Nonlinear Effects on the Propagation and Absorption of Ultra-Intense, Short Laser Pulses in the Fast Ignitor Fusion Concept

Abstract

The Fast Ignitor1 is a novel approach to inertial confinement fusion that employs two types of ultra-intense, short laser pulses.2,3 The basic idea in this approach is to couple the energy available in an ultra-intense laser pulse, via energetic electrons, into a precompressed target in a time short compared to the disassembly time. For electrons with energy ~ 1 MeV, the electron range is about equal to the necessary alpha particle range. These electrons then initiate a localized burn in the core, which can then propagate to the rest of the fuel. The potential benefits of this scheme are the use of less energy for ignition and less stringent requirements on implosion symmetry, relative to currently used ICF schemes. As currently considered, the Fast Ignitor requires two different types of short laser pulses. First, a beam of roughly 10-100 ps in duration and Iλ2 ≤ 1018 W μm2/cm2 is used to create a channel through the corona of a precompressed pellet. Next, an ultrashort pulse is sent down the channel (1-10 ps, Iλ2 ≥ 1019 W μm2/cm2)to generate the energetic electrons which transport to the compressed core.