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