Numerical simulation of the stability in a cable-in-conduit conductor developed for fusion-magnet applications

The stability margins of the US-Demonstration Poloidal Coil (US-DPC) and the International Thermonuclear Experimental Reactor (ITER) TF coils have been modeled numerically using the computer program CICC. The computed US-DPC limiting current, I{sub lim}, compares favorably with the values determined experimentally. Using the detailed program CICC output, we investigated the DPC quench initiation mechanism in each of the three stability regions. In the ill-cooled region, the imposed heat pulse heats the conductor to the current-sharing temperature, T{sub cs}. In the transition region, the resistance heating after the pulse must be strong enough to overcome the induced flow reversal. In the well-cooled region, good heat transfer heats the helium during the pulse. After the pulse, these high helium temperatures along with poor heat transfer cause the conductor to quench. Changes in I{sub lim} agree with Dresner's relationship. I{sub lim} can be improved by decreasing the copper resistivity, the helium fraction, or the conductor diameter. Preliminary results show the ITER and TF coil operating point is in the well-cooled region. 10 refs., 7 figs., 1 tab