分类: 物理学 >> 核物理学 分类: 天文学 >> 天文仪器与技术 分类: 材料科学 >> 材料科学(综合) 提交时间: 2023-12-15
摘要: The GECAM series of satellites utilizes LaBr3(Ce), LaBr3(Ce,Sr), and NaI(Tl) crystals as sensitive materials for gamma-ray detectors (GRDs). To investigate the non-linearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship, comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons, radioactive sources, and monoenergetic X-rays. The non-linearity test results of the Compton electrons and X-rays demonstrated substantial differences, with all three crystals presenting a higher non-linearity for X/-rays than for Compton electrons. Despite the LaBr3(Ce) and LaBr3(Ce,Sr) crystals having higher absolute light yields, they exhibited a noticeable non-linear decrease in the light yield, especially at energies below 400 keV. The NaI(Tl) crystal demonstrated an excess light output in the 6200 keV range, reaching a maximum excess of 9.2% at 30 keV in the X-ray testing and up to 15.5% at 14 keV during Compton electron testing, indicating a significant advantage in the detection of low-energy gamma rays. Furthermore, we explored the underlying causes of the observed non-linearity in these crystals. This study not only elucidates the detector responses of GECAM, but also initiates a comprehensive investigation of the non-linearity of domestically produced lanthanum bromide and sodium iodide crystals.
分类: 物理学 >> 核物理学 提交时间: 2023-07-25
摘要: We extend the Coulomb and Proximity Potential Model (CPPM) to study two-proton ($2p$) radioactivity from excited states while the proximity potential is chosen as AW95 proposed by Aage Withner in 1995. Demonstration reveals that the theoretical results acquired by CPPM exhibit a high level of consistency with prior theoretical models, such as the unified fission model (UFM), generalized liquid drop model (GLDM) and effective liquid drop model (ELDM). Furthermore, within the CPPM, we predicted the half-lives of potential $2p$ radioactive nuclei for which experimental data are currently unavailable. The predicted results were then assessed, compared with UFM, ELDM, and GLDM models, and examined in detail.
分类: 物理学 >> 核物理学 提交时间: 2023-05-23
摘要: In this study, we theoretically investigate the feasibility of using laser-wakefield accelerated (LWFA) electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser Plasma Accelerator (CLAPA) laboratory. The experiments at the CLAPA show that a stable electron beam with an energy of 78135 MeV and a charge of 300-600 pC can be obtained. The bremsstrahlung spectra were simulated using Geant4, which suggests that a bremsstrahlung source with a peak intensity of 1019 photons/s can be generated. Theoretical calculations of isomer production cross-sections from the photonuclear reactions on six target nuclei, 197Au, 180Hf, 159Tb, 115In, 103Rh, and 90Zr were performed and compared with the available experimental data in EXFOR, which suggest that further experiments are required for a series of photonuclear reaction channels. Flux-averaged cross-sections and isomer ratios (IR) resulting from such bremsstrahlung sources are theoretically deduced. The results suggest that IR measurements can be used to constrain nuclear components, such as strength function and optical model potential. In addition, the detection of the decay characteristics was evaluated with Geant4 simulations. The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2021-12-31
摘要: The muon radiography imaging technique for high-atomic-number objects (Z) and large-volume objects via muon transmission imaging and muon multiple scattering imaging remains a popular topic in the field of radiation detection imaging. However, few imaging studies have been reported on low and medium Z objects at the centimeter scale. This paper presents an imaging system that consists of three layers of a position-sensitive detector and four plastic scintillation detectors. It acquires data by coincidence detection technique of cosmic-ray muon and its secondary particles. A 3D imaging algorithm based on the density of the coinciding muon trajectory was developed, and 4D imaging that takes the atomic number dimension into account by considering the secondary particle ratio information was achieved. The resultant reconstructed 3D images could distinguish between a series of cubes with 5-mm side lengths and 2-mm intervals. If the imaging time is more than 20 days, this method can distinguish intervals with a width of 1 mm. The 4D images can specify target objects with low, medium, and high Z values.