The Search for Improved Wavelength Shifting Plate Performance - PowerPoint PPT Presentation

The Search for Improved Wavelength Shifting Plate Performance Stuart Mufson, Brice Adams, Brian Baugh DUNE Photon Detector Workshop May 17, 2016

Motivation: The properties of the photon detectors are separable and can be studied/optimized independently. These PD properties include – 1. attenuation length a. Eljen light guides are a commercial product with uniformly excellent attenuation length (> 2m) b. issue resolved for IU technology 2. brightness a. relative brightness - optimization of wavelength shifting plates b. absolute brightness/efficiency 3. SiPM aging a. reasonable performance in IU tests

Testing Plan: 1. Establish technology performance @ 128 nm in VUV monochromator - (relatively) rapid method for testing/comparing many technologies 2. Show that technology performance in VUV monochromator correlates with performance in liquid argon without Eljen light guide - setup in local dewar at IU: α source/plate technology/SiPM 3. Test performance with Eljen light guides to demonstrate PD system performance in local dewar - if feasible, test at Fermilab in TallBo/Blanche under under controlled conditions

Search Matrix method of wavelength substrate application shifting solution 1side/2side ° acrylic 1/16" spray/bake * IU 1 side * * * polycarbonate 1mm paint MIT polycarbonate 0.004" dip coated heat shrink (Walmart) spray heat shrink 0.001" HVLP vinyl sheet by hand vinyl 1/16" mylar 0.004" saran wrap fused silica crystal quartz * TallBo plates ° IU solution: TPB, DCM MIT: TPB, toluene, acrylic, alcohol

VUV Monochromator Measurements • McPherson model 234 VUV Monochromator with H 2 lamp • Vacuum connection to a turbo pump, pumped down to purge N 2 , O 2 , H 2 O • Backfilled with pure gaseous argon (slightly overpressured) • Calibrate H 2 lamp with NIST calibrated photodiode VUV light

Issues: - MgF 2 window becomes less transparent with exposure to 128 nm light - characterize technology performance with metric: ( waveshifted optical light as measured by SiPM)/ (128 nm light as measured by NIST photodiode) VUV current measured by NIST photodiode vs date: cleaned 3/21; 4/1; 4/14; 5/3 4.0E-09 3.5E-09 VUV (current - dark current) [A] 3.0E-09 2.5E-09 2.0E-09 1.5E-09 1.0E-09 5.0E-10 0.0E+00 3/11/16 3/21/16 3/31/16 4/10/16 4/20/16 4/30/16 5/10/16 5/20/16

Issues: - Monitor systematics by continuously measuring a standard wavelength shifting plate: sprayed/baked acrylic plate, similar to TallBo #5 plate - radiation damage to standard, when corrected, shows stable system performance 7.E+04 6.E+04 corrected for radiation y = 65950x -0.438 5.E+04 damage 4.E+04 3.E+04 2.E+04 1.40 1.E+04 1.20 0.E+00 0 5 10 15 20 25 30 35 40 45 50 1.00 0.80 0.60 (SiPM current – dark current)/ y = 0.0001x + 1.0089 0.40 ( VUV current – dark current) 0.20 0.00 0 5 10 15 20 25 30 35 40 45 50

Summary of all technologies tested: - measurement standard red - TallBo #5 waveshifting plates (Denver’s talk) blue SiPM current/VUV current 7.0 6.0 SiPM current/VUV current 5.0 4.0 3.0 2.0 1.0 0.0 1 6 11 16 21 26 31 36 41 46 51 56 62 67 72 77 82 87 92 97 102 measurement

Summary of all technologies tested: - measurement standard red - TallBo #5 waveshifting plates (Denver’s talk) blue SiPM current/VUV current for all technologies tested SiPM current/VUV current SiPM current/VUV current Entries Entries 104 104 50 Mean 1.559 Mean 1.559 SiPM current/VUV current RMS 1.526 RMS 1.526 7.0 40 6.0 SiPM current/VUV current 5.0 30 4.0 3.0 20 2.0 1.0 10 0.0 1 6 11 16 21 26 31 36 41 46 51 56 62 67 72 77 82 87 92 97 102 measurement 0 0 1 2 3 4 5 6 7 8

Sprayed/Baked technology used in TallBo #5: - sprayed with computer controlled spray apparatus, baked at 80 C - good performance with room for improvement over TallBo performance - VUV enables QC to select best performance SiPM current/VUV current for all technologies tested SiPM current/VUV current SiPM current/VUV current Entries Entries 104 104 1/16" acrylic, sprayed & baked 50 Mean 1.559 Mean 1.559 TallBo plates solid RMS 1.526 RMS 1.526 11 40 9 30 7 5 20 3 1 10 0.00 1.00 2.00 3.00 4.00 5.00 6.00 SiPM current/VUV current 0 0 1 2 3 4 5 6 7 8

Heat shrink material (Walmart) shows best consistent performance - currently being tested at MTS for contamination issues - has only been fixed to small samples of Eljen light guides - promising but obviously needs some work SiPM current/VUV current for all technologies tested SiPM current/VUV current SiPM current/VUV current Entries Entries 104 104 Heatshrink (Walmart), dipped, brushed, sprayed 50 Mean 1.559 Mean 1.559 RMS 1.526 RMS 1.526 11 40 9 7 30 5 3 20 1 0.0 1.0 2.0 3.0 4.0 5.0 6.0 10 SiPM current/VUV current 0 0 1 2 3 4 5 6 7 8

2. Show that technology performance in VUV monochromator correlates with performance in liquid argon without Eljen light guide - setup in local dewar at IU: α source/plate technology/SiPM Comparison of Wavelength Shifting Plates in LAR LAr dewar 9000 8000 7000 6000 ADC counts 5000 TallBo plate 4000 3000 heat shrink 2000 Am 241 3 SensL 1000 5.5 MeV α SiPMs 0 1 2 3 SiPM position wavelength performance in LAr correlates shifting with performance in VUV plate

3. Test performance with Eljen light guides to demonstrate PD system performance in local dewar - preliminary studies encouraging, more work needed 3-day turnaround 1. light guides loaded into frame 2. dewar pumped down overnight; backfilled with gaseous Ar 3. LAr fill and measurements 4. warm up second α source added 3 SensL SiPMs

Eljen Light Guide/Wavelength Shifting Plate QC Plans Eljen light guides: - commercial product, if made correctly, will work - attenuation length measured > 2m multiple times at room temperature and in LAr - test in dark box at room temperature - demonstrate correlation between dark box and LAr Wavelength shifting plates: - demonstrated that VUV monchromator wavelength performance at room temperature correlates with performance in LAr - current work at IU concerns uniformity over 3 3/8” x 12” wavelength shifting plates as a function of technology

Conclusions • demonstrated that technology performance @ 128 nm can be studied in VUV monochromator • performance in VUV correlates with performance in LAr • two technologies have been identified as improving the performance as see in TallBo #5 • preliminary studies are encouraging that wavelength shifting plates work efficiently with Eljen light guides • QC plans are being developed for both wavelength shifting plates and Eljen light guides