Siam Physics Congress SPC2013 Thai Physics Society on the Road to ASEAN Community 21-23 March 2013 277 Light Yield Non-proportionality and Energy Resolution of Lu 0.7 Y 0.3 AlO 3 :Ce and Bi 4 Ge 3 O 12 Scintillators A. Phunpueok 1 *, V. Thongpool 1 , K. Bandholnopparat 1 , S. Yoo-Kong 2 , and W. Chewpraditkul 2 1 Division of Physics, Faculty of Science and Technology, Rajamangala University of Technology Thanyaburi, Pathumthani 12110, Thailand 2 Department of Physics, Faculty of Science, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand *Corresponding author. E-mail: aumaum18@hotmail.com Abstract In the last decade, many efforts were devoted to the development of new heavy scintillators for medical imaging, especially, perovskite type based on ceriumed-doped crystals. The scintillation response of two difference sizes of the new Ce-doped lutetium-yttrium aluminum perovskite (Lu 0.7 Y 0.3 AlO 3 :Ce, LuYAP:Ce) crystals were investigated and compared to bismuth germanate (Bi 4 Ge 3 O 12 :BGO) crystal. The light yield and energy resolution were measured using photomultiplier tube (XP5200B PMT) readout. For 662 keV gamma rays ( 137 Cs source), the small LuYAP:Ce showed the light yield of 10,900 ph/MeV, which is higher than that of 8,900 and 8,500 ph/MeV obtained for BGO and big LuYAP:Ce, respectively. The energy resolution of 7.4 % obtained with small LuYAP:Ce is better than that of 9.0 and 8.9 % obtained with big LuYAP:Ce and BGO, respectively. The light yield non- proportionality and energy resolution versus gamma energy were measured and the intrinsic resolution of the crystals was calculated. Over the energy range from 22.1 to 1,274.5 keV, the non-proportionality of about 19 % for small LuYAP:Ce is better than that of about 21 and 38 % for big LuYAP:Ce and BGO, respectively. The photofraction was determined for all tested crystals and compared with the cross-sections ratio calculated using WinXCOM program. Keywords: BGO, light yield non-proportionality, LuYAP:Ce, scintillators Introduction Inorganic scintillators play an important role in detection and spectroscopy of energetic photons and nuclear particles. Important requirements for the scintillation crystals used in these applications include high light yield, fast response time, high stopping power, good energy resolution, good proportionality of light yield, minimal afterglow and low production costs. Good reviews on development of inorganic- scintillators and inorganic scintillation detectors have been published by Moszynski [1], van Eijk [2], and recently by Lecoq et al. [3]. The phenomenon of non- proportionality response and its relation with energy resolution have been studied for many alkali halide scintillators [4] and oxide based scintillators[5]. The scintillation response of alkali halides decreases as the photon energy increases, whereas oxide based scintillators in general show an increasing scintillation response with increasing photon energy, which levels at higher energies. The aims of this work are to perform a further study of light yield non-proportionality and energy resolution of Bi 4 Ge 3 O 12 (BGO) and two difference sizes of Lu 0.7 Y 0.3 AlO 3 :Ce (LuYAP:Ce) crystals covering energies from 22.1 to 1,274.5 keV. From the obtained data on photoelectron yield versus the energy of gamma rays and corresponding energy resolution, the light yield non-proportionality and the intrinsic energy resolution of tested crystals were calculated. The estimated photofraction for all tested crystals at 662 keV gamma peak will also be discussed. Materials and Methods Two difference size of the new cerium-doped crystals, LuYAP:Ce, with the dimensions of 10x10x5 and 10x10x2 mm 3 supplied by Opto Materials S.r.l. (Italy) were studied and compared to BGO crystal with the dimension of 7x7x1 mm 3 supplied by Shonan Institute of Technology (Fujisawa, Japan). The crystals were optically coupled to a Photonis XP5200B photomultiplier tube using silicone grease. All measurements were made using standard NIM level electronics. The sources were positioned along the cylindrical axis of the scintillator and the PMT. The signal from the PMT anode was passed to a