| 摘要 |
PURPOSE:To secure uniform distribution of the emitted electron and form an efficient crossover, by compensating the differential of electron current density projected on a plane crossing at right angles to the axid of the electron gun. CONSTITUTION:The means of compensating uneven density of a electron beam flux is adopted by reforming an Wehnelt electrode. As the means, for example, a new Wehnelt electrode 4' is constituted by attaching on the outer circle of the small hole 41 rotationally assymmetric projection directed toward the central area of the small hole 41 on the Wehnelt electrode, through a process of welding sticklike auxiliary electrodes or the like, and the projections of the Wehnelt cylinder 4' are arranged so as to oppose to the direction in which the density of projected electron beam is high. |
