Intense laser pulse propagation and channel formation through plasmas relevant for the fast ignitor scheme

Measurements of self-channeling of picosecond laser pulses due to relativistic and ponderomotive expulsion effects have been obtained in preformed plasmas at laser irradiances between ${\text{5–9×10}}^{18}$ ${\mathrm{Wcm}}^{\mathrm{-2}}.$ The self-focused channel was surrounded by a multi-megagauss magnetic field. The orientation of the field was consistent with a forward going relativistic electron beam propagating along the laser pulse. Self-channeling and magnetic field generation mechanisms were modeled by multidimensional particle-in-cell (PIC) simulations and good agreement was obtained with the experimental observations. Measurements of the channel expansion after the interaction were obtained and the rate of expansion was consistent with a blast wave solution. The level of transmission of an intense laser pulse through such performed density channels was observed to increase significantly compared to the case without a channel. High levels of transmission of an intense laser pulse through microtubes were also observed. The relevance of these results to the fast ignitor is discussed.