SCINTILLATION LIGHT YIELD OF Ce-ACTIVATED LSO, LYSO, LuAP AND
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Transcript SCINTILLATION LIGHT YIELD OF Ce-ACTIVATED LSO, LYSO, LuAP AND
SCINTILLATION LIGHT
YIELD OF
Ce-ACTIVATED
LSO, LYSO, LuAP AND
LuYAP
1
AUTHORS:
Andrzej J. Wojtowicz and
Winicjusz Drozdowski
N. Copernicus University (UMK)
Research, characterization of scintillator materials
Jean-Luc Lefaucheur, Zbigniew Galazka and
Zhenhui Gou
Photonic Materials Ltd (PML)
R&D on LYSO:Ce, LuAP:Ce, LuYAP:Ce
PML manufactures LYSO and is the only company
supplying large LuAP and LuYAP crystals on
commercial scale
2
CRYSTALS:
LSO (Lu2SiO5:Ce, oxyorthosilicate)
2x2x10 pixels, grown by CTI Inc, provided by
dr C. Melcher, dr P. Lecoq, dr C. Kuntner,
prof. S. Tavernier
LYSO (Lu2(1-x)Y2x SiO5:Ce, oxyorthosilicate), LuAP
(LuAlO3:Ce, aluminum perovskite), LuYAP (LuxY1-xAlO3:Ce,
x=0.7, aluminum perovskite)
2x2x10 pixels and 5x5x1 plates grown by PML
3
SCINTILLATION LIGHT YIELD
and ENERGY SPECTRA
Incoming gamma particle may:
get absorbed by giving up all its energy to a single electron
(photoelectron)
get scattered away by a single electron
(Compton electron) and escape
Energy of (photo- or Compton) electron is transformed into
scintillation
Scintillations differ; a plot showing number of scintillations (y
axis) vs amount of light in a single scintillation
(x axis) is called energy spectrum
4
Energy spectrum, BGO, pixel 2x2x10mm, vertically
Intensity [counts]
7000
6000
center 227 ch.
FWHM 51 ch.
5000
resolution 22.5 %
4000
3000
2000
1000
0
0
100
200
300
400
Channel no.
10000
]
Hamamatsu R1104 950 V, Cs 137 (662 keV), spectr. ampl. gain 3,
note photopeak, Compton edge, backscatter peak
1000
5
Energy spectrum
LSO 1050 CTI
2x2x10 mm pixel
vertically
Hamamatsu
R2059 (1500 V)
Na-22 (511 i 1274 keV)
spectr. ampl. gain 3
Note:
two photopeaks and
two Compton edges,
the third developing
peak (between 800 and
1000) and edge (at 720)
20000
15000
10000
5000
0
10000
1000
100
10
1
0
100 200 300 400 500 600 700 800 900 1000
i
6
Light yield measurement:
standard method
LSO 1050 CTI and two BGO
2x2x10 mm pixels, vertically
Hamamatsu R2059 (1500 V)
Cs 137 (662 keV) and
Na22 (511, 1274 keV)
7
1000
10*0.3
10*0.6
30*0.3
30*0.6
100*0.3
100*0.6
500
0
10000
1000
100
10
Energy spectra
BGO „old” 2x2x10
vertically
Hamamatsu
R2059 (1500 V)
Cs137 (662 keV)
spectr. ampl. gain
variable
Note:
photopeaks shift
with gain
1
0
100 200 300 400 500 600 700 800 900 1000
i
8
Photopeak positions vs spectr.
ampl. gain; PP vs G)
BGO „old” 2x2x10 pixel
R2059 1500 V, Cs 137 (662 keV)
note offset y0
800
y = y0 + a x
700
Photopeak:
y0 = -13.4 ± 3.3
a = 12.0 ± 0.2
peak position (channel no.)
