| US 7,582,885 B2 | ||
| Charged particle beam apparatus | ||
| Souichi Katagiri, Kodaira (Japan); Takashi Ohshima, Higashimurayama (Japan); Toshihide Agemura, Hitachinaka (Japan); Mitsugu Sato, Hitachinaka (Japan); and Takashi Furukawa, Sagamihara (Japan) | ||
| Assigned to Hitachi High-Technologies Corp., Tokyo (Japan) | ||
| Filed on Apr. 12, 2006, as Appl. No. 11/401,878. | ||
| Claims priority of application No. 2005-115233 (JP), filed on Apr. 13, 2005. | ||
| Prior Publication US 2006/0231773 A1, Oct. 19, 2006 | ||
| Int. Cl. H01J 1/50 (2006.01) | ||
| U.S. Cl. 250—492.3 [250/396 ML; 313/153] | 5 Claims |
| 1. A magnetic-field-superposed electron gun comprising:
a differential pumping system comprising two or more vacuum chambers coupled together via an aperture;
a nonevaporative getter pump on an upstream side;
an ion pump in any of the vacuum chambers on a downstream;
an electron source on a most upstream vacuum chamber;
a permanent magnet in the proximity of the electron source,
wherein the permanent magnet is positioned as a center axis; and
at least two different magnetic poles at axisymmetric positions with respect to the electron source as the center axis.
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