【作者】 张琪；

【导师】 黄文会；

【作者基本信息】 清华大学 ， 核科学与技术， 2018， 硕士

【摘要】 西安质子应用装置（XiPAF）由清华大学与西北核技术研究所共同建设,主要用作空间辐射效应地面模拟试验研究。该装置的主要设计目标是提供最高能量230 MeV的质子束流,单个脉冲至少2×10¹¹个质子。为了满足辐照实验的需求,束流引出采取慢引出方式,利用RF-KO技术实现,使得引出束流的脉冲宽度可在1¹0s范围内调整。本文首先从单粒子辐照效应需求角度,分析了XiPAF慢引出束流可以达到的累计剂量精度。并根据自行开发的慢引出C++并行程序,对多种慢引出方式进行了模拟,并探究了RF-KO作用下粒子发射度增长机制及渡越时间,同时对RF-KO相关的各项参数进行了优化。本文还从整个引出时间尺度（1¹0s）及单个扫频周期（ms量级）两个时间维度,研究了慢引出束流的均匀性,并提出了改善引出束流均匀性的方法:对于全局束流均匀性,可以通过设置前馈曲线、以及PID反馈来改善;对于单个扫频周期内束流均匀性,可以通过双频扫描、同步振荡等方法来加以改善。以上方法均通过自行开发的C++慢引出并行程序进行了模拟确认。论文还提出了多阶段变速率引出模型,提高了空间电荷存在的情况下慢引出束流的均匀性。在引出过程中,由于二极铁、四极铁电源纹波的存在,束流相空间稳定区与不稳定区分界线会因纹波而抖动,使边界粒子不受控引出,影响引出束流均匀性和引出效率。本文从理论和模拟两方面研究了二极铁、四极铁电源电流纹波对引出束流的影响,并根据模拟结果确定出以下单种磁铁电源电流纹波标准:对于聚焦四极铁电源,电流纹波/设定值应小于120ppm;对于散焦四极铁电源,电流纹波/设定值应小于2000ppm;对于二极铁电源,电流纹波/设定值应小于400ppm。因西安质子应用装置同步环上所有磁铁电源采用同一纹波标准,综合考虑所有磁铁电源电流纹波后,最终确定电源电流纹波/设定值应小于100ppm。更多还原

【Abstract】 Xi’an Proton Application Facility was built by Tsinghua University and Northwest Institution of Nuclear Technology,and was designed for the ground experiments for space irradiation effects.The design objective of XiPAF is to provide proton beam from 7MeV to 230MeV with a beam intensity of at least2×10¹¹ protons per pulse.To satisfy the requirements of irradiation experiment,the third resonant slow extraction and RF-Knockout technology was adopted.In this article,the resolution of accumulated dose was analyzed in terms of the requirements of proton single event experiments.The growth process of the particle’s emittance and the transit time for extraction were explored by theory and simulation.The uniformity of extracted spill was studied in both the global extracted time（1¹0s）and single FM period（^ms）,and the method to improve the uniformity of extracted was raised:for the global extracted time,the uniformity can be improved by feedforward or feedback;for the sin gle FM period,dual FM method and synchrotron oscillation can be used to improve uniformity of the extracted spill.All these methods hav e been verified by the self-developed C++parallel program for slow extraction.When the strong space charge effect exists,the multi-stage-and-variable-rate extraction method was raised.And the uniformity of the extracted spill was improved significantly using this method.The separatrix of the stable region fluctuates during slow extraction due to power ripple,which causes uncontrollable spill and affects the extracted beam uniformity as well as the extraction efficiency.The influence of dipole and quadrupole power ripple on extracted spill was explored theoretically and simulated via TrackAll.According to a series o f simulation results,?I/Iset≤120ppm for the QF power converter,?I/Iset≤2000ppm for the QD converter and?I/Iset≤400ppm for the dipole converter are acceptable.Since the power converters of the synchrotron in XiPAF satisfy the same standard in terms of power ripple,it is confirmed that?I/Iset should be limited to 100ppm for all power converters.更多还原