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MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY - LÊ TUẤN ANH STUDY ON PARAMETRIZATION OF PHOTOFISSION CROSS-SECTION OF 238U AND OPTIMIZATION SIMULATION USING GEANT4 FOR DESIGN OF THE IGISOL FACILITY AT ELI-NP PROJECT PhD THESIS IN ATOMIC AND NUCLEAR PHYSICS Hanoi – 2021 luan an MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY - LÊ TUẤN ANH STUDY ON PARAMETRIZATION OF PHOTOFISSION CROSS-SECTION OF 238U AND OPTIMIZATION SIMULATION USING GEANT4 FOR DESIGN OF THE IGISOL FACILITY AT ELI-NP PROJECT Major: Atomic and Nuclear physics Code: 9440106 PhD THESIS IN ATOMIC AND NUCLEAR PHYSICS SUPERVISORS: Dr, PHAN VIET CUONG Prof, DIMITER L BALABANSKI Hanoi – 2021 luan an LỜI CAM ĐOAN Tôi xin cam đoan cơng trình nghiên cứu mà phần chủ yếu trực tiếp thực hiện, phần cịn lại có tham gia hỗ trợ đồng nghiệp nhóm RA4, thuộc dự án ELI-NP Romania Các kết nghiên cứu trung thực chưa sử dụng cơng trình khác Luận án sử dụng số thông tin, số liệu thực nghiệm từ nhiều nguồn số liệu khác chúng trích dẫn rõ nguồn gốc Tác giả NCS Lê Tuấn Anh i luan an Acknowledgements First and foremost, I gratefully express my best thanks to my supervisors, Dr Phan Viet Cuong at Research and Development Center for Radiation Technology and Prof Dimiter L Balabanski at ELI-NP Romania for giving me an opportunity to join ELI-NP project, to work in an international researching environments, and for their limitless support and help me when I was in need I would like to thank Dr Paul Constantin in RA4-ELI-NP group, who was alway ready to spend his treasure time to help me through when I got problem not in this work but also daily life in Romania And I am also grateful to Dr Bo Mei, Dr Deepika Choudhury, and all the members of RA4, as well as ELI-NP, who help me a lot when I was at Romania I would like to thank the Board of Directors and all members of Graduate University of Science and Technology for helping me during the process of doing my thesis I also would like to thank my colleagues and friends in the VNU University of Science, in Centre of Nuclear Physics, Institute of Physics, and in Vietnam Atomic Energy Institute for their friendships and encouragements I would like to express my special thank to all my colleagues at Research and Development Center for always giving me convenience to finish my work I would like to thank to all my colleagues at Institute for Nuclear Science and Technology for their unlimited supports I would like to give my deep gratitude to my parents, my grandma, brother and other members in my big family for their encouragements at all time And aftermost, I would like to express the most special thank to my wife who has been always beside me, taken care of my two angel babies, to my beloved children who are the motivation of my working ii luan an This work was supported by Extreme Light Infrastructure Nuclear Physics (ELINP) Phase II, a project co-financed by the Romanian Government and the European Union through the European Regional Development Fund -the Competitiveness Operational Program (1/07.07.2016, COP, ID 1334) iii luan an Contents Acknowledgements ii Abbreviations vii List of tables viii List of figures xi Abstract Introduction OVERVIEW 1.1 The Extreme Light Infrastructure Nuclear Physics facility Gamma Beam System Methods for production of RIB 1.2.1 The ISOL technique 1.2.2 The in-flight method 10 1.2.3 Ion guide isotope separation online technique 11 1.2.4 Method for production of RIB at ELI-NP 12 1.3 The future ELI-NP IGISOL 13 1.4 Introduction of Geant4 toolkit 16 1.4.1 Energy loss of ions 18 1.4.2 Physics processes for e− and e+ 21 1.1.1 1.2 iv luan an 1.4.3 Processes induced by gamma beam 24 1.4.4 Mandatory method and classes of a Geant4-based application 25 1.5 Photofission process 26 1.6 Purposes of the Thesis 28 STUDY ON PARAMETRIZATION OF PHOTOFISSION CROSSSECTION OF 2.1 238 U 30 Empirical parametrization for total cross-section, mass yield and isobaric charge distribution of 238 U photofission 30 2.1.1 Parametrization