SuRF:Three-Dimensional Self-Consistant Simulations of Multipacting in Superconducting Radio Frequencies

Superconducting radio frequency (SRF) accelerator cavities lose power to stray electrons, especially when the electron motion is in resonance with the fields and the electrons strike the cavity surface repeatedly (multipacting). One of the main tools for studying multipacting is numerical simulation, but none of the existing codes has sufficiently realistic models of all the physical processes. One main limitation of present modeling approaches is the lack of three-dimensionality. A related need is for parallel computing to handle the increased computational requirements of running in three dimensions. Typically, new designs for SRF cavities are tested by building physical prototypes and examining their performance. This practice renders the use of a large variety of different geometries (for different accelerating sections) problematic, due to the high cost of prototyping the different designs. This project will add needed models and features to the VORPAL plasma simulation code so it can function as a virtual prototyping tool for understanding multipacting in SRF cavities. Phase I demonstrated that VORPAL¿s higher-order conformal boundary algorithms and flexible interface could be used to accurately model the electromagenetic fields in typical SRF cavities. Phase II will fully integrate the field emission and secondary electron emission routines with the conformal boundaries in VORPAL. Diagnostics will be added, VORPAL¿s post-processing tools will be improved to measure common quantities used by SRF researchers, and VORPAL¿s interface will be simplified to make it easier to specify SRF cavity geometries. Commercial Applications and other Benefits as described by the awardee: In addition to the application for Nuclear Physics accelerators, SRF cavities are major component of free electron lasers. Consequently, the new design tool for SRF cavities should provide low cost prototyping for industries that use free electron lasers, such as defense and surface processing.