2. Associated particle technique

The associated particle technique (APT) is a method of interrogating matter using fast neutrons produced by a gas pedal. Initially implemented in physics experiments, non-laboratory applications were made possible in the late 1990s with the advent of transportable associated particle sealed tubes, producing 14 MeV neutrons by deuterium-tritium fusion reaction t(d, n)α (figure 1 ). With each neutron, an alpha particle is emitted at approximately 180°, and its measurement by a localization detector enables the direction of emission of the associated neutron to be determined. The solid angle of the "tagged" neutrons is determined by the size of the alpha detector. The tagged neutron beam can be...