24 lines
1.7 KiB
Markdown
24 lines
1.7 KiB
Markdown
# Detector geometry
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At the moment Jungfraujoch supports solely flat detectors. The default option is to place modules in their actual location
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vs. detector frame. It is not recommended to place detector modules stacked.
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The simplest case is detector perpendicular to the beam. In this case it is enough to provide beam center, detector distance
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and wavelength.
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For more complex case, one can provide tilt of the detector rotation in PyFAI convention.
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This convention uses Point Of Nominal Interaction (PONI) definition. Beam X and Y would correspond to the location on the detector,
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where beam from the sample is perpendicular to the detector surface and not to the actual direct beam location. Then tilt of the detector
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is defined with three rotation angles: `rot1` (rotating detector right), `rot2` (rotating detector downwards), `rot3` (rotating detector clockwise).
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See [PyFAI documentation](https://pyfai.readthedocs.io/en/stable/) for more details.
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## Macromolecular crystallography convention for the vertical direction
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One place of confusion is the convention to have point (0,0) of the detector in the top left corner of the detector,
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with Y values increasing downwards. This is also consistent with computer image formats.
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However, other techniques (as well as internal operation of PSI X-ray detectors) might follow convention, for point (0,0)
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being in the bottom left corner and Y values increasing upwards. Such a convention is used, for example, by PyFAI.
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In general, convention is controlled in Jungfraujoch with a setting in the JSON configuration file, which allows mirroring detector in Y.
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Extra care has to be taken by the user to ensure that no errors are made. |