Progress on ion based fast ignition

Abstract

Research at Los Alamos on fusion fast ignition (FI) [1] initiated by laser-driven ion beams heavier than protons has produced encouraging results. The minimum requirements for FI are relatively well understood [2]. Based on simple considerations and on those requirements, it is shown that FI of the compressed DT fuel using laser-driven heavy ion beams has advantages compared to laser-driven proton or electron beams, along with different risks compared to those approaches. Using a technologically convenient light-ion species such as Carbon, ∼ 100-fold fewer ions may deliver the energy necessary to ignite, simplifying target fabrication. Key requirements for success include the generation of a monoenergetic beam (energy spread ≤ ∼ 10%), a sufficiently high ion kinetic energy (∼ 450 MeV for C), and a sufficiently high conversion efficiency of laser to beam energy. An important benefit of this scheme is that such a high-energy, quasi-monoenergetic beam may be generated far from the capsule (∼ 1 cm away), eliminating the need for a reentrant cone in the capsule, a tremendous practical benefit. This paper summarizes our progress in meeting those requirements, and the results of an integrated 2D design for a proof of principle FI experiment based on this concept.