The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 20, 1991
Filed:
Feb. 21, 1990
Applicant:
Inventors:
Assignee:
Nippon Telegraph and Telephone Corporation, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
H01J / ;
U.S. Cl.
CPC ...
2503 / ; 2504 / ; 3133611 ;
Abstract
In a charged particle beam generating apparatus, the emitter is so arranged that its distal end is disposed at a level below a peak of a distribution of a magnetic flux density. An inner diameter of a lower portion of a pole piece is smaller than an inner diameter of an upper portion of the pole piece. The peak of the magnetic flux density is disposed close to the lower end of the pole piece, and at the same time the magnetic field is prevented from extending downwardly beyond the lower end of the pole piece.