The NOvA Timing System: A system for synchronizing a long baseline neutrino experiment

The NOvA experiment is designed to measure key parameters in neutrino physics related to the neutrino mass hierarchy and the asymmetry between matter and anti-matter. To make these measurements the NOvA experiment must correlate the extraction of beam to the NuMI target with individual hits in both a near detector and a far detector located 810 km from Fermilab. Precisely correlating hits across these detectors and reconstructing particle trajectories require that all of the readout electronics be precisely synchronized to an absolute wall time with a channel to channel variation less than 15.6 ns. The NOvA Timing Distribution System accomplishes this through an integration of commercial GPS receiver technology and custom electronics. This paper describes the timing system, its component hardware and the synchronization method that is employed by it.