JEM 100 CX, Description of the apertures.

Todo : More pictures of the fourth aperture. Links to adjustment procedure Overview : The apertures consists of thin metal foils with holes that are used for screening off parts of the electron beam that isn't used or wanted. They also assists in creating dark view imaging and diffraction patterns. The apertures in the column from top to bottom. Condensor lens aperture Objective lens aperture Field limiting aperture Subsidiary field limiting aperture Condensor lens aperture The condensor lens aperture is used for adjusting the illumination beam intensity and profile. Knob setting Aperture diameter (um) Purpose 0 Retracted Alignment 1 400 High beam current work. 2 300 Normal observation. 3 200 High resolution work and beam sensitive specimens. 4 20 Micro beam diffraction work. The aperture assembly The aperture holes Objective lens aperture The objective lens aperture is used for setting the contrast. Knob setting Aperture diameter (um) Purpose 0 Retracted Alignment 1 120 High contrast specimen or wide field observations. 2 60 Normal observation. 3 40 Low contrast specimens. 4 20 High contrast specimen or uneven specimens. The aperture assembly The aperture holes Field limiting aperture The field limiting aperture is used for selected area diffraction observations. Knob setting Aperture diameter (um) Purpose 0 Retracted Alignment and normal microscopy. 1 1000 Diffraction work, depends on area selected. 2 250 Diffraction work, depends on area selected. 3 80 Diffraction work, depends on area selected. 4 20 Diffraction work, depends on area selected. The aperture assembly The aperture holes Subsidiary field limiting aperture. The subsidiary field limiting aperture is used with the field limiting aperture for selected area diffraction observations. Knob setting Aperture diameter (mm) Purpose out Retracted Alignment and normal microscopy. in 3 Diffraction work???