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Coolidge tube, United States, 1920

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American physicist William Coolidge (1832-1919) patented his ‘hot cathode’ tube in 1913. The cathode was a heated, electron-emitting tungsten filament. It produced a high output of X-rays that did not fluctuate and were easily adjusted. This eliminated many problems of the older so-called ‘gas tubes’. Combined with more reliable power supplies, it allowed X-ray techniques to become standardised and reproducible. The fins at the end of the tube disperse the heat generated in the tungsten anode which the larger currents use.

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    Techniques and Technologies:


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    The scientific study of X-rays and other high energy radiation, especially as used in medicine.

    Glossary: x-ray tube

    The part of an X-ray machine that produces X-rays. The tube itself operates under vacuum conditions.

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