34ID-E Data Analysis Overview
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A wide variety of measurements can be carried out at 34ID-E: white beam or mono beam, step scans or slew scans, with area detectors or point detectors, depth-resolving or not, etc. Hence a collection of tools are developed to tackle different types of data sets.
A majority of analysis and visualization functions are built into LaueGo, a package developed at 34ID-E based on IGOR Pro, which runs on a single PC or Mac. A few heavier tasks require using a multi-node Linux cluster at APS.
Data types and formats
- Each exposure of an area detector, if file-saving is turned on, creates a file containing 2D data. By default our detector images are saved in the NeXus format NeXus format, which is based on HDF-5.
- Note: with special configurations, such as the fly-scan mode, multiple exposures can be saved in a single data file as a 3D array.
- Each scan automatically creates a *.mda file that is sequentially numbered. The mda file stores motor positions and pre-selected scaler counts at each scan step.
- Only the motors that are being scanned are recorded in mda files.
- For multichannel analyzer (MCA) fluorescence detectors, total counts of each window of channels are recorded as scalers, and stored in the mda files.
Types of Analysis
Depth-resolved scans (wire scans)
Data from depth-resolved measurements requires reconstruction. A reconstruction takes a depth-profiling wire scan data as input, and generates a series of 2D image files each representing the diffracted intensities from a specific depth along the x-ray's penetration. The process is carried out by the computer cluster. Reconstructed image files are also written in NeXus format.
The reconstruction process is the same for white-beam or mono-beam scans.
White-beam Laue images
Single image
Main Article: Single Laue Image Analysis with LaueGo
Single Laue images, depth-reconstructed or not, can be indexed with LaueGo. One can index a single Laue Image and get the crystal orientation, deviatoric strain, predict energies of specific Bragg peaks, or identify the existence of certain phases.
Multiple images
Indexing of a large number of images can be automated on the Linux cluster through ORNL Client. It is recommended that one first try indexing a few images with LaueGo and get all the input parameters optimized before submitting a batch indexing job.
Each multiple-indexing job creates an xml report file that contains the indexing results for each image. This report can be imported to LaueGo for further analysis, such as strain refinement, 2D/3D plotting, pole figures, etc.
Monochromatic beam data (energy scans)
Mono beam are mostly used for energy scans near specific Bragg peaks to measure lattice d-spacings, they can be done with or without depth-profiling.
Depth-resolved wire scans need to be reconstructed first.
Energy scan data can be analyzed with functions listed in the "E scans" tab of LaueGo.
Scaler data (mda files)
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There are a few ways of visualizing scaler scan data:
- Plotting window by MEDM (for 1D scans)
- scanSee (1D and 2D)
- LaueGo has built-in functions for reading and displaying mda files
- An IDL utitlity on beamline PC can display 2D mda data
