中国散裂中子源快循环同步加速器束团长度研究  

Bunch Length Study in Rapid Cycling Synchrotron of China Spallation Neutron Source

作　　者：黄良生[1,2] 刘汉阳 李明涛 刘星光 许守彦 王生[1,2] HUANG Liangsheng;LIU Hanyang;LI Mingtao;LIU Xingguang;XU Shouyan;WANG Sheng(Institute of High Energy Physics,Chinese Academy of Sciences,Beijing 100049,China;Spallation Neutron Source Science Center,Dongguan 523803,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院高能物理研究所,北京100049 [2]散裂中子源科学中心,广东东莞523803 [3]中国科学院大学,北京100049

出　　处：《原子能科学技术》2022年第7期1456-1464,共9页Atomic Energy Science and Technology

基　　金：国家自然科学基金联合基金重大支持项目(U1832210)。

摘　　要：束团长度是中国散裂中子源(CSNS)快循环同步加速器(RCS)束流动力学的关键参数,通过对束团长度的研究,可了解RCS的机器性能并进一步指导机器优化研究。本文对RCS 100 kW时的束团长度进行精确测量,100 kW引出时的束团长度为105 ns。RCS 500 kW时束团长度可能超过无损引出允许值,需压缩束团长度。理论上提高腔压可压缩束团长度,本文模拟研究500 kW时束团长度随腔压曲线的变化规律,模拟结果表明提高加速后半阶段的腔压可压缩束团长度,给出了500 kW时无束流损失引出的腔压曲线。基于100 kW束流条件实验验证了通过提高加速后半阶段腔压来压缩束团长度的有效性和可行性,实验测量结果与模拟结果一致。因此,提高加速后半阶段腔压是500 kW时无损引出束流的有效方法。The rapid cycling synchrotron(RCS)of the China Spallation Neutron Source(CSNS)is a high intensity proton accelerator,which accumulates the 80 MeV proton beam and accelerates it to 1.6 GeV with the repetition frequency of 25 Hz.The designed beam power is 100 kW.The beam commissioning of RCS began in May,2017 and reached the target beam power of 100 kW in February,2020.Two buckets are perfectly filled with two bunches in the RCS.The two bunches are extracted from the RCS within one turn by the kicker magnet and the rise time of the kicker field is 256 ns after the manufacture with the kicker field trigger and jitter error of about 20 ns.The revolution time at extraction energy is 818 ns in the RCS.The bunch length is the main parameter of the beam dynamics and its maximum of about 130 ns is allowed without beam loss at extraction.The measured bunch length is accurate(105±1)ns in the operation,which is consistent with the simulation result.A forthcoming linac energy upgrade will allow the beam power to reach 500 kW by increasing the linac beam energy to 300 MeV in order to decrease the space charge effect at low energy and increase the beam current intensity in the RCS.The final bunch length of 500 kW may be bigger than the allowed value,so it must be compressed.The bunch length can be compressed by enhancing the cavity voltage in theory and the bunch length as a function of the voltage curve was simulated in the paper.The bunch length can be compressed by enhancing the cavity voltage in the last half of the acceleration cycle.Without beam loss,the voltage at extraction should be enhanced to 140 kV and the bunch length is about 120 ns.Based on the state of 100 kW beam,the bunch length compression method was tested under the condition of keeping the cavity stable operation and the bunch length can be compressed about 20 ns by enhancing the cavity voltage in the last half of the acceleration cycle.The simulation and experiment result shows that the bunch length compression method by enhancing the voltage is the effec

关 键 词：中国散裂中子源 快循环同步加速器 纵向束流动力学 束团长度 压缩 

分 类 号：TL54[核科学技术—核技术及应用]