Electron gun with large aperture auxiliary electrode

摘要

An electron gun for producing and directing at least one electron beam along a beam path comprises a beam forming section and a main lens section for focusing the electron beam. The main lens section includes first and second electrodes arranged along the beam path and having an aperture through which the electron beam is passed, and at least one auxiliary electrode which is located between the first and second electrodes, the auxiliary electrode having an aperture through which the electron beam is passed. The aperture of the auxiliary electrode is greater than each of the apertures of the first and second electrodes. Different voltages are applied to the first and second electrodes, and the auxiliary electrode is supplied with a middle voltage intermediate between the two voltages applied to the first and second electrodes.