50 µm micro focus x-ray tube for diagnostic use and its computer aided design

Geometrical enlargement radiography for observing the fine details of an object for diagnosis requires an extremely small X-ray source. Such an X-ray source in an X-ray tube must make use of a very narrow electron beam. Conventional X-ray tubes have coiled filaments for electron emitter and electro-static focusing electrodes, all of which are at the same potential. It is difficult to focus the electron beam compared with other electron guns like TWT. We have not had X-ray tubes with a focused electron beam less than 0.2 mm. We have developed the 50 µm micro-focus X-ray tube utilizing computer aided design technique to obtain electron beam trajectries. The space charge effect was taken advantage of in the design. The diameter of the coiled filament for the electron emitter is 0.56 mm and the width of the focused electron beam is approximately 50 µm.