3.3.2.18. NXstxm¶
Status:
application definition, extends NXobject
Description:
Application definition for a STXM instrument.
The interferometer position measurements, monochromator photon energy values and detector measurements are all treated as NXdetectors and stored within the NXinstrument group as lists of values stored in chronological order. The NXdata group then holds another version of the data in a regular 3D array (NumE by NumY by NumX, for a total of nP points in a sample image stack type scan). The former data values should be stored with a minimum loss of precision, while the latter values can be simplified and/or approximated in order to fit the constraints of a regular 3D array. ‘Line scans’ and ‘point spectra’ are just sample_image scan types with reduced dimensions in the same way as single images have reduced E dimensions compared to image ‘stacks’.
Symbols:
These symbols will be used below to coordinate the shapes of the datasets.
nP: Total number of scan points
nE: Number of photon energies scanned
nX: Number of pixels in X direction
nY: Number of pixels in Y direction
detectorRank: Rank of data array provided by the detector for a single measurement
- Groups cited:
NXdata, NXdetector, NXentry, NXinstrument, NXmonitor, NXmonochromator, NXsample, NXsource
Structure:
ENTRY: (required) NXentry
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:
NXstxmINSTRUMENT: (required) NXinstrument
SOURCE: (required) NXsource
monochromator: (required) NXmonochromator
energy: (required) NX_FLOAT (Rank: 1, Dimensions: [nP])
DETECTOR: (required) NXdetector
data: (required) NX_NUMBER (Rank: 1+detectorRank, Dimensions: [nP])
sample_x: (optional) NXdetector
Measurements of the sample position from the x-axis interferometer.
data: (required) NX_FLOAT (Rank: 1, Dimensions: [nP])
sample_y: (optional) NXdetector
Measurements of the sample position from the y-axis interferometer.
data: (required) NX_FLOAT (Rank: 1, Dimensions: [nP])
sample_z: (optional) NXdetector
Measurements of the sample position from the z-axis interferometer.
data: (required) NX_FLOAT (Rank: 1, Dimensions: [nP])
SAMPLE: (required) NXsample
rotation_angle: (required) NX_FLOAT
DATA: (required) NXdata
stxm_scan_type: (required) NX_CHAR
- Label for typical scan types as a convenience for humans.
Each label corresponds to a specific set of axes being scanned to produce a data array of shape:
sample point spectrum: (photon_energy,)
sample line spectrum: (photon_energy, sample_y/sample_x)
sample image: (sample_y, sample_x)
sample image stack: (photon_energy, sample_y, sample_x)
sample focus: (zoneplate_z, sample_y/sample_x)
osa image: (osa_y, osa_x)
osa focus: (zoneplate_z, osa_y/osa_x)
detector image: (detector_y, detector_x)
The “generic scan” string is to be used when none of the other choices are appropriate.
Any of these values:
sample point spectrum
sample line spectrum
sample image
sample image stack
sample focus
osa image
osa focus
detector image
generic scandata: (required) NX_NUMBER
- Detectors that provide more than one value per scan point should be summarised
to a single value per scan point for this array in order to simplify plotting.
Note that ‘Line scans’ and focus type scans measure along one spatial dimension but are not restricted to being parallel to the X or Y axes. Such scans should therefore use a single dimension for the positions along the spatial line. The ‘sample_x’ and ‘sample_y’ fields should then contain lists of the x- and y-positions and should both have the ‘axis’ attribute pointing to the same dimension.
energy: (required) NX_FLOAT (Rank: 1, Dimensions: [nE])
- List of photon energies of the X-ray beam. If scanned through multiple values,
then an ‘axis’ attribute will be required to link the field to the appropriate data array dimension.
sample_y: (required) NX_FLOAT (Rank: 1, Dimensions: [nY])
- List of Y positions on the sample. If scanned through multiple values,
then an ‘axis’ attribute will be required to link the field to the appropriate data array dimension.
sample_x: (required) NX_FLOAT (Rank: 1, Dimensions: [nX])
- List of X positions on the sample. If scanned through multiple values,
then an ‘axis’ attribute will be required to link the field to the appropriate data array dimension.
control: (optional) NXmonitor
data: (required) NX_FLOAT
- Values to use to normalise for time-variations in photon flux. Typically, the synchrotron storage ring
electron beam current is used as a proxy for the X-ray beam intensity. Array must have same shape as the NXdata groups.
Hypertext Anchors¶
List of hypertext anchors for all groups, fields, attributes, and links defined in this class.