Research on edge ionization and star mode discharge physics in inertial electrostatic confinement neutron/proton sources

Small portable gaseous discharge plasma neutron/proton sources have been recently commercialized based on the Star Mode Inertial Electrostatic Confinement (IEC) nuclear fusion concept. This represents the first commercial application of a fusion confinement system with a developmental path that could ultimately lead to high-flux neutron/proton delivery systems, commercial power generation and space propulsion. Thus, there is considerable interest in expanding the knowledge base of the underlying glow discharge physics and properties of the Star Mode IEC device, specifically related to enhancing fusion reactivity and efficiency.; This combined computational and experimental work focused on developing the foundation for a new discharge model to examine fundamental physical plasma processes, and to evaluate a new device enhancement to the basic Star Mode of operation to increase the system efficiency. The proposed Passive/Active Ion Generator System (PAIGS) maintains the focusing benefits of the Star Mode of operation, while increasing the amount of high-energy ions generated within the discharge plasma system, and hence increasing fusion yield. This is achieved through manipulation of the edge-region potential shape and collisional processes.; Substantive improvements over existing IEC discharge models were made, yielding key insight into the effects of collisional discharge processes, specifically the combined effect of electrons, ions and fast neutrals in maintaining the Star Mode discharge. The SPIFFY steady-state computational code was able to predict with certainty the Paschen relations for Star Mode discharges, generating a scaling law for all transparent geometries of V[ kV] = 1.06 (P[Torr] d[cm])−1.44, predict fusion reactivity trends that correlate with experiments, and solve several physics dilemmas, including the neutron-yield vs. cathode-radius minima and ion-recirculation paradox.; The PAIGS-enbanced SPIFFY steady-state code was able to show that the coupled nature of the IEC requires collisional processes and input parameters, such as pressure, to be solved self-consistently for global current balance and discharge sustainment. The simulations predicted a modest increase in fusion yield of ∼×1.8 over standard Star Mode operation for a “passive” double-grid PAIGS configuration, which agrees with the experimentally observed value of ∼×1.6.; The end result of the research program was a development of the first steady-state discharge treatment of the IEC Star Mode incorporating the new physics understandings unearthed over the last eight years. Experimental benchmarking was successful at testing key model assumptions and validating the code simulation results. And finally, the PAIGS concept was studied and found to provide a modest (×1–2.5) increase in fusion reaction rate.