Performance of the Thermionic RF Gun Injector for Linac-based IR Free Electron Laser at FEL-SUT

(MO-3-22)

F. Oda, M. Yokoyama, M. Kawai, M. Sobajima, H. Koike  

Kawasaki Heavy Industries, Ltd.

Kawasaki Heavy Industries Ltd. (KHI) has developed a linac-based, compact IR free electron laser device and had installed it in the FEL-SUT (IR FEL Research Center of Science University of Tokyo). The FEL device adopts a combination of an RF gun with a thermionic cathode and an $\alpha$-magnet as an injector. The fundamental design of this RF gun is the /2 mode standing wave structure. It has two accelerating cells and a coupling cell located on the beam axis, so called on axis coupled structure (OCS). Output beam of more than 60pC per bunch (i.e. average current of more than 200mA during the macropulse) was obtained. Momentum distribution of the output beam was also measured with the peak momentum of 1.4 ; 2.0 MeV, and the results have a good agreement with beam dynamics simulations. We also describe a bunch length measurement system using optical transition radiation (OTR).