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 | 4 | Minimum guessed peak width for fit. It is in unit of number of pixels. |
| MaxGuessedPeakWidth | Input | number | 4 | 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’] |
| OutputCalibrationTable | Output | TableWorkspace | Mandatory | An output workspace containing the Calibration Table |
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.
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')
# 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