Obituary of Arthur Hemmendinger (1912-2012)

Arthur Hemmendinger, known best for measuring neutron-capture cross-sections, died on June 17, 2012, at the Good Shepherd Hospice House in Manhattan, KS. Born on July 11, 1912, in Bernardsville, NJ, he spend much of his boyhood building radios in his family’s basement as he recovered from polio that affected his leg. Arthur graduated from Cornell University and then earned a PhD in physics at the California Institute of Technology (Cal Tech). After spending four years as an Assistant Professor of Physics at the University of Oklahoma, he worked as a civilian for the US Naval Ordinance Laboratory (NOL) developing sonar detection equipment. In 1945 he joined the Manhattan Project, working briefly in the Metallurgical Laboratory at the University of Chicago. From there he was sent with his new wife Margaret (Peggy) to the laboratory directed by J. Robert Oppenheimer in Los Alamos, NM. After World War II, and until his retirement in 1977, Arthur remained in Los Alamos as it became a permanent National Laboratory (LANL).

As a graduate student at Cal Tech, Arthur measured the abundance of the naturally occurring radioactive isotope, ⁴⁰K, using a mass spectrometer. Later for NOL, he often lived on a barge anchored in the Chesapeake Bay. There helped develop sonar detonators for underwater mines and torpedoes, as well as a device that was used successfully to save many seamen’s lives by detonating torpedoes fired from German U boats before they reached targeted American naval transport ships in the North Atlantic. Arriving at Los Alamos several months before the nuclear weapons detonations over Hiroshima and Nagasaki, Japan, Arthur helped to design and build test equipment that was sent to the Pacific island of Tinian in support of those attacks that ended World War II. During the next three decades, his work focused on neutron cross-section measurements made using proton beams from particle accelerators, and later from time of flight experiments that used underground nuclear explosions as a neutron source.

Arthur once reminisced that when he joined the Manhattan Project in Chicago, “I really didn’t know just what it was all about, but I had an idea that it was something new and scientifically very exciting. I did this not so much out of patriotism, for it was obvious that I would be supporting the war effort by working in a laboratory somewhere, but out of sheer scientific curiosity. For similar reasons I stayed at Los Alamos after the war. I grew up as a physicist in the sealing wax and string era when money for equipment was really very scarce. The prospect of working with what then must have been the best equipment in the world, and with virtually unlimited funds, was to me irresistible.”

During their 24 years in Los Alamos, Art and Peggy raised three children. Art was active in the local ski club, and he served as the Los Alamos Democratic County Chairman. From 1969 to 2007 Art and Peggy lived in Santa Fe, NM, where Art enjoyed skiing, playing tennis and bridge, and repairing tape recorders for the blind at the State library. In 2007, they moved to Meadowlark Hills retirement community in Manhattan, KS, where Peggy died six weeks later. There until recently, Art played bridge at the Manhattan Senior Center, read numerous journals, and shot occasional games of pool at the Meadowlark billiard table.