Mode error analysis of impedance measurement using twin wires

Both longitudinal and transverse coupling impedance for some critical components need to be measured for accelerator design. The twin wires method is widely used to measure longitudinal and transverse impedance on the bench. A mode error is induced when the twin wires method is used with a two-port network analyzer. Here, the mode error is analyzed theoretically and an example analysis is given. Moreover, the mode error in the measurement is a few percent when a hybrid with no less than 25 dB isolation and a splitter with no less than 20 dB magnitude error are used.     

300MeV质子同步加速器概念设计优化（英文）

目前处于设计阶段的哈尔滨工业大学空间辐照效应装置,其核心部件是由1台10 MeV的注入器、1台300MeV的同步加速器以及输运线构成的加速器装置。同步加速器中引出的质子束流被用于辐照研究。基于装置的概念设计,优化了其同步加速器部分的设计。设计了新的磁聚焦结构,优化了基于新的磁聚焦结构的多圈注入系统的凸轨变化模式,提高了注入效率。为了更好地优化引出束流的时间结构,慢引出系统采用了RF knock-out的方法。为了满足精准辐照的要求,研究了RF Kicker的频率调制,发现RF Kicker的双频调制能使得引出束流更均匀。A research complex for aerospace radiation effects research is in the designing stage in Harbin Institute of Technology. Its core part is a proton accelerator complex, which consists of a 10 MeV injector, a 300 MeV synchrotron and beam transport lines. The proton beam extracted from the synchrotron is utilized for the radiation effects research. Based on the conceptual design, the design study for optimizing the synchrotron has been done. A new lattice design was worked out, and the decreasing pattern of the bump of the multi-turn injection system was optimized to increase the injection efficiency. In order to improve the time structure of the extracted beam, a RF knock-out method is employed in the slow extraction system. To meet the requirement of accurate control of dose, the frequency modulation of the RF kicker is well investigated, and the dual frequency modulation has been found to have a better performance for a uniform spill.     

CSNS/RCS中的阻抗和束流不稳定性

中国散裂中子源（CSNS）的快循环同步加速器（RCS）是一台强流质子加速器,其束流平均功率达到100 kW。在此强流加速器中,真空部件的阻抗是引起束流不稳定的主要原因,它严重限制了束流强度及品质。对CSNS/RCS设计中的各种真空部件阻抗进行了详细计算,并以计算结果为出发点,理论分析了各种不稳定性强弱,确定了各种不稳定性发生的阻抗阈值,为真空部件结构设计提供了参考。对比较严重的电阻壁阻抗,采用阻抗壁尾场模型进行跟踪模拟,得到不稳定性增长率与理论计算值符合较好。自然色品有助于束流稳定,加入自然色品后模拟,电阻壁不稳定性消失。