Fix beam shift during data collection
Added by Anchi Cheng over 9 years ago
Question from Thomas Marlovits
i am trying to fix the beamshift remotely since the beam is moving a bit … does the node FIX BEAM do this job? cannot find a documentation of this node the alternative is to change the beamshift settings in the presets - but this is pretty tedious - or is there any other better procedure
Replies (1)
RE: Fix beam shift during data collection - Added by Anchi Cheng over 9 years ago
Hi, Thomas,
The documentation of the node FIX BEAM is here. I have added more in Fix_beam_shift_during_data_collection. The node was originally designed for JEOL1230 where this problem is severe. The algorithm in there is primitive. just looked for the beam shift giving the highest intensity in the 3x3 matrix. It may not work well in your situation with small change where all you see is the appearance of Fresnel fringes.
If you are observing the shift remotely through the Leginon gui, you can use the preset manager "Shift beam for this preset" tool, assuming that you have calibrated that at the mag of the exposure. Then it will just be one click.
The Beam_Shift_matrix_calibration is hard for DDD such as K2. You may try to reduce C2 aperture and use spot size that gives even weaker beam than usual so that you can reduce the beam size during the calibration. The matrix is not C2/spot size dependent.