A low energy micro-focus transmission x-ray source

摘要

A transmission target 13 of an X-ray tube 11 is operable to have a ground potential and an electro-optical system 19 is floated at a positive potential in a vacuum chamber 12. An electron beam 16, which is converged by means of the electro-optical system 19, is decelerated immediately before the electron beam is incident on the transmission target 13. The electron beam 16 has energy that is several times of the final set value until the electron beam passes through the electro-optical system, and a divergence action exerted by a spatial electric charge effect is reduced. Colour aberration of the electro-optical system is proportional to energy of the electron beam; thus, if the electron beam is decelerated after it has passed through the electro-optical system, aberration is reduced in proportion to the degree of deceleration, making it possible to concurrently reduce a focus size to microscopic dimensions.