The CLEO-c Trigger System: More Than Just Blinking Lights ! LEPP Lunch Talk Mats Selen

M. Selen, 7/24/03 LEPP Lunch: Pg 1www.hep.uiuc.edu/cleo/trig3/

The CLEO-c TriggerThe CLEO-c Trigger System:System:More Than Just Blinking Lights !More Than Just Blinking Lights !

LEPP Lunch Talk

Mats Selen

Overview Tracking Calorimeter Timing Performance

What the Trigger & DAQ DoesWhat the Trigger & DAQ Does

Suppose you want to keep only pink hexagonal widgets moving down a conveyor belt.

y yn n

Trigger

You are the trigger: You stamp “y” on the pink hexagonal widgets You stamp “n” on the others

Your friend DAQsaves only widgetslabeled “y”

The problem is: Working fast means you make some mistakes !

Requirements: Decision TimeRequirements: Decision Time

Each widget must get examined and stamped

y yn n

Trigger

- You need to decide on one before the next one comes along.

- Your decision can’t take longer than t = d/v.

- Taking more time means making less mistakes.

Requirements: EfficiencyRequirements: Efficiency

You can’t stamp too many pink hexagonal widgets ”n”:

n nn n

Trigger

Requirements: RejectionRequirements: Rejection

y yy y

Trigger

The rate of widgets stamped “y” can’t exceed the capacity of your friend (the DAQ) to save them.

Whenever the DAQ is busy saving something it causes “dead-time” (he will miss the next few widgets). If he misses any marked “y”, thiscauses a loss of efficiency.

Working in Steps: PipeliningWorking in Steps: Pipelining

Have more than one person working in series

- Each individually one takes less than t = d/v- Collectively, much more work is done- A smarter decision can be made – less mistakes

y yn n

Trigger

14 feet

800 feet

d = 14 feet, v = 1 foot/ns

t = 14 ns

There are 183 RF buckets in CESR

The trigger runs at1/3 the CESR RF freq

(i.e. each step is 42 ns)

This smears together 3 beam collisions every time we look. We can do this

since its very rare that anything happens during a collision.

In CESR/CLEO, beam collisions are

spaced a minimum of 14 ns apart.

This is not enough time to do any serious trigger processing

Only ~45 of thesebuckets contain beam ‘bunches’

0 1 2 3 . . . . . . 58 59 60

More about thisin a few minutes

Trigger Philosophy Use only drift chamber (DR) and calorimeter (CC) information. Make trigger decision every 42ns (i.e. trigger clock rate). Take enough time (number of pipelined steps) to make a sophisticated Level-1

trigger decision: About 2 s. The readout deadtime is about 20 s, so we need to keep the trigger rate < 1000

RF bucket

Pipeline clk

Early DR

Late DR

Early CC

Late CC

look here for CC info

72 MHz

24 MHz

look here for DR infoSuppose eventhappens here

Mixer/ShaperBoards

TILE(8)

TILE (16)

AXTR(16) AXX(16)

DR3 - TQT

STTR(12)

G / CAL

Mixer/Shaper Crates (24)

TPRO(2)

DM/CTL

TPRO(4) TIM

DM/CTL

Drift Chamber Crates

CLEO-III/cTriggerSystem

Overview

What it Looks LikeWhat it Looks Like (all more or less alike to untrained (all more or less alike to untrained

eye)eye)

Common FeatureCommon Feature

FPGA based Logic

DAQ/VME

CircularBuffer

Inputs Outputs

TDITMSTCK

TDO JTAG

16 AXTRtrigger boards

backplane(single ended)

16 AXX receiver boards

LVDS fromDR3 preampstrack info to

106 x 2Repeatingunit (x 8)

Axial Tracking TriggerAxial Tracking Trigger

Layer 9 = “key”

InnerLookup

OuterLookup

Inner/Outer track correlator

Stereo Stereo Tracking Tracking TriggerTrigger

There are too many wires to form allcombinations in LUT

- Combine these into 4x4 blocks

stereo trigger hardware

1 superlayer

= Hit wire location at z = 0

Track trajectory:Pperp = 350 MeV/c = 35o

-shifted curve, Pperp = 350 MeV/c = 35o

Track in U and V IndependentlyTrack in U and V Independently

Axial – Axial – Stereo Stereo

CorrelationCorrelation

Axial – Axial – Stereo Stereo

CorrelationCorrelation

Axial112

Raw key wires

Clustered key wires

Axial matching cells

48 high

48 low

Stereo - U

48 high

48 low

Stereo - V

Axial - Stereo CorrelationAxial - Stereo Correlation

high highlow

Calorimeter TriggerCalorimeter Trigger

Energy sharing between boardscan result in a loss of efficiency:

Present summing = Tile summing =

containedshower

Threshold = 500 MeV

Wrinkle – We need to work fast!Wrinkle – We need to work fast!

