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Proceedings Paper

Improvements to the electrostatic lens optimization method SOEM
Author(s): Jim Edmond Barth; H. W. G. van der Steen; Jaroslav Chmelik
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Paper Abstract

Lens optimization can be based on the very fast approximate axial potential calculation of the Second Order Electrode Method (SOEM). In this method the free optimization parameters are the physical quantities of an electrostatic lens system. The optimization, to a merit function based on the optical properties of the lens, is within engineering constraints such as the maximum off-axis field between electrodes. Several improvements to the method have been brought into the program SOEM extending the class of electrostatic lenses that can be optimized. The off-axis geometrical aberrations and the chromatic magnification error can now be included in the merit function. The first and last electrodes can intersect the axis, thus allowing non-field-free spaces at the ends of the lens. Electrode parameters (radii/length/gaps/potential) can be required to be equal giving greater control over the lens configuration freedom in the optimization process.

Paper Details

Date Published: 25 September 1995
PDF: 10 pages
Proc. SPIE 2522, Electron-Beam Sources and Charged-Particle Optics, (25 September 1995); doi: 10.1117/12.221569
Show Author Affiliations
Jim Edmond Barth, Delft Univ. of Technology (Netherlands)
H. W. G. van der Steen, Delft Univ. of Technology (Netherlands)
Jaroslav Chmelik, Institute of Scientific Instruments (Czech Republic)

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

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