Study of isomeric ratio and related effects in photonuclear and neutron capture reactions

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY - BÙI MINH HUỆ STUDY OF ISOMERIC RATIO AND RELATED EFFECTS IN PHOTONUCLEAR AND NEUTRON CAPTURE REACTIONS ATOMIC AND NUCLEAR PHYSICS DOCTORAL THESIS Ha Noi – 2023 BỘ GIÁO DỤC VÀ ĐÀO TẠO VIỆN HÀN LÂM KHOA HỌC VÀ CÔNG NGHỆ VIỆT NAM HỌC VIỆN KHOA HỌC VÀ CÔNG NGHỆ - BÙI MINH HUỆ NGHIÊN CỨU TỶ SỐ ĐỒNG PHÂN VÀ CÁC HIỆU ỨNG LIÊN QUAN TRONG PHẢN ỨNG QUANG HẠT NHÂN VÀ PHẢN ỨNG BẮT NEUTRON LUẬN ÁN TIẾN SỸ VẬT LÝ NGUYÊN TỬ VÀ HẠT NHÂN Hà Nội – 2023 MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY - BÙI MINH HUỆ Major: Atomic and Nuclear Physics Code: 9440106 STUDY OF ISOMERIC RATIO AND RELATED EFFECTS IN PHOTONUCLEAR AND NEUTRON CAPTURE REACTIONS ATOMIC AND NUCLEAR PHYSICS DOCTORAL THESIS SUPERVISORS: Prof Dr Trần Đức Thiệp Dr Sergey Mikhailovich Lukyanov Ha Noi – 2023 ii Abstract The isomeric ratio (IR) of 152m1,m2 Eu, 195m,g;197m,g Hg, 115m,g Cd, 109m,g Pd, 137m,g Ce and 81m,g Se produced from photonuclear reactions (γ, n) with bremsstrahlung endpoint energies in the Giant Dipole Resonance region and IR of 115m,g;117m,g Cd, 109m,g;111m,g 137m,g Pd, Ce and 81m,g Se in thermal- epithermal neutron capture reactions (n, γ) have been experimentally determined using the activation technique and measurement of off-line γ-ray spectroscopy The bremsstrahlung photons and neutrons were generated using the MT-25 Microtron of the Flerov Laboratory of Nuclear Reaction (FLNR), JINR, Dubna, Russia Radioisotope activity was determined with a high-resolution γ-ray HPGe detector and dedicated analysis software This work reports, obtained from reactions (γ, n), the IRs of 195m,g Hg within 14 - 24 MeV, 197m,g Hg within 18 - 24 MeV, and for the őrst time Furthermore, the IR results of 109m,g;111m,g 152m1,m2 Pd and resonant neutron capture reactions (n, γ), as well as those of Eu at 19, 21 and 23 MeV 115m,g;117m,g 111m,g Cd in mixed thermal Pd in the resonance neutron capture reaction (n, γ) have been the őrst measurements The impact of the nucleon conőguration, spin difference, excitation energy, and reaction channel effects on the experimental IRs was considered The measured IRs were compared not only with the literature but also with the theoretically calculated IRs for the cases in the photonuclear reaction The calculated IRs were yielded from calculated cross sections based on TALYS 1.95 code in conjunction with simulated bremsstrahlung based on the GEANT4 toolkit Six-level density models and eight radiative strength functions were taken into consideration for the theoretical calculations iii Acknowledgements Honestly, I could not complete this thesis without the support and help of many people First and foremost, I owe special and great thanks to my supervisors, Prof.Dr.Tran Duc Thiep and Dr.Sergey Mikhailovich Lukyanov, for allowing me to start my Ph.D and for their guidance, support, and inspiration I am always thankful for them and consider them not only my supervisor, but also my father Prof.Dr.Tran Duc Thiep inspired and encouraged me on the abrupt road to science since 2012, when I started as a junior researcher at the Center for Nuclear Physics, Institute of Physics He was always available to illuminate my questions I have gained a lot of knowledge and experience from him in research, work, and life I would also like to thank Dr.Truong Thi An, Dr.Phan Viet Cuong and Dr.Le Tuan Anh for cooperating on the research projects I am grateful to the Board of Directors, Mrs.Nguyen Thi Dieu Hong, and the staff of the Institute of Physics, as well as my colleagues at the Center for Nuclear Physics for always helping, encouraging, and giving me convenience I had precious time and beautiful memories in Dubna I always remember the warm hugs and the advice of Prof.Dr.Y.E.Penionzhkevich I am thankful for the opportunity to exchange ideas and discuss work with my colleagues at the FLNR, JINR, made me feel like part of their group I express my deepest gratitude to the MT-25 Microtron crew for providing the irradiation beam as well as the