Cryogenic rf test of the first plasma etched SRF cavity

TL;DR

This study demonstrates the first cryogenic RF testing of a plasma-etched superconducting RF cavity, showing the potential of plasma etching as an alternative surface processing method for SRF cavities.

Contribution

It introduces a novel apparatus and method for plasma etching of SRF cavities and evaluates its impact on cavity RF performance at cryogenic temperatures.

Findings

Plasma etching can be integrated into SRF cavity processing.

Cryogenic RF tests show the plasma-etched cavity maintains performance.

Segmented plasma processing is feasible for complex cavity geometries.

Abstract

Plasma etching has a potential to be an alternative processing technology for superconducting radio frequency (SRF) cavities. An apparatus and a method are developed for plasma etching of the inner surfaces of SRF cavities. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity is used. The single cell cavity is mechanically polished, buffer chemically etched afterwards and rf tested at cryogenic temperatures for a baseline test. This cavity is then plasma processed. The processing was accomplished by moving axially the inner electrode and the gas flow inlet in a step-wise manner to establish segmented plasma processing. The cavity is rf tested afterwards at cryogenic temperatures. The rf test and surface condition results are presented.