Study of Multipacting in a Coaxial Coupler with Bias Voltage for Srf Operation with High Beam Current
Zong-Kai Liu1*, Chaoen Wang1, Lung-Hai Chang1, Mei-Hsia Chang1, Ling-Jhen Chen1, Fu-Tsai Chung1, Ming-Chyuan Lin1, Chih-Hung Lo1, Chi-Lin Tsai1, Ming-Hsun Tsai1, Meng-Shu Yeh1, Tsung-Chi Yu1
1Light Source Division, National Synchrotron Radiation Research Center, Hsinchu, Taiwan
* presenting author:Zong-Kai Liu,
A superconducting radio-frequency (SRF) module is commonly used for a high-energy accelerator; its purpose is to provide energy to the particle beam. Because of the low power dissipation and smaller impedance of a higher-order mode for this module, it can provide more power to the particle beam with better stability through decreasing the couple bunch instability. A RF coupler is necessary to transfer the high power from a RF generator to the cavity. A coupler of coaxial type is a common choice. With high-power operation, it might suffer from multipacting, which is a resonance phenomenon due to re-emission of secondary electrons. Applying a bias voltage between inner and outer conductors of the coaxial coupler might increase or decrease the strength of the multipacting effect. We studied the effect of a bias voltage on multipacting using numerical simulation to track the motion of the electrons. We will present the simulation results and an application for SRF operation with a large beam current.

Keywords: Couplers, Multipacting, Superconducting RF