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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
  • 18-01-2021 til 19-01-2021: last fixes for beamtime 2021

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


  • 19-Jan-2021: maintenance timing system ends
  • 18-Jan-2021: maintenance timing system starts
    • updated all WRS to new firmware
  • 15-Jan-2021: dry-run ends
  • 11-Jan-2021: dry-run starts
  • 23-Dec-2020: ad-hoc maintenance timing system (White Rabbit @ UNILAC only)
    • WRS memory leak: bug found and fixed, new WRS firmware available
    • WRS @ UNILAC: firmware updated
  • 16-Dec-2020: maintenance timing system ends
  • 14-Dec-2020: maintenance timing system starts
    • installed repaired GPSDO
    • rebooted all White Rabbit Switches
    • installed clockmaster backup
    • established a hack for WRS memory leak
    • updated Data Master
  • 27-Nov-2020: dry-run ends
  • 25-Nov-2020: unexpected major power-cut
  • 23-Nov-2020: dry-run starts
  • 16-Nov-2020: maintenance timing system ends
  • 13-Nov-2020: maintenance timing system starts
    • all timing networks are affected
    • White Rabbit Switch: firmware and configuration updated
    • network management updated
    • gateways updated (UNILAC: 'SIS-Anforderung' + 'WR-Pulszentrale')
    • gateways updated (WR->MIL, SIS18, ESR)
    • Data Master updated
    • PXE config 'scuxl.fallout' updated to ramdisk 2020-11-09
  • 05-Nov-2020: normal operation
  • 04-Nov-2020: exceptional power-cut announced for today at 1730
    • affected buildings are "BG, RT, TR, EX, TH, AR, PLH, TG1, TG2, TG3 und der L√∂schcontainer auf dem Ring"
    • timing system down in parts of the facility
  • 03-Nov-2020
  • 20-Oct-2020: maintenance timing system ends
    • White Rabbit Switch firmware updated
    • White Rabbit Switch configuration updated
    • 802.1x (MAC based authentication) enabled
  • 19-Oct-2020: maintenance timing system starts
  • 01-Oct-2020: Fallout 6.0.0 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 56 K 12 Nov 2020 - 07:24 DietrichBeck another plan for the next weeks ...
Topic revision: r350 - 20 Jan 2021, DietrichBeck
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