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Beta Decay of Neutron-Rich Isotopes of Zinc and Gallium

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Beta Decay of Neutron-Rich Isotopes of Zinc and Gallium University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2015 Beta decay of neutron-rich isotopes of zinc and gallium Mohammad Faleh M. Al-Shudifat University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Nuclear Commons Recommended Citation Al-Shudifat, Mohammad Faleh M., "Beta decay of neutron-rich isotopes of zinc and gallium. " PhD diss., University of Tennessee, 2015. https://trace.tennessee.edu/utk_graddiss/3288 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Mohammad Faleh M. Al-Shudifat entitled "Beta decay of neutron-rich isotopes of zinc and gallium." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Physics. Robert Grzywacz, Major Professor We have read this dissertation and recommend its acceptance: Soren Sorensen, Thomas Papenbrock, Jason P. Hayward Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Beta decay of neutron-rich isotopes of zinc and gallium A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Mohammad Faleh M. Al-Shudifat May 2015 c by Mohammad Faleh M. Al-Shudifat, 2015 All Rights Reserved. ii All praise due to Allah (God) who guided me and gave me strength and patience to do this work. I dedicate this work to: My mother, and My wife Alia who supported my journey to complete the PhD degree iii Acknowledgments I would like to thank my advisor for his guidance to complete this work. Robert Grzywacz taught us how to work as one team, he gave me several opportunities to participate in conferences and experiments in different places during my research period. Also, I would like to thank my mother. A special thanks to my wife (Alia) for her continuous care for our small lovely family, she was a great wife and mother. iv Abstract Beta-decays of neutron-rich nuclei near the doubly magic 78Ni [78Ni] were studied at the Holifield Radioactive Ion Beam Facility. The half-life and the gamma-gamma coincidence spectra were used to study the nuclear structure. A new 82;83Zn [82Zn, 83Zn] decay-scheme was built, where a 71 7% beta-delayed neutron branching ratio ± was assigned in 82Zn [82Zn] decay. New gamma-ray lines and energy levels observed in 82;83Ga [82Ga, 83Ga] beta-decay were used to update previously reported decay- schemes. The experimental results were compared to shell model calculations, which postulate the existence of Gamow-Teller transitions in these decays. The half-lives of 155 17 and 122 28 ms were determined for 82;83Zn, respectively. ± ± In order to enable future studies of very neutron rich isotopes a new detector was developed as a second project. This detector is intended for use in fragmentation type experiments, which require segmentation in order to enable implantation-decay correlations. In addition, the detector requires good timing resolution for neutron time-of-flight experiments. A Position Sensitive Photo-Multiplier Tube (PSPMT) from Hamamatsu coupled with a 16 16 fast pixelated plastic scintillator was used. × The PSPMT's anodes form 8 8 segment panel used for position reconstruction. × Position localization has been achieved for energies range of 0.5-5 MeV. A single signal dynode (DY12) shows a sufficient time resolution between this signal and the anode's signals, which enable us to used DY12 signal alone as a trigger for timing purposes. The detector's DY12 signals was tested with reference detectors and it provided a sub-nanosecond time resolution through the use of a pulse-shape analysis v algorithm, which is sufficient for use in experiments with the requirement for the fast timing. The detector ability to survive after implanting high-energy ions was tested using a laser that simulated energy of 1 GeV. The recovery time of the detector in this situation was 200 nanosecond. vi Table of Contents 1 Introduction1 1.1 Beta-decay spectroscopy.........................1 1.2 Fast segmented scintillator detector...................2 2 Theoretical Background4 2.1 Shell model................................4 2.1.1 Nuclear energy levels.......................5 2.1.2 Spin-orbit splitting........................8 2.2 β-Decay and the weak interaction....................9 2.3 Allowed β-decay.............................. 12 2.3.1 Isospin............................... 12 2.3.2 β-decay transition rates..................... 