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

<strong>Tecnai</strong> on-line help Alignments 54<strong>Tecnai</strong> 12 Software version 211 Stigmator Procedure11.1 Condenser stigmator calibrationThe microscope contains a condenser stigmator to correct for beam astigmatism. When this stigmator ismisaligned, adjustment of the stigmator setting will lead to an apparent beam shift. When the stigmator isaligned correctly, these shifts are compensated by an identical but opposite beam shift - this time usingthe beam deflection coils. In order to align the stigmator, it is necessary to determine the relationbetween a change in stigmator setting and the beam shift. This relation is determined in the procedurefor aligning the stigmator.The procedure follows these steps:• A preparation step in which the beam is nearly (not completely) focused.• The current through the stigmator is wobbled in the X direction and the operator minimizes beammovement.• The same is done for the Y direction.• Two highly astigmatic beams (almost lines) should become visible. If the beams do not look like that,change the INTENSITY until they do. With the condenser stigmator misaligned the two lines will notcross each other in the middle. Adjust the Multifunction knobs until they do.Condenser stigmator misaligned.Condenser stigmator aligned.11.2 Objective stigmator calibrationThe microscope contains an objective stigmator to correct for astigmatism in HM image and LMdiffraction. When this stigmator is misaligned, adjustment of the stigmator setting will lead to an apparentHM image (or LM diffraction shift). When the stigmator is aligned correctly, these shifts are compensatedby an identical but opposite shift - this time using the image deflection coils. In order to align thestigmator, it is necessary to determine the relation between a change in stigmator setting and the HMimage shift. This relation is determined in the procedure for aligning the stigmator.