Attenuation Length Measurements of DUNE Prototype Light Guides - - PowerPoint PPT Presentation

Attenuation Length Measurements of DUNE Prototype Light Guides

Stuart Mufson, Brice Adams, Brian Baugh, Bruce Howard, Denver Whittington October 20, 2015

128 nm LAr scintillation light SiPM Array 430 nm shifted light (in bar)

LS Radiator (VUV → Blue) WLS bar (blue → green)

Indiana U, cartoon below

S i P M A r r a y 128 nm LAr scintillation light ~490 nm shifted light (in bar) 430 nm shifted light from plate

Several light guide technologies tested Technologies selected for next (final) TallBo run: a) acrylic light guide with waveshifter embedded in plastic (MIT) b) commercial Eljen light guide with waveshifting plate (IU)

Parameters to optimize for photon detector paddle performance:

• SiPM performance

noise, gain, cross talk, aging characteristics discussed at last PD telecon

0" 20" 40" 60" 80" 100" 0" 50" 100" 150" 200" 250"

noise rate [Hz] # days in LN2

Noise Rate @ 24.5 V, SiPMs 4-6 bias voltage = 30.5 V pulsed SiPMs shown at 200 days

SiPM"4" SiPM"5" SiPM"6" 1.4e9"pulses" 0" 10" 20" 30" 40" 50" 60" 0" 50" 100" 150" 200" 250"

cross talk prob [%] # days in LN2

Cross Talk Prob @ 24.5 V, SiPMs 4-6 bias voltage = 30.5 V

pulsed SiPMs shown at 200 days

SiPM"4" SiPM"5" SiPM"6" 1.4e9"pulses"

Pulse Test: SiPM response falls (conservatively) by ~25%/100 yrs = 0.25%/yr ¡ ¡

• light guide performance
• brightness of light guide
• attenuation length of light guide

Signal [PE] 50 100 150 200 250 300 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

High-Front Low-Front

Signal [PE] 50 100 150 200 250 300 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

High-Front Low-Front

Eljen light guide + waveshifting plate x 2 Dip-coated MIT light guide

Relative brightness of “best” two light guide technologies in last TallBo run, which includes attenuation length effects

• WLS Polystyrene + Acrylic Plate (TPB)
• WLS Polystyrene + Acrylic Plate (bis-MSB)
• WLS PVT + Acrylic Plate (TPB)
• WLS PVT + Acrylic Plate (bis-MSB)
• WLS Polystyrene + Fused Silica Plate (TPB)
• Dip-coated Acrylic (TPB), IU design
• Dip-coated Acrylic (TPB), IU design
• WLS PVT + Fused Silica Plate (TPB)
• WLS PVT + Acrylic Plate (TPB), double-sided
• Dip-coated Acrylic (TPB), MIT design
• WLS Polystyrene + Acrylic Plate (TPB), double-sided
• WLS Polystyrene + Acrylic Plate (bis-MSB), double-sided

Light guides in Phase 1

Light guide technologies tested TallBo Run #4, second fill TallBo dewar

second α source added

Independent attenuation length measurements in the IU dewar measurements of pulse height vs distance along light guide

• 1. light guides loaded

into frame

• 2. dewar pumped down
• vernight
• 3. LAr fill and

measurements

• 4. warm up

3-day turnaround

241Am source gives monoenergetic 5.5 MeV α’s

Analysis – plot relative measurements of pulse height as a function

• f distance

ratio = pulse height measurementn

( )

pulse height measurement1

( )

= exp(− Δx xattn) Slope of a straight line fit to ln(ratio) is proportional to

• (1/attenuation length)

y"="$0.0131x"+"4.5266"

3.00" 3.50" 4.00" 4.50" 5.00" 5.50" 6.00" 0" 5" 10" 15" 20" 25" 30" 35"

ln(pe) inches

TallBo MIT bar attnLen = 194 cm

y"="$0.0124x"+"5.6996"

3.00" 3.50" 4.00" 4.50" 5.00" 5.50" 6.00" 0" 5" 10" 15" 20" 25"

ln(pe)' inches'

Eljen Bar, fused silica plate, TPB evaportively coated attnLen = 205 cm

(measurements give attenuation length, not relative brightness)

More sophisticated analyses are consistent with these results single exponential fit, attenuation length = 29.5” MIT light guide #3 MIT light guide #1 double exponential fit

• short attnLen = 17.6”
• long attnLen = 53.5”

Position 5 10 15 20 25 30 35 Integrated Signal [PE] 50 100 150 200 250 20 40 60 80 100 120 140 160

Integrated Signal in Waveform vs Source Position

• ­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑-­‑ ¡

0" 50" 100" 150" 200" 250" 300" 1" 2" 3" 4" 5" 6" 7"

a"enua&on(length([cm]( light(guide(

Attenuation Lengths MIT Light Guides

0" 50" 100" 150" 200" 250" 300" 1" 2" 3" 4" 5"

a"enua&on(length([cm]( light(guide(

Attenuation Lengths Eljen Light Guides + waveshifting disk

Results: MIT light guides: variable attenuation lengths Eljen light guides: consistently long attenuation lengths

Absolute “brightness” or VUV photon efficiency measurements planned at IU (Bruce Howard) Use VUV monochromator back-filled with Ar gas

D2 lamp spectrum D2 lamp vacuum chamber:

• pumped down
• back-filled with Ar gas

light guide, illuminated from the side, viewed from the end D2 lamp grating

• rder-sorting

filter slit stop

NIST-calibrated SiPM

VUV Monochromator Setup

(1) Calibrate D2 lamp

NIST-calibrated SiPM

# VUV photons/cm2/s emitted by lamp

light guide, illuminated from the side, viewed from the end

VUV Monochromator Setup

(1) Make measurements with calibrated photodiode

D2 lamp grating

• rder-sorting

filter slit stop

NIST-calibrated SiPM # VUV photons/cm2/s

measured

Summary

• Next (last) TallBo test in early 2016 to include 2 technologies:
• hand-dipped MIT technology
• commercial light guide/waveshifting plate technology
• To optimize for photon detector paddle performance
• SiPM performance: noise, gain, cross talk,

aging characteristics no show stoppers so far

• light guide attenuation length

variable for hand-dipped design; Eljen light guides uniformly long

• light guide “brightness”, or VUV photon detection efficiency

hand-dipped design bright wavelength shifting plate design not optimized