Capacitor bank of power supply for J-PARC MR main magnets

The main ring (MR) of the Japan Proton Accelerator Research Complex (J-PARC) is a high-intensity proton synchrotron that supplies proton beams for the long-baseline neutrino experiment, called the Tokai to Kamioka (T2K). To satisfy the experimental condition for the T2K, the increase in the present beam power of 450  kW to 750  kW and beyond is mandatory. The scheme of the high-repetition-rate operation is adopted for the MR upgrade. The repetition cycle is planned to be shortened from 2.48  s at present to 1.28  s in this scheme. This upgrade involves the increase in the power variation of the electrical system. To suppress the power variation, an energy storage that consists of capacitor banks (CBs) was developed and installed in the power supply of the main magnets, since the main magnets are the primary source of power variation. The CB was designed with a sufficient consideration to avoid serious failures. The number of fuses were installed in the CB to avoid energy concentration on a short-circuited capacitor. The scheme for the safe dissipation of the concentrated energy was also employed. A fuse arcing test was carried out to clearly show the fuse reliability since the CB safety is strongly dependent upon the fuses.