Kenneth T. Bainbridge, Leverett Professor of Physics Emeritus and director of the first atomic bomb test, died July 14 in his Lexington home. He was 91.

In 1943 he was recruited by J. Robert Oppenheimer to work on the Manhattan Project at Los Alamos, N.M. In July 1945 he oversaw the first test of an atomic bomb -- Project Trinity.

Bainbridge was aware of the dangers of his discoveries and after World War II he actively opposed nuclear testing, and was one member of a group of scientists who lobbied President Harry S. Truman to pledge that the United States would not be the first nation to use a hydrogen bomb. He also joined the Federation of Atomic Scientists, which opposed nuclear weapons and the arms race.

Physicist Bainbridge was also noted for his work in measuring the masses of atomic nuclei. He designed and built spectrometers that measured mass with extreme accuracy.

Born in Cooperstown, N.Y., on July 27, 1904, he received his bachelor's and master's degrees from the Massachusetts Institute of Technology (M.I.T.) and his doctorate from Princeton University.

Bainbridge was a 1933 Guggenheim Fellow at Cavendish Laboratory in Cambridge, England. In 1934, he was invited to come to Harvard. Here, he designed and aided in the construction of two important cyclotrons.

Bainbridge was a member of the American Academy of Arts and Sciences and the National Academy of Sciences. He received the Presidential Certificate of Merit (1948) for his work at the M.I.T. Radiation Laboratory.

Bainbridge leaves two daughters, Joan Bainbridge Safford of Evanston, Ill., and Margaret Bainbridge Robinson of Cleveland Heights, Ohio; and five grandchildren.

A memorial service will be held at the University at a later date.