Stability of superconductors for poloidal field coil application

Experiments were performed where a Cu/CuNi/NbTi mixed matrix conductor is supplied with a transport current and exposed to magnetic field pulses of typically ten milliseconds length and with a dB/dt up to a few hundred Tesla per second. Cooling conditions of the conductor were bath cooling, supercritical helium, and liquid helium in a closed, small volume (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 helium layer due to the transient heat transfer. The proposed model seems to be a useful tool to estimate the stability behaviour with respect to spacially extended heat inputs