Correction of higher order geometrical aberration by triple 3-fold astigmatism field
- 8 July 2009
- journal article
- Published by Oxford University Press (OUP) in Journal of Electron Microscopy
- Vol. 58 (6), 341-347
- https://doi.org/10.1093/jmicro/dfp033
Abstract
A new concept of a spherical aberration correction system using three dodecapoles is proposed. The system compensates for higher order aberration of 6-fold astigmatism, which generally limits a uniform phase area for image forming and probe forming in an electron microscope with a conventional two-hexapole corrector. Triple 3-fold astigmatism field is used to correct the spherical aberration of the objective lens, and the total 3-fold astigmatism is eliminated by their combination. The optimum azimuth relationship among three dodecapoles is calculated to eliminate the 6-fold astigmatism. The principle of the method was verified using a mathematically complex representation. This new concept was experimentally tested with a scanning transmission electron microscope at 60 kV acceleration. The 6-fold astigmatism was certainly compensated and the coherent convergent angle became almost twice compared to a conventional double hexapole system.Keywords
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