VIII - "Externals"
WinSPA's file formats
Instead of creating yet another proprietory binary file format, the usage of NetCDF was decided for WinSPA. This file format is
- Self-Describing
- Architecture-independent
- Sharable
- Direct-access
You can find many resources for and about this file format in the world wide web, for example
- Free browser NCbrowse
- Free browser Panoply
- IDL-based NetCDF browser and tools at David Fanning's IDL site
Even though in principle NetCDF files are self-describing, the variables in WinSPA files are described in detail below.
Note: If you want to import/export NetCDF files with the programming language Delphi, you can use the same interface library that was used for WinSPA. It is an improved version of the Delphi NetCDF interface declaration by Sandy Ballard of Sandia.
Global attributes
The global attributes are defined in all NetCDF files saved by WinSPA. They describe the type of the file and contain information about the WinSPA release the file was created with.
| Name of NetCDF variable | Full name | Comments |
|---|---|---|
| Title | Title of the file. | This describes the type of the file. |
| History | History of file changes. | Contains only the creation by default. |
| Creator | Program that created the file. | Contains "WinSPA". |
| Version | Version of the creating software. | Version and date of the WinSPA release the file was created with. |
The different file "types" WinSPA uses are:
- 1D scan. Title is "one dimensional scan of electron diffraction pattern" in this case.
- 2D scan. Title is "two dimensional scan of electron diffraction pattern" in this case.
- RSM scan. Title is "reciprocal space map with SPA-LEED" in this case.
- SEM scan. Title is "real space scan with SPA-LEED" in this case.
- I(t) scan. Title is "observation of diffraction intensities versus time" in this case.
Note: WinSPA accepts also 2D scans with scan units Volts as SEM scan and vice versa.
General scan information
The general scan information parameters are the same for all WinSPA save files, independent of the scan type. They describe how the scan data were acquired (gate time, scan time, min/max counts, cycles, etc.).
| Name of NetCDF variable | Full name | Units | Comments |
|---|---|---|---|
| MinCnts | Minimum number of counts within scan | -- | ... |
| MaxCnts | Maximum number of counts within scan | -- | ... |
| CycleCnt | Number of scan cycles with averaging | -- | ... |
| TStart | Start time of scan | Days since 12/30/1899 | ... |
| TStop | Stop time of scan | Days since 12/30/1899 | ... |
| TStartRel | Relative start time of scan | msecs. since t=0 of stop watch | ... |
| GateTime | Counter gate time | msecs. | ... |
| Interrupted | Scan interrupted? | 0 = no, 1 = yes | ... |
| RawData | Scan data unaltered? | 0 = no, 1 = yes | ... |
| Comment | User's comment to scan | None (string variable) | As entered in the "comment" field in the respective "file settings" group box. |
| Usr1,Usr2,Usr3,Usr4 | User defined values #1..#4 | Unknown | A legacy of Spa4.1d only. Not used or written by WinSPA. May only contains values, if a .d2d file was imported and saved as a WinSPA file. |
Sample information
The global sample parameter settings are saved for documentation.
| Name of NetCDF variable | Full name | Units |
|---|---|---|
| SName | Surface name | None (string variable) |
| SLConst | Surface lattice constant | Å |
| SSHeight | Surface step height | Å |
Data scaling information
The original scan data and the scaling of the data are fundamentally distinguished in WinSPA. Consequently there are explicit variables which only affect the scaling of the scan data upon loading the respective scan data file.
| Name of NetCDF variable | Full name | Units | Comments |
|---|---|---|---|
| ScMinCnts | Min. value to display | Counts | ... |
| ScMaxCnts | Max. value to display | Counts | ... |
| MinXValue | X axis start | ... | ... |
| MaxXValue | X axis stop | ... | ... |
| SclType | Type of scaling (lin/log) | -- | 0 = lin, 1 = log |
The zoom for all 2D scan data (2D, SEM, RSM) is described by a rational fraction consisting of numerator and denominator, where both are small integer numbers.
| Name of NetCDF variable | Full name | Units | Comments |
|---|---|---|---|
| ScMinCnts | Min. value to display | Counts | ... |
| ScMaxCnts | Max. value to display | Counts | ... |
| CTIndex | Index of used colour table | -- | As in table of color tables. |
| CTInvert | Invert color table? | -- | 0 = no, 1 = yes |
| SclType | Type of scaling (lin/log) | -- | 0 = lin, 1 = log |
| XZoomNum | X zoom numerator | -- | X zoom factor. |
| XZoomDenom | X zoom denominator | -- | X zoom divider. Yet unused |
| YZoomNum | Y zoom numerator | -- | Y zoom factor. |
| YZoomDenom | Y zoom denominator | -- | Y zoom divider. Yet unused |
Scan data
For each of the five scan modes of WinSPA (1D, 2D, RSM, SEM, I(t)) there is one set of parameters for the range of the measurement and the scan data.
