| 摘要 |
PROBLEM TO BE SOLVED: To make a round focus, using a combination of electromagnets of more than two electromagnets. SOLUTION: The energy filter 1 is constructed of four sets of the first to the fourth electromagnets 2-5, each made of a pair of electromagnet arranged into anΩshape. In order to make the energy filter 1 perform a round lens focus, each pair of magnetic pole face of all electromagnets 2, 3, 4, 5 are mutually slanted and made to generate an uneven magnetic field. Furthermore, in order to make perform the round lens focus, the angle made by the top end face of the electromagnet, when the electron beam enters the magnetic pole face and the incidence axis of the electron beam is set to be right angles or at nearly right angles. By this arrangement, the focus of the dispersing direction (X-direction) and the direction crossing the X angle at right angles (Y-direction) of the energy filter 1 almost coincides from the incidence to the exit of energy filter 1 for its round lens focus.
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