CalibrateRectangularDetectors v1¶

CalibrateRectangularDetectors dialog.

Table of Contents

Summary
- See Also
Properties
Description
Features to improve performance of peak finding
- Define peak fit-window
- Define accepted range of peak’s width
Source

Summary ¶

Calibrate the detector pixels and write a calibration file

Properties ¶

Name	Direction	Type	Default	Description
RunNumber	Input	list of str lists	Mandatory	Event file. Allowed extensions: [‘_event.nxs’, ‘.nxs.h5’]
Background	Input	int list	0
XPixelSum	Input	number	1	Sum detector pixels in X direction. Must be a factor of X total pixels. Default is 1.
YPixelSum	Input	number	1	Sum detector pixels in Y direction. Must be a factor of Y total pixels. Default is 1.
SmoothSummedOffsets	Input	boolean	False	If the data was summed for calibration, smooth the resulting offsets workspace.
SmoothGroups	Input	string		Comma delimited number of points for smoothing pixels in each group. Default is no Smoothing.
UnwrapRef	Input	number	0	Reference total flight path for frame unwrapping. Zero skips the correction
LowResRef	Input	number	0	Reference DIFC for resolution removal. Zero skips the correction
MaxOffset	Input	number	1	Maximum absolute value of offsets; default is 1
CrossCorrelation	Input	boolean	True	CrossCorrelation if True; minimize using many peaks if False.
PeakPositions	Input	dbl list		Comma delimited d-space positions of reference peaks. Use 1-3 for Cross Correlation. Unlimited for many peaks option.
PeakWindowMax	Input	number	0	Maximum window around a peak to search for it. Optional.
FitwindowTableWorkspace	Input	TableWorkspace		Name of input table workspace containing the fit window information for each spectrum.
MinimumPeakHeight	Input	number	2	Minimum value allowed for peak height
MinimumPeakHeightObs	Input	number	0	Minimum value of a peak’s maximum observed Y value for this peak to be used to calculate offset.
DetectorResolutionWorkspace	Input	MatrixWorkspace		Name of optional input matrix workspace for each detector’s resolution (D(d)/d).
AllowedResRange	Input	dbl list	0.25,4	Range of allowed individual peak’s resolution factor to input detector’s resolution.
PeakFunction	Input	string	Gaussian	Type of peak to fit. Used only with CrossCorrelation=False. Allowed values: [‘BackToBackExponential’, ‘Gaussian’, ‘Lorentzian’]
BackgroundType	Input	string	Flat	Used only with CrossCorrelation=False. Allowed values: [‘Flat’, ‘Linear’, ‘Quadratic’]
DetectorsPeaks	Input	int list		Comma delimited numbers of detector banks for each peak if using 2-3 peaks for Cross Correlation. Default is all.
PeakHalfWidth	Input	number	0.05	Half width of d-space around peaks for Cross Correlation. Default is 0.05
CrossCorrelationPoints	Input	number	100	Number of points to find peak from Cross Correlation. Default is 100
Binning	Input	dbl list	0,0,0	Min, Step, and Max of d-space bins. Logarithmic binning is used if Step is negative.
DiffractionFocusWorkspace	Input	boolean	False	Diffraction focus by detectors. Default is False
GroupDetectorsBy	Input	string	All	Detector groups to use for future focussing: All detectors as one group, Groups (East,West for SNAP), Columns for SNAP, detector banks. Allowed values: [‘All’, ‘Group’, ‘Column’, ‘bank’]
FilterBadPulses	Input	boolean	True	Filter out events measured while proton charge is more than 5% below average
FilterByTimeMin	Input	number	0	Relative time to start filtering by in seconds. Applies only to sample.
FilterByTimeMax	Input	number	0	Relative time to stop filtering by in seconds. Applies only to sample.
SaveAs	Input	string	calibration	Allowed values: [‘dspacemap’, ‘calibration’, ‘dspacemap and calibration’]
OutputDirectory	Input	string	Mandatory
OutputFilename	Output	string

Description ¶

Here are examples of input and output from PG3 and SNAP:

The purpose of this algorithm is to calibrate the detector pixels and write a calibration file. The calibration file name contains the instrument, run number, and date of calibration. A binary Dspacemap file that converts from TOF to d-space including the calculated offsets is also an output option. For CrossCorrelation option: If one peak is not in the spectra of all the detectors, you can specify the first n detectors to be calibrated with one peak and the next n detectors to be calibrated with the second peak. If a color fill plot of the calibrated workspace does not look good, do a color fill plot of the workspace that ends in cc (cross correlation) to see if the CrossCorrelationPoints and/or PeakHalfWidth should be increased or decreased. Also plot the reference spectra from the cc workspace.

Features to improve performance of peak finding ¶

Define peak fit-window ¶

There are two exclusive approaches to define peak’s fit-window.

PeakWindowMax All peaks will use this value to define their fitting range.
FitwindowTableWorkspace This is a table workspace by which each peak will have its individual fit window defined.

Define accepted range of peak’s width ¶

Optional input property DetectorResolutionWorkspace is a matrix workspace containing the detector resolution $\Delta(d)/d$ for each spectrum. Combining with property AllowedResRange, it defines the lower and upper limit for accepted fitted peak width.

Let $c_l = AllowedResRange[0]$ , $c_h = AllowedResRange[1]$ and $fwhm$ as the peak’s fitted width. Then,

$c_l\times\frac{\Delta(d)}{d} < fwhm < c_h\times\frac{\Delta(d)}{d}$

Source ¶

Python: CalibrateRectangularDetectors.py (last modified: 2019-03-11)