Modelling the X-ray response of charge coupled devices

Based on the physics of charge generation, diffusion and collection, we have developed a simple three-dimensional Monte Carlo model to predict the X-ray response of deep depletion front-illuminated CCDs. It is shown that the measurable properties of the device (i.e., energy resolution, quantum efficiency and event morphology) can all be reproduced by a simple treatment of charge creation and diffusion within each of the active layers of the device. The simulation reproduces the distinct spectral signatures of X-ray interactions in the depletion layer and the field-free regions. Pulse height spectra can be reproduced to good accuracy and quantum efficiencies and energy resolutions could be predicted to within a few percent over the energy range 500 eV to ∼ 10 keV. Refinements such as the effect of altering electrode voltages have been incorporated into the model.