| 摘要 |
<p>The influence of the aberration of the optical system is suppressed, the shot noise of a multiemitter is reduced, and the Wehnelt electrode is simply and precisely aligned. Primary electron beams produced by irradiating a first aperture plate (204) are directed to a sample (209). Secondary electrons emitted from the sample are separated from a primary optical system and received by sensing means (215). A second aperture plate (214) is disposed in front of the sensing means to prevent entrance of secondary electrons of different groups. In another working example, the multiemitter hot-cathode is fabricated by mirror-finishing a work for the multiemitter hot-cathode and machining the work by electrical discharge. In further another working example, the position of the Wehnelt electrode is finely adjusted with respect to the multiemitter by a screw thread.</p> |
