STABILITY OF SUPERCONDUCTORS IN RAPIDLY CHANGING MAGNETIC-FIELDS

The stability behaviour of low loss Cu/CuNi/NbTi mixed matrix conductors in rapidly changing magnetic fields was investigated. The test conductors are supplied with a transport current and exposed to half cycle sinusoidal field pulses, typically of length 10 ms and a dB/dt value up to a few hundred tesla per second. Cooling conditions of the conductor were pool boiling, supercritical helium and liquid helium in a closed, small volume (for the case of a cable in conduit conductor). The stability limit is mainly determined by the transient heat transfer during the pulse. A stability model is developed which compares the energy coupled into the conductor by the field pulse with the energy which can be absorbed by the surface near the helium layer due to the transient heat transfer. The proposed model seems to be a useful tool with which to estimate the stability behaviour with respect to spatially extended heat inputs. © 1990.