高能质子降能器的物理研究

Physical study of a high-energy proton degrader

中国散裂中子源(China Spallation Neutron Source,CSNS)是一台基于强流质子加速器的大型多学科研究平台。CSNS的1.6 GeV高能质子束流在航天设备测试和粒子探测器测试方面都有重要应用。但是,由于单一的质子能量无法满足辐照应用及高性能探测器对束流不同能量的需求,研究设计可行的降能方案将质子束从1.6 GeV降至指定能量范围是十分必要的。本文研究发现,可以通过放置金属降能片的方式实现CSNS 1.6 GeV质子束流的能量调节。使用降能片产生弱流的π粒子测试束也具有可行性。通过比较铜、铁和钨等几种材料降能器后的次级质子及π粒子产额,降能片的活化及辐射屏蔽等多种因素,建议选择铁作为CSNS高能质子降能器的材料。

[Background]The China Spallation Neutron Source(CSNS)is a multidisciplinary research platform.Its high-energy 1.6 GeV proton beam serves various applications in aerospace devices and particle detector testing.However,certain irradiation applications and high-performance detectors require different beam energies.A degrader was designed to adjust the proton energy to a desired range.[Purpose]This study presents a reasonable degrader scheme for the 1.6 GeV proton test beam at the CSNS.[Methods]The physical process of the 1.6 GeV high-energy proton beam passing through a degrader made of either of three different materials(iron,copper,and tungsten)was simulated using FLUKA,a Monte Carlo particle transport code.Parameters such as the degrader thickness,the energy deposition,the outgoing proton beam intensity,and the irradiation dose were determined through simulations.The optimal degrader material was identified.In addition,a continuously adjustable structure of the degrader was given.[Results]Iron displays slight advantages in terms of energy deposition and radiation dose distribution,compared to copper and tungsten.Furthermore,the phase-space distribution of the outgoing proton beam and the secondary pion beam were also given,providing important references for future beam-line design.[Conclusion]An optimal degrader structure made of iron for the CSNS high-energy proton beam is proposed.The secondary pion test beam is also feasible at the proton test end station.This is a significant development for future engineering design.