Development of a large-current high-precision pulse power supply

JAEA and KEK are jointly constructing a high-intensity proton accelerator project J-PARC. Its main accelerator is a 3-GeV synchrotron. Its injection bump magnets, especially horizontal paint bump magnets, are excited by large pulse currents. Their rated currents are over 10 kA and pulse widths are about 1 ms. Tracking errors are required to be less than 1%. Multiple connected two-quadrant IGBT choppers are adopted for their power supplies. Their output currents are controlled by feedback control with minor loop voltage control (m-AVR). When output current of a chopper intermits at small current, its output voltage rises and current control becomes difficult. In this paper, response of m-AVR and output voltage characteristics at current intermittent region are studied and an improved control scheme is proposed. The performance is confirmed by a test.