A computer program to calculate composite conductor losses in pulsed poloidal coil systems

In the design of the cryogenic system and superconducting magnets for a poloidal field system in a tokamak fusion reactor, it is important to have an accurate estimate of the heat produced in the superconducting magnets as a result of the rapidly changing magnetic fields. Until recently, this estimate was obtained by assuming that the field and the time rate of change of the field were constant throughout the coil windings. A more accurate method of estimation involves integrating the losses over the coil windings, thus taking into account the spatial variation of the magnetic field. A computer code, PLASS (Pulsed Losses in Axisymmetric Superconducting Solenoids), has been written to perform this integration. PLASS has been used to analyze the present design for the poloidal coil system of the ORNL Experimental Power Reactor (EPR). This design requires that superconductor hysteresis losses, superconductor coupling losses, stabilizing material eddy current losses, and structural material eddy current losses be taken into consideration in the calculation of conductor losses. A tabulation of individual losses vs variations in superconductor characteristics and coil current changes is presented to demonstrate the parameters which significantly affect the design. Results indicate that the total energy released into the cryogenic system is less than one-half of that predicted by the previously oversimplified calculation.