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White Rabbit is an extension of Ethernet which allows remote synchronization of nodes with jitters of around 10ps. The technology can be used for a variety of purposes. This paper presents a fixed-latency trigger distribution system for the study of instabilities in the LHC. Fixed latency is achieved by precisely time-stamping incoming triggers, notifying other nodes via an Ethernet broadcast containing these time stamps and having these nodes produce pulses at well-defined time offsets. The same system is used to distribute the 89us LHC revolution tick. This paper also describes current efforts for distributing multiple RF signals over a WR network, using a Distributed DDS paradigm., Proceedings of the 15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2015, Melbourne, Australia

The radiofrequency and transverse damper feedback systems of the Large Hadron Collider digitize beam phase and position measurements at the bunch repetition rate of 40 MHz. Embedded memory buffers allow a few milliseconds of full rate bunch-by-bunch data to be retrieved over the VME bus for diagnostic purposes, but experience during LHC Run I has shown that for beam studies much longer data records are desirable. A new "observation box" diagnostic system is being developed which parasitically captures data streamed directly out of the feedback hardware into a Linux server through an optical fiber link, and permits processing and buffering of full rate data for around one minute. The system will be connected to an LHC-wide trigger network for detection of beam instabilities, which allows efficient capture of signals from the onset of beam instability events. The data will be made available for analysis by client applications through interfaces which are exposed as standard equipment devices within CERN's controls framework. It is also foreseen to perform online Fourier analysis of transverse position data inside the observation box using GPUs with the aim of extracting betatron tune signals., Proceedings of the 15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2015, Melbourne, Australia