  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 &#61616;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.
