Shape of electrodes for high performance of inertial electrostatic confinement fusion

Inertial electrostatic confinement (IEC) fusion is a scheme of producing deuterium, tritium, and helium-3 ions between the anode and the hollow cathode in the concentric sphere by glow discharge, accelerating the ions into the spherical center and giving rise to the fusion reactions between the accelerated ions or between the accelerated ions and the background neutrals. The current feed-through is connected to the cathode through the anode in order to apply the negative high potential. Some of accelerated ions directly bombard the feed-through as well as the cathode, and the ions, the orbits of which are deformed by lack of symmetry, hit the cathode after several bounce motions through it. The existence of the feed-through breaks the spherical symmetry of the device and shortens the lifetime of the accelerated ions. The hollow cathode also distorts a spherical potential near it. First, the effects of the structure of the spherical hollow cathode on the life are studied at various birth positions of the ions by numerically tracking the trajectory of ions in three dimensional spaces. Second, the effects of the shapes of the cathode and the anode on the life are investigated. The shapes of the cathode and the anode that assure a longer life are examined, and the virtual transparency of the cathode is numerically derived from the time dependent reduction of ions. It is revealed that the lifetime of accelerated ions becomes three times longer by deforming a hemisphere of the anode pierced by the feed-through into a hemi-ellipsoid. The results are useful in designing an anode and cathode to achieve high performance of an IEC fusion neutron source.