RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER TO PHOTONS IN THE ENERGY RANGE 10 – 120 MeV

Stockholm University, Uppsala University, Lund University(Klas Marcks von Würtemberg)

Status report, PAC Nuclear Physics, Lund, November 9, 2010

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

PANDA (@FAIR) Aim of project Review Experimental set-up, analysis Results and current situation Future

Outline

Tord JohanssonErik ThoméKjell FranssonPawel MarciniewskiMagnus Wolke

Bent SchröderKurt HansenMagnus LundinJason BrudvikLennart Isaksson

Klas Marcks von WürtembergLinda Gerén

Per-Erik TegnérChristoph BargholtzPia Thörngren Engblom

Olle Lundberg

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

PANDA (@FAIR)

Study of gluonic excitations and the physics of strange and charm quarks

Demands on calorimeter: High resolution and low energy threshold

Calorimeter material: Scintillating PWO-crystals cooled to -25 ° C

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Aim Determine the energy resolution and spatial resolution of a realistic set-up

of a 5x5 matrix of PWO-crystals.

VPT (vacuum photo triods) as light converters Flash-ADC read-out system

Support structure: Carbon fibre alveoli Pre-shaped wrapping

Crystal shape (slightly tapered)

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Review2007

3x3 matrix, straight crystals

PM-tubes, Peak sensing ADCs

Today 2010

5x5 matrix, tapered crystals Carbon fibre

alveoli Provisional support structure

PM-tubes, Peak sensing ADCs / Flash-ADC

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Tomorrow (2011)

VPTs will be used. A complete setup can be tested.

Adjustable support structure planned

Current setup representative of central part of forward end-cap

Peripheral part of forward end-cap

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

5x5 PWO crystals

Climate chamber -25 °C

PM-tubes (anode signal) Preamplifiers

Cave

2x16 chn shapers 0.8 μs Peak-sensing ADC

DAQ

Radiator

Cave Daq

e-

e-

γ

B

Foca

l plan

e

Focal plane 62 detectors δE ~ 1 MeV (std 0.29 MeV) Covers 13 – 64 MeV

Schematic view of experiment

164.7 MeV

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Data and calibration

Novosibirsk function 35.2*FWHM35.2*FWHM

2nd degree polynomial fit

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Results

Threshold 0.5 MeV

35.2/FWHM

Beam: central crystal

Tagger plane not in focus

PWO 5x5

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Independent measurement of focal plane resolution with CATS

500 kg NaI in 7 segments

Calibrated by 15.11 MeV line of Carbon

Revealed features

Decreased resolution of focal plane below 35 MeV

Nominal energies of focal plane detectors scaled by a factor 1.075

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Independent measurement of tagged photon energies with CATS

Fitting region

Tagger detector 61

Tagger detector 8

E_CATS=0.18+0.94*E_Nominal

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Contribution from focal plane summed quadratically to contribution from CATS

Contribution from CATS

NaI - CATS

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Threshold: 0.5 MeV

Results after deconvolution

PWO 5x5

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Threshold: 0.5 MeV

Beam off centre

Beam position

PWO 5x5

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Position of a photon striking the detector estimated by weighted average of energy depositions (non-linear weights)

Fine structures of estimated position when deposited energy is spread over few crystals.

Spatial resolution13 - 30 MeV

40 - 63 MeV

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Spatial profile of beam measured with ccd-camera

Total width: 14 mm

Standard deviation: 2.9 mm

Contribution from beam width to measured spatial resolution small if quadratical summing assumed :

][0.7][9.26.7 22 mmmmx mmmmx 0.79.26.7 22

RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER

Future

Next experiment: March 2011 New light converters: Vacuum triods

Thank you for your attention!

Increased energy resolution of focal plane below 35 MeV would be valuable.

From the projects point of view: