Improved Dynamic Filters for the Main Ring Magnet Power Supply of the KEK 12 GeV PS

The dynamic filters of the KEK 12 GeV PS were improved in the voltage ripple detector, in the control system and in the power-up of the PWM and B-class amplifiers. Especially, a use of new developed voltage ripple detector was able to change from the former feed forward system to the feed back control system. As the results, the low frequency ripple voltage across the magnet coil (< 300 Hz) could be reduced to less than -26 db to the inputs in the B, QF and QD magnet power supply and the current ripple is considered to be about 8 × 10-6 at flat top current 2,850 A during extraction.