Progress with Nb Hipims Films on 1.3 GHz Cu Cavities

Abstract

In recent years, efforts have been invested to leverage the different processes involved in energetic condensation to tailor Nb film growth in sequential steps. The resulting Nb/Cu films display high quality material properties and show promise of high RF performance. The lessons learned are now applied to 1.3 GHz Nb on Cu cavity deposition via high power impulse magnetron sputtering (HiPIMS). RF performance is measured at different temperatures. Particular attention is given to the effect of cooldown and sensitivity to external applied magnetic fields. The results are evaluated in light of the Nb film material and superconducting properties measured with various microscopy and magnetometry techniques in order to better understand the contributing factors to the residual and flux induced surface resistances. This contribution presents the insights gained in exploiting energetic condensation as a path towards RF Q-slope mitigation for Nb/Cu films, correlating film material characteristics with RF performance.