Verification of the CNGS Timing System using Ultra-Fast Diamond Detectors

A new ultra-fast diagnostic tool was installed in the CNGS facility in 2011 following the neutrino time-of-flight results published by OPERA in September 2011. Several polycrystalline CVD diamond detectors were placed in the secondary beam line about 1200m downstream of the CNGS target in order to measure the time structure of the muons which are produced together with the muon neutrinos. This allows an accurate measurement of the GPS timing of individual secondary particle bunches crossing these detectors, and provides an independent timing measurement at CERN, which has previously been based solely on the fast beam current transformers installed in the primary proton beam line upstream of the CNGS target. Both the position of the detectors, and the time between the detection of the particles at the beam current transformer and the diamond detectors have been measured very carefully and a sound analysis of the detector signals was done. This allows comparison of the measurements between the beam current transformer and the diamond detectors. The results reveal that the GPS timing measurements performed at CERN are consistent.