kW e-LINAC can provide a thermal neutron flux of 7.28×104n/cm2/s at 10 meters away from the electron target, with an energy resolution less than 20%. By using a low temperature (10K) moderator, the cold neutron flux at the same position can be 2.13×104n/cm2, and the energy resolution is less than 2%. This study may help realize the energy selective neutron imaging with an e-LINAC driven photoneutron source.
关键词： Neutron imaging,e-LINAC,energy selective neutron imaging,photoneutron source,time of flight (TOF)
更新于2025-09-04 15:30:14
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Investigation of the Atomic Structure of Ge-Sb-Se Chalcogenide Glasses
摘要： Glasses with composition of GexSb40-xSe60 (x= 40, 35, 32, 27, 20, 15 at. %) have been synthesized. Neutron and X-ray diffraction techniques were used to study the atomic glassy structure, and Reverse Monte Carlo (RMC) simulations were applied to model the 3-dimensional atomic configurations and thorough mapping of the atomic parameters, such as first and second neighbour distances, coordination numbers, and bond-angle distributions. The results are explained with formation of GeSe4 and SbSe3 structural units, which correlate with the Ge/Sb ratio. For all the studied compositions, the Ge-Se, Sb-Se, Ge-Ge, and Se-Se bonds are significant. RMC simulations reveal the presence of Ge-Sb and Sb-Sb bonds, being dependent on Ge/Sb ratio. All atomic compositions satisfy formal valence requirements, i.e., Ge is fourfold coordinated, Sb is threefold coordinated, and Se is twofold coordinated. By increasing the Sb content, both the Se-Ge-Se bonds angle of 107±3° and Se-Sb-Se bonds angle of 118±3° decrease, respectively, indicating distortion of the structural units. Far infrared Fourier Transform spectroscopic measurements conducted in the range of 50-450 cm-1 of oblique (75°) incidence radiation have revealed clear dependences of the IR band’s shift and intensity on the glassy composition, showing features around x=27 at.% supporting the topological phase transition to a stable rigid network consisting mainly of SbSe3 pyramidal and GeSe4 tetrahedral clusters. These results are in agreement with the Reverse Monte Carlo models, which define the Ge and Sb environment.
关键词： X-ray diffraction,chalcogenide glasses,atomic structure,FTIR spectroscopy,Ge-Sb-Se,neutron diffraction,Reverse Monte Carlo
更新于2025-09-04 15:30:14
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Stored energy release in neutron irradiated silicon carbide
摘要： The purpose of this investigation is to experimentally quantify the stored energy release upon thermal annealing of previously irradiated high-purity silicon carbide (SiC.) Samples of highly-faulted poly-crystalline CVD b-SiC and single crystal 6HeSiC were irradiated in a mixed spectrum ?ssion reactor near 60 (cid:1)C in a ?uence range from 5 (cid:3) 1023 to 2 (cid:3) 1026 n/m2 (E > 0.1 MeV), or about 0.05e20 dpa, in order to quantify the stored energy release and correlate the release to the observed microscopic swelling, lattice dilation, and microstructure as observed through TEM. Within the ?uence of this study the crystalline material was observed to swell to a remarkable extent, achieving 8.13% dilation, and then cross a threshold dose for amorphization at approximately 1 (cid:3) 1025 n/m2 (E > 0.1 MeV) Once amorphized the material attains an as-amorphized swelling of 11.7% at this irradiation condition. Coincident with the extraordinary swelling obtained for the crystalline SiC, an equally impressive stored energy release of greater than 2500 J/g at the critical threshold for amorphization is inferred. As expected, following amorphization the stored energy in the structure diminishes, measured to be approximately 590 J/g. Generally, the ?ndings of stored energy are consistent with existing theory, though the amount of stored energy given the large observed crystalline strain is remarkable. The overall conclusion of this work ?nds comparable stored energy in SiC to that of nuclear graphite, and similar to graphite, a stored energy release in excess of its speci?c heat in some irradiation conditions.
