Beam path through Kapton window

danweber

Dear forum,

my group is measuring air sensitive samples in a Bragg-Brentano geometry through a Kapton window. Does anyone have experience whether the additional path length through Kapton dampens the intensity, especially at very low and high angles? If so, how is this considered in an inp file?

Looking forward to your feedback and best,
Dan

jlstapper

danweber
Hi Dan,

Kapton is quite X-ray transparent but does cause some diffuse scattering in the range 10-30˚ 2Th (for Cu Ka radiation). You can measure a sample (which is not air sensitive) with the Kapton window and without it and obtain the contribution of the Kapton window, which you can subtract from other scans.
Another option is to create a peaks phase or hkl phase for Kapton. I have used the hkl phase method for Kapton film layers on air-sensitive samples and gotten good results. After creating the phase model, you can paste it into the structures section of your inp file. It will then be considered in the refinement along with the other phases.
This method has been used several times for hydrating cementitious samples (like my own samples), and was reviewed here https://doi.org/10.1016/j.cemconres.2022.106988 in section 3.2.1

Julian

rowlesmr

You do need to use the thin stuff, so the < 10 um films.

In my experience (which isn't much with kapton), the main contribution is to the background, rather than intensity reduction. The main contribution to the latter would be at low angles, and essentially nothing at high angles. I think you'd need to be more worries about beam overspill at low angles, as opposed to intensity reduction.

If you want to worry about intensity reduction in an inp, then take guidance from Rowles & Buckley
https://journals.iucr.org/paper?kc5052 or https://espace.curtin.edu.au/handle/20.500.11937/50104