High-power RF Conditioning of a Hybrid e-Gun at Ariel University

Abstract

A novel hybrid photo injector is being commissioned at the Schlesinger center for compact accelerators in Ariel University. The hybrid gun is composed of a standing wave section (3.5 cells) and a traveling wave section (9 cells) in a single structure, and therefore has a much larger inner surface than a typical 1.5 cell electron gun. This gun will be driving a THz Free Electron Laser (FEL), operating at the super-radiance regime, and therefore requires extraordinary beam properties. First operation of the RF gun was in January 2018. High-power RF field entering a metallic cavity can severely damage the RF structure or the RF window. For this reason, in order to achieve the desired high-field gradients in the RF gun, a careful and extensive conditioning work on the gun is required. This is done by applying slowly increasing power levels into the structure, while monitoring the response constantly. To increase the efficiency and safety aspects of the conditioning work, we developed in-house routines and interlocks, controlled by a dedicated software. Methods and information of diagnostics elements in the RF system are presented, and the necessary requirements to simplify the conditioning work are outlined.