L. Donald Pearlstein

L. Donald Pearlstein passed away on 9 July 2020 at age 87.

Don was a major contributor to the physics of hot plasmas. Trained in high-energy physics at the University of Pennsylvania, Don entered the plasma field at General Atomics, working with plasma pioneers Marshall Rosenbluth, William Drummond, Nick Krall, and others, many of whom, like Don, moved on in 1967, adding their expertise to other plasma groups across the country.

Don joined Lawrence Livermore National Laboratory, where he soon became head of the theory group developing the physics of magnetic mirror devices for fusion energy. In 1976 Don, with Herb Berk and Dave Baldwin, published the seminal paper explaining why the nonlinear development of plasmas subject to ion cyclotron instability always relaxed to the well-confined hot ion plasma observed in experiments. This explanation paved the way for using mirrors to “plug up” the ends of a long solenoid, known as the tandem mirror, which was the mainstay of plasma research at Livermore in the 1970s and 1980s, and is still pursued in Russia and China as well as at the University of Wisconsin. Meanwhile, the theory group Don assembled to study mirrors has made valuable contributions to the physics of tokamaks. Don’s own efforts, specifically the analysis of magnetohyrdrodynamic equilibrium, stability, and control, were applied to the international ITER project and several other fusion experiments around the world.

Born in Los Angeles, Don grew up in the Bronx and never lost his memorable accent, heard down the halls as he stood his ground in arguments with fellow New Yorker Herb. Don’s colleagues remember his receptivity to ideas and his helpful suggestions, often with deep insight. His tutelage was effective in the scientific development of younger colleagues, including Ron Cohen, Lynda Lodestro, Bill Nevins, and others.

Throughout his career, Don published important discoveries in each plasma physics area he touched. In 1966 he and Nick Krall produced pioneering work on the study of plasma rotational instability. A frequently cited work is his 1969 paper with Herb on the stability of drift waves in a sheared toroidal magnetic field. As already mentioned, Don was an active participant in research on plasma stability in mirror machines, including the key paper on ion-cyclotron modes mentioned above. Don also contributed to the unique Astron concept invented by Nick Christofilos. With Herb, in 1972 Don published a model of the current injection dynamics in Astron. The role of wall currents in Astron contributed to Don’s work with Ed Lee on electron beam propagation in air as a potential defense against missile attack.

On a personal note, Herb remembers fondly those productive arguments with Don; Dave, Don’s companionship on bike rides and the golf course; and Ken, the Fowler–Pearlstein tours of all seven continents.