AN IMPROVED X-RAY SHADOW PROJECTION MICROSCOPE

An apparatus for producing a point source of X-rays, less than 1 μ in diameter, is described. A tungsten hairpin filament is employed, and two magnetic electron lenses form a demagnified image of it on a metal foil which serves as both target and window. The tube is demountable; a variety of different targets has been employed (copper, silver, tungsten) for producing X-rays of different characteristic wavelength. The maximum voltage applied has been 20 kV, but simple modifications would permit 30 to 40 kV to be used. The optimum conditions of operation are briefly discussed. The tube has been constructed primarily for the projection of X-ray shadow images of small specimens.