for total cross-section 30 2.1.2 Parametrization for photofission mass yield 33 2.1.3 Parametrization for isobaric charge distributions 35 2.2 Validation of the empirical parametrization 39 2.3 Prediction of neutron-rich nuclei yield 44 2.4 Chapter conclusion 47 OPTIMIZING THE DESIGN OF CRYOGENIC STOPPING CELL FOR IGISOL FACILITY AT ELI-NP 48 3.1 The structure of the implemented Geant4-based code 48 3.2 Implementation of photofission process into Geant4 50 3.3 Ionic effective charge 52 3.4 Target geometry optimization 54 3.4.1 The beam spot size 54 3.4.2 Target geometry 56 v luan an 3.4.3 Optimize the thinkness of foil targets 57 3.4.4 The thinkness of backing layers 59 3.4.5 The dependence of the photofission fragment release rate on foil transverse size A, the foil tilting angle a, and the inter-foil distance 60 3.4.6 3.5 Remarks for target geometry 62 The stopping length of photofission fragments in Helium gas Guidance for choosing the width of CSC 3.5.1 63 The characteristics of release photofission fragments from backing layers 64 Ion stopping in the gas cell Choosing the width of CSC 64 3.6 The extraction of photofission fragments out of CSC 68 3.7 Chapter conclusion 71 3.5.2 Conclusion 73 Bibliography 75 Publications 81 Appendix 82 vi luan an Abbreviations ELI Extreme Light Infrastructure ELI-NP Extreme Light Infrastructure-Nuclear Physics RIB Radioactive Ion Beam ISOL Isotope Separation On-line IGISOL Ion Guide Isotope Separation On-line CSC Cryogenic Stopping Cell LIP Low energy Interaction Point HIP High energy Interaction Point DC Direct Current RF Radio Frequency HPLS High-Power Laser System PW Peta-Watt CBS Compton Backscattering GBS Gamma Beam System NRF Nuclear Resonance Fluorescence SM Symmetric Mode ASM Asymmetric Mode KE Kinetic energy PS Potential Energy Surface GDR Giant Dipole Resonance GSI The GSI Helmholtz Centre for Heavy Ion Research vii luan an List of Tables 2.1 The values of constants used in the empirical parametrization for 238 U photofission total cross-section 2.2 The values of constants used in the empirical parametrization for 238 U photofission mass yield 2.3 The values of constants used in the empirical parametrization for 32 34 238 U photofission isobaric charge 37 3.1 Results for target geometry 62 3.2 Gas density dependence of various parameters 68 viii luan an 95 col_slit_rot[col_iter]->rotateZ( col_set_angle_span/col_set_slit_nb*(col_iter-1)); col_slit_pos_z[col_iter] = -col_set_mother_z/2 + col_min_dist + (col_iter-1)*col_slit_dist + (col_iter-1./2.)*col_slit_mother_z; new G4PVPlacement(col_slit_rot[col_iter], G4ThreeVector(0.,0.,col_slit_pos_z[col_iter]), col_slit_mother_log, "col_slit_mother", col_set_mother_log, false, 0, checkOverlaps);} G4RotationMatrix* col_set_rot[col_set_nb+1]; for(G4int col_iter = 1; col_iter rotateZ(col_set_phi_zero[col_iter]); new G4PVPlacement(col_set_rot[col_iter], G4ThreeVector(0.,0., ELIColl_z+(col_iter-1./2.)*col_set_mother_z+ (col_iter-1)*col_set_dist),col_set_mother_log, "col_set_mother", expHall_log, false, 0, checkOverlaps);}} // BUILDS THE ENTIRE CSC TARGET SYSTEM: void DetectorConstruction::BuildTargetSystem( G4LogicalVolume* logicCell, G4bool checkOverlaps) { G4double foilThick = runInput->GetFoilThick(); G4double backThick = runInput->GetBackThick(); // DEFINITION OF THE MATERIALS: G4NistManager* nist = G4NistManager::Instance(); // G4Material* m_targ = nist->FindOrBuildMaterial("G4_U"); G4Material* m_targ = nist->FindOrBuildMaterial("G4_URANIUM_DICARBIDE"); G4Material* m_back = nist->FindOrBuildMaterial("G4_GRAPHITE"); G4Material* m_fram = nist->FindOrBuildMaterial("G4_Al"); G4Material* m_rod = nist->FindOrBuildMaterial("G4_Fe"); // DEFINITION OF THE BASIC SHAPES: G4Box* TA_shape = new G4Box("TargetBox", 0.5*foilLength, 0.5*foilThick); luan an 0.5*foilSize, 96 G4Box* BK_shape = new G4Box("BackingBox", 0.5*foilSize, 0.5*foilLength, 0.5*backThick); // THE 2D SHAPE OF THE FRAME FOR THE TARGET FOILS: G4double frameThick = foilThick + 2*backThick + 2*frameWidth; if(frameDepth>=frameLength) { G4cout