3.3.2.13. NXsas

Status:

application definition, extends NXobject, version 1.0b

Description:

raw, monochromatic 2-D SAS data with an area detector

This is an application definition for raw data (not processed or reduced data) from a 2-D small angle scattering instrument collected with a monochromatic beam and an area detector. It is meant to be suitable both for neutron SANS and X-ray SAXS data.

It covers all raw data from any monochromatic SAS techniques that use an area detector: SAS, WSAS, grazing incidence, GISAS

It covers all raw data from any SAS techniques that use an area detector and a monochromatic beam.

Symbols:

No symbol table
Groups cited:
NXcollimator, NXdata, NXdetector, NXentry, NXgeometry, NXinstrument, NXmonitor, NXmonochromator, NXsample, NXshape, NXsource

Structure:

(entry): (required) NXentry

@entry: (required) NX_CHAR

NeXus convention is to use entry1, entry2, … for analysis software to locate each entry

title: (required) NX_CHAR

start_time: (required) NX_DATE_TIME

end_time: (required) NX_DATE_TIME

definition: (required) NX_CHAR

Official NeXus NXDL schema to which this file conforms

Obligatory value: NXsas

instrument: (required) NXinstrument

name: (required) NX_CHAR

Name of the instrument actually used to perform the experiment

source: (required) NXsource

type: (required) NX_CHAR

type of radiation source

name: (required) NX_CHAR

Name of the radiation source

probe: (required) NX_CHAR

Any of these values: neutron | x-ray

monochromator: (required) NXmonochromator

wavelength: (required) NX_FLOAT {units=NX_WAVELENGTH}

The wavelength of the radiation

wavelength_spread: (required) NX_FLOAT

delta_lambda/lambda (\(\Delta\lambda/\lambda\)): Important for resolution calculations

collimator: (required) NXcollimator

geometry: (required) NXgeometry

shape: (required) NXshape

shape: (required) NX_CHAR

Any of these values: nxcylinder | nxbox

size: (required) NX_FLOAT {units=NX_LENGTH}

The collimation length

detector: (required) NXdetector

data[nXPixel, nYPixel]: (required) NX_NUMBER

This is area detector data, of number of x-pixel versus number of y-pixels. Since the beam center is to be determined as a step of data reduction, it is not necessary to document or assume the position of the beam center in acquired data.

distance: (required) NX_FLOAT {units=NX_LENGTH}

The distance between detector and sample

x_pixel_size: (required) NX_FLOAT {units=NX_LENGTH}

Physical size of a pixel in x-direction

y_pixel_size: (required) NX_FLOAT {units=NX_LENGTH}

Size of a pixel in y direction

polar_angle: (required) NX_FLOAT {units=NX_ANGLE}

azimuthal_angle: (required) NX_FLOAT {units=NX_ANGLE}

rotation_angle: (required) NX_FLOAT {units=NX_ANGLE}

aequatorial_angle: (required) NX_FLOAT {units=NX_ANGLE}

beam_center_x: (required) NX_FLOAT {units=NX_LENGTH}

This is the x position where the direct beam would hit the detector. This is a length, not a pixel position, and can be outside of the actual detector.

beam_center_y: (required) NX_FLOAT {units=NX_LENGTH}

This is the y position where the direct beam would hit the detector. This is a length, not a pixel position, and can be outside of the actual detector.

sample: (required) NXsample

name: (required) NX_CHAR

Descriptive name of sample

aequatorial_angle: (required) NX_FLOAT {units=NX_ANGLE}

control: (required) NXmonitor

mode: (required) NX_CHAR

Count to a preset value based on either clock time (timer) or received monitor counts (monitor).

Any of these values: monitor | timer

preset: (required) NX_FLOAT

preset value for time or monitor

integral: (required) NX_FLOAT {units=NX_ANY}

Total integral monitor counts

data: (required) NXdata

data –> /NXentry/NXinstrument/NXdetector/data
NXDL Source:
https://github.com/nexusformat/definitions/blob/master/applications/NXsas.nxdl.xml