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

<strong>Tecnai</strong> on-line help Alignments 75<strong>Tecnai</strong> 12 Software version 214.10 HM-EFTEM Mi Cross-over pre-alignmentPurpose: Make sure the cross-over correction is set correctly, so the beam passes unhindered throughthe differential pumping aperture.Importance: ESSENTIAL for having the image visible on the Imaging Filter, especially at the lowermagnifications.Method: Change the cross-over correction until there is no shadowing by the differential pumpingaperture. For best results, change the cross-over correction first on Multifunction-X in one direction untila shadow appears. Turn the other way while 'counting' turns until the shadow on the other side appears.Turn back halfway. Repeat for Multifunction Y.ProcedureThe alignment procedure consists of two steps :• A preparation step in the lowest EFTEM-SA magnification.• A step in which the cross-over corrections are set for all EFTEM-Mi magnifications.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 image shift is strongly misaligned, it is possible to switch to the image shift adjustmentand back by pressing the R2 button.14.11 HM-EFTEM Mh Image shiftPurpose: Aligning the Mh-magnification images for EFTEM (as seen on the Filter) with the Mh imagesfor the normal mode, and finding the difference in focus.Importance: CONVENIENCE for being able to find the image at high magnifications.Method: Focus the image for the lowermost Mh magnification and center the image relative to thehighest SA image.ProcedureThe alignment procedure consists of four steps :• A preparation step in which an image feature is centered (with the specimen stage) in the highest SAmagnification for the normal mode.• A step in which the highest EFTEM-SA magnification is focused and centered relative to the normalmode.• A step in which the lowest EFTEM-Mh magnification is focused and aligned relative to the highestEFTEM-SA magnification.• A step in which all other EFTEM-Mh magnifications are focused and aligned.Note: Because of the difficulty of aligning the microscope for EFTEM (image/diffraction shift and crossovercorrection 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 the Filteritself. Once the microscope has been aligned properly, the pre-alignment should not be necessaryanymore and the final alignment can be used for fine-tuning.