Study on new niobium material for cost-reduction of superconducting cavities and the results of vertical test measurement

The cost-reduction method of fabricating niobium superconducting cavities has much importance in spreading and applying superconducting accelerators. Cavity Fabrication Facility (CFF) in KEK is working on fabricating cavities with lower cost niobium material that can achieve higher performance. Last fiscal year, niobium materials from different companies were smelted by ULVAC, and cavity fabrication was done in CFF. One is fine-grain single-cell cavity (KEK-R12), and others are large-grain 3-cell cavities (KEK-R16, R16b, R17 and R17b). We will report the progress of surface treatments and the vertical test results of these 5 cavities. (author)