Ciovati, G. Dhakal, P. Kneisel, P. Myneni, G.R. Spradlin, J.K. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-MOPB001 English 61-65 MOPB001 cavity SRF vacuum operation radio-frequency Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-MOPB001 http://srf2015.vrws.de/papers/mopb001.pdf Superconducting radio-frequency cavities made of ingot niobium with residual resistivity ratio (RRR) greater than 250 have proven to have similar or better performance than fine-grain Nb cavities of the same purity, after standard processing. The high purity requirement contributes to the high cost of the material. As superconducting accelerators operating in continuous-wave typically require cavities to operate at moderate accelerating gradients, using lower purity material could be advantageous not only to reduce cost but also to achieve higher Q0-values, because of the well-known dependence of the BCS-surface resistance on mean free path. In this contribution we present the results from cryogenic RF tests of 1.3-1.5 GHz single-cell cavities made of ingot Nb of medium (RRR=100-150) and low (RRR=60) purity from different suppliers. Cavities made of medium-purity ingots routinely achieved peak surface magnetic field values greater than 70 mT with Q0-values above 1.5·10¹⁰ at 2 K. The performance of cavities made of low-purity ingots were affected by significant pitting of the surface after chemical etching.