3.9

RefinePowderDiffProfileSeq v1

../_images/RefinePowderDiffProfileSeq-v1_dlg.png

RefinePowderDiffProfileSeq dialog.

Summary

Refine powder diffractomer profile parameters sequentially.

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace   Name of data workspace containing the diffraction pattern in .prf file.
WorkspaceIndex Input number 0 Spectrum (workspace index starting from 0) of the data to refine against in input workspace.
SeqControlInfoWorkspace InOut TableWorkspace   Name of table workspace containing sequential refinement information.
InputProfileWorkspace Input TableWorkspace   Name of table workspace containing starting profile parameters.
InputBraggPeaksWorkspace Input TableWorkspace   Name of table workspace containing a list of reflections.
InputBackgroundParameterWorkspace Input TableWorkspace   Name of table workspace containing a list of reflections.
StartX Input number 0 Start X (TOF) to refine diffraction pattern.
EndX Input number 0 End X (TOF) to refine diffraction pattern.
FunctionOption Input string Refine Options of functionality. Allowed values: [‘Setup’, ‘Refine’, ‘Save’, ‘Load’]
RefinementOption Input string Random Walk Options of algorithm to refine. Allowed values: [‘Random Walk’]
ParametersToRefine Input str list   List of parameters to refine.
NumRefineCycles Input number 1 Number of refinement cycles.
ProfileType Input string   Type of peak profile function. Allowed values: [‘’, ‘Neutron Back-to-back exponential convoluted with pseudo-voigt’, ‘Thermal neutron Back-to-back exponential convoluted with pseudo-voigt’]
BackgroundType Input string   Type of background function. Allowed values: [‘’, ‘Polynomial’, ‘Chebyshev’, ‘FullprofPolynomial’]
FromStep Input number -1 If non-negative, the previous code is not set from last step, but the step specified.
OutputProjectFilename Input string   Name of sequential project file. Allowed extensions: [‘.nxs’]
InputProjectFilename Input string   Name of sequential project file. Allowed extensions: [‘.nxs’]
ProjectID Input string   Project ID.

Description

The purpose of this algorithm is to provide users a tool to control the workflow to refine powder diffractometer’s peak profile. For Time-Of-Flight powder diffractometers in SNS, back-to-back exponential convoluted with pseudo-voigt profile functions are used. The function is complicated with strong correlated parameters. Thus, the refinement on these parameters contains multiple steps, within each of which only a subset of profile parameters are refined.

In order to control the workflow, there are four major functions supported by this algorithm

* ``Setup`` : set up a few workspaces that will be used to refine profile parameters in multiple steps;
* ``Refine`` : select a subset of peak parameters and do Le Bail fit on them;
* ``Save`` : save the current refinement status and refinement history to a project file;
* ``Load`` : set up a few workspaces used for refining by loading them from a previously created project file. 

Input and output workspaces

* InputWorkspace : data workspace containing the diffraction pattern to refine profile parameters with;
* SeqControlInfoWorkspace : table workspace used to track refinement; Below is the introduction on the fields/columns of this workspace. 
    *  "Step" : refinement step.  User can start a refinement from the result of any previous ``Step``; 
    *  "OutProfile" : name of the table workspace containing refined profile parameters;
    *  "OutReflection": name of the table workspace containing Bragg peaks' peak parameters calculated from refined parameters' value; 
    *  "OutBackgroud": name of the table workspace containing the output background parameters' value; 
    *  "OutBckgroundParam": name of the output background parameters;
    *  "Refine": profile parameters that are refined in this step;
    *  "RwpOut": output Rwp from refinement; 
    *  "LastStep": last step where this step is based on; 
    *  "RwpIn": input Rwp
    *  "InProfile": input profile parameter workspace's name;
    *  "InReflection": input Bragg peak parameters workspace' name;
    *  "InBackgroud": input background workspace; 
    *  "InBckgroundParam": input background parameters. 
* InputProfileWorkspace : table workspace contraining starting values of profile parameters;
* InputBraggPeaksWorkspace : table workspace containing the Bragg peaks' information for Le Bail fit;
* InputBackgroundParameterWorkspace : table workspace containing the background parameters' value

Supported peak profiles

* Neutron Back-to-back exponential convoluted with pseudo-voigt : Fullprof profile 9 and GSAS TOF profile 3;
* Thermal neutron Back-to-back exponential convoluted with pseudo-voigt: Fullprof profile 10 (a.k.a. Jason Hodges function). 

Supported background types

* Polynomial
* Chebyshev
* FullprofPolynomial

Hint for using

This is just a brief description for how to use this algorithm.

1. ``Setup``;
2. ``Refine``: refine ``Dtt1`` and ``Zero`` from step 0;
3. ``Refine``: reifne ``Alph0`` and ``Beta0`` from step 1;
4. ``Refine``: refine ``Alph1`` from step 1 with failure;
5. ``Refine``: refine ``Beta1`` from step 1 because step 2 fails; 
6. ``Refine``: refine ``Sig-1`` from last step;
7. ``Save``: save current work and history to a Nexus file.

Categories: Algorithms | Diffraction\Fitting