Thermal and cold neutron phase-contrast radiography

Polychromatic neutron phase-contrast imaging of weakly absorbing samples enabled by phase retrieval

The use of a phase-retrieval technique for propagation-based phase-contrast neutron imaging with a polychromatic beam is demonstrated. This enables imaging of samples with low absorption contrast and/or improving the signal-to-noise ratio to facilitate e.g. time-resolved measurements. A metal sample, designed to be close to a phase pure object, and a bone sample with canals partially filled with D2O were used for demonstrating the technique. These samples were imaged with a polychromatic neutron beam followed by phase retrieval. For both samples the signal-to-noise ratios were significantly improved and, in the case of the bone sample, the phase retrieval allowed for separation of bone and D2O, which is important for example for in situ flow experiments. The use of deuteration contrast avoids the use of chemical contrast enhancement and makes neutron imaging an interesting complementary method to X-ray imaging of bone.

A digital approach to neutron-γ imaging with a narrow tungsten collimator aperture and a fast organic liquid scintillator detector

A digital neutron-γ imaging technique for mixed radiation field is described. The imaging system is based upon an organic liquid scintillator detector, a narrow tungsten collimator, fast digitiser and adjustable equatorial mount. Radioactive sources have been attached to a vertical plane and the digitiser has been used to digitise neutron and γ events. The digitised events have been discriminated using pulse gradient analysis and images have been generated of the count distribution in the source plane.