In the J-PARC MR, 96 bending magnets (BMs) are used in total. They are divided into 6 groups of 16 BMs. The 16 BMs in each group are connected in series and driven by a single power supply. Since all 96 BMs are symmetrically located in the ring, the magnet currents regulated by the 6 power supplies need to be same. Each power supply performs output current feedback control using electronic circuits including analog amplifications and AD / DA conversions. Due to individual differences of the electronic circuits, output current is generally expected to be different for each power supply. Therefore, we developed a current measurement unit with the portable DCCT as an independent reference. Further, we measured the magnet currents regulated by the 6 BM power supplies using the unit. We report the details of the unit as well as the results of the current measurements.
Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia