Bimodal Imaging Using Neutrons and X-rays

Experiments that combines the information from two different radiation sources can provide more information than experiments using single radiation sources. This claim was confirmed using the bimodal installation at the thermal neutron imaging beamline NEUTRA at Paul Scherrer Institut. This installation is equipped with a 60-320kV X-ray source and is used for mid-sized samples. The combination of the neutron and X-ray imaging can be used in different ways depending on sample composition and purposes of the experiments. The first and most obvious operation mode is to exploit the fact that the two modalities have different attenuation coefficients with a non-linear relation. A bivariate segmentation algorithm to improve the reconstruction in the presence of sample and radiation related artefacts: sample responses will be affected by differently for the two modalities and thus cause artefact on different positions in the sample. We describe the new X-ray installation which is under construction at the cold neutron imaging beamline ICON. The aim of this installation is to increase the resolution obtained at NEUTRA and match the high-resolution neutron imaging options available at ICON. The design at ICON is based on a dual detector concept with a short X-ray beamline across the neutron beamline using cone beam geometry for magnification. A micro-spot 40-150kV X-ray source was chosen for the new beamline. The dual-mode installation is mainly intended for computed tomography. The oblique arrangement of the two radiation sources has the advantage that bimodal image sequences can be obtained with less or no delay since the source does not have to be removed from the beamline at modality change. Strategies for the data evaluation are outlined for the future analysis of the bimodal data. A soil sample with roots was scanned to demonstrate the differences between the two images from the two radiation sources.