This is a repository copy of Nuclear Fission: : A Review of Experimental Advances and Phenomenology. White Rose Research Online URL for this paper: https://eprints.whiterose.ac.uk/119672/ Version: Accepted Version Article: Andreyev, Andrei orcid.org/0000-0003-2828-0262, Nishio, Katsuhisa and Schmidt, Karl- Heinz (2017) Nuclear Fission: : A Review of Experimental Advances and Phenomenology. Reports on progress in physics. 016301. ISSN 0034-4885 https://doi.org/10.1088/1361-6633/aa82eb Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. 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When available, you can view the Version of Record for this article at: http://iopscience.iop.org/article/10.1088/1361-6633/aa82eb Page 1 of 77 AUTHOR SUBMITTED MANUSCRIPT - ROPP-100800.R2 CONTENTS 1 1 2 3 Nuclear Fission: A Review of Experimental Advances and 4 5 Phenomenology 6 7 8 A.N. Andreyev1,2,K.Nishio2, K.-H. Schmidt3 9 1 Department of Physics, University of York, York, YO10 5DD, United Kingdom 10 2 Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Iberaki, 319-1195, Japan 11 3 Rheinstr. 4, D 64390 Erzhausen, Germany 12 13 14 Abstract In the last two decades, through technological, experimental and theoretical advances, the situation 15 in experimental fission studies has changed dramatically. With the use of advanced production and detection 16 techniques both much more detailed and precise information can now be obtained for the traditional regions of 17 fission research and, crucially, new regions of nuclei have become routinely accessible for fission studies. 18 This work first of all reviews the recent developments in experimental fission techniques, in particular the 19 resurgence of transfer-induced fission reactions with light and heavy ions, the emerging use of inverse-kinematic 20 approaches, both at Coulomb and relativistic energies, and of fission studies with radioactive beams. 21 The emphasis on the fission-fragment mass and charge distributions will be made in this work, though some of 22 the other fission observables, such as prompt neutron and γ-ray emission will also be reviewed. 23 A particular attention will be given to the low-energy fission in the so far scarcely explored nuclei in the very 24 neutron-deficient lead region. They recently became the focus for several complementary experimental studies, 25 such as β-delayed fission with radioactive beams at ISOLDE(CERN), Coulex-induced fission of relativistic 26 secondary beams at FRS(GSI), and several prompt fusion-fission studies. The synergy of these approaches 27 allows a unique insight in the new region of asymmetric fission around 180Hg, recently discovered at ISOLDE. 28 Recent extensive theoretical efforts in this region will also be outlined. 29 The unprecedented high-quality data for fission fragments, completely identified in Z and A, by means of reactions 30 in inverse kinematics at FRS(GSI) and VAMOS(GANIL) will be also reviewed. These experiments explored an 31 extended range of mercury-to-californium elements, spanning from the neutron-deficient to neutron-rich nuclides, 32 and covering both asymmetric, symmetric and transitional fission regions. 33 Some aspects of heavy-ion induced fusion-fission and quasifission reactions will be also discussed, which reveal 34 their dynamical features, such as the fission time scale. The crucial role of the multi-chance fission, probed by 35 means of multinucleon-transfer induced fission reactions, will be highlighted. 36 The review will conclude with the discussion of the new experimental fission facilities which are presently being 37 brought into operation, along with promising ’next-generation’ fission approaches, which might become available 38 within the next decade. 39 Contents 3.1.2 Prompt multi-nucleon transfer- 40 induced fission technique. 13 41 1 Introduction 2 3.2 Spontaneous and neutron-induced fis- 42 sion, the measurements of prompt fis- 43 2 General features of fission experiments in sion γ raysandneutrons......... 15 44 direct and inverse kinematics 4 3.2.1 2v-2E ’double velocity - dou- 45 2.1 Fission experiments in direct kinematics 5 ble energy’ method for fission- 46 2.2 Boosting the fission-fragment energies fragment measurements. 15 47 for improving the mass/charge resolu- 3.2.2 Measurements of prompt neu- 48 tion in inverse-kinematics fission studies 9 tron and γ-ray decays from fis- 49 sionfragments........... 16 50 3 Selected examples of experimental fission 3.2.3 Fission with neutron spallation 51 techniques 9 sources at n−TOF at CERN, 52 3.1 Measurements of fission-fragment mass LANSCE at LANL, JSNS at J- 53 distributions in prompt-fission studies PARC................ 16 54 in direct kinematics at near-Coulomb- 3.3 Current photofission experiments with 55 barrierenergies.............. 9 γ-ray beams, Compton-backscattered γ- 56 3.1.1 Typical setups for prompt fusion- raysourcesforfission........... 19 57 fissionexperiments......... 10 58 59 60 Accepted Manuscript AUTHOR SUBMITTED MANUSCRIPT - ROPP-100800.R2 Page 2 of 77 CONTENTS 2 1 2 3.4 β-delayed fission with stable and ra- 4.6.2 Prompt γ-ray emission from 3 dioactivebeams.............. 19 fissionfragments.......... 53 4 3.5 Fission in inverse kinematics . 21 4.7 Spallation-fission studies for ADS . 54 5 3.5.1 Coulomb-induced fission with 6 secondary relativistic beams at 5 Future developments in fission tech- 7 GSI................ 21 niques 56 8 3.5.2 Multi-nucleon-transfer-induced fis- 5.1 Fission of secondary RIBs at relativistic 9 sion with a 238UbeamatVA- energies at GSI/FAIR and RIKEN . 56 10 MOS(GANIL).......... 25 5.2 Fission of post-accelerated RIBs in 11 transfer-induced reactions in inverse 12 4 Discussion 26 kinematics at energies around the 13 4.1 Mapping fission in the neutron-deficient Coulomb barrier at HIE-ISOLDE (CERN) 57 14 lead region by means of βDF, relativistic 5.3 Recent technical developments for neutron- 15 Coulex and prompt-fission techniques . 27 inducedfissionresearch......... 57 16 4.1.1 New island and a new mech- 5.3.1 Prospective fission studies with 17 anism of asymmetric fission the FIPPS spectrometer at ILL . 57 18 180 19 around Hg............ 27 5.3.2 Neutrons for Science(NSF) facil- 20 4.1.2 Multimodal fission and asymmetric- ityatSPIRAL(GANIL)..... 57 to-symmetric transition in the 5.4 Future photofission experiments with 21 180 210 22 region between Hg and Ra. 30 brilliant, tunable, high-intensity γ-ray 23 4.1.3 Asymmetric-to-symmetric tran- beams................... 58 24 sition along the chain of mercury 180 198 25 isotopes, from Hg to Hg . 31 6 Some of the open questions in fission 26 4.2 New results on fission in the astatine- studies 58 27 to-californium region from inverse kine- 6.1 Fission-fragment properties in scarcely- 28 maticsexperiments............ 33 exploredregions............. 58 29 4.2.1 Overall variation of fission channels 34 6.2 Needs for signatures of fission dynamics 58 30 4.2.2 General characteristics of odd- 6.3 Fission-fragment angular momentum . 59 31 evenstructures.......... 36 6.4 Dissipation and time scales in fission . 59 32 4.2.3 Nuclear dissipation from inverse- 33 kinematics experiments . 37 7 Summary and Conclusions 60 34 4.3 Fission studies by means of few- and 8 Acknowledgments 61 35 multi- nucleon transfer reactions . 38 36 4.3.1 Fission-fragment mass distribu- 9 References 61 37 tions of the heavy actinides mea- 38 suredatJAEA.........