Z.FANG, S.FUKUDA, S.YAMAGUCHI, S.ANAMI (KEK)
The high power 324 MHz klystron is being developed as the microwave source of the 200 MeV Linac of the KEK/JEARI Joint Project for high-intensity proton accelerator facility. However during the high voltage processing of the first prototype a strong spurious oscillation occurred without any driving input power. After some investigation, this oscillation was identified due to the back-going electrons from the collector. In order to analyze the fundamental mechanism of the oscillation due to the back-going electrons and to design a suitable collector of klystron, a new simulation code of back-going electrons from a collector has been developed. It consists of three parts: 1) calculation of dispersion of incident electron beam in the collector: 2) simulation of back-going electrons resulted from multi-scattering using the EGS4 Monte Carlo method: 3) plotting of electron trajectories. Space-charge forces, relativistic effects, self and external magnetic fields, are considered. Back-going electron coefficient and energy distribution are outputted as simulation results. Using this simulation code, the oscillation conditions are understood, and a proper collector could be proposed. Some of simulation results will be presented in this paper.
Comments or Questions to