B-1804

Dispersive Line-Consistent Optical Potential for Accurate Predictions of Nucleon-Nucleus Reactions Cross-Sections for Different Applications

Project Status: 8 Project completed
Commencement Date: 24.11.2023
Duration in months: 0 months

Objective

Main purpose of the Project

The main goal of the suggested Project is the development of the dispersive Lane-consistent optical potential allowing reliable, guaranteed accuracy predictions of nucleon-induced reaction cross-sections with nuclei for different applications. Calculations should be based on realistic saturated coupling scheme, built on wave functions of soft-rotator nuclear model Hamiltonian. Optical calculations, using developed potential, must allow to cover the recent practical requests for evaluated optical data in a wide nuclear mass region and incident nucleon energy up to at least 200MeV including accurate predictions of direct (p,n), process on light nuclei, significant for proton and neutron beam radiotherapy.

The State of art in the field and the impact of the proposed Project on the progress in the field

The coupled-channels (CC) optical model calculations are reliable approach providing the bases for many theoretical analyses and/or nuclear data evaluations providing nuclear data for applications. Optical model calculations give reaction, direct scattering, (neutron) total cross sections. Adjusted optical model potentials (OMP) are used in quantum-mechanical pre-equilibrium and direct reaction theory calculations, simultaneously supplying users with particle transmission coefficients, necessary for Hauser-Feshbach statistical-theory codes to analyze compound mechanism process cross sections, valid for nuclear data evaluation. The implementation of the CC theory in computer code is rather complicated and cumbersome, so the world scientific community practically uses only three such codes: JUPITER, ECIS and OPTMAN.

CC optical model code OPTMAN had been many years developed at Joint Institute for Power and Nuclear Research to investigate nucleon-nucleus interaction mechanism and as a basic tool for nuclear data evaluation for different applications. First the code had been developed to have the options available in JUPITER and ECIS codes and had been used to analyze experimental data and for fissile isotopes nuclear data evaluations for BROND library. Later, realistic level coupling schemes based on nuclear Hamiltonian of even-even non-axial soft-rotator nucleus had been included in the code. Current version of soft-rotator code takes into consideration non-axial quadrupole, octupole and hexadecapole deformations and the ?2-, ?3- and ?- vibrations, thus it takes into account more complicated collective nuclear motions, absent in widely used JUPITER and ECIS codes. With this option, code got the new features, allowing analyses of collective level structure (at least four positive parity and K=0- rotational bands), E2, E3, E4 ? - transition probabilities and optical data (total, reaction and angular distributions of scattered particles) in self-consistent approach, making cross sections predictions more reliable.

In 1995-1998 years code was successfully used as theoretical base for nuclear data evaluation for minor actinide nuclides, experimental data for which are very scarce. Successful interpretation of Geel experiments for groups of 238U levels with excitation energies Ex=0.63 – 0.89 MeV and Ex=0.89 – 1.32 MeV became possible due to soft-rotator code option. In 1997 year soft-rotator code was installed at Nuclear Data Center of Japan Atomic Energy Agency and in 1999 at Korea Atomic Energy Research Institute and international cooperation started. Calculations became possible both for neutrons and protons; the upper incident nucleon energy possible in the code had been extended to about 200 MeV.

After modernization in 2001-2005 OPTMAN code became a tool for testing sophisticated theoretical models of nucleon-nucleus interaction mechanism phenomena, and for nuclear structure and CC optical model calculations, which meet the demands for accurate prediction of optical data for nucleons. Issued manual, supplementing the modernized program complex allows non-authors to use the code with full understanding of involved physical and mathematical ideas, and also be ready to improve it, as new physical or mathematical ideas will appear. In close cooperation with our Collaborators (Dr. S. Chiba from JAEA, Ass. Professor Yu. Watanabe from Kyushu University), we had supplied created CC optical model code with the best fit individual optical parameter sets for all even-even nuclides, experimental data for which are available in a A=24 - 120 region: 24,26Mg, 28,30Si, 32S, 40Ar, 40Ca, 48Ti, 52Cr, 54,56Fe, 58,60,62Ni, 90,92Zr, 92,94,94,98Mo, 116,118,120,122Sn, which are needed for High Energy file evaluation, making the code ready for applications. Evaluated optical data for 12C, 24-26Mg and 28-30Si isotopes had been used as a base for evaluated Japanese High Energy files for these isotopes.

Our fruitful scientific collaboration on OM with scientists from different countries and International organizations, had lead us to understanding, that optical parameters found for individual nuclides should be a starting point for constricting of Global parameters systematics, as this allows solution of the recent practical demands for optical data from light to actinides nuclides, experimental data for which are scares or unavailable, including poorly experimentally investigated or short-living, but nevertheless significant, in a wide 20<A<190 mass region, so that to cover fission products. As we know, up to now nobody could suggest such CC Global optical potential, because individual optical parameters of conventional CC approaches are influenced by not accounted individually of collective level structure and thus have no smooth dependencies, while our parameters are more free of individual collective level structure effects, as the latter are accounted by realistic saturated coupling built on wave functions of soft-rotator nuclear model. From the other hand our joint research with our Collaborators proved that account of dispersive relations between imaginary and real potentials, which is a natural result of causality principle should be incorporated into the OPTMAN code. This sophisticated approach significantly decreases the number of free optical parameters, necessary to predict optical cross-sections, that makes CC Global optical parameters systematic search possible, much more efficient and stable and predictions of cross-sections more reliable.

