| 摘要 |
PURPOSE:To keep the error in measuring the electron beam diameter constant by providing a movable holder above an aperture, attaching a knife edge to the movable holder, and previously adjusting the distance between the top end of the knife edge and the inner end of the aperture to a given value. CONSTITUTION:A distance l between a nonmagnetic thin wire 5 and the inner end of an aperture 3 is measured, and a voltage is applied to a piezoelectric transducer 8 to adjust the position of a holding plate 7 so that the distance l is equal to a given value. Performing measurement with the distance l kept constant permits an angle theta made by the path of a beam component 4'' reflected by the nonmagnetic thin wire 5 and the optical axis of the beam to be constant at all times, so that a constant relation is established between the real value of the electron beam diameter and the measuring result, and therefore excellent reproducibility can be obtained.
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