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Principle - Structured Scintillator CsI:Tl SiO2 Si
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Characterization of CsI:Tl recrystalization after liquid phase deposition
Ulrik Lund Olsen, Ph.D. studentsupervisors: H.F. Poulsen, S. Schmidt
SCINT’07, Salem Winston, June 4-8 2007
Aims of project
DiffractedBeam
Grain in Aluminum Sample Scintillator
Mirror
MicroscopeLens
CCD
photons
540nm
X-rays50keV
Submicron grains structure resolved at high energy (30-100keV) at fast kinetic low flux diffraction meassurements.
fundamental relationship between scintillator thickness and resolution
Principle - Structured Scintillator
CsI:Tl
SiO2
Si
Electrochemical etching
HF solution etches surfaces with positive donors
Light induced donors are guided by an applied electric field
Field determined by silicon resistivity and bias
HF
e-e-
+
+
+ e-
R.L. Smith and J.D. Collins, J. Appl. Phys. 71, 8, R1 (1992)
Pore Structure
10µm
1µm
SiO2
Pore Filling Process
• CsI:Tl powder on Silicon surface• Sealed sample holder• Tube furnace• Controlled cooling rate
Bulk characterization
• Focused Ion Beam(FIB) milling
4µm
10µm
Ions
Crystal characterization - EBSD
Grain size Distribution
Electron Backscatter Diffraction
0 20 40 600
0.05
0.1
0.15
0.2
0.25
Grain Area [µm2]
Are
a/ T
otal
Are
a
500 1000 1500 2000 2500 30000
20
40
60
80
100
Channel No.
Ene
rgy
[keV
]
y = 0.027*x - 0.13
data linear
Compositional characterization - Fluorescence
Flourescence exited with 90keV synchrotron radiation:
•local (w/ focused beam)
•large lead(Pb) background
Au
SnKβ1
Kβ1
Kα1
Kα1Kα2
fit
9 10 11 12 13 140
200
400
600
800
Energy [keV]
Inte
nsity
[a.u
.]
Referencelow evaporationhigh evaporation
Tl -L1&2
Tl-L1&2
Compositional characterization - PIXE
0 10 20 30 400
0.5
1
1.5
2
2.5
3
3.5x 104
Energy [keV]
Inte
nsity
[a.u
.]
Referencelow evaporationhigh evaporation
Tl -L1&2
Tl-L1&2
I-K1&2
Cs - K1&2I - K1
Cs - K1
Particle induced X-ray Emission:•40keV protons•bulk information (250µm penetration)•global probe (2mm2 beam)
Compositional characterization - PIXE
0
0.02
0.04
0.06
0.08
0.1
0.12
Low evap. High evap. as recieved
Tl- c
onte
nt [w
t %]
manufacturers specs on as-received was 0.2 wt%
(GB crystals)
Composition characterization - SIMSSecondary Ion Mass Spectroscopy:
•local information•surface probing•high compositional sensitivity (>ppm)•uneven sensitivity to different species
No. Ion CentMass CI
1 I 126.8895 434
2 Cs 132.8742 564067
3 ^203Tl 203.0080 1069
4 Tl 205.0127 1362
5 Cs_2 265.7874 170843
Conclusion
• Multiple characterization tools needed• textural information from high resolution EBSD• absolute composition from PIXE• meso-scale relative composition from x-ray induced fluorescence• local composition – SIMS
Thanks to: T. Martin (ESRF)V. Honkimaki (ESRF)M. di Michiel (ESRF)X. Badel (KTH)J. Linnros (KTH)
N.B. Larsen (RISØ)J.C. Grivel (RISØ)C. Gundlach (ESRF)
Funding:
Danish FundamentalResearch Foundation &