HOM Measurements for Cornell's High-current CW ERL Cryomodule
HOM Measurements for Cornell's High-current CW ERL Cryomodule
复制标题
康奈尔大学高电流 CW ERL 低温模块的 HOM 测量
DOI：
10.18429/jacow-ipac2016-wepmr021
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发表时间：
2016
影响因子：
1.4
通讯作者：
V. Veshcherevich
中科院分区：
文献类型：
--
作者：
F. Furuta;R. Eichhorn;M. Ge;D. Gonnella;G. Hoffstaetter;M. Liepe;P. Quigley;V. Veshcherevich
康奈尔大学未来基于能量回收直线加速器 (ERL) 的 X 射线源的主直线加速器冷冻模块 (MLC) 已经设计、制造和测试。它包含六个 7cell SRF 腔体，带有单独的高阶模 (HOM) 吸收器、腔体频率调谐器和高功率 RF 输入耦合器。 MLC 腔体中的 HOM 在 1.8K 的工作温度下进行了扫描。结果显示了 HOM 的有效阻尼，并且与模拟结果和之前在一个 7 单元腔原型测试低温模块上的 HOM 扫描结果非常吻合。在这里，我们报告 MLC HOM 研究的第一个结果。简介 康奈尔大学提议建造能量回收直线加速器 (ERL) 作为硬 X 射线源的驱动器，因为它能够以高重复率产生具有小、灵活横截面和短长度的电子束。所提出的康奈尔 ERL 设计为以 1.3 GHz、2 ps 束长、每个加速和减速光束中 100 mA 平均电流、0.3 mm-mrad 归一化发射度和从 5 GeV 到 10 MeV 的能量范围运行，此时用过的光束被引导到光束停止器 [1, 2]。对于这种类型的高电流机器，抑制 SRF 腔中光束激发的高阶模 (HOM) 至关重要，因为 HOM 可能导致光束偏转。特别是，偶极子模式可能会在束束上产生横向冲击并在设计轨道周围启动束团振荡，需要强烈阻尼以避免由此产生的束破裂（BBU）。 MLC 中的 HOM 减震器
The main linac cryomodule (MLC) for the future energy-recovery linac (ERL) based X-ray source at Cornell has been designed, fabricated, and tested. It houses six 7cell SRF cavities with individual higher order-modes (HOMs) absorbers, cavity frequency tuners, and high power RF input couplers. HOMs in MLC cavities have been scanned at the operating temperature of 1.8K. The results show effective damping of HOMs, and also agree well with simulation results and previous HOM scan results on one 7-cell cavity prototype test cryomodule. Here we report first results from the MLC HOM study. INTRODUCTION Cornell University has proposed to build an Energy Recovery Linac (ERL) as drivers for a hard x-ray source because of its ability to produce electron bunches with small, flexible cross sections and short lengths at high repetition rates. The proposed Cornell ERL is designed to operate in CW at 1.3 GHz, 2 ps bunch length, 100 mA average current in each of the accelerating and decelerating beams, normalized emittance of 0.3 mm-mrad, and energy ranging from 5 GeV down to 10 MeV, at which point the spent beam is directed to a beam stop [1, 2]. For this type of high current machine, the suppression of high order modes (HOMs) excited by the beam in the SRF cavities is essential, because HOMs could lead a deflection of the beam. Especially, the dipole modes which could make a transverse kick on the beam bunch and start a bunch oscillation around the design orbit need to be damped strongly to avoid resulting beam break up (BBU). HOM ABSORBER IN MLC