Relativistic filamentation of laser beams in plasma

The results of a numerical code which models the relativistic self-focussing of high-intensity laser beams in plasmas by the nonlinear relativistic dependence of the optical constants on laser intensity are described. The plasma dynamics of 10 trillion W Nd glass lasers of 30-micron initial beam diameter in nearly cutoff density plasmas is followed for a few picoseconds interaction time and 25-micron depth into the plasma. Rapid relativistic self-focussing down to a beam diameter of one micron in a distance of the order of the original beam diameter is observed, as well as the production of GeV ions moving against the laser light.