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William David Coolidge (1873-1975), US physicist, engineer and inventor, holding an early portable X-ray tube. Coolidge obtained his doctorate in physics in 1899. He taught physical chemistry until 1905, and then joined the General Electric Company (GEC). It was there, in 1908, that he discovered how to make tungsten ductile, greatly increasing the life of the tungsten filaments in electric light bulbs. In 1916, he improved X-ray tubes by replacing the cold aluminium cathode with a hot tungsten cathode. He also helped to develop the first submarine detection system. In 1940, he became Director of Research at GEC. Photographed circa 1918.
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