tinely transmit evaluations electronically and use electronic mail to communicate with the coordinators.
Although most of the ENSDF file has an 80-character column format inherited from IBM cards, a concentrated effort has been made in the past 2 years to transform the file into a more modem, relational database. Complete conversion will not be possible until a commercial database program is available that can meet the needs of such a large, diverse file, probably after another 2 to 3 years of development. So far, however, the conversion has proceeded smoothly, and it has facilitated the development of software overlay programs that give the user transparent access to the data. One subset of ENSDF, the nuclear database NUDAT, is a true relational database that can be accessed on-line.
Traditionally, the evaluations of nuclear structure data were disseminated via a monthly hard-copy journal. Now on-line access, introduced about a decade ago, is available by logging into the NNDC (guest accounts are available for individuals who want to explore the files) or via the World Wide Web.1 On-line access is menu-driven but has limited graphic capabilities. Users can generate high-quality PostScript files of tables and level spectra, which can be downloaded to a local machine. More than 2,000 registered users from 49 countries on six continents currently have on-line access to ENSDF.
To minimize the problems with intercontinental electronic links, ENSDF has mirror sites in Vienna and Paris and plans to provide the same at the center in Obninsk, Russia, when Russia's Internet link is established. These mirror sites are maintained by the host foreign government, with support from the IAEA. While the mirror sites have minimized problems with trans-Atlantic electronic links, delays do occur with trans-Pacific links (except those with Japan) and links to South America. To complement on-line access, various modes of dissemination are being used, including CD-ROM and floppy diskettes. Although users in less developed countries may prefer hard copies, for many the cost of the printed journal is prohibitive. Therefore, to maximize international data flow, increased access to the Internet is critical.
While nuclear scientists are the most common users of ENSDF, some of the data have important applications in other areas of science. For example, radioactive decay data are used in medical physics. To facilitate access by the medical community, a dynamically generated form of ENSDF, called MIRD, was created that can be accessed on-line. As a portion of the data in the Evaluated Nuclear Data File/B (ENDF/B), ENSDF data are also used in the design of nuclear reactors and devices. Before the early 1980s the distribution of ENDF/B was restricted, because the information was considered sensitive with respect to national security. This file, which is available electronically and on tape, contains results of nuclear reaction model calculations that could be useful to other scientists, for example, stellar astrophysicists seeking to understand nuclear processes in stars.