Re #9578 SANSBeamSpreaderTransmission

Code/Mantid/docs/source/algorithms/SANSBeamSpreaderTransmission-v1.rst

@@ -9,6 +9,32 @@
 Description
 -----------
 
-Compute transmission using the beam spreader method
+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 <http://www.mantidproject.org/CalculateTransmission>`_
+as follows:
+
+:math:`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 :math:`N_{gc}`, sample and :math:`N_{gc}`, empty are the sums of all pixel counts 
+for the sample and direct beam data sets with glass carbon, and 
+:math:`N_{sample}` and :math:`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 <http://www.mantidproject.org/ApplyTransmissionCorrection>`_
+as follows:
+
+:math:`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 <http://www.mantidproject.org/HFIRSANSReduction>`_.
 
 .. categories::

Code/Mantid/docs/source/algorithms/SANSDirectBeamTransmission-v1.rst

@@ -35,4 +35,8 @@ as follows:
 :math:`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 <http://www.mantidproject.org/HFIRSANSReduction>`_ or
+`EQSANSDirectBeamTransmission <http://www.mantidproject.org/EQSANSDirectBeamTransmission>`_.
+
 .. categories::