Background with continous ripple artefacts

jandinger

Hello,

I try to do Rietfeld refinement of neutron data from the E6 at HZB Berlin. The data shows a continous ripple along the whole background with a distance of 1 °2Th. It looks like that the ripple is intensity dependent. Every diffraction peak shows a higher ripple in the difference plot if I refine the data. Is it possible to get rid of such an artefact?

The investigated material is magnetic in the investigated temperature range. So, the ripples seem to disturb the real magnetic intensities.

I hope someone can help me.

Thanks a lot.

e691880-deq-exported.txt

15kB

I use Topas 7 in combination with jedit.

rowlesmr

Looks like you have a sinusoid in your background.

Maybe add something like

	prm amp  45.37525`_LIMIT_MIN_5 min 5 max 1000
prm phase  47.57355` min -500 max 500
prm scal  6.28657` min 1 max 1000

fit_obj = amp Sin(scal X + phase);

to your input file to model that contribution?

jandinger

Thank you very much for the fast reply!
It works quite well. I think it looks like the ripple is minimized in background regions. But the ripple intensity seems to be larger at diffraction peaks.

Is there a way to include an intensity factor to the ripple compensation?

rowlesmr

Your idea tickles my mind. I'm pretty sure there is a way to do that, but I haven't tried anything like it.

jandinger

Your first idea has already helped a lot. Perhaps someone has an extension to your code...