Development of an ultra stable high-voltage inverter power supply for the PAL-XFEL

The Pohang Accelerator Laboratory (PAL) is persuading to construct a self-amplified spontaneous emission X-ray free-electron laser (SASE-XFEL) coherent X-rays. A bright and stable electron beam is essential for the PAL XFEL. If a reasonably stable SASE output is to be provided, all rms RF stability of 0.02 % rms is required for both the RF phase and the RF amplitude. This is a technologically challenging issue for the PAL XFEL. Inverter technology is to be applied to charge the pulse-forming network (PFN) of the new modulator. The new inverter system keeps an ultra-stable output voltage (<= 0.01 %) and a high efficiency (> 85 %) for output voltage of 50-kV. This paper presents the initial test results for the ultra-stable inverter power supply for the PAL XFEL.