Design of remote handling, nuclear and vacuum compatible connectors for mineral insulated thermocouples of ITER neutral beam injectors

Mineral insulated (MI) thermocouples will be connected to the MI extension cables through custom connectors for sensors positioned on the in-vessel components of the ITER neutral beam injectors. A first connector position is located at the vessel wall to allow for junction of the in-vessel components with the in-vessel extension cables, the second one at the signal feedthroughs in order to pass the vacuum barrier and arrive at signal conditioning. This in-vessel mating plug and socket design allows for maintenance and replacement of components with multiple connections and reliable signal transmission. The connectors have been developed from previous experience on connectors manufactured for other fusion diagnostics and can house up to 63 metal-ceramic terminations of MI thermocouples locked in position by insulating plates and bushes; an external shielding shell will be mounted as protection. Coupling between shields and insulating plates have been developed with shadow edges to avoid deposition of conductive coatings of sputtered materials, so preserving the electrical insulation. Electrical design has been developed to shield signals from electromagnetic interference and to isolate the sensor shield from the vessel grounding, so avoiding ground loops. Remote handling design incorporates a long ball-ended dowel that locates in a circular hole and short parallel dowels that locate in a short slot to provide high level of position control within a compact arrangement. The plug has been provided with two grip linkage for the manipulator interface. Mechanical design has been accomplished by selecting materials and solutions compatible with vacuum and radiation resistance in the ITER environment, considering the manufacturing feasibility especially for machinable glass-ceramic used for plates and bushes, verifying the mating alignment of standard contact pins also at the signal feedthrough interface.