canSAS-XI/ExtendedQrange

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Media:Example.ogg== Discussion session on Extended Q-Range == Chair : Wim Bouwman

<<upload introductory presentation from plenary as PDF and link here >>

Contents

Session Notes

Double crystal and SESANS for anisotropic scattering samples

It might be possible to model these measurements, but direct deconvolution is troublesome. The general agreement was to try to go to pinhole geometry instruments for these samples. This will give much more reliable interpretation of the measurements.

Software

Software is not an issue. All participants agree that the most used software has now the options to analyse data measured at small Q.

Calibration

There is a need for samples to calibrate both distance and intensity. Three different options were discussed:

  1. Mildly charged colloids can be redispersed. There are some small issues with stability in size, concentration and contrast on the long term.
  2. Commercial available aluminium oxide membrames (AOO), used as filters could be promissing. Some people have good experiences to use these. This is certainly an interesting option to try for several people. Possible providers that were mentioned are Sigma and Merck.
  3. Silicon wafer with a patterned grating can be produced at a very high precission. Several groups are working with these.

Discrimination between scattering and refraction

At very low Q you can have both scattering and refraction. We don't see methods to discriminate between the phenomena. This gives ambigouity in the data-analysis. Air bubbles give refraction. If you have bubbles then you see them. We have no solution for this. It is best to avoid having air bubbles in your sample, except if you want to study them.

Combination with imaging

How to get connection with microscopy? There are more groups working on this and publishing about it. It can help to get more users. How to get users to look into Q-space? For this education in scattering is needed. We have to work on this. Fitting is an important skill that is needed to interpret scattering results. Students don't always have the skill, so we have to be aware that we teach this skill to our users.

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