Initial Testing of a Compact Portable Microwave-Driven Neutron Generator

A portable, moderate yield D-D neutron generator based on permanent magnet microwave ion source is being developed at Lawrence Berkeley National Laboratory for applications such as short range SNM detection in suitcases and small parcels. Microwave power (2.45 GHz) can be coupled to a pyrex tube through a standard wave guide and generate plasma. In this source configuration, the wave guide serves as a secondary containment for sealed tube design. Hydrogen plasma has been successfully ignited in the pyrex tube at a microwave power of 200 W. The 2.45 GHz microwave signal can also be directly coupled to the wave guide through a standard coaxial cable with a N-type connection and generate plasma. Preliminary results show that over 60% of atomic hydrogen ions were generated at a microwave power of 300 W. Higher atomic fraction is expected with insertion of boron nitride liner. The current density at power of 200 W (with an extraction aperture of 2 mm in diameter, and gas flow at 0.2 sccm) was approximately 22 mA/cm².