Renowned physicist steps down from Theory Department leadership at PPPL to devote full time to teaching and research

When Amitava Bhattacharjee returned to his academic roots to head the Theory Department at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) in 2012, the department had lacked stable leadership for several years and was nearing a funding crunch. Within a year of Bhattacharjee’s arrival, “the department had a budget crisis that forced us to institute a voluntary separation plan,” he said. “From that budget crisis, with solid support from the DOE and PPPL leadership, we pivoted toward greater cooperation and teamwork.”

World-class department

The world-class department, where Bhattacharjee earned his Princeton University doctorate in 1980 and stepped down from as leader on May 31, 2021, plays wide-ranging roles at PPPL. Among them is exploring the scientific basis for reproducing on Earth the fusion energy that powers the sun and stars and investigating the physics of plasma, the fourth state of matter that makes up 99 percent of the visible universe. Theory department functions include studying and predicting fusion experiments and exploring the rich properties of plasma, which consists of free electrons and atomic nuclei, or ions, in forms ranging from those thousands of times thinner than a human hair to space plasmas of vast astrophysical dimensions.

Theorists think about and try to understand controlling fusion plasmas and the forces at work in our universe, from the causes of space weather and black holes to the formation of stars and planets. Findings of the department have shed new light on wide-ranging plasma issues and prepared the way for future discoveries.

Bhattacharjee arrived as head of Theory from an endowed professorship at the University of New Hampshire, after teaching at the University of Iowa and Columbia University. He was renowned as a theoretician in plasma physics disciplines that included fusion energy and space and astrophysical plasmas. “When I was recruited, I promised that I would serve as Theory Head for a minimum of five years,” Bhattacharjee recalled.

But PPPL’s flagship fusion facility, the National Spherical Torus Experiment—Upgrade (NSTX-U), shut down in Fall 2016 for extended repairs.

During that period, “I was concerned about the future of PPPL and the Theory Department and felt that I had an important role to play,” Bhattacharjee said. “In those times, the Theory Department continued to be a high performer and a shining light of the laboratory. Now the Lab has more stable leadership which seeks to take the laboratory in new directions. As Theory head I have largely accomplished the goals I have set and think it is time for new voices to be heard.”

Opportunities for growth

The Theory Department under Bhattacharjee has seized opportunities for growth in fields ranging from advanced computing and high-energy-density physics to space science and plasma astrophysics. During his nine years as leader, researchers have won significant DOE grants in computing and the Exascale Computing Project (ECP), which aims for a 50-fold increase in high-performance computation speed on exascale computers. Taken all together, the department’s annual budget has grown from $9 million a year to more than $15 million, with much of that growth coming in the last five years.

In addition, Bhattacharjee and his team at Princeton University have been able to attract significant new funding from a NASA-National Science Foundation (NSF) collaboration on Space Weather in the Princeton Center for Heliophysics and a Simons Foundation collaboration on stellarators at Princeton University,

Theory has also added interdisciplinary breadth and depth through inter-departmental collaborations within PPPL and the University. “The Theory Department has long been a major strength of the Laboratory,” Lab Director Steve Cowley said. “Under Amitava, expansions have opened the door to new opportunities and accelerated our growth.”

New recruits

With new opportunities have come new recruits and a near doubling of the staff from 45 theorists to more than 80, including researchers ranging from graduate students, faculty members and research staff, to postdoctoral scholars and affiliates from the Princeton Center for Heliophysics, which Bhattacharjee directs. Recruits at PPPL have won two DOE Early Career Awards and a pair of Thomas H. Stix Awards from the American Physical Society for excellence in plasma physics research. The Department has also grown significantly more diverse, from three women in 2012 to seven women and a Latino man today.

Former PPPL Director Stewart Prager stresses Bhattacharjee’s far-reaching achievements. “When we recruited Amitava, we expected he would be a terrific Theory Department head,” Prager said. “But he has been better than that! Amitava has expanded the scientific breadth, the age and gender distribution, the size, and the overall vitality of the department. His ideas, creativity and energy are boundless. And he does it all with a warm smile. He leaves an amazing legacy.”

Jon Menard, PPPL deputy director for research, cites Bhattacharjee’s scope and outreach. “Amitava’s breadth of theoretical knowledge of plasma physics is truly impressive, and he has been a great representative for the Laboratory’s theory program,” Menard said. “I especially enjoyed working with Amitava helping to expand the NSTX/Theory partnership and engaging theorists in the NSTX research team and theory in the broader research program. And more recently, his leadership of the Exascale Computing Project is expanding our horizons and helped spawn our new computational science efforts.”

