MIT Light Guides Jarrett Moon CSU DUNE Workshop 5/17/16 Overview - - PowerPoint PPT Presentation

MIT Light Guides

Jarrett Moon CSU DUNE Workshop 5/17/16

2

Overview

Light Detection Goals Building Our Light Guides Attenuation Measurements Argon/Air Behavior Modeling Future Improvements & Construction Costs and Final Analysis Conclusions

3

Light Detection Goals

(1) Efficient space usage

– Want to use minimal space, need a low profile system

(2) Collect lots of light

– However we design our system, we need to ensure that

lots of light is collected and subsequently transmitted to photodetectors

How about SiPMs and flat panel light guides? Definitely space efficient, but can we collect lots of light?

4

Checklist...

Breaking down some attributes we want from our system Space Efficient Collects lots of light Robust Design Economical Ease of Building

5

Checklist...

Breaking down some attributes we want from our system Space Efficient Collects lots of light Robust Design Economical Ease of Building

6

Overview

Light Detection Goals Building Our Light Guides Attenuation Measurements Argon/Air Behavior Modeling Future Improvements & Construction Costs and Final Analysis Conclusions

7

Building Our Light Guides

• Two well known major problems

– Bars needed for (proto)DUNE will be long, we may lose lots

• f light to attenuation

– Standard photodetectors can't see the 128 nm light from LAr

8

Wavelength Shifting With TPB

• Tetraphenyl Butadiene (TPB) is a well

known and studied solution to the 128 nm insensitivity problem

• Use TPB to shift the VUV light to visible

– Absorbs VUV and isotropically re-emits

at 425 nm

A TPB coated guide illuminated by a UV flashlight

9

Light Guide Construction

• Bars made of diamond polished UTRAN

UVT acrylic

• The bars are annealed to prevent

crazing

• The wavelength shifting coating is

applied

– TPB (shifter) – Toluene (solvent) – Ethanol (surfactant) – Dissolved acrylic (equal n)

An acrylic bar being hand dipped in TPB solution

10

Light Guide Construction

• Latest and greatest series of bars (MIT 'wunderbars')

are produced using the following recipe

– 0.1 g TPB – 0.1 g Dissolved acrylic – 50 mL Toluene – 12 mL Ethanol

• Bars are dipped in this solution for 10 minutes then

allowed to dry

See our latest paper for a full description of the technique! http://arxiv.org/pdf/1604.03103v1.pdf

11

Light Guide Construction

• The latest bars have also been partly produced using

a mechanized dipping system as opposed to hand dipping

– Necessary for control over humidity – Allows for consistent dipping procedure

12

Overview

Light Detection Goals Building Our Light Guides Attenuation Measurements Argon/Air Behavior Modeling Future Improvements & Construction Costs and Final Analysis Conclusions

13

Measurement in Air

• Measurements in LAr are costly and slow
• Use air data as input to model performance in LAr
• Use a position adjustable UV LED in a dark box to extract

attenuation performance

Dark box setup with PMT, bar, and stepper Example readout distribution

14

Results of Air Measurement

• Measurements in air show

multi-meter attenuation lengths!

• Performance is tightly

distributed

15

LAr vs Air Results

• Measurements in air are a great guide, but ultimately

we really need a benchmark for LAr performance

• LAr measurements just too slow and expensive to do

them for every bar

• Can we link the behavior in LAr to that in air in a

rigorous fashion?

16

Overview

Light Detection Goals Building Our Light Guides Attenuation Measurements Argon/Air Behavior Modeling Future Improvements & Construction Costs and Final Analysis Conclusions

17

Modeling LAr/Air Connection

• Try a 3 parameter ray tracing model

– Internal reflection depends only on nair and nAr – Photon loss per reflection – Coating thickness gradient

• Simultaneously fit forward and backward bar runs in air to

extract these parameters

18

Model Results

• The model agrees well with our data, yielding a good prediction of the

LAr curve based on air data

– It correctly predicts the attenuation in LAr using only air data and nAr – Essentially, can characterize LAr performance via air measurements

An example of air measurements, predicted LAr attenuation curve, and overlaid LAr measured performance.

19

Model Predictions

• How do we anticipate our latest bars performing in LAr based on our air

data?

20

Overview

Light Collection in Liquid Argon Building Our Light Guides Attenuation Measurements Argon/Air Behavior Modeling Future Improvements & Construction Costs and Final Analysis Conclusions

21

Better Acrylic

• We noted that for our latest 'wunderbars' that the results were

consistent with the bulk attenuation of pure acrylic

• Leads us to think we may not have actually seen the full

potential of our current coating!

• Research currently underway has identified acrylics with

attenuations ~2X better, tests on these will be carried out later this year

– These acrylics have bulk attenuation > 4m – Every reason to expect substantial improvement with better

acrylic!

22

Full Scale Construction

Preparations to ramp up for full scale construction are underway! Suitable locations for performing bar coating and testing have already been identified at FNAL Main problem is sufficient clearance to dip/dry long bars Also need good climate control, ventilation, clean working conditions

23

Full Scale Construction

Need to make modifications to dipping / testing equipment to facilitate large scale production

Upgraded testing unit to run air measurements

• n multiple bars simultaneously

Upgraded mechanical dipping unit to perform multiple dry air dips simultaneously

24

Construction Schedule

Additional reinforcements arrive this fall as Len Bugel and new postdoc Adrien Hourlier join us at FNAL

25

Overview

Light Collection in Liquid Argon Building Our Light Guides Attenuation Measurements Argon/Air Behavior Modeling Future Improvements & Construction Costs and Final Analysis Conclusions

26

Checklist...

• We have >2m attenuation length with more improvement

possible! As a major bonus, quality control can be done in air

• Minimal number of parts, all of which are known to be stable

under cryogenic conditions

Space Efficient Collects lots of light Robust Design Economical Ease of Building Easy Quality Control

27

Easy to build?

• The construction and testing process is straightforward,well

documented, and uses easily obtained parts

• With minimal training, the process is amenable to being

performed by any interested university

Space Efficient Collects lots of light Robust Design Economical Ease of Building Easy Quality Control

28

What Does it Cost?

Item Cost for 2.2m x 4” bar UVT Acrylic, polished ~ $185 Coating ~ $68 Labor

How hungry are the students?

• The bars and coating themselves are relatively cheap ~$253

each

• The labor involved can easily be done by students (i.e. both

educational and cheap)

29

Checklist...

• So we can afford it too!

Space Efficient Collects lots of light Robust Design Economical Ease of Building Easy Quality Control

Yay!!!

30

Conclusions

• The attenuation length of the MIT 'wunderbars' is >2m,

more than sufficient to be an effective light collection system

• It has a well established production and quality control

protocol with several associated papers

• It is both spatially and economically efficient
• Production can be done at universities, resulting in

greater collaboration and educational opportunities as well as low overhead

31

Acknowledgments

Special thanks to the whole light guide team! Janet Conrad Len Bugel Gabriel Collin Ben Jones Zander Moss Kanika Sachdev Matthew Toups Stefano Vergani Taritree Wongjirad

32

Thank You!

Questions?