Plasma Processing Of SRF Cavities at Jefferson Lab: Experiment Results and Simulation Insight

TL;DR

This paper reports on plasma processing experiments and simulations at Jefferson Lab aimed at improving SRF cavity performance by optimizing plasma ignition parameters using different gas mixtures and higher-order mode frequencies.

Contribution

It provides new experimental data and simulation insights into plasma ignition processes for SRF cavities, enhancing understanding and optimization of plasma surface treatments.

Findings

Successful plasma ignition at various pressures and gas mixtures.

Simulation results align with experimental data, guiding process optimization.

Identification of key parameters for effective plasma processing.

Abstract

Plasma processing of superconducting radio frequency (SRF) cavities has been an active research effort at Jefferson Lab (JLab) since 2019, aimed at enhancing cavity performance by removing hydrocarbon contaminants and reducing field emission. In this experiment, processing using argon-oxygen and helium-oxygen gas mixtures to find minimum ignition power at different cavity pressure was investigated. Ongoing simulations are contributing to a better understanding of the plasma surface interactions and the fundamental physics behind the process. These simulations, combined with experimental studies, guide the optimization of key parameters such as gas type, RF power, and pressure to ignite plasma using selected higher-order mode (HOM) frequencies. This paper presents experimental data from argon-oxygen and helium-oxygen gas mixture C75 and C100 cavity plasma ignition studies, as well as simulation results for the C100-type cavity based on the COMSOL model previously applied to the C75 cavity.