Search

An inertial electrostatic confinement (IEC) fusion device accelerates ions, such as deuterium (D) or tritium (T), to produce nuclear fusion and generate neutrons. The IEC’s straightforward configuration consists of a concentric spherical transparent cathode at a negative bias in a grounded spherical anode center. The effects of cathode properties on the neutron production rate (NPR) remains, to date, inadequately studied. This study aims to determine the impact of cathode material on NPR by investigating fusion reactions on the cathode surface. Two buckyball-shaped cathodes made of stainless steel (SS) and titanium (Ti), both of 5 cm diameter, fabricated using selective laser melting and a 3D printer, are used for this investigation. A SS spherical chamber of 25 cm inner diameter is used as an anode in this experiment. A performance evaluation of surface fusion reaction in the IEC using SS and Ti grids is conducted by scanning the NPR as a function of the applied voltage and grid currents at different gas pressures. So far, IEC with Ti and SS cathodes achieves NPRs of 2.32 and 1.41×107 n/s, respectively, at 5.6 kW (70 kV, 80 mA). The normalized NPR (NPR/I-cathode) from IEC using SS and Ti cathode are compared. The results demonstrate that fusion reactions occur on the cathode surface, while the fusion reaction ratio increases with the applied voltage. The measured NPR/I-cathode for IEC with Ti cathode is more elevated than the SS cathode with 1.36 to 1.64 times for 20 to 70 kV range. Moreover, fusion on the cathode surface enhances the total NPR from the IEC with Ti cathode significantly compared to IEC with SS cathode under the same conditions. The Ti’s considerable ability to accumulate D ions and molecules compared with that of SS explains the difference of measured NPR results.

Inertial electrostatic confinement is a method of producing nuclear fusion in which concentric spherical electrodes are used to accelerate ions to fusion relevant energies. Fusion events are generally attributed to collisions between accelerated ions and neutral gas molecules in the centre of the device, with ion–grid collisions considered detrimental. In this paper, we present data that indicate that collisions between ions and neutral gas molecules adsorbed on the grid surface may, in fact, contribute significantly to the observed fusion rate in deuterium fuelled systems. When operating in the 1 × 10−4–1 × 10−3 Torr, V ≤ 40 kV regime, fusion on the grid surface is found to contribute up to 80% of the measured fusion rate, as determined from hysteresis effects between the fusion rate and system pressure. Surface fusion measurements were also carried out for a selection of cathode materials, with graphite found to produce a fusion rate that is an order of magnitude greater than the highest performing metal targets.