3.3.1.3. NXbeam

Status:

base class, extends NXobject, version 1.0

Description:

Properties of the neutron or X-ray beam at a given 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:

NXdata

Structure:

distance: NX_FLOAT {units=NX_LENGTH}

Distance from sample

incident_energy[i]: NX_FLOAT {units=NX_ENERGY}

Energy on entering beamline component

final_energy[i]: NX_FLOAT {units=NX_ENERGY}

Energy on leaving beamline component

energy_transfer[i]: NX_FLOAT {units=NX_ENERGY}

Energy change caused by beamline component

incident_wavelength[i]: NX_FLOAT {units=NX_WAVELENGTH}

Wavelength on entering beamline component

incident_wavelength_spread[i]: NX_FLOAT {units=NX_WAVELENGTH}

Wavelength spread FWHM on entering component

incident_beam_divergence[2, j]: NX_FLOAT {units=NX_ANGLE}

Divergence of beam entering this component

final_wavelength[i]: NX_FLOAT {units=NX_WAVELENGTH}

Wavelength on leaving beamline component

incident_polarization[2, j]: NX_FLOAT {units=NX_ANY}

Polarization vector on entering beamline component

final_polarization[2, j]: NX_FLOAT {units=NX_ANY}

Polarization vector on leaving beamline component

final_wavelength_spread[i]: NX_FLOAT {units=NX_WAVELENGTH}

Wavelength spread FWHM of beam leaving this component

final_beam_divergence[2, j]: NX_FLOAT {units=NX_ANGLE}

Divergence FWHM of beam leaving this component

flux[i]: NX_FLOAT {units=NX_FLUX}

flux incident on beam plane area

(data): 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.

NXDL Source:

https://github.com/nexusformat/definitions/blob/master/base_classes/NXbeam.nxdl.xml