Performance of the main ring magnet power supply of the KEK 12 GeV proton synchrotron

The main ring magnet power supply of the Japan National Laboratory for High-Energy Physics (KEK) 12-GeV PS (proton synchrotron) consists of several twelve-pulse thyristor rectifiers with DC filters, two reactive power compensators with tuned AC harmonic filter and an analog and digital hybrid control system. This magnet power system was upgraded to extend the flat top. The current capability of the bending magnet power supply has been increased, and the analog and hybrid control system was remade in the past decade. Eight twelve-pulse rectifiers for the bending magnets are still controlled by six groups of voltage patterns. The hybrid control system with the analog automatic current regulator and automatic voltage regulator loops, as real-time negative feedback control, and repetitive current and voltage control algorithms have been implemented. This upgrade makes it possible to perform stable operation of the PS and to achieve the most effective utilization of the slow extracted beam spill. After the last upgrade of the reactive power compensator and the multicomputer control system, a flat-top current precision in the 10/sup -5/ range was obtained.<>