• A.E. Gustafsson, S. Calatroni, W. Vollenberg
  CERN, Geneva
• R. Seviour
  Cockcroft Institute, Lancaster University, Lancaster

Nio­bi­um thin film cav­i­ties have shown good and re­li­able per­for­mance for LEP and LHC, al­though there are lim­i­ta­tions to over­come if this tech­nique should be used for new ac­cel­er­a­tors such as the ILC. New coat­ing tech­niques like High Power Im­pulse Mag­netron Sput­ter­ing (HiP­IMS) has shown very promis­ing re­sults and we will re­port on its pos­si­ble im­prove­ments for Nb thin film cav­i­ty per­for­mance. Cur­rent ma­te­ri­als used in ac­cel­er­a­tor SRF tech­nolo­gies op­er­ate at tem­per­a­tures below 4 K, which re­quire com­plex cryo­genic sys­tems. Re­searchers have in­ves­ti­gat­ed the use of High Tem­per­a­ture Su­per­con­duc­tors (HTS) to form RF cav­i­ties, with lim­it­ed suc­cess*. We pro­pose a new ap­proach to achieve a high-tem­per­a­ture SRF cav­i­ty based on the su­per­con­duct­ing 'prox­im­i­ty ef­fect'**. The su­per­con­duct­ing prox­im­i­ty ef­fect is the ef­fect through which a su­per­con­duct­ing ma­te­ri­al in close prox­im­i­ty to a non-su­per­con­duct­ing ma­te­ri­al in­duces a su­per­con­duct­ing con­den­sate in the lat­ter. Using this ef­fect we hope to over­come the prob­lems that have pre­vent­ed the use of HTS for ac­cel­er­at­ing struc­tures so far. We will re­port the pre­lim­i­nary stud­ies of mag­netron sput­tered thin films of Cu on Nb.

* E. J. Minehara et al, Superconductivity 3, p277 (1990)
** R. Seviour et al, Superlattices and Microstructures, 25, p647 (1999)