. The electron microscope, its development, present performance and future possibilities . I \ Photographic I / / \ / \ 4. Fig. 10 fact, most of the technique of these early microscopes originated in high voltage cathode ray oscillography, and the first instru- ment of Knoll and Ruska was a slightly modified oscillograph. (For the history of this development, cf. reference 2.) In a gas discharge tube, it is almost impossible to keep the voltage varia- tion below about 1 per cent; it was therefore a very essential step when this was replaced by a high vacuum—hot cathode discharge. The magnetic
. The electron microscope, its development, present performance and future possibilities . I \ Photographic I / / \ / \ 4. Fig. 10 fact, most of the technique of these early microscopes originated in high voltage cathode ray oscillography, and the first instru- ment of Knoll and Ruska was a slightly modified oscillograph. (For the history of this development, cf. reference 2.) In a gas discharge tube, it is almost impossible to keep the voltage varia- tion below about 1 per cent; it was therefore a very essential step when this was replaced by a high vacuum—hot cathode discharge. The magnetic lenses very soon assumed a shape from which later designs have departed only in minor points. Figure 12 shows details of the design of the objective in Ruska's microscope
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