GTS synchronizes electronic cards at the sub-nanossecond level. GTS also triggers the data acquisition of the experiment. Structurally, it is a tree of cards connected by gigabit optical fibers. All the trigger decisions are made in real-time in a central trigger processor. The system is currently in use in the nuclear physics experiment AGATA. Moreover, following this presentation, it has been chosen (with some hardware integration planned) to trigger and synchronize the experiments of SPIRAL2 in GANIL.

1. GTS
Trigger and synchronize :
AGATA + ancillaries
Orsay, 10 december 2009,
for the selection process of the trigger and synchronization
system for nuclear physics experiments in GANIL (SPIRAL2) Joël Chavas

2. Outline
• GTS – Main features
• GTS – Hardware / software
• GTS – Status and characteristics

3. The DAQ in AGATA

4. GTS – Function
• Provides the global clock
• Handles centrally all trigger requests
• Transport medium for trigger activity
• Equalizes downlinks
– No calibration run required
• Provides the absolute time (48-bit counter)

5. GTS – Structure
Leaf
Trigger
Leaf Root
processor
Leaf
Fanin-
fanout
Leaf

6. GTS – AGATA requirements
• Individual trigger requests – 50 kHz
• Trigger validation – 1 MHz (Mult. 1)
• Trigger validation – 300kHz (Mult. 30)
• Repeatability of the phase skew on the sub-ns
scale

7. GTS – Originality and novelty
• Digital trigger system
• Replaces analog triggers – without dead-time
• Optical fibers, to transmit clock and trigger events
• Modularity

8. Hardware
• Trigger processor :
– a commercial card inside a PCIexpress slot of the computer
• GTS card :
– Mezzanine
– ATCA card in development
• Links :
– Optical links
– Mezzanine connectors

9. GTS card
TDC
DELAY
PLL
MGT
optic mux M
FPGA trigger bus

10. GTS mezzanine
GTS mezzanine
XXX

11. GTS
GTS
GTS mezzanine – on LLP carrier

12. GTS mezzanine – On LLP carrier
GTS

13. Firmware / software
• Trigger processor :
– edk project, home made slow control through
PCIexpress
• GTS :
– edk project, embedded software (vxWorks)
– slow control through udp/ip

14. How it works : a modular approach
Trigger processor
vhdl trigger
GTS tree cores

15. Trigger processor – structure
Multiplicity
Partition 0
Multiplicity
Partition 1
Multiplicity
Partition 2
Online Multiplicity Validation
Partition 3 Coincidence broadcast
sorter
Multiplicity
Partition 4
Multiplicity
Partition 5
Multiplicity
Partition 6
Multiplicity
Partition 7

16. Trigger processor
• Partition coincidence
– Ex : Mult(Ge) ≥ 4 and Mult(Ancillary) ≥ 1 after 5µs
– Delayed multiplicity window : clock precision

17. GTS tree – General
• A unique hardware for all nodes
• A unique firmware for all leaves
• A unique embedded software for all nodes

18. GTS tree – Clocks
• Clock recovered from gigabit optical links
• Clock cleaned by external PLL
• Downlink times are measured
• Downlink times are equalized through a FIFO and
an external delay line

19. GTS tree – Alignment
downlink
tdownlink = t2 – 1/2 × t1
clocked
t2
combinatorial
combinatorial
t1
combinatorial

20. GTS – Communication with carriers

21. Trigger cores
• Handle all trigger activity
• Purely vhdl Leaf
• Uplink : Leaf Root
– Trigger requests Leaf
– Periodic idles
Leaf
• Downlink : uplink
– Trigger validation
– Absolute time downlink
– Synchronous command
• No dead-time

22. Measurements – Jitters
p-p jitter (ps)
clk 70
leaf-leaf 200
leaf-root 170

23. Measurements – Skews
Max (ps)
phase alignment +/- 250
phase repeatability +/- 50

24. Measurements – latencies
• Local latency : hundreds of ns
• No dead-time, except for a technical 2 µs one
• GTS tree latencies :
– Max = 12 µs (4-layer tree) with trigger processor
• Depends on idle rate and delayed coincidence
– 7 µs without trigger processor
– 2 µs added at each FANIN-FANOUT layer

25. GTS commissioning : november 2009
• 4-layer GTS tree
• 7 leaves (6 for germanium detectors, 1 for
ancillary detectors)
• 2 partitions (germanium detectors and ancillary
detectors) with two decision equations used :
– Mult(Ge, 3,+0)
– Mult(Ge,2,+0) + Mult(Anc,1,+2µs)
• Technical trigger validation rate : 2 MHz

26. Trigger processor -- Status
• 2 multiplicity partitions implemented on a FX100
• Firmware done for 8 partitions – to be
implemented on a more powerful hardware
• On-line reconfiguration through a pseudo-C
configuration file
• GUI based on ncurses library

27. GTS tree -- Status
• Done : firmware, embedded software, host server
software
• Under development : python-based GUI
• ATCA card development

28. GTS hardware – Status
• V2 : 4 complete GTS cards + 1 GTS that can be
used only as root
• V3 : 20 produced and tested
• V3 : 10 under production for june 2009
• Comments :
– Production is not the problem : testing and support are
the problem
– Stand-alone GTS card : no support is needed
– GTS tree : support is needed

29. Discussion and future needs
• Ancillaries and the GTS tree latency
• Feeding the root and the leave with an external
clock – links with BUTIS?
• Customization (software) of the trigger processor
– Physics is done on the trigger processor

30. Work load
• Roberto Isocrate (hardware)
• Damiano Bortolato (firmware/software GTS tree
prototype)
• Joël Chavas (firmware/software/commissioning GTS tree,
testing)
• Luciano Berti (trigger processor)
• Marco Bellato (trigger cores, conception, organization)
• Dino Bazzacco (validation)

31. Conclusion
• GTS : an innovative digital trigger system
• Successful commissioning with the ancillary
detectors included : november 2009