Propagation velocities of normal zones in a forced-flow cooled superconductor

Propagation characteristics of normal zones in a forced-flow cooled superconductor (FFCS) are investigated by analyzing the thermal equilibrium equations. If the amount of energy of a disturbance to which an FFCS is subject is small enough, the conductor recovers to the superconductive state; however, if it is large, a normal zone remains and propagates. The analyses are presented with non-dimensional FFCS constants. Charts to evaluate the propagation velocities are given. For an arbitrary FFCS, one can evaluate the propagation velocities of the normal zone by drawing the straight lines on the charts or referring to the graphs. The behavior of normal zones in FFCS is also investigated. It is shown that, once a normal zone remains and propagates after the FFCS is subject to disturbances, the normal zone keeps spreading and stops spreading only when the conductor current is reduced to zero. Normal zone propagation characteristics of example FFCS's (hollow type and cables-in-conduit type) are also investigated.