Evidence for surface fusion in inertial electrostatic confinement devices

Abstract

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.