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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

GMT-schedule 2017-10-12.jpg
Figure: Schedule for the next weeks based on shutdown planning. For an overview, click here.


  • 10-May-2019: maintenance finished
  • 16-Apr-2019: beam operation ends
  • 01-Apr-2019: contract signed for the delivery of White Rabbit Switches for FAIR
  • 19-Mar-2019: technical stop: DM update (hardened against 'self-flushing of queues')
  • 08-Mar-2019: technical stop: DM update (stricter testing of schedules/cmds)
  • 12-Feb-2019: technical stop: DM update (added software reset)
  • 05-Feb-2019: beam operation starts
  • 01-Feb-2019: ready for beam operation (see here)
  • 25-Jan-2019: job opportunity in our team (see here)
  • 17-Dec-2018: SIS18, HEST, ESR: beam operation stops
  • 04-Dec-2018: technical stop in the morning; DM update followed by MASP and BSS testing
  • 26-Nov-2018: SIS18, HEST, ESR: beam operation starts (dry run stops)
  • 19-Nov-2018: technical stop in the morning; DM update followed by MASP and BSS testing
  • 12-Nov-2018: SIS18, HEST: dry-run starts
  • 11-Nov-2018: CRYRING: beam operation ends
  • 29-Oct-2018: CRYRING: beam operation starts
  • 23-Oct-2018: maintenance production system ends (switch-over GPSDO tested, update Data Master + UNIPZ ...)
  • 22-Oct-2018: maintenance production system starts
  • 04-Sep-2018: CRYRING: beam operation ends

GSI Timing Team

-- DietrichBeck - 16 Apr 2019
Topic attachments
I Attachment Action Size Date Who Comment
GMT-schedule_2017-10-12.jpgjpg GMT-schedule_2017-10-12.jpg manage 80 K 05 Jun 2019 - 10:19 DietrichBeck plan for the next weeks....
Topic revision: r252 - 05 Jun 2019, DietrichBeck
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