Beam tilt

In order to properly address the problem of measuring intensities with minimum dynamical dififaction contributions we used the technique where the electron beam is precessed by means of beam tilt coils in the TEM. These coils are situated before the sample in combination with a similar precession of the ED pattern via deflection coils below the sample. ... 

The signal to control the beam tilt angle for hollow cone. 

Determining the c component of the long axis of C02 requires measuring a crystal in a different orientation. Ideally one would measure spectra with the ac or be plane perpendicular to the incident beam, but with flat plates this was not possible. Instead the crystal was tilted about the horizontal b axis, so that the IR beam and its electric vector had both a and c components for vertical polarization of the IR beam. Tilting by as much as 35-40° still allowed measuring accurate polarized spectra. 

In addition, there are various technical corrections that must be made to the image data to allow an unbiased model of the structure to be obtained. These include correction for the phase-contrast transfer function (CTF) and, at high resolution, for the effects of beam tilt. For crystals, it is also possible to combine electron diffraction amplitudes with image phases to produce a more accurate structure (7), and in general to correct for loss of high resolution contrast for any reason by "sharpening" the data by application of a negative temperature factor (22). 

Beam Tilt (X4) inclination of the laser beam with respect to its nominal trajectory perpendicular to the tilt axis (T). Is decomposed into its projections on the tilt axis (X4t) and the beam perpendicular to the beam (X4m). The latter is not considered for having the same meaning as X3. 

Beam Axis tilt (I) laser beam tilt about the vertical axis (Z) into its components X, Y (Ix, ly)-... 

Electrical beam tUt can also be designed into a high-gain antenna. A conventional antenna typically radiates more than half of its energy above the horizon. This energy is lost for practical purposes in most applications. Electrical beam tilt, caused by delaying the RF current to the lower elements of a multi-element antenna, can be used to provide more useful power to the service area. 

In contrast, the branch feed configuration employs feed lines that are nominally of equal length. Therefore the phase relationships of the radiating elements are maintained over a wide span of frequencies. This provides vertical patterns with stable beam tilt, a requirement for multi-channel applications. 

Please note that the diffraction vector to form a CDF image is opposite to the diffraction vector in the corresponding BF image. So, in order to obtain a CDF diffraction condition, the transmitted beam has to be moved to the diffraction beam position using dark-field beam tilt. In order have the same diffraction vector in both BF and DF images, it is recommended to just obtain a conventional DF image by displacing the objective aperture to the diffracted beam. 

Check one more time the TEM alignment, especially pay attention to specimen height, pivot point alignment and beam-tilt alignment. 

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