Designing Control System for Front End Electronics of EMCal Detectors
1 ALICE EMCal Electronics Outline: PHOS Electronics review Design Specifications –Why PHOS readout...
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Transcript of 1 ALICE EMCal Electronics Outline: PHOS Electronics review Design Specifications –Why PHOS readout...
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ALICE EMCal Electronics
Outline:
• PHOS Electronics review
• Design Specifications– Why PHOS readout is suitable– Necessary differences from PHOS
• Shaping time / data volume problem
• EMCal vs PHOS comparison summary
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Crystal APD+PreAmp Transition-card FEE-card w/ ALTRO8 4
PHOS Electronics,Schematic
32 ChannelsOne Channel
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PHOS Module Assembly
FEE Card
32 Channels
35cm x 21cm
5.5 Watts (170mW/ch)
870SF (27SF/ch)
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Crystal APD+PreAmp Transition Card FEE-card w/ ALTRO8 4
TRU = Trigger Router Unit
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RCU = Read-out Control Unit
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4 RCU = 1 PHOS Module = 3584 Crystals
Level 0Level 1
8 OR
In total 5 PHOS Modules
PHOS Electronics,Schematic
32 Channels
448 Channels
896 Channels
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Tower/module structure: “shashlik” design
Total Pb depth = 124 mm = 22.1 X0
Comparisons:PHOS = 180 mm/8.9 mm = 20.2 X0
ATLAS LiqAr/Pb = 25 X0
CMS PbWO = 25 X0
Trapezoidal module: transverse size varies in depth from 63x63 to 63x67 mm2
78 layers of 1.6 mm scint/1.6 mm PbMoliere radius ~ 2 cm
Pb absorber has dimensions of module
Towers defined by smaller optically isolated scintillator tiles
Going to Shashlik design allows to use thinner sampling layers to improve intrinsic energy resolution.
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Use PHOS APD + Charge Sensitive PreAmplifier
• Must operate in Magnetic Field.• Need gain (and gain adjustment for trigger)• Light yield from EMCal similar to PHOS
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inclusive jets10 Hz @ 50 GeV
few x 104/year for ET>150 GeV
EFS = 250 GeV(PHOS 80 GeV)
Full Scale energy…
From Peter Jacobs
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Light yield
Light Yield (in photo-electrons) measured at WSU with Cosmic rays in prototype tower using well-calibrated PMT.
For APD, with Gain M=1 expect ~2.5 photoelectrons/MeVCompare PHOS: 4.4 pe/MeV @ M=1. For same fullscale signal amplitude MEmcal = 50(MPHOS)*(4.4*80GeV)/(2.5*250GeV)=28
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Intrinsic Energy Resolution
GEANT Simulation results:• Sampling fraction 8.1%• Intrinsic energy resolution ~12%
Calculations by Aleksei Pavlinov
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The PHOS APD + CSP Electronic Noise
• PHOS measurement 625e @ 2s shaping : 625/(4.4*50)=2.8 MeV• If EMCal uses 100ns shaping, expect ~1500e : 1500/(2.5*50)=12 MeV (36MeV 3x3)
from PHOS Electronics Document
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Resolution
0.001
0.01
0.1
1
0 5 10 15 20 25 30
Energy (GeV)
sigma/E
Series1Series2Series3Series4
Blue: Intrinsic resolution 12%Green: Digitization resolutionPink: Calibration 1%Light Blue: Electronics 2000 eNC = 60MeV
Energy Resolution: All contributions
Even with pessimistic assumptions (eNC=2000) electronics contributions to resolution are unimportant in energy region of primary interest.Important open question: slow neutrons
drives choice to investigate short shaping time ~100 ns.
12% intrinsic
1% calibrationDigitization(full scale=250 GeV)PA/shaper
eNC=2000 (60MeV) Dual 10-bit ADCs (high and low gain)
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EMCal Resolution: The ALICE “Environment”
EMCAL only All ALICE material
GEANT Simulations for single photons (i.e. p+p)Significant degradation of resolution
A. Pavlinov
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The ALICE “Environment”
Before 30ns After 30 ns
Large background from moderately slow neutrons.
Central HIJING Simulations: Production point of particles with EDeposit
Calculations by Heather Gray
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Soft,Slow (neutron) Background
Calculations by Heather Gray
Total EMCal EDeposit vs Time Tower neutron EDeposit
Mean neutron EDeposit =36 MeV (i.e. 3 times electronic noise!) with rms=41MeVNote: This is for Central HIJING (worse case, the problem is centrality dependent).
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Bandwidth: Another shaping time argument• Propose to use peak = 100ns with 20MHz sampling
• Ex: PHOS Bandwidth– Number of samples = 5*peak/tsample = 5*4s/100ns = 200– Average hit rate (>30MeV) = 200Hz– GTL bus rate = (14FEE)(32chan)(2Gain)(10bit)(200samples)
(200Hz)=44.8MB/s– RCU data rate = 2*GTL/RCU partition=89MB/s (limit 100MB/s)
• EMCal Bandwidth– Number of samples = 5*peak/tsample = 5*200ns/50ns = 20– Average hit rate (>30MeV) = 2000Hz (from 6x6/2x2, or 80% occupancy
in central Pb+Pb(GEANT) -> 25% min bias -> 2kHz)– GTL bus rate = (12FEE)(32chan)(2Gain)(10bit)(20samples)
(2000Hz)=38.4MB/s– RCU data rate = 2*GTL/RCU partition=77MB/s – If peak = 4s with 200 samples then GTL bus rate=384MB/s - Death!
