IPAC'23 - Student Poster Session Guide

IPAC’23 / STUDENT POSTER SESSION GUIDE 38 Student Poster Session Mechanical Polishing of Nb3Sn Thin-Film Cavities Eric Viklund (Northwestern University) . David Burk, Sam Posen (Fermi National Accelerator Laboratory), David Seidman (Northwestern Uni- versity). Nb3Sn superconducting radiofrequency (SRF) cavities have been an ongoing research topic for many years motivated by the potential for higher accelerating gradients and quality fac- tors compared to niobium SRF cavities. The highest performing Nb3Sn cavities are manufac- tured using tin vapor-diffusion coating, which creates a Nb3Sn film with a surface roughness of around 100-200 nm. This is thought to be one of the limiting factors for the accelerating gra- dient of Nb3Sn cavities due to enhancement of magnetic field near sharp surface features. To smooth Nb3Sn SRF cavities, we have developed a mechanical polishing procedure which uses centrifugal barrel polishing to smooth the surface followed by a secondary tin coating step to repair the surface. We show that the accelerating field of a Nb3Sn SRF cavity is improved by ap- plying this procedure. We also investigate the quench mechanism of the polished cavity by uti- lizing temperature mapping to measure which regions of the cavity experience heating during RF operation. We then cut samples from these regions and analyze the film microstructure and chemical composition in 3D using EDS and EBSD measurements together with a focused ion- beam (FIB) tomography technique. SUPM069 The Collaborative Effects of Intrinsic and Extrinsic Impurities in Low RRR SRF Cavities Katrina Howard (University of Chicago) . Anna Grassellino, Daniel Bafia (Fermi National Accelerator Laboratory), Young-Kee Kim (University of Chicago). The superconducting radio-frequency (SRF) community has shown that introducing certain im- purities into high-purity niobium can improve quality factors and accelerating gradients. We question why some impurities improve RF performance while others hinder it. The purpose of this study is to characterize the impurity profile of niobium with a low residual resistance ratio (RRR) and correlate these impurities with the RF performance of low RRR cavities so that the mechanism of impurity-based improvements can be better understood and improved upon. The combination of RF testing and material analysis reveals a microscopic picture of why low RRR cavities experience low temperature-dependent BCS resistance behavior more prominent- ly than their high RRR counterparts. We performed surface treatments, low temperature baking and nitrogen-doping, on low RRR cavities to evaluate how the intentional addition of oxygen and nitrogen to the RF layer further improves performance through changes in the mean free path and impurity profile. The results of this study have the potential to unlock a new under- standing on SRF materials and enable the next generation of SRF surface treatments. SUPM070 Manufacturing and Testing of the 800 MHz RFQ at KAHVE-Lab Atacan Kilicgedik (Marmara University) . Aslihan Caglar (Yildiz Technical University), Aytul Adiguzel, Seyma Esen (Istanbul University), Birant