EVIDENCE FOR WHOLE-BEAM SELF-FOCUSING OF INDUCED SPATIALLY INCOHERENT LASER-LIGHT IN LARGE UNDERDENSE PLASMA

The propagation of an intense electromagnetic pulse in a large underdense plasma has been investigated using spatially and temporally incoherent laser light. Spatial incoherence was obtained using the induced spatial incoherence (ISI) technique. The first observation of the occurrence of thermal whole-beam self-focusing with ISI laser light is presented. Thermal imaging with a multiframe x-ray camera (140 ps gate time) was used to record the propagation characteristics of the interaction beam through the plasma. A direct measurement of the self-focusing growth length has been made.