chemistry of the transactinides department of the Flerov Laboratory of Nuclear Reaction, JINR for furnishing the experimental apparatus I am also grateful to Mrs.Trinh Thi Thu My and my Vietnamese friends in Dubna for making my stay very pleasant I always had you by my side when I took a lunch break or gathered for BBQs on the Volga riverside I am also thankful to Dr.S.Nishimura for lending me the equipment when I was at RIKEN I am grateful to the Board of Directors and employees of the Graduate University of Science and Technology (GUST) for helping and supporting me throughout the process of doing this thesis I would like to acknowledge the scientiőc research support of the GUST for excellent Ph.D students in 2021 And I offer my gratitude and special thanks to Vingroup JSC and Ph.D Scholarship Programme of Vingroup Innovation Foundation (VINIF), Institute of Big Data, for funding and supporting my Ph.D studies within two years under the VINIF.2020.TS.18 and VINIF.2021.TS.081 codes Last but not least, from the bottom of my heart, I would like to express my deepest thanks to my family and my parents-in-law who supported and cherished me on this long journey I am very grateful to my aunt, N.T.Mai, for helping and taking care of me in the stressful period of őnalizing this thesis Especially, I would like to thank my honey husband, Dr.Vi Ho Phong, for helping me a lot with coding He has always encouraged and given me a happy life He is the main motivation for me to carry out the present thesis iv Contents Declaration of Authorship i Abstract ii Acknowledgements iii Contents iv List of Abbreviations vii List of Physical Quantities ix List of Tables xi List of Figures xiii Introduction xvii Overview 1.1 Formation and classiőcation of isomers 1.2 Isomeric ratio and related effects 1.2.1 Deőnition of isomeric ratio 1.2.2 Nuclear effects on isomeric ratio 1.2.3 Theoretical IR calculation 10 Photonuclear reaction 17 1.3.1 Formation of photonuclear reaction and photon sources 17 1.3.2 Cross-section of photonuclear reaction 18 Above particle emission threshold up to 30 MeV 19 Below particle emission threshold 21 In the energy range of 30 to 140 MeV 22 (γ, n) reaction 23 Neutron capture reaction 24 1.4.1 Neutron and neutron sources 24 1.4.2 (n, γ) reaction 25 1.4.3 Neutron capture cross-section 26 Level density and γ-ray strength function 28 1.3 1.3.3 1.4 1.5 v 1.6 1.5.1 Nuclear level density 28 1.5.2 Gamma-ray strength function 32 Objectives 36 Experimental and theoretical methods 2.1 2.2 37 Experimental method 37 2.1.1 Irradiation sources 37 Microtron MT-25 38 Bremsstrahlung source 39 Thermal and epithermal neutron source 39 2.1.2 Sample irradiation 41 2.1.3 Gamma spectroscopy 44 2.1.4 Experimental IR determination 46 2.1.5 Spectrum analysis-necessary correction 49 Self-absorption effect 49 Coincidence summing corrections 50 Theoretical IR calculation in (γ, n) reaction 50 2.2.1 Bremsstrahlung spectra simulation in GEANT4 50 2.2.2 Cross-section calculation in TALYS 52 Results and Discussion 3.1 3.2 3.3 56 Isomeric Ratios in (γ, n) reactions 3.1.1 152m1,m2 3.1.2 195m,g Eu 197m,g Hg and 57 57 Hg 64 Isomeric Ratios in (n, γ) reactions 70 3.2.1 109m,g Pd and 111m,g Pd 70 3.2.2 115m,g Cd and 117m,g Cd 76 Inŕuence of nuclear channel effect on IRs in (γ, n) and (n, γ) reactions 84 3.3.1 For 109m,g Pd 84 3.3.2 For 115m,g Cd 86 137m,g 115m,g 109m,g 3.4 IRs of Se in inverse reactions 90 3.5 Theoretically calculated IRs in (γ, n) reactions 94 3.5.1 Bremsstrahlung spectra simulation 94 3.5.2 Cross-section calculation 95 3.5.3 IRs in (γ, n) reactions 99 Ce, Cd, Pd, and 81m,g Conclusions and Outlooks 117 List of Publications used for the Thesis content 120 References 122 vi A Geant4 simulation codes A1 A.1 Main program A1 A.2 Geometry declaration A2 A.2.1 Bremsstrahlung irradiation A2 A.2.2 Neutron irradiation A5 A.3 Stepping Actions A11 A.4 Run Actions A12 A.4.1 Bremsstrahlung irradiation A12 A.4.2 Neutron irradiation A15 B Input őle of TALYS code A18 C CERN ROOT analysis code to calculate IRs using energy ŕux spectra from GEANT4 and the cross-section outputs from TALYS A20