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Diffraction Calibration Workspace

The calibration workspace contains information to convert data to/from time-of-flight and d-space using the GSAS parameters DIFC, DIFA, TZERO. The workspace itself is a TableWorkspace with the columns

name

type

detid

int32

difc

double

difa

double

tzero

double

The order of the rows and columns will not matter to algorithms that use the workspace. Algorithms that create the TableWorkspace will use this column order with the rows sorted by detid (smallest first). Any missing column, other than detid, will be assumed to be all zeros.

Diffraction Calibration File

Stored in HDF5 using as simple a nexus-style format to allow for external programs to read/write them without excessive effort. Missing values will be assumed to be zero. The data will be stored as multiple parallel 1-dimensional arrays (of length n) as described below. In addition there will be sufficient information to denote which instrument geometry file to use. This geometry will only be used for plotting the various parameters on an instrument view.

  • calibration [with attribute NX_class=NXentry]

    • instrument [with attribute NX_class=NXinstrument]

      • name (e.g. NOMAD)

      • instrument_source (e.g. NOMAD_Definition.xml or NOMAD_Definition_20120701-20120731.xml)

    • difc (double array)

    • difa (double array)

    • tzero (double array)

    • detid (int32 array)

    • dasid (int32 array) not used. The pixel number in prenexus files.

    • group (int32 array) 1 being smallest number. 0 will set to not use. This can be used in addition to

    • use (int32 array) 0=false and 1=true

    • offset (double array) not used. Value of the legacy calibration file.

The group information will still be extracted into separate GroupingWorkspace and MaskWorkspace.

Category: Concepts