Simulation of beam-induced plasma in gas-filled rf cavities

TL;DR

This paper uses advanced numerical simulations with the SPACE code to study plasma processes in high-pressure gas-filled RF cavities interacting with proton beams, supporting experimental efforts and muon cooling device design.

Contribution

It demonstrates the use of the SPACE simulation code to accurately model plasma dynamics in RF cavities, validated against experimental data, aiding muon cooling device development.

Findings

Simulations match experimental plasma loading measurements.

Quantified plasma properties like recombination rates and electron attachment times.

Validated predictive capability of the SPACE code for muon cooling applications.

Abstract

Processes occurring in a radio-frequency (rf) cavity, filled with high pressure gas and interacting with proton beams, have been studied via advanced numerical simulations. Simulations support the experimental program on the hydrogen gas-filled rf cavity in the Mucool Test Area (MTA) at Fermilab, and broader research on the design of muon cooling devices. SPACE, a 3D electromagnetic particle-in-cell (EM-PIC) code with atomic physics support, was used in simulation studies. Plasma dynamics in the rf cavity, including the process of neutral gas ionization by proton beams, plasma loading of the rf cavity, and atomic processes in plasma such as electron-ion and ion-ion recombination and electron attachment to dopant molecules, have been studied. Through comparison with experiments in the MTA, simulations quantified several uncertain values of plasma properties such as effective recombination rates and the attachment time of electrons to dopant molecules. Simulations have achieved very good agreement with experiments on plasma loading and related processes. The experimentally validated code SPACE is capable of predictive simulations of muon cooling devices.