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EMCAL vs PHOS Readout ParametersQuantity PHOS EMCal
Digitization Ranges10bit x16 and x1 ranges
HiGain: 5MeV-5GeVLoGain: 80MeV-80GeVLSB=5MeV
HiGain: 16MeV-16GeVLoGain: 250MeV-250GeVLSB=16MeV
Light Yield 4.4e-/MeV at M=1220e-/MeV at M=50
2.5 e-/MeV at M=1125e-/MeV at M=50
Channel rate at E>30 MeV ~200Hz ~2kHzAPD Hamamatsu S8664-55
5x5mmCAPD=90pFF=2.27 at –25C M=50
Hamamatsu S8664-555x5mmCAPD=90pFF=2.27 at +25C M=50
Charge Senstive Preamp JFET:2SK932Cin=10pF0.78mV/fC or 0.128V/ -e
J FET:2S 9K 32Cin=10pF0.7 8mV/f C or 0.128 V/ -e
CS P Ou tputrange 0.1 47mV-2.348 V( 5MeV-80Ge V )
0.4 5mV-4V( 16MeV-250Ge V )
ENC 520 - e (2.4MeV) ~150 0 - e (10MeV)Shaper CR-2 RD typ ; e Semi-Gauss
in t= 2speak = 4s
CR-2 RD typ ; e Semi-Gaussin t= 100nspeak = 200ns
Fas t O R signa l shaping FWHM=100ns FWHM=100nsADC ALTRO-16S , T 16*10bit
2@ 0/40Mhz,LSBnoise<0.5mVALTRO-16S , T 16*10bit2@ 0/40Mhz,LSBnoise<0.5mV
Samplin g R : 1ate /t 10MHz, 14 presamples 20MhzMax.N . r Samples/signal5*peak /t
200 20
D atar /ateChannel 200H *z (2 range)*(200sample )s *10bits=100kB/s
2k *Hz (2 range)*(20sample )s *10bits=100kB/s
Pow erconsumption 112 FEE*10 = W 1.12kW8 TRU*30 =W 0.24kWTota l 1.36 k /W Module(380mW/channel)
36 FEE*10 = W 0.3 6kW3 TRU*30 =W 0.09kWTota l 0.45 k /W SuperModule(390mW/channel)
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PHOS vs EMCal Readout comparison
• Commonalities:– Same APD + preamplifier
– Same GTL bus (but not identical)
– ~Same FEE
– Same RCU,TRU, etc
• Differences– Different T-Card: FEE located far away, need signals driver on T-
card+twisted pair
– Same FEE but with shorter shaping time, 100ns
– Numerology, FEE to GTL to RCU, TRU
– New (later option) TRU’ to form larger area energy sums for jet trigger.
• Other– Power consumption: 63mW*1152 = 73W in SM, 450W in FEE region of SM
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Tower APD+PreAmp Transition Card FEE-card w/ ALTRO8 4
TRU = Trigger Router Unit
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RCU = Read-out Control Unit
2(1.5) RCU/SuperModule = 1152 Towers (cf. 896 PHOS)
Level 0
Level 1
3 ORper SM
EMCal Electronics: Numerology
32 Channels
384 Towers
1152 Towers(768 + 384)
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TRU’ = Trigger Router Unit’
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13824 Towers
Level 1 , . .
