1. CALOR 2012 Vardan Tadevosyan XVth International Conference on Calorimetry in High Energy Physics Santa Fe, NM, June 4 – 8, 2012 1

2. CALOR 2012 Vardan Tadevosyan Outline HMS/SOS calorimeters (6 GeV CEBAF beam) HMS/SOS spectrometers and detector packages Construction of the calorimeters Performance of the calorimeters Summary SHMS calorimeter (12 GeV CEBAF beam) SHMS spectrometer and its detector package Design construction of the calorimeter Pre-assembly studies Expected performance Summary 2

3. CALOR 2012 Vardan Tadevosyan 6 GeV Hall C spectrometers configuration Hall C configuration at 6 GeV CEBAF beam energy: HMS and SOS magnetic spectrometers for coincident electro-production measurements, complementary to each other, with well matched acceptances. SOS HMS 3

4. CALOR 2012 Vardan Tadevosyan SOS & HMS spectrometers’ parameters SOS operated at lower energies, in unfavorable background conditions. 4

5. CALOR 2012 Vardan Tadevosyan HMS & SOS detector packages  A pair of MWDC’s at the FP, for track reconstruction.  4 planes of X and Y oriented scintillator hodoscopes for timing.  Gas Č counter & EM calorimeter for electron/hadron separation.  Aerogel detector for separation of hadrons. SOS detector package was similar to the HMS package. 5 A HMS detectors

6. CALOR 2012 Vardan Tadevosyan HMS & SOS calorimeters’ construction The left side PMTs in the first 2 layers added in 1998. SOS calorimeter was of identical design, except the number of rows 11. Particle flux HMS calorimeter Thickness14.6 rad.length Effective area60×120 cm 2 # of modules52 # of channels78 Arrangement4×13 Čer. RadiatorTF-1 lead glass Block sizes10×10×70 cm 3 Light detectorXP3462B PMT In operation1995 - present 6

7. CALOR 2012 Vardan Tadevosyan HMS & SOS calorimeters’ construction continued 1 HMS calorimeter module 10×10×70 cm 3 TF-1 lead glass block optically isolated with 25 µm aluminized Mylar and 40 µm black Tedlar film. 3” XP3462B Photonis PMT optically coupled to the block with Bycron ND-703 optical grease of refractive index 1.46. 6 turns of 100 µm thick µ-metal foil for magnetic shielding of the PMT. 7

8. CALOR 2012 Vardan Tadevosyan XP3462B PMT A 3”, 8-stage PMT from Photonis, with Ø 68 mm semitransparent bi- alkaline photocathode, with peak Quantum Efficiency 29% at 400 nm. 8

9. CALOR 2012 Vardan Tadevosyan HMS & SOS calorimeters’ radiator Density3.86 g/cm 3 Refr. Index1.65 Rad. length2.74 cm Fractional composition: 51.2% PbO, 41.3% SiO 2, 3.5% K 2 O, 3.5% Na 2 O. 9

10. CALOR 2012 Vardan Tadevosyan Calibration of HMS & SOS calorimeters  Calibration with electrons selected in the gas Čerenkov counter.  Minimization of the variance of the estimated energy with respect to the calibration constants, subject to the constraint that the estimate is unbiased. 10

11. CALOR 2012 Vardan Tadevosyan Resolution of HMS & SOS calorimeters HMS calorimeter’s resolution, similar to other lead glass calorimeters. SOS calorimeter ‘s experimental resolution was reported ~5%/√E. 11

12. CALOR 2012 Vardan Tadevosyan Electron detection efficiency in the HMS calorimeter e - detection efficiency from GEANT4/QGSP_BERT simulations in reasonable agreement with experiment in few GeV energy range. 12

13. CALOR 2012 Vardan Tadevosyan Pion suppression in the HMS calorimeter Pion suppression from GEANT4 simulation with QGSP-BERT physics list in reasonable agreement with experimental data. 13

