Applications and characteristics of imaging plates as detector in neutron radiography at SINQ

Imaging plate technique is a commonly accepted method in many fields as in medicine, biology and physics for detection of the distribution of β- and γ-radiation or X-rays on large areas. Recently a new type of imaging plate sensitive to neutrons has been developed. The storage layer is doped with gadolinium, which, after absorption of neutrons, produces radiation detectable by the same sensitive crystals used in conventional imaging plates. At the spallation neutron source, SINQ, at the Paul Scherrer Institut (CH) some of the characteristics of the neutron radiography station in combination with the imaging plate technique were investigated. The intensity distribution of the source was measured to check the accuracy for quantification of the image data. Also, the reproducibility of results obtained by this detection system was stated. For a test object, the high selectivity for different neutron absorption is demonstrated at details with low contrast. The obtainable spatial resolution was determined recording an image of a gadolinium edge, from which the line spread function and the modulation transfer function can be calculated. By use of conventional X-ray sensitive imaging plates the exposure time for a indirect detection method using a dysprosium foil can be reduced significantly. For the measurement of the latent image in the neutron activated foil it is sufficient to excite the imaging plate by the radiation of the isotope 165mDy with a short life time. The possibility to measure effective cross-sections of materials with pretty strong absorption by imaging plates as detector because of their high dynamic range was proved as well.