Cyclotron Bows Out

After an energetic, merciful, and long life, the Harvard Cyclotron Laboratory will close this fall. Massachusetts General Hospital, the cyclotron's principal user these days, is completing a new facility in Boston to replace it, and the machine's useful days are done.

Harvard's first particle accelerator, built in 1937, went to Los Alamos for the Manhattan Project during World War II and never came back. Just as Harry Truman started his second term as president, the University's physics researchers--among them Edward M. Purcell, now Gade University Professor emeritus and a Nobel laureate--got a fine, new machine; they accelerated the first beam with it 50 years ago last June.

This bigger cyclotron, built with funds provided by the Office of Naval Research, had magnetic coils 14 feet in diameter. Made by General Electric in western Massachusetts, the coils came to Cambridge by rail and might have been bigger except that their size was limited by the clearance of the lowest bridge en route. The cyclotron was for a time the third largest in the country. Harvard scientists--among them another who would win a Nobel Prize, Norman Ramsey, Higgins professor of physics emeritus--undertook an assortment of medium-energy proton-nucleus and nucleon-nucleon experiments.

Built to scrutinize the basic structure of matter, Harvard's cyclotron was soon outclassed by more powerful accelerators elsewhere. Fifteen years after its opening, the laboratory changed focus and pioneered the development of charged-particle radiation therapy in the treatment of inoperable cancers, mostly of the brain and eye. Bombarding diseased tissue with strong, focused radiation, the cyclotron has treated more than 7,500 sufferers at its Oxford Street facility. In 1995, for example, 339 people got 3,400 treatments.

Short term, the vacated cyclotron building will be used as office space by the College Observatory. The structure sits at the edge of a large University parking lot, a significant hunk of open land on the Cambridge campus, and is thus choice real estate. The property is one of numerous pieces in play in a strategic physical-planning exercise now unfolding.

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