Multipacting of 325 MHz spoke cavity for Accelerator Driven sub-critical System

This paper discusses a method of calculating the growth rate of the secondary electron number after electron multipacting in the spoke superconductive cavity for Accelerator Driven sub-critical System(ADS) with CST Particle Studio. The result shows that there are two types of multipacting in the spoke cavity above: two-point one order multipacting on the top of the spoke pole and one-point one-order multipacting at the corner of the spoke cylinder face. The crest of the growth rate of multipacting is at the accelerator cavity voltage of 0.65 MV while there is no multipacting when the voltage is higher than 1 MV in the simulation. A comparison about the growth rate curve between two different secondary electron emission coefficients of niobium in the inner face of the cavity is also showed.