VIII - "Externals"

[ file formats | config file | SpaDAQ || main help index ]

1. WinSPA's file formats

Even though in principle NetCDF files are self-describing, the variables in WinSPA files are described in detail below.

The file format NetCDF is

• Self-Describing
• Architecture-independent
• Sharable
• Direct-access

• Free browser NCbrowse
• Free browser Panoply
• IDL-based NetCDF browser and tools at David Fanning's IDL site

Note: If you want to import/export NetCDF files with the programming language Delphi, you can use the same interface library that was developed 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.

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.).

Sample information

The global sample parameter settings are saved for documentation.

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.

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.

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

2. 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).

3. The library SpaDAQ

The library SpaDAQ creates an abstraction layer around all "real" data acquisition (DAQ) hardware accesses. WinSPA can therefore immediately work with any DAQ hardware, if a dynamic link library with the name SpaDAQ.dll is present and supplies the same functions as the original one.

If you are interested in testing another commercially available DAQ hardware with WinSPA or developing a new DAQ hardware for SPA-LEED instead of the antique PCI-20001 system, please contact Omicron NanoTechnology for further details.