Tungsten filamentsIn 1913, Dr William David Coolidge patented (U.S. No. 1,082,933) a method for making ductile tunsten for the purpose of making filaments for electric lamps. When Coolidge joined the General Electric Research Laboratory (1905), he was given the task of replacing the fragile carbon filaments in electric light bulbs with tungsten filaments, although tungsten was difficult to work. He developed a way to superheat the metal tunsten in order to draw it out into the fine threads used for lamp filaments. Coolidge then improved the X-ray tube by using a heated tungsten filament cathode in vacuum producing electrons, instead of residual gas molecules in the tube. This permitted higher operating voltages, higher energy X rays and the treatment of deeper-seated tumors. |
