Sample thickness?

[spark]

Dear all,
again another general SAXS question, I would like to throw out into the space

Everybody is talking about optimal sample thickness in bioSAXS. But what are the criterias for the minimum (!) sample thickness. Let's assume 12.4keV standard wavelength.
The maximum thickness is probably limited through multiple scattering events which should be avoided as the Born theory breaks down as single scattering events are not present anymore.

I would be really thankfull if one could point me into the right direction or point out some literature.
Thank you.
Kind regards,
S.

[SAXSIST]

As far as I can remember the criteria for optimum sample thickness is where the absorption is equal to 1/e. So it is energy dependent and defined by the mass absorption coefficient of the sample.
I cannot recall the calculation behind that rule - it may also be a rule of thumb, but it worked quite well to find a compromise between multiple scattering and having enough (sample) electrons for the x-ray photons to interact.
BRs,
SAXSIST