A plasma beam passing from the ionizing to the recombining state

A photograph of the plasma beam in the linear PSI-II device shows the transition of an ionizing plasma to a recombining plasma. Plasma recombination occurs in the center of the beam where the temperature has a minimum due to a hollow profile. Simultaneously, the density peaks here above a certain neutral pressure. These conditions are favorable for plasma recombination. The peaking of the density is not fully understood, however, and is subject of current investigations.