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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 and 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); https://doi.org/10.1117/12.370120
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