NO A Liquid Scintillator Production Stuart Mufson, Indiana - - PowerPoint PPT Presentation

Stuart Mufson, Indiana University FroST 2016 March 19, 2016

NOνA Liquid Scintillator Production

The NOνA Experiment

NuMI Off-axis 𝝃e Appearance Experiment

NuMI = Neutrinos at the Main Injector Long-baseline (anti-)neutrino oscillation experiment 14 mrad off-axis with L/E ~ 400 km/GeV Two functionally identical detectors,

• ptimized for νe identification

Fermilab Ash River

Bloomington

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Neutrino beamline

Slip-stacking Booster batches since March 2015

• Beam power record: 521 kW
• 85% uptime

Beam back Oct-Nov 2015 after upgrades to achieve 700 kW, NOvA design power

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The NOνA Detectors

Near Detector: 300 ton,1 km from source

• 100m underground, 20,000 channels

Far Detector: 14 kton, 810 km from source

• On the surface, 3m concrete+barite overburden; 344,000 channels

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Designed for electron ID Massive, Low-Z, 65% active

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The NOνA Far Detector in perspective

Far Detector site: Ash River, MN

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Near Detector at Fermilab

Near Detector fully instrumented and cooled

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The NOνA Collaboration

231 collaborators from 41 ins:tu:ons and 8 countries

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• NOνA was optimized to search for the rare νe's at Ash River that

have oscillated from the νµ's in the NuMI beam.

• The primary design requirement for the NOνA far detector was

the efficient detection of νe interactions at 2 GeV.

• Furthermore, to minimize infrastructure costs, the plan was to
• perate the massive 14.4 kt far detector on the surface.
• After considering several technologies, the NOνA collaboration

built a segmented liquid scintillator detector.

• liquid scintillator was chosen over plastic because of its

significant cost advantage for massive detectors.

NOνA Design Philosophy

• A large water Cherenkov detector on the surface does not yield

enough light per unit path length for fine segmentation

• Cherenkov detectors perform best on the relatively simple event

topologies resulting from E < 1 GeV neutrino interactions

• above this energy, the Chrenekov threshold does not

provide good hadronic energy reconstruction.

• particle ID becomes complicated by multiple
• verlaping Chrenkov rings
• Further: to provide a veto and enough distance for ring

formation on the nearest wall, Super-K only analyzes events recorded in the inner 22.5 kt of its 50 kt detector mass.

• A segmented detector, is sensitive over a significant fraction of

its active volume, enabling a smaller detector to achieve the same physics.

Segmented NOνA Detector Design

Alternative Technologies Considered

• Resistive Plate Chamber (RPC) sampling calorimeters
• inferior particle ID efficiency for detecting νe’s
• more expensive to construct
• uninstrumented absorber regions provide paths for

comic-rays to penerate into the fiducial volume

• degraded performance as the gas-handling system ages
• Low-Z sampling calorimeters with particle board as the absorber

uses building materials with sufficient structural strength to support a massive detector

• only half the νe detection efficiency of a segmented liquid

scintillator detector

• require a significant increase in detector mass for the

same physics reach

Alternative Technologies Considered

• Liquid Argon TPC’s
• enormous potential for neutrino physics was recognized
• however, the largest detector operated at the time of the

NOvA technology decision in 2007 was ICARUS, with 500 tons of imaging mass that needed to be scaled up by a factor of thirty

• deemed insufficiently mature

NOvA Liquid Scintillator

NOνA liquid scintillator is an organic fluorescent compound, which have a long history in particle physics It was formulated to meet the requirements of the NOνA experiment, but based initially on commercially available scintillators

component purpose mass mass mass mass fraction (kg) fraction (kg) blends: #1, #2 blends: #3 – #25 mineral oil solvent 94.91% 691,179 94.63% 7,658,656 pseudocumene scintillant 4.98% 36,2677 5.23% 423,278 PPO waveshifter 0.11% 801 0.14% 11,331 bis-MSB waveshifter 0.0016% 11.7 0.0016% 129 Stadis-425 antistatic 0.001% 7.3 0.001% 81 Vitamin E antioxidant 0.001% 7.1 0.001% 78 Total 728,247 8,093,264

NOνA liquid scintillator cell (extruded PVC) with WLS fiber

• A charged particle incident on the cell excites the primary

scintillant – pseudocumene

To 1 APD pixel W D

pical charged particle path

L To 1 APD pixel W D

pical charged particle path

L

L D W fibers to 1 APD pixel

typical charged particle path

L = 15.5 m D = 5.9 cm W = 3.8 cm

• pseudocumene molecules decay by emitting photons in

the range 270 – 320 nm

• these UV photons excite the wavelength shifter PPO,

which in turn decays and emits in the range 340 – 380 nm

• these down-converted scintillation photons excite the second

wavelength shifter bis-MSB which subsequently decays to photons in the range 390 – 440 nm that excite the WLS fiber

wavelength (nm)

300 350 400 450 500 550 600 650

normalized emission profile

0.0 0.2 0.4 0.6 0.8 1.0

NOvA scintillator PPO bis-MSB

Emission Profiles

NOvA Scintillator & Waveshifters

The scintillation light is dominated by the emission from bis-MSB. Normalized emission profiles for blended NOνA scintillator

Far detector performance Scintillator × PVC × Fiber × APD

90% efficiency for seeing hits on muon tracks at the far end of the cells – meeting TDR specifications

#photons/cm transparency reflectivity capture efficiency attenuation length noise gain threshold

TDR requirement

Efficiency for far end for 6-7.5 cm path length TDR requirement Light yield at far end of cells ←far side near side ➞

