Charles T. Zahn, 80, who retired in 1964 as a senior physicist for the National Bureau of Standards, died of cancer Thursday at the Carroll County General Hospital in Westminister, Md. He lived in Silver Spring.

Dr. Zahn joined the bureau as a senior physicist in 1946.

He was born in Westminster and earned a bachelor's degree in electrical engineering from Johns Hopkins University in 1919. He was a Proctor fellow at Princeton University and earned a doctorate in physics there in 1924.

Before joining the Bureau of Standards, Dr. Zahn was on the faculties of Princeton, the California Institute of Technology, the University of Michigan and the University of Wisconsin.

A veteran of World War I, he also served in the Army during World War II. In 1942 and 1943, he was a senior physicist and authority on minesweeping for the Department of the Navy.

Dr. Zahn gave lectures in his field and contributed more than 35 papers and articles to scientific publications here and abroad during his career.

Following his retirement, he devoted his time to research on genealogy and the history of the Pennsylvania Dutch Country.

He was divorced from Eileen Shea.

Survivors include a son, Charles T. Jr., of Scarsdale, N.Y.; a daughter, Rachel M., of New York City; a sister, Emma Frounfelter of Bradenton, Fla., and one granddaughter.