3.12

SANSBeamSpreaderTransmission v1

../_images/SANSBeamSpreaderTransmission-v1_dlg.png

SANSBeamSpreaderTransmission dialog.

Table of Contents

Summary

Compute transmission using the beam spreader method

Properties

Name Direction Type Default Description
InputWorkspace Input MatrixWorkspace Mandatory  
SampleSpreaderFilename Input string Mandatory Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’]
DirectSpreaderFilename Input string Mandatory Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’]
SampleScatteringFilename Input string Mandatory Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’]
DirectScatteringFilename Input string Mandatory Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’]
SpreaderTransmissionValue Input number 1 Transmission of the beam spreader
SpreaderTransmissionError Input number 0 Error on the transmission of the beam spreader
ThetaDependent Input boolean True If true, a theta-dependent correction will be applied
DarkCurrentFilename Input string   Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’]
UseSampleDarkCurrent Input boolean False If true, the sample dark current will be used
ReductionProperties Input string __sans_reduction_properties Property manager name for the reduction
OutputWorkspace Output MatrixWorkspace Mandatory  
MeasuredTransmission Output number    
MeasuredError Output number    
OutputMessage Output string   Output message

Description

Worfklow algorithm used to compute and apply the sample transmission correction using the beam spreader (“glassy carbon”) method. The transmission is calculated by the CalculateTransmission as follows:

T=\frac{N_{gc,\ sample}/T_{gc,\ sample} - T_{gc}N_{sample}/T_{sample}}{N_{gc,\ empty}/T_{gc,\ empty} - T_{gc}N_{empty}/T_{empty}}

where N_{gc}, sample and N_{gc}, empty are the sums of all pixel counts for the sample and direct beam data sets with glass carbon, and N_{sample} and N_{empty} are the sums of all the pixel counts for the sample and direct beam without glassy carbon. The T values are the corresponding counting times. If the user chose to normalize the data using the beam monitor when setting up the reduction process, the beam monitor will be used to normalize all data sets instead of the timer. If the user chose to use a dark current data set when starting the reduction process, that dark current data will be subtracted from all data sets before the transmission is calculated.

For each detector pixel, the transmission correction is applied by the ApplyTransmissionCorrection as follows:

I'(x,y)=\frac{I(x,y)}{T^{[1+\sec(2\theta)]/2}} \sigma_{I'(x,y)}=[[{\frac{\sigma_I}{{T^{[1+\sec(2\theta)]/2}}}}]^2 + [{\frac{I(x,y)\sigma_T(\frac{1+\sec(2\theta)}{2})}{{T^{[\sec(2\theta)-1]/2}}}}]^2]^{1/2}

This algorithm is rarely called directly. It is called by HFIRSANSReduction.

Categories: Algorithms | Workflow\SANS\UsesPropertyManager

Source

Python: SANSBeamSpreaderTransmission.py (last modified: 2017-09-27)