The polarization tab defines the type of incident X-ray and is an experimental parameter. It is defined as common as possible as two complex numbers defining the real part and imaginary part (amplitude and phase as complex number) of the electric field in sigma and pi direction of the light. (Look in “terms and definition” for an exact definition) The most common polarizations can are predefined and can be set directly. The “Norm” Button sets the amplitude of the complex numbers to 1. For the dichroic calculations the other polarization can set as well.
Approximation for the Parratt algorithm
In the Parratt algorithm the polarization is indirectly implemented as part of the Fresnel-equations. So, the polarizations sigma and pi are treated separately and are in the end averaged dependent on the amplitudes given by the complex numbers.