Many members of the BAND group support nuclear data evaluation. Evaluation is the most painstaking part of the nuclear data pipeline process described in our recent review article. Evaluation takes different forms depending on the type of nuclear data.
Information about low-lying nuclear structure (e.g., level energies, Jπ values, lifetimes etc.) resides in the Evaluated Nuclear Structure Data File (ENSDF). The governing philosophy behind ENSDF evaluation is to take all information that is known about discrete states in a given nucleus from nuclear reactions and decay and combine them to create a recommended set of Adopted Levels and Gammas for general use. ENSDF is grouped into “A-chains” comprised of nuclei with the same mass number since most of these nuclei in an A-chain are connected via β-decay. Structure data for a given nucleus from different sources is usually inconsistent and it falls to ENSDF Evaluators to determine the recommended values and uncertainties. Most ENSDF evaluators come to the field from experimental low energy nuclear physics backgrounds and train for years to gain a broad enough knowledge of nuclear measurement techniques and the rules and regulations set forth by the Nuclear Structure and Decay Data section of the International Atomic Energy Agency (IAEA-NDS).
The BAND ENSDF evaluation team is led by Dr. M. Shamsuzzoha Basunia and includes Dr. Aaron Hurst and Dr. Jon Batchelder. Dr. Basunia has also taken on the training of new evaluators in the US and internationally.
In addition to A-chains evaluators often produce Horizontal Evaluations that cover a particular area of nuclear structure physics. In 2020 Dr. Batchelder produced the first evaluation of neutron-deficient nuclides that decay by β-decay followed by proton and/or α-emission. The results were published in Atomic Data and Nuclear Data Tables.
To help raise awareness of issues in nuclear structure data, Dr. Aaron Hurst created the Nuclear Structure Experimental Issues website to provide a mechanism for nuclear data evaluators and the low-energy community, in general, to report and track problems. This task was carried out upon the recommendation of the 22nd Technical Meeting of the IAEA Nuclear Structure and Decay Data Network.
Evaluated nuclear reaction data, including reaction cross sections, fission product yields and some parts of atomic data resides in a number of databases maintained by different organizations throughout the world and is described in our recent review article. In the United States evaluated nuclear reaction data is stored in the Evaluated Nuclear Data File (ENDF). ENDF evaluators uses state-of-the-art theory and modeling to produce nuclear reaction data that best represents experimental measurements. ENDF is almost entirely comprised of neutron-induced nuclear reaction data which is key to nuclear energy, defense and nonproliferation applications. ENDF evaluators produce energy- and angle-differential data that are compared to models of benchmark measurements that are very sensitive to many different nuclear data quantities at the same time in a process called validation. The canonical example of such an integral benchmark is a critical assembly which is producing and losing neutrons at a constant rate. The validation process provides an overall constraint on the evaluated nuclear reaction data needed to ensure reactor safety and the integrity and effectiveness of radiation shielding.
Unfortunately, integral measurements are not available for all classes of nuclear data. One area of particular need are gamma-rays produced in neutron capture and inelastic scattering reactions. The BAND group has been working to address this need through the development of the Evaluated Gamma Activation File (EGAF) and the development of the first-ever database of gamma-rays from the inelastic scattering of reactor fast neutrons. This latter effort is being led by BAND research scientist Dr. Aaron Hurst in collaboration Professor Lee Bernstein with BAND Alumna, Dr. Amanda Lewis.
While neutron-induced reactions form the vast majority of evaluated nuclear reaction data, charged-particle reactions are also important for a number of applications. One of these is the production of radionuclides for use in a wide variety of applications from the treatment of disease to environmental monitoring to geochronology to non-proliferation. BAND student Morgan Fox is developing an approach to produce evaluated reaction cross sections for high-energy proton-induced reactions using the Talys code. This work is part of a broader experimental program involving researchers from Los Alamos and Brookhaven National Laboratory.