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The Experimental Nuclear Reaction Data (EXFOR): Extended Computer Database and Web Retrieval System

V. V. Zerkin, B. Pritychenko

arXiv:1802.05714v1physics.comp-phmath.NA

TL;DR

Nuclear researchers need broad, rapidly accessible experimental reaction data and associated bibliographic information. The paper describes EXFOR’s international database and Web system, including data storage, retrieval, processing, and newer analysis capabilities. EXFOR supports nuclear data evaluation, application development, and research through a large public repository with broad worldwide use.

  • Problem

    Nuclear science and technology require rapid access to extensive low- and intermediate-energy experimental nuclear reaction data and associated information.

  • Method

    The paper describes EXFOR’s international relational database and Web interface, including data compilation, storage, retrieval, renormalization, covariance calculation, and inverse-reaction tools.

  • Results

    EXFOR contains data for approximately 22,000 experiments, and its Web interface shows broad worldwide use, including approximately 100,000 interactions per year and 2,500 unique users per month.

  • Takeaways & Limitations

    EXFOR provides public access to experimental nuclear reaction and bibliographic information and supports nuclear data evaluation, application development, and research activities.

Abstract

from arXiv · show

The EXchange FORmat (EXFOR) experimental nuclear reaction database and the associated Web interface provide access to the wealth of low- and intermediate-energy nuclear reaction physics data. This resource is based on numerical data sets and bibliographical information of $\sim$22,000 experiments since the beginning of nuclear science. The principles of the Web and database applications development are described. New capabilities for the data sets uploads, renormalization, covariance matrix, and inverse reaction calculations are presented. The EXFOR database, updated monthly, provides an essential support for nuclear data evaluation, application development, and research activities. It is publicly available at the websites of the International Atomic Energy Agency Nuclear Data Section, {\it http://www-nds.iaea.org/exfor}, the U.S. National Nuclear Data Center, {\it http://www.nndc.bnl.gov/exfor}, and the mirror sites in China, India and Russian Federation.

1. Introduction

The paper describes the evolution of nuclear-data dissemination from paper copies to Web-accessible computer databases and presents EXFOR as an internationally coordinated repository for experimental reaction data.

  • 1. Introduction: The work focuses on the storage, analysis, and worldwide distribution of low- and intermediate-energy nuclear reaction data.
  • 1. Introduction: Nuclear data dissemination evolved from paper copies for designated users into computer files distributed through the World Wide Web.
  • 1. Introduction: EXFOR is an international collaboration established in 1967 by four major nuclear data centers to compile experimental nuclear reaction data.Thirteen nuclear data centers currently contribute regularly under IAEA auspices.

2. EXFOR Database

EXFOR is a large, historically developed library of experimental nuclear reaction data, organized in structured entries and expanded across reaction types, formats, and archival functions.

  • 2. EXFOR Database: Neutron-induced reactions form the database backbone, while charged-particle and photon-induced reactions were added later and covered energies below the pion production threshold.
  • 2. EXFOR Database: As of November 27, 2017, EXFOR contained 21,885 experiments, 170,088 data sets, and 15,213,129 data points covering 968 targets, 386 projectiles, and 2,606 reactions.
  • 2. EXFOR Format: A single EXFOR entry may contain multiple data subentries, reaction strings, reaction combinations, and publications, so compilation counts can exceed experiment counts.
  • 2.2. EXFOR Format: The human-readable EXFOR format supports inter-center exchange, while X4TOC4 converts data into simplified columns used for plotting and dissemination.
  • 2.2. EXFOR Format: Each entry contains bibliographical and data subentries, with unique accession numbers and common information associated at entry, subentry, or table level.

3. Platform-Independent Data Storage and Dissemination System

The modern EXFOR system replaced obsolete dissemination infrastructure with a platform-independent Web and relational-database environment designed for broad data access and continued development.

  • 3. Platform-Independent Data Storage and Dissemination System: Earlier systems such as CSISRS became obsolete as computing and World Wide Web technologies advanced, prompting a data-migration project beginning in 1999.
  • 3. Platform-Independent Data Storage and Dissemination System: The current EXFOR system is a multiuser, platform-independent environment using Java technologies together with Web servlets, database connectivity, plotting wrappers, and legacy codes.

