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Neutron Tomography (NT) is an established technique to non-destructively investigate the inner structure of a wide range of objects. The major drawback of NT is the long acquisition time required to perform a tomographic scan compared to an X-ray Computed Tomography (CT) scan, due to the limited particle flux of the existing neutron sources. Therefore, in the NT field there is great interest in the reduction of scan time, dictated by the high neutrons production cost, aimed at optimizing the beamtime use at neutron imaging beamlines. A way for decreasing the total scan time is to reduce the number of projections. Generally, iterative reconstruction methods have advantages over analytical algorithms, such as the widely used Filtered Back-Projection (FBP), when data are noisy and limited. This research is focused on the comparative analysis of different reconstruction techniques, aimed at finding the data processing procedure suitable for NT, that reduces the scan time without reduction of the reconstructed image quality. For this purpose, a phantom sample was analysed by means of a white beam NT performed at the IMAT beamline, ISIS Neutron Source, U.K . Experimental data were used to test the performances of the FBP algorithm and different iterative reconstruction methods as a function of the number of projections and for different setups of the imaging system. The reconstructed images were quantitatively compared in terms of image quality indexes and the benefits of iterative methods for the limited data problem are discussed.

IMAT is a new cold-neutron imaging facility at the neutron spallation source ISIS at the Rutherford Appleton Laboratory, U.K.. The ISIS pulsed source enables energy-selective and energy-resolved neutron imaging via time-of-flight (TOF) techniques, which are available in addition to the white-beam neutron radiography and tomography options. A spatial resolution of about 50 μm for white-beam neutron radiography was achieved early in the IMAT commissioning phase. In this work we have made the first steps towards achieving higher spatial resolution. A white-beam radiography with 18 μm spatial resolution was achieved in this experiment. This result was possible by using the event counting neutron pixel detector based on micro-channel plates (MCP) coupled with a Timepix readout chip with 55 μm sized pixels, and by employing an event centroiding technique. The prospects for energy-selective neutron radiography for this centroiding mode are discussed.