Commissioning of Vacuum Furnace and First Successful Heat Treatment of SRF Bulk Nb Cavities at IPN Orsay

A new vacuum furnace dedicated to high temperature heat treatment under vacuum (VH2T2) of superconducting radio frequency (SRF) bulk Nb cavities was developed, and operated. This furnace will be used for interstitial hydrogen removal (10h00@ 650 °C) of ~26 spoke 352 MHz ESS cavities. We commissioned the furnace in May 2016: all the measured parameters of the intrinsic performances (i.e., residual pressure, thermal performance) are better than the specified values. Prior to applying VH2T2 to SRF cavities various qualification tests were performed on several samples: RRR, SIMS analysis, mechanical, and thermal properties at cryogenic temperature (as received samples versus VH2T2 samples). After the successful qualification, we performed VH2T2 at 650 °C on various bulk Nb SRF cavities (i.e., 1.3 GHz elliptical resonators and 352 MHz spoke resonators). All these heat treatments were successful. In this paper, we will report about: 1) furnace commissioning and qualification tests on samples, 2) RF tests of VH2T2 cavities.