3.1. EXFOR Relational Database

EXFOR uses a modern relational database system to store and manage extensive experimental nuclear reaction data, metadata, dictionaries, and associated documents. Its schema and integrations support data access, exchange, and use across nuclear-data applications.

  • Database platform: ∼22,000 experiments are stored in EXFOR’s nuclear reaction data sets.The modern system uses relational database servers and SQL-based requests to retrieve database outputs.
  • Database platform: MySQL servers replaced earlier Sybase deployments at the IAEA and NNDC services.Both centers later migrated to MySQL community edition servers.
  • System integration: EXFOR is integrated with ENDF, CINDA, Nuclear Science References, Sigma, and components of JANIS.These integrations extend the database’s use across evaluated data, bibliographical information, and nuclear-data information systems.
  • Database structure: The schema defines tables and relationships for storing experimental nuclear reaction data sets.ENTRY and SUBENT metadata tables are linked through an EntryID relationship.
  • Database structure: EXFOR combines nuclear data, bibliographical metadata, dictionaries, and article or document PDF files in a relational database.The schema includes tables such as X4SRC, ENTRIES, and AUTHORS, with relationships linking metadata tables.

3.2. EXFOR Web Interface

The EXFOR Web Interface provides scalable access to complex nuclear reaction data through multiple retrieval levels and output formats. It supports both straightforward searches for less experienced users and advanced queries based on bibliographical, experimental, and compilation information.

  • Web architecture: The interface separates Web and database servers to improve scalability, satisfy cybersecurity requirements, and reduce single-point failure risk.It runs in an Apache/Tomcat and Linux environment.
  • Outputs and analysis: The interface returns HTML, Text, BibTex, and PDF outputs, plus C4/C5, API/XML, and R33 specialized formats.These outputs support nuclear model codes, application developers, and IBANDL users.
  • Outputs and analysis: ZVView enables interactive plotting and comparison of cross-section data and can display two-dimensional correlation matrices.Users can vary visualization types and parameters, including curves, histograms, maps, 3D views, animations, symbols, colors, and error bars.
  • Retrieval capabilities: Four retrieval levels—basic, extended, keywords, and expert—accommodate different user needs.The levels range from simple cross-section retrievals to searches involving detailed experimental and compilation parameters.
  • Simple retrievals: Simple retrievals search by target, reaction, quantity, product, energy range, authors, publication year, and accession number.The search fields use a logical OR operator, and missing fields are ignored by SQL queries.
  • Simple retrievals: A Google-like text search was added to help less sophisticated users mine experimental data using common nuclear-physics concepts.Online help buttons also explain search inputs and provide access to EXFOR dictionaries.
  • Retrieval capabilities: Advanced retrievals expose extensive experimental descriptions, facilities, bibliographical metadata, geographical origins, detectors, methods, monitors, and data origins.These data are presented as distinctive resources for research-trend investigation and nuclear-data evaluation.

3.3. EXFOR Examples of Requests and Video Guides

Because EXFOR’s advanced capabilities can challenge new users, the system provides examples, updates, and video guides to explain requests and promote effective use. These educational resources contributed to improved user experiences and the service’s worldwide popularity.

  • User guidance: Examples, request demonstrations, a News display box, and video guides address the complexity of the mature EXFOR system.The resources provide updates on new features and share best practices for using the interface.
  • User guidance: The broad scope of examples helped improve EXFOR user experiences and contributed to the service’s worldwide popularity.The examples are intended for user education and provide additional insight into interface capabilities.

3.4. Worldwide Impact of EXFOR Web Interface

EXFOR Web usage is broad and measurable through retrieval statistics, citation trends, and interaction patterns. Most operations involve interpreted data downloads and plotting, while specialized tools account for smaller shares.

  • Usage scale: Approximately 300 successful database retrievals per day are recorded from the IAEA and NNDC websites.The statistics exclude browser hits and reject retrievals that return empty results.
  • Usage scale: Approximately 1,100 citations mention the IAEA EXFOR address and approximately 770 mention the NNDC address.The citation growth curve closely matches Web retrieval statistics.
  • Operation patterns: Approximately 50% of operations are EXFOR data downloads in interpreted formats, exceeding original-format retrievals at less than 9%.The interpreted formats include iTree, X4+, and T4.
  • Operation patterns: Approximately 27% of operations involve EXFOR plotting followed by plotted-data downloads, while covariance-matrix construction accounts for approximately 1%.The usage analysis also identifies publisher, NSR, and PDF access as additional operations.
  • Operation patterns: Publisher DOI access accounts for 6.4% of operations, NSR retrieval for approximately 1%, and PDF downloads for approximately 2%.PDF access is restricted to authorized users because of copyright restrictions.

