Problem sem4160 SNF 2009-01-28 17:47:24: Aperture (& gun?) very misaligned

ahryciw at ahryciw at
Wed Jan 28 17:47:25 PST 2009

When I arrived, the aperture was VERY misaligned:  when manually wobbling the focus, the image shift was very large.  Trying to do an aperture alignment, the shifting got better as the edge of ther aperture was reached (i.e., intensity dropped when image shift was nearly minimized).  I was therefore unable to align the aperture as normal, and even when stigmatism was best, the resolution was very poor (blurry for scale bar ~2 um), and was unable take any images for 5 kV, 10 kV, or 25 kV acceleration voltages.  Could the gun itself be misaligned?  

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