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Compact, Safe and Energy Efficient Neutron Generator





Scientists at Berkeley Lab have developed a compact neutron source that requires low energy to drive deuterium-deuterium, deuterium-tritium, or tritium-tritium fusion reactions that generate neutrons. Because the device generates neutrons from an electric field, it can be turned off, unlike isotope sources (e.g., Am-Be) that constantly emit radiation. This reduces risks to health and the environment. Nonetheless, the device closely reproduces the energy spectrum of radioactive isotopes, ensuring that it can be used for similar purposes. In addition, because the invention does not require a plasma chamber, it can be as compact or even more compact than existing generators, such as Penning sources.

The device takes advantage of the fact that when objects with sharp tips, such as carbon nanotubes (see figure), are placed in an electrical field, the equipotential field lines are compressed around the tip, generating a local electrical field that is several thousand times stronger than that generated by a parallel plate capacitor under the same conditions. This enhanced electrical field is sufficient to cause field ionization of atoms and molecules, which are then accelerated toward a biased target containing deuterium or tritium. The scientists optimized the nanotube geometry (height, width, distance apart) for the most efficient field ionization and were able to use the device to produce neutrons.

By coating the nanotubes with a catalyst or adding a separate “gas cracker” to the system, monatomic species can be generated from molecular deuterium. This further increases the neutron yield because monatomic species are propelled toward the target with a greater velocity than are molecular species.

Existing sources of neutrons, especially those used in oil well logging, are either radioactive isotopes or neutron generators, such as Penning and radiofrequency plasma sources. Radioactive isotopes pose serious risks to health, security, and the environment. On the other hand, neutron generators are of limited use because of their bulkiness, energy demand, expense, limited lifetime, and potential generation of undesired secondary particles. The Berkeley Lab invention overcomes these limitations to provide a safe and efficient source of neutrons.

DEVELOPMENT STAGE: Proven principle.

STATUS: Patent pending. Available for licensing or collaborative research.

Persaud A., I. Allen, M.R. Dickinson, T. Schenkel, R. Kapadia, K. Takei, A. Javey. “Development of a compact neutron source based on field ionization processes,” Journal of Vacuum Science and Technology B. 29(2):02B107 (2011). (doi: 10.1116/1.3531929)



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