RF Synchronization and Distribution for AWAKE at CERN

The AdvancedWakefield Experiment at CERN (AWAKE) requires two particle beams and a high power laser pulse to arrive simultaneously in a rubidium plasma cell. A proton bunch from the Super Proton Synchrotron (SPS) extracted about once every 30 seconds must be synchronized with the AWAKE laser and the electron beam pulsing at a repetition rate of 10Hz. The latter is directly generated using a photo cathode triggered by part of the laser light, but the exact time of arrival in the plasma cell still depends on the phase of the RF in the accelerating structure for electrons. Each beam requires RF signals at characteristic frequencies: 6GHz, 88.2MHz and 10Hz for the synchronisation of the laser pulse, 400.8MHz and 8.7 kHz for the SPS, as well as 3GHz to drive the accelerating structure of the electron beam. A low-level RF system has been designed to generate all signals derived from a common reference. Additionally, precision triggers, synchronous with the arrival of the beams, will be distributed to beam instrumentation equipment. To suppress delay drifts of the several kilometre long optical fibres between AWAKE and the SPS RF systems, a compensated fibre link is being developed.