NaI:Tl-based radiation detector with improved light output and energy resolution

1 Ivan Khodyuk – SCINT15

Improvement of NaI:Tl light output and energy resolution by co-doping

I.V. Khodyuk, S. Messina, T. Hayden, S.E. Derenzo, E.D. Bourret, G. A. Bizarri

Lawrence Berkeley Na.onal Laboratory, Berkeley, CA -‐ USA


NaI – Performance Engineering

Factor Level 1 Level 2 Level 3 Level 4 Dopant Tl - - -

[Dopant], % 0.0 0.1 0.25 0.5 Co-dopant Mg Ca Sr Ba [co-dopant] 0.1 0.2 0.4 0.8 [Eu2+], % 1.0 0.5 0.1 0.0

Sequential trial of different compositions – 256 crystals Design of Experiment using L16 orthogonal array – 16 crystals

Goal: Improvement of NaI Light Output and Energy Resolution by co-doping

Benchmark: NaI:Tl – 44,000 ph/MeV and 6.3% at 662 keV

Factorial (parametric) space to discover:

Best value reported - Shiran et al.: NaI:Tl,Eu – 48,000 ph/MeV and 6.2% at 662 keV


Design of Experiment

-XRD -OE -XRL -PXR -XRF

Response to Gammas

-PHM

Non-proportionality in house and at the ALS Advanced characterization: -TSL, -OSL, -Afterglow, -ICP/GDMS

Powder chemistry &

melt-mix crystal synthesis

mm-size crystals

processing

Single crystal growth

cm-size crystals processing

Phase I Phase II

Design of Experiment + HTCF

Mul

ti-re

gres

sion

dat

a an

alys

is

Selected samples Hig

h Th

roug

hput

Cha

ract

eriz

atio

n Fa

cilit

y


Design of Experiment

# [Tl+] Co-d [co-d] [Eu2+] ER,% LO, ph/KeV

0 0.1 - 0.0 0.0 7.0 43

1 0.0 Mg 0.1 1.0 8.5 24.6

2 0.0 Ca 0.2 0.5 6.4 37.3

3 0.0 Sr 0.4 0.1 9.9 14.5

4 0.0 Ba 0.8 0.0 21 5.1

5 0.1 Mg 0.2 0.0 13.4 18.3

6 0.1 Ca 0.1 0.1 6.9 41.6

7 0.1 Sr 0.8 0.5 8 35.5

8 0.1 Ba 0.4 1.0 13.1 4.1

9 0.25 Mg 0.4 0.5 20 12.4

10 0.25 Ca 0.8 1.0 7 33.9

11 0.25 Sr 0.1 0.0 6.1 29.9

12 0.25 Ba 0.2 0.1 5.9 47

13 0.5 Mg 0.8 0.1 17.5 33.4

14 0.5 Ca 0.4 0.0 10.9 22.6

15 0.5 Sr 0.2 1.0 12 23.8

16 0.5 Ba 0.1 0.0 17.5 16.7

Fractional factorial design using L16 orthogonal array

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

Homemade reference

C ommerc ia l reference

Ene

rgy Res

olution @

662

keV (%)

D es ign number

Mg

C a

S r

B a

B aMg

C a S r

B a

Mg

C a

S r

B aMg

C aS r

S tatis tica l limit for 44000 photons /MeV

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

35

40

45

50

Homemade reference

Ligh

t Outpu

t (ph

oton

s/ke

V)

D es ign number

Mg

C a

S r

B a

Mg

C a

S r

B a

Mg

C a

B a

S r

Mg

C a

B a

S r

C ommerc ia l reference


Experimental design output -‐ visualizaAon

Performance (ER) optimization in 4 dimensional parametric space


OpAmum composiAon synthesis (melt-‐mix)

0 1000 2000 3000 4000 50000

100

200

300

400

Cou

nts

P MT 1 C hanne l

S 4

L Y = 46200 ph/MeV*E R = 5.4%

*LO corrected for PMT QE

Multi-regression analysis

Optimal composition Factor Level 1 Level 2 Level 3 Level 4

[Tl+] 0.0 0.1 0.25 0.5

Co-dopant Mg Ca Sr Ba

[co-dopant] 0.1 0.2 0.4 0.8

[Eu2+] 1.0 0.5 0.1 0

NaI: 0.25%Tl, 0.1%Eu, 0.2%Ca

Quick optimal composition synthesis and performance evaluation


OpAmum composiAon synthesis (Bridgman)