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Totals/SuperModule
36 FEE cards
3 GTL bus
3 TRU
1 RCU
EMCal Readout Matrix per Supermodule
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Additional Slides
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EMCAL Physical Parameters
Quantity Value
Sampling Ratio, dPb/dSc 1.6 mm Pb / 1.6mm Scintillator
Sampling Fraction, fs=ESc/EPb 0.0811 (including all ALICE materials)
Energy Resolution 12% / √E
Calibration LED, π0’s, electrons
Total depth 24.8 cm
Number of Pb/Sc layers 78
Number of Radiation Lengths 22.3 (active detector only)
Module Size 12.7 X 12.6 X 31 cm3
Tower Size (at η=0) Δφ x Δη = 0.015 x 0.015
Occupancy (dNch/dη=25 00) Hit:16% Tower:~80%
Number of Towers 2x2=13,824
Number of Modules 12x12x24=3456
Number of Supermodules 12
Weight of Supermodule ~9.6 tons
Total Coverage Δφ =120o, -0.7 < η < 0.7
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EMCAL Readout Parameters
Quantity Value
Digitization Ranges10bit x16 and x1 ranges; 14bits effective
HiGain: 16MeV-16GeVLoGain: 250MeV-250GeVLSB=16MeV
Light Yield 2.5 e-/MeV at M=1; 125e-/MeV at M=50Channel rate at E>30 MeV 2kHzAPD e.g. Hamamtsu S8664-55 (5x5mm2); CAPD=90pF;
Excess noise factor F=3.6; Dark current ~10nACharge Senstive Preamp (PHOS) JFET:2SK932; Cin=10pF; 60mW;
0.78mV/fC or 0.128V/e-C SP Outpu trange 0.45mV-4 (16V MeV-250GeV)Electronic Noise Charg e(ENC) 1500e- (~12MeV)Shape (r PHOS) CR-2R D type; Semi-Gauss; τ int = 100ns; τpeak = 200nsFast OR signal shaping FWHM=100nsTiming Resolution ~1 nsTrigger LVL0(<800ns)=Shower: LVL1(<6ms)=Shower, Patch
ADC ALTRO-16ST, 16*10bit@20/40MHz,LSBnoise<0.5mVEffective Number of Bits (ENOB) = 9.5
Sampling Rate: 1/Δt 20MHzMax.Nr.Samples/Signal (5*τpeak/Δt) 20
Data rate per channel 2kHz*(2 range)*(20 samples)*(10bits)=100kByte/s
Power consumption <400mW/channel
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PHOS FEE
• 9 Pre-production prototypes produced at Huaxiang University of science and technology.• Used in PHOS test beam period of Oct.’04).
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EMCAL: main jet physics capabilities
1. Level 1 trigger for jets, 0/• essential for jet ET>50 GeV
2. Improved jet energy resolution• charged-only jets: poor resolution (>50%)• TPC+EMCAL: resolution ~30%
• main effect: out-of-cone energy (R~0.3 for heavy ions)• also: intrinsic resolution; missing n, K0
L,
3. 0 discrimination to pT~30-40 GeV (cross section limit for +jet coincidences in acceptance)
S. Blyth, QM04
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Tower granularity (cont’d)
0 opening angle 0 shower shape discrimination
Heather Gray, LBNL/Cape Town
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0 rejection for pT<~30 GeV/c
More sophisticated SSA underway, possible large improvementsAdditional +jet issues: • other backgrounds: fragmentation , radiative decays, …• isolation cuts
+jet is important but limited measurement fixed $$$: maximize acceptance for jets, granularity driven by cost
preliminary
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Soft,Slow (neutron) Background
Tower Cut1 100MeV2 150MeV3 200MeV4 500MeVTime Integ.0 20ns1 30ns2 50ns3 100ns4 200ns5 500ns6 1000ns
Calculations by Heather Gray
Kill the number of neutron hits by tower threshold or (integration) time cut.
Tower threshold cut of ~150MeV is effective, but it doesn’t remove neutron energy deposit in tower with real gamma hit!
Integration time cut can also reduce the number of neutron hits. Benefit also applies to tower with real hit.
Note: Using PHOS cluster algorithm without splitting.
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Soft,Slow (neutron) Background
Tower Cut1 100MeV2 150MeV3 200MeV4 500MeVTime Integ.0 20ns1 30ns2 50ns3 100ns4 200ns5 500ns6 1000ns
10-20 GeV/c + HIJING (b<3fm) Full ALICE
Calculations by Heather Gray
Tower energy threshold and integration time cuts are correlated.
Shortening integration time allows to lower tower energy resolution, which will improve performance especially at low pT.
Note: Using PHOS cluster algorithm without splitting.
Feasible to use a shaping time of ~100ns with PHOS electronics?
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Soft,Slow (neutron) Background
Calculations by Heather Gray
The Alarming Plot… Taking the shower core only…
Conclusion: Neutrons cause large occupancy - difficulty for cluster finding.Will need to use shower core with high tower threshold. Shorter shaping time will improve the situation.Again: This is for Central HIJING (worse case, the problem is centrality dependent).
due to large clusters
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EMCal L0 trigger input concerns…
• Upon receipt of L0, the ALTRO chip keeps 14 presamples:– For PHOS with 10MHz sampling this is region of 1.4 s prior to L0.
– For EMCal with 20MHz sampling this is region of 700ns prior to L0.
– With ALICE L0 latency of 1.2 s • For 10MHz sampling this is just okay with ~no presamples
• For 20MHz sampling this is 300ns after 200ns peaking time - Death!
• Proposed PHOS solution is to use local PHOS L0 trigger output as ALTRO L0 trigger input. Would “solve” problem for EMCal also, but…– This seems to be a very dangerous solution…
• L0(PHOS) .ne. L0(CTP): might have L0(CTP) without L0(PHOS) then L2 request when there was no L0…
• Danger of filling ALTRO buffer with noisely local L0’s?
– Only alternative for EMCal seems to be to keep 10MHz sampling and go to 200ns shaping time.
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EMCal Jet Trigger (TRU’?)
Calculations by Bill Mayes
Conclusion: Increasing trigger region requires in increase trigger threshold for same trigger rejection factor (e.g. central HIJING). Not much difference in trigger efficiency (on PYTHIA jets) versus trigger region size - except for large patch sizes. PHOS TRU size (4x4 tower) works quite well…