A neutron imaging apparatus for obtaining an image of the general shape of
a neutron emitting source and a bearing of the source relative to the
apparatus, the apparatus comprising a chamber comprising a gas with a
high probability of interacting with low energy neutrons, releasing
collision products that maintain the neutron momentum, and generating
ionization particles. The chamber comprises an electrode for providing an
electronic signal indicative of the impact location of ionization
particles on the electrode and a field to drift the ionization particles
to the electrode. A readout indicates the location and time of impact of
each ionization particle on the electrode; a memory stores a plurality of
the electronic signals; and a computer receives and analyzes the signals
and impact times and indicates the location of the source of neutrons by
using back projection algorithms to calculate three-dimensional vectors
indicative of the neutron path directions.