550 𝜈s exposure of the Far Detector

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Close-up of neutrino interaction in the Far Detector

Side view Top view Color denotes deposited charge Beam direc?on

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Mineral Oil

Toll Blender Operations

scintillator blend tank tanker trailers to Ash River/Fermilab waveshifters pseudocumene fluor mix tank anti-static

• Vit. E

(II) (I) (III) (IV)

Toll Blending Operations (I) Mineral oil brought to blender from storage/rail cars and pumped into the scintillator blend tank (II) Fluors and additives mixed in the fluor mix tank at the NOvA mixing station, then pumped into the blend tank. (III) Scintillator blended with bubbles of N2 gas (IV) Scintillator was shipped to the NOvA detectors by tanker trailer

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Scintillator Blending Operations

600,000 gal epoxy-lined tank, Westway Terminals, Riverdale, IL

mineral oil storage

120,000 gal blend tanks Wolf Lake Terminals, Hammond, IN blending with Pulsair system using N2 bubbles

Fluor Blend Loop

Fluor mix tank “Powder” blending shed powder blending tank fluor blending pumps

attenuation length (m)

2 4 6 8 10 12 14 16

(mineral oil transmission)/(glass transmission)

0.95 1.00

Renkert 70-T NOvA scintillator blended with Renkert 70-T experimental calibration curve

mineral oil requirement scintillator requirement

QC: Attenuation Length of Mineral Oil and Blended Scintillator

transmission of large quantities were rapidly measured relative to glass with a Lovibond tintometer tintometer calibrated at IU with a spectrophotometer

blend #

5 10 15 20 25

(scintillator transmission)/(glass transmission)

0.94 0.95 0.96 0.97 0.98 0.99 1

Scintillator Transmission by Blend

requirement

transmission relative to glass 0.96 0.98 1.00 1.02 1.04 2 4 6 8 10 12 14 16 18 20 Mineral Oil Transmission

(delivered by rail & barge)

requirement

• 2 m scintillator attenuation length requirement established by

simulation

• mineral oil attenuation length requirement by experimental program

to find mineral oil that could meet the 2 m scintillator requirement

Attenuation Length of Mineral Oil and Blended Scintillator

blend #

5 10 15 20 25

[PPO]/[PS] x 10^4

2.0 2.5 3.0

(PPO/pseudocumene) ratio by mass : blends #1, #2 : blends #3 - #25 blend #

5 10 15 20 25

[bis-MSB]/[PS] x 10^4

2.5 3.0 3.5

(bis-MSB/pseudocumene) ratio by mass : blends #1, #2 : blends #3 - #25

QC: Chemical composition of fluor blend

• chemical composition determined with GC-MS for

PPO and pseudocumene, and HPLC for bis-MSB

• if fluor ratios correct, adding the correct quantity of

mineral oil will result in scintillator with the proper ratio of fluors

days since blend #3

100 200 300 400 500

(Compton edge)/(alpha peak)

0.24 0.26 0.28 0.3 0.32 0.34 0.36 0.38 0.4 0.42

Light Yield for Blends #3 - #25

) t t fit function: exp(

test finds the ratio of the Compton edge (gammas) relative to a fiducial Alpha peak: (Compton edge/Alpha peak)

• - a measure of the light output
• f scintillator as a function
• f its composition

QC: Scintillator Light Yield

25% of anthracene Gamma Test

increasing ratio due to radiological damage in plastic scintillator -- scintillator was certified so long as test followed radiation damage law

light yield ∝1/exp −t /t0

( )

Summary

detector volume mass (gal) (kg) near detector 40,141 130,672 far detector 2,674,041 8,690,929 Total 2,714,182 8,821,511

• successfully blended 8.8 kt of liquid scintillator for the

NOνA experiment

• details can be found NIM A 799 (2015) 1-9.
• scintillator was produced commercially at Wolf Lake Terminals,

Hammond, IN

• scintillator met all performance requirements

backups

NOνA Readout Cell

15.5m long (FD), 4m long (ND), 3.9x6.6cm Made of reflective PVC structure Filled with 11M litres of liquid scintillator

• Mineral oil + 5% psuedocumene

Looped 0.7mm wavelength-shifting fibre for light transport

Fiber pairs from 32 cells 32-pixel APD

Extruded plastic (PVC) cells filled with 11M litres of scintillator instrumented with 𝜇-shifting fiber and APDs

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detector volume mass (gal) (kg) near detector 40,141 130,672 far detector 2,674,041 8,690,929 Total 2,714,182 8,821,511

property value flash point: blends: #1, #2 100 C blends: #3 – #25 96 C density (15.6 C) 0.862 g/cm3 water content ≤ 50 ppm kinematic viscosity (40 C) 11 cSt boiling point >165 C vapor pressure (37.8 C) 5 mm Hg

Time-zoom on 10 𝜈s interval during NuMI beam pulse

Side view Top view Color denotes deposited charge Beam direc?on

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Far Detector selected 𝝃µ CC candidate

Side view Top view Color denotes deposited charge Beam direc?on

3/18/16 GAVIN S. DAVIES: UNIVERSITY of NOTRE DAME PARTICLE PHYSICS SEMINAR 31

date shipped from blender

10/01/12 12/31/12 04/01/13 07/02/13 10/01/13 12/31/13 04/02/14 07/02/14

total volume (million gal)

0.0 0.5 1.0 1.5 2.0 2.5

Cumulative volume of scintillator delivered to the NOvA Near and Far detectors tanker trailer loads