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Design Studies for a Compact Tungsten Scintillator Electromagnetic Calorimeter

Design Studies for a Compact Tungsten Scintillator Electromagnetic Calorimeter . C.Woody , S.Cheung , J.Haggerty , E.Kistenev , S.Stoll For the PHENIX Collaboration and Brookhaven National Lab. October 26, 2011. N29-2 2011 IEEE NSS/MIC Valencia, Spain.

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Design Studies for a Compact Tungsten Scintillator Electromagnetic Calorimeter

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  1. Design Studies for a Compact Tungsten Scintillator Electromagnetic Calorimeter C.Woody, S.Cheung, J.Haggerty, E.Kistenev, S.Stoll For the PHENIX Collaboration and Brookhaven National Lab October 26, 2011 N29-2 2011 IEEE NSS/MIC Valencia, Spain

  2. What do we mean by “Compact Calorimetry” ? • Compact implies: • showers have limited extent in both transverse • and longitudinal dimensions • (ideally would like showers to be point-like) • calorimeter is physically small ( dense) so that it • occupies a minimal amount of space • To achieve this, one requires: • Small Moliere radius • Short radiation length • However, there is a tradeoff between “compactness” • and energy resolution (determined by the sampling fraction and photostatistics) C.Woody, 2011NSS N29-2, 10/26/11

  3. The Present PHENIX Experiment C.Woody, 2011 NSS N29-2, 10/26/11

  4. The Transformation to sPHENIX C.Woody, 2011NSS N29-2, 10/26/11

  5. The sPHENIX Detector C.Woody, 2011NSS N29-2, 10/26/11

  6. Calorimeter Simulation (GEANT4) Energy Resolution vs Sampling Thickness Moliere Radius RM = 21.1 MeV ~ 2.6 X0 9.3 mm for W 1 X0 (3.5 mm) W 1.5 mm scint 30 % scint by volume 3.7% energy fraction Approximately 90% of energy is contained within 1 RM, nearly independent of E = + b ( a only includes sampling fluctuations, 1.5 mm scintillator plates ) sPHENIX requires 15% Want small photostatistics contribution to the overall resolution C.Woody, 2011NSS N29-2, 10/26/11

  7. Preshower and Longitudinal Segmentation Super conducting Magnet (~ 1X0) Hadronic Calorimeter Compact EMCAL (~ 15 X0) Preshower • ~ 3-4 X0 Silicon-Tungsten • ~ 2 mm W plates, ~ 1 mm Si strips • → See NP5.S-180 (E.Kistenev) Preshower • Longitudinal segmentation required for: • g/p0 separation for single g and jet • measurements up to pT~ 40 GeV/c • e/p separation (~ 10-3) for measuring • J/Y’s and U’s p0 g C.Woody, 2011NSS N29-2, 10/26/11

  8. Compact EMCAL for sPHENIX • Requirements: • Compact • Projective • Hermetic • Readout works in magnetic field • Low cost • Three designs being considered: • Optical Accordion • Projective Shashlik • Scintillating Fiber (SciFi) C.Woody, 2011NSS N29-2, 10/26/11

  9. Optical Accordion Accordion design similar to ATLAS Liquid Argon Calorimeter • Optical readout with either scintillating • fibers or scintillating plates with embedded • wavelength shifting fibers • Fibers read out with SiPMs or APDs Needs to be hermetic and projective • Volume increases with radius • Scintillator thickness doesn’t increase with • radius, so either tungsten thickness must • increase or the amplitude of the oscillation • must increase, or both • Plate thickness cannot be totally uniform • due to the undulations • Small amplitude oscillations minimize both • of these problems C.Woody, 2011NSS N29-2, 10/26/11

  10. Accordion Shaped Tungsten Plates Tungsten Heavy Powder, Inc (San Diego, CA) • Sintered from tungsten powder • Final density ~ 17.5 g/cm3 • Shape and thickness variation not a problem • Fibers can be glued in between plates with tungsten/epoxy composite • (density ~ 10-11 g/cm3) C.Woody, 2011NSS N29-2, 10/26/11

  11. SiPM 90Sr source Fibers Trigger pmt Light Output of Scintillating Fibers with SiPM PMT2 Sr90 source above PMT3 trigger MPPC Light output ~16 p.e./0.2 MeV  ~ 80 p.e./MeV Challenge is to collect all this light onto a relatively small area SiPM or APD. C.Woody, 2011NSS N29-2, 10/26/11

  12. Light Output of Scintillating Tiles + WLS Fibers + SiPM Possible readout using scintillating plates and WLS fibers Light output with ~ 25 p.e./MeV with looped fibers Advantage of fewer fibers compared with pure scintillating fiber design WLS fibers Scint tile SiPM C.Woody, 2011 NSS N29-2, 10/26/11

  13. Projective Shashlik • Size of absorber and scintillator plates would both increase as a function of depth • Small size improves light collection • Fewer fibers to collect light onto a SiPM or APD C.Woody, 2011NSS N29-2, 10/26/11

  14. Light Output of Scintillating Tiles + WLS Fibers + SiPMShashlik Configuration 137Cs source SiPM Trigger pmt Tile stack Light output depends linearly on number of fibers ~ 12 p.e./MeV with 4-5 fibers C.Woody, 2011NSS N29-2, 10/26/11

  15. Summary • Both physics requirements and cost limitations drive the need for highly compact calorimeters in future collider experiments. • We believe a highly segmented optical readout tungsten-scintillator calorimeter can meet those requirements. • Several calorimeter configurations have been studied that appear to be able to be able to meet those needs. • Work will continue to develop one or more of these designs into a working prototype for beam testing next year. C.Woody, 2011NSS N29-2, 10/26/11

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