EMI NOISE SUPPRESSION IN THE KLYSTRON PULSE POWER SUPPLY FOR XFEL/SPring-8

Klystron modulator power supply of XFEL/SPring-8 is required low electro-magnetic interference (EMI), in order to realize a high stable beam by a feedback loops of high-precision beam monitors. We suppressed the EM noise of the modulator by the enclosure of the steel tank, eliminating a DC core bias circuit, and inserting pair noise filters into heater power lines. To estimate the effect of the noise filter, we measured the conducting noise on the heater power line. The amplitude of the noise was suppressed to less than 10 V peak-to-peak. In the prior operation test, we confirmed that the modulator noise hardly affects the low-level rf devices.