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The process of evaluating nuclear reaction data involves combining experimental measurements with theoretical models to come up with a best judgement of the real values of the underlying nuclear reaction data. Some evaluation efforts are devoted to determining a single reaction cross section (e.g., for dosimetry or activation), and others attempt to provide a complete representation of all the cross sections, product yields, and product distributions in energy and angle. The latter are needed for full-scale calculations of the performance of nuclear systems; therefore, they must be in a standard computer-readable format. At the current time, almost all full-scale evaluations use the ENDF (Evaluated Nuclear Data File) format originally developed in the US and now used all over the world (the ENDL format used at Livermore is one exception). Individual evaluations are normally combined into libraries intended to provide full coverage for nuclear calculations by national or multi-national organizations. These libraries are given a characteristic name with a version identifier for easy reference. Some of the prominent nuclear data libraries available now include
The T-2 Nuclear Information Service provides easy access to these various libraries of evaluated nuclear data in two ways: through index lists of the materials available for a particular library, or through the "Map to the Nuclides." Through each of these routes, the user can browse through the evaluation using interpreted pages in HTML format. Using the index route, you can also get access to the raw ENDF evaluation for viewing or downloading. |
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Currently, the T-2 Nuclear Information Service contains index lists
for ENDF/B-VI,
JEF-2.2,
JENDL-3.2,
BROND-2.2, and
CENDL-2. They
are all accessible from the Data area.
The indexes contain the material identification number (MAT),
the nuclide name, the date of the work, and the evaluators for
each material in the library. For ENDF/B-VI, there are some additional
codes that describe the contents of the evaluation. Each index contains a line for each material (element, isotope, isomer) that is included in the library. There is a link at the beginning of each line (shown as @@) that will take you to a new page giving links to the various kinds of data currently available for that material. This may include standard ENDF formatted data for viewing or downloading, interpreted HTML pages for easy browsing, or files of plots. |
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The Map to the Nuclides is something like
the Chart of the Nuclides. It provides a graphic interface to a variety
of data for the nuclides, including the evaluated data files. The Map
is available in the Data area of our Information
Service. When you link to the Map, it will give you a choice of 5 different Z ranges for materials (we did this to speed up the download time). Selecting a range will give you a graphic representation of the isotopes that might be possible for each element. Just click on the square for a desired isotope to see what data are available. For stable (blue colored) and long-lived isotopes, there may be evaluated data files, plot files, and decay data. For short-lived nuclei, there may be decay data. There are experimental or calculated masses and other calculated properities available for everything out to both drip lines. As an example, if you click on the square for Fe-56, you will find the the interpreted evaluated data for ENDF/B-VI, JENDL-3.2, and JEF-2.2. There are also plot files of the pointwise cross sections for ENDF/B-VI, JENDL-3.2, and JEF-2.2. For isotopes that have prominent isomers, there may also be links to isomer data. For isotopes that have only elemental evaluations available, selecting an isotope will also provide you with links to the elemental evaluation (the yellow element fields on the Map give access to chemical data about the element). For libraries that have both isotopic and elemental evaluations (e.g., JENDL), both will appear. |
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When you select the raw, or standard, ENDF data, we will see the
normal text of an ENDF-format file on your screen. You can easily
save this file to your home system using the Save button of your
browser (or you can skip the display by using Shift-Select and
telling the system where to store the file). This is a convenient
way to obtain evaluations for further processing at your home site.
Note that we have divided the "tapes" that originally contained a
number of materials into single-material files. To obtain the
official unmodified distribution tapes, please use the home site
for the evaluated library of interest (see above for the links). Experts can read ENDF-format files easily, because they are used to the structures and the numerical codes (e.g., MAT, MF, MT). Others will have to learn how to read the files by studying the format documentation, or use the interpreted HTML interface that is provided on this Information Service to browse the files. (The system that provides the interpreted listings also provides quite a bit of help on the ENDF format.) |
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When you select interpreted ENDF data, our Web server runs a process
to read the raw ENDF file and generate pages in HTML format. The
first page gives the basic isotope identification (ZA, AWR, MAT,
incident particle), followed by the descriptive information provided
for this material (MF=1/MT=451). After the descriptive text, the
server provides a set of links to each of the different sections (MF, MT)
of data for the material. The code numbers used to define the sections
are converted into easily readable text. You just scan through the
choices to find the kind of data you want to view (Cross Sections,
Angular Distributions), and then select the desired reaction. Note that there is help information available for some of the types of data---just click on the info symbol. The pages for a particular data type and reaction typically translate the values for control parameters into labelled values. As an example, you don't have to remember which column contains the Lab/CM flag for an angular distribution; the listing will tell you, "Distributions are in the laboratory system." In some cases, the name for a particular parameter will appear as an underlined link. Just click on such entries for a definition of that parameter. The actual tables of values are normally printed out just as they appear on the raw ENDF file, except column headers are generated to make the tables easier to read. Some things are still pretty cryptic (e.g., interpolation tables), and not all of the help information is present. These things will be improved in the future. |