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General Machine Timing System at GSI and FAIR

whiterabbit logo.png

The FAIR facility involves a long chain of accelerators which need to be tightly synchronized. This is achieved by the General Machine Timing (GMT) system, a distributed event generation system based on the notion of time. Time synchronization is achieved by using White Rabbit (WR), a fully deterministic Ethernet-based field bus for clock transfer and synchronization. The key components of the GMT are a so-called Data Master (DM) that schedules actions by broadcasting messages, a WR network and Timing Receiver (TR) nodes executing machine relevant actions on time.

The primary tasks of the timing system are the following.
  • Time-Synchronization of ~2000 - 3000 nodes with sub-ns accuracy over fiber lengths of up to 2 km.
  • Distribution of TAI counters with ns accuracy.
  • Generation of timing events for synchronization of equipment.


The aim of this timing web is to provide an overview on the timing system and its relationship to other systems. Moreover, it is the central point for documentation. Please note, that the timing system is still under development.



Scheduled downtime of the GMT production system as agreed with operations
  • DD-MM-YYYY: see current planning
  • 19-10-2020 til 20-10-2020: preparation for Controls Integration Test
  • 02-11-2020 til 09-11-2020: operation of the GMT is probably affected by power cuts that have been announced for this period
  • 16-11-2020 til 17-11-2020: preparation for Dry Run
  • 14-12-2020 til 16-12-2020: lots of recabeling, preparation for 2021
  • 11-01-2021 til 12-01-2021: last fixes for beamtime 2021

Figure: Schedule for the next weeks based on shutdown planning. For an overview, click here.


  • 19-Oct-2020: maintenance timing system starts
  • 01-Oct-2020: Fallout released! click
  • 29-Sep-2020: maintenance timing system ends
    • White Rabbit Switch configuration updated
    • cabeling works in White Rabbit network
    • WR-MIL gateways (SIS18, ESR) updated to the upcoming timing release
    • DM-UNIPZ gateway ('SIS Anforderung') updated to the upcoming timing release
  • 28-Sep-2020: maintenance timing system starts
  • 08-Sep-2020: GPSDO broken, switched to backup system (incident not related to maintenance)
  • 08-Sep-2020: maintenance timing system ends
    • all White Rabbit Switches updated to v6 plus a recent update
    • autodiscovery of network topology
  • 07-Sep-2020: maintenance timing system starts
  • 31-Aug-2020: we have a 'release candidate' for our next release, click
    • SCU4 support
    • PEXP support
  • 18-Aug-2020: maintenance timing system ends
    • updated White Rabbit Switch configuration
  • 17-Aug-2020: maintenance timing system starts
  • 14-Aug-2020: UNILAC: White Rabbit Pulszentrale and MIL Pulszentrale integrated
  • 03-Jul-2020: maintenance timing system ends
    • all White Rabbit Switches updated to v6
    • all White Rabbit networks connected to common PTP Grandmaster
    • all White Rabbit networks have identical infrastructure (BOOTP, service ...)
  • 22-Jun-2020: maintenance timing system starts
  • 15-Jun-2020: shutdown period starts

GSI Timing Team

-- DietrichBeck - 30 September 2020
Topic attachments
I Attachment Action Size Date Who Comment
GMT-schedule.pngpng GMT-schedule.png manage 70 K 16 Oct 2020 - 15:28 DietrichBeck another plan for the next weeks ...
Topic revision: r328 - 19 Oct 2020, DietrichBeck
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