| 摘要 |
PURPOSE:To prevent a life of an emitter from being shortened due to electron beam radiation by forming an exhaustion port on a side part of a drawing electrode and setting respective prescribed values of the following parameters: a distance from a tip of the emitter to the drawing electrode, and a diameter of an opening for electron beam drawing. CONSTITUTION:An exhaustion port 4b is formed on a side part of a drawing electrode 4, and an acceleration electrode 8 is additionally disposed between the electrode 4 and an acceleration electrode 6, and a potential intermediate between the potential at an emitter 3 and that at the electrode 6 is applied to the electrode 8. A distance from the emitter 3 to the electrode 4, a distance from the emitter 3 to the electrode 6 or 8, and a diameter of an opening 4a for electron beam drawing in the electrode 4 are made to be l, L, and d, respectively, where d=8mm to 14mm, and l=4mm to 10mm. Hence, a large amount of gaseous molecules, which are generated at the acceleration electrode by impingement of electron beams radiated from the emitter 3, can be prevented from advancing to the emitter through the opening of the drawing electrode.
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