Development of compact neutron generator using metal deuteride cathode

A compact neutron generator, i.e., an IEC (Inertial Electrostatic Confinement) fusion device has been studied for its suitability as a compact and economical fusion neutron source using a metal deuteride cathode. In this study, we used hydrogen absorption metal. If the cathode is made of deuteride metal, the density of deuteron becomes very high not only inside but area near around cathode so that the D-D nuclear reaction seems to be enhanced. As a result, when the hydrogen absorption metal was used as compared with the use of stainless steel, an increase in the generated neutrons was observed. The device consists of a spherical cathode grid mounted within a grounded cylindrical vacuum chamber (approximately 200 mm diameter, 400 mm height), which serves as the anode. The system is maintained at a constant gas pressure of 0.10-0.15 Pa by regulating the inflow and bleeding deuterium gas through the mass flow controller and a leak valve, with the rotary pump running. The grid-type cathodes employed in the IEC device is constructed of a 1.0 mm diameter titanium, zirconium, tantalum, and stainless steel wire, spot welded. The spherical grids (25 mm diameter) have approximately 85% geometric transparencies. A neutron detector utilizes for ³He proportional counter. Detection efficiency is 0.13%, calibrated with a ²⁵²Cf neutron source. The neutron output from the apparatus is steady and reproducible. Operating time is typically several minutes. It is limited only by overheating the cathode, which is not equipped with auxiliary cooling. In conclusion, the use of hydrogen absorption metal brings the increase of generated neutrons at low current region. D-D neutron generation rate of 10³ s^-1 was observed at a discharge of 20 kV, 2 mA with using hydrogen absorption metal. However, in high voltage and current, is not so enhanced the neutron generation rate.