Growing up in the Bronx, Stewart Prager was busy being a kid while all the other five-year-old science prodigies were experimenting with chemistry sets and wires. He didn’t find science until high school, and even after he wandered into electrical engineering in college, he had no idea how big a player in the field of plasma physics he would become.
But after 31 years researching fusion energy and plasma physics at the University of Wisconsin in Madison, Prager’s potential has been realized by the federal Department of Energy. The DOE has named Prager to be the sixth director of the Princeton Plasma Physics Laboratory on the James Forrestal Campus, effective this fall. The lab, which houses studies in fusion energy, is operated by Princeton University, where Prager is also expected to be named a professor of astrophysical sciences in September.
Prager will succeed Robert Goldston, who has been director of PPPL since 1997, and who also is a professor of astrophysical sciences at Princeton. Goldston said last December that he would step down when a successor was found.
Prager is the director of the Madison Symmetric Torus experiment at UW-Madison, seeking to generate and harness near-thermonuclear plasmas reaching 10 million degrees via the doughnut-shaped reverse field pinch, or RFP, device. Prager joined the Wisconsin faculty in 1977 after two years as a researcher with General Atomic Co. (now known as General Atomics) in San Diego.
Prager has served as chairman of the DOE’s Fusion Energy Sciences Advisory Committee, as chairman of the Division of Plasma Physics of the American Physical Society, as president of the University Fusion Association, and as a member of the fusion review panel of President Clinton’s Committee of Advisors on Science and Technology. He holds a joint bachelor’s in liberal arts from Queens College and electrical engineering from Columbia, which he received in 1970. His studies at Columbia led him unexpectedly to plasma physics, so he stayed to earned his Ph.D. in the subject.
The largest challenge for fusion scientists looking to craft a commercial reactor has remained constant from the beginning — how to generate the electrically heated gases called plasmas to 100 million degrees and contain them within a magnetic field that itself is contained in a material that will not vaporize when touched by such extreme heat. As an energy source it certainly is possible — fusion fuels the sun, after all — but coaxing it into a practical nuclear energy source on Earth has proven a lengthy task.
The Department of Energy launched PPPL, one of 10 DOE research sites in the country, in 1951 to harness the energy potential of nuclear fusion by working with plasmas but, so far, the outcome has only worked in science fiction.
But that is only part of what plasma physics has attained. Prager says the full picture of research into plasma-based fusion has been misrepresented. “It’s often reported as if there’s one prize at the end, and then that’s it,” he says, referring to the completion of a fusion reactor. But, he says, the work of plasma physicists has yielded breakthroughs in televisions (think plasma screen TVs), food sanitation, waste management, and, perhaps most important to industry, microchips. At least a third of a microchip’s existence is made possible by fine plasma etching, and the semiconductor field, where many plasma scientists end up, is still growing in leaps and bounds.
The potential is part of what keeps Prager fascinated, even if the work can be frustratingly slow. The extent of plasma physics’ influence on the world has surprised scientists, he says, but few in the field have been surprised that the field would make contributions far beyond the search for a new energy source. The necessity of finding new energy drove fusion science when he joined UW in 1977. Then, as now, the world worried deeply about running out of energy, though today, the added threats of global warming and skyrocketing petroleum prices “certainly make it interesting and compelling” to be in plasma physics, he says.
In the search for the fusion reactor, Prager made significant headway at UW, where his researchers have experimented with weaker magnetic — and considerably more economical — fields to hold the plasma. The work has not solved the fusion question, but it has been credited with leading to new insights about the properties of plasma.
Though Prager’s research experience is on the RFP-style generator and PPPL operates a tokamak generator, Prager says the two are “cousins of each other” and that he is comfortable with stepping into Princeton. He says PPPL, with roughly 425 employees and an operating budget of more than $200 million, offers a “bigger, broader scale of experiments” than UW.
As for the state of fusion energy research, Prager says, “We’re more than halfway there.” He bases the statement on the increase in the amount of energy scientists have been able to generate — more than 1 million-fold since the beginning — and the number of steps those scientists foresee as a stairway toward that oft-reported single prize.
He says that the pioneers in the field, with high hopes after cracking the atomic secrets of the 1940s, simply underestimated the complexities of converting fusion into a workable form of energy. “There’s a joke in the field that we always have another 20 years to go no matter what year it is,” he says. “But if you look at where we were in 1960 compared to where we are today, we’ve made enormous progress.” Still, at 59, Prager says he will not be working when scientists crack the fusion reactor puzzle. He expects to be alive, but cozily in retirement.
Though Prager says it will be extremely difficult to pack up 31 years of memories in Madison, he is extremely excited about coming to Princeton, and will even be reunited with longtime colleague Michael Zarnstorff. Zarnstorff is a one-time UW graduate student and now principal research physicist at PPPL. He and Prager are credited with discovering the “bootstrap current,” named because the electrical current is generated by the plasma itself. Both men will receive the American Physical Society’s Dawson Prize for Excellence in Plasma Physics this November.