EXFOR is the library and format for the collection, storage, exchange and retrieval of experimental nuclear reaction data. The library is the product of the co-operation of the international Network of Nuclear Reaction Data Centres which is co-ordinated by the IAEA Nuclear Data Section.
The EXFOR format, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in a format:
The data presently included EXFOR include:
The basic unit of EXFOR is an entry, which corresponds to one experiment which is usually described in one or more bibliographic references (journal articles, laboratory reports, conference proceedings etc.). Each entry is divided into a number of subentries (data sets). Each entry is assigned an accession number; each subentry is assigned a subaccession number (the accession number plus a subentry number). The subaccession numbers are associated with a data table throughout the life of the EXFOR system.
The subentries are further divided into:
The first subentry contains the information which is common to the whole entry, i.e. usually the bibliographic reference(s), essentials about the experimental method, and any common data (common parameters for the whole work). The following subentries contain the actual experimental results (tables), plus any bibliographic and experimental information or common parameters specific to the individual subentry (table).
The bibliographic and experimental information is specified in variable length fields whose contents is defined by "information identifier keywords". An entry contains only those keywords relevant for the particular work. The information attached to a keyword may consist of "codes" (standard abbreviations taken from a "dictionary") and/or "free text".
The table below gives a list of the information identifier keywords. For many of these there is a specific dictionary of permitted standard abbreviations (codes). These dictionaries are open ended in the sense that new codes may be added whenever need arises.
The data of each table in a subentry are defined in the keyword REACTION which defines both the nuclear reaction as such (e.g. neutron-induced fission on 235U, or the microscopic production cross section of a certain radionuclide by bombarding a lead target with protons) and the quantity measured (e.g. integral or differential cross section, fission product yield, resonance parameters, etc.) The REACTION code therefore consists of up to 9 subfields, subfield 1 through 4 for defining the nuclear reaction, and subfields 5 through 9 for a detailed definition of the quantity measured and its representation.
Subfields 1 through 4 are usually self-explanatory:| 1-H-1(N,G)1-H-2 | 1H(n,g)2H |
| 92-U-235(N,F) | 235U(n,f) |
Subfields 5 through 8 define the quantity measured. They are separated by commas; only subfield 6 is always present. All existing quantity codes and their explanations are given in the extended retrieval form (Reaction subfields, SF5-8 pull-down list "Quantity Code"). E.g., the code for a simple integral cross section is ,SIG .