Robert L. Walker
1919 – 2005

Robert L. Walker, professor of physics, emeritus, died January 4 at his home in Tesuque near Santa Fe, New Mexico, where he had lived since his retirement in 1981. He was 85.

Born June 29, 1919, in St. Louis, Walker earned his BS from the University of Chicago in 1941. While a graduate student at Cornell, he was recruited for the Manhattan Project and spent the rest of the war years at the Metallurgical Laboratory of the University of Chicago and at Los Alamos, where he built pressure gauges to measure the size of explosions. After the war, he returned to Cornell as a student of Boyce McDaniel; they invented a pair spectrometer for measuring gamma-ray energies from light nuclei. He finished his PhD in 1948 and stayed on for postdoctoral research for a year before Robert Bacher (whom he knew from Los Alamos and Cornell) lured him to Caltech, as one of Bacher’s first hires in an expanded program in high-energy physics (see page 39).

Walker’s immediate task, along with Bruce Rule and Robert Langmuir, was to build a billion-volt electron synchrotron, the design of which had been funded by the Office of Naval Research and the Atomic Energy Commission. It was housed in what was then called the Optical Shop, where the 200-inch mirror for the Hale Telescope had been ground and polished before vacating the premises for Palomar Mountain two years earlier.

Walker supervised most of the work with magnetic spectrometers at the synchrotron until the machine was shut down in 1969, as more energetic accelerators became available elsewhere. For a number of years thereafter, he continued his research at Fermilab (Fermi National Accelerator Laboratory), outside Chicago.

According to Charles Peck, professor of physics, emeritus, who earned his doctorate under Walker, his collaborative research on the synchrotron helped lay the foundation work that led to what is now known as the Standard Model of elementary particle physics. His particular work involved pion photoproduction (in which a proton or neutron is bombarded with a high-energy photon, which produces a pi meson). His research was also useful to his longtime colleague Richard Feynman in his theoretical studies of the underlying mechanisms of particles, according to Peck.

“Bob was also a superb teacher,” said Peck. For many years he taught Ph 129, “Mathematical Methods of Physics,” and Ph 125, “Quantum Mechanics.” He was reportedly the only experimentalist whom the theorists trusted to teach these courses. With Jon Mathews, he coauthored a textbook, Mathematical Methods of Physics, described in a review in the January 1965 issue of E&S as “a book that not only meets the didactic needs of the first-year graduate student, but also satisfies the practicing physicist who for some time has been hungry for a readable book on mathematical methods written for physicists by physicists.”

He was made associate professor in 1953 and professor of physics in 1959. He was executive officer for physics from 1976 to 1981.

Walker retired quite suddenly in 1981. He loaded all his belongings in a U-Haul one day, said Peck, and he and his wife, Dorothy, took off for New Mexico. Peck wrote to Walker on the occasion: “There was no question among the naïve and eager young physics graduate students of 25 years ago about who our favorite prof was. We richly enjoyed your ‘Walkerisms,’ your occasionally wildly misspelled printing on the blackboard, and especially your subsequently oft-quoted line about something being ‘well known—to those who know it well.’ I am sure that we all have carried into our careers important lessons from your classroom. I know I have.”

On the same occasion, Bacher, who noted that their paths had “run close together for nearly 40 years,” wrote: “Without you, I doubt if we would have been successful in setting up a high energy physics program at Caltech. You made major contributions at every stage from the earliest ideas of what we would do to the present. These contributions were of wide variety from the initial plans of our synchrotron, to its construction and successful use for elucidating the first nucleon resonance, and to many subsequent photonucleon experiments.” In listing Walker’s “major contributions,” Bacher wrote: “As I put them down I realize even more how impressive they are and how much we are in your debt.”

In New Mexico, Walker turned to something completely different: he built harpsichords, which have been in great demand by professional musicians throughout the Southwest. Several years ago Walker tackled a fortepiano. It took him, he wrote, about 650 hours to build and another 200 hours “to cure its deficiencies.” The “principal challenges were forming the bentside, taming the idiosyncrasies of the action, and figuring out how to convince the upper notes to make more musical sound and less clunk.

Walker’s project in the year 2000 was to build a fortepiano (an 18th-century forerunner of the modern piano). He took its design from a full-scale drawing in the Smithsonian Institution, believed to be of an instrument built about 1795 by Johan Ludewijk Dulcken. Walker’s wife, Dottie, sits at the keyboard.

“Why would anyone want to make a fortepiano? Well, it’s something different and it was fun.”

Dorothy Walker died in 2003. They are survived by their two children, Robert Craig Walker and Jan Walker Roenisch. —JD