Scientist and historian Louis Brown, of the Carnegie Institution of Washington, died Saturday, September 25, as he left an afternoon performance of the opera in New York City. Dr. Brown is best known for his work in physics and geochemistry and for building instruments to explore nuclear phenomena and make isotopic measurements. He spent the majority of his scientific career at Carnegie’s Department of Terrestrial Magnetism in northwest Washington, beginning in 1961.

Despite a decade of retirement, Brown went to the laboratory every day and was in the process of building a mass analyzer to study the isotopic composition of meteorites. The author of dozens of scientific papers, he took the most pleasure from writing history. He recently completed a history about the past 100 years of science at his Carnegie department, which will be published this fall by Cambridge University Press. His work, the Radar History of World War II, Technical and Military Imperatives, published in 1999 by the Institute of Physics Publishing, was considered by historian Richard Rhodes, "a great book, of permanent value: powerful…and freighted with deep insight into science and human affairs.”

Brown was born January 7, 1929, in San Angelo, Texas. He graduated from St. Mary’s University in 1950 and joined the U.S. Army shortly thereafter. In 1952 he married his wife Lore Elisabeth Frick of Ludwigsburg, Germany. After his army tour, Brown attended the University of Texas where he received a Ph.D. in 1958. He began his career at the Department of Terrestrial Magnetism working on the Carnegie Van de Graaff accelerator project, an American-Swiss collaboration to study nuclear interactions and beams of heavy ions. For the next 15 years Brown directed a program in nuclear physics at the Carnegie Institution in collaboration with the University of Basel. This work led to his exploration of the isotopic composition of terrestrial rocks and soils, with his geochemistry colleagues, which required the design and fabrication of novel ion detectors for mass spectrometry. Brown helped develop and use the method of the accelerator mass spectrometry with members of the Tandem Laboratory of the University of Pennsylvania. He played a pivotal role in the demonstration by such methods that oceanic sediments are carried deep into the Earth at subduction zones and contribute to the magmas that erupt at volcanic island arcs. Brown also served as acting director of the Department of Terrestrial Magnetism from July 1991 through August 1992.

Brown was a Fellow of the American Physical Society and received the Amerbach Prize from the University of Basel. He is survived by his wife Lore, brother Michael, sister-in-law Teresa, and nephew Matthew, all of Washington, D.C.