Tecnai on-line help manual -- Options - UT Southwestern

<strong>Tecnai</strong> on-line help Options 48Options Software version 2Calibrations have a set hierarchy (some calibrations can only be done once others have been done).They are specific to a number of conditions :• CCD camera used in combination with the microscope lens series (Normal or EFTEM)• High tension• Microscope mode (LM, Microprobe, Nanoprobe, Lorentz)For the microscope modes, only the Nanoprobe mode does not require full calibrations. For that modeonly the Focus/Stigmator calibration must be done separately (the rest of the calibrations if the same asin the Microprobe mode).Calibrations can only be done by TEM Experts (private calibrations for these users) and Supervisor,Service or Factory (dependent on availability, these calibrations are what basic microscope Users get.Calibration is done on the basis of a standard specimen, a cross-grating. This specimen has squares onit with a spacing of 463 nm.3.16.4 Magnification calibrationThe software will acquire an image of the cross-grating and analyse that to find the basic spacing. Theanalysis is done using an auto-correlation (at high magnifications) or an FFT (at low magnifications) inwhich the two basic vectors will be outlined by circles.An image of a cross-grating, showing the 463 nm squares.The result of the magnification calibration. The autocorrelationof the cross-grating image (zoomed in 2x) shows the centralpeak pointed at by the line (which has been added manually forclarity). The software adds the two circles around the two basevectors of the pattern. It is important that these circles arelocated at the correct positions and not e.g. at the diagonals ofthe squares. Additional circles are placed at the multiples of thebase vectors used to show how many base vectors were usedtogether for the analysis.