Coolidge, William David

(1873–1975) US physicist and chemist.

Coolidge studied electrical engineering at MIT, physics at Leipzig, and chemistry on his return to MIT. With this highly suitable background he joined GEC’s research lab at Schenectady in 1905: he became its Director in 1932. In a long active career he made two outstanding innovations, both involving the high-melting metal tungsten. The first was the use of it for the filaments of electric lamps used carbon for this, but the life and efficiency of carbon filaments were both low: it was clear that tungsten should be better (m.p. 3380°C), but early attempts failed because of the brittle fragility of the wire. Coolidge found that the answer was to limit the crystallinity of the metal by precise control of manufacturing conditions, to secure it in a ductile form that could be drawn into wire through diamond dies at 550°C. Lamps using the wire cut the cost of electric light to that of gas-light by 1914, with GEC dominating the market. Before that date Coolidge had vastly improved X-ray tubes, to the level where they became routinely manageable for clinical use. In place of a cold aluminium cathode, his tubes used a hot tungsten cathode as target for the electrons from a hot filament, with a lowered gas pressure and controlled cooling. His participation in allied science linked with both World Wars and included viewing the Bikini atoll atom bomb tests in 1946.