Studies of electron activities in SNS-type superconducting rf cavities

During vertical testing of SNS superconducting RF cavities, a lot of electron activity was observed. This could be evidence of in-cell multipacting, cell to cell electron mitigation or near-axis dark current. To study the potential for these electron activities in SRF cavities, a multi-purpose electron tracking code (FishPact) was developed based on the Poisson/Superfish Field solvers. Electron trajectories between the impacts in both medium-β and high-β cavities are tracked under varying accelerating gradient (Eacc), RF phases, and emission locations. It is found that the high beta cavities show a greater propensity for potential sources of dark current than their medium beta counterparts. It is further proposed that field emission induced multipacting is a potential, though rare, source of further Q0 degradation