Repair of the NSTX-U, successor to the NSTX and the world’s most powerful spherical torus fusion facility, is scheduled for completion in 2022. The lengthy shutdown slowed the partnership between Theory and NSTX-U experimentalists, Bhattacharjee said. Reopening the compact spherical facility, which is shaped more like a cored apple than the doughnut-like shape of conventional tokamaks, will reinvigorate the partnership and produce fresh data for Theory to explore, he said.

Team of rivals

An early innovation that Bhattacharjee constructed after consulting Theory thought leaders was a “team of rivals” — a management technique that dates back to Abraham Lincoln. The technique called for appointing people with differing views to co-lead some research efforts. “This team attempted to persuade colleagues that it is much better to work together through their differences than to become insular and competitive.” he said. “Working together has produced rich dividends for the department, especially for SciDAC [Scientific Discovery Through Advanced Computing] centers and the Exascale Computing Project where we have had major funding victories. The NSTX-U-Theory Partnership also brought people together in the service of PPPL’s main facility.”

Bhattacharjee has worked closely with leaders of the Fusion Energy Sciences (FES) unit of the DOE Office of Science while initiating changes. “Amitava brought much-needed stability to the PPPL Theory Department during a critical period,” said John Mandrekas, FES Research Division Director and theory program manager. “His successful leadership and vision are evidenced by the Department’s success in multiple competitive reviews, including SciDAC and the ECP. One of the first steps he took after assuming the Department’s leadership was to establish regular and frequent communication with me, which I greatly appreciated since it made me and FES aware of the successes, challenges, and emerging issues at the Department.”

Looking back over his years as department head, Bhattacharjee noted that “my colleagues knew what they were doing and I learned much from listening to them. I am most proud that together we have recreated an environment of intellectual excitement and ferment,” he said. “We have expanded the intellectual reach of the department and brought forth new ideas in plasma theory and computing that have been attractive to early and mid-career talent, including graduate students.”

Moreover, he said, “there has been a significant change in people’s ideas about diversity, equity, and inclusion that goes beyond numbers — one that recognizes that we have critical issues in our culture that have precluded diverse leadership and belonging. I plan to continue my work in this crucial area as a member of the department and the larger community.”

Leadership of the department now passes, on an interim basis, to deputy department head Stuart Hudson as Bhattacharjee devotes full-time to teaching and research at PPPL and the University, which manages the Laboratory and where he holds a professorship. “The dominant passions of my professional life are research, teaching, and mentorship,” Bhattacharjee said. “Now I am looking forward to the pleasure of uninterrupted hours of thinking and work.”

Uninterrupted hours

The upside of that plan for “uninterrupted hours” resonates with Bhattatcharjee’s colleagues.
“Amitava will be a hard act to follow as head of Theory,” said Nat Fisch, Princeton Professor of Astrophysical Sciences and Director of the Program in Plasma Physics. “And I am grateful for all the amazing things that he has done within his administrative position. However, from an admittedly selfish standpoint, I am looking forward to getting Amitava now as a full-time colleague. He has a wonderful gift for lecturing and mentoring that will strengthen our graduate program. And I am personally excited to join him more frequently now, given his reduced administrative responsibilities, in those delightful, collegiate and informative conversations that range from his own scintillating research agenda to just about everything else.”

Bhattacharjee’s research pursuits remain widely varied. They include leading the Whole Device Modeling Application, an exascale project that aims to simulate an entire magnetically confined fusion plasma, and directing the Simons Collaboration on Hidden Symmetries and Fusion Energy. That partnership between Princeton University and the Simons Foundation of New York City seeks to optimize the design of twisty stellarators, the leading alternative to tokamak fusion facilities. In addition, he serves as founding director of the Princeton Center for Heliophysics and as Director of the Max Planck Princeton Center.

When not working on such projects Bhattacharjee now has more time to spend with his wife, Melissa, who has established her own company, Princeton Executive and Academic Coaching specializing in neurodiversity, and their family. Members include their 14-year-old son, Arun, who attends Princeton High School, two adult daughters and a grandson born in October 2019 to elder daughter Shikha, a doctoral student in jurisprudence and social policy at the University of California, Berkeley. Younger daughter Maya is co-founder and chief program officer of The Marcy Lab School, which teaches software engineering to underrepresented minority students in New York City, preparing them to work in the growing software industry.

Asked what advice he would give to a successor, Bhattacharjee cited steps that include, “Be a good listener, do not shoot from the hip, be kind, speak truth to power, do not be afraid, PPPL belongs to you as you belong to PPPL — and please take my free advice with a grain of salt!”

PPPL, on Princeton University’s Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit energy.gov/science.