DIGISTAR is the instrument that takes control of the TEM lighting and deflection system to lean the electron beam few degrees while rotating it around the microscope’s axis (precession movement), over a point on the sample. This reduces the effects of dynamic diffraction caused in the TEM by multiple dispersion; therefore the intensities of the reflection obtained may be interpreted as “quasi-kinematic” diffraction. This technique is called “Precession” or PED (Precession Electron Diffraction).
Precession can be applied to acquiring the diffraction patterns of a crystal manually or automatically tilted a series of degrees (minimum +/- 30º, separated by 1º). ADT3D (Automatic Diffraction Tomography 3D) software allows you to reconstruct the reciprocal space to determine the unit cell and quantify the intensities of the reflections measured to obtain the crystal structure.
The ASTAR comprises a CCD that acquires the diffraction patterns generated in any crystalline sample under a TEM electron beam using the software necessary to process this structural information. The software compares the diffraction patterns measured with all those possible in the sample, determining the distribution of the crystallites present and the orientation of the sample grains. As this information is quantitative and collected point-by-point, it enables us to establish, with nanometric resolution, details of the grain edges, distribution of grain size, pole figure analysis, etc.