Experimental investigation of multibunch, multipass beam breakup in the Jefferson Laboratory Free Electron Laser Upgrade Driver
Experimental investigation of multibunch, multipass beam breakup in the Jefferson Laboratory Free Electron Laser Upgrade Driver
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杰斐逊实验室自由电子激光升级驱动器中多束、多程光束分裂的实验研究
DOI：
10.1103/physrevstab.9.064403
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发表时间：
2006
影响因子：
--
通讯作者：
G. Hoffstaetter
中科院分区：
文献类型：
--
作者：
D. Douglas;K. Jordan;L. Merminga;E. Pozdeyev;C. Tennant;Haipeng Wang;T. Smith;S. Simrock;I. Bazarov;G. Hoffstaetter
在再循环加速器中，特别是在能量回收直线加速器中，最大电流可以受到多程多聚束分裂（BBU）的限制，这发生在电子束与加速通道上的加速腔的高阶模（HOM）相互作用并再次在能量回收通道上相互作用时。这种效应在利用超导射频技术的现代高平均电流能量回收加速器的设计中特别受到关注。本文介绍了在杰斐逊实验室10千瓦自由电子激光器上对不稳定性的实验表征和观测结果。的阈值电流的不稳定性的测量是在各种光束条件下，并比较几个BBU模拟代码的预测。这是第一次对代码进行实验基准测试。由于BBU对自由电子激光驱动器强流束的工作构成威胁，人们提出了几种抑制方案。这些措施包括使用腔反馈直接阻尼危险的HOM和修改电子束光学器件，以减少光束和模式之间的耦合。这两种方法都被证明可以提高阈值电流的稳定性。光束光学抑制技术，特别是，已被证明是如此有效，他们经常使用的自由电子激光升级驱动程序的正常操作。
In recirculating accelerators, and, in particular, energy-recovery linacs, the maximum current can be limited by multipass, multibunch beam breakup (BBU), which occurs when the electron beam interacts with the higher-order modes (HOMs) of an accelerating cavity on the accelerating pass and again on the energy recovering pass. This effect is of particular concern in the design of modern high average current energy-recovery accelerators utilizing superconducting rf technology. Experimental characterization and observations of the instability at the Jefferson Laboratory 10 kW free electron laser (FEL) are presented. Measurements of the threshold current for the instability are made under a variety of beam conditions and compared to the predictions of several BBU simulation codes. This represents the first time in which the codes have been experimentally benchmarked. With BBU posing a threat to high current beam operation in the FEL driver, several suppression schemes were developed. These include direct damping of the dangerous HOM using cavity feedback and modifying the electron beam optics so as to reduce the coupling between the beam and mode. Both methods were shown to increase the threshold current for stability. Beam optical suppression techniques, in particular, have proved to be so effective that they are routinely used in the normal operations of the FEL Upgrade Driver.