Fusion has been conventionally done by heating a gas to such a high temperature that the average particle of gas has enough energy to overcome the Coulombic repulsion of another particles nucleus so that it can fuse. This poses two problems: how do you heat the plasma to such a high temperature, and how do you contain it? The traditional approach is magnetic confinement, but this has challenges.
Instead in the Farnsworth-Hirsch two concentric spherical grids are used, one of which is at a high negative potential to produce an electric field that accelerates the ionized gas to high enough velocities to fuse. This solves both the problem of heating the plasma (temperature is a macroscopic expression averaging the individual particle velocities) and containing it; If ionization occurs within the volume of the chamber any ions produced will be unable to escape the potential well. The associated technology and cost of operations is many times less that the big budget fusion projects like ITER, while still producing a continuous nuclear fusion reaction.
The system consists of a vacuum system which evacuates a stainless steel vessel. A variable autotransformer is used to control an input voltage for the high-voltage transformer. The transformer supplies anywhere from negative 10,000 to 50,000 volts to the central grid. This video highlights the first plasma achieved. No fusion is actually occurring in this video as the chamber is filled with air at medium vacuum pressure. To actually produce fusion reactions the chamber should be filled with deuterium, and in the simplest case glow discharge ionization produces all the ions for reaction.