Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session S6: Heavy Nuclei and Matter |
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Sponsoring Units: DNP Chair: Jeff Carroll, Army Research Laboratory Room: 200 |
Monday, April 7, 2014 1:30PM - 1:42PM |
S6.00001: Single-neutron excitations in $^{96}$Mo from the $^{95}$Mo(d,p) reaction Shuya Ota, J.A. Cizewski, A. Ratkiewicz, S. Burcher, B. Manning, S.L. Rice, C. Shand, J.T. Burke, R.J. Casperson, J.E. Escher, N.D. Scielzo, I. Thompson, M. McCleskey, W.A. Peters, R.A.E. Austin, C.W. Beausang, R.O. Hughes, T.J. Ross Uncertainties in neutron capture cross sections can affect \textit{r}-process nucleo-synthesis at late times. Neutron transfer reactions are important in determining direct neutron capture cross sections and may be a promising surrogate for neutron capture when the desired reaction involves short-lived nuclei. As part of the effort to validate (d,p$\gamma$) as a surrogate for neutron capture, the $^{95}$Mo(d,p) reaction was studied at a cyclotron at Texas A\&M University with a 12.5-MeV deuteron beam. The reaction protons were measured at forward angles of 30-60$^{\circ}$ with the STARS (Silicon Telescope Array for Reaction Studies) array of three segmented Micron S2 silicon detectors to populate discrete states below 5 MeV in excitation. This is the first study of the $^{95}$Mo(d,p) reaction. Angular distributions of protons populating low-spin discrete excitations and a comparison with distorted-wave calculations will be presented. [Preview Abstract] |
Monday, April 7, 2014 1:42PM - 1:54PM |
S6.00002: Investigation of the structure of neutron-deficient Cd isotopes Anna Simon, P. Humby, C.W. Beausang, J.T. Burke, R.J. Casperson, M. McCleskey, A. Saastamoinen, J.M. Allmond, R. Chyzh, M. Dag, J. Koglin, S. Ota, T.J. Ross The STARLITER setup at Texas A\&M University consists of an array of six Compton suppressed HPGe clover $\gamma$-ray detectors coupled with a segmented Si $\Delta$E-E charged particle telescope. The combination allows for coincident $\gamma$ ray and particle spectroscopy and provides a powerful tool for precise determination of the nuclear level structure. A recent experiment conducted using STARLITER aimed at the investigation of structures of neutron-deficient Cd isotopes (A = 104, 105, 106) using an enriched $^{106}$Cd target and 35 MeV proton beam supplied by the K-150 Cyclotron at TAMU. Low mass cadmium isotopes are a great environment for analysis of the evolution from vibrational to rotational sequences in A$\sim$100-110 region and provide insight into the structure phenomena around Z=50 shell closure. Here, the first results of the experiment will be presented. This work was partly supported by the US Department of Energy Grants No. DE-FG52-06NA26206 and No. DE-FG02-05ER41379. [Preview Abstract] |
Monday, April 7, 2014 1:54PM - 2:06PM |
S6.00003: Investigation of low/medium spin excited states in $^{150-154}$Sm via the (p,d) and (p,t) reactions P. Humby, A. Simon, C. Beausang, K. Gell, T. Tarlow, G. Vyas, T.J. Ross, R.O. Hughes, J.T. Burke, R.J. Casperson, J. Koglin, S. Ota, J.M. Allmond, M. McCleskey, E. McCleskey, A. Saastamoinen, R. Chyzh, M. Dag Low/medium spin excited states of $^{151,153}$Sm and $^{150,152}$Sm were studied via the (p,d) and (p,t) reactions, respectively, utilizing the STARLITER arrays at the Cyclotron Institute of Texas A\&M University. In the experiment $^{152}$Sm and $^{154}$Sm targets were bombarded with 25 MeV protons and the outgoing light charged particles (p, d and t) in the exit channels were detected using the STARS $\Delta E$-$E$ silicon telescope, thus allowing particle identification and a measurement of the nuclear excitation energy. Six BGO shielded HPGe detectors were used to observe the emitted gamma rays in coincidence with the particles. A post-run measurement of gamma rays emitted from the activated target allowed an improved measurement of the half life of the 96 minute $J^{\pi}=8^{-}$ isomer of $^{152}$Eu. Preliminary results are presented. [Preview Abstract] |
Monday, April 7, 2014 2:06PM - 2:18PM |
S6.00004: ABSTRACT WITHDRAWN |
Monday, April 7, 2014 2:18PM - 2:30PM |
