Polarization correction against chi disc

[giuseppe-abbondanza]

Hi,

This might be an obvious question but I hope I can get some help.

The documentation says that a fully horizontal polarization factor corresponds to a value of +1 in the polarization factor. But how does it relate to the azimuth orientation? This is especially tricky in the case where you use multi-geometry and change the orientation of the chi disc (for instance from (-180,180) to (0,360)).

I assume that chi=0° is the "horizontal" direction, but is this true when the orientation of the chi disc is changed?

Thanks, Giuseppe

[kif]

Hi Giuseppe,

I foresee no issue with the change of azimuthal range with the polarization factor ... since all trigonometric functions are 2pi-periodic, changing the position of the discontinuity will have no effect.

If you wish to play (more) with polarization correction, the function calculating the polarization takes an offset parameter to deal with this. Another solution is to consider the detector is rotated and tune (manually) rot3. The later solution has been used by several groups successfully.

When it comes to multi-geometry integration with change of the position of the discontinuity, this is likely to be a problem with 2d-integration since pyFAI expects the bin position (2theta, chi) to superimpose from one geometry to another... I would not recommend this configuration.

Cheers,

Jerome