NeXus Groups

NXentry

Name	Type	Attributes	Description
user	NXuser		Group containing user contact information
sample	NXsample		Group describing sample
instrument	NXinstrument		Group describing instrument (including source and detectors)
monitor	NXmonitor		Monitor counts
data	NXdata		Plottable data
analysis	NX_CHAR	version URL	Definition of NeXus file type. The version and URL attributes define the XML DTD or schema that defines the contents of this file.
title	NX_CHAR		Title of measurement
run_number	NX_INT32		Number of run or scan stored in NXentry
program_name	NX_CHAR		Name of program that generated the data. The version number should be stored as an attribute.
command_line	NX_CHAR		Command line used to initiate current measurement
start_time	ISO 8601		Starting time of measurement
end_time	ISO 8601		Ending time of measurement
duration	NX_FLOAT32		elapsed time of experiment
notes	NX_CHAR		Any notes concerning the measurement

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NXdata

This contains plottable data and its dimension scales.

Name	Type	Attributes	Description
variable	NX_FLOAT32[]	long_name axis primary histogram_offset	Dimension scales (number to match rank of data)
data	NX_FLOAT32[]	signal	Data
errors	NX_FLOAT32[]		Standard deviations of data

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NXuser

Name	Type	Description
name	NX_CHAR	User name
affiliation	NX_CHAR	User's affiliation
address	NX_CHAR	User's postal address (complete)
telephone_number	NX_CHAR	User's telephone number
fax_number	NX_CHAR	User's fax number
email	NX_CHAR	User's e-mail address

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NXsample

Name	Type	Description
name	NX_CHAR	Sample name
chemical_formula	NX_CHAR
temperature	NX_FLOAT32[]	Sample temperature. This could be a scanned variable, in which case it is also attached to a NXdata group.
electric_field	NX_FLOAT32[3]	Applied electric field vector
magnetic_field	NX_FLOAT32[3]	Applied magnetic field vector
stress_field	NX_FLOAT32[3]
pressure	NX_FLOAT32
changer_position	NX_INT32	Sample changer position
unit_cell	NX_FLOAT32[6]	unit cell parameters (lengths and angles)
unit_cell_volume	NX_FLOAT32	volume of unit cell
orientation_matrix	NX_FLOAT32[9]
symmetry_cell_setting	NX_CHAR	e.g. orthorhombic
shape	NX_CHAR	Shape of sample: plate sphere cylinder hollow_cylinder
dimension	NX_FLOAT32[3]	length of plate edges
radius	NX_FLOAT32	radius of cylinder or sphere
inner_radius	NX_FLOAT32	inner radius of hollow cylinder
height	NX_FLOAT32	height of cylinder
mass	NX_FLOAT32
density	NX_FLOAT32
molecular_weight	NX_FLOAT32
coherent_cross_section	NX_FLOAT32
incoherent_cross_section	NX_FLOAT32
absorption_cross_section	NX_FLOAT32
shear_speed	NX_FLOAT32
solvent_mass	NX_FLOAT32
volume_fraction	NX_FLOAT32
temperature_log	NXlog	Log of sample temperature.
electric_field_log	NXlog
magnetic_field_log	NXlog

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NXinstrument

Name	Type	Description
name	NX_CHAR	Instrument name
source	NXsource	Group containing source information
monochromator	NXcrystal NXchopper	Group describing monochromator (which may be a crystal or a chopper)
analyser	NXcrystal NXchopper	Group describing analyser (which may be a crystal or a chopper)
collimator	NXcollimator	Group defining the physical characteristics of a beamline collimator.
aperture	NXaperture	Group defining a beam aperture
attenuator	NXattenuator	Group defining a beam attenuator
polarizer	NXpolarizer	Group defining a beam polarizer
flipper	NXflipper	Group defining a polarizing flipper
mirror	NXmirror	Group defining a mirror guide
detector	NXdetector	Group defining a detector, bank of detectors or multi-detector

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NXmonitor

This contains monitor data and/or integrals.

Name	Type	Description
distance	NX_FLOAT32	Position of monitor with respect to the sample
integral	NX_FLOAT32	Monitor integral
range	NX_FLOAT32[2]	Range over which monitor integral is determined (TOF only)
time_of_flight	NX_FLOAT32[]	Time-of-flight of monitor counts (TOF only)
data	NX_FLOAT32[]	Monitor counts (must be same dimension as time_of_flight)
type	NX_CHAR	type of monitor
efficiency	NX_FLOAT32[]	monitor efficiency (versus time-of-flight if required)

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NXsource

This contains information about the neutron or X-ray source.

