U.S. Nuclear Data Resources for a Coordinated U.S. Effort in Nuclear Data for Nuclear Astrophysics

Michael S. Smith, Oak Ridge National Laboratory
F. Edward Cecil, Colorado School of Mines
Richard B. Firestone, Lawrence Berkeley National Laboratory
Gerald M. Hale, Los Alamos National Laboratory
Duane C. Larson, Oak Ridge National Laboratory
David A. Resler, Lawrence Livermore National Laboratory

• Overview
• Nuclear Data Needs for Nuclear Astrophysics
• Nuclear Data Resources for Nuclear Astrophysics
• A Cooperative Data Effort
• A Coordinated U.S. Data Effort
• Important Issues
• Summary
• Acknowledgements
• Appendix 1: U.S. Nuclear Data Resources
• Appendix 2: Proposed Organizational Structure
• Appendix 3: Recent Organizational Activities
• References
• World Wide Web Nuclear Data Sites

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Overview

There is a strong need to produce and disseminate high-quality evaluations of nuclear data for nuclear astrophysics. Specifically, more complete, precise, and up-to-date evaluated nuclear data are required for models of diverse astrophysical phenomena. This is especially true for a new generation of sophisticated models attempting to explain observations ranging from precision abundance measurements in meteorites to spectacular images from the Hubble Space Telescope and the Compton Gamma Ray Observatory. Launching a nuclear data effort to meet these needs would significantly enhance progress in many fundamental problems in nuclear astrophysics, and would be an appropriate tribute to Willy Fowler, the most active proponent and compiler of nuclear data for nuclear astrophysics.

There are many valuable resources in the nuclear data community that can be utilized to help meet these nuclear astrophysics data needs, in the form of existing nuclear data evaluations and in the expertise to produce these evaluations. Cooperation between the nuclear astrophysics and nuclear data communities in a nuclear data effort for astrophysics would minimize duplication of effort and enhance the potential for success. Additionally, coordination of such a data effort for nuclear astrophysics on a national scale would maximize the use of available resources and facilitate coordination with international efforts.

We briefly describe the nuclear data needs of nuclear astrophysics, then list and describe some of the nuclear data resources appropriate to meet these needs. We discuss the advantages of a cooperative and coordinated U.S. data effort for nuclear astrophysics, and list some important issues surrounding the launching of such an effort. Finally, we include suggestions for an organizational structure to implement this data effort.



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Nuclear Data Needs for Nuclear Astrophysics

Nuclear astrophysics involves study of the synthesis of elements and the evolution of cosmic sites where such syntheses occur. Systems as diverse as the early universe, the interstellar medium, red giant stars, and supernova explosions are currently the focus of intense studies utilizing sophisticated computer models -- models which require large quantities of nuclear data as input. Measurements in the nuclear laboratory form the empirical foundation for the current models of element synthesis. These models require, in general, the rates of and energy released in nuclear reactions occurring in astrophysical environments. The rates are derived from laboratory measurements of cross sections of relevant reactions -- primarily fusion, transfer, and decay reactions -- convoluted with a thermal (Maxwell-Boltzmann) relative velocity distribution; the released energies of the relevant reactions (Q-values) are derived from measurements and calculations of masses. Additionally, models require information on properties of relevant nuclei, such as one- and two-particle separation energies, single-particle energy levels, level densities, partition functions, and parameters of resonances near particle capture thresholds.

There are a number of existing evaluations of nuclear data important for astrophysical models. However, most of these need updating to include recent experimental and nuclear modeling results. Furthermore, more complete, precise, and current nuclear data are required for a new generation of models (e.g., multi-dimensional supernova codes, multi-zone calculations of inhomogeneous big bang nucleosynthesis) attempting to explain new astrophysical observations (e.g., Supernova 1987a, light elements in the interstellar medium and on the surfaces of halo stars). Progress in many fundamental problems in nuclear astrophysics can be significantly aided by more effective utilization of existing measurements. This can be done via data stewardship activities such as: making high-quality data evaluations, complete compilations, and timely and useful disseminations; and using nuclear reaction and structure models to extend existing measurements to unmeasured reactions, energy ranges, and isotopes. Such activities are routinely carried out by scientists in the nuclear data community.



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Nuclear Data Resources for Nuclear Astrophysics

The nuclear data community has two types of valuable resources which could be effectively used to help meet nuclear astrophysics data needs:

1. Evaluations -- Existing evaluations of nuclear data which are useful in astrophysical models, either directly or with some modifications (e.g., updating or selective expansion);
2. Expertise -- The data stewardship expertise to produce and disseminate these evaluations.
Some activities in the data community are sponsored by and closely coupled to the basic research community -- an example is the Evaluated Nuclear Structure Data File (ENSDF) and the nuclear structure community. Many other activities are sponsored by applied science programs such as Fusion Energy, Reactor Technology, and Weapons Technology. However, the products of these activities, and the expertise to produce them, are vital resources to the basic research community.

An example of an existing evaluation useful for astrophysics is the Thermonuclear Data File (TDF) at LLNL, which includes thermonuclear rates and spectral information on outgoing particles, as a function of temperature (from 100 eV to 1 MeV), for the ²H(d,n)³He, ²H(d,p)³H, ³H(t,2n)⁴He, ³H(d,n)⁴He, and ³He(d,p)⁴He reactions [White et al., WH91]. These reactions are important in, for example, the synthesis of nuclei in the Big Bang and in the core of our sun. TDF was developed for Fusion Energy applications, and some of its evaluations are duplicated independently by work in the nuclear astrophysics community -- e.g., Smith et al. [SM93] -- and by others in the nuclear data community -- e.g., Bosch and Hale [BO92]. More nuclear data evaluations useful for astrophysics with origins in the nuclear data community are described in Appendix 1.

Besides data evaluation work, the nuclear data community has expertise in a number of activities appropriate for astrophysics. An example is their experience in establishing and maintaining online information services, especially those based around World Wide Web (WWW) sites. A list of online services is given in Appendix 1 and in the References. A dedicated WWW site for evaluated data for nuclear astrophysics would be a timely, useful, and cost efficient manner of disseminating evaluations; such a site is discussed in more detail in Appendix 2.

