Redmine issue 2417 on z component of magnetic field
For reference, here an old issue from the Redmine issue tracker.
As long as old-apps.jcns.frm2 = 172.25.83.208 is still running, old issues can be retrieved with curl 172.25.83.208/redmine/issues/2417.
Issue 2417 has been authored by Dmitry on 20 nov 2019. Randolf referred to it in document PolarizedImplementation, subsection "Magnetic field in BornAgain", saying "The z-component is afaik currently explicitly set conserved. Imo this is bit funny, as Dmitry also remarked in Issue 2417."
So here is the text of issue 2417:
As described in section 1.1 of ba-intern/theory/SpecularReflectivity/PolarizedSpecular.pdf, external magnetic field is subtracted during the computation of the wave reflected from magnetized sample.
In the section 1.2 of the same document it is stated, that z-component of the magnetic field (that is, the one normal to the sample surface) must be constant across the sample.
As the result, z-component of magnetic field, B_z, is always nullified during the computation. It would be useful to check how it is treated in other codes. For example, GenX considers only the angle between beam polarization and the direction of the magnetic field, thus avoiding direct treatment of z-component. This approach however does not allow for not fully polarized beams and imperfect analyzers.
Anyhow, B_z nullifying has a counter-intuitive behavior, since a user can specify any B_z in the layers, but it will not affect the result of computation.