3.3.1.26. NXguide¶
Status:
base class, extends NXobject
Description:
A neutron optical element to direct the path of the beam.
NXguide is used by neutron instruments to describe a guide consists of several mirrors building a shape through which neutrons can be guided or directed. The simplest such form is box shaped although elliptical guides are gaining in popularity. The individual parts of a guide usually have common characteristics but there are cases where they are different. For example, a neutron guide might consist of 2 or 4 coated walls or a supermirror bender with multiple, coated vanes.
To describe polarizing supermirrors such as used in neutron reflection, it may be necessary to revise this definition of NXguide to include NXpolarizer and/or NXmirror.
When even greater complexity exists in the definition of what constitutes a guide, it has been suggested that NXguide be redefined as a NXcollection of NXmirror each having their own NXgeometry describing their location(s).
For the more general case when describing mirrors, consider using NXmirror.
NOTE: The NeXus International Advisory Committee welcomes comments for revision and improvement of this definition of NXguide.
Symbols:
nsurf: number of reflecting surfaces
nwl: number of wavelengths
- Groups cited:
Structure:
@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.
description: (optional) NX_CHAR
A description of this particular instance of
NXguide.incident_angle: (optional) NX_FLOAT {units=NX_ANGLE}
TODO: documentation needed
bend_angle_x: (optional) NX_FLOAT {units=NX_ANGLE}
TODO: documentation needed
bend_angle_y: (optional) NX_FLOAT {units=NX_ANGLE}
TODO: documentation needed
interior_atmosphere: (optional) NX_CHAR
Any of these values:
vacuum|helium|argonexternal_material: (optional) NX_CHAR
external material outside substrate
m_value[nsurf]: (optional) NX_FLOAT
The
mvalue for a supermirror, which defines the supermirror regime in multiples of the critical angle of Nickel.substrate_material[nsurf]: (optional) NX_FLOAT
TODO: documentation needed
substrate_thickness[nsurf]: (optional) NX_FLOAT {units=NX_LENGTH}
TODO: documentation needed
coating_material[nsurf]: (optional) NX_FLOAT
TODO: documentation needed
substrate_roughness[nsurf]: (optional) NX_FLOAT {units=NX_LENGTH}
TODO: documentation needed
coating_roughness[nsurf]: (optional) NX_FLOAT {units=NX_LENGTH}
TODO: documentation needed
number_sections: (optional) NX_INT {units=NX_UNITLESS}
number of substrate sections (also called
nsurfas an index in theNXguidespecification)GEOMETRY: (optional) NXgeometry
TODO: Explain what this NXgeometry group means. What is intended here?
reflectivity: (optional) NXdata
Reflectivity as function of reflecting surface and wavelength
@signal: (optional) NX_CHAR
Obligatory value:
data@axes: (optional) NX_CHAR
Obligatory value:
surface wavelength@surface_indices: (optional) NX_CHAR
Obligatory value:
0@wavelength_indices: (optional) NX_CHAR
Obligatory value:
1data[nsurf, nwl]: (optional) NX_NUMBER
reflectivity of each surface as a function of wavelength
surface[nsurf]: (optional) NX_NUMBER {units=NX_ANY}
List of surfaces. Probably best to use index numbers but the specification is very loose.
wavelength[nwl]: (optional) NX_NUMBER {units=NX_WAVELENGTH}
wavelengths at which reflectivity was measured
Hypertext Anchors¶
Table of hypertext anchors for all groups, fields, attributes, and links defined in this class.
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