ARCHITECTURE DESIGN FOR THE SwissFEL LLRF SYSTEM

The SwissFEL under construction at the Paul Scherrer Institut (PSI) requires high quality electron beams to generate X-ray Free Electron Laser (FEL) for various experiments. The Low Level Radio Frequency (LLRF) system is used to control the klystrons to provide highly stable RF field in cavities for beam acceleration. There are more than 30 RF stations in the SwissFEL accelerator with different frequencies (S-band, C-band and X-band) and different types of cavities (normal conducting standing wave cavities or traveling wave structures). Each RF station will be controlled by a LLRF node and all RF stations will be connected to the real-time network in the scope of the global beam based feedback system. High level applications and automation procedures will be defined to facilitate the operation of the RF systems. In order to handle the complexity of the LLRF system, the system architecture is carefully designed considering the external interfaces, functions and performance requirements to the LLRF system. The architecture design of the LLRF system will be described in this paper with the focus on the fast networks, digital hardware, firmware and software.