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SANSDirectBeamTransmission v1¶
Summary¶
Compute transmission using the direct beam method
Properties¶
Name |
Direction |
Type |
Default |
Description |
|---|---|---|---|---|
InputWorkspace |
Input |
Mandatory |
||
SampleDataFilename |
Input |
string |
Mandatory |
Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’] |
EmptyDataFilename |
Input |
string |
Mandatory |
Allowed values: [‘xml’, ‘nxs’, ‘nxs.h5’] |
BeamRadius |
Input |
number |
3 |
Beam radius [pixels] |
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 |
BeamCenterX |
Input |
number |
0 |
Beam center position in X |
BeamCenterY |
Input |
number |
0 |
Beam center position in Y |
ReductionProperties |
Input |
string |
__sans_reduction_properties |
Property manager name for the reduction |
OutputWorkspace |
Output |
Mandatory |
Workspace containing the data corrected for the transmission. |
|
TransmissionWorkspace |
Output |
Workspace containing the fitted transmission distribution. |
||
RawTransmissionWorkspace |
Output |
Workspace containing the transmission distribution before fitting. |
||
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 direct beam method. The transmission is calculated by the CalculateTransmission as follows:
\(T=\frac{\sum_{i;\ d(i,j)<R}\ \sum_{j} \frac{I_{sample}(i,j)}{T_{sample}}}{\sum_{i;\ d(i,j)<R}\ \sum_{j} \frac{I_{beam}(i,j)}{T_{beam}}}\)
where \(I_{sample}\) and \(I_{beam}\) are the pixel counts for the sample data set and the direct beam data set, respectively. The sums for each data set runs only over the pixels within a distance R of the beam center equal to the beam radius. \(T_{sample}\) and \(T_{beam}\) are the counting times for each of the two data sets. 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 the sample and direct beam 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 both 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 or EQSANSDirectBeamTransmission.
Categories: AlgorithmIndex | Workflow\SANS\UsesPropertyManager
Source¶
Python: SANSDirectBeamTransmission.py