—by Jose Alonso
Edward Joseph Lofgren passed away peacefully at the age of 102 on Sept. 6, 2016. He was among the pioneering physicists at UC Berkeley’s Radiation Laboratory, also known as the “Rad Lab,” which would later become Lawrence Berkeley National Laboratory (Berkeley Lab). He played key roles in many of the projects throughout the lab’s history. He was a close associate of E.O. Lawrence, and chief physicist for the development, construction and operation of the Bevatron, an early particle accelerator at Berkeley Lab. Before his retirement in 1979 he also served as associate laboratory director, and was the first director of the newly formed Accelerator Division.
Born Jan. 18, 1914, in Chicago, Lofgren was the youngest of seven in a family of Swedish immigrants. In 1927 he moved to Los Angeles, finishing high school there. At the depth of the depression in 1931 he was not able to accept the invitation to attend Caltech in Pasadena, Calif., because of financial limitations and the scarcity of job opportunities. He attended Los Angeles Junior College and in 1936 transferred to UC Berkeley, having read about, and becoming extremely interested in, its Radiation Laboratory and the cyclotron developments there. He arrived at Berkeley by bus with his worldly possessions: two suitcases and $200.
As an undergraduate student he developed an interest in cosmic rays and worked on a cloud-chamber spectrometer aimed at measuring meson masses. He received his undergraduate degree in 1938 and then enrolled as a graduate student. In 1940 he joined the Rad Lab’s staff as a research assistant, working on the 37-inch cyclotron. One of his activities was assisting in the development of techniques for medical isotope production.
With World War II imminent, Ernest Lawrence redirected Rad Lab activities toward development of the Calutron for electromagnetic uranium-isotope separation, focusing on the newly completed magnet for a 184-inch cyclotron.
Lofgren interrupted his graduate studies to become a full-time employee of the Rad Lab and led development of the ion sources for the Calutron. He spent much of the early war years in Oak Ridge, Tenn., assisting in the development of the Calutron farm there to enrich uranium-235 for the Manhattan Project.
In the fall of 1944 he moved to Los Alamos, joining the Alvarez group working on detonators for the atomic bomb. He assumed leadership of this group when Alvarez moved to a different area. Lofgren was present at the Trinity atomic bomb test in New Mexico, manning a radiation-monitoring station six miles from ground zero.
After the war he returned to Berkeley and wrote his PhD thesis on his uranium hexafluoride ion source work. He received his PhD degree in June 1946.
Proving out a concept introduced by lab physicist Ed McMillan called “phase stability” for particle beams in circular accelerators, Lofgren modified the design of the 37-inch cyclotron, which became the first “synchrocyclotron.” This concept was also incorporated into the 184-inch, whose performance then far exceeded the original design.
In the summer of 1946 Lofgren took a position at the University of Minnesota because of its very strong program in cosmic rays, an interest he continued to nurture. During his two-year tenure there he participated in several high-altitude balloon flights, developing compact, lightweight cloud chambers that could fit in the balloon payload. Noteworthy was the observation of heavy nuclei (up to about the weight of iron) in cosmic rays, which hadn’t been seen before.
At Lawrence’s invitation, Lofgren returned to the Rad Lab in 1949 to participate in the development of the Bevatron project. Because of its enormous scale and complex design, Lawrence felt it important to first build a scale model of the proposed Bevatron synchrotron. Lofgren’s main task, initially, was the design and build-out of the injector for the quarter-scale synchrotron. He rapidly built a pulsed cyclotron that produced the required 20 microamps of current, and the scale model was a success.
In late 1949, much of the Rad Lab’s efforts focused on the MTA project, a very large, high-current linear accelerator being built at Livermore (now Lawrence Livermore National Laboratory), with the aim of breeding fissionable fuel. Lofgren was dedicated to development of the ion sources for this project, though the project was abandoned in 1952 with the discovery of plentiful uranium sources in Colorado.
Lofgren then returned to lead the lab’s Bevatron project. Analyzing results of the scale-model test, and along with those from the newly commissioned Cosmotron accelerator at the Brookhaven National Lab, the team found a way to boost the energy of the Bevatron to 6 billion electronvolts—well above the threshold for production of antiprotons, the antiparticles of protons. This made the Bevatron the world’s highest-energy accelerator at that time.
In September 1954, seven months after the commissioning of the Bevatron, the successful antiproton discovery experiment was completed by the Owen Chamberlain-Emilio Segrè group.
Lofgren was instrumental in the Bevatron’s commissioning and in setting its experimental program. He also headed his own research group that had worked to discover the antiproton. While losing that race to the Chamberlain-Segrè group, members of Lofgren’s group were successful in discovering the antineutron in 1956.
By 1960 the Bevatron had been surpassed by other newer accelerators and Lofgren initiated a campaign to modernize the Bevatron. This included the addition of a new injector for higher currents, an extraction system to bring beam out of the machine into an experimental hall, and new shielding around the whole machine. The upgrades were completed in 1963, giving the Bevatron a new lease on life. In the mid-’60s he oversaw an Atomic Energy Commission design study for an even more powerful, 200 billion-electronvolt accelerator.
Lofgren came to the rescue of the Bevatron again in 1970 by spearheading, with Herman Grunder, it conversion into a high-energy heavy-ion accelerator known as the Bevalac. This was done by implementing the idea of Berkeley Lab nuclear scientist Albert Ghiorso to connect a lab accelerator called the SuperHILAC to the Bevatron by means of a quarter-mile transfer line. This and other upgrades allowed the Bevatron to accelerate ions of any atomic species to very high energies, and enabled programs in relativistic heavy-ion nuclear physics, Earth-based heavy-cosmic-ray studies, and cancer treatments for deep tumors.
In 1973, Lofgren was appointed as the first director for the lab’s Accelerator Division, and was named as a lab associate director. During his tenure and until his retirement in 1979, Lofgren oversaw development of the PEP project at SLAC, two studies for dedicated medical synchrotrons, development of a compact superconducting ring (ESCAR), and initiation of studies towards inertial confinement fusion with heavy-ion beams as drivers.
Lofgren’s long, prolific and inspiring career has been truly noteworthy and contributed immensely to the evolution of accelerators as important research tools.
He is preceded in death by Lenore Lofgren, his first wife and the mother of his three children; and Selma Lofgren, his second wife. Lofgren is survived by his three daughters: Helen Lofgren, Laurel Phillipson, and Claire Lofgren; four grandchildren; and two great-grandchildren.
Memorial donations can be made to two groups that Lofgren supported for many decades because of his passionate concern for the environment: Save the Bay (savesfbay.org) and Save the Redwoods League (savetheredwoods.org).
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