Neutron Generators

Three main types of neutron generators have been developed at the Plasma and Ion Source Technology Group. These neutron generators are axial, single beamlet neutron generator; co-axial, high yield, multibeam neutron generator and point neutron generator. The applications of these neutron generators include special nuclear material (SNM) detection for nuclear non-proliferation, airline cargo screening and boron neutron capture therapy (BNCT) cancer therapy studies. The status of these developments is shown in the following paragraphs.

Axial, Single Beamlet Neutron Generator for Special Nuclear Material Detection Applications

The axial D-D neutron generator has three main components; actively water cooled, external antenna RF-ion source, multi-stage ion beam accelerator structure and water cooled, explosive bonded titanium-on-copper target. The neutron generator is shown in figure 1.

	Figure 1. Sectioned accelerator, axial neutron generator.

The ion source generates >95% atomic species and >100 mA/cm2 of current density at 3 kW of discharge power. At 2 mA of D+ ion beam and 100 kV of acceleration voltage, the neutron yield is 10^8 n/s.

An axial neutron generator without exposed high voltage elements is been developed in the P&IST group. The neutron yield will be similar to the sectioned accelerator axial neutron generator. See for figure 2 of the picture of the generator.

	Figure 2. Fully high voltage protected axial neutron generator design.

Co-Axial Multibeamlet Neutron Generator for BNCT Applications

The high yield D-D neutron generator uses unique cylindrical target geometry to achieve large target area in compact outer dimensions. The ion source in this geometry is placed in the middle of the generator. The deuterium beam is extracted from the source toward co-axially placed cylinder target. The latest co-axial neutron generator developed in the Plasma and Ion Source Technology Group will be able to generate 10^11 n/s at 400 mA of beam current and 120 kV of acceleration energy. The co-axial neutron generator was delivered to hospital/university consortium in Turin, Italy, in December 2004. See figure 3 of a picture of the neutron generator.

Point Neutron Generator for Airline Cargo Screening

Plasma and Ion Source Technology Group and Tensor Technology Inc. is developing a airline (LD-3 containers) cargo container screening system. P&IST is responsible in developing the neutron generator and Tensor Technologies is responsible for the detector system. The system is based on PFNTS (Pulsed Fast Neutron Transmission Spectroscopy), which requires point neutron source with nanosecond beam pulsing and wide energy spectrum T-T neutrons. The ion source in this application has torroidal shape. Beamlets are extracted toward the middle of the neutron generator, to a small diameter target tube. See Figure 4 for a drawing of the point neutron generator. The project started on October 2004 and we are currently operating test ion sources and fabricating prototype beam pulser system.

	Figure 4. Point neutron generator with nanosecond pulsing capability. Wide energy spectrum T-T neutrons are used.

Copyright 2005 Taneli Kalvas (TVKalvas@lbl.gov)
and Jani Reijonen (JReijonen@lbl.gov)