Provide a multi-shell cylinder model (Trac #1080)

[smk78]

In the last 6 months Dave Adams (Glasgow), Jian Lu (Manchester) and Irena Levin (Technion) have all wanted a core-shell or core-shell-shell cylinder model.

The only fitting program with anything remotely like this model is Olivier Tache's pySAXS, but it is a less user-friendly, less robust, program than !SasView and does not handle resolution or polydispersity smearing, nor orientation.

We should provide a better alternative.

Migrated from http://trac.sasview.org/ticket/1080

{
    "status": "new",
    "changetime": "2019-03-03T01:10:06",
    "_ts": "2019-03-03 01:10:06.390271+00:00",
    "description": "In the last 6 months Dave Adams (Glasgow), Jian Lu (Manchester) and Irena Levin (Technion) have all wanted a core-shell or core-shell-shell cylinder model.\n\nThe only fitting program with anything remotely like this model is Olivier Tache's pySAXS, but it is a less user-friendly, less robust, program than !SasView and does not handle resolution or polydispersity smearing, nor orientation.\n\nWe should provide a better alternative.",
    "reporter": "smk78",
    "cc": "",
    "resolution": "",
    "workpackage": "SasModels New Model",
    "time": "2018-03-19T14:27:21",
    "component": "sasmodels",
    "summary": "Provide a multi-shell cylinder model",
    "priority": "critical",
    "keywords": "",
    "milestone": "SasView 4.3.0",
    "owner": "",
    "type": "enhancement"
}

[smk78]

Trac update at 2018/03/19 14:28:05:

• smk78 changed attachment from "" to "PCylinder_six_layers - Copy.py"
• smk78 commented:

pySAXS multi-shell cylinder model

[smk78]

Trac update at 2018/03/20 14:54:41: smk78 commented:

Also see #109

[butlerpd]

Trac update at 2019/03/03 01:10:06: butler changed type from "defect" to "enhancement"

[RichardHeenan]

I will make a start on a core plus 3 shell cylinder/disk model, though someone else may have to edit the docs part.
It will have core radius & length, thick1, thick2, thick3, face1, face2, face3 for the shells, will leave the user to keep the overall shape physically sensible.

[pkienzle]

Maybe an array function like onion.py, where you have `n_shells`, `sld[n_shells]` and `thickness[n_shells]`?

…

On Mon, Apr 12, 2021 at 7:45 AM RichardHeenan ***@***.***> wrote: I will make a start on a core plus 3 shell cylinder/disk model, though someone else may have to edit the docs part. It will have core radius & length, thick1, thick2, thick3, face1, face2, face3 for the shells, will leave the user to keep the overall shape physically sensible. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#172 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADTS4CPIDA6DY5GWOLZ3ULTILMPHANCNFSM4HCOWKVA> .

[RichardHeenan]

I was going to keep it simple but tedious, so as to make it easier to customize for cases such as a belt around the middle, or the core sticking out of the end faces.

[RichardHeenan]

I was going to keep it simple but tedious, so as to make it easier to customize for cases such as a belt around the middle, or the core sticking out of the end faces.

OK, having looked at Onion, I will try that route. as is more elegant, and constraints can be used.

[RichardHeenan]

I have a prototype model now, which seems to work, needs a bit more testing, proper docs, and some improvements to the c++ code for efficiency.

[RichardHeenan]

I have a working prototype if anyone wants to try it. Currently struggling with the docs and need to either fix or remove the sld vs radius plot (which seems to cause the docs build to fail)

[RichardHeenan]

core_multishell_cylinder is available to try from myself. It will do discs as well as cylinder. It is now in almost final state with proper docs and unit tests . One external tester is happy with it.
(As with the other cylinder models, more work is needed to deal automatically with extreme geometries, such as carbon nanotubes.)

[RichardHeenan]

Currently ( 19 Sept 2023) working on getting core_multi_shell_cylinder set up in sasmodels, will be in branch newmodels0923