Spectroscopy applications for the Medipix photon counting X-ray system

Since the Medipix system is a photon counting system with selectable threshold, it is possible to use it as a spectroscopic device, which is sensitive to the energy of the incoming photons. One feature of the Medipix system is the possibility to adjust the threshold for each pixel by a three-bit mask. A simple method for creating threshold equalisation masks for different threshold settings including both detector and channel stability influences is proposed. The method is suitable for systems using X-ray sources with a wide energy range, since the threshold adjustment is energy dependent. This is an alternative to the well-known method for correction of non-uniformity, which uses mono energetic sources. oposed method is based on the analysis of histograms of series of images. The model for the histograms was created assuming a standard dental X-ray source, which allows mask-creating parameters such as threshold range to be found. This procedure can be performed for each of the energies of interest. Based on these arrays, mask files that narrowed the threshold distribution close to the theoretical limit, were prepared. The limit of the spectroscopic resolution for the system was measured by analysing histograms for a series of flat images under identical conditions.