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

<strong>Tecnai</strong> on-line help Alignments 77<strong>Tecnai</strong> 12 Software version 214.14 HM-EFTEM Mi Image shiftPurpose: Aligning the EFTEM Mi magnification images with SA and finding the difference in focus.Importance: CONVENIENCE so that the image remains centered when the magnification is changed.Method: Center a recognizable image with the specimen stage. Lower the magnification one step,center the image with the Multifunction X,Y knobs. Repeat for all magnifications.ProcedureThe alignment procedure consists of three steps :• A preparation step in which an image feature is centered (with the specimen stage) at the lowermostEFTEM-SA magnification.• A step in which the highest EFTEM-Mi magnification is aligned relative to the lowermost EFTEM-SAmagnification.• A step in which all EFTEM-Mi magnifications are aligned to the lowermost EFTEM-SA magnification.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.14.15 HM-EFTEM Mi Cross-over correctionPurpose: 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.