Large Area Avalanche Photodiodes in X-rays and scintillation detection

The performance of 10 and 16 mm diameter beveled edge Large Area Avalanche Photodiodes (LAAPD) was studied in X-rays and scintillation detection. A good linearity of the LAAPD response to X-rays was observed up to energies of about 20 keV. The ratio of the APD gain for X-rays and light pulses remained constant (within 1%) for both the 5.9 and 16.6 keV photopeaks in the APD gain range up to 100. This allowed for use of soft X-rays as an accurate reference in APD scintillation detection study. The study covered measurements of the number of generated e–h pairs and energy resolution for several scintillators. Particularly, the energy resolution of 4.8±0.2% was measured with a small CsI(Tl) crystal for 662 keV γ-rays from a 137Cs source and 4.3±0.2% with YAP:Ce. The measured energy resolutions were comparable or better than those measured with a photomultiplier.