SPIDER high voltage bushings: Design, development and first experimental tests

The SPIDER plasma source- housed in a stainless steel vessel maintained in high vacuum − is polarized at 112 kV (12 kV extraction voltage and 100 kV accelerating voltage), so that the vacuum vessel must be equipped with three large alumina feedthroughs, ring shaped insulators (820 mm in diameter) necessary to supply the electric, hydraulics gas and diagnostic services to the plasma source. These insulators (bushings) belong to the most critical items in the SPIDER assembly and they required a particular effort in designing, manufacturing and testing. This paper gives an overview of the insulator design, development, manufacturing activities and presents the results of the high voltage acceptance tests.