DYNAMICS OF SUBPICOSECOND RELATIVISTIC LASER-PULSE SELF-CHANNELING INAN UNDERDENSE PREFORMED PLASMA

The formation and evolution of density channels created by the interac tion of a short bright (600 fs, 5 x 10(18) W cm(-2) mu m(2)) laser pul se with a preformed plasma are studied by means of experiments and 2D particle-in-cell (PIC) simulations. Hollow density channels are observ ed by interferometry, and a fast radial expansion (5 x 10(8) cm/s) is measured. Magnetic fields around 50 MG inferred from Faraday rotation measurements suggest the occurrence of self-focusing. The PIC simulati ons support this hypothesis and shaw ion depletion during the laser pu lse as well as radial expansion in agreement with experiments.