Experimental investigation of self-guiding using a matched laser beam in a CM scale length underdense plasma

Abstract

High-intensity short-pulse laser guiding in plasma channels has extended the length over which acceleration occurs in laser wake field accelerators[1]. Recent multidimensional nonlinear plasma wave theory[2] predicts a range of optimal characteristics for self-guiding of laser pulses in the blowout regime for pulses shorter than a plasma wavelength. This theory predicts a robust, stable parameter space for self-guiding and wake production and has been verified through multidimensional particle-in-cell simulations. We experimentally explore the plasma dynamics and laser pulse propagation using a 50 fs multi-terawatt Ti:Sapphire laser in a helium plasma at plasma densities, laser powers, and spot sizes within this parameter space. Our parameters are in the range where the plasma is underdense and the laser power is much greater than the critical power for self focusing. The evolution of the laser pulse and plasma channel will be followed over several Rayleigh lengths.