Fusion Science and Technology / Volume 64 / Number 4 / November 2013 / Pages 705-710
The quench of one of the ITER magnet systems is an irreversible transition of the conductor from superconducting to normal resistive state. The normal zone propagates along the cable-in-conduit conductor, dissipating a large power. The detection has to be fast enough (1 to 2 s) to initiate the dumping of the magnetic energy and avoid irreversible damage of the systems.
The experience of CEA is based on the operation of the superconducting tokamak Tore Supra for more than 20 years. In support of ITER, CEA was also very involved in quench detection investigations during these past 3 years.
The primary quench detection in ITER is based on voltage detection, the most rapid detection. The very magnetically disturbed environment during a plasma scenario makes the voltage detection particularly difficult, inducing large inductive components across the pulsed coils (10 kV) or coil subcomponents. Voltage compensations therefore have to be designed to discriminate the resistive voltage associated with the quench.
A secondary detection based on a thermohydraulic signals system also has to be investigated to protect the environment in case of a nondetected quench, especially for the largest ITER system, which is the toroidal field system with a stored energy of 40 GJ.