[SasView Users] Bug Report – Unexpected Behavior of Polydispersity in SASview v6

[Abdoltajedini, Fatemeh via users]

Dear SASview Team,
I would like to report a possible bug I encountered in SASview v6 related to polydispersity.
Description of the issue:
When I add polydispersity to a model, the scattering curve changes far more dramatically than expected. Even small values (e.g., 0.05 on radius) cause the intensity and curve shape to shift disproportionately, which does not seem physically reasonable.
Steps to reproduce:

  1.
Open SASview v6.
  2.
Load the [Core-Shell Cylinder].
  3.
Fit the model without polydispersity – the curve looks reasonable.
  4.
Add a small polydispersity (e.g., 0.05 on radius).
  5.
The curve changes strongly in both shape and magnitude.

Expected behavior:
Polydispersity should broaden or smooth features of the scattering curve, but not cause large intensity changes or unrealistic distortions.
Observed behavior:
Even small polydispersity values produce a strong, unrealistic effect.
Environment:

  *
SASview version: 6.x

  *
Operating system: Windows
  *
Data used: experimental data

Thank you for your help and for maintaining this valuable software.
Best regards,
Fatemeh


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