Detection of hermetic defects in HTS wire

There are important applications of HTS in which the wire comes into direct contact with liquid coolants. If the coolant penetrates into the wire filaments through small leakage paths then a catastrophic failure may result upon warming of the wire as the liquid rapidly expands into a gas. It is therefore desirable to have a simple nondestructive test for hermeticity of long lengths of tapes. A number of tests for detecting hermetic defects with an emphasis on their feasibility within a manufacturing context are considered. The most promising technique is a colormetric test using ammonia as a tracer gas. We correlate results from colormetric tests with pressurized liquid nitrogen testing.