4. Related Nuclear Reaction Data Projects

EXFOR operates within a broader nuclear-data Web ecosystem that links experimental measurements with evaluated libraries and bibliographic resources. Related interfaces support searching and comparing reaction data, including evaluated and experimental cross sections.

  • System integration: The combined development of experimental, evaluated, and bibliographical databases reduced application-development and testing time through shared Java classes and Web plotting packages.EXFOR is described as an integral part of nuclear-data Web services and as closely related to evaluations and bibliography.
  • ENDF: ENDF provides evaluated nuclear-reaction data, emphasizing neutron-induced reactions and basing evaluations on theoretical calculations normalized to experimental measurements.The neutron-resonance region is an exception, where experimental data receive priority.
  • EXFOR and evaluations: EXFOR supplies experimental nuclear-reaction data for neutron cross-section evaluations and connects with model codes such as EMPIRE and TALYS.These codes calculate theoretical curves, analyze data, and compare results with experiments.
  • ENDF Web interface: The ENDF Web interface searches evaluated libraries by target, reaction, quantity, product, and other parameters while integrating evaluated and experimental data.The interface provides multiple output formats and supports comparisons such as ENDF/B-VII.1 and JEFF-3.2 for 235U(n,f) cross sections.
  • CINDA: CINDA preserves extensive nuclear bibliography, including historic publications grouped by experiment and searchable by energy range, and integrates with EXFOR.Its interface supports major EXFOR search fields and text and HTML outputs.

5. New Features of EXFOR Web Interface

The EXFOR Web interface has expanded from basic search and presentation into a system for users, compilers, and evaluators. Its newer tools support data uploads, renormalization, covariance calculations, and inverse-reaction calculations.

  • Interface expansion: EXFOR now provides extended functionality for regular users, compilers, and ENDF and ENSDF evaluators beyond basic search, retrieval, and presentation.The highlighted feature set includes experimental-data processing, renormalization, covariance matrices, and inverse-reaction cross-section calculations.
  • Data compilation and uploads: Researchers and NRDC compilers use direct interaction to obtain original data, complementary details, and comparisons with existing datasets before database submission.The complementary myPlot package also lets users upload and display their own data through a Web interface extension.
  • Renormalization: Automatic renormalization updates EXFOR measurements to new monitor data or recommended corrections when compilations include monitor-reaction information.The 25-MN-55(n,α)23-V-52 example shows original and renormalized data using latest monitor data and associated uncertainties.
  • Covariance calculations: Interactive covariance calculations derive correlation-matrix elements from experimental uncertainties, addressing demand for covariance information among evaluators, model developers, and experimentalists.The database contains limited covariance data alongside extensive total, statistical, and systematic uncertainty compilations.
  • Inverse reactions: The inverse-reaction calculator uses the nuclear reaction reciprocity theorem to extract a reaction cross section from a known inverse reaction.It can process EXFOR or user-submitted datasets and calculate angular distributions when the theorem applies.

6. Conclusion and Outlook

EXFOR and its Web interface form a publicly available nuclear-reaction data portal with broad access and advanced processing capabilities. Continued integration and analysis development support completeness, quality, and future nuclear science needs.

  • EXFOR provides public Web access to nuclear reaction and bibliographic information, with links to original data sets and articles where possible.The interface also supports user-friendly uploads, renormalization, covariance matrices, and inverse reaction calculations.
  • Advanced analysis implementation and integration with ENDF and NSR databases improve EXFOR completeness and extend its scope.
  • EXFOR has evolved over fifteen years into a premier nuclear reaction data portal based on current computer technologies.
  • The system is positioned to address current and future nuclear science and technology needs and challenges.The authors plan further development of data access, processing, dissemination, and analysis capabilities for applied and fundamental science users.
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