Laser Fusion Milestone
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The announcement of the latest progress in laser fusion was a model of careful statement by all of the people involved. They were Secretary of Energy Jennifer Granholm, Under Secretary for Nuclear Security and National Nuclear Security Administration (NNSA) Administrator Jill Hruby, White House Office of Science and Technology Policy Director Arati Prabhakar, NNSA Deputy Administrator for Defense Programs Marvin “Marv” Adams, and LLNL Director Kim Budil.
Their comments emphasized the time it’s taken to get to this point – 60 years since the National Ignition Facility (NIF) was proposed, generations of researchers, many ups and downs in constructing NIF and making it work, the development of the tiny, multilayered targets and the hohlraums, containers for the targets that concentrate the energy of 192 lasers still further.
The prospect of commercial fusion plants producing electricity, so beloved of reporters, was not mentioned until the last member of the panel that followed the announcement. What was emphasized instead was deterrence. NIF is an NNSA facility, intended for the study of fusion to understand the processes in nuclear weapons. Fusion is easy to produce if you have a fission device handy. Finding a way to control fusion on a small scale is the hard part.
In the early 1990s, the decision was made not to do any more full-up nuclear explosion tests. Instead, the DOE and its nuclear weapons organization, NNSA, developed a program of modeling and small-scale tests called Stockpile Stewardship. NIF is part of that program. Commercial electricity, if it ever results from these experiments, is a secondary result.
So there was a lot of mention of deterrence and the nuclear deterrent, meaning the nuclear arsenal. Even in this context, the experiment is something of a long shot. It will help to understand what is going on in thermonuclear weapons, which will help to understand how they’re standing up to the passage of time and perhaps for the design of new weapons, if the decision is ever made to do that again.
Commercial electricity from fusion is still decades off. LLNL Director Kim Budil was quite clear about that, and that it would require big advances both in science and “technology” – her word, which means materials science and chemistry to fabricate targets and hohlraums, and ways to use not such enormous lasers. And finding whether laser fusion or the alternative, magnetic confinement fusion, is likely to work better.
If you want the technical part, it looks like improvements in fabricating the targets and upping the laser power were what led to the results. Kevin Drum provides a simple diagram illustrating the energy used in the experiment. The energy gain reported was over the laser input. Getting to that laser input, though, required a lot of electricity. Overall, 300 megajoules of energy was needed to produce 3.15 megajoules from the target.
Cross-posted to Nuclear Diner