NDE of Defects in Superconducting Wires Using SQUID Microscopy

Abstract

Using a scanning Superconducting Quantum Interference Device (SQUID) microscope we have examined small samples of Nb-Ti wire with known defects and a sample with artificial defects. We orient the SQUID to measure the field parallel to the wire, which is near zero unless a defect is present. We also have examined known defects using a multi-channel scanning SQUID microscope. In addition, we have modified the nose cone of our SQUID microscope to enable fast NDE of long wires by positioning a thin tube immediately beneath the SQUID chip, while feeding the wire through the tube.