Stability characteristics of a cable-in-conduit conductor by subcooled supercritical helium

The stability and limiting current of a NbTi forced-cooled superconducting coil have been investigated experimentally and analytically at the subcooled condition below 4.5 K. The test coil was wound in a one layer solenoid from a cable-in-conduit type conductor of critical current of 5.1 kA at 4.2 K and 6.5 T, whose total length was 10 m. It was installed in the bore of a back-up superconducting magnet that provided field 8 T at the test coil. The stability margin of the coil as a function of normalized current (transport current/critical current) were measured. The results are compared with the formula proposed by Dresner and reported to predictions of stability margin and limiting current at subcooled condition below 4.5 K