Herbert L. Berk

A towering figure in plasma and fusion theory, Herbert L. Berk passed away on 30 November 2021.

He was born in New York City on 29 September 1938 and attended the Bronx High School of Science, which sparked his love for science and mathematics. He received his undergraduate degree in 1960 from New York University and his PhD in 1964 from Princeton University, with Carl Oberman as his thesis adviser. Known to his family and colleagues as Herb, he spent his career investigating plasma physics with the goal of developing an energy source from nuclear fusion. As a postdoc at the University of California, San Diego, with Marshall Rosenbluth, he participated in a year-long stint in 1965–66 at the International Centre for Theoretical Physics in Trieste. There Soviet, American, and European physicists collaborated on nonlinear theory as well as on other pressing problems of thermonuclear fusion, largely setting the basis of the field for subsequent decades of research. He worked with several of the most prominent plasma theoreticians, such as Rosenbluth, Roald Sagdeev, Alec Galeev, Bruno Coppi, Charlie Kennel, and Tom O’Neil.

Throughout his career, Herb developed rigorous theoretical work with practical experimental applications in mind and often provided original and elegant solutions and insights to complicated problems, which he frequently shared without looking for anything in return. His 13 years of work on the theory of mirror confinement concepts at Lawrence Livermore National Laboratory were influential in focusing the US fusion program. Herb then became a professor of physics at the University of Texas physics department in 1980 as well as a founding member of the university’s Institute for Fusion Studies.

Herb subsequently became an internationally recognized leader in the nonlinear dynamics of Alfvén waves interacting with suprathermal particles. In the 1990s, together with Boris Breizman, he wrote several seminal papers on topics of basic and applied nonlinear kinetic theory. For example, their work on wave chirping and collisional effects on resonant phenomena and wave amplitude saturation became paradigmatic for interpreting experiments and simulations and is generally known in the field of energetic particles as the Berk–Breizman model. Their work also formed the basis for the prediction of the now widely observed reversed shear Alfvén modes in tokamaks. Herb’s last decade of research was largely devoted to developing resonance-broadened quasilinear theory and interpretation of simulations with the aim of whole device transport modeling of tokamaks, which greatly influenced our research.

A champion of international collaboration and human rights for scientists, Herb chaired the American Physical Society Committee on International Freedom of Scientists. Upon his retirement from teaching in 2018, he became professor emeritus. In his distinguished career, he published more than 250 papers, supervised 18 graduate theses, and was elected a fellow of the American Physical Society and of the American Society for the Advancement of Science. He also served on the board of several journals.

It was always a pleasure to communicate with Herb and learn from his broad physics and life knowledge, which provided immense inspiration to those around him. Herb is survived by his wife Susan, their sons Joseph and Adam, and their families. In his memory, his family has established the Herbert L. Berk Endowed Graduate Fellowship in Physics , toward which donations can be made.