Manipulating Spectra with DTSA-II
Nicholas W. M. Ritchie National Institute of Standards and Technology, Gaithersburg, MD 20899-8371
nicholas.ritchie@nist.gov
Introduction Te previous article in this series [1] introduced DTSA-II
and provided some background information including how to configure DTSA-II for your x-ray detector and how to read spectra from disk. Tis article presents more basic background material. It discusses how to display and perform basic manipulations on spectra including reading the contextual properties of spectra, visualizing spectra, labeling characteristic x-ray lines, and exporting the results as publication-quality graphics. You are encouraged to follow along using DTSA-II and example spectra, which may be downloaded for free from
http://www.cstl.nist.gov/ div837/837.02/epq/dtsa2/
index.html or equivalently http://
goo.gl/MI1Ku. With this background material, we will be ready to consider more sophisticated tasks like spectrum quantification and simulation in upcoming articles.
Displaying Spectra Spectrum display panel. As discussed in the previous
article, DTSA-II supports the reading of many different kinds spectral formats, including the ISO standard EMSA file format [2]. Te number of spectra that DTSA-II can have open simultaneously is only limited by available memory. A full list of open spectra is displayed
in
list on the leſt edge of the spectrum utility
the spectrum panel (see
Figure 1). You may select up to 50 open spectra to display in the spectrum display panel. To select multiple spectra, you can hold down either the shiſt key (contiguous selection) or the control key (discontiguous selection) while clicking on the name of the spectrum. Clicking the right mouse
button while the cursor hovers over the spectrum list panel will display a context menu containing actions to “select all,” “select none,” or “clear selected.” Te first two items modify which spectra are highlighted and thus which spectra are displayed in the spectrum display panel. Te last item removes spectra from the spectrum list and clears them from memory. Be careful
34
though because all modifications to cleared spectra will be lost unless the modified spectra have been written to disk. Spectrum properties panel. To the right of the spectrum
list is the spectrum properties panel (see Figure 2). When one spectrum is selected in the spectrum list, the spectrum properties panel displays all the properties associated with the selected spectrum. Tese properties include those properties read from the spectrum file and those properties applied from the default detector. (See the previous article for a description of the default detector [1].) In addition, there may be properties that are added as the spectrum is manipulated within DTSA-II. One such example is the “Duane-Hunt” limit property. Te Duane-Hunt limit, an estimate of the effective electron beam accelerating potential, is calculated when the spectrum is read from disk. If the Duane-Hunt limit is substantially less than the nominal beam energy, it suggests that the sample is charging. Other properties that can be added by DTSA-II include the “microanalytical composition,” the “standard composition,” and the “k-ratio set.” If the microanalytical or standard composition is defined, then these are displayed in the lower right corner of the spectrum tab in the composition table panel.
Figure 1: The primary panels used to manipulate spectra. doi:10.1017/S1551929511000290
www.microscopy-today.com • 2011 May
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