# 3.3.2.28. NXxbase¶

**Status**:

application definition, extends NXobject

**Description**:

This definition covers the common parts of all monochromatic single crystal raw data application definitions.

**Symbols**:

The symbol(s) listed here will be used below to coordinate datasets with the same shape.

nP: Number of points

nXPixels: Number of X pixels

nYPixels: Number of Y pixels

**Groups cited**:NXdata, NXdetector, NXentry, NXinstrument, NXmonitor, NXmonochromator, NXsample, NXsource

**Structure**:

entry: (required) NXentry

title: (required) NX_CHAR

start_time: (required) NX_DATE_TIME

definition: (required) NX_CHAROfficial NeXus NXDL schema to which this file conforms

Obligatory value:

`NXxbase`

instrument: (required) NXinstrument

source: (required) NXsource

monochromator: (required) NXmonochromator

wavelength: (required) NX_FLOAT {units=NX_WAVELENGTH}

detector: (required) NXdetectorThe name of the group is detector if there is only one detector, if there are several, names have to be detector1, detector2, …detectorn.

data: (required) NX_INT (Rank: 3, Dimensions: [nP, nXPixels, nYPixels])The area detector data, the first dimension is always the number of scan points, the second and third are the number of pixels in x and y. The origin is always assumed to be in the center of the detector. maxOccurs is limited to the the number of detectors on your instrument.

@signal: (required) NX_POSINTObligatory value:

`1`

x_pixel_size: (required) NX_FLOAT {units=NX_LENGTH}

y_pixel_size: (required) NX_FLOAT {units=NX_LENGTH}

distance: (required) NX_FLOAT {units=NX_LENGTH}

frame_start_number: (required) NX_INTThis is the start number of the first frame of a scan. In PX one often scans a couple of frames on a give sample, then does something else, then returns to the same sample and scans some more frames. Each time with a new data file. This number helps concatenating such measurements.

sample: (required) NXsample

name: (required) NX_CHARDescriptive name of sample

orientation_matrix: (required) NX_FLOAT (Rank: 2, Dimensions: [3, 3])The orientation matrix according to Busing and Levy conventions. This is not strictly necessary as the UB can always be derived from the data. But let us bow to common usage which includes the UB nearly always.

unit_cell: (required) NX_FLOAT (Rank: 1, Dimensions: [6])The unit cell, a, b, c, alpha, beta, gamma. Again, not strictly necessary, but normally written.

temperature: (required) NX_FLOAT (Rank: 1, Dimensions: [nP])The sample temperature or whatever sensor represents this value best

x_translation: (required) NX_FLOAT {units=NX_LENGTH}Translation of the sample along the X-direction of the laboratory coordinate system

y_translation: (required) NX_FLOAT {units=NX_LENGTH}Translation of the sample along the Y-direction of the laboratory coordinate system

distance: (required) NX_FLOAT {units=NX_LENGTH}Translation of the sample along the Z-direction of the laboratory coordinate system

control: (required) NXmonitor

DATA: (required) NXdataThe name of this group id data if there is only one detector; if there are several the names will be data1, data2, data3 and will point to the corresponding detector groups in the instrument hierarchy.

data: link (suggested target:`/NXentry/NXinstrument/NXdetector/data`

)

## Hypertext Anchors¶

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.