The resources which are specifically appropriate for an astrophysics data effort can be grouped into seven categories. Brief examples are given here for each category; detailed lists and descriptions are given in Appendix 1.

1. Compilations -- such as the experimental cross sections in CSISRS; these can be subdivided into categories of Experimental Data; Modeled Quantities (e.g., calculations of unmeasured cross sections or nuclear masses); Evaluated Data (e.g., combining a set of measurements, augmented by model results, into a complete set of useful results in a standardized, well-documented manner); and Derived Quantities (e.g., reaction rates derived from evaluated cross sections);
2. Nuclear Modeling -- such as the Hauser-Feshbach statistical model code GNASH or the reaction rate network calculational ability of FISPACT;
3. Evaluation Software Tools -- such as the Bayesian code GLUCS used to combine cross section measurements;
4. Evaluation Testing and Standardization -- to maintain high quality standards and ensure compatibility with existing data processing codes;
5. Data Formats -- such as ENDF for evaluated cross sections and EXFOR for experimental cross section data;
6. Bibliographic Information -- such as the Computer Index of Neutron Data (CINDA); and
7. Online Information Services -- such as the T2 Nuclear Information Service (LANL) and services at the National Nuclear Data Center (BNL) and the Isotopes Project (LBNL).


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A Cooperative Data Effort

The wealth of nuclear data resources listed above and in Appendix 1 suggests that the nuclear data community can significantly contribute to a nuclear astrophysics data effort. We give three compelling reasons that the potential for the success of such a data effort would be enhanced by cooperation between the nuclear data and nuclear astrophysics communities.

1. Increase Manpower -- Scientists in the nuclear data community are experts at many data stewardship activities needed in nuclear astrophysics. Both nuclear astrophysicists and nuclear data scientists can potentially benefit from the recent redirection of some nuclear data resources from applied to basic nuclear physics research.
2. Minimize Duplication -- A cooperative effort would minimize duplication of existing expertise and efforts in data stewardship. This is very important in a time of shrinking resources.
3. Ensure Quality -- The nuclear data community has established methods of testing nuclear data evaluations to uniformly ensure that high-quality standards are met. High quality is essential if the products of this data effort are to be widely used to improve astrophysical models.


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A Coordinated U.S. Data Effort

There are also a number of compelling reasons to coordinate a nuclear astrophysics data effort among the U.S. nuclear astrophysics and nuclear data communities.

1. Set Priorities -- Because of the substantial nuclear astrophysics data needs and limited available manpower, it will be very important to prioritize the data needs. These priorities should represent a consensus of the nuclear astrophysics community -- and such a consensus can most easily be reached and updated through a coordinated effort.
2. Maximize Output -- A coordinated effort would minimize duplication of efforts and maximize utilization of existing resources. This is very important in light of the substantial data requirements for nuclear astrophysics.
3. Ensure Utilization -- Evaluations which are chosen, produced, and endorsed through a coordinated effort with the consensus of the community have an excellent chance of becoming widely used and accepted tools for nuclear astrophysics research. A uniform use of nuclear data evaluations would help enable comparisons of astrophysical models independent of their nuclear data input.
4. Enlist Manpower -- A coordinated effort may have an increased effectiveness at enlisting nuclear astrophysicists and nuclear data scientists.
5. International Effort -- Coordination of this effort on a national scale would ease coordination with international (e.g., European) data efforts.
For these reasons, an important first step in launching a nuclear astrophysics data effort involves forming a group of individuals to coordinate this effort among the nuclear astrophysics and data communities -- an Nuclear Astrophysics Data Effort Steering Committee. This Steering Committee should be comprised of nuclear astrophysicists and nuclear data scientists with relevant expertise who are committed to producing high-quality nuclear data products of vital importance to the nuclear astrophysics community. The best way to organize this data effort should be decided through discussions among members of the two communities, and should be the one which best matches the nuclear astrophysics data needs. Some important organizational issues are listed in the next section. In an effort to initiate such discussions, we suggest and describe a zeroth-order organizational structure in Appendix 2. Recent organizational activities undertaken since the original writing of this document are briefly described in Appendix 3.


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Important Issues

A number of very important issues should be addressed in launching a cooperative, coordinated U.S. effort in nuclear data for nuclear astrophysics. Some of these issues include:

1. Organizational Structure -- Steering Committee
   • Is there community support for a steering committee?
   • What are its general guidelines?

   • What are its responsibilities and capabilities:

     for setting data project priorities?

     for enlisting manpower for data projects?

     for ensuring high quality standards in the evaluations?

2. Organizational Structure -- Other Issues
   • What is the best structure to implement this data effort?
   • How can we obtain a consensus of the astrophysics community?
   • What is division of labor between the astrophysics and data communities?
   • What is the relationship with existing U.S. data organizations, such as the U.S. Nuclear Reaction Data Network (USNRDN), the U.S. Nuclear Data Network (USNDN), and the Cross Section Evaluation Working Group (CSEWG)?
3. Coordination with International efforts
   • What is the best way to coordinate this effort with the European Nuclear Astrophysics Effort and with other international organizations (e.g., International Atomic Energy Agency (IAEA))?
4. Funding
   • What is the balance between seeking additional funding and redirection of current funding and efforts?
5. Dissemination
   • Is there community support for a centralized, dedicated WWW site for evaluated nuclear data for nuclear astrophysics?
   • Should this site be an extension of an existing nuclear data site, or a site constructed independently?


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Summary

We endorse launching a coordinated U.S. effort to produce and disseminate critically important, high-quality evaluations of nuclear data for nuclear astrophysics. This effort can have a substantial impact on progress in a number of research areas in nuclear astrophysics. Because of the substantial overlap between astrophysics data needs and data community resources, it would be very beneficial to make this a cooperative venture between the nuclear astrophysics and nuclear data communities. This effort should also be coordinated within the U.S. to maximize the use of available resources and to ease coordination with international efforts.



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Acknowledgements

The authors wish to thank Mulki Bhat, Janis Dairiki, Robert MacFarlane, Robin Forest, Victoria McLane, Peter Möller, Pavel Oblozinsky, Erich Ormand, Peter Parker, S. Raman, Robert Stokstad, and Phil Young for useful suggestions and information.



