CPC H01J 37/08 (2013.01) [H01J 37/3053 (2013.01); H01J 2237/022 (2013.01); H01J 2237/152 (2013.01)] | 27 Claims |
1. An ion gun comprising:
an anode;
a cathode opposed to the anode and having a first portion and a second portion; and
a magnet configured to form a magnetic field space between the first portion and the second portion,
wherein an annular gap including a curved portion and no linear portion is provided between the first portion and the second portion of the cathode, and
wherein the magnet is configured to form, between the first portion and the second portion of the curved portion, a magnetic field line having a bottom inside a cross-sectional centerline of the gap.
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