The TORE SUPRA Cryogenic System Behaviour During Long Plasma Discharges with a High Injected Energy

摘要

After the CIEL project completion including the upgrade of the plasma facing components and the water cooling system, the superconducting Tore Supra Tokamak achieved a world record of injected energy (1.1 GJ), during long duration (6 min) plasma discharges, which was enabled by the upgrade of the transfer system capacities, but also by the steady state toroidal field. The Tore Supra cryogenic refrigerator enables the toroidal field coils to be operated at nominal current along the full daily plasma operation shift. It has capacities of 300 W at 1.8 K, 750 W at 4.5 K and 30 kW at 80 K and was operated with a high reliability for more than 16 years. After a brief recall on the cryogenic refrigeration of the toroidal superconducting magnet, the distribution of the heat loads at the various levels of temperature (in standby mode 150W at 1.8 K and 200W at 4.5 K) is presented. The inventory of the calculated static and variable heat loads deposited within each part of toroidal field coils and thermal shields, is given with the factors of dependence. This analysis identifies and quantifies the major magnetic disturbances like a disruption (about 12 kJ onto the coils and 300 kJ onto the thick casings) which generate additional heat loads for the refrigerator.The measurements associated with the He II saturated bath pumping system, and the supercritical helium loop cooling the thick casings, allow us to verify thereafter the behaviour of the cryo-refrigerator during the long duration discharges, and the compliance with the theoretical model.The conclusions bring results also applicable to the cyoplant of future plant like ITER which will operate with long duration discharges.