Comparison of Resolution and Contrast Performances of Silver Film, Imaging Plate and Scintillator Images in Neutron Radiography

Abstract

In the last decades, neutron imaging facilities have implemented systems such as imaging plates and CCD or sCMOS cameras coupled to a scintillator screen [1]. However, for some applications, such as detection of micro cracks in large-size metallic or organic materials such as pyrotechnic equipment, these methods have disadvantages, mostly related to their small field of view when high resolutions are required. On the other hand, the use of silver radiographic films, although an old technology restricted to static 2D imaging, allows observing details with very good spatial resolution (<50 µm) and over very large areas (30x30cm²), which compensates for their low efficiency. Since there is currently no technology that fulfills these needs, radiographic films were used on the Orphée reactor at the CEA Saclay until its shutdown in 2019. The CEA aims at potentially continuing the previous historical radiography activities on a new French HiCANS source, the ICONE project. Within this context, we aim at comparing radiographic films and other technologies. Hence radiographies were taken with films at PSI/SINQ on the NEUTRA beam line (with thermal neutrons, which will probably will be used at the ICONE facility) in order to compare them with measurements on the same objects taken at the Orphée nuclear reactor (with cold neutrons). Images were obtained with different neutron energies, different L/D and different fluence levels. High-resolution digitalization of the film was performed for quantitative analysis. We compared these images to those obtained with imaging plates or CCD cameras. A study of the quality and the statistics of the images after digitalization was done in order to quantify the evolutions of the dynamic range and the spatial resolution. We also aim at evaluating the effect of thermal energies vs cold energies. With these results, it could be determined if the usage of films can complement modern neutron imaging methods to fulfil specific requirements.