Suppression scheme of COD variation caused by switching ripple in J-PARC 3GeV dipole magnet power supply

Watanabe, Yasuhiro  ; Tani, Norio  ; Adachi, Toshikazu*; Igarashi, Susumu*; Someya, Hirohiko*

In the J-PARC 3 GeV synchrotron, the horizontal closed-orbit-distortion (COD) variation was observed at first of beam commissioning. The COD correction was very difficult to archive because the beam orbit of each shot changes periodically at a period of about 140 seconds. This paper clarifies that the horizontal COD is caused by the switching noise of the dipole magnet power supply and the periodic variation of the beam orbit is caused by the phase sweep of 1 kHz component that include switching noise. Moreover, it has been demonstrate that the dipole magnet power supply using the improved Pulse Width Modulation (PWM) circuit with a synchronized timing system of the accelerator has successfully suppressed the beam orbit variation.