EXTRUDED PLASTIC SCINTILLATOR FOR THE MINOS …

MINOS

EXTRUDED PLASTIC SCINTILLATOR FOR THE MINOS CALORIMETERS

Anna Pla-Dalmau

MINOS Scintillator Group

Fermilab

Calorimetry 2000 Workshop

LAPP - Annecy

October 12, 2000

MINOS

MINOS: MAIN INJECTOR NEUTRINO OSCILLATION SEARCH

MINOS

MINOS NEAR DETECTOR

• 16.6 m long, 980 tons

• 280 “squashed octagon” planes

• Forward section: 120 planes

4/5 partially instrumented

1/5 planes: full area coverage

• Spectrometer section:160 planes

3/4 planes not instrumented

1/4 planes: full area coverage

Coil hole

Beam fiducial region

Instrumented area

MINOS

MINOS FAR DETECTOR

MINOS

MINOS: 4 PLANE PROTOTYPE

MINOS

CAST SCINTILLATORS

ADVANTAGES• Fast response• Ease of manufacture• Versatile: plates, fibers, tiles

DISADVANTAGE FOR LARGE DETECTORS• Expensive: price of cast scintillator ~ $40/kgÔMINOS needs 300,000 kg of scintillator!

èOBJECTIVE:USE LOW COST SCINTILLATOR

MINOS

EXTRUDED SCINTILLATOR

TO LOWER COSTS: EXTRUDED SCINTILLATOR

ADVANTAGES:• Use commercial polystyrene (PS) pelletsÔMany grades, many prices

• Processing flexibilityÔManufacture of essentially any shape

DISADVANTAGES• Poorer optical qualityÔParticulate matter in PS pelletsÔAdditives in PS pellets

MINOS

EXTRUDED SCINTILLATORS

Ô Extrude a scintillator shape and use wavelength shifting (WLS) fibers as readout.

scintillator

1.2 mm WLS fiber

aluminized Mylar tape

optical epoxy

0.25 mm TiO2 reflective cap

10 mm

41 mm

MINOS

SELECTION OF RAW MATERIALS

BLUE SCINTILLATOR CORE• Polystyrene: Dow Styron 663 W• Dopants: 1% PPO + 0.03% POPOP

WHITE CAPSTOCKING• Polystyrene with 12% TiO2 – 0.25 mm thick

GREEN FIBER• K-27 fiber – 1.2 mm diameter

MINOS

MANUFACTURING TECHNIQUE

PS pellets and dopantmixture

EXTRUDER(64-mm single screw)

DIECO-EXTRUDER

(32-mm single screw)

Scintillator strip with white reflector coating

titanium dioxidemixture

MINOS

MANUFACTURING TECHNIQUE

DRYER

Dry PS purged with nitrogen

PS mixed with PPO+POPOP

PS mixture purged with nitrogen

Hopper purged with nitrogen

MINOS

EXTRUSION AT ITASCA PLASTICS

MINOS


MINOS


MINOS


MINOS


MINOS


MINOS

EXTRUDED SCINTILLATOR STRIPS

MINOS

PRODUCTION SAMPLES

MINOS

QC: PROFILE DIMENSIONS

W H Groove Width Groove Depth h

Week 1Average 40.92 9.94 2.52 2.36 7.37

Std Deviation 0.02 0.07 0.16 0.09 0.07

Week 2Average 40.94 9.92 2.92 2.31 7.52

Std Deviation 0.02 0.06 0.17 0.05 0.08

Week 3Average 40.96 10.01 2.73 2.66 7.13

Std Deviation 0.02 0.07 0.14 0.14 0.09

All units in millimeters

W

H h

MINOS

QC: LIGHT YIELD

XenonLamp

Mono-chromator

Photomultiplier

Mono-chromator

Fiberoptics

Sample to be measured

450 nm

QC SETUP AT THE FACTORYCOMPARISON OF MEASUREMENTS

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2.0

3250 3350 3450 3550 3650 3750 3850 3950 4050 4150 4250

SAMPLE NUMBER

LIG

HT Y

IELD

FNAL (Cs-source)

Itasca (UV)

Baseline

MINOS

QC: DOPANT CONCENTRATION

1.2

1.0

0.8

0.6

0.4

0.2

Inte

nsity

(rel

. to

A)

550500450400350

Wavelength(nm)

A

B

164% (1.34:1) 84% (1.12:1) 50% (1.06:1)

Fluorescence Spectrum320 nm excitation

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2000 2200 2400 2600 2800 3000 3200 3400

SAMPLE NUMBERP

EA

K R

ATI

O &

LIG

HT

YIE

LD

Cs LY

Peak Ratio

MINOS

LIGHT OUTPUTMAY 2000 MODULE PRODUCTION

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AVERAGE SUMMED LIGHT OUTPUT > 7.0 pe

MINOS

CONCLUSIONS

• Extruded scintillator is being produced:• Industrial environment• Low cost• High quality material

• MINOS uses extruded scintillator:• Total of 300 tons• Cost: $6 per kg (vs. cast $40 per kg)• Average summed light output > 7 pe

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EXTRUDED PLASTIC SCINTILLATOR FOR THE MINOS …