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

<strong>Tecnai</strong> on-line help Options 7Options Software version 2d) Switch to Exposure, Focus and Search again and check the conditions (especially centering ofthe beam).e) If necessary, recenter the beam and repeat the procedure.2. Operationa) Switch to the Search state and locate a number of good specimen areas. Store these using theStage control panel function.(If the microscope is equipped with an off-axis TV that must be used in the Search state, usethe TV toggle (Detector configuration) to switch to the off-axis detector position.)b) Press the Blank button (blank the beam).c) Move to the first good area (or the best) and wait a short time to allow the goniometer to settle.d) Press the Blank button again (unblank the beam).e) If necessary, center the area accurately with the goniometer.f) Switch to Focus and focus the image.(If the microscope is equipped with an on-axis CCD that must be used in the Focus state, usethe TV toggle (Detector configuration) to switch to the on-axis detector position.)g) If necessary, press the Blank button (blank the beam).h) Press the Expose button (or the Exposure button on the <strong>Tecnai</strong> Control Pad) to make theexposure.(If the microscope is equipped with an off-axis TV that must be used in the Search state, thedetector shift is set to on-axis automatically before the exposure and reset to its originalposition afterwards.)i) After the exposure is finished, go to the Exposure state and check the conditions (unlessanother low-dose exposure must be made at the same position).1.1.4 An overview of Search, Focus and Exposure opticsThe settings of Search, Focus and Exposure achieve a certain amount of decoupling between the states.In general the Search state is almost totally independent of Focus and Exposure, while some settings ofthe Focus state are coupled to the Exposure state.Spotsize The spotsize (C1 lens) is independent for all three states.Intensity The intensity (C2 lens) is independent for all three states.Illumination modes The illumination modes are independent between Search on the one hand andFocus and Exposure on the other (Focus and Exposure are thus the same by definition). This meanse.g. that Search may be in Microprobe and Focus/Exposure in Nanoprobe.Imaging modes The imaging modes are independent between Search on the one hand and Focus andExposure on the other (Focus and Exposure are thus the same by definition). This means e.g. thatSearch may be in diffraction or LM and Focus/Exposure in HM imaging (Microprobe).Focus The focus settings are independent between Search on the one hand and Focus and Exposureon the other (Focus and Exposure are thus the same by definition). Separate settings are stored by thesoftware for:• HM Image focus• LM Image focus• D (HM) diffraction• LAD (LM) diffractionFocus differences between magnifications used for the Focus and Exposure states can be eithercompensated (properly) by using the Parfocal Magnification series alignment. As an alternative, thefocus difference can be measured and entered as a single-exposure series and series switched on. Thesoftware will the automatically apply the focus change (but only during the actual recording of theexposure, not when the state is changed from Focus to Exposure).Beam shift The Search and Focus states react to beam shifts in Exposure states and in their ownstates. The beam shift is built up as follows. First of all any 'User' beam shift at the start of using Low