Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session FF: Reactions: Halos/ Clusters/ Transfers |
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Chair: Jerry Peterson, University of Colorado Room: Blue Point II |
Thursday, October 24, 2013 4:00PM - 4:12PM |
FF.00001: Coulomb dissociation of one- and two-neutron halos in halo EFT Bijaya Acharya, Daniel Phillips In neutron halo nuclei the neutron distribution extends significantly beyond the region occupied by the nuclear``core.'' Halo effective field theory (Halo-EFT) exploits the consequent separation of scales in order to predict relationships between low-energy observables in these systems as a systematic expansion in $R_{core}/R_{halo}$. This talk will discuss results for the Coulomb dissociation of neutron halo nuclei in this framework. In particular, we consider the Coulomb dissociation of ${}^{19}$C~[1]. We compute the reduced transition probability $(\mathrm{d} B(E1)/\mathrm{d}E)$ for excitation of the bound-state neutrons to the continuum up to N$^2$LO in the Halo-EFT expansion. By comparing the predcition with data from RIKEN~[2] we are able to extract accurate results for $^{19}$C's one-neutron separation energy and asymptotic normalization coefficient. Good agreement between data and Halo-EFT is also found for the longitudinal momentum distribution of $^{19}$C. Results from ongoing work to extend ths calculation to two-neutron halos will also be presented~[3]. \\[4pt] [1] B Acharya and D R Phillips, Nucl.~Phys.~A.~{\bf 913},~103~(2013).\\[0pt] [2] T Nakamura et al., Phys.~Rev.~Lett.~{\bf 83},~1112~(1999).\\[0pt] [3] B Acharya, P Hagen, H -W Hammer and D R Phillips, in preparation. [Preview Abstract] |
Thursday, October 24, 2013 4:12PM - 4:24PM |
FF.00002: Investigating halo features with the $^{11}$Be(p, d)$^{10}$Be$^*$ transfer reaction at 110 MeV at TRIUMF-ISAC II K. Kuhn, R. Braid, F. Sarazin, D. Smalley, U. Hager, S. Ilyushkin, P. O'Malley, M. Alvarez, C. Andreoiu, P.C. Bender, G. Hackman, C. Unsworth, Z. Wang, W.N. Catford, C.Aa. Diget, A. DiPietro, P. Figuera, T.E. Drake, J. Gomez, E. Nacher, A. Perea, O. Tengblad, C.E. Svensson To simultaneously study the halo wavefunction of the $^{11}$Be ground-state, and also possible excited halo states in $^{10}$Be, the $^{11}$Be(p, d)$^{10}$Be$^*$ reaction was studied at 10 MeV/nucleon at TRIUMF-ISAC II. This one-neutron transfer reaction allows the study of the single-particle states in $^{11}$Be and in $^{10}$Be by removing either the halo neutron or a core neutron respectively. A compact silicon array along with the TRIUMF ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS) was used to detect the outgoing deuteron in coincidence with gamma-rays to determine the final state of the $^{10}$Be nucleus. Results from the May 2013 experiment will be shown. [Preview Abstract] |
Thursday, October 24, 2013 4:24PM - 4:36PM |
FF.00003: Study of the $^{10}$B(p,$\alpha$) and $^{10}$B(p,$\gamma$) reactions A. Kafkarkou, M.W. Ahmed, R.H. France III, H.J. Karwowski, D.P. Kendellen, I. Mazumdar, J.M. Mueller, L.S. Myers, R.M. Prior, M.H. Sikora, M.C. Spraker, H.R. Weller, W.R. Zimmerman The cross sections of the $^{10}$B(p,$\alpha$)$^{7}$Be and $^{10}$B(p,$\gamma$)$^{11}$C reactions have been measured for bombarding proton energies between 2.0 and 6.0 MeV. The experiments were performed at Triangle Universities Nuclear Laboratory using a 10 MV FN Tandem accelerator. These reactions are relevant to potential next-generation nuclear reactors which propose to use boron as a fuel. For the $^{10}$B(p,$\alpha$)$^{7}$Be reaction, the differential cross section was measured at seven laboratory angles with 100 keV steps. A Legendre polynomial analysis was performed to extract the total cross sections and astrophysical S-factors. Final results will be presented. The $^{10}$B(p,$\gamma$)$^{11}$C reaction has never been studied for energies above 2 MeV. For this reaction, a $^{10}$B target was irradiated with protons with 500 keV steps for one hour ($\sim$3 $^{11}$C half-lives) at each energy. After the irradiation, the 511 keV $\gamma$-rays from the $\beta^{+}$ decay of $^{11}$C were detected in coincidence using two LaBr$_{3}$ detectors for another one hour. From these data the total cross section can be determined and preliminary results will be presented. [Preview Abstract] |
Thursday, October 24, 2013 4:36PM - 4:48PM |
FF.00004: Search for Cluster Structure in $^{14}$C by Investigation of $^{10}$Be($^4$He,$^4$He) Scattering with the Prototype AT-TPC Adam Fritsch, Daisuke Suzuki, Wolfgang Mittig, Tan Ahn, Daniel Bazin, Zbigniew Chajecki, William Lynch, Aimee Shore, James Kolata, Alan Howard, Amy Roberts, Xiaodong Tang, Fred Becchetti A half-scale prototype Active Target-Time Projection Chamber (AT-TPC) was built at the National Superconducting Cyclotron Laboratory (NSCL) as part of the development of the eventual full-scale AT-TPC device. The prototype AT-TPC was used to investigate $^{14}$C cluster structures by way of a 40 MeV $^{10}$Be beam incident on He:CO$_2$ gas at the University of Notre Dame in October 2011. The $^{10}$Be beam was produced by Notre Dame's Twinsol before being delivered to the prototype AT-TPC. Elastic and inelastic scattering of $^{10}$Be on $^4$He were observed and will be presented. [Preview Abstract] |
Thursday, October 24, 2013 4:48PM - 5:00PM |
