3.6

SANSDarkRunBackgroundCorrection v1

../_images/SANSDarkRunBackgroundCorrection-v1_dlg.png

SANSDarkRunBackgroundCorrection dialog.

Summary

Correct SANS data with a dark run measurement.

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace Mandatory  
DarkRun Input MatrixWorkspace Mandatory  
OutputWorkspace Output MatrixWorkspace Mandatory The corrected SANS workspace.
NormalizationRatio Input number 1 Number to scale the dark run in orderto make it comparable to the SANS run
Mean Input boolean False If True then a mean value of all spectra is used to calculate the value to subtract
Uniform Input boolean True If True then we treat the treat the tim ebins a
ApplyToDetectors Input boolean True If True then we apply the correction to the detector pixels
ApplyToMonitors Input boolean False If True then we apply the correction to the monitors
SelectedMonitors Input int list   List of selected detector IDs of monitors to which the correction should be applied. If empty, all monitors will be corrected, if ApplyToMonitors has been selected.

Description

This algorithm subtracts a dark run from a workspace. InputWorkspace and DarkRun have to be of type Workspace2D and need to contain the same spectra. The user can choose to either subtract spectra which are assoicated with detecors (ApplyToDetectors) and/or monitors (ApplyToMonitors). In the case of monitors, the user can select specific monitors (SelectedMonitors) according to their detecotor IDs.

The NormalizationRatio is used to scale the signal values of the DarkRun workspace before subtraction.

The background subtraction can be performed in several ways.

  • Uniform disabled: DarkRun is subtracted bin by bin from the InputWorkspace.
  • Uniform enabled: An average value for each spectra of the DarkRun is calculated. This average value is subtracted from the corresponding spectrum of the InputWorkspace. Note that Mean cannot be enabled when Uniform is disabled.
  • Mean enabled: This calculates an average over all spectra. This average is subtracted from all the spectra
  • Mean disabled: The subtraction happens for all spectra separately.

Usage

**Example - SANSDarkRunBackgroundCorrection for **

# Create sample workspaces. Note that the dark run is here the same as the sample run
ws_sample = CreateSampleWorkspace()
ws_dark_run = CloneWorkspace(ws_sample)

out_ws = SANSDarkRunBackgroundCorrection(InputWorkspace = ws_sample,
                                         DarkRun = ws_dark_run,
                                         NormalizationRatio = 0.5,
                                         Uniform = False,
                                         Mean = False,
                                         ApplyToDetectors = True,
                                         ApplyToMonitors = False)

# We should have effectively halfed the data values
in_y = ws_sample.dataY(0)
out_y = out_ws.dataY(0)

print "The first bin of the first spectrum of the input was " + str(in_y[0])
print "After the dark run correction it is " + str(out_y[0])

Output:

The first bin of the first spectrum of the input was 0.3
After the dark run correction it is 0.15

Categories: Algorithms | Workflow\SANS\UsesPropertyManager