Preamp out

Mixer/shaper out

Trigger signal

Discriminator out

2 s/div

Calorimeter trigger informationcomes ~ 1.8 us after crossing.

twicedifferentiated

1 m/s crate

1 m/s card

lowmed

“Tiling” sets too many bits Must Sparsify

H M L proj

proj 11

lowmed

highAvailable

to decisionboards

Time Bucket

5 10 15 20

#trackEv-time

Timing IssuesLOW

CC time – TR time

0 1 2 3 . . . . . . 58 59 60

That’s how thisplot is made !

Compare to Simulation

(1995)

Mean = 17.5RMS = 0.73

Mean = 16.9RMS = 0.51

Mean = 16.7RMS = 0.41

Mean = 16.6RMS = 0.37

1 track events 4 track events

7 track events 10 track events

Trigger Time (42ns bucket) Trigger Time (42ns bucket)

Pipe-delay

MAKE 48MATCHINGCELLS

Pipe-delay

FINDEVENTTIME

Pipe-delay

AXIALCELLCOUNT

CB & DAQ

Typical Trigger Board

For timealignment

TRCR-1

TRCR-2

From AXTRCrate

From STTRCrate

From TPROCrate

To DAQ

L1D Trigger Crate

8 FPGAs

Timing (3)

Info (185)

Timing (TR, CB or CE)

Info (valid at timing edge)

Route48 Prescale24 Bunch24

Scaler

L1-accept

Trigger Decision Boards (L1D)Trigger Decision Boards (L1D)

How To Define How To Define a CLEO-c a CLEO-c

Trigger LineTrigger Line

% Generic Hadron Line, Barrel Timing%SUBDESIGN line0(

in[117..0] : INPUT;out : OUTPUT;

Variable1cblow : SOFT;3tracks : SOFT;evtime : SOFT;

Begin-- trigger bit mappings:

tr_time[1..0] = in[1..0];cb_time[1..0] = in[3..2];ce_time[1..0] = in[5..4];cc_time[1..0] = in[7..6];

tr_n_hi[3..0] = in[11..8];tr_n_lo[3..0] = in[15..12];tr_n_ax[3..0] = in[19..16];tr_lowpos[1..0] = in[21..20];

cb_l_phi[7..0] = in[29..22];cb_h_phi[7..0] = in[37..30];

cb_low_old[1..0] = in[39..38];cb_med_old[1..0] = in[41..40];cb_high_old[1..0] = in[43..42];ce_low_old[1..0] = in[45..44];ce_med_old[1..0] = in[47..46];ce_high_old[1..0] = in[49..48];

cb_n_low[2..0] = in[52..50];cb_n_med[2..0] = in[55..53];cb_n_high[2..0] = in[58..56];ce_n_low[2..0] = in[61..59];ce_n_med[2..0] = in[64..62];ce_n_high[2..0] = in[67..65];

bha_theta[7..0] = in[75..68];

cc_spare[15..0] = in[91..76];

cpu_trig[1..0] = in[93..92];

control[23..0] = in[117..94];

------------------------------------------------ trigger line definition

1cblow = cb_n_low[] > 0;

3tracks = (tr_n_hi[]>2) # ((tr_n_hi[]>1)&(tr_n_lo[]>0)) #((tr_n_hi[]>0)&(tr_n_lo[]>1)) ;

evtime = cb_time[0];

out = 1cblow & 3tracks & evtime;

1/PT 1/PT

“Non-IsolatedTracks”

InHadronEvents

All TracksNo Trigger

- hardware

No Trigger

-missing hits

Total Efficiency

200 MeV

Axial Trigger

Performance

“IsolatedElectronTracks”

All Tracks

No Trigger

Total Efficiency

210 MeV

Stereo Trigger

Performance(with axial)

B = 1.5 T

“IsolatedElectronTracks”

All Tracks

No Trigger

Total Efficiency

140 MeV

Stereo Trigger

Performance(with axial)

B = 1.0 T

CC Trigger Performance

Needsmorestudy

For Lots More InfoFor Lots More Info

http://www.hep.uiuc.edu/cleo/trig3/

The CLEO-c Trigger System: More Than Just Blinking Lights ! LEPP Lunch Talk Mats Selen

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