Post on 24-Feb-2016
description
New Trigger Possibilities
Peter-Bernd Otte – Sep. 2009CB 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
A new Trigger for our experiments
Think of: building trigger electronics1. 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?
What is an FPGA? (1/3)
Scale: mm
More sophisticated trigger electronics:
What is an FPGA? (2/3)
input output
Scale: meters
Can act as: logic, scaler, TDC, …
is smaller, faster, needs less power, cheaper
Field-programmable gate array (FPGA) (3/3)
outputinputclock
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 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
New trigger hardware
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!
Connected detectors
S=1232x
Algorithm steps1. 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)
Cluster Counter Algorithm
crystal scheme of CB
(coffee break)
more details:
during July run 128 crystals used for test (~ 20% of CB)
Cluster Counter test (1/2)
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
Cluster Counter test (2/2)
(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
Trigger electronics: Outlook
(coffee break)
Thank you for your attention
AppendixFor 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 (~106)
(LUTs, adder, etc.)◦ routing matrix◦ I/O pads
Field-programmable gate array (FPGA) (1/2)
Field-programmable gate array (FPGA) (2/2)
microprocessor FPGA (electronics)Input u, v and w
Output z
Important difference:Concurrent processing ⇔ unlike microprocessors
Example:
sequ
entia
l
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
Actual Trigger possibilities
New Triggercan removeall 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
What can the new trigger achieve?
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.
Interesting facts / Outlook
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)
Unveil new possibilities
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
Cluster Counter Algorithm (1/4)
14
5 10
9
6
8
72
3
up down
7 26 5
1 4
93
10
8
Algorithm steps1. 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
Cluster Counter Algorithm (2/4)
15 replacement rules1. Leave cluster number constant2. No overlap between rules3. Relevant neighbours vary
Colour code:
Cluster Counter Algorithm (3/4)
actual considered crystal crystal to be unmarked
marked (fired) crystalunmarked (not fired) crystal
crystal to be marked
14
52
3
14
52
3
14
52
3
1 2
3
14
52
3
15 10 6
2
3
+ 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
Cluster Counter Algorithm (4/4)