General Machine Timing System at GSI and FAIR

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.

About...

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.

Topics

• Introduction
  • Accelerator Control System, Clocks and Time, Network Basics
• Getting Started
  • Essentials, Timing Receiver: ECA, Timing Receiver: Usage
• Documentation
  • Documents, HOW-TOs, Current Release, Releases, Getting an IP for Timing Receivers
• Acronyms

Announcements

White Rabbit GMT

Please checkout this mattermost channel.

Scheduled downtime of the GMT production system as agreed with operations are marked with bold letters. Non-bold letters are activities by others are only listed for information.

• DD-DD MM YYYY: maintenance window INN
• 25-29 01 2027: maintenance window White Rabbit timing
• 02-06 08 2027: maintenance window White Rabbit timing

Operation and Experiments

For an overview, click here or here.

A long term schedule is available here.

News

• 15-Oct-2026
  • goodbye leap-seconds (after 2027-May-20)
  • hello leap-hours
• 28-Sep-2026
  • begin physics run at CRYRING
• 14-Sep-2026
  • start-up of beam operation at CRYRING
  • note: CRYRING has a local ion-source and injector and can be operated independently of UNILAC ...
• 07-Aug-2026
  • maintenance window closed
    • rework parts of the cabeling in BG.2.009
    • update bunch-2-bucket system
    • wr-mil: updates and port to yocto
    • installed new servers for Data Master ('rings' and 'unilac')
• 06-Aug-2026
  • maintenance window opened
• 30-Apr-2026
  • maintenance window closed
• 29-Apr-2026
  • maintenance window opened
• 24-Mar-2026
  • maintenance window closed
• 23-Mar-2026
  • maintenance window opened
  • update WRS config and firmware
• 09-Mar-2026
  • maintenance window INN
  • power-cuts for maintenance reasons, see here
  • unavailability of some aspects of White Rabbit timing
• 08-Mar-2026
  • end wet-run at CRYRING
• 27-Feb-2026
  • begin wet-run at CRYRING
• 23-Feb-2026
  • begin commissioning for wet-run at CRYRING
• 11-Feb-2026
  • stopped White Rabbit timing to the west of the transfer channel (TK)
  • stopped MIL timing to the west of the transfer channel
• 05-Feb-2026
  • fire incident at GSI
  • end of wet-run
• 19-Jan-2026
  • begin startup for wet-run, see here
• Older News

GSI Timing Team

-- DietrichBeck - 18 Oct 2026