Relativistic laser plasma interaction studies in magnetized plasma

The physics of relativistic laser plasma has renewed the interest in laser-plasma interaction in the recent past. Promising applications such as fast-ignitor for thermonuclear fusion, proton radiography, high energy particles and X-ray sources are foreseen. For a wide range application, it is required that a high intensity laser propagates over long distance, well in excess of the Rayleigh length. In the high intensity regime, electrons oscillate at relativistic velocities, which causes their mass to increase by the Lorentz factor. This effect has to be taken into account when defining plasma parameters relevant for the interaction. However, in laser plasma experiments, nonlinear self-focusing permits high intensity propagation over much longer distances and this happens when the laser power is greater than the critical power for relativistic self-focusing. When an ultra-intense laser pulse undergoes self-focusing in a plasma, one has to consider relativistic effects due to the mass increase of electrons oscillating in the laser field and charge displacement effects due to the ponderomotive radial expansion of electrons. Relativistic and ponderomotive self-focusing have been observed in many experiments and have proven to be an efficient way to guide a pulse over distance much larger than Rayleigh length. The self-guided propagation of a short pulse laser in magnetized plasma is based on the extraordinary mode propagation in magnetized plasma, with static magnetic field parallel to the oscillating magnetic field of the electromagnetic wave. Such a static magnetic field can be created by the pulse itself if the condition for ultrafast volume ionization are fulfilled. It is demonstrated that external magnetic field affects the channels, causing them to bend .These effect cast new light on the phenomena of self-focusing .They raise the possibility of combining the energy from several channels into one. Magnetic field is found to have a significant effect on overall propagation and plasma dynamics. (author)