Scintillation light yield of Ce-doped LuAP and LuYAP pixel crystals

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

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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

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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

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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

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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)

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2R-MODEL, selected LuAP pixels

Loss 1.4-1.6 cm-1, LY(0) =2800-3600 phel/MeV

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2R-MODEL, selected LuYAP pixels

Loss 0.8-1.5 cm-1, LY(0) =2200-3200 phel/MeV

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Absorption, undoped LuAP, plate

Corrections: Fresnel reflection, constant term

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Absorption, LuAP:Ce pixel transversally

Corrections: Fresnel reflection, constant term

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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