• K. Czuba, K. Antoszkiewicz
  Warsaw University of Technology, Institute of Electronic Systems, Warsaw
• S. Simrock, H.C. Weddig
  DESY, Hamburg

One of the most important requirements for the XFEL RF system is to assure a very precise RF field stability within the accelerating cavities. The required amplitude and phase stability equals respectively dA/A <3·10^-5, dphi<0.01 deg @ 1.3GHz in the injector and dA/A<10^-3, dphi <0.1 deg @1.3GHz in the main linac section of the XFEL facility. Fulfilling such requirements is a very challenging task for the 1.5 km long main linac system and about 3.4 km length of the entire facility. Thousands of electronic and RF devices must be precisely phase synchronized for effective controlling of the RF field parameters. We describe the the proposed architecture of the RF Master Oscillator and the Phase Reference Distribution System for the XFEL. Design choices were based on the experience gained during the commissioning of the FLASH phase reference distribution system and on many laboratory experiments with distribution system components. Proposed system parameter analysis shows that the given requirements for the distributed signal phase stability can be fulfilled easily for the main linac section. Fulfilling the injector requirements may require using optical distribution techniques.