Experimental investigation of multibunch, multipass beam breakup in the Jefferson Laboratory Free Electron Laser Upgrade Driver

• DOI: 10.1103/physrevstab.9.064403
• Publication Date: 2006-06-27T12:46:57Z
• Authors: David R. Douglas; Kevin C. Jordan; Lia Merminga; Eduard G. Pozdeyev; Christopher D. Te...; Haipeng Wang; Todd I. Smith; Stefan Simrock; Ivan V. Bazarov; Georg H. Hoffstae...
• Keywords: Free-electron laser; Upgrade

In recirculating accelerators, and, in particular, energy-recovery linacs, the maximum current can be limited by multipass, multibunch beam breakup (BBU), which occurs when electron interacts with higher-order modes (HOMs) of an accelerating cavity on pass and again energy recovering pass. This effect is particular concern design modern high average accelerators utilizing superconducting rf technology. Experimental characterization observations instability at Jefferson Laboratory 10 kW free laser (FEL) are presented. Measurements threshold for made under a variety conditions compared to predictions several BBU simulation codes. represents first time codes have been experimentally benchmarked. With posing threat operation FEL driver, suppression schemes were developed. These include direct damping dangerous HOM using feedback modifying optics so as reduce coupling between mode. Both methods shown increase stability. Beam optical techniques, proved effective that they routinely used normal operations Upgrade Driver.