SpecularReflectionCalculateTheta v2¶

SpecularReflectionCalculateTheta dialog.

Table of Contents

Summary
Properties
Description
Previous Versions
Usage
Source

Summary ¶

Calculate the specular reflection two theta scattering angle (degrees) from the detector and sample locations .

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	An Input workspace to calculate the specular relection theta on.
AnalysisMode	Input	string	PointDetectorAnalysis	The type of analysis to perform. MultiDetectorAnalysis, LineDetectorAnalysis or MultiDetectorAnalysis. Used to help automatically determine the detector components to move. Allowed values: [‘PointDetectorAnalysis’, ‘LineDetectorAnalysis’, ‘MultiDetectorAnalysis’]
DetectorComponentName	Input	string		Name of the detector component i.e. point-detector. If these are not specified, the algorithm will attempt lookup using a standard naming convention.
SampleComponentName	Input	string		Name of the sample component i.e. some-surface-holder. If these are not specified, the algorithm will attempt lookup using a standard naming convention.
SpectrumNumbersOfDetectors	Input	int list		A list of spectrum numbers making up an effective point detector.
StrictSpectrumChecking	Input	boolean	True	Enable, disable strict spectrum checking. Strict spectrum checking protects against non-sequential integers in which spectrum numbers are not in {min, min+1, ..., max}
TwoTheta	Output	number		Calculated two theta scattering angle in degrees.

Description ¶

Uses the Specular reflection condition $\theta_{In} \equiv \theta_{Out}$ to calculate and return a corrected $\theta_{In}$ .

$2\theta = \arctan\left(\frac{UpOffset}{BeamOffset}\right)$

The calculated $2\theta$ value in degrees is returned by the algorithm.

Also see SpecularReflectionPositionCorrect v2

Previous Versions ¶

For version 1 of the algorithm, please see SpecularReflectionCalculateTheta-v1.. Note that version 1 worked with detectors at $\theta$ rather than $2\theta$ for historical reasons.

Usage ¶

Example - Point detector theta calculation

# Set up an instrument with a 45 degree final two theta angle.
import os
instrument_def = os.path.join( config.getInstrumentDirectory() , "INTER_Definition.xml")
ws = LoadEmptyInstrument(instrument_def)
inst = ws.getInstrument()
ref_frame = inst.getReferenceFrame()
upoffset = ref_frame.vecPointingUp()
det_position = {ref_frame.pointingUpAxis(): 1.0, ref_frame.pointingAlongBeamAxis(): 1.0, ref_frame.pointingHorizontalAxis():0}
MoveInstrumentComponent(ws, 'point-detector',RelativePosition=False, **det_position)
MoveInstrumentComponent(ws, 'some-surface-holder',RelativePosition=False,  X=0, Y= 0, Z=0)

# Calculate the two theta.
two_theta = SpecularReflectionCalculateTheta(InputWorkspace=ws, DetectorComponentName='point-detector', AnalysisMode='PointDetectorAnalysis')
print(two_theta)