| 摘要 |
PURPOSE:To improve the focus performance by optionally selecting the set angle of core projections and the number of coil turns to make the generated two-pole magnetic field nearly the uniform magnetic field. CONSTITUTION:In a core protruded with eight rectangular projections 1 and 2 in all to the inside on a ring-shaped section at the uniform angle of theta=45 deg., coils 3 and 4 (5 and 6) are wound on the projections to generate the two-pile magnetic field 7 (8) so that one magnetic pole is formed with three core projections: a core projection 1 on the horizontal axis or the vertical axis and the core projections 2 on both sides of it. The number of coil turns of the core projections 2 arranged at the distance of the uniform angle on both sides of the core projection 1 is increased as it approaches the axis, thus the magnetic flux density on the periphery is increased, and the whole electrode is operated as an auxiliary electrode generating nearly the uniform magnetic field. The focus performance can be thereby improved. |
