1 Scintillation light yield of Ce-doped LuAP and LuYAP pixel crystals A.J. Wojtowicz 1), W. Drozdowski 1), M. Ptaszyk 1) Z. Galazka 2), J.L. Lefaucheur 2) 1) Institute of Physics, N. Copernicus University, Torun, Poland 2) Photonic Materials Ltd, Bellshill, Scotland International Conference on Inorganic Scintillators and their Industrial Applications SCINT 2005, Crimea, Ukraine

A.J. Wojtowicz, Crimea, Sept OUTLINE Introduction Light yield from pixel crystals of LuAP and LuYAP; results 2R-model Results: intrinsic light yields and loss parameters; absorption Summary and conclusions

A.J. Wojtowicz, Crimea, Sept INTRODUCTION LuAP: 8.34 g/cm 3, 0.3 photofraction, 365 nm emission, ns decay time, LY over 2xBGO (thickness!!) difficult to grow, hence LuYAP ClearPet TM project: 2x2x8 and 2x2x10mm pixels of LYSO and LuYAP

A.J. Wojtowicz, Crimea, Sept 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 SAMPLES Photonic Materials Ltd, PML 2x2x10 mm pixels and 5x5x1 plates close to 60 samples of LuAP, YAP and LuYAP, delivered in BOULES (Czochralski): diameter up to 53 mm, cylinder length up to 130 mm

A.J. Wojtowicz, Crimea, Sept 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 PEAK POSITONS vs 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 ENERGY SPECTRUM Na22, LuYAP pixel vertically gain 3 Third peak gone, less light, wider peaks

A.J. Wojtowicz, Crimea, Sept PEAK POSITIONS vs GAIN * ENERGY gain 3 LuYAP pixel vertically V2H = 0.42

A.J. Wojtowicz, Crimea, Sept ENERGY SPECTRA Na22, LuAP pixel vertically variable gain

A.J. Wojtowicz, Crimea, Sept PEAK POSITIONS VS GAIN VS GAIN * ENERGY

A.J. Wojtowicz, Crimea, Sept ENERGY SPECTRA, Na22, LuAP pixel vertically X-axis offset shifted, gain rescaled: peaks coincide

A.J. Wojtowicz, Crimea, Sept SINGLE PHOTOELECTRON SPECTRA variable gain

A.J. Wojtowicz, Crimea, Sept PEAK POSITIONS from single photoelectron spectra gain variable note offset of for gain of 600 true peak position is 28.7 instead of 10!! slope coefficient 0.049

A.J. Wojtowicz, Crimea, Sept SINGLE PHOTOELECTRON SPECTRA X-axis offset shifted gain rescaled peak position is offset independent norm. to gain Hamamatsu R V

A.J. Wojtowicz, Crimea, Sept LuAP (PML) V2H= 1) 900/2104 = ) 909/2247 = ) 856/2068 = ) 909/2122 = ) 740/1837 = ) 873/2110 = ) 855/1982 = 0.43 SUMMARY OF LIGHT YIELD MEASURMENTS LuYAP (PML) V2H = 1) 999/1774 = ) 793/1614 = ) 856/1712 = ) 1186/2533 = ) 1061/2555 = ) 945/2271 = 0.42

A.J. Wojtowicz, Crimea, Sept R – 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

A.J. Wojtowicz, Crimea, Sept R – model (2 rays model) Experimental points, Balcerzyk et al., 2005 Solid line 2R-model

A.J. Wojtowicz, Crimea, Sept LuAP (PML) 1) 1.46 / ) 1.61 / ) 1.55 / ) 1.46 / ) 1.62 / ) 1.55 / ) 1.44 / 2610 SUMMARY OF RESULTS from 2R-MODEL LuYAP (PML) 1) 0.86 / ) 1.14 / ) 1.10 / ) 1.24 / ) 1.54 / ) 1.53 / 3040 Loss (cm -1 ) / LY(0) (phel/MeV)

A.J. Wojtowicz, Crimea, Sept R-MODEL, selected LuAP pixels Loss cm -1, LY(0) = phel/MeV

A.J. Wojtowicz, Crimea, Sept R-MODEL, selected LuYAP pixels Loss cm -1, LY(0) = phel/MeV

A.J. Wojtowicz, Crimea, Sept Absorption, undoped LuAP, plate Corrections: Fresnel reflection, constant term

A.J. Wojtowicz, Crimea, Sept Absorption, LuAP:Ce pixel transversally Corrections: Fresnel reflection, constant term

A.J. Wojtowicz, Crimea, Sept 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