Assessing the performance of future White Rabbit RF and timing distribution system for HL-LHC under real conditions

Abstract To meet the demand of the High-Luminosity Large Hadron Collider (LHC) for enhanced phase stability and to replace the aging Timing, Trigger and Control (TTC) backbone distribution system which is subject to high variations due to environmental changes, an upgrade to a White Rabbit-based (WR) system is planned. An earlier compliance test showed a phase variation of <33 ps in a proof of concept system in the lab. To assess the quality of the new system in real conditions a test campaign was started in several points of LHC. The objective was to monitor the phase stability of the bunch clock with respect to the Radio Frequency (RF) signal driving the accelerating cavities and compare the performance of the new system to the TTC backbone currently in operation. We measured a peak-to-peak phase variation between the WR-generated RF and the RF reference signal of <38 ps within one stable beam period and <56 ps over several fills. Knowing that the WR-based RF generation is insensitive to environmental changes, this result confirms that the planned WR-based update is an improvement over the current RF distribution system.