关键词： Neutron irradiation,Amorphization,Silicon carbide,Swelling,Stored energy
更新于2025-09-04 15:30:14
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The Effects of Thermal Neutron Irradiation on Current-Voltage and Capacitance-Voltage Characteristics of Au/n-Si/Ag Schottky Barrier Diodes
摘要： To observe the neutron transmutation and displacement damage effects, Au/n-Si/Ag Schottky barrier diodes were exposed to thermal neutron irradiation. Irradiation induced changes in Schottky barrier height, saturation current, and donor concentration were investigated by using current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the diodes. The irradiation for 10 s caused a little change in the Schottky diode parameters which were obtained from I-Vand C-V measurements. Observable changes in the parameters occurred after the second irradiation of 30 s duration. After the total dose, an increase in saturation current and barrier height inhomogeneties took into place and a decrease in carrier concentration was observed due to the carrier removal effect of thermal neutron-induced damages. Whereas the values of zero bias barrier height have little change after irradiations, the values of ideality factor increased after irradiations. The values of zero-bias barrier height for all diodes was also calculated from reverse bias current characteristics. After second dose, the values of zero-bias barrier height decreased for all diodes. The values of series resistance were determined by Cheung functions before and after irradiations. Before irradiations, the values were found between 2.10 kΩ and 2.76 kΩ. After second dose, the values of series resistance of all diodes decreased and were found between 1.59 kΩ and 2.20 kΩ. Furthermore, the proof of thermal neutron transmu- tation of elements in the devices was given via energy dispersive spectroscopy (EDS) mapping.
关键词： Semiconductor device radiation effects,Schottky diode,Electrical characterization,EDS mapping,Silicon,Thermal neutron irradiation
更新于2025-09-04 15:30:14
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Weak measurement and weak values — New insights and effects in reflectivity and scattering processes
摘要： Recently, the notions of Weak Measurement (WM), Weak Value (WV) and Two-State-Vector Formalism (TSVF), firstly introduced by Aharonov and collaborators, have extended the theoretical frame of standard quantum mechanics, thus providing a quantum-theoretical formalism for extracting new information from a system in the limit of small disturbance to its state. Here we provide an application to the case of two-body scattering with one body weakly interacting with its environment — e.g. a neutron being scattered from a H2 molecule physisorbed in a carbon nanotube. In particular, we make contact with the field of incoherent inelastic neutron scattering from condensed systems. We provide a physically compelling prediction of a new quantum effect — a momentum transfer deficit; or equivalently, an enhanced energy transfer; or an apparent reduction of the mass of the struck particle. E.g., when a neutron collides with a H2 molecule in a C-nanotube and excites its translational motion along the nanotube, it apparently exchanges energy and momentum with a fictitious particle with mass of 0.64 atomic mass units. Experimental results are shown and discussed in the new theoretical frame. The effect under consideration has no conventional interpretation, thus also supporting the novelty of the quantum theoretical framework of WV and TVSF. Some speculative remarks about possible applications being of technological interest (fuel cells and hydrogen storage; Li+ batteries; information and communication technology) are shortly mentioned.
关键词： energy transfer,mass reduction,neutron scattering,momentum transfer deficit,Two-State-Vector Formalism,Weak Value,Weak Measurement
更新于2025-09-04 15:30:14
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Polarimetric and spectroscopic optical observations of the ultra-compact X-ray binary 4U 0614+091
摘要： Aims. We present a polarimetric and spectroscopic study of the persistent ultra-compact X-ray binary 4U 0614+091 aimed at searching for the emission of a relativistic particle jet and at unveiling the orbital period Porb of the system. Methods. We obtained r-band polarimetric observations with the Telescopio Nazionale Galileo (TNG) equipped with the PAOLO polarimeter and with the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument, covering ～2 h and ～0.5 h observations, respectively. We carried out low resolution spectroscopy of the system using the ESO Very Large Telescope equipped with FORS1 for ～1.5 h (16 spectra covering the range 4300?8000 ?). Results. The polarimetric analysis performed starting from the TNG dataset revealed a polarisation degree in the r-band of 3% ± 1%. From the NOT dataset, due to the lower signal-to-noise ratio, we could obtain only a 3σ upper limit of 3.4%. From the joining of a spectroscopic and photometric analysis, through the study of the equivalent width variations of the CII 7240 ? line and the r-band light curve, we could ?nd a hint of a ～45 min periodicity. Conclusions. A polarisation degree P of ～3% in the r-band is consistent with the emission of a relativistic particle jet, which is supposed to emit intrinsically linearly polarised synchrotron radiation. Since no variations of P with time have been detected, and the accretion disc of the system does not contain ionised hydrogen, scattering by free electrons in the accretion disc has been rejected. The period of ～45 min obtained through the analysis of the system light curve and of the equivalent width variations of the selected spectral line is probably linked to the presence of a hot spot or a superhump in the accretion disc, and lead to an orbital period (cid:38)1 h for the binary system.
关键词： stars: jets,X-rays: binaries,stars: neutron,polarisation
更新于2025-09-04 15:30:14