S6.00005: Progress in Electromagnetic Alteration of Nuclear Decay Properties R.J. Casperson, R.O. Hughes, J.T. Burke, N.D. Scielzo, R. Soufli Significant alteration of nuclear decay properties would have important consequences, ranging from novel approaches to nuclear batteries and gamma-ray lasers, to improved viability for physics experiments with short-lived targets. Quantum systems that decay by photon emission must couple to the electromagnetic modes of the local environment, and by modifying these modes, one can manipulate the rate of spontaneous emission. The nuclear isomer $^{235m}$U is low-energy, long-lived, and is easily populated through $^{239}$Pu $\alpha$-decay, which makes it an excellent benchmark for this effect. The decay rate of this isomer in a variety of environments is currently under investigation. Implications of this work will be discussed, and first results will be presented. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, April 7, 2014 2:30PM - 2:42PM |
S6.00006: Measurement of the $\alpha$/SF branching ratio of $^{252}$Cf with the NIFFTE fission TPC Lucas Snyder Neutron-induced fission cross sections are important in the simulation and modeling nuclear fuel cycles. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration is developing a fission Time Projection Chamber (TPC) to measure neutron-induced fission cross sections with total uncertainty of better than 1\%. To achieve such precision, the systematic uncertainties of the previously used measurement techniques must be addressed. The fission TPC will do this, in part, by providing detailed 3-dimensional images of fission fragments and other charged-particles produced in a neutron beam environment. Throughout the fission TPC's development phase the $\alpha$-decay and spontaneous fission of $^{252}$Cf has been used to benchmark its performance. Recently the first $^{252}$Cf data were collected using the fully instrumented fission TPC, which has nearly 6000 individual channels and provides 4$\pi$ coverage. A preliminary analysis of the $\alpha$/SF branching ratio will be presented. [Preview Abstract] |
Monday, April 7, 2014 2:42PM - 2:54PM |
S6.00007: Fusion, fission, and quasi-fission using TDHF Sait Umar, Volker Oberacker We study fusion, fission, and quasi-fission reactions using the time-dependent Hartee-Fock (TDHF) approach together with the density-constrained TDHF [1] method for fusion. The only input is the Skyrme NN interaction, there are no adjustable parameters. We discuss the identification of quasi-fission in 40Ca+238U, the scission dynamics in symmetric fission of 264Fm, as well as calculating heavy-ion interaction potentials $V(R)$, mass parameters $M(R)$, and total fusion cross sections from light to heavy systems. Some of the effects naturally included in these calculations are: neck formation, mass exchange, internal excitations, deformation effects, as well as nuclear alignment for deformed systems.\\[4pt] [1] Umar and Oberacker, PRC 74, 021601(R) (2006) [Preview Abstract] |
Monday, April 7, 2014 2:54PM - 3:06PM |
S6.00008: Auxiliary-field quantum Monte Carlo simulations of neutron matter in chiral effective field theory Jeremy Holt, Aurel Bulgac, Sergej Moroz, Kenneth Roche, Gabriel Wlazlowski We report on recent variational calculations of the neutron matter equation of state using chiral nuclear interactions. The ground-state wavefunction of neutron matter, containing nonperturbative many-body correlations and nucleon pairing, is obtained from auxiliary-field quantum Monte Carlo simulations of up to 200 neutrons interacting on a $10^3$ discretized lattice with spacing 1.5 fm, consistent with a momentum-space cutoff of 414 MeV. The evolution Hamiltonian is chosen to best reproduce broad features of chiral nuclear forces while at the same time avoiding the Fermion sign problem, and to account for the presence of nuclear three-body forces it is constructed as a function of the nucleon density. Differences between this evolution Hamiltonian and the full chiral nuclear interaction are then treated perturbatively. Our results for the equation of state are in good agreement with previous auxiliary-field quantum Monte Carlo simulations which employed only chiral two-body forces at next-to-next-to-leading order (N2LO). In addition we include the effects of three-body forces at N2LO, which provide important repulsion at densities higher than 0.02 fm$^{-3}$, as well as two-body forces at N3LO. [Preview Abstract] |
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