Defense of the dissertation of Dabylova Saltanat Bolatkyzy for the degree of Doctor of Philosophy (PhD) in the specialty «6D060500 - Nuclear physics»

L.N. Gumilyov Eurasian National University, a dissertation defense for the degree of Doctor of Philosophy (PhD) by Dabylova Saltanat Bolatkyzy on the topic «Study of nuclear reactions under the influence of fast neutrons using the tagged neutron method» by specialty «6D060500 – Nuclear physics».

The dissertation was carried out at the Department of «Nuclear Physics, New Materials and Technologies» of L.N. Gumilyov Eurasian National University.

The language of defense is russian.

Official reviewers:

Nauruzbayev Dosbol Kabdrashievich – candidate of physical and mathematical sciences, research fellow at NU Research and Innovation System (NURIS) (Astana, Republic of Kazakhstan);

Kurmangaliyeva Venera Orazkhanovna – candidate of physical and mathematical sciences, senior lecturer at Al-Farabi Kazakh National University (Almaty, Republic of Kazakhstan).

Temporary members of the Dissertation Council:

Vyacheslav Valeryevich Dyachkov – Candidate of Physical and Mathematical Sciences, Associate Professor at the Department of Nuclear Physics, Faculty of Physics, Voronezh State University (Voronezh, Russian Federation);

Abishev Medeu Yerzhanovich – Doctor of Physical and Mathematical Sciences, Professor, Head of the Department of Theoretical and Nuclear Physics, KazNU named by Al-Farabi (Almaty, Republic of Kazakhstan);

Imambekov Onlasyn – candidate of physical and mathematical sciences, acting professor of the Department of Theoretical and Nuclear Physics of the Al-Farabi Kazakh National University (Almaty, Republic of Kazakhstan).

Scientific consultants:

Sakhiyev Sayabek Kuanyshbekovich – Doctor of Physical and Mathematical Sciences, Director General of the RSE INP ME RK, Academician of KazNANS (Almaty, Republic of Kazakhstan);

Kopach Yuri Nikolaevich – candidate of physical and mathematical sciences, deputy director for research work of the Laboratory of Neutron Physics (FLNP), JINR (Dubna, Russian Federation).

The defense will take place on September 27, 2024, at 12:00 PM in the Dissertation Council for the training direction «8D053 – Physical and chemical sciences» in the specialty «6D060500 – Nuclear physics» of L.N. Gumilyov Eurasian National University. The defense meeting is planned to be held offline and online.

Link: https://clck.ru/3CkM33

Address: Astana, Satpayev St. 2, room 302.

