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


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


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


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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Tower Cut1 100MeV2 150MeV3 200MeV4 500MeVTime Integ.0 20ns1 30ns2 50ns3 100ns4 200ns5 500ns6 1000ns


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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Tower Cut1 100MeV2 150MeV3 200MeV4 500MeVTime Integ.0 20ns1 30ns2 50ns3 100ns4 200ns5 500ns6 1000ns

10-20 GeV/c + HIJING (b<3fm) Full ALICE


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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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…

1 alice emcal electronics outline: phos electronics review design specifications –why phos readout...

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