Permanent Magnet Lenses

Permanent magnets have been successfully utilized to energize magnetic lens pole pieces for high resolution electron microscopy at direct magnifications of 7000 times with 30-kilovolt electrons, and 6000 times at 50 kilovolts. Stray magnetic fields, which have previously limited high magnification a...

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Bibliographic Details
Published in:Journal of applied physics 1951-01, Vol.22 (5), p.561-565
Main Author: Reisner, John H.
Format: Article
Language:English
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Summary:Permanent magnets have been successfully utilized to energize magnetic lens pole pieces for high resolution electron microscopy at direct magnifications of 7000 times with 30-kilovolt electrons, and 6000 times at 50 kilovolts. Stray magnetic fields, which have previously limited high magnification and high resolution, have been minimized by using two circuit gaps in parallel and by surrounding the assembly with a magnetic shield connected to the external pole pieces of the two gaps. Magnetomotive forces of 1400 gilberts have been obtained. A single magnet, magnets in bucking arrangement, and configurations involving magnets disposed either radially or parallel to the optical axis of the lens, have been successfully utilized. The effects of various magnetic circuit parameters on the design and operation of the lens system have been studied.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.1700006