Indirect Data Reduction¶

Table of Contents

Overview ¶

The Indirect Data Reduction interface provides the initial reduction that is used to convert raw instrument data to S(Q, w) for analysis in the Indirect Data Analysis and Indirect Bayes interfaces.

The tabs shown on this interface will vary depending on the current default facility such that only tabs that will work with data from the facility are shown, this page describes all the tabs which can possibly be shown.

Instrument Options ¶

Instrument: Used to select the instrument on which the data being reduced was created on.
Analyser: The analyser bank that was active when the experiment was run, or for which you are interested in seeing the results of.
Reflection: The reflection plane of the instrument set up.

Tip

If you need clarification as to the instrument setup you should use please speak to the instrument scientist who dealt with your experiment.

Action Buttons ¶

?: Opens this help page.
Py: Exports a Python script which will replicate the processing done by the current tab.
Manage Directories: Opens the Manage Directories dialog allowing you to change your search directories and default save directory and enable/disable data archive search.

ISIS/ILL Energy Transfer ¶

If the default facility has been set to ISIS, then the ISIS Energy Transfer tab will be available. However, this tab will be replaced by the ILL Energy Transfer tab if the default facility has been set to ILL. A further explanation of each tab can be found below.

ISIS Energy Transfer ¶

This tab provides you with the functionality to convert the raw data from the experiment run into units of $\Delta E$ . See the algorithm ISISIndirectEnergyTransfer.

Options ¶

Run Files: Allows you to select the raw data files for an experiment. You can enter these either by clicking on the Browse button and selecting them, or entering the run numbers. Multiple files can be selected, multiple run numbers can be separated by a comma (,) or a range can be specified by using a dash (-).
Sum Files: If selected the data from each raw file will be summed and from then on treated as a single run.
Load Log Files: If selected the sample logs will be loaded from each of the run files.
Use Calib File & Calibration File: Allows you to select a calibration file created using the Calibration tab.
Efixed: This option allows you to override the default fixed final energy for the analyser and reflection number setting. This can be useful in correcting an offset peak caused by the sample being slightly out of centre.
Spectra Min/Spectra Max: Used to specify a range of spectra.
Detector Grouping: Used to specify a method for grouping spectra. Possible grouping options include Individual, All, File, Groups and Custom. The TOSCA instrument also has the Default grouping option which will use the grouping specified in the IPF.
Background Removal: Allows removal of a background given a time-of-flight range.
Detailed Balance: Gives the option to perform an exponential correction on the data once it has been converted to Energy based on the temperature.
Scale by Factor: Gives the option to scale the output by a given factor.
Do Not Rebin: If selected it will disable the rebinning step.
Rebin Steps: Select the type of rebinning you wish to perform.
Plot Time: Creates a time of flight plot of the grouping of the spectra in the range defined in the Plot Time section. To include a single spectrum, set the Spectra Min and Spectra Max selectors to the same value. Note that this first rebins the sample input to ensure that each detector spectrum has the same binning in order to be grouped into a single spectrum.
Spectra Min & Spectra Max: Select the range of detectors you are interested in, default values are chosen based on the instrument and analyser bank selected.
Run: Runs the processing configured on the current tab.
Plot Output: Allows the result to be plotted as either a spectrum plot or contour plot.
Fold Multiple Frames: This option is only relevant for TOSCA. If checked, then multiple-framed data will be folded back into a single spectra, if unchecked the frames will be left as is with the frame number given at the end of the workspace name.
Output in $cm^{-1}$: Converts the units of the energy axis from $meV$ to wave number ( $cm^{-1}$ ).
Select Save Formats: Allows you to select multiple output save formats to save the reduced data as, in all cases the file will be saved in the default save directory.

Grouping ¶

The following options are available for grouping output data:

Custom

Follows the same grouping patterns used in the GroupDetectors algorithm. An example of the syntax is 1,2+3,4-6,7-10

This would produce spectra for: spectra 1, the sum of spectra 2 and 3, the sum of spectra 4-6 (4+5+6) and individual spectra from 7 to 10 (7,8,9,10)

Individual

All detectors will remain on individual spectra.

Groups

The detectors will automatically be divided into a given number of equal size groups. Any left over will be added as an additional group.

All

All detectors will be grouped into a single spectra.

File

Gives the option of supplying a grouping file to be used with the GroupDetectors algorithm.

Default

This grouping option is only available for TOSCA. It uses the spectra grouping specified in the IPF.

Rebinning ¶

Rebinning can be done using either a single step or multiple steps as described in the sections below.

Single: In this mode only a single binning range is defined as a range and width.

../_images/Data_Reduction_pgSingleRebin_widget.png

Multiple: In this mode multiple binning ranges can be defined using the rebin string syntax used by the Rebin algorithm.

