Quench pressure, thermal expulsion, and normal zone propagation in internally cooled superconductors

When a nonrecovering normal zone appears in an internally cooled superconductor, the pressure in the conductor rises, helium is expelled from its ends, and the normal zone grows in size. A model of these processes is presented that allows calculation of the pressure, the expulsion velocity, and the propagation velocity with simple formulas. The model is intended to apply to conductors such as the cable-in-conduit conductor of the Westinghouse LCT (Large Coil Task) coil, the helium volumes of which have very large length-to-diameter ratios (3×10⁵). The predictions of the model agree with the rather limited data available from propagation experiments carried out on the coil