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Sample records for neutron-rich argon beams

  1. Production of very neutron-rich nuclei with a {sup 76}Ge beam

    SciTech Connect

    Tarasov, O. B.; Portillo, M.; Baumann, T.; Bazin, D.; Ginter, T. N.; Hausmann, M.; Pereira, J.; Stolz, A.; Amthor, A. M.; Gade, A.; Nettleton, A.; Sherrill, B. M.; Thoennessen, M.; Inabe, N.; Kubo, T.; Morrissey, D. J.

    2009-09-15

    Production cross sections for neutron-rich nuclei from the fragmentation of a {sup 76}Ge beam at 132 MeV/u were measured. The longitudinal momentum distributions of 34 neutron-rich isotopes of elements 13{<=}Z{<=}27 were scanned using a novel experimental approach of varying the target thickness. Production cross sections with beryllium and tungsten targets were determined for a large number of nuclei, including 15 isotopes first observed in this work. These are the most neutron-rich nuclides of the elements 17{<=}Z{<=}25 ({sup 50}Cl, {sup 53}Ar, {sup 55,56}K, {sup 57,58}Ca, {sup 59,60,61}Sc, {sup 62,63}Ti, {sup 65,66}V, {sup 68}Cr, and {sup 70}Mn). A one-body Q{sub g} systematics is used to describe the production cross sections based on thermal evaporation from excited prefragments. Some of the fragments near {sup 58}Ca show anomalously large production cross sections.

  2. Heavy Ion Reactions with Neutron-Rich Beams - Proceedings of the Riken International Workshop

    NASA Astrophysics Data System (ADS)

    Yamaji, S.; Ishihara, M.; Takigawa, N.

    1993-11-01

    The Table of Contents for the book is as follows: * Preface * Opening Address * Fusion I * Heavy Ion Fusion at Subbarrier Energies: Progress and Questions * Angular Momentum in Heavy Ion Subbarrier Interaction * Fusion II * High Precision Fusion Excitation Function Measurements: What Can We Learn from Them? * Transfer Reactions for 16O + 144,152Sm near the Coulomb Barrier * Fusion III * Recent Theoretical Developments in the Study of Subbarrier Fusion * Direct Reaction Approach to Heavy Ion Scattering and Fusion at Energies near Coulomb Barrier * Fusion IV * Roles of Multi-Step Transfer in Fusion Process Induced by Heavy Ion Reactions * Special Session * RIKEN Accelerator Research Facility (RARF) * Fission I * Bimodal Nature of Nuclear Fission * Systematics of Isotope Production Rates: Mass Excess Dependence of Fission Products * Semiclassical Methods for the Multi-Dimensional Quantum Decay * Dynamics of Di-Nucleus Systems: Molecular Resonances * Fission II * The Competition Between Fusion-Fission and Deeply Inelastic Reactions in the Medium Mass Systems * Unstable Nuclei I * Coulomb Dissociation and Momentum Distributions for 11Li → 9Li+n+n Breakup Reactions * Unstable Nuclei II * Elastic Scattering and Fragmentation of Halo Nuclei * Secondary Reactions of Neutron-Rich Nuclei at Intermediate Energies * Life Time of Soft Dipole Excitation * Unstable Nuclei III * Shell Structure of Exotic Unstable Nuclei * Properties of Unstable Nuclei Within the Relativistic Many-Body Theory * Fusion with Unstable Nuclei * Barrier Distributions for Heavy Ion Fusion * Heavy Ion Reactions with Neutron-Rich Beams * Heavy Ion Fusion with Neutron-Rich Beams * Superheavy Elements * Study of α Decays Following 40Ar Bombardment on 238U * Production of Superheavy Elements via Fusion: What is Limiting Us? * Panel Session * Comments * List of Participants

  3. First in-beam γ -ray study of the level structure of neutron-rich 39S

    NASA Astrophysics Data System (ADS)

    Chapman, R.; Wang, Z. M.; Bouhelal, M.; Haas, F.; Liang, X.; Azaiez, F.; Behera, B. R.; Burns, M.; Caurier, E.; Corradi, L.; Curien, D.; Deacon, A. N.; Dombrádi, Zs.; Farnea, E.; Fioretto, E.; Gadea, A.; Hodsdon, A.; Ibrahim, F.; Jungclaus, A.; Keyes, K.; Kumar, V.; Lunardi, S.; Mǎrginean, N.; Montagnoli, G.; Napoli, D. R.; Nowacki, F.; Ollier, J.; O'Donnell, D.; Papenberg, A.; Pollarolo, G.; Salsac, M.-D.; Scarlassara, F.; Smith, J. F.; Spohr, K. M.; Stanoiu, M.; Stefanini, A. M.; Szilner, S.; Trotta, M.; Verney, D.

    2016-08-01

    The neutron-rich 39S nucleus has been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of 36S ions with a thin 208Pb target. The magnetic spectrometer, PRISMA, and the γ -ray array, CLARA, were used in the measurements. Gamma-ray transitions of the following energies were observed: 339, 398, 466, 705, 1517, 1656, and 1724 keV. Five of the observed transitions have been tentatively assigned to the decay of excited states with spins up to (11 /2- ). The results of a state-of-the-art shell-model calculation of the level scheme of 39S using the SDPF-U effective interaction are also presented. The systematic behavior of the excitation energy of the first 11 /2- states in the odd-A isotopes of sulfur and argon is discussed in relation to the excitation energy of the first excited 2+ states of the adjacent even-A isotopes. The states of 39S that have the components in their wave functions corresponding to three neutrons in the 1 f7 /2 orbital outside the N =20 core have also been discussed within the context of the 0 ℏ ω shell-model calculations presented here.

  4. Production of neutron-rich Ca, Sn, and Xe isotopes in transfer-type reactions with radioactive beams

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Lacroix, D.

    2010-12-15

    The production cross sections of neutron-rich isotopes {sup 52,54,56,58,60}Ca, {sup 136,138,140,142}Sn, and {sup 146,148,150,152}Xe are predicted for future experiments in the diffusive multinucleon transfer reactions {sup 86,90,92,94}Kr, {sup 124,130,132,134}Sn, {sup 136,140,142,146}Xe, and {sup 138,144,146}Ba+{sup 48}Ca with stable and radioactive beams at incident energies close to the Coulomb barrier. Because of the small cross sections, the production of neutron-rich isotopes requires the optimal choice of projectile-target combinations and bombarding energies.

  5. Production of beams of neutron-rich nuclei between Ca and Ni using the ion-guide technique

    SciTech Connect

    Perajarvi, K.; Cerny, J.; Hager, U.; Hakala, J.; Huikari, J.; Jokinen, A.; Karvonen, P.; Kurpeta, J.; Lee, D.; Moore, I.; Penttila, H.; Popov, A.; Aysto, J.

    2004-09-28

    Since several elements between Z = 20-28 are refractory in their nature, their neutron-rich isotopes are rarely available as low energy Radioactive Ion Beams (RIB) in ordinary Isotope Separator On-Line facilities [1-4]. These low energy RIBs would be especially interesting to have available under conditions which allow high-resolution beta-decay spectroscopy, ion-trapping and laser-spectroscopy. As an example, availability of these beams would open a way for research which could produce interesting and important data on neutron-rich nuclei around the doubly magic {sup 78}Ni. One way to overcome the intrinsic difficulty of producing these beams is to rely on the chemically unselective Ion Guide Isotope Separator On-Line (IGISOL) technique [5]. Quasi- and deep-inelastic reactions, such as {sup 197}Au({sup 65}Cu,X)Y, could be used to produce these nuclei in existing IGISOL facilities, but before they can be successfully incorporated into the IGISOL concept their kinematics must be well understood. Therefore the reaction kinematics part of this study was first performed at the Lawrence Berkeley National Laboratory using its 88'' cyclotron and, based on those results, a specialized target chamber was built[6]. The target chamber shown in Fig. 1 was recently tested on-line at the Jyvaaskylaa IGISOL facility. Yields of mass-separated radioactive projectile-like species such as {sup 62,63}Co are about 0.8 ions/s/pnA, corresponding to about 0.06 % of the total IGISOL efficiency for the products that hit the Ni-degrader. (The current maximum 443 MeV {sup 65}Cu beam intensity at Jyvaaskylaa is about 20 pnA.) This total IGISOL efficiency is a product of two coupled loss factors, namely inadequate thermalization and the intrinsic IGISOL efficiency. In our now tested chamber, about 9 % of the Co recoils are thermalized in the owing He gas (p{sub He}=300 mbar) and about 0.7 % of them are converted into the mass-separated ion beams. In the future, both of these physical

  6. Near and sub-barrier fusion of neutron-rich oxygen and carbon nuclei using low-intensity beams

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy K.

    Fusion between neutron-rich light nuclei in the crust of an accreting neutron star has been proposed as a heat source that triggers an X-ray superburst. To explore the probability with which such fusion events occur and examine their decay characteristics, an experimental program using beams of neutron-rich light nuclei has been established. Evaporation residues resulting from the fusion of oxygen and 12C nuclei, are directly measured and distinguished from unreacted beam particles on the basis of their energy and time-of-flight. Using an experimental setup developed for measurements utilizing low-intensity (< 105 ions/s) radioactive beams, the fusion excitation functions for 16O + 12C and 18O + 12C have been measured. The fusion excitation function for 18O + 12C has been measured in the sub-barrier domain down to the 820 mub level, a factor of 30 lower than previous direct measurements. This measured fusion excitation function is compared to the predictions of a density constrained time-dependent Hartree-Fock model. This comparison reveals a shape difference in the fusion excitation functions, indicating a larger tunneling probability for the experimental data as compared to the theoretical calculations. In addition to the measured cross-section, the measured angular distribution of the evaporation residues provides insight into the relative importance of the different de-excitation channels. These evaporation residue angular distributions are compared to the predictions of a statistical model code, evapOR, revealing an under-prediction of the de-excitation channels associated with alpha particle emission.

  7. Theoretical study on production of heavy neutron-rich isotopes around the N = 126 shell closure in radioactive beam induced transfer reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou

    2017-04-01

    In order to produce more unknown neutron-rich nuclei around N = 126, the transfer reactions 136Xe + 198Pt, 136-144Xe + 208Pb, and 132Sn + 208Pb are investigated within the framework of the dinuclear system (DNS) model. The influence of neutron excess of projectile on production cross sections of target-like products is studied through the reactions 136,144Xe + 208Pb. We find that the radioactive projectile 144Xe with much larger neutron excess is favorable to produce neutron-rich nuclei with charge number less than the target rather than produce transtarget nuclei. The incident energy dependence of yield distributions of fragments in the reaction 132Sn + 208Pb are also studied. The production cross sections of neutron-rich nuclei with Z = 72- 77 are predicted in the reactions 136-144Xe + 208Pb and 132Sn + 208Pb. It is noticed that the production cross sections of unknown neutron-rich nuclei in the reaction 144Xe + 208Pb are at least two orders of magnitude larger than those in the reaction 136Xe + 208Pb. The radioactive beam induced transfer reactions 139,144Xe + 208Pb, considering beam intensities proposed in SPIRAL2 (Production System of Radioactive Ion and Acceleration On-Line) project as well, for production of neutron-rich nuclei around the N = 126 shell closure are investigated for the first time. It is found that, in comparison to the stable beam 136Xe, the radioactive beam 144Xe shows great advantages for producing neutron-rich nuclei with N = 126 and the advantages get more obvious for producing nuclei with less charge number.

  8. Exploiting neutron-rich radioactive ion beams to constrain the symmetry energy

    NASA Astrophysics Data System (ADS)

    Kohley, Z.; Christian, G.; Baumann, T.; DeYoung, P. A.; Finck, J. E.; Frank, N.; Jones, M.; Smith, J. K.; Snyder, J.; Spyrou, A.; Thoennessen, M.

    2013-10-01

    The Modular Neutron Array (MoNA) and 4 Tm Sweeper magnet were used to measure the free neutrons and heavy charged particles from the radioactive ion beam induced 32Mg+9Be reaction. The fragmentation reaction was simulated with the constrained molecular dynamics model (CoMD), which demonstrated that the of the heavy fragments and free neutron multiplicities were observables sensitive to the density dependence of the symmetry energy at subsaturation densities. Through comparison of these simulations with the experimental data, constraints on the density dependence of the symmetry energy were extracted. The advantage of radioactive ion beams as a probe of the symmetry energy is demonstrated through examination of CoMD calculations for stable and radioactive-beam-induced reactions.

  9. Characterization of uranium carbide target materials to produce neutron-rich radioactive beams

    NASA Astrophysics Data System (ADS)

    Tusseau-Nenez, Sandrine; Roussière, Brigitte; Barré-Boscher, Nicole; Gottberg, Alexander; Corradetti, Stefano; Andrighetto, Alberto; Cheikh Mhamed, Maher; Essabaa, Saïd; Franberg-Delahaye, Hanna; Grinyer, Joanna; Joanny, Loïc; Lau, Christophe; Le Lannic, Joseph; Raynaud, Marc; Saïd, Abdelhakim; Stora, Thierry; Tougait, Olivier

    2016-03-01

    In the framework of a R&D program aiming to develop uranium carbide (UCx) targets for radioactive nuclear beams, the Institut de Physique Nucléaire d'Orsay (IPNO) has developed an experimental setup to characterize the release of various fission fragments from UCx samples at high temperature. The results obtained in a previous study have demonstrated the feasibility of the method and started to correlate the structural properties of the samples and their behavior in terms of nuclear reaction product release. In the present study, seven UCx samples have been systematically characterized in order to better understand the correlation between their physicochemical characteristics and release properties. Two very different samples, the first one composed of dense UC and the second one of highly porous UCx made of multi-wall carbon nanotubes, were provided by the ActILab (ENSAR) collaboration. The others were synthesized at IPNO. The systems for irradiation and heating necessary for the release studies have been improved with respect to those used in previous studies. The results show that the open porosity is hardly the limiting factor for the fission product release. The homogeneity of the microstructure and the pore size distribution contributes significantly to the increase of the release. The use of carbon nanotubes in place of traditional micrometric graphite particles appears to be promising, even if the homogeneity of the microstructure can still be enhanced.

  10. In-Beam {gamma}-Ray Spectroscopy of the N=50 Isotones on the Neutron-Rich Side

    SciTech Connect

    Prevost, A.; Astier, A.; Deloncle, I.; Porquet, M.-G.; Lucas, R.

    2005-11-21

    High-spin states of 84Se, produced as a fission fragment in the fusion-fission reaction 18O+208Pb and studied with the EUROBALL IV array, have been identified for the first time. Their interpretation gives new insights about the evolution of the N=50 shell gap at the vicinity of 78Ni. To characterize this evolution, it would be worth using a new device devoted to the high-spin studies of neutron-rich nuclei produced by asymmetric fission modes. Such dedicated studies are reported in a second part.

  11. Neutron-rich rare-isotope production from projectile fission of heavy nuclei near 20 MeV/nucleon beam energy

    NASA Astrophysics Data System (ADS)

    Vonta, N.; Souliotis, G. A.; Loveland, W.; Kwon, Y. K.; Tshoo, K.; Jeong, S. C.; Veselsky, M.; Bonasera, A.; Botvina, A.

    2016-12-01

    We investigate the possibilities of producing neutron-rich nuclides in projectile fission of heavy beams in the energy range of 20 MeV/nucleon expected from low-energy facilities. We report our efforts to theoretically describe the reaction mechanism of projectile fission following a multinucleon transfer collision at this energy range. Our calculations are mainly based on a two-step approach: The dynamical stage of the collision is described with either the phenomenological deep-inelastic transfer model (DIT) or with the microscopic constrained molecular dynamics model (CoMD). The de-excitation or fission of the hot heavy projectile fragments is performed with the statistical multifragmentation model (SMM). We compared our model calculations with our previous experimental projectile-fission data of 238U (20 MeV/nucleon) + 208Pb and 197Au (20 MeV/nucleon) + 197Au and found an overall reasonable agreement. Our study suggests that projectile fission following peripheral heavy-ion collisions at this energy range offers an effective route to access very neutron-rich rare isotopes toward and beyond the astrophysical r-process path.

  12. Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

    NASA Astrophysics Data System (ADS)

    Tetsuya Ohnishi,; Toshiyuki Kubo,; Kensuke Kusaka,; Atsushi Yoshida,; Koichi Yoshida,; Masao Ohtake,; Naoki Fukuda,; Hiroyuki Takeda,; Daisuke Kameda,; Kanenobu Tanaka,; Naohito Inabe,; Yoshiyuki Yanagisawa,; Yasuyuki Gono,; Hiroshi Watanabe,; Hideaki Otsu,; Hidetada Baba,; Takashi Ichihara,; Yoshitaka Yamaguchi,; Maya Takechi,; Shunji Nishimura,; Hideki Ueno,; Akihiro Yoshimi,; Hiroyoshi Sakurai,; Tohru Motobayashi,; Taro Nakao,; Yutaka Mizoi,; Masafumi Matsushita,; Kazuo Ieki,; Nobuyuki Kobayashi,; Kana Tanaka,; Yosuke Kawada,; Naoki Tanaka,; Shigeki Deguchi,; Yoshiteru Satou,; Yosuke Kondo,; Takashi Nakamura,; Kenta Yoshinaga,; Chihiro Ishii,; Hideakira Yoshii,; Yuki Miyashita,; Nobuya Uematsu,; Yasutsugu Shiraki,; Toshiyuki Sumikama,; Junsei Chiba,; Eiji Ideguchi,; Akito Saito,; Takayuki Yamaguchi,; Isao Hachiuma,; Takeshi Suzuki,; Tetsuaki Moriguchi,; Akira Ozawa,; Takashi Ohtsubo,; Michael A. Famiano,; Hans Geissel,; Anthony S. Nettleton,; Oleg B. Tarasov,; Daniel P. Bazin,; Bradley M. Sherrill,; Shashikant L. Manikonda,; Jerry A. Nolen,

    2010-07-01

    A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: 71Mn, 73,74Fe, 76Co, 79Ni, 81,82Cu, 84,85Zn, 87Ga, 90Ge, 95Se, 98Br, 101Kr, 103Rb, 106,107Sr, 108,109Y, 111,112Zr, 114,115Nb, 115,116,117Mo, 119,120Tc, 121,122,123,124Ru, 123,124,125,126Rh, 127,128Pd, 133Cd, 138Sn, 140Sb, 143Te, 145I, 148Xe, and 152Ba.

  13. In-beam gamma-ray spectroscopy of very neutron-rich nuclei: excited states in 46S and 48Ar.

    PubMed

    Gade, A; Adrich, P; Bazin, D; Brown, B A; Cook, J M; Diget, C Aa; Glasmacher, T; McDaniel, S; Ratkiewicz, A; Siwek, K; Weisshaar, D

    2009-05-08

    We report on the first in-beam gamma-ray spectroscopy study of the very neutron-rich nucleus 46S. The N=30 isotones 46S and 48Ar were produced in a novel way in two steps that both necessarily involve nucleon exchange and neutron pickup reactions 9Be(48Ca,48K)X followed by 9Be(48K,48Ar+gamma)X at 85.7 MeV/u midtarget energy and 9Be(48Ca,46Cl)X followed by 9Be(46Cl,46S+gamma)X at 87.0 MeV/u midtarget energy, respectively. The results are compared to large-scale shell-model calculations in the sd-pf shell using the SDPF-NR effective interaction and Z-dependent modifications.

  14. In-Beam {gamma}-Ray Spectroscopy of Very Neutron-Rich Nuclei: Excited States in {sup 46}S and {sup 48}Ar

    SciTech Connect

    Gade, A.; Brown, B. A.; Cook, J. M.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Siwek, K.; Adrich, P.; Bazin, D.; Diget, C. A.; Weisshaar, D.

    2009-05-08

    We report on the first in-beam {gamma}-ray spectroscopy study of the very neutron-rich nucleus {sup 46}S. The N=30 isotones {sup 46}S and {sup 48}Ar were produced in a novel way in two steps that both necessarily involve nucleon exchange and neutron pickup reactions {sup 9}Be({sup 48}Ca,{sup 48}K)X followed by {sup 9}Be({sup 48}K,{sup 48}Ar+{gamma})X at 85.7 MeV/u midtarget energy and {sup 9}Be({sup 48}Ca,{sup 46}Cl)X followed by {sup 9}Be({sup 46}Cl,{sup 46}S+{gamma})X at 87.0 MeV/u midtarget energy, respectively. The results are compared to large-scale shell-model calculations in the sd-pf shell using the SDPF-NR effective interaction and Z-dependent modifications.

  15. Identification of 45 new neutron-rich isotopes produced by in-flight fission of a {sup 238}U beam at 345 MeV/nucleon.

    SciTech Connect

    Ohnishi, T.; Kubo, T.; Kusaka, K.; Yoshida, A.; Yoshida, K.; Manikonda, S.; Nolen, J.

    2010-07-12

    A search for new isotopes using in-flight fission of a 345 MeV/nucleon {sup 238}U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: {sup 71}Mn, {sup 73,74}Fe, {sup 76}Co, {sup 79}Ni, {sup 81,82}Cu, {sup 84,85}Zn, {sup 87}Ga, {sup 90}Ge, {sup 95}Se, {sup 98}Br, {sup 101}Kr, {sup 103}Rb, {sup 106,107}Sr, {sup 108,109}Y, {sup 111,112}Zr, {sup 114,115}Nb, {sup 115,116,117}Mo, {sup 119,120}Tc, {sup 121,122,123,124}Ru, {sup 123,124,125,126}Rh, {sup 127,128}Pd, {sup 133}Cd, {sup 138}Sn, {sup 140}Sb, {sup 143}Te, {sup 145}I, {sup 148}Xe, and {sup 152}Ba.

  16. Experimental and numerical study of high intensity argon cluster beams

    SciTech Connect

    Korobeishchikov, N. G.; Kalyada, V. V.; Shmakov, A. A.; Zarvin, A. E.; Skovorodko, P. A.

    2014-12-09

    Experimental and numerical investigations of expansion of argon with homogeneous condensation in supersonic conical nozzle and in free jet behind it were carried out. Optimal parameters (stagnation pressure, nozzle-skimmer distance) for the formation of cluster beam with maximum intensity were determined. Two available models for nonequilibrium nucleation were tested. The numerical results are in satisfactory agreement with the measured data.

  17. Spectroscopy of Argon Excited in an Electron Beam Ion Trap

    SciTech Connect

    Trabert, E

    2005-04-18

    Argon is one of the gases best investigated and most widely used in plasma discharge devices for a multitude of applications that range from wavelength reference standards to controlled fusion experiments. Reviewing atomic physics and spectroscopic problems in various ionization stages of Ar, the past use and future options of employing an electron beam ion trap (EBIT) for better and more complete Ar data in the x-ray, EUV and visible spectral ranges are discussed.

  18. Pulsed electron beam propagation in argon and nitrogen gas mixture

    SciTech Connect

    Kholodnaya, G. E.; Sazonov, R. V.; Ponomarev, D. V.; Remnev, G. E.; Zhirkov, I. S.

    2015-10-15

    The paper presents the results of current measurements for the electron beam, propagating inside a drift tube filled in with a gas mixture (Ar and N{sub 2}). The experiments were performed using the TEA-500 pulsed electron accelerator. The main characteristics of electron beam were as follows: 60 ns pulse duration, up to 200 J energy, and 5 cm diameter. The electron beam propagated inside the drift tube assembled of three sections. Gas pressures inside the drift tube were 760 ± 3, 300 ± 3, and 50 ± 1 Torr. The studies were performed in argon, nitrogen, and their mixtures of 33%, 50%, and 66% volume concentrations, respectively.

  19. Photoneutron cross sections for unstable neutron-rich oxygen isotopes.

    PubMed

    Leistenschneider, A; Aumann, T; Boretzky, K; Cortina, D; Cub, J; Datta Pramanik, U; Dostal, W; Elze, T W; Emling, H; Geissel, H; Grünschloss, A; Hellstr, M; Holzmann, R; Ilievski, S; Iwasa, N; Kaspar, M; Kleinböhl, A; Kratz, J V; Kulessa, R; Leifels, Y; Lubkiewicz, E; Münzenberg, G; Reiter, P; Rejmund, M; Scheidenberger, C; Schlegel, C; Simon, H; Stroth, J; Sümmerer, K; Wajda, E; Walús, W; Wan, S

    2001-06-11

    The dipole response of stable and unstable neutron-rich oxygen nuclei of masses A = 17 to A = 22 has been investigated experimentally utilizing electromagnetic excitation in heavy-ion collisions at beam energies about 600 MeV/nucleon. A kinematically complete measurement of the neutron decay channel in inelastic scattering of the secondary beam projectiles from a Pb target was performed. Differential electromagnetic excitation cross sections d sigma/dE were derived up to 30 MeV excitation energy. In contrast to stable nuclei, the deduced dipole strength distribution appears to be strongly fragmented and systematically exhibits a considerable fraction of low-lying strength.

  20. Excited states of neutron rich Pd from fragmentation

    NASA Astrophysics Data System (ADS)

    Hecht, A. A.; Walters, W. B.; Hoteling, N.; Mantica, P. F.; Becerril, A.; Fleckenstein, T.; Lorusso, G.; Pereira, J.; Pinter, J.; Stoker, J.; Quinn, M.

    2007-04-01

    The neutron rich region approaching N=82 and Z=50 is interesting for nuclear structure and nuclear astrophysics, both as a test of the shell closures far from stability and as the path for r-process nucleosynthesis. This region is difficult to access with fusion-evaporation reactions and novel techniques must be used. At the National Superconducting Cyclotron Laboratory (NSCL) an experiment was recently performed by fragmentation of a Xe beam using a Be target to examine isomers and beta decay from these neutron rich nuclei. The radioisotope fragments passed through several Si planar detectors and were implanted in a double-sided Si strip detector (DSSD) in the Beta Counting System (BCS). Fragments were identified via δE and TOF. Particle emitting decays were tracked in several layers of single sided strip detectors following the DSSD, while the SEGA array surrounding the DSSD was used to collect gamma emission following beta and isomer decay. Several neutron rich nuclei were observed in this experiment, including Ru, Rh, Pd, Ag, Cd, and In. Results on Pd will be discussed.

  1. Concerning Apparent Similarity of Structures of Fluoropolymer Surfaces Exposed to an Argon Plasma or Argon Ion Beam

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Covington, M. Alan (Technical Monitor)

    1995-01-01

    X-ray photoelectron spectroscopy (XPS) C(sub 1s) spectra of fluoropolymers exposed to either an argon plasma or argon ion beam show remarkable similarity, implying that the surface-modification reactions for these two processes likely proceed through comparable mechanisms, revolving predominantly ion-surface interactions. The importance of working with a monochromatized x-ray source for XPS analysis of the surface-modified fluoropolymers is once again emphasized.

  2. Probing neutron rich matter with parity violation

    NASA Astrophysics Data System (ADS)

    Horowitz, Charles

    2016-03-01

    Many compact and energetic astrophysical systems are made of neutron rich matter. In contrast, most terrestrial nuclei involve approximately symmetric nuclear matter with more equal numbers of neutrons and protons. However, heavy nuclei have a surface region that contains many extra neutrons. Precision measurements of this neutron rich skin can determine properties of neutron rich matter. Parity violating electron scattering provides a uniquely clean probe of neutrons, because the weak charge of a neutron is much larger than that of a proton. We describe first results and future plans for the Jefferson Laboratory experiment PREX that measures the thickness of the neutron skin in 208Pb. Another JLAB experiment CREX will measure the neutron radius of 48Ca and test recent microscopic calculations of this neutron rich 48 nucleon system. Finally, we show how measuring parity violation at multiple momentum transfers can determine not just the neutron radius but the full radial structure of the neutron density in 48Ca. A neutron star is eighteen orders of magnitude larger than a nucleus (km vs fm) but both the star and the neutron rich nuclear skin are made of the same neutrons, with the same strong interactions, and the same equation of state. A large pressure pushes neutrons out against surface tension and gives a thick neutron skin. Therefore, PREX will constrain the equation of state of neutron rich matter and improve predictions for the structure of neutron stars. Supported in part by DOE Grants DE-FG02-87ER40365 (Indiana University) and DE-SC0008808 (NUCLEI SciDAC Collaboration).

  3. Temporal evolution of electron beam generated Argon plasma in pasotron device

    NASA Astrophysics Data System (ADS)

    Khandelwal, Neha; Pal, U. N.; Prakash, Ram; Choyal, Y.

    2016-10-01

    The plasma- assisted slow wave oscillator (PASOTRON) is a high power microwave source in which the electron beam in the interaction region is confined by the background plasma. The plasma is generated by impact ionization of background gas with the electron beam. A model has been developed for temporal evolution of Argon plasma in pasotron device. In this model, we consider electron beam of energy E interacting with Argon gas. The resulting ionization creates quasi neutral argon plasma composed of argon Ar atoms, singly ionized ions Ar+1and electrons having energy from 0 to E. Electron impact excitation, ionization, radiative decay, radiative recombination and three body recombination processes are considered in this model. Population of ground and excited states of argon atom, ground state of argon ion as well as the population of electron energy groups is calculated by solving time dependent rate equations. Temporal evolution of electron beam generated plasma is given.

  4. Time-of-Flight Mass Measurements of Neutron Rich Nuclides

    NASA Astrophysics Data System (ADS)

    Estrade, A.; Matos, M.; Amthor, A. M.; Becerril, A.; Elliot, T.; Lorusso, G.; Rogers, A.; Schatz, H.; Bazin, D.; Gade, A.; Portillo, M.; Stolz, A.; Galaviz, D.; Pereira, J.; Shapira, D.; Smith, E.; Wallace, M.

    2008-10-01

    Nuclear masses of neutron rich isotopes in the region of Z ˜ 20-30 have been measured using the time-of-flight technique at the National Superconducting Cyclotron Laboratory (NSCL). The masses of 5 isotopes have been measured for the first time, and the precision of several other masses has been improved. The time-of-flight technique has shown the potential to access nuclear masses very far from stability when applied at radioactive beam facilities like the NSCL. Such measurements are important for understanding nuclear structure far from the valley of β-stability, and provide valuable information for astrophysical model calculations of processes involving very unstable nuclides.

  5. Dipole response of neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Klimkiewicz, A.; Adrich, P.; Boretzky, K.; Fallot, M.; Aumann, T.; Cortina-Gil, D.; Datta Pramanik, U.; Elze, Th. W.; Emling, H.; Geissel, H.; Hellstroem, M.; Jones, K. L.; Kratz, J. V.; Kulessa, R.; Leifels, Y.; Nociforo, C.; Palit, R.; Simon, H.; Surowka, G.; Sümmerer, K.; Typel, S.; Walus, W.

    2007-05-01

    The neutron-rich isotopes 129-133Sn were studied in a Coulomb excitation experiment at about 500 AMeV using the FRS-LAND setup at GSI. From the exclusive measurement of all projectile-like particles following the excitation and decay of the projectile in a high-Z target, the energy differential cross section can be extracted. At these beam energies dipole transitions are dominating, and within the semi-classical approach the Coulomb excitation cross sections can be transformed into photoabsorption cross sections. In contrast to stable Sn nuclei, a substantial fraction of dipole strength is observed at energies below the giant dipole resonance (GDR). For 130Sn and 132Sn this strength is located in a peak-like structure around 10 MeV excitation energy and exhibits a few percent of the Thomas-Reiche Kuhn (TRK) sum-rule strength. Several calculations predict the appearance of dipole strength at low excitation energies in neutron-rich nuclei. This low-lying strength is often referred to as pygmy dipole resonance (PDR) and, in a macroscopic picture, is discussed in terms of a collective oscillation of excess neutrons versus the core nucleons. Moreover, a sharp rise is observed at the neutron separation threshold around 5 MeV for the odd isotopes. A possible contribution of 'threshold strength', which can be described within the direct-breakup model is discussed. The results for the neutron-rich Sn isotopes are confronted with results on stable nuclei investigated in experiments using real photons.

  6. Effective Interactions in Neutron-Rich Matter

    SciTech Connect

    Sammarruca, F.; Krastev, P.; Barredo, W.

    2005-10-14

    We are generally concerned with probing the behavior of the isospin-asymmetric equation of state. In particular, we will discuss the one-body potentials for protons and neutrons obtained from our Dirac-Brueckner-Hartree-Fock calculations of neutron-rich matter properties. We will also present predictions of proton-proton and neutron-neutron cross sections in the isospin-asymmetric nuclear medium.

  7. Fission and Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Hamilton, Joseph H.; Ramayya, A. V.; Carter, H. K.

    2008-08-01

    Opening session. Nuclear processes in stellar explosions / M. Wiescher. In-beam [symbol]-ray spectroscopy of neutron-rich nuclei at NSCL / A. Gade -- Nuclear structure I. Shell-model structure of neutron-rich nuclei beyond [symbol]Sn / A. Covello ... [et al.]. Shell structure and evolution of collectivity in nuclei above the [symbol]Sn core / S. Sarkar and M. S. Sarkar. Heavy-ion fusion using density-constrained TDHF / A. S. Umar and V. E. Oberacker. Towards an extended microscopic theory for upper-fp shell nuclei / K. P. Drumev. Properties of the Zr and Pb isotopes near the drip-line / V. N. Tarasov ... [et al.]. Identification of high spin states in [symbol] Cs nuclei and shell model calculations / K. Li ... [et al.]. Recent measurements of spherical and deformed isomers using the Lohengrin fission-fragment spectrometer / G. S. Simpson ... [et al.] -- Nuclear structure II. Nuclear structure investigation with rare isotope spectroscopic investigations at GSI / P. Boutachkov. Exploring the evolution of the shell structures by means of deep inelastic reactions / G. de Anaelis. Probing shell closures in neutron-rich nuclei / R. Krücken for the S277 and REX-ISOLDEMINIBALL collaborations. Structure of Fe isotopes at the limits of the pf-shell / N. Hoteling ... [et al.]. Spectroscopy of K isomers in shell-stabilized trans-fermium nuclei / S. K. Tandel ... [et al.] -- Radioactive ion beam facilities. SPIRAL2 at GANIL: a world leading ISOL facility for the next decade / S. Gales. New physics at the International Facility for Antiproton and Ion Research (FAIR) next to GSI / I. Augustin ... [et al.]. Radioactive beams from a high powered ISOL system / A. C. Shotter. RlKEN RT beam factory / T. Motobayashi. NSCL - ongoing activities and future perspectives / C. K. Gelbke. Rare isotope beams at Argonne / W. F. Henning. HRIBF: scientific highlights and future prospects / J. R. Beene. Radioactive ion beam research done in Dubna / G. M. Ter-Akopian ... [et al.] -- Fission I

  8. Lead Pipe Scale Analysis Using Broad-Beam Argon Ion Milling to Elucidate Drinking Water Corrosion

    EPA Science Inventory

    Herein, we compared the characterization of lead pipe scale removed from a drinking water distribution system using two different cross section methods (conventional polishing and argon ion beam etching). The pipe scale solids were analyzed using scanning electron microscopy (SEM...

  9. Structure of neutron-rich nuclei

    SciTech Connect

    Nazarewicz, W. ||

    1997-11-01

    One of the frontiers of today`s nuclear science is the ``journey to the limits``: of atomic charge and nuclear mass, of neutron-to-proton ratio, and of angular momentum. The new data on exotic nuclei are expected to bring qualitatively new information about the fundamental properties of the nucleonic many-body system, the nature of the nuclear interaction, and nucleonic correlations at various energy-distance scales. In this talk, current developments in nuclear structure of neutron-rich nuclei are discussed from a theoretical perspective.

  10. ARCS 3 ionospheric artificial argon ion beam injections - Waves near the heavy ion gyrofrequencies

    NASA Technical Reports Server (NTRS)

    Erlandson, R. E.; Cahill, L. J., Jr.; Kaufmann, R. L.; Arnoldy, R. L.; Pollock, C. J.

    1989-01-01

    Low-frequency electric field data below the proton gyrofrequency are presented for the duration of the argon ion beam experiment conducted as part of the Argon Release for Controlled Studies (ARCS) program. An argon ion beam was injected from the subpayload antiparallel or perpendicular to the magnetic field at altitudes from 250 to 405 km. During the injections, the wave spectra were broadband near the subpayload and narrow-band near heavy ion gyrofrequencies at perpendicular separation distances between 42 and 254 m. It is suggested that the narrow-band waves are associated with both the perpendicular argon ion beam and an unexpected flux of low-energy ions which peaked in energy near 15 eV and pitch angle near 90 deg with respect to the magnetic field.

  11. Studies of neutron-rich nuclei using the CPT mass spectrometer at CARIBU

    NASA Astrophysics Data System (ADS)

    Chaudhuri, A.; Bertone, P. F.; Buchinger, F.; Caldwell, S.; Clark, J. A.; Crawford, J. E.; Deibel, C. M.; Gulick, S.; Lascar, D.; Levand, A. F.; Li, G.; Savard, G.; Segel, R. E.; Sharma, K. S.; Sternberg, M. G.; Sun, T.; Van Schelt, J.

    2011-09-01

    The nucleosynthetic path of the astrophysical r-process and the resulting elemental abundances depend on neutron-separation energies which can be determined from the masses of the nuclei along the r-process reaction path. Due to the current lack of experimental data, mass models are often used. The mass values provided by the mass models are often too imprecise or disagree with each other. Therefore, direct high-precision mass measurements of neutron-rich nuclei are necessary to provide input parameters to the calculations and help refine the mass models. The Californium Rare Isotope Breeder Upgrade (CARIBU) facility of Argonne National Laboratory will provide experiments with beams of short-lived neutron-rich nuclei. The Canadian Penning Trap (CPT) mass spectrometer has been relocated to the CARIBU low-energy beam line to extend measurements of the neutron-rich nuclei into the mostly unexplored region along the r-process path. This will allow precise mass measurements (~ 10 keV/c2) of more than a hundred very neutron-rich isotopes that have not previously been measured.

  12. Clusters in neutron-rich light nuclei

    NASA Astrophysics Data System (ADS)

    Jelavić Malenica, D.; Milin, M.; Di Pietro, A.; Figuera, P.; Lattuada, M.; Miljanić, D.; Musumarra, A.; Pellegriti, M. G.; Prepolec, L.; Scuderi, V.; Skukan, N.; Soić, N.; Torresi, D.; Uroić, M.

    2016-05-01

    Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly simple for investigations of α-particle clustering (because α-particle has Jπ=0+, which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10B+10B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay.

  13. Fusion of neutron-rich oxygen isotopes in the crust of accreting neutron stars

    SciTech Connect

    Horowitz, C. J.; Dussan, H.; Berry, D. K.

    2008-04-15

    Fusion reactions in the crust of an accreting neutron star are an important source of heat, and the depth at which these reactions occur is important for determining the temperature profile of the star. Fusion reactions depend strongly on the nuclear charge Z. Nuclei with Z{<=}6 can fuse at low densities in a liquid ocean. However, nuclei with Z=8 or 10 may not burn until higher densities where the crust is solid and electron capture has made the nuclei neutron rich. We calculate the S factor for fusion reactions of neutron rich nuclei including {sup 24}O+{sup 24}O and {sup 28}Ne+{sup 28}Ne. We use a simple barrier penetration model. The S factor could be further enhanced by dynamical effects involving the neutron rich skin. This possible enhancement in S should be studied in the laboratory with neutron rich radioactive beams. We model the structure of the crust with molecular dynamics simulations. We find that the crust of accreting neutron stars may contain micro-crystals or regions of phase separation. Nevertheless, the screening factors that we determine for the enhancement of the rate of thermonuclear reactions are insensitive to these features. Finally, we calculate the rate of thermonuclear {sup 24}O+{sup 24}O fusion and find that {sup 24}O should burn at densities near 10{sup 11} g/cm{sup 3}. The energy released from this and similar reactions may be important for the temperature profile of the star.

  14. Dual beam organic depth profiling using large argon cluster ion beams.

    PubMed

    Holzweber, M; Shard, A G; Jungnickel, H; Luch, A; Unger, Wes

    2014-01-01

    Argon cluster sputtering of an organic multilayer reference material consisting of two organic components, 4,4'-bis[N-(1-naphthyl-1-)-N-phenyl- amino]-biphenyl (NPB) and aluminium tris-(8-hydroxyquinolate) (Alq3), materials commonly used in organic light-emitting diodes industry, was carried out using time-of-flight SIMS in dual beam mode. The sample used in this study consists of a ∽400-nm-thick NPB matrix with 3-nm marker layers of Alq3 at depth of ∽50, 100, 200 and 300 nm. Argon cluster sputtering provides a constant sputter yield throughout the depth profiles, and the sputter yield volumes and depth resolution are presented for Ar-cluster sizes of 630, 820, 1000, 1250 and 1660 atoms at a kinetic energy of 2.5 keV. The effect of cluster size in this material and over this range is shown to be negligible. © 2014 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd.

  15. Preparation of a primary argon beam for the CERN fixed target physics.

    PubMed

    Küchler, D; O'Neil, M; Scrivens, R; Thomae, R

    2014-02-01

    The fixed target experiment NA61 in the North Area of the Super Proton Synchrotron is studying phase transitions in strongly interacting matter. Up to now they used the primary beams available from the CERN accelerator complex (protons and lead ions) or fragmented beams created from the primary lead ion beam. To explore a wider range of energies and densities a request was made to provide primary argon and xenon beams. This paper describes the results of the setting up and 10 week test run of the Ar(11+) beam from the 14.5 GHz ECR ion source and the linear accelerator (Linac3) at CERN.

  16. Relativistic mean field calculations in neutron-rich nuclei

    SciTech Connect

    Gangopadhyay, G.; Bhattacharya, Madhubrata; Roy, Subinit

    2014-08-14

    Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrange's equations have been solved in the co-ordinate space. The effect of the continuum has been effectively taken into account through the method of resonant continuum. It is found that BCS approximation performs as well as a more involved Relativistic Continuum Hartree Bogoliubov approach. Calculations reveal the possibility of modification of magic numbers in neutron rich nuclei. Calculation for low energy proton scattering cross sections shows that the present approach reproduces the density in very light neutron rich nuclei.

  17. Structure of Light Neutron-rich Nuclei Studied with Transfer Reactions

    SciTech Connect

    Wuosmaa, A. H.

    2015-01-01

    Transfer reactions have been used for many years to understand the shell structure of nuclei. Recent studies with rare-isotope beams extend this work and make it possible to probe the evolution of shell structure far beyond the valley of stability, requiring measurements in inverse kinematics. We present a novel technical approach to measurements in inverse kinematics, and apply this method to different transfer reactions, each of which probes different properties of light, neutron-rich nuclei.

  18. Krypton and argon isotope analysis by collinear fast beam diode laser spectroscopy

    SciTech Connect

    Lehmann, Bernhard; Ludin, Andrea; Tschannen, Thomas

    1995-04-01

    Argon and Krypton ions are accelerated and focused through a Cs-vapour charge exchange cell. Neutral atoms in the emerging beam are optically excited from the metastable 1s5 state to the 2pg state by tunable cw diode lasers at 811.5nm. At 10keV beam energy the spectra of Ar and Kr are separated by {approx}0.5nm with counterpropagating beams and by less than 0.1 nm with copropagating beams. The absorption lines of the individual isotopes cover a spectral range of {approx}10GHz for each element. Linewidths of less than 100 MHz were observed.

  19. Multiquasiparticle states in the neutron-rich nucleus 174Tm

    NASA Astrophysics Data System (ADS)

    Hughes, R. O.; Lane, G. J.; Dracoulis, G. D.; Byrne, A. P.; Nieminen, P.; Watanabe, H.; Carpenter, M. P.; Chowdhury, P.; Janssens, R. V. F.; Kondev, F. G.; Lauritsen, T.; Seweryniak, D.; Zhu, S.

    2013-07-01

    Deep inelastic and transfer reactions with an 820-MeV, 136Xe beam and various ytterbium and lutetium targets have been employed to study high-spin structures in the neutron-rich thulium isotopes beyond 171Tm. Results in the doubly odd nucleus, 174Tm, include the identification of numerous new two- and four-quasiparticle intrinsic states including several isomers below 1 MeV, and the observation of the Kπ=4- ground state rotational band populated via direct decay from a τ=153(10)-μs, Kπ=14- isomer at 2092 keV. The 398-keV, M1 transition linking the isomer and ground state band is abnormally fast for a highly forbidden, ΔK=10 decay. This relative enhancement is explained in terms of mixing of the 13- level with the nearby 13- member of a Kπ=8- rotational band, with an interaction strength of V ≈ 1.4 keV. Multiquasiparticle calculations are compared with the observed states.

  20. TOF-Bρ Mass Measurement of Neutron Rich Nuclei at the NSCL

    NASA Astrophysics Data System (ADS)

    Estradé, Alfredo; Matoš, Milan; Amthor, Matthew A.; Bazin, Daniel; Becerril, Ana D.; Elliot, Thom J.; Gade, Alexandra; Galaviz, Daniel; Lorusso, Giuseppe; Pereira, Jorge; Portillo, Mauricio; Rogers, Andrew; Schatz, Hendrik; Shapira, Dan; Smith, Edward; Stolz, Andreas; Wallace, Mark S.

    2007-10-01

    Experimental knowledge of nuclear masses of exotic nuclei is important for understanding nuclear structure far from the valley of β-stability, and as a direct input into astrophysical models. In the case of astrophysical processes involving neutron rich nuclei, such as nucleosynthesis during the r-process and the evolution of matter in the crust of an accreting neutron star, we are mostly limited to using theoretical mass models. The time of flight (TOF) mass measurement technique allows measuring very short-lived nuclei. It has been effectively applied using the fast fragment beams produced at the A1900 fragment separator at the National Superconducting Cyclotron Lab (NSCL) to reach masses very far from stability. We describe a recent mass measurement experiment in the neutron rich Fe region performed at the NSCL, and present preliminary results.

  1. Nuclear structure in the neutron-rich doubly magic sup 78 Ni region

    SciTech Connect

    Hill, J.C.; Wohn, F.K.; Winger, J.A.; Warburton, E.K.; Gill, R.L.; Schuhmann, R.B.; Brookhaven National Lab., Upton, NY; Clark Univ., Worcester, MA )

    1989-01-01

    The magic numbers Z=28 and N=50 imply that very neutron-rich {sup 78}Ni, which has not yet been observed, is doubly magic. The {sup 78}Ni region was investigated by studying the N=50 isotones and neutron-rich Zn isotopes. Results on the level structure of {sup 83}As, {sup 74}Zn, and {sup 76}Zn populated in the decays of {sup 83}Ge, {sup 74}Cu, and {sup 76}Cu are presented. The parent nuclides were produced and mass separated using the TRISTAN facility on-line to the High-Flux Beam Reactor at Brookhaven. The systematics of the N=50 isotones and even-A Zn isotopes are discussed and compared with shell-model calculations involving active nucleons outside of a {sup 78}Ni and {sup 66}Ni core, respectively. The extent to which the {sup 78}Ni region can be considered doubly magic is assessed. 43 refs., 7 figs.

  2. K-isomers in Hf nuclei at and beyond the neutron-rich edge of {beta}-stability.

    SciTech Connect

    Chowdhury, P.; Alarcao, R. D.; Seabury, E. H.; Walker, P. M.; Wheldon, C.; Ahmad. I.; Carpenter, M. P.; Hackman, G.; Janssens, R. V. F.; Khoo, T. L.; Nisius, D.; Reiter, P.

    1999-03-30

    New high-K isomers are populated in {sup 180,181,182}Hf nuclei via inelastic excitation and transfer reactions, using pulsed {sup 238}U beams on Hf targets. The new data explore K-hindrances for different multipolarities and the role of residual spin-spin interactions for multi-quasiparticle (qp) configurations at the neutron-rich edge of the {beta}-stability line. The mapping of 4-qp K-isomers in the A {approx} 180 region is extended into neutron-rich territory.

  3. New isotope {sup 44}Si and systematics of the production cross sections of the most neutron-rich nuclei

    SciTech Connect

    Tarasov, O. B.; Baumann, T.; Bazin, D.; III, C. M. Folden; Ginter, T. N.; Hausmann, M.; Matos, M.; Portillo, M.; Schiller, A.; Stolz, A.; Amthor, A. M.; Gade, A.; Nettleton, A.; Sherrill, B. M.; Thoennessen, M.; Morrissey, D. J.

    2007-06-15

    The results of measurements of the production of neutron-rich nuclei by the fragmentation of a {sup 48}Ca beam at 142 MeV/nucleon are presented. Evidence was found for the production of a new isotope that is the most neutron-rich silicon nuclide, {sup 44}Si, in a net neutron pickup process. A simple systematic framework was found to describe the production cross sections based on thermal evaporation from excited prefragments that allows extrapolation to other weak reaction products.

  4. {beta}{sup -}-delayed spectroscopy of neutron-rich tantalum nuclei: Shape evolution in neutron-rich tungsten isotopes

    SciTech Connect

    Alkhomashi, N.; Regan, P. H.; Podolyak, Zs.; Pietri, S.; Garnsworthy, A. B.; Steer, S. J.; Farrelly, G.; Cullen, I. J.; Gelletly, W.; Walker, P. M.; Benlliure, J.; Caserejos, E.; Estevez, M. E.; Morales, A. I.; Casten, R. F.; Gerl, J.; Wollersheim, H. J.; Gorska, M.; Kojouharov, I.; Schaffner, H.

    2009-12-15

    The low-lying structure of {sup 188,190,192}W has been studied following {beta} decays of the neutron-rich mother nuclei {sup 188,190,192}Ta produced following the projectile fragmentation of a 1-GeV-per-nucleon {sup 208}Pb primary beam on a natural beryllium target at the GSI Fragment Separator. The {beta}-decay half-lives of {sup 188}Ta, {sup 190}Ta, and {sup 192}Ta have been measured, with {gamma}-ray decays of low-lying states in their respective W daughter nuclei, using heavy-ion {beta}-{gamma} correlations and a position-sensitive silicon detector setup. The data provide information on the low-lying excited states in {sup 188}W, {sup 190}W, and {sup 192}W, which highlight a change in nuclear shape at {sup 190}W compared with that of lighter W isotopes. This evolution of ground-state structure along the W isotopic chain is discussed as evidence for a possible proton subshell effect for the A{approx}190 region and is consistent with maximization of the {gamma}-softness of the nuclear potential around N{approx}116.

  5. Test beam results from the D0 liquid argon end calorimeter electromagnetic module

    SciTech Connect

    Spadafora, A.L.

    1991-08-01

    Results are presented from a test beam study of the D0 liquid argon end calorimeter electromagnetic module prior to its installation at the Fermilab Tevatron Collider. Using electron beams with energies ranging from 10--150 GeV we have obtained an energy resolution of 15.7%/{radical}E(GeV) with a small constant term of 0.3% and a linearity of better than {plus minus}0.5%. The position resolution of the calorimeter is found to approximately 1 mm for 100 GeV electrons. 7 refs., 8 figs., 3 tabs.

  6. Measurement of picosecond lifetimes in neutron-rich Xe isotopes

    NASA Astrophysics Data System (ADS)

    Ilieva, S.; Kröll, Th.; Régis, J.-M.; Saed-Samii, N.; Blanc, A.; Bruce, A. M.; Fraile, L. M.; de France, G.; Hartig, A.-L.; Henrich, C.; Ignatov, A.; Jentschel, M.; Jolie, J.; Korten, W.; Köster, U.; Lalkovski, S.; Lozeva, R.; Mach, H.; Mǎrginean, N.; Mutti, P.; Paziy, V.; Regan, P. H.; Simpson, G. S.; Soldner, T.; Thürauf, M.; Ur, C. A.; Urban, W.; Warr, N.

    2016-09-01

    Background: Lifetimes of nuclear excited states in fission fragments have been studied in the past following isotope separation, thus giving access mainly to the fragments' daughters and only to long-lived isomeric states in the primary fragments. For the first time now, short-lived excited states in the primary fragments, produced in neutron-induced prompt fission of 235U and 241Pu, were studied within the EXILL&FATIMA campaign at the intense neutron-beam facility of the Institute Laue-Langevin in Grenoble. Purpose: We aim to investigate the quadrupole collective properties of neutron-rich even-even 138,140,142Xe isotopes lying between the double shell closure N =82 and Z =50 and a deformed region with octupole collectivity. Method: The γ rays emitted from the excited fragments were detected with a mixed array consisting of 8 HPGe EXOGAM Clover detectors (EXILL) and 16 LaBr3(Ce) fast scintillators (FATIMA). The detector system has the unique ability to select the interesting fragment making use of the high resolution of the HPGe detectors and determine subnanosecond lifetimes using the fast scintillators. For the analysis the generalized centroid difference method was used. Results: We show that quadrupole collectivity increases smoothly with increasing neutron number above the closed N =82 neutron shell. Our measurements are complemented by state-of-the-art theory calculations based on shell-model descriptions. Conclusions: The observed smooth increase in quadrupole collectivity is similar to the evolution seen in the measured masses of the xenon isotopic chain and is well reproduced by theory. This behavior is in contrast to higher Z even-even nuclei where abrupt change in deformation occurs around N =90 .

  7. Collectivity at N=40 in neutron-rich {sup 64}Cr

    SciTech Connect

    Gade, A.; Baugher, T.; Brown, B. A.; McDaniel, S.; Ratkiewicz, A.; Stroberg, S. R.; Walsh, K. A.; Janssens, R. V. F.; Carpenter, M. P.; Hoffman, C. R.; Kay, B. P.; Lauritsen, T.; Zhu, S.; Bazin, D.; Grinyer, G. F.; Weisshaar, D.; Winkler, R.; Chiara, C. J.; Deacon, A. N.; Freeman, S. J.

    2010-05-15

    {sup 9}Be-induced inelastic scattering of {sup 62,64,66}Fe and {sup 60,62,64}Cr was performed at intermediate beam energies. Excited states in {sup 64}Cr were measured for the first time. Energies and population patterns of excited states in these neutron-rich Fe and Cr nuclei are compared and interpreted in the framework of large-scale shell-model calculations in different model spaces. Evidence for increased collectivity and for distinct structural changes between the neighboring Fe and Cr isotopic chains near N=40 is presented.

  8. Collectivity at N = 40 in neutron-rich {sup 64}Cr.

    SciTech Connect

    Gade, A.; Janssens, R. V. F.; Baugher, T.; Bazin, D.; Brown, B. A.; Carpenter, M. P.; Chiara, C. J.; Deacon, A. N.; Freeman, S. J.; Grinyer, G. F.; Hoffman, C. R.; Kay, B. P.; Kondev, F. G.; Lauritsen, T.; McDaniel, S.; Meierbachtol, K.; Ratkiewicz, A.; Stroberg, S. R.; Walsh, K. A.; Weisshaar, D.; Zhu, S.; Winkler, R.; Michigan State Univ.; Univ. of Maryland; Univ. of Manchester

    2010-05-01

    9Be-induced inelastic scattering of 62,64,66Fe and 60,62,64Cr was performed at intermediate beam energies. Excited states in 64Cr were measured for the first time. Energies and population patterns of excited states in these neutron-rich Fe and Cr nuclei are compared and interpreted in the framework of large-scale shell-model calculations in different model spaces. Evidence for increased collectivity and for distinct structural changes between the neighboring Fe and Cr isotopic chains near N=40 is presented.

  9. Decay spectroscopy of neutron-rich rare-earth isotopes and collectivity around double midshell

    SciTech Connect

    Watanabe, Hiroshi

    2015-10-15

    Neutron-rich rare-earth isotopes with A ≈ 170, which locate near the middle of the major shells for both proton and neutron between the doubly magic nuclei {sup 132}Sn and {sup 208}Pb, have been investigated by means of decay spectroscopy techniques at the RIBF facility at RIKEN. The nuclei of interest were produced by in-flight fission of a high-intensity {sup 238}U beam at 345 MeV/u. In this contribution, scientific motivations, the details of experimental procedures, and some prospects of the data analysis are reported.

  10. Studies of neutron-rich nuclei far from stability at TRISTAN

    SciTech Connect

    Gill, R.L.

    1984-01-01

    The ISOL facility, TRISTAN, is a user facility located at Brookhaven National Laboratory's High Flux Beam Reactor. Short-lived, neutron-rich nuclei, far from stability, are produced by thermal neutron fission of /sup 235/U. An extensive array of experimental end stations are available for nuclear structure studies. These studies are augmented by a variety of long-lived ion sources suitable for use at a reactor facility. Some recent results at TRISTAN are presented as examples of using an ISOL facility to study series of nuclei, whereby an effective means of conducting nuclear structure investigations is available.

  11. TOF-SIMS with argon gas cluster ion beams: a comparison with C60+.

    PubMed

    Rabbani, Sadia; Barber, Andrew M; Fletcher, John S; Lockyer, Nicholas P; Vickerman, John C

    2011-05-15

    Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an established technique for the characterization of solid sample surfaces. The introduction of polyatomic ion beams, such as C(60), has provided the associated ability to perform molecular depth-profiling and 3D molecular imaging. However, not all samples perform equally under C(60) bombardment, and it is probably naïve to think that there will be an ion beam that will be applicable in all situations. It is therefore important to explore the potential of other candidates. A systematic study of the suitability of argon gas cluster ion beams (Ar-GCIBs) of general composition Ar(n)(+), where n = 60-3000, as primary particles in TOF-SIMS analysis has been performed. We have assessed the potential of the Ar-GCIBs for molecular depth-profiling in terms of damage accumulation and sputter rate and also as analysis beams where spectral quality and secondary ion yields are considered. We present results with direct comparison with C(60) ions on the same sample in the same instrument on polymer, polymer additive, and biomolecular samples, including lipids and small peptides. Large argon clusters show reduced damage accumulation compared with C(60) with an approximately constant sputter rate as a function of Ar cluster size. Further, on some samples, large argon clusters produce changes in the mass spectra indicative of a more gentle ejection mechanism. However, there also appears to be a reduction in the ionization of secondary species as the size of the Ar cluster increases.

  12. New K isomers in the neutron-rich N =100 isotones 162Sm, 163Eu, and 164Gd

    NASA Astrophysics Data System (ADS)

    Yokoyama, R.; Go, S.; Kameda, D.; Kubo, T.; Inabe, N.; Fukuda, N.; Takeda, H.; Suzuki, H.; Yoshida, K.; Kusaka, K.; Tanaka, K.; Yanagisawa, Y.; Ohtake, M.; Sato, H.; Shimizu, Y.; Baba, H.; Kurokawa, M.; Nishimura, D.; Ohnishi, T.; Iwasa, N.; Chiba, A.; Yamada, T.; Ideguchi, E.; Fujii, T.; Nishibata, H.; Ieki, K.; Murai, D.; Momota, S.; Sato, Y.; Hwang, J. W.; Kim, S.; Tarasov, O. B.; Morrissey, D. J.; Sherrill, B. M.; Simpson, G.; Praharaj, C. R.

    2017-03-01

    Very neutron-rich Z ˜60 isotopes produced by in-flight fission of a 345 MeV/nucleon 238U beam at the RI Beam Factory, RIKEN Nishina Center, have been studied by delayed γ -ray spectroscopy. New isomers were discovered in the neutron-rich N =100 isotones 162Sm, 163Eu, and 164Gd. Half-lives, γ -ray energies, and relative intensities of these isomers were obtained. Level schemes were proposed for these nuclei and the first 2+ and 4+ states were assigned for the even-even nuclei. The first 2+ and 4+ state energies decrease as the proton numbers get smaller. The energies and the half-lives of the new isomers are very similar to those of 4- isomers known in less neutron-rich N =100 isotones 168Er and 170Yb. A deformed Hartree-Fock with angular momentum projection model suggests Kπ=4- two-quasiparticle states with ν 7 /2 [633 ]⊗ν 1 /2 [521 ] configurations with similar excitation energy. The results suggest that neutron-rich N =100 nuclei are well deformed and the deformation gets larger as Z decreases to 62. The onset of K isomers with the same configuration at almost the same energy in N =100 isotones indicates that the neutron single-particle structures of neutron-rich isotones down to Z =62 do not change significantly from those of the Z =70 stable nuclei. Systematics of the excitation energies of new isomers can be explained without the predicted N =100 shell gap.

  13. CAPTAIN-Minerνa. Neutrino-Argon Scattering in a Medium-Energy Neutrino Beam

    SciTech Connect

    Mauger, Christopher M.

    2015-10-29

    The NuMI facility at Fermilab is currently providing an extremely intense beam of neutrinos for the NOνA, MINERνA and MINOS+ experiments. By installing the 5-ton CAPTAIN liquid argon TPC in front of the MINERνA detector in the NuMI beamline and combining the data from the CAPTAIN, MINERνA and MINOS+ detectors, a broad program of few-GeV neutrino cross section measurements on argon can be pursued. These measurements will be extremely helpful for future oscillation experiments. By directly comparing the cross sections on argon to MINERνA’s scintillator (CH) target, a new level of precision can be achieved in the measurements of the effects of the nucleus on neutrino interactions. These effects are of interest to not only the particle physics but also the nuclear physics community. This document describes in detail the physics goals of the CAPTAIN-MINERνA experiment, in addition to a first estimate of the technical resources required to install, commission and operate the CAPTAIN detector in front of the MINERVA detector.

  14. Systematic study of neutron-rich rare isotope production in peripheral heavy-ion collisions below the Fermi energy

    NASA Astrophysics Data System (ADS)

    Fountas, P. N.; Souliotis, G. A.; Veselsky, M.; Bonasera, A.

