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

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The CLEO-c Trigger SystemMore Than Just
Blinking Lights ! LEPP Lunch TalkMats Selen

• Overview
• Tracking
• Calorimeter
• Timing
• Performance

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What the Trigger DAQ Does
Suppose you want to keep only pink hexagonal
widgets moving down a conveyor belt.
The problem is Working fast means you make some
mistakes !
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Requirements Decision Time
Each widget must get examined and stamped
- You need to decide on one before the next one
comes along. - Your decision cant take longer
than Dt d/v. - Taking more time means making
less mistakes.
Trigger
d
y/n
y
n
y
n
v
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Requirements Efficiency
You cant stamp too many pink hexagonal widgets
n
Trigger
DAQ
?
?
?
y/n
n
n
n
n
SAVE
n
n
n
trash
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Requirements Rejection
The rate of widgets stamped y cant 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.
Trigger
DAQ
y/n
y
y
y
y
y
SAVE
y
trash
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Working in Steps Pipelining
Have more than one person working in series -
Each individually one takes less than Dt d/v-
Collectively, much more work is done- A smarter
decision can be made less mistakes
Trigger
DAQ
d
y
n
y
n
y
v
SAVE
n
trash
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d 14 feet, v 1 foot/ns ? Dt 14 ns
There are 183 RF buckets in CESR
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In CESR/CLEO, beam collisions arespaced a
minimum of 14 ns apart.
This smears together 3 beam collisions every
time we look. We can do this since its very rare
that anything happens during a collision.
This is not enough time to do any serious
trigger processing
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More about thisin a few minutes
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• 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 ms.
• The readout deadtime is about 20 ms, so we need
  to keep the trigger rate lt 1000 Hz.

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CLEO-III/cTriggerSystemOverview
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What it Looks Like (all more or less alike to
untrained eye)
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Common Feature
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Axial Tracking Trigger
16 AXX receiver boards
16 AXTR trigger boards
Repeating unit (x 8)
106 x 2

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LVDS from DR3 preamps
track info to TRCR
backplane (single ended)
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Stereo Tracking Trigger
There are too many wires to form
allcombinations in LUT- Combine these into
4x4 blocks
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Track in U and V Independently
Hit wire location at z 0
f-shifted curve, Pperp 350 MeV/c q 35o f
17o
Track trajectory Pperp 350 MeV/c q 35o f
15o
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Axial Stereo Correlation
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Axial Stereo Correlation
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Axial - Stereo Correlation
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Calorimeter Trigger
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Wrinkle We need to work fast!
Preamp out
twice differentiated
Mixer/shaper out
Trigger signal
Discriminator out
2 ms/div
Calorimeter trigger information comes 1.8 us
after crossing.
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1 m/s crate
1 m/s card
?
?
Tiling sets too many bits ? Must Sparsify
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01
11
11
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Availableto decisionboards
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H
M
L
proj
SH
011
SM
001
SL
001
L1-D Crate
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Timing Issues
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Thats how thisplot is made !
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Compare to Simulation (1995)
Mean 17.5 RMS 0.73
Mean 16.9 RMS 0.51
1 track events
4 track events
Trigger Time (42ns bucket)
Trigger Time (42ns bucket)
Mean 16.7 RMS 0.41
Mean 16.6 RMS 0.37
7 track events
10 track events
Trigger Time (42ns bucket)
Trigger Time (42ns bucket)
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Typical Trigger Board
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From AXTRCrate
AXPR
TRCR-1
From STTRCrate
L1D Trigger Crate
TRCR-2
From TPROCrate
CCGL
L1D
To DAQ
LUMI
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Trigger Decision Boards (L1D)
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Route
Prescale
Bunch
LUT 8 FPGAs
Info (185)
L1-accept
Backplane
Timing (3)
Scaler
Info (valid at timing edge)
Timing (TR, CB or CE)
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How To Define a CLEO-c Trigger Line
Generic Hadron Line, Barrel Timing SUBDESIGN
line0( in117..0 INPUT out
OUTPUT ) Variable 1cblow SOFT 3tracks
SOFT evtime SOFT Begin -- trigger bit
mappings tr_time1..0 in1..0 cb_time1..
0 in3..2 ce_time1..0
in5..4 cc_time1..0 in7..6 tr_n_hi3.
.0 in11..8 tr_n_lo3..0
in15..12 tr_n_ax3..0 in19..16 tr_lowp
os1..0 in21..20 cb_l_phi7..0
in29..22 cb_h_phi7..0 in37..30 cb_lo
w_old1..0 in39..38 cb_med_old1..0
in41..40 cb_high_old1..0
in43..42 ce_low_old1..0
in45..44 ce_med_old1..0
in47..46 ce_high_old1..0
in49..48 cb_n_low2..0
in52..50 cb_n_med2..0 in55..53 cb_n_h
igh2..0 in58..56 ce_n_low2..0
in61..59 ce_n_med2..0 in64..62 ce_n_h
igh2..0 in67..65 bha_theta7..0
in75..68 cc_spare15..0
in91..76 cpu_trig1..0
in93..92 control23..0 in117..94

• ----------------------------------------------
• -- trigger line definition
• 1cblow cb_n_low gt 0
• 3tracks (tr_n_higt2)
• ((tr_n_higt1)(tr_n_logt0))
• ((tr_n_higt0)(tr_n_logt1))
• evtime cb_time0
• out 1cblow 3tracks evtime
• End

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No Trigger - hardware
Axial TriggerPerformance
All Tracks
PT
1/PT
1/PT
Non-Isolated Tracks In Hadron Events
No Trigger -missing hits
200 MeV
Total Efficiency
1/PT
1/PT
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Stereo TriggerPerformance(with axial)
All Tracks
IsolatedElectronTracks
No Trigger
B 1.5 T
Total Efficiency
210 MeV
1/PT
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Stereo TriggerPerformance(with axial)
All Tracks
IsolatedElectronTracks
No Trigger
B 1.0 T
Total Efficiency
140 MeV
1/PT
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CC Trigger Performance
1.0
.8
.6
.4
.2
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For Lots More Info
http//www.hep.uiuc.edu/cleo/trig3/