The low level radio frequency system architecture for the european X-FEL

The Low-Level Radio Frequency System (LLRF) for the superconducting cavities of the European X-FEL must provide exceptional stability of the accelerating RF field amplitude (0.01%) and phase (0.01 degrees) at a frequency of 1.3 GHz. These requirements must be achieved in pulsed operation mode with one klystron driving 32 cavities. It is thus necessary to design and build a modern LLRF control system, consisting of state of the art hardware and sophisticated control algorithms requiring high gain, low noise, fast and high resolution ADCs (up 16 bits, >100MHz), and high performance data processing using FPGAs and DSPs with low latency. A complete LLRF system must support more than 100 analogue input channels. This paper describes one possible architecture, which will be tested at DESY by the end of 2006.