A detailed investigation of many aspects of the physics
of laser–plasma interaction at very high laser
intensities is required in order to assess the feasibility
and the promise of the fast ignitor scheme for inertial
confinement fusion. Relevant results, obtained in a series
of experiments carried out at the Rutherford Appleton Laboratory,
Chilton (UK) and at the Centre d'Etudes Atomique,
Limeil Valenton (France), are presented and discussed here.
In particular, the formation of plasma channels was observed
following the propagation of relativistically intense,
ps laser pulses through underdense plasmas. The channels
persist long after the interaction, and their expansion
has been measured. Efficient guiding of ultraintense laser
pulses, both through preformed density channels and through
solid guides, has been demonstrated. Finally, indication
of collimated fast electron propagation through solid targets
has been obtained from the observation of filamentary ionization
tracks in laser irradiated solid targets.