Advances in Nb₃Sn superconducting radiofrequency cavities towards first practical accelerator applications

Nb3Sn is a promising next-generation material for superconducting radiofrequency cavities, with significant potential both large scale and compact accelerator applications. However, so far, cavities have been limited to cw accelerating fields <18 MV/m. In this paper, new results are presented significantly higher fields, as high 24 MV/m in single cell cavities. Results also from the first ever Nb3Sn-coated 1.3 GHz 9-cell cavity, full-scale demonstration on cavity type used production European XFEL LCLS-II. together heat dissipation curves emphasize industrial applications using cryocooler-based cooling systems. The studied an atypical shiny visual appearance, microscopy studies of witness samples reveal reduced surface roughness smaller film thickness compared typical films Possible mechanisms increased maximum field discussed well implications physics RF superconductivity low coherence length regime. Outlook continued development presented.