Repetitive high stability modulator for PAL-XFEL

The Pohang Accelerator Laboratory (PAL) had started the 10 GeV PAL-XFEL project from 2011. The PAL-XFEL needs a highly stable electron beam. The very stable beam voltage of a klystron- modulator is essential to provide the stable acceleration field for an electron beam. Thus, the modulator system for the XFEL requires less than 50 ppm PFN voltage stability. To get this high stability on the modulator system, the inverter type HVPS is a pivot component. And the modulator needs lower noise and smart. We discuss the measurement of the stability and the test results of the pulse modulator system.