October-November 2003 China - ALICE meeting 1
PHOS in ALICE
A PHOton Spectrometer with unique capabilities for the detection/identification of photons and neutral hadrons
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PHOS
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Rails for PHOS
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What is PHOS ?
PHOS is a photon spectrometer consisting of A high resolution, highly granular EM calorimeter Associated to a MWPC acting as a charge particle veto detector,
… offering unique particle detection With high energy resolution (~ 1.5% @ 10 GeV) And high position resolution (~ 1.25mm @10 GeV)
And particle identification from very low (0.5 GeV) to fairly high (100 GeV) transverse momentum: Direct photon Decay photon Electrons Charged hadrons Neutral hadrons (0 and ) Neutral baryons (n and n)
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22
2
2
cE
b
E
a
E
E
a = 0.013 ± 0.007 GeVb = 0.036 ± 0.002 GeV1/2
c = 0.0112 ± 0.0003
Energy resolution Position resolution
Detection with PHOS
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Identification with PHOS 1/3
Photons
Shower topology
Efficien
cy
90%
Purity5%
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Identification with PHOS 2/3
Soft neutral hadrons (pt < 20 GeV/c)
Invariant mass
0
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Identification with PHOS 3/3
Hard direct photon (pt > 20 GeV/c)
Shower topology & isolation cut
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PHOS provides access to an unique scientific program Dynamical characterization of the medium by its
radiation spectrum: Early hard QCD processes: initial state structure (hard
photons and neutral hadrons @ pt 20-100 GeV/c) Hot partonic phase (Quark-Gluon Plasma)
Thermal EM radiation (black body, photons @ pt < 2 GeV) Medium effects on jets (jet quenching, 0 @ pt > 10 GeV/c, jet
photon tagging) Late hadronic phase (soft photons and neutral hadrons)
To study soft QCD effects and medium effects Hadrons gas – partons gas phase transition Chiral symmetry restoration Gluon saturation
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Photon production @ LHC
Prompt photons
Decay photons
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PHOS hardware Elementary detection cell
PWO4 crystal: 22 22180 mm3 (20 X0) Photo-readout: Avalanche Photo-Diodes
(APD)
Modular structure 17920 lead-tungstate crystals (PWO) 5 independent modules each of 3584 crystal
detector units: Total area: 8m2 Total crystal weight: 12.5t
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PHOS FE & RO electronics
A challenging project: convert weak light signal into energy and time signals and construct trigger signals. Energy
Dual gain energy channels and digitization for covering a very large dynamic range up to ~100 GeV
Separate fast energy signal for trigger and timing Time
Resolution ~2 ns to discriminate against low energy baryons Trigger
L0 (< 900 ns) for min-bias pp, low threshold (100 MeV) L1 (< 6.2 s) for high pT Pb-Pb, high threshold (5-10 GeV)
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PHOS FEE & RO electronics in ALICE
EVENT DATA
ALICE DDL (optical)DAQ PC
DCSEthernet
CONTROL
ALICETriggerSystem
PHOS L0/L1
ALICE L0/L1/L2/TTC
Optical links, coax
PHOSpower+ bias400V, 12V, 6V, 3.3V
Cabling
FEE
PW
O c
rysta
ls
Counting room area
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PHOS FE & RO electronics: details4 x 8
crystals
FEE board 32 crystals
Trigger/RouterBoard TRU
energy
trigger
control
RCUcontrol
data
L0, L1
ALICEDAQ
TriggerDCS
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UV Photon Detector Avalanche Photodiode from Hamamatsu
55 mm2 C ~ 80 pF at 250 V bias
Preamplifier (Bergen & Kurchatov) Sensivity 1V/pC Noise 470 e- Rise time 10 ns Dynamic range 1mV – 8 V
T card (Bergen & Kurchatov) Connection to FEB 2 2 8 analog signals
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FEE board 32 channels
Functions: Shaper/amplifier: slow dual
gain outputs for energy, fast energy output for trigger
Energy digitization (10 bit, base-line restoration, zero suppression)
Quadlet (2x2) analog summing of fast energy signals for PHOS trigger
Timing APD bias control (2%)+ other
control channels
T cards
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Trigger Router Card 448 channels Functions:
Data and Control GTL cable bus with FEE’s and RCU
Digitization of quadlets from FEE boards
PHOS L0/L1 Trigger generation
Router for event data stream via RCU to ALICE DAQ
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Readout Control Unit
Functions: Main Controller,
DDL to ALICE DAQ,
DCS Ethernet Provides timing
information
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PHOS FE & RO electronics: Status
R&D for a few elements has ended Most of the elements in design/development phase There is a lot of work in all areas Designed as state-of-the-art technologies (programmable logic) Construction sites not yet defined
4 x 8 crystal
s
FEE board 32 crystals
Trigger/RouterBoard TRU
energy
trigger
control
RCUcontrol
data
L0, L1
ALICEDAQ
TriggerDCS
Unit # module chs/unit Status / commentsAPD 3584 1 OKPreamplifier 3584 1 OKT-card 448 8 OKFEE board 112 32 Partly prototypedTrigger/Router board TRU 8 448 DesigningReadout Controller Unit 2 1792 TPC RCU
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PHOS collaboration China:
Beijing, China Institute of Atomic Energy Wuhan, Huazhong Normal University, Institute for Particle Physics
Czech Republic: Prague, Academy of Science of the Czech Republic, Institute of Physics
France: Nantes, Laboratoire de Physique Subatomic et des Technologies Associées
Norway: Bergen, University of Bergen, Department of Physics Oslo, University of Oslo, Department of Physics
Poland: Warsaw, Soltan Institute for Nuclear Studies
Russia: Moscow, Russian Research Center ‘Kurchatov Institute’ Protvino, Institute for High Energy Physics Sarov, Russian Federal Nuclear Center ‘VNIIEF’ Dubna, Joint Institute for Nuclear Research