Low energy /spl gamma/-rays scintillation detection with large area avalanche photodiodes

Energy resolution of NaI(Tl), CsI(Tl), LSO and YAP crystals coupled to 16 mm diameter Large Area Avalanche Photodiodes (LAAPD) was studied for low energy /spl gamma/-rays. Energy resolutions of 11.3% and 8.4% were obtained for 59.6 keV /spl gamma/-rays from /sup 241/Am and 122 keV /spl gamma/-rays from /sup 57/Co sources, respectively, as measured with a 10 mm diameter by 10 mm high NaI(Tl) crystal. The optimization of the LAAPD performance is presented, being essential for improvement of energy resolution at low energy /spl gamma/-rays. Measured numbers of primary electron-hole pairs produced in LAAPDs and evaluation of noise contribution of these devices allowed for quantitative discussion of the results. Particularly, the intrinsic energy resolution of the crystals vs. energy of /spl gamma/-rays has been evaluated. Obtained data for NaI(Tl) crystal showed a good agreement (within 30%) with calculated component due to nonproportional light yield for energies above 50 keV.