Abstract: Roentgen lithography aparatus comprises a roentgen tube for producing long wave roentgen radiation for forming an image of a mask on a substrate. The roentgen tube comprises an electron gun having a glow cathode and a grid, electron beam deflecting and focussing coils, a target on which the electron beam is projected and an exit window through which roentgen rays from the target are projected through a lithography mask onto a substrate. The glow cathode and the target are of high atomic number high melting point material, such as tunsten. The grip has an annular flange with a central opening in which the tip of the glow cathode is disposed. The front face of the flange facing the target is frustoconical with an included angle of about 100.degree. to 140.degree. while the rear face is plane. The angle between the front and rear faces as measured in a radial plane is about 15.degree. to 60.degree.. The focussing coil focusses the electron beam into a focal spot on the target having a diameter less than 10.sup.

Abstract: In an X-ray tube having a glow cathode for emitting an electron beam, an anode, focusing and deflecting coils and a target in an evacuated envelope, the cathode is a U-bent filament the dimensions of which are large in relation to the electron emitting area. The cathode is heated by passing electric current through it and is differentially cooled so that a small surface area at the site of electron emission is at a substantially higher temperature than remaining surface areas of the cathode. Cooling is effected by a thick-walled cylindrical grid which surrounds the cathode and has at its outer end an annular inward projection which absorbs heat rays from the cathode. The grid has a funnel-shaped outer end surface having an included angle of about 100.degree. to 140.degree.. The electron emitting surface of the cathode lies approximately in a plane defined by the inner peripheral edge of the funnel-shaped end surface of the grid.