1. 1IEEE NSS 2015 San Diego
Combinatorial Approach to Bulk Detector Material Engineering
I.V. Khodyuk, D. Perrodin, S.E. Derenzo, E.D. Bourret, G. A. Bizarri
Lawrence Berkeley Na@onal Laboratory, Berkeley, CA - USA
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 Na=onal Laboratory under Contract no.
AC02-05CH11231. This work does not cons=tute an express or implied endorsement on the part of the government.

2. 2IEEE NSS 2015 San Diego
Outline
q IntroducHon
o Global trends in radia=on detec=on materials
§ Complex hosts
§ Co-doping
o Parameter space for scin=llators R&D
q Tools to search through the parameter space
o Combinatorial chemistry
o Full factorial design
o Frac=onal factorial design
o Response surface methodology
q NaI performance engineering
o Experimental design
o Data analysis and result verifica=on
o Bridgman crystal growth
o NaI:TEC characteriza=on
q Conclusion and future work

3. 3IEEE NSS 2015 San Diego
Outline
q IntroducHon
o Global trends in radia=on detec=on materials
§ Complex hosts
§ Co-doping
o Parameter space for scin=llators R&D
q Tools to search through the parameter space
o Combinatorial chemistry
o Full factorial design
o Frac=onal factorial design
o Response surface methodology
q NaI performance engineering
o Experimental design
o Data analysis and result verifica=on
o Bridgman crystal growth
o NaI:TEC characteriza=on
q Conclusion and future work

4. 4IEEE NSS 2015 San Diego
ApplicaHon driven research
How can we enhance spectroscopic capabili=es of “low cost” scin=llators?
Is it possible to decrease price of exis=ng “advanced” materials?
Real world applicaHons are the main driving forces behind radiaHon materials
discovery and development
NaI:Tl
CsI:Tl,Na
BeYer Energy
resolu=on
Isotope
discrimina=on
LaBr3:Ce
SrI2:Eu
Lower price
More
applica=ons
Discover new materials or Improve already exisHng
Homeland security:

5. 5IEEE NSS 2015 San Diego
Discovery of new material
Binary
Ternary
Quaternary
Global trend in materials for radiaHon detecHon
Time
Number of elements
in the host
NaI, CsI
LSO, YAG
GYAG, CLYC
More and more systems with complex hosts are
introduced as scin=llators
Same or similar trend can be seen in scinHllators, semiconductors, phosphors…

6. 6IEEE NSS 2015 San Diego
Mixed materials perform beRer Luminosity, arb. un.
Cs(Br,I) (La,Ce)F3
La(Cl,Br)3
(Lu,Y)AP
(Lu,Gd)SO Gd(Al,Ga)G
Y(Al,Ga)G (Zn,Mg)WO (Ca,Sr)S
From: GekHn, A.V.; Belsky, A.N.; Vasil'ev, A.N., "ScinHllaHon Efficiency Improvement by Mixed Crystal Use," in Nuclear Science, IEEE
Transac1ons on , vol.61, no.1, pp.262-270, Feb. 2014
In many cases complex hosts lead to beRer scinHllaHon performance

7. 7IEEE NSS 2015 San Diego
Trend in materials discovery
Sta=s=cal analysis of 500+ scin=llator materials from scinHllator.lbl.gov
Number of composiHons grown as a power law of number of elements
PublicaHon year 1960 2015
102
103
104
105
N of possible composiHons

8. 8IEEE NSS 2015 San Diego
Example 1 - Mixed caHons
PublicaHon year 1960 2015
Gd3Al5O12
(Gd,Y)3Al5O12
(Gd,Y)3(Ga,Al)5O12
Dorenbos, P. et al., Rad. Eff. Def. in Sol., p.135, 1995 Cherepy, N.J et al, IEEE TNS 56 (3) p.873, 2009
K. Kamada et al., Crystal Growth & Design, 11, p.4484, 2011
Significant improvement of light output in mixed ca=ons systems
From 10,000 to
60,000 ph/MeV

9. 9IEEE NSS 2015 San Diego
CsI
CsBa2I5
BaBr2
BaBrI
J. Bonanomi and J. Rossel, Helv. Phys. Acta., vol. 25, p. 725, 1952.
E. D. Bourret-Courchesne et al., NIM A, 612:138, 2009.
J. Selling et al., J. of Appl. Phys., 101:034901, 2007.
E. D. Bourret-Courchesne, NIM A, 613:95, 2010.
Example 1 - Mixed anions
Significant improvement of energy resoluHon and light output
PublicaHon year 1960 2015
From 50,000 to
~90,000 ph/MeV
From >5% to ~3%
at 662 keV