    2014-12-01

    Detailed calculations of the yields of projectilelike fragments (with focus on the neutron-rich isotopes) are presented for the interaction of 86Kr (15 MeV/nucleon) with 64Ni, 58Ni, and 124Sn, 112Sn, as well as 86Kr (25 MeV/nucleon) with 124Sn and compared with our recently published experimental data for these reactions. The calculations are based on a two-step approach: the dynamical stage of the collision was described with the microscopic constrained molecular dynamics (CoMD) model, as well as the phenomenological deep-inelastic transfer (DIT) model and its modified (DITm) version. The deexcitation of the hot projectile fragments was performed with the statistical multifragmentation model (SMM) and the binary-decay model gemini, which provided nearly similar results for the neutron-rich products from the reactions studied. An overall good agreement of the calculations with the experimental results, especially for near-projectile isotopes was observed using both the CoMD model and the DITm model for the dynamical stage. The successful description of the production of neutron-rich isotopes with the CoMD model is of particular importance, due to the predictive power of the microscopic approach that essentially does not depend on the reaction dynamics. Our studies to date suggest that peripheral heavy-ion collisions at this energy range (i.e., well above the Coulomb barrier, but below the Fermi energy), if induced by neutron-rich rare-isotope beams of adequate intensity may offer a unique route to access extremely neutron-rich rare isotopes toward the astrophysical r -process path and the presently uncharted neutron drip line.

  15. Proton radii of neutron-rich B isotopes and neutron surface thickness in 17B

    NASA Astrophysics Data System (ADS)

    Kanungo, Rituparna; Estrade, Alfredo; Horiuchi, Wataru

    2014-09-01

    As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications of the results in understanding the neutron surface thickness in the Borromean 17B and its possible halo structure will be discussed. As the neutron to proton asymmetry increases nuclei develop exotic structures such as neutron skin and halo. It is important to investigate how this asymmetry affects the proton distribution. The matter and proton radii have started unfolding a complete picture of the halo. For two-neutron halos the correlation between the halo neutrons and their distance from the core can be derived to define the average halo geometry. The proton radii are crucial information to extract the neutron skin thickness to constrain the equation of state of asymmetric nuclear matter. Very limited information is available on the proton radii of very neutron-rich nuclei. In this presentation, we will describe the new technique of extracting proton radii from charge changing cross sections using relativistic beams at GSI, Germany. The presentation will show first measurements of proton radii of the neutron-rich boron isotopes. The implications

  16. Shell Evolution in the Neutron-Rich Cu and Zn Isotopes

    NASA Astrophysics Data System (ADS)

    Belarge, Joe; Bazin, Daniel; Gade, Alexandra; Ayyad, Yassid; Bender, Peter; Elder, Robert; Elman, Brandon; Iwasaki, Hiro; Kobayashi, Nobuyuki; Loelius, Charles; Longfellow, Brenden; Lunderberg, Eric; Morfouace, Pierre; Sullivan, Chris; Weisshaar, Dirk; Whitmore, Kenneth

    2016-09-01

    Recent shell model calculations predict a gradual reduction of the Z=28 shell gap in Ni isotopes as the ν 1g9 / 2 orbital is filled from 68Ni to 78Ni [Otsuka et al. PRL 95, 232502]. These predictions can be experimentally tested by measuring the spectroscopic strength of a given orbital in an isotopic chain. The neutron-rich Cu isotopes, with one proton outside of a filled π 1f7 / 2 orbital, are some of the best candidates to exhibit the effects of the underlying structure evolution in this region. The high luminosity provided by fast beam, thick target experiments performed at the NSCL, coupled with the high resolution, high efficiency gamma-ray array GRETINA, provide a unique opportunity to study the neutron-rich Cu isotopes. The current experiment aims to measure the strength of 2p-1h excitations in 69-77Cu, populated through one proton knockout from 70-78Zn beams on a Be target, thereby probing the effective single particle energy and spectroscopic strength of the π 1f7 / 2 orbital. Results from the ongoing analysis will be presented.

  17. Extreme-ultraviolet beam-foil spectroscopy of highly ionized neon and argon. Doctoral thesis

    SciTech Connect

    Demarest, J.A.

    1986-08-01

    A study of the extreme-ultraviolet radiation emitted by ion beams of highly ionized neon and argon after passage through thin foils was conducted. A grazing-incidence spectrometer was equipped with a position-sensitive microchannel plate (MCP) detector, which improved the detection efficiency by two orders of magnitude. The position information of the MCP was determined to be linear over 90% of the 50-mm-wide detector. Spectra spanning regions of over 100 A were accumulated at a resolution of less than 1 A. A wavelength calibration based on a second order equation of spectrometer position was found to result in an accuracy of - 0.1 A. Over 40 transitions of Ne VIII, Ne IX, and Ne X were observed in the wavelength region from 350 to 30 A from n=2-3,4,5; n=3-4,5,6,7,8; n=4-6,7; and n=5-9. An intensity calibration of the detection system allowed the determination of the relative populations of n=3 states of Ne VIII and Ne IX. An overpopulation of states with low orbital angular momenta support electron-capture predictions by the first-order Born approximation. The argon beam-foil data confirmed the wavelength predictions of 30 previously unobserved transitions in the wavlength region from 355 to 25 A from n=2-2; n=3-4; n=4-5,6,7; and n=6-8. Lifetime determinations were made by the simultaneous measurement of 26 argon lines in the spectral region from 295-180 A. Many of the n=2-2 transitions agreed well with theory.

  18. Possibility of production of neutron-rich Zn and Ge isotopes in multinucleon transfer reactions at low energies

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-02-15

    The production cross sections of new neutron-rich {sup 84,86}Zn and {sup 90,92}Ge isotopes beyond N=50 are estimated for the first time in the multinucleon transfer reactions {sup 48}Ca + {sup 238}U and {sup 48}Ca + {sup 244}Pu. The production of new isotopes in reactions with a {sup 48}Ca beam is discussed for future experiments.

  19. A microscopic description of neutron-rich lithium isotopes

    SciTech Connect

    Burov, V.V.; Rzjanin, M.V.; Miller, H.G.; Shitikova, K.V.; Yen, G.D.

    1994-12-01

    A unified calculation of neutron-rich isotopes in lithium is performed using the hyperspherical basis in which the underlying symmetry of each isotope exhibits a simple structure. The variation of the binding energy as a function of mass number is qualitatively reproduced, and the asymptotic of radial distribution of each isotope decreases exponentially. The form factors of the lithium isotopes are calculated and display diffraction minima. 27 refs., 3 figs., 3 tabs.

  20. Fission and Properties of Neutron-Rich Nuclei - Proceedings of the Second International Conference

    NASA Astrophysics Data System (ADS)

    Hamilton, J. H.; Phillips, W. R.; Carter, H. K.

    Stability, Fission Barrier and Nuclear Structure of the Z = 102 Isotope 254No * Neutron Capture on Radioactive Targets: Probing the S-Process * Angular Momentum Generation in Spontaneous Fission Fragments Without Thermal Excitation of Collective Modes * First Excited States in Neutron-Rich Neon and Sodium Isotopes * Production and Identification of New Heavy Neutron-Rich Isotopes * The Munich Accelerator for Fission Fragments MAFF, the Recycling of Radioactive Beams and Superheavy Elements * SIRIUS: A UK Facility to Provide Parallel Radioactive Beams for Research * Spectroscopy of Halo Nuclei From Reaction Measurements * Possibilities for Experiments with Neutron-Rich Beams in Nuclear Astrophysics * Superheavy Nuclei Revisited * Prospects for the Production of Neutron-Rich Nuclei by Relativistic Beams * Coulomb Dissociation of 19C and its Halo Structure * New Results on the Role of Shell Effects in Nuclear Fission From Experiments with Secondary Beams * How to Interpret the Correlations Preceding Spontaneous Fission Events Observed in Reactions of 48Ca with the Heaviest Actinide Targets * Charge and Mass Distributions of Fission Fragments From Intermediate Energy Collisions of 238U Projectiles. Generation of Very Neutron-Rich Nuclei * Fission Modes in 238U + d Reaction at Intermediate Energy * SU(3) Dynamical Symmetry and Odd-Even (ΔL = 1) Staggering in Heavy Deformed Nuclei * Deformation of Fragments with A ≃ 130 in Two Mode Fission * List of Participants

  1. Two Dimensional LIF Measurements and Potential Structure of Ion Beam Formation in an Argon Helicon Plasma

    NASA Astrophysics Data System (ADS)

    Aguirre, Evan; Scime, Earl; Good, Timothy

    2016-10-01

    We report 2-dimensional, spatially resolved observations of ion beam formation in an expanding helicon plasma. Previous studies found that a current free double layer (CFDL) spontaneously arises at low pressure, below 1 mT. We use Laser Induced Fluorescence (LIF), a non-perturbative diagnostic to measure the ion velocity distribution functions (IVDFs) of argon ions both parallel and perpendicular to the background magnetic field. We report ion beam formation as a function of the expansion chamber magnetic field (0-108 G). The ion beam appears peaked in the center of the expansion chamber and decays over a few centimeters radially. We also report the potential structure of the plasma obtained with a planar Langmuir probe. To obtain meaningful Langmuir probe measurements, averages of tens of current-voltage are needed to reduce the effects of large electrostatic fluctuations that arise in plasmas that generate ion beams. We report the dependence of density, electron temperature, and floating potential on radial and axial position in the expansion plume. NSF Award PHYS-1360278.

  2. Decay Pattern of Pygmy States Observed in Neutron-Rich Ne26

    NASA Astrophysics Data System (ADS)

    Gibelin, J.; Beaumel, D.; Motobayashi, T.; Blumenfeld, Y.; Aoi, N.; Baba, H.; Elekes, Z.; Fortier, S.; Frascaria, N.; Fukuda, N.; Gomi, T.; Ishikawa, K.; Kondo, Y.; Kubo, T.; Lima, V.; Nakamura, T.; Saito, A.; Satou, Y.; Scarpaci, J.-A.; Takeshita, E.; Takeuchi, S.; Teranishi, T.; Togano, Y.; Vinodkumar, A. M.; Yanagisawa, Y.; Yoshida, K.

    2008-11-01

    Coulomb excitation of the exotic neutron-rich nucleus Ne26 on a Pb208 target was measured at 58MeV/u in order to search for low-lying E1 strength above the neutron emission threshold. This radioactive beam experiment was carried out at the RIKEN Accelerator Research Facility. Using the invariant mass method in the Ne25+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV excitation energy. By performing a multipole decomposition of the differential cross section, a reduced dipole transition probability of B(E1)=0.49±0.16e2fm2 is deduced, corresponding to 4.9±1.6% of the Thomas-Reiche-Kuhn sum rule. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is measured. The extracted decay pattern is not consistent with several mean-field theory descriptions of the pygmy states.

  3. Promises and Challenges of Two-Step Targets for Production of Neutron-rich RIBs

    SciTech Connect

    Talbert, W.L.; Drake, D.M.; Hsu, H.-H.; Wilson, M.T.

    2003-08-26

    Development of a prototype two-step target to produce neutron-rich RIBs is presented, with particular emphasis on thermal analysis under high-power operation. The two-step target is an attractive concept for production of fission-product activities without interference by high-energy spallation reactions which occur in direct production targets. In this concept, a high-energy production beam interacts with a primary target of refractory metal, depositing beam energy in the primary target and producing low-energy neutrons that cause fissions in a surrounding secondary target of mixed UC2 and excess C. Thermal analysis of the composite target presents challenges in cooling the primary target while maintaining the secondary target at temperatures suitable for release of the fission products. The effects of fission energy deposition in the secondary target are discussed, along with the complexities resulting from the thermally insulating character of the secondary target material.

  4. New neutron-rich microsecond isomers observed among fission products of {sup 238}U at 80 MeV/nucleon

    SciTech Connect

    Folden, C. M. III; Ginter, T. N.; Hausmann, M.; Portillo, M.; Nettleton, A. S.; Amthor, A. M.; Sherrill, B. M.; Kubo, T.; Takeda, H.; Loveland, W.; Manikonda, S. L.; Morrissey, D. J.; Nakao, T.; Souliotis, G. A.; Strong, B. F.; Tarasov, O. B.

    2009-06-15

    Eight new isomeric states in neutron-rich nuclides have been discovered in fission fragments produced by the reaction of an 80 MeV/nucleon {sup 238}U beam with a {sup 9}Be target and separated in-flight using the A1900 fragment separator. The experiment was conducted at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. Gamma rays were detected in a high-purity germanium detector located at the focal plane within a time window of 20 {mu}s following ion implantation. In some cases the isomers were observed to decay into previously reported states, allowing us to assign the initial decay from the isomeric state. Among the outcomes, the results suggest that many studies on the nuclear structure of medium-mass neutron-rich nuclei are feasible at projectile fragmentation facilities using induced fission.

  5. Spectroscopy of Neutron-rich Nuclei of the A{approx_equal}60 region populated through binary heavy-ion collisions

    SciTech Connect

    Lunardi, S.

    2008-11-11

    Neutron-rich nuclei of the mass A = 60 region (from V to Fe) have been studied through multi-nucleon transfer reactions by bombarding a {sup 238}U target with beams of {sup 64}Ni and {sup 70}Zn. Unambiguous identification of prompt {gamma} rays belonging to each nucleus has been achieved by using the efficient gamma-array CLARA coupled to the large-acceptance magnetic spectrometer PRISMA installed at the Legnaro National Laboratories. With the new data, the existence of the N = 32 sub-shell closure has been corroborated through the study of odd V isotopes, whereas a new region of deformation appears for neutron-rich Fe nuclei close to N = 40. The results obtained for all these nuclei are compared with shell model calculations which reproduces quite well the experimental data also for the most neutron-rich nuclei when excitations from the fp shell into the upper g{sub 9/2} orbital are allowed.

  6. Lead pipe scale analysis using broad-beam argon ion milling to elucidate drinking water corrosion.

    PubMed

    Nadagouda, Mallikarjuna N; White, Colin; Lytle, Darren

    2011-04-01

    Herein, we characterized lead pipe scale removed from a drinking water distribution system using argon ion beam etching and a variety of solids analysis approaches. Specifically, pipe scale cross sections and solids were analyzed using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and acid digestion followed by inductively coupled plasma mass spectrometry analyses. The pipe scale consisted of at least five layers that contained Pb(II) and Pb(IV) minerals, and magnesium, aluminum, manganese, iron, and silicon solids. The outer layer was enriched with crystalline amorphous manganese and iron, giving it a dark orange to red color. The middle layers consisted of hydrocerussite and plattnerite, and the bottom layer consisted primarily of litharge. Over the litharge layer, hydrocerussite crystals were grown vertically away from the pipe wall, which included formations of plattnerite. Significant amounts of trace contaminant vanadium, likely in the form of vanadinite, and copper accumulated in the scale as well.

  7. New Neutron Rich Nuclei Near {sup 208}Pb

    SciTech Connect

    Aeystoe, J.; Andreyev, A.; Evensen, A.-H.; Hoff, P.; Huhta, M.; Huyse, M.; ISOLDE Collaboration; Jokinen, A.; Karny, M.; Kugler, E.; Kurpeta, J.; Lettry, J.; Nieminen, A.; Plochocki, A.; Ramdhane, M.; Ravn, H.; Rykaczewski, K.; Szerypo, J.; VanDuppen, P.; Walter, G.; Woehr, A.

    1998-11-13

    The level properties near the stable doubly-magic nuclei formed the experimental grounds for the theoretical description of nuclear structure. However with a departure from the beta-stability line, the classical well-established shell structure might be modified. In particular, it may even vanish for extremely exotic neutron-rich nuclei near the neutron-drip line. Presently, it is impossible to verify such predictions by a direct experimental studies of these exotic objects. However, one may try to observe and understand the evolution of the nuclear structure while departing in the experiment as far as possible from the stable nuclei. An extension of experimental nuclear structure studies towards the nuclei characterized by high neutron excess is crucial for such verifications as well as for the {tau}-process nucleosynthesis scenario. Heavy neutron-rich nuclei, south-east of doubly-magic {sup 208}Pb, were always very difficult to produce and investigate. The nuclei like {sup 218}Po and {sup 214}Pb or {sup 210}Tl marked the border line of known nuclei from the beginning of the radioactivity era for over ninety years. To illustrate the difficulties, one can refer to the experiments employing the on-line mass separator technique. A spallation of heavy targets like {sup 232}Th and {sup 238}U by high-energy protons was proven as a source of heavy neutron-rich nuclei. The isotopes near and beyond doubly-magic {sup 208}Pb were produced too. However, such studies often suffered from an isobaric contamination of much more strongly produced and efficiently released elements like francium or radon and their decay products. A new experimental technique, based on the pulsed release element selective method recently developed at the PS Booster-ISOLDE at CERN [7,8,9] greatly reduces the contamination of these very short-lived {alpha}-emitters (Z {ge} 84) for the isobaric mass chains A=215 to A=218.

  8. Scanning-probe-microscopy of polyethylene terephthalate surface treatment by argon ion beam

    NASA Astrophysics Data System (ADS)

    Espinoza-Beltran, Francisco; Sanchez, Isaac C.; España-Sánchez, Beatriz L.; Mota-Morales, Josué D.; Carrillo, Salvador; Enríquez-Flores, C. I.; Poncin-Epaillard, Fabienne; Luna-Barcenas, Gabriel

    2015-11-01

    The effect of argon (Ar+) ion beam treatment on the surface of polyethylene terephthalate (PET) samples was studied by scanning probe microscopy (SPM) and the changes in surface topography were assessed by atomic force microscopy (AFM). Kelvin probe force microscopy (KPFM) sheds light of adhesion force between treated polymer films and a Pt/Cr probe under dry conditions, obtaining the contact potential difference of material. As a result of Ar+ ion bombardment, important surface chemical changes were detected by X-ray photoelectron spectroscopy (XPS) measurements such as chains scission and incorporation of nitrogen species. Ion beam treatment increases the surface roughness from 0.49 ± 0.1 nm to 7.2 ± 0.1 nm and modify the surface potential of PET samples, decreasing the adhesive forces from 12.041 ± 2.1 nN to 5.782 ± 0.06 nN, and producing a slight increase in the electronic work function (Φe) from 5.1 V (untreated) to 5.2 V (treated). Ar+ ion beam treatment allows to potentially changing the surface properties of PET, modifying surface adhesion, improving surface chemical changes, wetting properties and surface potential of polymers.

  9. New mass measurements of neutron rich nuclides at the NSCL.

    NASA Astrophysics Data System (ADS)

    Estrade, Alfredo; Matos, Milan; Amthor, Matthew; Bazin, Daniel; Becerril, Ana; Elliot, Thom; Gade, Alexandra; Galaviz, Daniel; Lorusso, Giuseppe; Pereira, Jorge; Portillo, Mauricio; Rogers, Andrew; Schatz, Hendrik; Shapira, Dan; Smith, Ed; Stolz, Andreas; Wallace, Mark

    2007-10-01

    A mass measurement of exotic isotopes in the region of 68Fe has been performed at the NSCL using the time-of-flight technique recently established. Experimental knowledge of the mass of very neutron rich nuclides is an important input for astrophysical applications, such as nucleosynthesis during the r-process and the evolution of matter in the crust of an accreting neutron star, where present calculations are mostly limited to using theoretical mass extrapolations. We present the details of the experimental set up, as well as preliminary results.

  10. Level structures of neutron-rich Xe isotopes

    SciTech Connect

    Ahmad, I.; Lister, C.J.; Morss, L.R.

    1995-08-01

    The level structures of neutron-rich Xe isotopes were determined by observing prompt gamma-ray coincidences in {sup 248}Cm fission fragments. A 5-mg {sup 248}Cm, in the form of {sup 248}Cm-KCl pellet, was placed inside Eurogam array which consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. Transitions in Xe isotopes were identified by the appearance of new peaks in the {gamma}-ray spectra obtained by gating on the gamma peaks of the complementary Mo fragments.

  11. Exotic modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2011-05-06

    Low-lying dipole excitation mode in neutron-rich Mg isotopes close to the drip line is investigated in the framework of the Hartree-Fock-Bogoliubov and the quasiparticle random-phase approximation employing the Skyrme and the pairing energy-density functionals. It is found that the low-lying dipole-strength distribution splits into the K{sup {pi}} = 0{sup -} and 1{sup -} components due to the nuclear deformation. The low-lying dipole strength increases as the neutron drip-line is approached.

  12. Search for octupole deformation in neutron rich Xe isotopes

    SciTech Connect

    Bentaleb, M.; Schulz, N.; Lubkiewicz, E.

    1994-07-01

    A search for octupole deformation in neutron rich Xe isotopes has been conducted through gamma-ray spectroscopy of primary fragments produced in the spontaneous fission of {sup 248}Cm. The spectrometer consisted of the Eurogam array and a set of 5 LEPS detectors. Level schemes were constructed for Xe isotopes with masses ranging from 138 to 144. Except for {sup 139}Xe, none of them exhibit an alternating parity quasimolecular band, {alpha} feature usually encountered in octupole deformed nuclei. Substantial evidence for reflection asymmetric shape in the intrinsic system of the nucleus exists for the light actinide nuclei.

  13. CARIBU: a new facility for the study of neutron-rich isotopes

    NASA Astrophysics Data System (ADS)

    Savard, G.; Pardo, R. C.; Baker, S.; Davids, C. N.; Levand, A.; Peterson, D.; Phillips, D. G.; Sun, T.; Vondrasek, R.; Zabransky, B. J.; Zinkann, G. P.

    2011-07-01

    The Californium Rare Ion Breeder Upgrade (CARIBU) to the ATLAS superconducting linac facility is currently being commissioned. It provides low-energy and re-accelerated beams of neutron-rich isotopes obtained from 252Cf fission. The fission products from a 252Cf source are stopped in a large high-intensity gas catcher, thermalized and extracted through an RFQ cooler, accelerated to 50 kV and mass separated in a high-resolution separator before being sent to either an ECR charge breeder for post-acceleration through the ATLAS linac or to a low-energy experimental area. This approach gives access to beams of very neutron-rich isotopes, many of which have not been available at low or Coulomb barrier energies previously. These beams provide unique opportunities for measurements along the r-process path. To take advantage of these unique possibility, the reaccelerated beams from CARIBU will be made available at the experimental stations of ATLAS to serve equipment such as Gammasphere, HELIOS and the reaction spectrometers. In addition, the Canadian Penning Trap (CPT) mass spectrometer has been moved to the CARIBU low-energy experimental area and a new injection line has been built. The new injection line consists of a RFQ buncher sitting on a 50 kV high-voltage platform that will accumulate the mass separated 50 kV radioactive beams, cool and extract them as a pulsed beam of 3 keV. This beam can be sent either to a tape station for diagnostics and tuning, or a cryogenic linear trap for preparation before transfer to the high-precision Penning trap where the mass measurements will take place. Initial CARIBU commissioning is proceeding with a 2 mCi source that will be replaced by a 100 mCi source as the commissioning proceeds. Final operation will use a 1 Ci source and attain yield in excess of 107 ions/sec for the most intense beams at low energy, an order of magnitude less for reaccelerated beams.

  14. Unexpectedly large charge radii of neutron-rich calcium isotopes

    NASA Astrophysics Data System (ADS)

    Garcia Ruiz, R. F.; Bissell, M. L.; Blaum, K.; Ekström, A.; Frömmgen, N.; Hagen, G.; Hammen, M.; Hebeler, K.; Holt, J. D.; Jansen, G. R.; Kowalska, M.; Kreim, K.; Nazarewicz, W.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Papenbrock, T.; Papuga, J.; Schwenk, A.; Simonis, J.; Wendt, K. A.; Yordanov, D. T.

    2016-06-01

    Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain `magic’ numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known calcium isotopes have been successfully described by nuclear theory, it is still a challenge to predict the evolution of their charge radii. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-rich atomic nuclei.

  15. Neutron-rich hypernuclei: H6Λ and beyond

    NASA Astrophysics Data System (ADS)

    Gal, A.; Millener, D. J.

    2013-10-01

    Recent experimental evidence presented by the FINUDA Collaboration for a particle-stable H6Λ has stirred renewed interest in charting domains of particle-stable neutron-rich Λ hypernuclei, particularly for unbound nuclear cores. We have studied within a shell-model approach several neutron-rich Λ hypernuclei in the nuclear p shell that could be formed in (π-, K+) or in (K-, π+) reactions on stable nuclear targets. Hypernuclear shell-model input is taken from a theoretically inspired successful fit of γ-ray transitions in p-shell Λ hypernuclei which includes also ΛN ↔ ΣN coupling (ΛΣ coupling). The particle stability of H6Λ is discussed and predictions are made for binding energies of He9Λ, Li10Λ, Be12Λ, B14Λ. None of the large effects conjectured by some authors to arise from ΛΣ coupling is borne out, neither by these realistic p-shell calculations, nor by quantitative estimates outlined for heavier hypernuclei with substantial neutron excess.

  16. Isomers of Pm Isotopes on the Neutron-Rich Frontier of the Deformed Z ~ 60 Region

    NASA Astrophysics Data System (ADS)

    Yokoyama, Rin; Ideguchi, Eiji; Simpson, Gary; Tanaka, Mana; Nishimura, Shunji; Doornnbal, Pieter; Söderström, Pär-Anders; Lorusso, Giuseppe; Xu, Zhengyu; Wu, Jin; Sumikama, Toshiyuki; Aoi, Nori; Baba, Hidetada; Bello, Frank; Browne, Frank; Daido, Rie; Fang, Yifan; Fukuda, Naoki; Gey, Guillaume; Go, Shintaro; Inabe, Naohiro; Isobe, Tadaaki; Kameda, Daisuke; Kobayashi, Kazuma; Kobayashi, Motoki; Komatsubara, Tetsuro; Kubo, Toshiyuki; Kuti, Istvan; Li, Zhihuan; Matsushita, Masafumi; Michimasa, Shin'ichiro; Moon, Chang-Bum; Nishibata, Hiroki; Nishizuka, Ippei; Odahara, Atsuko; Patel, Zena; Rice, Simon; Sahin, Eda; Sinclair, Laura; Suzuki, Hiroshi; Takeda, Hiroyuki; Taprogge, Jan; Vajta, Zsolt; Watanabe, Hiroshi; Yagi, Ayumi

    Neutron-rich Pm (Z = 61) isotopes were studied by delayed γ-ray spectroscopy at RIBF, Riken Nishina Center using the in-flight fission of 345 MeV/u 238U beam. An array of cluster-type Ge detectors, EURICA, was used to measure the delayed γ rays from stopped ions. Isomers were observed in 158Pm, 159Pm and 161Pm with half-lives of >16, 4.64(21), and 0.88(10) µs respectively. Preliminary level schemes for 159Pm and 161Pm were constructed in this study. They have ground-state bands similar to those of 153Pm and 155Pm. The isomeric state of 161Pm could be interpreted as a two quasi-particle excitation of neutrons with configuration of ν 7/2[633] otimes ν 1/2[521] as other Kπ = 4 - isomers observed systematically in other N = 100 isotones.

  17. g-Factors of Isomeric States in the Neutron-Rich Nuclei

    SciTech Connect

    Georgiev, G.; Neyens, G.; Hass, M.; Balabanski, Dimiter Loukanov; Bingham, Carrol R; Borcea, C.; Coulier, N.; Coussenment, R.; Daugas, J. M.; De France, Gilles M; Gorska, M.; Grawe, Hubert H; Grzywacz, Robert Kazimierz; Lewitowicz, Marek; Mach, Henryk A; Matea, I.; de Oliveira Santos, F.; Page, R. D.; Pfutzner, Marek; Penionzhkevich, Yu. E.; Podolyak, Zsolt F; Regan, Patrick H; Rykaczewski, Krzysztof Piotr; Sawicka, M.; Smirnova, N. A.; Sobolev, Yu.; Stanoiu, M.; Teughels, S.; Vyvey, K.

    2004-02-01

    We report the results from the first experiment to measure gyromagnetic factors of {micro}s isomers in neutron-rich nuclei produced by intermediate-energy projectile-fragmentation reactions. The Time Dependent Perturbed Angular Distribution (TDPAD) method was applied in combination with the heavy-ion-gamma correlation technique. The nuclides in the vicinity of {sup 68}Ni were produced and spin-oriented following the fragmentation of a {sup 76}Ge, 61.4 MeV/ u beam at GANIL. The results obtained, |g|({sup 69 m}Cu) = 0.225(25) and |g|({sup 67 m}Ni) = 0.125(6) provide another indication of the importance of proton excitation across the Z = 28 shell gap for the description of these states.

  18. β and β -n decay of the neutron-rich

    NASA Astrophysics Data System (ADS)

    Korgul, A.; Rykaczewski, K. P.; Grzywacz, R. K.; Bingham, C. R.; Brewer, N. T.; Gross, C. J.; Ciemny, A. A.; Jost, C.; Karny, M.; Madurga, M.; Mazzocchi, C.; Mendez, A. J.; Miernik, K.; Miller, D.; Padgett, S.; Paulauskas, S. V.; Piersa, M.; Stracener, D. W.; Stryjczyk, M.; Wolińska-Cichocka, M.; Zganjar, E. F.

    2016-06-01

    The β -decay properties of the very neutron-rich Beam Facility at Oak Ridge National Laboratory. Several new γ -transitions and levels were added to its decay scheme and the order of the two lowest-lying levels in the daughter

  19. Synthesis of neutron-rich transuranic nuclei in fissile spallation targets

    NASA Astrophysics Data System (ADS)

    Mishustin, Igor; Malyshkin, Yury; Pshenichnov, Igor; Greiner, Walter

    2015-04-01

    A possibility of synthesizing neutron-rich superheavy elements in spallation targets of Accelerator Driven Systems (ADS) is considered. A dedicated software called Nuclide Composition Dynamics (NuCoD) was developed to model the evolution of isotope composition in the targets during a long-time irradiation by intense proton and deuteron beams. Simulation results show that transuranic elements up to 249Bk can be produced in multiple neutron capture reactions in macroscopic quantities. However, the neutron flux achievable in a spallation target is still insufficient to overcome the so-called fermium gap. Further optimization of the target design, in particular, by including moderating material and covering it by a reflector could turn ADS into an alternative source of transuranic elements in addition to nuclear fission reactors.

  20. Fluoropolymer Films Deposited by Argon Ion-Beam Sputtering of Polytetrafluoroethylene

    NASA Technical Reports Server (NTRS)

    Golub, Morton A.; Banks, Bruce A.; Kliss, Mark (Technical Monitor)

    1998-01-01

    The FT-IR, XPS and UV spectra of fluoropolymer films (SPTFE-I) deposited by argon ion-beam sputtering of polytetrafluoroethylene (PTFE) were obtained and compared with prior corresponding spectra of fluoropolymer films (SPTFE-P) deposited by argon rf plasma sputtering of PTFE. Although the F/C ratios for SPTFE-I and -P (1.63 and 1.51) were similar, their structures were quite different in that there was a much higher concentration of CF2 groups in SPTFE-I than in SPTFE-P, ca. 61 and 33% of the total carbon contents, respectively. The FT-IR spectra reflect that difference, that for SPTFE-I showing a distinct doublet at 1210 and 1150 per centimeter while that for SPTFE-P presents a broad, featureless band at ca. 1250 per centimeter. The absorbance of the 1210-per centimeter band in SPTFE-I was proportional to the thickness of the film, in the range of 50-400 nanometers. The SPTFE-I was more transparent in the UV than SPTFE-P at comparable thickness. The mechanism for SPTFE-I formation likely involves "chopping off" of oligomeric segments of PTFE as an accompaniment to "plasma" polymerization of TFE monomer or other fluorocarbon fragments generated in situ from PTFE on impact with energetic Ar ions. Data are presented for SPTFE-I deposits and the associated Ar(+) bombarded PTFE targets where a fresh target was used for each run or a single target was used for a sequence of runs.

  1. Beta decay rates of neutron-rich nuclei

    SciTech Connect

    Marketin, Tomislav; Huther, Lutz; Martínez-Pinedo, Gabriel

    2015-10-15

    Heavy element nucleosynthesis models involve various properties of thousands of nuclei in order to simulate the intricate details of the process. By necessity, as most of these nuclei cannot be studied in a controlled environment, these models must rely on the nuclear structure models for input. Of all the properties, the beta-decay half-lives are one of the most important ones due to their direct impact on the resulting abundance distributions. Currently, a single large-scale calculation is available based on a QRPA calculation with a schematic interaction on top of the Finite Range Droplet Model. In this study we present the results of a large-scale calculation based on the relativistic nuclear energy density functional, where both the allowed and the first-forbidden transitions are studied in more than 5000 neutron-rich nuclei.

  2. Quadrupole collectivity in neutron-rich Fe and Cr isotopes.

    PubMed

    Crawford, H L; Clark, R M; Fallon, P; Macchiavelli, A O; Baugher, T; Bazin, D; Beausang, C W; Berryman, J S; Bleuel, D L; Campbell, C M; Cromaz, M; de Angelis, G; Gade, A; Hughes, R O; Lee, I Y; Lenzi, S M; Nowacki, F; Paschalis, S; Petri, M; Poves, A; Ratkiewicz, A; Ross, T J; Sahin, E; Weisshaar, D; Wimmer, K; Winkler, R

    2013-06-14

    Intermediate-energy Coulomb excitation measurements are performed on the N ≥ 40 neutron-rich nuclei (66,68)Fe and (64)Cr. The reduced transition matrix elements providing a direct measure of the quadrupole collectivity B(E2;2(1)(+) → 0(1)(+)) are determined for the first time in (68)Fe(42) and (64)Cr(40) and confirm a previous recoil distance method lifetime measurement in (66)Fe(40). The results are compared to state-of-the-art large-scale shell-model calculations within the full fpgd neutron orbital model space using the Lenzi-Nowacki-Poves-Sieja effective interaction and confirm the results of the calculations that show these nuclei are well deformed.

  3. Conservation of Isospin in Neutron-rich Fission Fragments

    SciTech Connect

    Jain, A.K.; Choudhury, D.; Maheshwari, B.

    2014-06-15

    On the occasion of the 75{sup th} anniversary of the fission phenomenon, we present a surprisingly simple result which highlights the important role of isospin and its conservation in neutron rich fission fragments. We have analysed the fission fragment mass distribution from two recent heavyion reactions {sup 238}U({sup 18}O,f) and {sup 208}Pb({sup 18}O,f) as well as a thermal neutron fission reaction {sup 245}Cm(n{sup th},f). We find that the conservation of the total isospin explains the overall trend in the observed relative yields of fragment masses in each fission pair partition. The isospin values involved are very large making the effect dramatic. The findings open the way for more precise calculations of fission fragment distributions in heavy nuclei and may have far reaching consequences for the drip line nuclei, HI fusion reactions, and calculation of decay heat in the fission phenomenon.

  4. New Band Structures in Aapprox110 Neutron-Rich Nuclei

    SciTech Connect

    Zhu, S. J.; Wang, J. G.; Ding, H. B.; Gu, L.; Xu, Q.; Yeoh, E. Y.; Xiao, Z. G.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Liu, S. H.; Li, K.; Luo, Y. X.; Rasmussen, J. O.; Lee, I. Y.; Qi, B.; Meng, J.

    2010-05-12

    The high spin states of neutron-rich nuclei in Aapprox110 region have been carefully investigated by measuring prompt gamma-gamma-gamma coincident measurements populated in the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. Many new collective bands have been discovered. In this proceeding paper, we introduce some interesting new band structures recently observed by our cooperative groups, that is, the one-phonon- and two-phonon gamma-vibrational bands in odd-A {sup 103}Nb, {sup 105}Mo and {sup 107}Tc, the chiral doublet bands in even-even {sup 106}Mo, {sup 110}Ru and {sup 112}Ru, and the pseudospin partner bands with in {sup 108}Tc. The characteristics of these band structures have been discussed.

  5. Measuring the collectivity of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Görgen, Andreas

    2012-10-01

    Measuring the lifetimes of excited nuclear states provides direct information on electromagnetic transition rates and on the collectivity of nuclear excitations. The recoil distance Doppler-shift (RDDS) method is a well-established technique for measuring picosecond lifetimes of excited states, which has been extensively used in combination with fusion-evaporation reactions to measure lifetimes in neutron-deficient nuclei. Here we discuss novel ways of combining the RDDS technique with multi-nucleon transfer and fusion-fission reactions, which allow measurement of picosecond lifetimes in neutron-rich nuclei. Experiments were performed at both GANIL and Legnaro National Laboratories (LNL) with the goal to investigate the onset of collectivity around 68Ni and the evolution of shapes and shape coexistence in medium-heavy fission fragments.

  6. Characterization and literature review of bowel perforation injuring using argon beam coagulation

    NASA Astrophysics Data System (ADS)

    Barnes, Kelli S.; Merchel, Renée. A.; Taylor, Kenneth D.

    2015-03-01

    INTRODUCTION: Argon Beam Coagulation (ABC®) technology is used in conjunction with the ConMed ABCFlex® Probe to provide non-contact hemostasis, coagulation, and tissue devitalization during endoscopic procedures. ABC provides a superficial tissue effect; however, there is a risk of bowel perforation. To better understand the settings that lead to perforation, this study reviews the literature and provides an ex vivo characterization of the ABCFlex Probe tissue effect at different settings when used at small distances. METHODS: Depth of thermal tissue effect was characterized to determine the effect of three parameters: power (W), distance from probe tip to tissue (mm) and application duration (s). 3 ABCFlex Probes were used to create 15 samples on ex vivo porcine small intestine for each combination of parameters. The depth of tissue effect for each sample was measured using a light microscope. RESULTS: Depth of tissue effect increases as power and application time increases. An increase of distance from the probe tip to the tissue results in a decrease in depth of tissue effect from a near contact to 1mm distance. Depth of tissue effect doesn't significantly change from 1mm to 3mm distance. CONCLUSION: ABCFlex Probe can be used to achieve hemostasis in endoscopic procedures. Increasing power and application time increases the depth of thermal effect while increasing distance from the probe time to the surface of the tissue decreases the depth of tissue effect.

  7. Low-energy Coulomb excitation of neutron-rich zinc isotopes

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Behrens, T.; Bildstein, V.; Blazhev, A.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Davinson, T.; Delahaye, P.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Gernhauser, R.; Georgiev, G.; Habs, D.; Heyde, K.; Huber, G.; Huyse, M.; Ibrahim, F.; Ivanov, O.; Iwanicki, J.; Jolie, J.; Kester, O.; Köster, U.; Kröll, T.; Krücken, R.; Lauer, M.; Lisetskiy, A. F.; Lutter, R.; Marsh, B. A.; Mayet, P.; Niedermaier, O.; Pantea, M.; Raabe, R.; Reiter, P.; Sawicka, M.; Scheit, H.; Schrieder, G.; Schwalm, D.; Seliverstov, M. D.; Sieber, T.; Sletten, G.; Smirnova, N.; Stanoiu, M.; Stefanescu, I.; Thomas, J.-C.; Valiente-Dobón, J. J.; Duppen, P. Van; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2009-01-01

    At the radioactive ion beam facility REX-ISOLDE, neutron-rich zinc isotopes were investigated using low-energy Coulomb excitation. These experiments have resulted in B(E2,21+→01+) values in Zn74-80, B(E2,41+→21+) values in Zn74,76 and the determination of the energy of the first excited 21+ states in Zn78,80. The zinc isotopes were produced by high-energy proton- (A=74,76,80) and neutron- (A=78) induced fission of U238, combined with selective laser ionization and mass separation. The isobaric beam was postaccelerated by the REX linear accelerator and Coulomb excitation was induced on a thin secondary target, which was surrounded by the MINIBALL germanium detector array. In this work, it is shown how the selective laser ionization can be used to deal with the considerable isobaric beam contamination and how a reliable normalization of the experiment can be achieved. The results for zinc isotopes and the N=50 isotones are compared to collective model predictions and state-of-the-art large-scale shell-model calculations, including a recent empirical residual interaction constructed to describe the present experimental data up to 2004 in this region of the nuclear chart.

  8. Intruder configurations in neutron-rich {sup 34}P

    SciTech Connect

    Ollier, J.; Chapman, R.; Liang, X.; Labiche, M.; Spohr, K.-M.; Davison, M.; De Angelis, G.; Axiotis, M.; Kroell, T.; Napoli, D.R.; Martinez, T.; Bazzacco, D.; Farnea, E.; Lunardi, S.; Smith, A.G.; Haas, F.

    2005-03-01

    Extensions to the yrast and near-yrast decay sequences of the neutron-rich nucleus {sub 15}{sup 34}P{sub 19} have been established through an analysis of the {gamma} deexcitation of fragments produced in deep-inelastic processes which occur when 230-MeV {sup 36}S ions interact with a thick target of {sup 176}Yb. The highly sensitive GASP array of escape-suppressed Ge detectors was used to measure the resulting {gamma}-ray deexcitations of both projectilelike and targetlike fragments. Previously unobserved excited states in {sup 34}P were observed at 3351, 6236, 2320, and (4723) keV. Several states above an excitation energy of 2.3 MeV involve intruder configurations from the f{sub 7/2} shell. The investigation of negative parity intruder states on the periphery of the 'island of inversion' has an important role to play in our understanding of the evolution of nuclear structure as the island of inversion is approached.

  9. Transition probabilities in neutron-rich Se,8684

    NASA Astrophysics Data System (ADS)

    Litzinger, J.; Blazhev, A.; Dewald, A.; Didierjean, F.; Duchêne, G.; Fransen, C.; Lozeva, R.; Sieja, K.; Verney, D.; de Angelis, G.; Bazzacco, D.; Birkenbach, B.; Bottoni, S.; Bracco, A.; Braunroth, T.; Cederwall, B.; Corradi, L.; Crespi, F. C. L.; Désesquelles, P.; Eberth, J.; Ellinger, E.; Farnea, E.; Fioretto, E.; Gernhäuser, R.; Goasduff, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hackstein, M.; Hess, H.; Ibrahim, F.; Jolie, J.; Jungclaus, A.; Kolos, K.; Korten, W.; Leoni, S.; Lunardi, S.; Maj, A.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Mijatovic, T.; Million, B.; Möller, O.; Modamio, V.; Montagnoli, G.; Montanari, D.; Morales, A. I.; Napoli, D. R.; Niikura, M.; Pollarolo, G.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Rosso, D.; Sahin, E.; Salsac, M. D.; Scarlassara, F.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Theisen, Ch.; Valiente Dobón, J. J.; Vandone, V.; Vogt, A.

    2015-12-01

    Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se,8684 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali di Legnaro using the Cologne Plunger device for the RDDS technique and the AGATA Demonstrator array for the γ -ray detection coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 86Se the level lifetime of the yrast 21+ state and an upper limit for the lifetime of the 41+ state are determined for the first time. The results of 86Se are in agreement with previously reported predictions of large-scale shell-model calculations using Ni78-I and Ni78-II effective interactions. In addition, intrinsic shape parameters of lowest yrast states in 86Se are calculated. In semimagic 84Se level lifetimes of the yrast 41+ and 61+ states are determined for the first time. Large-scale shell-model calculations using effective interactions Ni78-II, JUN45, jj4b, and jj4pna are performed. The calculations describe B (E 2 ;21+→01+) and B (E 2 ;61+→41+) fairly well and point out problems in reproducing the experimental B (E 2 ;41+→21+) .

  10. Cluster emissions with ? daughter from neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kumar, Satish; Batra, J. S.; Gupta, Raj K.

    1996-02-01

    Cluster emissions from neutron-rich 0954-3899/22/2/006/img2, and 0954-3899/22/2/006/img3 nuclei are studied within the preformed cluster model of Malik and Gupta. Q-value estimates of the decays selected on the basis of shell effects in binding energies and their relative preformation probabilities show that these nuclei are stable (Q<0) against 0954-3899/22/2/006/img4 and 0954-3899/22/2/006/img5 decays and all the metastable (Q>0) decays are of non-alpha-like heavy clusters. The most probable decays (minimum half-life times) are the ones with a doubly magic 0954-3899/22/2/006/img6 nucleus as the daughter nucleus, arising due to the WKB penetrability. Compared to the presently measurable alpha-like cluster decays of the corresponding neutron-deficient parents into a 0954-3899/22/2/006/img7 daughter nucleus, these decays are suppressed by many orders of magnitude.

  11. Gamma-ray spectroscopy of neutron-rich products of heavy-ion collisions

    SciTech Connect

    Carpenter, M.P.; Janssens, R.V.F.; Ahmad, I.

    1995-08-01

    Thick-target {gamma}{gamma} coincidence techniques are being used to explore the spectroscopy of otherwise hard-to-reach neutron-rich products of deep-inelastic heavy ion reactions. Extensive {gamma}{gamma} coincidence measurements were performed at ATLAS using pulsed beams of {sup 80}Se, {sup 136}Xe, and {sup 238}U on lead-backed {sup 122,124}Sn targets with energies 10-15% above the Coulomb barrier. Gamma-ray coincidence intensities were used to map out yield distributions with A and Z for even-even product nuclei around the target and around the projectile. The main features of the yield patterns are understandable in terms of N/Z equilibration. We had the most success in studying the decays of yrast isomers. Thus far, more than thirty new {mu}s isomers in the Z = 50 region were found and characterized. Making isotopic assignments for previously unknown {gamma}-ray cascades proves to be one of the biggest problems. Our assignments were based (a) on rare overlaps with radioactivity data, (b) on the relative yields with different beams, and (c) on observed cross-coincidences between {gamma} rays from light and heavy reaction partners. However, the primary products of deep inelastic collisions often are sufficiently excited for subsequent neutron evaporation, so {gamma}{gamma} cross-coincidence results require careful interpretation.

  12. Enhancing ion yields in time-of-flight-secondary ion mass spectrometry: a comparative study of argon and water cluster primary beams.

    PubMed

    Sheraz née Rabbani, Sadia; Razo, Irma Berrueta; Kohn, Taylor; Lockyer, Nicholas P; Vickerman, John C

    2015-02-17

    Following from our previous Letter on this topic, this Article reports a detailed study of time-of-flight-secondary ion mass spectrometry (TOF-SIMS) positive ion spectra generated from a set of model biocompounds (arginine, trehalose, DPPC, and angiotensin II) by water cluster primary ion beams in comparison to argon cluster beams over a range of cluster sizes and energies. Sputter yield studies using argon and water beams on arginine and Irganox 1010 have confirmed that the sputter yields using water cluster beams lie on the same universal sputtering curve derived by Seah for argon cluster beams. Thus, increased ion yield using water cluster beams must arise from increased ionization. The spectra and positive ion signals observed using cluster beams in the size range from 1,000 to 10,000 and the energy range 5-20 keV are reported. It is confirmed that water cluster beams enhance proton related ionization over against argon beams to a significant degree such that enhanced detection sensitivities from 1 μm(2) in the region of 100 to 1,000 times relative to static SIMS analysis with Ar2000 cluster beams appear to be accessible. These new studies show that there is an unexpected complexity in the ionization enhancement phenomenon. Whereas optimum ion yields under argon cluster bombardment occur in the region of E/n ≥ 10 eV (where E is the beam energy and n the number of argon atoms in the cluster) and fall rapidly when E/n < 10 eV; for water cluster beams, ion yields increase significantly in this E/n regime (where n is the number of water molecules in the cluster) and peak for 20 keV beams at a cluster size of 7,000 or E/n ∼3 eV. This important result is explored further using D2O cluster beams that confirm that in this low E/n regime protonation does originate to a large extent from the water molecules. The results, encouraging in themselves, suggest that for both argon and water cluster beams, higher energy beams, e.g., 40 and 80 keV, would enable larger

  13. Production and identification of new, neutron-rich nuclei in the [sup 208]Pb region

    SciTech Connect

    Rykaczewski, K. ); Szerypo, J.; Evensen, A.-H.; Kugler, E.; Lettry, J.; Ravn, H. ); Kurpeta, J.; Pkochocki, A.; Karny, M.; Szerypo, J. ); Szerypo, J. ); Andreyev, H.; Huyse, M.; Wo uml; hr, A. ); Aystuml, J.; Nieminen, A.; Huhta, M. ); Walter, G. ) Hoff, P. )

    1998-12-01

    The recently developed methods allowing the experimental studies on new neutron-rich nuclei beyond doubly-magic [sup 208]Pb are briefly described. An identification of new neutron-rich isotopes [sup 215]Pb and [sup 217]Bi, and new decay properties of [sup 216]Bi studied by means of a pulsed release element selective technique at PS Booster-ISOLDE are reported. [copyright] [ital 1998 American Institute of Physics.

  14. The Spectroscopy of Neutron-Rich sdf-Shell Nuclei Using the CLARA-PRISMA Setup

    SciTech Connect

    Liang, X.; Hodsdon, A.; Chapman, R.; Burns, M.; Keyes, K.; Ollier, J.; Papenberg, A.; Spohr, K.; Azaiez, F.; Ibrahim, F.; Stanoiu, M.; Haas, F.; Caurier, E.; Curien, D.; Nowacki, F.; Salsac, M.-D.; Bazzacco, D.; Beghini, S.; Farnea, E.; Menegazzo, R.

    2006-08-14

    Since the discovery of the breakdown of shell effects in very neutron-rich N=20 and 28 nuclei, studies of the properties of nuclei far from stability have been of intense interest since they provide a unique opportunity to increase our understanding of nuclear interactions in extreme conditions and often challenge our theoretical models.Deep-inelastic processes can be used to populated high spin states of neutron-rich nuclei. In the deep-inelastic processes, an equilibration in N/Z between the target and projectile nuclei is achieved. For most heavy neutron-rich target nuclei, the N/Z ratio is 1.5 - 1.6, while for the possible neutron-rich sdf-shell projectile it is about 1.2. Thus by using deep-inelastic processes one can populate neutron-rich nuclei around N=20 and N=28.New results for the spectroscopy of neutron-rich N=22 36Si and 37P are presented here.

  15. Decay spectroscopy of neutron-rich 134Sb at the CARIBU facility

    NASA Astrophysics Data System (ADS)

    Kolos, Karolina; Scielzo, Nicholas; Padgett, Stephen; McCutchan, Elizabeth A.; Mitchell, Alan John; Lister, Christopher J.; Copp, Patrick; Clark, Jason A.; Carpenter, Mike P.; Savard, Guy; Zhu, Shaofei; Norman, Eric B.; Apbrahamian, Ani; Siegl, Kevin; Heckmaier, Elizabeth; Marley, Scott

    2016-09-01

    Neutron-rich 134Sb is one of a few isotopes (together with 92Rb, 96Y and 142Cs) that have a large branching ratio to decay to the ground state via a 0- ->0+ first-forbidden transition. Previous measurements have indicated that 97.5% of the decays of 134Sb ground state populate the ground state of 134Te directly. However, a recent experiment using an ion trap indicated that this number may be lower. In order to confirm the β-decay branching ratios, an experiment was carried out to measure the decay properties of 134Sb/134mSb using the X-Array (a highly efficient HPGe clover array) and SATURN (a plastic scintillators and tape-transport system) decay-spectroscopy station at the CARIBU radioactive ion-beam facility at Argonne National Laboratory. Results on the analysis will be presented. The U.S. DOE No. DE-AC52-07NA27344, DE-FG02-94ER40848, DE-AC02-98CH10886, DE-AC02-06CH11357, DE-NA-0000979. The NSF under Grant No. PHY-1203100 and the ARCD Project 120104176. This research used resources of ANL's ATLAS facility.

  16. Intruder negative-parity states of neutron-rich {sup 33}Si

    SciTech Connect

    Wang, Z. M.; Chapman, R.; Liang, X.; Burns, M.; Hodsdon, A.; Keyes, K.; Kumar, V.; Papenberg, A.; Smith, J. F.; Spohr, K. M.; Haas, F.; Bouhelal, M.; Caurier, E.; Curien, D.; Nowacki, F.; Azaiez, F.; Ibrahim, F.; Verney, D.; Behera, B. R.; Corradi, L.

    2010-06-15

    Yrast states in the neutron-rich {sub 14}{sup 33}Si{sub 19} nucleus have been studied using binary grazing reactions produced by the interaction of a 215-MeV beam of {sup 36}S ions with a thin {sup 208}Pb target. An experimental setup that combines the large-acceptance magnetic spectrometer PRISMA and the high-efficiency gamma-ray detection array CLARA was used in the experiment. Four new gamma-ray photopeaks at energies of 971, 1724, 1772, and 2655 keV were observed and assigned to the {sup 33}Si level scheme. The experimental level scheme is compared with the results of 1(Planck constant/2pi)omega p-sd-pf large-scale shell-model calculations using the recently developed PSDPFB effective interaction; good agreement is obtained. The structure of the populated states of {sup 33}Si is discussed within the context of an odd neutron coupled to states of the {sup 32}Si core.

  17. gamma-ray spectroscopy of neutron-rich {sup 40}S

    SciTech Connect

    Wang, Z. M.; Chapman, R.; Liang, X.; Burns, M.; Hodsdon, A.; Keyes, K.; Kumar, V.; Papenberg, A.; Smith, J. F.; Spohr, K. M.; Haas, F.; Caurier, E.; Curien, D.; Nowacki, F.; Azaiez, F.; Ibrahim, F.; Verney, D.; Behera, B. R.; Corradi, L.; Fioretto, E.

    2010-05-15

    Yrast states up to (6{sup +}) in the neutron-rich {sup 40}S nucleus have been studied using binary grazing reactions produced by the interaction of a 215 MeV beam of {sup 36}S ions with a thin {sup 208}Pb target. The novel experimental setup that combines the large acceptance magnetic spectrometer, PRISMA, and the high-efficiency gamma-ray detection array, CLARA, was used. A new gamma-ray transition at an energy of 1572 keV was observed and tentatively assigned to the (6{sup +})->(4{sup +}) transition. A comparison of experimental observations and the results of large-scale 0(Planck constant/2pi)omega sd-pf shell-model calculations indicates that one- and two-proton excitations from the 2s{sub 1/2} to the 1d{sub 3/2} orbitals play an important role in reproducing the {sup 40}S yrast level structure and the published B(E2;0{sub g.s.}{sup +}->2{sub 1}{sup +}) value. The structure of the yrast states of the even-A isotopes of sulfur is interpreted in terms of the configurations of valence protons and neutrons within the context of large-scale 0(Planck constant/2pi)omega sd-pf shell-model calculations.

  18. Shape coexistence in neutron-rich odd-mass S isotopes

    NASA Astrophysics Data System (ADS)

    Mijatovic, Tea; Kobayashi, Nobuyuki; Iwasaki, Hiro; Loelius, Charles; Whitmore, Kenneth; Elder, Robert; Gade, Alexandra; Bazin, Daniel; Weisshaar, Dirk; Bender, Peter; Belarge, Joe; Lunderberg, Eric; Elman, Brandon; Longfellow, Brenden; Dewald, Alfred; Haylett, Thoryn; Mathry, Michael; Heil, Sebastian

    2017-01-01

    Collective motions in atomic nuclei at low excitation energies have been characterized by the ground-state shape as a single basis. This picture can be altered in exotic nuclei with unusual proton-to-neutron ratios if the nuclear shape can change drastically at low spin. Recently, there has been an increasing interest for shape-coexistence phenomena in neutron-rich S isotopes and studies suggested fairly large collectivity in 40 , 42 , 44S isotopes. We will discuss the search for isomeric or long-lived states in 45S for which no excited states are known in the literature and the pursuit to fully characterize the band structure of the low-lying states in 43,45S, which provide key information to establish a comprehensive picture of the shape coexistence in this region. Direct model-independent measurements of the 43,45S excited states were realized by applying the Recoil Distance Method with the TRIPLEX Plunger in conjunction with GRETINA to fast rare isotope beams at the NSCL.

  19. Direct evidence of octupole deformation in neutron-rich 144Ba

    SciTech Connect

    Bucher, B.; Zhu, S.; Wu, C. Y.; Janssens, R. V. F.; Cline, D.; Hayes, A. B.; Albers, M.; Ayangeakaa, A. D.; Butler, P. A.; Campbell, C. M.; Carpenter, M. P.; Chiara, C. J.; Clark, J.; Crawford, H. L.; Cromaz, M.; David, H. M.; Gregor, E. T.; Kondev, F. G.; Harker, J.; Hoffman, C. R.; Kay, B. P.; Korichi, A.; Lauritsen, T.; Macchiavelli, A. O.; Pardo, R. C.; Richard, A.; Riley, M. A.; Savard, G.; Scheck, M.; Seweryniak, D.; Smith, M. K.; Wiens, A.; Vondrasek, R.

    2016-03-17

    Here, the neutron-rich nucleus 144Ba (t1/2 = 11.5 s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV 144Ba beam on a 1.0–mg/cm2 208Pb target. The measured value of the matrix element, < 31–∥M(E3)∥01+ >= 0.65(+17–23) eb3/2, corresponds to a reduced B(E3) transition probability of 48(+25–34) W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.

  20. Direct evidence of octupole deformation in neutron-rich 144Ba

    DOE PAGES

    Bucher, B.; Zhu, S.; Wu, C. Y.; ...

    2016-03-17

    Here, the neutron-rich nucleus 144Ba (t1/2 = 11.5 s) is expected to exhibit some of the strongest octupole correlations among nuclei with mass numbers A less than 200. Until now, indirect evidence for such strong correlations has been inferred from observations such as enhanced E1 transitions and interleaving positive- and negative-parity levels in the ground-state band. In this experiment, the octupole strength was measured directly by sub-barrier, multistep Coulomb excitation of a post-accelerated 650-MeV 144Ba beam on a 1.0–mg/cm2 208Pb target. The measured value of the matrix element, < 31–∥M(E3)∥01+ >= 0.65(+17–23) eb3/2, corresponds to a reduced B(E3) transition probabilitymore » of 48(+25–34) W.u. This result represents an unambiguous determination of the octupole collectivity, is larger than any available theoretical prediction, and is consistent with octupole deformation.« less

  1. Evidence for a Change in the Nuclear Mass Surface with the Discovery of the Most Neutron-Rich Nuclei with 17{<=}Z{<=}25

    SciTech Connect

    Tarasov, O. B.; Morrissey, D. J.; Amthor, A. M.; Gade, A.; Nettleton, A.; Sherrill, B. M.; Thoennessen, M.; Baumann, T.; Bazin, D.; Ginter, T. N.; Hausmann, M.; Pereira, J.; Portillo, M.; Stolz, A.; Inabe, N.; Kubo, T.

    2009-04-10

    The results of measurements of the production of neutron-rich nuclei by the fragmentation of a {sup 76}Ge beam are presented. The cross sections were measured for a large range of nuclei including 15 new isotopes that are the most neutron-rich nuclides of the elements chlorine to manganese ({sup 50}Cl, {sup 53}Ar, {sup 55,56}K, {sup 57,58}Ca, {sup 59,60,61}Sc, {sup 62,63}Ti, {sup 65,66}V, {sup 68}Cr, {sup 70}Mn). The enhanced cross sections of several new nuclei relative to a simple thermal evaporation framework, previously shown to describe similar production cross sections, indicates that nuclei in the region around {sup 62}Ti might be more stable than predicted by current mass models and could be an indication of a new island of inversion similar to that centered on {sup 31}Na.

  2. Investigations on the time evolution of the plasma density in argon electron-beam plasma at intermediate pressure

    NASA Astrophysics Data System (ADS)

    Xiaoyan, BAI; Chen, CHEN; Hong, LI; Wandong, LIU

    2017-03-01

    The time evolution of the argon electron-beam plasma at intermediate pressure and low electron beam intensity was presented. By applying the amplitude modulation with the frequency of 20 Hz on the stable beam current, the plasma evolution was studied. A Faraday cup was used for the measurement of the electron beam current and a single electrostatic probe was used for the measurement of the ion current. Experimental results indicated that the ion current was in phase with the electron beam current in the pressure range from 200 Pa to 3000 Pa and in the beam current range lower than 20 mA, the residual density increased approximately linearly with the maximum density in the log-log plot and the fitting coefficient was irrelative to the pressure. And then three kinds of kinetic models were developed and the simulated results given by the kinetic model, without the consideration of the excited atoms, mostly approached to the experimental results. This indicated that the effect of the excited atoms on the plasma density can be ignored at intermediate pressure and low electron beam current intensity, which can greatly simplify the kinetic model. In the end, the decrease of the plasma density when the beam current was suddenly off was studied based on the simplified model and it was found that the decease characteristic at intermediate pressure was approximate to the one at high pressure at low electron beam intensity, which was in good accordance with the experimental results. Supported by National Natural Science Foundations of China (No. 11375187) and the Foundation of State key Laboratory of China (No. SKLIPR1510).

  3. Comparisons of cross-section predictions for relativistic iron and argon beams with semiempirical fragmentation models

    NASA Technical Reports Server (NTRS)

    Townsend, Lawrence W.; Tripathi, Ram K.; Khan, Ferdous

    1993-01-01

    Cross-section predictions with semi-empirical nuclear fragmentation models from the Langley Research Center and the Naval Research Laboratory are compared with experimental data for the breakup of relativistic iron and argon projectile nuclei in various targets. Both these models are commonly used to provide fragmentation cross-section inputs into galactic cosmic ray transport codes for shielding and exposure analyses. Overall, the Langley model appears to yield better agreement with the experimental data.

  4. Beta Decay Spectroscopy of Neutron-Rich Nuclei at RIBF

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P.-A.; Browne, F.; Daido, R.; Yifan, F.; Nishibata, H.; Yagi, A.; Gey, G.; Li, Z.; Wu, J.; Lubos, D.; Moschner, K.; Patel, Z.; Rice, S.; Sinclair, L.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Watanabe, H.; Xu, Z. Y.; Yoshinaga, K.

    2015-11-01

    The development of a high intensity 238U beam at the Radioactive Isotope Beam Factory (RIBF) has opened a new opportunity to explore exotic regions of the nuclear chart that were not accessible before. Along with beam development, the installation of the high efficiency γ-detector EURICA has made β-decay spectroscopy measurements of these regions possible, and a large international effort named the EURICA project has been launched to take advantage of this new opportunity.