14. CALOR 2012 Vardan Tadevosyan Summary on the HMS & SOS calorimeters  HMS and SOS calorimeters have been in operation for more than 15 years, showed remarkably stable performance;  Resolution of the detectors is similar to the other lead glass calorimeters;  Pion suppression of a few tens and electron detection efficiency better than 99% was routinely achievable under the Hall C experimental conditions;  GEANT4 based simulations show performance of the HMS calorimeter in the reasonable agreement with existing experimental data in few GeV energy range;  The simulations predict performance of the calorimeter in the extended HMS momentum range, within the required specifications of the 12 GeV upgrade. 14

15. CALOR 2012 Vardan Tadevosyan Hall C 12 GeV upgrade, SHMS spectrometer SuperHMS supersedes SOS. Will operate at small angles, high energies. High rate charged particle fluxes are expected. Good PID is crucial. 15 Central Momentum: 2 to 11 GeV/c Momentum Accept.: (-10%, +22%) Scattering Angle: 5.5 to 40° Solid Angle: 4.0 msr

16. CALOR 2012 Vardan Tadevosyan SHMS detector package 16 1 – Nobel Gas Cerenkov 2 – MWDC 3 – Scint. Hodoscope 4 – Heavy Gas Cerenkov 5 – Quartz Hodoscope 6 – EM calorimeter

17. CALOR 2012 Vardan Tadevosyan Design construction of SHMS calorimeter 17 Particle flux PRESHOWER SHOWER CALORIMETER: Number of channels252 Effective Area (cm 2 ) 116x134 Thickness (Rad.L.)21.6 PRESHOWER: Number of blocks28 Blocks & PMTs fromSOS Block size (cm 3 ) 10x10x70 Lead Glass typeTF-1 Thickness (Rad.L.)3.6 SHOWER: Number of blocks224 Modules fromHERMES Block size (cm 3 ) 9x9x50 Lead Glass typeF-101 Thickness (Rad.L.)18.0 Radiators : TF-1 Rad.L.(cm)2.74 F-1 Rad.L.(cm)2.78 Density (g/cm 3 )3.86 Refractive Index1.65

18. CALOR 2012 Vardan Tadevosyan Construction of SHOWER module 18 HERMES module is similar to HMS/SOS modules, differs only in details. F-101 lead glass is similar to TF-1 in chemical composition. Small amount of CeO added for radiation hardness, absorbs light at short wavelengths. 3” XP3461 Photonis PMT, with green extended bialkali photo- cathode, of the same structure as XP3462B in PRESHOWER.

19. CALOR 2012 Vardan Tadevosyan Pre-assembly checks of SHMS PRESHOWER constituents 19 Light transmittance of TF-1 lead glass blocks, before and after use in SOS calorimeter. Signs of marginal degradation from radiation. Gain measurement of XP3462B PMTS, before and after use in SOS calorimeter. No deterioration was detected.

20. CALOR 2012 Vardan Tadevosyan Pre-assembly checks of SHMS SHOWER constituents 20 UV light curing test of the HERMS F- 101 lead glass blocks. No significant changes were found. Relative quantum efficiency tests of XP3461 PMTs from HEREMES. A 15% (marginal) degradation was detected.

21. CALOR 2012 Vardan Tadevosyan Simulation code for SHMS calorimeter Based on GEANT4-9.2, QGSP-BERT physics list.  Track sampling at FP  Passage through material before the calorimeter,  Čerenkov light generation and tracing  p.e. knock-out from PMT photocahode  Digitization Calibration with electrons. 21

22. CALOR 2012 Vardan Tadevosyan Resolution of SHMS calorimeter Resolution similar to other lead glass calorimeters. Lower than for HMS, due to excess of light absorption in the Shower, and more material in front. 22

23. CALOR 2012 Vardan Tadevosyan Pion suppression in SHMS calorimeter At high SHMS momenta, cuts at higher energies render descent pion suppression. 23

24. CALOR 2012 Vardan Tadevosyan Pion suppression in SHMS calorimeter continued 1 Use of PRESHOWER requires optimization of the separation boundary. 24

25. CALOR 2012 Vardan Tadevosyan Pion suppression in SHMS calorimeter continued 2 25 Use of PRESHOWER in combination with SHOWER improves pion suppression.

