A High-Vacuum Camera

A camera for use in a demountable, continuously evacuated cathode-ray oscillograph is described. It incorporates an air-lock system so that the photographic plate can be replaced without letting down the main vacuum. The volume of air to be pumped out after each change is only of the order of one-quarter litre and the whole operation is accomplished by the rotation of a single ground joint. The camera may be used equally well in an electron microscope or in an electron diffraction apparatus.