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 JC: Nuclear Reactions: Heavy Ions & Rare Isotope Beams |
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Chair: Kate Jones, University of Tennessee Room: Sweeny C |
Friday, November 5, 2010 2:00PM - 2:12PM |
JC.00001: Neutron-Induced Fission Cross Section Measurements for Full Suite of Uranium Isotopes Alexander Laptev, Fredrik Tovesson, Tony Hill A well established program of neutron-induced fission cross section measurement at Los Alamos Neutron Science Center (LANSCE) is supporting the Fuel Cycle Research program (FC~R{\&}D). The incident neutron energy range spans energies from sub-thermal energies up to 200 MeV by measuring both the Lujan Center and the Weapons Neutron Research center (WNR). Conventional parallel-plate fission ionization chambers with actinide deposited foils are used as a fission detector. The time-of-flight method is implemented to measure neutron energy. Counting rate ratio from investigated and standard U-235 foils is translated into fission cross section ratio. Different methods of normalization for measured ratio are employed, namely, using of actinide deposit thicknesses, normalization to evaluated data, etc. Finally, ratios are converted to cross sections based on the standard U-235 fission cross section data file. Preliminary data for newly investigated isotopes U-236 and U-234 will be reported. Those new data complete a full suite of Uranium isotopes, which were investigated with presented experimental approach. When analysis of the new measured data will is completed, data will be delivered to evaluators. Having data for full set of Uranium isotopes will increase theoretical modeling capabilities and make new data evaluations much more reliable. [Preview Abstract] |
Friday, November 5, 2010 2:12PM - 2:24PM |
JC.00002: Neutron Induced Fission Measurements of $^{242m}$Am at DANCE A. Chyzh, C.Y. Wu, R.A. Macri, U. Agvaanlusan, W.E. Parker, P.A. Wilk, J.A. Becker, M. Jandel, T.A. Bredeweg, M.M. Fowler, E.M. Bond, M.B. Chadwick, R.R. Clement, A. Couture, J.M. O'Donnell, R.C. Haight, A.L. Keksis, R. Reifarth, R.S. Rundberg, J.L. Ullmann, D. Vieira, J.B. Wilhelmy, J.M. Wouters Neutron capture and fission reactions on actinieds often present challenges in measuring each of the reaction. Fission tagging detector used along with the Detector for Advanced Neutron Capture Experiments (DANCE) provides a way to measure $(n,f)$ and $(n,\gamma)$ reactions simultaneously. DANCE was used to measure $^{242m}$Am$(n,f)$ reaction along with a custom made fission-tagging parallel plate avalanche counter (PPAC). The results on fission related $\gamma$-ray multiplicity distribution, the $^{242m}$Am$(n,f)$ cross section, and the average $\gamma$-ray energy distribution are presented. [Preview Abstract] |
Friday, November 5, 2010 2:24PM - 2:36PM |
JC.00003: High-Spin Isomeric States in Nuclear Reactions Induced by He Isotopes Tatjana Chuvilskaya, Alla Shirokova The high-spin states production in nuclear reactions is reviewed. The analysis of various experiments, our estimates and calculations reveal that in different compound nucleus energy regions maximal relative yield of high-spin states can be realized by different projectiles: at low energies -- by neutrons, in $\sim $ 20 -- 50 MeV region -- by $\alpha $-particles, at higher energies -- by heavy ions. It was predicted [1] that there are energy ranges in which neutron-rich radioactive ions ($^{6,8}$He, for example) are favorable. $\sigma _{m}$/$\sigma _{g}$ (the ratio between the yields of high-spin $J_{m}$ and low-spin $J_{g}$ metastable states of a nucleus in one and the same reaction) e.g. the isomeric cross-section ratio is a very good indicator of high-spin states production capability of a nuclear reaction. These experiments demonstrate that maximal values of isomeric cross-section ratios (up to 30) are obtained in $\alpha $-particle induced reactions. Experiment with $^{6}$He beam [2] confirms the predictions of the work [1] concerning the prospects of neutron-rich radioactive-ion beams in high-spin states population. The results of calculations of the isomeric cross section ratios using the code EMPIRE-II-18 approach to statistical theory of nuclear reactions demonstrate rather good agreement with the experimental data. Due to that these prediction power of these calculation is confirmed. The results of widespread calculations of the isomeric cross-section ratios of the reactions with $^{6,8}$He are presented. [1] T.V.Chvilskaya et al., AIP-Conference Proceedings ENAM-98 1998. V. 455. P. 482. [2] P.A.DeYoung et al., Phys.Rev.C. 2000. V. 62. P.047601. [Preview Abstract] |
Friday, November 5, 2010 2:36PM - 2:48PM |
JC.00004: Single Particle States in $^{56}$Ni Alisher Sanetullaev, W.G. Lynch, M.B. Tsang, D. Bazin, D. Coupland, V. Henzl, D. Henzlova, M. Kilburn, Jenny Lee, A.M. Rogers, A. Signoracci, Z.Y. Sun, M. Youngs, M. Famiano, S. Hudan, P. O'Malley, W.A. Peters, K. Schmitt, D. Shapira, R.J. Charity, L.G. Sobotka Neutron spectroscopic factor of $^{56}$Ni using (p, d) neutron transfer reaction has been measured using 37 MeV/u $^{56}$Ni beam in inverse kinematics. The measurement was performed at NSCL using the high resolution silicon array, HiRA, to detect the deuterons in coincidence with the recoil residues detected in the S800 spectrometer. To test if $^{56}$Ni is a good core, the most direct way is to measure the single particle nature of the neutrons or protons in the f$_{7/2}$ orbits. Direct measurements of the spectroscopic factors of the neutron hole state in $^{56}$Ni using the pickup (p,d) reaction will determine if the neutron f$_{7/2}$ orbit is indeed a closed shell. In present work, preliminary experimental results will be presented. [Preview Abstract] |
Friday, November 5, 2010 2:48PM - 3:00PM |
JC.00005: Magnetic Moment Measurements on Sr-isotopes G.J. Kumbartzki, N. Benczer-Koller, D.A. Torres, G. Gurdal, K.-H. Speidel, T. Ahn, V. Anagnostatou, M. Elvers, P. Goddard, G. Ilie, A. Heinz, D. Raddeck, D. Savran, V. Werner Beams of even Sr isotopes were accelerated to 270 MeV at the Yale WNSL ESTU tandem accelerator. These beams were used to measure spin precessions of excited projectiles while and after traversing a polarized gadolinium foil. Transient field measurements in inverse kinematics is the method of choice when measuring magnetic moments of states with picoseconds life times with high statistical precision. However there are limiting factors, like power input to the target and lack of independent calibration points to extend and refine the parameterizations. The projectiles often pick up an alpha particle from the carbon of the multilayer target. Therefore, precession measurement on isotopes which are not available as stable beam can be simultaneously performed. Especially interesting is the reaction $^{12}$C($^{84}$Sr,2$\alpha$)$^{88}$Zr. The results of these measurements and the limitations of the method will be discussed. [Preview Abstract] |
Friday, November 5, 2010 3:00PM - 3:12PM |
JC.00006: Measurement of parallel and perpendicular momentum distributions of neutron-deficient projectile fragments M. Mosby, D.J. Morrissey, A. Gade, D. Weisshaar The parallel and perpendicular momentum widths of a variety of projectile fragments were measured for the first time using the S800 spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. A set of secondary beams from an $^{36}$Ar primary beam at 150 MeV/nucleon were fragmented in a beryllium target with the spectrograph centered at 0$^{\circ}$. The fragmentation products were identified at the focal plane and both the longitudinal and perpendicular momentum distributions were observed in a single setting. The resulting longitudinal momentum distributions have the expected growth with mass-loss (A$_{beam}$-A$_{frag}$). New information on the widths of the perpendicular momentum distribution will be presented and compared to the predictions in the literature. [Preview Abstract] |
