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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
  • 22-06-2020 til 03-07-2020: maintenance White Rabbit network. no White Rabbit Timing in none of the networks, no MIL timing in SIS18 and ESR
  • 13-07-2020 til 14-07-2020: maintenance White Rabbit Timing system(s)
  • 27-07-2020 til 28-07-2020: maintenance White Rabbit Timing system(s)
  • 17-08-2020 til 18-08-2020: maintenance White Rabbit Timing system(s)
  • 07-09-2020 til 08-09-2020: maintenance White Rabbit Timing system(s)
  • 28-09-2020 til 29-09-2020: maintenance White Rabbit Timing system(s)
  • 19-10-2020 til 20-10-2020: preparation for Controls Integration Test
  • 16-11-2020 til 17-11-2020: preparation for Dry Run
  • 14-12-2020 til 15-12-2020: preparation for 2021

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


  • 22-Jun-2020: maintenance timing system starts
  • 15-Jun-2020: shutdown period starts
  • 10-Jun-2020: end of short dry-run
  • 08-Jun-2020: start of a short dry-run for LSA people
  • 07-Jun-2020: our big beam-time 2020 has come to an end!
  • 02-Jun-2020: smooth operation ........
  • 25-May-2020: smooth operation .......
  • 18-May-2020: smooth operation ......
  • 11-May-2020: smooth operation .....
  • 05-May-2020: smooth operation ....
  • 27-Apr-2020: smooth operation ...
  • 20-Apr-2020: smooth operation during beamtime
  • 15-Apr-2020: Data Master power-cycled
  • 10-Apr-2020: smooth operation during beamtime
  • 20-Mar-2020: smooth operation during beamtime
  • 17-Mar-2020: one White Rabbit Switch restarted after power-cut
  • 12-Feb-2020: maintenance timing network USER (~ DEV)
  • 07-Feb-2020: physics run starts ('noon meeting' handed over to beamtime coordinator)
  • 03-Feb-2020: beam is back in SIS18; accelerated and extracted (to Cave M)
  • 27-Jan-2020: SIS18 commissioning starts
  • 23-Jan-2020: dry-run ends
  • 21-Jan-2020: dry-run starts
  • 14-Jan-2020: maintenance timing system ends
  • 13-Jan-2020: maintenance timing system starts (Enigma 5.0.4)

GSI Timing Team

-- DietrichBeck - 08 June 2020
Topic attachments
I Attachment Action Size Date Who Comment
GMT-schedule.pngpng GMT-schedule.png manage 69 K 18 May 2020 - 11:10 DietrichBeck another plan for the next weeks ...
Topic revision: r312 - 22 Jun 2020, DietrichBeck
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