Quench and safety tests on a toroidal field coil of TORE SUPRA

As a part of the safety analysis of the magnet, results of three quenches initiated in one of the toroidal-field (TF) coils are reported and discussed. While transporting a given current, the coil is insulated from the refrigerator, and the temperatures of the helium and of the coil increase slowly due to thermal losses. At the current sharing temperature a quench rapidly propagates and the protection system makes the coil discharge into the dump resistor. Electrical, hydraulic, and thermal measurements were performed at three different current levels to confirm the safety concepts in use in the TORE SUPRA design. Using these results it has been possible to gain further information about the quench propagation inside the coil. Moreover, the hydraulics of the helium evacuation circuit has been investigated in detail by pressure and temperature sensors installed along the external cryogenic circuit of the coil. Measurements of pressures and flow rate during quenches have led to a better understanding of the behavior of the different safety valves and have provided characteristics to calculate the maximum pressure inside the coil in case of quench.