分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-02
摘要: High-energy proton microbeam facilities are powerful tools in space science, biology, and cancer therapystudies. The primary limitationsof the 50 MeV proton microbeam system are the poor beam quality provided by the cyclotron and the problem of intense scattering in the slit position. Here, we present an optical design for a cyclotron-based 50 MeV high-energy proton microbeam system with a micron-sized resolution. The microbeam system,which hasan Oxford triplet lens configuration,has relatively small spherical aberrations and is insensitive to changes in the beam divergence angle and momentum spread. In addition, the energy filtrationincluded in the system can reducethe beam momentum spread from 1% to 0.02%. The effects of lens parasitic aberrations and the lens fringe fieldon the beam spot resolution are also discussed. In addition, owing to the severe scattering of 50 MeV protons in slit materials, a slit system model based on the Geant4 toolkit enables the quantitative analysis of scattered protons and secondary particles. For the slit system settings under a 10-micron final beam spot, very few scattered protons can enter the quadrupole lens system and affect the focusing performance of the microbeam system, but thesecondary radiation of neutrons and gamma rays generatedat the collimationsystem should be considered for the 50 MeV protonmicrobeam. These data demonstrate thata 50 MeV proton microbeam system with a micron-sized beam spot based on a cyclotron is feasible.
分类: 物理学 >> 核物理学 提交时间: 2023-06-02
摘要: In this study, the rapidity distribution, collective flows, and nuclear stopping power in 197Au+197 Au collisions at intermediate energies were investigated using the ultrarelativistic quantum molecular dynamics (UrQMD) model with GEMINI++ code. The UrQMD model was adopted to simulate the dynamic evolution of heavy-ion collisions, whereas the GEMINI++ code was used to simulate the decay of primary fragments produced by UrQMD. The calculated results were compared with the INDRA and FOPI experimental data. It was found that the rapidity distribution, collective flows, and nuclear stopping power were affected to a certain extent by the decay of primary fragments, especially at lower beam energies. Furthermore, the experimental data of the collective flows and nuclear stopping power at the investigated beam energies were better reproduced when the sequential decay effect was included.
分类: 物理学 >> 核物理学 提交时间: 2023-06-02
摘要: 银纳米团簇(AgNCs)是一种与分子性质相似的新型纳米材料,它具有独特的应用前景。通过将AgNCs与不同的基体材料结合制备AgNC复合材料,可以极大的扩展AgNCs的应用范围。利用辐照技术,我们开发了一种简单的两步法制备银纳米团簇复合材料的合成方法。首先,将聚丙烯酸(PAA)链接枝到PE薄膜表面得到固体模板(PE-g-PAA)。随后,在模板材料表面原位还原银离子,得到AgNC复合材料(AgNCs@PE-g-PAA)。通过调整反应条件,可以很容易地控制AgNCs在复合膜上的负载程度。负载的AgNCs被锚定在PAA的羧基上并包裹在接枝链中。AgNCs的粒径仅为4.380.85 nm,粒径分布非常均匀。AgNCs@PE-g-PAA表现出AgNCs的荧光特性。AgNCs@PE-g-PAA的荧光很容易被Cr3+离子猝灭。该复合材料可作为荧光试纸,实现对Cr3+的目视检测。