This technology has applications in the development of portable neutron sources for incorporation into compact, lightweight, and low power devices for radiography and sensing of nuclear materials in the field.
The ion source is an important component of a neutron source. Successful development of a portable neutron source depends on the development of a compact, lightweight, and low power ion source. Conventional methods of ionizing deuterium uses microwave plasma sources, which are attractive because of the high ion current and current density attainable. However, even considering power savings enabled by recent advances in inductively coupled microwave plasma sources, size, weight, and power requirements remain major limitations for these devices. This invention describes a novel MEMS-based deuterium ionizer that significantly outperforms existing ion sources on all three criteria.
This invention proposes a MEMS-based design for a deuterium ionizer, where diatomic deuterium molecules (D2) are dissociated into deuterium ions (D+) using arrays of self-aligned gate field emitter structures. Each field emitter consists of a conical silicon tip on a high-aspect ratio silicon column. When a bias voltage is applied to the emitter, the pointed geometry of the tip creates a concentrated electric field which severely distorts D2 molecules and induces dissociation. In an alternate mode of operation, a positive voltage is applied between emitter tips and their respective gates, causing them to emit electrons. These electrons are subsequently accelerated and collided with D2 molecules, leading to ionization. In both operational modes, the high-aspect ratio silicon columns underlying the emitter tips serve as built-in current limiters, which protect the sharp emitter tips from premature degradation as a result of bombardment by backstreaming deuterium ions.
Deuterium ions generated by the field emitter array can be focused into a beam and accelerated towards a tritiated or deuterated target to generate neutrons.
Significantly outperforms conventional RF ion sources in size, weight, and power consumption (volume < 2 L; weight < 10 lbs; power consumption < 200 W)