4.3.2.13. NXsas¶
Status:
application definition, extends NXobject
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:
The symbol(s) listed here will be used below to coordinate fields with the same shape.
nXPixel: Number of pixels in x direction.
nYPixel: Number of pixels in y direction.
- Groups cited:
NXcollimator, NXdata, NXdetector, NXentry, NXgeometry, NXinstrument, NXmonitor, NXmonochromator, NXsample, NXshape, NXsource
Structure:
ENTRY: (required) NXentry
title: (optional) NX_CHAR
start_time: (optional) NX_DATE_TIME
end_time: (optional) NX_DATE_TIME
definition: (required) NX_CHAR
Official NeXus NXDL schema to which this file conforms.
Obligatory value:
NXsasINSTRUMENT: (required) NXinstrument
name: (required) NX_CHAR
Name of the instrument actually used to perform the experiment.
SOURCE: (required) NXsource
MONOCHROMATOR: (required) NXmonochromator
wavelength: (required) NX_FLOAT {units=NX_WAVELENGTH}
The wavelength (\(\lambda\)) of the radiation.
wavelength_spread: (optional) NX_FLOAT
delta_lambda/lambda (\(\Delta\lambda/\lambda\)): Important for resolution calculations.
COLLIMATOR: (optional) NXcollimator
GEOMETRY: (required) NXgeometry
DETECTOR: (required) NXdetector
data: (required) NX_NUMBER (Rank: 2, Dimensions: [nXPixel, nYPixel])
This is area detector data, 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.
It is necessary to define which are the x and y directions, to coordinate with the pixel size and compute Q.
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}
Physical size of a pixel in y-direction.
polar_angle: (optional) NX_FLOAT {units=NX_ANGLE}
azimuthal_angle: (optional) NX_FLOAT {units=NX_ANGLE}
rotation_angle: (optional) NX_FLOAT {units=NX_ANGLE}
aequatorial_angle: (optional) NX_FLOAT {units=NX_ANGLE}
beam_center_x: (optional) 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.
It is expected that data reduction will determine beam center from the raw data, thus it is not required here. The instrument can provide an initial or nominal value to advise data reduction.
beam_center_y: (optional) 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.
It is expected that data reduction will determine beam center from the raw data, thus it is not required here. The instrument can provide an initial or nominal value to advise data reduction.
SAMPLE: (optional) NXsample
MONITOR: (optional) NXmonitor
DATA: (required) NXdata
Hypertext Anchors¶
List of hypertext anchors for all groups, fields, attributes, and links defined in this class.