.. algorithm::

.. summary::

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Description
-----------

Performs beam flux correction for TOF SANS data.

The correction goes as follows:

        :math:`I({\lambda}) = I_0({\lambda}) / \Phi_{sample}`

where

        :math:`\Phi_{sample} = \frac{M_{sample}}{M_{ref}} \Phi_{ref}`

Workflow
########

.. diagram:: SANSBeamFluxCorrection-v1_wkflw.dot

Usage
-----

**Example - Performing a Beam Flux Correction on Dummy Data**

.. testcode:: ExTable

   # Create some dummy data, as well as a dummy monitor ws for EQSANS.
   x = [1,2,3,4,5,6,7,8,9,10,11]
   y = 491520*[0.1]
   ws = CreateWorkspace(DataX=x,DataY=y,DataE=y,NSpec='49152',UnitX='Wavelength')
   LoadInstrument(ws, InstrumentName="EQSANS", RewriteSpectraMap=True)
   monitor = SumSpectra(ws)

   # Do the correction, dragging in the file which contains the reference flux spectrum.
   corrected = SANSBeamFluxCorrection(ws, InputMonitorWorkspace=monitor, ReferenceFluxFilename="SANSBeamFluxCorrectionMonitor.nxs")

   print("The expected value of each bin should be {:.11e}.".format(0.1/(49152*0.1)/(49152*0.1)))
   print("The actual value of the first bin is {:.11e}.".format(corrected[0].readY(0)[0]))


Output:

.. testoutput:: ExTable

   The expected value of each bin should be 4.13921144274e-09.
   The actual value of the first bin is 4.13921144273e-09.

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