A High Output Neutron Tube Using an Occluded Gas Ion Source

A neutron tube capable of generating 1010 14 MeV neutrons in a 1.2 ms pulse has been developed for the Nuclear Regulatory Commission for use in flow measurements using the Pulsed Neutron Activation technique. The tube consists of an occluded deuterium gas ion source, a single gap accelerator and scandium tritide target, A unique feature of the tube design is its complete demountability, permitting easy replacement or modification of critical components. The ion source is a modified version of a stacked occluded washer source. However, in contrast to previous designs, this source utilizes only a single scandium deuteride washer and needs no independent trigger. Outputs of 1.2 × 1010 neutrons per pulse from a 250 mA deuterium ion beam at 125 kV have been obtained for over 1500 consecutive operations with a standard deviation of only ±5%. The ultimate operational lifetime is believed to be in excess of 3000 shots based on the present knowledge of ion source behavior. Recent experiments using nonmagnetic structural components in the ion source resulted in a 26% increase in output with a simultaneous 35% reduction in the source drive current. This implies that even higher outputs with greater source efficiencies may be achievable.