School of Electrical Engineering & Automation, Harbin Institute of Technology, Harbin 150001, China; School of Physics, University of Melbourne, VIC 3010, Australia.
School of Physics, University of Melbourne, VIC 3010, Australia.
Phys Med. 2016 Dec;32(12):1841-1845. doi: 10.1016/j.ejmp.2016.10.008. Epub 2016 Oct 27.
In Harbin, we are developing a 300MeV proton microbeam for many applications in space science including upset studies in microelectronic devices, radiation hardness of materials for satellites and radiation effects in human tissues. There are also applications of this facility proposed for proton therapy. The microbeam system will employ a purpose-built proton synchrotron to provide the beam. However there are many challenges to be addressed in the design, construction and operation of this facility. Here we address two important design aspects for which we apply GEANT4 modeling. First, the high energy proton beam interacts strongly with beam line materials, especially the collimation slits, to produce showers of secondary particles which could introduce significant background signals and degrade the resolution of the proton microbeam. Second, the beam transport within the residual vacuum of the beam line may also introduce undesirable background radiation. In both cases mitigation strategies need to be incorporated during the design phase of the new system. We study the use of a dipole magnet following the aperture collimator to reduce the flux of secondary particles incident on the analysis chamber. Monte Carlo simulations are performed using GEANT4 and SRIM. By inserting the dipole magnet, we find as expected a significant reduction in the scattering of protons and other particles, such as neutrons and gamma rays, at the collimation system exit position. Secondary radiation from the residual gas pressure within the beam line vacuum system are also modelled and found to be negligible under the standard operating conditions.
在哈尔滨，我们正在开发一个 300MeV 的质子微束，用于太空科学的许多应用，包括微电子器件的故障研究、卫星用材料的辐射硬度以及人体组织的辐射效应。该设施还提议用于质子治疗。微束系统将采用专门设计的质子同步加速器来提供束流。然而，在该设施的设计、构建和运行中存在许多挑战。在这里，我们将介绍两个重要的设计方面，并应用 GEANT4 建模来解决这些问题。首先，高能质子束与束线材料（尤其是准直狭缝）相互作用强烈，会产生二次粒子簇射，这可能会引入显著的背景信号，并降低质子微束的分辨率。其次，在束线残余真空内的束流传输也可能会引入不期望的背景辐射。在这两种情况下，都需要在新系统的设计阶段纳入缓解策略。我们研究了在孔径准直器之后使用一个磁偶极子来减少入射到分析室的二次粒子通量。使用 GEANT4 和 SRIM 进行了蒙特卡罗模拟。通过插入磁偶极子，我们发现，如预期的那样，在准直系统出口位置，质子和其他粒子（如中子和伽马射线）的散射显著减少。此外，还对束线真空系统内残余气体压力产生的二次辐射进行了建模，发现其在标准操作条件下可忽略不计。
