Evaluation of a LaB6cathode electron gun

Abstract
The brightness of the lanthanum hexaboride, LaB6, cathode electron gun of the Stereoscan S-4 scanning electron microscope has been evaluated. This gun is an indirectly heated Broers type of LaB6 gun design, and the several variables which affect its brightness have been evaluated using a cage device for the brightness measurements. The results indicate that when proper operating conditions are employed the LaB6 brightnesses are of the order of 15 to 20 times that of tungsten operated at 40 h life conditions, and that single crystal cathodes are more reliable for producing high brightnesses.

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