Simulations of Waveguide Breakdown

Future neutrino experiments will require neutrino beam intensities beyond the capabilities of today's sources. These experiments will require high-energy neutrinos from muon decay. The muons need to be cooled, and, in order to reduce costs, the number of cooling elements should minimized. However, breakdown of the accelerating cavities is expected to limit the performance of any proposed beam system. This project will help researchers use simulation to understand the breakdown of metallic structures planned for muon beam systems, enabling them to reduce the length and thereby the cost of future accelerators. It will implement new physics algorithms relevant to breakdown and add them to an existing library of routines developed to model plasma/material interactions. The project will also make existing codes easier to use for non-experts.The Phase I project successfully modeled breakdown with parameters relevant to present muon cooling systems using two well-known commercial particle-in-cell codes. It also improved the user interface to one of the codes by improving the parallel computing features, allowing users to get answers more quickly. The work demonstrated the utility of these code enhancements by successfully modeling breakdown near a micron-sized surface imperfection with applied magnetic field for conditions similar to copper cavities presently being tested by muon collider researchers. The Phase II project will extend the physics algorithms improvements and improvements to the code user interface. Commercial Applications and other Benefits as described by the awardee: Routines implemented here, such as plasma radiation effects and models of multiple ionization processes, are important to the Air Force community and to researchers developing more energy-efficient commercial lighting.