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

In order to use the slow extracted beam of the KEK (Japan National Laboratory for High Energy Physics) proton synchrotron more effectively, the period of slow extraction has been extended. An upgrade of the main ring magnet power supply is described. The main power supply consists of thyristor rectifiers, DC filters, reactive power compensators, AC harmonic filters and control systems. To increase the current capacity during flat top, the rectifiers and transformers were improved. The AC network and DC filters were left unchanged, since the acceleration and deceleration times were not varied. Analog control devices and the computer control software have also been improved to realize a 2 s flat top with a 4 s repetition rate, compared with the former 0.6 s flat top with a 2.5 s repetition rate.<
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