QUALITY ASSURANCE AND ACCEPTANCE TESTING OF NIOBIUM MATERIAL FOR USE IN THE CONSTRUCTION OF THE FACILITY FOR RARE ISOTOPE BEAMS (FRIB) AT MICHIGAN STATE UNIVERSITY (MSU)

Niobium is the current material of choice for the fabrication of superconducting radio frequency (SRF) cavities used in SRF based accelerators. Although niobium specifications for this application have been well established, material properties of as-received materials can still vary substantially. Required for the FRIB accelerator, $13.2M of niobium materials (sheet, tube, and flange) have been contracted to several niobium vendors. The FRIB cavity designs require very large niobium sheets, increasing the difficulty in fabrication and potential for contamination. FRIB has developed and initiated plans to control niobium specifications and perform incoming acceptance checks to ensure quality is maintained. Acceptance results from several niobium shipments will be presented, looking at several production lots from the same vendor and across multiple vendors. Non-conforming results were observed and will be discussed including follow-up investigations and mitigation strategies to improve quality of future shipments.