../_images/Data_Reduction_pgMultipleRebin_widget.png

ILL Energy Transfer ¶

This tab handles the reduction of data from the IN16B instrument and will appear when the default facility is set to be the ILL. See the algorithm IndirectILLEnergyTransfer.

Reduction Type ¶

There are two reduction types of IN16B data: Quasi-Elastic Neutron Scattering (QENS) or Fixed Window Scans (FWS). The latter can be either Elastic (EFWS) or Inelastic (IFWS). If one or another reduction type is checked, the corresponding algorithm will be invoked (see IndirectILLReductionQENS and IndirectILLReductionFWS). There are several properties in common between the two, and several others that are specific to one or the other. The specific ones will show up or disappear corresponding to the choice of the reduction type.

Common Options ¶

Input File: Used to select the raw data in .nxs format. Note that multiple files can be specified following MultipleFileProperty instructions.
Detector Grouping: Used to switch between grouping as per the IDF (Default) or grouping using a mapping file (Map File). This defines e.g. the summing of the vertical pixels per PSDs.
Background Subtraction: Used to specify the background (i.e. empty can) runs to subtract. A scale factor can be applied to background subtraction.
Detector Calibration: Used to specify the calibration (i.e. vanadium) runs to divide by.
Background Subtraction for Calibration: Used to specify the background (i.e. empty can) runs to subtract from the vanadium calibration runs.
Output Name: This will be the name of the resulting reduced workspace group.
Spectrum Axis: This allows the spectrum axis to be converted to elastic momentum transfer or scattering angle if desired.
Plot: If enabled, it will plot the result (of the first run) as a contour plot.
Save: If enabled the reduced workspace group will be saved as a .nxs file in the default save directory.

QENS-only Options ¶

Sum All Runs: If checked, all the input runs will be summed while loading.
Crop Dead Monitor Channels: If checked, the few channels in the beginning and at the end of the spectra that contain zero monitor counts will be cropped out. As a result, the doppler maximum energy will be mapped to the first and last non-zero monitor channels, resulting in narrower peaks. Care must be taken with this option; since this alters the total number of bins, problems might occur while subtracting the background or performing unmirroring if the number of dead monitor channels are different.
Calibration Peak Range: This defines the integration range over the peak in calibration run in meV.
Unmirror Options: This is used to choose the option of summing of the left and right wings of the data, when recorded in mirror sense. See IndirectILLReductionQENS for full details. Unmirror option 5 and 7 require vanadium alignment run.

FWS-only Options ¶

Observable: This is the scanning observable, that will become the x-axis of the final result. It can be any numeric sample parameter defined in Sample Logs (e.g. sample.*) or a time-stamp string (e.g. start_time). It can also be the run number. It can not be an instrument parameter.
Sort X Axis: If checked, the x-axis of the final results will be sorted.
Sum/Interpolate: Both background and calibration have options to use the summed (averaged) or interpolated values over different observable points. Default behaviour is Sum. Interpolation is done using cubic (or linear for 2 measured values only) splines. If interpolation is requested, x-axis will be sorted automatically.

ISIS Calibration ¶

This tab gives you the ability to create Calibration and Resolution files, and is only available when the default facility is set to ISIS.

The calibration file is normalised to an average of 1.

../_images/Data_Reduction_tabISISCalibration_widget.png

Options ¶

Run No: This allows you to select a run for the function to use, either by selecting the .raw file with the Browse button or through entering the number in the box.
Plot Raw: Updates the preview plots.
Intensity Scale Factor: Optionally applies a scale by a given factor to the raw input data.
Load Log Files: This will load the log files if enabled.
Run: Runs the processing configured on the current tab.
Plot Result: If enabled will plot the result as a spectra plot.
Save Result: If enabled the result will be saved as a NeXus file in the default save directory.

Calibration ¶

Peak Min & Peak Max: Selects the time-of-flight range corresponding to the peak. A default starting value is generally provided from the instrument’s parameter file.
Back Min & Back Max: Selects the time-of-flight range corresponding to the background. A default starting value is generally provided from the instrument’s parameter file.

Resolution ¶

Create RES File: If selected, it will create a resolution file when the tab is run.
Smooth RES: If selected, the WienerSmooth algorithm will be applied to the output of the resolution algorithm.
Scale RES: Applies a scale by a given factor to the resolution output.
Spectra Min & Spectra Max: Allows restriction of the range of spectra used when creating the resolution curve.
Background Start & Background End: Defines the time-of-flight range used to calculate the background noise.
Low, Width & High: Binning parameters used to rebin the resolution curve.

Options ¶

Input Files: File for the calibration (e.g. vanadium) run. If multiple specified, they will be automatically summed.
Grouping: Used to switch between grouping as per the IDF (Default) or grouping using a mapping file (Map File).
Peak Range: Sets the integration range over the peak in $meV$
Scale Factor: Factor to scale the intensities with

ISIS Diagnostics ¶

This tab allows you to perform an integration on a raw file over a specified time of flight range, and is equivalent to the Slice functionality found in MODES. It is only available when the default facility is set to ISIS.

