Effect of Electropolishing on Nitrogen Doped and Undoped Niobium Surfaces

TL;DR

This study investigates how electropolishing temperature affects the surface quality of nitrogen-doped and undoped niobium, revealing temperature-sensitive surface pitting and features relevant for superconducting RF cavity performance.

Contribution

It provides a systematic analysis of electropolishing temperature effects on N-doped and undoped niobium surfaces, highlighting temperature-induced pitting and surface feature variations.

Findings

Higher EP temperatures increase surface pitting in N-doped niobium.

N-doped surfaces are more susceptible to temperature effects during EP.

Detailed surface features vary with electropolishing temperature.

Abstract

Cold electropolishing (EP) of a nitrogen-doped (N-doped) niobium (Nb) superconducting RF (SRF) cavity was found to improve its quality factor. In order to understand the effect of EP temperature on N-doped and undoped surfaces, a systematic EP study was conducted with 2/0 N-doped and heat-treated Nb samples in a beaker. The Nb samples were electropolished at different surface temperatures ranging from 0 to 42 C. The results showed that the doped surface was susceptible to the sample temperature during EP. EP resulted in the surface pitting on the doped samples where the number density of pits increased at a higher temperature. The surface results were compared with the surface of cutouts from a 9-cell cavity which was 2/0 N-doped and electropolished. This paper shows de-tailed surface features of the N-doped and undoped Nb surfaces electropolished at different temperatures.