Joseph W. Motz

Joseph W. Motz, a physicist who retired from NIST in 1988, died 26 April 2020 in his home in Gaithersburg, Maryland at the age of 102. He died of natural causes according to his son Jay Motz. Joe was born and raised in Binghamton, New York, and received his BS degree in physics from the University of Wisconsin in 1941. He received his MS in physics from Cornell University in 1942 with a thesis on hysteresis loss of high polymers. During World War II, Joe worked at the US Army Signal Corps Radar Laboratory in New Jersey (1942–1943) and at the Armour Research Corporation in Illinois (1943–1946). After the war, Joe obtained his PhD in physics in 1949 from Purdue University in Indiana with a thesis on low-energy beta-ray spectra.

Joe was recruited to National Bureau of Standards (NBS) by Lauriston Taylor in 1949 and assigned to the Nuclear Instrumentation Section in the Atomic and Radiation Physics Division, where he worked on nuclear instrumentation with his longtime colleague Louis Costrell. Taylor soon had significant funding from the Department of Defense and the Atomic Energy Commission (AEC) and assigned Joe and Costrell to assist in mapping the gamma-ray dose rates from atomic tests. Joe participated in part of that classified work at the Eniwetok Atoll in the Marshall Islands.

Joe’s research with H. William (Bill) Koch led to an experimental and theoretical analysis of bremsstrahlung production in high-energy accelerators. Their landmark 1959 Reviews of Modern Physics paper, “Bremsstrahlung Cross-section Formulas and Related Data,” and the related 1969 Reviews of Modern Physics paper, “Pair Production by Photons” by Motz, Olsen, and Koch, are widely cited as landmarks in midcentury radiation physics. In 1964 Joe was promoted to Chief of the Radiological Physics Branch, which included x-ray physics, radiation dosimetry, and x-ray standards. After the NBS move to Gaithersburg, he was promoted in 1970 to Chief of the Applied Radiation Division in the Center for Radiation Research. Joe used his collaborations with the AEC and the DOD to bring other agency funds to NBS to construct several high-energy x-ray sets and particle accelerators in the Radiation Physics Building in Gaithersburg between 1965 and 1987.

Later in his career Joe turned his attention to applied radiation physics using the new accelerators and x-ray sources along with his partners in radiation theory, Michael Danos and Stephen Seltzer, and his collaborators, including Charles Dick, Julian Sparrow, Robert Placious, and Daniel Polansky. Their experimental work led to databases on electron and photon interactions with matter. The pulsed electron accelerators in Joe’s group were used for defense-related projects and for radiation-chemistry research by guest researchers, including Mohamad Al Shiekhly from the University of Maryland and Pedatsur Neta and Robert Huie from the NBS Center for Chemical Physics.

Joe’s research interests included experimental investigations of the elementary process of bremsstrahlung production, interaction of electrons and protons with matter in the energy range from 0.05 MeV to 4 MeV, and design of components and systems for x-ray inspection for medical and industrial applications. After retiring from NIST, Joe was the founder of Rayex Corporation in Gaithersburg. With Michael Danos, he continued work to develop x-ray sources and detection systems for industry and federal agency use in medical imaging and industrial radiography. Many of his innovative ideas on x-ray systems design have been incorporated in the current high-throughput scanners in use in airports around the world.

Joe was elected a fellow of the American Physical Society in 1958. He was awarded the Department of Commerce Silver Medal in 1959 for pre-eminence in the determination of x-ray production cross sections and x-ray polarization and for accomplishments resulting in national and international leadership of NBS in the field.

Joe loved music of all kinds and played several instruments, as evidenced by the baby grand piano he kept until his death. He enjoyed travel, culture, international folk and contra dancing, crisp Cortland apples, family reunions, and deep conversations. Despite his extraordinary intellect and considerable accomplishments, Joe was a humble man with a gentle, soft-spoken demeanor. He is remembered by his many colleagues at NIST for his friendship and support as well as for his legacy of work in applied x-ray physics.