Superconducting niobium thin film sputtering onto copper quarter wave resonators for heavy ion accelerators

Niobium sputtered copper quarter wave resonators (QWRs) represent an innovative and promising alternative to lead electroplated copper cavities, or to those made of niobium, both bulk and explosively bonded on copper. The authors describe the R&D efforts of the first niobium sputtered copper prototypes. The results obtained and the progressive improvements achieved test by test make Nb sputtered QWRs an intriguing possibility for the acceleration of heavy ions whenever the need for changing from Pb to Nb is encountered. A prototype with a Q-value of 7*10/sup 8/ and maximum accelerating field of 4 MV/m has been produced.<
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