• M. Bousonville
  GSI, Darmstadt
• J. Rausch
  TU Darmstadt, Darmstadt

In this paper, a method for the generation of RF reference signals for synchrotrons and storage rings will be presented. With these reference signals, the RF cavities in the Facility for Antiproton and Ion Research (FAIR) shall be synchronised. Digital frequency generators that work according to the DDS (direct digital synthesis) principle will be used as reference generators. Via an optical network with star topology, these reference generators will be fed with two clock signals that show a certain correlation of frequency and phase. Due to delay measurements, their phases at different end points of the optical network are known. From these clock signals, reference signals with specific frequencies can be derived. The phases of these reference signals can be fine-tuned against the phases of the clock signals, allowing the phases of different reference signals to be synchronised. With the commercially available DDS generators used in the prototype, phase steps of 0.022° are possible. At a reference signal frequency of 50 MHz, this corresponds to 1.22 ps. The presentation describes the functionality of this method for reference signal generation and shows under which conditions the step size of the phase adjustment can be improved further.

• M. Lechartier, D. Besnier, J.F. Leyge, M. Michel
  GANIL, Caen

The Spiral 2 project uses normal conducting rebunchers to accelerate high intensity beams of protons, deuterons and heavier ions. All cavities work at 88 MHz, the beta is 0.04 and 3 rebunchers are located in the MEBT line, which accepts ions with A/q up to 6. The paper describes the RF design and the technological solutions proposed for an original 3-gap cavity, characterised by very large beam aperture (60 mm) and providing up to 120 kV of effective voltage.