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Data file formats

Data file formats

Mythen-II Detector Overview

The Mythen detector consists of 16 modules allowing 80° of data to be simultaneously acquired.  There are small gaps between each module (covering ~0.2°) resulting in missing data every ~4.8°.  Data must be collected in pairs (e.g. p1 & p2 or p3 & p4) with a small angular difference between the histograms (e.g. 2θ p1 = 5.0° and 2θ p2 = 5.5°) so that the data sets can be spliced/merged later to remove the gaps.

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As the detector modules are flat, automatic processing is required to convert the data from channel versus intensity data into 2-theta angular geometry.  This is performed for all data sets automatically, resulting in variable step sizes between points.

Six files are generated for each data acquisition at each detector position. Files with the extensions “.raw” contain raw channel data. The raw detector data is automatically processed (flatfield normalisation and a channel-to-angle conversion) to produce “.xye” files. The files with the “.parab”, “.mda” and “.asc” extensions contain detector meta-data.  Further description of these files is shown below. All files will be located in the same directory, and should be copied by the user to their own storage media. Users should use the .xye files.

  • RAW Files – Files with the extension .raw are comprised of the raw channel data without flat field correction. The data is in xy format, where x = detector channel number and y = counts.

  • XYE Files – These are the final data files that are produced after flatfield normalisation and channel-to-angle processing. The data is in xye format, where x = 2theta angle, y = corrected counts and e = error.

The error is calculated from the error propagation of the following equation:

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where ncorr,i is the corrected intensity at point ’i’ in the data file; nunc,i is the uncorrected intensity at point ‘i’ in the data file; and ffaver and ffi are the average intensity and the intensity at point ‘i’ in the flatfield file respectively.  

  • Parab, MDA and ASC Files – These files contain meta-data, additional information relating to the experiment. These data include: a time stamp, the data acquisition time, the integrated ion chamber counts, and the 2-theta axis position as well as many other positioner and temperature values.