Boyce Dawkins “Mac” McDaniel died from cardiac arrest on 8 May 2002 at his home in Ithaca, New York. For more than half a century, Mac played a leading role in the birth, development, and mature phases of accelerators and experimental particle physics. Throughout his career, his time was seamlessly divided—often on a daily basis—among administration, accelerator physics, instrumentation, and particle physics.
Mac was born on 11 July 1917 in Brevard, North Carolina. He graduated from Ohio Wesleyan University with a BA in 1938. Two years later, he received his MA in physics under Eugene Crittenden at the Case School of Applied Science (now Case Western Reserve University) in Cleveland, Ohio. He then entered a PhD program at Cornell University. There, as a student of Robert Bacher from 1940 to 1943, he built a multichannel, high-resolution time-of-flight energy spectrometer, which he used to carry out precision measurements of the energy levels of indium for his thesis. Following the completion of his PhD, Mac accepted a postdoctoral position at MIT, where he learned to apply techniques of the rapidly evolving field of fast electronics to particle physics research.
Alter only a lew months in Cambridge, Massachusetts, Mac was recruited by telephone to join a secret government project. Without any knowledge of its nature and location, Mac abruptly pulled up stakes and joined the Manhattan Project in Los Alamos, New Mexico, where there was a pressing need for accurate measurements of neutron cross sections. Using the neutron spectrometer he had developed for his PhD thesis, Mac led the Los Alamos research team that soon discovered and made accurate measurements of fission induced by the resonant absorption of epithermal neutrons in uranium and plutonium. That work was an important contribution to the design of the first nuclear bombs. Subsequently transferred to a group set up to assemble the bomb, Mac played a key role in the test of the first plutonium bomb near Alamogordo, New Mexico.
After World War II, Mac returned to Cornell to take charge of the 2-MeV proton cyclotron built by Stanley Livingston before the war. Mac studied the energy levels of light nuclei by measuring the gamma-ray spectra emitted from elements bombarded by protons. To do so, he needed to measure the gamma-ray energies more accurately than was possible with existing detectors. In his characteristic style, Mac, together with Robert Walker, invented the pair spectrometer in 1948; for many years, it was the best available instrument for measuring gamma-ray energies.
Mac was instrumental in establishing, in 1946, the Cornell Laboratory of Nuclear Studies (CLNS), and played a leading role in designing and building the 300-MeV electron synchrotron that, on its completion in 1949, was one of the first such accelerators in the world. Over the next 20 years, Mac and his colleagues, in a group led by Robert Rathbun Wilson (see Physics Today, April 2000, page 82), built three more electron synchrotrons of successively higher energies, each of which enabled physicists to study phenomena in a new energy range. Each accelerator was a masterpiece of technology, built rapidly and economically by a small team of physicists. Mac was key to the construction of each machine and brilliantly completed the construction of the last one: the 10-GeV synchrotron.
After a decade as the associate director of the CLNS, Mac became its director in 1967, and remained in that position until he retired from the Cornell faculty in 1985. In addition to his administrative responsibilities, he continued an active research program. He pioneered the technique of tagged gamma rays and performed important measurements with each of the accelerators, including work in K meson and λ meson photoproduction, and neutron electromagnetic form factors.
In 1972, Mac took a one-year leave from Cornell to serve as acting head of the accelerator section at Fermilab. Although the accelerator had operated at a near-design energy, frequent component failure and intermittent operation made it a difficult time for both the lab and the particle physics community. Mac threw himself into the fray with his usual enthusiasm. Thanks to his leadership, by the end of the year the accelerator was working as it should. According to Wilson, who directed Fermilab at the time, “this bravura performance demonstrated Mac’s skill for leadership as well as his celebrated sixth sense for finding sources of trouble and fixing them.”
In November 1974, Mac sensed that the discovery of the J/Ψ, the first charmonium meson, signaled an abrupt change in the frontier of particle physics research. With a bold stroke, he convinced his colleagues to abandon their program of electron synchrotrons of ever-increasing energy and instead upgrade the existing 10-GeV synchrotron into an 8-GeV electron-positron collider using the synchrotron as an injector and adding a storage ring in the same tunnel. That radical and risky proposal, if it worked, would significantly reduce the cost and construction time and make its funding possible. Mac convinced NSF to support the project and threw himself heart and soul into the job of making it work. The gamble succeeded, and the rich treasure trove of 25 years of b-quark physics that it uncovered was the ultimate reward for the daring, innovative, and low-cost style of physics practiced by Mac, Wilson, and their Cornell colleagues.
After his retirement in 1985, Mac remained active at CLNS and played important roles in both the Cornell Electron Storage Ring and the CLEO collaboration. In addition, he served on many advisory and visiting committees for NSF and the US Department of Energy. He was a trustee of the Associated Universities (1963–75) and Universities Research Association (1971–77); a member of the DOE’s High Energy Advisory Panel (1975–78); and a member of the Superconducting Supercollider Board of Overseers (1984–91), which he chaired for part of this period. He was elected to the National Academy of Sciences in 1981. His modesty, integrity, and sound judgment, and his passion for life, physics, and making things work were widely recognized and admired by the scientific community.