  5. Production of neutron-rich transcalifornium nuclei in 238U-induced transfer reactions

    NASA Astrophysics Data System (ADS)

    Zhu, Long; Su, Jun; Xie, Wen-Jie; Zhang, Feng-Shou

    2016-11-01

    In order to produce more unknown neutron-rich transcalifornium nuclei, the collisions of 238U with the targets 248Cm, 249Cf, and 250Cm are investigated within the framework of the dinuclear system model. The production cross sections of unknown neutron-rich nuclei with Z =99 -104 in these reactions are predicted. The influences of N /Z ratios and charge numbers of the targets on the production cross sections are studied. It is found that high N /Z ratios of 248Cm and 250Cm targets enhance the production cross sections of neutron-rich transcalifornium nuclei. However, due to high charge number of the target 249Cf the predicted production cross sections of unknown neutron-rich nuclei with Z =104 in the reaction 238U+249Cf are higher than those in 238U+248Cm . We also have studied the entrance angular momentum effects on production probabilities of transfer products in the reaction 238U+248Cm . It is found that the formation probabilities of the final neutron-rich products increase first and then decrease with the increasing J .

  6. Chemical effect of inert argon beam on nitride nanolayer formed by ion implantation into GaAs surface

    NASA Astrophysics Data System (ADS)

    Mikoushkin, V. M.

    2010-12-01

    The composition of a nitride nanolayer formed on a GaAs(100) surface by the implantation of ions with an energy of E i = 2.5 keV and the chemical state of nitrogen in this layer have been studied by the method of Auger electron spectroscopy. It is established that, in addition to GaN, a GaAsN solid solution phase is formed in the ion-implanted layer. The energies of N KVV Auger electron transitions in these phases are determined as E A (GaN) = 379.8 ± 0.2 eV and E A (GaAsN) = 382.8 ± 0.2 eV (relative to the Fermi level), which allowed the distribution of nitrogen between these phases to be evaluated as [N(GaN)] = 70% and [N(GaAsN)] = 30%. It is established that an argon ion beam produces a chemical effect on the nitride layer, which is related to a cascade mixing of the material. Under the action of the argon ion bombardment, the distribution of nitrogen in the indicated phases changes to opposite. As a result a nitride nanolayer is formed in which the narrow-bandgap semiconductor (GaAsN) predominates rather than the wide-bandgap component (GaN).

  7. β-decay of neutron-rich Z∼60 nuclei and the origin of rare earth elements

    SciTech Connect

    Wu, J.; Nishimura, S.; Lorusso, G.; Baba, H.; Doornenbal, P.; Isobe, T.; Söderström, P. A.; Sakurai, H.; Xu, Z. Y.; Browne, F.; Daido, R.; Fang, Y. F.; Yagi, A.; Nishibata, H.; Odahara, A.; Yamamoto, T.; Ideguchi, E.; Aoi, N.; Tanaka, M.; Collaboration: EURICA Collaboration; and others

    2014-05-02

    A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a β-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z∼60 that are progenitors of the rare-earth elements with mass number A∼460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

  8. Spectroscopic Quadrupole Moments in Sr,9896 : Evidence for Shape Coexistence in Neutron-Rich Strontium Isotopes at N =60

    NASA Astrophysics Data System (ADS)

    Clément, E.; Zielińska, M.; Görgen, A.; Korten, W.; Péru, S.; Libert, J.; Goutte, H.; Hilaire, S.; Bastin, B.; Bauer, C.; Blazhev, A.; Bree, N.; Bruyneel, B.; Butler, P. A.; Butterworth, J.; Delahaye, P.; Dijon, A.; Doherty, D. T.; Ekström, A.; Fitzpatrick, C.; Fransen, C.; Georgiev, G.; Gernhäuser, R.; Hess, H.; Iwanicki, J.; Jenkins, D. G.; Larsen, A. C.; Ljungvall, J.; Lutter, R.; Marley, P.; Moschner, K.; Napiorkowski, P. J.; Pakarinen, J.; Petts, A.; Reiter, P.; Renstrøm, T.; Seidlitz, M.; Siebeck, B.; Siem, S.; Sotty, C.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van de Walle, J.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.; De Witte, H.; Wrzosek-Lipska, K.

    2016-01-01

    Neutron-rich Sr,9896 isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N =60 .

  9. Use of Neutron Transfer Reactions to Indirectly Determine Neutron Capture Cross Sections on Neutron-Rich Nuclei

    SciTech Connect

    McCleskey, M.; Mukhamedzhanov, A. M.; Tribble, R. E.; Simmons, E.; Spiridon, A.; Banu, A.; Roeder, B.; Goldberg, V.; Trache, L.; Chen, X. F.; Lui, Y.-W.

    2010-03-01

    {sup 14}C(n,gamma){sup 15}C is being used as a test case in the development of an indirect method to determine neutron capture cross sections on neutron-rich unstable nuclei at astrophysical energies. Our approach makes use of two reactions: one peripheral used to find the asymptotic normalization coefficient (ANC) and a second non-peripheral reaction to determine the spectroscopic factor. The ANC for {sup 15}C has been determined using a HI neutron transfer reaction with a 12 MeV/nucleon {sup 14}C beam on a {sup 13}C target. The spectroscopic factor will be determined using {sup 14}C(d,p) in forward kinematics with an incident deuteron energy of 60 MeV. Both experiments were performed using the MDM high-resolution spectrometer at Texas A and M University.

  10. -decay measurements for N > 40 Mn nuclei and inference of collectivity for neutron-rich Fe isotopes

    SciTech Connect

    Daugas, J; Delaroche, J. P.; Pfutzner, M.; Sawicka, M.; Becker, F.; Belier, G.; Bingham, C. R.; Borcea, C.; Bouchez, E.; Buta, A.; Dragulescu, E.; Georgiev, G.; Giovinazzo, J.; Grawe, H.; Grzywacz, R.; Hammache, F.; Libert, J.; Meot, V.; Negoita, F.; de Oliveira Santos, F.; Perru, O.; Roig, O.; Rykaczewski, Krzysztof Piotr; Saint-Laurent, M. G.; Sauvestre, J. E.; Sorlin, O.; Stanoiu, M.; Stefan, I.; Theisen, Ch.

    2011-01-01

    A decay spectroscopic study of the neutron-rich isotopes has been performed using fragmentation of a 86Kr primary beam. Fragments from this reaction have been selected by the LISE2000 spectrometer at the Grand Acc el erateur National d Ions Lourds (GANIL). Half-lives of 29 isotopes, including the first ones identified for 61Ti (15 4 ms), 64V (19 8 ms), and 71Fe (28 5 ms), have been determined and compared with model predictions. 67,68Mn -delayed rays were observed for the first time. The branching for the -delayed neutron emission was measured to be greater than 10(5)% in the 67Mn decay. The 67Fe isomeric level is firmly determined at higher energy than assigned in previous works. The excitation energies of the first (2+) and (4+) states of 68Fe are suggested to lie at 522(1) and 1389(1) keV, respectively, thus bringing confirmation of assignments based on in-beam -ray spectroscopy. Beyond-mean-field calculations with the Gogny D1S force have been performed for even-mass nuclei through the Fe isotopic chain. Not only 68Fe but most of the neutron-rich Fe isotopes with neutron numbers below N = 50 are interpreted as soft rotors. The calculated mean occupancy of the neutron g9/2 and d5/2 orbitals in correlated ground states is steadily growing with increasing neutron number throughout the isotopic chain. Interpretation of 67Fe data is based upon the present calculations for the 66Fe and 68Fe even cores.

  11. Two-Beam multiplexed laser-induced fluorescence measurements of an argon arcjet plume

    NASA Astrophysics Data System (ADS)

    Ruyten, Wilhelmus M.; Keefer, Dennis

    1993-11-01

    We describe a multiplexed, laser-induced fluorescence (LIF) technique with which radial and axial profiles of vector velocities of excited propellant species were obtained in the exhaust plume from a 300-W argon arcjet. Although the arcjet is a prototype, and although argon is not an interesting propellant from a propulsion perspective, the technique clearly demonstrates how a narrowband, frequency-stabilized ring-dye laser can be used to obtain simultaneous measurements of two velocity components in an arcjet plume and how a third signal from an optogalvanic cell can be used as a frequency reference. We also show that much information on the flow can be obtained by analyzing the Doppler widths and fluorescence intensities of the LIF data. Specifically, the data identify a boundary layer in the radial direction of the plume and a shock in the downstream region of the flow. Also, some flow anisotropy is observed, consistent with the assumption that the magnitude of the mean flow velocity fluctuates. The peak velocity on centerline remains roughly constant at 3 km/s throughout the expansion.

  12. Two-Beam multiplexed laser-induced fluorescence measurements of an argon arcjet plume

    NASA Technical Reports Server (NTRS)

    Ruyten, Wilhelmus M.; Keefer, Dennis

    1993-01-01

    We describe a multiplexed, laser-induced fluorescence (LIF) technique with which radial and axial profiles of vector velocities of excited propellant species were obtained in the exhaust plume from a 300-W argon arcjet. Although the arcjet is a prototype, and although argon is not an interesting propellant from a propulsion perspective, the technique clearly demonstrates how a narrowband, frequency-stabilized ring-dye laser can be used to obtain simultaneous measurements of two velocity components in an arcjet plume and how a third signal from an optogalvanic cell can be used as a frequency reference. We also show that much information on the flow can be obtained by analyzing the Doppler widths and fluorescence intensities of the LIF data. Specifically, the data identify a boundary layer in the radial direction of the plume and a shock in the downstream region of the flow. Also, some flow anisotropy is observed, consistent with the assumption that the magnitude of the mean flow velocity fluctuates. The peak velocity on centerline remains roughly constant at 3 km/s throughout the expansion.

  13. From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism

    SciTech Connect

    Thirolf, P. G.

    2015-02-24

    High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called ‘fission-fusion’, which will be introduced in the second part of the article. Accelerating fissile species (e.g. {sup 232}Th) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. ‘Waiting points’ at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in ‘terra incognita’ of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional

  14. From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism

    NASA Astrophysics Data System (ADS)

    Thirolf, P. G.

    2015-02-01

    High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called `fission-fusion', which will be introduced in the second part of the article. Accelerating fissile species (e.g. 232Th ) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. `Waiting points' at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in `terra incognita' of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional nuclear reaction

  15. Structure and reactions of light neutron rich nuclei

    SciTech Connect

    Esbensen, H.

    1993-01-01

    Radioactive beam experiments have made it possible to study the structure of nuclei at the neutron drip line. Pair correlations play a crucial role in such nuclei and characteristic features include an extended neutron halo density and a large dipole strength near threshold. The most detailed studies have been performed for [sup 11]Li. I will present a 3-body model that explains the main features of the data obtained for this nucleus.

  16. Structure and reactions of light neutron rich nuclei

    SciTech Connect

    Esbensen, H.

    1993-04-01

    Radioactive beam experiments have made it possible to study the structure of nuclei at the neutron drip line. Pair correlations play a crucial role in such nuclei and characteristic features include an extended neutron halo density and a large dipole strength near threshold. The most detailed studies have been performed for {sup 11}Li. I will present a 3-body model that explains the main features of the data obtained for this nucleus.

  17. Single and multilayered materials processing by argon ion beam etching: study of ion angle incidence and defect formation

    NASA Astrophysics Data System (ADS)

    Gosset, N.; Boufnichel, M.; Bahette, E.; Khalfaoui, W.; Ljazouli, R.; Grimal-Perrigouas, V.; Dussart, R.

    2015-09-01

    Ion beam etching (IBE) is a very promising technique in microelectronics because of its capability to etch small patterns with a high resolution and inert materials. In this study, the angular incidence of an argon ion beam on the etch rate and uniformity is discussed in the case of several materials often used in microelectronics. The capability of the IBE technique to etch multilayered stack samples with positive anisotropic profiles was demonstrated on TiNiAu, TiNiCuAu, BST and PZT. Two typical defects involved in IBE processing (fences and not etched pattern foots) due to shadow masking and redeposition effect, are explained and solutions are presented to avoid them. Deep IBE was performed on GaN with an etch depth as high as 10 μm, using a 8 μm thick SiO2 mask. The etching of other mask materials, such as TiN, was investigated in order to improve the selectivity. Using a TiN mask, a selectivity to GaN as high as 5 is reported. Finally, the etch rate enhancement needed for deep etching was studied.

  18. Bands and Isomers in Neutron-Rich Rare-Earth Nuclei in PHF Model

    NASA Astrophysics Data System (ADS)

    Praharaj, C. R.; Ghorui, S. K.; Naik, Z.; Sahu, B. B.

    Rotational structures of neutron-rich Gd and Dy nuclei in the REE peak region are studied with deformed Hartee-Fock (HF) and angular momentum (J) projection model. Spectra of ground band and a few more excited, positive and negative parity bands have been studied up to high spin values. Some 4-quasiparticle K-isomeric bands and their electromagnetic properties are predicted.

  19. New Isomers in the Full Seniority Scheme of Neutron-Rich Lead Isotopes: The Role of Effective Three-Body Forces

    NASA Astrophysics Data System (ADS)

    Gottardo, A.; Valiente-Dobón, J. J.; Benzoni, G.; Nicolini, R.; Gadea, A.; Lunardi, S.; Boutachkov, P.; Bruce, A. M.; Górska, M.; Grebosz, J.; Pietri, S.; Podolyák, Zs.; Pfützner, M.; Regan, P. H.; Weick, H.; Alcántara Núñez, J.; Algora, A.; Al-Dahan, N.; de Angelis, G.; Ayyad, Y.; Alkhomashi, N.; Allegro, P. R. P.; Bazzacco, D.; Benlliure, J.; Bowry, M.; Bracco, A.; Bunce, M.; Camera, F.; Casarejos, E.; Cortes, M. L.; Crespi, F. C. L.; Corsi, A.; Denis Bacelar, A. M.; Deo, A. Y.; Domingo-Pardo, C.; Doncel, M.; Dombradi, Zs.; Engert, T.; Eppinger, K.; Farrelly, G. F.; Farinon, F.; Farnea, E.; Geissel, H.; Gerl, J.; Goel, N.; Gregor, E.; Habermann, T.; Hoischen, R.; Janik, R.; Klupp, S.; Kojouharov, I.; Kurz, N.; Lenzi, S. M.; Leoni, S.; Mandal, S.; Menegazzo, R.; Mengoni, D.; Million, B.; Morales, A. I.; Napoli, D. R.; Naqvi, F.; Nociforo, C.; Prochazka, A.; Prokopowicz, W.; Recchia, F.; Ribas, R. V.; Reed, M. W.; Rudolph, D.; Sahin, E.; Schaffner, H.; Sharma, A.; Sitar, B.; Siwal, D.; Steiger, K.; Strmen, P.; Swan, T. P. D.; Szarka, I.; Ur, C. A.; Walker, P. M.; Wieland, O.; Wollersheim, H.-J.; Nowacki, F.; Maglione, E.; Zuker, A. P.

    2012-10-01

    The neutron-rich lead isotopes, up to Pb216, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond Pb208.

  20. Strong enhancement of dynamical emission of heavy fragments in the neutron-rich {sup 124}Sn+{sup 64}Ni reaction at 35A MeV

    SciTech Connect

    Russotto, P.; Amorini, F.; Cavallaro, S.; Di Toro, M.; Giustolisi, F.; Porto, F.; Rizzo, F.; De Filippo, E.; Pagano, A.; Cardella, G.; Lanzano, G.; Papa, M.; Pirrone, S.; Piasecki, E.; Auditore, L.; Trifiro, A.; Trimarchi, M.

    2010-06-15

    A quantitative comparison is made between the absolute cross sections associated with statistical and dynamical emission of heavy fragments in the {sup 124}Sn+{sup 64}Ni and {sup 112}Sn+{sup 58}Ni collisions experimentally investigated at 35A MeV beam energy using the multidetector CHIMERA. The result shows that the dynamical process is about twice as probable in the neutron-rich {sup 124}Sn+{sup 64}Ni system as in the {sup 112}Sn+{sup 58}Ni neutron-poor one. This unexpected and significant difference indicates that the reaction mechanism is strongly dependent on the entrance-channel isospin (N/Z) content.

  1. Theoretical study of triaxial shapes of neutron-rich Mo and Ru nuclei

    SciTech Connect

    Zhang, C. L.; Bhat, G. H.; Nazarewicz, W.; Sheikh, J. A.; Shi, Yue

    2015-09-10

    Here, whether atomic nuclei can possess triaxial shapes at their ground states is still a subject of ongoing debate. According to theory, good prospects for low-spin triaxiality are in the neutron-rich Mo-Ru region. Recently, transition quadrupole moments in rotational bands of even-mass neutron-rich isotopes of molybdenum and ruthenium nuclei have been measured. The new data have provided a challenge for theoretical descriptions invoking stable triaxial deformations. The purpose of this study is to understand experimental data on rotational bands in the neutron-rich Mo-Ru region, we carried out theoretical analysis of moments of inertia, shapes, and transition quadrupole moments of neutron-rich even-even nuclei around 110Ru using self-consistent mean-field and shell model techniques. Methods: To describe yrast structures in Mo and Ru isotopes, we use nuclear density functional theory (DFT) with the optimized energy density functional UNEDF0. We also apply triaxial projected shell model (TPSM) to describe yrast and positive-parity, near-yrast band structures. As a result, our self-consistent DFT calculations predict triaxial ground-state deformations in 106,108Mo and 108,110,112Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-gamma structure, associated with the aligned ν(h11/2)2 pair, becomes energetically favored. The computed transition quadrupole moments vary with angular momentum, which reflects deformation changes with rotation; those variations are consistent with experiment. The TPSM calculations explain the observed band structures assuming stable triaxial shapes. Lastly, the structure of neutron-rich even-even nuclei around Ru-110 is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.

  2. Improved mass resolution and mass accuracy in TOF-SIMS spectra and images using argon gas cluster ion beams.

    PubMed

    Shon, Hyun Kyong; Yoon, Sohee; Moon, Jeong Hee; Lee, Tae Geol

    2016-06-09

    The popularity of argon gas cluster ion beams (Ar-GCIB) as primary ion beams in time-of-flight secondary ion mass spectrometry (TOF-SIMS) has increased because the molecular ions of large organic- and biomolecules can be detected with less damage to the sample surfaces. However, Ar-GCIB is limited by poor mass resolution as well as poor mass accuracy. The inferior quality of the mass resolution in a TOF-SIMS spectrum obtained by using Ar-GCIB compared to the one obtained by a bismuth liquid metal cluster ion beam and others makes it difficult to identify unknown peaks because of the mass interference from the neighboring peaks. However, in this study, the authors demonstrate improved mass resolution in TOF-SIMS using Ar-GCIB through the delayed extraction of secondary ions, a method typically used in TOF mass spectrometry to increase mass resolution. As for poor mass accuracy, although mass calibration using internal peaks with low mass such as hydrogen and carbon is a common approach in TOF-SIMS, it is unsuited to the present study because of the disappearance of the low-mass peaks in the delayed extraction mode. To resolve this issue, external mass calibration, another regularly used method in TOF-MS, was adapted to enhance mass accuracy in the spectrum and image generated by TOF-SIMS using Ar-GCIB in the delayed extraction mode. By producing spectra analyses of a peptide mixture and bovine serum albumin protein digested with trypsin, along with image analyses of rat brain samples, the authors demonstrate for the first time the enhancement of mass resolution and mass accuracy for the purpose of analyzing large biomolecules in TOF-SIMS using Ar-GCIB through the use of delayed extraction and external mass calibration.

  3. Enhancement of fusion at near-barrier energies for neutron-rich light nuclei: 19O +12 C

    NASA Astrophysics Data System (ADS)

    Singh, Varinderjit; Vadas, J.; Steinbach, T. K.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Kuvin, S. A.; Tripathi, Vandana; Wiedenhover, I.; Umar, A. S.

    2017-01-01

    Measuring the fusion excitation function for an isotopic chain of projectile nuclei provides a sensitive test of a microscopic description of fusion. To investigate the theoretically predicted fusion enhancement for neutron-rich light nuclei, an experiment was performed to measure the fusion excitation functions for 19 O +12 C and 18 O +12 C . Using the 18O(d,p) reaction and the RESOLUT mass spectrometer at Florida State University, a beam of 19O was produced with an intensity of 2-4 x 103 p/s. This beam bombarded a 100 μg/cm2 carbon target. Using an approach optimized for the measurement of fusion with a low-intensity beam, evaporation residues (ERs) resulting from the de-excitation of the fusion product were measured. The ERs were identified by measuring their energy and time-of-flight. At near-barrier energies, an enhancement of fusion by a factor of three has been observed for 19 O +12 C in comparison to 18 O +12 C . Comparison of the experimental results with the predictions of a density constrained time-dependent Hartree-Fock (DC-TDHF) model provide evidence for the importance of pairing in the fusion process. Supported by the US DOE under Grant No. DEFG02-88ER-40404.

  4. Beta Decay Study of Neutron-rich Magnesium

    NASA Astrophysics Data System (ADS)

    Ash, John; Rajabali, Mustafa; Griffin Collaboration

    2015-10-01

    Within the ``island of inversion'' around the N = 20 shell gap, isotopes of magnesium, and aluminum deviate from the expected closed-shell structure. Particles promoted across the N = 20 shell gap result in a lower energy deformed ground state configuration rather than the expected spherical configuration. An experiment was conducted at TRIUMF laboratory in the summer of 2015 to study the decay of ``island of inversion'' isotopes 33 , 34 , 35Mg and the structure of the respective daughter nuclei. The isotopes of interest were produced by a proton beam from TRIUMF's 500 MeV cyclotron impacting on a UCx target. The magnesium decays populated states along the decay chain in Al, Si, P, and S isotopes. The new GRIFFIN spectrometer in the ISAC-I facility was used to detect the gamma rays. Two sets of scintillators, one for detecting the beta particles (SCEPTAR) and the other for detecting beta-delayed neutrons (DESCANT), were also used in conjunction with GRIFFIN. The GRIFFIN data were energy calibrated and partially analyzed for this project. New algorithms were developed for the analysis. Preliminary results for new transitions detected in 34Mg as well as the half lives obtained will be presented in their current form. This research was supported by the Tennessee Tech research office.

  5. Transparent and electrically conductive GaSb/Si direct wafer bonding at low temperatures by argon-beam surface activation

    NASA Astrophysics Data System (ADS)

    Predan, F.; Reinwand, D.; Klinger, V.; Dimroth, F.

    2015-10-01

    Direct wafer bonds of the material system n-GaSb/n-Si have been achieved by means of a low-temperature direct wafer bonding process, enabling an optical transparency of the bonds along with a high electrical conductivity of the boundary layer. In the used technique, the surfaces are activated by sputter-etching with an argon fast-atom-beam (FAB) and bonded in ultra-high vacuum. The bonds were annealed at temperatures between 300 and 400 °C, followed by an optical, mechanical and electrical characterization of the interface. Additionally, the influence of the sputtering on the surface topography of the GaSb was explicitly investigated. Fully bonded wafer pairs with high bonding strengths were found, as no blade could be inserted into the bonds without destroying the samples. The interfacial resistivities of the bonded wafers were significantly reduced by optimizing the process parameters, by which Ohmic interfacial resistivities of less than 5 mΩ cm2 were reached reproducibly. These promising results make the monolithic integration of GaSb on Si attractive for various applications.

  6. Experimental and Theoretical Estimation of Excited Species Generation in Pulsed Electron Beam-Generated Plasmas Produced in Pure Argon, Nitrogen, Oxygen, and Their Mixtures

    DTIC Science & Technology

    2011-05-13

    Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6750--11-9333 Experimental and Theoretical Estimation of Excited Species Generation in ...Pulsed Electron Beam–Generated Plasmas Produced in Pure Argon, Nitrogen, Oxygen, and Their Mixtures May 13, 2011 Approved for public release...PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Experimental and Theoretical Estimation of Excited Species Generation in Pulsed Electron Beam

  7. Charge Radius Changes Of Even-even Neutron-Rich Tellurium Isotopes

    SciTech Connect

    Sifi, R.; Le Blanc, F.; Barre, N.; Ducourtieux, M.; Essabaa, S.; Lau, C.; Oms, J.; Roussiere, B.; Sauvage, J.; Cabaret, L.; Pinard, J.; Crawford, J.; Lee, J. K. P.; Genevey, J.; Huber, G.; Kowalska, M.; Seliverstov, M.; Le Scornet, G.; Stroke, H.

    2006-04-26

    Laser spectroscopy based on resonant ionization of laser-desorbed atoms has been used to study the neutron-rich tellurium isotopes with the COMPLIS facility at ISOLDE-CERN. The isotope shift and the hyperfine structure of several neutron-rich Te isotopes: 120-136Te and 123m-133mTe have been measured. From the hyperfine structure and the isotope shift we can extract the magnetic and quadrupole moments and the change in the mean square charge radius respectively. The mean square charge radii of the even-even isotopes have been deduced and their comparison with the known data for the other elements near Z=50 is presented. The experimental {delta} is compared with that obtained from the relativistic mean field calculations.

  8. Beta-Decay and Delayed Neutron Emission of Very Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Borzov, I. N.

    2014-09-01

    Extended self-consistent beta-decay model has been applied for beta-decay rates and delayed multi-neutron emission probabilities of quasi-spherical neutron-rich isotopes. The Gamow-Teller and first-forbidden decays are treated within the coordinate-space formalism of the continuum QRPA based on the density functional theory description of the ground state. A new set of the Fayans density functional parameters (DF3a) have been employed giving a better spin-orbit splitting due to a stronger tensor term. A provision has been included to fix the odd particle in the proper orbit (before variation). This accounts for ground-state spin inversion effect which has been shown to exist in the region of the most neutron-rich doubly-magic nucleus 78Ni.

  9. Reflection Asymmetric Shapes in the Neutron-Rich 140,143Ba Isotopes

    NASA Astrophysics Data System (ADS)

    Zhu Sheng-jiang (S, J. Zhu; Wang, Mu-ge; J, H. Hamilton; A, V. Ramayya; B, R. S. Babu; W, C. Ma; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; T, N. Ginter; J, Komicki; J, D. Cole; R, Aryaeinejad; Y, K. Dardenne; M, W. Drigert; J, O. Rasmussen; Ts, Yu Oganessian; M, A. Stoyer; S, Y. Chu; K, E. Gregorich; M, F. Mohar; S, G. Prussin; I, Y. Lee; N, R. Johnson; F, K. McGowan

    1997-08-01

    Level schemes for the neutron-rich 140,143Ba nuclei have been determined by study of prompt γ-rays in spontaneous fission of 252Cf. The level pattern and enhanced E1 transitions between π = + and π = - bands show reflection asymmetric shapes with simplex quantum number s = +1 in 140Ba and s = ±i in 143Ba, respectively. The octupole deformation stability with spin variation has been discussed.

  10. Theoretical study of triaxial shapes of neutron-rich Mo and Ru nuclei

    DOE PAGES

    Zhang, C. L.; Bhat, G. H.; Nazarewicz, W.; ...

    2015-09-10

    Here, whether atomic nuclei can possess triaxial shapes at their ground states is still a subject of ongoing debate. According to theory, good prospects for low-spin triaxiality are in the neutron-rich Mo-Ru region. Recently, transition quadrupole moments in rotational bands of even-mass neutron-rich isotopes of molybdenum and ruthenium nuclei have been measured. The new data have provided a challenge for theoretical descriptions invoking stable triaxial deformations. The purpose of this study is to understand experimental data on rotational bands in the neutron-rich Mo-Ru region, we carried out theoretical analysis of moments of inertia, shapes, and transition quadrupole moments of neutron-richmore » even-even nuclei around 110Ru using self-consistent mean-field and shell model techniques. Methods: To describe yrast structures in Mo and Ru isotopes, we use nuclear density functional theory (DFT) with the optimized energy density functional UNEDF0. We also apply triaxial projected shell model (TPSM) to describe yrast and positive-parity, near-yrast band structures. As a result, our self-consistent DFT calculations predict triaxial ground-state deformations in 106,108Mo and 108,110,112Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-gamma structure, associated with the aligned ν(h11/2)2 pair, becomes energetically favored. The computed transition quadrupole moments vary with angular momentum, which reflects deformation changes with rotation; those variations are consistent with experiment. The TPSM calculations explain the observed band structures assuming stable triaxial shapes. Lastly, the structure of neutron-rich even-even nuclei around Ru-110 is consistent with triaxial shape deformations. Our DFT and TPSM frameworks provide a consistent and complementary description of experimental data.« less

  11. A continuous microwave discharge maintained by two crossing millimeter-wave beams in hydrogen and argon: numerical simulation and experiment

    NASA Astrophysics Data System (ADS)

    Chernov, V. V.; Gorbachev, A. M.; Vikharev, A. L.; Radishev, D. B.; Kozlov, A. V.

    2016-12-01

    The results of numerical simulation of a continuous microwave discharge in two crossing wave beams of 30 GHz radiation in a mixture of hydrogen and argon are presented. The model describes the steady state of the gas discharge in Ar-H2-H through the self-consistent solution of the following equations: Maxwell’s equations, the electron balance equation, the transport of hydrogen atoms in the ternary mixture, the heat conduction equation and the equation of state of ideal gas. In Maxwell’s equations the effect of the plasma is taken into account through the conduction current. It is assumed that the generation of electrons occurs due to ionization processes and their loss occurs due to processes of electron-ion recombination and ambipolar diffusion. In the model the heat transfer is considered to be due to gas thermal conductivity and transfer of dissociation energy through the flow of hydrogen atoms. The gas pressure is assumed to be constant, and convection effects are neglected. The other approximations and reductions used in the model are discussed. The adequacy of the obtained model is confirmed by comparing the calculation results to experimental data. For comparison the distributions of gas temperature along the substrate in the center of the discharge and the atomic hydrogen flow to the substrate are used. The temperature is experimentally obtained through the analysis of the optical emission of the C2 Swan line. The atomic hydrogen flow to the substrate is measured from the etching of graphite samples imbedded into the substrate. The possibility of obtaining large-area uniform plasma layers in hydrogen with a small addition of methane is predicted. The applications of such gas discharge are discussed.

  12. The study of neutron-rich nuclei production in the region of the closed shell N=126 in the multi-nucleon transfer reaction 136Xe+208Pb

    NASA Astrophysics Data System (ADS)

    Novikov, K.; Harca, I. M.; Kozulin, E. M.; Dmitriev, S.; Itkis, J.; Knyazheva, G.; Loktev, T.; Corradi, L.; Valiente-Dobon, J.; Fioretto, E.; Montanari, D.; Stefanini, A. M.; Vardaci, E.; Quero, D.; Montagnoli, G.; Scarlassara, F.; Strano, E.; Pollarolo, G.; Piot, J.; Mijatović, T.; Szilner, S.; Ackermann, D.; Chubarian, G.; Trzaska, W. H.

    2016-04-01

    The unexplored area of heavy neutron rich nuclei is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. For the production of heavy neutron rich nuclei located along the neutron closed shell N=126 (probably the last "waiting point" in the r-process of nucleosynthesis) the low-energy multi-nucleon transfer reaction 136Xe+208Pb at Elab=870MeV was explored. Due to the stabilizing effect of the closed neutron shells in both nuclei, N=82 and N=126, and the rather favorable proton transfer from lead to xenon, the light fragments formed in this process are well bound and the Q-value of the reaction is nearly zero. Measurements were performed with the PRISMA spectrometer in coincidence with an additional time-of-flight (ToF) arm on the +20 beam line of the PIAVE-ALPI accelerator in Legnaro, Italy. The PRISMA spectrometer allows identification of the A, Z and velocity of the projectile-like fragments (PLF), while the second arm gives access to the target-like fragments (TLF). Details on the experimental setup and preliminary results are reported.

  13. Neutron-Rich {sup 62,64,64}Fe Show Enhanced Collectivity: The Washout of N = 40 in Terms of Experiment, Valence Proton Symmetry and Shell Model

    SciTech Connect

    Rother, W.; Dewald, A.; Fransen, C.; Hackstein, M.; Jolie, J.; Pissulla, Th.; Zel, K.-O.; Iwasaki, H.; Baugher, T.; Brown, B. A.; Gade, A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Voss, P.; Walsh, K. A.; Lenzi, S. M.; Ur, C. A.; Starosta, K.; Bazin, D.

    2011-10-28

    Probing shell structure at a large neutron excess has been of particular interest in recent times. Neutron-rich nuclei between the proton shell closures Z = 20 and Z = 28 offer an exotic testing ground for shell evolution. The development of the N = 40gap between neutron fp and lg{sub 9/2} shells gives rise to highly interesting variations of collectivity for nuclei in this region. While {sup 68}Ni shows doubly magic properties in level energies and transition strengths, this was not observed in neighbouring nuclei. Especially neutron-rich Fe isotopes proved particularly resistant to calculational approaches using the canonical valence space (fpg) resulting in important deviations of the predicted collectivity. Only an inclusion of the d{sub 5/2}-orbital could solve the problem [1]. Hitherto no transition strengths for {sup 66}Fe have been reported. We determined B(E2,2{sup +}{sub 1}{yields}0{sup +}{sub 1}) values from lifetimes measured with the recoil distance Doppler-shift method using the Cologne plunger for radioactive beams at National Superconducting Cyclotron Laboratory at Michigan State University. Excited states were populated by projectile Coulomb excitation for {sup 62,64,66}Fe. The data show a rise in collectivity for Fe isotopes towards N = 40. Results [2] are interpreted by means of a modified version of the Valence Proton Symmetry [3] and compared to shell model calculations using a new effective interaction recently developed for the fpgd valence space [4].

  14. β -decay half-lives of neutron-rich nuclei at A ~ 110 on r-process path

    NASA Astrophysics Data System (ADS)

    Nishizuka, Ippei; Sumikama, Toshiyuki; Browne, Frank; Bruce, Alison; Nishimura, Shunji; Doornenbal, Pieter; Lorusso, Giuseppe; Patel, Zena; Rice, Simon; Sinclair, Laura; Soderstom, Par-Ander; Watanabe, Hiroshi; Wu, Jin; Xu, Zhengyu; Yagi, Ayumi; Eurica Collaboration

    2014-09-01

    About half of the elements heavier than iron are thought to be produced by rapid-neutron capture process (r-process). The observed natural abundance in solar system was underestimated by a theoretical model at A ~ 110 , which uses β-decay half-lives. In the present study, we measured new β half-lives of neutron-rich nuclei on r-process path at RIBF in RIKEN. The nuclei of interest were produced by in-flight fission of uranium beam in beryllium target. The WAS3ABi detector which was 5 stacked double-sided silicon strip detectors (60 × 40 × 1 mm3), was used for the implantation of ions and the detection of both the implanted ions and the subsequently-emitted β rays. It is essential to make a position correlation between the mother nucleus and the β rays. In this talk, the analysis of the position correlation will be presented in detail. Preliminary results will be also shown.

  15. Medium-spin states of the neutron-rich 87,89Br isotopes: configurations and shapes

    NASA Astrophysics Data System (ADS)

    Nyakó, B. M.; Timár, J.; Csatlós, M.; Dombrádi, Zs; Krasznahorkay, A.; Kuti, I.; Sohler, D.; Tornyi, T. G.; Czerwiński, M.; Rząca-Urban, T.; Urban, W.; Bączyk, P.; Atanasova, L.; Balabanski, D. L.; Sieja, K.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; de France, G.; Simpson, G. S.; Ur, C. A.

    2016-06-01

    Medium-spin excited states of the neutron-rich 87Br and 89Br nuclei were observed and studied for the first time. They were populated in fission of 235U induced by the cold-neutron beam of the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level schemes were compared with results of large valence space shell model calculations. Both medium-spin level schemes consist of band-like structures, which can be understood as bands built on the πf 5/2, πp 3/2 and πg 9/2 configurations. Both nuclei have 5/2- ground state spin-parity contrary to the odd-mass Br isotopes containing fewer neutrons, which have 3/2- ground state spin-parity. On the basis of the properties of the πg 9/2 decoupled bands the deformations of the 87Br and 89Br fit to the systematics of nuclei in the region. 87Br is close to the vibrational limit, while 89Br is more rotational.

  16. Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the 21+ State in Zn80

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Ames, F.; Behrens, T.; Bildstein, V.; Blazhev, A.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Davinson, T.; Delahaye, P.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Gernhauser, R.; Georgiev, G.; Habs, D.; Heyde, K.; Huber, G.; Huyse, M.; Ibrahim, F.; Ivanov, O.; Iwanicki, J.; Jolie, J.; Kester, O.; Köster, U.; Kröll, T.; Krücken, R.; Lauer, M.; Lisetskiy, A. F.; Lutter, R.; Marsh, B. A.; Mayet, P.; Niedermaier, O.; Nilsson, T.; Pantea, M.; Perru, O.; Raabe, R.; Reiter, P.; Sawicka, M.; Scheit, H.; Schrieder, G.; Schwalm, D.; Seliverstov, M. D.; Sieber, T.; Sletten, G.; Smirnova, N.; Stanoiu, M.; Stefanescu, I.; Thomas, J.-C.; Valiente-Dobón, J. J.; van Duppen, P.; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2007-10-01

    Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 21+ state in Zn78 could be firmly established and for the first time the 2+→01+ transition in Zn80 was observed at 1492(1) keV. B(E2,21+→01+) values were extracted for Zn74,76,78,80 and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, Zn80 is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus Ni78.

  17. On-line experimental results of an argon gas cell-based laser ion source (KEK Isotope Separation System)

    NASA Astrophysics Data System (ADS)

    Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Jung, H. S.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

    2016-06-01

    KEK Isotope Separation System (KISS) has been developed at RIKEN to produce neutron rich isotopes with N = 126 to study the β -decay properties for application to astrophysics. The KISS is an element-selective mass-separation system which consists of an argon gas cell-based on laser ion source for atomic number selection and an ISOL mass-separation system. The argon gas cell of KISS is a key component to stop and collect the unstable nuclei produced in a multi-nucleon transfer reaction, where the isotopes of interest will be selectively ionized using laser resonance ionization. We have performed off- and on-line experiments to study the basic properties of the gas cell as well as of the KISS. We successfully extracted the laser-ionized stable 56Fe (direct implantation of a 56Fe beam into the gas cell) atoms and 198Pt (emitted from the 198Pt target by elastic scattering with a 136Xe beam) atoms from the KISS during the commissioning on-line experiments. We furthermore extracted laser-ionized unstable 199Pt atoms and confirmed that the measured half-life was in good agreement with the reported value.

  18. A Systematic Study of β- Decay of Neutron-Rich Rh and Ag Isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Y.-B.; Dendooven, P.; Huikari, J.; Jokinen, A.; Kolhinen, V. S.; Lhersonneau, G.; Nieminen, A.; Nummela, S.; Penttilä, H.; Peräjärvi, K.; Rinta-Antila, S.; Szerypo, J.; Wang, J. C.; ńystö, J.

    2006-11-01

    Beta decay of neutron-rich even-mass 114-118Rh and 116-120Ag isotopes has been studied using on-line mass-separated sources that were produced by applying 25 MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β-γ and γ-γ coincidence spectroscopy is employed in all cases that enables for the construction of the decay scheme and for the deduction of the decay properties. Systematics for two-quasineutron states in 114,116,118Pd and for three-phonon multiplet in 114,116,118Cd are presented and discussed.

  19. Decay of the neutron-rich isotope 171Ho and the identification of 169Dy

    NASA Astrophysics Data System (ADS)

    Chasteler, R. M.; Nitschke, J. M.; Firestone, R. B.; Vierinen, K. S.; Wilmarth, P. A.

    1990-10-01

    Neutron-rich rare-earth isotopes were produced in multinucleon transfer reactions between 170Er ions and natW targets. On-line mass separation was used together with β- and γ-ray spectroscopy in these studies. At mass A=169, the heaviest known dysprosium isotope, 39(8) s,169Dy, was identified. It was observed to β- decay to the ground state of 169Ho or through a level at 1578 keV. In the A=171 mass chain, a partial decay scheme for 55(3)-s 171Ho was determined.

  20. Two-Neutron Separation Energies Of Even-Even Rare-Earth Neutron-Rich Nuclei

    SciTech Connect

    Benhamouda, N.; Oudih, M. R.; Allal, N. H.; Fellah, M.

    2007-04-23

    The variation of the two-neutron separation energy (S2N), as a function of N, is studied using a microscopic model that includes the pairing effects rigorously within the Fixed-Sharp-BCS method. The model has been tested for ''ordinary'' nuclei and has correctly reproduced the experimental data. The study has then been extended to the neutron-rich nuclei and has shown a relatively important variation of S2N when N= 100 which may be attributed to the existence of a new magic number.

  1. Structure of neutron-rich nuclei around the N = 50 shell-gap closure

    SciTech Connect

    Faul, T.; Duchene, G.; Nowacki, F.; Thomas, J.-C.; Huyse, M.; Van Duppen, P.

    2010-04-26

    The structure of neutron-rich nuclei in the vicinity of {sup 78}Ni have been investigated via the beta-decay of {sup 71,73,75}Cu isotopes (ISOLDE, CERN). Experimental results have been compared with shell-model calculations performed with the ANTOINE code using a large (2p{sub 3/2}1 f{sub 5/2}2 p{sub 1/2}1 g{sub 9/2}) valence space and a (56/28)Ni{sub 28} core.

  2. Application of the generator coordinate method to neutron-rich Se and Ge isotopes

    NASA Astrophysics Data System (ADS)

    Higashiyama, Koji; Yoshinaga, Naotaka

    2014-03-01

    The quantum-number projected generator coordinate method (GCM) is applied to the neutron-rich Se and Ge isotopes, where the monopole and quadrupole pairing plus quadrupole-quadrupole interaction is employed as an effective interaction. The energy spectra obtained by the GCM are compared to both the shell model results and the experimental data. The GCM reproduces well the energy levels of high-spin states as well as the low-lying states. The structure of the low-lying collective states is analyzed through the GCM wave functions.

  3. Thermal effects on the Fission Barrier of neutron-rich nuclei

    SciTech Connect

    Minato, Futoshi; Hagino, Kouichi

    2008-11-11

    We discuss the fission barrier height of neutron-rich nuclei in a r-process site at highly excited state, which is resulted from the beta-decay or the neutron-capture processes. We particularly investigate the sensitivity of the fission barrier height to the temperature, including the effect of pairing phase transition from superfluid to normal fluid phases. To this end, we use the finite-temperature Skyrme-Hartree-Fock-Bogolubov method with a zero-range pairing interaction. We also discuss the temperature dependence of the fission decay rate.

  4. Direct Mass Measurements of Fluorine Through Chlorine Neutron-Rich Nuclei.

    NASA Astrophysics Data System (ADS)

    Zhou, Xiao-Gang

    1991-02-01

    Mass measurements have been made of the neutron -rich isotopes of fluorine through chlorine at the Los Alamos Meson Physics Facility. The masses of 34 neutron-rich isotopes are reported. Ten of these measurements represent first-time mass determinations of these species. The nuclei of interest are produced in fragmentation reaction. A transport line is used to capture a small fraction of the ions and transport them into the time-of-flight isochronous (TOFI) spectrometer. The TOFI spectrometer is isochronously designed, such that the transit time of the ion passing through the spectrometer is independent of the ion velocity, and only depends on its mass-to-charge ratio. A gas ionization counter located at the exit of the TOFI spectrometer is used to identify the ion atomic number and to measure the total energy. Three fast timing detectors are placed in the middle of the transport line, entrance, and exit of the TOFI spectrometer to determine the ion velocity and the M/Q ratio. We calculate each ion's charge state by using velocity, total energy, and M/Q ratio. With A, Z, Q assigned to each ion, we fit M/Q linearly to the known masses to obtain a high precision M/Q calibration. The masses of unknown nuclei are calculated through the M/Q calibration. The final results are generated by taking a weighted average for all runs and charge states. These results have confirmed the anomaly of enhanced binding found in neutron-rich Na and Mg isotopes and also suggest that the binding energies for those nuclei are less than that originally reported. The masses of several F through Al isotopes are compared with the shell model calculations. These comparisons demonstrate that the anomaly can be understood in terms of one or two neutron promotions from the sd shell to the fp shell. The results for some neutron-rich isotopes of P through Cl are compared to several mass models and good agreement in all cases is found.

  5. Evolution of collectivity in neutron-rich nuclei in the Sn132 region

    NASA Astrophysics Data System (ADS)

    Kshetri, Ritesh; Sarkar, M. Saha; Sarkar, S.

    2006-09-01

    Motivated by the observed regularity in the energy spectra and the structure of the shell model wave functions for the levels of Te137 and I137, a few weakly and moderately deformed neutron-rich odd-A nuclei above the doubly magic nucleus Sn132 were studied using the particle rotor model (PRM). The calculated energy spectra and branching ratios agree reasonably well with the most recent experimental data. In a few cases ambiguity in level ordering was resolved and spin-parities were assigned to the levels. Observed octupole correlation in some of these nuclei is discussed in the light of the present results.

  6. Nuclear structure of the odd-odd N=85 neutron-rich nucleus {sup 140}Cs

    SciTech Connect

    Liu, S. H.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Luo, Y. X.; Rasmussen, J. O.; Daniel, A. V.; Ter-Akopian, G. M.; Zhu, S. J.; Ma, W. C.

    2010-03-15

    High-spin excited states in the neutron-rich nucleus {sup 140}Cs were re-investigated from the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. Seven new transitions at low and moderate spin and 13 at high spin were observed in {sup 140}Cs and the level scheme of {sup 140}Cs was extended to 3794 keV with a new sideband. Spins and parities were assigned to levels based on angular correlation measurements and the systematics in the N=85 isotones.

  7. Evidence for octupole excitations in the odd-odd neutron-rich nucleus {sup 142}Cs

    SciTech Connect

    Liu, S. H.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Luo, Y. X.; Rasmussen, J. O.; Zhu, S. J.; Ma, W. C.; Daniel, A. V.; Ter-Akopian, G. M.

    2010-05-15

    High-spin states in the neutron-rich nucleus {sup 142}Cs are reinvestigated from a study of the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. A new level scheme is built and spin-parities are assigned to levels based on angular correlation measurements and systematics. The new structure of {sup 142}Cs is proposed to be related to octupole correlations. The electric dipole moment of {sup 142}Cs is measured and a dramatic decrease of the dipole moments with increasing neutron numbers in the Cs isotopic chain is found.

  8. Argon laser for otosclerosis

    NASA Astrophysics Data System (ADS)

    Michalski, Wojciech; Pospiech, Lucyna; Jankowska-Kuc, Malgorzata

    1995-03-01

    Up to now, among different kinds of lasers an argon laser is mostly used for otosclerosis. Exposure conditions at use of the laser beam are still not well defined. In order to achieve the optimum conditions a series of experiments has been made. Obtained results are presented in this paper.

  9. Microscopic dynamics simulations of heavy-ion fusion reactions induced by neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Ou, Li; Zhang, Yingxun; Li, Zhuxia

    2014-06-01

    The heavy-ion fusion reactions induced by neutron-rich nuclei are investigated with the improved quantum molecular dynamics (ImQMD) model. With a subtle consideration of the neutron skin thickness of nuclei and the symmetry potential, the stability of nuclei and the fusion excitation functions of heavy-ion fusion reactions O16 + Ge76, O16 + Sm154, Ca40 + Zr96, and Sn132 + Ca40 are systematically studied. The fusion cross sections of these reactions at energies around the Coulomb barrier can be well reproduced by using the ImQMD model. The corresponding slope parameter of the symmetry energy adopted in the calculations is L ≈78 MeV and the surface energy coefficient is gsur=18±1.5 MeV fm2. In addition, it is found that the surface-symmetry term significantly influences the fusion cross sections of neutron-rich fusion systems. For sub-barrier fusion, the dynamical fluctuations in the densities of the reaction partners and the enhanced surface diffuseness at neck side result in the lowering of the fusion barrier.

  10. Residue Coulomb Interaction Among Isobars and Its Influence in Symmetry Energy of Neutron-Rich Fragment

    NASA Astrophysics Data System (ADS)

    Ma, Chun-Wang; Wang, Shan-Shan; Zhang, Yan-Li; Zhao, Yi-Long; Wei, Hui-Ling

    2015-09-01

    The residue Coulomb interaction (RCI), which affects the result of symmetry-energy coefficient of neutron-rich nucleus in isobaric yield ratio (IYR) method, is difficult to be determined. Four RCI approximations are investigated: (i) The M1-RCI adopting the ac/T (the ratio of Coulomb energy coefficient to temperature) determined from the IYR of mirror-nucleus fragments; (ii) The M2-RCI by fitting the difference between IYRs; (iii) The M3-RCI adopting the standard Coulomb energy at a temperature T = 2 MeV; and (iv) Neglecting the RCI among isobars. The M1-, M2- and M3-RCI are no larger than 0.4. In particular, the M2-RCI is very close to zero. The effects of RCI in asym/T of fragment are also studied. The M1- and M4-asym/T are found to be the lower and upper limitations of asym/T, respectively. The M2-asym/T overlaps the M4-asym/T, which indicates that the M2-RCI is negligible in the IYR method, and the RCI among the three isobars can be neglected. The relative consistent low values of M3-asym/T (7.5 ± 2.5) are found in very neutron-rich isobars. Supported by the Program for Science & Technology Innovation Talents in Universities of Henan Province (13HASTIT046), and Young Teacher Project in Henan Normal University (HNU), China

  11. New neutron-rich isotope production in 154Sm+160Gd

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Guo, Lu

    2016-09-01

    Deep inelastic scattering in 154Sm+160Gd at energies above the Bass barrier is for the first time investigated with two different microscopic dynamics approaches: improved quantum molecular dynamics (ImQMD) model and time dependent Hartree-Fock (TDHF) theory. No fusion is observed from both models. The capture pocket disappears for this reaction due to strong Coulomb repulsion and the contact time of the di-nuclear system formed in head-on collisions is about 700 fm/c at an incident energy of 440 MeV. The isotope distribution of fragments in the deep inelastic scattering process is predicted with the simulations of the latest ImQMD-v2.2 model together with a statistical code (GEMINI) for describing the secondary decay of fragments. More than 40 extremely neutron-rich unmeasured nuclei with 58 ≤ Z ≤ 76 are observed and the production cross sections are at the order of μb to mb. The multi-nucleon transfer reaction of Sm+Gd could be an alternative way to synthesize new neutron-rich lanthanides which are difficult to be produced with traditional fusion reactions or fission of actinides.

  12. Isospin quartic term in the kinetic energy of neutron-rich nucleonic matter

    NASA Astrophysics Data System (ADS)

    Cai, Bao-Jun; Li, Bao-An

    2015-07-01

    The energy of a free gas of neutrons and protons is well known to be approximately isospin parabolic with a negligibly small quartic term of only 0.45 MeV at the saturation density of nuclear matter ρ0=0.16 fm-3 . Using an isospin-dependent single-nucleon momentum distribution including a high (low) momentum tail (depletion) with its shape parameters constrained by recent high-energy electron scattering and medium-energy nuclear photodisintegration experiments as well as the state-of-the-art calculations of the deuteron wave function and the equation of state of pure neutron matter near the unitary limit within several modern microscopic many-body theories, we show for the first time that the kinetic energy of interacting nucleons in neutron-rich nucleonic matter has a significant quartic term of 7.18 ±2.52 MeV. Such a large quartic term has broad ramifications in determining the equation of state of neutron-rich nucleonic matter using observables of nuclear reactions and neutron stars.

  13. Spectroscopy of neutron-rich {sup 168,170}Dy: Yrast band evolution close to the N{sub p}N{sub n} valence maximum

    SciTech Connect

    Soederstroem, P.-A.; Nyberg, J.; Regan, P. H.; Ashley, S. F.; Catford, W. N.; Gelletly, W.; Jones, G. A.; Liu, Z.; Pietri, S.; Podolyak, Zs.; Steer, S. J.; Thompson, N. J.; Williams, S. J.; Algora, A.; Angelis, G. de; Corradi, L.; Fioretto, E.; Gottardo, A.; Grodner, E.; He, C. Y.

    2010-03-15

    The yrast sequence of the neutron-rich dysprosium isotope {sup 168}Dy has been studied using multinucleon transfer reactions following collisions between a 460-MeV {sup 82}Se beam and an {sup 170}Er target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2{sup +} and 4{sup +} members of the previously measured ground-state rotational band of {sup 168}Dy have been confirmed and the yrast band extended up to 10{sup +}. A tentative candidate for the 4{sup +}->2{sup +} transition in {sup 170}Dy was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of total Routhian surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed.

  14. Introduction of argon beam coagulation functionality to robotic procedures using the ABC D-Flex probe: equivalency to an existing laparoscopic instrument

    NASA Astrophysics Data System (ADS)

    Merchel, Renée. A.; Barnes, Kelli S.; Taylor, Kenneth D.

    2015-03-01

    INTRODUCTION: The ABC® D-Flex Probe utilizes argon beam coagulation (ABC) technology to achieve hemostasis during minimally invasive surgery. A handle on the probe allows for integration with robotic surgical systems and introduces ABC to the robotic toolbox. To better understand the utility of D-Flex, this study compares the performance of the D-Flex probe to an existing ABC laparoscopic probe through ex vivo tissue analysis. METHODS: Comparisons were performed to determine the effect of four parameters: ABC device, tissue type, activation duration, and distance from tissue. Ten ABC D-Flex probes were used to create 30 burn samples for each comparison. Ex vivo bovine liver and porcine muscle were used as tissue models. The area and depth of each burn was measured using a light microscope. The resulting dimensional data was used to correlate tissue effect with each variable. RESULTS: D-Flex created burns which were smaller in surface area than the laparoscopic probe at all power levels. Additionally, D-Flex achieved thermal penetration levels equivalent to the laparoscopic probe. CONCLUSION: D-Flex implements a small 7F geometry which creates a more focused beam. When used with robotic precision, quick localized superficial hemostasis can be achieved with minimal collateral damage. Additionally, D-Flex achieved equivalent thermal penetration levels at lower power and argon flow-rate settings than the laparoscopic probe.

  15. ToF-SIMS and laser-SNMS analysis of Madin-Darby canine kidney II cells with silver nanoparticles using an argon cluster ion beam.

    PubMed

    Nees, Ricarda; Pelster, Andreas; Körsgen, Martin; Jungnickel, Harald; Luch, Andreas; Galla, Hans-Joachim; Arlinghaus, Heinrich F

    2015-06-15

    The use of nanoparticles is one of the fastest expanding fields in industrial as well as in medical applications, owing to their remarkable characteristics. Silver nanoparticles (AgNPs) are among the most-commercialized nanoparticles because of their antibacterial effects. Laser postionization secondary neutral mass spectrometry (laser-SNMS) and time-of-flight secondary ion mass spectrometry in combination with argon cluster ion sputtering was used for the first time to investigate the effects of AgNPs on Madin-Darby canine kidney (MDCK) II cells. Depth profiles and high-resolution three dimensional (3D) images of nanoparticles and organic compounds from cells were obtained using an Ar cluster ion beam for sputtering and Bi3 (+) primary ions for the analysis. The 3D distribution of AgNPs and other organic compounds in MDCK II cells could be readily detected with very high efficiency, sensitivity, and submicron lateral resolution. The argon cluster ion beam is well suited for the sputtering of biological samples. It enables a high sample removal rate along with low molecular degradation. The outer membrane, the cytoplasm, and the nuclei of the cells could be clearly visualized using the signals PO(+) and C3H8N(+) or CN(+) and C3H8N(+). The laser-SNMS images showed unambiguously that AgNPs are incorporated by MDCK II cells and often form silver aggregates with a diameter of a few micrometers, mainly close to the outside of the cell nuclei.

  16. Examination of Ion Beam Acceleration in A High Power-Low Pressure and Gas Flow Rates Argon Plasma Created in the MadHeX Helicon Source

    NASA Astrophysics Data System (ADS)

    Sung, Yung-Ta; Devinney, Michael; Scharer, John

    2012-10-01

    The modified MadHeX experimental system consists of a Pyrex tube connected to a stainless steel chamber with an axial magnetic nozzle field, variable up to 1 kG at the source region that has been upgraded to minimize neutral reflux and reduce neutral concentrations in the chamber. A half-turn double-helix antenna is used to excite helicon waves in the source. An ion beam of energy, E = 160 eV at 500 W RF power, has been observed in a low flowing argon plasma formed in the expanding region with a 340 G magnetic field. The role of plasma positive ``self-bias'' and the effects of boundary conditions are discussed. The measured density decrease factor of 18 at 100 W RF power across the expansion region yields a higher ion acceleration and agrees with a conservation-of-flux calculation. The effect of lower flow rates and pressures, higher RF powers and magnetic field strength dependence on the ion beam acceleration, plasma potential, electron density and temperature are further explored. The axial ion velocity distribution function and temperatures at higher powers are observed by argon 668 nm laser induced fluorescence with density measurements by interferometry. The electron energy distribution and its possible non-Maxwellian tail are examined using optical emission spectroscopy (ADAS and Vlcek models).

  17. Elastic Scattering of Neutron-Rich Helium Isotopes from Polarized Protons at 71 MeV/A

    NASA Astrophysics Data System (ADS)

    Sakaguchi, S.; Uesaka, T.; Kawabata, T.; Wakui, T.; Aoi, N.; Hashimoto, Y.; Ichikawa, Y.; Itoh, K.; Itoh, M.; Iwasaki, H.; Kawahara, T.; Kondo, Y.; Kuboki, H.; Maeda, Y.; Nakamura, T.; Nakao, T.; Nakayama, Y.; Okamura, H.; Sakai, H.; Sasamoto, Y.; Sasano, M.; Satou, Y.; Sekiguchi, K.; Shimamura, T.; Shimizu, Y.; Shinohara, M.; Suda, K.; Suzuki, D.; Takahashi, Y.; Tamii, A.; Yako, K.; Yamaguchi, M.

    2011-09-01

    The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He and 8He from polarized protons at 71 MeV/A making use of a newly constructed solid polarized proton target operated in a low magnetic field of 0.1 T and at a relatively high temperature of 100 K. An optical model analysis revealed that the spin-orbit potentials for 6He and 8He are characterized by shallow and long-ranged shape compared with the global systematics of stable nuclei. Such a characteristics reflect a diffused density distribution of the neutron-rich isotopes.

  18. A large liquid argon time projection chamber for long-baseline, off-axis neutrino oscillation physics with the NuMI beam

    SciTech Connect

    Finley, D.; Jensen, D.; Jostlein, H.; Marchionni, A.; Pordes, S.; Rapidis, P.A.; Bromberg, C.; Lu, C.; McDonald, T.; Gallagher, H.; Mann, A.; Schneps, J.; Cline, D.; Sergiampietri, F.; Wang, H.; Curioni, A.; Fleming, B.T.; Menary, S.; /York U., Canada

    2005-09-01

    Results from neutrino oscillation experiments in the last ten years have revolutionized the field of neutrino physics. While the overall oscillation picture for three neutrinos is now well established and precision measurements of the oscillation parameters are underway, crucial issues remain. In particular, the hierarchy of the neutrino masses, the structure of the neutrino mixing matrix, and, above all, CP violation in the neutrino sector are the primary experimental challenges in upcoming years. A program that utilizes the newly commissioned NuMI neutrino beamline, and its planned upgrades, together with a high-performance, large-mass detector will be in an excellent position to provide decisive answers to these key neutrino physics questions. A Liquid Argon time projection chamber (LArTPC) [2], which combines fine-grained tracking, total absorption calorimetry, and scalability, is well matched for this physics program. The few-millimeter-scale spatial granularity of a LArTPC combined with dE/dx measurements make it a powerful detector for neutrino oscillation physics. Scans of simulated event samples, both directed and blind, have shown that electron identification in {nu}{sub e} charged current interactions can be maintained at an efficiency of 80%. Backgrounds for {nu}{sub e} appearance searches from neutral current events with a {pi}{sup 0} are reduced well below the {approx} 0.5-1.0% {nu}{sub e} contamination of the {nu}{sub {mu}} beam [3]. While the ICARUS collaboration has pioneered this technology and shown its feasibility with successful operation of the T600 (600-ton) LArTPC [4], a detector for off-axis, long-baseline neutrino physics must be many times more massive to compensate for the low event rates. We have a baseline concept [5] based on the ICARUS wire plane structure and commercial methods of argon purification and housed in an industrial liquefied-natural-gas tank. Fifteen to fifty kton liquid argon capacity tanks have been considered. A very

  19. Shell quenching in Ni78: A hint from the structure of neutron-rich copper isotopes

    NASA Astrophysics Data System (ADS)

    Sieja, K.; Nowacki, F.

    2010-06-01

    Recent progress in experimental techniques allows us to study very exotic systems like neutron-rich nuclei in the vicinity of Ni78. The spectroscopy of this region can nowadays be studied theoretically in the large scale shell model calculations. In this work, we perform a shell model study of odd copper nuclei with N=40-50, in a large valence space with the Ca48 core, using a realistic interaction derived from the CD-Bonn potential. We present the crucial importance of the proton core excitations for the description of spectra and magnetic moments, which are for the first time correctly reproduced in theoretical calculations. Shell evolution from Ni68 to Ni78 is discussed in detail. A weakening of the Z=28 gap when approaching the N=50 shell closure, suggested by the experimental evidence, is confirmed in the calculations.

  20. β -decay properties of neutron-rich rare-earth isotopes

    NASA Astrophysics Data System (ADS)

    Sarriguren, P.

