Index

Image dictionary (imgCIF) version 1.3.2

_diffrn_radiation.div_x_y_source

Definition:

   Beam crossfire correlation in degrees squared between the
   crossfire laboratory X-axis component and the crossfire
   laboratory Y-axis component (see AXIS category).

   This is a characteristic of the X-ray beam as it illuminates
   the sample (or specimen) after all monochromation and
   collimation.

   This is the mean of the products of the deviations of the
   direction of each photon in XZ plane times the deviations
   of the direction of the same photon in the YZ plane
   around the mean source beam direction.  This will be zero
   for uncorrelated crossfire.

   Note that for some synchrotrons, this value is specified in
   milliradians squared, in which case a conversion is 
   needed. To convert a value in milliradians squared to a value 
   in degrees squared, multiply by 0.180**2 and divide by pi**2.

Type: float

Mandatory item: no

Category: diffrn_radiation