Dielectric breakdown and measures of the connectors for kicker magnet in J-PARC 3-GeV synchrotron

This is a report on the dielectric breakdown at connectors for high-voltage coaxial cables and countermeasures. In March 2010, dielectric breakdown occurred in the polyethylene insulation layer at connector. There were scratches on the surfaces of the polyethylene insulation layers of all cables. These scratches are considered due to electric discharge by air. A connector that can inhibit electric discharge was discussed. As a result, the concentration of electric fields can be prevented by covering the edges of a semiconductive layer with high-dielectric materials. (author)