STABILITY AND PROTECTION OF AG BSCCO MAGNETS OPERATED IN THE 20-40-K RANGE/

The rate of growth of normal zones has been calculated for Ag/BSCCO co mposites operated in the 20-40 K range. Formulae are presented for the propagation velocity and for the normal zone voltage as a function of the hot spot temperature. These formulae take into account the strong temperature dependence of the specific heats of silver and BSCCO, as well as the temperature dependences of the thermal conductivity and re sistivity of silver. In spite of very slow propagation (of the order o f 1 cm s-1), normal zone voltages seem adequate to allow the detection of normal zones before the conductor overheats. Finally, a formula fo r estimating the minimum quench energy is proposed. Estimates based on this formula indicate that potted magnets wound with Ag/BSCCO conduct ors should not train.