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Appendix 1: U.S. Nuclear Data Resources

The nuclear data resources appropriate for an astrophysics data effort can be grouped into the categories of Compilations, Nuclear Modeling, Evaluation Software Tools, Evaluation Testing and Standardization, Data Formats, Bibliographic Information, and Online Information Services. Some of these nuclear data community resources may reside both in the data and basic research community -- this is especially true for the nuclear modeling resources. Some specific examples of nuclear data resources in each of these categories follows below.

1. Compilations
   The nuclear data community has established and maintained a number of compilations (i.e., collections) of nuclear data that may be useful -- with some modifications or some selective expansion -- for nuclear astrophysics studies. These can be divided into categories of Experimental Data, Modeled Quantities (e.g., predictions of unmeasured cross sections), Evaluated Data (e.g., combining a set of measurements, augmented by modeled results, into a complete set of useful results in a standardized, well-documented manner), and Derived Quantities (e.g., reaction rates derived from evaluated cross sections).
   1. Experimental Data

      CSISRS

      The Cross Section Information Storage and Retrieval System is an online compilation at NNDC that stores cross sections in the EXFOR format. This database has relatively good coverage of neutron induced reactions, and sparse coverage for charged-particle induced reactions. It also includes photon-induced reactions, and has search, retrieval, and (limited) display tools online. It includes energy dependent total and partial cross sections, energy and angular distributions of outgoing particles, resonance parameters, fission product yields, and thick target yields. It may be very useful for astrophysics to merge the CSISRS database with the databases listed below.

      ECSIL

      The LLNL Experimental Cross Section Information Library This library contains experimental data for neutron induced reactions from over 6,000 references dating back to 1938. Many of these data were obtained from the NNDC at BNL in the EXFOR format and were translated into a common units base and format. This library will soon be accessible online to outside users. (LLNL)

      ECSIL2

      An extension of ECSIL to hold charged-particle induced reaction cross sections. Approximately 425 data sets are included, with reaction cross sections, elastic scattering data, excitation functions, angular distributions, and polarization data. This library may soon be accessible online to outside users. (LANL / LLNL)

   2. Modeled Quantities
      Many of the compilations of calculated or modeled quantities useful for astrophysical models have originated within the nuclear astrophysics community. These include the Hauser-Feshbach statistical model calculations of reaction rates in Holmes et al. [HO76] and Woosley et al. [WO78], and the recent update by Hoffman and Woosley [HO92]. The earlier two studies contain calculations of nuclear level densities and partition functions using a Back-Shifted Fermi Gas formalism [Hauser and Feshbach, HA52]; [HO92] contains partition function tabulations but not level densities. There are also two alternative level density models -- the Gilbert-Cameron and generalized superfluid models. Improvements since 1978 have been made in level density calculations, including the use of moment calculations and studies of systematics and of the non-equipartition of level parity [GR94]. New tabulations for isotopes of astrophysical interest would be helpful in calculations of rates with statistical models.
      
      Nuclear masses are a very important quantity in nucleosynthesis models and in calculations of unmeasured reaction rates. Masses of nuclei far from stability, very important for studies of nucleosynthesis through the rp-, p- and r-processes, are experimentally inaccessible, and must be modeled. The particular mass model used, for example, in network calculations can have a substantial effect on the results of the calculations. For example, recent calculations suggest that two-proton capture reactions can bridge the waiting points in network calculations of the extended rp-process (thought to occur in x-ray bursts) when the Hilf mass model is used, but cannot bridge the waiting points when the Möller mass model is used [SC95].
      
      Nuclear masses and deformations have recently been calculated in Möller, Nix, Meyers, and Swiatecki [MO95a]; and modeling of other nuclear properties of astrophysical interest by Möller, Nix, and Kratz [MO95b] -- a collaboration between nuclear structure physicists and nuclear astrophysicists. This latter work includes calculations of pairing gaps, particle separation energies, beta decay energies and lifetimes, beta-delayed particle emission probabilities, and alpha decay lifetimes and energies, for 8979 isotopes ranging from Z=8, A=16 to Z=136, A=339, between the proton- and neutron-drip lines.
      
      There are a number of other mass models, both theoretical and semi- empirical. Haustein [HA88] compares 10 different mass models with the 1988 experimental values. This work contains descriptions of each of the theoretical models by their respective authors. It is stored online at LBL; see section 1.G.
      
      Reduced transition probabilities for Gamow-Teller decays B(GT) are modeled and compared to a comprehensive set of experimental values in Brown and Wildenthal [BR85b] for sd-shell nuclei (A=8, A=17 to Z=20,A=30). Tabulated information includes half-lives, Q-values, final-state excitation energies, branching ratios, ft-values, and GT matrix elements. An important compilation of calculated weak interaction rates is that of Fuller, Fowler, and Newman [FU82]. This work from the astrophysics community contains e- capture rates, neutrino energy loss rates, and electron and positron decay rates for 226 sd- and fp-shell nuclei. The rates are tabulated for temperatures ranging from 10 million to 100 billion degrees kelvin, and electron densities from 10 to 100 billion g/cm3. A number of these rates have significantly changed in the updated compilation of Oda et al. [OD94]. They calculate rates for 79 nuclei in the sd-shell, A=17-39, with an improved shell model code, over the same temperature and density grid as the first study. They use the latest, most complete description of the residual interaction in the sd-shell. In the absence of a well-established residual interaction for the fp-shell, Oda et al. did not update the weak rates for these nuclei. Rates on fp-shell nuclei are very important for supernova nucleosynthesis, so there is a great need for further work in this area. Furthermore, the recent experimental results on the quenching of the Gamow-Teller strength function need to be incorporated into rate calculations. [HO92] also includes tabulations of weak rates.
      