600
500
1500 V
400
G (gain)
3
6
9
18
30
60
300
200
100
0
0
10
20
30
40
gain
50
60
70
80
fit: PP=a*G+y0; a = 12, y0 = 13.4
PP (peak
PP/G
(PP-y0)/G
position)
19
6.33
10.80
55
9.17
11.40
97
10.78
12.27
211
11.72
12.47
343
11.43
11.88
705
11.75
11.97
Photopeak position at 1 MeV:
12.0/0.662 = 18.1
9
Energy spectra
BGO „new” 2x2x10
vertically
Hamamatsu
R2059 (1500 V)
Na 22 (511, 1274 keV)
spectr. ampl. gain
variable
Note:
photopeaks shift
with gain
600
10*0.3
30*0.3
100*0.3
400
200
1000
0
100
10
1
0
100
200
300
400
500
i
10
1000
900
y = y0 + a x
peak position (channel no.)
800
y0 = -16.3 ± 5.6
a = 23.1 ± 0.4
700
600
500
400
300
200
100
0
0
5
10
15
20 25
30
35
40
Photopeak positions
vs spectr. ampl. gain
(PP vs G)
BGO „new” 2x2x10
pixel
R2059 1500 V
Na22 (511, 1274 keV)
note offset y0
gain * energy
BGO new, 1500 V, Na-22
PP from experiment FIT: PP = a*G*PE+y0 a = 23.1
y0 = -16.3
(PP-y0)/
(PP-y0)/
PE =
PE =
PP/(G*PE) PP/(G*PE)
G (gain)
(G*PE)
(G*PE)
0.511MeV 1.274MeV 0.511MeV 1.274MeV
0.511MeV 1.274MeV
3
17
70
11,09
18,32
21,72
22,58
9
92
263
20,00
22,94
23,55
24,36
30
326
869
21,27
22,74
22,33
23,16
11
1000
10*0.3
10*0.6
30*0.3
750
500
250
0
1000
100
Energy spectra
LSO 1050 2x2x10
vertically
Hamamatsu
R2059 (1500 V)
Cs 137 (662 keV)
spectr. ampl. gain
variable
10
1
0
100 200 300 400 500 600 700 800 900 1000
i
12
1000
Photopeak:
y0 = -45.7 ± 25.0
a = 96.7 ± 3.9
800
peak position (channel no.)
Photopeak positions
(PP) vs spectr. ampl.
gain (G)
(PP vs G)
LSO 1050 2x2x10
R2059 1500 V
Cs 137 (662 keV)
y = y0 + a x
900
700
600
500
400
1500 V
STANDARD METHOD:
300
G (gain)
LSO (N01050): a = 96.7
BGO (N03008): a = 12.0
200
3
6
9
100
fit: PP=a*G+y0; a=96.7, y0=-45.7
PP (peak
PP/G
(PP-y0)/G
position)
251
83.67
98.900
521
86.83
94.450
831
92.33
97.411
LYLSO = 8.06 LYBGO
0
0
1
2
3
4
5
gain
6
7
8
9
10
Photopeak position at 1 MeV:
96.7/0.662 = 146.1
13
STANDARD METHOD; summary of LSO 1050
PP (1 MeV,
LY(LSO)/
LY(LSO)/
gain 1)
LY(BGO old) LY(BGO new)
LSO 1050
146,1
8,06
6,32
BGO old
18,1
BGO new
23,1
1500 V
Does it work well?
What if we change the voltage?
voltage
1500
1200
900
Experimental PP for different PMT voltages
LY(LSO)/ LY(LSO)/
LSO 1050 BGO old BGO new
LY(BGOo) LY(BGOn)
146,1
18,1
23,1
8,07
6,32
17,7
2,54
3,32
6,96
5,32
1,20
0,180
0,216
6,65
5,55
This can’t be right! LY must be constant!
