Coupled eddy current and thermodynamic analysis with the SPARK code

In order to accurately model the dynamic response of the Compact Ignition Tokamak (CIT) toroidal field (TF) coil system, it became necessary to include the temperature dependence of both the electrical resistivity and the heat capacity of the conducting material. Because of the Bitter-type design of the TF system, the coil currents undergo a significant redistribution during normal operation. The eddy current code SPARK was modified to incorporate a loop voltage driver option and the primary magnetodynamic differential equations were augmented by a set of differential equations representing the adiabatic thermal response driven by the resistive power dissipation. The modifications necessary for dynamically solving the coupled electrical and thermal systems of equations are described. Both a SPARK 1.2 model and a SPARK 2.0 model were analyzed in this manner. The models are briefly described. Additional modifications were also included to model the nuclear power dissipation and the current clamping of the power supply. The resulting temperature and Lorentz loads at the nodes of the model are in compatible form with the codes employed in the corresponding structural analysis. The results produced by the modified SPARK code are in good agreement with the original modeling by U.R. Christensen (Proc IEEE Thirteenth Symp. Fus. Eng., p.1142)