Sadayuki Okada

Numerical analysis of thermal stability of an immersion-cooled, pancake type superconducting coil☆

Abstract A numerical analysis of the thermal stability of an immersion-cooled, single pancake type superconducting coil has been carried out, taking into account transient boiling heat transfer and the temperature dependence of the physical properties of the superconducting composite. The unsteady heat conduction equation, with source terms allowing for heat conduction through an electric insulation film, thermal disturbance, heat transfer and Joule heat generation, has been solved by a control volume finite method. The stability limit of the variable property solution (VPS) is compared with that of the constant property solution (CPS). The result shows that the VPS is 1.5 times as large as the CPS. Also, the effects of the transport current density and the magnetic flux density on the stability of the superconducting coil are clarified.

Visualization of thermal disturbance and quench propagation in an immersion-cooled superconducting coil in liquid helium

Abstract Thermal disturbance and quench propagation have been visualized byutilizing attenuation of the luminous energy of reflected light from the interface of conductor surface and liquid helium. The results of optical measurement with a high-speed video system were in very close agreement with the measured time history of tap voltages and temperatures on the test coil. The visualizability and luminous attenuation characteristics were examined for various conditions.