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 (estimated standard
deviation, e.s.d.) of the directions of photons in
the XZ plane around the mean source beam direction.
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.