PIC codes follow electrons and ions in fusion plasmas with self-consistent fields.
This means that the fields generated by the charged particles act as forces accelerating the particles themselves. The motion of electrons and ions is followed in five-dimensional space with two spatial and three velocity dimensions in addition to time. Trajectories of millions of charged particles can be easily solved with a modern workstation. Accurate diagnostics, which is often difficult or even impossible in real fusion experiments, is easy in these numerical experiments. In microwave range of frequencies, the launcher, which is often called a grill, is a phased waveguide array which emits the rf power into a plasma.