Extraction of instrumentation wires through the high-voltage insulation of the ITER magnet feeder system

The ITER magnet quench detection system relies on voltage taps to detect the development of resistive voltages across the coils and busbars. These voltage taps may be at high voltage, up to 30 kV during high voltage tests, and the signals from them must be led from the coils and feeders to the quench detection electronics, requiring that they must penetrate the ground insulation on the coils and feeders. This paper describes the R&D effort to develop and qualify the technology to extract these wires through the feeder busbar ground insulation. The voltage tap wires are 3 mm in diameter, and are a significant perturbation to the 6 mm thick glass/Kapton ground insulation. Techniques to fill the void between wire and ground insulation are presented, as well as techniques to inhibit unwanted resin flow and locally reinforce the wires. Specimens have been thermally cycled and qualified through highvoltage Paschen tests.