.. algorithm::

.. summary::

.. relatedalgorithms::

.. properties::

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

The final unit of the x-axis is changed to momentum (Y) space as defined
by the formula:

.. raw:: html

   <center>

:math:`Y = 0.2393\frac{M}{\epsilon_i^{0.1}}(\omega - \frac{q^2}{2M})`

.. raw:: html

   </center>

where :math:`M` is the mass in atomic mass units,
:math:`\displaystyle\epsilon` is the incident energy,
:math:`\displaystyle\omega` is the energy change and :math:`q` is
defined as :math:`\sqrt{(k_0^2 + k_1^2 - 2k_0k_1\cos(\theta))}`.

The TOF is used to calculate :math:`\displaystyle\epsilon_i` and the
:math:`\displaystyle1/\epsilon` dependence causes an increasing set of
TOF values to be mapped to a decreasing set of :math:`\displaystyle Y`
values. As a result the final :math:`Y`-space values are reversed to
give a workspace with monotonically increasing :math:`Y` values.

Usage
-----

**Example - simple convert to Y-space:**

.. testcode:: ExConvetToYSp

    ###### Simulates Load workspace for and Indirect spectrometer #################
    tof_ws = CreateSimulationWorkspace(Instrument='MAR',BinParams=[-50,2,50],UnitX='TOF')
    SetInstrumentParameter(tof_ws,ParameterName='t0',ParameterType='Number',Value='0.5')
    SetInstrumentParameter(tof_ws,ParameterName='efixed',ParameterType='Number',Value='30.')
    ###### Convert data to format acceptable by ConvertToYSpace
    tof_ws = ConvertToPointData(tof_ws)
    ###### Convert to Y Space
    wsY=ConvertToYSpace(InputWorkspace='tof_ws',Mass='30')
    #
    # Look at sample results:
    print('part of the converted workspace:')
    for i in range(0,10): print("{:.9f} {:.11f} {}".format(wsY.readX(0)[i], wsY.readY(0)[i], wsY.readE(0)[i]))



.. testcleanup:: ExConvetToYSp

   DeleteWorkspace(wsY)
   DeleteWorkspace(tof_ws)

**Output:**

.. testoutput:: ExConvetToYSp

   part of the converted workspace:
   218.179247674 4.44978825566 0.0
   217.970903402 4.44292943299 0.0
   217.763039952 4.43608530232 0.0
   217.555655487 4.42925581439 0.0
   217.348748180 4.42244092015 0.0
   217.142316213 4.41564057078 0.0
   216.936357776 4.40885471770 0.0
   216.730871069 4.40208331255 0.0
   216.525854298 4.39532630718 0.0
   216.321305680 4.38858365367 0.0


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