Electrostatic Electron-Optics

Electrostatic Electron-Optics By FRANK GRAY Certain types of electrostatic fields may be used as lenses to focus electron beams. The theory of these lenses is developed for electric fields that are symmetrical about a central axis. The introduction of two velocity functions exactly reduces the partial differential equations of electron motion to a series of ordinary differential equations. The first equation describes the action of a lens for electron paths near the axis; the remaining equations determine the higher order aberration terms. Sections on the following subjects are included: the general equations of electronoptics, thin lenses, thick lenses, aberration, the reduction of aberraration, apertured plates, and concentric tubes. A list of symbols and lens equations is also included at the end of the article.