STABILITY ANALYSIS OF A FORCED-FLOW COOLED SUPERCONDUCTING COIL - NUMERICAL-SIMULATION OF MULTIPLE STABILITY

The stability of a forced-flow cooled superconducting coil is investigated by use of numerical simulation. A numerical code to integrate the simultaneous partial differential equation system composed of the 1D hydrodynamic equations and the 1D thermal conduction equation has been developed. By using the code, stability margins are evaluated as functions of coolant mass flow rate, operation current and imposed magnetic field. The results of computations show that the stability margin is multivalued with respect to these operation parameters, as expected from the experimental results. It is also shown that the appearance of the first unstable regime is closely related to the existence of the stagnant region located on the upstream side of the heated zone and that the second stable regime appears because the heat transfer is appreciably enhanced by the induced fast backflow due to the thermal expansion of coolant.