      RIPL -- The Reference Input Parameter Library [OB94], currently under construction, is a library of numerical data to serve as input parameters for nuclear model calculations of nuclear reaction data. It contains seven parameter categories, with a total of approximately 30 MB of data: atomic masses, shell corrections, and deformations; discrete level schemes; average neutron resonance parameters; optical model parameters; level densities; gamma ray strength functions; and angular distributions. The library, when completed in 1997, will be available online via ftp. This is an effort of a Cooperative Research Program (CRP) sponsored by the International Atomic Energy Agency (IAEA).
   3. Evaluated Data

      ENDF/B

      The Evaluated Nuclear Data File B contains evaluations by the Cross Section Evaluation Working Group (CSEWG); it is currently in its sixth version, the first produced in 1967. It has extensive neutron induced reaction cross section information -- 240 isotopes between hydrogen and the actinides, approximately 150 with resonance parameters. Since this file has been sponsored in large part by the reactor technology and fusion energy programs, there is not a complete overlap with isotopes of interest for astrophysics. Even more importantly, some of the ENDF/B evaluations, especially the ones more than 10 years old, need to be updated. ENDF/B has a sparse coverage of charged-particle induced reaction cross sections -- an extensive expansion and update would be required to improve its usefulness for nuclear astrophysics. ENDF/B also includes a decay data file, with decay data and radioactive decay spectra for approximately 2000 nuclides. ENDF/B is accessible online at a number of locations, such as the National Nuclear Data Center (NNDC) at BNL and at the T2 Nuclear Information Service at LANL -- see Section 1.G. ENDF/B will also soon be published on CD-ROM by the American Nuclear Society. Evaluated data in ENDF/B is stored in the ENDF format.

      JENDL, BROND, JEF

      The Japanese Evaluated Nuclear Data Library, the Russian Data Library, and the Joint European File are files of evaluated cross sections with some overlap with ENDF/B. There is very good coverage of neutron cross section data on materials relevant for fusion and fission applications, including fission products. Evaluated data from these three files (along with FENDL) could be very useful for some astrophysics applications.

      FENDL

      The Fusion Evaluated Nuclear Data Library contains a selection of neutron cross section evaluations for materials of interest to fusion from ENDF/B-VI (the majority of the set), JENDL 3.1 (the Japanese Evaluated Nuclear Data Library) and BROND-2 (the Russian Data Library). The materials are those needed for calculations of neutronics for the ITER fusion reactor. This library is targeted towards the ITER application, and therefore does not include fission-product materials.

      Neutron Cross Sections

      These valuable NNDC works contain resonance parameters, thermal cross sections, average resonance parameters, and cross sections for neutron-induced reactions on targets with Z=1-60 (Vol. 1, Part A) [MU81] and Z=61-100 (Vol. 1, Part B) [MU84]; Vol. 2 contains cross section curves [MC88].

      ENSDF

      The Evaluated Nuclear Structure Data File contains information on nuclear properties (energy levels, masses, decay modes, some resonance parameters). This information includes nuclear properties that are published in Nuclear Data Sheets (for masses greater than 44). It also contains the evaluations of Fay Ajzenberg-Selove for masses A=5-20 published in Nuclear Physics A -- the last in 1991. References for the most recent evaluations in this mass range are given in [AJ91]. ENSDF also includes the evaluations of Endt [EN90] (and previously Endt and van der Leun) for masses 21 - 44, as published in Nuclear Physics A. Responsibility for masses 3 - 20 have now passed to the Triangle Universities Nuclear Laboratory (TUNL) Data Project. ENDSF is accessible online -- see Section 1.G. Additional nuclear structure information is accessible online through the World Wide Web (WWW) homepages of laboratories comprising the U.S. Nuclear Data Network (NDN). For example, the diagrams of the energy levels of light nuclei (mass A<21) are accessible online at the TUNL website.

      EAL

      The European Activation Library contains evaluated cross sections for neutron induced reactions (0-20 MeV) on 729 targets -- stable isotopes and radioactive isotopes with half-lives greater than 0.5 day. The file includes approximately 13000 reactions, includes uncertainty information, and handles isomers properly. It utilizes a pointwise ENDF style format, as well as other formats for fusion energy and other applications. An inventory code FISPACT [Forrest and Sublet, FO95] calculates the abundances of nuclides in materials resulting from neutron exposure.

      Table of Isotopes

      produced by the Isotopes Project at LBL, this work contains information on nuclear properties. The seventh edition is Lederer et al. [LE78]; the eighth edition will be released in early 1996 in paper and on CD-ROM.

      NUDAT

      This online database (at NNDC) has nuclear levels, gamma decays, ground state properties, radiations, and thermal neutron cross section information taken from a number of other databases (including ENSDF).

      Audi and Wapstra 1995 Mass Evaluation

      This is the latest [AU95] in a series of mass evaluations. These masses and Q-values are based on experimental values and on masses near stability derived from systematic trends. A covariant error matrix, which can be used to generate uncertainties in masses and Q-values, is produced and will soon be accessible. A program to calculate reaction Q-values from this compilation, QCALC, is online at NNDC.

      LLNL Evaluated Data Libraries

      the following libraries are maintained at Livermore:

      ACTL

      Evaluated Neutron Activation Cross Section Library

      (360 materials, incident energy from 10^-10n to 20 MeV)

      EADL

      Evaluated Atomic Data Library

      (Z = 1-100)

      ECPL

      Evaluated Charged-Particle Data Library

      (14 materials, incident energy up to 20 MeV)

      EEDL

      Evaluated Electron Data Library

      (Z = 1-100, incident energy from 10 eV to 100 GeV)

      EGDL

      Evaluated Gamma-Ray Interaction Data Library

      (Z = 1-100, incident energy from 100 eV to 100 MeV)

      ENDL

      Evaluated Neutron Data Library

      (109 materials, incident energy from 10^-10 to 20 MeV, some to 30 MeV)

      EPDL

      Evaluated Photon Data Library

      (Z = 1-100, incident energy from 10 eV to 100 GeV)

      PCSL

      Production Cross Section Library

      (6 materials; incident neutron energy from 10^-10 to 100 MeV, incident proton energy up to 100 MeV)