Friday, November 5, 2010 3:12PM - 3:24PM |
JC.00007: Study of the $^{15}$C$(d,p)^{16}$C reaction A.H. Wuosmaa, J.C. Lighthall, S.T. Marley, D.V. Shetty, J.P. Schiffer, B.B. Back, S. Baker, C.M. Deibel, C.R. Hoffman, B.P. Kay, R.C. Pardo, K.E. Rehm, B.A. Brown, P. Fallon, A.O. Macchiavelli, H.Y. Lee, M. Wiedeking We report on a study of the neutron transfer reaction $^{15}$C($d,p)^{16}$C in inverse kinematics, using HELIOS (the HELIcal Orbit Spectrometer) at Argonne National Laboratory. Previous measurements of electromagnetic transition rates suggested exotic phenomena in $^{16}$C. The spectroscopic factors for neutron stripping provide complementary information about the wave functions of the relevant states in $^{16}$C. An 8 MeV/u $^{15}$C beam with intensity 1-2$\times 10^6$ particles per second bombarded a 110 $\mu$g/cm$^2$ CD$_2$ target. The emitted protons were transported in the HELIOS magnetic field and detected in the HELIOS silicon array. Angular distributions were measured for the lowest 5 states in $^{16}$C and relative spectroscopic factors were extracted. Mixing parameters for the two 0$^+$ states were determined. Results will be compared to shell-model calculations. Work supported by the U. S. DOE, Office of Nuclear Physics, under Contracts DE-FG02-04ER41320, DE-AC02-06CH11357, DE-AC02-05CH11231, DE-AC52-06NA25396, and DEAC52-07NA27344, and NSF Grants PHY-02-16783 and PHY-07-58099. [Preview Abstract] |
Friday, November 5, 2010 3:24PM - 3:36PM |
JC.00008: g-factor measurements using $\alpha$-transfer reactions above the Coulomb barrier D.A. Torres, N. Benczer-Koller, G.J. Kumbartzki, G. G\"urdal, Y.Y. Sharon, K.-H. Speidel, G. Illie, A. Heinz, T. Ahn, V. Werner, D. Radeck, M. Elvers, D. Savran, P. Goddard, V. Anagnostatou Magnetic moments of short-lived nuclear states, of the order of picoseconds, have been measured during the last decade thanks to significant improvements of the experimental techniques, from the production and acceleration of stable and radioactive beams, to the realization of highly segmented, high resolution $\gamma$-detector arrays coupled with charged particle detectors. Projectile excitation in inverse kinematics, using carbon as a scatters, facilitates the transfer of one $\alpha$ particle to the projectile. This reaction near to the Coulomb barrier can lead to probe ions not available in stable beams. In this talk experimental results of g-factor measurements of the first $2^+$ state of $^{92}$Zr and $^{100}$Pd will be presented (the latter has been measured for the first time). The states were populated using beams of $^{88}$Sr (at 260~MeV) and $^{96}$Ru (at 350 MeV), respectively, accelerated using the Tandem at the Wright Nuclear Structure Laboratory at Yale University. The experiments made use of $\alpha$-transfer reactions in inverse kinematic, combined with the transient magnetic field. Results and experimental challenges for future experiments will be discussed. [Preview Abstract] |
Friday, November 5, 2010 3:36PM - 3:48PM |
JC.00009: Fusion of $^{130}$Te and $^{58,64}$Ni near the Coulomb barrier J.F. Liang, J.M. Allmond, C.J. Gross, K. Lagergren, P.E. Mueller, D. Shapira, R.L. Varner Large sub-barrier fusion enhancement has been observed in reactions where a large number of neutron transfer channels with positive Q-values exists. The fusion excitation functions for $^{130}$Te on $^{58}$Ni and $^{64}$Ni have been measured. The slope of the fusion excitation function for $^{130}$Te+$^{58}$Ni was found to be less steep than that for $^{130}$Te+$^{64}$Ni in the sub-barrier region. This may be related to the fact that there are ten neutron transfer channels with positive Q-values in $^{130}$Te+$^{58}$Ni. In contrast, $^{130}$Te+$^{64}$Ni has only one neutron transfer channel with a positive Q-value. A comparison of the sub-barrier fusion enhancement and the number of neutron transfer channels with positive Q-values in other reactions will be presented. [Preview Abstract] |
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