Direct drive with the argon fluoride laser as a path to high fusion gain with sub-megajoule laser energy

Abstract

Argon fluoride (ArF) is currently the shortest wavelength laser that can credibly scale to the energy and power required for high gain inertial fusion. ArF's deep ultraviolet light and capability to provide much wider bandwidth than other contemporary inertial confinement fusion (ICF) laser drivers would drastically improve the laser target coupling efficiency and enable substantially higher pressures to drive an implosion. Our radiation hydrodynamics simulations indicate gains greater than 100 are feasible with a sub-megajoule ArF driver. Our laser kinetics simulations indicate that the electron beam-pumped ArF laser can have intrinsic efficiencies of more than 16%, versus about 12% for the next most efficient krypton fluoride excimer laser. We expect at least 10% ‘wall plug' efficiency for delivering ArF light to target should be achievable using solid-state pulsed power and efficient electron beam transport to the laser gas that was demonstrated with the U.S. Naval Research Laboratory's Electra facility. These advantages could enable the development of modest size and lower cost fusion power plant modules. This would drastically change the present view on inertial fusion energy as being too expensive and the power plant size too large. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)'.

Pathways towards break even for low convergence ratio direct-drive inertial confinement fusion

“…The higher frequency laser has a higher critical density and thus propagates further into the plasma, resulting in more laser absorption and a higher density blow-off (Obenschain et al. 2020). Furthermore, the lower wavelength permits higher laser intensities before the onset of parametric instabilities (Montgomery 2016), enabling higher laser powers to be used for equivalent instability growth.…”

“…Recent simulation work by Obenschain et al. (2020) demonstrated that significant gains can be achieved at low laser energy using wavelength nm ArF laser drivers when applied to shock ignition, leading the authors to highlight the potential role of such lasers for IFE applications. In order to investigate these advantages further the optimisation process performed in Paddock et al .…”

“…Following results from Obenschain et al. (2020) highlighting the increase in IFE performance that could be achieved by using argon fluoride (ArF) lasers, applied to shock ignition ICF, § 3 investigates performance in the low-instability regime when using higher frequency laser drivers. The optimisation process from Paddock et al .…”

Prospects for high gain inertial fusion energy: an introduction to the second edition

“…Part I concluded with a fascinating discussion of the benefits of deploying the Naval Research Laboratory's argon-fluoride (ArF) driver, operating at a wavelength of 193 nm, for direct drive of inertial fusion targets. Their work suggests that a significant saving on drive energy (and capital costs) might be realized using this approach [14].…”

Prospects for high gain inertial fusion energy: an introduction to the first special edition

“…The first edition of this special issue concludes with Stephen Obenschain et al ’s very interesting article ‘Direct-drive with the Argon Fluoride laser as a path to high-gain with sub-megajoule laser energy’ [13] describing the potential benefits of using still shorter wavelengths (193 nm) that are available with argon-fluoride excimer lasers as the driver to achieve high gains for inertial fusion energy.…”