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)