Valery Dormenev Institute for Nuclear Problems, Minsk
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Transcript of Valery Dormenev Institute for Nuclear Problems, Minsk
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Gomel, 23.07-03.08 2007
Experiment PANDA. Electromagnetic calorimeter
based on the improved Lead Tungstate (PbWO4) crystals.
Valery DormenevInstitute for Nuclear Problems, Minsk
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Facility for Antiproton and Ion Research (FAIR) at GSI (Darmstadt, Germany)
Double ring with 1100 m circumferences.Pulse intensity SIS100: 4*1013 proton per pulse at 29 GeV,
5*1011 U28+ ions per pulse at 1 GeV/uSIS300: 1.5*1010 U92+ ions per pulse at 35 GeV/u
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Basic Data of High Energy Storage Ring (HESR)
Experiment Mode High Resolution Mode High Luminosity Mode
Target Pellet target with 4*1015 atoms/cm2
Momentum range 1.5 – 8.9 GeV/c 1.5 – 15.0 GeV/c
Pulse intensity, s-1 1*1010 1*1011
Luminosity 2*1031 cm-2 s-1 2*1032 cm-2 s-1
Momentum resolution 1*10-5 1*10-4
Antiprotons/protons storage and acceleration
Injection
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The PANDA Physics Program
• Charmonium spectroscopy
• Exotics: hybrids, glueballs and other exotics
• Mesons in nuclear matter
• Hypernuclear physics
• D mesons physics
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Objects of research
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PANDA detector
2 T superconducting solenoid
Pellet target with 4*1015 atoms/cm2
2 T dipole magnet
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PANDA electromagnetic calorimeterOn lead tungstate scintillation crystals with increased light yield (PWO-II)
• photon detection with energy- high position- resolution
time-• a wide energy range: 10 MeV < E < 10 GeV
• located inside a superconducting solenoid (B = 2T)• necessary crystal size: length 20-22X0=18-20 cm,
cross section RM*RM=2.2*2.2 cm2
Total crystals number: Barrel: 11520Endcap upstream: 816Endcap downstream: 6864
PWO
X0=0.89 cm
RM=2.19 cm
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Lead tungstate crystal (PbWO4) CMS-type properties
Density,
g/cm3
X0, cm
RM, cm
Zeff Decay time, ns
Light yield temp. coef.,
%/0C
Refraction index at 600 nm, no/ne
LY rel. NaI:Tl, %
Max.
lum, nm
8.28 0.89 2.19 75.6 4 (95%)15 (5%)
100 (< 1%)
-1.9 2.30/2.16 1.3 440
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Properties optimization of PWO crystals for PANDA EMC To detect low energy -quanta light yield increase is necessaryThere are 3 way:
1) Growth technology optimization to suppress amount of structure defects2) Crystal activation by La, Y ions to achieve optimal Light Yield/ Kinetics/Radiation Hardness relation
CMS crystals have been optimized for high radiation hardness requirement.3) Operation at low temperature
INP team activities (present and future):• Optimization of the PWO crystal growth technology CMS EMC (1992-2007) • Development of PANDA EMC specification (2002-2006)• Quality improvement (PWO-II) for PANDA (2003-2007)• Spectroscopy studies of preproduction crystals (2004-2007)• Beam tests with 3*3 and 5*5 matrix of PWO-II (2004-2008)• Development of the monitoring system for calorimeter (2005-2008)• Quality tests of PWO-II crystals for PANDA EMC (2008-2009)
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Performed measurements
1) Light Yield measurements at different temperatures and time gates to study LY and kinetics dependences
2) Beam test measurements of 3*3 PWO-II crystals matrix with APD read out at 00 C to evaluate energy resolution
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Light yield temperature dependence (1)
Amplitude spectra of PWO-II (20x20x200mm3)crystal. 60Co source.
0
300
600
900
1200
1500
0 200 400 600 800 1000 1200 1400 1600
Channels
Cou
nts
Time gate=4s
+250C-250C
factor 4.5
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Light yield temperature dependence (2)
Light Yield of PWO-II (20x20x200 mm3) crystal vs timegate at different temperatures
0
10
20
30
40
50
60
70
80
90
100
0 500 1000 1500 2000 2500 3000 3500 4000
time gate, ns
LY
, phe
/MeV
-25 C
-10 C
0 C
+10 C
+25 C
Fast enough time response at -250C
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Beam test of 3*3 matrix of PWO-II crystals with Avalanche photodiodes readout (MAMI/ Mainz,
Germany)
16 photon energies: 40.9-674.5 MeV,
width E ~ 2MeV
Time gate=1 s
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beam
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Energy response. Line shape.
Energy, a.u.
Cou
nts
E=40.9MeV E=674.5 MeV
9 crystals
Central crystal
8 surroundingcrystals
9 crystals
Central crystal
8 surroundingcrystals
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Energy resolution
For CMS ECAL :
Stochastic term
...)GeV(E
%3.2
E
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Conclusions (1)• Technology optimization of PWO-II crystals gives
double increase of the Light Yield in comparison with CMS PWO crystals
• Cooling from +250C down -250C allows to increase the Light Yield in 4-4.5 times with 90% of the light collection in 200 ns at -250C
• Energy resolution at 00C of PWO-II with APD: stochastic term 1.21% (00 C) is better then 2.3% (+180C) for CMS EMC
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Conclusions (2)
• Extrapolation of the energy resolution of the 3x3 matrix of PWO crystals with APD readout at 00C gives /E=2.46 % @E=1 GeV
• Previous test results of the 3x3 matrix of PWO crystals with PMT readout at -250C gives extrapolated energy resolution /E= 1.86% @E=1 GeV with 0.95 % stochastic term
• Unfortunately transversal shower leakage is large at 3*3 crystals matrix geometry
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Future plans
• PROTO60 Beam tests: 60 PWO-II crystals of the PANDA EMC geometry with APD readout at -250 C
• Radiation hardness investigation at -250 C