2.3.3.1.2. NXattenuator

Status:

base class, extends NXobject

Description:

A device that reduces the intensity of a beam by attenuation. ...

A device that reduces the intensity of a beam by attenuation.

If uncertain whether to use NXfilter (band-pass filter) or NXattenuator (reduces beam intensity), then choose NXattenuator.

Symbols:

No symbol table

Groups cited:

NXoff_geometry, NXtransformations

Structure:

@default: (optional) NX_CHAR

Declares which child group contains a path leading ...

Declares which child group contains a path leading to a NXdata group.

It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion.

distance: (optional) NX_FLOAT {units=NX_LENGTH}

Distance from sample. Note, it is recommended to use NXtransformations instead.

type: (optional) NX_CHAR

Type or composition of attenuator, e.g. polythene

thickness: (optional) NX_FLOAT {units=NX_LENGTH}

Thickness of attenuator along beam direction

scattering_cross_section: (optional) NX_FLOAT {units=NX_CROSS_SECTION}

Scattering cross section (coherent+incoherent)

absorption_cross_section: (optional) NX_FLOAT {units=NX_CROSS_SECTION}

Absorption cross section

attenuator_transmission: (optional) NX_FLOAT {units=NX_DIMENSIONLESS}

The nominal amount of the beam that gets through ...

The nominal amount of the beam that gets through (transmitted intensity)/(incident intensity)

status: (optional) NX_CHAR

In or out or moving of the beam ...

In or out or moving of the beam

Any of these values: in | out | moving

@time: (optional) NX_DATE_TIME

time stamp for this observation

depends_on: (optional) NX_CHAR

NeXus positions components by applying a set of translations and rotations ...

NeXus positions components by applying a set of translations and rotations to apply to the component starting from 0, 0, 0. The order of these operations is critical and forms what NeXus calls a dependency chain. The depends_on field defines the path to the top most operation of the dependency chain or the string “.” if located in the origin. Usually these operations are stored in a NXtransformations group. But NeXus allows them to be stored anywhere.

The reference point of the attenuator is its center in the x and y axis. The reference point on the z axis is the surface of the attenuator pointing towards the source.

In complex (asymmetic) geometries an NXoff_geometry group can be used to provide an unambiguous reference.

../../_images/attenuator.png

TRANSFORMATIONS: (optional) NXtransformations

shape: (optional) NXoff_geometry

Shape of this component. Particulary useful to define the origin for position and orientation in non-standard cases.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source:

https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/base_classes/NXattenuator.nxdl.xml