Artefacts in Neutron CT – Their effects and how to Reduce some of Them

Neutron computed tomography relies on plain mathematical projections of the sample onto an ideal detector to reconstruct a three-dimensional model of the sample. However, several effects disturb this assumption, like buildup of afterglow on the scintillation screen, degradation of the screen during the measurement, background by neutrons scattered in the sample, and edge effects by reflection and refraction on sample edges and surfaces.Calculating a correct mathematical correction, e.g. using a point spread function, requires a lot of a priori knowledge about the sample and the detection system and cannot be given universally. This publication describes the observation of artefacts in neutron imaging and gives physical arguments for simple mathematical corrections to reduce, but not fully remove these artefacts in the reconstructed image. Often, awareness of these error sources is even more important than full removal.