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BASISCrystalDiffraction v1

../_images/BASISCrystalDiffraction-v1_dlg.png

BASISCrystalDiffraction dialog.

Summary

Multiple-file BASIS crystal reduction for diffraction detectors.

See Also

AlignDetectors, DiffractionFocussing, SNSPowderReduction

Properties

Name

Direction

Type

Default

Description

RunNumbers

Input

string

Sample run numbers

MaskFile

Input

string

/SNS/BSS/shared/autoreduce/new_masks_08_12_2015/BASIS_Mask_default_diff.xml

See documentation for latest mask files. Allowed extensions: [‘.xml’]

OutputWorkspace

Output

Workspace

Mandatory

Output Workspace. If background is subtracted, _data and _background workspaces will also be generated

BackgroundRuns

Input

string

Background run numbers

BackgroundScale

Input

number

1

The background will be scaled by this number before being subtracted.

VanadiumRuns

Input

string

Vanadium run numbers

PsiAngleLog

Input

string

SE50Rot

log entry storing rotation of the samplearound the vertical axis

PsiOffset

Input

number

0

Add this quantity to PsiAngleLog

LatticeSizes

Input

dbl list

0,0,0

three item comma-separated list “a, b, c”

LatticeAngles

Input

dbl list

90,90,90

three item comma-separated list “alpha, beta, gamma”

VectorU

Input

dbl list

1,0,0

three item, comma-separated, HKL indexesof the diffracting plane

VectorV

Input

dbl list

0,1,0

three item, comma-separated, HKL indexesof the direction perpendicular to VectorVand the vertical axis

Uproj

Input

dbl list

1,0,0

three item comma-separated Abscissa viewof the diffraction pattern

Vproj

Input

dbl list

0,1,0

three item comma-separated Ordinate viewof the diffraction pattern

Wproj

Input

dbl list

0,0,1

Hidden axis view

NBins

Input

number

400

number of bins in the HKL slice

Description

Run numbers: The syntax for the run numbers designation allows runs to be segregated into sets. The semicolon symbol “;” is used to separate the runs into sets. Runs within each set are jointly reduced. However, when Single Crystal Diffraction is selected, all run numbers provided will be reduced together.

Examples:

  • 2144-2147,2149,2156 is a single set. All runs jointly reduced.

  • 2144-2147,2149;2156 is set 2144-2147,2149 and set 2156. The sets are reduced separately from each other (except for Single Crystal Diffraction).

Mask file: The default mask (BASIS_Mask_default_diff.xml) covers all inelastic detectors as well as the tips of the diffraction tubes. The file is in directory /SNS/BSS/shared/autoreduce/new_masks_08_12_2015.

Lambda Range: a list containing a minimum and maximum values are required. Incoming neutrons with a wavelength outside this range will be filtered out. The default range is [5.86, 6.75].

OutputWorkspace: a two-dimensional MDHistoWorkspace containing the intensities projected onto the reciprocal slice, integrated over the independent axis Wproj. The diffraction pattern can be visualized with the Sliceviewer.

Background runs: one or more run numbers to describe the background, and a scaling factor between zero and one.

Vanadium runs: a set of runs to be reduced jointly provide an incoherent and isotropic scattering to determine instrument efficiency per detector. If no vanadium is provided, all detectors are assumed to have the same efficiency

Determine Single Crystal Diffraction

Creates a diffraction pattern from a set of runs implementing a rotational scan of the sample around the vertical axis. The corresponding goniometer’s rotation should be logged under log name PsiAngleLog. Option PsiOffset allows user to enter a shift for this angle.

Sample orientation

VectorU: Vector along k_i, when goniometer is at offset.

VectorV: In plane vector perpendicular to VectorU, when goniometer is at offset.

Diffraction preferences

Most of the scattering occurs in the plane defined by VectorU and VectorV. Please choose Uproj and Vproj defining a plane that is as close as possible to the scattering plane.

Uproj: Defines the first projection vector. Default (1,0,0).

Vproj: Defines the second projection vector. Default (0,1,0).

Wproj: Defines the third projection vector. Default (0,0,1).

Nbins: the diffraction pattern to be viewed is partitioned into an Nbins x Nbins grid, each grid rectangle assigned a particular scattered intensity.

If background is provided, two additional workspaces are generated. Workspace _bkg will contain the scattered intensity by the background, and workspace _dat will contain the scattered intensity by the sample with no background subtracted.

Timing: 10 to 15 seconds per sample run. A typical scan made up of 50 runs will take about 10 minutes to complete.

Usage

Determine single crystal diffraction pattern:

from mantid.simpleapi import BASISCrystalDiffraction
BASISCrystalDiffraction(RunNumbers='74799-74869',
                 VanadiumRuns='75524-75526',
                 BackgroundRuns='75527',
                 PsiAngleLog='SE50Rot',
                 PsiOffset=-27.0,
                 LatticeSizes=[10.71, 10.71, 10.71],
                 LatticeAngles=[90.0, 90.0, 90.0],
                 VectorU=[1, 1, 0],
                 VectorV=[0, 0, 1],
                 Uproj=[1, 1, 0],
                 Vproj=[0, 0, 1],
                 Wproj=[1, -1, 0],
                 Nbins=400,
                 OutputWorkspace='peaks')
../_images/BASISCrystalDiffraction.png

Categories: AlgorithmIndex | Diffraction\Reduction

Source

Python: BASISCrystalDiffraction.py