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GROUP C NOTES
NOTES FOR GROUP C


Brian Pauw Leading
Grethe Jensen Leading


=== Discussed: ===
* Lack of tools and/or awareness thereof outside of biosas - In particular fitting and modeling tools
* Publishing best practice data correction for different standard types of measurements
** specially GI
** multiple scattering estimation and ways to handle
* Q and resolution standard
* More complex round robins
* Certification of range of validity of instruments?
* Database of corrected measurements for a wide range of materials with associated metada in NXcanSAS format preferably - maybe something like a like a PDB for materials? Or other? – good metadata important, tags need to be defined so you don't end up using different names for the same thing – new SLAC effort could potentially be co-opted for such a purpose?
* Uncertainties in multiple techniques fits
* Tools for multiple scattering would be useful


=== Top Thoughts for Going Forward ===
We discussed approaches for considering multiple scattering effects. The following points were identified
* Publishing best practice data correction and terminology for different standard types of measurements
 
* Database of corrected measurements for a wide range of materials with associated metada in NXcanSAS format preferably
1. A flag signalling significant multiple scattering would be good for both data reduction software (to allow for immediate action!) and data analysis/modelling software.
* Requires data on absolute scale, together with values for wavelength and sample path length – or a well-determined measured SAS transmission. Good example of a situation where wavelength and path length would be nice to have accessible in the final reduced data file.
* Could identify the maximum scattering order that should be included in the data analysis – or suggest a proper sample path length or wavelength that would be required to exclude significant multiple scattering effects.
* Could suggest measurements for a small series of wavelengths/path lengths/contrasts, to identify features influenced by multiple scattering. These data could/should (?) be published with the data to address/prove the presence/non-presence of these effects.
 
 
2. Including multiple scattering effects in the data analysis
* Relevant for both SAS in transmission geometry and for GISAS.
* Include calculation of higher order scattering functions in model calculations and parameter optimization loop? By 2D convolution or MC simulations?
* To speed calculations up, one might consider: Only include the relevant scattering orders, starting out with ‘just’ including second order scattering, only updating higher order scattering functions every N steps in the optimization, ...

Latest revision as of 22:44, 8 June 2017

NOTES FOR GROUP C

Grethe Jensen Leading


We discussed approaches for considering multiple scattering effects. The following points were identified

1. A flag signalling significant multiple scattering would be good for both data reduction software (to allow for immediate action!) and data analysis/modelling software.

  • Requires data on absolute scale, together with values for wavelength and sample path length – or a well-determined measured SAS transmission. Good example of a situation where wavelength and path length would be nice to have accessible in the final reduced data file.
  • Could identify the maximum scattering order that should be included in the data analysis – or suggest a proper sample path length or wavelength that would be required to exclude significant multiple scattering effects.
  • Could suggest measurements for a small series of wavelengths/path lengths/contrasts, to identify features influenced by multiple scattering. These data could/should (?) be published with the data to address/prove the presence/non-presence of these effects.


2. Including multiple scattering effects in the data analysis

  • Relevant for both SAS in transmission geometry and for GISAS.
  • Include calculation of higher order scattering functions in model calculations and parameter optimization loop? By 2D convolution or MC simulations?
  • To speed calculations up, one might consider: Only include the relevant scattering orders, starting out with ‘just’ including second order scattering, only updating higher order scattering functions every N steps in the optimization, ...
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