NaI: 0.25%Tl+, 0.1%Eu2+, 0.2%Ca2+ – nominal concentrations in the melt

Part of boule [Tl+], ppm wt

[Ca2+], ppm wt

[Eu2+], ppm wt

nominal in melt 3470 540 1000 top 14641 580 890 center 1500 490 940 bottom 880 580 940

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) results:

Conclusions: 1) Significant Tl segregation during the Bridgman growth; 2) Parts of the crystal with lower [Tl+] show better ER and LO

42 43 44 45 46 47 48 49 50 51 522.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

top center bottom

Ene

rgy Res

olution @

662

keV (%)

L ig ht O utput (photons /keV )

5.2% (51.1ph/keV )

S ta tis tica l limit for 44000 photons /MeV

R eference Na I:T l #0

C ommerc ia l Na I:T l


NaI:TEC – OpAmum composiAon (Bridgman)

NaI with lower concentration of Tl+ – 0.1 mole % in the melt was grown using same Bridgman furnace

550 600 650 700

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Normalized

cou

nts

G amma energy (keV )

Na I:T l commerc ia l reference -‐ 6.3±0.2% Na I:T l,C a ,E u co-‐doped -‐ 4.9±0.2%

52000 ph/MeV 4.9% at 662keV

NaI:TEC (Tl, Eu, Ca) – with 52,000 ph/MeV and 4.9% resolution at 662 keV


NaI:Tl vs NaI:TEC characterizaAon (i)

250 300 350 400 450 500 550 600 650

Na I:T E C Na I:T l re ference

XRL em

ission

intens

ity, a

rb. u

n.

W aveleng th, nm

0 1000 2000 3000 4000 5000

Na I:T l re ference Na I:T E C

Cou

nts/bin

T ime (ns )

Na I:T l -‐ 195 nsNa I:T l, E u, C a -‐ 195 ns (20% ) 1790 ns (80% )

X-ray luminescence Scintillation decay time

XRL emission max at 450nm 80% of the light emitted through “long” 1.8µs component


NaI:TEC characterizaAon (ii)

NaI:Tl reference NaI:TEC


NaI:TEC characterizaAon (ii)

6s à 6p

4f à 5d

Tl+

Eu2+

[Eu2++Vac]

Tl+


NaI:Tl vs NaI:TEC characterizaAon (iii)

-  Non-proportionality was measured at the ALS (LBNL) using micro-tomography beamline

-  Systematic change of Photon-nPR curve at 6-60keV enregy range

Photon non-proportional response

Early stages of scintillation process are affected bythe co-doping of NaI:Tl

NaI:Tl LO 44ph/keV à ER 6.3% NaI:TEC LO 52ph/keV à ER 5.9% à ER 4.9%


Conclusion

•  Design of experiment (fractional factorial design) has been used to speed up discovery of Eu2+ and IIA influence on scintillation performance of NaI:Tl and will be applied to other materials and factors

•  Optimal composition – NaI:TEC (0.1%Tl+, 0.1%Eu2+,

0.2%Ca2+) determined with multi-regression analysis gives 52000 photons/MeV and 4.9% grown by Bridgman

•  NaI:TEC under X-rays and optical excitation is emitting light predominantly through Eu2++Vac cluster with max at 450nm and main decay component of 1.8µs


Acknowledgements The authors would like to thank S. Hanrahan, D. Wilson, and Dr. J. Powell for their technical and engineering support and Drs. G. Gundiah, M. Gascon, E. Samulon, D. Perrodin and T. Shalapska for their scientific input. Combinatorial and high throughput material synthesis part of this work was supported by the US Department of Homeland Security/DNDO and crystal growth effort by the US Department of Energy/NNSA/DNN R&D and carried out at Lawrence Berkeley National Laboratory under Contract no. AC02-05CH11231. This work does not constitute an express or implied endorsement on the part of the government.

Date post:	08-Apr-2017
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NaI:Tl-based radiation detector with improved light output and energy resolution

Science