Comparison of an Argon-Fluoride Gas Laser with a Solid-State Laser for Application to Laser Fusion Energy

With direct symmetric laser illumination of a spherical target, there is the potential for high enough target gains to produce economically viable fusion power. Proposed solutions to the various laser-target physics problems have mostly relied upon modifications to the laser, while keeping the target relatively simple. Necessary but not sufficient laser constraints include a short laser wavelength, very uniform illumination of the target in both high and low spherical perturbation modes, a wide bandwidth, temporal pulse shaping, and a reduction of the focal spot size during the implosion. An electron-beam-pumped argon-fluoride gas laser best satisfies all of these constraints and has the potential for fusion energy gains that far exceed requirements for an economically viable power plant. Various diode-pumped solid-state laser concepts are reviewed. None can simultaneously satisfy most if not all of the constraints. For example, the recently proposed PolyKrōm design produces a set of narrowband discrete wavelengths. The intensity coherence time of this discrete set is too long, and it could not produce the required uniform laser illumination. It is also shown that solid state lasers cannot produce with sufficient efficiency the subnanosecond pulse that is required for the shock-ignition target design.