Nb3Sn Deposition for RF Analysis

Increasingly, superconducting radio-frequency (SRF) technology is replacing conventional copper radio frequency (RF) technology in new and upgraded particle accelerators. SRF cavities consume less power than conventional cavities to produce a given accelerating gradient, leading to smaller accelerators and higher beam energies. Currently, niobium is the only superconductor in wide usage by the SRF community. Other superconductors ¿ e.g., those with higher values for critical temperature and critical magnetic field, such as compounds of niobium, A-15 superconductors (Nb3Sn, V3Ga and Mo3Re), and MgB2 ¿ may replace niobium, but these materials are not structural and thus cannot be formed into cavity structures directly. One approach is to coat a cavity made from a conventional conductor such as copper with a thin superconducting film. However, the techniques used to deposit these materials rely on high temperature process steps to produce the microstructure necessary for high quality films. These processing temperatures are well above the thermal limits for copper, the preferred structural material for thin film SRF cavities. This project will utilize a high-energy cathodic-arc-based process to deposit Nb3Sn onto coupon substrates without the need for high temperature heating. The RF performance of the films will be characterized to determine whether Nb3Sn can replace niobium in future SRF particle accelerators.