26. CALOR 2012 Vardan Tadevosyan Summary on the SHMS calorimeter  Design construction of the SHMS calorimeter is chosen, based on extensive Monte Carlo simulations, and available constituents.  Parts from the retired SOS calorimeter are used in the PRESHOWER, while modules from the HERMES calorimeter will be used in the SHOWER assembling.  Pre-assembly studies indicate little degradation of the radiators and PMTs for both PRESHOWER and SHOWER parts.  A simulation code, based on GEANT4 package and QGSP-BERT physics model, was developed and used for evaluation of the performance of the calorimeter.  The expected resolution is similar to the other lead glass calorimeters, but somewhat lower than for the HMS calorimeter.  The pion suppression is expected to be lower than in HMS if total energy deposition alone is used, and similar to or better if it is used in combination with deposited in the PRESHOWER energy. 26

27. CALOR 2012 Vardan Tadevosyan END 27

28. CALOR 2012 Vardan Tadevosyan Back up 28

29. CALOR 2012 Vardan Tadevosyan 29

30. CALOR 2012 Vardan Tadevosyan 30

31. CALOR 2012 Vardan Tadevosyan Optimization of the HMS & SOS calorimeter construction The design was optimized before construction, by means of test measurements, optics calculations, and Monte Carlo simulations. The used simulation packages were: ELSS-1, EGS-4, GEANT 3.21, GEANT4. Two examples of the optical calculations are below: Reflection of Čerenkov light from the block side for different wrappings. Transmission from the block to PMT window for different optical couplings. 31 ND-703

32. CALOR 2012 Vardan Tadevosyan Electron detection efficiency in the HMS calorimeter cont’d 32 Disagreement between experimental and GEANT4/QGSP_BERT e- detection efficiencies at low energies < 1.5 GeV.

33. CALOR 2012 Vardan Tadevosyan Choice of design construction of SHMS calorimeter 3 versions considered. GEANT3 simulations predicted nearly same performance. 33

34. CALOR 2012 Vardan Tadevosyan SHMS detector package continued 34 The calorimeter will partially sit in the rear concrete wall of the HMS shield house.

35. CALOR 2012 Vardan Tadevosyan PRESHOWER Construction Optically isolated TF-1 blocks stacked in light tight aluminum box. XP3462B PMT assemblies attached to the sides. Simulations show the counter is not sensitive to up to ~1mm gaps between the blocks. PMTs & dividers can be swapped if needed. 35

36. CALOR 2012 Vardan Tadevosyan Gain in pion suppression 36

37. CALOR 2012 Vardan Tadevosyan TF-1 Refracive Index 37

38. CALOR 2012 Vardan Tadevosyan Signal coordinate dependence 38

39. CALOR 2012 Vardan Tadevosyan TF-1 Figure of Merit 39

40. CALOR 2012 Vardan Tadevosyan Divider for XP3462B PMT 40 R1 = 10 MΩ, R2 = 5.62 k Ω, R3 = 33.2 k Ω, R4 = 110.4 k Ω, R5 = 71.8 k Ω, R6 = R7 = R8 = R9 = 47.5 k Ω, R10 = 59.3 k Ω, R11 = 95 k Ω, R12 = 50 Ω, R13 = 71.8 k Ω, R14 = R15 = 1.0 k Ω. Capacitors 10 nF.

41. CALOR 2012 Vardan Tadevosyan HMS Calorimeter Electronics Diagram 41

42. CALOR 2012 Vardan Tadevosyan PRESHOWER/SHOWER π Suppression in HMS calorimeter 42

43. CALOR 2012 Vardan Tadevosyan F-101 Block Transmittance 43

44. CALOR 2012 Vardan Tadevosyan TF-1 UV curing test 44

45. CALOR 2012 Vardan Tadevosyan Gain in π Suppression in SHMS Calorimeter 45