This book (Practical Electron Microscopy and Database) is a reference for TEM and SEM students, operators, engineers, technicians, managers, and researchers.

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The energy resolution of conventional EEL spectrometers can be limited by both the aberrations of spectrometers and the energy spread of incident electron beams.

Curved entrance and exit edges of the magnetic prism spectrometer are usually made to appropriate radii to correct geometric aberration [1 - 2], for instance, curved entrance was used to design a TEM postcolumn imaging filter.[3] However, the performance of curved edge depends highly on the machining tolerances and alignment accuracy [4–6].

Note that by using an entrance aperture that is small enough, the effect of spectrometer aberrations will be minimized, although a portion of the signal is lost.

[1] R. F. Egerton, Electron Energy-Loss Spectroscopy in the Electron Microscope, 2nd ed. (Plenum, New York, 1996), pp. 63–68.
[2] J. R. Fields, Ultramicroscopy 2, 311 (1977).
[3] O. L. Krivanek, A. J. Gubbens, N. Dellby, and C. E. Meyer, Microsc. Microanal. Microstruct. 3, 187 (1992).
[4] R. F. Egerton, Optik 57, 229 (1987).
[5] T. T. Tang, Scan Electron Microsc. 1, 39 (1982).
[6] M. Sheinfein and M. Isaacson, Scan Electron Microsc. 4, 1681 (1984).