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D4ILLReduction v1

Summary

Performs diffraction data reduction for the D4 instrument at the ILL.

See Also

LoadILLDiffraction

Properties

Name	Direction	Type	Default	Description
Run	Input	list of str lists	Mandatory	File path of run(s). Allowed values: [‘nxs’]
OutputWorkspace	Output	WorkspaceGroup	Mandatory	The output workspace based on the value of ProcessAs.
BankPositionOffsetsFile	Input	string		The path to the file with bank position offsets.
ZeroPositionAngle	Input	number	0	The angular position correction common to all banks.
EfficiencyCalibrationFile	Input	string		The path to the file with relative detector efficiencies.
DeadTimeTauDetector	Input	number	7e-06	The count rate coefficient for detectors.
DeadTimeTauMonitor	Input	number	2.4e-06	The count rate coefficient for the monitor.
Wavelength	Input	number	0.5	The measurement wavelength, in Angstrom. Will be used if not default or if Ei in metadata is 0.
NormaliseBy	Input	string	Monitor	What normalisation approach to use on data. Allowed values: [‘Monitor’, ‘Time’, ‘None’]
NormalisationStandard	Input	number	1000000	Standard value against which the normalisation which be performed. The default is for normalisation to monitor.
ScatteringAngleBinSize	Input	number	0.5	Scattering angle bin size in degrees used for expressing scan data on a single TwoTheta axis.
ExportASCII	Input	boolean	True	Whether or not to export the output workspaces as ASCII files.
ClearCache	Input	boolean	True	Whether or not to clear the cache of intermediate workspaces.
DebugMode	Input	boolean	False	Whether to create and show all intermediate workspaces at each correction step.

Description

This is the main algorithm performing the liquid diffraction reduction for data recorded with the ILL instrument D4. The algorithm’s workflow diagram can be found below.

The raw data will be corrected for, in order:

1. Dead time, applied separately to monitor and detectors data

2. Imperfect banks placement, using both zero angle correction and ASCII input file correcting bank angle around the sample

3. Relative efficiency, using input ASCII file with one efficiency value per detector

4. Normalisation to a standard, either time or monitor counts.

The user has an option to not perform operations 2-4 by not providing relevant inputs or choosing None as the normalisation method.

The output are diffractograms as a function of scattering angle \(2\theta\), and momentum exchange \(q\). The output can be saved in the ASCII format, as .dat files, if requested.

Caching with ADS

This algorithm cleans-up the intermediate workspaces if ClearCache property is checked (True by default).

Default naming schemes are imposed to ensure smooth communication of workspace contents. While user can specify the name for the output WorkspaceGroup, the names of contents will consist of the name of the group as a prefix, diffractogram as the middle part, and the X-axis unit (either q or 2theta as the suffix).

Saving output

When ExportASCII property is checked, the output workspaces are saved in the default save directory. Each of diffractograms is saved in a separate file with .dat extension.

Workflows

General workflow

Note

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

Example - vanadium reduction at two positions

output_ws = 'vanadium_ws'

D4ILLReduction(
  Run='387229:387230',
  OutputWorkspace=output_ws,
  NormaliseBy='Monitor',
  ExportAscii=False)

tthAxis = mtd[output_ws][0].readX(0)
print('{}: 2theta range: {:.3}...{:.3}A'.format(
      mtd[output_ws][0].name(), tthAxis[0], tthAxis[-1]))
qAxis = mtd[output_ws][1].readX(0)
print('{}: Q range: {:.3}...{:.3}A'.format(
      mtd[output_ws][1].name(), qAxis[0], qAxis[-1]))

Output:

vanadium_ws_diffractogram_2theta: 2theta range: 9.69...1.39e+02A
vanadium_ws_diffractogram_q: Q range: 2.12...23.5A

Categories: AlgorithmIndex | ILL\Diffraction

Source

Python: D4ILLReduction.py