Speaker
Description
Abstract: In the superconducting magnets system of the International Thermonuclear Experimental Reactor (ITER) project, the heater chains are used to avoid heavy condensation or ice formation on the current leads of feeder. As an insulating and heat-conducting component, the heater chains should satisfy electrical insulation and thermal conduction properties at the same time. Due to no alternative commercial solutions, the heater chains for the current leads of the superconducting system of ITER were developed in the Institute of Plasma Physics, Chinese Academy of Sciences. The heater chains were manufactured with heater resistance, Al2O3 ceramic, MgO filling insulator, polyimide and aluminum (Al) at room temperature but operated at high temperatures. Development of the heater chains aims at satisfying the electrical and thermal requirements involving high electrical insulation and high thermal conductive properties at high temperature. For the 68 kA current leads for the toroidal field (TF) superconducting magnets, in order to operate without significant delays, an approximate heating power of 3 kW at the warm terminals of current leads are provisioned to compensate the overcooling at standby condition. When the TF superconducting magnet is quenching, the warm terminals of the current leads have the same electric potential (or high voltage) as the TF superconducting magnet, however, the assuming electric potential 56 kV DC of the TF superconducting magnet is much higher than the electric potential 220 V DC of the resistance wire of heater. In this paper, the electrical and thermal analyses of the developed prototype heater chains based on finite element models were performed. In particular, the relationship between the structure and the electrical field distribution and temperature distribution of the heater chains were investigated, the simulating results indicate the structural design of the heater chains is feasible. Further insulating property and thermal property tests verify that the developed prototype heater chains can satisfy the functional requirements.
Keywords: Current leads, Superconducting magnet, ITER, Insulation, High voltage, Polyimide
