1. 03/22/2007HCal Electronics Meeting HO LIGHT GUIDE SIMULATIONS Justin Parsons, University of Iowa Jim Freeman, FNAL HO LIGHT GUIDE SIMULATIONS 1

2. 03/22/2007HCal Electronics Meeting Outline Problem and proposed solution Light guide material, and geometry Simulation software : LITRANI Testing the software Simulations Results and future plans 2

3. 03/22/2007HCal Electronics Meeting 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 3

4. 03/22/2007HCal Electronics Meeting 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 4

5. 03/22/2007HCal Electronics Meeting Geometry and Source Source emits at 520nm, laser or fiber with 30deg aperture SiPM active area is 4.41mm 2 => R u =1.485mm Fiber bundle diameter is 3.5mm => R L= 1.75mm (wrong FB diameter, will correct in future) 5 Software Tests HO Simulations

6. 03/22/2007HCal Electronics Meeting 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 6

7. 03/22/2007HCal Electronics Meeting Testing Software 7 [cm] - 1cm long, R U /R L =1, 520nm laser X-Y scan - Aimed laser for single scattering at Z=1/2 the total length, varied reflectivity

8. 03/22/2007HCal Electronics Meeting Testing Software - Mask Test Created mask with aperture same size as fiber diameter (0.094 cm), did X-Y scan with laser 8 [cm]

9. 03/22/2007HCal Electronics Meeting 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 9

10. 03/22/2007HCal Electronics Meeting 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  E center - E edge –XY Scan (really +X scan, symmetry allows) 10

11. 03/22/2007HCal Electronics Meeting Simulations - ACC 11 -3.5mm to 2.96mm diameter taper - Note graphs at 0.2mm - 0.2mm => ∆E = 7.5%

12. 03/22/2007HCal Electronics Meeting Simulations - FC - Same LG filled with n=1.59 material - 0.4cm notable compared to 0.2cm for ACC 12

13. 03/22/2007HCal Electronics Meeting Simulations - ACT 13 - ∆E references chosen to be center and corner of LG - E down, but ∆E also down compared to ACC

14. 03/22/2007HCal Electronics Meeting Simulations - FT 14 -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

15. 03/22/2007HCal Electronics Meeting Simulations - XY Scans 15 Z filled =4mmZ air =2mm

16. 03/22/2007HCal Electronics Meeting 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

17. 03/22/2007HCal Electronics Meeting 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

18. 03/22/2007HCal Electronics Meeting 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

19. 03/22/2007HCal Electronics Meeting 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