   4. Derived Quantities
      TDF -- The Thermonuclear Data File at LLNL [WH91] is an ASCII file containing thermonuclear reaction rates, and spectral information on the outgoing particles, as a function of plasma temperature for five reactions: ²H(d,n)³He, ²H(d,p)³H, ³H(t,2n)⁴He, ³H(d,n)⁴He, and ³He(d,p)⁴He. Note that these reactions are important in, for example, Big Bang Nucleosynthesis and in the nucleosynthesis occurring in the core of our sun. This file contains interpolatable data for all plasma temperatures from 100 eV to 1 MeV, and assumes that the distribution of the reacting particles in the plasma is Maxwellian. The file can easily be expanded to other reactions. There is a library of four subprograms for accessing TDF. (LLNL)
      
      The majority of the compilations of quantities derived from evaluated experimental data that are useful for astrophysical models have originated within the nuclear astrophysics community. These include Caughlan and Fowler [CA88], the last in a series of charged-particle induced rate evaluations coauthored by Willy Fowler, and the neutron-induced reaction rate evaluations of Bao and Kappeler [BA87] and Beer, Voss, and Winters [BE92]. Some previous versions of the Caughlan and Fowler [CA88] evaluation, e.g. Fowler et al. [FO67], contained parameterizations of astrophysical S-factors derived from evaluated data. These are charged-particle cross sections with the s-wave penetrability and geometric cross section (~1/E) divided out. Since this is generally a slowly-varying function of energy, it is very useful when extrapolating charged-particle cross section measurements from lab energies to stellar energies. Another useful quantity, often used in studies of heavy element nucleosynthesis through neutron capture reactions, is Maxwellian-averaged cross sections. These are reaction rates divided by the relative thermal velocity ( <sigma*v> / v_thermal ). These are tabulated, instead of reaction rates, in Bao and Kappeler [BA87]. Note that S-factors, maxwellian-averaged cross sections, and reaction rates could be derived online from processing evaluated cross section data by simple online software codes. However, compilations of analytical expressions of these quantities as functions of energy or temperature are very useful for astrophysics.
2. Nuclear Modeling
   Nuclear reaction and structure theorists, both within and outside of the nuclear data community, have developed and maintained a number of software codes to calculate unmeasured, experimentally inaccessible quantities such as cross sections and masses. A list of some of these useful codes follows.

   GNASH

   a Hauser-Feshbach statistical model code for cross section calculations. This code handles neutrons and protons incident on heavier isotopes, at energies of 10 keV to 200 MeV. Incident photons can also be calculated, important for calculations of photodissociation reactions. Various optical-model codes are also used in connection with GNASH to compute the transmission functions (SCAT, SCAT2, ECIS). (LANL / LLNL)

   FKK-GNASH

   an extension of GNASH for more accurate work at higher energies, treating the preequilibrium regime with the FKK formalism. This may be useful for cosmic ray nucleosynthesis and for the designs of targets and shielding for future radioactive ion beam facilities planned to produce beams of interest for nuclear astrophysics studies. (LANL/LLNL)

   TNG

   a Hauser-Feshbach statistical model code for cross section calculations, with consistent pre-equilibrium model. This handles neutrons, protons, and alphas in the incident channel, and neutrons, protons, alphas, and photons in the exit channel. Useful for incident energies from 10 keV to 20 MeV. (ORNL)

   ALICE

   a Hauser-Feshbach statistical model code for calculating nuclear reaction cross sections. (LLNL)

   FRDM

   the Finite Range Droplet Model is used by Möller et al. [MO95a,MO95b] in their calculation of nuclear masses and properties for astrophysics, described in Section 1.A.2. In the FRDM, nuclear ground-state masses and other properties for astrophysical applications are calculated by use of the macroscopic-microscopic method, with the macroscopic contribution calculated from a finite-range droplet model and the microscopic shell and pairing corrections calculated from a folded- Yukawa single-particle potential. Strutinsky's method is used for the shell correction, and the Lipkin-Nogami extension of the BCS method is used for the pairing correction.

   OXBASH

   the Oxford-Buenos Aires Shell Model code [Brown, Etchegoyan, and Rae, BR85a] is a general, multi-purpose shell model code using a J and T-projected m-scheme. This code is widely used for predicting unmeasured nuclear properties such as spectroscopic factors, and level energies and widths. These are critical ingredients in, for example, the calculation of unmeasured reaction rates.

   CRUNCHER

   code system for nuclear and atomic shell model calculations. Has been used for calculations of astrophysics interest such as Gamow-Teller strength functions and in conjunction with R-matrix theory for predicting nuclear cross sections. (LLNL/Ohio University)

   FISPACT

   A code which calculates the abundances of nuclides in materials resulting from neutron exposure [FO95]. This is used in conjunction with the EAL library of evaluated activation neutron cross sections. This code (or portions thereof) may be useful in network calculations of heavy element nucleosynthesis.

3. Evaluation Software Tools
   The nuclear data community has developed and maintained a number of software codes that are very valuable tools for data evaluation. An incomplete list with brief descriptions follows.

   GLUCS

   Generalized Least-Squares Cross Section Evaluation Code [TA94], uses a Bayesian principle of updating existing information on nuclear cross section measurements. (ORNL)

   NJOY

   system for processing evaluated cross section libraries into a variety of forms used for applications (e.g., the MCNP transport code, nuclear engineering codes). Capabilities useful for astrophysical applications include resonance reconstruction, Doppler broadening, cross section averaging, plotting, and other peripheral subroutines. (LANL)

   EDA

   Multichannel, multilevel R-matrix analysis code for reactions involving any type of particles incident on light-mass (A<20) targets, including photons (for capture and photodissociation reactions), 3-body final states, and full uncertainty and covariance information. (LANL)

   BAYES

   general purpose computer code for fitting a functional form to experimental data via Bayes Equations. (ORNL)

   SAMMY

   multilevel R-matrix code for analysis of neutron capture and transmission experimental data [LA94], with full uncertainty and covariance information. Output resonance parameters in ENDF format. (ORNL)

   Utility tools for data evaluation -- many laboratories have useful sets of software utility codes that can aid data evaluation efforts. For example, a list of some of these tools at LLNL, which are summarized in Resler and White [RE92], are:

   CSGEN and SFGEN

   software utility that allow a user to easily convert between cross sections and astrophysical S-factors. (LLNL)

   XDIGITIZE

   a utility code for extracting numerical values from graphs when tabulated experimental data are unavailable. (LLNL)

