Beam crossfire in degrees parallel to the laboratory X axis
(see AXIS category).
This is a characteristic of the X-ray beam as it illuminates
the sample (or specimen) after all monochromation and
This is the standard uncertainty (e.s.d.) of the directions of
photons in the XZ plane around the mean source beam
Note that for some synchrotrons this value is specified
in milliradians, in which case a conversion is needed.
To convert a value in milliradians to a value in degrees,
multiply by 0.180 and divide by \p.