.. algorithm::

.. summary::

.. relatedalgorithms::

.. properties::

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

This is a part of multi-algorithm reduction workflow for **IN16B** indirect geometry instrument at **ILL**.
It handles the first steps of the reduction chain, such as grouping of the detectors, normalizing to monitor dependent on the reduction type.
It performs transformation of the axes; x-axis from channel number to energy transfer, and optionally y-axis to scattering angle or elastic momentum transfer.
It handles **automatically** all four types of data (QENS, EFWS, IFWS, BATS) recorded with or without mirror sense.
Note, that following the standard, the ``Unit`` for energy transfer (``DeltaE``) will be milli-electron-volts (``mev``).
This algorithm is intended to handle only single file at a time, although if multiple files are given, they will be automatically summed at raw level, i.e. while loading.
In this case ``MergeRuns`` algorithm will be invoked, which will forbid the merges across different types of data
(e.g. different mirror senses, doppler energy or velocity profiles).
Note, that this algorithm is compatible with the data recorded from 03.2014 onwards
(i.e. where Doppler's ``mirror_sense``, ``maximum_delta_energy`` and ``velocity_profile`` entries are defined in ``.nxs`` files).
It returns a :ref:`WorkspaceGroup <WorkspaceGroup>`, containing one (no mirror sense) or two workspaces (with mirror sense) for left and right wings respectively.
This algorithm is **not** intended to be used directly by the end users. Instead it is used as a child algorithm by :ref:`IndirectILLReductionQENS <algm-IndirectILLReductionQENS>`
and :ref:`IndirectILLReductionFWS <algm-IndirectILLReductionFWS>` for QENS and FWS type of reductions correspondingly.


Workflow
--------

.. diagram:: IndirectILLEnergyTransfer-v1_wkflw.dot


BATS
----

This algorithm support also the Backscattering And Time-of-flight Spectrometer (BATS) mode of IN16B.
In this mode it will fit the elastic peak positions for each group of pixels, with grouping defined as a user input.
Elastic peak will be searched in the middle half of the TOF window.
Then each group of pixels will be calibrated to center the elastic peak at 0 energy transfer.
However in the output there will be no grouping of pixels by default.
The actual energy transfer range will be derived from the monitor window, taking the user defined cutoff value into account.
The frame offset of the monitor will be deduced automatically.
ElasticChannelWorkspace can be optionally output, which can be used as input for the measurements with inelastic offset, where there is no elastic peak in the recorded frame.
Values for single detectors will be computed similarly but separately, and they can be ignored if needed, using the ``DiscardSingleDetectors`` flag.

Usage
-----

**Example - IndirectILLEnergyTransfer : QENS data without mirror sense**

.. testsetup:: ExIndirectILLEnergyTransfer

   config['default.facility'] = 'ILL'
   config['default.instrument'] = 'IN16B'

.. testcode:: ExIndirectILLEnergyTransfer

    ws = IndirectILLEnergyTransfer(Run='ILL/IN16B/090661.nxs')
    print("Reduced workspace has {:d} wing".format(ws.getNumberOfEntries()))
    print("which has {:d} spectra".format(ws.getItem(0).getNumberHistograms()))
    print("and {:d} bins".format(ws.getItem(0).blocksize()))

Output:

.. testoutput:: ExIndirectILLEnergyTransfer

    Reduced workspace has 1 wing
    which has 18 spectra
    and 1024 bins

.. testcleanup:: ExIndirectILLEnergyTransfer

   DeleteWorkspace('ws')

**Example - IndirectILLEnergyTransfer : QENS data with mirror sense**

.. testsetup:: ExIndirectILLEnergyTransferMirrorSense

   config['default.facility'] = 'ILL'
   config['default.instrument'] = 'IN16B'

.. testcode:: ExIndirectILLEnergyTransferMirrorSense

    ws = IndirectILLEnergyTransfer(Run='ILL/IN16B/136553:136555.nxs', CropDeadMonitorChannels=True)
    print("Reduced workspace has {:d} wings".format(ws.getNumberOfEntries()))
    print("which have {:d} spectra".format(ws.getItem(0).getNumberHistograms()))
    print("and {:d} bins".format(ws.getItem(0).blocksize()))

Output:

.. testoutput:: ExIndirectILLEnergyTransferMirrorSense

    Reduced workspace has 2 wings
    which have 18 spectra
    and 1017 bins

.. testcleanup:: ExIndirectILLEnergyTransferMirrorSense

   DeleteWorkspace('ws')

**Example - IndirectILLEnergyTransfer : BATS data**

.. testsetup:: ExIndirectILLEnergyTransferBATS

   config['default.facility'] = 'ILL'
   config['default.instrument'] = 'IN16B'

.. testcode:: ExIndirectILLEnergyTransferBATS

    ws = IndirectILLEnergyTransfer(Run='ILL/IN16B/215962.nxs', PulseChopper='34', GroupDetectors=False)
    print("The output workspace has {:d} spectra".format(ws.getItem(0).getNumberHistograms()))
    print("and {:d} bins".format(ws.getItem(0).blocksize()))

Output:

.. testoutput:: ExIndirectILLEnergyTransferBATS

    The output workspace has 2050 spectra
    and 1121 bins

.. testcleanup:: ExIndirectILLEnergyTransferBATS

   DeleteWorkspace('ws')

.. categories::

.. sourcelink::