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: A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed. Based on the new code, four commonly used parameter sets, SLy4, SkI2, SkM* and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables, namely isospin transport ratios, single and double ratios of the yields of neutrons and protons are investigated. The isospin transport ratios are strongly sensitive to the slope of symmetry energy, and are not very sensitive to the nucleon effective mass splitting. On the other hand, the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting. By comparing our calculations with the data, we find that the constrained L value (the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models, and the isospin diffusion data prefer to mn*>mp*, but it is not a strong constraint with deep 2 minimum.
分类: 物理学 >> 核物理学 提交时间: 2023-06-24
摘要: The multinucleon transfer (MNT) reaction is one promising way to produce neutron-rich heavy nuclei and even super heavynuclei and attracts more and more attentions theoretically and experimentally. A low energy nuclear structure spectrometer calledLENSHIAF specific to the MNT reactions will be designed and constructed in the ongoing big project HIAF in China. In theLENSHIAF spectrometer, the most challenge part is how to collect and stop efficiently the high-energy MNT products into the gascell. By using Monte-Carlo method, the geometry of the gas cell, the thickness of the titanium window/degrader, and the optimalgas pressure filled in the gas cell have been calculated and estimated. For neutron-rich nuclei around N=126 from 136Xe+198Ptreaction, with a titanium window/degrader with a thickness of 2.53.5 um, a cylindrical helium gas cell with a length of 0.6 m and adiameter of 1.2 m can satisfy the requirements to stop the target-like fragments. For heavier and super heavy nuclei from 238U+238Ureaction, with a 58 um thick titanium window/degrader, the cylindrical gas cell has to be as big as a length of at least 1.6 m and adiameter of 1.6 m.
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 accurate and fast sampling method was developed on the modeling of a voxel phantom called Rad-HUMAN for radiation protection of MC-based radiation transport and simulation. The segmented organ voxels, which were assigned with three dimensional (3D) coordinates, were simplified through a two-step hybrid sampling algorithm. Firstly, certain voxels were sampled into a coordinate matrix by the nearest neighbor sampling. Secondly, the coordinate matrix was renewed using a weighted sampling. To compare visualization with the sampling, the resultant matrix was used to extract the contour of organs/tissues for constructing polygon-surface phantom. The feasibility and effectiveness of the sampling method was verified through the modeling of large organs (e.g. skeleton system) and application of transformation to MC computational geometries.