accelerating (acceleration) voltage center

When fluctuations are added to accelerating voltage using a high-tension wobbler, a TEM image spirally enlarges and shrinks. The center of this enlargement and shrinkage is called "accelerating (acceleration) voltage center." Alignment of the accelerating voltage center is carried out to bring the accelerating voltage center to the center of the fluorescent screen for viewing the image by the use of a double-deflection coil system. Since the fluctuations of the high voltage are small (<10^-6), this alignment is used to minimize the effect of energy spread due to inelastic scattering (plasmon scattering) in a specimen rather than the effect of high-voltage fluctuations. This alignment is required when taking images at a medium magnification lower than 100,000×.

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