Optimization of laser–target coupling efficiency for direct drive laser fusion

Abstract

An arbitrary beam shaping-zooming concept is proposed for direct drive fusion on the Laser Mégajoule and the National Ignition Facility. It is based on the intrinsic conception of these facilities which use four beamlets per beam. A substantial improvement of the laser–target coupling efficiency is achieved with a lowering of ignition threshold. A design providing a thermonuclear energy of about 30 MJ with less than 1 MJ energy-laser has been investigated. The control of low-modes irradiation uniformity is achieved dynamically with an enhancement of the hydrodynamic stability of the acceleration and deceleration phases.