Abstract (English): Dissertation work of Dabylova Saltanat Bolatkyzy on the topic of "Study of nuclear reactions under the influence of fast neutrons using the tagged neutron method", submitted for the degree of Doctor of Philosophy (PhD) in the specialty: "6D060500 - Nuclear Physics". This dissertation is devoted to experimental and theoretical studies of angular correlations in the inelastic scattering of neutrons with energy 14.1 MeV on sodium, phosphorus, sulfur, and chlorine nuclei. Relevance of the research topic. Nuclear reactions under the influence of fast neutrons are important both for practical applications and from the point of view of fundamental research of atomic nuclei. The characteristics of the interaction of neutrons with atomic nuclei, collected in the database, are used in various fields. Comparison of the measured spectra of γ-rays with the characteristic spectra of individual elements makes it possible to determine the elemental composition of various samples. It is used in geological and inspection installations. In addition, a more detailed and broader neutron database is needed to accurately model the performance of fast neutron reactors. Of particular interest in this context are elements used in structural materials, fuel cells and coolants, such as sodium (Na), phosphorus (P), sulfur (S) and chlorine (Cl). For example, sodium is used as a coolant in the IBR-2 pulsed fast neutron research reactor at FLNP JINR. Phosphorus, sulfur and chlorine form various chemical compounds with uranium. In addition, all these elements play an important role in geology, mining, and agriculture. Also, at present, not enough is known about γ-radiation and its angular distribution, which arise in processes caused by fast neutrons, and about the mechanisms of such reactions. Based on this, this research is important for nuclear physics for the following reasons: Firstly, by studying the mechanism of reactions using fast neutrons, we can better understand the structure of the atomic nucleus. The cross sections for reactions that occur when a nucleus collides with fast neutrons depend on the internal structure of the nucleus. Therefore, experimental facts can be used to test which theoretical model is best suited to describe a particular isotope, and from this draw conclusion about the properties of the nucleus. Second, measuring the angular distribution of emitted γ-rays provides important data for the protection of fast reactors and other high-neutron flux devices. By studying the angular distribution of γ quanta emitted from oriented states as a result of nuclear reactions, it is possible to determine the dependence of the differential cross section of the angle θ between the incident neutron and the emitted γ quanta. In addition, we can theoretically study the spin, parity and multipolarity of γ-rays. After all, the angular distribution of the emitted γ-quantum, in turn, depends on the spin/parity of the states involved and the multipolarity of the transitions. Thus, these studies are considered relevant from the point of view of studying the mechanism of nuclear reactions, measuring angular distributions and verifying existing results, as well as presenting new results. The purpose of this dissertation is to measure the yields and angular distributions of γ-quanta emitted during the deexcitation of nuclei resulting from inelastic scattering of fast neutrons. Research objectives: To achieve this goal, the following tasks were identified: 1.Planning the experiment: creating the geometry of the installation, determining the most suitable sizes of irradiated samples, assembling and setting up the equipment. 2.Development of methods for analyzing experimental data. Calculation and application of corrections for the effects of self-absorption and rescattering of particles in irradiated samples. 3. Carrying out experiments and subsequent study of data on the scattering of fast neutrons on atomic nuclei Na, P, S and Cl. 4.Search for theoretical explanations of the reactions of the research object; comparative analysis of the results obtained and the data found. Object of study. The object of study of this work is neutron-nuclear reactions on Na, P, S and Cl nuclei. Subject of study. The subject of the study was the yields and angular distributions of γ-quanta emitted in reactions with neutrons with an energy of 14.1 MeV. Research methods. Experimental results were obtained in various configurations of the TANGRA facility using the tagged neutron method, which significantly reduces the number of background events. The γ-energy spectra of the low-resolution detectors were fitted using a special response function, and the spectra of the high-purity germanium (HPGe) detectors were fitted using Gaussians on a smooth substrate. As a first approximation of the relation between close photopeaks and γ-quantum energy, we used data from calculations in TALYS 1.9 using the TalysLib library developed by us. Corrections to the experimental data on self-absorption and scattering of particles in matter were made by calculations in the GEANT4 software environment, for which a special program was created. Main provisions submitted for defense: 1. The use of the tagged neutron method using a small-sized neutron generator in experiments can significantly reduce the number of background events, which in turn increases the accuracy of the experimental data obtained. In addition, such setups can be easily changed in geometry depending on the requirements of a particular experiment. For the first time, a neutron generator with a built-in α-detector was used in studies of the properties of nuclear reactions, which made it possible to use the tagged neutron method (TNM). The data obtained in the TANGRA Collaboration experiments on inelastic neutron scattering at 14 MeV with the yield of intense γ-ray lines on Na, P, S and Cl nuclei provide an opportunity to refine the information available in databases for these nuclei. 