I have a question relating to describing cylindrical detectors (e.g. Debye-Scherrer camera using image plates) in imgCIF. There appear to be no examples in the 'canonical' imgCIF literature relating to such non-flat detectors, let me give my best shot here - I would appreciate any feedback as to the correctness of this description, particularly the characterisation of the array structure axis as a detector rotation axis located at the sample. Is it reasonable to use _array_structure_list_axis.angle_increment instead of displacement_increment? Note that the radius of curvature of the detector is implied by the offset of the other detector axis, and once this is given the pixel displacement increment can be converted to degrees. For a cylindrically curved detector located 573mm from the sample, I would guess the following axis definitions: ########## loop_ _axis.id _axis.type _axis.equipment _axis.depends_on _axis.offset[1] _axis.offset[2] _axis.offset[3] _axis.vector[1] _axis.vector[2] _axis.vector[3] source . source . 0 0 0 0 0 1 omega rotation goniometer . 0 0 0 1 0 0 det_up . detector . 0 0 -573 1 0 0 #parallel to sample rotation axis but on surface of det_along rotation detector . 0 0 0 1 0 0 #coincident with sample rotation # the image that comes off is 2000x4000 pixels, with the fast and short direction in the cylindrical z #direction: loop_ _array_structure_list.axis_set_id _array_structure_list.dimension _array_structure_list.precedence det_up 2000 1 det_along 4000 2 #vertical and horizontal pixels are 100 microns in size... loop_ _array_structure_list_axis.axis_id _array_structure_list_axis.displacement_increment det_up 0.1 det_along 0.1 _______________________________________________ imgcif-l mailing list imgcif-l@iucr.org http://scripts.iucr.org/mailman/listinfo/imgcif-l
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