A second-generation approach to controlled fusion power involves combining helium-3 and deuterium (). This reaction produces a helium-4 ion () (like an alpha particle, but of different origin) and a high-energy proton (positively charged hydrogen ion). The most important potential advantage of this fusion reaction for power production as well as other applications lies in its compatibility with the use of electrostatic fields to control fuel ions and the fusion protons. High speed protons, as positively charged particles, can have their kinetic energy converted directly into electricity, through use of solid-state conversion materials as well as other techniques. Potential conversion efficiencies of 70% may be possible, as there is no need to convert proton energy to heat in order to drive a turbine-powered electrical generator.