Filamentation of a laser in a high Z plasma embedded with light ions

A high power laser propagating through a high Z plasma space, embedded with light ions, is unstable to the filamentation instability. A perturbation i n the amplitude of the laser across its wavefront gives rise to a ponderomo tive force on the electrons. As the electrons are displaced, they drag the light ions with them, causing a density depletion from the high intensity r egion. The perturbed density profile has a tendency to concentrate the lase r energy around density minima. Thus the amplitude of the perturbation grow s and the laser breaks into filaments. On a longer time scale the heavier i ons are also displaced via the space charge held and enhanced growth of the filamention occurs.