and center the beam by adjusting the C2 aperture position
using the multifunction X and Y knobs. Focus the beam to a
spot and recenter using beam shift. Expand the beam to the
40 mm circle and recenter the C2 aperture using the multifunction knobs. Iterate until minimal improvements are
obtained. Turn off the “Adjust” button.
5. Select the “High-Resolution” setting of the fluorescent screen
in the Tecnai User Interface and focus the beam to a spot. In
the Tecnai User Interface, click on the “Condenser” tab in the
Stigmator panel and use the multifunction X and Y knobs to
adjust the currents through the condenser stigmators while
cycling above and below the crossover point to make the
beam circular. Iterate until the beam is properly stigmated
(i.e., the beam shape is similar on both sides of crossover).
6. With the specimen at eucentric height and proper focus, focus
the beam to a spot and align the beam tilt pivot points using the
direct alignments feature in the Tecnai User Interface. For each
direction (e.g., X or Y), use the multifunction X and Y knobs to
center the bright spots of each beam on top of each other. The
step size on the Focus knob can be used to adjust the frequency
of tilting.
7. Insert and align the objective aperture. Press “Diffraction
Mode” on the hand panel to switch to diffraction mode
(D 850 mm) and center the central spot of the diffraction
image by adjusting Diffraction shift X and Y (multifunction
knobs X and Y, respectively). Insert the 100 μm (or larger
diameter) objective aperture, click on the “Adjust” tab for the
objective aperture within Tecnai User Interface, and use the
multifunction X and Y knobs to center the aperture around the
gold powder diffraction rings (see Note 7).
8. Exit Diffraction Mode and minimize the astigmatism of the
objective lens. Manually set the defocus to ~1 μm using the
Focus knob on the hand panels and use Digital Micrograph®
to display the FFT of a live image (see Note 17). In the Tecnai
User Interface, click on the “Objective” tab in the Stigmator
panel and use the multifunction X and Y knobs to adjust the
currents through the objective stigmators until the ellipticity of
the Thon rings observed in the live FFT is minimized (see
Notes 18 and 19).
9. Switch to a higher magnification (e.g., SA 120,000Â) in Nano
probe mode and center on an image feature (e.g., at the edge of
a calibration grating waffle). Perform the rotation center alignment of the objective lens using the direct alignments feature
within Tecnai User Interface (see Notes 20 and 21). This final
step attempts to align the unscattered electron beam with the
optical axis, minimizing image coma. Accurately performing
this step will minimize time spent on Subheading 3.2.
Parallel Illumination on the Talos Arctica
133
using the multifunction X and Y knobs. Focus the beam to a
spot and recenter using beam shift. Expand the beam to the
40 mm circle and recenter the C2 aperture using the multifunction knobs. Iterate until minimal improvements are
obtained. Turn off the “Adjust” button.
5. Select the “High-Resolution” setting of the fluorescent screen
in the Tecnai User Interface and focus the beam to a spot. In
the Tecnai User Interface, click on the “Condenser” tab in the
Stigmator panel and use the multifunction X and Y knobs to
adjust the currents through the condenser stigmators while
cycling above and below the crossover point to make the
beam circular. Iterate until the beam is properly stigmated
(i.e., the beam shape is similar on both sides of crossover).
6. With the specimen at eucentric height and proper focus, focus
the beam to a spot and align the beam tilt pivot points using the
direct alignments feature in the Tecnai User Interface. For each
direction (e.g., X or Y), use the multifunction X and Y knobs to
center the bright spots of each beam on top of each other. The
step size on the Focus knob can be used to adjust the frequency
of tilting.
7. Insert and align the objective aperture. Press “Diffraction
Mode” on the hand panel to switch to diffraction mode
(D 850 mm) and center the central spot of the diffraction
image by adjusting Diffraction shift X and Y (multifunction
knobs X and Y, respectively). Insert the 100 μm (or larger
diameter) objective aperture, click on the “Adjust” tab for the
objective aperture within Tecnai User Interface, and use the
multifunction X and Y knobs to center the aperture around the
gold powder diffraction rings (see Note 7).
8. Exit Diffraction Mode and minimize the astigmatism of the
objective lens. Manually set the defocus to ~1 μm using the
Focus knob on the hand panels and use Digital Micrograph®
to display the FFT of a live image (see Note 17). In the Tecnai
User Interface, click on the “Objective” tab in the Stigmator
panel and use the multifunction X and Y knobs to adjust the
currents through the objective stigmators until the ellipticity of
the Thon rings observed in the live FFT is minimized (see
Notes 18 and 19).
9. Switch to a higher magnification (e.g., SA 120,000Â) in Nano
probe mode and center on an image feature (e.g., at the edge of
a calibration grating waffle). Perform the rotation center alignment of the objective lens using the direct alignments feature
within Tecnai User Interface (see Notes 20 and 21). This final
step attempts to align the unscattered electron beam with the
optical axis, minimizing image coma. Accurately performing
this step will minimize time spent on Subheading 3.2.
Parallel Illumination on the Talos Arctica
133