CRYSTALS

NaIL™ (NaI:Tl, Li)

−a large volume neutron-gamma

scintillator with exceptional pulse shape discrimination

Kan YangPeter R. Menge

Saint-Gobain CrystalsHiram, Ohio USA

Vladimir OuspenskiSaint-Gobain Recherche

Aubervilliers, France

IEEE NSS−MIC29 Oct. – 5 Nov., 2016Strasbourg, France

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OUTLINE

�Introduction of NaIL™ (NaI:Tl, Li)

�n-γ pulse shape discrimination (PSD)

�Scintillation properties

�High temperature performance

�Neutron detection efficiency

�Conclusions

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� NaI:Tl is the most widely used γ-ray scintillator.� Fully industrialized� Large volume production� Low cost� Mature detector designs

� Introducing efficient neutron detection to NaI:Tl by Li doping.� n + 6Li → t (2.75 MeV) + α (2.05 MeV)� NaI - LiI forms solid solution at any ratio.� Polycrystalline NaI:Tl,Li does not have sufficient

PSD.*

� Our researches focus on large format single crystals of NaI:Tl, Li (NaIL™)� [Tl] = 0.1 at%; [Li] = 0 – 8 at%

INTRODUCTION − NaIL™

*Brubaker et al., IEEE NSS/MIC Conf. Rec.(2011)

Nagarkar et al., IEEE NSS/MIC Conf. Rec.(2013)

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PULSE SHAPE DISCRIMINATION

*FFT based PSD algorithm, 8 µs integration time

K. Yang, et al., IEEE NSS-MIC Conf. Rec., NPO1-73 (2013)

Room temperature, measured with 252Cf

� Typical PSD FoM is 2 − 4 depending on [Li].� Better than 10-8 gamma rejection

Neutron

Gamma

662 keV3.2 MeVee

Gamma

Neutron

1% 6Li in crystalPSD FoM = 2.8

PS

D R

atio

Energy (MeVee)

*

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DECAY CONSTANTS AND PULSE SHAPESRoom temperature

� Neutron pulses decay faster than gamma pulses.� Both fast and slow decay times increase with [Li].

� ~ 250 ns with 1% Li loading; ~ 290 ns with 2% Li loading

Decay constants of NaI:Tl, LiAveraged neutron pulses

0.7% Li

2.2% Li

7.7% Li

Gamma

Neutron

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LIGHT YIELD AND ENERGY RESOLUTION

� LY decreases gradually with increasing [Li].

� ~ 34,000 ph/MeV with 1% Li loading

� ~ 31,000 ph/MeV with 2% Li loading

� ∆E/E is comparable to standard NaI:Tl.

� LY and ∆E/E are relatively insensitive to [Li].

� Synthesis process is not yet optimized.

[Li] = 0 – 8% in crystal

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IMPROVED HIGH TEMPERATURE LIGHT YIELDNaI:Tl + 1% Li in crystal

Shaping time = 12 µs

NaIL™ (1% Li)

Standard NaI:Tl

� Better high temperature stability than standard NaI:Tl

LY loss @160 oC < 10%

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PSD AT DIFFERENT TEMPERATURES

� Excellent neutron-gamma PSD up to 160 oC

NaI: Tl + 1% Li

*Measured with Photonis XP2020 PMT through a ⌀ 1” quartz light pipe; PSD FoM’swere scaled based on reference points of which the sample were coupled directly to PMT.

PSD is enhanced between 40 – 120 oC.

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NEUTRON DETECTION EFFICIENCY – SMALL FORM FACTORSimulation Results

0

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

the

rmal ne

utr

on

dete

ction

effic

iency

Li doping (%at.)

50mm x 50mm NaIL™

3He ⌀0.5”x2” tube, 8atm(⌀12 mm x 50 mm)

2”x2” CLYC w/ 6Li

2”x2”CLLB w/ 6Li

Det. Eff. (NaI + 1%6Li) = 53%

Det. Eff. (NaI + 2%6Li) = 74%

Handheld, backpack,

SPRD, oil-well logging etc.

Trade-off between performance, cost and amount of Li loadingQuestion: how much Li loading is needed? Trade-off between performance, cost and amount of Li loadingQuestion: how much Li loading is needed?

Example #1 : ⌀⌀⌀⌀ 50 mm x 50 mm NaIL™ Detector, 6Li enriched

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0

5

10

15

20

25

0 2 4 6 8 10

nth

de

tectio

n e

ffic

iency *

are

a

(ε*A

, cm

2)

Li doping (%at.)

NEUTRON DETECTION EFFICIENCY – SMALL FORM FACTORSimulation Results

50mm x 50mm NaIL™

3He 0.5”x2” tube, 8atm(⌀12 mm x 50 mm)

2”x2” CLYC w/ 6Li

2”x2”CLLB w/ 6Li

NaIL™ + 0.25%6Li= a typical handheld 3He tube

NaIL™ + 2%6Li= C6LYC of the same size

Handheld, backpack,

SPRD, oil-well logging etc.

Trade-off between performance, cost and amount of Li loadingQuestion: how much Li loading is needed? Trade-off between performance, cost and amount of Li loadingQuestion: how much Li loading is needed?

Example #1 : ⌀⌀⌀⌀ 50 mm x 50 mm NaIL™ Detector, 6Li enriched

NaIL™ + 1%6Li= 3x a typical handheld 3He tube

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NEUTRON DETECTION EFFICIENCY – LARGE FORM FACTORSimulation Results

Standard PNNL setup

Simulated with MCNPX 2.6.0.Detectors share one standard moderator box

Four 2x4x16 NaI™ + 1%6Li = a standard portal 3He tube

3He tube 2”x72” @ 2.9atm

Four 2x4x16

Three 2x4x16

Two 2x4x16

One 2x4x16

Spectroscopic

portal, RPM stand-

off and mobile

system

Example #2 : ⌀⌀⌀⌀ 50 x 100 x 400 mm3 NaIL™ Detector (2”x4”x16”)

�Promising solution for spectroscopic portal�< 3% enriched 6Li loading is needed for most

detection applications.

�Promising solution for spectroscopic portal�< 3% enriched 6Li loading is needed for most

detection applications.

Diminishing gain if 6Li is increased beyond 3%

Three 2x4x16 NaIL™ + 2%6Li = a standard portal 3He tube

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SUMMARY AND CONCLUSIONS

�NaI:Tl, Li (NaIL™) is an excellent n-γ dual mode scintillator with exceptional PSD. Production of large volume detector (> 500 cm3) is planned.

�Scintillation performance of NaIL™ is comparable to

standard NaI. NaIL™ maintains excellent LY and n-γ PSD

from room temperature up to 160 oC.

�NaIL™ with < 3 % enriched 6Li is sufficient for most detection applications. Higher doping is possible if needed.

Thank you!Visit us at booth 56/57

Thank you!Visit us at booth 56/57

⌀⌀⌀⌀ 50 mm NaIL™ detector

First ⌀⌀⌀⌀ 200 mm NaIL™ pilot ingot

�Production scale-up progress� Pilot trials (8”/ 200 mm) currently

underway � Full size production trials (>600 mm)

planned by year end

Patents pending