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FindGoniometerAngles v1¶
Summary¶
Do a brute force search for the goniometer rotation angles that maximize the number of peaks indexed by the specified UB.
See Also¶
Properties¶
Name |
Direction |
Type |
Default |
Description |
|---|---|---|---|---|
PeaksWorkspace |
Input |
IPeaksWorkspace |
Mandatory |
Workspace of Peaks with UB loaded |
MaxAngle |
Input |
number |
5 |
The maximum change in angle to try for any of the goniometer angles, phi, chi and omega, in degrees. |
Tolerance |
Input |
number |
0.15 |
The tolerance on Miller indices for a peak to be considered indexed |
Apply |
Input |
boolean |
False |
Update goniometer in peaks workspace |
Phi |
Output |
number |
Phi found |
|
Chi |
Output |
number |
Chi found |
|
Omega |
Output |
number |
Omega found |
Description¶
Do a brute force search for the goniometer rotation angles that maximize the number of peaks indexed by the UB on the peaks workspace. The peaks must have peaks from only one run. The search will start with the goniometer position set on the PeaksWoskpace and deviations from that goniometer up to MaxAngle will be tried, seaching for the gonomater angles that maximize the number of peaks indexed and minimize the total indexing error. This algorithm was ported from ISAW.
The best goniometer angles found will be returned in terms of phi, chi, omega (“YZY”) and if Apply is selected then the goniometer will be updated on the PeaksWorkspace and the Peaks.
Usage¶
Example - FindGoniometerAngles
# create a peaks workspace with particular lattice and goniometer
ws = LoadEmptyInstrument(InstrumentName="TOPAZ")
SetGoniometer(ws, Axis0="45,0,0,1,1")
SetUB(ws, a=5, b=5, c=5, alpha=90, beta=90, gamma=90)
peaks = PredictPeaks(ws)
num_peaks = peaks.getNumberPeaks()
# create new peaks workspace with wrong goniometer
new_peaks = CreatePeaksWorkspace(ws, 0)
SetGoniometer(new_peaks, Axis0="42,0,0,1,1")
SetUB(new_peaks, a=5, b=5, c=5, alpha=90, beta=90, gamma=90)
# copy peak q_lab vectors, q_sample will be wrong since wrong goniometer
from mantid.kernel import SpecialCoordinateSystem
for i in range(num_peaks):
new_peaks.addPeak(peaks.getPeak(i).getQLabFrame(), SpecialCoordinateSystem.QLab)
results = IndexPeaks(new_peaks, 0.05)
print(f"Starting with {results.NumIndexed} out of {num_peaks} peaks indexed")
angles = FindGoniometerAngles(new_peaks, Apply=True)
results = IndexPeaks(new_peaks, 0.05)
print(f"Found Chi={angles.Chi:.2f} and there are now {results.NumIndexed} out of {num_peaks} peaks indexed")
Output:
Starting with 0 out of 65 peaks indexed
Found Chi=44.99 and there are now 65 out of 65 peaks indexed
Categories: AlgorithmIndex | Crystal\Corrections
Source¶
C++ header: FindGoniometerAngles.h
C++ source: FindGoniometerAngles.cpp