2. The angular distributions of γ-quanta produced during the interaction of neutrons with an energy of 14 MeV with the nuclei Na, P, S and Cl were obtained and the parameters of the expansion of the angular distributions in Legendre polynomials were determined. Scientific novelty. • The use of compact neutron generators with tagged neutrons for the first time shows the possibility of creating installations with easily variable geometry and the ability to measure yields and angular correlations of γ-radiation and neutron radiation with high accuracy. • For the first time, the angular distribution of γ-radiation was measured during the reaction of neutrons with an energy of 14.1 MeV with P, Cl and the parameters of angular anisotropy were refined. • The yields of γ-quanta produced during the interaction of neutrons with an energy of 14.1 MeV with the nuclei Na, P, S and Cl have been refined. The yields of low-intensity γ-lines for these nuclei have been determined for the first time. Scientific and practical value of the work. The results of the research performed have high scientific and practical value. Practical significance of the work consists in approbation of the experimental technique of investigation of inelastic neutron scattering reaction with energy 14.1 MeV by the method of tagged neutrons of a small-size neutron generator. The obtained experimental data on γ-quantum yields and angular distributions can be used to improve the accuracy of Monte Carlo simulations for various physical objects. Another possible application of the obtained experimental results is rapid elemental analysis sensitive to light elements. Personal contribution of the author. The results presented in the dissertation were obtained by the author together with JINR staff (Dubna, Russian Federation) and reflected in joint publications. The author took direct personal part in setting up and conducting experiments, processing experimental data and interpreting experimental results as a full member of the scientific group. Reliability of work results The correctness of the conducted experimental studies and the reliability of the obtained results in the thesis work are substantiated by the use of well-known and mastered methods. Analysis of the systematic error and statistical error of the experiment, as well as comparison with other experimental data ensure the reliability of the results. The experimental data obtained were processed using the ROOT software package, developed at the European Nuclear Research Center and written in the well-known C++ programming language. The scientific results obtained are in good agreement with the work of other authors in this field. The main results of the dissertation were published in peer-reviewed international scientific journals and presented in the proceedings of leading international conferences on neutron physics. Approbation of work. The materials of the dissertation work were presented and reported at the following republican and international conferences:  XXV Международная научная конференция студентов, аспирантов и молодых учёных «Ломоносов-2018», МГУ, Москва, Россия, Апрель 9-13, 2018;  The XXII International Scientific Conference of Young Scientists and Specialists (AYSS-2018), Joint Institute for Nuclear Research, Dubna, Russia, April 23-27, 2018;  53-я Зимняя Школа Петербургского института ядерной физики им. Б. П. Константинова НИЦ Курчатовский Институт, Петербургским институтом ядерной физики им. Б. П. Константинова НИЦ Курчатовский Институт, Институт теоретической и экспериментальной физики им. А. И. Алиханова НИЦ Курчатовский Институт, Санкт-Петербург, Россия, Март 2-7, 2019;  LXX International conference "NUCLEUS – 2020: Nuclear physics and elementary particle physics. Nuclear physics technologies“,Saint Petersburg State University, Russia, October 11-17, 2020;  28-th International Seminar оn Interaction of Neutrons with Nuclei (ISINN-28) JINR, Russia, Dubna, May 24-28, 2021; Publications. On the topic of a scientific dissertation, the author published 5 scientific works: 2 articles in peer-reviewed journals with a nonzero impact factor, included in the first and third quartile (Q1,Q3) of the JCR database, as well as cited in the Web of Science and Scopus databases, 3 articles in scientific journals of the Republic of Kazakhstan. The structure and scope of the thesis. The dissertation consists of an introduction, 4 sections, a conclusion and a list of used sources of 71 titles. The total volume of the work is 94 pages, including 16 tables and 44 figures. The introduction shows the relevance of the research topic and provides a literature review of the available data on the topic of the dissertation. The problem considered in this work is formulated, the goals, the novelty of the results obtained are formulated, and their scientific and practical value is substantiated. The main provisions submitted for defense, the personal contribution of the author, approbation and a summary of the dissertation are given. The first section provides a literature review of the main theoretical and experimental works on the study of the interaction of neutrons and γ-quanta with matter. The method of tagged neutrons is described. In addition, the types of detectors and their basic operational capabilities and functions are described. The second section describes the system of detector instruments of the “TANGRA” project and the objects of study. The methodology for collecting data is outlined. The contribution of the TANGRA project to nuclear physics is described. The third section of the dissertation is devoted to the experimental methodology. Details of the procedure for analyzing experimental data are given. Procedures for determining the angular distributions and yields of γ quanta are described. The fourth section is devoted to a discussion of the results. The main results of this work are the yields and angular distributions of γ-quanta for sodium, phosphorus, sulfur and chlorine. In conclusion, the results are summed up and the main results of the dissertation work are formed.

Dissertation

List of Scientific Works

Consultant's Review

Foreign Consultant's Review

Conclusion of the Research Ethics Committee

Official Reviewer's Review

Official Reviewer's Review