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RefinePowderDiffProfileSeq v1¶

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.

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 value of the output background parameter;
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.

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

Categories: AlgorithmIndex | Diffraction\Fitting

Source ¶

Python: RefinePowderDiffProfileSeq.py