Peter-Bernd Otte – Sep CB collaboration meeting, Edinburgh

 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

 Think of: building trigger electronics 1.take CAMAC/NIM logic modules (AND/OR) 2.set it up:  using cables  program modules  So far so good: ◦ What if it becomes more complex?

Scale: mm  More sophisticated trigger electronics: inputoutput Scale: meters

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

 New electronic cards already ordered  „VUPROM 2“ from GSI ◦ also and ◦ FPGA: „Virtex 4“ from Xilinx, 400 MHz ◦ 224 inputs, 32 outputs, LVDS ◦ 6U form factor ◦ VMEbus connectivity ◦ cheap: 2k€ apiece ◦ 10 cards ordered

 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!  =1232x

 Algorithm steps 1.Load hit pattern 2.Shrink clusters (using set of rules) 3.Count number of cells = number of clusters 4.If desired cluster count  trigger!  “cellular automata logic” (each crystal = cell) crystal scheme of CB (coffee break)  more details:

 during July run  128 crystals used for test (~ 20% of CB)

 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)

 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)

Thank you for your attention

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

Field-programmable gate array

 Semiconductor device that can be configured via software  Architecture: ◦ logic blocks (~1 0 6 ) (LUTs, adder, etc.) ◦ routing matrix ◦ I/O pads

microprocessorFPGA (electronics) Input u, v and w Output z  Important difference: Concurrent processing ⇔ unlike microprocessors  Example: sequential

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

 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.

 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

 Is it possible to trigger on TAPS? ◦ Inner rings  standard electronics  Yes. ◦ Rest of TAPS  T. Rostomyan building analog splitter  More digital signals welcome: o Č, TOF, endpoint tagger, test paddles, etc.

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

Cellular Cluster Counter Algorithm

 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

 Algorithm steps 1.Load hit pattern into cells 2.Apply “replacement rules”, until no more changes occur (  see next slide) 3.Count number of marked cells = number of clusters 4.If desired number of clusters  trigger

 15 replacement rules 1.Leave cluster number constant 2.No overlap between rules 3.Relevant neighbours vary  Colour code: + their rotated versions Not for up/down cells at the same time

 Problem: Stops, if holes are bigger than 1 crystal  Fortunately not critical: happens only ~once a day