Resonant-frequency discharge in a multi-cell radio frequency cavity

Abstract

We are reporting experimental results on a microwave discharge operating at resonant frequency in a multi-cell radio frequency (RF) accelerator cavity. Although the discharge operated at room temperature, the setup was constructed so that it could be used for plasma generation and processing in fully assembled active superconducting radio-frequency cryo-module. This discharge offers a mechanism for removal of a variety of contaminants, organic or oxide layers, and residual particulates from the interior surface of RF cavities through the interaction of plasma-generated radicals with the cavity walls. We describe resonant RF breakdown conditions and address the issues related to resonant detuning due to sustained multi-cell cavity plasma. We have determined breakdown conditions in the cavity, which was acting as a plasma vessel with distorted cylindrical geometry. We discuss the spectroscopic data taken during plasma removal of contaminants and use them to evaluate plasma parameters, characterize the process, and estimate the volatile contaminant product removal. V

Insight into reactive oxygen plasma characteristics and reaction mechanism on SRF accelerator plasma cleaning

“…In recent years, the reactive oxygen plasma cleaning technique has become an effective method to remove hydrocarbon contaminant from the surface of the SRF cavity. This technique is particularly beneficial because it can be used for in-situ cleaning [15,16]. So far, many research groups have successfully applied plasma cleaning technique to clean the SRF cavities.…”

“…The reactive oxygen plasma cleaning technique has been demonstrated to be highly effective in eliminating hydrocarbon contaminant, achieving notable successes across a range of SRF accelerator facilities [16,[21][22][23]. However, along with the expansion of engineering applications, some fundamental scientific problems have been gradually exposed, such as the mechanism of plasma-hydrocarbon interaction, surface reaction kinetic, cleaning process optimization, oxide growth, etc.…”