1.5GHz超导加速腔双输入耦合器研究

本实验室设计的1.5 GHz 5-cell超导腔设计工作加速梯度为15-20 MV·m~(-1),至少需要使用两支输入耦合器才能满足高流强运行要求。借助三维电磁仿真模拟软件CST(Computer Simulation Technology),完成了相应的输入耦合器的电磁仿真,驻波比小于1.05的频带宽度达到18 MHz。从理论上计算加速腔双端口功率馈入,并通过铜腔双输入实验进行验证。结果表明,当两端均为欠耦合时,双输入对每个端口耦合度起到增强的作用;但当两者均为过耦合且差异较大时,耦合度小的一端则被减弱,甚至出现欠耦合的情况。对横向力场的计算显示,即使插入深度相差1 mm,使用双输入耦合器所引起的横向作用力仍比使用单耦合器情况小一个量级。

Study on twin input coupler for a 1.5-GHz superconducting cavity

Background:The 1.5-GHz 5-cell superconducting cavity designed by the Shanghai Key Laboratory of Cryogenics & Superconducting Radio Frequency Technology was optimized to accelerate a high current electron beam under continuous wave (CW) operation mode.Purpose: Considering the accelerating gradient 15?20 MV·m?1, it is necessary to use twin input coupler.Methods:Electromagnetic simulations of the input coupler were implemented using CST (Computer Simulation Technology), and the results showed a 18-MHz bandwidth where standing-wave ratio was better than 1.05. Power feeding by two couplers was calculated theoretically and testified on a set-up.Results:Theoretical derivation and experimental results showed an enhancing when both couplers were under coupled but a reduction to the weaker coupled one when both couplers were over coupled. Results from simulations showed that transverse kick to beam can be diluted drastically even when difference of insert depths is 1mm.Conclusion:Adopting twin input coupler is the only option for high average beam current CW accelerator.