ELECTRON GUN, ELECTRON OPTICAL SYSTEM, AND ELECTRON BEAM DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an electron gun capable of adjusting both the position and diameter of a cross-over to the desired values. SOLUTION: A primary electron beam 28 emitted by a cathode 1 is released in widening, but constricted near between a Wehnelt 2 and first anode 3 under influence of a negative suppression voltage impressed on the Wehnelt 2 so that a first cross-over 29 is formed. The electron beam 28 is again constricted by regulating the voltages of a second anode 4 and a third anode 5 so that a second cross-over 30 is formed, which is located at the position of a gun aperture 6, and also it is possible to adjust the size of the second cross-over 30.