<Li> A: anode (+) </Li> <Li> W and W: water inlet and outlet of the cooling device </Li> <P> The Crookes tube was improved by William Coolidge in 1913 . The Coolidge tube, also called hot cathode tube, is the most widely used . It works with a very good quality vacuum (about 10 Pa, or 10 Torr). </P> <P> In the Coolidge tube, the electrons are produced by thermionic effect from a tungsten filament heated by an electric current . The filament is the cathode of the tube . The high voltage potential is between the cathode and the anode, the electrons are thus accelerated, and then hit the anode . </P>

Who invented the hot cathode x ray tube