Recent Developments in the Experimental Nuclear Reaction Data Library EXFOR

The International Network of Nuclear Reaction Data Centres (NRDC) provides nuclear reaction data services to users through collection and compilation of experimental nuclear reaction data in the EXFOR database. The database includes neutron-induced, charged-particle-induced, and photonuclear data for projectile energies up to 1 GeV. Sophisticated search options and user-friendly retrieval interface for downloading data in different formats have been developed at IAEA Nuclear Data Section. Additional output options such as data plotting capabilities are provided as well. The database is constantly revised and extended and at present contains about 20,000 experimental works accumulated in its 40 years of history. The paper will present several recent IAEA NDS activities related to the development of the EXFOR database and retrieval system.

(http://www-nds.iaea.org/exfor/)or stand-alone CD-ROM distributed by NDS at requests.Retrieval system developed at NDS allows sophisticated search that include not only EXFOR but also a number of relevant databases such as Evaluated Nuclear Reaction Data (ENDFs), Evaluated Nuclear Structure and Decay Data (ENSDF), Bibliographic databases (CINDA, NSR) [2].The paper describes the basic principles of EXFOR compilation and data retrieval as well some recent and future developments aimed at improved qualities and present-day needs in science and technologies.

EXFOR compilation
Collection, compilation and dissemination of experimental nuclear reaction data and the related bibliographic information in the EXFOR database is the main task of the International Network of Nuclear Reaction Data Centres (NRDC).The Network constitutes of worldwide cooperation of 14 data centres from 10 countries and 2 international organisations under the auspices of the International Atomic Energy Agency (Table 1): The database is also cross-checked with extensive bibliographic compilation found in the literature or some specialized databases.Such comparisons with proton-induced total reaction cross sections in Carlson's compilation [3], isotope production cross sections by light-charged particle induced reactions from Landolt-Börnstein compilation [4] etc. were carried out recently and missing articles were added to the database.
Specialized software related to compilation work, digitization of graphical images, and checking for compliances with EXFOR format have been developed and are available for downloading at the NRDC website (http://www-nds.iaea.org/nrdc/)Quality assurance of EXFOR content is an important issue.Feedback from users, recommendations from the WPEC subgroup "Quality Improvements of the EXFOR Database (SG30)" [5] or mistakes found by users and compilers are thoroughly investigated and registered on the NRDC web site (http://www-nds.iaea.org/nrdc/error/)for corrections.Quality of digitization was recently reviewed by a benchmark exercise organized by NDS.Results from the benchmark were discussed at a consultants' meeting and recommendations to software developers and compilers were distributed [6].

EXFOR retrieval system
Web services for data search and retrieval (Fig 1 ) have been developed at the IAEA Nuclear Data Section.The EXFOR format and coding of the information allow users to set criteria of search.List of possible codes with short description is provided for each of available search fields.The data/information can be retrieved in: extended EXFOR format (X+), BibTeX, TABLE, BIB and XREF, T4 format, C4 format, extended C4 and R33 format [7].The data can be displayed on graphs in static and interactive plots with option for uploading of users' data for comparison.

Recent and future developments
Availability of complete information required for the proper interpretation of the experimental results is essential for the compilation in EXFOR.Many nuclear reaction data, included in the EXFOR database, have been obtained by experiments with neutron sources that have a relatively broad energy (or non-monoenergetic) distribution.Several types of neutron fields applied in spectrum average cross section measurements were discussed during the CM "Neutron Sources Spectra for EXFOR" [8] and the neutron spectral distributions provided by authors were compiled with link to the spectrum average cross section data.Neutron-induced reaction cross section data in the resonance range are important for many fields of science and technology.Many facilities employ accelerators for production of neutrons in a broad energy range and data are obtained by transmission and capture measurements by time-of-flight method.Proper analysis of the differential data in the resonance range (total, capture, fission cross sections, and time-of-flight spectra) requires knowledge of response functions of the complete target to detector measurement equipment employed at particular experimental facility.There are on-going activities to collect and include detectors response functions for TOF data in EXFOR.
The gamma scattering (γ,γ´) with excitation of strong dipole resonances in the nucleus and consecutive prompt γ-ray decay can be applied for the identification and quantification of the isotopes (stable, radioactive or actinide).A novel non-destructive method for detecting clandestine materials has been developed recently based on Nuclear Resonance Fluorescence (NRF).Compilation of photonuclear scattering reaction data was recently initiated by IAEA NDS.
Beta-delayed neutron emission data are important for nuclear physics, nuclear astrophysics, reactor physics etc. Regarding the characteristics of the delayed neutrons emitted from the fission products total average delayed fission neutron yields are extensively compiled in EXFOR as well as several energy spectra for specific delayed neutron groups.Development of new radioactive-ion beam facilities, mass separators, Penning-trap methods, etc. widen the bounds for measurement of betadelayed neutrons in different mass regions.Inclusion of beta-delay neutron emission data in EXFOR database is considered as beneficial for further experimental investigations, evaluations and theoretical analysis.

Summary
The member centres of the International Network of Nuclear Reaction Data Centres provide comprehensive collection of experimental nuclear reaction data compilations in its EXFOR data library.The scope and the type of the data evolved and presently neutron-, charged-particle-induced and photonuclear data in the energy range up to 1 GeV are compiled.The database is updated on a monthly basis and at present contains about 20,000 experimental works.Web services for data search and retrieval are provided to users.Different outputs allow retrieval in forms ready for further processing.