doi:10.1017/S155192951000132X26www.microscopy-today.com • 2011 JanuaryGetting Started with NIST* DTSA-IINicholas W. M. RitchieNational Institute of Standards & Technology, Material Measurement Laboratory, Gaithersburg, MD [email protected] its introduction in 2007, DTSA-II [1–3] has been adopted by numerous researchers, and it has been integrated into numerous educational programs. This is the first of a series of articles in Microscopy Today that will appear in the upcoming months to provide an introduction to use of the product. These articles also will provide details of how DTSA-II can be used to implement best practices for microanalysis in your laboratory or in your teaching environment. These articles will demonstrate how to form the most accurate type of spectrum quantification—standards-base quantification—as well as how to use simulation to optimize various types of measurement problems. They will focus on using DTSA-II to understand the physical process including the interaction of energetic electrons with your sample and the propagation of x-rays through matter and to the detector.DTSA-II provides many different tools, but the primary ones are for quantification, simulation, visualization, and manipulation of energy-dispersive x-ray spectra. Each of these tools will be introduced separately in forthcoming articles. The remainder of this article will provide an overview of the tools and introduce two important aspects of the program: (1) The way DTSA-II implements detectors for both quantification and simulation and (2) the way DTSA-II imports spectra from disks.Development of DTSA-IINIST DTSA-II is a software tool for quantifying and simulating electron-excited energy-dispersive x-ray spectra. It is being developed within the Surface and Microanalysis Science Division at the National Institute of Standards and Technology and is freely available to all from http://www.cstl.nist.gov/div837/837.02/epq/dtsa2/index.html. You are encour-aged to download, install the application and follow along. In subsequent articles, example spectra, scripts and other data files will be made available for download to supplement the print content. DTSA-II was inspired by the original Desktop Spectrum Analyzer (DTSA) (see Figure 1) developed at the National Bureau of Standards (forerunner of NIST) and National Institute of Health by Chuck Fiori, Bob Myklebust and Carol Swyt-Thomas [4]. Following its introduction in the late 1980s the original DTSA developed a cult following in the microanalysis field. The original DTSA only ran on older generations of Apple Macintosh computers (pre-OS 9) with 680X0 and PowerPC processors. When Apple stopped making these in the late 1990s, many researchers held on tight to these aging computers. Many started to ask, when would DTSA be updated? When would there be a version for Windows/OS X/Linux? Was this the end of the line?I was familiar with DTSA when I joined NIST. When I worked for an instrument vendor, we delved into DTSA’s source code to jump-start some of our own product development. We had gone so far as to print out the source code. As I recall, it filled six three-ring binders. Over the years it had grown into a product that served a number of communities that were too small or too poor to interest the commercial vendors. DTSA was innovative and is sorely missed by many.Around 2005 it was clear that the time was ripe to revisit DTSA. A port of the code from Mac to PC had been discussed. However this was easier said than done. The code mixed algorithms with user interface code. It was written in a Mac-specific dialect of Pascal, a language that is much less popular on the PC. There were many aspects of the program that were beginning to show their age.Instead we decided to take the best ideas from DTSA—algorithms, data, simulation, low-level tools, and many others—and to reinvent it from the ground up. I decided to separate algorithms from user interface code. This facilitates reusing the algorithms for other purposes in other programs. I wouldn’t limit myself to one operating system. The rein- vention would use the most robust multi-platform develop-ment solution available—Oracle Corporation’s (formerly Sun Microsystem’s) Java platform. As a result DTSA-II runs and looks like a native application on many generations of Windows PCs, Apple OS X from version 10.5 and most Linux distributions from the last few years, Solaris, and even a few Unix distributions. DTSA-II is regularly tested on Windows XP, Windows 7, OS X, and Ubuntu Linux; it behaves substan-tively the same on each.Finally, like the original, we would make the source code available to all. There are many reasons this is valuable. I hope others will benefit from being able to study the code like I did with the original. Furthermore many believe that it is important that the algorithms we rely on to process our data should not be black boxes. Whether or not we ever decide to look, it should at least be possible to open the box and peer in. Most of the algorithms in DTSA-II are documented in journal articles (which I typically reference in the source code). Quite often it takes pulling together many journal articles to implement a single algorithm. Sometimes the articles leave important implementation details ambiguous, and occasionally there are even errors in the text. As a result “correct” implementations from different researchers may produce subtly different results. Computer source code is the closest thing we have to an unambiguous method to document an algorithm implementation.Out of respect for the original product, I decided to call the result DTSA-II, although the acronym no longer stands for anything. The versions are labeled with the name of an astronomical object selected in alphabetical order. The current release is called “DTSA-II Deneb” after the brightest star in the *Disclaimer: Certain commercial equipment, instruments, or materials are identified in this article to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it