| 摘要 |
PURPOSE:To make it possible to adjust the electron beam current density distribution form, by furnishing a cathode, a Wehnelt electrode, the second anode, and the first anode at the middle area between the cathode and the second anode. CONSTITUTION:Linear electron beams 4 injected from an electron gun which consists of a linear cathode 1, a Wehnelt electrode 2, and the first anode 21 in a mirror cylinder 7, are given a specific speed by the second anode 22, and then projected over a sample 11 through an electron lens 5. The electron permeable holes of the Wehnelt electrode 2 and the first anode 21 (not shown in the figure) are made rectangular, and the electron beams 4 radiated from the rectangular electron discharge surface of the cathode 1 are focused strongly to the shorter side direction. And it is made in an unrotating symmetry electric field distribution suitable to form a linear beam section. Therefore, the potential and the position of the first anode 21 can be converted while the atmospheres of the electrodes are kept vacuum. Consequently, the electron beam current density distribution form can be adjusted even though the beam current value is varied in a broad scope.
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