   QPX

   a code for highly-interactive, general purpose graphics. (LLNL)

   CSPLINE and THINER

   utility codes for spline fitting and thinning of tabulations. (LLNL)

   RATIO

   a code for comparing two data files. (LLNL)

   POLYFIT, SEGFIT, SPLINEFIT, DATAFIT

   a series of codes for various least-squares fitting ranging from simple polynomial to cubic-spine fits. (LLNL)

4. Evaluation Testing and Standardization
   The nuclear data community has established methods of testing nuclear data evaluations to uniformly ensure that high-quality standards are met. These standards are required in, for example, reactor technology applications -- where safety is a crucial issue. Testing evaluations involve checking formats, checking physics parameters, and calculating basic quantities, as well as benchmarking the evaluated data against high precision measurements. One approach developed by CSEWG (the Cross Section Evaluation Working Group) for testing evaluations (such as those in ENDF/B) involves three phases. Phase I is an automated test of the evaluation followed by a careful review of the new or revised evaluation by another evaluator. The review checks, for example, that reasonable methods were used, that references are complete, and that the calculated curves match existing experimental data reasonably well. Phase II uses the evaluation to compute real benchmark assemblies in order to see how it will perform for applications. A third phase is to release the evaluation for use in the field. Feedback from the users is then used to improve the next version of the evaluation.
   
   An effort to make integral benchmark tests of ENDL, ENDF/B-V and -VI, JENDL-3, JEF-2, and BROND-2 is described in Resler et al. [RE94]. The evaluated data files are being transformed from the ENDF formats to a simpler format, "Format2000", which allows for easier comparison of the basic data, as well as for the use of LLNL processing codes to consistently create application files for Monte Carlo calculations.
   
   Additionally, some software has been developed to aid in evaluation testing and standardization activities.

   ENDF/B testing suite

   STANEF, CHECKR, FIZCON, PSYCHE. In addition, data sets are run through standard processing codes like RECENT and NJOY to be sure they work correctly, to provide additional consistency checks, and to provide data for plotting. (available at many national labs)

   FMTCHK

   format checking code for ENSDF formats. (NNDC)

Data Formats
The nuclear data community has established and maintained formats for the online storage of information. It would be very useful to utilize these formats whenever possible, perhaps with some modifications, for storing the results of an astrophysics nuclear data effort. This would avoid duplicating existing data format work, and would lead to compatibility with existing data processing codes. Some of the established formats are listed below.

ENDF

format for evaluated cross sections and decay data. (NNDC)

ENSDF

format for nuclear structure information. (NNDC)

EXFOR

format for experimental cross section data (used in CSIRS). (NNDC)

ENDL

format for evaluated nuclear and atomic data. All data are represented by simple two-, three-, or four-column formats in which the tabulations almost always use linear-linear interpolation. (LLNL)

ECSIL

format for experimental nuclear data. (LLNL)

TDF

format for thermonuclear data library, includes a set of access routines. (LLNL)

ECSIL2

format for experimental cross section data. (LANL)

6. Bibliographic Information

   CINDA

   The Computer Index of Neutron Data bibliography contains information on neutron induced reactions over a wide range of neutron energies. CINDA is online at NNDC, and has excellent coverage of journal articles as well as unpublished laboratory reports. This database is widely used both in basic and applied research programs.

   NSR

   The Nuclear Science References (formerly Nuclear Structure References) online bibliography at NNDC has approximately 130,000 low and intermediate energy nuclear physics references, covering about 80 international journals. There is good coverage for nuclear astrophysics articles in Nuclear Physics A, for example, and some coverage for articles in The Astrophysical Journal. This is also available on CD-ROM -- Papyrus NSR, and an update CD will soon be available. Online info is available at http://www.fysik.lu.se/nucleardata/nsr_.htm.

   Integral Charged Particle Nuclear Data Bibliography

   This is the last update [HO89] of a charged particle bibliography compilation started at the NNDC in 1978 [BU78a]. These contain citations from 27 core journals of work with minimal energies below 100 MeV in CINDA-style format, as well as useful lists of related bibliographies. Later versions also include titles and keyword listings extracted from NSR for cited works.

   Reaction List for Charged-Particle Induced Nuclear Reactions, Z=1 to Z=98

   The last [MC76] in a series of 8 charged-particle bibliographies by these authors, covering the years 1967-1976 and 32 core journals. This compilation sorts by reaction and also by measured quantities.

   A Source List of Nuclear Data Bibliographies, Compilations, and Evaluations

   This work [BU78b] contains references up to 1978.

7. Online Information Services
   There are a number of internet sites established and maintained by the nuclear data community where nuclear data are archived and remotely accessible. Some of these extremely valuable services are listed below. A number of these sites are linked together through their WWW homepages, such as those of the U.S. Nuclear Structure Data Network (USNDN).

   T2 Nuclear Information Service (LANL)

   an online service with a WWW interface, providing access to CSISRS cross sections, Möller and Nix mass calculations, a chart of the nuclides, and the ENDF/B cross section and decay data files. There is a flexible online viewer for this data. Recently, charged-particle data have been added to the system, as well as data and plots of the S-factor and reaction rate for the t(d,n)⁴He reaction -- to test display formats of astrophysical data. Their address is http://t2.lanl.gov.

   NNDC (BNL)

   The National Nuclear Data Center at BNL has a VT-100 style interface that accesses evaluated data files ENDF/B, ENSDF, and NUDAT, the cross section database CSISRS, the bibliographic databases NSR and CINDA, and the QCALC Reaction Q-values program. They also have a WWW homepage, and development of a WWW interface for access to the databases is in progress. Their address is http://www.dne.bnl.gov/nndc.html; telnet access to the databases is at bnlnd2.dne.bnl.gov (130.199.112.132).

