Design developments for the ITER in-vessel equilibrium pick-up coils and halo current sensors

The ITER magnetic diagnostics must provide essential information for plasma diagnostic purposes and for the machine control. The sensors will be installed in a hostile environment characterized by severe neutron irradiation and heat loads, which can reduce the sensor lifetime and also generate undesired DC signals, which might compromise the accuracy of the measurements obtained by time-integration. The paper is focused on the design development and optimisation of the in-vessel tangential pick-up coils and blanket halo sensors. The work is aimed at achieving the required measurement precision in spite of the thermal effect due to the neutron irradiation. Within the limits of several tight engineering constraints, a new concept of magnetic pick-up coil has been developed. A winding made of a ceramic-coated conductor (instead of a mineral insulated cables) and “impregnated” with ceramic filler is proposed. Similar issues are also related to the halo sensor design.