13 I The Beta Decay of 82;83Zn and Nuclear Structure around N=50 Shell Closure 18 abstract 19 3 Experiment Setup 20 3.1 ISOL technique at the HRIBF...................... 20 3.2 LeRIBSS.................................. 23 3.2.1 Moving tape collector (MTC).................. 23 vii 3.2.2 Detectors system......................... 25 3.3 Experimental issues............................ 28 4 82Zn β-decay chain analysis 30 4.1 Data analyzing methods......................... 31 4.1.1 Time walk correction....................... 32 4.1.2 β-gated spectra.......................... 33 4.1.3 β-γ-γ coincidence spectra.................... 35 4.1.4 Half-life calculation........................ 35 4.2 82Zn β-decay spectroscopy........................ 36 4.3 82Ga β-decay spectroscopy........................ 42 4.4 81;82Ge β-decay spectroscopy....................... 45 4.5 Beta delayed neutron branching ratio calculation of 82Zn β-decay.. 46 5 83Zn β-decay chain analysis 51 5.1 83Zn β-decay spectroscopy........................ 52 5.2 83Ga β-decay spectroscopy........................ 54 5.3 Isomeric 197 keV γ-ray line from 18F.................. 56 5.4 83;82Ge β-decay spectroscopy....................... 57 6 Shell model calculation of the Gamow-Teller strength 59 6.1 NuShellX Calculations.......................... 59 6.2 Gamow-Teller transition probability calculation method........ 63 6.3 Gamow-Teller transition probability of zinc and gallium isotopes... 66 7 Discussions and conclusions of the Zn β-decay experiments 69 7.1 82Zn β-decay analysis.......................... 69 7.1.1 82Zn energy levels and β transition............... 69 7.1.2 β-decay energy-scheme of 82Zn.................. 70 7.2 82Ga β-decay analysis........................... 73 viii 7.3 83Zn β-decay analysis........................... 75 7.4 83Ga β-decay analysis........................... 75 7.5 82;83Zn half-lives.............................. 76 7.6 Gamow-Teller decays of zinc and gallium isotopes........... 78 7.7 Low-excited states in gallium and germanium isotopes......... 80 II Development of a segmented scintillator for decay studies 83 abstract 84 8 Development of a segmented scintillator for decay studies 85 8.1 Detector system.............................. 87 8.1.1 Motivation............................. 88 8.2 Physical processes inside the PSPMT detector............. 89 8.3 Digital data acquisition system..................... 91 8.4 Position localization........................... 93 8.4.1 Center-of-gravity method..................... 93 8.5 Results of the position localization tests................ 94 8.6 Time resolution.............................. 96 8.6.1 Pulse-shape analysis....................... 97 8.6.2 Results of time resolution tests................. 98 8.7 Response to high-energy signals..................... 100 8.8 Conclusions................................ 101 9 Conclusion 104 9.1 Zinc and gallium β-decay spectroscopy................. 104 9.2 Fast segmented scintillator detector................... 105 Bibliography 107 ix Appendix 116 A Summary of theoretical proofs 117 A.1 Potential well............................... 117 A.2 Harmonic oscillator potential....................... 118 A.3 Isospin................................... 120 Vita 123 x List of Tables 2.1 Quarks types............................... 11 2.2 β-decay types and selection rules.................... 16 3.1 Standard reference material sources................... 26 4.1 γ-ray energy lines and its β-gated γ-γ coincidences produced by 82Zn β-decay.................................. 38 4.2 A comparison between some γ-ray lines intensities in 81Ge to fined the doublet intensities of 530 keV....................... 41 4.3 γ-ray energy lines and its β-gated γ-γ coincidences produced by 82Ga β-decay.................................. 43 4.4 γ-ray energy lines and its β-gated γ-γ coincidences produced by 81;82Geβ-decay............................... 46 4.5 γ-ray energy-levels of 81;82Ga and its feeding.............. 49 5.1 γ-ray energy lines and its β-gated γ-γ coincidences produced by 83Ga β-decay.................................. 55 8.1 Physical properties of the Detector................... 88 A.1 Nucleons energy levels of HO potential................. 120 xi List of Figures 2.1 Nuclear landscape.............................5 2.2 Nuclear Potentials............................7 2.3 Neutron separation energies.......................9 2.4 beta-decay Feynman diagrams...................... 11 3.1 ISOL in HRIBF.............................
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