    2017-01-01

    In this paper, β -decay properties of even-even neutron-rich isotopes in the rare-earth mass region are studied within a microscopic theoretical approach based on a proton-neutron quasiparticle random-phase approximation. The underlying mean field is constructed self-consistently from a deformed Hartree-Fock calculation with Skyrme interactions and pairing correlations to which particle-hole and particle-particle residual interactions are added. Nuclei in this mass region participate in the astrophysical rapid neutron capture process and are directly involved in the generation of the rare-earth peak in the isotopic abundance pattern centered at A ≃160 . The energy distributions of the Gamow-Teller strength as well as the β -decay half-lives and the β -delayed neutron-emission probabilities are discussed and compared with the available experimental information and with calculations based on different approaches.

  1. Enhanced Quadrupole Collectivity at N=40: The Case of Neutron-Rich Fe Isotopes

    SciTech Connect

    Rother, W.; Dewald, A.; Fransen, C.; Hackstein, M.; Jolie, J.; Pissulla, Th.; Zell, K.-O.; Iwasaki, H.; Baugher, T.; Brown, B. A.; Gade, A.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Voss, P.; Walsh, K. A.; Lenzi, S. M.; Ur, C. A.; Starosta, K.; Bazin, D.

    2011-01-14

    The transition rates for the 2{sub 1}{sup +} states in {sup 62,64,66}Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N=40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N=40 as governed by the number of valence protons with respect to Z{approx_equal}30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

  2. Enhanced quadrupole collectivity at N = 40: the case of neutron-rich Fe isotopes.

    PubMed

    Rother, W; Dewald, A; Iwasaki, H; Lenzi, S M; Starosta, K; Bazin, D; Baugher, T; Brown, B A; Crawford, H L; Fransen, C; Gade, A; Ginter, T N; Glasmacher, T; Grinyer, G F; Hackstein, M; Ilie, G; Jolie, J; McDaniel, S; Miller, D; Petkov, P; Pissulla, Th; Ratkiewicz, A; Ur, C A; Voss, P; Walsh, K A; Weisshaar, D; Zell, K-O

    2011-01-14

    The transition rates for the 2(1)+ states in (62,64,66)Fe were studied using the recoil distance Doppler-shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N = 40. The results are interpreted using the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N = 40 as governed by the number of valence protons with respect to Z ≈ 30. The trend of collectivity suggested by the experimental data is described by state-of-the-art shell-model calculations with a new effective interaction developed for the fpgd valence space.

  3. Spectroscopy of Moderately Neutron-rich Nuclei with the CLARA-PRISMA Setup

    SciTech Connect

    Gadea, A.; Marginean, N.; De Angelis, G.; Napoli, D. R.; Corradi, L.; Stefanini, A. M.; Fioretto, E.; Axiotis, M.; Behera, B. R.; Latina, A.; Rusu, C.; Zhimin, W.; Valiente-Dobon, J.; Pokrovskiy, I.; Della Vedova, F.; Farnea, E.; Lenzi, S. M.; Bazzacco, D.; Beghini, S.; Ur, C.

    2006-04-26

    Deep-inelastic and multi-nucleon transfer reactions can be used to populate nuclei with relatively large neutron excess. Recently, at the Laboratori Nazionali di Legnaro, a setup consisting on an efficient {gamma}-ray detection system CLARA coupled to the large acceptance magnetic spectrometer PRISMA, capable of tracking the trajectories of the reaction products, has been assembled. During the first year of activity, the experiments performed with the CLARA-PRISMA setup, have been focused mainly on the nuclear structure of neutron-rich nuclei. In particular, nuclei around N=20, N=50 and lying in the A{approx}60 transitional region with N<40, have been investigated. In this contribution, results of these experiments will be reported.

  4. Charge-exchange modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2015-10-15

    Gamow-Teller (GT) mode of excitation and β-decay properties of deformed neutron-rich even-N Zr isotopes are investigated in a self-consistent Skyrme energy-density-functional approach, in which the Hartree-Fock-Bogoliubov equation is solved in the coordinate space and the proton-neutron Quasiparticle-RPA equation is solved in the quasiparticle basis. It is found that a stronger collectivity is generated for the GT giant resonance as an increase in the neutron number. Furthermore, we find that the T = 0 pairing enhances the low-lying GT strengths cooperatively with the T = 1 pairing correlation depending on the microscopic structure of the low-lying mode and the shell structure around the Fermi levels, and that the enhanced strength shortens the β-decay half-lives by at most an order of magnitude.

  5. Alpha decay and cluster decay of some neutron-rich actinide nuclei

    NASA Astrophysics Data System (ADS)

    Carmel Vigila Bai, G. M.; Agnes, R. Nithya

    2017-03-01

    Nuclei in the actinide region are good in exhibiting cluster radioactivity. In the present work, the half-lives of α-decay and heavy cluster emission from certain actinide nuclei have been calculated using cubic plus Yukawa plus exponential model (CYEM). Our model has a cubic potential for the overlapping region which is smoothly connected by a Yukawa plus exponential potential for the region after separation. The computed half-lives are compared with those of other theoretical models and are found to be in good agreement with each other. In this work, we have also studied the deformation effects on half-lives of cluster decay. These deformation effects lower the half-life values and it is also found that the neutron-rich parent nuclei slow down the cluster decay process. Geiger-Nuttal plots for various clusters are found to be linear and most of the emitted clusters are α-like nuclei.

  6. Stellar electron capture rates on neutron-rich nuclei and their impact on stellar core collapse

    NASA Astrophysics Data System (ADS)

    Raduta, Ad. R.; Gulminelli, F.; Oertel, M.

    2017-02-01

    During the late stages of gravitational core-collapse of massive stars, extreme isospin asymmetries are reached within the core. Due to the lack of microscopic calculations of electron-capture (EC) rates for all relevant nuclei, in general simple analytic parametrizations are employed. We study here several extensions of these parametrizations, allowing for a temperature, electron density, and isospin dependence as well as for odd-even effects. The latter extra degrees of freedom considerably improve the agreement with large-scale microscopic rate calculations. We find, in particular, that the isospin dependence leads to a significant reduction of the global EC rates during core collapse with respect to fiducial results, where rates optimized on calculations of stable f p -shell nuclei are used. Our results indicate that systematic microscopic calculations and experimental measurements in the N ≈50 neutron-rich region are desirable for realistic simulations of the core collapse.

  7. Nuclear shape transitions in neutron-rich medium-mass nuclei

    SciTech Connect

    Sarriguren, P.; Rodriguez-Guzman, R.; Robledo, L. M.

    2012-10-20

    We study the isotopic evolution of the ground-state nuclear shapes in neutron-rich Kr, Rb, Sr, Y, Zr, Nb, and Mo isotopic chains. Both even-even and odd-A nuclei are included in the analysis. For the latter we also study the systematics of their one-quasiparticle low-lying configurations. The theoretical approach is based on a selfconsistent Hartree-Fock-Bogoliubov formalism with finite range Gogny energy density functionals. Neutron separation energies, charge radii, and the spin-parity of the ground states are calculated and compared with available data. Shape-transition signatures are identified around N= 60 isotones as discontinuities in both charge radii isotopic shifts and spin-parities of the ground states. The nuclear deformation including triaxiality is shown to play a relevant role in the understanding of the bulk and spectroscopic features of the ground and low-lying one-quasiparticle states.

  8. Identification of a quasiparticle band in very neutron-rich {sup 104}Zr

    SciTech Connect

    Yeoh, E. Y.; Wang, J. G.; Ding, H. B.; Gu, L.; Xu, Q.; Xiao, Z. G.; Zhu, S. J.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Liu, S. H.; Liu, Y. X.; Sun, Y.; Luo, Y. X.; Rasmussen, J. O.; Lee, I. Y.

    2010-08-15

    The high spin levels of a very neutron-rich {sup 104}Zr nucleus have been reinvestigated by measuring the prompt {gamma} rays in the spontaneous fission of {sup 252}Cf. The ground-state band has been confirmed. A new sideband has been identified with a band-head energy at 1928.7 keV. The projected shell model is employed to investigate the band structure of {sup 104}Zr. The results of calculated levels are in good agreement with the experimental data, and suggest that the new band in {sup 104}Zr may be based on the neutron {nu}5/2{sup -}[532] x {nu}3/2{sup +}[411] configuration.

  9. Nuclear shape and structure in neutron-rich {sup 110,111}Tc

    SciTech Connect

    Luo, Y. X.; Hamilton, J. H.; Ramayya, A. V.; Hwang, J. K.; Gore, P. M.; Jones, E. F.; Fong, D.; Rasmussen, J. O.; Lee, I. Y.; Stefanescu, I.; Che, X. L.; Zhu, S. J.; Wu, S. C.; Ginter, T. N.; Ma, W. C.; Ter-Akopian, G. M.; Daniel, A. V.; Stoyer, M. A.; Donangelo, R.; Gelberg, A.

    2006-08-15

    The high-spin nuclear structure of Tc isotopes is extended to more neutron-rich regions based on the measurements of prompt {gamma} rays from the spontaneous fission of {sup 252}Cf at the Gammasphere. The high-spin level scheme of N=67 neutron-rich {sup 110}Tc (Z=43) is established for the first time, and that of {sup 111}Tc is extended and expanded. The ground band of {sup 111}Tc reaches the band-crossing region, and the new observation of the weakly populated {alpha}=-1/2 member of the band provides important information on signature splitting. The systematics of band crossings in the isotopic and isotonic chains and a CSM calculation suggest that the band crossing of the ground band of {sup 111}Tc is due to alignment of a pair of h{sub 11/2} neutrons. The best fit to signature splitting, branching ratios, and excitations of the ground band of {sup 111}Tc by the rigid triaxial rotor plus particle model calculations result in a shape of {epsilon}{sub 2}=0.32 and {gamma}=-26 deg. for this nucleus. Its triaxiality is larger than that of {sup 107,109}Tc, which indicates increasing triaxiality in Tc isotopes with increasing neutron number. The identification of the weakly populated K+2 satellite band provides strong evidence for the large triaxiality of {sup 111}Tc. In {sup 110}Tc, the four lowest-lying levels observed are very similar to those in {sup 108}Tc. At an excitation of 478.9 keV above the lowest state observed, ten states of a {delta}I=1 band are observed. This band of {sup 110}Tc is very analogous to the {delta}I=1 bands in {sup 106,108}Tc, but it has greater and reversal signature splitting at higher spins.

  10. Histologic evaluation of the depth of necrosis produced by argon beam coagulation: implications for use as adjuvant treatment of bone tumors.

    PubMed

    Heck, Robert K; Pope, Wood D; Ahn, Jae I; Smith, Richard A; Webber, Bruce L

    2009-01-01

    Argon beam coagulation (ABC) has been advocated as adjuvant treatment after curettage of aggressive benign bone tumors. This study was done to evaluate the depth of necrosis in cancellous bone treated with ABC. A 6-month-old pig was sacrificed and 20 1.5-cm cortical windows were created in the metaphyseal areas of the humeri, femora, and tibiae, exposing the underlying cancellous bone. The defects were randomly assigned to four groups: A, control; B, ABC at 50 W; C, 100 W; and D, 150 W. Histologic evaluation determined the depth of necrosis at each setting: A, 0.1 +/- 0.1 mm; B, 1.0 +/- 0.5 mm; C, 2.9 +/- 1.0 mm; and D, 4.2 +/- 0.7 mm. There were statistically significant differences between each of the experimental groups and the control (p < .0001), between groups B and C (p < .0001), and groups C and D (p = .0002).

  11. β decay of neutron-rich 118Ag and 120Ag isotopes

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Rinta-Antila, S.; Dendooven, P.; Huikari, J.; Jokinen, A.; Kolhinen, V. S.; Lhersonneau, G.; Nieminen, A.; Nummela, S.; Penttilä, H.; Peräjärvi, K.; Szerypo, J.; Wang, J. C.; Äystö, J.

    2003-06-01

    β decays of on-line mass-separated neutron-rich 118Ag and 120Ag isotopes have been studied by using β-γ and γ-γ coincidence spectroscopy. Extended decay schemes to the 118,120Cd daughter nuclei have been constructed. The three-phonon quintuplet in 118Cd is completed by including a new level at 2023.0 keV, which is tentatively assigned the spin and parity of 2+4. The intruder band in 118Cd is proposed up to the 4+ level at 2322.4 keV. The measured β-decay half-life for the high-spin isomer of 120Ag is 0.40±0.03 s. Candidates for the three-phonon states, as well as the lowest members of the intruder band in 120Cd, are also presented. These data support the coexistence of quadrupole anharmonic vibration and proton particle-hole intruder excitations in 118,120Cd.

  12. Resonant states of the neutron-rich Λ hypernucleus He7Λ

    NASA Astrophysics Data System (ADS)

    Hiyama, E.; Isaka, M.; Kamimura, M.; Myo, T.; Motoba, T.

    2015-05-01

    The structure of the neutron-rich Λ hypernucleus, He7Λ is studied within the framework of an α +Λ +n +n four-body cluster model. We predict second 3 /2+ and 5 /2+ states, corresponding to a 0 s Λ coupled to the second 2+ state of 6He, as narrow resonant states with widths of Γ ˜1 MeV to be at 0.03 and 0.07 MeV with respect to the α +Λ +n +n threshold. From a separate estimate of the differential cross section for the 7Li (γ ,K+) He7Λ reaction, we suggest a possibility to observe these states at the Thomas Jefferson National Accelerator Facility (JLab) in the future. We also calculate the second 2+ state of 6He as a resonant state within the framework of an α +n +n three-body cluster model. Our result is 2.81 MeV with Γ =4.63 MeV with respect to the α +n +n threshold. This energy position is ˜1 MeV higher, and with a much broader decay width, than the recent SPIRAL data. We suggest that an experiment at JLab to search for the second 3 /2+ and 5 /2+ states of He7Λ would provide an opportunity to confirm the second 2+ state of the core nucleus 6He.

  13. First Results From GRIFFIN: Half-Lives of Neutron Rich 128-130Cd

    NASA Astrophysics Data System (ADS)

    Dunlop, Ryan; Griffin Collaboration

    2016-09-01

    Half-lives of N = 82 nuclei below doubly-magic 132Sn are key input parameters for any astrophysical r-process scenario and play an important role in the formation and shape of the second r-process abundance peak. Shell-model calculations for neutron-rich nuclei near the N = 82 neutron shell closure that are not yet experimentally accessible have been performed by adjusting the quenching of the Gamow-Teller (GT) operator to reproduce the 130Cd half-life. The calculated half-lives of other nuclei in the region are known to be systematically too long. Recently, a shorter half-life for 130Cd was measured by the EURICA collaboration that resolves this discrepancy by scaling the GT quenching by a constant factor for all of the nuclei in the region. Distinguishing between these discrepant half-life measurements for 130Cd is thus of critical importance. We have measured the half-lives of 128-130Cd using the high-efficiency GRIFFIN γ-ray spectrometer at TRIUMF, which improves the precision of the 128,129Cd half-lives, and confirms the shorter half-life of 130Cd recently reported by the EURICA collaboration. Details of the GRIFFIN experiments will be presented and the implications of the resulting half-lives discussed.

  14. Astrophysical implication of low E(21+) in neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Sarkar, M. Saha

    2009-10-01

    The observation and prediction of unusually depressed first excited 21+ states in even-A neutron-rich isotopes of semi-magic Sn above 132Sn provide motivations for reviewing the problems related to the nuclear astrophysics in general. In the present work, the β-decay rates of the exotic even Sn isotopes (134,136Sn) above the 132Sn core have been calculated as a function of temperature (T). In order to get the necessary ft values, B(GT) values corresponding to allowed Gamow Teller (GT-) β-decay have been theoretically calculated using shell model. The total decay rate shows decrease with increasing temperature as the ground state population is depleted and population of excited states with slower decay rates increases. The abundance at each Z value is inversely proportional to the decay constant of the waiting point nucleus for that particular Z. So the increase in half-life of isotopes of Sn, like 136Sn, might have substantial impact on the r-process nucleosynthesis.

  15. Configuration assignments to isomers in the neutron-rich 186Ta (Z =73 ) nucleus

    NASA Astrophysics Data System (ADS)

    Sood, P. C.; Gowrishankar, R.

    2014-12-01

    Though the neutron-rich odd-odd nucleus Ta18673113 was first produced in 1955, even after 60 years its ground state (g.s.) and both of its two other isomers remain undefined. We use the well-tested two-quasiparticle rotor model, which explicitly includes residual neutron-proton n -p interaction and other contributing factors, to evaluate the bandhead energies of the physically admissible low-lying two-particle structures in 186Ta with inputs from experimentally observed structures in neighboring isotopes and isotones to characterize these levels. Our analysis assigns Kπ = 5-{p :7 /2 [404 ]⊗n :3 /2 [512 ]} configuration to the 10.5 min 186Ta (g.s.) and the antiparallel-spin Kπ=2- of the same configuration to the 1.54 min isomer with Ex = 90(10) keV. We further assign Kπ=8-{p :7 /2 [404 ]⊗n :9 /2 [505 ]} configuration to the recently identified 3.0 min isomer with Ex=336 (20) keV. These assignments are shown to be consistent with all the available experimental data. Further, they are seen to fit nicely as another instance of highly hindered Δ I =3 isomeric transitions, and also of low-lying long-lived isomer triplets, frequently observed in numerous odd-odd Z =61 (2 )75 nuclides.

  16. Excited State Properties in Neutron-rich Nuclei near N = 40

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Prokop, C. J.; Liddick, S. N.; Chiara, C. J.; Ayangeakaa, A. D.; Carroll, J. J.; Chen, J.; David, H. M.; Go, S.; Grzywacz, R.; Harker, J.; Janssens, R. V. F.; Lauritsen, T.; Seweryniak, D.; Walters, W. B.

    2015-10-01

    The neutron-rich nuclei near N = 40 have recently been the focus of many experimental and theoretical efforts. In this region, the competing energy cost for promoting pairs of nucleons across either Z = 28 or N = 40 and the energy gain from residual nucleon-nucleon interactions gives rise to several low-energy 0+ states and is a hallmark of shape coexistence. Low-energy 0+ states have been observed in 68Ni, and predicted for other nuclei in the region. Recent theoretical calculations are able to reproduce the energies of known states in 68Ni and stress the importance of the tensor component of the monopole interaction. Yet, while energies of the levels are a useful comparison, a more stringent test is the reproduction of level lifetimes, where the predicted half-lives can vary by several orders of magnitude depending on the interaction. To further benchmark theoretical calculations in this region, a setup designed to measure level lifetimes has been constructed. A description of the array and preliminary results will be presented. This work was supported by the DOE NNSA Award No. DE-NA0000979, NSF Contract No. PHY1102511, DOE SC NP Contract No. DE-AC-06CH11357 and Grant No. DE-FG02-94ER40834.

  17. Pygmy dipole mode in deformed neutron-rich Mg isotopes close to the drip line

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenichi

    2009-10-01

    We investigate the microscopic structure of the low-lying isovector-dipole excitation mode in neutron-rich Mg36,38,40 close to the drip line by means of the deformed quasiparticle random-phase approximation employing the Skyrme and the local pairing energy-density functionals. It is found that the low-lying bump structure above the neutron emission-threshold energy develops when the drip line is approached, and that the isovector dipole strength at Ex<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule in Mg40. We obtained the collective dipole modes at around 8-10 MeV in Mg isotopes, that consist of many two-quasiparticle excitations of the neutron. The transition density clearly shows an oscillation of the neutron skin against the isoscalar core. We found significant coupling effects between the dipole and octupole excitation modes due to the nuclear deformation. It is also found that the responses for the compressional dipole and isoscalar octupole excitations are much enhanced in the lower energy region.

  18. Low-lying dipole resonance in neutron-rich Ne isotopes

    NASA Astrophysics Data System (ADS)

    Yoshida, Kenichi; van Giai, Nguyen

    2008-07-01

    Microscopic structure of the low-lying isovector dipole excitation mode in neutron-rich Ne26,28,30 is investigated by performing deformed quasiparticle-random-phase-approximation (QRPA) calculations. The particle-hole residual interaction is derived from a Skyrme force through a Landau-Migdal approximation. We obtain the low-lying resonance in Ne26 at around 8.6 MeV. It is found that the isovector dipole strength at Ex<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule. This excitation mode is composed of several QRPA eigenmodes, one is generated by a ν(2s1/2-12p3/2) transition dominantly and the other mostly by a ν(2s1/2-12p1/2) transition. The neutron excitations take place outside of the nuclear surface reflecting the spatially extended structure of the 2s1/2 wave function. In Ne30, the deformation splitting of the giant resonance is large, and the low-lying resonance overlaps with the giant resonance.

  19. Searching for isovector signatures in the neutron-rich oxygen and calcium isotopes

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Chia; Piekarewicz, Jorge

    2015-04-01

    We search for potential isovector signatures in the neutron-rich oxygen and calcium isotopes within the framework of a relativistic mean-field theory with an exact treatment of pairing correlations. To probe the isovector sector we calibrate a few relativistic density functionals using the same isoscalar constraints but with one differing isovector assumption. It is found that under certain conditions, the isotopic chain in oxygen can be made to terminate at the experimentally observed 24 O isotope. In the case of the calcium isotopes, the drip line is predicted to be reached beyond 60 Ca. To produce such behavior, the resulting symmetry energy must be soft, with predicted values for the symmetry energy and its slope at saturation density being J = (30 . 92 +/- 0 . 47) MeV and L = (51 . 0 +/- 1 . 5) MeV, respectively. As a consequence, the neutron-skin thickness of 208 Pb is rather small: Rskin208 = (0 . 161 +/- 0 . 011) fm. This same model, labelled FSUGarnet , predicts R1 . 4 = (13 . 1 +/- 0 . 1) km for the radius of a ``canonical'' 1.4M⊙ neutron star, yet is also able to support a two-solar-mass neutron star.

  20. Lattice HFB calculations for nuclei far from stability: neutron-rich sulfur and tin isotopes

    NASA Astrophysics Data System (ADS)

    Oberacker, Volker; Umar, Sait; Teran, Edgar

    2002-10-01

    We have developed a new Hartree-Fock-Bogoliubov (HFB) code to study ground state and pairing properties of nuclei near the neutron and proton drip lines. The unique feature of our code is that it takes into account the strong coupling to high energy continuum states (up to an equivalent s.p. energy of about 60 MeV). We solve the HFB equations for deformed, axially symmetric even-even nuclei on a two-dimensional lattice using high accuracy Basis-Spline methods (Galerkin and collocation schemes). The effective N-N interaction in the p-h channel is of Skyrme-type (SLy4), and in the p-p and h-h channel it is a (modified) delta interaction. We present results for binding energies, 2-neutron separation energies, Fermi levels, pairing gaps, normal densities and pairing densities, and other observables. In particular, we will discuss neutron-rich sulfur (S-48,S-52) and tin (Sn-150) isotopes. [1] E. Teran, V.E. Oberacker and A.S. Umar, "Axially symmetric Hartree-Fock-Bogoliubov Calculations for Nuclei Near the Drip-Lines; nucl-th/0205042 * Research supported by U.S. DOE grant DE-FG02-96ER40963, and by the National Energy Research Scientific Computing Center (NERSC)

  1. Ground-state nuclear-moment measurement of neutron-rich sulfur isotopes

    NASA Astrophysics Data System (ADS)

    Ohtomo, Yuichi; Ichikawa, Yuichi; Shirai, Hazuki; Ueno, Hideki; Ishibashi, Youko; Suzuki, Takahiro; Furukawa, Takeshi; Yoshimi, Akihiro; Abe, Yasushi; Asahi, Koichiro; Daugasu, J. M.; Fujita, Tomomi; Hayasaka, Miki; Imamura, Kei; Kishi, Shota; Kojima, Shuichiro; Nagae, Daisuke; Nakao, Aiko; Sagayama, Tsubasa; Sakamoto, Yu; Sato, Tomoya

    2014-09-01

    Recently the erosion of N = 28 shell gap has been suggested from several spectroscopic experimental data on neutron-rich nuclei. In particular, 43S isotope is of much interest since shape coexistence is expected to occur which provides key information to understand the evolution of shell gaps far from the stability. The isomeric state of 43S at 320 keV is suggested to have a shape close to sphericity with spin-parity of 7/2, but both the spin-parity and deformed parameter of the ground-state have not been determined directly. In order to investigate mechanisms leading to such an anomalous nuclear structure, we aim at measuring the ground-state nuclear-moment for 41,43S. As the first step, the measurement of μ moment of 41S was performed using the technique of β-NMR method at the RIPS facility at RIKEN. In the presentation, the result of this work will be reported.

  2. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    SciTech Connect

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Zhu, S.

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudes for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.

  3. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    DOE PAGES

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; ...

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudesmore » for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.« less

  4. Measurement of the Isoscalar Monopole Response in the Neutron-Rich Nucleus Ni68

    NASA Astrophysics Data System (ADS)

    Vandebrouck, M.; Gibelin, J.; Khan, E.; Achouri, N. L.; Baba, H.; Beaumel, D.; Blumenfeld, Y.; Caamaño, M.; Càceres, L.; Colò, G.; Delaunay, F.; Fernandez-Dominguez, B.; Garg, U.; Grinyer, G. F.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Keeley, N.; Mittig, W.; Pancin, J.; Raabe, R.; Roger, T.; Roussel-Chomaz, P.; Savajols, H.; Sorlin, O.; Stodel, C.; Suzuki, D.; Thomas, J. C.

    2014-07-01

    The isoscalar monopole response has been measured in the unstable nucleus Ni68 using inelastic alpha scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1±1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9±1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L =0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

  5. Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Holt, J. D.; Menéndez, J.; Schwenk, A.

    2013-03-01

    We study the spectra of neutron-rich oxygen isotopes based on chiral two- and three-nucleon interactions. First, we benchmark our many-body approach by comparing ground-state energies to coupled-cluster results for the same two-nucleon interaction, with overall good agreement. We then calculate bound excited states in 21, 22, 23O , focusing on the role of three-nucleon forces, in the standard sd shell and an extended sdf_{7/2}p_{3/2} valence space. Chiral three-nucleon forces provide important one- and two-body contributions between valence neutrons. We find that both these contributions and an extended valence space are necessary to reproduce key signatures of novel shell evolution, such as the N = 14 magic number and the low-lying states in 21O and 23O , which are too compressed with two-nucleon interactions only. For the extended space calculations, this presents first work based on nuclear forces without adjustments. Future work is needed and open questions are discussed.

  6. Measurement of the isoscalar monopole response in the neutron-rich nucleus 68Ni.

    PubMed

    Vandebrouck, M; Gibelin, J; Khan, E; Achouri, N L; Baba, H; Beaumel, D; Blumenfeld, Y; Caamaño, M; Càceres, L; Colò, G; Delaunay, F; Fernandez-Dominguez, B; Garg, U; Grinyer, G F; Harakeh, M N; Kalantar-Nayestanaki, N; Keeley, N; Mittig, W; Pancin, J; Raabe, R; Roger, T; Roussel-Chomaz, P; Savajols, H; Sorlin, O; Stodel, C; Suzuki, D; Thomas, J C

    2014-07-18

    The isoscalar monopole response has been measured in the unstable nucleus (68)Ni using inelastic alpha scattering at 50A  MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1 ± 1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9 ± 1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L = 0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

  7. Production of heavy and superheavy neutron-rich nuclei in neutron capture processes

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, Walter

    2011-10-01

    The neutron capture process is considered as an alternative method for production of superheavy (SH) nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in the laboratory frame and by supernova explosions in nature. All these cases are discussed in the paper. There are two gaps of short-lived nuclei (one is the well-known fermium gap and the other one is located in the region of Z=106-108 and N˜170) which impede the formation of SH nuclei by rather weak neutron fluxes realized at available nuclear reactors. We find that in the course of multiple (rather “soft”) nuclear explosions these gaps may be easily bypassed, and thus, a measurable amount of the neutron-rich long-living SH nuclei located at the island of stability may be synthesized. Existing pulsed reactors do not allow one to bypass these gaps. We formulate requirements for the pulsed reactors of the next generation that could be used for production of long-living SH nuclei. Natural formation of SH nuclei (in supernova explosions) is also discussed. The yield of SH nuclei relative to lead is estimated to be about 10-12, which is not beyond the experimental sensitivity for a search of SH elements in cosmic rays.

  8. Exotic neutron-rich medium-mass nuclei with realistic nuclear forces

    NASA Astrophysics Data System (ADS)

    Tsunoda, Naofumi; Otsuka, Takaharu; Shimizu, Noritaka; Hjorth-Jensen, Morten; Takayanagi, Kazuo; Suzuki, Toshio

    2017-02-01

    We present the first application of the newly developed extended Kuo-Krenciglowa (EKK) theory of the effective nucleon-nucleon interaction to shell-model studies of exotic nuclei, including those where conventional approaches with fitted interactions encounter difficulties. This EKK theory enables us to derive an interaction that is suitable for several major shells (s d +p f in this work). By using such an effective interaction obtained from the Entem-Machleidt QCD-based χ N3LO interaction and the Fujita-Miyazawa three-body force, the energies, E 2 properties, and spectroscopic factors of low-lying states of neutron-rich Ne, Mg, and Si isotopes are nicely described, as the first shell-model description of the "island of inversion" without fit of the interaction. The long-standing question as to how particle-hole excitations occur across the s d -p f magic gap is clarified with distinct differences from the conventional approaches. The shell evolution is shown to appear similarly to earlier studies.

  9. Decay Spectroscopy of Neutron-Rich Cd Around the N = 82 Shell Closure

    NASA Astrophysics Data System (ADS)

    Bernier, Nikita; Dillmann, Iris; Kruecken, Reiner; Griffin Collaboration

    2016-09-01

    The neutron-rich region around A = 132 is of special interest for nuclear astrophysics and nuclear structure. This region is connected with the second r-process abundance peak at A 130 and the waiting-point nuclei around N = 82. For nuclear structure studies, the neighbours of the doubly-magic 132Sn (Z = 50, N = 82) are an ideal test ground for shell model predictions. The beta-decay of the N = 82 isotope 130Cd into 130In was first investigated a decade ago, but the information for states of the lighter indium isotopes (128,129In) is still limited. In the present experiment, a detailed gamma-spectroscopy of the beta-decay of 128-132Cd was achieved with the newly commissioned GRIFFIN (Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei) gamma-ray spectrometer, which is capable of measuring down to rates of 0.1 pps. The low-energy cadmium isotopes were implanted into a movable tape at the central focus of the array from the ISAC-I facility at TRIUMF. The beta-tagging was performed using the auxiliary beta-particle detector SCEPTAR. The required beta-gamma(-gamma) coincidence data in high statistics needed to fill the spectroscopic gaps described in literature were obtained. The ongoing analysis of these data will be presented. Work supported by the Natural Sciences and Engineering Research Council of Canada and the National Research Council of Canada.

  10. Spectroscopy of neutron-rich nickel isotopes: Experimental results and microscopic interpretation

    NASA Astrophysics Data System (ADS)

    Girod, M.; Dessagne, Ph.; Bernas, M.; Langevin, M.; Pougheon, F.; Roussel, P.

    1988-06-01

    The spectroscopy of neutron-rich isotopes of 67Ni and 68Ni is studied using the quasi-elastic transfer reactions (14C,16O) and (14C,17O) on a 70Zn mass separated target. The structure of these exotic nuclei is investigated in the framework of a microscopic collective model based on the Hartree-Fock-Bogoliubov theory. Gogny's two-body effective interaction is used. Collective excited states of 68Ni are obtained by solving the Bohr Hamiltonian in which inertia parameters are calculated in the cranking approximation. Spin and parity assignments to observed excited levels are suggested on the basis of information deduced from this analysis. This assignment is further checked by comparing measured angular distributions to predictions. Predictions of the level structure of 70Ni and 78Ni isotopes are given. A more precise test of the 0+ wave functions is provided by the calculation of monopole operator of the 0+1-->0+2 transition in 68Ni. An impressive agreement is obtained between the measured and calculated half-life.

  11. High-spin structure and multiphonon {gamma} vibrations in very neutron-rich {sup 114}Ru

    SciTech Connect

    Yeoh, E. Y.; Wang, J. G.; Ding, H. B.; Gu, L.; Xu, Q.; Xiao, Z. G.; Zhu, S. J.; Hamilton, J. H.; Li, K.; Ramayya, A. V.; Hwang, J. K.; Liu, Y. X.; Liu, S. H.; Sheikh, J. A.; Bhat, G. H.; Luo, Y. X.; Rasmussen, J. O.; Lee, I. Y.; Ma, W. C.

    2011-05-15

    High-spin levels of the neutron-rich {sup 114}Ru have been investigated by measuring the prompt {gamma} rays in the spontaneous fission of {sup 252}Cf. The ground-state band and one-phonon {gamma}-vibrational band have been extended up to 14{sup +} and 9{sup +}, respectively. Two levels are proposed as the members of a two-phonon {gamma}-vibrational band. A back bending (band crossing) has been observed in the ground-state band at ({h_bar}/2{pi}){omega}{approx_equal} 0.40 MeV. Using the triaxial deformation parameters, the cranked shell model calculations indicate that this back bending in {sup 114}Ru should originate from the alignment of a pair of h{sub 11/2} neutrons. Triaxial projected shell model calculations for the {gamma}-vibrational band structures of {sup 114}Ru are in good agreement with the experimental data. However, when using the oblate deformation parameters, both of the above-calculated results are not in agreement with the experimental data.

  12. Precision mass measurements of neutron-rich nuclei, and limitations on the r-process environment

    NASA Astrophysics Data System (ADS)

    Van Schelt, Jonathon A.

    2012-05-01

    The masses of 65 neutron-rich nuclides and 6 metastable states from Z = 49 to 64 were measured at a typical precision of δm/m= 10-7 using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements are on fission fragments from 252Cf spontaneous fission sources, including those measurements made at the new Californium Rare Isotope Breeder Upgrade facility (CARIBU) and an earlier source. The measured nuclides lie on or approach the predicted path of the astrophysical r process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in β-endpoint measurements. Simulations of the r process were undertaken to determine how quickly material can pass through the studied elements for a variety of conditions, placing limits on what temperatures densities allow passage on a desired timescale. The new masses produce manifold differences in effective lifetime compared to simulations performed with some model masses.

  13. β-decay spectroscopy of neutron-rich 160,161,162Sm isotopes

    NASA Astrophysics Data System (ADS)

    Patel, Z.; Podolyák, Zs.; Walker, P. M.; Regan, P. H.; Söderström, P.-A.; Watanabe, H.; Ideguchi, E.; Simpson, G. S.; Nishimura, S.; Browne, F.; Doornenbal, P.; Lorusso, G.; Rice, S.; Sinclair, L.; Sumikama, T.; Wu, J.; Xu, Z. Y.; Aoi, N.; Baba, H.; Bello Garrote, F. L.; Benzoni, G.; Daido, R.; Dombrádi, Zs.; Fang, Y.; Fukuda, N.; Gey, G.; Go, S.; Gottardo, A.; Inabe, N.; Isobe, T.; Kameda, D.; Kobayashi, K.; Kobayashi, M.; Komatsubara, T.; Kojouharov, I.; Kubo, T.; Kurz, N.; Kuti, I.; Li, Z.; Liu, H. L.; Matsushita, M.; Michimasa, S.; Moon, C.-B.; Nishizuka, H.; Nishizuka, I.; Odahara, A.; Şahin, E.; Sakurai, H.; Schaffner, H.; Suzuki, H.; Takeda, H.; Tanaka, M.; Taprogge, J.; Vajta, Zs.; Xu, F. R.; Yagi, A.; Yokoyama, R.

    2016-09-01

    Neutron-rich 160,161,162Sm isotopes have been populated at the RIBF, RIKEN via β first time. β-coincident γ rays were observed in all three isotopes including γ rays from the isomeric decay of 160Sm and 162Sm. The isomers in 160Sm and 162Sm have previously been observed but have been populated via β decay for the first time. The isomeric state in 162Sm is assigned a {4^ - }v{{7 over 2}^ + }≤ft[ {633} right] otimes v{{1 over 2}^ - }≤ft[ {521} right] configuration based on the decay pattern. The level schemes of 160Sm and 162Sm are presented. The ground states in the parent nuclei 160Pm and 162Pm are both assigned a {6^ - }v{{7 over 2}^ + }≤ft[ {633} right] otimes π {{5 over 2}^ - }≤ft[ {532} right] configuration based on the population of states in the daughter nuclei. Blocked BCS calculations were performed to further investigate the spin-parities of the ground states in 160Pm, 161Pm, and 162Pm, and the isomeric state in 162Sm

  14. Symmetry energy and surface properties of neutron-rich exotic nuclei

    SciTech Connect

    Gaidarov, M. K.; Antonov, A. N.; Sarriguren, P.; Moya de Guerra, E.

    2014-07-23

    The symmetry energy, the neutron pressure and the asymmetric compressibility of spherical Ni, Sn, and Pb and deformed Kr and Sm neutron-rich even-even nuclei are calculated within the coherent density fluctuation model using the symmetry energy as a function of density within the Brueckner energy-density functional. The correlation between the thickness of the neutron skin and the characteristics related with the density dependence of the nuclear symmetry energy is investigated for isotopic chains of these nuclei in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method. The mass dependence of the nuclear symmetry energy and the neutron skin thickness are also studied together with the role of the neutron-proton asymmetry. The studied correlations reveal a smoother behavior in the case of spherical nuclei than for deformed ones. We also notice that the neutron skin thickness obtained for {sup 208}Pb with SLy4 force is found to be in a good agreement with the recent data. In addition to the interest that this study may have by itself, we give some numerical arguments in proof of the existence of peculiarities of the studied quantities in Ni and Sn isotopic chains that are not present in the Pb chain.

  15. Ambient air particle transport into the effluent of a cold atmospheric-pressure argon plasma jet investigated by molecular beam mass spectrometry

    NASA Astrophysics Data System (ADS)

    Dünnbier, M.; Schmidt-Bleker, A.; Winter, J.; Wolfram, M.; Hippler, R.; Weltmann, K.-D.; Reuter, S.

    2013-10-01

    Ambient air species, which are transported into the active effluent of an atmospheric-pressure plasma jet result in highly reactive oxygen and nitrogen species (RONS). Especially for the envisaged application field of plasma medicine, these RONS are responsible for strong biological responses. In this work, the effect of ambient air transport into the effluent of an atmospheric-pressure plasma argon jet on the on-axis densities of nitrogen, oxygen and argon was investigated by means of absolutely calibrated molecular beam mass spectrometry (MBMS). According to biomedical experiments a (bottomless) Petri dish was installed in front of the MBMS. In the following, the near flow field is referring to the region close to the nozzle exit and the far flow field is referring to the region beyond that. The absolute on-axis densities were obtained by three different methods, for the near flow field with VUV-absorption technique, for the far flow field with the MBMS and the total flow field was calculated with a computational fluid dynamics (CFD) simulation. The results of the ambient air particle densities of all independent methods were compared and showed an excellent agreement. Therefore the transport processes of ambient air species can be measured for the whole effluent of an atmospheric-pressure plasma jet. Additionally, with the validation of the simulation it is possible in future to calculate the ambient species transport for various gas fluxes in the same turbulent flow regime. Comparing the on-axis densities obtained with an ignited and with a non-ignited plasma jet shows that for the investigated parameters, the main influence on the ambient air species transport is due to the increased temperature in the case when the jet is switched on. Moreover, the presence of positive ions (e.g. ArN_{2}^{+} ) formed due to the interaction of plasma-produced particles and ambient air species, which are transported into the effluent, is shown.

  16. Comparison of yields of neutron-rich nuclei in proton- and photon-induced 238U fission

    NASA Astrophysics Data System (ADS)

    Khan, F. A.; Bhowmick, Debasis; Basu, D. N.; Farooq, M.; Chakrabarti, Alok

    2016-11-01

    A comparative study of fission of actinides, especially 238U, by proton and bremsstrahlung photon is performed. The relative mass distribution of 238U fission fragments has been explored theoretically for both proton- and photon-induced fission. The integrated yield along with charge distribution of the products are calculated to find the neutron richness in comparison with the nuclei produced by the r process in nucleosynthesis. Some r -process nuclei in the intermediate-mass range for symmetric fission mode are found to be produced almost two orders of magnitude more for proton-induced fission than for photofission, although the rest of the neutron-rich nuclei in the asymmetric mode are produced in comparable proportion for both processes.

  17. On the synthesis of neutron-rich isotopes along the N = 126 shell in multinucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Beliuskina, O.; Heinz, S.; Zagrebaev, V.; Comas, V.; Heinz, C.; Hofmann, S.; Knöbel, R.; Stahl, M.; Ackermann, D.; Heßberger, F. P.; Kindler, B.; Lommel, B.; Maurer, J.; Mann, R.

    2014-10-01

    We performed experimental and theoretical studies of deep inelastic multinucleon transfer reactions in heavy-ion collisions at Coulomb barrier energies. Our goal was to investigate if deep inelastic transfer is superior to fragmentation reactions for producing neutron-rich isotopes in the astrophysically interesting region along the closed neutron shell N = 126 . Here, we will present our results obtained in reactions of 64Ni + 207Pb at 5.0 MeV/nucleon. The experiment was performed at the velocity filter SHIP at GSI Darmstadt. Several transfer products on the neutron-rich side were populated but new isotopes were not observed. A comparison of the measured transfer cross-sections and production yields with those from fragmentation reactions allowed for interesting conclusions.

  18. Proton Scattering on Liquid Argon

    NASA Astrophysics Data System (ADS)

    Bouabid, Ryan; LArIAT Collaboration

    2017-01-01

    LArIAT (Liquid Argon In A Test-beam) is a liquid argon time projection chamber (LArTPC) positioned in a charged particle beamline whose primary purpose is to study the response of LArTPC's to charged particle interactions. This previously unmeasured experimental data will allow for improvement of Monte Carlo simulations and development of identification techniques, important for future planned LArTPC neutrino experiments. LArIAT's beamline is instrumented to allow for the identification of specific particles as well as measurement of those particles' incoming momenta. Among the particles present in the beamline, the analysis presented here focuses on proton-Argon interactions. This study uses particle trajectories and calorimetric information to identify proton-Argon interaction candidates. We present preliminary data results on the measurement of the proton-Argon cross-section. Liquid Argon In A Test Beam. The work is my analysis made possible through the efforts of LArIAT detector, data, and software.

  19. Study of weakening of shell N = 28 for neutron rich nuclei through particle number fluctuation and pairing energy

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Rupayan

    2017-03-01

    Evolution of shells has been studied through fluctuations of particle numbers, pairing energies of large number of isotopes and isotones of nuclei evaluated through Skyrme-Hartree-Fock theory after inclusion of optimized tensor interaction. For neutron rich isotopes of Mg, Si, S and Ar no indication of shell closure at N = 28 has been observed. Calculations show occurrence of a doubly shell closed nucleus 114 Fl 184 .

  20. Discovery of Highly Excited Long-Lived Isomers in Neutron-Rich Hafnium and Tantalum Isotopes through Direct Mass Measurements

    SciTech Connect

    Reed, M. W.; Cullen, I. J.; Walker, P. M.; Deo, A. Y.; Kempley, R. S.; Swan, T. P. D.; Litvinov, Yu. A.; Winckler, N.; Blaum, K.; Bosch, F.; Dimopoulou, C.; Farinon, F.; Heil, M.; Knoebel, R.; Kozhuharov, C.; Kurcewicz, J.; Kuzminchuk, N.; Litvinov, S.; Nociforo, C.; Nolden, F.

    2010-10-22

    A study of cooled {sup 197}Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides {sup 183,184,186}Hf and {sup 186,187}Ta. The results support the prediction of a strongly favored isomer region near neutron number 116.

  1. Setup with Laser Ionization in Gas Cell for Production and Study of Neutron-Rich Heavy Nuclei

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Zemlyanoy, S. G.; Kozulin, E. M.; Kudryavtsev, Yu.; Fedosseev, V.; Bark, R.; Janas, Z.; Othman, H. A.

    2015-11-01

    The present limits of the upper part of the nuclear map are very close to stability while the unexplored area of heavy neutron-rich nuclides along the neutron closed shell N=126 is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleosynthesis. This area of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of exotic nuclei. A new way was recently proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions. The estimated yields of neutron-rich nuclei are found to be significantly high in such reactions and several tens of new nuclides can be produced, for example, in the near-barrier collision of 136Xe with 208Pb. A new setup is proposed to produce and study heavy neutron-rich nuclei located along the neutron closed shell N=126.

  2. Coulomb breakup of neutron-rich 29,30Na isotopes near the island of inversion

    NASA Astrophysics Data System (ADS)

    Rahaman, A.; Datta, Ushasi; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; De Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Johansson, H.; Jonson, B.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, M. V.; Rigollet, C.; Rossi, D.; Scheidenberger, C.; Scheit, H.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

    2017-04-01

    First results are reported on the ground state configurations of the neutron-rich 29,30Na isotopes, obtained via Coulomb dissociation (CD) measurements. The invariant mass spectra of these nuclei have been obtained through measurement of the four-momenta of all decay products after Coulomb excitation of those nuclei on a 208Pb target at energies of 400–430 MeV/nucleon using the FRS-ALADIN-LAND setup at GSI, Darmstadt. Integrated inclusive CD cross-sections (CD) of 89 (7) mb and 167 (13) mb for one neutron removal from 29Na and 30Na, respectively, have been extracted up to an excitation energy of 10 MeV. The major part of one neutron removal, CD cross-sections of those nuclei populate the core, in its ground state. A comparison with the direct breakup model, suggests the predominant occupation of the valence neutron in the ground state of 29Na (3/{2}+) and 30Na ({2}+) is the d-orbital with a small contribution from the s-orbital, which are coupled with the ground state of the core. One of the major components of the ground state configurations of these nuclei are 28Na{}{gs}({1}+)\\otimes {ν }s,d and 29Na{}{gs}(3/{2}+)\\otimes {ν }s,d, respectively. The ground state spin and parity of these nuclei obtained from this experiment are in agreement with earlier reported values. The spectroscopic factors for the valence neutron occupying the s and d orbitals for these nuclei in the ground state have been extracted and reported for the first time. A comparison of the experimental findings with shell model calculation using the MCSM suggests a lower limit of around 4.3 MeV of the sd–pf shell gap in 30Na.

  3. Lifetimes in neutron-rich Nd isotopes measured by Doppler profile method

    SciTech Connect

    Ahmad, I.; Lister, C.J.; Morss, L.R.

    1995-08-01

    Lifetimes of the rotational levels in neutron-rich even-even Nd isotopes were deduced from the analysis of the Doppler broadened line shapes. The experiment was performed at Daresbury with the Eurogam array, which at that time consisted of 45 Compton-suppressed Ge detectors and 5 Low-Energy Photon Spectrometers. The source was in the form of a 7-mm pellet which was prepared by mixing 5-mg; {sup 248}Cm and 65-mg KCl and pressing it under high pressure. Events for which three or more detectors fired were used to construct a cubic data array whose axes represented the {gamma}-ray energies and the contents of each channel the number of events with that particular combination of {gamma}-ray energies. From this cubic array, one-dimensional spectra were generated by placing gates on peaks on the other two axes. Gamma-ray spectra of even-even Nd isotopes were obtained by gating on the transitions in the complimentary Kr fragments. The gamma peaks de-exciting states with I {>=} 12 h were found to be broader than the instrumental line width due to the Doppler effect. The line shapes of they-ray peaks were fitted separately with a simple model for the feeding of the states and assuming a rotational band with constant intrinsic quadruple moment and these are shown in Fig. I-27. The quadrupole moments thus determined were found to be in good agreement with the quadrupole moments measured previously for lower spin states. Because of the success of this technique for the Nd isotopes, we intend to apply this technique to the new larger data set collected with the Eurogam II array. The results of this study were published.

  4. Nuclear-decay studies of neutron-rich rare-earth nuclides

    SciTech Connect

    Chasteler, R.M. . Dept. of Chemistry Lawrence Berkeley Lab., CA )

    1990-04-26

    Neutron-rich rare-earth nuclei were produced in multinucleon transfer reactions of {sup 170}Er and {sup 176}Yb projectiles on {sup nat}W targets at the Lawrence Berkeley Laboratory SuperHILAC and their radioactive decays properties studied at the on-line mass separation facility OASIS. Two unknown isotopes, {sup 169}Dy (t {sub 1/2} {equals} 39 {plus minus} 8 s) and {sup 174}Er(t{sub 1/2} {equals} 3.3 {plus minus} 0.2 m) were discovered and their decay characteristics determined. The decay schemes for two previously identified isotopes, {sup 168}Dy (t{sub 1/2} {equals} 8.8 {plus minus} 0.3 m) and {sup 171}Ho (t{sub 1/2} {equals} 55 {plus minus} 3 s), were characterized. Evidence for a new isomer of 3.0 m {sup 168}Ho{sup g}, {sup 168}Ho{sup m} (t{sub 1/2} {equals} 132 {plus minus} 4 s) which decays by isomeric transition (IT) is presented. Beta particle endpoint energies were determined for the decay of {sup 168}Ho{sup g}, {sup 169}Dy, {sup 171}Ho, and {sup 174}Er, the resulting Q{beta}-values are: 2.93 {plus minus} 0.03, 3.2 {plus minus} 0.3, 3.2 {plus minus} 0.6, and 1.8 {plus minus} 0.2 MeV, respectively. These values were compared with values calculated using recent atomic mass formulae. Comparisons of various target/ion source geometries used in the OASIS mass separator facility for these multinucleon transfer reactions were performed. 73 refs., 40 figs., 11 tabs.

  5. Antisymmetrized molecular dynamics studies for exotic clustering phenomena in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kimura, M.; Suhara, T.; Kanada-En'yo, Y.

    2016-12-01

    We present a review of recent works on clustering phenomena in unstable nuclei studied by antisymmetrized molecular dynamics (AMD). The AMD studies in these decades have uncovered novel types of clustering phenomena brought about by the excess neutrons. Among them, this review focuses on the molecule-like structure of unstable nuclei. One of the earliest discussions on the clustering in unstable nuclei was made for neutron-rich Be and B isotopes. AMD calculations predicted that the ground state clustering is enhanced or reduced depending on the number of excess neutrons. Today, the experiments are confirming this prediction as the change of the proton radii. Behind this enhancement and reduction of the clustering, there are underlying shell effects called molecular and atomic orbits. These orbits form covalent and ionic bonding of the clusters analogous to the atomic molecules. It was found that this "molecular-orbit picture" reasonably explains the low-lying spectra of Be isotopes. The molecular-orbit picture is extended to other systems having parity asymmetric cluster cores and to the three cluster systems. O and Ne isotopes are the candidates of the former, while the 3 α linear chains in C isotopes are the latter. For both subjects, many intensive studies are now in progress. We also pay a special attention to the observables which are the fingerprint of the clustering. In particular, we focus on the monopole and dipole transitions which are recently regarded as good probe for the clustering. We discuss how they have and will reveal the exotic clustering.

  6. Analysis of a Partial Male-Sterile Mutant of Arabidopsis thaliana Isolated from a Low-Energy Argon Ion Beam Mutagenized Pool

    NASA Astrophysics Data System (ADS)

    Xu, Min; Bian, Po; Wu, Yuejin; Yu, Zengliang

    2008-04-01

    A screen for Arabidopsis fertility mutants, mutagenized by low-energy argon ion beam, yielded two partial male-sterile mutants tc243-1 and tc243-2 which have similar phenotypes. tc243-2 was investigated in detail. The segregation ratio of the mutant phenotypes in the M2 pools suggested that mutation behaved as single Mendelian recessive mutations. tc243 showed a series of mutant phenotypes, among which partial male-sterile was its striking mutant characteristic. Phenotype analysis indicates that there are four factors leading to male sterility. a. Floral organs normally develop inside the closed bud, but the anther filaments do not elongate sufficiently to position the locules above the stigma at anthesis. b. The anther locules do not dehisce at the time of flower opening (although limited dehiscence occurs later). c. Pollens of mutant plants develop into several types of pollens at the trinucleated stage, as determined by staining with DAPI (4',6-diamidino-2-phenylindole), which shows a variable size, shape and number of nucleus. d. The viability of pollens is lower than that of the wild type on the germination test in vivo and vitro.

  7. Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

    SciTech Connect

    Tomizawa, H.; Yamaguchi, T.; Akita, S.; Ishibashi, K.

    2015-07-28

    We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots with serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.

  8. Shell-model states with seniority ν =3 , 5, and 7 in odd-A neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Iskra, Ł. W.; Broda, R.; Janssens, R. V. F.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Wrzesiński, J.; Zhu, S.

    2016-01-01

    Excited states with seniority ν =3 , 5, and 7 have been investigated in odd neutron-rich 119,121,123,125Sn isotopes produced by fusion-fission of 6.9-MeV/A 48Ca beams with 208Pb and 238U targets and by fission of a 238U target bombarded with 6.7-MeV/A 64Ni beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known 27 /2- isomers were expanded by identifying new deexcitation paths feeding 23 /2+ long-lived states and 21 /2+ levels. Competing branches in the decay of 23 /2- states toward two 19 /2- levels were delineated as well. In 119Sn, a new 23 /2+ isomer was identified, while a similar 23 /2+ long-lived state, proposed earlier in 121Sn, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of ν =3 excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the 27 /2- isomers, an elaborate structure of negative-parity levels was established reaching the (39 /2- ), ν =7 states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity (35 /2+ ), (31 /2+ ), and (27 /2+ ) states were established, feeding the 23 /2+ isomers via cascades of three transitions. In the ,123Sn121 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43 /2+ ) states. In 123Sn, a short half-life was determined for the (35 /2+ ) state. Shell-model calculations were carried out for all the odd Sn isotopes, from 129Sn down to 119

  9. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N =82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    NASA Astrophysics Data System (ADS)

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P.-A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A ≈130 ) and the rare-earth-element (A ≈160 ) abundance peaks may result from the freeze-out of an (n ,γ )⇄(γ ,n ) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  10. New Levels in 118Pd Observed in the β Decay of Very Neutron-Rich 118Rh Isotope

    NASA Astrophysics Data System (ADS)

    Wang, You-Bao; Dendooven, P.; Huikari, J.; Jokinen, A.; Kolhinen S., V.; Lhersonneau, G.; Nieminen, A.; Nummela, S.; Penttilä, H.; Peräjärvi, K.; Rinta-Antila, S.; Szerypo, J.; Wang C., J.; Äystö, J.

    2006-04-01

    We investigate the β decay of very neutron-rich 118Rh isotope using on-line mass-separated sources which are produced by applying 25 MeV proton induced symmetric fission of natural uranium at the IGISOL facility. The β-γ and γ-γ coincidence spectroscopy is employed to establish the level scheme of daughter nucleus 118Pd. Five low-lying new levels are identified for the first time with tentative spin and parity assignments based on the even-mass Pd systematics.

  11. Decay of the neutron-rich isotope sup 171 Ho and the identification of sup 169 Dy

    SciTech Connect

    Chasteler, R.M.; Nitschke, J.M.; Firestone, R.B.; Vierinen, K.S.; Wilmarth, P.A. )

    1990-10-01

    Neutron-rich rare-earth isotopes were produced in multinucleon transfer reactions between {sup 170}Er ions and {sup nat}W targets. On-line mass separation was used together with {beta}- and {gamma}-ray spectroscopy in these studies. At mass {ital A}=169, the heaviest known dysprosium isotope, 39(8) s,{sup 169}Dy, was identified. It was observed to {beta}{sup {minus}} decay to the ground state of {sup 169}Ho or through a level at 1578 keV. In the {ital A}=171 mass chain, a partial decay scheme for 55(3)-s {sup 171}Ho was determined.

  12. Structure And Decay Of Neutron-Rich Nuclides In The 115 {<=} A {<=} 138 Mass Range And r-Process Nucleosynthesis

    SciTech Connect

    Walters, W.B.; Stoyer, M.A.; Shergur, J.; Hoteling, N.; Ressler, J.J.; Rikovska, J.; Kratz, K.-L.; Woehr, A.; Pfeiffer, B.; Arndt, O.; Mantica, P.F.; Tomlin, B.; Schatz, H.; Montes, F.; Brown, B.A.; Seweryniak, D.; Ravn, H.; Fedoseyev, V.; Koester, U.; Wu, C.Y.

    2005-04-05

    The structure and decay of neutron-rich r-process nuclides has been studied by a variety of means that take advantage of enhanced selectivity to permit identification of exotic nuclides. New level structures are presented for 134,135Sb along with data for Ag isomers and Cd yrast structures. Some of the properties measured play an important role in calculations of the yields of elements and isotopes produced in r-process nucleosynthesis that takes place at high temperature in the presence of large densities of neutrons.

  13. IDENTIFICATION OF HIGH-SPIN STATES IN NEUTRON-RICH 88,90,92Kr AND 86Se

    SciTech Connect

    J. D. Cole

    2011-08-01

    Level schemes of even-even neutron-rich {sup 88-92}Kr and {sup 86}Se have been investigated by measuring triple-{gamma} coincidence data from the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. The level scheme of {sup 88}Kr has been extended up to 7169 keV state. Several new excited states with new transitions have been identified in {sup 90,92}Kr and {sup 86}Se. Spins and parities have been assigned to levels in these nuclei by following regional systematics and angular correlation measurements. The level structures of the N = 52, 54, Se, Kr, and Sr isotones are discussed.

  14. Exotic clusters in an unbound region of light neutron-rich systems

    NASA Astrophysics Data System (ADS)

    Ito, Makoto

    2009-10-01

    In light neutron-rich systems, many kinds of molecular structures are discussed from the view point of the clustering phenomena.In particular, much attention has been concentrated on Be isotopes. The molecular orbital (MO), such as &-circ; and &+circ; associated with the covalent binding of atomic molecules, have been shown to give a good description for the low-lying states of these isotopes. In their highly-excited states, furthermore, recent experiments revealed the existence of the interesting resonant states which dominantly decay to the ^6,8He fragments. In this report, we show the unified study of the exotic structures of ^12Be=α+α+4N in an unbound region and the α+^6,8He resonant scattering. We applied the generalized two-center cluster model in which the covalent MO and the atomic orbital (AO) configurations with ^xHe+^yHe could be described in a unified manner. First, we calculated the energy spectra below an α decay-threshold. The (π32^-)^2 (σ12^+)^2 configuration corresponding to ν(0p)^4(sd)^2 becomes the ground state, while (π3 2^-)^2(π12^-)^2 having a large overlap with ν(0p)^6 appears as the first excited state. The rotational band of the ground state reaches to the maximum spin of J^π = 8^+. This result means that the magicity of N=8 is broken in ^12Be due to the formation of (π3 2^-)^2(σ12^+)^2. Next, we solved the scattering problem of α+^8He and identified the several resonance poles. In the continuum region, we found the rotational bands having the AO configurations of α+^8He, ^6He+^6He, and ^5He+^7 He. Furthermore, a much more exotic band appears in the same energy region. In this band, two valence neutrons are localized at individual α-cores (the ^5He+^5He cluster), while the other two neutrons form the covalent &+circ;- bonding between two ^5He clusters; hence, it has a ``hybrid structure'' between the MO configuration and the AO one. In the J^π=0^+ state, it is strongly excited by the two-neutron transfer reaction, α+^8He

  15. Bustling argon: biological effect

    PubMed Central

    2013-01-01

    Argon is a noble gas in group 18 of the periodic table. Certificated to exist in air atmosphere merely one century ago, discovery of argon shows interesting stories of researching and exploring. It was assumed to have no chemical activity. However, argon indeed present its biological effect on mammals. Narcotic effect of argon in diving operation and neur-protective function of argon in cerebral injury demonstrate that argon has crucial effect and be concentrated on is necessary. Furthermore, consider to be harmless to human, argon clinical application in therapy would be another option. PMID:24088583

  16. Stellar (n ,γ ) cross sections of neutron-rich nuclei: Completing the isotope chains of Yb, Os, Pt, and Hg

    NASA Astrophysics Data System (ADS)

    Marganiec, J.; Dillmann, I.; Domingo-Pardo, C.; Käppeler, F.

    2014-12-01

    The (n ,γ ) cross sections of the most neutron-rich stable isotopes of Yb, Os, Pt, and Hg have been determined in a series of activation measurements at the Karlsruhe 3.7 MV Van de Graaff accelerator, using the quasistellar neutron spectrum for k T =25 keV that can be produced with the 7Li(p ,n ) 7Be reaction. In this way, Maxwellian averaged cross sections could be directly obtained with only minor corrections. After irradiation the induced activities were counted with a HPGe detector via the strongest γ -ray lines. The stellar neutron capture cross sections of Yb,176174, Os,192190, Pt,198196, and Hg,204202, extrapolated to k T =30 keV, were found to be 157 ±6 mb, 114 ±8 mb, 278 ±11 mb, 160 ±7 mb, 171 ±19 mb, 94 ±4 mb, 62 ±2 mb, and 32 ±15 mb, respectively. In the case of 196Pt the partial cross section to the isomeric state at 399.5 keV could be determined as well. With these results the cross section data for long isotopic chains could be completed for a discussion of the predictive power of statistical model calculations towards the neutron-rich and proton-rich sides of the stability valley.

  17. Novel triaxial structure in low-lying states of neutron-rich nuclei around A ≈100

    NASA Astrophysics Data System (ADS)

    Xiang, J.; Yao, J. M.; Fu, Y.; Wang, Z. H.; Li, Z. P.; Long, W. H.

