A silicon continuous position sensitive diode and associated electronics: modelling and simulation

In contrast to the segmented detectors (micro-strips and pixels) widely used in high energy physics experiments, continuous detectors such as position sensitive diodes (whose localisation principle is based on charge division) remain of interest when count rate and multiplicity are not critical. That is the case with several imaging applications in nuclear medicine and biology. In that context, our group has developed a γ camera dedicated to the detection of body tumour tissue during operative cancer surgery. This per-operative compact imager consists of an image intensifier tube viewed by a PSD of 25×25 mm2. In order to improve detection performances of this camera we have developed a simulation model of the PSD (schematic form) and associated electronics (behaviour form) using CAO AWB/Cadence. This allows an accurate estimate of both spatial resolution and linearity. These simulations provide an exhaustive study of the performance of various types of PSD and readout electronics configurations. In our application which requires high resolution imaging, we have demonstrated that a classical detector filtered by a trapezoidal shape offers the best compromise between linearity and spatial resolution.