Distributed RF on White Rabbit network

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Bányász Gábor
Department of Automation and Applied Informatics

At ELI-ALPS the diagnostic devices, actuators, etc. has to be timed against the arrival of the laser pulse with high accuracy. For this it is necessary to ensure the reliable and precise distribution of electric trigger signals – produced by laser sources –over the facility. The devices which need accurate timing should synchronize their operation to these trigger pulses. A possible instrument for this purpose is the White Rabbit system developed by the engineers of CERN and other research institutes. The White Rabbit is able to synchronize the time of its nodes with sub-ns accuracy to a reference clock (for e.g. GPS). On the White Rabbit optical network, besides the packets responsible for time synchronization, conventional Ethernet packets are also able to be distributed. Thus the network is capable of dealing with control and data packets.

In the course of my work I implemented the distribution of electric trigger pulses with White Rabbit. The sampling and re-generation of pulses was made on a White Rabbit node with an FMC Fine-Delay card. Between the two nodes the connection was realized with the White Rabbit optical network and with a conventional copper Ethernet network. While the optical network is responsible for synchronization to the reference clock, the copper wired Ethernet was used to distribute the timestamps of trigger pulses. It was clear from the measurements, that the created system has a significant frequency limit. In order to increase the maximal available trigger frequency, it is worthy to investigate additional White Rabbit technologies.


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