NORMAL-ZONE PROPAGATION PROPERTIES IN BI-2223 AG SUPERCONDUCTING MULTIFILAMENT TAPES/

It is expected that the normal-zone propagation of a high-temperature superconductor (HTS) is slower than that of a low-temperature supercon ductor (LTS) because of its large heat capacity. If the normal-zone pr opagates too slowly, hot spots will develop, possibly resulting in per manent conductor damage. Accordingly, there is a need to measure propa gation quantitatively for designing HTS magnets. This paper describes the electromagnetic and thermal behavior of Bi-2223/Ag superconducting multifilament tapes during normal transition by conduction cooling. S ome experiments were carried out under the conditions of operating tem perature at 10-40 K and transport current as parameters in a zero magn etic field. Sample tapes were transited normally with a heater to init iate a quench. The voltage and temperature properties corresponding to normal transition were measured by voltage taps and thermocouples att ached to the sample tapes. We also calculated longitudinal and transve rse-direction normal-zone propagation velocities from the voltage and temperature traces. In the case of conduction cooling, we investigated the cooling effect due to the length of the sample tape because its c ooling condition is different from the case of using a coolant-for exa mple, liquid helium. (C) 1998 Published by Elsevier Science Ltd. All r ights reserved.