   IP (LBNL)

   The Isotopes Project at LBNL provides online access to the following resources: ENSDF; EHSDF (Evaluated High Spin Data File); EDDF (Evaluated Decay Data File); VuENSDF (a viewer for ENSDF); The Table of Isotopes; and Papyrus NSR. Their address is http://isotopes.lbl.gov/isotopes/ip.html. The Haustein [HA88] Theoretical Mass Comparison and the Möller et al. masses [MO95a,MO95b] are online at http://isotopes.lbl.gov/isotopes/toimass.html. Additionally, an astrophysics data page by Richard Firestone and Stan Woosley is being constructed at http://isotopes.lbl.gov/isotopes/astro.html. This site currently contains stellar nucleosynthesis data from Hoffman and Woosley [HO92], abundances, masses, nuclear structure and decay data, chemical properties, and physical constants.

   Particle Data Group

   particle properties and short review articles (for example, on Big Bang Nucleosynthesis). The address is http://pdg.lbl.gov.

   TUNL Nuclear Data Project

   This group has responsibilities for the properties of the light nuclei with masses from 3 to 21 (formerly held by Fay Ajzenberg-Selove) that are regularly published in the Nuclear Physics A journal [AJ91]. Their WWW site has A=3-20 evaluations of nuclear properties, with online energy level diagrams and ENSDF information. Their address is hppt://www.tunl.duke.edu/NuclData.

   LLNL Nuclear Data System-2000

   This service is currently undergoing internal testing and should be available January 1996. It will provide access to elemental and isotopic information including masses, abundances, and half-lives. Additionally, it will provide access to the LLNL data libraries (Section 1.A.3) and to the other major international evaluated data libraries that have been converted to Format2000 such as ENDF/B-VI. It will also provide access at all levels to both reaction and structure information from other sites such as LANL, TUNL, etc. Their address is http://www-ndg.llnl.gov.

   USNDN

   the WWW homepage for the U.S. Nuclear Data Network is at http://www.dne.bnl.gov/~burrows/usndn.



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Appendix 2: Proposed Organizational Structure

The best organization for a coordinated, cooperative nuclear data effort for nuclear astrophysics should be decided through discussions among members of nuclear astrophysics and data communities, and should be the one which best matches the nuclear astrophysics data needs. These discussions are more important because of, and are made more difficult by, the absence of a group that organizes research within the nuclear astrophysics community. In an effort to initiate these discussions, we propose the zeroth-order organizational structure shown in Figure 1.

This structure contains a Steering Committee (SC) to coordinate the effort; and Evaluating Groups (EGs) and appropriate working groups (WGs) to carry out these projects, where the EGs are concerned with specific evaluations and the WGs address other activities (such as dissemination).

In this plan, the Steering Committee has a number of very important roles:

1. Prioritize the data projects;
2. Enlist nuclear astrophysicists and nuclear data scientists to form the EGs;
3. Divide projects (e.g., an update of the Caughlan and Fowler [CA88] reaction rate compilation) into smaller components (e.g., the evaluation of a few reactions), and prioritize and distribute these to EGs.
4. Enlist and coordinate additional nuclear data mentors for the EGs;
5. Form appropriate WGs for both continuing and special activities;
6. Actively participate in the data effort through the EGs and WGs;
7. Interact with both the U.S. and the international nuclear astrophysics and nuclear data communities, as well as with funding agencies.

Figure 1



The SC should be comprised of nuclear astrophysicists and nuclear data scientists with relevant expertise who are committed to producing high-quality nuclear data products of vital importance to the nuclear astrophysics community. The EGs and WGs should be comprised of nuclear astrophysicists and nuclear data scientists with relevant expertise (e.g., evaluating charged-particle reactions or nuclear properties) who will divert resources towards this effort. It may be useful to have nuclear data mentors -- experts in the relevant data stewardship activities who are unable (e.g., because of funding) to join an EG but are willing to advise or assist in these projects. Mentors may prefer to be assigned to particular EGs, to serve as a general advisor to any EG, or to develop evaluation tools (e.g., codes like GLUCS) and distribute them to all EGs. The formation of EGs and WGs is not meant to exclude others from working on their specific projects; rather, these are meant to facilitate the coordination of efforts of those with similar interests and expertise.

Note that it is likely that this effort will primarily involve the redirection of existing resources by both nuclear astrophysicists and nuclear data scientists, although new funding may be sought.

The SC will form WGs necessary to compile and disseminate the evaluated nuclear data, as well as for special activities. Four possible WGs may focus on Evaluation Testing, Code Development, the Website, and Dissemination. Their activities could include the following:

Evaluation Testing WG

coordinate work necessary to maintain a standard of excellence in the nuclear data evaluations.

Code Development WG

coordinate development and distribution of software tools for evaluations (e.g., GLUCS), for testing (e.g., FMTCHK), for predicting unmeasured quantities (e.g., GNASH), and utilities for the dedicated WWW site (e.g., an online code to convert evaluated cross sections to S-factors.)

Website WG

establish and maintain a dedicated World Wide Web site. The most timely, useful, and cost efficient manner of disseminating the results of these data projects would be via online computer access. World Wide Web sites, with their easy accessibility, customizability, and retrievability of stored information, represent an excellent approach to dissemination. A dedicated Nuclear Astrophysics Data Evaluation website could contain the products of our new evaluation efforts (or links to the products), as well as a wealth of additional information useful for nuclear astrophysics researchers. A broader vision of this site would be that it serve (a) as a repository of vital nuclear data for nuclear astrophysics, and (b) as a dynamic work environment for nuclear astrophysicists. This could evolve into a site that members of the community would regularly connect to, and a site that those outside the community could browse to learn about exciting research projects. This site would also contain hypertext links to related sites in the nuclear physics, astrophysics, and nuclear data communities.

Dissemination WG

organize regular meetings of the contributors to this data effort -- possibly at the APS Spring Meeting, the APS DNP Fall meeting, or at specialized nuclear astrophysics conferences; seek out and promote research projects and papers in which the products of this data effort are used; and periodically report progress and findings in a web-posted newsletter.

Three examples of other, more specialized WGs: one to do a thorough literature search for existing compilations of reaction rates published in journal articles; one to focus on detailed astrophysics needs and resources for information on nuclear properties; and one to compile a thorough list of U.S. researchers in nuclear astrophysics, to be used as a resource of the Steering Committee. These and other specialized WGs could perhaps be disbanded upon completion of their specific tasks.

