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

<strong>Tecnai</strong> on-line help Alignments 78<strong>Tecnai</strong> 12 Software version 214.16 HM-EFTEM Camera-length pre-alignmentPurpose: Determine the shifts necessary for aligning all camera lengths, so that the diffraction patternremains in the center when the camera length is changed.Importance: CONVENIENCE for having the diffraction patterns centered when the camera length ischanged.Method: Center the diffraction pattern for the reference camera length, then align all camera lengths tothe reference camera length.ProcedureThe alignment procedure consists of five steps :• A preparation step in which the image for the normal mode is focused.• A step in which the reference camera length for the normal mode (~500mm) is focused andcentered.• A step in which the equivalent EFTEM camera length is focused and centered.• A step in which all other camera lengths are focused and centered.• A step in which for each camera length the cross-over correction is set.Notes:• Because of the difficulty of aligning the microscope for EFTEM (image/diffraction shift and cross-overcorrection are often quite critical, otherwise there is no image or diffraction pattern visible on theImaging Filter), the EFTEM alignment procedure contains two parts, one a pre-alignment, where allalignments are done with the screen down, the other the final alignment where all is aligned on theFilter itself. Once the microscope has been aligned properly, the pre-alignment should not benecessary anymore and the final alignment can be used for fine-tuning.• In case the cross-over correction is strongly misaligned, it is possible to switch to the cross-overcorrection adjustment and back by pressing the R2 button.• Although the camera length series for EFTEM typically will contain low camera lengths, this does notimply that such camera lengths are usable on all instruments (very much dependent on a number offactors such as the mechanical alignment of the projector lenses). Typical lowermost usable cameralengths are as follows:BioTWIN lens 700mmTWIN lens 320mmS-TWIN lens 200mmU-TWIN lens 260mm14.17 HM-EFTEM Camera-length alignmentPurpose: Determine the shifts necessary for aligning all camera lengths, so that the diffraction patternremains in the center when the camera length is changed.Importance: CONVENIENCE for having the diffraction patterns centered when the camera length ischanged.Method: Center the diffraction pattern for the reference camera length, then align all camera lengths tothe reference camera length.ProcedureThe alignment procedure consists of five steps :• A preparation step in which the image for the normal mode is focused.• A step in which the reference camera length for the normal mode (~500mm) is focused andcentered.• A step in which the equivalent EFTEM camera length is focused and centered.