The FANS Data Reduction program is part of the Data Analysis and Visualization
Environment (DAVE) application suite. Since neutron scattering instruments are
usually unique in some way, it is typical to have a custom reduction program to
handle the data generated from each instrument supported in DAVE. In a reduction
module a user is able to load the instrument raw file, perform all necessary
instument-specific corrections and then produce an output which can be analyse
further in a general way without much reference to how the data was initially
collected.
The Main Application Window
The FANS Reduction program is a typical GUI application which consists of the following main components.
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FANS Data Reduction |
This module can only read raw FANS files (*.bt4). When loading a dataset you must decide how it should be used (sample, background or fast background) since there is no way to automatically determine the dataset type from the file. Based on intended dataset type, select from one of the following menu items:
Menu to Select | Dataset type | Data Browser tab |
Data Input -> Load Sample Data | sample | Sample |
Data Input -> Load Backgroud Data | background | Background |
Data Input -> Load Fast Background Data | fast background | Fast Bkgd |
Loaded datasets appear as nodes in the tree view of the Data Browser section under the tab matching the dataset type as shown in the table above.
To display a dataset in the graphics window, select it from the Data Browser tree. Switch between the tabs to display data from Sample, Background or Fast Bkgd data. The screenshot below shows a plot of a single sample dataset.
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Visualize dataset by clicking on entry in the Data Browser tree widget |
You can modify or alter the behaviour of the application by customizing the preferences from the property sheet section of the main window. A brief description of each available property is given next.
Note Any changes to your preferences are saved and will be pessistent even between sessions! However, when a previous session is loaded, the preferences that were stored with that session will become current. |
When this option is changed, the graphics window is updated immediately to reflect the change.
Sum Bkgd Data?
Use this option to specify whether or not to sum Background datasets. Obviously this only apples when multiple background datasets are loaded.
When two datasets are summed, it means the counts are averaged where their energy values overlap or appended where they do not. The result is also normalized to the monitor counts of the first dataset. Note that when multiple datasets are loaded, they are either treated individually if this option is set to No or they are all summed if option is set to Yes - it is not possible to selectively sum a subset of the loaded datasets. Therefore, if multiple Background datasets are loaded but only a subset are to be included in a sum then you must delete the datasets that should not be summed. To delete, right click on the dataset(s) and select the Delete option from the context menu.
When this option is changed, the graphics window is updated immediately to reflect the change.
Sum Fast Data?
Use this option to specify whether or not to sum Fast Background datasets. Obviously this only apples when multiple fast background datasets are loaded.
When two datasets are summed, it means the counts are averaged where their energy values overlap or appended where they do not. The result is also normalized to the monitor counts of the first dataset. Note that when multiple datasets are loaded, they are either treated individually if this option is set to No or they are all summed if option is set to Yes - it is not possible to selectively sum a subset of the loaded datasets. Therefore, if multiple Fast Background datasets are loaded but only a subset are to be included in a sum then you must delete the datasets that should not be summed. To delete, right click on the dataset(s) and select the Delete option from the context menu.
When this property is changed, the graphics window is updated immediately to reflect the change.
Rem Masked Dets
If this property is set to Yes then the detectors specified in the Masked Detectors list (next property) will be removed from further consideration.
Masked Detectors
Use this property to specify detectors to be masked or removed from further consideration. This property will be inactive unless the Rem Masked Dets property above is set to Yes. To make changes to this property, click on the field to the right of the label and then select the triangular button that appears at the extreme right of the field. A separate dialog will be displayed. Follow the instructions in
Masking Detectors to modify the detectors to be masked.
Fast Fit Func
Use this property to specify the function to be used for fitting the fast background data.
Fast Fit params
Use this property to perform a least-squares fit of the fast background data to the function specified by the Fast Fit Func property above. This property will be inactive if there is no fast background dataset loaded. To activate the fit, click on the field to the right of the label and then select the triangular button that appears at the extreme right of the field. A separate dialog will be displayed. To proceed, follow the instructions in
Fitting Fast Background.
Sub Bkgd?
If this property is set to Yes, then the background dataset, if loaded, will be subtracted from the sample dataset when calculating the final result. This property will be inactive if there is no background dataset loaded.
Sub Fast Bkgd?
If this property is set to Yes, then the fast background fit, if present, will be subtracted from the sample dataset when calculating the final result. This property will be inactive if there is no fast background dataset loaded.
Rescale Data?
Use this property to specify whether or not to rescale the data to a different monitor count as specified by the New Monitor Scale property below.
New Monitor Scale
Use this property to specify a new monitor scale to be used for calculating the final result. When this property is changed the graphics display will be updated immediately.
Overplot Fast Fit?
If this property is set to Yes then the fast background fit, if present, will be plotted together with the fast background dataset. Obviously this will only have an effect when viewing a fast background dataset.
Overplot Bkgd?
If this property is set to Yes then the background dataset, if loaded, will be plotted together with the sample dataset. The background dataset will only be overplotted when viewing a sample dataset.
Masking Detectors
Fitting Fast Background
Printing or Exporting Graphics
Saving or Exporting Datasets
Session Managemens