分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: An experimental method was used to evaluate the primary isotope yields of semi-central collisions in the reaction system 64Zn+112Sn at 40A MeV. The characteristic nature of the hot nuclear matter at the time of the isotope formation was studied. The multiplicities of light particles (LPs) associated with intermediate mass fragments (IMFs) were determined experimentally by using a kinematical focusing technique. The primary isotope distributions, reconstructed by a Monte Carlo method, were compared with those of the AMD-Gemini simulations. ac/T=0.11 and asym/T=3.34 were extracted from the reconstructed primary fragments yield. These are consistent with those of the primary fragments of the AMD simulation.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The symmetry energy at the time of the production of intermediate mass fragments (IMFs) is studied using experimentally observed IMF multiplicities combined with quantum statistical model calculations (QSM of Hahn and Stcker). The ratios of difference in chemical potentials between neutrons and protons relative to the temperature, (np)/T, and the double ratio temperature, T, were extracted experimentally in the reactions of 64,70Zn, 64Ni+58,64Ni, 112,124Sn, 197Au, 232Th at 40A MeV. The extracted (np)/T scales linearly with NN, where NN is the asymmetry parameter, (NZ)/A, of the emitting source and (np)/T=(11.11.4)NN0.21 was derived. The experimentally extracted (np)/T and the double ratio temperatures are compared with those from the QSM calculations. The temperatures, T, and densities, , extracted from the (np)/T values agreed with those from the double ratio thermometer which used the yield ratios of d, t, h and particles. However the two analyses of the differential chemical potential analysis and the initial temperature analysis end up almost identical relation between T and . T=5.250.75 MeV is evaluated from the (np)/T analysis, but no density determination was possible. From the extracted T value, the symmetry energy coefficient Esym=14.63.5 MeV is determined for the emitting source of T=5.250.75 MeV.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: CBCT scanners have been widely used in angiography, radiotherapy guidance, mammography and oral maxillofacial imaging. To cut detector size, reduce manufacturing costs and radiation dose while keeping a reasonable FOV, the flat panel detector can be placed off-center horizontally. This scanning configuration extends the FOV effectively. However, each projection is transversely truncated, bringing errors and artifacts in reconstruction. In this paper, a simple but practical method is proposed for this scanning geometry based on truncation compensation and the modified FDK algorithm. Numerical simulations with jaw phantom were conducted to evaluate the accuracy and practicability of the proposed method. A novel CBCT system for maxillofacial imaging is used for clinical test, which is equipped with an off-center small size flat panel detector. Results show that reconstruction accuracy is acceptable for clinical use, and the image quality appears sufficient for specific diagnostic requirements. It provides a novel solution for clinical CBCT system, in order to reduce radiation dose and manufacturing cost.