THE C-BAND RF PULSE COMPRESSION FOR SOFT XFEL AT SINAP

A compact soft X-ray free electron laser facility is presently being constructed at Shanghai Institute of Applied Physics Chinese Academy of Science (SINAP) in 2012 and will be accomplished in 2014. This facility will be located to the shanghai synchrotron radiation facility (SSRF) which is a third generation light source in china. It requires a compact linac with a high-gradient accelerating structure for a limited overall length less than 230m.The c-band technology which is already used in KEK/Spring-8 linear accelerator is a good compromise for this compact facility and a c-and traveling-wave accelerating structure was already fabricated and tested at SINAP[1], and a c-band pulse compression will be required. There are some reasons, why RF pulse compression devices are quite useful to be applied in RF power supply of the soft XFEL. For it can enhance the peak RF power by expense of RF pulse length, so it will not increase the average power and at the same time reduce the total number of the klystron, it also increases the gradient of the accelerating structure, so we need the c-band pulse compressor. AND a SLED type RF pulse compression scheme is proposed for the C-band RF system of the soft XFEL and this scheme uses TE0.1.15 mode energy storage cavity for high Q-energy storage. The C-band pulse compression under development at SINAP has a high power gain about 3.1 and it is designed to compress the pulse width from 2.5μs to 0.5μs and multiply the input RF power of 50MW to generate 160MW peak RF power, and the coupling coefficient will be 8.5. It has three components: 3-dB coupler, mode convertors and the resonant cavities. In this paper C-band pulse compression and some components for the c-band pulse compression will be described.