Tisi M, Mares V, Schreiber J, Englbrecht F S, Rühm W
Institute of Radiation Medicine, Helmholtz Zentrum München, Neuherberg, Germany.
Department of Medical Physics, Faculty of Physics, Ludwig-Maximilians-Universität, Garching bei München, Germany.
Sci Rep. 2021 Dec 24;11(1):24418. doi: 10.1038/s41598-021-03897-2.
At the Center for Advanced Laser Applications (CALA), Garching, Germany, the LION (Laser-driven ION Acceleration) experiment is being commissioned, aiming at the production of laser-driven bunches of protons and light ions with multi-MeV energies and repetition frequency up to 1 Hz. A Geant4 Monte Carlo-based study of the secondary neutron and photon fields expected during LION's different commissioning phases is presented. Goal of this study is the characterization of the secondary radiation environment present inside and outside the LION cave. Three different primary proton spectra, taken from experimental results reported in the literature and representative of three different future stages of the LION's commissioning path are used. Together with protons, also electrons are emitted through laser-target interaction and are also responsible for the production of secondary radiation. For the electron component of the three source terms, a simplified exponential model is used. Moreover, in order to reduce the simulation complexity, a two-components simplified geometrical model of proton and electron sources is proposed. It has been found that the radiation environment inside the experimental cave is either dominated by photons or neutrons depending on the position in the room and the source term used. The higher the intensity of the source, the higher the neutron contribution to the total dose for all scored positions. Maximum neutron and photon ambient dose equivalent values normalized to 10 simulated incident primaries were calculated at the exit of the vacuum chamber, where values of about 85 nSv (10 primaries) and 1.0 μSv (10 primaries) were found.
在德国加兴的先进激光应用中心（CALA），正在对LION（激光驱动离子加速）实验进行调试，目标是产生能量高达数兆电子伏特且重复频率高达1赫兹的激光驱动质子束和轻离子束。本文介绍了一项基于Geant4蒙特卡罗方法的研究，该研究针对LION不同调试阶段预期产生的次级中子和光子场。这项研究的目的是对LION实验洞穴内外的次级辐射环境进行表征。使用了三种不同的初级质子能谱，这些能谱取自文献报道的实验结果，代表了LION调试路径的三个不同未来阶段。除了质子，电子也通过激光与靶的相互作用发射出来，并且也会产生次级辐射。对于三个源项中的电子部分，使用了一个简化的指数模型。此外，为了降低模拟复杂度，提出了一个质子和电子源的双组分简化几何模型。研究发现，实验洞穴内的辐射环境由光子或中子主导，这取决于房间内的位置和所使用的源项。源的强度越高，对于所有计分位置，中子对总剂量的贡献就越高。在真空腔出口处计算了归一化为10个模拟入射初级粒子的最大中子和光子环境剂量当量值，发现约为85纳希沃特（10个初级粒子）和1.0微希沃特（10个初级粒子）。
