Computational analysis of MP activation and suppression in 325 MHz FPC

A 325 MHz RF Fundamental Power Coupler (FPC) designed to operate under 20 kW CW in the high energy SC Linac of the RAON. One of the most important consideration in the FPC EM design is to reduce and eliminate a multipacting (MP) activation in both TW mode and SW mode. Prior to the MP reduction design, the MP bands of the FPC was computed with CST Particle Studio. It was confirmed that third or higher order of MP bands were activated within the operating range on the surface condition of the coupler. Therefore, designs to suppress MP are needed. To eliminate MP, a DC voltage was applied to center conductor of the FPC. Detailed the simulation modeling and computational analysis results where MP was effectively suppressed for both modes are presented.