Multipacting Behavior Research in a PEFP Low-Beta Superconducting RF Cavity and in a PEFP Fundamental Power Coupler

Abstract

A low-beta superconducting radio-frequency (RF) cavity has been designed to accelerate a proton beam at an energy above 100 MeV at 700 MHz in the linac of the Proton Engineering Frontier Project (PEFP) and its extended project. Each low-beta superconducting cavity is composed of 5 cells and has a fundamental power coupler (FPC) to transfer the RF power from the klystron to the proton beam. The performance of the superconducting cavity and the FPC may be limited due to electron multipacting on the walls of the cavity, in the coaxial line, or in the RF window. In order to predict and prevent multipacting harm to a PEFP low-beta cavity and a FPC, we used MultiPac 2.1 for Windows to research the multipacting behaviors in those RF structures. By calculating the multipacting electron trajectories, the threshold values for the occurring multipacting and the nal energy of the secondary electron, we identi ed the location of multipacting occurrence and the power threshold. A reasonable design was obtained to prevent multipacting in the FPC.