1. 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

2. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER  PANDA (@FAIR)  Aim of project  Review  Experimental set-up, analysis  Results and current situation  Future Outline Tord Johansson Erik Thomé Kjell Fransson Pawel Marciniewski Magnus Wolke Bent Schröder Kurt Hansen Magnus Lundin Jason Brudvik Lennart Isaksson Klas Marcks von Würtemberg Linda Gerén Per-Erik Tegnér Christoph Bargholtz Pia Thörngren Engblom Olle Lundberg

3. 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

4. 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)

5. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER Review 2007  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

6. 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

7. 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 CaveDaq e-e- e-e- γ B Focal plane  62 detectors  δE ~ 1 MeV (std 0.29 MeV)  Covers 13 – 64 MeV Schematic view of experiment 164.7 MeV

8. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER Data and calibration Novosibirsk function 2nd degree polynomial fit

9. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER Results Threshold 0.5 MeV Beam: central crystal Tagger plane not in focus PWO 5x5

10. 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

11. 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

12. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER Contribution from focal plane summed quadratically to contribution from CATS Contribution from CATS NaI - CATS

13. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER Threshold: 0.5 MeV Results after deconvolution PWO 5x5

14. RESPONSE OF THE PANDA ELECTROMAGNETIC CALORIMETER Threshold: 0.5 MeV Beam off centre Beam position PWO 5x5

15. 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 resolution 13 - 30 MeV 40 - 63 MeV

16. 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 :

17. 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: