BARC, Mumbai
JLAB, Newport News, Virginia
BARC-EBC, Mumbai
In recent years, large-grain/single-crystal niobium has become a viable alternative to the standard fine grain (ASTM grain size>6), high purity (RRR ) niobium for the fabrication of high-performance SRF cavities for particle accelerators In this contribution we present the results of a systematic study of the superconducting properties of samples obtained from four Niobium ingots (from CBMM, Brazil) of different purity. Measurements of bulk magnetization, surface pinning, critical temperature and thermal conductivity have been carried out on the samples subjected to different surface treatments such as buffered chemical polishing (BCP), 600C heat treatment, and low temperature baking (LTB). A correlation has been established between the LTB and the ratio of Hc3/Hc2. In addition, the phonon peak in the thermal conductivity data is suppressed by the presence of trapped magnetic vortices in the samples