10. 10IEEE NSS 2015 San Diego
Improvement of exisHng materials
Development has been done by different means:
Crystal growth
• CondiHons
• Techniques
Control of impuriHes
• Raw materials
• Synthesis
Defect engineering
• Band gap
• Co-doping
For example co-doping was successfully used to target specific properHes
We keep the lacce and try to
improve performance
Global approach:

11. 11IEEE NSS 2015 San Diego
Targeted improvement by co-doping
Mechanical proper=es
were addressed by
aliovalent co-doping: Sr,
Ca, Ba, Mg
Improved scin=lla=on
performance has been
discovered: Ba, Sr, Ca
Record Energy
Resolu=on
Improved Mechanical
proper=es
LSO:Ce Ca
Decay time
Light
Output
PbWO4 La
Traps
removal
Decay =me
There are a few examples when specific properHes of exisHng materials have been
improved by co-doping with a small amount of op1cally passive elements
Zoom in example: LaBr3:Ce and CeBr3
Significant improvement of scinHllaHon and mechanical properHes has
been achieved by co-doping with few hundred ppm of Sr2+
Harrison, M.J. et al., IEEE TNS 56 (3) 2009 Yang, K. et al., IEEE NSS/MIC 2012 N1-135 Alekhin, M.S. Appl. Phys. LeR. 102, 161915 (2013)

12. 12IEEE NSS 2015 San Diego
Ideal scinHllators discovery and improvement
Lapce
• Elemental
composiHon
• Stoichiometry
• Enhanced defect
formaHon
Dopants
• Dopant type and
concentraHon
• Co-dopant 1 type and
concentraHon
• Co-dopant 2…
Synthesis
• Synthesis technique
and condiHons
• Purity of raw
• IniHal reactants
Even with very good guidance we have from physics and crystal growth it is essenHal
to have effecHve tools to search through the parameter space
Energy
ResoluHon
Light Output
Mechanical
properHes
Decay Hme
Price
Self
AbsorpHon
Parameter space is expanding drasHcally when we account for all possible
combinaHons

13. 13IEEE NSS 2015 San Diego
Outline
q IntroducHon
o Global trends in radiaHon detecHon materials
§ Complex hosts
§ Co-doping
o Parameter space for scinHllators R&D
q Tools to search through the parameter space
o Combinatorial chemistry
o Full factorial design
o Frac=onal factorial design
o Response surface methodology
q NaI performance engineering
o Experimental design
o Data analysis and result verificaHon
o Bridgman crystal growth
o NaI:TEC characterizaHon
q Conclusion and future work

14. 14IEEE NSS 2015 San Diego
Combinatorial chemistry
Very efficient for powders and thin
films when probing luminescent
proper=es
BiSrCaCuOx
DescripHon
Combinatorial chemistry - all the possible
combina=ons in the parameter space are
probed
Requirements
Possibility of simultaneous synthesis
Desired proper=es of the materials can
be automa=cally tested

15. 15IEEE NSS 2015 San Diego
Combinatorial chemistry and scinHllator?
• Cannot use powder/thin film
• Need single crystal of representative quality
Requirement to access scintillation properties:
Gamma response and photopeak for energy
resolution and light output
The speed of the approach is as fast as the
slowest part of the process.
Numerous possibility
Extremely time
consuming
Not applicable!
Crystal growth/
Material Synthesis
A = Li, Na, K, Cs
X = F, Cl, Br, I
Y = 0.01, 0.05, 0.1, 0.2
54 = 625 crystals
Cs2ALa1-yCeyX6:IIA
5 factors x 4 levels Full factorial design
IIA = Mg, Ca, Sr, Ba
[IIA] = 0.05%, 0.1%,
0.25%, 0.5%

16. 16IEEE NSS 2015 San Diego
From FULL to FRACTIONAL factorial design
F2
F3
F1
Can we search through the parameter space more efficiently?
Cs2ALa1-yCeyX6
33 = 27 crystals
3 factors x 3 levels
Full factorial design
A, X, Y -> factors
Li, Na, Cs -> levels of Factor A
A=Li, Na, Cs
X=Cl, Br, I
Y=0.01, 0.05, 0.1
Example:

17. 17IEEE NSS 2015 San Diego
Factor Level 1 Level 2 Level 3
F1 L11 L21 L31
F2 L12 L22 L32
F3 L13 L23 L33
Fractional factorial design 33 using L9 OA
F2
F3
F1
FracHonal factorial design
L9 Orthogonal Array
Design F1 F2 F3
1 L11 L12 L13
2 L11 L22 L23
3 L11 L32 L33
4 L21 L12 L23
5 L21 L22 L33
6 L21 L32 L13
7 L31 L12 L33
8 L31 L22 L13
9 L31 L32 L23
33 = 27 9 crystals
54 = 625 16 crystals

18. 18IEEE NSS 2015 San Diego
Fractional factorial design 33 using L9 OA
Example: Cs2ALa1-yCeyX6
Orthogonal Experimental Set
Design A X Y
1 Li Cl 0.01
2 Li Br 0.05
3 Li I 0.1
4 Na Cl 0.05
5 Na Br 0.1
6 Na I 0.01
7 Cs Cl 0.1
8 Cs Br 0.01
9 Cs I 0.05
Factor Level 1 Level 2 Level 3
A Li Na Cs
X Cl Br I
Y 0.01 0.05 0.1
#1 Cs2LiLaCl6:1%Ce
#5 Cs2NaLaBr6:10%Ce
#9 Cs3LaI6:5%Ce
X
Y
A
#1
#5
#9

19. 19IEEE NSS 2015 San Diego
Complementary space probing
Projection of all 9
points on YZ plain
Orthogonal array based experimental design requires the fewest number of
experiments to probe full combinatorial space
Knots are arranged to form complete projecHon on all planes: XY, XZ, YZ

20. 20IEEE NSS 2015 San Diego
Full space reconstrucHon
Visualiza=on can be used only
for factors that can be
represented by con=nuous
func=on – concentra=on, ra=o,
temperature, etc.
Combinatorial technique
itself is not limited to that!
By having all 3 projecHons taken the full map of the space can be reconstructed
Risk – part of the information can be lost
Advantage – minimal N of experiments

21. 21IEEE NSS 2015 San Diego
Outline
q IntroducHon
o Global trends in radiaHon detecHon materials
§ Complex hosts
§ Co-doping
o Parameter space for scinHllators R&D
q Tools to search through the parameter space
o Combinatorial chemistry
o Full factorial design
o FracHonal factorial design
o Response surface methodology
q NaI performance engineering
o Experimental design
o Data analysis and result verifica=on
o Bridgman crystal growth
o NaI:TEC characteriza=on
q Conclusion and future work

22. 22IEEE NSS 2015 San Diego
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
Full factorial design would require trial of 256 different crystals
L16 orthogonal array based FracHonal Factorial design - only 16 crystals
Goal: Improvement of NaI Energy ResoluHon by co-doping
Benchmark: NaI:Tl – 40,000 ph/MeV and 6.3% at 662 keV
Best value reported - Shiran et al.: NaI:Tl,Eu – 48,000 ph/MeV and 6.2% at 662 keV
Best unreported value: NaI:Tl - 44,000 ph/MeV and 5.9% at 662 keV
Factorial (parametric) space to discover:
Shiran, N.V. et al, IEEE TNS 57 (3) p.1233, 2010

23. 23IEEE NSS 2015 San Diego
Synthesis and characterizaHon
Work flow
Design of
Experiment
Selected crystal
growth
Pulse-height
characteriza=on
Data analysis
For every composiHon 3-5 single crystalline pieces of 3x3x3mm3 were measured

24. 24IEEE NSS 2015 San Diego
Design of Experiment
FracHonal factorial design using L16 orthogonal array
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
0
5
10
15
20
H omemade reference
C ommercial reference
Energy Resolution @ 662keV (%)
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 a
S r
S tatistical limit for 44000 photons/MeV
None of the experimental composi=ons significantly over perform the reference
InformaHon on the direcHon of improvement is encoded in the design

25. 25IEEE NSS 2015 San Diego
Experimental design output
ProjecHons of 4 dimensional parametric space on surface:
Zone of
interest
MulH-regression analysis is necessary to esHmate opHmal concentraHons

26. 26IEEE NSS 2015 San Diego
OpHmum composiHon synthesis
0 1000 2000 3000 4000 5000
0
100
200
300
400
Counts
P MT 1 C hannel
S 4
L Y = 46200 ph/MeV *
E R = 5.4%
*LO corrected for PMT QE NaI: 0.25%Tl, 0.1%Eu, 0.2%Ca
Quick op=mal composi=on synthesis
and performance evalua=on
OpHmal composiHon over perform the benchmark reference even when we operate in
the nominal concentraHons parametric space
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
Factorial space to discover:

