Improvements relating to Electron Guns

摘要

1,196,103. Automatic temperature control systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. March 26, 1969 [Feb. 2, 1968], No. 5481/68. Heading G3R. An electron beam apparatus has a photosensitive device PD sensitive to light from a filament F reflected at M through a lens L, which device controls the filament current to maintain the filament temperature constant. The device may respond to a wide or a limited range of frequencies such as visible or infrared radiation. Preferably the light from the filament is restricted e.g. by an apertured screen S so that only light from tip region is incident on the device. The reflector M should be located below the anode in a free field space. The apparatus may be an electron microscope.