Simulation on a Photocathode-based Microtron Using a 3D PIC Code

Abstract

The Korea Atomic Energy Research Institute (KAERI) has used a microtron accelerator basedon a thermionic cathode for operating a compact terahertz (THz) FEL, where the electrons areemitted and accelerated automatically during the radio-frequency (RF) macro-pulse over thresholdpower for their emission. Usually a thermionic cathode is embedded inside the microtron cavity forelectron-beam emission, and at the same time acceleration is due to the input RF source. In thiscase, the accelerator scheme is simple, but just a fraction of the emitted electrons are accelerated,and the electron bunch length is uncontrollable due to the RF phase condition for acceleration. In this paper, a photocathode-based microtron which is able to produce high peak (∼100 A) andultrashort (∼1 ps) electron bunch is studied to adapt it for an electron injector of a THz generator. Especially, we analyzed the electron beam dynamics along the accelerating trajectory with a 3DPIC-code to find the optimized RF phase and laser input time.