    2016-05-01

    Background: In recent years, the study of triaxiality in the low-lying states of atomic nuclei with transition character or shape coexistence has been of great interest. Previous studies indicate that the neutron-rich nuclei in the A ˜100 mass region with Z ˜40 ,N ˜60 serve as good grounds for examining the role of triaxiality in nuclear low-lying states. Purpose: The aim of this work is to provide a microscopic study of low-lying states for nuclei in the A ˜100 mass regions and to examine in detail the role of triaxiality in the shape-coexistence phenomena and the variation of shape with the isospin and spin values at the beyond mean-field level. Method: The starting point of our method is a set of relativistic mean-field plus BCS wave functions generated with a constraint on triaxial deformations (β ,γ ) . The excitation energies and electric multipole transition strengths of low-lying states are calculated by solving a five-dimensional collective Hamiltonian (5DCH) with parameters determined by the mean-field wave functions. Results: The low-lying states of Mo isotopes and of N =60 isotones in the A ˜100 mass region are calculated. The results indicate that triaxiality is essential to reproduce the data of excitation energies and electric quadrupole transition strengths in low-lying states and plays an important role in the shape evolution as a function of nucleon number. However, the decrease of nuclear collectivity with the increase of angular momentum in neutron-rich Mo isotopes has not been reproduced. Conclusions: The evolution of nuclear collectivity in the low-lying states of neutron-rich nuclei in the A ˜100 mass region as a function of nucleon number is governed by the novel triaxial structure. However, the mechanism that governs the variation of nuclear shape with spin in Mo isotopes remains unclear and deserves further investigation by taking into account the effects other than the collective motions.

  18. Neutron multiplicity distributions for neutron-rich projectile fragments at the NSCL

    NASA Astrophysics Data System (ADS)

    Mazza, Maria; Christ, Peter; Stephenson, Sharon; MoNA Collaboration

    2016-09-01

    Projectile fragmentation is one of the mechanisms used at nuclear science facilities around the world for the production of rare isotope beams. The study of the projectile fragmentation mechanism informs beam simulation codes, but relatively few studies of the fragmentation process have been done, especially at intermediate energies. The MoNA Collaboration used an 86 MeV/u 32Mg beam on a natural beryllium target at the National Superconducting Cyclotron Laboratory to produce neutron multiplicities distributions in coincidence with charged fragments for isotopes ranging from 29Na to 20F. Particle identification for the isotopes from fluorine, neon, and sodium will be presented, as well as preliminary neutron multiplicities distributions. Supported by NSF Grants 1203357, 1613429 and HHMI Grant 52007540.

  19. {beta}-Decay Half-Lives of New Neutron-Rich Isotopes of Elements from Pm to Tb

    SciTech Connect

    S. Ichikawa; M. Asai; K. Tsukada; A. Osa; M. Sakama; Y. Kojima; M. Shibata; I. Nishinaka; Y. Nagame; Y. Oura; K. Kawade

    1999-12-31

    Eight new neutron-rich lanthanide isotopes produced in the proton-induced fission of {sup 238}U have been identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. For six of these, each half-life was determined: {sup 159}Pm (2 {+-} 1 s), {sup 161}Sm (4.8 {+-} 0.8 s), {sup 165}Gd (10.3 {+-} 1.6 s), {sup 166}Tb (21 {+-} 6 s), {sup 167}Tb (19.4 {+-} 2.7 s) and {sup 168}Tb (8.2 {+-} 1.3 s). The observed half-lives were compared with theoretical calculations. The recent calculation by the gross theory with the new one-particle strength function shows quite good agreement with the experimental half-lives.

  20. {beta}-decay half-lives of new neutron-rich isotopes of elements from Pm to Tb

    SciTech Connect

    Ichikawa, S.; Asai, M.; Tsukada, K.; Nishinaka, I.; Nagame, Y.; Osa, A.; Sakama, M.; Oura, Y.; Kojima, Y.; Shibata, M.; Kawade, K.

    1999-11-16

    Eight new neutron-rich lanthanide isotopes produced in the proton-induced fission of {sup 238}U have been identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. For six of these, each half-life was determined: {sup 159}Pm (2{+-}1 s), {sup 161}Sm (4.8{+-}0.8 s), {sup 165}Gd (10.3{+-}1.6 s), {sup 166}Tb (21{+-}6 s), {sup 167}Tb (19.4{+-}2.7 s) and {sup 168}Tb (8.2{+-}1.3 s). The observed half-lives were compared with theoretical calculations. The recent calculation by the gross theory with the new one-particle strength function shows quite good agreement with the experimental half-lives.

  1. Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Matsuo, Masayuki

    2015-03-01

    I formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random-phase approximation (QRPA). A focus is put on very-neutron-rich nuclei and low-energy neutron kinetic energy in the range from 1 keV to several MeV, which is relevant to the rapid neutron capture process of nucleosynthesis. I begin with the photoabsorption cross section and the E 1 strength function. Next, in order to apply the reciprocity theorem, I decompose the cross section into partial cross sections corresponding to different channels of one- and two-neutron emission decays of photo-excited states. A numerical example is shown for the photo-absorption of 142Sn and the neutron capture of 141Sn .

  2. Quadrupole transition strength in the (74)Ni nucleus and core polarization effects in the neutron-rich Ni isotopes.

    PubMed

    Marchi, T; de Angelis, G; Valiente-Dobón, J J; Bader, V M; Baugher, T; Bazin, D; Berryman, J; Bonaccorso, A; Clark, R; Coraggio, L; Crawford, H L; Doncel, M; Farnea, E; Gade, A; Gadea, A; Gargano, A; Glasmacher, T; Gottardo, A; Gramegna, F; Itaco, N; John, P R; Kumar, R; Lenzi, S M; Lunardi, S; McDaniel, S; Michelagnoli, C; Mengoni, D; Modamio, V; Napoli, D R; Quintana, B; Ratkiewicz, A; Recchia, F; Sahin, E; Stroberg, R; Weisshaar, D; Wimmer, K; Winkler, R

    2014-10-31

    The reduced transition probability B(E2;0(+)→2(+)) has been measured for the neutron-rich nucleus (74)Ni in an intermediate energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory at Michigan State University. The obtained B(E2;0(+)→2(+))=642(-226)(+216)  e(2) fm(4) value defines a trend which is unexpectedly small if referred to (70)Ni and to a previous indirect determination of the transition strength in (74)Ni. This indicates a reduced polarization of the Z=28 core by the valence neutrons. Calculations in the pfgd model space reproduce well the experimental result indicating that the B(E2) strength predominantly corresponds to neutron excitations. The ratio of the neutron and proton multipole matrix elements supports such an interpretation.

  3. Shell quenching in {sup 78}Ni: A hint from the structure of neutron-rich copper isotopes

    SciTech Connect

    Sieja, K.; Nowacki, F.

    2010-06-15

    Recent progress in experimental techniques allows us to study very exotic systems like neutron-rich nuclei in the vicinity of {sup 78}Ni. The spectroscopy of this region can nowadays be studied theoretically in the large scale shell model calculations. In this work, we perform a shell model study of odd copper nuclei with N=40-50, in a large valence space with the {sup 48}Ca core, using a realistic interaction derived from the CD-Bonn potential. We present the crucial importance of the proton core excitations for the description of spectra and magnetic moments, which are for the first time correctly reproduced in theoretical calculations. Shell evolution from {sup 68}Ni to {sup 78}Ni is discussed in detail. A weakening of the Z=28 gap when approaching the N=50 shell closure, suggested by the experimental evidence, is confirmed in the calculations.

  4. Neutron-proton effective mass splitting in neutron-rich matter and its impacts on nuclear reactions

    NASA Astrophysics Data System (ADS)

    Li, Bao-An; Chen, Lie-Wen

    2015-04-01

    The neutron-proton effective mass splitting in neutron-rich nucleonic matter reflects the spacetime nonlocality of the isovector nuclear interaction. It affects the neutron/proton ratio during the earlier evolution of the Universe, cooling of proto-neutron stars, structure of rare isotopes and dynamics of heavy-ion collisions. While there is still no consensus on whether the neutron-proton effective mass splitting is negative, zero or positive and how it depends on the density as well as the isospin-asymmetry of the medium, significant progress has been made in recent years in addressing these issues. There are different kinds of nucleon effective masses. In this mini-review, we focus on the total effective masses often used in the non-relativistic description of nuclear dynamics. We first recall the connections among the neutron-proton effective mass splitting, the momentum dependence of the isovector potential and the density dependence of the symmetry energy. We then make a few observations about the progress in calculating the neutron-proton effective mass splitting using various nuclear many-body theories and its effects on the isospin-dependence of in-medium nucleon-nucleon cross-sections. Perhaps, our most reliable knowledge so far about the neutron-proton effective mass splitting at saturation density of nuclear matter comes from optical model analyses of huge sets of nucleon-nucleus scattering data accumulated over the last five decades. The momentum dependence of the symmetry potential from these analyses provide a useful boundary condition at saturation density for calibrating nuclear many-body calculations. Several observables in heavy-ion collisions have been identified as sensitive probes of the neutron-proton effective mass splitting in dense neutron-rich matter based on transport model simulations. We review these observables and comment on the latest experimental findings.

  5. ZIRCONIUM—HAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

    SciTech Connect

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-10

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (≤1ε in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (∼2ε). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ≤ 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ☉}) SNII.

  6. Single-Neutron Structure of Neutron-Rich Nuclei near N=50 and N=82

    SciTech Connect

    Cizewski, J. A.; Jones, K. L.; Kozub, R. L.; Pain, S. D.; Bardayan, Daniel W; Blackmon, Jeff C; Adekola, Aderemi S; Chae, K. Y.; Chipps, K.; Erikson, Luke; Gaddis, A. L.; Harlin, Christopher W; Hatarik, Robert; Howard, Joshua A; Kaplan, Ron; Krolas, W.; Liang, J Felix; Livesay, Jake; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Patterson, N. P.; Paulauskas, Stanley; Shapira, Dan; Shriner, Jr., John F; Sissom, D. J.; Smith, Michael Scott; Swan, T. P.; Thomas, J. S.; Wilson, Gemma L

    2009-01-01

    The 82Ge, 84Se, 132Sn, 130Sn, and 134Te (d,p) reactions have been measured with {approx}4-5-MeV-A rare isotope beams and CD2 targets at the HRIBF at ORNL. Energies and spectroscopic strengths have been measured for excitations in 83Ge and 85Se. Direct neutron capture calculations on 82Ge are presented. Preliminary results for single-neutron excitations in 131Sn, 133Sn, and 135Te are reported.

  7. Deformation in the neutron rich sulfur isotopes {sup 40}S and {sup 42}S

    SciTech Connect

    Glasmacher, T.; Scheit, H.; Brown, B.A.

    1996-12-31

    In the experiment described here radioactive beams of {sup 40,42}S and {sup 44,46}Ar (E{approx}40 MeV/nucl.) were produced in the A1200 fragment separator at the National Superconducting Cyclotron Laboratory at Michigan State University by fragmenting an 80 MeV/nucleon {sup 48}Ca{sup 13+} beam in a 379 mg/cm{sup 2} {sup 9}Be target. The exotic ions were positively identified by a time of flight measurement before interacting with the secondary gold target (93.5 mg/cm{sup 2} or 184.1 mg/cm{sup 2}). After interacting with the virtual photon field in the gold target, fragments scattered into a lab angle of less than 4.1{degrees} were detected in a fast/slow plastic phoswich detector located downstream from the secondary target. The energy loss - total energy measurement allowed the rejection of events which led to the breakup of the projectile in the target. Photons from the deexcitation of the projectile were measured in coincidence with beam particles. The photons emitted from the excited projectile can be clearly distinguished from photons coming from the target by their Doppler shift and Doppler broadening.

  8. Neutron-Rich Isotopes from 208Pb at 86 MeV/u

    NASA Astrophysics Data System (ADS)

    Tarasov, O. B.; Portillo, M.; Amthor, A. M.; Baumann, T.; Bazin, D.; Folden, C.; Ginter, T.; Hausmann, M.; Morrissey, D. J.; Pereira, J.; Sherrill, B. M.; Thoennessen, M.; Nociforo, C.

    2008-10-01

    An experiment to measure production yields from a beam of ^208Pb (86 MeV/u) on Be and Ni-targets has recently been performed. The A1900 fragment-separator [1] was used to analyze products from projectile fragmentation and abrasion-fission [2]. Isotopic identification of nuclides having A˜200 has been achieved, demonstrating that adequate A,Z,Q resolution at this energy region is possible when using silicon detectors. The verification of PID is done via detection of multiple charge state distributions of the primary beam, as well as γ-decay of known isomers with half-lives in the microsecond range. The results demonstrate that experiments with heavy nuclei are possible at the NSCL using beams of A>200. Production cross-sections have been extracted from the data that can help improve the accuracy of production models such as Abrasion-Ablation and Abrasion-Fission used in the LISE++ code [3]. The data reveal the existence of previously unreported isomeric transitions and further analysis is ongoing that may also lead to the observation of new isotopes. References: [1] D.J.Morrissey et al., Nucl. Instrum. Meth. B204 (2003) 90--96. [2] O.B. Tarasov, Tech. Rep. MSUCL1300, NSCL, Michigan St.Univ., 2005. [3] O.B. Tarasov, D. Bazin, Nucl. Phys. A 746 (2004) 411; www.nscl.msu.edu/lise .

  9. Predicted yields of new neutron-rich isotopes of nuclei with Z=64-80 in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-05-15

    The production cross sections of new neutron-rich isotopes of nuclei with charge numbers Z=64-80 are estimated for future experiments in the multinucleon transfer reaction {sup 48}Ca+{sup 238}U at bombarding energy E{sub c.m.}=189 MeV close to the Coulomb barrier.

  10. Evolution of deformation in the neutron-rich krypton isotopes: The Kr96 nucleus

    NASA Astrophysics Data System (ADS)

    Mărginean, N.; Bucurescu, D.; Ur, C. A.; Mihai, C.; Corradi, L.; Farnea, E.; Filipescu, D.; Fioretto, E.; Ghiţă, D.; Guiot, B.; Górska, M.; Ionescu-Bujor, M.; Iordăchescu, A.; Jelavić-Malenica, D.; Lenzi, S. M.; Mason, P.; Mărginean, R.; Mengoni, D.; Montagnoli, G.; Napoli, D. R.; Pascu, S.; Pollarolo, G.; Recchia, F.; Stefanini, A. M.; Silvestri, R.; Sava, T.; Scarlassara, F.; Szilner, S.; Zamfir, N. V.

    2009-08-01

    The energy of the first excited 2+ state in Kr96 was measured as 241 keV. The nucleus was produced in the fission of U238 induced by a 954-MeV Xe136 beam and prompt γ rays were observed using the clover array CLARA in coincidence with fission products identified with the PRISMA spectrometer. The evolution of the quadrupole collectivity in the Kr isotopes with N⩾50 is discussed by comparison with that from the Rb to Mo isotones and with predictions of various theoretical calculations.

  11. Invariant-Mass Spectroscopy of Extremely Neutron-Rich Nuclei with SAMURAI at RIBF

    NASA Astrophysics Data System (ADS)

    Kondo, Yosuke; Nakamura, Takashi; Achouri, N. Lynda; Aumann, Thomas; Baba, Hidetada; Delaunay, Franck; Doornenbal, Pieter; Fukuda, Naoki; Gibelin, Julien; Hwang, Jongwon; Inabe, Naohito; Isobe, Tadaaki; Kameda, Daisuke; Kanno, Daiki; Kim, Sunji; Kobayashi, Nobuyuki; Kobayashi, Toshio; Kubo, Toshiyuki; Leblond, Sylvain; Lee, Jenny; Marqués, F. Miguel; Minakata, Ryogo; Motobayashi, Tohru; Murai, Daichi; Murakami, Tetsuya; Muto, Kotomi; Nakashima, Tomohiro; Nakatsuka, Noritsugu; Navin, Alahari; Nishi, Seijiro; Ogoshi, Shun; Orr, Nigel A.; Otsu, Hideaki; Sato, Hiromi; Satou, Yoshiteru; Shimizu, Yohei; Suzuki, Hiroshi; Takahashi, Kento; Takeda, Hiroyuki; Takeuchi, Satoshi; Tanaka, Ryuki; Togano, Yasuhiro; Tuff, Adam G.; Vandebrouck, Marine; Yoneda, Ken-ichiro

    A first experimental campaign for three physics programs using a spectrometer SAMURAI, which is newly constructed at RIBF at RIKEN, was performed in May 2012. In this campaign, the unbound nuclei 25O and 26O produced by one-proton removal reactions at ˜200 MeV/nucleon were investigated by means of invariant mass method. High statistics data compared with previous experiments could be obtained together with good particle identification resolution for outgoing heavy ion. Preliminary results show high performance of the SAMURAI spectrometer combined with high intense RI beams provided by RIBF.

  12. β-decay study of neutron-rich ^102Rb at TRIUMF-ISAC

    NASA Astrophysics Data System (ADS)

    Wang, Zhimin

    2012-10-01

    Experimental investigations of the β-decay properties of nuclei which lie along the astrophysical r-process are becoming possible with modern facilities and detection systems. In this experiment, a ^102Rb beam was produced by 500 MeV, 10 μA protons impinging on a multilayer UCx target at TRIUMF-ISAC Facility. The beam of ^102Rb ions was implanted on a movable tape at the center of the 8π spectrometer. The 20 HPGe 8π γ-ray detectors were coupled with SCEPTAR, an hemispherical array of scintillators for β-tagging and DANTE, an array of five LaBr3 detectors for fast γ-ray timing. A preliminary analysis has allowed the first identification of the 4^+ to 2^+ transition in the daughter nucleus, ^102Sr. A near identical low-lying band structure of ^102Sr with ^98, 100Sr nuclei has been observed, indicating the rigidly deformed rotational nature continues towards to the N=66 midshell. The current experimental measurements of ^102Rb β-decay half life as well as the β-delayed neutron emission branching ratio compared with reported values, the shorter β-decay half life and the larger β-delayed neutron emission branching ratio will locally reshape astrophysical r-process predictions.

  13. Single-neutron excitations in neutron-rich Ge83 and Se85

    NASA Astrophysics Data System (ADS)

    Thomas, J. S.; Arbanas, G.; Bardayan, D. W.; Blackmon, J. C.; Cizewski, J. A.; Dean, D. J.; Fitzgerald, R. P.; Greife, U.; Gross, C. J.; Johnson, M. S.; Jones, K. L.; Kozub, R. L.; Liang, J. F.; Livesay, R. J.; Ma, Z.; Moazen, B. H.; Nesaraja, C. D.; Shapira, D.; Smith, M. S.; Visser, D. W.

    2007-10-01

    The H2(Ge82,p)Ge83 and H2(Se84,p)Se85 reactions were studied with radioactive beams of Ge82 and Se84 at beam energies of Ebeam=330 and 380 MeV, respectively. Excitation energies, proton angular distributions, and asymptotic normalization coefficients have been determined for the lowest lying states of Ge83 and Se85. Spectroscopic factors have also been extracted under normal assumptions of the bound-state potential properties in the distorted waves Born approximation analysis. However, the peripheral character of the measurements leads to large uncertainties in this extraction. Shell-model calculations have been performed in the region above Ni78, comparing the single-particle properties of the even-Z,N=51 nuclei up to Zr91 and including Ge83 and Se85. Direct-semidirect neutron capture calculations to Ge83 and Se85 have also been performed using the spectroscopic input from these (d,p) reaction measurements.

  14. A binding energy study of the Atomic Mass Evaluation 2012 and an updated beta-decay study of neutron-rich 74Cu

    NASA Astrophysics Data System (ADS)

    Tracy, James L., Jr.

    A study of ground state binding energy values listed in the Atomic Mass Evaluation 2012 (AME2012) using an interpretive approach, as opposed to the exploratory methods of previous models, is presented. This model is based on a postulate requiring all protons to pair with available neutrons to form bound alpha clusters as the ground state for an N = Z core upon which excess neutrons are added. For each core, the trend of the binding energy as a function of excess neutrons in the isotopic chain can be fit with a three-term quadratic function. The quadratic parameter reveals a smooth decaying exponential function. By re-envisioning the determination of mass excess, the constant-term fit parameters, representing N = Z nuclei, reveal a near-symmetry around Z = 50. The linear fit parameters exhibit trends which are linear functions of core size. A neutron drip-line prediction is compared against current models. By considering the possibility of an alpha-cluster core, a new ground-state structure grouping scheme is presented; nucleon-nucleon pairing is shown to have a greater role in level filling. This model, referred to as the Alpha-Deuteron-Neutron Model, yields promising first results when considering root-mean-square variances from the AME2012. The beta-decay of the neutron-rich isotope 74Cu has been studied using three high-purity Germanium clover detectors at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. A high-resolution mass separator greatly improved the purity of the 74Cu beam by removing isobaric contaminants, thus allowing decay through its isobar chain to the stable 74Ge at the center of the LeRIBSS detector array without any decay chain member dominating. Using coincidence gating techniques, 121 gamma-rays associated with 74Cu were isolated from the collective singles spectrum. Eighty-seven of these were placed in an expanded level scheme, and updated beta-feeding level intensities and log( ft) values are presented based on

  15. A 30-cm diameter argon ion source

    NASA Technical Reports Server (NTRS)

    Sovey, J. S.

    1976-01-01

    A 30 cm diameter argon ion source was evaluated. Ion source beam currents up to 4a were extracted with ion energies ranging from 0.2 to 1.5 KeV. An ion optics scaling relation was developed for predicting ion beam extraction capability as a function of total extraction voltage, gas type, and screen grid open area. Ignition and emission characteristics of several hollow cathode geometries were assessed for purposes of defining discharge chamber and neutralizer cathodes. Also presented are ion beam profile characteristics which exhibit broad beam capability well suited for ion beam sputtering applications.

  16. Dependence of Fission-Fragment Properties On Excitation Energy For Neutron-Rich Actinides

    NASA Astrophysics Data System (ADS)

    Ramos, D.; Rodríguez-Tajes, C.; Caamaño, M.; Farget, F.; Audouin, L.; Benlliure, J.; Casarejos, E.; Clement, E.; Cortina, D.; Delaune, O.; Derkx, X.; Dijon, A.; Doré, D.; Fernández-Domínguez, B.; de France, G.; Heinz, A.; Jacquot, B.; Navin, A.; Paradela, C.; Rejmund, M.; Roger, T.; Salsac, M. D.; Schmitt, C.

    2016-03-01

    Experimental access to full isotopic fragment distributions is very important to determine the features of the fission process. However, the isotopic identification of fission fragments has been, in the past, partial and scarce. A solution based on the use of inverse kinematics to study transfer-induced fission of exotic actinides was carried out at GANIL, resulting in the first experiment accessing the full identification of a collection of fissioning systems and their corresponding fission fragment distribution. In these experiments, a 238U beam at 6.14 AMeV impinged on a carbon target to produce fissioning systems from U to Am by transfer reactions, and Cf by fusion reactions. Isotopic fission yields of 250Cf, 244Cm, 240Pu, 239Np and 238U are presented in this work. With this information, the average number of neutrons as a function of the atomic number of the fragments is calculated, which reflects the impact of nuclear structure around Z=50, N=80 on the production of fission fragments. The characteristics of the Super Long, Standard I, Standard II, and Standard III fission channels were extracted from fits of the fragment yields for different ranges of excitation energy. The position and contribution of the fission channels as function of excitation energy are presented.

  17. Nature of Collective Dipole and Octupole Transitions in Neutron-Rich Barium Isotopes

    NASA Astrophysics Data System (ADS)

    Bucher, B.; Zhu, S.; ANL, LBNL, LLNL, Rochester, FSU, Liverpool, Maryland, Notre Dame, Ohio, W. Scotland Collaboration

    2016-09-01

    Recently, a direct measurement of octupole strength in 144Ba was carried out via Coulomb excitation with a radioactive beam from Argonne's CARIBU facility using GRETINA and CHICO2. The results verify the presence of enhanced octupole collectivity in this isotope, as predicted by theory. In the neighboring isotope 146Ba, however, the importance of octupole correlations is more uncertain. Specifically, the electric dipole strength, expected to be closely correlated with the octupole one, displays what is perhaps the most significant drop in strength between neighboring isotopes of any medium- to heavy-mass nuclei. To address this puzzling question, a Coulomb excitation experiment was also performed on 146Ba under the same conditions. The new measurement yields an enhanced octupole strength of the same magnitude as that observed in 144Ba. This supports the notion that the strong-weak dipole behavior in this region results from the unique single-particle structure characteristic of Z 56 and N 90 in the presence of a pear-shaped mean-field potential. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 (ANL), DE-AC02-05CH11231 (LBNL, GRETINA), DOE DE-AC52-07NA27344 (LLNL), and NSF.

  18. β--Decay Study of the Deformed, Neutron-Rich Nucleus 160Eu

    NASA Astrophysics Data System (ADS)

    Hartley, D. J.; Kondev, F. G.; Savard, G.; Ayangeakaa, A. D.; Bottoni, S.; Carpenter, M. P.; Clark, J. A.; Hoffman, C. R.; Janssens, R. V. F.; Lauritsen, T.; Zhu, S.; Copp, P.; Hu, C.; Zhang, H.; Zhu, Y.; Nystrom, A.; Orford, R.; Sethi, J.

    2017-01-01

    A new experimental program at Argonne National Laboratory has been initiated in the pursuit of understanding the structure of deformed nuclei in the A 160 region. Of particular interest is the evolution of collectivity towards mid shell (N = 104). In addition, these results will provide valuable information for understanding the rare-earth ``pygmy peak'' in the r-process abundance distribution. A high-purity beam of 160Eu from the CARIBU facility was directed onto the SATURN moving tape system. The X-Array spectrometer (with multiple Ge clover detectors and plastic scintillators) was placed around the tape system for γ and β detection. Two β-decaying states in 160Eu were observed, and the decay scheme of the 160Gd daughter nucleus was greatly extended. Multi-quasiparticle blocking calculations were performed to help interpret the structure of the parent and daughter states. This work is funded by the NSF (PHY-1502092) and the US DOE, Office of Science (DE-AC02-06CH11357). This research used resources of Argonne National Laboratory's ATLAS facility, which is a DOE, Office of Science User Facility.

  19. Scintillation efficiency of liquid argon in low energy neutron-argon scattering

    NASA Astrophysics Data System (ADS)

    Creus, W.; Allkofer, Y.; Amsler, C.; Ferella, A. D.; Rochet, J.; Scotto-Lavina, L.; Walter, M.

    2015-08-01

    Experiments searching for weak interacting massive particles with noble gases such as liquid argon require very low detection thresholds for nuclear recoils. A determination of the scintillation efficiency is crucial to quantify the response of the detector at low energy. We report the results obtained with a small liquid argon cell using a monoenergetic neutron beam produced by a deuterium-deuterium fusion source. The light yield relative to electrons was measured for six argon recoil energies between 11 and 120 keV at zero electric drift field.

  20. Dineutron correlations in quasi-two-dimensional systems in a simplified model, and possible relation to neutron-rich nuclei

    SciTech Connect

    Kanada-En'yo, Yoshiko; Hinohara, Nobuo; Suhara, Tadahiro; Schuck, Peter

    2009-05-15

    Two-neutron correlation in the {sup 1}S channel in quasi-two-dimensional (2D) neutron systems at zero temperature is studied by means of the BCS theory with finite-range effective nuclear forces. The dineutron correlation in low density neutron systems confined in an infinite slab is investigated in a simplified model that neutron motion of one direction is frozen. When the slab is thin enough, two neutrons form a tightly bound dineutron with a small size in the quasi-2D system, and a Bose dineutron gas is found in low density limit. With increase of Fermi momentum, the neutron system changes from the Bose-gas phase to the superfluid Cooper pair phase. The density dependence of the neutron pairing shows the BCS-BEC crossover phenomena at finite low-density region. In the transition region, the size shrinking of neutron pair and enhancement of pairing gap are found. The relation to dineutron correlation at surface of neutron-rich nuclei is also discussed.

  1. Precision Mass Measurements of Short-Lived, Neutron-Rich, R-Process Nuclei About the N=82 Waiting Point

    NASA Astrophysics Data System (ADS)

    Lascar, Daniel David

    This thesis details the precision mass measurements of 33 neutron-rich ground-state nuclei and isomeric states that approach or lie on the proposed rapid neutron capture process (r-process) path. For many of the nuclei measured the work presented here will be the rst direct mass measurements of these nuclei, including 130In, 137Sb, 133I, and 134I. The measurements were made using the Canadian Penning Trap mass spectrometer (CPT), located at the ATLAS heavy ion-linac at Argonne National Laboratory. Ground states and isomers have been measured with the CPT at fractional precisions (δm/m) between 10-7, and 10-8. The nuclei were produced at the new CAlifornium Rare Isotope Breeder Upgrade (CARIBU) to ATLAS. Because nuclear masses are required for measuring neutron separation energies, and neutron separation energies are important inputs in r-process network calculations, precision mass measurements are critical for advancing our knowledge of the r-process. This thesis will give the astrophysical motivation for making these mass measurements, the theoretical background behind ion trapping and mass measurements using ion traps, an explanation of the CPT apparatus, the mass measurements themselves, and the results of those measurements as they pertain to r-process network calculations. Results of these mass measurements show significant shifts in the r-process path over a range of temperatures and neutron densities.

  2. Tetrahedral shapes of neutron-rich Zr isotopes from a multidimensionally constrained relativistic Hartree-Bogoliubov model

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; Lu, Bing-Nan; Zhao, En-Guang; Zhou, Shan-Gui

    2017-01-01

    We develop a multidimensionally constrained relativistic Hartree-Bogoliubov (MDC-RHB) model in which the pairing correlations are taken into account by making the Bogoliubov transformation. In this model, the nuclear shape is assumed to be invariant under the reversion of x and y axes; i.e., the intrinsic symmetry group is V4 and all shape degrees of freedom βλ μ with even μ are included self-consistently. The RHB equation is solved in an axially deformed harmonic oscillator basis. A separable pairing force of finite range is adopted in the MDC-RHB model. The potential energy curves of neutron-rich even-even Zr isotopes are calculated with relativistic functionals DD-PC1 and PC-PK1 and possible tetrahedral shapes in the ground and isomeric states are investigated. The ground state shape of 110Zr is predicted to be tetrahedral with both functionals and so is that of 112Zr with the functional DD-PC1. The tetrahedral ground states are caused by large energy gaps around Z =40 and N =70 when β32 deformation is included. Although the inclusion of the β30 deformation can also reduce the energy around β20=0 and lead to minima with pear-like shapes for nuclei around 110Zr, these minima are unstable due to their shallowness.

  3. The effect of the dc bias voltage on the x-ray bremsstrahlung and beam intensities of medium and highly charged ions of argon

    SciTech Connect

    Rodrigues, G.; Lakshmy, P. S.; Kanjilal, D.; Roy, A.; Baskaran, R.

    2010-02-15

    X-ray bremsstrahlung measurements from the 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Pantechnik-Delhi Ion Source were measured as a function of negative dc bias voltage, keeping all other source operating parameters fixed and the extraction voltage in the off condition. The optimization of medium and highly charged ions of argon with similar source operating parameters is described. It is observed that the high temperature component of the electron is altered significantly with the help of bias voltage, and the electron population has to be maximized for obtaining higher current.

  4. Small-beam, low-power argon-pumped tunable dye laser at 585 nm for the treatment of cherry angiomas

    NASA Astrophysics Data System (ADS)

    Littler, Curt M.

    1990-06-01

    An argon-pumped tunable dye laser tuned to 585 nm was used to treat clinically typical cherry angiomas in a preliminary study. A spot size of 0.1 mm and low power (0.1 - 0.15W) in the continuous mode was used for treatment. Results ranged from decrease in size of the cherry angioma to complete regression. In all cases, there was minimal to no scarring. Further study in the treatment of elevated cutaneous vascular lesions with the continuous wave dye laser seems warranted.

  5. The effect of the dc bias voltage on the x-ray bremsstrahlung and beam intensities of medium and highly charged ions of argon.

    PubMed

    Rodrigues, G; Lakshmy, P S; Baskaran, R; Kanjilal, D; Roy, A

    2010-02-01

    X-ray bremsstrahlung measurements from the 18 GHz High Temperature Superconducting Electron Cyclotron Resonance Ion Source, Pantechnik-Delhi Ion Source were measured as a function of negative dc bias voltage, keeping all other source operating parameters fixed and the extraction voltage in the off condition. The optimization of medium and highly charged ions of argon with similar source operating parameters is described. It is observed that the high temperature component of the electron is altered significantly with the help of bias voltage, and the electron population has to be maximized for obtaining higher current.

  6. Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of {sup 238}U projectiles at 1A GeV

    SciTech Connect

    Alvarez-Pol, H.; Benlliure, J.; Casarejos, E.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Pereira, J.; Audouin, L.; Enqvist, T.; Schmidt, K.-H.; Yordanov, O.; Junghans, A. R.; Jurado, B.; Rejmund, F.

    2010-10-15

    The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

  7. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $$(n,\\gamma )$$ reaction rates

    DOE PAGES

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; ...

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  8. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $(n,\\gamma )$ reaction rates

    SciTech Connect

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Bracco, A.; Brown, B. A.; Camera, F.; Eriksen, T. K.; Frauendorf, S.; Giacoppo, F.; Guttormsen, M.; Gorgen, A.; Harissopulos, S.; Leoni, S.; Liddick, S. N.; Naqvi, F.; Nyhus, H. T.; Rose, S. J.; Renstrom, T.; Schwengner, R.; Siem, S.; Spyrou, A.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  9. Commissioning of the ATLAS Liquid Argon Calorimeters

    SciTech Connect

    Cooke, Mark S.

    2009-12-17

    A selection of ATLAS liquid argon (LAr) calorimeter commissioning studies is presented. It includes a coherent noise study, a measurement of the quality of the ionization pulse shape prediction, and energy and time reconstruction analyses with cosmic and single beam signals.

  10. SLD liquid argon calorimeter prototype test results

    SciTech Connect

    Dubois, R.; Eigen, G.; Au, Y.; Sleeman, J.; Breidenbach, M.; Brau, J.; Ludgate, G.A.; Oram, C.J.; Cook, V.; Johnson, J.

    1985-10-01

    The results of the SLD test beam program for the selection of a calorimeter radiator composition within a liquid argon system are described, with emphasis on the study of the use of uranium to obtain equalization of pion and electron responses.

  11. IRiS—Exploring new frontiers in neutron-rich isotopes of the heaviest elements with a new Inelastic Reaction Isotope Separator

    NASA Astrophysics Data System (ADS)

    Dvorak, J.; Block, M.; Düllmann, Ch. E.; Heinz, S.; Herzberg, R.-D.; Schädel, M.

    2011-10-01

    A dedicated Inelastic Reaction Isotope Separator (IRiS) for multi-nucleon transfer products will be designed and installed at GSI. Research at IRiS will focus on the investigation of new neutron-rich isotopes of the heaviest elements, study of which will advance various research fields, such as nuclear chemistry, nuclear and atomic physics, as well as nuclear astrophysics. The scientific motivation for this project and the alternative design options for the separator and its main components are discussed.

  12. β-Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process.

    PubMed

    Lorusso, G; Nishimura, S; Xu, Z Y; Jungclaus, A; Shimizu, Y; Simpson, G S; Söderström, P-A; Watanabe, H; Browne, F; Doornenbal, P; Gey, G; Jung, H S; Meyer, B; Sumikama, T; Taprogge, J; Vajta, Zs; Wu, J; Baba, H; Benzoni, G; Chae, K Y; Crespi, F C L; Fukuda, N; Gernhäuser, R; Inabe, N; Isobe, T; Kajino, T; Kameda, D; Kim, G D; Kim, Y-K; Kojouharov, I; Kondev, F G; Kubo, T; Kurz, N; Kwon, Y K; Lane, G J; Li, Z; Montaner-Pizá, A; Moschner, K; Naqvi, F; Niikura, M; Nishibata, H; Odahara, A; Orlandi, R; Patel, Z; Podolyák, Zs; Sakurai, H; Schaffner, H; Schury, P; Shibagaki, S; Steiger, K; Suzuki, H; Takeda, H; Wendt, A; Yagi, A; Yoshinaga, K

    2015-05-15

    The β-decay half-lives of 110 neutron-rich isotopes of the elements from _{37}Rb to _{50}Sn were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r-process calculations and reinforce the notion that the second (A≈130) and the rare-earth-element (A≈160) abundance peaks may result from the freeze-out of an (n,γ)⇄(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r-process events.

  13. 94 β -Decay Half-Lives of Neutron-Rich Cs 55 to Ho 67 : Experimental Feedback and Evaluation of the r -Process Rare-Earth Peak Formation

    NASA Astrophysics Data System (ADS)

    Wu, J.; Nishimura, S.; Lorusso, G.; Möller, P.; Ideguchi, E.; Regan, P.-H.; Simpson, G. S.; Söderström, P.-A.; Walker, P. M.; Watanabe, H.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Gey, G.; Isobe, T.; Lee, P. S.; Liu, J. J.; Li, Z.; Korkulu, Z.; Patel, Z.; Phong, V.; Rice, S.; Sakurai, H.; Sinclair, L.; Sumikama, T.; Tanaka, M.; Yagi, A.; Ye, Y. L.; Yokoyama, R.; Zhang, G. X.; Alharbi, T.; Aoi, N.; Bello Garrote, F. L.; Benzoni, G.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Z.; Estrade, A.; Gottardo, A.; Griffin, C. J.; Kanaoka, H.; Kojouharov, I.; Kondev, F. G.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lane, G. J.; Lee, E. J.; Lokotko, T.; Lotay, G.; Moon, C.-B.; Nishibata, H.; Nishizuka, I.; Nita, C. R.; Odahara, A.; Podolyák, Zs.; Roberts, O. J.; Schaffner, H.; Shand, C.; Taprogge, J.; Terashima, S.; Vajta, Z.; Yoshida, S.

    2017-02-01

    The β -decay half-lives of 94 neutron-rich nuclei Cs-151144 , Ba-154146 , La-156148 , Ce-158150 , Pr-160153 , Nd-162156 , Pm-163159 , Sm-166160 , Eu-168161 , Gd-170165 , Tb-172166 , Dy-173169 , Ho-175172 , and two isomeric states Erm174 , Dym172 were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β -decay half-lives are observed at neutron-number N =97 for Ce 58 , Pr 59 , Nd 60 , and Sm 62 , and N =105 for Eu 63 , Gd 64 , Tb 65 , and Dy 66 . Features in the data mirror the interplay between pairing effects and microscopic structure. r -process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.

  14. 94 β-Decay Half-Lives of Neutron-Rich _{55}Cs to _{67}Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation.

    PubMed

    Wu, J; Nishimura, S; Lorusso, G; Möller, P; Ideguchi, E; Regan, P-H; Simpson, G S; Söderström, P-A; Walker, P M; Watanabe, H; Xu, Z Y; Baba, H; Browne, F; Daido, R; Doornenbal, P; Fang, Y F; Gey, G; Isobe, T; Lee, P S; Liu, J J; Li, Z; Korkulu, Z; Patel, Z; Phong, V; Rice, S; Sakurai, H; Sinclair, L; Sumikama, T; Tanaka, M; Yagi, A; Ye, Y L; Yokoyama, R; Zhang, G X; Alharbi, T; Aoi, N; Bello Garrote, F L; Benzoni, G; Bruce, A M; Carroll, R J; Chae, K Y; Dombradi, Z; Estrade, A; Gottardo, A; Griffin, C J; Kanaoka, H; Kojouharov, I; Kondev, F G; Kubono, S; Kurz, N; Kuti, I; Lalkovski, S; Lane, G J; Lee, E J; Lokotko, T; Lotay, G; Moon, C-B; Nishibata, H; Nishizuka, I; Nita, C R; Odahara, A; Podolyák, Zs; Roberts, O J; Schaffner, H; Shand, C; Taprogge, J; Terashima, S; Vajta, Z; Yoshida, S

    2017-02-17

    The β-decay half-lives of 94 neutron-rich nuclei ^{144-151}Cs, ^{146-154}Ba, ^{148-156}La, ^{150-158}Ce, ^{153-160}Pr, ^{156-162}Nd, ^{159-163}Pm, ^{160-166}Sm, ^{161-168}Eu, ^{165-170}Gd, ^{166-172}Tb, ^{169-173}Dy, ^{172-175}Ho, and two isomeric states ^{174m}Er, ^{172m}Dy were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β-decay half-lives are observed at neutron-number N=97 for _{58}Ce, _{59}Pr, _{60}Nd, and _{62}Sm, and N=105 for _{63}Eu, _{64}Gd, _{65}Tb, and _{66}Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. r-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.

  15. The CAPTAIN Liquid Argon Neutrino Experiment

    NASA Astrophysics Data System (ADS)

    Liu, Qiuguang

    The CAPTAIN liquid argon experiment is designed to make measurements of scientific importance to long-baseline neutrino physics and physics topics that will be explored by large underground detectors. The experiment employs two detectors - a primary detector with approximately 10-ton of liquid argon that will be deployed at different facilities for physics measurements and a prototype detector with 2-ton of liquid argon for configuration testing. The physics programs for CAPTAIN include measuring neutron interactions at Los Alamos Neutron Science Center, measuring neutrino interactions in medium energy regime (1.5-5 GeV) at Fermilab's NuMI beam, and measuring neutrino interactions in low energy regime (< 50 MeV) at stopped pion sources for supernova neutrino studies.

  16. The CAPTAIN liquid argon neutrino experiment

    SciTech Connect

    Liu, Qiuguang

    2015-01-01

    The CAPTAIN liquid argon experiment is designed to make measurements of scientific importance to long-baseline neutrino physics and physics topics that will be explored by large underground detectors. The experiment employs two detectors – a primary detector with approximately 10-ton of liquid argon that will be deployed at different facilities for physics measurements and a prototype detector with 2-ton of liquid argon for configuration testing. The physics programs for CAPTAIN include measuring neutron interactions at Los Alamos Neutron Science Center, measuring neutrino interactions in medium energy regime (1.5–5 GeV) at Fermilab's NuMI beam, and measuring neutrino interactions in low energy regime (< 50 MeV) at stopped pion sources for supernova neutrino studies.

  17. The CAPTAIN liquid argon neutrino experiment

    DOE PAGES

    Liu, Qiuguang

    2015-01-01

    The CAPTAIN liquid argon experiment is designed to make measurements of scientific importance to long-baseline neutrino physics and physics topics that will be explored by large underground detectors. The experiment employs two detectors – a primary detector with approximately 10-ton of liquid argon that will be deployed at different facilities for physics measurements and a prototype detector with 2-ton of liquid argon for configuration testing. The physics programs for CAPTAIN include measuring neutron interactions at Los Alamos Neutron Science Center, measuring neutrino interactions in medium energy regime (1.5–5 GeV) at Fermilab's NuMI beam, and measuring neutrino interactions in low energymore » regime (< 50 MeV) at stopped pion sources for supernova neutrino studies.« less

  18. Lunar exospheric argon modeling

    NASA Astrophysics Data System (ADS)

    Grava, Cesare; Chaufray, J.-Y.; Retherford, K. D.; Gladstone, G. R.; Greathouse, T. K.; Hurley, D. M.; Hodges, R. R.; Bayless, A. J.; Cook, J. C.; Stern, S. A.

    2015-07-01

    Argon is one of the few known constituents of the lunar exosphere. The surface-based mass spectrometer Lunar Atmosphere Composition Experiment (LACE) deployed during the Apollo 17 mission first detected argon, and its study is among the subjects of the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) and Lunar Atmospheric and Dust Environment Explorer (LADEE) mission investigations. We performed a detailed Monte Carlo simulation of neutral atomic argon that we use to better understand its transport and storage across the lunar surface. We took into account several loss processes: ionization by solar photons, charge-exchange with solar protons, and cold trapping as computed by recent LRO/Lunar Orbiter Laser Altimeter (LOLA) mapping of Permanently Shaded Regions (PSRs). Recycling of photo-ions and solar radiation acceleration are also considered. We report that (i) contrary to previous assumptions, charge exchange is a loss process as efficient as photo-ionization, (ii) the PSR cold-trapping flux is comparable to the ionization flux (photo-ionization and charge-exchange), and (iii) solar radiation pressure has negligible effect on the argon density, as expected. We determine that the release of 2.6 × 1028 atoms on top of a pre-existing argon exosphere is required to explain the maximum amount of argon measured by LACE. The total number of atoms (1.0 × 1029) corresponds to ∼6700 kg of argon, 30% of which (∼1900 kg) may be stored in the cold traps after 120 days in the absence of space weathering processes. The required population is consistent with the amount of argon that can be released during a High Frequency Teleseismic (HFT) Event, i.e. a big, rare and localized moonquake, although we show that LACE could not distinguish between a localized and a global event. The density of argon measured at the time of LACE appears to have originated from no less than four such episodic events. Finally, we show that the extent of the PSRs that trap

  19. Argon broad ion beam tomography in a cryogenic scanning electron microscope: a novel tool for the investigation of representative microstructures in sedimentary rocks containing pore fluid.

    PubMed

    Desbois, G; Urai, J L; Pérez-Willard, F; Radi, Z; Offern, S; Burkart, I; Kukla, P A; Wollenberg, U

    2013-03-01

    The contribution describes the implementation of a broad ion beam (BIB) polisher into a scanning electron microscope (SEM) functioning at cryogenic temperature (cryo). The whole system (BIB-cryo-SEM) provides a first generation of a novel multibeam electron microscope that combines broad ion beam with cryogenic facilities in a conventional SEM to produce large, high-quality cross-sections (up to 2 mm(2)) at cryogenic temperature to be imaged at the state-of-the-art SEM resolution. Cryogenic method allows detecting fluids in their natural environment and preserves samples against desiccation and dehydration, which may damage natural microstructures. The investigation of microstructures in the third dimension is enabled by serial cross-sectioning, providing broad ion beam tomography with slices down to 350 nm thick. The functionalities of the BIB-cryo-SEM are demonstrated by the investigation of rock salts (synthetic coarse-grained sodium chloride synthesized from halite-brine mush cold pressed at 150 MPa and 4.5 GPa, and natural rock salt mylonite from a salt glacier at Qom Kuh, central Iran). In addition, results from BIB-cryo-SEM on a gas shale and Boom Clay are also presented to show that the instrument is suitable for a large range of sedimentary rocks. For the first time, pore and grain fabrics of preserved host and reservoir rocks can be investigated at nm-scale range over a representative elementary area. In comparison with the complementary and overlapping performances of the BIB-SEM method with focused ion beam-SEM and X-ray tomography methods, the BIB cross-sectioning enables detailed insights about morphologies of pores at greater resolution than X-ray tomography and allows the production of large representative surfaces suitable for FIB-SEM investigations of a specific representative site within the BIB cross-section.

  20. Spectroscopy of 36Mg: interplay of normal and intruder configurations at the neutron-rich boundary of the "island of inversion".

    PubMed

    Gade, A; Adrich, P; Bazin, D; Bowen, M D; Brown, B A; Campbell, C M; Cook, J M; Ettenauer, S; Glasmacher, T; Kemper, K W; McDaniel, S; Obertelli, A; Otsuka, T; Ratkiewicz, A; Siwek, K; Terry, J R; Tostevin, J A; Utsuno, Y; Weisshaar, D

    2007-08-17

    We report on the first spectroscopy study of the very neutron-rich nucleus (36)(12)Mg24 using the direct two-proton knockout reaction 9Be(38Si,36Mg+gamma)X at 83 MeV/nucleon. The energy of the first excited 2+ state of 36Mg, E(2+(1)=660(6) keV, was measured. The magnitude of the partial cross sections to the ground state and the 2+(1) state is indicative of strong intruder admixtures in the lowest-lying states as suggested by Monte Carlo shell-model calculations.

  1. Depleted Argon from Underground Sources

    SciTech Connect

    Back, H. O.; Galbiati, C.; Goretti, A.; Loer, B.; Montanari, D.; Mosteiro, P.; Alexander, T.; Alton, A.; Rogers, H.; Kendziora, C.; Pordes, S.

    2011-04-27

    Argon is a strong scintillator and an ideal target for Dark Matter detection; however {sup 39}Ar contamination in atmospheric argon from cosmic ray interactions limits the size of liquid argon dark matter detectors due to pile-up. Argon from deep underground is depleted in {sup 39}Ar due to the cosmic ray shielding of the earth. In Cortez, Colorado, a CO{sub 2} well has been discovered to contain approximately 600 ppm of argon as a contamination in the CO{sub 2}. We first concentrate the argon locally to 3% in an Ar, N{sub 2}, and He mixture, from the CO{sub 2} through chromatographic gas separation, and then the N{sub 2} and He will be removed by continuous distillation to purify the argon. We have collected 26 kg of argon from the CO{sub 2} facility and a cryogenic distillation column is under construction at Fermilab to further purify the argon.

  2. β -Decay Half-Lives of 110 Neutron-Rich Nuclei across the N=82 Shell Gap: Implications for the Mechanism and Universality of the Astrophysical r Process

    SciTech Connect

    Lorusso, G.; Nishimura, S.; Xu, Z. Y.; Jungclaus, A.; Shimizu, Y.; Simpson, G. S.; Söderström, P. -A.; Watanabe, H.; Browne, F.; Doornenbal, P.; Gey, G.; Jung, H. S.; Meyer, B.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Baba, H.; Benzoni, G.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Inabe, N.; Isobe, T.; Kajino, T.; Kameda, D.; Kim, G. D.; Kim, Y. -K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lane, G. J.; Li, Z.; Montaner-Pizá, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Patel, Z.; Podolyák, Zs.; Sakurai, H.; Schaffner, H.; Schury, P.; Shibagaki, S.; Steiger, K.; Suzuki, H.; Takeda, H.; Wendt, A.; Yagi, A.; Yoshinaga, K.

    2015-05-01

    The β -decay half-lives of 110 neutron-rich isotopes of the elements from Rb 37 to Sn 50 were measured at the Radioactive Isotope Beam Factory. The 40 new half-lives follow robust systematics and highlight the persistence of shell effects. The new data have direct implications for r -process calculations and reinforce the notion that the second (A≈130 ) and the rare-earth-element (A≈160 ) abundance peaks may result from the freeze-out of an (n,γ)⇌(γ,n) equilibrium. In such an equilibrium, the new half-lives are important factors determining the abundance of rare-earth elements, and allow for a more reliable discussion of the r process universality. It is anticipated that universality may not extend to the elements Sn, Sb, I, and Cs, making the detection of these elements in metal-poor stars of the utmost importance to determine the exact conditions of individual r -process events.

  3. Thermophysical properties of argon

    SciTech Connect

    Jaques, A.

    1988-02-01

    The entire report consists of tables of thermodynamic properties (including sound velocity, thermal conductivity and diffusivity, Prandtl number, density) of argon at 86 to 400/degree/K, in the form of isobars over 0.9 to 100 bars. (DLC)

  4. A novel approach for the characterization of a bilayer of phenyl-c71-butyric-acid-methyl ester and pentacene using ultraviolet photoemission spectroscopy and argon gas cluster ion beam sputtering process

    SciTech Connect

    Yun, Dong-Jin; Chung, JaeGwan; Jung, Changhoon; Chung, Yeonji; Kim, SeongHeon; Lee, Seunghyup; Kim, Ki-Hong; Han, Hyouksoo; Park, Gyeong-Su; Park, SungHoon

    2013-09-07

    The material arrangement and energy level alignment of an organic bilayer comprising of phenyl-c71-butyric-acid-methyl ester (PCBM-71) and pentacene were studied using ultraviolet photoelectron spectroscopy (UPS) and the argon gas cluster ion beam (GCIB) sputtering process. Although there is a small difference in the full width at half maximum of the carbon C 1s core level peaks and differences in the oxygen O 1s core levels of an X-ray photoemission spectroscopy spectra, these differences are insufficient to clearly distinguish between PCBM-71 and pentacene layers and to classify the interface and bulk regions. On the other hand, the valence band structures in the UPS spectra contain completely distinct configurations for the PCBM-71 and pentacene layers, even when they have similar atomic compositions. According to the valence band structures of the PCBM-71/pentacene/electrodes, the highest unoccupied molecular orbital (HOMO) region of pentacene is at least 0.8 eV closer to the Fermi level than that of PCBM-71 and it does not overlap with any of the chemical states in the valence band structure of PCBM-71. Therefore, by just following the variations in the area of the HOMO region of pentacene, the interface/bulk regions of the PCBM/pentacene layers were distinctly categorized. Besides, the variation of valence band structures as a function of the Ar GCIB sputtering time fully corroborated with the surface morphologies observed in the atomic force microscope images. In summary, we believe that the novel approach, which involves UPS analysis in conjunction with Ar GCIB sputtering, can be one of the best methods to characterize the material distribution and energy level alignments of stacks of organic layers.

  5. Shell-model Monte Carlo studies of neutron-rich nuclei in the 1s-0d-1p-0f shells

    NASA Astrophysics Data System (ADS)

    Dean, D. J.; Ressell, M. T.; Hjorth-Jensen, M.; Koonin, S. E.; Langanke, K.; Zuker, A. P.

    1999-05-01

    We demonstrate the feasibility of realistic shell-model Monte Carlo (SMMC) calculations spanning multiple major shells, using a realistic interaction whose bad saturation and shell properties have been corrected by a newly developed general prescription. Particular attention is paid to the approximate restoration of translational invariance. The model space consists of the full sd-pf shells. We include in the study some well-known T=0 nuclei and several unstable neutron-rich ones around N=20,28. The results indicate that SMMC calculations can reproduce binding energies, B(E2) transitions, and other observables with an interaction that is practically parameter free. Some interesting insight is gained into the nature of deep correlations. The validity of previous studies is confirmed.

  6. Spectroscopy of {sup 36}Mg: Interplay of Normal and Intruder Configurations at the Neutron-Rich Boundary of the 'Island of Inversion'

    SciTech Connect

    Gade, A.; Bowen, M. D.; Brown, B. A.; Campbell, C. M.; Cook, J. M.; Glasmacher, T.; McDaniel, S.; Ratkiewicz, A.; Siwek, K.; Terry, J. R.; Adrich, P.; Bazin, D.; Ettenauer, S.; Obertelli, A.; Weisshaar, D.; Kemper, K. W.; Otsuka, T.; Tostevin, J. A.; Utsuno, Y.

    2007-08-17

    We report on the first spectroscopy study of the very neutron-rich nucleus {sub 12}{sup 36}Mg{sub 24} using the direct two-proton knockout reaction {sup 9}Be({sup 38}Si,{sup 36}Mg+{gamma})X at 83 MeV/nucleon. The energy of the first excited 2{sup +} state of {sup 36}Mg, E(2{sub 1}{sup +})=660(6) keV, was measured. The magnitude of the partial cross sections to the ground state and the 2{sub 1}{sup +} state is indicative of strong intruder admixtures in the lowest-lying states as suggested by Monte Carlo shell-model calculations.

  7. d{sub 5/2} proton hole strength in neutron-rich {sup 43}P: Shell structure and nuclear shapes near N=28

    SciTech Connect

    Riley, L. A.; Baugher, T. R.; Hosier, K. E.; Adrich, P.; Bazin, D.; Diget, C. A.; Weisshaar, D.; Brown, B. A.; Cook, J. M.; Gade, A.; Garland, D. A.; Glasmacher, T.; Ratkiewicz, A.; Siwek, K. P.; Cottle, P. D.; Kemper, K. W.; Otsuka, T.; Rae, W. D. M.; Tostevin, J. A.; Utsuno, Y.

    2008-07-15

    We report on the use of the one-proton knockout reaction from {sup 44}S to determine the location of d{sub 5/2} proton strength in neutron-rich {sup 43}P. The results are used to test two shell-model frameworks with different pictures of the evolution of single-proton energies along the N=28 isotones near the neutron dripline. We observe a concentration of d{sub 5/2} proton hole strength near 1 MeV in excitation energy. This result favors the recent shell-model interaction of Utsuno et al. [Eur. Phys. J. Spec. Top. 150, 187 (2007)] and provides additional evidence for an oblate shape for {sup 42}Si.

  8. Shape coexistence in the N = 19 neutron-rich nucleus 31Mg explored by β-γ spectroscopy of spin-polarized 31Na

    NASA Astrophysics Data System (ADS)

    Nishibata, H.; Shimoda, T.; Odahara, A.; Morimoto, S.; Kanaya, S.; Yagi, A.; Kanaoka, H.; Pearson, M. R.; Levy, C. D. P.; Kimura, M.

    2017-04-01

    The structure of excited states in the neutron-rich nucleus 31Mg, which is in the region of the "island of inversion" associated with the neutron magic number N = 20, is studied by β-γ spectroscopy of spin-polarized 31Na. Among the 31Mg levels below the one neutron separation energy of 2.3 MeV, the spin values of all five positive-parity levels are unambiguously determined by observing the anisotropic β decay. Two rotational bands with Kπ = 1 /2+ and 1 /2- are proposed based on the spins and energies of the levels. Comparison on a level-by-level basis is performed between the experimental results and theoretical calculations by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM). It is found that various nuclear structures coexist in the low excitation energy region in 31Mg.

  9. Direct mass measurements of neutron-rich 86Kr projectile fragments and the persistence of neutron magic number N=32 in Sc isotopes

    NASA Astrophysics Data System (ADS)

    Xu, Xing; Wang, Meng; Zhang, Yu-Hu; Xu, Hu-Shan; Shuai, Peng; Tu, Xiao-Lin; Yuri, A. Litvinov; Zhou, Xiao-Hong; Sun, Bao-Hua; Yuan, You-Jin; Xia, Jia-Wen; Yang, Jian-Cheng; Klaus, Blaum; Chen, Rui-Jiu; Chen, Xiang-Cheng; Fu, Chao-Yi; Ge, Zhuang; Hu, Zheng-Guo; Huang, Wen-Jia; Liu, Da-Wei; Lam, Yi-Hua; Ma, Xin-Wen; Mao, Rui-Shi; Uesaka, T.; Xiao, Guo-Qing; Xing, Yuan-Ming; Yamaguchi, T.; Yamaguchi, Y.; Zeng, Qi; Yan, Xin-Liang; Zhao, Hong-Wei; Zhao, Tie-Cheng; Zhang, Wei; Zhan, Wen-Long

    2015-10-01

    In this paper, we present direct mass measurements of neutron-rich 86Kr projectile fragments conducted at the HIRFL-CSR facility in Lanzhou by employing the Isochronous Mass Spectrometry (IMS) method. The new mass excesses of 52-54Sc nuclides are determined to be -40492(82), -38928(114), -34654(540) keV, which show a significant increase of binding energy compared to the reported ones in the Atomic Mass Evaluation 2012 (AME12). In particular, 53Sc and 54Sc are more bound by 0.8 MeV and 1.0 MeV, respectively. The behavior of the two neutron separation energy with neutron numbers indicates a strong sub-shell closure at neutron number N=32 in Sc isotopes. Supported by 973 Program of China (2013CB834401), the NSFC (U1232208, U1432125, 11205205, 11035007) and the Helmholtz-CAS Joint Research Group (HCJRG-108)

  10. Isentropic Compression of Argon

    SciTech Connect

    H. Oona; J.C. Solem; L.R. Veeser, C.A. Ekdahl; P.J. Rodriquez; S.M. Younger; W. Lewis; W.D. Turley

    1997-08-01

    We are studying the transition of argon from an insulator to a conductor by compressing the frozen gas isentropically to pressures at which neighboring atomic orbitals overlap sufficiently to allow some electron motion between atoms. Argon and the other rare gases have closed electron shells and therefore remain montomic, even when they solidify. Their simple structure makes it likely that any measured change in conductivity is due to changes in the atomic structure, not in molecular configuration. As the crystal is compressed the band gap closes, allowing increased conductivity. We have begun research to determine the conductivity at high pressures, and it is our intention to determine the compression at which the crystal becomes a metal.

  11. Argon ion pollution of the magnetosphere

    NASA Technical Reports Server (NTRS)

    Lopez, R. E.

    1985-01-01

    Construction of a Solar Power Satellite (SPS) would require the injection of large quantities of propellant to transport material from Low Earth Orbit (LEO) to the construction site at Geostationary Earth Orbit (GEO). This injection, in the form of approx 10 to the 32nd power, 2 KeV argon ions (and associated electrons) per SPS, is comparable to the content of the plasmasphere (approx 10 to the 31st power ions). In addition to the mass deposited, this represents a considerable injection of energy. The injection is examined in terms of a simple model for the expansion of the beam plasma. General features of the subsequent magnetospheric convection of the argon are also examined.

  12. The Argon Geochronology Experiment (AGE)

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.; Bode, R.; Fennema, A.; Chutjian, A.; MacAskill, J. A.; Darrach, M. R.; Clegg, S. M.; Wiens, R. C.; Cremers, D.

    2006-01-01

    This viewgraph presentation reviews the Argon Geochronology Experiment (AGE). Potassium-Argon dating is shown along with cosmic ray dating exposure. The contents include a flow diagram of the Argon Geochronology Experiment, and schematic diagrams of the mass spectrometer vacuum system, sample manipulation mechanism, mineral heater oven, and the quadrupole ion trap mass spectrometer. The Laser-Induced Breakdown Spectroscopy (LIBS) Operation with elemental abundances is also described.

  13. Developing Detectors for Scintillation Light in Liquid Argon for DUNE

    SciTech Connect

    Howard, Bruce

    2016-12-22

    The Deep Underground Neutrino experiment will conduct a broad program of physics research by studying a beam of neutrinos from Fermilab, atmospheric neutrinos, neutrinos from potential supernovae, and potential nucleon decay events. In pursuit of these studies, the experiment will deploy four 10kt fiducial mass liquid argon time projection chambers underground in Lead, South Dakota. Liquid argon time projection chambers allow high-resolution tracking and energy measurements. A precise timing signal is needed to provide the necessary time stamp to localize events in the drift direction. As liquid argon is a natural scintillator, a photon detection system will be deployed to provide such a signal, especially for non-beam events. In the baseline design for the single-phase time projection chamber, the detectors are contained within the anode plane assemblies. The design of two prototypes utilizing wavelength shifters and light guides are presented, and aspects of the research and development program are discussed.

