Multi-Megajoule Nd:Glass Fusion Laser Design

Abstract

Virtually inexhaustible controlled fusion power motivated the construction of high power lasers during the last decade. A sequence of ever more powerful machines evolved at the Lawrence Livermore National Laboratory, each design taking advantage of information gathered with its predecessor. The largest and most recent laser of this group is a 100-kJ machine called Nova, which is even now irradiating its first targets. From the review paper by J. H. Nuckolls, L. L. Wood, A. R. Thiessen and G. B. Zimmerman in 1972 to the present day, it has been clear that between 1 and 10 MJ will be needed to demonstrate high gain in an inertially confined fusion plasma.¹ Controversy over where ignition at low gain will first be observed raged throughout the 1970’s. Nova and its smaller antecedents have been research machines dedicated to studying the physics of plasmas at high temperatures, pressures and densities. The results provide the measured efficiencies needed to accurately predict gain in ICF pellets. There has never been any doubt that a large enough driver can ignite a fusion event; nuclear weapons tests have often demonstrated the feasibility of the process. However extrapolation from laser driven experiments is a far from certain calculation; nevertheless, Fig. 1 shows that the size of a laser capable of efficiently causing fusion fuel to burn would need to deliver between 3 and 10 MJ to the fusion target, given today’s best simulations.²