Monitoring and controlling TORE SUPRA toroidal field system status after a year of operating experience at nominal current

The superconducting toroidal field system of TORE SUPRA stands out as one of the major aspects of this Tokamak. The system was tested in November 1989 at up to 1455 A (4.5 T on the plasma axis), followed by operation for a year. During this period, special attention was paid to system monitoring. Five detection systems acting independently ensure the reliability of the safety system in case of resistive transition. Classical differential voltage detection plays an important part. In addition, experience has been gained on the thermal behavior of a coil in case of local heating, providing a practical basis for overpressure and temperature increase detection. The quench of coil BT4 due to nuclear radiation in December 1989, following a severe plasma disruption at 1.9 MA, demonstrates the ability of the safety system to efficiently detect the transition and to limit the energy dissipated inside the coil through a low voltage oriented discharge.