base class, extends NXobject


A neutron moderator


No symbol table

Groups cited:

NXdata, NXgeometry, NXlog, NXoff_geometry, NXtransformations


@default: (optional) NX_CHAR

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}

Effective distance as seen by measuring radiation. Note, it is recommended to use NXtransformations instead.

type: (optional) NX_CHAR

Any of these values:

  • H20

  • D20

  • Liquid H2

  • Liquid CH4

  • Liquid D2

  • Solid D2

  • C

  • Solid CH4

  • Solid H2

poison_depth: (optional) NX_FLOAT {units=NX_LENGTH}

coupled: (optional) NX_BOOLEAN

whether the moderator is coupled

coupling_material: (optional) NX_CHAR

The material used for coupling. Usually Cd.

poison_material: (optional) NX_CHAR

Any of these values: Gd | Cd

temperature: (optional) NX_FLOAT {units=NX_TEMPERATURE}

average/nominal moderator temperature

depends_on: (optional) NX_CHAR

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 moderator is its center in the x and y axis. The reference point on the z axis is the surface of the moderator pointing towards the source (the negative part of the z axis).


GEOMETRY: (optional) NXgeometry

DEPRECATED: Use the field depends_on and NXtransformations to position the moderator and NXoff_geometry to describe its shape instead

“Engineering” position of moderator

temperature_log: (optional) NXlog

log file of moderator temperature

pulse_shape: (optional) NXdata

moderator pulse shape

OFF_GEOMETRY: (optional) NXoff_geometry

This group describes the shape of the moderator

TRANSFORMATIONS: (optional) NXtransformations

This is the group recommended for holding the chain of translation and rotation operations necessary to position the component within the instrument. The dependency chain may however traverse similar groups in other component groups.

Hypertext Anchors

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

NXDL Source: