J-PARC has three accelerators, 400MeV linear accelerator (LINAC), 3GeV rapid cycling synchrotron (RCS), and 50GeV (currently 30GeV) main ring (MR), which are connected by beam transport lines. The proton beam is delivered from the RCS to muon and neutron targets in the materials and life science experimental facility (MLF) via a beam transport line called 3NBT. A pulsed bending magnet in the 3NBT, which is also the first magnet of another beam transport line called 3-50BT, provides 8 bunches of proton beams to the MR. A power supply excites the pulsed bending magnet according to the cycle of MR to deliver the proton beam at the injection timing of MR. In near future, the repetition rate of MR will be higher to increase the output beam power. However, the current power supply of the pulsed bending magnet does not support higher repetitive operation, so we planned to manufacture a new power supply that supports 1 Hz operation. In this proceeding, the specifications of the new power supply, and the measured results of operating tests using dummy loads and the pulsed bending magnet will be reported.

The main ring (MR) of the Japan proton accelerator research complex (J-PARC) delivers the high-intensity proton beams to the T2K long-baseline neutrino experiment. To observe charge-conjugation and parity-transformation violation in the lepton sector with high accuracy, the upgrade of the MR toward the beam power of 1.3 MW is mandatory. One promising method for increasing the beam power is to shorten the repetition cycle of the MR. The crucial point in the success of this scheme is the upgrade of the magnet power supply system corresponding to the increase in the output voltages of the magnet power supplies and the power fluctuation of the electric system. During the long-term shutdown period of MR in FY2021, a wide range of works were carried out, including installations of new power supplies, rearrangement of existing power supplies, split of magnet families, and cable rewiring. The upgrade scheme of the power supply system in the J-PARC MR and the results of this upgrade will be presented.