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Hokkaido University Nuclear Reaction Data Center
Masaaki Kimura
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Hokkaido University Nuclear Reaction Data Center


The main building of the faculty of science, which houses the Nuclear Reaction Data Center.


The main goal of the Hokkaido University Nuclear Reaction Data Center (JCPRG) is the compilation, maintenance and application of databases for nuclear reactions. More specifically, our primary focus is to compile a database for all charged-particle or photon induced nuclear reactions that are measured in Japanese facilities. As a member of the International Network of Nuclear Reaction Data Centres (NRDC), we provide a database in Exchange Format (EXFOR), which is the universal common format maintained by NRDC. Our contribution to the EXFOR database reaches approximately 10% of the total entries.


Since the very early stages of nuclear science, nuclear reactions have been utilized for various purposes such as energy generation, and industrial and medical use. For the effective and peaceful use of nuclear energy, broad and accurate knowledge regarding nuclear reactions is indispensable. For the aforementioned purposes, a nuclear database plays an essential role: it provides the best estimate of data for nuclear reactions and supplies this information to a wide range of data users in various fields of science and their applications.

The EXFOR database [1,2] is the universal common repository for nuclear reactions, which was established in 1967 following a meeting of four major nuclear data centers: Brookhaven National Laboratory (USA), the Nuclear Energy Agency Data Bank (NEA, France), the International Atomic Energy Agency (IAEA, Austria) and the Institute of Physics and Power Engineering (USSR). In the beginning, the scope of EXFOR was limited to neutron-induced reactions, but later it was extended to charged-particle and photon-induced reactions. Today, EXFOR includes approximately 22,000 experiments, 170,000 data sets, and 15,000,000 data points for 2600 nuclear reactions. The EXFOR database, which is the world's largest data library for nuclear reactions, is developed and maintained by the International Network of Nuclear Reaction Data Centres (NRDC), and it is supplied to users by web interfaces.

Our group (JCPRG) was founded at Hokkaido University in 1973 for the research of nuclear reaction databases, and we developed an original nuclear reaction database called the Nuclear Reaction Data File (NRDF), which contains the data of the charged-particle and photon-induced reactions measured in Japanese facilities. In 1975 we joined NRDC, and we were the first member institution based in an Asian country. Since then, we have been providing our compiled nuclear reaction data to the EXFOR database. Today, our contribution to the EXFOR database amounts to approximately 10% of the total entries (see Fig. 1). Furthermore, in 2010 we organized an NRDC meeting at Hokkaido University, which was the first time that the center's meeting was held in Asia (Fig. 2).

Fig. 1: Our contribution to the EXFOR database is approximately 10% of the total entries.

Fig. 2: Group Photo of the NRDC center meeting held at Hokkaido University in 2010.

In addition to our contributions to the EXFOR database, research and development in nuclear data science is our important mission. We are studying, from a theory-based perspective, neutron-induced reactions such as 7Li(n,n'), which are important for nuclear fusion reactor design [3]. The reaction analysis is based on the microscopic theory called continuum discretized coupled channels (CDCC). We also have been part of an ImPACT (Impulsing PAradigm Change through disruptive Technology) program since 2014. The project aims for the reduction and transmutation of nuclear reactor residues, and we are performing Monte Carlo simulations for the fragmentation reactions.

We have also developed computer tools for database compilation. Our database editor called HENDEL (Hyper Editor for Nuclear Data Exchange Libraries) [4] has user friendly web interfaces that make database compilation much easier and faster. In addition, HENDEL is being used not only by us but also by other center. The graph digitization system GSYS [5] is another major tool that has been developed by us and is becoming the de facto standard tool for compilation.

Currently, we have two faculty members and four researchers who are working in the areas of nuclear data compilation, research and development mentioned above.


As explained previously, EXFOR is the major nuclear reaction database commonly used in a wide range of research areas. Here, I explain how users can access data retrieval on the web interface, and how we are marking the database behind users.

Web Interface
The majority of EXFOR users are nuclear scientists, engineers, and graduate students who need direct access to the latest nuclear reaction data sets. They are typically not familiar with the detailed format of EXFOR, and so the web interface provides users easy and direct access to EXFOR.


On the web interfaces linked above, the users can input the target, reaction, experimental quantities, reaction product, energy range, etc., and can obtain the related articles, raw EXFOR data and a graphical plot for the data. Figs. 3a-3c demonstrate the result of a simple data retrieval for 6Li (n,t)4He. Usually, there are over 300 data retrievals per day.

Fig. 3a: Reaction code input for the data retrieval.

Fig. 3b: Available data and evaluations are shown.

Fig. 3c: One can see the graphical plot of the data.

EXFOR Compilation
Supporting the EXFOR users, researchers at nuclear data centers are compiling the database from published papers. The IAEA nuclear data section assigns the papers to be compiled at each nuclear data center. Our center is assigned the charged-particle and photon-induced reactions performed at Japanese experimental facilities. Usually, the number of assigned papers is approximately 100 per year. The compilers extract the bibliographic information, experimental set up, measured physical quantities, measured numerical data and error information. The collected data from a published paper are inputted in a single entry of EXFOR. To ensure the accuracy of the data input, we usually ask the authors of papers to provide their original data. If it is not available, we digitize the numerical data from the PDF files. I would like to take this opportunity to express our thanks to the authors of the papers for their kind cooperation with the EXFOR compilation process.

Each EXFOR entry has a unique assignment number and constitutes of various subentries that contains the extracted experimental information. The detailed EXFOR format is explained in the manual document, LEXFOR. Fig. 4 shows an EXFOR entry numbered E1920 [6], which corresponds to the first paper for the finding of the 113th element named 'Nihonium' [7]. As you see, the EXFOR format has readable, fixed columns that are 80 characters long, which was is a format that is convenient for both human readers and computers. Efforts for improvement and modernization of the EXFOR format are currently underway.

Fig. 4: Part of an EXFOR entry numbered E1920, which contains the data of the first report of the synthesis of the 113th element, which was named Nihonium in 2017.


Recently, the presence of Asian countries in the NRDC is increasing. Many countries are building accelerator facilities and are starting to produce large amounts of experimental data. However, there are not enough EXFOR compilers. To accelerate the production of nuclear data and to reinforce international cooperation regarding research in Asian countries, we initiated a series of international workshops, called the "Asian Nuclear Reaction Database Development Workshop (AASPP)" in 2010. In the last year, 8th AASPP workshop was held at the National University of Mongolia, and the 9th AASPP will be held in Korea in this year. We hope that the growth of nuclear data science activities in the Asia-Pacific region continues.

Acknowledgements: The contribution of the JCPRG members is gratefully acknowledged.


[1] N. Otsuka et al., Nucl. Data Sheets 120, 272 (2014).
[2] V.V. Zerkin and B. Pritychenko, Nucl. Inst. and Meth. in Phys. Res. A 888, 31 (2018).
[3] D. Ichinkhorloo et al., Phys. Rev. C89, 044610 (2014).
[4] http://www.jcprg.org/manuals/hendel/
[5] http://www.jcprg.org/gsys/
[6] http://www.jcprg.org/master/exfor/E/e1920.txt
[7] K. Morita et al., J. Phys. Soc. Jpn. 73, 2593 (2004).


Masaaki Kimura is an associate professor of the Department of Physics and the head of the Nuclear Reaction Data Center at Hokkaido University. After receiving his Ph.D. from Kyoto University, he worked at RIKEN, the Yukawa Institute for Theoretical Physics, and Tsukuba University before joining Hokkaido University in 2008. His research field is theoretical nuclear physics. He is a member of the editorial board of Chinese Physics C.