A.J. Wojtowicz, Crimea, Sept. 2005 1
Scintillation light yield of Ce-doped
LuAP and LuYAP pixel crystals
A.J. Wojtowicz 1), W. Drozdowski 1), M. Ptaszyk 1) Z. Galazka2), J.L. Lefaucheur 2)
1) Institute of Physics, N. Copernicus University, Torun, Poland2) Photonic Materials Ltd, Bellshill, Scotland
International Conference on Inorganic Scintillators and their Industrial Applications
SCINT 2005, Crimea, Ukraine
A.J. Wojtowicz, Crimea, Sept. 2005 2
OUTLINE
Introduction
Light yield from pixel crystalsof LuAP and LuYAP; results
2R-model
Results:intrinsic light yields and loss parameters;
absorption
Summary and conclusions
A.J. Wojtowicz, Crimea, Sept. 2005 3
INTRODUCTION
LuAP: 8.34 g/cm3, 0.3 photofraction,
365 nm emission, 17-18 ns decay time,
LY over 2xBGO (thickness!!)
difficult to grow, hence LuYAP
ClearPetTM project:
2x2x8 and 2x2x10mm pixels of
LYSO and LuYAP
A.J. Wojtowicz, Crimea, Sept. 2005 4
PROBLEM:
poor vertical and horizontal light yield ratio
V2H initially as low as 0.3
OTHER CRYSTALS
(the highest measured V2H today):
BGO 0.6
LSO, LYSO 0.63
LuAP 0.43
LuYAP 0.56
A.J. Wojtowicz, Crimea, Sept. 2005 5
SAMPLES
Photonic Materials Ltd, PML
2x2x10 mm pixels and 5x5x1 plates
close to 60 samples of LuAP, YAP and
LuYAP, delivered in 2003-2005
BOULES (Czochralski):
diameter up to 53 mm,
cylinder length up to 130 mm
A.J. Wojtowicz, Crimea, Sept. 2005 6
LIGHT YIELD
ENERGY SPECTRUM
Na 22, LuYAP pixel, horizontal,
gain 3
Positions of full energy peaks depend
on the amount of scintillation light
produced by gamma particle
A.J. Wojtowicz, Crimea, Sept. 2005 7
PEAK POSITONSvs
ENERGY * GAIN
note offset:peak 1, 9%
peak 2, 3.5%peak 3, 2.5%
slope coefficient:peak position for gain
1 and energy 1MeV
A.J. Wojtowicz, Crimea, Sept. 2005 8
ENERGY SPECTRUM
Na22, LuYAP pixel vertically
gain 3
Third peak gone, less light, wider
peaks
A.J. Wojtowicz, Crimea, Sept. 2005 9
PEAK POSITIONS vs
GAIN * ENERGYgain 3
LuYAP pixelvertically
V2H = 0.42
A.J. Wojtowicz, Crimea, Sept. 2005 10
ENERGY SPECTRA
Na22, LuAP pixel vertically
variable gain
A.J. Wojtowicz, Crimea, Sept. 2005 11
PEAK POSITIONS VS GAIN
VS GAIN * ENERGY
A.J. Wojtowicz, Crimea, Sept. 2005 12
ENERGY SPECTRA, Na22, LuAP pixel
vertically
X-axisoffset shifted, gain rescaled:peaks coincide
A.J. Wojtowicz, Crimea, Sept. 2005 13
SINGLE PHOTOELECTRON
SPECTRA
variable gain
A.J. Wojtowicz, Crimea, Sept. 2005 14
PEAK POSITIONS from single
photoelectron spectra
gain variable
note offset of -18.7
for gain of 600 true peak position is 28.7
instead of 10!!
slope coefficient 0.049
A.J. Wojtowicz, Crimea, Sept. 2005 15
SINGLE PHOTOELECTRON
SPECTRA
X-axis offset shiftedgain rescaled
peak position is offset independent
norm. to gain 1
0.049Hamamatsu R2059
1500 V
A.J. Wojtowicz, Crimea, Sept. 2005 16
LuAP (PML)
V2H=1) 900/2104 = 0.432) 909/2247 = 0.403) 856/2068 = 0.414) 909/2122 = 0.435) 740/1837 = 0.406) 873/2110 = 0.417) 855/1982 = 0.43
SUMMARY OF LIGHT YIELD MEASURMENTS
LuYAP (PML)
V2H =1) 999/1774 = 0.562) 793/1614 = 0.493) 856/1712 = 0.50
4) 1186/2533 = 0.475) 1061/2555 = 0.426) 945/2271 = 0.42
A.J. Wojtowicz, Crimea, Sept. 2005 17
2R – model (2 rays model)
Experimental grounds: early papers by Lempicki et al, recently Dujardin et al:
LY depends mostly on heigth not on length or width
dx xL2expxexp2
1LYdLY 0
L
0
dLYLY
L2
L2exp1LYLY 0
A.J. Wojtowicz, Crimea, Sept. 2005 18
2R – model (2 rays model)
Experimental points, Balcerzyk et al., 2005Solid line 2R-model
A.J. Wojtowicz, Crimea, Sept. 2005 19
LuAP (PML)
1) 1.46 / 27802) 1.61 / 30503) 1.55 / 27804) 1.46 / 28005) 1.62 / 25006) 1.55 / 28307) 1.44 / 2610
SUMMARY OF RESULTS from 2R-MODEL
LuYAP (PML)
1) 0.86 / 21002) 1.14 / 20103) 1.10 / 21204) 1.24 / 32105) 1.54 / 3420 6) 1.53 / 3040
Loss (cm-1) / LY(0) (phel/MeV)
A.J. Wojtowicz, Crimea, Sept. 2005 20
2R-MODEL, selected LuAP pixels
Loss 1.4-1.6 cm-1, LY(0) =2800-3600 phel/MeV
A.J. Wojtowicz, Crimea, Sept. 2005 21
2R-MODEL, selected LuYAP pixels
Loss 0.8-1.5 cm-1, LY(0) =2200-3200 phel/MeV
A.J. Wojtowicz, Crimea, Sept. 2005 22
Absorption, undoped LuAP, plate
Corrections: Fresnel reflection, constant term
A.J. Wojtowicz, Crimea, Sept. 2005 23
Absorption, LuAP:Ce pixel transversally
Corrections: Fresnel reflection, constant term
A.J. Wojtowicz, Crimea, Sept. 2005 24
Summary and conclusions
We have introduced 2R-model to describe LY dependence on height of differently shaped crystals
The model can be used to describe the pixel shaped crystals for PET
The model allows to estimate intrinsic scintillation light yield and loss parameter from measurements of vertical
and horizontal light yields
Intrinsic light yields of LuAP and LuYAP are close. Loss parameter of LuAP at 1.4 to 1.6 cm-1 is higher than
LuYAP (0.8 cm-1)
The loss consists of Rayleigh term, constant term and unidentified UV absorption