| 摘要 |
PURPOSE:To make an electro-optical body tube smaller in size as well as to facilitate adjustment of an electron beam by locating part of or whole alignment coils for electron beam projectors closer to the cathode than to the anode of the electron gun. CONSTITUTION:Electrons emitted from the electron gun 1 which consists of the quad electrode 1a, Wehnelt cylinder 1b, and anode 1c made of lanthanumhexaboride are converged by a condenser 3 through the alignment coils for condenser 2. The converged beam shoots through a beam shaping aperture 4 for shaping the beam and irradiates a specimen 9 by means of the objective lens 8 through the blanking deflection unit 5, alignment coils for objective lens 6, and scanning deflection unit 7. In such a setup, the alignment coils for condenser 2 are positioned closer to the cathode 1a than to the anode 1c so as to make the distance a between the anode 1c and the beam shaping aperture 4 small enough within the limit of a require distance. |
