1. 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

2. A.J. Wojtowicz, Crimea, Sept. 20052 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

3. A.J. Wojtowicz, Crimea, Sept. 20053 INTRODUCTION LuAP: 8.34 g/cm 3, 0.3 photofraction, 365 nm emission, 17-18 ns decay time, LY over 2xBGO (thickness!!) difficult to grow, hence LuYAP ClearPet TM project: 2x2x8 and 2x2x10mm pixels of LYSO and LuYAP

4. A.J. Wojtowicz, Crimea, Sept. 20054 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

5. A.J. Wojtowicz, Crimea, Sept. 20055 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

6. A.J. Wojtowicz, Crimea, Sept. 20056 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

7. A.J. Wojtowicz, Crimea, Sept. 20057 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

8. A.J. Wojtowicz, Crimea, Sept. 20058 ENERGY SPECTRUM Na22, LuYAP pixel vertically gain 3 Third peak gone, less light, wider peaks

9. A.J. Wojtowicz, Crimea, Sept. 20059 PEAK POSITIONS vs GAIN * ENERGY gain 3 LuYAP pixel vertically V2H = 0.42

10. A.J. Wojtowicz, Crimea, Sept. 200510 ENERGY SPECTRA Na22, LuAP pixel vertically variable gain

11. A.J. Wojtowicz, Crimea, Sept. 200511 PEAK POSITIONS VS GAIN VS GAIN * ENERGY

12. A.J. Wojtowicz, Crimea, Sept. 200512 ENERGY SPECTRA, Na22, LuAP pixel vertically X-axis offset shifted, gain rescaled: peaks coincide

13. A.J. Wojtowicz, Crimea, Sept. 200513 SINGLE PHOTOELECTRON SPECTRA variable gain

14. A.J. Wojtowicz, Crimea, Sept. 200514 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

15. A.J. Wojtowicz, Crimea, Sept. 200515 SINGLE PHOTOELECTRON SPECTRA X-axis offset shifted gain rescaled peak position is offset independent norm. to gain 1 0.049 Hamamatsu R2059 1500 V

16. A.J. Wojtowicz, Crimea, Sept. 200516 LuAP (PML) V2H= 1) 900/2104 = 0.43 2) 909/2247 = 0.40 3) 856/2068 = 0.41 4) 909/2122 = 0.43 5) 740/1837 = 0.40 6) 873/2110 = 0.41 7) 855/1982 = 0.43 SUMMARY OF LIGHT YIELD MEASURMENTS LuYAP (PML) V2H = 1) 999/1774 = 0.56 2) 793/1614 = 0.49 3) 856/1712 = 0.50 4) 1186/2533 = 0.47 5) 1061/2555 = 0.42 6) 945/2271 = 0.42

17. A.J. Wojtowicz, Crimea, Sept. 200517 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

18. A.J. Wojtowicz, Crimea, Sept. 200518 2R – model (2 rays model) Experimental points, Balcerzyk et al., 2005 Solid line 2R-model

19. A.J. Wojtowicz, Crimea, Sept. 200519 LuAP (PML) 1) 1.46 / 2780 2) 1.61 / 3050 3) 1.55 / 2780 4) 1.46 / 2800 5) 1.62 / 2500 6) 1.55 / 2830 7) 1.44 / 2610 SUMMARY OF RESULTS from 2R-MODEL LuYAP (PML) 1) 0.86 / 2100 2) 1.14 / 2010 3) 1.10 / 2120 4) 1.24 / 3210 5) 1.54 / 3420 6) 1.53 / 3040 Loss (cm -1 ) / LY(0) (phel/MeV)

20. A.J. Wojtowicz, Crimea, Sept. 200520 2R-MODEL, selected LuAP pixels Loss 1.4-1.6 cm -1, LY(0) =2800-3600 phel/MeV

21. A.J. Wojtowicz, Crimea, Sept. 200521 2R-MODEL, selected LuYAP pixels Loss 0.8-1.5 cm -1, LY(0) =2200-3200 phel/MeV

22. A.J. Wojtowicz, Crimea, Sept. 200522 Absorption, undoped LuAP, plate Corrections: Fresnel reflection, constant term

23. A.J. Wojtowicz, Crimea, Sept. 200523 Absorption, LuAP:Ce pixel transversally Corrections: Fresnel reflection, constant term

24. A.J. Wojtowicz, Crimea, Sept. 200524 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