  14. Isentropic compression of argon

    SciTech Connect

    Veeser, L.R.; Ekdahl, C.A.; Oona, H.

    1997-06-01

    The compression was done in an MC-1 flux compression (explosive) generator, in order to study the transition from an insulator to a conductor. Since conductivity signals were observed in all the experiments (except when the probe is removed), both the Teflon and the argon are becoming conductive. The conductivity could not be determined (Teflon insulation properties unknown), but it could be bounded as being {sigma}=1/{rho}{le}8({Omega}cm){sub -1}, because when the Teflon breaks down, the dielectric constant is reduced. The Teflon insulator problem remains, and other ways to better insulate the probe or to measure the conductivity without a probe is being sought.

  15. Study of cluster structures in 10Be and 16C neutron-rich nuclei via break-up reactions

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Acosta, L.; Amorini, F.; Andolina, R.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Minniti, T.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-05-01

    Projectile break-up reactions induced on polyethylene (CH2) target are used in order to study the spectroscopy of 10Be and 16C nuclei. For the present experiment we used 10Be and 16C beams delivered by the FRIBs facility at INFN-LNS, and the CHIMERA 4π multi-detector. 10Be and 16C structures are studied via a relative energy analysis of break-up fragments. The 4He+6He break-up channel allowed us to study the spectroscopy of 10Be; in particular we find evidence of a new state in 10Be at 13.5 MeV excitation energy. The 16C nucleus is studied via 6He-10Be correlation; we find the fingerprint of a possible state at about 20.6 MeV

  16. Nuclear astrophysics and electron beams

    SciTech Connect

    Schwenk, A.

    2013-11-07

    Electron beams provide important probes and constraints for nuclear astrophysics. This is especially exciting at energies within the regime of chiral effective field theory (EFT), which provides a systematic expansion for nuclear forces and electroweak operators based on quantum chromodynamics. This talk discusses some recent highlights and future directions based on chiral EFT, including nuclear structure and reactions for astrophysics, the neutron skin and constraints for the properties of neutron-rich matter in neutron stars and core-collapse supernovae, and the dark matter response of nuclei.

  17. Recent activities for β-decay half-lives and β-delayed neutron emission of very neutron-rich isotopes

    SciTech Connect

    Dillmann, Iris; Abriola, Daniel; Singh, Balraj

    2014-05-02

    Beta-delayed neutron (βn) emitters play an important, two-fold role in the stellar nucleosynthesis of heavy elements in the 'rapid neutron-capture process' (r process). On one hand they lead to a detour of the material β-decaying back to stability. On the other hand, the released neutrons increase the neutron-to-seed ratio, and are re-captured during the freeze-out phase and thus influence the final solar r-abundance curve. A large fraction of the isotopes inside the r-process reaction path are not yet experimentally accessible and are located in the (experimental) 'Terra Incognita'. With the next generation of fragmentation and ISOL facilities presently being built or already in operation, one of the main motivation of all projects is the investigation of these very neutron-rich isotopes. A short overview of one of the planned programs to measure βn-emitters at the limits of the presently know isotopes, the BRIKEN campaign (Beta delayed neutron emission measurements at RIKEN) will be given. Presently, about 600 β-delayed one-neutron emitters are accessible, but only for a third of them experimental data are available. Reaching more neutron-rich isotopes means also that multiple neutron-emission becomes the dominant decay mechanism. About 460 β-delayed two-, three-or four-neutron emitters are identified up to now but for only 30 of them experimental data about the neutron branching ratios are available, most of them in the light mass region below A=30. The International Atomic and Energy Agency (IAEA) has identified the urgency and picked up this topic recently in a 'Coordinated Research Project' on a 'Reference Database for Beta-Delayed Neutron Emission Data'. This project will review, compile, and evaluate the existing data for neutron-branching ratios and half-lives of β-delayed neutron emitters and help to ensure a reliable database for the future discoveries of new isotopes and help to constrain astrophysical and theoretical models.

  18. Argon Welding Inside A Workpiece

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E.

    1988-01-01

    Canopies convert large hollow workpiece into inert-gas welding chamber. Large manifold serves welding chamber for attachment of liner parts in argon atmosphere. Every crevice, opening and passageway provided with argon-rich environment. Weld defects and oxidation dramatically reduced; also welding time reduced.

  19. First direct mass measurements of stored neutron-rich 129,130,131Cd isotopes with FRS-ESR

    NASA Astrophysics Data System (ADS)

    Knöbel, R.; Diwisch, M.; Bosch, F.; Boutin, D.; Chen, L.; Dimopoulou, C.; Dolinskii, A.; Franczak, B.; Franzke, B.; Geissel, H.; Hausmann, M.; Kozhuharov, C.; Kurcewicz, J.; Litvinov, S. A.; Martinez-Pinedo, G.; Matoš, M.; Mazzocco, M.; Münzenberg, G.; Nakajima, S.; Nociforo, C.; Nolden, F.; Ohtsubo, T.; Ozawa, A.; Patyk, Z.; Plaß, W. R.; Scheidenberger, C.; Stadlmann, J.; Steck, M.; Sun, B.; Suzuki, T.; Walker, P. M.; Weick, H.; Wu, M.-R.; Winkler, M.; Yamaguchi, T.

    2016-03-01

    A 410 MeV/u 238U projectile beam was used to create cadmium isotopes via abrasion-fission in a beryllium target placed at the entrance of the in-flight separator FRS at GSI. The fission fragments were separated by the FRS and injected into the isochronous storage ring ESR for mass measurements. Isochronous Mass Spectrometry (IMS) was performed under two different experimental conditions, with and without Bρ-tagging at the high-resolution central focal plane of the FRS. In the experiment with Bρ-tagging the magnetic rigidity of the injected fragments was determined with an accuracy of 2 ṡ10-4. A new method of data analysis, which uses a correlation matrix for the combined data set from both experiments, has provided experimental mass values of 25 rare isotopes for the first time. The high sensitivity and selectivity of the method have given access to nuclides detected with a rate of a few atoms per week. In this letter we present for the 129,130,131Cd isotopes mass values directly measured for the first time. The experimental mass values of cadmium as well as for tellurium and tin isotopes show a pronounced shell effect towards and at N = 82. Shell quenching cannot be deduced from a single new mass value, nor by a better agreement with a theoretical model which explicitly takes into account a quenching feature. This is in agreement with the conclusion from γ-ray spectroscopy and confirms modern shell-model calculations.

  20. Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust

    DOE PAGES

    Meisel, Z.; George, S.; Ahn, S.; ...

    2016-03-22

    Here, we present the mass excesses of 59-64Cr, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of 64Cr is determined for the first time, with an atomic mass excess of -33.48(44) MeV. We find a significantly different two-neutron separation energy S2n trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at N = 38. Additionally, we extend the S2n trend for chromium to N = 40, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-artmore » shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell, including the g9/2 and d5/2 orbits for the neutron valence space. We employ our result for the mass of 64Cr in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the A = 64 isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the >1-MeV reduction in binding for 64Cr with respect to values from commonly used global mass models.« less

  1. {beta}-decay half-lives of new neutron-rich rare-earth isotopes {sup 159}Pm,{sup 162}Sm, and {sup 166}Gd

    SciTech Connect

    Ichikawa, S.; Asai, M.; Tsukada, K.; Nagame, Y.; Haba, H.; Shibata, M.; Sakama, M.; Kojima, Y.

    2005-06-01

    The new neutron-rich rare-earth isotopes {sup 159}Pm, {sup 162}Sm, and {sup 166}Gd produced in the proton-induced fission of {sup 238}U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport system. The half-lives of {sup 159}Pm, {sup 162}Sm, and {sup 166}Gd were determined to be 1.5 {+-} 0.2, 2.4 {+-} 0.5, and 4.8 {+-} 1.0 s respectively. The partial decay scheme of {sup 166}Gd was constructed from {gamma}{gamma}-coincidence data. A more accurate half-life value of 25.6 {+-} 2.2 s was obtained for the previously identified isotope {sup 166}Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by Audi and Wapstra.

  2. Distinction between elastic scattering of weakly bound proton- and neutron-rich nuclei: The case of 8B and 11Be

    NASA Astrophysics Data System (ADS)

    Yang, Y. Y.; Liu, X.; Pang, D. Y.

    2016-09-01

    Experimental data show that the elastic scattering cross sections of the neutron-rich nucleus 11Be are greatly reduced by the coupling effects from the breakup channels, while those of the proton-rich nucleus 8B are not. Such difference is found to persist in results of systematic calculations of 8B elastic scattering from 208Pb at 60 and 170.3 MeV and from 64Zn at 32 and 86 MeV, and 11Be elastic scattering from 208Pb at 55 and 143 MeV and from 64Zn at 29 and 66 MeV with the continuum-discretized coupled channel (CDCC) method. The Coulomb and centrifugal barriers experienced by the valence proton in the ground state of 8B, which do not exist for the valence neutron in the ground state of 11Be, are found to be the reason for such differences in the angular distributions of elastic scattering cross sections of these two weakly bound nuclei.

  3. Filamentation of ultrashort laser pulses of different wavelengths in argon

    NASA Astrophysics Data System (ADS)

    Qi, Xiexing; Lin, Wenbin

    2017-02-01

    We investigate the filaments formed by the ultrashort laser pulses with different wavelengths of 400 nm, 586 nm and 800 nm propagating in argon. Numerical results show that, when the input power or the ratio of the input power to the critical power is given, the pulse with 400 nm wavelength has the largest on-axis intensity, as well as the narrowest filament and the most stable beam radius. These results indicate that the pulse with shorter wavelength is more suitable for the long-range propagation in argon.

  4. Depleted argon from underground sources

    SciTech Connect

    Back, H.O.; Alton, A.; Calaprice, F.; Galbiati, C.; Goretti, A.; Kendziora, C.; Loer, B.; Montanari, D.; Mosteiro, P.; Pordes, S.; /Fermilab

    2011-09-01

    Argon is a powerful scintillator and an excellent medium for detection of ionization. Its high discrimination power against minimum ionization tracks, in favor of selection of nuclear recoils, makes it an attractive medium for direct detection of WIMP dark matter. However, cosmogenic {sup 39}Ar contamination in atmospheric argon limits the size of liquid argon dark matter detectors due to pile-up. The cosmic ray shielding by the earth means that Argon from deep underground is depleted in {sup 39}Ar. In Cortez Colorado a CO{sub 2} well has been discovered to contain approximately 500ppm of argon as a contamination in the CO{sub 2}. In order to produce argon for dark matter detectors we first concentrate the argon locally to 3-5% in an Ar, N{sub 2}, and He mixture, from the CO{sub 2} through chromatographic gas separation. The N{sub 2} and He will be removed by continuous cryogenic distillation in the Cryogenic Distillation Column recently built at Fermilab. In this talk we will discuss the entire extraction and purification process; with emphasis on the recent commissioning and initial performance of the cryogenic distillation column purification.

  5. New statistical boundary conditions for argon-tungsten interactions.

    PubMed

    Ozhgibesov, M S; Leu, T S; Cheng, C H; Utkin, A V

    2012-09-01

    In this study, scattering processes of argon beam impinging on tungsten surface are investigated numerically by applying molecular dynamics (MD) simulations. Energy transfer, momentum change, and scattering processes of argon gas atoms from W(110) surface are discussed. A new model of argon-tungsten (Ar-W) interaction is proposed. Based on the new proposed model, one can simplify the boundary conditions of this problem. The new boundary conditions are proved to be in line with previous experimental and theoretical results. This paper demonstrates how to proceed normalization and further conversion of the MD simulation results into boundary conditions. Application of the new proposed boundary conditions for Ar-W interactions provides a significant speedup of computations.

  6. The Liquid Argon Purity Demonstrator

    SciTech Connect

    Adamowski, M.; Carls, B.; Dvorak, E.; Hahn, A.; Jaskierny, W.; Johnson, C.; Jostlein, H.; Kendziora, C.; Lockwitz, S.; Pahlka, B.; Plunkett, R.; Pordes, S.; Rebel, B.; Schmitt, R.; Stancari, M.; Tope, T.; Voirin, E.; Yang, T.

    2014-07-01

    The Liquid Argon Purity Demonstrator was an R&D test stand designed to determine if electron drift lifetimes adequate for large neutrino detectors could be achieved without first evacuating the cryostat. We describe here the cryogenic system, its operations, and the apparatus used to determine the contaminant levels in the argon and to measure the electron drift lifetime. The liquid purity obtained by this system was facilitated by a gaseous argon purge. Additionally, gaseous impurities from the ullage were prevented from entering the liquid at the gas-liquid interface by condensing the gas and filtering the resulting liquid before returning to the cryostat. The measured electron drift lifetime in this test was greater than 6 ms, sustained over several periods of many weeks. Measurements of the temperature profile in the argon, to assess convective flow and boiling, were also made and are compared to simulation.

  7. Self-consistent quasiparticle formulation of a multiphonon method and its application to the neutron-rich O20 nucleus

    NASA Astrophysics Data System (ADS)

    De Gregorio, G.; Knapp, F.; Lo Iudice, N.; Vesely, P.

    2016-04-01

    A Bogoliubov quasiparticle formulation of an equation-of-motion phonon method, suited for open-shell nuclei, is derived. Like its particle-hole version, it consists of deriving a set of equations of motions whose iterative solution generates an orthonormal basis of n -phonon states (n =0 ,1 ,2 ,... ), built of quasiparticle Tamm-Dancoff phonons, which simplifies the solution of the eigenvalue problem. The method is applied to the open-shell neutron-rich O20 for illustrative purposes. A Hartree-Fock-Bogoliubov canonical basis, derived from an intrinsic two-body optimized chiral Hamiltonian, is used to derive and solve the eigenvalue equations in a space encompassing a truncated two-phonon basis. The spurious admixtures induced by the violation of the particle number and the center-of-mass motion are eliminated to a large extent by a Gram-Schmidt orthogonalization procedure. The calculation takes into account the Pauli principle, is self-consistent, and is parameter free except for the energy cutoff used to truncate the two-phonon basis, which induces an increasing depression of the ground state through its strong coupling to the quasiparticle vacuum. Such a cutoff is fixed so as to reproduce the first 1- level. The two-phonon states are shown to enhance the level density of the low-energy spectrum, consistently with the data, and to induce a fragmentation of the E 1 strength which, while accounting for the very low E 1 transitions, is not sufficient to reproduce the experimental cross section in the intermediate energy region. This and other discrepancies suggest the need of including the three-phonon states. These are also expected to offset the action of the two phonons on the quasiparticle vacuum and, therefore, free the calculation from any parameter.

  8. Half-lives and branchings for {beta}-delayed neutron emission for neutron-rich Co-Cu isotopes in the r-process

    SciTech Connect

    Hosmer, P.; Estrade, A.; Montes, F.; Ouellette, M.; Pellegrini, E.; Schatz, H.; Aprahamian, A.; Arndt, O.; Pfeiffer, B.; Clement, R. R. C.; Mueller, W. F.; Morton, A. C.; Pereira, J.; Santi, P.; Steiner, M.; Stolz, A.; Farouqi, K.; Kratz, K.-L.; Liddick, S. N.; Mantica, P. F.

    2010-08-15

    The {beta} decays of very neutron-rich nuclides in the Co-Zn region were studied experimentally at the National Superconducting Cyclotron Laboratory using the NSCL {beta}-counting station in conjunction with the neutron detector NERO. We measured the branchings for {beta}-delayed neutron emission (P{sub n} values) for {sup 74}Co (18{+-}15%) and {sup 75-77}Ni (10{+-}2.8%, 14{+-}3.6%, and 30{+-}24%, respectively) for the first time, and remeasured the P{sub n} values of {sup 77-79}Cu, {sup 79,81}Zn, and {sup 82}Ga. For {sup 77-79}Cu and for {sup 81}Zn we obtain significantly larger P{sub n} values compared to previous work. While the new half-lives for the Ni isotopes from this experiment had been reported before, we present here in addition the first half-life measurements of {sup 75}Co (30{+-}11 ms) and {sup 80}Cu (170{sub -50}{sup +110} ms). Our results are compared with theoretical predictions, and their impact on various types of models for the astrophysical rapid neutron-capture process (r-process) is explored. We find that with our new data, the classical r-process model is better able to reproduce the A=78-80 abundance pattern inferred from the solar abundances. The new data also influence r-process models based on the neutrino-driven high-entropy winds in core collapse supernovae.

  9. Time-of-flight mass measurements of neutron-rich chromium isotopes up to N = 40 and implications for the accreted neutron star crust

    SciTech Connect

    Meisel, Z.; George, S.; Ahn, S.; Bazin, D.; Brown, B. A.; Browne, J.; Carpino, J. F.; Chung, H.; Cyburt, R. H.; Estrade, A.; Famiano, M.; Gade, A.; Langer, C.; Matos, M.; Mittig, W.; Montes, F.; Morrissey, D. J.; Pereira, J.; Schatz, H.; Schatz, J.; Scott, M.; Shapira, Dan; Sieja, K.; Smith, K.; Stevens, J.; Tan, W.; Tarasov, O.; Towers, S.; Wimmer, K.; Winkelbauer, J. R.; Yurkon, J.; Zegers, R. G. T.

    2016-03-22

    Here, we present the mass excesses of 59-64Cr, obtained from recent time-of-flight nuclear mass measurements at the National Superconducting Cyclotron Laboratory at Michigan State University. The mass of 64Cr is determined for the first time, with an atomic mass excess of -33.48(44) MeV. We find a significantly different two-neutron separation energy S2n trend for neutron-rich isotopes of chromium, removing the previously observed enhancement in binding at N = 38. Additionally, we extend the S2n trend for chromium to N = 40, revealing behavior consistent with the previously identified island of inversion in this region. We compare our results to state-of-the-art shell-model calculations performed with a modified Lenzi-Nowacki-Poves-Sieja interaction in the fp shell, including the g9/2 and d5/2 orbits for the neutron valence space. We employ our result for the mass of 64Cr in accreted neutron star crust network calculations and find a reduction in the strength and depth of electron-capture heating from the A = 64 isobaric chain, resulting in a cooler than expected accreted neutron star crust. This reduced heating is found to be due to the >1-MeV reduction in binding for 64Cr with respect to values from commonly used global mass models.

  10. Performance of a total absorption clover detector for Qβ measurements of neutron-rich nuclei far from the β-stability line

    NASA Astrophysics Data System (ADS)

    Hayashi, H.; Shibata, M.; Asai, M.; Osa, A.; Sato, T. K.; Koizumi, M.; Kimura, A.; Oshima, M.

    2014-05-01

    To measure β-decay energies (Qβs) of neutron-rich nuclei far from the β-stability line, we have improved upon the previously described total absorption detector, composed of a clover Ge detector (80 mmϕ×90 mmL×4 crystals) and 4π BGO Compton suppressors. This detector can directly determine the Qβ from the end-point of the measured spectrum. Nuclei of interest such as new isotopes have Qβ values over 4 MeV; therefore, high detection efficiencies are needed. This total absorption detector has a through-hole (alongside its vertical axis) at the center of the four Ge crystals, and the radioactive sources can be placed in this hole to measure the total absorption spectrum. The β- and γ-rays are absorbed by the detector with almost 4π geometry while escaping radiations from the Ge detector can be detected by the 4π BGO Compton suppressors. We also developed a practical analytic procedure based on the folding method, in which response functions of γ- and β-rays were considered with an assumed decay scheme. The systematic uncertainty of the deduced Qβs was evaluated to be ±30 keV using 18 fission products whose Qβ values were precisely measured. With the detector and an on-line mass separator, we have determined the Qβ values of 166Eu and 165Gd for the first time, and have proposed more precise Qβ values for 160-165Eu and 163Gd than previously found. Owing to the especially good energy resolution of the detector, the isomeric state in 163Gd was also successfully observed for the first time through end-point analysis and analysis of the observed γ-rays. This result contributes to the determination of reliable Qβ values for 163Gd and 163Eu.

  11. Nuclear Structure Studies with Stable and Radioactive Beams: The SPES radioactive ion beam project

    NASA Astrophysics Data System (ADS)

    de Angelis, G.; SPES Collaboration; Prete, G.; Andrighetto, A.; Manzolaro, M.; Corradetti, S.; Scarpa, D.; Rossignoli, M.; Monetti, A.; Lollo, M.; Calderolla, M.; Vasquez, J.; Zafiropoulos, D.; Sarchiapone, L.; Benini, D.; Favaron, P.; Rigato, M.; Pegoraro, R.; Maniero, D.; Calabretta, L.; Comunian, M.; Maggiore, M.; Lombardi, A.; Piazza, L.; Porcellato, A. M.; Roncolato, C.; Bisoffi, G.; Pisent, A.; Galatà, A.; Giacchini, M.; Bassato, G.; Canella, S.; Gramegna, F.; Valiente, J.; Bermudez, J.; Mastinu, P. F.; Esposito, J.; Wyss, J.; Russo, A.; Zanella, S.

    2015-04-01

    A new Radioactive Ion Beam (RIB) facility (SPES) is presently under construction at the Legnaro National Laboratories of INFN. The SPES facility is based on the ISOL method using an UCx Direct Target able to sustain a power of 10 kW. The primary proton beam is provided by a high current Cyclotron accelerator with energy of 35-70 MeV and a beam current of 0.2-0.5 mA. Neutron-rich radioactive ions are produced by proton induced fission on an Uranium target at an expected fission rate of the order of 1013 fissions per second. After ionization and selection the exotic isotopes are re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV for masses in the region A=130 amu. The expected secondary beam rates are of the order of 107 - 109 pps. Aim of the SPES facility is to deliver high intensity radioactive ion beams of neutron rich nuclei for nuclear physics research as well as to be an interdisciplinary research centre for radio-isotopes production for medicine and for neutron beams.

  12. The new neutron rich nuclei

    SciTech Connect

    Gridnev, K. A.; Gridnev, D. K.; Tarasov, V. N.; Tarasov, D. V.; Viñas, X.; Greiner, W.

    2014-07-23

    Using HF+BCS method with Skyrme forces we analyze the neutron drip line. It is shown that around magic and new magic numbers the drip line may form stability peninsulas. It is shown that the location of these peninsulas does not depend on the choice of Skyrme forces. It is found that the size of the peninsulas is sensitive to the choice of Skyrme forces and the most extended peninsulas appear with the SkI2 set.

  13. Initial results from the operation of two argon ion generators in the auroral ionosphere

    NASA Technical Reports Server (NTRS)

    Erlandson, R. E.; Cahill, L. J., Jr.; Pollock, C. J.; Arnoldy, R. L.; Scales, W. A.

    1987-01-01

    Two argon ion generators have been lofted by sounding rockets in order to investigate ion beam dynamics and beam effects on the ionosphere, and auroral electrodynamics during rocket passage over auroral arcs. The ion generators were on a subpayload that was separated from the main payload early in the flight. The main payload conducted the diagnostic measurements during ion beam operations. Evidence of heating of the ionosphere around the subpayload during each ion beam emission is noted.

  14. Shell-model states with seniority ν=3 , 5, and 7 in odd- A neutron-rich Sn isotopes

    SciTech Connect

    Iskra, Ł. W.; Broda, R.; Janssens, R. V. F.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Wrzesiński, J.; Zhu, S.

    2016-01-01

    Excited states with seniority ν=3, 5, and 7 have been investigated in odd neutron-rich Sn119,121,123,125 isotopes produced by fusion-fission of 6.9-MeV/ACa48 beams with Pb208 and U238 targets and by fission of a U238 target bombarded with 6.7-MeV/ANi64 beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known 27/2- isomers were expanded by identifying new deexcitation paths feeding 23/2+ long-lived states and 21/2+ levels. Competing branches in the decay of 23/2- states toward two 19/2- levels were delineated as well. In Sn119, a new 23/2+ isomer was identified, while a similar 23/2+ long-lived state, proposed earlier in Sn121, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of ν=3 excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the 27/2- isomers, an elaborate structure of negative-parity levels was established reaching the (39/2-), ν=7 states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity (35/2+), (31/2+), and (27/2+) states were established, feeding the 23/2+ isomers via cascades of three transitions. In the Sn121,123 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43/2+) states. In Sn123, a short half-life was determined for the (35/2+) state. Shell-model calculations were carried out for all the odd Sn isotopes, from Sn129 down to Sn119, and the results were

  15. Changes in a surface of polycrystalline aluminum upon bombardment with argon ions

    NASA Astrophysics Data System (ADS)

    Ashkhotov, O. G.; Ashkhotova, I. B.; Bliev, A. P.; Magkoev, T. T.; Krymshokalova, D. A.

    2014-10-01

    The interaction between argon ions and a natural oxide layer of polycrystalline aluminum is studied via Auger electron (AE) and electron energy loss (EEL) spectroscopy. It is found that bombardment with argon ions whose energy is lower than the Al2O3 sputtering threshold results in the accumulation of bombarding ions in interstitial surface voids, thus forming a supersaturated solid solution of target atoms and bombarding ions of argon and nitrogen entrapped by the ion beam from the residual gas of the working chamber of the spectrometer.

  16. Liquid-Argon Time Projection Chambers in the U.S

    SciTech Connect

    Soderberg, M.

    2009-10-01

    Liquid Argon Time Projection Chamber (LAr TPC) detectors are ideally suited for studying neutrino interactions and probing the parameters that characterize neutrino oscillations. The ability to drift ionization particles over long distances in purified argon and to trigger on abundant scintillation light allows for excellent particle identification and triggering capability. Recent U.S. based work in the development of LAr TPC technology for massive kiloton size detectors will be discussed in this talk, including details of the ArgoNeuT (Argon Neutrino Test) test-beam project, which is a 175 liter LAr TPC exposed to Fermilab's NuMI neutrino beamline.

  17. Addition of photosensitive dopants to the D0 liquid argon calorimeter

    SciTech Connect

    Amos, N.A.; Anderson, D.F.

    1992-10-01

    The addition of photosensitive dopants to liquid argon greatly enhances the signal from heavily ionizing particles. Since binding energy losses we correlated with the heavily ionizing component in hadronic showers, the addition of photosensitive dopants has been suggested as a mechanism to tune the e/[pi] ratio in liquid argon calorimeters. A measurement was performed at the FNAL test beam, adding 4 ppM tetramethylgermanium to the D[phi] uranium-liquid argon calorimeter. An increase in response for electromagnetic and hadronic showers was observed, with no net change in the e/[pi] ratio.

  18. Addition of photosensitive dopants to the D0 liquid argon calorimeter

    SciTech Connect

    Amos, N.A.; Anderson, D.F.; The D0 Collaboration

    1992-10-01

    The addition of photosensitive dopants to liquid argon greatly enhances the signal from heavily ionizing particles. Since binding energy losses we correlated with the heavily ionizing component in hadronic showers, the addition of photosensitive dopants has been suggested as a mechanism to tune the e/{pi} ratio in liquid argon calorimeters. A measurement was performed at the FNAL test beam, adding 4 ppM tetramethylgermanium to the D{phi} uranium-liquid argon calorimeter. An increase in response for electromagnetic and hadronic showers was observed, with no net change in the e/{pi} ratio.

  19. Effect of CW YAG and argon green lasers on experimentally detached retinas.

    PubMed

    Peyman, G A; Conway, M D; House, B J

    1984-06-01

    We evaluated the effects of argon-green (514.5 nm) and CW neodymium YAG (1060 nm) wavelengths on experimentally detached retinas of primates. Neither laser produced damage to the sensory retina of the fovea. The argon green wavelength, which was absorbed by haemoglobin in the vessel or by extravasated red blood cells, created vasospasm and nerve fiber layer damage. The beam of the CW YAG was not absorbed by haemoglobin; therefore, no vasospasm could be produced on experimentally detached retinas.

  20. Photo-fission for the production of radioactive beams ALTO project

    NASA Astrophysics Data System (ADS)

    Essabaa, S.; Arianer, J.; Ausset, P.; Bajeat, O.; Baronick, J. P.; Clapier, F.; Coacolo, L.; Donzaud, C.; Ducourtieux, M.; Galès, S.; Gardès, D.; Grialou, D.; Hosni, F.; Guillemaud-Mueller, D.; Ibrahim, F.; Junquera, T.; Lau, C.; Le Blanc, F.; Lefort, H.; Le Scornet, J. C.; Lesrel, J.; Mueller, A. C.; Obert, J.; Perru, O.; Potier, J. C.; Proust, J.; Pougheon, F.; Roussière, B.; Rouvière, N.; Sauvage, J.; Sorlin, O.; Tkatchenko, A.; Verney, D.; Waast, B.; Rinolfi, L.; Rossat, G.; Forkel-Wirth, D.; Muller, A.; Bienvenu, G.; Bourdon, J.-C.; Garvey, T.; Jacquemard, B.; Omeich, M.

    2003-05-01

    In order to probe neutron rich radioactive noble gases produced by photo-fission, a PARRNe-1 experiment (Production d'Atomes Radioactifs Riches en Neutrons) has been carried out at CERN. The incident electron beam of 50 MeV was delivered by the LIL machine: LEP Injector Linac. The experiment allowed us to compare under the same conditions two production methods of radioactive noble gases: fission induced by fast neutrons and photo-fission. The obtained results show that the use of the electrons is a promising mode to get intense neutron rich ion beams. After the success of this photo-fission experiment, a conceptual design for the installation at IPN Orsay of a 50 MeV electron accelerator close to the PARRNe-2 device has been worked out: ALTO Project. This work has started within a collaboration between IPNO, LAL (Laboratoire de l'Accélérateur Linéaire) and CERN groups.

  1. Experimental study of neutron-rich nuclei near the N = 82 closed shell using the {sub 40}{sup 96}Zr+{sub 50}{sup 124}Sn reaction with GASP and PRISMA-CLARA arrays

    SciTech Connect

    Rodríguez, W.; Torres, D. A.; Cristancho, F.; Medina, N. H.; Chapman, R.; Smith, J. F.; Mengoni, D.; Truesdale, V.; Grocutt, L.; Mulholland, K.; Kumar, V.; Hadinia, B.; Labiche, M.; Liang, X.; O'Donell, D.; Ollier, J.; Orlandi, R.; Smith, J. F.; Spohr, K. M.; Wady, P.; and others

    2014-11-11

    In this contribution an experimental study of the deep-inelastic reaction {sub 40}{sup 96}Zr+{sub 50}{sup 124}Sn at 530 MeV, using the GASP and PRISMA-CLARA arrays, is presented. The experiments populate a wealth of projectile-like and target-like binary fragments, in a large neutron-rich region around N ≥ 50 and Z ≈ 40. Preliminary results on the study of the yrast and near-yrast states for {sup 95}Nb will be shown, along with a comparison of the experimental yields obtained in the experiments.

  2. Transfer reactions using a low-energy {sup 11}Be beam

    SciTech Connect

    Johansen, Jacob

    2011-10-28

    A series of experiments have been performed to investigate neutron rich beryllium isotopes. Scattering as well as one neutron transfer reactions have been studied using a {sup 11}Be beam on deuteron targets. Bound states of {sup 10,11,12}Be have been studied and reaction cross sections have been calculated. The elastic scattering cross section has shown remarkable structure due to the halo structure of {sup 11}Be.

  3. Attainable superheat of argon-helium, argon-neon solutions.

    PubMed

    Baidakov, Vladimir G; Kaverin, Aleksey M; Andbaeva, Valentina N

    2008-10-16

    The method of lifetime measurement has been used to investigate the kinetics of spontaneous boiling-up of superheated argon-helium and argon-neon solutions. Experiments were made at a pressure of p = 1.5 MPa and concentrations up to 0.33 mol% in the range of nucleation rates from 10 (4) to 10 (8) s (-1) m (-3). The homogeneous nucleation regime has been distinguished. With good agreement between experimental data and homogeneous nucleation theory in temperature and concentration dependences of the nucleation rate, a systematic underestimation by 0.25-0.34 K has been revealed in superheat temperatures over the saturated line attained by experiment as compared with theoretical values calculated in a macroscopic approximation. The revealed disagreement between theory and experiment is connected with the dependence of the properties of new-phase nuclei on their size.

  4. Attachment cooling of electrons in oxygen-argon and SF6-argon mixtures

    NASA Astrophysics Data System (ADS)

    Babaeva, Natalia; Kim, Sung Jin; Park, Gan Young; Lee, Jae Koo

    2004-09-01

    In e-beam sustained plasma different electron temperature can be obtained. Thus, in plasma of capacitive RF discharges in inert gases typical electron temperature is of the order of 2-3 eV. At certain conditions, in plasma of electronegative gases electron temperature can approach ion/neutral temperature. We consider e-beam sustained plasma of electronegative gases and their mixtures with argon where the main mechanism of plasma neutralization is connected with electron-molecule attachment. In such plasma, due to retardation of fast electrons of e-beam secondary electrons are created which loose their energy due to attachment. It is shown, that at certain conditions (in dependence of the e-beam intensity and spectrum of secondary electrons) electron temperature can obtain the values comparable or even less than temperature of neutral component. The effect can be explained by the increase of attachment rate coefficient with the increase of electron temperature (mean electron energy). Such a dependence leads to attachment of the fastest plasma electrons and selective loss of electrons whose energy exceeds the mean electron energy and, as a result, to effective electron cooling. The theoretical and numerical analysis of the problem has been conducted. The numerical results obtained using ELENDIF code are compared with Particle-in-cell/Monte Carlo simulations under similar conditions.

  5. The SPES Radioactive-Ion Beam Facility of INFN

    NASA Astrophysics Data System (ADS)

    de Angelis, G.; Prete, G.; Andrighetto, A.; Manzolaro, M.; Corradetti, S.; Scarpa, D.; Rossignoli, M.; Monetti, A.; Lollo, M.; Calderolla, M.; Vasquez, J.; Zafiropoulos, D.; Sarchiapone, L.; Benini, D.; Favaron, P.; Rigato, M.; Pegoraro, R.; Maniero, D.; Comunian, M.; Maggiore, M.; Lombardi, A.; Piazza, L.; Porcellato, A. M.; Roncolato, C.; Bisoffi, G.; Pisent, A.; Galatà, A.; Giacchini, M.; Bassato, G.; Canella, S.; Gramegna, F.; Valiente, J.; Bermudez, J.; Mastinu, P. F.; Esposito, J.; Wyss, J.; Russo, A.; Zanella, S.; Calabretta, L.

    2015-11-01

    A new radioactive-ion beam (RIB) facility (SPES) is presently under construction at the Legnaro National Laboratories of INFN. The SPES facility is based on the ISOL method using a UCx direct target able to sustain a power of 10 kW. The primary proton beam will be provided by a high-current cyclotron accelerator with energy of 35-70 MeV and a beam current of 0.2-0.5 mA. Neutron-rich radioactive ions will be produced by proton-induced fission on a uranium target at an expected fission rate of the order of 1013 fissions per second. After ionization and selection the exotic isotopes will be re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV for masses in the region A=130 amu. The expected secondary beam rates are of the order of 107-109 pps. The aim of the SPES facility is to deliver high-intensity radioactive-ion beams of neutron-rich nuclei for nuclear physics research, as well as to be an interdisciplinary research center for radioisotope production for medicine and for neutron beams.

  6. The SPES Radioactive Ion Beam facility of INFN

    NASA Astrophysics Data System (ADS)

    de Angelis, G.; Spes Collaboration; Prete, G.; Andrighetto, A.; Manzolaro, M.; Corradetti, S.; Scarpa, D.; Rossignoli, M.; Monetti, A.; Lollo, M.; Calderolla, M.; Vasquez, J.; Zafiropoulos, D.; Sarchiapone, L.; Benini, D.; Favaron, P.; Rigato, M.; Pegoraro, R.; Maniero, D.; Calabretta, L.; Comunian, M.; Maggiore, M.; Lombardi, A.; Piazza, L.; Porcellato, A. M.; Roncolato, C.; Bisoffi, G.; Pisent, A.; Galatà, A.; Giacchini, M.; Bassato, G.; Canella, S.; Gramegna, F.; Valiente, J.; Bermudez, J.; Mastinu, P. F.; Esposito, J.; Wyss, J.; Russo, A.; Zanella, S.

    2015-02-01

    A new Radioactive Ion Beam (RIB) facility (SPES) is presently under construction at the Legnaro National Laboratories of INFN. The SPES facility is based on the ISOL method using an UCx Direct Target able to sustain a power of 10 kW. The primary proton beam is provided by a high current Cyclotron accelerator with energy of 40 MeV and a beam current of 0.2-0.5 mA. Neutron-rich radioactive ions are produced by proton induced fission at an expected fission rate of the order of 1013 fissions per second. After ionization and selection the exotic isotopes are re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV for masses in the region A=130 amu. The expected secondary beam rates are of the order of 107 - 109 pps. Aim of the SPES facility is to deliver high intensity radioactive ion beams of neutron rich nuclei for nuclear physics research as well as to be an interdisciplinary research center for radio-isotopes production for medicine and for neutron beams.

  7. New modeling of scattering behaviors of argon atoms on tungsten substrate.

    PubMed

    Leu, Tzong-Shyng; Cheng, Chin-Hsiang; Ozhgibesov, Mikhail Sergeevich

    2011-11-01

    In this study argon beam-tungsten surface scattering processes were investigated numerically by applying molecular dynamics simulations. Energy transfer, momentum change and the scattering processes of argon gas atoms from the W(110) surface were discussed. The molecular dynamics results showed that Maxwell boundary conditions fail to describe the behaviors of a high mean kinetic energy argon beam impinging on a tungsten surface. A new three-dimensional model of argon-tungsten interaction was thus proposed, and its results proved to be in line with experimental and theoretical results that have been obtained previously by other researchers. Specifically, we developed a method for the normalization of the parameters of a gas beam scattered by a metal surface. We found that the ratio of the average velocity of the scattered beam to the appropriate root mean square deviation (RMSD) allowed us to determine whether the distribution of the scattered atoms was Maxwellian or not. We found that the shape of the functions representing the angular distributions of the scattered Ar atoms could be determined using the ratio of the RMSD of an angle (azimuthal or polar) of the scattered beam to the RMSD of a uniform distribution. The distribution of the azimuthal angle of the scattered atoms was found to be uniform regardless of the incident's kinetic energy, when the incident of the beam on the surface was normal.

  8. Alloy dissolution in argon stirred steel

    NASA Astrophysics Data System (ADS)

    Webber, Darryl Scott

    Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I low carbon ferromanganese, nickel and tin (as a surrogate for low melting alloys) and Class II ferroniobium. The alloys ranged in size and form from granular to 30 mm diameter lumps. Experimental results were evaluated using a theoretically based numerical model for the steel shell period, alloy mixing (Class I) and alloy dissolution (Class II). A CFD model of the experimental ladle was used to understand steel motion in the ladle and to provide steel velocity magnitudes for the numerical steel shell model. Experiments and modeling confirmed that smaller sized alloys have shorter steel shell periods and homogenize faster than larger particles. Increasing the argon flow rate shortened mixing times and reduced the delay between alloy addition and the first appearance of alloy in the melt. In addition, for every five degree increase in steel bath temperature the steel shell period was shortened by approximately four percent. Class II ferroniobium alloy dissolution was an order of magnitude slower than Class I alloy mixing.

  9. RADIATION CHEMISTRY OF HIGH ENERGY CARBON, NEON AND ARGON IONS: INTEGRAL YIELDS FROM FERROUS SULFATE SOLUTIONS

    SciTech Connect

    Christman, E.A.; Appleby, A.; Jayko, M.

    1980-07-01

    Chemical yields of Fe{sup 3+} have been measured from FeSO{sub 4} solutions irradiated in the presence and absence of oxygen with carbon, neon, and argon ions from the Berkeley Bevalac facility. G(Fe{sup 3+}) decreases with increasing beam penetration and with increasing atomic number of the incident ion. The results are compared with current theoretical expectations of the behavior of these particles in an aqueous absorber. The chemical yields are consistently higher than theoretically predicted, by amounts varying from <6.2% (carbon ions) to <13.2% (argon ions). The additional yields are possibly attributable to fragmentation of the primary particle beams.

  10. Radioactive beams from Californium fission at the CARIBU facility

    NASA Astrophysics Data System (ADS)

    Savard, Guy; Pardo, Richard; Baker, Sam; Davids, Cary; Peterson, Don; Phillips, Don; Vondrasek, Rick; Zabransky, Bruce; Zinkann, Gary

    2009-10-01

    The Californium Rare Ion Breeder Upgrade (CARIBU) of the ATLAS superconducting linac facility aims at providing low energy and reaccelerated neutron-rich radioactive beams to address key nuclear physics and astrophysics questions. These beams are obtained from fission fragments of a 1 Ci ^252Cf source, thermalized and collected into a low-energy particle beam by a helium gas catcher, mass analyzed by an isobar separator, and charge breed to higher charge states for acceleration in ATLAS. The method described is fast and universal and short-lived isotope yield scale essentially with Californium fission yields. Expected intensities of reaccelerated beams are up to ˜5x10^5 (10^7 at low energy) far-from-stability ions per second on target. Initial commissioning is being performed with weaker 2.5 and 80 mCi sources. Commissioning results, together with the nuclear physics and astrophysics program that will be pursued with the neutron-rich beams made available, will be presented. Plans for installation of the 1 Ci source will be discussed.

  11. Observation of new neutron-rich micro-second isomers among fission products of ^238U at 345 MeV/u

    NASA Astrophysics Data System (ADS)

    Kameda, Daisuke; Nakao, Taro; Kubo, Toshiyuki; Ohnishi, Tetsuya; Takeda, Hiroyuki; Fukuda, Naoki; Kusaka, Kensuke; Yoshida, Atsushi; Yoshida, Koichi; Ohtake, Masao; Inabe, Naohito; Yanagisawa, Yoshiyuki; Tanaka, Kanenobu; Gono, Yasuyuki

    2009-10-01

    In the production of the radioactive isotope (RI) beam using projectile fragment separators, γ rays emitted from metastable states, isomers, of the reaction products can be used as a fingerprint of the isotope that is analyzed in the separator. In the operation of the superconducting in-flight RI beam separator BigRIPS [1] at RIKEN RI Beam Factory, the detection of such γ rays plays important roles not only in the identification of the RI beam [2] but also in searching for new isomers, providing valuable spectroscopic information on the isotopes. In the recent new-isotope production experiment with BigRIPS using in-flight fission of 345 MeV/nucleon ^238U at the beam intensity around 0.3 pnA, we have observed a number of short-lived isomeric decays which include unknown decays from more than 10 isotopes, using three clover-type Ge detectors with a beam stopper of aluminum. The primal result of the observations will be reported. [1] T. Kubo: Nucl. Instr. and Meth. B 204 (2003) 97. [2] T. Ohnishi et al.: J. Phys. Soc. Japan, 77 (2008) 083201.

  12. Spes: Exotic Beams for Nuclear Physics Studies

    NASA Astrophysics Data System (ADS)

    Andrighetto, Alberto; Manzolaro, Mattia; Corradetti, Stefano; Scarpa, Daniele; Vasquez, Jesu; Rossignoli, Massimo; Monetti, Alberto; Calderolla, Michele; Prete, Gianfranco

    2014-02-01

    The SPES project at Laboratori di Legnaro of INFN (Italy) is concentrating on the production of neutron-rich radioactive nuclei for nuclear physics experiments using uranium fission at a rate of 1013 fission/s. The emphasis on neutron-rich isotopes is justified by the fact that this vast territory has been little explored. The Radioactive Ion Beam (RIB) will be produced by the ISOL technique using proton induced fission on a direct target of UCx. The most critical element of the SPES project is the Multi-Foil Direct Target. Up to the present time, the proposed target represents an innovation in terms of its capability to sustain the primary beam power. This talk will present the status of the project financed by INFN, which is actually in the construction phase at Legnaro. In particular, developments related to the target and the ion-source activities using the surface ion source, plasma ion source, and laser ion source techniques will be reported.

  13. Beam test of a grid-less multi-harmonic buncher.

    SciTech Connect

    Ostroumov, P. N.; Aseev, V. N.; Barcikowski, A.; Clifft, B.; Pardo, R.; Sharamentov, S. I.; Sengupta, M.; Physics

    2008-01-01

    The Argonne Tandem Linear Accelerator System (ATLAS) is the first superconducting heavy-ion linac in the world. Currently ATLAS is being upgraded with the Californium Rare Ion Breeder Upgrade (CARIBU). The latter is a funded project to expand the range of shortlived, neutron-rich rare isotope beams available for nuclear physics research at ATLAS. To avoid beam losses associated with the existing gridded multi-harmonic buncher (MHB), we have developed and built a grid-less four-harmonic buncher with fundamental frequency of 12.125 MHz. In this paper, we report the results of the MHB commissioning and ATLAS beam performance with the new buncher.

  14. Identification of new neutron-rich isotopes produced by in-flight fission of ^238U at 345 MeV/u

    NASA Astrophysics Data System (ADS)

    Ohnishi, Tetsuya; Kubo, Toshiyuki; Takeda, Hiroyuki; Fukuda, Naoki; Kameda, Daisuke; Kusaka, Kensuke; Yoshida, Atsushi; Yoshida, Koichi; Ohtake, Masao; Inabe, Naohito; Yanagisawa, Yoshiyuki; Tanaka, Kanenobu

    2009-10-01

    At RI Beam Factory (RIBF) at RIKEN Nishina Center, an in-flight radioactive isotope beam separator BigRIPS[1] was commissioned in 2007. Then we made a search for new isotopes using in-flight fission of a ^238U beam at 345 MeV/u, and observed two new palladium isotopes ^125Pd and ^126Pd.[2] In November 2008, we revisited this experiment with improved experimental conditions and better tuning of BigRIPS. The intensity of the ^238U beam was 1.6x10^9 particle/sec on average, which was about 40 times higher than in 2007. The search was performed for three Bρ settings that targeted different isotope regions. The achieved resolution of particle identification was good enough to well identify fission fragments even if some of them were not fully stripped. We observed more than 20 new isotopes with Z = 26 to 53, including ^128Pd, which demonstrated the RI-beam production power of BigRIPS at RIBF. The details of the experiment will be reported. [1]T. Kubo, Nucl. Instr. and Meth. B204, 97(2003). [2]T. Ohnishi et al, J. Phys. Soci. Jpn. 77, 083201(2008).

  15. Vibrational spectrum of CO2/-/ in an argon matrix

    NASA Technical Reports Server (NTRS)

    Jacox, M. E.; Milligan, D. E.

    1974-01-01

    Ar:CO:N2O samples of mole ratio 250:1:1 and 500:1:1 were codeposited at 14 K with an atomic beam of sodium or potassium. The infrared spectrum of the resulting deposit was basically identical to that for CO and N2O isolated in an argon matrix in the absence of alkali metal atoms. Spectral absorption features were studied of Ar:CO2 samples of mole ratio ranging from 250 to 500 codeposited with an atomic beam of potassium. Ar:CO2 samples with a mole ratio in the range from 250 to 1000, which had been codeposited with an atomic beam of cesium, were also investigated.

  16. Shockwave Interactions with Argon Glow Discharges

    DTIC Science & Technology

    2006-03-01

    SHOCKWAVE INTERACTIONS WITH ARGON GLOW DISCHARGES THESIS Nicholas S. Siefert, Lieutenant, USAF AFIT/GAP/ENP/06-18 DEPARTMENT OF THE AIR FORCE AIR...the United States Government. AFIT/GAP/ENP/06-18 SHOCKWAVE INTERACTIONS WITH ARGON GLOW DISCHARGES THESIS Presented to the Faculty Department of...APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED AFIT/GAP/ENP/06-18 SHOCKWAVE INTERACTIONS WITH ARGON GLOW DISCHARGES Nicholas S. Siefert, BS

  17. Prospects for photosensitive dopants in liquid argon

    SciTech Connect

    Anderson, D.F.

    1990-12-01

    Evidence is presented that the addition of a few ppM of a photosensitive dopant to a U/liquid argon or Pb/liquid argon calorimeter will make a substantial reduction in the e/{pi} ratio. Previous results indicating high voltage problems and no change in the e/{pi} ratio in tests of photosensitive dopants with the Fermilab D0 experiment's U/liquid argon tests calorimeter are also explained. 13 refs., 3 figs.

  18. Dissipative Dynamics with Exotic Beams

    NASA Astrophysics Data System (ADS)

    di Toro, M.; Colonna, M.; Greco, V.; Ferini, G.; Rizzo, C.; Rizzo, J.; Baran, V.; Wolter, H. H.; Zielinska-Pfabe, M.

    2008-04-01

    Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation and at high nucleon momenta. In this report we present a selection of reaction observables particularly sensitive to the isovector part of the interaction, i.e. to the symmetry term of the nuclear Equation of State (EoS) At low and Fermi energies the behavior of the symmetry energy around saturation influences dissipation and fragment production mechanisms. Predictions are shown for fusion, deep-inelastic and fragmentation collisions induced by neutron rich projectiles. At all energies the isospin transport data are supplying valuable information on value and slope of the symmetry term below saturation. The importance of studying violent collisions with radioactive beams in this energy range is finally stressed.

  19. Enhancement of the EUV emission of a metallic capillary discharge operated with argon ambient gas

    SciTech Connect

    Chan, L. S. Tan, D. Saboohi, S. Yap, S. L. Wong, C. S.

    2014-03-05

    In this work, the metallic capillary discharge is operated with two different ambients: air and argon. In the experiments reported here, the chamber is first evacuated to 10{sup −5} mbar. The discharge is initiated by the transient hollow cathode effect generated electron beam, with either air ambient or argon ambient at 10{sup −4} mbar. The bombardment of electron beam at the tip of the stainless steel anode gives rise to a metallic vapor, which is injected into the capillary and initiates the main discharge through the capillary. The EUV emission is measured for different discharge voltages for both conditions and compared. It is found that the metallic capillary discharge with argon ambientis able to produce higher EUV energy compared to that with air ambient.

  20. Liquid Argon Calorimetry for ATLAS

    NASA Astrophysics Data System (ADS)

    Robinson, Alan

    2008-05-01

    This summer, the largest collaborative physics project since the Manhattan project will go online. One of four experiments for the Large Hadron Collider at CERN in Geneva, ATLAS, employs over 2000 people. Canadians have helped design, construct, and calibrate the liquid argon calorimeters for ATLAS to capture the products of the high energy collisions produced by the LHC. From an undergraduate's perspective, explore how these calorimeters are made to handle their harsh requirement. From nearly a billion proton-proton collisions a second, physicists hope to discover the Higgs boson and other new fundamental particles.

  1. Opportunities using gamma-ray arrays with radioactive beams

    NASA Astrophysics Data System (ADS)

    Catford, Wilton N.

    1998-08-01

    The design of a gamma-ray array suitable for use with radioactive beams must take into account criteria additional to those which have previously defined large arrays, which were developed for fusion-evaporation high-spin experiments with stable beams. The radioactive decay of beam particles imposes a new set of constraints, and the relatively low intensity demands an exceptionally high efficiency. Beyond this the kinematics of, for example, nucleon transfer reactions performed in inverse kinematics can require coincident gamma-ray detection in order to achieve good energy resolution and hence Doppler broadening imposes extra constraints. A wide variety of physics is made available with radioactive beams, including fusion-evaporation studies along the N = Z line, Coulomb excitation on both sides of stability, transfer reactions on light nuclei on both sides of stability, deep inelastic studies of heavier neutron-rich nuclei and scattering experiments with isomeric beams.

  2. MicroBooNE, A Liquid Argon Time Projection Chamber (LArTPC) Neutrino Experiment

    SciTech Connect

    Katori, Teppei

    2011-07-01

    Liquid Argon time projection chamber (LArTPC) is a promising detector technology for future neutrino experiments. MicroBooNE is a upcoming LArTPC neutrino experiment which will be located on-axis of Booster Neutrino Beam (BNB) at Fermilab, USA. The R&D efforts on this detection method and related neutrino interaction measurements are discussed.

  3. Nuclear structure studies with gamma-ray beams

    SciTech Connect

    Tonchev, Anton; Bhatia, Chitra; Kelley, John; Raut, Rajarshi; Rusev, Gencho; Tornow, Werner; Tsoneva, Nadia

    2015-05-28

    In stable and weakly bound neutron-rich nuclei, a resonance-like concentration of dipole states has been observed for excitation energies below the neutron-separation energy. This clustering of strong dipole states has been named the Pygmy Dipole Resonance (PDR) in contrast to the Giant Dipole Resonance (GDR) that dominates the E1 response. Understanding the PDR is presently of great interest in nuclear structure and nuclear astrophysics. High-sensitivity studies of E1 and M1 transitions in closed-shell nuclei using monoenergetic and 100% linearly-polarized photon beams are presented.

  4. ATLAS liquid argon calorimeter front end electronics

    NASA Astrophysics Data System (ADS)

    Buchanan, N. J.; Chen, L.; Gingrich, D. M.; Liu, S.; Chen, H.; Damazio, D.; Densing, F.; Duffin, S.; Farrell, J.; Kandasamy, S.; Kierstead, J.; Lanni, F.; Lissauer, D.; Ma, H.; Makowiecki, D.; Muller, T.; Radeka, V.; Rescia, S.; Ruggiero, R.; Takai, H.; Wolniewicz, K.; Ghazlane, H.; Hoummada, A.; Hervas, L.; Hott, T.; Wilkens, H. G.; Ban, J.; Boettcher, S.; Brooijmans, G.; Chi, C.-Y.; Caughron, S.; Cooke, M.; Copic, K.; Dannheim, D.; Gara, A.; Haas, A.; Katsanos, I.; Parsons, J. A.; Simion, S.; Sippach, W.; Zhang, L.; Zhou, N.; Eckstein, P.; Kobel, M.; Ladygin, E.; Auge, E.; Bernier, R.; Bouchel, M.; Bozzone, A.; Breton, D.; de la Taille, C.; Falleau, I.; Fournier, D.; Imbert, P.; Martin-Chassard, G.; Perus, A.; Richer, J. P.; Seguin Moreau, N.; Serin, L.; Tocut, V.; Veillet, J.-J.; Zerwas, D.; Colas, J.; Dumont-Dayot, N.; Massol, N.; Perrodo, P.; Perrot, G.; Wingerter-Seez, I.; Escalier, M.; Hubaut, F.; Laforge, B.; LeDortz, O.; Schwemling, Ph; Collot, J.; Dzahini, D.; Gallin-Martel, M.-L.; Martin, P.; Cwienk, W. D.; Fent, J.; Kurchaninov, L.; Citterio, M.; Mazzanti, M.; Tartarelli, F.; Bansal, V.; Boulahouache, C.; Cleland, W.; Liu, B.; McDonald, J.; Paolone, V.; Rabel, J.; Savinov, V.; Zuk, G.; Benslama, K.; Borgeaud, P.; de la Broïse, X.; Delagnes, E.; LeCoguie, A.; Mansoulié, B.; Pascual, J.; Teiger, J.; Dinkespiler, B.; Liu, T.; Stroynowski, R.; Ye, J.; Zarzhitsky, P.; Grahn, K.-J.; Hansson, P.; Lund-Jensen, B.; Chu, M. L.; Lee, S.-C.; Su, D. S.; Teng, P. K.; Braun, H. M.

    2008-09-01

    The ATLAS detector has been designed for operation at CERN's Large Hadron Collider. ATLAS includes a complex system of liquid argon calorimeters. This paper describes the architecture and implementation of the system of custom front end electronics developed for the readout of the ATLAS liquid argon calorimeters.

  5. Argon purge gas cooled by chill box

    NASA Technical Reports Server (NTRS)

    Spiro, L. W.

    1966-01-01

    Cooling argon purge gas by routing it through a shop-fabricated chill box reduces charring of tungsten inert gas torch head components. The argon gas is in a cooled state as it enters the torch and prevents buildup of char caused by the high concentrations of heat in the weld area during welding operations.

  6. New photosensitive dopants for liquid argon

    NASA Astrophysics Data System (ADS)

    Anderson, D. F.

    1986-05-01

    Thirteen photosensitive dopants for liquid argon are presented, and the criteria for selecting prospective new dopants are discussed. A substantial improvement in energy resolution for 5.5 MeV alpha particles is measured in liquid argon when a photosensitive dopant is added.

  7. Neutron-proton effective mass splitting in neutron-rich matter at normal density from analyzing nucleon-nucleus scattering data within an isospin dependent optical model

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Hua; Guo, Wen-Jun; Li, Bao-An; Chen, Lie-Wen; Fattoyev, Farrukh J.; Newton, William G.

    2015-04-01

    The neutron-proton effective mass splitting in asymmetric nucleonic matter of isospin asymmetry δ and normal density is found to be mn-p* ≡ (mn* - mp*) / m = (0.41 ± 0.15) δ from analyzing globally 1088 sets of reaction and angular differential cross sections of proton elastic scattering on 130 targets with beam energies from 0.783 MeV to 200 MeV, and 1161 sets of data of neutron elastic scattering on 104 targets with beam energies from 0.05 MeV to 200 MeV within an isospin dependent non-relativistic optical potential model. It sets a useful reference for testing model predictions on the momentum dependence of the nucleon isovector potential necessary for understanding novel structures and reactions of rare isotopes.

  8. Study of Collectivity in n-rich A=80 Nuclei using Radioactive Ion Beams

    NASA Astrophysics Data System (ADS)

    Padilla, E.; Galindo-Uribarri, A.; Baktash, C.; Fuentes, B.; Gross, C.; Mueller, P.; Radford, D. C.; Stracener, D.; Yu, C.-H.; Bijker, R.; Castanos, O.; Batchelder, J.; Hartley, D. J.

    2002-04-01

    We report on recent experiments performed at the HRIBF of Oak Ridge National Laboratory (ORNL) aimed to study neutron-rich nuclei in the A 80 mass region. First time use of Radioactive Ion Beams (RIBs) (78,80)Ge complemented with stable beam information allowed a systematic study of B(E2)-values that characterize the n-rich even-even Ge and Se isotopes. A comparison of the experimental results with IBA2 calculations will be presented. *Supported by US-DOE under the contract DE-AC05-00AOR22725.

  9. The SPES radioactive ion beam project of LNL: status and perspectives

    NASA Astrophysics Data System (ADS)

    de Angelis, Giacomo; Prete, G.; Andrigetto, A.; Manzolaro, M.; Corradetti, S.; Scarpa, D.; Rossignoli, M.; Monetti, A.; Lollo, M.; Calderolla, M.; Vasquez, J.; Zafiropoulos, D.; Sarchiapone, L.; Benini, D.; Favaron, P.; Rigato, M.; Pegoraro, R.; Maniero, D.; Calabretta, L.; Comunian, M.; Maggiore, M.; Lombardi, A.; Porcellato, A. M.; Roncolato, C.; Bisoffi, G.; Pisent, A.; Galatà, A.; Giacchini, M.; Bassato, G.; Canella, S.; Gramegna, F.; Valiente, J.; Bermudez, J.; Mastinu, P. F.; Esposito, J.; Wyss, J.; Russo, A.; Zanella, S.

    2016-01-01

    A new Radioactive Ion Beam (RIB) facility (SPES) is presently under construction at the Legnaro National Laboratories of INFN. The SPES facility is based on the ISOL method using an UCx Direct Target able to sustain a power of 8 kW. The primary proton beam is provided by a high current Cyclotron accelerator with energy of 35-70 MeV and a beam current of 0.2-0.7 mA. Neutron-rich radioactive ions are produced by proton induced fission on an Uranium target at an expected fission rate of the order of 1013 fissions per second. After ionization and selection the exotic isotopes are re-accelerated by the ALPI superconducting LINAC at energies of 10A MeV for masses in the region A=130 amu. The expected secondary beam rates are of the order of 107 - 109 pps. Aim of the SPES facility is to deliver high intensity radioactive ion beams of neutron rich nuclei for nuclear physics research as well as to be an interdisciplinary research centre for radio-isotopes production for medicine and for neutron beams.

  10. Luminosity limits for liquid argon calorimetry

    NASA Astrophysics Data System (ADS)

    J, Rutherfoord; B, Walker R.

    2012-12-01

    We have irradiated liquid argon ionization chambers with betas using high-activity Strontium-90 sources. The radiation environment is comparable to that in the liquid argon calorimeters which are part of the ATLAS detector installed at CERN's Large Hadron Collider. We measure the ionization current over a wide range of applied potential for two different source activities and for three different chamber gaps. These studies provide operating experience at exceptionally high ionization rates. We can operate these chambers either in the normal mode or in the space-charge limited regime and thereby determine the transition point between the two. From the transition point we indirectly extract the positive argon ion mobility.

  11. 21 CFR 868.1075 - Argon gas analyzer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Argon gas analyzer. 868.1075 Section 868.1075 Food... DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1075 Argon gas analyzer. (a) Identification. An argon gas analyzer is a device intended to measure the concentration of argon in a gas mixture to aid...

  12. 21 CFR 868.1075 - Argon gas analyzer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Argon gas analyzer. 868.1075 Section 868.1075 Food... DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1075 Argon gas analyzer. (a) Identification. An argon gas analyzer is a device intended to measure the concentration of argon in a gas mixture to aid...

  13. 21 CFR 868.1075 - Argon gas analyzer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Argon gas analyzer. 868.1075 Section 868.1075 Food... DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1075 Argon gas analyzer. (a) Identification. An argon gas analyzer is a device intended to measure the concentration of argon in a gas mixture to aid...