14
n
V
Let us see ifSwe can
understand
what is wrong.
ph e l
The signal from thePMT
look like this:
V0 should
V
S BGO K BGO
V0
V
S LS O K LS O
V0
'n
''n
S is a signal at PMT, V voltage, K number of
photoelectrons at photocathode, n number of
PMT stages, and α constant (assumed different
in each case)
15
from these expressions for Ss it follows that:
S LSO K LSO V
S BGO K BGO V0
'' 'n
and now we see why the ratio of Ss for LSO and BGO
depends on V; this is because alphas are different.
Now, does it make sense, can they really be different?
Different scintillators produce different load on
photocathode distributed differently in time
16
SLSO and SBGO vs PMT voltage
Photopeak position
fits:
LSO 1050
Y = X^9.39826*
2.05489E-028
662 keV
peak position (gain 1, 1 MeV)
Hamamatsu R2059
100.00
LSO 1050
photopeak
10.00
BGO old
Y=X^9.05*3.31
BGO
old (diamonds)
and new (circles)
photopeaks
1.00
0.10
6
7
8
9 1000
2
BGO new
Y = X^9.16* 1.89E-028,
511 and 1274 keV
voltage
17
SUMMARY of results from fits:
BGO old, fit S = (V/2139)^9,05*3,31e-28
K(BGOo), K(BGOo),
voltage
exp.
fit
exp
fit
1500
18,1
18,7255
451
466
1200
2,54
2,4838
477
466
900
0,180
0,1837
457
466
BGO new, fit S = (V/2139)^9,16*1,89e-28
K(BGOn), K(BGOn),
voltage
exp.
fit
exp
fit
1500
23,1
23,9889
598
621
1200
3,32
3,1046
664
621
900
0,216
0,2224
603
621
LSO 1050, fit S = (V/2139)^9,40*1,33e-28
K(LSO),
voltage
exp.
fit
K(LSO), fit
exp
1500
146,1 145,3194
4115
4094
1200
17,7
17,8340
4057
4094
900
1,20
1,1931
4111
4094
18
SUMMARY of results from fits:
voltage
1500
1200
900
voltage
1500
1200
900
LY(LSO)/
LY(LSO)/
LY(BGOo),
LY(BGOo), fit
experiment
9,12
8,79
8,51
8,79
8,99
8,79
LY(LSO)/
LY(LSO)/
LY(BGOn),
LY(BGOn), fit
experiment
6,88
6,59
6,11
6,59
6,82
6,59
No systematic dependence on V. Fits give good averaged
LY value from a number of spectra
19
ENERGY SPECTRA and scintillation light yield: LYSO (PML)
25000
-1
y = y0 + A w (/2)
20000
-1/2
-2
2
exp (-2 w (x - xC) )
xC = 299, 785
w = 30.9, 48.7 (fit)
15000
10000
5000
0
10000
3h energy spectrum
of LYSO 2x2x10
vertically
R2059, 1500 V, Na 22
the best pixel so far
Energy resolution:
12.2% (511 keV)
7.3% (1274 keV)
1000
100
10
1
0
100 200 300 400 500 600 700 800 900 1000
i
20
ENERGY SPECTRA and scintillation light yield: LYSO (PML)
3h energy spectrum of
LYSO 2x2x10 horizontally
R2059, 1200 V, Na 22
the best pixel so far
400000
-1
y = y0 + A w (/2)
300000
-1/2
-2
2
exp (-2 w (x - xC) )
xC = 126, 345, 486
w = 12.1, 22.2, 28.6 (fit)
200000
Energy resolution:
11.3% (511 keV)
7.6% (1274 keV)
6.9% (1785 keV)
100000
0
100000
10000
Note the third peak
1000
The vertical/horizontal
ratio 0.61, the highest
ever
100
10
0
100
200
300
i
400
500
600
21
ENERGY SPECTRA and scintillation light yield: LYSO (PML)
1000
300
10*0.3
10*0.4
10*0.5
900
800
peak position (channel no.)
