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.

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 a multi-node Linux cluster at APS. 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 the energy 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:

1. Plotting window by MEDM (for 1D scans)
2. scanSee (1D and 2D)
3. LaueGo has built-in functions for reading and displaying mda files
4. An IDL utitlity on beamline PC can display 2D mda data