Joel Fajans next to the ALPHA antihydrogen experiment, circa 2008
Professor Joel Fajans, distinguished plasma physicist, celebrated researcher, and devoted mentor at the University of California, Berkeley, passed away on November 17 at the age of 66, after a battle with cancer. Joel was internationally renowned for his pioneering contributions to nonneutral plasma physics and antimatter research. He was locally famous for his challenging but rewarding Physics 111A Instrumentation Laboratory course, as well as for his expertise in the classical mechanics of bicycles.
Joel Fajans was born on March 29, 1958, in Queens, New York City, to Jack and Eleanor Fajans. Jack was a physics professor at Stevens Institute of Technology. Joel’s early years were shaped by his experiences living with his family in Afghanistan from 1963 to 1965 and again from 1967 to 1969, where he attended the American International School in Kabul. Returning to the United States, Joel found his calling as a scientist. He won 6th place in the prestigious Westinghouse Science Talent Search in 1976 for his project, "Graphics Station for a Data General Nova Microcomputer," an early foray into computer display technology. He graduated as valedictorian of Teaneck High School in 1976.
Joel applied to only one university—MIT—and was accepted. There, he earned his B.S. in Physics in 1980, followed by a Ph.D. in 1985, under the guidance of George Bekefi, supported by a prestigious Hertz Fellowship. His doctoral dissertation, "Radiation Measurements of an Intermediate Energy Free Electron Laser," focused on the fundamental physics of interacting electrons and microwave radiation in FEL devices. It earned both the inaugural American Physical Society Simon Ramo Thesis Prize and the Hertz Foundation Thesis Prize. While still at MIT, he began a decades-long collaboration with his future Berkeley colleague Jonathan Wurtele.
Joel Fajans with long-time scientific collaborator Jonathan Wurtele
Following his doctorate, Joel shifted research emphases and took a postdoctoral position at UC San Diego, working with John Malmberg on nonneutral plasmas. The UCSD group’s emphasis on innovative and precise experiments, as well as their exploration of new parameter regimes to rigorously test plasma theory, proved an ideal match for Joel’s talents and interests. In 1988, he brought this same spirit of experimental rigor and creativity to the UC Berkeley Physics Department, where he continued a prolific career as a faculty member. Over the next decades, Joel made numerous significant contributions to the field of nonneutral plasma physics, cementing his reputation as a leader in the discipline, while training a generation of graduate students. His physics insights and experimental instincts enhanced our understanding of nonlinear plasma stability, autoresonant plasma control, and diagnostics.
His understanding of magnetically trapped nonneutral plasmas led to Joel becoming a founding member of the Antihydrogen Laser Physics Apparatus (ALPHA) collaboration at CERN. His work played a pivotal role in the successful generation, confinement, cooling, and measurement of neutral antihydrogen atoms. With invaluable guidance from Joel, the ALPHA group became a nexus of innovative instrumentation, ground-breaking fundamental physics research, and multidisciplinary physics training and education. He greatly valued interacting with undergraduate researchers, as he guided over two dozen students through transformative summer projects at CERN.
Always enjoying working closely with graduate students and postdocs, Joel contributed decisively to the success of ALPHA’s experimental program. Examples include the early and critical decision to use an octupole rather that a quadrupole magnetic confinement scheme, improved plasma temperature diagnostics, novel techniques leading to enhanced plasma reproducibility, and plasma-based magnetic field measurements. These plasma advances were key achievements that enabled controlled production and trapping of neutral antihydrogen and opened the door to the studies of the fundamental symmetries of matter and antimatter.
Joel at the ALPHA experiment at CERN
Beyond his leadership of the plasma trapping and manipulation work at ALPHA, Joel was deeply involved in the ALPHA physics program, including tests of the weak equivalence principle, charge neutrality, and optical and microwave spectroscopy. Joel was especially proud of the conceptualization and design of ALPHA’s apparatus that resulted in pioneering measurements of the force of Earth’s gravity on antihydrogen.
Joel’s work was widely recognized with numerous honors, including the NSF Presidential Young Investigator Award, the ONR Young Investigator Award, and a Sloan Fellowship. He was a Fellow of the American Physical Society and led the plasma-physics team that was awarded the John Dawson Prize for Excellence in Plasma Physics Research.
Joel found time to become an early convert to household photovoltaic power, as well as an expert witness on the physics of electrical power transmission, testifying in legal cases with multibillion dollar implications for utility regulation in North America. Outside of his devotions to physics and family, Joel was an avid cyclist. He rode several thousand miles each year, enjoying the varied terrain in the Berkeley hills and greater Bay Area, and in the Jura mountains near CERN. Often, he would invite students or colleagues, most of whom would struggle to keep up.
Professor Fajans is survived by his wife, Karen, children, Rose and Abe, and sister, Anita. He will be remembered with fondness and admiration by his many colleagues, friends, and former students. A memorial service will be held at a future date, celebrating his life and profound contributions to science.
Joel was passionate about his Physics 111A course and can be seen soldering components for kits that were shipped out to students during the COVID pandemic