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Proceedings Paper

Fringe-field-induced 12-pole component of magnetic quadrupole lenses
Author(s): B. Pfreundtner; Hermann Wollnik
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Paper Abstract

Energetic ions or electron beams can be focused to very small diameters by the use of electrostatic or magnetic quadrupole lenses or by combinations thereof. In all cases the fringing fields cause image aberrations of third and fifth order that are many times larger than the corresponding aberrations caused by the main field. Though the 12-pole component in the fringing field only influences the fifth order image aberrations their magnitude can be relatively large. For this reason we have investigated the 3D fringing-field distribution for differently cutoff ends of the electrodes or pole faces. It can be shown that by this method the effects of the 12-pole component of the fringing field can be reduced drastically or even be adjusted to compensate corresponding effects of the main field region.

Paper Details

Date Published: 25 September 1995
PDF: 10 pages
Proc. SPIE 2522, Electron-Beam Sources and Charged-Particle Optics, (25 September 1995); doi: 10.1117/12.221590
Show Author Affiliations
B. Pfreundtner, Univ. Giessen (Germany)
Hermann Wollnik, Univ. Giessen (Germany)

Published in SPIE Proceedings Vol. 2522:
Electron-Beam Sources and Charged-Particle Optics
Eric Munro; Henry P. Freund, Editor(s)

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