Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session JE: Nuclear Reactions/Rare Isotope Beams II |
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Chair: William Lynch, Michigan State University Room: 103AB |
Friday, October 28, 2011 2:00PM - 2:12PM |
JE.00001: Measuring Cluster Fusion Plasma Temperature and Density from $^{3}$He(D,p)$^{4}$He and D(D,p)T Reactions Marina Barbui, A. Bonasera, K. Hagel, J.B. Natowitz, K. Schmidt, H. Zheng, M. Barbarino, W. Bang, T. Ditmire, G. Dyer, H. Quevedo, A. Bernstein The interaction of intense ultrafast laser pulses with molecular clusters produces the explosion of the clusters with enough kinetic energy to drive nuclear reactions. If we assume the thermalization of the plasma, the ratio of the yields from two different nuclear reactions occurring simultaneously will allow the determination of the ion temperature at the time when the reaction occurred. We performed two experiments: one using pure deuterium to drive the D(D,p)T and D(D,n)$^{3}$He reactions, another mixing D$_{2}$ and $^{3}$He into the gas jet target to allow us to measure simultaneously yields from the $^ {3}$He(D,p)$^{4}$He and the D-D reactions. We detected both the 2.45 MeV neutrons and 3.02 MeV protons from the D-D reactions and the 14.7 MeV protons from the $^{3}$He(D,p)$^{4}$He reaction. Preliminary results will be shown. [Preview Abstract] |
Friday, October 28, 2011 2:12PM - 2:24PM |
JE.00002: Elastic Scattering of $^6$He based on a Cluster Description Stephen Weppner, Charlotte Elster Recently elastic scattering of $^6$He off a polarized proton target has been measured for the first time at an energy of 71~MeV/nucleon. The experiment finds that the analyzing power becomes negative around 50$^{\circ}$, a feature which can not be described by simple folding models for the optical potential, which do not take into account the halo character of the $^6$He nucleus. In this work, the cluster structure of $^6$He is incorporated in an optical potential for the reaction $p+^6$He in the framework of the Watson ansatz for the multiple scattering theory. We find that the analyzing power at 71~MeV/nucleon is sensitive to the cluster structure of $^6$He, whereas the differential cross section is not. We also present predictions for higher energies which also show a lack of sensitivity. [Preview Abstract] |
Friday, October 28, 2011 2:24PM - 2:36PM |
JE.00003: Testing formalisms for deuteron breakup and transfer reactions Neelam Upadhyay, Arnoldas Deltuva, Filomena Nunes The Continuum Discretized Coupled Channels (CDCC) [1] method is a well established theory for the direct nuclear reactions which includes breakup to all orders. In CDCC, the 3-body problem is solved by expanding the full wave function in terms of a complete basis of the projectile's bound and continuum states. Alternatively, the 3-body problem can be solved exactly within the Faddeev formalism [2,3] which explicitly includes breakup and transfer channels to all orders. Thus with the aim to understand how the CDCC compares with the exact 3-body Faddeev formulation, we study scattering of deuterons on $^{10}Be$, $^{12}C$, and $^{48}Ca$ at low and intermediate energies. We calculate elastic, breakup and transfer observables. Results indicate that for transfer cross section at low energy, CDCC is in better agreement with the Faddeev formalism. The discrepancy in two methods increases with beam energy. [1] N. Austern {\it et al.}, Phys. Rep. {\bf 154}, 125 (1987). [2] L. D. Faddeev, Zh. Eksp. Theor. Fiz. {\bf 39}, 1459 (1960). [3] E. O. Alt, P. Grassberger, and W. Sandhas, Nucl. Phys. {\bf B2}, 167 (1967). [Preview Abstract] |
Friday, October 28, 2011 2:36PM - 2:48PM |
