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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

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


  • 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 - 05 Feb 2020
Topic attachments
I Attachment Action Size Date Who Comment
GMT-schedule.pngpng GMT-schedule.png manage 47 K 19 Feb 2020 - 15:23 DietrichBeck another plan for the next weeks ...
Topic revision: r297 - 19 Feb 2020, DietrichBeck
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