"It's just all been fun, and this is the most fun job I've ever had," Steve Cowley says of his much-decorated career and his new position, which he assumed July 1, as the seventh director of the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL), the place where the British-born physicist earned his doctorate and that he calls "the most important fusion laboratory in the world."
Cowley, a 6-ft.-5 former University of Oxford basketball player, has made his life-long work advancing the development of fusion—the power that drives the sun and stars—to generate electricity on Earth. In October the Queen of England knighted Cowley, a world-class physicist and broad scientific leader, "for contributions to science and the development of nuclear fusion." His achievements range from the modeling of plasma turbulence, which must be controlled to produce nuclear fusion, to ensuring the vitality of the Culham Centre for Fusion Energy, Britain's national fusion laboratory, while serving as its director from 2008 to 2016 and as chief executive officer of the United Kingdom Atomic Energy Authority, which operates the laboratory.
At PPPL, which is managed by Princeton University, Cowley's immediate task is overseeing repair of the National Spherical Torus Experiment-Upgrade (NSTX-U), the lab's flagship experiment. The facility, a compact variation of a device called a "tokamak," superheats and confines plasma—the state of matter composed of free electrons and atomic nuclei—in magnetic fields to produce fusion reactions such as those that occur in the sun. The cored-apple-like design of the NSTX-U contrasts with the bulkier doughnut-like shape of more widely used conventional tokamaks, and produces high-pressure plasmas—a key to fusion reactions—with relatively low and cost-effective magnetic fields.
Such capability makes the innovative facility a candidate for furthering development of magnetically controlled fusion energy. Cowley, who walks, bikes, and takes the shuttle bus to and from the laboratory, is eager to complete the repair of the NSTX-U as the world's most powerful spherical tokamak to fulfill its mission in the development of fusion research. "I'd like to see us really explore whether we can push the spherical tokamak to a real reactor concept," he says.
Together with that he's eager to explore and implement ideas for a new type of stellarator, a fusion facility that confines plasma in twisting magnetic fields. An advanced new device would combine the freedom from plasma disruptions of a stellarator with the ability to maintain plasma confinement of a tokamak, and would be relatively simple to construct. "We need to design a machine that's not so complicated that building it becomes fiendishly expensive and difficult," Cowley says. "And we need to view the physics as servant to the engineering, not just the engineering as servant to the physics."
Princeton's job now is to develop fusion as a smaller and cheaper source of energy, he says. "We've got a lot of ideas to work on, a lot of clever things that have not yet been tried. Princeton's always been the intellectual driving force in the fusion community, and that's where we should be."
Leading a laboratory is a simple matter, says Cowley, who is also a Professor of Astrophysical Sciences at Princeton University and whose accolades include election as a Fellow of the Royal Society, which counts Isaac Newton, Charles Darwin, and Albert Einstein among past members, and a Fellow of the Royal Academy of Engineering. "The only skill you need to be a good lab director is to know, appreciate, and understand the quality of the people you're working with," he says. "I have no problem walking into congressional offices and telling them that some of the smartest people in the world work for me at the lab. If you've got good people, then the rest is easy."
Cowley first heard about fusion as a teenager from his engineer father, an "incredibly silent man" except when talking about science and technology. "When he told me about fusion I was excited by the idea, and as an undergraduate at Oxford I thought I might do fusion as a Ph.D.," Cowley says.
While a scholarship student at Oxford's Corpus Christi College, which he later served as president from 2016 to 2018, Cowley thought long and hard about developing fusion energy. He asked his father, who in turn asked his friends, "Where do you go to study if you want to spend your life doing fusion? And everybody said, 'Princeton'—the most famous place in the fusion universe."
Arriving at Princeton with a suitcase and a backpack in the summer of 1981, Cowley knew no one and felt "a long, long way from home." Through his new roommate he met Greg Hammett, a fellow graduate student and now a principal research physicist at PPPL, who brought him to the laboratory. "Steve was clearly one of the fun people to be around and was an intellectual leader among the students," Hammett says. "I think he's the brightest and broadest theorist in our field."
Shortly after arriving, Cowley met his future wife, Margaret Koval—now director of special projects for communications at Princeton University—on her first day as a graduate student. "She came into the dining hall and I sat next to her," Cowley recalls. They married in 1985 in the Princeton courthouse—roughly 50 yards from where they now live—just before Cowley defended his doctoral thesis. Sons Brendan, a software developer and basketball player in London, and Sean, a recent graduate of the University of California, Irvine, who plans to become a writer, are "both very musical," says Cowley, a former trumpet player with a love for jazz greats. He also enjoys following the Golden State Warriors, champions of the National Basketball Association.
As a graduate student at PPPL, Cowley had generous support from the Harkness Foundation of New York, which required those funded to spend 12 weeks touring America. So he bought an old Ford Mustang during his second summer and drove coast-to-coast, recalling the time as "a marvelous experience." He found Americans to be quite welcoming and remembers his travels that summer as "a wonderful trip."
Back at PPPL, Cowley studied plasma physics under Russell Kulsrud, a theoretician who supervised his thesis and "had a searing impact on the kind of physicist that I wanted to be." Kulsrud taught that everything in physics had to be seen in its simplest form and physicists had to understand the simplest thing and move forward from there. "Working with Russell was one of the best decisions I ever made," Cowley says.
Kulsrud, now a Princeton University professor emeritus, recalls the period clearly. "I found that a trouble with Steve was that his complete and accurate solution of important problems was too difficult for me to understand," Kulsrud says. "So I stressed that it would be easier if he would first find a simplified version of the problem to clarify the solution and make the physics easier to understand."
With his doctorate in hand, Cowley spent the next three decades teaching and conducting research on both sides of the Atlantic before becoming director of PPPL. He served two years as a post-doctoral fellow at the Culham Centre before returning to PPPL as a staff researcher from 1987 to 1993. He next joined the University of California, Los Angeles, where he served as a professor from 1993 to 2008—minus two years as leader of the plasma physics group at the Imperial College in London. He went on to co-lead the national Center for Multiscale Plasma Dynamics for UCLA in partnership with the University of Maryland and served as a member of the Culham advisory board.
On becoming director of Culham in 2008, Cowley took over a laboratory whose future was uncertain. Its major experiment, the Joint European Torus (JET), the world's largest operating tokamak, was scheduled to close and its spherical neighbor, the Mega Amp Spherical Tokamak (MAST), was nearing its end as a useful experiment. Cowley secured funding to keep JET running and to design and upgrade MAST, the sister experiment to the NSTX-U. Phasing out the laboratory "is not what you want to do," he stressed to the British government. "Fusion is important and we should have a lab of this quality and move it forward."
Cowley brings a similar attitude to his work at PPPL, whose advisory board he sat on from 2009 to 2016 while director of Culham. "If you look at the history of fusion, so much of the great scientific steps forward have happened at Princeton," he says. "And when the day comes that fusion energy is powering the electric light bulbs in the United States, people will remember that the intellectual foundation of the machines has come from us."
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