Production of evaporated tungsten foils on resistively heated substrates

Pure natural tungsten (W) circular mounted foils with an unsupported diameter of 20 mm, thickness of 100–300 nm, and as flat and smooth as possible were needed. Vacuum evaporation was used as the method of production. Copper-coated Ta, Mo and mica strips were heated to the necessary high temperatures by passing current directly through them and used as removable substrates for W foils. Characteristics of this method of production are described.