High-gradient RF box cavity breakdown simulations using 3-D particle tracking code VORPAL

Researchers are designing next-generation accelerator cavities that will provide high-gradient electric fields, on the order of 50 MV/m, and strong magnetic fields (~3T), which are desired in the operation of muon colliders and neutrino experiments. However, the metallic breakdown processes occur in these cavities limit the possibilities of achieving such high gradient electric and strong magnetic fields. Hence it becomes important to understand in detail the metallic breakdown processes occurring in these cavities when operating under high gradient electric fields and strong magnetic fields. In this work, we develop a three-dimensional computational model to study the rf breakdown processes in detail using particle-in-cell (PIC) code VORPAL. We use the 805 MHz rf box cavity for this study which is actively under development by the Muon Collaboration. The self-consistent breakdown model considers both the field-emitted electrons and the secondary electrons emitted from the metallic surfaces and tracks them in detail. We investigate the effects of high gradient electric fields, magnetic field strength, and the magnetic field orientation in the operation of 805 MHz rf box cavity. In addition, we provide detailed VORPAL simulation results such as particle distributions and particle impact energies.