The U.S. Department of Energy is creating three research hubs in the hopes of harnessing miniature laser-driven thermonuclear explosions for future power plants, officials announced on Thursday.
The three hubs — based at Lawrence Livermore National Laboratory in California, Colorado State University and the University of Rochester in New York State — will share a total of $42 million over four years.
The research effort will be “focused more on the underlying technologies needed for any inertial fusion system,” said Scott Hsu, the lead fusion coordinator at the Department of Energy.
Combining two small atoms — typically hydrogen — into a heavier one produces energy. This process, known as fusion, is what powers the sun and other stars. If controlled fusion could be recreated on Earth, that could lead to a bountiful energy source that does not generate planet-warming carbon dioxide or long-lived radioactive waste.
Most fusion energy research to date, and most of the department’s fusion science budget, has focused on reactors that use powerful magnetic fields to contain super-hot hydrogen until the nuclei collide and combine. But a successful experiment last year at the National Ignition Facility, or NIF, at Livermore highlighted a different approach — firing powerful lasers at a single pellet of hydrogen, squeezing its atoms together to generate a flash of fusion.
NIF was not designed as a prototype for fusion energy generation. It has primarily been used to help maintain U.S. nuclear weapons since nuclear testing was discontinued in 1992.
The NIF science experiment fired one laser pulse at one hydrogen fuel pellet. A practical power plant would need to fire laser pulses repeatedly — at a cadence of perhaps 10 per second — with a new fuel pellet inserted for each pulse.
Those lasers would have to be more powerful, more reliable and much more energy efficient than those at NIF. The hydrogen fuel targets would have to be cheap and easy to manufacture. A single power plant would need a steady supply of millions of pellets. The new research hubs will help address these hurdles.
The Energy Department received many applications, and a review panel picked Livermore, Rochester and Colorado State, said Kramer Akli, who manages the government’s inertial fusion energy sciences program. Each of the winning proposals includes collaborations with other universities, national laboratories and private companies.
“You want to bring the brightest in your field together so that you can innovate and tackle some of the challenges for inertial fusion energy,” Dr. Akli said.
One of the main aims of the University of Rochester hub would be to test a new laser that would fire directly on the hydrogen fuel. This approach is more energy efficient than the one used in the NIF experiment at Livermore. But if slight variations in the laser light generate instabilities, that thwarts the fusion.
The instabilities can be tamed if the laser light is spread across a range of wavelengths. Scientists at the University of Rochester have been pursuing this approach, known as direct drive, for years, and the hub’s research money will go to experiments that test whether a new high-power laser can overcome this problem. “This is really opening up the direct drive path,” said Dustin Froula, the physicist leading the Rochester hub.
The Colorado State hub will study multiple kinds of lasers proposed for differing inertial fusion concepts and also examine different designs for the fuel targets. Carmen Menoni, a professor of electrical and computer engineering who led the hub’s proposal, said she would be looking at new materials for the coatings used on laser optics so that they could better survive the continual high-energy laser barrage.
Tammy Ma, the plasma physicist leading the Livermore hub, said its focus would expand beyond the indirect drive approach used by NIF and start to tackle what would be needed to build an actual power plant. “It’s not just, you have a target, and you shoot it, and you create energy,” Dr. Ma said.
The $42 million — $16 million each for Livermore and Colorado State, and $10 million for Rochester — is the first of a series of modest initial investments that will be made in laser fusion in the coming years. It represents a small slice of the Energy Department’s fusion energy science budget, which is spending more than half a billion dollars this year.
“These hubs are right now just the seed of a U.S. program,” Dr. Ma said.
The initial research should help illuminate which approaches are the most promising. “It’s not enough investment really to fully get at those answers,” Dr. Ma said. “But I think at the end of four years, we can lay out a promising path forward for the U.S. to really demonstrate a full-scale pilot plant.”
Kenneth Chang
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