3.12

SCDCalibratePanels v1

../_images/SCDCalibratePanels-v1_dlg.png

SCDCalibratePanels dialog.

Summary

Panel parameters and L0 are optimized to minimize errors between theoretical and actual q values for the peaks

Properties

Name Direction Type Default Description
PeakWorkspace InOut PeaksWorkspace Mandatory Workspace of Indexed Peaks
a Input number Optional Lattice Parameter a (Leave empty to use lattice constants in peaks workspace)
b Input number Optional Lattice Parameter b (Leave empty to use lattice constants in peaks workspace)
c Input number Optional Lattice Parameter c (Leave empty to use lattice constants in peaks workspace)
alpha Input number Optional Lattice Parameter alpha in degrees (Leave empty to use lattice constants in peaks workspace)
beta Input number Optional Lattice Parameter beta in degrees (Leave empty to use lattice constants in peaks workspace)
gamma Input number Optional Lattice Parameter gamma in degrees (Leave empty to use lattice constants in peaks workspace)
ChangeL1 Input boolean True Change the L1(source to sample) distance
ChangeT0 Input boolean False Change the T0 (initial TOF)
ChangePanelSize Input boolean True Change the height and width of the detectors. Implemented only for RectangularDetectors.
EdgePixels Input number 0 Remove peaks that are at pixels this close to edge.
CalibrateBanks Input boolean True Calibrate the panels of the banks.
CalibrateSNAPPanels Input boolean False Calibrate the 3 X 3 panels of the sides of SNAP.
DetCalFilename Input string SCDCalibrate.DetCal Path to an ISAW-style .detcal file to save. Allowed extensions: [‘.detcal’, ‘.det_cal’]
XmlFilename Input string   Path to an Mantid .xml description(for LoadParameterFile) file to save. Allowed extensions: [‘.xml’]
ColFilename Input string ColCalcvsTheor.nxs Path to a NeXus file comparing calculated and theoretical column of each peak. Allowed extensions: [‘.nxs’]
RowFilename Input string RowCalcvsTheor.nxs Path to a NeXus file comparing calculated and theoretical row of each peak. Allowed extensions: [‘.nxs’]
TofFilename Input string TofCalcvsTheor.nxs Path to a NeXus file comparing calculated and theoretical TOF of each peak. Allowed extensions: [‘.nxs’]

Description

This algorithm calibrates panels of Rectangular Detectors or packs of tubes in an instrument. The initial path, panel centers and orientations are adjusted so the error in Q positions from the theoretical Q positions is minimized. Given a set of peaks indexed by (h_i, k_i, l_i), we modify the instrument parameters, p, and then find Q in the sample frame, \rm Q_{sample} that mininizes the following:

\left\vert 2\pi \rm U \rm B \left( \begin{array}{c} NINT(h_i) \\ NINT(k_i) \\ NINT(l_i) \\ \end{array} \right) - \rm Q_{sample,i}(p) \right\vert ^2

NINT is the nearest integer function. B is fixed from the input lattice parameters, but U is modified by CalculateUMatrix for all peaks before and after optimization. When the peaks are indexed, sample offsets are adjusted to better index the peaks. The initial time-of-flight, T0, is optimized for all peaks before any parameters are optimized. The initial path, L1, is optimized for all peaks before and after all panels or packs’ parameters are optimized. The panels and packs’ parameters are optimized in parallel. An option is available to adjust the panel widths and heights for Rectangular Detectors in a second iteration with all the other parameters fixed.

OUTPUT workspaces and files:

  1. The results are saved to an ISAW-like DetCal file and optionally in an xml file that can be used with the LoadParameterFile algorithm.
  2. There are two output workspace groups that are output when this algorithm calls the Fit algorithm.
    1. Fit_Parameters: workspaces beginning with ‘params’ contains the results from fitting for each bank and for L1.
      • XShift, YShift,and ZShift are in meters.
      • XRotate, YRotate, and ZRotate are in degrees.
    2. Fit_Residuals: workspaces beginning with ‘fit’ contain the differences in the calculated and theoretical Q vectors for each peak.
  3. There are three output files that show the goodness of the calibration.
    1. ColFilename contains the calculated and theoretical column for each peak. Each spectra is labeled by the bank. To plot use python script, scripts/SCD_Reduction/SCDCalibratePanelsResults.py
    2. RowFilename contains the calculated and theoretical row for each peak. Each spectra is labeled by the bank. To plot use python script, scripts/SCD_Reduction/SCDCalibratePanelsResults.py
    3. TofFilename contains the calculated and theoretical TOF for each peak. Each spectra is labeled by the bank.

After Calibration

After calibration, you can save the workspace to Nexus (or Nexus processed) and get it back by loading in a later Mantid session. You can copy the calibration to another workspace using the same instrument by means of the CopyInstrumentParameters v1 algorithm. To do so select the workspace, which you have calibrated as the InputWorkspace and the workspace you want to copy the calibration to, the OutputWorkspace.

Usage

#Calibrate peaks file and load to workspace
LoadIsawPeaks(Filename='MANDI_801.peaks', OutputWorkspace='peaks')
#TimeOffset is not stored in xml file, so use DetCal output if you need TimeOffset
SCDCalibratePanels(PeakWorkspace='peaks',DetCalFilename='mandi_801.DetCal',XmlFilename='mandi_801.xml',a=74,b=74.5,c=99.9,alpha=90,beta=90,gamma=60)
LoadEmptyInstrument(Filename=config.getInstrumentDirectory() + 'MANDI_Definition_2013_08_01.xml', OutputWorkspace='MANDI_801_event_DetCal')
CloneWorkspace(InputWorkspace='MANDI_801_event_DetCal', OutputWorkspace='MANDI_801_event_xml')
LoadParameterFile(Workspace='MANDI_801_event_xml', Filename='mandi_801.xml')
LoadIsawDetCal(InputWorkspace='MANDI_801_event_DetCal', Filename='mandi_801.DetCal')
det1 = mtd['MANDI_801_event_DetCal'].getInstrument().getDetector(327680)
det2 = mtd['MANDI_801_event_xml'].getInstrument().getDetector(327680)
if det1.getPos() == det2.getPos():
    print("matches")

Output:

matches

Categories: Algorithms | Crystal\Corrections

Source

C++ source: SCDCalibratePanels.cpp (last modified: 2018-01-09)

C++ header: SCDCalibratePanels.h (last modified: 2017-08-18)