CERN to Gran Sasso Time Transfer

This project is devoted to discussing the time transfer between CERN (Switzerland) and Gran Sasso National Lab (Italy) for the neutrino velocity measurement experiment. It covers more in detail the part designed and calibrated by the CERN timing team. This includes all CERN internal cabling, the GPS-based common view time transfer system and the fiber taking the timing reference from the location of the GPS receiver in Gran Sasso to the Opera detector. The electronics after that point are handled by the Opera team and have not been reviewed by us. If you would like to help us check all the system, please subscribe to the mailing list and post your questions or comments there. You might want to read the FAQ first.

A quick introduction to the subsystems covered by this project:

We have divided the timing chain in four elements.

  1. The GPS link, that has been calibrated by METAS and PTB
  2. Central Control Room to Hall HCA442
  3. CTRI to Scope
  4. BCT to Scope
In May 2012 the White Rabbit timing network has been used to verify the timing in the whole system.

Some useful abbreviations:

  • BCT: Beam Current Transformer.
  • CCR: CERN Control Room.
  • cfc-ccr-ctpps: The FEC where we have installed the CTRI that logs the time stamps of the PPS coming from the PolaRx2e.
  • cfc-hca4-saos12: The FEC where we do the BCT logging. It has a CTRI and a DC110.
  • CS4000: A cesium clock by Symmetricom.
  • CTG: Central Timing Generator
  • CTRI: Control Timing Receiver, PCI format.
  • CTSYN: A VME board which takes the 10MHz and PPS from the XLi and regenerates a 40MHz and a PPS locked to them.
  • DP110: Acqiris oscilloscope card in PCI format.
  • FEC: Front End Computer. This can be an industrial PC or a VME crate, both running SLC5 Linux.
  • HCA442: It is the hall where we have the CTRI time tagging the extraction kicker pulse and the DC110 logging the BCT signal.
  • PolaRx2e: A Septentrio timing GPS receiver.
  • PPS: Pulse Per Second.
  • SPS: Super Proton Synchrotron.
  • XLi: A Symmetricom GPS receiver.