Test of thin-film samples

This study evaluates the superconducting radio-frequency (SRF) performance of alternative materials to niobium for accelerator cavities. Using the Quadrupole Resonator (QPR) at Helmholtz-Zentrum Berlin (HZB), four different Nb₃Sn and Nb-on-Cu samples, fabricated by various collaboration partners, were tested at cryogenic temperatures. The results showed that Nb₃Sn films from INFN Legnaro exhibited the best performance, with a low surface resistance (~25 nΩ at 4K) and strong flux expulsion. The STFC sample demonstrated lower uniformity and higher resistance (~90 nΩ), indicating contamination issues. Siegen University’s Nb-on-Cu coating achieved excellent RF properties, confirming its readiness for application. In contrast, the HZB bronze-route Nb₃Sn-on-Cu sample suffered from stoichiometric inconsistencies and high surface resistance (~76 nΩ at 2K), requiring further process refinements. These findings provide crucial insights for
optimizing alternative SRF material deposition techniques for future accelerator applications.