EnggVanadiumCorrections v1¶

Summary¶

Calculates correction features and / or uses them to correct diffraction data with respect to reference Vanadium data.

Properties¶

Description¶

This algorithm performs calculations related to two types of corrections with respect to a reference Vanadium diffraction dataset (workspace), in the following order:

1. sensitivity correction
2. pixel-by-pixel correction

The algorithm outputs the features extracted from the Vanadium data that are used to perform the two types of corrections, respectively:

1. the integration of every individual Vanadium spectrum
2. a list of curves of aggregated counts as a function of time-of-flight (one per bank)

If an input/output workspace with diffraction data is passed, the algorithm applies the corrections on the diffraction data workspace by using the integration and curves calculated from the reference Vanadium datasset.

These outputs can be used to apply the corrections on a diffraction data workspace in the same algorithm run, or be used subsequently to apply corrections to different input workspaces. In practice, both outputs need to be calculated only once for every reference Vanadium dataset, while they would normally be used to correct a (possibly long) series of different diffraction data workspaces.

If a vanadium data workspace is passed, the algorithm will calculate features that can then be used to apply Vanadium corrections in other Engg algorithms. If in addition an input/output workspace with diffraction data is passed, the corrections will be applied on it. Afterwards the same corrections can be applied on different diffraction data workspaces by calling again this algorithm and providing as inputs the integraion and curves workspaces produced by the first call. The same correction features (integration and curves) can be re-used for as long as the same reference Vanadium diffraction data is still valid.

Normally this algorithm can be used in two different ways:

1. Pre-calculate correction features from a Vanadium data workspace.
2. Apply Vanadium corrections once the correction features have been calculated.

Examples of these two alternatives are shown below. In the first option, only the input VanadiumWorkspace is required, and the two outputs (integration and curves workspaces) are produced normally. Optionally, a diffraction data workspace can be passed in the input property InputWorkspace for it to be corrected. In the second option, the corrections can be applied by using pre-calculated features from a previous run of this algorithm (both IntegrationWorkspace and CurvesWorkspace have to be passed as input properties, If these two properties are not passed, they will be re-calculated provided that a VanadiumWorkspace is passed which is not recommended). All the calculations (integration, sums, divisions, etc.) are done in the d-spacing space.

This algorithm is used as a child algorithm in the algorithms EnggFocus v1 and EnggCalibrateFull v1.

Usage¶

Example - apply Vanadium corrections on a sample workspace from an EnginX run file:

# # To generate the pre-calculated features (integration and curves), for a new
# Vanadium run, and apply the corrections on a workspace:
#
# sample_ws = Load('ENGINX00213855.nxs')
# van_ws = Load('ENGINX00236516.nxs')
# EnggVanadiumCorrections(Workspace = sample_ws, VanadiumWorkspace = van_ws
#                         OutIntegrationWorkspace = 'integ_ws',
#                         OutCurvesWorkspace = 'curves_ws')
#
# # Now you can save the two pre-calculated features / workspaces:
# SaveNexus(InputWorkspace='integ_ws',
#           Filename='ENGINX_precalculated_vanadium_run000236516_integration.nxs',)
# SaveNexus(InputWorkspace='curves_ws',
#           Filename='ENGINX_precalculated_vanadium_run000236516_bank_curves.nxs')
#
# # (not done here because the Vanadium run file has a large number of events)
#
# # Below we use the pre-calculated features that can be obtained with
# # the commands listed above.

sample_ws = Load('ENGINX00213855.nxs')
integ_ws = LoadNexus('ENGINX_precalculated_vanadium_run000236516_integration.nxs')
curves_ws = LoadNexus('ENGINX_precalculated_vanadium_run000236516_bank_curves.nxs')
EnggVanadiumCorrections(Workspace = sample_ws,
                        IntegrationWorkspace = integ_ws,
                        CurvesWorkspace = curves_ws)

# Should have one spectrum only
print "No. of spectra:", sample_ws.getNumberHistograms()

# Print a few arbitrary integrated spectra
ws_idx = 400
idx_count = 3
integ_ws = Integration(sample_ws, StartWorkspaceIndex=ws_idx,
                       EndWorkspaceIndex=ws_idx+idx_count)
fmt = "For workspace index {0:d} the spectrum integration is {1:.3f}"
for i in range(idx_count):
   print fmt.format(ws_idx+i, integ_ws.readY(i)[0])

Output:

No. of spectra: 2513
For workspace index 400 the spectrum integration is 23.998
For workspace index 401 the spectrum integration is 23.799
For workspace index 402 the spectrum integration is 22.872

Categories: Algorithms | Diffraction | Engineering | PythonAlgorithms | CorrectionFunctions | BackgroundCorrections | CorrectionFunctions | EfficiencyCorrections | CorrectionFunctions | NormalisationCorrections

Source¶

Python: EnggVanadiumCorrections.py