A convenient way to find an electrical insulation break of MA cores in J-PARC synchrotrons

We employ Magnetic Alloy core loaded RF cavities for the Japan Proton Accelerator Research Complex synchrotrons to achieve a high accelerating voltage. To improve the electrical insulation of MA cores, we conceptualized a convenient way to find an electrical insulation break by measuring the DC resistance in the radial directions of MA cores. We call it the radial resistance method. This radial resistance method gives information of the radial location and degree of the electrical insulation breaks of MA cores. We checked the validity of the radial resistance method by comparing with a high power test result. The areas where the radial resistance method indicated the electrical insulation breaks corresponded with the areas that were damaged due to the electrical insulation breaks during the high power test. We modified the core manufacturing process by evaluating the electrical insulation of MA cores from the radial resistance data, and thus we could improve the electrical insulation of MA cores.