200
100
0
100
y = y0 + a x
y0 = -30.0 ± 4.4
a = 213 ± 2
700
600
500
400
300
200
10
100
1
0
0
0,0
100 200 300 400 500 600 700 800 900 1000
0,5
i
3
4
5
1,5
2,0
2,5
3,0
3,5
4,0
gain * energy
LYSO PML 1500 V, Na-22
PP from experiment
G (gain)
1,0
FIT: PP = a*G*PE+y0
PE =
0.511MeV
PE =
1.274MeV
PP/(G*PE)
0.511MeV
PP/(G*PE)
1.274MeV
299
406
512
787
195,04
198,63
200,39
205,91
0,00
0,00
a = 213
y0 = -30,0
(PP-y0)/
(PP-y0)/
(G*PE)
(G*PE)
0.511MeV 1.274MeV
214,61
213,76
213,31
5,89
212,13
4,71
22
ENERGY SPECTRA and scintillation light yield: LYSO (PML)
LYSO PML, 1200 V, Na-22
PP from experiment
G (gain)
PE =
0.511MeV
PE =
1.274MeV
PP/(G*PE)
0.511MeV
PP/(G*PE)
1.274MeV
65
113
244
193
312
645
21,20
24,57
26,53
25,25
27,21
28,13
6
9
18
LYSO PML, 900 V, Na-22
PP from experiment
G (gain)
FIT: PP = a*G*PE+y0
FIT: PP = a*G*PE+y0
PE =
0.511MeV
PE =
1.274MeV
PP/(G*PE)
0.511MeV
PP/(G*PE)
1.274MeV
71
160
260
206
432
685
1,54
1,74
1,70
1,80
1,88
1,79
90
180
300
SAMPLE
LYSO PML,
2x2x10
BGO new,
2x2x10
alpha*n
K
a = 29,2
y0 = -24,6
(PP-y0)/
(PP-y0)/
(G*PE)
(G*PE)
0.511MeV 1.274MeV
29,22
28,47
29,92
29,36
29,20
29,20
a = 1,84
y0 = -9,11
(PP-y0)/
(PP-y0)/
(G*PE)
(G*PE)
0.511MeV 1.274MeV
1,742
1,876
1,839
1,924
1,755
1,816
LY (BGO)
radioactive
source
9,32
6 020
9,69
Na-22
9,16
621
1,00
Na-22
23
ENERGY SPECTRA and scintillation light yield: LuAP (PML)
120000
-1
y = y0 + A w (/2)
90000
-1/2
-2
2
exp (-2 w (x - xC) )
xC = 163, 433, 611
w = 16.0, 28.5, 38.7 (fit)
60000
LuAP plate, 5x5x1
(PML)
30000
R2059, 1500 V,
spectr. ampl. gain 3,
Na22
0
100000
10000
1000
note the third peak
100
10
1
0
100 200 300 400 500 600 700 800 900 1000
measurement: 8 h
i
24
ENERGY SPECTRA and scintillation light yield: LuAP (PML)
Na 22 Peak Positions (gain 3)
Hamamatsu R2059, 1500 V
LuAP plate, 5x5x1
(PML)
LuAP:Ce, PML
Na 22 (0.511, 1.274, 1.785 MeV)
PP = G*PE*a + y0
Y = 117.274 * X - 16.334
600
R2059, 1500 V,
spectr. ampl. gain 3,
Na22
400
200
note the third peak
0
0
1
2
3
4
5
6
Gain x Peak Energy (MeV)
LuAP PML, 1500 V, Na-22
PE (peak
energy,
G (gain)
MeV)
0,511
3
1,274
3
1,785
3
FIT:
PP = a*G*PE+y0
Normalized peak position
experiment
no corr.
offset corr.
