Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session B3: Direct and Surrogate Nuclear Reactions for Applications and Basic ResearchInvited
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Sponsoring Units: DNP Chair: Melina Avila, Argonne National Laboratory Room: Ballroom B |
Saturday, April 16, 2016 10:45AM - 11:21AM |
B3.00001: Neutron capture by hook or by crook Invited Speaker: Shea Mosby The neutron capture reaction is a topic of fundamental interest for both heavy element (A>60) nucleosynthesis and applications in such fields as nuclear energy and defense. The full suite of interesting isotopes ranges from stable nuclei to the most exotic, and it is not possible to directly measure all the relevant reaction rates. The DANCE instrument at Los Alamos provides direct access to the neutron capture reaction for stable and long-lived nuclei, while Apollo coupled to HELIOS at Argonne has been developed as an indirect probe for cases where a direct measurement is impossible. The basic techniques and their implications will be presented, and the status of ongoing experimental campaigns to address neutron capture in the A=60 and A=100 mass regions will be discussed. [Preview Abstract] |
Saturday, April 16, 2016 11:21AM - 11:57AM |
B3.00002: Direct Reactions with MoNA-LISA Invited Speaker: Anthony Kuchera Nuclear reactions can be used to probe the structure of nuclei. Direct reactions, which take place on short time scales, are well-suited for experiments with beams of short-lived nuclei. One such reaction is nucleon knockout where a proton or neutron is removed from the incoming beam from the interaction with a target. Single nucleon knockout reactions have been used to study the single-particle nature of nuclear wave functions. A recent experiment at the National Superconducting Cyclotron Laboratory was performed to measure cross sections from single nucleon knockout reactions for several p-shell nuclei. Detection of the residual nucleus in coincidence with any gamma rays emitted from the target allowed cross sections to ground and excited states to be measured. Together with input from reaction theory, \textit{ab initio} structure theories can be tested. Simultaneously the accuracy of knockout reaction models can be validated by detecting the knocked out neutron with the Modular Neutron Array and Large multi-Institutional Scintillator Array (MoNA-LISA). Preliminary results from this experiment will be shown. Knockout reactions can also be used to populate nuclei which are neutron unbound, thus emit neutrons nearly instantaneously. The structure of these nuclei, therefore, cannot be probed with gamma ray spectroscopy. However, with large neutron detectors like MoNA-LISA the properties of these short-lived nuclei are able to be measured. Recent results using MoNA-LISA to study the structure of neutron-rich nuclei will be presented. [Preview Abstract] |
Saturday, April 16, 2016 11:57AM - 12:33PM |
B3.00003: Soft dipole resonance and halo structure of $^{\mathrm{11}}$Li Invited Speaker: Rituparna Kanungo The discovery of the nuclear halo [1,2] in rare isotopes has ushered a new era in nuclear science breaking the boundaries of conventional concepts. The halo properties elucidate new features that till date remain a challenge to decipher from fundamental principles. Our knowledge on the halo is still gradually unfolding and reaching new levels of precision as efforts continue towards new experimental developments. In recent times, low-energy reactions in inverse kinematics have become possible providing a wealth of new structure information. In this presentation we will introduce a new reaction spectroscopy facility, IRIS, [3] with a novel thin windowless solid H$_{\mathrm{2}}$/D$_{\mathrm{2}}$ target for studying transfer and inelastic scattering reactions of rare isotopes with very low yields. It was postulated [4] that the loosely bound halo of two neutrons may lead to a core-halo oscillation resulting in dipole resonance(s) at very low excitation energy, called soft dipole resonance. Despite decades of search for this new phenomenon using various techniques, such as [5-9], no firm conclusion was reached. The presentation will discuss new results from IRIS that shows evidence of a soft dipole resonance state and further unveils its isoscalar character [10]. New results of neutron transfer from $^{\mathrm{11}}$Li will be presented showing resonance state(s) in the neutron unbound $^{\mathrm{10}}$Li subsystem hence facilitating a description of the wavefunction of $^{\mathrm{11}}$Li. [1] I. Tanihata et al., Phys. Rev. Lett. 55 (1985) 2676. [2] P.G. Hansen and B. Jonson, Eur. Phys. Lett. B 4 (1987) 409. [3] R. Kanungo, Hyperfine Interact, 225 (2014) 235 [4] K. Ikeda, Nucl. Phys. A 538 (1992) 355c. [5] T. Kobayashi et al., Nucl. Phys. A 538 (1992) 343c. [6] M. G. Gornov et al., Phys. Rev. Lett. 81 (1998) 4325. [7] A.A. Korshennikov et al., Phys. Rev. C 53 (1996) R537. [8] T. Nakamura et al., Phys. Rev. Lett. 96 (2006) 252502. [9] M. Zinser et al., Nucl. Phys. A 619 (1997) 151. [10] R. Kanungo et al., Phys. Rev. Lett. 114 (2015) 192502. [Preview Abstract] |
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