Development of a RF-Driven Neutron Generator for Associated Particle Imaging

We present recent work in the development of a compact, radio frequency (RF) D-T neutron generator with a maximum neutron yield of 10⁸ n/s for the application of associated particle imaging (API) used in explosive and contraband detection. API makes use of alpha particles produced in conjunction with 14 MeV neutrons in the D-T reaction to locate the neutron interaction and reduce background noise. To achieve high spatial resolution in API, a beam diameter of les1 mm on target is desired. For portable neutron generators used in API, the ion source and target cannot be water-cooled and the power deposited on the target must be low. By increasing the atomic ion fraction, the ion beam can be used more efficiently to generate neutrons, resulting in a lower beam power requirement and an increased lifetime of the alpha detector inside the acceleration column. The RF ion source produces very high atomic ion fractions (> 90%) compared to traditional Penning ion sources that produce less than 10% of atomic ions. Experimental measurements of the ion source plasma parameters including ion current density, atomic ion fraction, ignition and operating pressures, will be presented along with a discussion on the ion optics and engineering challenges.