JE.00004: Knockout reactions from p-shell nuclei: tests of ab initio structure models Daniel Bazin, Geoff Grinyer, Sofia Quaglioni, James Terry, Dirk Weisshaar, Alexandra Gade, Jeff Tostevin, Alex Brown, Chris Campbell, Thomas Glasmacher, Sean Mcdaniel, Petr Navratil, Alexandre Obertelli, Robert Wiringa Absolute cross section measurements have been performed at the level of 5{\%} precision following single neutron knockout reactions from $^{10}$Be and $^{10}$C at intermediate beam energy. Theoretical nucleon densities and bound-state wavefunction overlaps obtained from Variational Monte-Carlo (VMC) and No-Core Shell Model (NCSM) ab initio calculations have been incorporated into the theoretical description of knockout reactions. Comparison to experimental cross sections demonstrates that the VMC approach provides the best agreement while the NCSM and conventional shell-model calculations both over-predict the cross section for $^{10}$Be by 20 to 30{\%} and $^{10}$C by 40 to 50{\%}, respectively. This study provides new insight into the importance of nucleon correlations and 3-body forces in light nuclei and the accuracy of the VMC and NCSM structure models for describing these effects at the microscopic level. [Preview Abstract] |
Friday, October 28, 2011 2:48PM - 3:00PM |
JE.00005: Analysis of Fusion Reactions with Carbon Isotopes Henning Esbensen, Cheng-Lie Jiang, Xiao-Dong Tang Fusion data for $^{13}$C+$^{13}$C are analyzed by coupled-channels calculations that are based on the M3Y+repulsion, double-folding potential. Quadrupole and octupole transitions to low-lying states in projectile and target are included, as well as mutual excitations of these states. The one-neutron transfer to the $^{12}$C+$^{14}$C mass partition is also considered. By adjusting the parameters of the M3Y+repulsion interaction it is possible to obtain an excellent fit to the data. This requires, however, that the absolute normalization of the calculation is adjusted, and justifications for doing that are discussed. The calibrated M3Y+repulsion interaction is applied to predict the fusion cross section for $^{12}$C+$^{13}$C and good agreement with the data is achieved. The prediction for $^{12}$C+$^{12}$C is in reasonable agreement with the maximum peak cross sections that have been measured, and provides an upper limit for the extrapolation to the low energies that are of interest to astrophysics. [Preview Abstract] |
Friday, October 28, 2011 3:00PM - 3:12PM |
JE.00006: Developing a technique for measuring the fusion of neutron-rich nuclei at near barrier energies Kyle Brown, M.J. Rudolph, Z.Q. Gosser, S. Hudan, R.T. deSouza, M. Famiano Enhancement of the fusion cross-section for neutron-rich light nuclei has been postulated as a heat source that triggers X-ray superbursts in the crust of an accreting neutron star. To investigate this question, one has begun an experimental program to measure near-barrier fusion of $^{20,22}$O ions incident with $^{12}$C nuclei. Fusion in $^{16}$O + $^{12}$C provides a necessary reference reaction. While this reference reaction has already been extensively studied, measuring the excitation function with the same experimental setup used for radioactive beam experiments will allow us to both demonstrate the feasibility of the experimental technique, as well as account for experimental uncertainties. Near and sub-barrier fusion cross-sections were measured for $^{16}$O + $^{12}$C at Western Michigan University for 20 MeV $<$ E$_{lab }<$ 31 MeV. The time-of-flight between two micro-channel plate detectors, spaced by approximately 80cm, allows selection of the incident particle's time-of-flight on an event-by-event basis. The carbon foil of the second MCP acts as the target and provides a start signal. Fusion residues are identified by energy and time-of-flight ($\delta $ = 425ps for E$_{\alpha }$ = 7.687 MeV) between the active target and two segmented, annular silicon detectors which cover the angular range, 3\r{ }$<\theta _{lab}<$20\r{ }. Results will be compared with established cross-sections. [Preview Abstract] |
Friday, October 28, 2011 3:12PM - 3:24PM |
