Low Level RF and Timing System for XFEL/SPring-8

The construction of XFEL/SPring-8 is progressing. In this accelerator, it is needed to obtain stabilities of 50 fs and 1E-4 in time and amplitude of the acceleration voltage. To satisfy these requirements, rf components, such as a reference rf oscillator with low phase noise, IQ modulators and so on, were developed. These modules were installed to an SCSS test accelerator. Their performance was confirmed by monitoring the beam arrival timing compared with the reference rf signal. The measured time jitter of the arrival timing was 46 fs, which implies that the rf modules have a potential to control the timing of the accelerator within several 10 fs. Using these modules, the SCSS test accelerator is operated stably and offers EUV light to user experiments. The compression factor of the XFEL is about 10-times larger than that of the test accelerator. Thus special care is taken for the XFEL to keep the temperature of rf modules constant. For delivery of the reference rf signals, an optical system is adopted instead of coaxial cables, because signal transmission loss with coaxial cable is not allowed for the long distance for the XFEL..