15 November 1999 Comparative study on magnetic variable axis lenses using electrostatic and magnetic in-lens deflectors
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Abstract
Variable axis lens (VAL) system for magnetic round lenses can be achieved by using electrostatic deflectors (ME-VAL) instead of magnetic deflectors (MM-VAL). The condition for the ME-VAL is obtained from the paraxial ray equation rather than from axial focusing field expansions. The study shows that the ME- VAL also reduces the off-axis aberrations significantly, though not as much as its MM-VAL counterpart. A ME-VAL has been proposed for a magnetic objective lens using octopole deflector electrodes, in which the VAL condition is slightly mismatched. The results shows that the ME-VAL is less sensitive to mismatches in the VAL fields than the MM-VAL counterpart in terms of off-axis aberrations, and comparable performance can be obtainable if the advantages of electrostatic deflection can be fully exploited.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yan Zhao, Anjam Khursheed, "Comparative study on magnetic variable axis lenses using electrostatic and magnetic in-lens deflectors", Proc. SPIE 3777, Charged Particle Optics IV, (15 November 1999); doi: 10.1117/12.370120; https://doi.org/10.1117/12.370120
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