Options ¶

Input Files: This allows you to select a run for the function to use, either by selecting the .raw file with the Browse button or through entering the number in the box. Multiple files can be selected, in the same manner as described for the Energy Transfer tab.
Use Calibration: Allows you to select either a calibration file or workspace to apply to the raw files.
Preview Spectrum: Allows selection of the spectrum to be shown in the preview plot to the right of the Time Slice section.
Spectra Min & Spectra Max: Allows selection of the range of detectors you are interested in, this is automatically set based on the instrument and analyser bank that are currently selected.
Peak: The time-of-flight range that will be integrated over to give the result (the blue range in the plot window). A default starting value is generally provided from the instrument’s parameter file.
Use Two Ranges: If selected, enables subtraction of the background range.
Background: An optional range denoting background noise that is to be removed from the raw data before the integration is performed. A default starting value is generally provided from the instrument’s parameter file.
Run: Runs the processing configured on the current tab.
Plot Result: This will plot the result as a spectra plot.
Save Result: If enabled the result will be saved as a NeXus file in the default save directory.

Transmission ¶

Calculates the sample transmission using the raw data files of the sample and its background or container. The incident and transmission monitors are converted to wavelength and the transmission monitor is normalised to the incident monitor over the common wavelength range. The sample is then divided by the background/container to give the sample transmission as a function of wavelength.

Options ¶

Sample: Allows the selection of a raw file or workspace to be used as the sample.
Background: Allows the selection of a raw file or workspace to be used as the background.
Run: Runs the processing configured on the current tab.
Plot Result: This will plot the result as a spectra plot.
Save Result: If enabled the result will be saved as a NeXus file in the default save directory.

Symmetrise ¶

This tab allows you to take an asymmetric reduced file (_red.nxs) and symmetrise it about the Y axis.

The curve is symmetrised such that the range of positive values between $EMin$ and $EMax$ are reflected about the Y axis and replaces the negative values in the range $-EMax$ to $-EMin$ , the curve between $-EMin$ and $EMin$ is not modified.

../_images/Data_Reduction_tabSymmetrise_widget.png

Options ¶

Input: Allows you to select a reduced NeXus file (_red.nxs) or workspace (_red) as the input to the algorithm.
EMin & EMax: Sets the energy range that is to be reflected about $y=0$ .
Spectrum No: Changes the spectrum shown in the preview plots.
XRange: Changes the range of the preview plot, this can be useful for inspecting the curve before running the algorithm.
Preview: This button will update the preview plot and parameters under the Preview section.
Run: Runs the processing configured on the current tab.
Plot Result: This will plot the result as a spectra plot.
Save Result: If enabled the result will be saved as a NeXus file in the default save directory.

Preview ¶

The preview section shows what a given spectra in the input will look like after it has been symmetrised and gives an idea of how well the value of EMin fits the curve on both sides of the peak.

Negative Y: The value of $y$ at $x=-EMin$ .
Positive Y: The value of $y$ at $x=EMin$ .
Delta Y: The difference between Negative and Positive Y. Typically this should be as close to zero as possible.

S(Q, w)¶

Provides an interface for running the SofQW algorithm.

../_images/Data_Reduction_tabSQw_widget.png

Options ¶

Input: Allows you to select a reduced NeXus file (_red.nxs) or workspace (_red) as the input to the algorithm. An automatic contour plot of _rqw will be plotted in the preview plot once a file has finished loading.
Q Low, Q Width & Q High: Q binning parameters that are passed to the SofQW algorithm. The low and high values can be determined using the neighbouring contour plot.
Rebin in Energy: If enabled the data will first be rebinned in energy before being passed to the SofQW algorithm.
E Low, E Width & E High: The energy rebinning parameters. The low and high values can be determined using the neighbouring contour plot.
Run: Runs the processing configured on the current tab.
Plot Spectrum: This will plot the spectrum from the result workspace which is selected in the neighbouring spinbox.
Plot Contour: This will produce a contour plot of the result.
Save Result: If enabled the result will be saved as a NeXus file in the default save directory.

Moments ¶

This interface uses the SofQWMoments algorithm to calculate the $n^{th}$ moment of an $S(Q, \omega)$ workspace created by the SofQW tab.

Options ¶

Input: Allows you to select an $S(Q, \omega)$ file (_sqw.nxs) or workspace (_sqw) as the input to the algorithm.
Scale By: Used to set an optional scale factor by which to scale the output of the algorithm.
EMin & EMax: Used to set the energy range of the sample that the algorithm will use for processing.
Run: Runs the processing configured on the current tab.
Plot Result: If enabled will plot the result as a spectra plot.
Save Result: If enabled the result will be saved as a NeXus file in the default save directory.

Categories: Interfaces | Indirect