William D. Coolidge

William D. Coolidge was an American physicist and engineer at the General Electric research laboratory whose 1910 process for producing ductile tungsten transformed incandescent lighting. Earlier tungsten filaments were brittle and had to be pressed from powder, but Coolidge's purification and working method let tungsten be drawn into fine, flexible wire, and General Electric began marketing lamps using his ductile tungsten filament in 1911, making tungsten the far more efficient and longer-lasting filament material that incandescent lighting used for the rest of the twentieth century. He also invented the Coolidge tube in 1913, an x-ray tube with a heated cathode that became the basic design still used in x-ray equipment, and later served as director of the GE research laboratory from 1932 and a vice president of General Electric from 1940.