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The Big and the Small MAR detector


Both the Big and the Small MAR detector have a raster size of 150 m. The Small MAR has 1200 by 1200 pixels (radius 180 mm), the Big MAR has 2000 by 2000 pixels (radius 300 mm). The program has been tested both for experiments where the spindle axis is coming from the left and from the right (seen from the direction of the direct beam). In both cases film rotation 0.0 is used in DENZO.

Let be the coordinates x beam y beam of the direct beam position in millimeters on the image plate. If there is no misorientation of the image plate ( cassette rotx roty rotz all equal to zero), the relations between the pixel coordinates written to the new x-file and the STRATEGY laboratory axes are given by:

The display program that is part of the DENZO package, XDISPLAYF, will display the image in the coordinate system with the origin in the upper left corner of the image and the axis horizontal. The pixel coordinates one gets when one clicks on an arbitrary position of the image are related to the coordinates according to:

where npixel is 2000 for the Big MAR and 1200 for the Small MAR detector.

STRATEGY can deal with misorientations of the detector, but does not correct for any radial offset or angular offset.

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