Observation of Weibel-like radial filamentation from time resolved dynamics of a kHz relativistic laser interaction with a sub-micron transparent sheet

A significant amount of work has been done on relativistic electron dynamics where results are inferred from emitted particles and various probes parallel to the target surface. In this work a free standing sub-micron transparent liquid sheet target is exploited to produce shadowgraphic movies of the transverse expansion of the relativistic electrons with 100 fs resolution. The ionization front expansion rate, extent, and duration are observable in addition to the subsequent hydrodynamic evolution of the target. Particle-in-cell (PIC) simulations indicate Weibel instability generated radial current filaments corroborated by features observed in the shadowgraphy.