Plasma Chemistry in a High Pressure Gas Filled RF Test Cell for use in a Muon Cooling Channel

Filling an RF cavity with a high pressure gas prevents breakdown when the cavity is placed in a multi-Tesla external magnetic field. A beam of particles traversing the cavity, be it muons or protons, ionizes the gas, creating an electron-ion plasma which absorbs energy from the cavity. In order to understand the nature of this plasma loading, a variety of gas species, gas pressures, dopants, and cavity electric fields were investigated. Plasma induced energy loss, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times were measured. The results for hydrogen, deuterium, helium, and nitrogen, doped with dry air will be presented.