Characterization of Silicon Detectors for the SiliPET Project: A Small Animal PET Scanner Based on Stacks of Silicon Detectors

In this paper we propose a new scanner for small animal positron emission tomography (PET) based on stacks of double sided silicon detectors. Each stack is composed of 40 planar detectors with dimension 60 mm x 60 mm x 1 mm and 128 orthogonal strips on both sides to read the two coordinates of interaction, the third being the detector number in the stack. Multiple interactions in a stack are discarded. In this way we achieve a precise determination of the first interaction point of the two 511 keV photons. The price to pay is an efficiency reduction for each stack of about 50%. The reduced dimensions of the scanner also improve the solid angle coverage resulting in a high sensitivity. Preliminary results were obtained with the MEGA prototype tracker. Here, we report on the results obtained with double sided silicon prototype detectors, manufactured by ITC-FBK, having an active area of 3 cm X 3 cm and a strip pitch of 500 μm. Two different strip widths of 300 μm and 200 μm, and two thicknesses of 1 mm and 1.5 mm, equipped with 64 orthogonal p and n strips on opposite sides were read out with the VATAGP2.5 ASIC, a 128channel "general purpose" charge sensitive amplifier. We describe the experimental setup, the measurements and the results in terms of spatial resolution, spectral and timing performances obtained with the prototype detectors.