Speaker
Description
In electrostatic fusion reactors like the Orbitron, maintaining reliable high-voltage levels is crucial for the confinement of charged particles. Avalanche Energy's ultra-compact bushing, MAKO, plays the key role of transferring voltage from ambient pressure to an ultra-high vacuum environment with pressures below 1e-8 Torr. It features a coaxial configuration with a 1.8-5 cm gap distance and is designed to handle a nominal voltage of 300 kV. However, the high voltages required present complex challenges, such as explosive field emission from the cathode and surface flashover across the insulator. These issues become more pronounced at voltages above 200 kV, where the system's stored energy is sufficient to increase the probability of explosive cathode emissions. The electric field strength across the cathode in the >200 kV regime can reach up to 30 MV/m, although the field at the triple-junction point is effectively shielded to never exceed 0.05 MV/m. Recent experiments have focused on using gases like Ar, N2, and Kr for surface conditioning to eliminate sharp emission sites on the cathode, with Kr proving particularly effective in removing tenacious field emission sites, as evidenced by both cathode current profiles and visual recordings. Despite a minimal triple-junction field, surface flashover may still occur due to surface charging of the ceramic insulator and charge accumulation from electron beam exposure. Nevertheless, explosive emissions from the cathode that result in persistent deposits can be substantially reduced through gas conditioning with heavier atomic species.