JE.00007: Fusion of neutron-rich O ions on a carbon target at near-barrier energies Romualdo deSouza, M.J. Rudolph, Z.Q. Gosser, K. Brown, S. Hudan, A. Chbihi, B. Jacquot, M. Famiano, F. Liang, D. Shapira, D. Mercier Experimental investigation of the sub-barrier fusion of neutron-rich light nuclei is important in understanding the crust of a neutron star, the structure of neutron-rich nuclei, and fusion dynamics of neutron-rich nuclei. It has recently been proposed that X-ray superbursts may originate from carbon burning ignited by heat from the fusion of neutron-rich oxygen nuclei in the crust of an accreting neutron stars [1]. An enhancement in the fusion probability, pronounced at energies near and below the Coulomb barrier, may signal the presence of different fusion dynamics as compared to the fusion of less neutron-rich nuclei. To assess if the fusion probability is enhanced for neutron-rich nuclei, we performed the first fusion excitation measurement for $^{20}$O + $^{12}$C for E$_{lab}$/A=1-2 MeV. Initial results of this experimental measurements will be presented. \\[4pt] [1] C.J. Horowitz, H. Dussan, and D.K. Berry, \textbf{Phys. Rev. C 77, 045807~(2008)} [Preview Abstract] |
Friday, October 28, 2011 3:24PM - 3:36PM |
JE.00008: Influence of neutron excess on fusion hindrance in neutron-rich radioactive Sn induced reactions J.F. Liang, J.M. Allmond, C.J. Gross, Z. Kohley, K. Largergren, P.E. Mueller, D. Shapira, R.L. Varner, A.L. Caraley Fusion enhancement has been observed in reactions induced by neutron-rich radioactive beams at energies near the Coulomb barrier. In heavier systems, fusion is hindered because of quasifission. Whether the hindrance will cancel out the enhancement brought by neutron-rich radioactive nuclei is an open question. We have measured evaporation residue cross sections for neutron-rich radioactive Sn on Ni targets to study the influence of neutron excess on the amalgamation process. A model independent comparison between $^{132}$Sn+$^{58}$Ni and $^{126}$Sn+$^{64}$Ni will be made. The isotope dependence of fusion hindrance in $^{124,126,127,128}$Sn on $^{64}$Ni will be examined. [Preview Abstract] |
Friday, October 28, 2011 3:36PM - 3:48PM |
JE.00009: The role of transfer couplings in the fusion of Sn+Ni and Te+Ni systems Z. Kohley, J.F. Liang, D. Shapira, R.L. Varner, C.J. Gross, J.M. Allmond, A.L. Caraley, E.A. Coello, F. Favela, K. Lagergren, P.E. Mueller Evaporation residue and fission cross sections have been measured for the radioactive $^{132}$Sn+$^{58}$Ni and stable $^{130}$Te+$^{58,64}$Ni systems at energies near the Coulomb barrier. Through a comparison with previous Sn+Ni measurements, the role of transfer couplings on the heavy-ion fusion has been examined. While the number of positive Q-value neutron transfer channels varied widely between the different Sn+Ni and Te+Ni systems, the reduced excitation functions were equivalent. This is in contrast to a number of previous studies where large enhancements in the sub-barrier fusion cross sections were observed in systems with positive Q-value neutron transfer channels. The present results suggest a significant change in the influence of transfer couplings on the fusion process for the Sn+Ni and Te+Ni systems. This work was supported by DOE Office of Nuclear Physics [Preview Abstract] |
Friday, October 28, 2011 3:48PM - 4:00PM |
JE.00010: Fusion reactions with the halo nucleus $^{15}$C M. Alcorta, K.E. Rehm, B.B. Back, P.F. Bertone, B. DiGiovine, H. Esbensen, J.P. Greene, C.R. Hoffman, C.L. Jiang, R.C. Pardo, A.M. Rogers, S. Bedoor, A.H. Wuosmaa, C.M. Deibel, J.C. Lighthall, S.T. Marley, M. Paul, C. Ugalde We have for the first time studied the fusion-fission excitation functions for the systems $^{14,15}$C + $^{232}$Th at energies in the vicinity of the Coulomb barrier. A radioactive $^{15}$C beam was produced using the ATLAS In-Flight Technique at Argonne National Laboratory. The intensity of the $^{15}$C beam was on the order of $1\times10^6$ ions/s at the highest energy with a $^{14}$C contamination of only 3\%. The results of the experiment show that at energies below the barrier, the fusion cross section of the halo nucleus $^{15}$C, with an s$_{1/2}$ neutron weakly bound to the closed neutron shell nucleus $^{14}$C, is enhanced by a factor of 2-5, while the fusion cross section for $^{14}$C follows a trend similar to that of $^{12,13}$C. The experimental results will be presented and compared to various theoretical models. [Preview Abstract] |
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