1D scan data
| Name of NetCDF variable | Full name | Units |
|---|---|---|
| Cnts | Scan data (counts) | -- |
| x0 | kx scan center | =kUnits |
| y0 | ky scan center | =kUnits |
| XYDist | Scan size in k|| direction | =kUnits |
| k | k|| axis | =kUnits |
| Points | Number of scan points | -- |
| Angle | Scan rotation (anti-clockwise) | ° |
| Energy | Electron energy | eV |
| Phase | Scattering phase | -- |
2D scan data
| Name of NetCDF variable | Full name | Units |
|---|---|---|
| Cnts | Scan data (counts) | -- |
| x0 | kx scan center | =kUnits |
| y0 | ky scan center | =kUnits |
| XDist | kx scan size | =kUnits |
| YDist | ky scan size | =kUnits |
| X | kx axis | =kUnits |
| Y | ky axis | =kUnits |
| PointsX | Number of scan points in x direction | -- |
| PointsY | Number of scan points in y direction | -- |
| Angle | Scan rotation (anti-clockwise) | ° |
| Energy | Electron energy | eV |
| Phase | Scattering phase | -- |
SEM scan data
| Name of NetCDF variable | Full name | Units |
|---|---|---|
| Cnts | Scan data (counts) | -- |
| x0 | X scan center | =xUnits |
| y0 | Y scan center | =xUnits |
| XDist | X scan size | =xUnits |
| YDist | Y scan size | =xUnits |
| X | X axis | =xUnits |
| Y | Y axis | =xUnits |
| PointsX | Number of scan points in kx direction | -- |
| PointsY | Number of scan points in ky direction | -- |
| Angle | Scan rotation (anti-clockwise) | ° |
| Energy | Electron energy | eV |
RSM scan data
| Name of NetCDF variable | Full name | Units |
|---|---|---|
| Cnts | Scan data (counts) | -- |
| x0 | X scan center | =kUnits |
| y0 | Y scan center | =kUnits |
| XYDist | XY scan size | =kUnits |
| Z1 | kz(1), scan start coordinate | =zUnits |
| Z2 | kz(2), scan stop coordinate | =zUnits |
| kx | k|| axis | =kUnits |
| kz | kz axis | =zUnits |
| PointsXY | Number of scan points in k|| direction | -- |
| PointsZ | Number of scan points in kz direction | -- |
| Energies | Electron energies | eV |
| Angle | Scan rotation (CCW) | ° |
| Energy | Electron energy | eV |
| Phase | Scattering phase | -- |
I(t) scan data
| Name of NetCDF variable | Full name | Units |
|---|---|---|
| Cps# | Intensities of spots (vs. time) | Counts per second |
| kx# | kx of spot # | =kUnits |
| ky# | ky of spot # | =kUnits |
| t | Time axis | Seconds |
| points | Number of measured data points | -- |
| x0 | kx(0) for reference spot. | =kUnits |
| y0 | ky(0) for reference spot. | =kUnits |
| Name# | Name of LEED spot # | None (string variables) |
| Energy | Electron energy | eV |
| Phase | Scattering phase | -- |
| FWHM | Assumed width of reference spot. | =kUnits |
| MaxD | Assumed maximum jump distance of reference spot. | =kUnits |
| AlgNr | Number of spot tracking algorith used. | -- |
| PtScan | Point scan activated? | 0 = no, 1 = yes |
| Thrshld | Threshold for point scan activation. | Counts per second |
The configuration file
WinSPA saves all global settings into a configuration file (config.txt) in the program path. You can open this file with any text file editor and make changes in it. Specifically, if you want to add other surfaces to the presets list, just enter the parameters for name, step height and lattice constant into the config file, separated by " / " (space slash space).
