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SANSBeamSpreaderTransmission v1

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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: AlgorithmIndex | Workflow\SANS\UsesPropertyManager

Source

Python: SANSBeamSpreaderTransmission.py