Such our activity had been supported by ISTC Project B-1319, which resulted in modernizing OPTMAN code by implementing dispersive relations in the formulation of the optical model potential. All the goals of this Project had been successfully reached: we developed Global dispersive potential for 20<A<190 A–mass nuclides, issued supplement to modernized OPTMAN code manual. Beyond the initial Project’s working plan we developed dispersive OMP for actinides, and Lane consistent potentials for 103Rh, 182-184W, 181Ta and 55Mn which to our knowledge are the best in the market.

We participated in the IAEA Coordinated Research Project on “Parameters for Calculation of Nuclear Reactions of Relevance to Energy and Non-Energy Nuclear Applications” - RIPL-III. All the developed potentials and OPTMAN code source files are uploaded to the IAEA web: http://www-nds.iaea.org/RIPL-3/, so that all the results of the finalized ISTC Project are opened for nuclear scientists from the IAEA Members of States.

As the result of the previous activity we established that developing dispersive Lane-consistent approach for coupled channels optical model, based on soft-rotator coupling, can significantly improve the accuracy of nucleon-nucleus cross-sections predictions, and what is significant such approach must allow predictions of direct (p,n) reaction cross-sections, that are of high priority for proton and neutron beam radiotherapy, with typical incident nucleon energies below 250 MeV.

The competence of the Project team in the specified area

The Project team is competent enough to solve the problems, arising from the project goals. Project manager - Dr. E. Sh. Soukhovitski is a distinguished specialist in theoretical nuclear physics, nuclear data evaluation and interpretation. He is the main author of the code, he developed most of the original physical and mathematical ideas and algorithms incorporated in the code, which are published in more than 70 publications, with overall number of publications which exceeds 200. He will develop new theory formulations (options), mathematical approaches and algorithms. Senior scientist with 30-year expertise in programming codes for nuclear data evaluation and manipulation with nuclear experimental and evaluated data will realize suggested new physical ideas into code and prepare inputs for individual dispersive Lane-consistent optical potential search. Leading programming engineer with 30-year expertise in programming and supporting of experimental and evaluated data processing will organize checking and formatting necessary experimental data into OPTMAN code inputs and support all necessary program’s coding activity.

Expected results and their application

The Applied Research objective of the Project will be development of dispersive Lane-consistent optical potentials for nucleon-nucleus interaction data prediction with guaranteed accuracy to meet the recent demands, coming from various applications significant for nuclear community: modern nuclear power reactors with inbuilt safety; nuclear devices shielding design; transmutation of nuclear wastes; (p,n) cross-sections for proton and neutron beam radiotherapy, effects of radiation exposure of astronauts, reliability of semi-conductor memory devices etc. and supplying data to such fundamental physical research as theory of nuclear matter and understanding of the origin of elements and evolution of the Galaxy.

The Basic Research objective of the Project will be creating a theoretical tool; for testing modern sophisticated optical potential forms, nuclear matter theory, theoretical models of nucleon-nucleus interaction mechanism phenomena, aimed to improve description of available experimental optical data and prediction of needed but experimentally unavailable ones.

Addressing ISTC Goals and Objectives

Addressing ISTC objectives and goals approved Project will:

  1. Allow sensitive knowledge scientists and engineers with skills in nuclear data prediction, evaluation, and processing to redirect their knowledge to internationally recognized peaceful applications such as nuclear power and nuclear safety.
  2. Promote to a new extant existing cooperation (integration) with scientists from Japan (JAEA, Kyushu University), IAEA, Spain (Seville University), Korea (KAERI, Sungkyunkwan University), China (CNDC, IAPCM), etc.


Scope of Activity

The project duration is estimated to be 36 months. The total project effort is 1,835 person-days, with 1,750 person-days dedicated to sensitive knowledge scientists and engineers.

The scope of activities is fixed by the goals of the Project, so the four correlated tasks should be solved one by one:

  1. Development of sophisticated dispersive Lane-consistent optical potential options, accounting isobar analog terms of the potential, coupling proton and neutron currents.
  2. Implementing Lane-consistent optical potential and scattering theory allowing predictions of direct (p,n) in OPTMAN.
  3. Checking and formatting of experimental data, including direct (p,n) charge exchange cross-sections into inputs for individual mass nuclides best fit optical potential parameter determination, using search option of OPTMAN.
  4. Determination of individual optical model parameters allowing best fit of all available experimental optical data both for neutrons and protons and direct isobar analog states excitation simultaneously for 20<A<190 A–mass nuclides.


Role of foreign collaborators

Close contacts with our collaborators for about ten years already fixed the most fruitful forms of cooperation:

  1. exchange of information and ideas concerning optical model theory developments;
  2. cross-checking of developed mathematical algorithms;
  3. assistance in preparing and submitting publications on the results achieved in the course of Project implementation;
  4. informing and invitation for participating in meetings and workshops organized by foreign collaborator’s side;
  5. promoting project results.


Technical approach and methodology

Project objectives will be realized using the following technical approach and methodology:

  1. sophisticated dispersive Lane-consistent optical potential options, accounting isobar analog terms of the potential, for coupling of proton and neutron currents will be developed and adopted;
  2. option allowing predictions of direct (p,n) charge exchange cross-sections on soft nucleus will be developed and implemented in OPTMAN code
  3. individual optical model parameters allowing best fit of all available experimental optical data for nucleons simultaneously with direct (p,n) isobar analog states excitation on light and 20<A<190 A–mass nuclides will be found.

Participating Institutions

LEADING

Joint Institute of Energy and Nuclear Research – Sosny (JIENR)

COLLABORATOR

University of California / Department of Physics and Astronomy

COLLABORATOR

International Atomic Energy Agency (IAEA)