Charge Diffusion Modelling for a Monolithic Active Pixel Sensor Detector with Application to Proton CT

Abstract

A model for charge diffusion in a monolithic active pixel sensor detector was studied with application to a digital tracking calorimeter, proposed for use in proton computed tomography. The model was implemented in C++, using the ROOT library. The resulting detector response yielded clusters of activated pixels with similar shapes as clusters from experimental data. The cluster sizes showed discrepancies at higher values of energy deposition, but similar cluster sizes for lower values of energy deposition. The resulting energy-size relationship for MIMOSA-23 sensor chips was n=7.6626*(Edep)^0.420307, assuming attenuation length λ=45μm. The charge diffusion model also produced results for 30 MeV protons incident to a pALPIDE chip, where the mean cluster size was similar to the experimental values.