Valery Dormenev Institute for Nuclear Problems, Minsk
description
Transcript of Valery Dormenev Institute for Nuclear Problems, Minsk
Gomel, 23.07-03.08 2007
Experiment PANDA. Electromagnetic calorimeter
based on the improved Lead Tungstate (PbWO4) crystals.
Valery DormenevInstitute for Nuclear Problems, Minsk
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
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
The PANDA Physics Program
• Charmonium spectroscopy
• Exotics: hybrids, glueballs and other exotics
• Mesons in nuclear matter
• Hypernuclear physics
• D mesons physics
Objects of research
PANDA detector
2 T superconducting solenoid
Pellet target with 4*1015 atoms/cm2
2 T dipole magnet
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
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
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)
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
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
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
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
beam
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
Energy resolution
For CMS ECAL :
Stochastic term
...)GeV(E
%3.2
E
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
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
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