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Enhancing Experimental Triggers with FPGA Technology

This presentation discusses the integration of Field-Programmable Gate Arrays (FPGAs) into triggering systems for modern experiments, drawing on experiences from institutions like GSI and ATLAS. The new FPGA Møller trigger operates alongside existing systems, enhancing the capabilities of trigger logic while facilitating advanced features such as parallel processing and real-time decision-making. The presentation covers the architecture of FPGAs, the implications for cluster counting algorithms, and the feasibility of including various detectors, ultimately heralding a new era of trigger electronics in experimental physics.

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Enhancing Experimental Triggers with FPGA Technology

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  1. New Trigger Possibilities Peter-Bernd Otte – Sep. 2009 CB collaboration meeting, Edinburgh

  2. A new Trigger for our experiments • All modern experiments rely on FPGA triggers • GSI, ATLAS, CMS, ... • Our FPGA Møller trigger works reliable • New trigger for our entire experiment: • works in parallel to the existing trigger • ability to map the existing trigger logic • can perform far much more advanced triggering • But: What is an FPGA? • semiconductor device, great capabilities

  3. What is an FPGA? (1/3) • Think of: building trigger electronics • take CAMAC/NIM logic modules (AND/OR) • set it up: • using cables • program modules • So far so good: • What if it becomes more complex?

  4. What is an FPGA? (2/3) • More sophisticated trigger electronics: input output Scale: meters Scale: mm

  5. Field-programmable gate array (FPGA) (3/3) logiccell („modules“): • Can act as: logic, scaler, TDC, … • is smaller, faster, needs less power, cheaper Interconnection (“cables”): input output • Comparison: FPGA... • “has” 1000’s of modules and cables • ~300 I/O signals • configuration via software(behaviour of cells and interconnection) clock programmableswitches

  6. New trigger hardware • New electronic cards already ordered • „VUPROM 2“ from GSI • also used @GSI and KAOS@A1 • FPGA: „Virtex 4“ from Xilinx, 400 MHz • 224 inputs, 32 outputs, LVDS • 6U form factor • VMEbus connectivity • cheap: 2k€ apiece • 10 cards ordered

  7. Connected detectors • With new hardware: Possible to include all detectors • All CB crystals (672x  720 cable pairs) • All PID stripes (24x) • Inner TAPS crystals (72x) • Tagger channels (352x) • Endpoint Tagger (~64x) • TOF-Panels • Energy sum • Feasibility unknown: • Remaining TAPS crystals and vetos • Request to responsible experimentalists! S=1232x

  8. Cluster Counter Algorithm • Algorithm steps • Load hit pattern • Shrink clusters(using set of rules) • Count number of cells= number of clusters • If desired cluster count  trigger! • “cellular automata logic” (each crystal = cell) crystal scheme of CB •  more details: (coffee break)

  9. Cluster Counter test (1/2) • during July run • 128 crystals used for test (~ 20% of CB)

  10. Cluster Counter test (2/2) • Required time only ~140ns • Sample results for cluster count = 3 • Works reliably, next: whole CB & more • Check: efficiency, purity, simulation • essential for each new trigger algorithm (a) (b) (c)

  11. Trigger electronics: Outlook • Enough inputs: • feasible to include signals from all detectors • New trigger electronics will be installed • in parallel to existing • Request to experimentalists: • Allocate digital signals from different apparati • New trigger algorithms • Grant: • strike up a discussion during coffee break (coffee break)

  12. Thankyouforyourattention

  13. Appendix For the coffee break: Peculiarities of FPGA? New trigger compounds Cellular Cluster Counter Algorithm in greater detail

  14. Field-programmable gate array

  15. Field-programmable gate array (FPGA) (1/2) • Semiconductor device that can be configured via software • Architecture: • logic blocks (~106) (LUTs, adder, etc.) • routing matrix • I/O pads

  16. Field-programmable gate array (FPGA) (2/2) • Important difference:Concurrent processing ⇔ unlike microprocessors • Example: microprocessor FPGA (electronics) Input u, vandw sequential Output z

  17. New trigger compounds (what is possible) Comparison to old trigger

  18. Actual Trigger possibilities • Included detectors: • Crystal Ball, TAPS, PID • Triggering on: • cluster count (simple logic) • energy sum (in CB only) • charged particles involved (PID-OR) • Disadvantages: • cluster count only a rough estimate • no complex conditions • (e.g. “planar 2 body hit, one uncharged”) • hard to apply changes • not all detectors included • some trigger relevant signals not recorded New Trigger can remove all disadvant.

  19. What can the new trigger achieve? • Planned so far: • Improved cluster counter(cellular automata logic) • Cluster counter for charged/uncharged particles • Detect planar events • Møller trigger • Include: • CB crystals, PID, inner TAPS and Tagger

  20. Interesting facts / Outlook • Is it possible to trigger on TAPS? • Inner rings  standard electronics  Yes. • Rest of TAPS  T. Rostomyan building analog splitter • More digital signals welcome: • Č, TOF, endpoint tagger, test paddles, etc.

  21. Unveil new possibilities • Possible (new) trigger compounds: • time (signal duration & distance) • handle EACH input channel differently • certain input pattern (AND, OR, …) • certain sequence of signals (1st … then …) • record intermediate trigger steps with data • Limit: space on FPGA (number of logic cells)

  22. Cellular Cluster Counter Algorithm

  23. Cluster Counter Algorithm (1/4) • Cellular automata, basic declarations: • Each crystal in CB is represented as a “cell” • Each cell: • has a status (marked/unmarked) • knows status of 10 neighbours: • can only toggle its own status

  24. Cluster Counter Algorithm (2/4) • Algorithm steps • Load hit pattern into cells • Apply “replacement rules”, until no more changes occur ( see next slide) • Count number of marked cells = number of clusters • If desired number of clusters  trigger

  25. Cluster Counter Algorithm (3/4) • 15 replacement rules • Leave cluster number constant • No overlap between rules • Relevant neighbours vary • Colour code: Not for up/down cells at the same time + their rotated versions

  26. Cluster Counter Algorithm (4/4) • Problem: Stops, if holes are bigger than 1 crystal • Fortunately not critical: happens only ~once a day

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