One final note on this suggested organizational structure. Recently, a Task Force on Nuclear Astrophysics was formed by the U.S. Nuclear Reaction Data Network to help launch a coordinated U.S. effort in nuclear data for nuclear astrophysics. This Task Force, which includes nuclear astrophysicists as well as nuclear reaction and nuclear structure data experts, produced this document. However, the Task Force and other existing nuclear data organizations (e.g., the U.S. Nuclear Structure Data Network, the U.S. Nuclear Reaction Data Network, the Cross Section Evaluating Working Group) are not shown on this organizational chart. The relationships of existing organizations with this new effort have yet to be defined, and is an important issue to resolve at the launching of this effort. For example, it is probably advantageous to absorb Task Force members into all levels of the organization proposed above -- so that one group would oversee all the activities for this data effort. In this case, the Task Force could play an important early role in identifying nuclear data resources and contributors to this effort.



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Appendix 3: Recent Organizational Activities

Since the original writing of this document in December 1995, a Workshop on Evaluation and Compilation of Nuclear Astrophysics Data was held at Caltech on December 16, 1995, following the Symposium on Nuclear Astrophysics - A Celebration of Willy Fowler. The Workshop was organized by Robert Stokstad (LBNL), with assistance from Ralph Kavanagh (Caltech), Peter Parker (Yale), Michael Smith (ORNL), Michael Wiescher (Notre Dame), and Stan Woosley (UC Santa Cruz). The purpose of the workshop was to discuss establishing and maintaining a coordinated program for the evaluation, compilation, and dissemination of nuclear reaction and nuclear structure data for nuclear astrophysics. A summary of the workshop can be found at http://stokstad.lbl.gov/DataWorkshop/homepage.html.

The goals of the workshop were to:

1. Review the status of compilations of measured and calculated data for nuclear astrophysics and discuss the immediate and long term needs.
2. Develop cooperation with the nuclear data community.
3. Look for ways to coordinate our efforts on an international scale.
4. Initiate a continuing process for assessing and meeting the data requirements of the nuclear astrophysics community.
Before the workshop, seven documents (including the original version of this document) on various aspects of launching a coordinated nuclear astrophysics data effort were prepared; this information was sent to registrants via email and posted on the workshop WWW page listed above.

There were 9 speakers at the workshop, with time equally balanced between presentations and discussions; the agenda is given at the workshop website. The speakers were asked to focus on the existing evaluations and compilations, what specific work each of these needs, how important this work is, and any other important matters relevant to evaluation, compilation, and dissemination of nuclear data for nuclear astrophysics. Copies of the transparencies are available from Bob Stokstad at LBNL.

One of the most important results of the workshop was the endorsement and nomination of a group of individuals -- a steering committee -- to lead a coordinated national effort in nuclear data for nuclear astrophysics. The members of the steering committee are Peter Parker (Chair; Yale), Charles Barnes (Caltech), Lothar Buchmann (TRIUMF), Gerry Hale (LANL), Franz Kaeppeler (KFK), Shigeru Kubono (INS Tokyo), Claus Rolfs (Bochum), Michael Smith (ORNL), Bob Stokstad (LBNL), Friedel Thielemann (Basel), Michael Wiescher (Notre Dame), and Stan Woosley (UC Santa Cruz).

The steering committee had its first meeting on Feb. 3, 1996 at Caltech. The topics discussed were:

1. Possible Evaluation Projects
2. Surveying the Nuclear Astrophysics Community for Projects
3. Possible Contributions of Committee Members to the Effort
4. Procedures for Evaluations
5. An Archive for Nuclear Astrophysics Data
6. Assignments for Committee Members
A detailed summary of this meeting is available from the Steering Committee Chair, Prof. Peter Parker (Yale). To very briefly summarize: two evaluation projects received strong endorsement for the first projects of a coordinated evaluation effort (listed below); and the Steering Committee will survey the nuclear astrophysics community to get input on evaluation projects and on a coordinated nuclear astrophysics data effort.
1. Evaluating rates for explosive H and He burning in the rp-process in the mass A=30-45 range -- an extension of the Caughlan and Fowler evaluation [CA88] to higher masses.
2. Evaluating rates along the proton drip line for the Hot CNO cycle and the beginning of the rp-process, combining indirect and direct measurements.


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References

• AJ91 -- F. Ajzenberg-Selove, Energy Levels of Light Nuclei; A = 5 - 10, Nucl. Phys. A490 (1988) 1; A = 11 - 12, Nucl. Phys. A506 (1990) 1; A = 13 - 15, Nucl. Phys. A523 (1991) 1; A = 16 - 17, Nucl. Phys. A460 (1986) 1; A = 18 - 20, Nucl. Phys. A475 (1987) 1.
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• GR94 -- S.M. Grimes, International Conference on Nuclear Data for Science and Technology, Gatlinburg, TN, American Nuc. Society, La Grange, IL (1994) 422; (1995), in preparation.
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• LA94 -- N.M. Larson, International Conference on Nuclear Data for Science and Technology, Gatlinburg, TN, American Nuc. Society, La Grange, IL (1994) 586.
• LE78 -- C.M. Lederer et al., Table of Isotopes, 7th edition, John Wiley, New York (1978).
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• MO95a -- P.M. Möller, J.R. Nix, W.D. Meyers, W.J. Swiatecki, At. Data Nucl. Data Tables 59 (1995) 185.
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World Wide Web Nuclear Data Sites

• T2 Nuclear Information Service (LANL) -- http://t2.lanl.gov.
• National Nuclear Data Center (BNL) -- http://www.dne.bnl.gov/nndc.html; or telnet to bnlnd2.dne.bnl.gov (130.199.112.132)
• Isotopes Project (LBNL) -- http://isotopes.lbl.gov/isotopes/ip.html.
• Triangle Universities Nuclear Laboratory Nuclear Data Project -- http://www.tunl.duke.edu/NuclData.
• LLNL -- http://www-ndg.llnl.gov (available January 1996)
• U.S. Nuclear Data Network -- http://www.dne.bnl.gov/~burrows/usndn.


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Tranlated into HTML by
Thomas W. Burrows
National Nuclear Data Center
Tue Feb 27 14:55 EST 1996; Updated Fri Jun 14, 15:15 EDT 1996.