3.6

StripVanadiumPeaks v1

../_images/StripVanadiumPeaks-v1_dlg.png

StripVanadiumPeaks dialog.

Summary

This algorithm removes peaks (at vanadium d-spacing positions by default) out of a background by linearly interpolating over the expected peak positions.

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace Mandatory Name of the input workspace. If you use the default vanadium peak positions are used, the workspace must be in units of d-spacing.
OutputWorkspace Output MatrixWorkspace Mandatory The name of the workspace to be created as the output of the algorithm. If the input workspace is an EventWorkspace, then the output must be different (and will be made into a Workspace2D).
PeakWidthPercent Input number 1 The estimated peak width as a percentage of the d-spacing of the center of the peak.
AlternativePeakPositions Input string   Optional: enter a comma-separated list of the expected X-position of the centre of the peaks. Only peaks near these positions will be fitted. If not entered, the default vanadium peak positions will be used.
WorkspaceIndex Input number Optional If set, peaks will only be removed from this spectrum (otherwise from all)

Description

  • A list of vanadium peak positions in d-spacing is used for the central peak positions: 0.5044,0.5191,0.5350,0.5526,0.5936,0.6178,0.6453,0.6768,0.7134,0.7566,0.8089,0.8737,0.9571,1.0701,1.2356,1.5133,2.1401
    • You can specify AlternativePeakPositions to use other value (e.g. in other units).
  • The PeakWidthPercent value is used to estimate the width of the peak (as a percentage of the d-spacing value).
  • The algorithm performs a simple linear fit of the background exluding the peak.
    • It uses two use averaging regions of 1/2 width, centered at +- width/2 from the center, and interpolates the linear background from it.
    • The values between the average regions are replaced with the interpolated linear background drawn as a straight line.

Usage

Note

To run these usage examples please first download the usage data, and add these to your path. In MantidPlot this is done using Manage User Directories.

Example:

ws = Load("PG3_733.nxs")
wsOut = StripVanadiumPeaks(ws,WorkspaceIndex=2,PeakWidthPercent=3,Version=1)
i = 1529
print "This peak at %.4f Angstroms has been reduced from %.0f to a background level of %.0f" % (wsOut.readX(2)[i],ws.readY(2)[i], wsOut.readY(2)[i])

Output:

This peak at 0.8116 Angstroms has been reduced from 11569 to a background level of 10869

Categories: Algorithms | CorrectionFunctions\PeakCorrections | Optimization\PeakFinding | Diffraction\Corrections