Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session FC: Mini-symposium on Decay Spectroscopy and the Drip Lines |
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Chair: Joseph Cerny, University of California, Berkeley Room: Sweeny C |
Thursday, November 4, 2010 4:00PM - 4:36PM |
FC.00001: Decay studies at and beyond the limits of known nuclei Invited Speaker: Studies of spontaneous nuclear decays make an important contribution to our understanding of atomic nuclei. These studies can be made at very low rates allowing us to reach and investigate the structure of very exotic isotopes offering the last verification points before extrapolating theories into unknown regions. There is also a strong need for nuclear decay data in astrophysics and applied research related to the nuclear fuel cycle. The recent results obtained using decay spectroscopy methods on nuclei very far from beta stability will presented. Among these investigations, there are new studies near exotic doubly-magic nuclei $^{78}$Ni and $^{100}$Sn, on nuclei around proton drip line and in the super heavy element region. The examples of results representing applied nuclear spectroscopy field will be given, too. [Preview Abstract] |
Thursday, November 4, 2010 4:36PM - 4:48PM |
FC.00002: The $\beta$ decay of $^{81}$Zn and excitations of the $^{78}$Ni core Stephen Padgett, Robert Grzywacz, Miguel Madurga, Carrol Bingham, Lucia Cartegni, Stanley Paulauskas, Iain Darby, Mustafa Rajabali, Agnieszka Korgul, Wojtek Krolas, Sergey Ilyushkin, Jeff Winger, Sean Liddick, Chiara Mazzocchi, Carl Gross, Krzysztof Rykaczewski, Dan Shapira, Jon Batchelder, Edward Zganjar The $\beta$ decay of the neutron rich N=51 nucleus $^{81}$Zn was investigated in order to establish the ground state configuration of $^{81}$Zn and to study excited states in the N=50 isotone $^{81}$Ga. A high detection efficiency, digital $\beta$$\gamma$ spectroscopy setup at the HRIBF (Oak Ridge) was used with an isotopically pure beam of $^{81}$Zn. The $^{81}$Zn decay properties result from a competition between high energy forbidden $\beta$ decays to negative parity states and allowed Gamow-Teller transitions to positive parity, core excited states in $^{81}$Ga. Our data on the $\beta$ decay branching ratios suggest a 5/2$^+$ assignment for the $^{81}$Zn ground state. The analysis also establishes the N=50 shell gap energy near $^{78}$Ni. [Preview Abstract] |
Thursday, November 4, 2010 4:48PM - 5:00PM |
FC.00003: $\beta$-delayed neutron precursors with the Versatile Array of Neutron Detectors at Low Energies (VANDLE) M. Madurga, S. Paulauskas, R. Grzywacz, S. Padgett, D. Bardayan, J. Blackmon, J. Cizewski, P. O'Malley, S. Liddick, W.A. Peters, F. Raiola, F. Sarazin The production of radioactive ion beams of nuclei away from stability in new facilities such as Lerribs offers the opportunity of studying the properties of nuclear matter dominated by large proton-neutron imbalances, resulting in new effects like shell evolution and new magic numbers. The $\beta$-decay is an excellent probe of nuclear structure, a selective and well understood mechanism. However, for exotic nuclei, a significant fraction of the $\beta$-strength will populate neutron unbound states. The proposed VANDLE will consist of an array of 164 plastic scintillator bars to measure the neutron energy using time of flight technique. The expected large neutron energy dynamic range and its modular design will give the flexibility necessary to use the detector in experiments with requirements as different as $\beta$-decay of neutron rich elements to (d,n) reaction experiments. Results of the proof-of-principle measurement of the $^{89}$Br $\beta$-delayed neutron emission will be presented. [Preview Abstract] |
Thursday, November 4, 2010 5:00PM - 5:12PM |
FC.00004: ABSTRACT WITHDRAWN |
Thursday, November 4, 2010 5:12PM - 5:24PM |
FC.00005: Production and Decay of Element 114 Isotopes with the BGS (LBNL) and TASCA (GSI) Jacklyn Gates During the last 10 years, the Dubna Gas Filled Recoil Separator (DGFRS) group has published numerous reports of the production and decay of superheavy elements (SHE) with Z=112-118 in $^{48}$Ca irradiations of actinide targets. Recently the production of element 114 in the $^{242}$Pu($^{48}$Ca,3-4$n)$ reaction was verified at the Lawrence Berkeley National Laboratory using the Berkeley Gas-filled Separator (BGS). Later experiments at the BGS successfully extended the region of known SHE nuclides along the neutron-deficient side using the $^{242}$Pu($^{48}$Ca,5$n)^{285}$114 reaction. Almost concurrently with the BGS, the TransActinide Separator and Chemistry Apparatus at the GSI Helmholtzzentrum f\"{u}r Schwerionenforschung investigated the $^{244}$Pu($^{48}$Ca,3{\-}4$n)$ reaction and observed cross sections on the order of 10 pb for the production of element 114 when the more neutron-rich $^{244}$Pu target was used. An alpha-decay branch in $^{281}$Ds was also discovered, leading to the new nucleus $^{277}$Hs. Cross sections, decay modes and decay properties all agree with those published by the DGFRS group. Implications of these results on the field of heavy elements will be discussed. [Preview Abstract] |
