Steven Cowley
Princeton Plasma Physics Laboratory
By Daniel Clery
It’s been quite a few weeks for Steven Cowley, the British astrophysicist who formerly headed the United Kingdom’s Culham Centre for Fusion Energy (CCFE). Last month, he was named as the new director of the Princeton Plasma Physics Laboratory (PPPL) in New Jersey, the United States’s premier fusion research lab. Then, last week he received a knighthood from the United Kingdom’s Queen Elizabeth II “for services to science and the development of nuclear fusion.”
Cowley, or Sir Steven, is now president of Corpus Christi College at the University of Oxford in the United Kingdom. He will take over his PPPL role on 1 July. He has a long track record in fusion research, having served as head of CCFE from 2008 to 2016 and as a staff scientist at PPPL from 1987 to 1993. PPPL is a Department of Energy (DOE)-funded national laboratory with a staff of more than 500 and an annual budget of $100 million. But in 2016, the lab took a knock when its main facility, the National Spherical Torus Experiment (NSTX), developed a series of disabling faults shortly after a $94 million upgrade. PPPL’s then-director, Stewart Prager, resigned soon after. DOE is now considering a recovery plan for the NSTX, which is expected to cost tens of millions of dollars.
During Cowley’s tenure at CCFE, that lab also started an upgrade of its rival to the NSTX, the Mega Amp Spherical Tokamak (MAST). Spherical tokamaks are a variation on the traditional doughnut-shaped tokamak design whose ultimate expression, the giant ITER device in France, is now under construction. The plan is for ITER to demonstrate a burning plasma, one where the fusion reactions themselves generate all or most of the heat required to sustain the burn. But once that is done, researchers hope spherical tokamaks, or some other variation, will provide a route to commercial reactors that are smaller, simpler, and cheaper than ITER. By upgrading the NSTX and the MAST, the labs hope to show that this type of compact reactor can achieve the same sort of performance as CCFE’s Joint European Torus (JET), the world’s largest tokamak right now and the record holder on fusion performance.
“We have to push down the cost and scale of fusion reactors,” Cowley told ScienceInsider shortly after the 16 May announcement of his PPPL appointment. “I fully support ITER because we have to do a burning plasma. But commercial reactors will need to be smaller and cheaper. A JET-sized machine would be so much more appealing. MAST and NSTX will be a dynamic team going forward.”
Despite the good food and well-stocked cellar on the Corpus Christi campus, Cowley says he is eager to return to the cut and thrust of laboratory life. “It’s too much fun. I was really feeling I missed the everyday discussions about physics and what was going on. I’m a fusion nut. We’re going to crack it one of these days and I want to be part of it,” he says. And PPPL, he adds, will be central to that effort. “Princeton is the place where much of what we know now was figured out. It’s a legendary lab in plasma physics. It’ll be fun to go and work with these people.”
His first job there will be to get the NSTX back on track. “I’m confident we can solve this problem. They’ve understood how the faults arose and they’ve understood how to fix them. If the money comes through, we will get NSTX back online,” he says.
Cowley says the key goal for spherical tokamaks and other variants is to reduce turbulent transport, the process that allows swirling plasma to move heat from the core of the device to the edge where it can escape. If designers can figure out how to retain the heat more effectively, the reactor doesn’t need to be so large. Spherical tokamaks do this by seeking to hold the plasma in the center of the device, close to the central column.
Another way to solve the heat problem is to increase a device’s magnetic field strength overall by using superconducting magnets, an approach being followed by researchers at the Massachusetts Institute of Technology in Cambridge. “That can push the scale down,” Cowley says, “but high field is not enough on its own. If there is a disruption [a sudden loss of confinement], that can be very damaging” to the machine.
Cowley thinks future machines may take elements from more then one type of reactor—including stellarators, a reactor type that has a doughnut shape that is similar to tokamaks, but with bizarrely twisted magnets that can confine current without needing the flow of current around the loop that tokamaks rely on. “There are beautiful ideas coming from the stellarators community,” he says. Wendelstein 7-X, a “phenomenal” new stellarator in Germany, has been a major driver, he says.
What has changed dramatically in the past couple of decades has been “the ability to calculate what’s going on,” Cowley says. Advances in both theory and computing power means “we have all these new ideas and can explore the spaces in silicon. The field is driven more by science and less by intuition,” he says. “It’s quite a revolution.”
Meanwhile, ITER construction trundles on despite numerous delays and price hikes. Cowley acknowledges that things have improved since the current director, Bernard Bigot, took over. “Bigot is an extremely good leader. He’s steadied the ship; he makes decisions,” Cowley says. “And they’ve got their team. It took time to find the right set of people.” Building ITER is “an amazingly tough thing to do. Assembly [of the tokamak] will be quite challenging and hard to stay on schedule. But when it is finished it will be a technological wonder.”
But perhaps the biggest obstacle to progress is a shortage of funding, which has been stagnant in the United States for many years. President Donald Trump has requested $340 million for DOE’s fusion research programs in the 2019 fiscal year that begins 1 October, a 36% cut from current levels, but Congress is unlikely to approve that cut. “There’s real hope [the 2019 budget] will move up, but it’s not energizing the field,” Cowley says. “If we can get NSTX to produce spectacular physics results—on a par with the performance of JET—we will energize the community with science.”
Source: Science Mag