27. 27IEEE NSS 2015 San Diego
OpHmum composiHon crystal growth
NaI: 0.25%Tl+, 0.1%Eu2+, 0.2%Ca2+ – nominal concentraHons 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
boRom 880 580 940
InducHvely Coupled Plasma Mass
Spectrometry (ICP-MS) results:
42 43 44 45 46 47 48 49 50 51 52
2.0
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
Energy Resolution @ 662keV (%)
L ight O utput (photons /keV )
5.2% (51.1ph/keV )
S tatis tical limit for 44000 photons /MeV
R eference NaI:T l #0
C ommercial NaI:T l
There is a significant difference between nominal and real Tl concentaHon
Parts of the crystal with lower Tl concentraHon perform beRer

28. 28IEEE NSS 2015 San Diego
NaI:TEC with corrected Tl concentraHon
NaI with lower concentra=on of Tl+ – 0.1 mole % in the melt was grown using
the same Bridgman technique
52000 ph/MeV
4.9% at 662keV
NaI:TEC (Tl, Eu, Ca) – with 52,000 ph/MeV and 4.9% resoluHon at 662 keV

29. 29IEEE NSS 2015 San Diego
CharacterizaHon: XRL and decay Hme
250 300 350 400 450 500 550 600 650
NaI:T E C
NaI:T l reference
XRL emission intensity, arb. un.
W avelength, nm
X-ray luminescence ScinHllaHon decay Hme
XRL emission max at 450nm
85% of the light emiRed through
“long” 1.4μs component
0 1000 2000 3000 4000 5000
0.01
0.1
1
τ1
= 240ns - 15%
τ2
= 1390ns - 85%
Counts/bin
T ime, ns
NaI:T E C
NaI:T l
τ = 225ns
background

30. 30IEEE NSS 2015 San Diego
Energy transfer from Tl+ to Eu2+
6s à 6p
4f à 5d
Tl+
Eu2+
[Eu2++Vac]
Tl+

31. 31IEEE NSS 2015 San Diego
Tl-Eu energy
transfer
maximization
Beneficial
defect
creation
Impurity
removal
Mechanisms of improvement
MulHple mechanisms work in synergy toward the improvement of light output and
energy resoluHon
High Oxygen affinity of
Ca and EuTrapping of carriers
during early stages
of scintillation
process with
subsequent
release
[Eu2+
Na + VacNa]
– hole trap
[Tl0
Na + Ca2+
Na]
– electron trap
Further invesHgaHon as well as industrial verificaHon is required to push
performance of NaI:TEC even further

32. 32IEEE NSS 2015 San Diego
Outline
q IntroducHon
o Global trends in radiaHon detecHon materials
§ Complex hosts
§ Co-doping
o Parameter space for scinHllators R&D
q Tools to search through the parameter space
o Combinatorial chemistry
o Full factorial design
o FracHonal factorial design
o Response surface methodology
q NaI performance engineering
o Experimental design
o Data analysis and result verificaHon
o Bridgman crystal growth
o NaI:TEC characterizaHon
q Conclusion and future work

33. 33IEEE NSS 2015 San Diego
Conclusion
• There are trends in radia=on detec=on materials discovery and
improvement which significantly increase poten=al combinatorial space
• Experimental design techniques can be very useful tools to probe this
space in a more efficient way
• FracHonal factorial design has been used to speed up discovery of Eu2+ and
IIA influence on scin=lla=on performance of NaI:Tl
• Op=mal composi=on – NaI:TEC (0.1%Tl+, 0.1%Eu2+, 0.2%Ca2+) determined
with mul=-regression analysis gives 52000 photons/MeV and 4.9% grown
by Bridgman
• NaI:TEC under X-rays and op=cal excita=on is emicng light predominantly
through Eu2++Vac cluster with max at 450nm and main decay components
of 240ns and 1.4μs
J. Appl. Phys. 118, 084901 (2015); http://dx.doi.org/10.1063/1.4928771

34. 34IEEE NSS 2015 San Diego
Future work
Formula
valida=on
Scaling up
Industrial
verifica=on
NaI:TEC – Can we get 2x2 inches with ER<5?
Methodology
improvement
Goals
broadening
Materials
diversifica=on
Experimental design

35. 35IEEE NSS 2015 San Diego
Acknowledgements
The authors would like to thank S. Hanrahan, D. Wilson, M. Boswell and Dr. J. Powell
for their technical and engineering support and Drs. G. Gundiah, M. Gascon,
E. Samulon and T. Shalapska for their scien=fic 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
Na=onal Laboratory under Contract no. AC02-05CH11231. This work does not
cons=tute an express or implied endorsement on the part of the government.
Thank you!