| 摘要 |
PURPOSE:To saturate magnetism in a pole piece and obtain a strong focusing magnetic field in a collector without restricting cooling process by making the thickness of the pole piece that is arranged at an end nearest to the collector thinner than that of other pole pieces. CONSTITUTION:The thickness of a pole piece 9 nearest to the first collector 10 is made thin up to approximately a half of the remaining pole piece 8 . Thus, magnetic saturation takes place in the pole piece 9 and leaked magnetism generates an intense inverse magnetic field at the inner part of the first collector 10. This intense inverse magnetic field prevents the sudden diffusion of an electron beam that flows in the collector, guides the electron beam up to the lower potential second collector 11, and improves the overall efficiency. Suppose that the thickness of the pole piece 8 is t1 and that of the pole piece 9 is t2, a condition of 0.5 t1>=t2 is required to generate magnetic saturation effectively. |
