High etching rates of bulk Nb in Ar/Cl2 microwave discharge

Niobium is the material of choice for production of superconducting radio frequency cavities used in linear particle accelerators. In this study, plasma etching of bulk Nb is performed on the surface of disk shaped samples with the goal of eliminating non-superconductive pollutants in the penetration depth region and mechanically damaged surface layer. We have demonstrated that, in the microwave glow discharge, the etchings rates of 1.5 ?m/min can be achieved using Cl2 as reactive gas. The influence of plasma parameters such as input power, pressure, and concentration of the reactive gas on the etching rates is determined.