EstimateResolutionDiffraction v1

../_images/EstimateResolutionDiffraction-v1_dlg.png

EstimateResolutionDiffraction dialog.

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.

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}

as

\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

Categories: Algorithms | Diffraction\Utility