Minutes of the 12^th Timing Working Group Meeting (TimWG)
Held on Friday the 14^th July 2000

Present:

Excused:

Phillipe BAUDRENGHIEN, Adriaan RIJLLART, Jean-Jacques SAVIOZ.

Agenda

• Approval of previous minutes
• TTC Test Beam results, Bruce TAYLOR
• BI progress with TTC, Jean-Jacques SAVIOZ
• GPS IRIG-B measurements, Christian ANTFOLK
• AOB

Approval of previous minutes

There were no corrections on the previous minutes.

TTC Test Beam results

Bruce TAYLOR reminded the objectives of the TTC project ("RD12 - Timing, Trigger and Control   (TTC) Systems for LHC Detectors") and reviewed briefly the different components involved in the TTC distribution chain. He presented the results of the tests performed on the distribution of SPS RF signals  to LHC experiment through the TTC system during the SPS operation period with an LHC structured beam (see slides attached).

The structured test beam comprised 2 µs trains of 81 bunches at 25 ns spacing, repeated once every SPS revolution of 23 µs over a slow extraction interval of 2.37 sec to the North and West areas. Both SPS orbit frequency (43 kHz) and LHC bunch clock frequency (40.079 MHz) have been successfully transmitted through the TTC system to the different  LHC experiments.

BI progress with TTC

Jean-Jacques SAVIOZ was unable to attend to the meeting.

GPS / IRIG-B measurements

Christian ANTFOLK presented the results of different tests performed on GPS and IRIG-B UTC distribution system (see slides attached). Precision and stability measurements of the "one pulse per second signal" (reference pulse locked on the GPS satellites) have been done under different operating conditions and for different type of receiver for each system. He concluded that:

• Using present day commercially available GPS equipment, one can guarantee a distribution of the time of the day referenced to the UTC within less than 1us throughout the whole CERN complex,
• Tests have proven that using IRIG-B synchronized to GPS can provide a time referenced to UTC with an error of less than 2us,
• GPS is still evolving quickly, technology is progressing and simultaneously prices are decreasing. Evaluate the current systems now but wait before deciding on the specific LHC hardware

Julian LEWIS explained that the PS division is actually evaluating the possibility of using this approach based on GPS for the distribution of events to PS accelerator hardware equipment.

AOB

Gary BEETHAM distributed two notes presenting in more details the work done within the SL/CO/TI section on GPS and IRIG-B stability and presision measurements;

1. Long Term Precision Measurements on GPS and IRIG-B Equipment, C. Antfolk, G. Beetham, J-B. Ribes, J. Williamsson, SL-Note 2000-037 (CO), June 2000.
2. Instructions for the Use of Test Equipement Related to Long Term GPS and IRIG-B Measurements, C. Antfolk, G. Beetham, J-B. Ribes, J. Williamsson, SL-Note 2000-038 (CO), July 2000.

Next meeting

Next Meeting will be held on Friday 01 September 2000 at 15:30 in 864 1C01.

Agenda

1. Approval of previous minutes
2. BI TTC developments
2. 10MHz distribution
3. LHC slow timing events
5. AOB