It commonly happens that the detector is not quite perpendicular to the
beam normal. In that case, what should be a circular pattern is elongated
perpendicular to the tilt axis. The combination of Det-Tilt and Azimuth correct for this.
(These options are only used in SAXS mode.)
Det-Tilt is the amount that the detector is tilted (in degrees) and Azimuth is
the angle with which the pattern is tilted. For a pattern that appears to
be stretched along the x-axis, you should set Azimuth=0 and play with Det-Tilt
until the pattern is circular. For a pattern that appears to be stretched along the
y-axis, Azimuth should be 90. In fact, any value of Azimuth between -360 and 360 is
allowed.
This feature also corrects for another problems that some detectors have, which is that the gains in the X and Y direction may not be the same, also resulting in noncircular patterns. In fact, if the X-gain is set too high this is equivalent to a tilt of the detector with Azimuth=0. |