PDCalibration dialog.
Table of Contents
| Name | Direction | Type | Default | Description |
|---|---|---|---|---|
| SignalWorkspace | InOut | MatrixWorkspace | Mandatory | Input signal workspace. If the workspace does not exist it will read it from the SignalFile into this workspace. |
| SignalFile | Input | string | Calibration measurement. Allowed extensions: [‘_event.nxs’, ‘.nxs.h5’, ‘.nxs’] | |
| BackgroundFile | Input | string | Calibration background. Allowed extensions: [‘_event.nxs’, ‘.nxs.h5’, ‘.nxs’] | |
| MaxChunkSize | Input | number | Optional | Get chunking strategy for chunks with this number of Gbytes. File will not be loaded if this option is set. |
| FilterBadPulses | Input | number | 95 | The percentage of the average to use as the lower bound |
| TofBinning | Input | dbl list | Mandatory | Min, Step, and Max of time-of-flight bins. Logarithmic binning is used if Step is negative. |
| PreviousCalibration | Input | string | Calibration measurement. Allowed extensions: [‘.h5’, ‘.cal’] | |
| PeakPositions | Input | dbl list | Mandatory | Comma delimited d-space positions of reference peaks. |
| PeakWindow | Input | number | 0.1 | The maximum window (in d space) around peak to look for peak. |
| FWHM | Input | number | 7 | Estimated number of points covered by the fwhm of a peak (default 7) |
| Tolerance | Input | number | 4 | A measure of the strictness desired in meeting the condition on peak candidates, Mariscotti recommends 2 (default 4) |
| PeakFunction | Input | string | Gaussian | Allowed values: [‘BackToBackExponential’, ‘Gaussian’, ‘Lorentzian’] |
| BackgroundType | Input | string | Linear | Type of Background. Allowed values: [‘Flat’, ‘Linear’, ‘Quadratic’] |
| HighBackground | Input | boolean | True | Relatively weak peak in high background |
| MinGuessedPeakWidth | Input | number | 2 | Minimum guessed peak width for fit. It is in unit of number of pixels. |
| MaxGuessedPeakWidth | Input | number | 10 | Maximum guessed peak width for fit. It is in unit of number of pixels. |
| MinimumPeakHeight | Input | number | 2 | Minimum allowed peak height. |
| MaxChiSq | Input | number | 100 | Maximum chisq value for individual peak fit allowed. (Default: 100) |
| StartFromObservedPeakCentre | Input | boolean | True | Use observed value as the starting value of peak centre. |
| CalibrationParameters | Input | string | DIFC | Select calibration parameters to fit. Allowed values: [‘DIFC’, ‘DIFC+TZERO’, ‘DIFC+TZERO+DIFA’] |
| TZEROrange | Input | dbl list | Range for allowable TZERO from calibration (default is all) | |
| DIFArange | Input | dbl list | Range for allowable DIFA from calibration (default is all) | |
| OutputCalibrationTable | Output | TableWorkspace | Mandatory | An output workspace containing the Calibration Table |
| DiagnosticWorkspaces | Output | WorkspaceGroup | Mandatory | Workspaces to promote understanding of calibration results |
This algorithm calibrates the detector pixels and creates a diffraction calibration workspace. Unlike CalibrateRectangularDetectors v1 the peak fitting and calibration is done in TOF not d spacing. The peak d values are converted to TOF based on either the old calibration or the instrument geometry. The SignalFile or SignalWorkspace contains the data from a standard sample. The results are then fitted with up to difc, t_zero and difa, these values are details in AlignDetectors v1.
The peak fitting properties are explained in FindPeaks v1. This also uses the same criteria on peaks as GetDetOffsetsMultiPeaks v1.
A mask workspace is created, named “OutputCalibrationTable” + ‘_mask’, with uncalibrated pixels masked.
The resulting calibration table can be saved with SaveDiffCal v1, loaded with LoadDiffCal v1 and applied to a workspace with AlignDetectors v1. There are also three workspaces placed in the DiagnosticWorkspace group. They contain the fitted positions in dspace( _dspacing), peak widths (_width), peak heights (_height), and instrument resolution (delta-d/d _resolution). Since multiple peak shapes can be used, see the documentation for the individual fit functions to see how they relate to the effective values displayed in the diagnostic tables. For Gaussian and Lorentzian, the widths and resolution are converted to values that can be directly compared with the results of EstimateResolutionDiffraction v1.
Example - PDCalibration
# If you have a old calibration it can be used as the starting point
oldCal = 'NOM_calibrate_d72460_2016_05_23.h5'
# list of d values for diamond
dvalues = (0.3117,0.3257,0.3499,0.4205,0.4645,0.4768,0.4996,0.5150,0.5441,0.5642,0.5947,0.6307,.6866,.7283,.8185,.8920,1.0758,1.2615,2.0599)
PDCalibration(SignalWorkspace='uncalibrated',
SignalFile='NOM_72460',
TofBinning=[300,-.001,16666.7],
PreviousCalibration=oldCal,
PeakPositions=dvalues,
OutputCalibrationTable='cal',
DiagnosticWorkspaces='diag')
# Print the result
print("The calibrated difc at detid {detid} is {difc}".format(**mtd['cal'].row(40000)))
Output:
The calibrated difc at detid 40896 is 5522.64160156
Categories: Algorithms | Diffraction\Calibration
C++ source: PDCalibration.cpp (last modified: 2018-03-07)
C++ header: PDCalibration.h (last modified: 2018-03-07)