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