Thursday, November 4, 2010 5:24PM - 5:36PM |
FC.00006: $\beta$ decay of $^{69,70,71}$Kr A.M. Rogers, C.J. Lister, J.A. Clark, S.M. Fischer, S. Gros, E.A. McCutchan, G. Savard, D. Seweryniak, J. Giovinazzo, B. Blank, G. Canchel, G. de France, S. Grevy, F. de Oliveira Santos, I. Stefan, J.-C. Thomas Proton-rich nuclei beyond the $N=Z$ line play a key role in our understanding of astrophysics, weak-interaction physics, and nuclear structure. The decay of $^{69}$Kr is of particular interest as it can be used to populate states in the proton unbound nucleus $^{69}$Br. During the $rp$-process, 2p-capture reactions through $^{69}$Br can bypass the ``waiting-point'' nucleus $^{68}$Se. This depends sensitively on the proton-capture Q-value. An implantation-decay experiment was recently conducted at GANIL which utilized $\beta$-p and $\beta$-$\gamma$ correlations to study physics related to the $\beta$ decay of $^{69,70,71}$Kr. Isotopes of Kr were implanted into a DSSD, also used to detect decay protons, located at the end of the LISE spectrometer. Coincident $\gamma$-rays from the implant decays were detected in the surrounding EXOGAM clovers. We were able to identify $\sim200$ $^{69}$Kr implantation-decay events, allowing us to extract the energy and constrain the angular momentum of the analog state in $^{69}$Br as well as improve the prediction for the $^{69}$Kr mass. An overview of the results from our analysis of $^{69}$Kr $\beta$ decay will be presented. This work is supported by the U.S. DOE Office of Nuclear Physics, Contract No.~DE-AC02-06CH11357. [Preview Abstract] |
Thursday, November 4, 2010 5:36PM - 5:48PM |
FC.00007: Beta-decay spectroscopy with a digital data acquisition system S.N. Liddick, H.L. Crawford, S.A. Suchyta, C.J. Chiara, W.B. Walters Decay spectroscopy is a sensitive technique for exploring the properties of exotic nuclei. The application of digital electronics to decay spectroscopy experiments further increases the reach of beta-decay studies. Recently, a complete digital data acquisition system has been implemented at NSCL for beta- delayed gamma-ray spectroscopy. The system consists of a highly- segmented double-sided Si strip detector surrounded by 16 Ge detectors of the SeGA array. Among the benefits of the digital data acquisition system are improved energy resolution and thresholds for signals in both the Si and Ge detectors. The lower threshold in the Si detector translates into an increased efficiency for detecting a beta-decay electron. Further, the dead time of the digital data acquisition system is dramatically reduced compared to the previous analog system. A description of the system and its performance in beta-decay spectroscopy studies in neutron-rich Cr and Mn isotopes will be presented. [Preview Abstract] |
Thursday, November 4, 2010 5:48PM - 6:00PM |
FC.00008: Alpha decay of 112and 111Xe Lucia Cartegni, C. Mazzocchi, R. Grzywacz, I.G. Darby, S.N. Liddick, K.P. Rykaczewski, J.C. Batchelder, L. Bianco, C.R. Bingham, E. Freeman, C. Goodin, C.J. Gross, A. Guglielmetti, D.T. Joss, S. Liu, M. Mazzocco, S. Padgett, R.D. Page, M.M. Rajabali, M. Romoli, P. Sapple, J. Thomson, H. Watkins Decay measurements of proton-rich nuclei can be useful to determine the mass of nuclei far from stability, test theoretical predictions for nucleon separation energies, and supply experimental data for simulation of astrophysical nucleosynthesis processes. We performed an experiment at the Holifield Radioactive Ion Beam Facility at ORNL to search for the alpha decay of 112Cs, a known proton emitter. The ions produced in the reaction 58Ni(58Ni,p3n)112Cs, separated through a Recoil Mass Spectrometer, were implanted in a double-sided silicon strip detector. We were able to establish an upper limit on the alpha branching ratio of 112Cs, and to measure the alpha branching ratio of 111Xe, while observing its fine structure. Results will be presented. [Preview Abstract] |
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