Name	Type	Description
name	NX_CHAR	Name of facility
type	NX_CHAR	Type of source: Reactor Neutron Source Spallation Neutron Source X-ray Synchrotron Source
power	NX_FLOAT32
proton_current	NX_FLOAT32
proton_voltage	NX_FLOAT32
frequency	NX_FLOAT32
period	NX_FLOAT32
target_material	NX_CHAR	e.g. Ta, W

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NXchopper

This contains information about disk choppers, Fermi choppers, velocity selectors etc.

Name	Type	Description
distance	NX_FLOAT32	Position of chopper with respect to the sample
type	NX_CHAR	Type of chopper: Fermi disk counter_rotating_disk velocity_selector
frequency	NX_FLOAT32
period	NX_FLOAT32
radius	NX_FLOAT32	radius of chopper body
curvature	NX_FLOAT32	radius of curvature (Fermi)
slit_width	NX_FLOAT32
blade_width	NX_FLOAT32
slit_number	NX_INT32
energy	NX_FLOAT32	Optimum transmitted energy
trigger_log	NXlog	Log of chopper trigger pulses
phasing_log	NXlog	Log of chopper phases

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NXcrystal

This contains information about crystal monochromators or analyzers.

Name	Type	Description
distance	NX_FLOAT32	Position of nominal center of crystal with respect to the sample
wavelength	NX_FLOAT32[]	Nominal wavelength
energy	NX_FLOAT32[]	Nominal energy
wavevector	NX_FLOAT32[]	Nominal wavevector
lattice_parameter	NX_FLOAT32	Lattice parameter of nominal reflection
reflection	NX_FLOAT32[3]	[h,k,l] values of Bragg reflection
horizontal_curvature	NX_FLOAT32	Horizontal curvature of focusing crystal
vertical_curvature	NX_FLOAT32	Vertical curvature of focusing crystal
horizontal_aperture	NX_FLOAT32	Horizontal size of aperture (if rectangular)
vertical_aperture	NX_FLOAT32	Vertical size of aperture (if rectangular)

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NXcollimator

This contains information about beamline collimators.

Name	Type	Description
distance	NX_FLOAT32	Position of center of collimator with respect to the sample
type	NX_CHAR	Type of collimator e.g. Soller
length	NX_FLOAT32	Overall length of collimator
soller_angle	NX_FLOAT32	Angular spread of Soller collimator
horizontal_aperture	NX_FLOAT32	Horizontal size of aperture (if rectangular)
vertical_aperture	NX_FLOAT32	Vertical size of aperture (if rectangular)
radius	NX_FLOAT32	Radius of aperture (if circular)

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NXaperture

Under Construction

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NXattenuator

This contains information about beam attenuators.

Name	Type	Description
distance	NX_FLOAT32	Position of attenuator with respect to the sample
type	NX_CHAR	Type of attenuator e.g. polythene
thickness	NX_FLOAT32	Thickness of attenuator
attenuation	NX_FLOAT32	Attenuation factor

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NXpolarizer

Under Construction

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NXflipper

Under Construction

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NXmirror

Under Construction

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NXdetector

This contains information about the detector or detector bank.

Name	Type	Description
distance	NX_FLOAT32[]	Position of detector with respect to the sample
type	NX_CHAR	Type of detector: He3 gas cylinder He3 PSD He3 multidetector BF3 gas scintillator fission chamber
gas_pressure	NX_FLOAT32	Pressure of detecting gas
efficiency	NX_FLOAT32	Detector efficiency prefactor
height	NX_FLOAT32	Detector height
radius	NX_FLOAT32	Detector radius
phi	NX_FLOAT32[]	Scattering angle of detector
time_of_flight	NX_FLOAT32[]	Time of flight channel values

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This NeXus group stores information required to define 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.

Name	Type	Description
incident_energy	NX_FLOAT32[]	Energy on entering beamline component
final_energy	NX_FLOAT32[]	Energy on leaving beamline component
energy_transfer	NX_FLOAT32[]	Energy change caused by beamline component
incident_wavelength	NX_FLOAT32[]	Wavelength on entering beamline component
final_wavelength	NX_FLOAT32[]	Wavelength on leaving beamline component
incident_polarization	NX_FLOAT32[3]	Incident polarization vector
final_polarization	NX_FLOAT32[3]	Final polarization vector
flux	NX_FLOAT32
spectrum	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.

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NXlog

Name	Type	Attributes	Description
value	NX_FLOAT32[]		Value of variable being logged e.g. temperature.
time_log	ISO 8601		Time at which variable is logged.

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Comments to: Ray Osborn <ROsborn@anl.gov>
Revised: Tuesday, November 23, 1999