High Resolution and Fast Scanning Speed SQUID Based Nondestructive Inspection System of Niobium Sheets for SRF Cavities

High energy physics accelerators and instruments in other fields require the use of thousands of superconducting radio frequency (SRF) cavities that are made of high purity niobium (Nb) material. The purity of Nb is critical for these cavities to reach the highest accelerating fields. Tantalum (Ta) is the most prolific of metal contaminants, can cause thermal breakdown, and can prevent the cavities from reaching their theoretical performance limits. Therefore, DOE Labs are searching for a technology that could detect small impurities in superconducting Nb. This project will develop an innovative superconducting quantum interference device (SQUID)-based nondestructive system that can scan Nb sheets used in the manufacturing of SRF cavities with both high speed and high resolution. The Phase I project modified an existing SQUID-based eddy current system to detect 100-micron size Ta defects. The Phase II project will prototype a working system capable of scanning 30cm x 30cm Nb sheets and detecting Ta defects down to 25 microns in less than 15 minutes. It will deliver a modern prototype scanning system, with fully integrated hardware and software, as a complete instrument for DOE lab users and for commercialization. Commercial Applications and other Benefits as described by the awardee: The SQUID-based scanner will help reach the highest accelerating field in SRF cavities and will provide a considerable cost reduction for new accelerators and for upgrades of existing accelerators. The SQUID-based scanner will also be useful for the detection of defects on the surface, inside the bulk, or at the back side of metallic sheets in other industries.