* Corresponding author. Tel.: #1-420-2-24311137; fax: #420-2-3123184. E-mail address: amares@fzu.Cz (J.A. Mares). Nuclear Instruments and Methods in Physics Research A 443 (2000) 331}341 Development of new mixed Lu  (RE)  AP:Ce scintillators (RE"Y or Gd): comparison with other Ce-doped or intrinsic scintillating crystals J. Chval, D. Cle H ment, J. Giba, J. Hybler, J.-F. Loude, J.A. Mares*, E. Mihokova, C. Morel, K. Nejezchleb, M. Nikl, A. Vedda, H. Zaidi Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 16253 Prague 6, Czech Republic Institute of High Energy Physics, University of Lausanne, CH-1015 Lausanne, Switzerland Division of Nuclear Medicine, Geneva University Hospitals, CH-1211 Geneva 4, Switzerland Crytur, Palackeho 175, 51119 Turnov, Czech Republic INFM and Dipartimento di Scienza dei Materiali dell'Universita+ di Milano, Via Cozzi 53, I-20125 Milano, Italy Received 20 May 1999; accepted 22 September 1999 Abstract This paper presents the development of new Ce-doped, fast and high e!ective-Z mixed Lu  (RE)  AP:Ce crystals. These crystals have been grown by the Czochralski method and good results have been obtained with x"0.1, 0.2 and 0.3 for Y ions and roughly between x"0.6 and 0.7 for Gd ions. Relative light yields measured for the Lu  (RE)  AP:Ce crystals are 40}75% higher than for BGO and are comparable to the light yield of YAP:Ce crystal. Measured energy resolutions at 662 keV range over 8}15.3% FWHM and are close to the energy resolution obtained with YAP:Ce. Thermally stimulated luminescence (TSL) measurements above room temperature have also been performed: in accordance with the expected e!ect of trap states on scintillation e$ciency, an anticorrelation between TSL intensity and light yield is found.  2000 Elsevier Science B.V. All rights reserved. PACS: 25.20.Dc; 29.40.Mc; 78.55.-m; 78.60.Ya Keywords: Scintillators; Lu  (RE)  AP:Ce crystals; Light yield; Energy resolution; Luminescence; Thermally stimulated lumines- cence (TSL) 1. Introduction At present, Bi  Ge  O  (BGO) intrinsic scintil- lating crystal is the most used one in positron emission tomography (PET) [1]. It is dense ("7.13 g/cm), its light yield is about 20}25% of NaI(Tl) [2] with a rather slow scintillation decay constant (  &300 ns) [3]. For the next generation of positron tomographs and coincidence gamma cameras, scintillating crystals should have a high e!ective-Z (high Z  ) as well as a higher light yield and a faster decay constant than BGO. The most promising materials among new or improved 0168-9002/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 9 0 0 2 ( 9 9 ) 0 1 0 6 6 - 9