On vibration characteristics of thermal field emission electron gun filament

Thermal field emission electron gun is used as electron source in scanning electron microscope. Its filament made by tungsten wire is bended like a hairpin and is prone to vibration disturbance, therefore deteriorating outcome images. To model filament's mechanical performance under vibrating conditions, finite element modal analysis was carried out, and frequency response was calculated. It was shown that the filament was more sensitive to lateral excitation, and due to its unique structure, vibration characteristics were different in two lateral directions. Stiffness of the two lateral directions was compared through static calculation to verify the calculated mode order. Besides, characteristics between room temperature and working temperature were compared. If allowed, electron gun should be mounted in the way that its sensitive direction be kept away from the most intensive excitation's direction.