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HO LIGHT GUIDE SIMULATIONS

HO LIGHT GUIDE SIMULATIONS. HO LIGHT GUIDE SIMULATIONS Justin Parsons, University of Iowa Jim Freeman, FNAL. 1. Outline. Problem and proposed solution Light guide material, and geometry Simulation software : LITRANI Testing the software Simulations Results and future plans. 2.

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HO LIGHT GUIDE SIMULATIONS

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  1. HO LIGHT GUIDE SIMULATIONS HO LIGHT GUIDE SIMULATIONS Justin Parsons, University of Iowa Jim Freeman, FNAL 1 HCal Electronics Meeting

  2. Outline • Problem and proposed solution • Light guide material, and geometry • Simulation software : LITRANI • Testing the software • Simulations • Results and future plans HCal Electronics Meeting 2

  3. Motivation for Simulations • HO HPDs must be replaced • SiPMs are best option but are not equal in active area or shape of HPDs • Need a LG which will couple fiber bundle with SiPM HCal Electronics Meeting 3

  4. Material of Light Guide • Bench tests @ Iowa show Mylar and HEM to be not rad hard enough • 17% reduction in eff after 10Mrad  exposure IEEE Transactions on Nuclear Science, Vol. 53, No. 3, 1547 • Two options, Aluminum or “German Mylar” (HF) • Chose Al for these simulations • Most common light guide material • May be processed to prevent oxidation and polished to improve reflectivity • Easy to work with HCal Electronics Meeting 4

  5. Geometry and Source • Source emits at 520nm, laser or fiber with 30deg aperture • SiPM active area is 4.41mm2 => Ru=1.485mm • Fiber bundle diameter is 3.5mm => RL=1.75mm (wrong FB diameter, will correct in future) Software Tests HO Simulations HCal Electronics Meeting 5

  6. Simulation Software • Need capable and accessible simulation software option • LITRANI • Extension of ROOT • Used for simulations in GLAST and ECAL • http://gentit.home.cern.ch/gentit/litrani/ • GEANT4, for future simulations • Slightly simpler to build simulation • Alleviates a few problems HCal Electronics Meeting 6

  7. Testing Software [cm] • 1cm long, RU/RL=1, 520nm laser X-Y scan • - Aimed laser for single scattering at Z=1/2 • the total length, varied reflectivity HCal Electronics Meeting 7

  8. Testing Software - Mask Test • Created mask with aperture same size as fiber diameter (0.094 cm), did X-Y scan with laser [cm] HCal Electronics Meeting 8

  9. Testing Software - Summary • Straight tubular LG transmits light as expected • Beam angled for a single scattering gives efficiences ~ reflectivity • Masking of most of detector also responds as expected • => LITRANI passes these simple tests • Results found to be symmetric with respect to +/- and X/Y for used LG geometries HCal Electronics Meeting 9

  10. Simulations • Simulations performed for 4 combinations of geometry and LG core • ACC = Air Core Conical LG • FC = Filled Conical LG • ACT = Air Core Trapezoidal tube LG • FT = Filled Trapezoidal tube LG • 3 simulations run for each • E vs. Length EEfficiency • ∆E vs. Length where ∆EEcenter - Eedge • XY Scan (really +X scan, symmetry allows) 10 HCal Electronics Meeting

  11. Simulations - ACC • 3.5mm to 2.96mm diameter taper • Note graphs at 0.2mm • 0.2mm => ∆E = 7.5% 11 HCal Electronics Meeting

  12. Simulations - FC - Same LG filled with n=1.59 material - 0.4cm notable compared to 0.2cm for ACC 12 HCal Electronics Meeting

  13. Simulations - ACT - ∆E references chosen to be center and corner of LG - E down, but ∆E also down compared to ACC 13 HCal Electronics Meeting

  14. Simulations - FT • As before, previous geometry is now filled with n= 1.59 material • Same similarities between plots as FC • Boost in E and decreased ∆E as in FC 14 HCal Electronics Meeting

  15. Simulations - XY Scans Zair=2mm Zfilled=4mm HCal Electronics Meeting 15

  16. Simulations - Summary • ACC: E~70% ∆E~7.5% for Z=0.2cm • FC: E~ 73% ∆E~3% for Z=0.4cm • ACT: E~55% ∆E~5% for Z=0.2cm • FT: E~60% ∆E~0.8% for Z=0.4cm 16 HCal Electronics Meeting

  17. Results • ~0.5cm too much scattering • < 0.2cm “masking effect” • Filling LG w/ n=1.59 boosts E allowing for larger Z => lower ∆E • If filling LG done effectively, also protect Al from oxidation 17 HCal Electronics Meeting

  18. Results • FC or FT => E or ∆E but ∆E diff small compared to E gain in FC geometry • Also, trapezoidal involves more complex machining • Research/Bench tests => Al best material 18 HCal Electronics Meeting

  19. Future Work • Bench tests at Iowa possible during late May / early June, Quarknet program • Include QE and other effects in simulations • Re-run simulations for correct, 2.7 mm diameter fiber bundle • Possible to test composite LG shapes • Although, conical LG simulations were actually truncated cone with square opening mating with SiPM 19 HCal Electronics Meeting

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