Experimental characterization of a small prototype of LSO-SDD Anger camera

In this work we present a small prototype of Anger camera based on a monolithic array of Silicon Drift Detectors (SDDs) coupled to a single LSO scintillator. The SDD photodetector consists of an array of 19 hexagonal units with onchip JFET and has about 1 cm² of total sensitive area. The SDD array was already successfully tested with a CsI(Tl) crystal. However, the long scintillation decay time of CsI(Tl) requires the use of a long shaping time to reduce the effect of the ballistic deficit. This requirement does not allow to fully exploit the low electronics noise of the SDD, which, on the contrary, reaches its minimum at short shaping times. Moreover, the use of a faster scintillator would improve the overall counting rate capability of the Anger Camera. On the other side, the LSO scintillator is characterized by a lower scintillation conversion efficiency with respect to CsI(Tl) and by a natural background. In this work the performances which could be expected from a LSO-SDD Anger Camera are first evaluated. Then, the results achieved in the experimental characterization of a prototype of this detector are presented. A position resolution better than 1 mm FWHM using a ⁵⁷Co source (122 keV) has been measured.