FF.00005: Validation of (d,p$\gamma$) as a Surrogate for (n,$\gamma$) A. Ratkiewicz, J.A. Cizewski, A. Adekola, S. Burcher, M.E. Howard, B. Manning, S.L. Rice, C. Shand, J.T. Burke, R.J. Casperson, N. Scielzo, R.A.E. Austin, N. Fotiades, R.O. Hughes, T.J. Ross, M. McCleskey, S.D. Pain, W.A. Peters Although the importance of neutron capture on very exotic nuclei to nucleosynthesis is well known, direct measurements of these reactions are impossible. The (d,p$\gamma$) reaction at low energies was identified as a promising surrogate for (n,$\gamma$), as both reactions transfer relatively little angular momentum to the system. We report on a program to validate (d,p$\gamma$) as an (n,$\gamma$) surrogate reaction, using $^{95}$Mo as a target. The completed components of the experimental campaign include measurements of (d,p$\gamma$) in normal kinematics and of the intensities of transitions from excited states populated in (n,$\gamma$) as a function of neutron energies. Preliminary results from completed measurements and plans for an inverse kinematics measurement of $^{95}$Mo(d,p$\gamma$) will be presented.\\[4pt] This work was supported in part by the NSF, the U.S. DOE (DE-FG52-08NA28552 (Rutgers, ORAU), DE-AC52-07NA27344 (LLNL), DE-FG02-05ER41379 and DE-FG52-06NA26206 (Richmond). [Preview Abstract] |
Thursday, October 24, 2013 5:00PM - 5:12PM |
FF.00006: ABSTRACT WITHDRAWN |
Thursday, October 24, 2013 5:12PM - 5:24PM |
FF.00007: Measurement of the low-lying excitations in $^{96}$Mo by the $^{95}$Mo (d,p) reaction Shuya Ota, Jolie A. Cizewski, Andrew Ratkiewicz, Sean Burcher, Brett Manning, Samantha L. Rice, Callum Shand, Jason T. Burke, Robert J. Casperson, Nicholas Scielzo, Robi A.E. Austin, Con Beausang, Richard O. Hughes, Timothy J. Ross, Matt McCleskey, William A. Peters The $^{95}$Mo(d,p) reaction was studied at the 88-Inch Cyclotron at Texas A\&M University with a 13-MeV (6.5 MeV/nucleon) deuteron beam and a self-supporting foil of 0.96~mg/cm$^{2}$ $^{95}$Mo target. 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 sillicon detectors. This is the first study of the $^{95}$Mo(d,p) reaction and is part of the effort to validate the (d,p$\gamma$) reaction as a surrogate for neutron capture. Preliminary angular distribution results and a comparison with distorted wave calculations will be presented. [Preview Abstract] |
Thursday, October 24, 2013 5:24PM - 5:36PM |
FF.00008: Neutron Spectroscopy without Time-of-Flight: Spectrum Unfolding and (d,n) Measurements with Deuterated Liquid Scintillators Michael Febbraro, Frederick Becchetti, Ramon Torres-Isea, Alan Howard, Anthony Riggins, Chris Lawrence, James Kolata Deuterated liquid scintillation detectors can provide neutron spectroscopic information without time-of-flight (ToF) [1] allowing for close proximity to the reaction chamber for large angular coverage and increased absolute detector efficiency. This has led to the development of the University of Michigan Deuterated Scintillator Array (UM-DSA) and its associated high-speed digital-signal processing system [1]. As part of the UM project, the response matrix for the deuterated scintillator (EJ-315) utilized in the UM-DSA was measured using a ToF slicing method with neutrons up to 30 MeV produced from the reaction of 15 MeV deuterons on a thick 11B target. A Maximum Likelihood Expectation Maximization (MLEM) method was used for extraction of data for excited states populated in 9Be, 11B, 13C, 14,15N, and 19F(d,n) reactions performed at Ed $=$ 16.0 MeV. Cross sections from 10 to 160 deg. (lab) permitted assignment of angular momentum transfers and extraction of spectroscopic information using a DWBA analysis. Other applications of these detectors will also be discussed. \\[4pt] [1] M. Febbraro, et al., IEEE TNS 60 (2013) 890 - 896. [Preview Abstract] |
Thursday, October 24, 2013 5:36PM - 5:48PM |
FF.00009: Level densities and spin cutoff parameters for $^{60}$Co and $^{62}$Ni from proton evaporation spectra Alexander Voinov, Steven Grimes, Carl R. Brune, Alexander Burger, Andreas Gorgen, Magne Guttormsen, Ann Cecilie Larsen, Tomas Massey, Sunniva Siem Prediction of reaction cross sections remains a major problem in applications such as data evaluations or/and astrophysics reaction rate calculations. There is big progress in the development of nuclear reaction codes which now include different reaction mechanisms. However, these codes use many input parameters. The variety of input parameters helps us to describe existing experimental data but it creates problems when it comes to predictions. The uncertainties of the level density and the spin cutoff parameter cause the major concern. The proton spectra from $\alpha $ and lithium induced reactions have been measured and analyzed with the Hauser-Feshbach model. Different input level density models have been tested. The level densities and spin cutoff parameters were obtained with Monte-Carlo technique taking into account known spins of discrete low-lying levels of residual nuclei. It was found that the best description is achieved with the Gilbert and Cameron model functions. Excitation energy dependence of spin cutoff parameters was found to be different for $^{60}$Co and $^{62}$Ni nuclei. It is inconsistent with Fermi-gas model which is usually used to calculate spin cutoff parameters. [Preview Abstract] |
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