| | The preparation of the cavity walls has been one of the
major challenges in the superconducting radio-frequency
(SRF) accelerator technology. Therefore, constant
research and development effort is devoted to develop
surface preparation processes that will improve roughness
and lower the level of impurities, like hydrogen or
oxygen, embedded in bulk Nb, having in the same time
reasonable etching rates. Plasma based surface
modification provides an excellent opportunity to achieve
these goals. We present Ar/Cl2 discharge treatment of
bulk Nb where we achieved etching rates comparable to
the rates obtained with the electropolishing method
without introducing impurities in Nb. The current
experiments were performed on disk shaped Nb samples,
exposed to plasma produced in a microwave discharge
system. Surface composition and topology measurements
were carried out before and after plasma treatment. Upon
determining optimal experimental conditions on disk
shaped samples, we will apply the same procedure on the
single cell cavities, pursuing improvement of their RF
performance. | |