  14. 21 CFR 868.1075 - Argon gas analyzer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Argon gas analyzer. 868.1075 Section 868.1075 Food... DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1075 Argon gas analyzer. (a) Identification. An argon gas analyzer is a device intended to measure the concentration of argon in a gas mixture to aid...

  15. 21 CFR 868.1075 - Argon gas analyzer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Argon gas analyzer. 868.1075 Section 868.1075 Food... DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1075 Argon gas analyzer. (a) Identification. An argon gas analyzer is a device intended to measure the concentration of argon in a gas mixture to aid...

  16. Argon Diffusion in Pyroxene and Albite

    NASA Astrophysics Data System (ADS)

    Weirich, J. R.; Isachsen, C. E.; Johnson, J. R.; Swindle, T. D.

    2010-03-01

    Shock greatly raises the diffusivity of albite, and also explains why meteorites often have low activation energies. Unshocked pyroxene cannot explain the high temperature release of argon in meteorites, though shocked pyroxene is a possibility.

  17. Clinical periodontics with the argon laser

    NASA Astrophysics Data System (ADS)

    Finkbeiner, R. L.

    1995-04-01

    The argon laser has proven to be a valuable tool for the thermodynamic debridement of the periodontal lesion, incisions and tissue fusion. Illustrations of clinical applications and discussion of laser parameters will be provided.

  18. Investigating nuclear shell structure in the vicinity of 78Ni: Low-lying excited states in the neutron-rich isotopes Zn,8280

    NASA Astrophysics Data System (ADS)

    Shiga, Y.; Yoneda, K.; Steppenbeck, D.; Aoi, N.; Doornenbal, P.; Lee, J.; Liu, H.; Matsushita, M.; Takeuchi, S.; Wang, H.; Baba, H.; Bednarczyk, P.; Dombradi, Zs.; Fulop, Zs.; Go, S.; Hashimoto, T.; Honma, M.; Ideguchi, E.; Ieki, K.; Kobayashi, K.; Kondo, Y.; Minakata, R.; Motobayashi, T.; Nishimura, D.; Otsuka, T.; Otsu, H.; Sakurai, H.; Shimizu, N.; Sohler, D.; Sun, Y.; Tamii, A.; Tanaka, R.; Tian, Z.; Tsunoda, Y.; Vajta, Zs.; Yamamoto, T.; Yang, X.; Yang, Z.; Ye, Y.; Yokoyama, R.; Zenihiro, J.

    2016-02-01

    The low-lying level structures of nuclei in the vicinity of 78Ni were investigated using in-beam γ -ray spectroscopy to clarify the nature of the nuclear magic numbers Z =28 and N =50 in systems close to the neutron drip line. Nucleon knockout reactions were employed to populate excited states in 80Zn and 82Zn. A candidate for the 41+ level in 80Zn was identified at 1979(30) keV, and the lifetime of this state was estimated to be 136-67+92 ps from a line-shape analysis. Moreover, the energy of the 21+ state in 82Zn is reported to lie at 621(11) keV. The large drop in the 21+ energy at 82Zn indicates the presence of a significant peak in the E (21+) systematics at N =50 . Furthermore, the E (41+) /E (21+) and B (E 2 ;41+→21+) /B (E 2 ;21+→0g.s . +) ratios in 80Zn were deduced to be 1.32 (3 ) and 1 .12-60+80 , respectively. These results imply that 80Zn can be described in terms of two-proton configurations with a 78Ni core and are consistent with a robust N =50 magic number along the Zn isotopic chain. These observations, therefore, indicate a persistent N =50 shell closure in nuclei far from the line of β stability, which in turn suggests a doubly magic structure for 78Ni.

  19. Long-lived K isomer and enhanced γ vibration in the neutron-rich nucleus 172Dy: Collectivity beyond double midshell

    NASA Astrophysics Data System (ADS)

    Watanabe, H.; Zhang, G. X.; Yoshida, K.; Walker, P. M.; Liu, J. J.; Wu, J.; Regan, P. H.; Söderström, P.-A.; Kanaoka, H.; Korkulu, Z.; Lee, P. S.; Nishimura, S.; Yagi, A.; Ahn, D. S.; Alharbi, T.; Baba, H.; Browne, F.; Bruce, A. M.; Carroll, R. J.; Chae, K. Y.; Dombradi, Zs.; Doornenbal, P.; Estrade, A.; Fukuda, N.; Griffin, C.; Ideguchi, E.; Inabe, N.; Isobe, T.; Kanaya, S.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kubono, S.; Kurz, N.; Kuti, I.; Lalkovski, S.; Lane, G. J.; Lee, C. S.; Lee, E. J.; Lorusso, G.; Lotay, G.; Moon, C.-B.; Nishizuka, I.; Nita, C. R.; Odahara, A.; Patel, Z.; Phong, V. H.; Podolyák, Zs.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Shand, C. M.; Shimizu, Y.; Sumikama, T.; Suzuki, H.; Takeda, H.; Terashima, S.; Vajta, Zs.; Valiente-Dóbon, J. J.; Xu, Z. Y.

    2016-09-01

    The level structure of 172Dy has been investigated for the first time by means of decay spectroscopy following in-flight fission of a 238U beam. A long-lived isomeric state with T1/2 = 0.71 (5) s and Kπ =8- has been identified at 1278 keV, which decays to the ground-state and γ-vibrational bands through hindered electromagnetic transitions, as well as to the daughter nucleus 172Ho via allowed β decays. The robust nature of the Kπ =8- isomer and the ground-state rotational band reveals an axially-symmetric structure for this nucleus. Meanwhile, the γ-vibrational levels have been identified at unusually low excitation energy compared to the neighboring well-deformed nuclei, indicating the significance of the microscopic effect on the non-axial collectivity in this doubly mid-shell region. The underlying mechanism of enhanced γ vibration is discussed in comparison with the deformed Quasiparticle Random-Phase Approximation based on a Skyrme energy-density functional.

  20. In-beam γ -ray spectroscopy of S-4238

    NASA Astrophysics Data System (ADS)

    Lunderberg, E.; Gade, A.; Bader, V.; Baugher, T.; Bazin, D.; Berryman, J. S.; Brown, B. A.; Hartley, D. J.; Recchia, F.; Stroberg, S. R.; Weisshaar, D.; Wimmer, K.

    2016-12-01

    The low-energy excitation level schemes of the neutron-rich S-4238 isotopes are investigated via in-beam γ -ray spectroscopy following the fragmentation of 48Ca and 46Ar projectiles on a 12C target at intermediate beam energies. Information on γ γ coincidences complemented by comparisons to shell-model calculations were used to construct level schemes for these neutron-rich nuclei. The experimental data are discussed in the context of large-scale shell-model calculations with the SDPF-MU effective interaction in the s d -p f shell. For the even-mass S isotopes, the evolution of the yrast sequence is explored as well as a peculiar change in decay pattern of the second 2+ states at N =26 . For the odd-mass 41S, a level scheme is presented that seems complete below 2.2 MeV and consistent with the predictions by the SDPF-MU shell-model Hamiltonian; this is a remarkable benchmark given the rapid shell and shape evolution at play in the S isotopes as the broken-down N =28 magic number is approached. Furthermore, the population of excited final states in projectile fragmentation is discussed.

  1. First observation of a rotational band and the role of the proton intruder orbital π1/2+[431] in very neutron-rich odd-odd Nb106

    NASA Astrophysics Data System (ADS)

    Luo, Y. X.; Rasmussen, J. O.; Hamilton, J. H.; Ramayya, A. V.; Wang, E.; Liu, Y. X.; Jiao, C. F.; Liang, W. Y.; Xu, F. R.; Sun, Y.; Frauendorf, S.; Hwang, J. K.; Liu, S. H.; Zhu, S. J.; Brewer, N. T.; Lee, I. Y.; Ter-Akopian, G. M.; Oganessian, Yu.; Donangelo, R.; Ma, W. C.

    2014-04-01

    A rotational band was observed for the first time in Nb106 by means of γ-γ-γ and γ-γ-γ-γ measurements of prompt fission γ rays from Cf252 by using the Gammasphere multidetector array. Projected shell model and potential-energy surface calculations were performed and were compared to the experimental data of Nb106 and the previously reported Nb104. Configurations and spin-parity were assigned to the ground level, low-lying levels, and rotational bandheads of the two Nb isotopes. The new rotational band in Nb106 was interpreted as a Kπ=2- band with a configuration π1/2+[431] × ν5/2-[532]. The same spin-parity and configuration were assigned to the analogous band in Nb104. π1/2+[431] × ν5/2+[413], Kπ=3+ were assigned to the 0.66-μs isomer and explained the M2 isomeric decay to the ground in Nb106. The proton intruder orbital π1/2+[431] plays an important role in shape evolution with regard to triaxial deformation in these neutron-rich Nb isotopes.

  2. On the use of the (π-,K0) reaction on nuclear targets for the precise determination of the lifetime of the hydrogen hyperisotopes and other neutron-rich Λ-hypernuclei

    NASA Astrophysics Data System (ADS)

    Agnello, M.; Botta, E.; Bressani, T.; Bufalino, S.; Feliciello, A.

    2016-10-01

    Recent results reported by experiments with relativistic (heavy) ions have raised again the question whether the lifetime of H3Λ is very close to the lifetime of the free Λ hyperon. An updated careful analysis of all the existing experimental data shows that it is not, contrary to theoretical calculations. A similar conclusion can be drawn for the neighbor H4Λ. A clear cut high precision measurement performed with the straightforward method of time delay spectra is however lacking and it is eagerly needed. The idea of using the (π- ,K0) charge-exchange associated production reaction on targets of liquid 3,4He is discussed. A possible realization exploiting a large part of existing facilities at J-PARC is presented. A measurement with a 5% precision seems within reach with a modest effort and in a reasonable amount of time. The same set-up would also serve very well for the measurement of the lifetime of several neutron-rich Λ-hypernuclei of the p-shell, in particular of B12Λ. More importantly, the Weak Decay partial widths Γπ-, Γp and Γπ0 could be simultaneously determined in order to confirm their predicted strong variation with mass number, A, due to nuclear structure effects.

  3. Signature inversion in odd-odd {sup 114}Rh: First identification of high-spin states in very neutron-rich {sup 114}Rh and application of the triaxial projected shell model

    SciTech Connect

    Liu, S. H.; Chen, Y. S.; Gao, Z. C.; Zhu, S. J.; Gu, L.; Yeoh, E. Y.; Luo, Y. X.; Rasmussen, J. O.; Ma, W. C.; Batchelder, J. C.; Ter-Akopian, G. M.; Oganessian, Yu. Ts.; Gelberg, A.

    2011-06-15

    High-spin excited states in the very neutron-rich nucleus {sup 114}Rh have been studied by examining the prompt {gamma} rays emitted in the spontaneous fission of {sup 252}Cf with the Gammasphere detector array. A high-spin level scheme of {sup 114}Rh has been established for the first time with 13 new levels. The level scheme is proposed to be built on a 7{sup -} state. The existence of a relatively large signature splitting and an yrare band show features which may indicate triaxial deformation. The phenomenon of signature inversion has been observed in {sup 114}Rh at I=12 ({h_bar}/2{pi}). The observed signature inversion of {sup 114}Rh is interpreted successfully in terms of the triaxial projected shell model. Theoretical calculations suggest that the negative-parity, yrast band of {sup 114}Rh has the two-quasi-particle configuration of {pi}g{sub 9/2} x {nu}h{sub 11/2}, consistent with the systematics of odd-odd Rh isotopes. The signature inversion at spin 12 ({h_bar}/2{pi}) may be attributed to the change of rotational mode, from quasi-particle aligned rotation at low spins to collective rotation at high spins.

  4. Argon Collection And Purification For Proliferation Detection

    SciTech Connect

    Achey, R.; Hunter, D.

    2015-10-09

    In order to determine whether a seismic event was a declared/undeclared underground nuclear weapon test, environmental samples must be taken and analyzed for signatures that are unique to a nuclear explosion. These signatures are either particles or gases. Particle samples are routinely taken and analyzed under the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) verification regime as well as by individual countries. Gas samples are analyzed for signature gases, especially radioactive xenon. Underground nuclear tests also produce radioactive argon, but that signature is not well monitored. A radioactive argon signature, along with other signatures, can more conclusively determine whether an event was a nuclear test. This project has developed capabilities for collecting and purifying argon samples for ultra-low-background proportional counting. SRNL has developed a continuous gas enrichment system that produces an output stream containing 97% argon from whole air using adsorbent separation technology (the flow diagram for the system is shown in the figure). The vacuum swing adsorption (VSA) enrichment system is easily scalable to produce ten liters or more of 97% argon within twelve hours. A gas chromatographic separation using a column of modified hydrogen mordenite molecular sieve has been developed that can further purify the sample to better than 99% purity after separation from the helium carrier gas. The combination of these concentration and purification systems has the capability of being used for a field-deployable system for collecting argon samples suitable for ultra-low-background proportional counting for detecting nuclear detonations under the On-Site Inspection program of the CTBTO verification regime. The technology also has applications for the bulk argon separation from air for industrial purposes such as the semi-conductor industry.

  5. New Measurement of ^39Ar in Underground Argon with a Low Background Liquid Argon Detector

    NASA Astrophysics Data System (ADS)

    Xu, Jingke

    2012-03-01

    A low background liquid argon detector has been developed for sensitive measurements of the beta radioactive ^39Ar in argon from underground sources. The measurement is motivated by the need to improve on earlier studies that showed no sign of ^39Ar in certain sources of underground argon, but with a limited sensitivity of ˜ 5% relative to ^39Ar in atmospheric argon[1]. We will report preliminary measurements taken with the low background detector that was commissioned and operated at the Kimballton Underground Research Facility (KURF) in Virginia. A combination of passive and active background reduction techniques resulted in a very low background and a null result with sensitivity to ^39Ar less than 1% of atmospheric. The results confirm that underground argon is well suited for direct detection of dark matter WIMPs. [4pt] [1] D. Acosta-Kane et al., Nucl. Instr. Meth. A 587:46 (2008)

  6. Argon ion beam induced surface pattern formation on Si

    SciTech Connect

    Hofsäss, H.; Bobes, O.; Zhang, K.

    2016-01-21

    The development of self-organized surface patterns on Si due to noble gas ion irradiation has been studied extensively in the past. In particular, Ar ions are commonly used and the pattern formation was analyzed as function of ion incidence angle, ion fluence, and ion energies between 250 eV and 140 keV. Very few results exist for the energy regime between 1.5 keV and 10 keV and it appears that pattern formation is completely absent for these ion energies. In this work, we present experimental data on pattern formation for Ar ion irradiation between 1 keV and 10 keV and ion incidence angles between 50° and 75°. We confirm the absence of patterns at least for ion fluences up to 10{sup 18} ions/cm{sup 2}. Using the crater function formalism and Monte Carlo simulations, we calculate curvature coefficients of linear continuum models of pattern formation, taking into account contribution due to ion erosion and recoil redistribution. The calculations consider the recently introduced curvature dependence of the erosion crater function as well as the dynamic behavior of the thickness of the ion irradiated layer. Only when taking into account these additional contributions to the linear theory, our simulations clearly show that that pattern formation is strongly suppressed between about 1.5 keV and 10 keV, most pronounced at 3 keV. Furthermore, our simulations are now able to predict whether or not parallel oriented ripple patterns are formed, and in case of ripple formation the corresponding critical angles for the whole experimentally studied energies range between 250 eV and 140 keV.

  7. Argon isotopic zoning in mantle phlogopite

    SciTech Connect

    Phillips, D.; Onstott, T.C.

    1988-06-01

    Incremental-heating and laser-probe /sup 40/Ar//sup 39/Ar analyses were performed on phlogopite extracted from a garnet-lherzolite mantle nodule entrained by the Precambrian (1200 Ma) Premier kimberlite, South Africa. The spatial resolution of the laser probe has enabled the characterization of argon isotopic zoning in a single phlogopite grain. An apparent age contour map records lower ages (1.2 Ga) along grain margins and high apparent ages (up to 2.4 Ga) at the core. The latter ages are caused by excess argon contamination and subsequent partial diffusive loss, and have no age significance. Comparison with step-heating results indicates that argon spatial distributions inferred from in-vacuo step-heating experiments are, at best, grossly approximate. Variations in the laser-probe apparent ages were observed only laterally across the phlogopite cleavage surface, indicating that argon transport occurs preferentially along phlogopite cleavage planes. Age profiles, when modeled using one-dimensional radial geometry (cylindrical coordinates), do not conform to classical Fick's law diffusion, suggesting that the characteristic dimension of diffusion for argon in phlogopite may be highly variable within individual grains.

  8. Nuclear physics with advanced brilliant gamma beams at ELI-NP

    NASA Astrophysics Data System (ADS)

    Ur, Călin A.; Filipescu, Dan; Gheorghe, Ioana; Iancu, Violeta; Suliman, Gabriel; Teşileanu, Ovidiu

    2016-01-01

    The Extreme Light Infrastructure - Nuclear Physics facility is dedicated to nuclear physics studies with the use of extreme electromagnetic radiation. One of the main research system to be installed and operated in the facility is an outstanding high brilliance gamma beam system. The Gamma Beam System of ELI-NP will produce intense, quasi-monochromatic gamma beams via inverse Compton scattering of short laser pulses on relativistic electron beam pulses. The gamma beams available at ELI-NP will allow for the performance of photo-nuclear reactions aiming to reveal the intimate structure of the atomic nucleus. Nuclear Resonance Fluorescence, photo-fission, photo-disintegration reactions above the particle threshold will be used to study the dipole response of nuclei, the structure of the Pygmy resonances, nuclear processes relevant for astrophysics, production and study of exotic neutron-rich nuclei.

  9. A High Rigidity Spectrometer for the Facility for Rare Isotope Beams.

    NASA Astrophysics Data System (ADS)

    Zegers, Remco

    2017-01-01

    The High Rigidity Spectrometer (HRS) will be the centerpiece experimental tool of the Facility for Rare-Isotope Beams (FRIB) fast-beam program. The fast-beam program has tremendous discovery potential, enabling experiments with beam intensities of a few ions per second or less through the luminosity afforded by thick targets. The high magnetic rigidity of the HRS (up to 8 Tm) will match the rigidities at which rare-isotope production yields at the FRIB fragment separator are maximum across the entire chart of nuclei and enable experiments with the most neutron-rich nuclei available at FRIB. Gain factors in luminosity of ten or more are achievable compared to running with existing spectrometers, which have a maximum rigidity of 4 Tm, with the highest gains for the most neutron-rich unstable isotopes. To enable a broad spectrum of experiments, the HRS will accommodate different ion-optical modes and provide the flexibility to run in coincidence with a diverse set of other detector systems, such as the Gamma Ray Energy Tracking Array (GRETA) and the Modular Neutron Array (MoNA-LISA). In the presentation, an overview of the scientific opportunities with the HRS and the present layout, based on ion-optical and magnet-feasibility studies, will be given. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office for Nuclear Physics, under Award Number DE-SC0014554.

  10. Extracting Spectroscopic Factors of Argon Isotopes from Transfer Reactions

    NASA Astrophysics Data System (ADS)

    Manfredi, Juan; Lee, J.; Tsang, M. B.; Lynch, W. G.; Barney, J.; Estee, J.; Sweany, S.; Brown, K. W.; Cerizza, G.; Anderson, C.; Setiawan, H.; Loelius, C.; Xu, Z.; Rogers, A. M.; Pruitt, C.; Sobotka, L. G.; Elson, J. M.; Langer, C.; Chajecki, Z.; Chen, G.; Jones, K. L.; Smith, K.; Xiao, Z.; Li, Z.; Winkelbauer, J. R.

    2017-01-01

    A spectroscopic factor (SF) quantifies the single particle occupancy of a given state in a nucleus. For the argon isotopes, there is a discrepancy of the SF between studies that use transfer reactions and knockout reactions. Understanding the SFs of these isotopes, and in particular how the SF changes across the isotopic chain, is important for understanding how single particle structure changes with neutron number. The transfer reactions 34Ar(p,d) and 46Ar(p,d) were measured at the National Superconducting Cyclotron Laboratory (NSCL) using the same beam energy (70 MeV/u) as from the previous knockout measurement. Spectroscopic factors were extracted from measured angular distributions via ADWA calculations. Preliminary findings will be presented. The National Superconducting Cyclotron Laboratory is supported by the NSF (PHY 1102511), and Juan Manfredi is supported by the DOE NNSA Stewardship Science Graduate Fellowship.

  11. Trapping cold ground state argon atoms.

    PubMed

    Edmunds, P D; Barker, P F

    2014-10-31

    We trap cold, ground state argon atoms in a deep optical dipole trap produced by a buildup cavity. The atoms, which are a general source for the sympathetic cooling of molecules, are loaded in the trap by quenching them from a cloud of laser-cooled metastable argon atoms. Although the ground state atoms cannot be directly probed, we detect them by observing the collisional loss of cotrapped metastable argon atoms and determine an elastic cross section. Using a type of parametric loss spectroscopy we also determine the polarizability of the metastable 4s[3/2](2) state to be (7.3±1.1)×10(-39)  C m(2)/V. Finally, Penning and associative losses of metastable atoms in the absence of light assisted collisions, are determined to be (3.3±0.8)×10(-10)  cm(3) s(-1).

  12. A simple velocity-tunable pulsed atomic source of slow metastable argon

    NASA Astrophysics Data System (ADS)

    Taillandier-Loize, T.; Aljunid, S. A.; Correia, F.; Fabre, N.; Perales, F.; Tualle, J. M.; Baudon, J.; Ducloy, M.; Dutier, G.

    2016-04-01

    A pulsed beam of metastable argon atoms having a low tunable velocity (10 to 150 m s-1) is produced with a very substantial brightness (9  ×  108Ar* s-1 sr-1). The present original experimental configuration leads to a variable velocity dispersion that can be smaller than the standard Brownian one. This behaviour, analysed using Monte Carlo simulations, exhibits momentum stretching (heating) or narrowing (cooling) entirely due to a subtle combination of Doppler and Zeeman effects.

  13. LArIAT: Worlds First Pion-Argon Cross-Section

    SciTech Connect

    Hamilton, Pip

    2016-11-02

    The LArIAT experiment has performed the world's first measurement of the total charged-current pion cross-section on an argon target, using the repurposed ArgoNeuT detector in the Fermilab test beam. Presented here are the results of that measurement, along with an overview of the LArIAT experiment and details of the LArIAT collaboration's plans for future measurements.

  14. Solid-liquid phase transition in argon

    NASA Technical Reports Server (NTRS)

    Tsang, T.; Tang, H. T.

    1978-01-01

    Starting from the Lennard-Jones interatomic potential, a modified cell theory has been used to describe the solid-liquid phase transition in argon. The cell-size variations may be evaluated by a self-consistent condition. With the inclusion of cell-size variations, the transition temperature, the solid and liquid densities, and the liquid-phase radial-distribution functions have been calculated. These ab initio results are in satisfactory agreement with molecular-dynamics calculations as well as experimental data on argon.

  15. Argon isotopes as recorders of magmatic processes

    NASA Astrophysics Data System (ADS)

    Layer, P. W.; Gardner, J. E.; Mora Chaparro, J. C.; Arce, J. L.

    2003-12-01

    Argon isotopic ratios vary enough between different reservoirs (atmosphere, crust, mantle) and diffuse fast enough through most minerals at magmatic temperatures (700-1200 C) to make them ideal for looking at magma chamber dynamics. Indeed, diffusion is sufficiently fast to allow short time scales to be deciphered, setting argon apart from many other isotopic methods. A mineral's ability to retain "excess" argon (40Ar/36Ar ratios greater than the atmospheric value and apparent ages older than the known eruption age) during post-eruption cooling is key to Ar studies. Previous work shows that both phenocrysts (crystallizing in the magma chamber; e.g. Mt St. Helens; Layer and Gardner, 2001) and xenocrysts (introduced into the magma chamber; e.g Toba; Gardner et al., 2002) preserve excess argon, which enables magma chamber processes to be deciphered through the variable diffusion rates between crystal phases. Single crystal 40Ar/39Ar step-heating of biotite from the 10.5 ka eruption of Nevado de Toluca volcano, Mexico indicates that they are xenocrystic and resided for only a short (< 1 year) time in the magma before it erupted. The biotite has reaction rims of hornblende, orthopyroxene and plagioclase, and failed to grow experimentally at pressure-temperature conditions of the magma, confirming the xenocrystic nature of this phase. Single-step fusion of plagioclase phenocrysts from eruptions of El Chichon volcano, Mexico, shows evidence of excess (mantle) argon, whereas hornblende from the same eruptions contains little or none. In this case, faster diffusion of Ar in plagioclase than in hornblende allow plagioclase to incorporate excess argon during magma recharge; hornblende does not. Combining such results with other isotopic systems may in fact better determine magma chamber processes. At El Chichon, Sr isotopes suggest magma recharges ocurred (Tepley et al., 2000), whereas the argon isotopes suggest such pulses occurred just before each eruption. The fast and

  16. Thermal evolution of Venus with argon degassing

    NASA Astrophysics Data System (ADS)

    O'Rourke, Joseph G.; Korenaga, Jun

    2015-11-01

    Decades-old measurements of atmospheric and elemental surface composition constrain the history of Venus. In this study, we search for a model featuring continuous evolution in the stagnant-lid regime that predicts the present-day atmospheric mass of radiogenic argon and satisfies the other available constraints. For comparison, we also consider the end-member scenario of a single catastrophic resurfacing event. Thermal evolution simulations are performed that track the mass transport of argon and potassium and include a simple model of upwelling mantle plumes. Sensitivity analyses and linear regression are used to quantify the range of initial conditions that will produce desired values for key model output parameters. Decompression melting of passively upwelling mantle causes considerable mantle processing and crustal growth during the early evolution of Venus. Mantle plumes have negligible effects on recent crustal production, but may be important to local surface features. For a wide range of initial conditions, continuous evolution in the stagnant-lid regime predicts the correct amount of argon degassing, along with the absence of a global magnetic field, crustal and lithosphere thicknesses matching modern estimates, and volcanism consistent with the cratering record. Argon degassing does not uniquely constrain mantle dynamics, but the success of simple stagnant-lid models diminishes the need to invoke dramatic changes like catastrophic resurfacing.

  17. Argon frost continuous cryopump for fusion applications

    SciTech Connect

    Foster, C.A.; McCurdy, H.C.

    1993-12-01

    A cryopumping system based on the snail continuous cryopump concept is being developed for fusion applications under a DOE SBIR grant. The primary pump is a liquid helium cooled compound pump designed to continuously pump and fractionate deuterium/tritium and helium. The D/T pumping stage is a 500 mm bore cryocondensation pump with a nominal pumping speed of 45,000 L/s. It will be continuously regenerated by a snail regeneration by head every 12 minutes. Continuous regeneration will dramatically reduce the vulnerable tritium inventory in a fusion reactor. Operating at an inlet pressure of 1 millitorr, eight of these pumps could pump the projected D/T flow in the ITER CDA design while reducing the inventory of tritium in the pumping system from 630 to 43 grams. The helium fraction will be pumped in a compound argon frost stage. This stage will also operate continuously with a snail regeneration head. In addition the argon spray head will be enclosed inside the snail, thereby removing gaseous argon from the process chamber. Since the cryocondensation stage will intercept over 90% of the D/T/H steam, a purified stream from this stage could be directly reinjected into the plasma as gas or pellets, thereby bypassing the isotope separation system and further simplifying the fuel cycle. Experiments were undertaken in Phase I which demonstrated continuous cryosorption pumping of hydrogen on CO{sub 2} and argon frosts. The pumping system and its relevance to fusion reactor pumping will be discussed.

  18. Diamond film growth argon-carbon plasmas

    DOEpatents

    Gruen, Dieter M.; Krauss, Alan R.; Liu, Shengzhong; Pan, Xianzheng; Zuiker, Christopher D.

    1998-01-01

    A method and system for manufacturing diamond film. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrogen and hydrocarbon and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous and deposition of a diamond film on a substrate.

  19. Hydrodynamic Simulations of Gaseous Argon Shock Experiments

    NASA Astrophysics Data System (ADS)

    Garcia, Daniel; Dattelbaum, Dana; Goodwin, Peter; Morris, John; Sheffield, Stephen; Burkett, Michael

    2015-06-01

    The lack of published Argon gas shock data motivated an evaluation of the Argon Equation of State (EOS) in gas phase initial density regimes never before reached. In particular, these regimes include initial pressures in the range of 200-500 psi (0.025 - 0.056 g/cc) and initial shock velocities around 0.2 cm/ μs. The objective of the numerical evaluation was to develop a physical understanding of the EOS behavior of shocked and subsequently multiply re-shocked Argon gas initially pressurized to 200-500 psi through Pagosa numerical hydrodynamic simulations utilizing the SESAME equation of state. Pagosa is a Los Alamos National Laboratory 2-D and 3-D Eulerian hydrocode capable of modeling high velocity compressible flow with multiple materials. The approach involved the use of gas gun experiments to evaluate the shock and multiple re-shock behavior of pressurized Argon gas to validate Pagosa simulations and the SESAME EOS. Additionally, the diagnostic capability within the experiments allowed for the EOS to be fully constrained with measured shock velocity, particle velocity and temperature. The simulations demonstrate excellent agreement with the experiments in the shock velocity/particle velocity space, but note unanticipated differences in the ionization front temperatures.

  20. Antiapoptotic activity of argon and xenon.

    PubMed

    Spaggiari, Sabrina; Kepp, Oliver; Rello-Varona, Santiago; Chaba, Kariman; Adjemian, Sandy; Pype, Jan; Galluzzi, Lorenzo; Lemaire, Marc; Kroemer, Guido

    2013-08-15

    Although chemically non-reactive, inert noble gases may influence multiple physiological and pathological processes via hitherto uncharacterized physical effects. Here we report a cell-based detection system for assessing the effects of pre-defined gas mixtures on the induction of apoptotic cell death. In this setting, the conventional atmosphere for cell culture was substituted with gas combinations, including the same amount of oxygen (20%) and carbon dioxide (5%) but 75% helium, neon, argon, krypton, or xenon instead of nitrogen. The replacement of nitrogen with noble gases per se had no effects on the viability of cultured human osteosarcoma cells in vitro. Conversely, argon and xenon (but not helium, neon, and krypton) significantly limited cell loss induced by the broad-spectrum tyrosine kinase inhibitor staurosporine, the DNA-damaging agent mitoxantrone and several mitochondrial toxins. Such cytoprotective effects were coupled to the maintenance of mitochondrial integrity, as demonstrated by means of a mitochondrial transmembrane potential-sensitive dye and by assessing the release of cytochrome c into the cytosol. In line with this notion, argon and xenon inhibited the apoptotic activation of caspase-3, as determined by immunofluorescence microscopy coupled to automated image analysis. The antiapoptotic activity of argon and xenon may explain their clinically relevant cytoprotective effects.

  1. 46 CFR 151.50-36 - Argon or nitrogen.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false Argon or nitrogen. 151.50-36 Section 151.50-36 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-36 Argon or nitrogen. (a) A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa...

  2. 46 CFR 151.50-36 - Argon or nitrogen.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false Argon or nitrogen. 151.50-36 Section 151.50-36 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-36 Argon or nitrogen. (a) A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa...

  3. 46 CFR 151.50-36 - Argon or nitrogen.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false Argon or nitrogen. 151.50-36 Section 151.50-36 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-36 Argon or nitrogen. (a) A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa...

  4. 46 CFR 151.50-36 - Argon or nitrogen.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Argon or nitrogen. 151.50-36 Section 151.50-36 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-36 Argon or nitrogen. (a) A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa...

  5. 46 CFR 151.50-36 - Argon or nitrogen.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false Argon or nitrogen. 151.50-36 Section 151.50-36 Shipping... BULK LIQUID HAZARDOUS MATERIAL CARGOES Special Requirements § 151.50-36 Argon or nitrogen. (a) A cargo tank that contains argon or nitrogen and that has a maximum allowable working pressure of 172 kPa...

  6. Etching of Bacillus atrophaeus by oxygen atoms, molecules and argon ions

    NASA Astrophysics Data System (ADS)

    Benedikt, J.; Flötgen, C.; Kussel, G.; Raball, V.; von Keudell, A.

    2008-10-01

    The etching of spores of Bacillus atrophaeus by oxygen atoms, molecules and argon ions is investigated in a particle beam experiment. Thereby, the conditions occurring in an argon oxygen plasma are mimicked and fundamental inactivation mechanisms are revealed. It is shown that only the combined impact of argon ions and of O atoms or O2 molecules causes significant etching of the spores. This is explained by the process of chemical sputtering, where an ion induced defect at the surface of the spore reacts with either the incident bi-radical O2 or with an incident O atom. This leads to the formation of CO, CO2 and H2O and thus to erosion. This process is compared to the plasma etching of hydrocarbon thin films as an atomistic model system for the spore coat. It is shown that the etch rate in an inductively coupled argon oxygen plasma is only maximal if both, the electron density and thus the ion flux towards the surface and the O atom flux are optimized simultaneously.

  7. Measurements of fusion reactions of low-intensity radioactive carbon beams on 12C and their implications for the understanding of X-ray bursts.

    PubMed

    Carnelli, P F F; Almaraz-Calderon, S; Rehm, K E; Albers, M; Alcorta, M; Bertone, P F; Digiovine, B; Esbensen, H; Niello, J O Fernández; Henderson, D; Jiang, C L; Lai, J; Marley, S T; Nusair, O; Palchan-Hazan, T; Pardo, R C; Paul, M; Ugalde, C

    2014-05-16

    The interaction between neutron-rich nuclei plays an important role for understanding the reaction mechanism of the fusion process as well as for the energy production through pycnonuclear reactions in the crust of neutron stars. We have performed the first measurements of the total fusion cross sections in the systems (10,14,15)C+(12)C using a new active target-detector system. In the energy region accessible with existing radioactive beams, a good agreement between the experimental and theoretical cross sections is observed. This gives confidence in our ability to calculate fusion cross sections for systems which are outside the range of today's radioactive beam facilities.

  8. Measurements of Fusion Reactions of Low-Intensity Radioactive Carbon Beams on C12 and their Implications for the Understanding of X-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Carnelli, P. F. F.; Almaraz-Calderon, S.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Digiovine, B.; Esbensen, H.; Niello, J. O. Fernández; Henderson, D.; Jiang, C. L.; Lai, J.; Marley, S. T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.; Ugalde, C.

    2014-05-01

    The interaction between neutron-rich nuclei plays an important role for understanding the reaction mechanism of the fusion process as well as for the energy production through pycnonuclear reactions in the crust of neutron stars. We have performed the first measurements of the total fusion cross sections in the systems C10,14,15+C12 using a new active target-detector system. In the energy region accessible with existing radioactive beams, a good agreement between the experimental and theoretical cross sections is observed. This gives confidence in our ability to calculate fusion cross sections for systems which are outside the range of today's radioactive beam facilities.

  9. Preferential site occupancy observed in coexpanded argon-krypton clusters

    SciTech Connect

    Lundwall, M.; Bergersen, H.; Lindblad, A.; Oehrwall, G.; Svensson, S.; Bjoerneholm, O.; Tchaplyguine, M.

    2006-10-15

    Free heterogeneous argon-krypton clusters have been produced by coexpansion and investigated by means of x-ray photoelectron spectroscopy. By examining cluster surface and bulk binding energy shifts, relative intensities, and peak widths, we show that in the mixed argon-krypton clusters the krypton atoms favor the bulk and argon atoms are pushed to the surface. Furthermore, we show that krypton atoms in the surface layer occupy high-coordination sites and that heterogeneous argon-krypton clusters produced by coexpansion show the same surface structure as argon host clusters doped with krypton. These observations are supported by site-dependent calculations of chemical shifts.

  10. Liquid argon scintillation light studies in LArIAT

    SciTech Connect

    Kryczynski, Pawel

    2016-10-12

    The LArIAT experiment is using its Liquid Argon Time Projection Chamber (LArTPC) in the second run of data-taking at the Fermilab Test Beam Facility. The goal of the experiment is to study the response of LArTPCs to charged particles of energies relevant for planned neutrino experiments. In addition, it will help to develop and evaluate the performance of the simulation, analysis, and reconstruction software used in other LAr neutrino experiments. Particles from a tertiary beam detected by LArIAT (mainly protons, pions and muons) are identified using a set of beamline detectors, including Wire Chambers, Time of Flight counters and Cherenkov counters, as well as a simplified sampling detector used to detect muons. In its effort towards augmenting LArTPC technology for other neutrino experiments, LArIAT also takes advantage of the scintillating capabilities of LAr and is testing the possibility of using the light signal to help reconstruct calorimetric information and particle ID. In this report, we present results from these studies of the scintillation light signal to evaluate detector performance and calorimetry.

  11. Abnormal epidermal changes after argon laser treatment

    SciTech Connect

    Neumann, R.A.; Knobler, R.M.; Aberer, E.; Klein, W.; Kocsis, F.; Ott, E. )

    1991-02-01

    A 26-year-old woman with a congenital port-wine stain on the forehead was treated three times at 2-month intervals with an argon laser. Six months after the last treatment, moderate blanching and mild scaling confined to the treated area was observed. A biopsy specimen of the treated area revealed a significant decrease in ectatic vessels. However, epidermal changes similar to those of actinic keratosis with disorganized cell layers and marked cytologic abnormalities were seen. Analysis of peripheral blood lymphocytes for a defect in DNA repair was negative. Multiple, argon laser-induced photothermal effects may be responsible for the changes observed in our case and may lead to premalignant epidermal transformation.

  12. Multishock Compression Properties of Warm Dense Argon

    PubMed Central

    Zheng, Jun; Chen, Qifeng; Yunjun, Gu; Li, Zhiguo; Shen, Zhijun

    2015-01-01

    Warm dense argon was generated by a shock reverberation technique. The diagnostics of warm dense argon were performed by a multichannel optical pyrometer and a velocity interferometer system. The equations of state in the pressure-density range of 20–150 GPa and 1.9–5.3 g/cm3 from the first- to fourth-shock compression were presented. The single-shock temperatures in the range of 17.2–23.4 kK were obtained from the spectral radiance. Experimental results indicates that multiple shock-compression ratio (ηi = ρi/ρ0) is greatly enhanced from 3.3 to 8.8, where ρ0 is the initial density of argon and ρi (i = 1, 2, 3, 4) is the compressed density from first to fourth shock, respectively. For the relative compression ratio (ηi’ = ρi/ρi-1), an interesting finding is that a turning point occurs at the second shocked states under the conditions of different experiments, and ηi’ increases with pressure in lower density regime and reversely decreases with pressure in higher density regime. The evolution of the compression ratio is controlled by the excitation of internal degrees of freedom, which increase the compression, and by the interaction effects between particles that reduce it. A temperature-density plot shows that current multishock compression states of argon have distributed into warm dense regime. PMID:26515505

  13. Diamond film growth argon-carbon plasmas

    DOEpatents

    Gruen, D.M.; Krauss, A.R.; Liu, S.Z.; Pan, X.Z.; Zuiker, C.D.

    1998-12-15

    A method and system are disclosed for manufacturing diamond film. The method involves forming a carbonaceous vapor, providing a gas stream of argon, hydrogen and hydrocarbon and combining the gas with the carbonaceous vapor, passing the combined carbonaceous vapor and gas carrier stream into a chamber, forming a plasma in the chamber causing fragmentation of the carbonaceous and deposition of a diamond film on a substrate. 29 figs.

  14. An impact hypothesis for Venus argon anomalies

    NASA Astrophysics Data System (ADS)

    Kaula, W. M.; Newman, W. I.

    1997-03-01

    The Ar-36+38 argon-excess anomally of Venus has been hypothesized to have its origin in the impact of an outer solar system body of about 100-km diameter. A critical evaluation is made of this hypothesis and its competitors; it is judged that its status must for the time being remain one of 'Sherlock Holmes' type, in that something so improbable must be accepted when all alternatives are eliminated.

  15. Current and future liquid argon neutrino experiments

    SciTech Connect

    Karagiorgi, Georgia S.

    2015-05-15

    The liquid argon time projection chamber (LArTPC) detector technology provides an opportunity for precision neutrino oscillation measurements, neutrino cross section measurements, and searches for rare processes, such as SuperNova neutrino detection. These proceedings review current and future LArTPC neutrino experiments. Particular focus is paid to the ICARUS, MicroBooNE, LAr1, 2-LArTPC at CERN-SPS, LBNE, and 100 kton at Okinoshima experiments.

  16. Distribution and Abundance of Mars' Atmospheric Argon

    NASA Technical Reports Server (NTRS)

    Sprague, A. L.; Boynton, W. V.; Kerry, K. E.; Nelli, Steven; Murphy, Jim; Reedy, R. C.; Metzger, A. E.; Hunten, D. M.; Janes, K. D.; Crombie, M. K.

    2005-01-01

    One and one half Mars years (MY 26 and 27) of atmospheric Argon measurements are described and studied in the context of understanding how Argon, a minor constituent of Mars atmosphere that does not condense at Mars temperatures, can be used to study martian circulation and dynamics. Argon data are from the 2001 Mars Odyssey Gamma Subsystem (GS) of the suite of three instruments comprising the Gamma Ray Spectrometer (GRS). A comprehensive data analysis including gamma-ray production and attenuation by the atmosphere is included. Of particular interest is the enhanced abundance of Ar over the observed Ar abundance at lower latitudes at south (up to a factor of 10) and north (up to a factor of 4) polar regions during winter. Calibration of the measurements to actual Ar abundance is possible because GS measurements cover the same latitude and season as measurements made by the gas chromatograph mass spectrometer (GCMS) on Viking Landers 1 and 2 (VL1 and VL2). [2].

  17. Photon detection in the Cryogenic Apparatus for Precision Tests of Argon Interactions with Neutrinos (CAPTAIN)

    NASA Astrophysics Data System (ADS)

    Rielage, K.

    2013-09-01

    The Cryogenic Apparatus for Precision Tests of Argon Interactions with Neutrinos (CAPTAIN) is being built at Los Alamos National Laboratory. A hexagonal time projection chamber (TPC) with a 1 m drift length will be constructed inside a cryostat containing 7,700L of liquid argon. CAPTAIN will be used to test interactions using beams of neutrons and neutrinos. It will serve as a test bed for various options for the Long Baseline Neutrino Experiment (LBNE) including in the photon detection system. The current photon detection system will be described and future options discussed. The system is composed of sixteen R8520-500 Hamamatsu photomultiplier tubes with a wavelength shifting coating on acrylic in front of the PMT. Various wavelength shifting coatings can be examined with the current default of tetraphenyl butadiene.

  18. First measurements of inclusive muon neutrino charged current differential cross sections on argon.

    PubMed

    Anderson, C; Antonello, M; Baller, B; Bolton, T; Bromberg, C; Cavanna, F; Church, E; Edmunds, D; Ereditato, A; Farooq, S; Fleming, B; Greenlee, H; Guenette, R; Haug, S; Horton-Smith, G; James, C; Klein, E; Lang, K; Laurens, P; Linden, S; McKee, D; Mehdiyev, R; Page, B; Palamara, O; Partyka, K; Patch, A; Rameika, G; Rebel, B; Rossi, B; Soderberg, M; Spitz, J; Szelc, A M; Weber, M; Yang, T; Zeller, G

    2012-04-20

    The ArgoNeuT Collaboration presents the first measurements of inclusive muon neutrino charged current differential cross sections on argon. Obtained in the NuMI neutrino beam line at Fermilab, the flux-integrated results are reported in terms of outgoing muon angle and momentum. The data are consistent with the Monte Carlo expectation across the full range of kinematics sampled, 0°<θ(μ)<36° and 0argon time projection chamber technology for neutrino detection, the measurements allow tests of low-energy neutrino scattering models important for interpreting results from long baseline neutrino oscillation experiments designed to investigate CP violation and the orientation of the neutrino mass hierarchy.

  19. Spectroscopy of heliumlike argon resonance and satellite lines for plasma temperature diagnostics

    NASA Astrophysics Data System (ADS)

    Biedermann, C.; Radtke, R.; Fournier, K. B.

    2002-12-01

    The n=2-1 spectral emission pattern of heliumlike argon, together with the associated satellite emission originating from lithiumlike argon have been measured with high-resolution x-ray spectroscopy at the Berlin electron-beam ion trap. The observed line intensity across a wide range of excitation energies was weighted by an electron-energy distribution to analyze as a function of plasma temperature the line ratios between KLL dielectronic recombination satellites, in particular the j+z, j, and k satellites, and the w-resonance line. A good agreement between various theoretical models is found, supporting the method of line-ratio measurement as a temperature diagnostic for plasmas. A value for the so-called R-line ratio is determined and calculations with the HULLAC suite of codes predict it to be electron density independent over a wide range.

  20. Molecular complexes of organometallic molecules with noble gases: the rotational spectrum of dimethylsilane-argon.

    PubMed

    Ottaviani, Paolo; Melandri, Sonia; Caminati, Walther; Banser, Deike; Schnell, Melanie; Grabow, Jens-Uwe

    2004-11-12

    The rotational spectrum of the molecular complex dimethylsilane-argon was investigated by free-jet absorption millimeter-wave and molecular-beam Fourier transform spectroscopy. The absolute energy minimum corresponds to a conformation in which the argon atom lies in the plane of symmetry of dimethylsilane, perpendicular to the C-Si-C plane. The distance of Ar atom is tilted 14 degrees away from the Si atom. The zero-point dissociation energy was estimated from the centrifugal distortion constant D(J) to be 2.2 kJ mol(-1). Small splitting, due to tunneling of the Ar atom and internal rotation of the two methyl groups, was observed, measured, and used to determine the potential energy surface for these motions.

  1. Measuring the Fusion Cross-Section of Light Nuclei with Low-Intensity Beams

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy; Brown, Kyle; Hudan, Sylvie; Desouza, Romualdo

    2014-03-01

    Reactions between neutron-rich light nuclei have been proposed as a heat source in the crust of an accreting neutron star that triggers an X-ray superburst. To explore the probability of such fusion events as well as better understand the fusion dynamics between neutron-rich nuclei, an experimental program to measure the dependence of the fusion cross-section on neutron number has been initiated. Key to these measurements is developing an approach to measure the total fusion cross-section for beams of low-intensity light nuclei (<105 ions/s) on light targets. Fusion residues resulting from the fusion of oxygen nuclei with 12C at energies near and below the Coulomb barrier are directly measured and distinguished from unreacted beam particles on the basis of their energy and time-of-flight (TOF). The TOF is measured between a microchannel plate (MCP) detector and a segmented Si detector. Two initial problems were charge trapping in the Si detector and slit scattering in the MCP detector. These problems have both been minimized by implementing a gridless MCP detector and a new Si design making the measurement feasible. Supported by the US DOE under Grant No. DEFG02-88ER-40404

  2. Comparison Of Expected Yields For Light Radioactive Beams At SPIRAL-1 And 2

    SciTech Connect

    Saint-Laurent, M.-G.; Pichard, A.; Lhersonneau, G.; Oliveira Santos, F. de; Pellemoine, F.; Delahaye, P.; Fadil, M.; Fraanberg, H.; Leroy, R.; Serani, L.; Alfaurt, P.; Demonchy, C.-E.; Fournier, A.

    2010-04-30

    Light-particles stable high-intensity beams (p, d, {sup 3,4}He...) will be available from the Linac driver accelerator of SPIRAL-2. Yields of neutron-deficient isotopes as well as of neutron-rich isotopes (by means of reactions with secondary neutrons) are compared with those presently available at the SPIRAL-1 facility. We explore, for light beams (Z<16) asked in the 'white book' of SPIRAL-2, the production methods taking into account the in-target yield but also the feasibility of making such beams by the ISOL method (considering reaction, target, thermal and release properties). We discuss some of the tests needed and planned. A comparison with the present and potentially attainable yields at SPIRAL-1 is presented.

  3. Perspectives in Nuclear Structure with Radioactive Beams at the Italian National Laboratories

    NASA Astrophysics Data System (ADS)

    Bracco, A.

    2003-04-01

    The nuclear physics community is presently discussing the future experimental program to be carried out at the two National Laboratories LNL and LNS which are both presently heavily involved in the construction of two radioactive beam facilities of ISOL type. While the EXCYTE facility at LNS uses the fusion evaporation reactions and is mainly devoted to medium light nuclei, the SPES facility, at LNL is based on 238U fission products and it is designed to provide much larger beam intensities. The SPES facility will provide medium heavy neutron rich beams including the double magic 132Sn nucleus. The research goals for the EXCYTE and SPES fecilities are the studies of the many-body aspects of the structure of nuclei far from stability. A number of selected examples is here presented and discussed. The focus is the understanding of the evolution of the nuclear properties towards the neutron drip line, evolution which has consequences on the single-particle and collective excitations.

  4. Intense Microsecond Electron Beam Interactions with Low-Pressure Gases

    DTIC Science & Technology

    1991-02-28

    Gilgenbach, J. E. Tucker, and C. L. Enloe, Laser and Particle Beams, 6 687 (1988). 4) "Undulation of a Magnetized Electron Beam by a Periodic Ion...Excitation by Relativistic Electrons: I. Collisions Cross Sections and Deposition Efficiencies", Laser and Particle Beams 8 493 (1990) 11) D.B...McGarrah and M.L. Brake, Argon Ion Excitation by Relativistic Electrons: II. Chemical Kinetics", Laser and Particle Beams 8 507 (1990) 9 T-PS/18/3//35709

  5. Study of argon-oxygen flowing afterglow

    NASA Astrophysics Data System (ADS)

    Mazánková, V.; Trunec, D.; Navrátil, Z.; Raud, J.; Krčma, F.

    2016-06-01

    The reaction kinetics in argon-oxygen flowing afterglow (post-discharge) was studied using NO titration and optical emission spectroscopy. The flowing DC post-discharge in argon-oxygen mixture was created in a quartz tube at the total gas pressure of 1000 Pa and discharge power of 90 W. The O(3P) atom concentration was determined by NO titration at different places along the flow tube. The optical emission spectra were also measured along the flow tube. Argon spectral lines, oxygen lines at 777 nm and 844.6 nm and atmospheric A-band of {{\\text{O}}2} were identified in the spectra. Rotational temperature of {{\\text{O}}2} was determined from the oxygen atmospheric A-band and also the outer wall temperature of the flow tube was measured by a thermocouple and by an IR thermometer. A zero-dimensional kinetic model for the reactions in the afterglow was developed. This model allows the time dependencies of particle concentrations and of gas temperature to be calculated. The wall recombination probability for O(3P) atoms {γ\\text{O≤ft(\\text{P}\\right)}}=≤ft(1.63+/- 0.06\\right)× {{10}-3} and wall deactivation probability for {{\\text{O}}2} (b {{}1}Σ\\text{g}+ ) molecules {γ{{\\text{O}2}≤ft(\\text{b}\\right)}}=≤ft(1.7+/- 0.1\\right)× {{10}-3} were determined from the fit of model results to experimental data. Sensitivity analysis was applied for the analysis of kinetic model in order to reveal the most important reactions in the model. The calculated gas temperature increases in the afterglow and then decreases at later afterglow times after reaching the maximum. This behavior is in good agreement with the spatial rotational temperature dependence. A similar trend was also observed at outer wall temperature measurement.

  6. Direct reaction experimental studies with beams of radioactive tin ions

    SciTech Connect

    Jones, K. L. Ayres, A.; Bey, A.; Burcher, S.; Cartegni, L.; Cerizza, G.; Ahn, S.; Allmond, J. M.; Beene, J. R.; Galindo-Uribarri, A.; Liang, J. F.; Nesaraja, C. D.; Pain, S. D.; Radford, D. C.; Schmitt, K. T.; Smith, M. S.; Stracener, D. W.; Varner, R. L.; Bardayan, D. W.; Baugher, T.; and others

    2015-10-15

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at {sup 100}Sn, through 10 stable isotopes and the N = 82 shell closure at {sup 132}Sn out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich {sup 130}Sn. Both techniques rely on selective particle identification and the measurement of γ rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  7. Direct Reaction Experimental Studies with Beams of Radioactive Tin Ions

    SciTech Connect

    Jones, K. L.; Ahn, S.H.; Allmond, James M; Ayres, A.; Bardayan, Daniel W; Baugher, T.; Bazin, D.; Beene, James R; Berryman, J. S.; Bey, A.; Bingham, C. R.; Cartegni, L.; Chae, K. Y.; Gade, A.; Galindo-Uribarri, Alfredo {nmn}; Garcia-Ruiz, R.F.; Grzywacz, Robert Kazimierz; Howard, Meredith E; Kozub, R. L.; Liang, J Felix; Manning, Brett M; Matos, M.; McDaniel, S.; Miller, D.; Nesaraja, Caroline D; O'Malley, Patrick; Padgett, S; Padilla-Rodal, Elizabeth; Pain, Steven D; Pittman, S. T.; Radford, David C; Ratkiewicz, Andrew J; Schmitt, Kyle; Smith, Michael Scott; Stracener, Daniel W; Stroberg, S.; Tostevin, Jeffrey A; Varner Jr, Robert L; Weisshaar, D.; Wimmer, K.

    2015-01-01

    The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at Sn-100, through 10 stable isotopes and the N = 82 shell closure at Sn-132 out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich Sn-130. Both techniques rely on selective particle identification and the measurement of gamma rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.

  8. A Transport Model for Nuclear Reactions Induced by Radioactive Beams

    SciTech Connect

    Li Baoan; Chen Liewen; Das, Champak B.; Das Gupta, Subal; Gale, Charles; Ko, C.M.; Yong, G.-C.; Zuo Wei

    2005-10-14

    Major ingredients of an isospin and momentum dependent transport model for nuclear reactions induced by radioactive beams are outlined. Within the IBUU04 version of this model we study several experimental probes of the equation of state of neutron-rich matter, especially the density dependence of the nuclear symmetry energy. Comparing with the recent experimental data from NSCL/MSU on isospin diffusion, we found a nuclear symmetry energy of Esym({rho}) {approx_equal} 31.6({rho}/{rho}0)1.05 at subnormal densities. Predictions on several observables sensitive to the density dependence of the symmetry energy at supranormal densities accessible at GSI and the planned Rare Isotope Accelerator (RIA) are also made.

  9. Low-energy Coulomb excitation of Sr,9896 beams

    NASA Astrophysics Data System (ADS)

    Clément, E.; Zielińska, M.; Péru, S.; Goutte, H.; Hilaire, S.; Görgen, A.; Korten, W.; Doherty, D. T.; Bastin, B.; Bauer, C.; Blazhev, A.; Bree, N.; Bruyneel, B.; Butler, P. A.; Butterworth, J.; Cederkäll, J.; Delahaye, P.; Dijon, A.; Ekström, A.; Fitzpatrick, C.; Fransen, C.; Georgiev, G.; Gernhäuser, R.; Hess, H.; Iwanicki, J.; Jenkins, D. G.; Larsen, A. C.; Ljungvall, J.; Lutter, R.; Marley, P.; Moschner, K.; Napiorkowski, P. J.; Pakarinen, J.; Petts, A.; Reiter, P.; Renstrøm, T.; Seidlitz, M.; Siebeck, B.; Siem, S.; Sotty, C.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van de Walle, J.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.; De Witte, H.; Wrzosek-Lipska, K.

    2016-11-01

    The structure of neutron-rich Sr,9896 nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E 2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N =60 , giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.

  10. Argon isotope fractionation induced by stepwise heating

    NASA Astrophysics Data System (ADS)

    Trieloff, Mario; Falter, Martina; Buikin, Alexei I.; Korochantseva, Ekaterina V.; Jessberger, Elmar K.; Altherr, Rainer

    2005-03-01

    Noble gas isotopes are widely used to elucidate the history of the rocks in which they have been trapped, either from distinct reservoirs or by accumulation following radioactive decay. To extract noble gases from their host rocks, stepwise heating is the most commonly used technique to deconvolve isotopically different components, e.g., atmospheric, in situ radiogenic, or excess radiogenic from mantle or crustal reservoirs. The accurate determination of the isotopic composition of these different components is of crucial importance, e.g., for ages obtained by 40Ar- 39Ar stepheating plateaus. However, diffusion theory-based model calculations predict that the stepwise thermal extraction process from mineral phases induces isotope fractionation and, hence, adulterates the original composition. Such effects are largely unconsidered, as they are small and a compelling experimental observation is lacking. We report the first unequivocal evidence for significant mass fractionation of argon isotopes during thermal extraction, observed on shungite, a carbon-rich Precambrian sedimentary rock. The degree of fractionation, as monitored by 38Ar/ 36Ar and 40Ar/ 36Ar ratios, very well agrees with theoretical predictions assuming an inverse square root dependence of diffusion coefficient and atomic mass, resulting in easier extraction of lighter isotopes. Hence, subatmospheric 40Ar/ 36Ar ratios obtained for argon extracted at low temperatures may not represent paleoatmospheric argon. Shungite argon resembles modern atmospheric composition, but constraints on the timing of trapping appear difficult to obtain, as shungites are multicomponent systems. In 40Ar- 39Ar stepwise heating, the isotope fractionation effect could cause systematic underestimations of plateau ages, between 0.15 and 0.4% depending on age, or considerably higher if samples contain appreciable atmospheric Ar. The magnitude of this effect is similar to the presently achieved uncertainties of this increasingly

  11. Dendritic microstructure in argon atomized superalloy powders

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Kumar, Mahundra

    1986-01-01

    The dendritic microstructure of atomized nickel base superalloy powders (Ni-20 pct Cr, NIMONIC-80A, ASTROALOY, and ZHS6-K) was studied. Prealloyed vacuum induction melted ingots were argon-atomized, the powders were cooled to room temperature, and various powder-size fractions were examined by optical metallography. Linear correlations were obtained for the powder size dependence of the secondary dendrite arm spacing, following the expected d-alpha (R) to the m power dependence on the particle size for all four superalloy compositions. However, the Ni-20 pct Cr alloy, which had much coarser arm spacing as compared to the other three alloys, had a much larger value of m.

  12. Near-infrared scintillation of liquid argon

    SciTech Connect

    Alexander, T.; Escobar, C. O.; Lippincott, W. H.; Rubinov, P.

    2016-03-03

    Since the 1970s it has been known that noble gases scintillate in the near infrared (NIR) region of the spectrum (0.7 $\\mu$m < $\\lambda$; < 1.5$\\mu$m). More controversial has been the question of the NIR light yield for condensed noble gases. We first present the motivation for using the NIR scintillation in liquid argon detectors, then briefly review early as well as more recent efforts and finally show encouraging preliminary results of a test performed at Fermilab.

  13. Analysis of the 222Rn concentration in argon and a purification technique for gaseous and liquid argon.

    PubMed

    Simgen, H; Zuzel, G

    2009-05-01

    We present an investigation of the (222)Rn concentration in argon with ultra-low background proportional counters. Argon purification tests by means of cryo-adsorption of radon on activated carbon were performed. For gaseous argon the purification process was found to be very efficient. Also in liquid phase the (222)Rn concentration could be reduced significantly, however, the efficiency is lower than in the gas phase. We also have analyzed the initial (222)Rn concentrations in commercial liquid argon. It was found to be significantly higher than in liquid nitrogen.

  14. Wavefront control to generate ultraviolet supercontinuum by filamentation of few-cycle laser pulses in argon.

    PubMed

    Wang, Zhanxin; Liu, Jiansheng; Li, Ruxin; Xu, Zhizhan

    2010-01-15

    We numerically demonstrated the filamentation dynamics of a 6 fs, 800 nm pulse focused in argon at atmospheric pressure by a zone plate and a concave mirror. In comparison with a concave mirror, the zone plate has a frequency-dependent focal length and can be used to control the wavefront of the laser beam in the frequency domain. A separate supercontinuum in the ultraviolet region extending from 250 to 300 nm and peaked at ~280 nm can be generated by using a proper zone plate.

  15. Afterglow emission from xenon, krypton, and argon dimers in nanosecond volume discharge at elevated pressures

    NASA Astrophysics Data System (ADS)

    Baksht, E. Kh.; Lomaev, M. I.; Rybka, D. V.; Tarasenko, V. F.

    2006-10-01

    The emission characteristics of plasma of a volume discharge initiated by electron avalanche beams in heavy inert gases at pressures up to 1.5 bar have been studied. It is established that more than 90% of the energy radiated in the wavelength range from 120 to 850 nm is emitted from xenon, krypton, and argon dimers. In the case of excited xenon plasma, an output radiation power of ˜300 kW and an energy of 45 mJ per cubic centimeter were obtained.

  16. A Large Liquid Argon TPC for Off-axis NuMI Neutrino Physics

    SciTech Connect

    Menary, Scott

    2006-07-11

    The ICARUS collaboration has shown the power of the liquid argon time projection chamber (LArTPC) technique to image events with bubble-chamber-like quality. I will describe a proposed long-baseline {nu}e appearance experiment utilizing a large ({>=} 15 kton1) LArTPC placed off-axis of Fermilab's NuMI {nu}{mu} beam. The total LArTPC program as it presently stands, which includes a number of smaller R and D projects designed to examine the key design issues, will be outlined.

  17. Sputtering of cobalt and chromium by argon and xenon ions near the threshold energy region

    NASA Technical Reports Server (NTRS)

    Handoo, A. K.; Ray, P. K.

    1993-01-01

    Sputtering yields of cobalt and chromium by argon and xenon ions with energies below 50 eV are reported. The targets were electroplated on copper substrates. Measurable sputtering yields were obtained from cobalt with ion energies as low as 10 eV. The ion beams were produced by an ion gun. A radioactive tracer technique was used for the quantitative measurement of the sputtering yield. Co-57 and Cr-51 were used as tracers. The yield-energy curves are observed to be concave, which brings into question the practice of finding threshold energies by linear extrapolation.

