This is an experiment in the direct conversion of heat to electricity. Practical applications of this device could allow any high-temperature waste heat (such as on the surface of re-entry vehicles, scram-jet combustion chambers, topping units for power plants, and space-based power cells using radioisotopes) to be converted into useful electrical power.
The hot electrode on the left, like any heated metal, has a layer of electrons boiling off of its surface. If these electrons could be collected onto a cooler surface they would effectively generate electrical power.
Unfortunately, under normal circumstances, very little current can be drawn from this sea of boiling electrons. This is because any such extraction creates a negative space-charge effect, making the process self-limiting. By using nanosecond-scale, high-voltage pulses, the xenon gas in the chamber is ignited to form a plasma. This plasma acts as a conduit to allow the electrical current to flow unhindered by any negative space-charge build-up, thus converting the heat into useful electrical power.