• S. Popović, M. Rašković, J. Upadhyay, L. Vušković
  ODU, Norfolk, Virginia
• H.L. Phillips, A-M. Valente-Feliciano
  JLAB, Newport News, Virginia

Plasma based surface modification provides an excellent opportunity to eliminate non-superconductive pollutants in the penetration depth region of the SRF cavity surface and to remove mechanically damaged surface layer improving surface roughness. We have demonstrated on flat samples that plasma etching in Ar/Cl₂ of bulk Nb is a viable alternative surface preparation technique to BCP and EP methods, with comparable etching rates. The geometry of SRF cavities made of bulk Nb defines the use of asymmetric RF discharge configuration for plasma etching. In a specially designed single cell cavity with sample holders, discharge parameters are combined with etched surface diagnostics to obtain optimum combination of etching rates, roughness and homogeneity in a variety of discharge types, conditions, and sequences. The optimized experimental conditions will ultimately be applied to single cell SRF cavities.