EstimateResolutionDiffraction v1¶

$../_images/EstimateResolutionDiffraction-v1_dlg.png$

EstimateResolutionDiffraction dialog.

Table of Contents

Summary
Alias
Properties
Description
Instrument resolution
Factor Sheet
- NOMAD
- POWGEN
Usage
Source

Summary ¶

Estimate the resolution of each detector for a powder diffractometer.

Alias ¶

This algorithm is also known as: EstimatePDDetectorResolution

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	Name of the workspace to have detector resolution calculated.
OutputWorkspace	Output	MatrixWorkspace	Mandatory	Name of the output workspace containing delta(d)/d of each detector/spectrum.
DeltaTOF	Input	number	Mandatory	DeltaT as the resolution of TOF with unit microsecond (10^-6m).
Wavelength	Input	number	Optional	Wavelength setting in Angstroms. This overrides what is in the dataset.

Description ¶

Instrument resolution ¶

Resolution of a detector in d-spacing is defined as $\frac{\Delta d}{d}$ , which is constant for an individual detector.

Starting from the Bragg equation for T.O.F. diffractometer,

$d = \frac{t}{252.777\cdot L\cdot2\sin\theta}$

$\Delta d = \sqrt{(\Delta T)^2 + (\Delta L)^2 + (\Delta\theta)^2}$

and thus

$\frac{\Delta d}{d} = \sqrt{(\frac{\Delta T}{T})^2 + (\frac{\Delta L}{L})^2 + (\Delta\theta\cdot\cot(\theta))^2}$

where,

$\Delta T$ is the time resolution from modulator;
$\Delta\theta$ is the coverage of the detector, and can be approximated from the square root of the solid angle of the detector to sample;
$L$ is the flight path of the neutron from source to detector.

Factor Sheet ¶

NOMAD ¶

Detector size

vertical: 1 meter / 128 pixel
Horizontal: half inch or 1 inch

POWGEN ¶

Detector size: 0.005 x 0.0543

Range of $\Delta\theta\cot\theta$ : $(0.00170783, 0.0167497)$

Usage ¶

Example - estimate PG3 partial detectors’ resolution:

# Load a Nexus file
Load(Filename="PG3_2538_2k.nxs", OutputWorkspace="PG3_2538")
# Run the algorithm to estimate detector's resolution
EstimateResolutionDiffraction(InputWorkspace="PG3_2538", DeltaTOF=40.0, OutputWorkspace="PG3_Resolution")
resws = mtd["PG3_Resolution"]

print "Size of workspace 'PG3_Resolution' = ", resws.getNumberHistograms()
print "Estimated resolution of detector of spectrum 0 = ", resws.readY(0)[0]
print "Estimated resolution of detector of spectrum 100 = ", resws.readY(100)[0]
print "Estimated resolution of detector of spectrum 999 = ", resws.readY(999)[0]

Output:

Size of workspace 'PG3_Resolution' =  1000
Estimated resolution of detector of spectrum 0 =  0.00323913250277
Estimated resolution of detector of spectrum 100 =  0.00323608373204
Estimated resolution of detector of spectrum 999 =  0.00354849279137

Source ¶

C++ source: EstimateResolutionDiffraction.cpp

C++ header: EstimateResolutionDiffraction.h