超导回旋加速器中束流损失对超导失超影响机理及控制研究

Due to its excellent performance, superconducting cyclotron is increasingly applied in the field of medical and science research. However, with the increase of beam energy and intensity, superconducting system will suffer severer radiation, which increases the risk of quench. It is an urgent problem needs to be resolved, however, there is no further study on this topic. This research project is in the background of R&D of a superconducting cyclotron for proton therapy, and much attention will be given to the study of beam loss damage on superconducting system, which aims to find an effective solution of the problem.. Compactness is one of the advantages of superconducting cyclotron, but it also creates two difficulties: 1) beam orbits are crowded together at extraction area that leads to beam extraction difficult, and 2) the superconducting system closes beam orbit that restricts the installation of radiation shield and is exposed much radiation. Beam loss occurred at extraction region has the severest damage to the superconducting system, which includes: a)nuclear heating to increase the temperature of cryogenic system, and b)radiation damage to decreases the critical currents of superconducting material and to destroy insulation material. Thus, control the extraction beam loss is extremely important for the stable operation of a superconducting cyclotron.. Based on beam tracking and beam-material interaction theory, this project will construct a model for analysis of nuclear reaction using Monte Carlo simulation code, which will be used to study the effects of beam loss on superconducting system. The study will focus on the distribution of deposit energy of beam loss in superconducting system in different cases, the method of control beam orbit and so on. This research project will have an important scientific significance for the development of superconducting cyclotron in China.

超导回旋加速器性能优异，越来越多地被应用于医疗和科研等领域。随着能量和流强的增大，超导系统遭受的辐射变得严重，增加了失超风险。这是亟待解决的问题，但目前缺乏深入的研究。本项目以质子治疗超导回旋加速器研发为背景，着重研究束流损失对超导系统的危害，探索解决此问题的办法。.超导回旋加速器结构紧凑的优点同时也带来2个问题：1）束流轨道密集导致引出困难；2）超导系统靠近束流，无法安装屏蔽，遭受辐射大。在引出区的束损对超导系统危害最大，主要是：a）核致热反应导致超导系统温升，b）辐射损伤导致超导材料临界电流降低和绝缘材料失效。因此，降低引出束损对加速器稳定运行至关重要。.本项目基于束流跟踪和束流物质反应理论，利用蒙特卡罗软件构建核反应物理模型，研究束损对超导系统状态的影响。重点研究不同束流损失在超导系统内的能量沉积分布，束流轨道的控制方法等。这对我国开展超导回旋加速器的研制具有重要的科学意义。

超导回旋加速器的结构紧凑，磁场强度高，导致束流的高效率引出更加困难。为解决以上关键问题，亟需首先深入分析引出的物理过程，设计相应的电磁结构，给出了引出区物理与工程设计。本文的主要研究内容：.1..利用虚拟材料实现2D/3D模型的等时性磁场验证，采用优化磁极结构快速穿越危险共振线，利用切削法获得谐波磁场产生7mm的引出圈距。.2..模拟了磁铁形变、磁特性变化和涡流效应对磁场影响，利用CYCLONE 进行了磁场补偿策略的分析验证。.3..借助束流动力学和电磁仿真软件模拟束团信号，将相位检测误差控制在0.5o 以下。.4..设计HUST-SCC250主磁铁的磁场分布，揭示了束流滑相，工作点的移动及共振线的穿越等特性。.5..设计了磁场与轨道计算的相关算法，包含了平衡轨道的求解，加速参考轨道求解，多粒子推进异构算法以及磁轭拓扑优化算法。.6..对偏转板进行了热流固耦合分析，模拟束流撞击切割板的核反应，计算了次级粒子产出率、能量分布以及空间角度通量分布。.7..分析静电偏转板电压对束流引出轨道的影响，计算引出束流轨道补偿方案，通过MADX设计了一种磁通道元件分布，给出引出系统三个主要部件的工程设计。.8..利用有限元仿真软件CST 模拟了电极表面场致发射电子在偏转板内的运动轨迹研究高压打火现象。利用电磁仿真软件OPERA-3D对比不同电极结构下静电偏转板内的电场分布，最终确定静电偏转板设计加工和测试。. 通过该项目，系统研究超导回旋加速器的共振引出理论其相应的关键技术，分析比较了增大引出圈剧的方法，采用边缘切削方法克服了传统引入扰动磁场对此主磁场的影响，且提高了方案的灵活性和有效性。在加速器重要期刊和会议发表了十多篇论文，申请成功3个专利。通过该项目开展的丰富的国际合作研究，与3个国际著名研究所签署了合作备忘录，派遣学生学习，邀请海外著名的专家作为客座教授，共同推进该项目的合作研究。. 由于我国对超导回旋加速器的研究处于起步阶段，该项目的完成对我国的超导回旋加速器的设计和质子放疗领域的研究提供了重要支撑。