Laser pulse propagation and enhanced energy coupling to fast electrons in dense plasma gradients

Dataset for a study of laser energy absorption to fast electrons during the interaction of an ultra-intense (1020 W cm−2), picosecond laser pulse with a solid as a function of the plasma density scale length. It is shown that there is an optimum density gradient for efficient energy coupling to electrons and that this arises due to strong self-focusing and channeling driving energy absorption over an extended length in the preformed plasma. At longer density gradients the laser filaments, resulting in significantly lower overall energy coupling. As the scale length is further increased, a transition to a second laser energy absorption process is observed experimentally via multiple diagnostics. The results demonstrate that it is possible to significantly enhance laser energy absorption and coupling to fast electrons by dynamically controlling the plasma density gradient. These results are of general importance for understanding absorption in laser-solid interactions but are specifically relevant for conditions where long plasma density scale lengths are expected such as in the corona of imploded targets in the fast ignition approach to inertial confinement fusion.

Experimental and simulation data published in New Journal of Physics 16 (11), 113075. Experimental data was taken in April 2010 using the VULCAN-TAP laser facility at the Rutherford Appleton Laboratory. Simulations were conducted using the PRISM hydrodynamic code and EPOCH PIC code on the ARCHIE-west cluster.