.. auto-generated by script ../../../../utils/nxdl2rst.py from the NXDL source ../../../../base_classes/NXbeam.nxdl.xml

.. index::
    ! NXbeam (base class)
    ! beam (base class)
    see: beam (base class); NXbeam

.. _NXbeam:

======
NXbeam
======

**Status**:

  base class, extends :ref:`NXobject`, version 1.0

**Description**:

  Template of the state of the neutron or X-ray beam at any location. It will be referenced
  by beamline component groups within the NXinstrument group or by the NXsample group. Note
  that variables such as the incident energy could be scalar values or arrays. This group is
  especially valuable in storing the results of instrument simulations in which it is useful
  to specify the beam profile, time distribution etc. at each beamline component. Otherwise,
  its most likely use is in the NXsample group in which it defines the results of the neutron
  scattering by the sample, e.g., energy transfer, polarizations.

**Symbols**:

  No symbol table

**Groups cited**:
  :ref:`NXdata`

.. index:: NXdata (base class); used in base class

**Structure**:

  .. index:: distance (data field)

  **distance**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_LENGTH <NX_LENGTH>`}

    Distance from sample

  .. index:: incident_energy (data field)

  **incident_energy[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ENERGY <NX_ENERGY>`}

    Energy on entering beamline component

  .. index:: final_energy (data field)

  **final_energy[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ENERGY <NX_ENERGY>`}

    Energy on leaving beamline component

  .. index:: energy_transfer (data field)

  **energy_transfer[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ENERGY <NX_ENERGY>`}

    Energy change caused by beamline component

  .. index:: incident_wavelength (data field)

  **incident_wavelength[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_WAVELENGTH <NX_WAVELENGTH>`}

    Wavelength on entering beamline component

  .. index:: incident_wavelength_spread (data field)

  **incident_wavelength_spread[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_WAVELENGTH <NX_WAVELENGTH>`}

    Wavelength spread FWHM on entering component

  .. index:: incident_beam_divergence (data field)

  **incident_beam_divergence[2, j]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANGLE <NX_ANGLE>`}

    Divergence of beam entering this component

  .. index:: final_wavelength (data field)

  **final_wavelength[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_WAVELENGTH <NX_WAVELENGTH>`}

    Wavelength on leaving beamline component

  .. index:: incident_polarization (data field)

  **incident_polarization[2, j]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}

    Polarization vector on entering beamline component

  .. index:: final_polarization (data field)

  **final_polarization[2, j]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANY <NX_ANY>`}

    Polarization vector on leaving beamline component

  .. index:: final_wavelength_spread (data field)

  **final_wavelength_spread[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_WAVELENGTH <NX_WAVELENGTH>`}

    Wavelength spread FWHM of beam leaving this component

  .. index:: final_beam_divergence (data field)

  **final_beam_divergence[2, j]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_ANGLE <NX_ANGLE>`}

    Divergence FWHM of beam leaving this component

  .. index:: flux (data field)

  **flux[i]**: :ref:`NX_FLOAT <NX_FLOAT>` {units=\ :ref:`NX_FLUX <NX_FLUX>`}

    flux incident on beam plane area

  **(data)**: :ref:`NXdata`

    Distribution of beam with respect to relevant variable e.g. wavelength. This is mainly
    useful for simulations which need to store plottable information at each beamline
    component.

**Source**:
  Automatically generated from https://github.com/nexusformat/definitions/blob/master/base_classes/NXbeam.nxdl.xml