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BilbySANSDataProcessor v1

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Summary

BILBY SANS data reduction. Converts a workspace in wavelength into a 1D or 2D workspace of momentum transfer, assuming elastic scattering.

See Also

Q1D, TOFSANSResolutionByPixel, SANSWideAngleCorrection

Properties

Name

Direction

Type

Default

Description

InputWorkspace

Input

MatrixWorkspace

Mandatory

Particle counts as a function of wavelength

InputMaskingWorkspace

Input

MatrixWorkspace

Mask for the scattering data

BlockedBeamWorkspace

Input

MatrixWorkspace

Blocked beam scattering

EmptyBeamSpectrumShapeWorkspace

Input

MatrixWorkspace

Mandatory

Empty beam transmission, where only a given wavelength slice is considered

SensitivityCorrectionMatrix

Input

MatrixWorkspace

Detector sensitivity calibration data set

TransmissionWorkspace

Input

MatrixWorkspace

Mandatory

Sample transmission workspace

TransmissionEmptyBeamWorkspace

Input

MatrixWorkspace

Mandatory

Empty beam transmission workspace

TransmissionMaskingWorkspace

Input

MatrixWorkspace

Mandatory

Mask for the transmission data

FitMethod

Input

string

log

Function to use to fit transmission; can be Linear, Log, Polynomial (first letter shall be capital)

PolynomialOrder

Input

string

3

Used only for Polynomial function, but needed as an input parameter anyway

ScalingFactor

Input

number

1

Attenuating factor

SampleThickness

Input

number

1

Thickness of sample

BinningWavelength

Input

dbl list

Mandatory

Wavelength boundaries for reduction: a comma separated list of first bin boundary, width, last bin boundary

BinningWavelengthTransm

Input

dbl list

Mandatory

Wavelengths boundaries for transmission binning: a comma separated list of first bin boundary, width, last bin

BinningQ

Input

dbl list

Mandatory

Output Q-boundaries: a comma separated list of first bin boundary, width, last bin boundary

Timemode

Input

boolean

True

If data collected in ToF or monochromatic mode

AccountForGravity

Input

boolean

True

Whether to correct for the effects of gravity

SolidAngleWeighting

Input

boolean

True

If True, pixels will be weighted by their solid angle

RadiusCut

Input

number

1

To increase resolution some wavelengths are excluded within this distance from the beam center (mm). Note that RadiusCut and WaveCut both need to be larger than 0 to affect the effective cutoff. See the algorithm description for a detailed explanation of the cutoff.

WaveCut

Input

number

1

To increase resolution by starting to remove some wavelengths below this threshold (angstrom). Note that WaveCut and RadiusCut both need to be larger than 0 to affect on the effective cutoff. See the algorithm description for a detailed explanation of the cutoff.

WideAngleCorrection

Input

boolean

True

If true, the wide angle correction for transmissions will be applied

Reduce2D

Input

boolean

False

If true, 2D data reduction will be performed

OutputWorkspace

Output

MatrixWorkspace

Mandatory

Name of the workspace that contains the result of the calculation. Created automatically.

OutputWorkspaceTransmissionFit

Output

MatrixWorkspace

Mandatory

Counts vs wavelength, fit for the sample transmission

Description

The main equation Bilby is using for the \(I(Q)\) calculation is the following:

\[I(Q)=\frac{1}{d_{sam}}.\frac{\sum_{R, \lambda \subset Q}C_{sam,corr}(R,\lambda)}{M \sum_{R,\lambda \subset Q}T_{corr}(R, \lambda)\frac{I_{empty\_beam}(\lambda)}{M_{empty\_beam}att_{empty\_beam}}\Omega(R)Det_{flood}(R)}\]

Where \(C_{sam, corr}\) is the measured counts per pixel per wavelength, \(I_{empty\_beam}\) is the intensity of the empty beam collected for \(M_{empty\_beam}\) time, M is a time measure for the data collection, \(att_{empty\_beam}\) is attenuation factor, \(\Omega(R)\) is solid angle, \(Det_{flood}\) is a detector response function, \(T_{corr}\) is the sample transmission, and \(d_{sam}\) is the sample thickness.

Details are described in the paper [1]. The core algorithms the BilbySANSDataProcessor is utilising are Q1D and TOFSANSResolutionByPixel. Please refer to those pages for details of the input parameters. The unit of the output workspace is 1/cm. Absolute scale calibration done relatively to the empty beam transmission measurements.

Usage

See https://github.com/hortica/Mantid_Bilby/tree/master/example_data_reduction_settings page to download a set of the test input data.

Please note, currently we do not have a User Interface, so we are working with csv lists.

The steps to make the Bilby data reduction work are listed below:

  • Two csv files, similar to (input_csv_example.csv and mantid_reduction_settings_example.csv) should be created during the experiment; the names can be different, the format (especially the top line in each) must stay the same

  • Download Mantid from http://download.mantidproject.org/

  • Add the folder with your *.tar files AND the two csv files (input_csv_example.csv and mantid_reduction_settings_example.csv) to the path (added to “Mantid User Directories”)

    • To keep it simple, one can put tar and csv files in one folder, but you can add as many folders on the paths as you want

  • Open the Script menu in Mantid: press “View”, and then “Script window”; alternalively just press F3

  • The script below shows an example script to run the Bilby reduction the reduction_settings_file options should be changed to the correct .csv file file and save_files set to true.

  • Run the reducer, Execute -> Execute All in the Menu

    • All output 1D files will be saved in the folder you define in the mantid_reduction_settings_example.csv

from BilbyReductionScript import RunBilbyReduction
run_bilby_reduction = RunBilbyReduction('mantid_reduction_settings_example.csv', '0', '0', 'shift_assembled.csv', False)
output_workspace, transmission_fit = run_bilby_reduction.run_bilby_reduction()

scale, aka attenuation factor 0.0029

References

Source

Python: BilbySANSDataProcessor.py

Categories: AlgorithmIndex | Workflow\SANS