An assessment of the driver energies required to robustly ignite targets for inertial fusion energy

Laser driven inertial confinement fusion (ICF) is the process whereby a cryogenic shell of deuterium and tritium (DT) is compressed inward to high pressures and temperatures by direct or indirect irradiation of laser energy to produce 17.6 MeV of fusion energy per DT nuclear reaction.  Last year, the first demonstration of breakeven (fusion energy out > laser energy in) was achieved on December 4, 2022 on the National Ignition Facility.  Although the primary purpose of ICF research in the United States is to support the stockpile stewardship mission, this breakthrough result has generated significant interest and investment in inertial fusion energy (IFE) which refers to using ICF implosions to create energy for a power plant.  Unlike standard ICF targets which are primarily optimized for performance, IFE targets are constrained by several important factors: namely cost, production time, availability of materials, and the ability to withstand injection into a practical IFE target chamber.  Such targets will likely employ liquid DT wetted foams in place of solid DT layers, they may be fielded at higher than optimal temperatures due to chamber heating, and the realities of limited tritium inventories also need to be anticipated and accounted for.  These differences will reduce yield, compression, and gain compared to traditional ICF implosions.  The purpose of the study presented here is to present conservative estimates of the driver energies needed to overcome these challenges.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and was supported by the LLNL-LDRD Program under Project No 23-ERD-023.