G*PE
1,533
3,822
5,355
a=
PP (peak
position)
163
433
611
117,3
PP/(G*PE)
106,3
113,3
114,1
y0 (offset) =
(PP-y0)/
(G*PE)
117,0
117,6
117,1
-16,3
25
ENERGY SPECTRA and scintillation light yield: LuAP (PML)
400000
-1
y = y0 + A w (/2)
300000
-1/2
-2
2
exp (-2 w (x - xC) )
xC = 124, 339, 469
w = 18.9, 29.8, 44.9 (fit)
200000
100000
LuAP plate, 5x5x1
(PML)
R2059, 900 V, spectr.
ampl. gain 300,
Na22
0
1000000
100000
10000
note the third peak
1000
100
10
1
0
100 200 300 400 500 600 700 800 900 1000
measurement: 8 h
i
26
ENERGY SPECTRA and scintillation light yield: LuAP (PML)
Na 22 Peak Positions (gain 300)
Hamamatsu R2059, 900 V
LuAP plate, 5x5x1
(PML)
LuAP:Ce, PML
Na 22 (0.511, 1.274, 1.785 MeV)
PP = G*PE*a + y0
Y = 0.95065 * X - 15.0486
600
R2059, 900 V, spectr.
ampl. gain 300,
Na22
400
200
note the third peak
0
0
100
200
300
400
500
600
700
Gain x Peak Energy (MeV)
LuAP PML, 900 V, Na-22
PE (peak
energy,
G (gain)
MeV)
0,511
300
1,274
300
1,785
300
FIT:
PP = a*G*PE+y0
Normalized peak position
experiment
no corr.
offset corr.
G*PE
153,3
382,2
535,5
a=
PP (peak
position)
130
350
493
0,950
PP/(G*PE)
0,848
0,916
0,921
y0 (offset) =
(PP-y0)/
(G*PE)
0,946
0,955
0,949
-15,0
27
ENERGY SPECTRA and scintillation light yield: LuAP (PML)
peak position (gain 1, 1 MeV)
Hamamatsu R2059
LuAP plate, 5x5x1
(PML)
100.00
full energy peak
LuAP, PML, plate
R2059, 1500 and
900 V, Na22
10.00
1.00
0.10
0.01
6
7
8
9 1000
2
voltage
SAMPLE
LuAP PML,
5x5x1
BGO new,
2x2x10
alpha*n
K
LY (BGO)
radioactive
source
9,43
3 340
5,38
Na-22
9,16
621
1,00
Na-22
28
ENERGY SPECTRA and scintillation light yield: LuYAP (PML)
300000
-1
-1/2
250000
y = y0 + A w (/2)
200000
xC = 150, 406, 560
w = 24.9, 37.5, 61.6 (fit)
-2
LuYAP plate, 5x5x1
(PML)
2
exp (-2 w (x - xC) )
150000
R2059, 1500 V,
spectr. ampl. gain 3,
Na22
100000
50000
0
1000000
100000
10000
SAMPLE
1000
LuYAP PML,
5x5x1
BGO new,
2x2x10
100
10
alpha*n
K
LY (BGO)
radioactive
source
9,35
2 980
4,80
Na-22
9,16
621
1,00
Na-22
1
0
100 200 300 400 500 600 700 800 900 1000
measurement: 8 h
i
29
SUMMARY
We have developed a new method to measure
scintillation light yield of scintillator materials
The method, unlike the standard method, requires that
a number of spectra for different amplifier gains and
PMT voltages are measured
The method takes into account offset of energy spectra
and unexpected voltage dependence and provides
good undistorted values
30
The method has been used to study a representative
set of LYSO, LuAP and LuYAP crystals grown by PML
The LYSO developed by PML reached a mature stage; the
best LYSO pixel is by 50% brighter than a good LSO pixel
1050
LuYAP and LuAP crystals developed by PML show LYs
that are comparable (LuAP slightly ahead)
The important source of loss of light must be some
unidentified absorption centers that quench
scintillation in longer samples
31