  18. WA105: a large-scale demonstrator of the Liquid Argon double phase TPC

    NASA Astrophysics Data System (ADS)

    Tonazzo, A.; WA105 Collaboration

    2016-05-01

    The physics case for a large underground detector devoted to neutrino oscillation measurements, nucleon decay and astrophysics is compelling. A time projection chamber based on the dual-phase liquid Argon technique is an extremely attractive option, allowing for long drift distances, low energy threshold and high readout granularity. It has been extensively studied in the LAGUNA-LBNO Design Study and is one of the two designs foreseen for the modules of the DUNE detector in the US. The WA105 experiment envisages the construction of a large scale prototype at CERN, to validate technical solutions and perform physics studies with charged particle beams.

  19. Angle dependence of argon gas cluster sputtering yields for organic materials.

    PubMed

    Seah, M P; Spencer, S J; Shard, A G

    2015-02-19

    The first angle-dependent measurements of the sputtering yield of an organic material using argon gas cluster ions under a wide range of conditions are reported in order to develop an analytical description of the behavior important for the development of the application of secondary ion mass spectrometry to organic and biological systems. Data are presented for Irganox 1010 using argon gas cluster ion beams of 5 and 10 keV energy, E, with cluster sizes, n, from 1000 to 5000. The measurements are conducted in an X-ray photoelectron spectrometer for a range of angles from 0 to 80° from the surface normal. The results support the Universal Equation for argon gas cluster sputtering yields with the angle dependence incorporated into the equation via a simple angle dependence of the parameter A. This explains how and why the angular dependence of the sputtering yield changes significantly with increasing E/n. These results are also accurately confirmed using the published measurements for polystyrene by Rading et al.

  20. The effects of argon ion bombardment on the corrosion resistance of tantalum

    NASA Astrophysics Data System (ADS)

    Ramezani, A. H.; Sari, A. H.; Shokouhy, A.

    2017-02-01

    Application of ion beam has been widely used as a surface modification method to improve surface properties. This paper investigates the effect of argon ion implantation on surface structure as well as resistance against tantalum corrosion. In this experiment, argon ions with energy of 30 keV and in doses of 1 × 1017-10 × 1017 ions/cm2 were used. The surface bombardment with inert gases mainly produces modified topography and morphology of the surface. Atomic Force Microscopy was also used to patterned the roughness variations prior to and after the implantation phase. Additionally, the corrosion investigation apparatus wear was applied to compare resistance against tantalum corrosion both before and after ion implantation. The results show that argon ion implantation has a substantial impact on increasing resistance against tantalum corrosion. After the corrosion test, scanning electron microscopy (SEM) analyzed the samples' surface morphologies. In addition, the elemental composition is characterized by energy-dispersive X-ray (EDX) analysis. The purpose of this paper was to obtain the perfect condition for the formation of tantalum corrosion resistance. In order to evaluate the effect of the ion implantation on the corrosion behavior, potentiodynamic tests were performed. The results show that the corrosion resistance of the samples strongly depends on the implantation doses.

  1. Electron scattering and transport in liquid argon

    SciTech Connect

    Boyle, G. J.; Cocks, D. G.; White, R. D.; McEachran, R. P.

    2015-04-21

    The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.

  2. Argon gas: a potential neuroprotectant and promising medical therapy

    PubMed Central

    2014-01-01

    Argon is a noble gas element that has demonstrated narcotic and protective abilities that may prove useful in the medical field. The earliest records of argon gas have exposed its ability to exhibit narcotic symptoms at hyperbaric pressures greater than 10 atmospheres with more recent evidence seeking to display argon as a potential neuroprotective agent. The high availability and low cost of argon provide a distinct advantage over using similarly acting treatments such as xenon gas. Argon gas treatments in models of brain injury such as in vitro Oxygen-Glucose-Deprivation (OGD) and Traumatic Brain Injury (TBI), as well as in vivo Middle Cerebral Artery Occlusion (MCAO) have largely demonstrated positive neuroprotective behavior. On the other hand, some warning has been made to potential negative effects of argon treatments in cases of ischemic brain injury, where increases of damage in the sub-cortical region of the brain have been uncovered. Further support for argon use in the medical field has been demonstrated in its use in combination with tPA, its ability as an organoprotectant, and its surgical applications. This review seeks to summarize the history and development of argon gas use in medical research as mainly a neuroprotective agent, to summarize the mechanisms associated with its biological effects, and to elucidate its future potential. PMID:24533741

  3. Commissioning and first radioactive beam experiments at the CARIBU facility

    NASA Astrophysics Data System (ADS)

    Savard, Guy; Baker, Sam; Caldwell, Shane; Clark, Jason; Davids, Cary; Lascar, Daniel; Levand, Anthony; Pardo, Richard; Peterson, Donald; Phillips, Don; Sternberg, Matthew; Sun, Tao; van Schelt, Jon; Vondrasek, Rick; Zabransky, Bruce

    2011-04-01

    The Californium Rare Ion Breeder Upgrade (CARIBU) of the ATLAS superconducting linac facility aims at providing low energy and reaccelerated neutron-rich radioactive beams to address key nuclear physics and astrophysics questions. These beams are obtained from fission fragments of a 1 Ci 252Cf source, thermalized and collected into a low-energy particle beam by a helium gas catcher, mass analyzed by an isobar separator, and charge breed to higher charge states for acceleration in ATLAS. The facility has ramped up with first operation with a weaker 2.5 mCi source and now a 100 mCi source. Low-energy mass separated radioactive beams have been extracted, charge bred with an efficiency of about 8%, and reaccelerated to 6 MeV/u. Commissioning results, together with the results from first astrophysics experiments at CARIBU using the beams from the 100 mCi source will be presented. The final 1 Ci source is expected to be available in the spring. This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under contract No. DE-AC02-06CH11357.

  4. Improved installation prototype for measurement of low argon-37 activity

    NASA Astrophysics Data System (ADS)

    Pakhomov, Sergei; Dubasov, Yuri

    2015-04-01

    On-site Inspection (OSI) is a key element of verification of State Parties' compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). An on-site inspection is launched to establish whether or not a nuclear explosion has been carried out. One of the most significant evidence of n underground nuclear explosion (UNE) is detection above background concentrations of argon-37 in near surface air. Argon-37 is formed in large amounts at interaction of neutrons of UNE with the potassium which is a part of the majority of rocks. Its estimated contents for the 100th days after explosion with a energy of 1000 t of TNT near a surface can vary from 1 to 1000 mBq/m3. The background concentrations of argon-37 in subsoil air vary 1 do100 mBq/m3. Traditionally, for argon-37 activity measurement the gas-proportional counters are used. But at Khlopin Radium institute the developments of the new type of highly sensitive and low-background installation capable to provide the required range of measurements of the argon-37 concentration are conducted. The liquid scintillation method of the registration of the low-energetic argon-37 electrons is the basic installation principle and as scintillator, the itself condensed air argon sample is used. Registration of scintillations of liquid argon is made by means of system from 3 PMT which cathodes are cooled near to the temperature of liquid nitrogen together with the measuring chamber in which placed the quartz glass ampule, containing the measured sample of the liquefied argon. For converse the short wavelength photons (λ = 127 nm) of liquid argon scintillations to more long-wave, corresponding to the range of PMT sensitivity, the polymer film with tetra-phenyl-butadiene (TPB) is provided. Even the insignificant impurities of nitrogen, oxygen and others gaseous in the liquid argon samples can to cause the quenching of scintillation, especially their slow components. To account this effect and it influence on change of registration

  5. Ion beam deposited protective films

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.

    1981-01-01

    Single or dual ion beam sources were used to deposit thin films for different applications. Metal and metal oxide films were evaluated as protective coatings for the materials. Film adherence was measured and the most promising films were then tested under environments similar to operating conditions. It was shown that some materials do protect die material (H-13 steel) and do reduce thermal fatigue. Diamondlike films have many useful applications. A series of experiments were conducted to define and optimize new approaches to the manufacture of such films. A dual beam system using argon and methane gases was developed to generate these films.

  6. Effect of Emergency Argon on FCF Operational Incidents

    SciTech Connect

    Charles Solbrig

    2011-12-01

    The following report presents analyses of operational incidents which are considered in the safety analysis of the FCF argon cell and the effect that the operability of the emergency argon system has on the course of these incidents. The purpose of this study is to determine if the emergency argon system makes a significant difference in ameliorating the course of these incidents. Six incidents were considered. The following three incidents were analyzed. These are: 1. Cooling failing on 2. Vacuum Pump Failing on 3. Argon Supplies Failing on. In the remaining three incidents, the emergency argon supply would have no effect on the course of these transients since it would not come on during these incidents. The transients are 1. Loss of Cooling 2. Loss of power (Differs from above by startup delay till the Diesel Generators come on.) 3. Cell rupture due to an earthquake or other cause. The analyses of the first three incidents are reported on in the next three sections. This report is issued realizing the control parameters used may not be optimum, and additional modeling must be done to model the inertia of refrigeration system, but the major conclusion concerning the need for the emergency argon system is still valid. The timing of some events may change with a more accurate model but the differences between the transients with and without emergency argon will remain the same. Some of the parameters assumed in the analyses are Makeup argon supply, 18 cfm, initiates when pressure is = -6 iwg., shuts off when pressure is = -3.1 iwg. 170,000 ft3 supply. Min 1/7th always available, can be cross connected to HFEF argon supply dewar. Emergency argon supply, 900 cfm, initiates when pressure is = -8 iwg. shuts off when pressure is =-4 iwg. reservoir 220 ft3, refilled when tank farm pressure reduces to 1050 psi which is about 110 ft3.

  7. Charge-changing collisions of argon ions on argon gas. One-electron capture

    SciTech Connect

    Aubert, J.; Bliman, S.; Geller, R.; Jacquot, B.; Van Houtte, D.

    1980-12-01

    Single-electron-capture cross sections have been measured for argon ions with initial charges 2< or =q< or =12 incident on an argon-gas target. The cross sections show little dependence on the incident ion energy in the range 1q--10q keV. A remarkable oscillating feature is seen for cross sections sigma/sub q/,q-1 when q> or =7. Particularly, sigma/sub 8,7/ is smaller than sigma/sub 7,6/ and sigma/sub 9,8/, the Ar/sup 8 +/ electronic structure being Ne-like. Variation of the cross section is shown as function of the initial charge at constant energy.

  8. Attosecond Time-Resolved Autoionization of Argon

    SciTech Connect

    Wang He; Chini, Michael; Chen Shouyuan; Zhang Changhua; Cheng Yan; Wu Yi; Thumm, Uwe; He Feng; Chang Zenghu

    2010-10-01

    Autoionization of argon atoms was studied experimentally by transient absorption spectroscopy with isolated attosecond pulses. The peak position, intensity, linewidth, and shape of the 3s3p{sup 6}np {sup 1}P Fano resonance series (26.6-29.2 eV) were modified by intense few-cycle near infrared laser pulses, while the delay between the attosecond pulse and the laser pulse was changed by a few femtoseconds. Numerical simulations revealed that the experimentally observed splitting of the 3s3p{sup 6}4p {sup 1}P line is caused by the coupling between two short-lived highly excited states in the strong laser field.

  9. Merging of high speed argon plasma jets

    SciTech Connect

    Case, A.; Messer, S.; Brockington, S.; Wu, L.; Witherspoon, F. D.; Elton, R.

    2013-01-15

    Formation of an imploding plasma liner for the plasma liner experiment (PLX) requires individual plasma jets to merge into a quasi-spherical shell of plasma converging on the origin. Understanding dynamics of the merging process requires knowledge of the plasma phenomena involved. We present results from the study of the merging of three plasma jets in three dimensional geometry. The experiments were performed using HyperV Technologies Corp. 1 cm Minirailguns with a preionized argon plasma armature. The vacuum chamber partially reproduces the port geometry of the PLX chamber. Diagnostics include fast imaging, spectroscopy, interferometry, fast pressure probes, B-dot probes, and high speed spatially resolved photodiodes, permitting measurements of plasma density, temperature, velocity, stagnation pressure, magnetic field, and density gradients. These experimental results are compared with simulation results from the LSP 3D hybrid PIC code.

  10. Vibrational relaxation of chloroiodomethane in cold argon

    NASA Astrophysics Data System (ADS)

    Jain, Amber; Sibert, Edwin L.

    2013-10-01

    Electronically exciting the C-I stretch in the molecule chloroiodomethane CH2ClI embedded in a matrix of argon at 12 K can lead to an isomer, iso-chloroiodomethane CH2Cl-I, that features a chlorine iodine bond. By temporally probing the isomer at two different frequencies of 435 nm and 485 nm, multiple timescales for isomerization and vibrational energy relaxation were inferred [T. J. Preston, et al., J. Chem. Phys. 135, 114503 (2011)]. This relaxation is studied theoretically using molecular dynamics by considering 2 and 3 dimensional models. Multiple decay rate constants of the same order of magnitude as the experiment are observed. These decay rate constants are interpreted within the context of the Landau-Teller theory. Sensitivity of the decay rate constants on the bath and system parameters shed more light into the mechanism of vibrational energy relaxation.

  11. Commissioning a Tape Transport System for Decay Studies and Beam Diagnostics at CARIBU

    NASA Astrophysics Data System (ADS)

    Bertone, P. F.; Digiovine, B.; Lister, C. J.; Teh, K.; Kondev, F. G.; Nair, C.; Chowdhury, P.; Deo, A. Y.; Lakshmi, S.

    2011-10-01

    The CAlifornium Rare Isotope Breeder Upgrade (CARIBU) to the ATLAS facility at Argonne utilizes the spontaneous fission of 252 Cf for producing neutron-rich radioactive nuclei. CARIBU will be used for a wide variety of experiments, involving both reaccelerated and stopped beams, in nuclear structure, nuclear astrophysics and applications. Many of these experiments will require a means of transporting radioactivity to and from detector counting stations for the purpose of assaying beam content, measuring half-lives, β- γ spectroscopy and determining Gamow-Teller strength distributions. We have commissioned the first of several tape transport systems that will perform these functions. An overview of the design and deployment of the system will be given along with preliminary test results. Supported by the U.S. DOE Office of Nuclear Physics DE-AC02-06CH11357.

  12. The TRIple PLunger for EXotic beams TRIPLEX for excited-state lifetime measurement studies on rare isotopes

    NASA Astrophysics Data System (ADS)

    Iwasaki, H.; Dewald, A.; Braunroth, T.; Fransen, C.; Smalley, D.; Lemasson, A.; Morse, C.; Whitmore, K.; Loelius, C.

    2016-01-01

    A new device, the TRIple PLunger for EXotic beams (TRIPLEX), has been developed for lifetime measurement studies with rare isotope beams. This plunger device holds up to three metal foils in the beam path and facilitates the recoil distance Doppler-shift technique to measure lifetimes of nuclear excited states in the range of 1 ps to 1 ns. The unique design allows independent movement of the target and the second degrader with respect to a fixed first degrader in between, enabling advanced experimental approaches, such as the differential recoil distance method and the double recoil distance method. The design and control of the device are presented in this paper, together with simulated performances of the new applications. As an example of actual experiments, results from the lifetime measurement of the neutron-rich 17C isotope performed at the National Superconducting Cyclotron Laboratory are shown.

  13. Argon laser radiation of human clots: differential photoabsorption in red cell rich and red cell poor clots

    SciTech Connect

    Lee, G.; Chan, M.C.; Seckinger, D.L.; Vazquez, A.; Rosenthal, P.K.; Lee, K.K.; Ikeda, R.M.; Reis, R.L.; Hanna, E.S.; Mason, D.T.

    1985-06-01

    Since argon laser radiation (454-514 nm) can vaporize human clots, the authors determined whether the absorption of laser energies can differ among different types of blood clots. Thus, they performed spectrophotometric studies and examined the ability of this laser to penetrate red cell rich and red cell poor clots. Fifty-four red cell rich and red cell poor clot samples, varying in depth from 1.8 to 5.0 mm, were subjected to 3, 5 and 7 watts from an argon laser beam. At a given power intensity, the deeper the red cell rich clot, the longer was the time needed to penetrate the clot. The higher the power used, the shorter was the red clot penetration time. In contrast, all power levels used up to 5 minutes did not penetrate any of the varying depths of red cell poor clots. Spectrophotometrically, the red cell rich clot had an absorption curve typical of hemoglobin pigment while the red cell poor clot, in the absence of hemoglobin, had poor absorption between 350 and 600 nm and was unable to absorb argon laser energies. Thus, the argon laser provides a therapeutic modality for human red cell rich clot dissolution but the present approach does not appear to be effective against red cell poor clots.

  14. Measuring the Fusion Cross-Section of 18O + 12C with Low-Intensity Beams near and below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy; Vadas, Justin; Singh, Varinderjit; Hudan, Sylvie; Desouza, Romualdo; Baby, Lagy; Kuvin, Sean; Wiedenhover, Ingo; Umar, Sait; Oberacker, Volker

    2016-03-01

    Fusion between neutron-rich light nuclei in the crust of an accreting neutron star has been proposed as a heat source that triggers an X-ray superburst. To explore the probability of such fusion events and examine their decay characteristics an experimental program using beams of neutron-rich light nuclei has been initiated. The evaporation residues (ERs) that result from the fusion of 18O and 12C nuclei, are directly measured and distinguished from unreacted beam particles on the basis of their energy and TOF. Using an experimental setup developed for the measurement with low-intensity (<105 ions/s) radioactive beams the fusion excitation function for 18O+12C has been measured in the sub-barrier domain down to the 820 μb level. The measured fusion excitation function is compared to the prediction of a density constrained TDHF model. In addition to the measured cross-section, the measured ER angular distributions provide insight into the relative importance of the different de-excitation channels. These ER angular distributions are compared to the predictions of a statistical model code, EVAPOR revealing an under-prediction of the de-excitation channels associated with α emission. The de-excitation channels associated with proton emission following fusion will also be investigated. Supported by the US DOE under Grant No. DEFG02-88ER-40404.

  15. GLADE Global Liquid Argon Detector Experiment: a letter of intent to FNAL

    SciTech Connect

    Thomas, Jennifer

    2012-05-13

    The recent measurements of the {theta}{sub 13} mixing angle, which controls the observable size of any CP violation effects, open a window of opportunity to take advantage of the world's most powerful existing neutrino beam together with recent successes in development of the ultimate detector technology for the detection of electron neutrinos : a liquid argon (LAr) time projection chamber. During this proposed project a 5kt LAr detector (GLADE) will be developed by European groups to be put in a cryostat in the NuMI neutrino beam at Fermi National Accelerator Laboratory in the US and will start taking data in 3-5 years time to address the neutrino mass ordering. The successful fruition of this project, along with nominal exposure at NO{nu}A and T2K, together with information from double beta decay experiments could ascertain that neutrinos are Dirac particles in the next decade.

  16. Cryosorption of helium on argon frost TFTR (Tokamak Fusion Test Reactor) neutral beamlines

    SciTech Connect

    Kamperschroer, J.H.; Cropper, M.B.; Dylla, H.F.; Garzotto, V.; Dudek, L.E.; Grisham, L.R.; Martin, G.D.; O'Connor, T.E.; Stevenson, T.N.; von Halle, A. . Plasma Physics Lab.)

    1989-11-01

    Helium pumping on argon frost has been investigated on TFTR neutral beam injectors and shown to be viable for limited helium beam operation. Maximum pumping speeds are {approximately} 25% less than those measured for pumping of deuterium. Helium pumping efficiency is low, > 20 argon atoms are required to pump each helium atom. Adsorption isotherms are exponential and exhibit a two-fold increase in adsorption capacity as the cryopanel temperature is reduced from 4.3 K to 3.7 K. Pumping speed was found to be independent of cryopanel temperature over the temperature range studied. After pumping a total of 2000 torr-l of helium, the beamline base pressure rose to 2{times}10{sup -5} torr from an initial value of 10{sup -8} torr. Accompanying this three order of magnitude increase in pressure was a modest 40% decrease in pumping speed. The introduction of 168 torr-l of deuterium prior to helium injection reduced the pumping speed by a factor of two with no decrease in adsorption capacity. 29 refs., 7 figs.

  17. Raman study of composite resins polymerized by a halogen lamp and an argon laser

    NASA Astrophysics Data System (ADS)

    Silva Soares, Luis E.; Martin, Airton A.; Pinheiro, Antonio L. B.; Pacheco, Marcos T. T.

    2002-06-01

    Raman Spectroscopy was used on the present investigation to monitor the degree of conversion of microparticled composite resin (Z100-3M), polymerized by both the conventional halogen light and the Argon Laser beam. Circular blocks of composite 6mm diameter and 3mm of thickness were used on this study. The tip of the halogen light source ((lambda) = 400-500nm, 478mW/cm2) or the Argon laser beam ((lambda) = 488nm, 624mW/cm2) was positioned on the surface of the composite resin and both activated for different irradiation times (5, 10, 20, 30, 40 and 60 seconds). The top surface which was directly irradiated and the non-irradiated (inferior) surface were analyzed immediately after curing by Raman Spectroscopy. The Raman results show systematic changes of the relative intensities between the peaks at 1610 (aromatic C=C stretching mode) and the 1640 cm-1 (methacrylate C=C stretching mode), as a function of irradiation time. The degree of conversion was calculated based on the relative intensity change of these two modes and compared for each light source. The change in the relative intensity shows that Raman Spectroscopy can be used as an effective method to study the degree of conversion of composite resins.

  18. Ion beam sputtering of fluoropolymers

    NASA Technical Reports Server (NTRS)

    Sovey, J. S.

    1978-01-01

    Etching and deposition of fluoropolymers are of considerable industrial interest for applications dealing with adhesion, chemical inertness, hydrophobicity, and dielectric properties. This paper describes ion beam sputter processing rates as well as pertinent characteristics of etched targets and films. An argon ion beam source was used to sputter etch and deposit the fluoropolymers PTFE, FEP, and CTFE. Ion beam energy, current density, and target temperature were varied to examine effects on etch and deposition rates. The ion etched fluoropolymers yield cone or spire-like surface structures which vary depending upon the type of polymer, ion beam power density, etch time, and target temperature. Also presented are sputter target and film characteristics which were documented by spectral transmittance measurements, X-ray diffraction, ESCA, and SEM photomicrographs.

  19. Extreme argon purity in a large, non-evacuated cryostat

    SciTech Connect

    Tope, Terry; Adamowski, Mark; Carls, B.; Hahn, A.; Jaskierny, W.; Jostlein, H.; Kendziora, C.; Lockwitz, S.; Pahlka, B.; Plunkett, R.; Pordes, S.; Rebel, B.; Schmitt, R.; Skup, E.; Stancari, M.; Yang, T.

    2014-01-29

    Liquid Argon Time Projection Chambers (LArTPCs) show promise as scalable devices for the large detectors needed for long-baseline neutrino oscillation physics. Over the last several years at Fermilab a staged approach to developing the technology for large detectors has been developed. The TPC detectors require ultra-pure liquid argon with respect to electronegative contaminants such as oxygen and water. The tolerable electronegative contamination level may be as pure as 60 parts per trillion of oxygen. Three liquid argon cryostats operated at Fermilab have achieved the extreme purity required by TPCs. These three cryostats used evacuation to remove atmospheric contaminants as the first purification step prior to filling with liquid argon. Future physics experiments may require very large detectors with tens of kilotonnes of liquid argon mass. The capability to evacuate such large cryostats adds significant cost to the cryostat itself in addition to the cost of a large scale vacuum pumping system. This paper describes a 30 ton liquid argon cryostat at Fermilab which uses purging to remove atmospheric contaminants instead of evacuation as the first purification step. This cryostat has achieved electronegative contamination levels better than 60 parts per trillion of oxygen equivalent. The results of this liquid argon purity demonstration will strongly influence the design of future TPC cryostats.

  20. Production of drip-line nuclei at RIKEN RI Beam Factory

    NASA Astrophysics Data System (ADS)

    Saito, Atsumi

    2014-09-01

    Production cross-sections and secondary-beam yields of very neutron rich nuclei near neutron drip-line at 200--250 MeV/u have been investigated at RIKEN RI Beam Factory (RIBF). RIBF is the next generation RI beam facility, which can produce a variety of exotic nuclei with high intensity. The measurement of production yields of 19B, 22C, which are located on the neutron drip-line, and neighboring isotopes was made on the occasion of the Coulomb and nuclear breakup experiments of these halo nuclei at SAMURAI (Superconducting Analyzer for MUlti-particle from RAdioIsotope beams) facility at RIBF. We used 345 MeV/u 48Ca beam as primary beam, which impinged on 30 mm-thick Be target, to obtain secondary beams by projectile fragmentation. The projectile fragments were then separated through Superconducting RI beam separator BigRIPS, and were identified by measuring time of flight (TOF), energy loss (ΔE), and magnetic rigidity (Bρ) by the standard detectors at 2nd stage of BigRIPS. We thus obtained production cross-sections and yields of carbon and boron isotopes. The production cross-sections and yields extracted were compared with the simulation code LISE using EPAX. We discuss these results and comparisons in this poster presentation.

  1. Quantitative low-energy ion beam characterization by beam profiling and imaging via scintillation screens

    NASA Astrophysics Data System (ADS)

    Germer, S.; Pietag, F.; Polak, J.; Arnold, T.

    2016-11-01

    This study presents the imaging and characterization of low-current ion beams in the neutralized state monitored via single crystal YAG:Ce (Y3Al5O12) scintillators. To validate the presented beam diagnostic tool, Faraday cup measurements and test etchings were performed. Argon ions with a typical energy of 1.0 keV were emitted from an inductively coupled radio-frequency (13.56 MHz) ion beam source with total currents of some mA. Different beam properties, such as, lateral ion current density, beam divergence angle, and current density in pulsed ion beams have been studied to obtain information about the spatial beam profile and the material removal rate distribution. We observed excellent imaging properties with the scintillation screen and achieved a detailed characterization of the neutralized ion beam. A strong correlation between the scintillator light output, the ion current density, and the material removal rate could be observed.

  2. Modeling Electronegative Impurity Concentrations in Liquid Argon Detectors

    NASA Astrophysics Data System (ADS)

    Tang, Wei; Li, Yichen; Thorn, Craig; Qian, Xin

    2017-01-01

    Achieving long electron lifetime is crucial to reach the high performance of large Liquid Argon Time Projection Chamber (LArTPC) envisioned for next generation neutrino experiments. We have built up a quantitative model to describe the impurity distribution and transportation in a cryostat. Henrys constants of Oxygen and water, which describe the partition of impurities between gas argon and liquid argon, have been deduced through this model with the measurements in BNL 20-L LAr test stand. These results indicate the importance of the gas purification system and prospects on large LArTPC detectors will be discussed.

  3. Practical reactor production of 41Ar from argon clathrate.

    PubMed

    Mercer, J R; Duke, M J; McQuarrie, S A

    2000-06-01

    The radionuclide 41Ar has many ideal properties as a gas flow tracer. However, the modest cross-section of 40Ar for thermal neutron activation makes preparation of suitable activities of 41Ar technically difficult particularly for low flux reactors. Argon can however be trapped in a molecular complex called a clathrate that can then be irradiated. We prepared argon clathrate and explored its irradiation and stability characteristics. Argon clathrate can be used to provide gigabecquerel quantities of 41Ar even with low power reactors.

  4. BEAM-BEAM 2003 SUMMARY.

    SciTech Connect

    FISCHER,W.SEN,T.

    2003-05-19

    This paper summarizes the presentations and discussions of the Beam-Beam'03 workshop, held in Montauk, Long Island, from May 19 to 23, 2003. Presentations and discussions focused on halo generation from beam-beam interactions; beam-beam limits, especially coherent limits and their effects on existing and future hadron colliders; beam-beam compensation techniques, particularly for long-range interactions; and beam-beam study tools in theory, simulation, and experiment.

  5. Analysis of tungsten carbide coatings by infrared laser-induced argon spark with inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Kanický, V.; Otruba, V.; Mermet, J.-M.

    2000-10-01

    Infrared laser ablation was studied for application to the analysis of plasma-sprayed tungsten carbide/cobalt coatings. The potential of the laser induced argon-spark (LINA-Spark™), as a sample introduction device in inductively coupled plasma atomic emission spectrometry was studied. The use of an IR laser along with defocusing led to laser-induced microplasma-based ablation. The mass ablation rate, represented by the ICP emission intensity per laser beam unit area, exhibited a flat increase in the irradiance range 2-250 GW/cm 2. A low slope (0.5) of this dependence in log-log scale gave evidence of plasma shielding. The steep increase in the measured acoustic signal when focused in front of the sample, i.e. in argon, indicated a breakdown of argon. Consequently, considerably lower ICP emissions were observed within the same range of irradiance. The cobalt/tungsten line intensity ratio in the ICP was practically constant from 1.5 up to at least 250 GW/cm 2. Acceptable precision (R.S.D.<5%) was obtained without internal standardization for irradiance between 2 and 8 GW/cm 2. Optimization of the laser pulse energy, repetition rate, beam focusing and sample displacement during interaction led to the linearization of dependences of signal vs. cobalt percentage, at least up to the highest studied value of 23% Co.

  6. The interaction of an atmospheric pressure plasma jet using argon or argon plus hydrogen peroxide vapour addition with bacillus subtilis

    NASA Astrophysics Data System (ADS)

    Deng, San-Xi; Cheng, Cheng; Ni, Guo-Hua; Meng, Yue-Dong; Chen, Hua

    2010-10-01

    This paper reports that an atmospheric pressure dielectric barrier discharge plasma jet, which uses argon or argon + hydrogen peroxide vapour as the working gas, is designed to sterilize the bacillus subtilis. Compared with the pure argon plasma, the bacterial inactivation efficacy has a significant improvement when hydrogen peroxide vapour is added into the plasma jet. In order to determine which factors play the main role in inactivation, several methods are used, such as determination of optical emission spectra, high temperature dry air treatment, protein leakage quantification, and scanning electron microscope. These results indicate that the possible inactivation mechanisms are the synergistic actions of chemically active species and charged species.

  7. Study of nuclear recoils in liquid argon with monoenergetic neutrons

    NASA Astrophysics Data System (ADS)

    Regenfus, C.; Allkofer, Y.; Amsler, C.; Creus, W.; Ferella, A.; Rochet, J.; Walter, M.

    2012-07-01

    In the framework of developments for liquid argon dark matter detectors we assembled a laboratory setup to scatter neutrons on a small liquid argon target. The neutrons are produced mono-energetically (Ekin = 2.45 MeV) by nuclear fusion in a deuterium plasma and are collimated onto a 3" liquid argon cell operating in single-phase mode (zero electric field). Organic liquid scintillators are used to tag scattered neutrons and to provide a time-of-flight measurement. The setup is designed to study light pulse shapes and scintillation yields from nuclear and electronic recoils as well as from alpha particles at working points relevant for dark matter searches. Liquid argon offers the possibility to scrutinise scintillation yields in noble liquids with respect to the population strength of the two fundamental excimer states. Here we present experimental methods and first results from recent data towards such studies.

  8. Mars Atmosphere Argon Density Measurement on MER Mission

    NASA Astrophysics Data System (ADS)

    Economou, T. E.

    2008-11-01

    Using the Alpha Particle X-ray Spectrometer (APXS) on board Spirit and Opportunity rovers on MER mission, we were able to measure the argon density variation in the martian atmosphere as a function of seasonal changes.

  9. Cryogenic CMOS cameras for high voltage monitoring in liquid argon

    NASA Astrophysics Data System (ADS)

    McConkey, N.; Spooner, N.; Thiesse, M.; Wallbank, M.; Warburton, T. K.

    2017-03-01

    The prevalent use of large volume liquid argon detectors strongly motivates the development of novel readout and monitoring technology which functions at cryogenic temperatures. This paper presents the development of a cryogenic CMOS camera system suitable for use inside a large volume liquid argon detector for online monitoring purposes. The characterisation of the system is described in detail. The reliability of such a camera system has been demonstrated over several months, and recent data from operation within the liquid argon region of the DUNE 35 t cryostat is presented. The cameras were used to monitor for high voltage breakdown inside the cryostat, with capability to observe breakdown of a liquid argon time projection chamber in situ. They were also used for detector monitoring, especially of components during cooldown.

  10. Electron avalanches in liquid argon mixtures

    SciTech Connect

    Kim, J.G.; Dardin, S.M.; Kadel, R.W.; Kadyk, J.A.; Wenzel, W.B.; Peskov, V.

    2004-03-19

    We have observed stable avalanche gain in liquid argon when mixed with small amounts of xenon in the high electric field (>7 MV/cm) near the point of a chemically etched needle in a point-plane geometry. We identify two gain mechanisms, one pressure dependent, and the other independent of the applied pressure. We conclude that the pressure dependent signals are from avalanche gain in gas bubbles at the tip of the needle, while the pressure independent pulses are from avalanche gain in liquid. We measure the decay time spectra of photons from both types of avalanches. The decay times from the pressure dependent pulses decrease (increase) with the applied pressure (high voltage), while the decay times from the pressure independent pulses are approximately independent of pressure or high voltage. For our operating conditions, the collected charge distribution from avalanches is similar for 60 keV or 122 keV photon sources. With krypton additives, instead of Xe, we measure behavior consistent with only the pressure dependent pulses. Neon and TMS were also investigated as additives, and designs for practical detectors were tested.

  11. Mars MITgcm and Argon in the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Lian, Yuan; Richardson, M.; Newman, C.; Lee, C. M.; Toigo, A.; Mischna, M.; Campin, J.

    2010-10-01

    Mars Odyssey observed that Argon abundance was greatly enhanced during winter solstice at southern pole in Martian atmosphere. The Argon enrichment factor can reach as high as 6-7. Several studies have examined the mechanisms that cause such enrichment. Current Mars GCMs can produce the seasonal variation of Argon enhancement to some degree. However, they only reproduce aspects of the trend and generally predict an enhancement factor of about 2-3 times smaller than observed. To address the problem of Argon transport, we have developed a new Mars GCM based on the MITgcm, a state-of-art global circulation model, and the Mars atmospheric physics as implemented in PlanetWRF. The Mars MITgcm uses cube-sphere grid finite volume numerics and has several options for the tracer advection scheme. The Mars MITgcm includes topography, a subsurface scheme, a planetary boundary layer, atmospheric dust distribution, radiative transfer and a CO2 cycle. Our model results show close agreement with the annual variability of pressure measured at the Viking Lander sites, as well as matches to MCS temperature profiles. For Argon, unlike prior studies, we tested various tracer advection schemes and found significant variations depending on the quality of the schemes used. We suggest that much of the variations between different prior modeling studies is plausibly related to differences in the advection schemes used. We found that, at 2.5-degree grid resolution, advection schemes with flux limiters provide good match to the Argon enhancement factor for observations for 75 degree poleward in southern winter. Preliminary diagnoses of model results suggest that the polar Argon enhancement during summer solstice results from: first, Argon is transported poleward and trapped by polar vortex; second, the enhancement factor gets larger when more CO2 is condensed. Our work thus far suggests that the Mars MITgcm is ready for solving future scientific questions.

  12. Common Blepharitis Related to Phthiriasis Palpebrarum: Argon Laser Phototherapy.

    PubMed

    Sundu, Cem; Dinç, Erdem; Kurtuluş, Umut Can; Yıldırım, Özlem

    2015-09-01

    A 42-year-old woman was admitted to Mersin University, Department of Ophthalmology Clinic with itching and burning sensation of the right eye for 3 weeks. In her slit-lamp examination, nits and lice, attached to the upper and lower eyelashes of her right eye, were observed. Lice and nits were destroyed by argon laser phototherapy and were removed with the help of a fine forceps thereafter. Argon laser phototherapy is a quick, effective, and safe treatment modality for phthiriasis palpebrarum.

  13. Radiant properties of strong shock waves in argon.

    PubMed

    Taylor, W H; Kane, J W

    1967-09-01

    Measurements of the visible radiation emitted by one dimensional, explosively generated, shock waves in argon initially at 1 atm are reported. A time-resolved spectrograph and calibrated photodetectors were used to measure the intensity of the source at 5450 A and 4050 A. The results show that explosive induced shock waves in argon having shock velocities in the range 8-9 mm/microusec radiate at these wavelengths like a blackbody having a temperature of approximately 23,000 degrees K.

  14. Surface wet-ability modification of thin PECVD silicon nitride layers by 40 keV argon ion treatments

    NASA Astrophysics Data System (ADS)

    Caridi, F.; Picciotto, A.; Vanzetti, L.; Iacob, E.; Scolaro, C.

    2015-10-01

    Measurements of wet-ability of liquid drops have been performed on a 30 nm silicon nitride (Si3N4) film deposited by a PECVD reactor on a silicon wafer and implanted by 40 keV argon ions at different doses. Surface treatments by using Ar ion beams have been employed to modify the wet-ability. The chemical composition of the first Si3N4 monolayer was investigated by means of X-ray Photoelectron Spectroscopy (XPS). The surface morphology was tested by Atomic Force Microscopy (AFM). Results put in evidence the best implantation conditions for silicon nitride to increase or to reduce the wet-ability of the biological liquid. This permits to improve the biocompatibility and functionality of Si3N4. In particular experimental results show that argon ion bombardment increases the contact angle, enhances the oxygen content and increases the surface roughness.

  15. Summary of the Second Workshop on Liquid Argon Time Projection Chamber Research and Development in the United States

    SciTech Connect

    Acciarri, R.; et al.

    2015-04-21

    The second workshop to discuss the development of liquid argon time projection chambers (LArTPCs) in the United States was held at Fermilab on July 8-9, 2014. The workshop was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that was initiated by the American Physical Society Division of Particles and Fields. All presentations at the workshop were made in six topical plenary sessions: i) Argon Purity and Cryogenics, ii) TPC and High Voltage, iii) Electronics, Data Acquisition and Triggering, iv) Scintillation Light Detection, v) Calibration and Test Beams, and vi) Software. This document summarizes the current efforts in each of these areas. It primarily focuses on the work in the US, but also highlights work done elsewhere in the world.

  16. Summary of the Second Workshop on Liquid Argon Time Projection Chamber Research and Development in the United States

    DOE PAGES

    Acciarri, R.; Adamowski, M.; Artrip, D.; ...

    2015-07-28

    The second workshop to discuss the development of liquid argon time projection chambers (LArTPCs) in the United States was held at Fermilab on July 8-9, 2014. The workshop was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that was initiated by the American Physical Society Division of Particles and Fields. All presentations at the workshop were made in six topical plenary sessions: i) Argon Purity and Cryogenics, ii) TPC and High Voltage, iii) Electronics, Data Acquisition and Triggering, iv) Scintillation Light Detection, v) Calibration and Test Beams, and vi) Software. This document summarizes the currentmore » efforts in each of these areas. It primarily focuses on the work in the US, but also highlights work done elsewhere in the world.« less

  17. Summary of the Second Workshop on Liquid Argon Time Projection Chamber Research and Development in the United States

    SciTech Connect

    Acciarri, R.; Adamowski, M.; Artrip, D.; Baller, B.; Bromberg, C.; Cavanna, F.; B. Carls; Chen, H.; Deptuch, G.; Epprecht, L.; Dharmapalan, R.; Foreman, W.; Hahn, A.; Johnson, M.; Jones, B. J.P.; Junk, T.; Lang, K.; Lockwitz, S.; Marchionni, A.; Mauger, C.; Montanari, C.; Mufson, S.; Nessi, M.; Back, H. Olling; Petrillo, G.; Pordes, S.; Raaf, J.; Rebel, B.; Sinins, G.; Soderberg, M.; Spooner, N.; Stancari, M.; Strauss, T.; Terao, K.; Thorn, C.; Tope, T.; Toups, M.; Urheim, J.; Water, R. Van de; Wang, H.; Wasserman, R.; Weber, M.; Whittington, D.; Yang, T.

    2015-07-28

    The second workshop to discuss the development of liquid argon time projection chambers (LArTPCs) in the United States was held at Fermilab on July 8-9, 2014. The workshop was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that was initiated by the American Physical Society Division of Particles and Fields. All presentations at the workshop were made in six topical plenary sessions: i) Argon Purity and Cryogenics, ii) TPC and High Voltage, iii) Electronics, Data Acquisition and Triggering, iv) Scintillation Light Detection, v) Calibration and Test Beams, and vi) Software. This document summarizes the current efforts in each of these areas. It primarily focuses on the work in the US, but also highlights work done elsewhere in the world.

  18. Effects of argon gas flow rate on laser-welding.

    PubMed

    Takayama, Yasuko; Nomoto, Rie; Nakajima, Hiroyuki; Ohkubo, Chikahiro

    2012-01-01

    The purpose of this study was to evaluate the effects of the rate of argon gas flow on joint strength in the laser-welding of cast metal plates and to measure the porosity. Two cast plates (Ti and Co-Cr alloy) of the same metal were abutted and welded together. The rates of argon gas flow were 0, 5 and 10 L/min for the Co-Cr alloy, and 5 and 10 L/min for the Ti. There was a significant difference in the ratio of porosity according to the rate of argon gas flow in the welded area. Argon shielding had no significant effect on the tensile strength of Co-Cr alloy. The 5 L/min specimens showed greater tensile strength than the 10 L/min specimens for Ti. Laser welding of the Co-Cr alloy was influenced very little by argon shielding. When the rate of argon gas flow was high, joint strength decreased for Ti.

  19. Study of argon flowing afterglow with nitrogen injection

    SciTech Connect

    Mazánková, V.; Krčma, F.; Trunec, D.

    2013-10-28

    In this work, the reaction kinetics in argon flowing afterglow with nitrogen addition was studied by optical emission spectroscopy. The DC flowing post-discharge in pure argon was created in quartz tube at the total gas pressure of 1000 Pa and discharge power of 60 W. The nitrogen was added into the afterglow at the distance of 9 cm behind the active discharge. The optical emission spectra were measured along the flow tube. The argon spectral lines and after nitrogen addition also nitrogen second positive system (SPS) were identified in the spectra. The measurement of spatial dependence of SPS intensity showed a very slow decay of the intensity and the decay rate did not depend on the nitrogen concentration. In order to explain this behavior a kinetic model for reaction in afterglow was developed. This model showed that C {sup 3}Π{sub u} state of molecular nitrogen, which is the upper state of SPS emission, is produced by excitation transfer from argon metastables to nitrogen molecules. However, the argon metastables are also produced at Ar{sub 2}{sup +} ion recombination with electrons and this limits the decay of argon metastable concentration and it results in very slow decay of SPS intensity.

  20. Communication: Trapping a proton in argon: Spectroscopy and theory of the proton-bound argon dimer and its solvation

    NASA Astrophysics Data System (ADS)

    McDonald, D. C.; Mauney, D. T.; Leicht, D.; Marks, J. H.; Tan, J. A.; Kuo, J.-L.; Duncan, M. A.

    2016-12-01

    Ion-molecule complexes of the form H+Arn are produced in pulsed-discharge supersonic expansions containing hydrogen and argon. These ions are analyzed and mass-selected in a reflectron spectrometer and studied with infrared laser photodissociation spectroscopy. Infrared spectra for the n = 3-7 complexes are characterized by a series of strong bands in the 900-2200 cm-1 region. Computational studies at the MP2/aug-cc-pVTZ level examine the structures, binding energies, and infrared spectra for these systems. The core ion responsible for the infrared bands is the proton-bound argon dimer, Ar-H+-Ar, which is progressively solvated by the excess argon. Anharmonic vibrational theory is able to reproduce the vibrational structure, identifying it as arising from the asymmetric proton stretch in combination with multiple quanta of the symmetric argon stretch. Successive addition of argon shifts the proton vibration to lower frequencies, as the charge is delocalized over more ligands. The Ar-H+-Ar core ion has a first solvation sphere of five argons.

  1. Behavior of Excited Argon Atoms in Inductively Driven Plasmas

    SciTech Connect

    HEBNER,GREGORY A.; MILLER,PAUL A.

    1999-12-07

    Laser induced fluorescence has been used to measure the spatial distribution of the two lowest energy argon excited states, 1s{sub 5} and 1s{sub 4}, in inductively driven plasmas containing argon, chlorine and boron trichloride. The behavior of the two energy levels with plasma conditions was significantly different, probably because the 1s{sub 5} level is metastable and the 1s{sub 4} level is radiatively coupled to the ground state but is radiation trapped. The argon data is compared with a global model to identify the relative importance of processes such as electron collisional mixing and radiation trapping. The trends in the data suggest that both processes play a major role in determining the excited state density. At lower rfpower and pressure, excited state spatial distributions in pure argon were peaked in the center of the discharge, with an approximately Gaussian profile. However, for the highest rfpowers and pressures investigated, the spatial distributions tended to flatten in the center of the discharge while the density at the edge of the discharge was unaffected. The spatially resolved excited state density measurements were combined with previous line integrated measurements in the same discharge geometry to derive spatially resolved, absolute densities of the 1s{sub 5} and 1s{sub 4} argon excited states and gas temperature spatial distributions. Fluorescence lifetime was a strong fi.mction of the rf power, pressure, argon fraction and spatial location. Increasing the power or pressure resulted in a factor of two decrease in the fluorescence lifetime while adding Cl{sub 2} or BCl{sub 3} increased the fluorescence lifetime. Excited state quenching rates are derived from the data. When Cl{sub 2} or BCl{sub 3} was added to the plasma, the maximum argon metastable density depended on the gas and ratio. When chlorine was added to the argon plasma, the spatial density profiles were independent of chlorine fraction. While it is energetically possible for

  2. Beam-beam simulations for separated beams

    SciTech Connect

    Furman, Miguel A.

    2000-04-10

    We present beam-beam simulation results from a strong-strong gaussian code for separated beams for the LHC and RHIC. The frequency spectrum produced by the beam-beam collisions is readily obtained and offers a good opportunity for experimental comparisons. Although our results for the emittance blowup are preliminary, we conclude that, for nominal parameter values, there is no significant difference between separated beams and center-on-center collisions.

  3. In vitro effects of argon laser radiation on blood: quantitative and morphologic analysis

    SciTech Connect

    Abela, G.S.; Crea, F.; Smith, W.; Pepine, C.J.; Conti, C.R.

    1985-02-01

    Use of the argon laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 84 samples of citrated whole blood were exposed to argon laser radiation with varying power (1, 2 and 3 watts) and duration (5, 10, 20 and 40 seconds). Compared with control samples, only blood samples exposed to a power of 3 watts for 40 seconds showed a marked decrease in hematocrit (from 37 +/- 1.3 to 33 +/- 1.4%, p less than 0.01) and a marked increase in both free hemoglobin concentration (from 0.2 +/- 0.2 to 1.3 +/- 0.5 g/100 ml, p less than 0.01) and debris weight (from 0.9 +/- 0.3 to 2.8 +/- 0.5 mg, p less than 0.01). Scanning electron microscopy of debris from samples of whole blood, washed erythrocytes and platelet-rich plasma lased at 3 watts for 40 seconds documented the presence of membrane denaturation of blood elements, resulting in their fusion to form complex mesh-like conglomerates. Similar morphologic changes were observed in whole blood samples exposed to a ''hot tip'' rather than laser radiation. These data indicate that: 1) argon laser radiation with a power of 3 watts does not produce apparent hemolysis or debris formation for exposure periods up to 20 seconds, and 2) the effects of laser radiation on blood are probably mediated by thermal denaturation of cell membranes, as suggested by the same morphologic changes produced by thermal injury from a ''hot tip.''

  4. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    SciTech Connect

    Jones, K. L.; Ahn, S.; Allmond, J. M.; Ayres, A.; Bardayan, D. W.; Baugher, T.; Bazin, D.; Berryman, J. S.; Bey, A.; Bingham, C.; Cartegni, L.; Cerizza, G.; Chae, K. Y.; Cizewski, J. A.; Gade, A.; Galindo-Uribarri, A.; Garcia-Ruiz, R. F.; Grzywacz, R.; Howard, M. E.; Kozub, R. L.; Liang, J. F.; Manning, B.; Matoš, M.; McDaniel, S.; Miller, D.; Nesaraja, C. D.; O'Malley, P. D.; Padgett, S.; Padilla-Rodal, E.; Pain, S. D.; Pittman, S. T.; Radford, D. C.; Ratkiewicz, A.; Schmitt, K. T.; Shore, A.; Smith, M. S.; Stracener, D. W.; Stroberg, S. R.; Tostevin, J.; Varner, R. L.; Weisshaar, D.; Wimmer, K.; Winkler, R.

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, N = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.

  5. Recent Direct Reaction Experimental Studies with Radioactive Tin Beams

    DOE PAGES

    Jones, K. L.; Ahn, S.; Allmond, J. M.; ...

    2015-01-01

    Direct reaction techniques are powerful tools to study the single-particle nature of nuclei. Performing direct reactions on short-lived nuclei requires radioactive ion beams produced either via fragmentation or the Isotope Separation OnLine (ISOL) method. Some of the most interesting regions to study with direct reactions are close to the magic numbers where changes in shell structure can be tracked. These changes can impact the final abundances of explosive nucleosynthesis. The structure of the chain of tin isotopes is strongly influenced by the Z = 50 proton shell closure, as well as the neutron shell closures lying in the neutron-rich, Nmore » = 82, and neutron-deficient, N = 50, regions. Here, we present two examples of direct reactions on exotic tin isotopes. The first uses a one-neutron transfer reaction and a low-energy reaccelerated ISOL beam to study states in Sn-131 from across the N = 82 shell closure. The second example utilizes a one-neutron knockout reaction on fragmentation beams of neutron-deficient Sn-106,108Sn. In conclusion, In both cases, measurements of γ rays in coincidence with charged particles proved to be invaluable.« less

  6. Argon Spill Trough Bellows - Leak Test

    SciTech Connect

    Jaques, A.; /Fermilab

    1990-04-30

    The four argon spill trough bellows were leak tested with helium during the week of March 12, 1990. Three passed without incident, but the fourth was found to have a leak in the weld at one of the ring/clamps. The hole was approximately 1/32-inch in diameter (a likely result of a welding burn through) and located on an inflexible portion of the bellows, the ring/clamp. Frank Juravic, who conducted the tests, suggested using grey structural epoxy to plug the leak. The epoxy is metallic with some inherent flexibility. The epoxy was applied and the bellows retested in the same manner as before. The repair was a success as the bellows proved to be leaktight. The bellows were then put in their original shipping crates and placed in storage at Lab C. Included in this report is the manufacturer's spec sheets on the bellows, a copy of the Quality Control Report form and a sketch of the test setup with an explanation of the procedure. On the bellows data sheet entitled 'Analysis of Stress in Bellows', the analysis output is obtained through a theoretical bellows program that uses quadratic equations to approximate characteristic curves for such data as axial, lateral and angular movement and spring rates. The program is best suited for bellows with a wall thickness of at least 0.015-inch and an operating pressure significantly above atmospheric. Thus EJS Inc. warned that the output data would not be very accurate in some instances. The data given on the EJS Inc. sketch sheet should be taken as accurate, though, for it was taken from the actual bellows delivered. The 72-inch length includes the 64.64-inch of bellows section, the (3) 1/2-inch ring/clamps and the (2) 1-1/2-inch end bands. The remainder of the discrepancy is accounted for by a 2.75-inch factory elongation of the bellows from the original free length. The 40-inch compression capability includes the 2.75-inch of factory elongation, the program determined 31.9-inch of compression from free length and 5.35-inch of

  7. The Molecular Pathway of Argon-Mediated Neuroprotection

    PubMed Central

    Ulbrich, Felix; Goebel, Ulrich

    2016-01-01

    The noble gas argon has attracted increasing attention in recent years, especially because of its neuroprotective properties. In a variety of models, ranging from oxygen-glucose deprivation in cell culture to complex models of mid-cerebral artery occlusion, subarachnoid hemorrhage or retinal ischemia-reperfusion injury in animals, argon administration after individual injury demonstrated favorable effects, particularly increased cell survival and even improved neuronal function. As an inert molecule, argon did not show signs of adverse effects in the in vitro and in vivo model used, while being comparably cheap and easy to apply. However, the molecular mechanism by which argon is able to exert its protective and beneficial characteristics remains unclear. Although there are many pieces missing to complete the signaling pathway throughout the cell, it is the aim of this review to summarize the known parts of the molecular pathways and to combine them to provide a clear insight into the cellular pathway, starting with the receptors that may be involved in mediating argons effects and ending with the translational response. PMID:27809248

  8. Characteristics of Knock in Hydrogen-Oxygen-Argon SI Engine

    SciTech Connect

    Killingsworth, N; Rapp, V; Flowers, D; Aceves, S; Chen, J; Dibble, R

    2010-02-23

    A promising approach for improving the efficiency of internal combustion engines is to employ a working fluid with a high specific heat ratio such as the noble gas argon. Moreover, all harmful emissions are eliminated when the intake charge is composed of oxygen, nonreactive argon, and hydrogen fuel. Previous research demonstrated indicated thermal efficiencies greater than 45% at 5.5 compression ratio in engines operating with hydrogen, oxygen, and argon. However, knock limits spark advance and increasing the efficiency further. Conditions under which knock occurs in such engines differs from typical gasoline fueled engines. In-cylinder temperatures using hydrogen-oxygen-argon are higher due to the high specific heat ratio and pressures are lower because of the low compression ratio. Better understanding of knock under these conditions can lead to operating strategies that inhibit knock and allow operation closer to the knock limit. In this work we compare knock with a hydrogen, oxygen, and argon mixture to that of air-gasoline mixtures in a variable compression ratio cooperative fuels research (CFR) engine. The focus is on stability of knocking phenomena, as well as, amplitude and frequency of the resulting pressure waves.

  9. The Molecular Pathway of Argon-Mediated Neuroprotection.

    PubMed

    Ulbrich, Felix; Goebel, Ulrich

    2016-10-31

    The noble gas argon has attracted increasing attention in recent years, especially because of its neuroprotective properties. In a variety of models, ranging from oxygen-glucose deprivation in cell culture to complex models of mid-cerebral artery occlusion, subarachnoid hemorrhage or retinal ischemia-reperfusion injury in animals, argon administration after individual injury demonstrated favorable effects, particularly increased cell survival and even improved neuronal function. As an inert molecule, argon did not show signs of adverse effects in the in vitro and in vivo model used, while being comparably cheap and easy to apply. However, the molecular mechanism by which argon is able to exert its protective and beneficial characteristics remains unclear. Although there are many pieces missing to complete the signaling pathway throughout the cell, it is the aim of this review to summarize the known parts of the molecular pathways and to combine them to provide a clear insight into the cellular pathway, starting with the receptors that may be involved in mediating argons effects and ending with the translational response.

  10. Determination of etching characteristics of a vacuum generators AG21 argon-ion gun by interference colour and ellipsometric assessment of craters etched in tantalum oxide films

    NASA Astrophysics Data System (ADS)

    Treverton, J. A.; Rosenfeld, A.

    1990-11-01

    Interference-coloured tantalum oxide films were used in a qualitative and quantitative assessment of crater shapes formed by a Vacuum Generators AG21 argon-ion gun. Changes in interference colours, as a result of argon etching, clearly showed the elliptical shape of the craters formed and, under suitable circumstances, the elliptical contours of constant thickness around the crater walls. Quantitative assessment by scanning ellipsometry established that craters have approximately Gaussian cross-sections. However, in certain areas of the crater the cross-section is modified as a result of the influence of a small diameter beam of neutrals atom within the ion beam. Deviations from the Gaussian cross-sections also occur after prolonged etching.

  11. Argon-40: excess in submarine pillow basalts from kilauea volcano, hawaii.

    PubMed

    Dalrymple, G B; Moore, J G

    1968-09-13

    Submarine pillow basalts from Kilauea Volcano contain excess radiogenic argon-40 and give anomalously high potassium-argon ages. Glassy rims of pillows show a systematic increase in radiogenic argon-40 with depth, and a pillow from a depth of 2590 meters shows a decrease in radiogenic argon40 inward from the pillow rim. The data indicate that the amount of excess radiogenic argon-40 is a direct function of both hydrostatic pressure and rate of cooling, and that many submarine basalts are not suitable for potassium-argon dating.

  12. First measurement of neutrino and antineutrino coherent charged pion production on argon

    SciTech Connect

    Acciarri, R.; Adams, C.; Asaadi, J.; Baller, B.; Bolton, T.; Bromberg, C.; Cavanna, F.; Church, E.; Edmunds, D.; Ereditato, A.; Farooq, S.; Fleming, B.; Greenlee, H.; Hatcher, R.; Horton-Smith, G.; James, C.; Klein, E.; Lang, K.; Laurens, P.; Mehdiyev, R.; Page, B.; Palamara, O.; Partyka, K.; Rameika, G.; Rebel, B.; Santos, E.; Schukraft, A.; Soderberg, M.; Spitz, J.; Szelc, A.  M.; Weber, M.; Yang, T.; Zeller, G. P.

    2014-12-23

    We report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be 2.6 +1.2-1.0 (stat)+0.3-0.4(syst) × 10⁻³⁸cm² / Ar for neutrinos at a mean energy of 9.6 GeV and 5.5+2.6-2.1(stat)+0.6-0.7(syst) × 10⁻³⁹ cm² / Ar for antineutrinos at a mean energy of 3.6 GeV.

  13. First measurement of neutrino and antineutrino coherent charged pion production on argon

    DOE PAGES

    Acciarri, R.; Adams, C.; Asaadi, J.; ...

    2014-12-23

    We report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be 2.6 +1.2-1.0 (stat)+0.3-0.4(syst) × 10⁻³⁸cm² / Ar for neutrinos at a mean energy of 9.6 GeV and 5.5+2.6-2.1(stat)+0.6-0.7(syst) × 10⁻³⁹ cm² / Ar for antineutrinos at a mean energy of 3.6 GeV.

  14. Grafting of acrylic acid onto polypropylene films irradiated with argon ions

    NASA Astrophysics Data System (ADS)

    Massa, G.; Mazzei, R.; García Bermúdez, G.; Filevich, A.; Smolko, E.

    2005-07-01

    Polypropylene (PP) foils were irradiated with 100 keV energy Argon ions at different fluences ranging from 1012 up to 2 × 1015 cm-2 and then grafted with acrylic acid (AA). The grafting yield was measured by weight difference and the structural changes on the films were analysed using Fourier transform infrared spectroscopy (FTIR). Different parameters that determined the grafting process such us fluence, grafting time and monomer concentration were analysed. The grafting reached an optimum value at 79% in aqueous solution at 30 min grafting time. The grafting yield as a function of the ion fluence plot, presented a maximum value, as previously found in a study of heavy beam on polymers.

  15. Spatially Resolved Measurements of a Double Layer in an Argon Helicon Plasma

    NASA Astrophysics Data System (ADS)

    Aguirre, Evan; Siddiqui, Umair; McKee, John; Scime, Earl

    2015-11-01

    We report 2-dimensional, spatially resolved observations of a double layer in an expanding helicon plasma. These new measurements investigate the origins of previously observed multiple ion beam populations in the downstream plasma. We use Laser Induced Fluorescence (LIF) to measure the ion velocity distribution functions (IVDFs) of argon ions and neutrals both parallel and perpendicular to the background magnetic field and an rf-compensated Langmuir probe to determine the local plasma potential. These are the first multi-dimensional LIF measurements of ion acceleration in a current-free double layer and were obtained with a recently installed, internal scanning probe system in the HELIX-LEIA experimental facility. This work is supported by US National Science Foundation grant number PHY-1360278.

  16. Experimental Investigation of Laser-sustained Plasma in Supersonic Argon Flow

    SciTech Connect

    Sperber, David; Eckel, Hans-Albert; Moessinger, Peter; Fasoulas, Stefanos

    2011-11-10

    Laser-induced energy deposition is widely discussed as a flow control technique in supersonic transportation. In case of thermal laser-plasma upstream of a blunt body, a substantial adaptation of shock wave geometry and magnitude of wave drag is predicted. Related to the research on laser supported detonation, the paper describes the implementation of laser-sustained plasma in a supersonic Argon jet. The stable plasma state is generated by the intersection of a Q-switched Nd:YAG-laser and a continuous wave CO{sub 2}-laser beams, for ignition and maintenance of the plasma respectively. A miniature supersonic Ludwieg tube test facility generates a supersonic jet at velocities of Mach 2.1. Modifications of the flow and plasma conditions are investigated and characterized by Schlieren flow visualisation, laser energy transmission and plasma radiation measurements. The results include the discussions of the flow field as well as the required laser and gas parameters.

  17. Collisionless “thermalization” in the sheath of an argon discharge

    SciTech Connect

    Coulette, David Manfredi, Giovanni

    2015-04-15

    We performed kinetic Vlasov simulations of the plasma-wall transition for a low-pressure argon discharge without external magnetic fields, using the same plasma parameters as in the experiments of Claire et al. [Phys. Plasmas 13, 062103 (2006)]. Experimentally, it was found that the ion velocity distribution function is highly asymmetric in the presheath, but, surprisingly, becomes again close to Maxwellian inside the sheath. Here, we show that this “thermalization” can be explained by purely collisionless effects that are akin to the velocity bunching phenomenon observed in charged particles beams. Such collisionless thermalization is also observed in the presheath region close to the sheath entrance, although it is much weaker there and in practice probably swamped by collisional processes (standard or enhanced by instabilities)

  18. First measurement of neutrino and antineutrino coherent charged pion production on argon

    DOE PAGES

    Acciarri, R.

    2015-01-20

    In this study, we report on the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The cross sections are measured to be 2.6 +1.2-1.0 (stat)+0.3-0.4(syst) x 10-38 cm2/Ar for neutrinos at a mean energy of 9.6 GeV and 5.5+2.6-2.1(stat)+0.6-0.7(syst) x 10-39 cm2/Ar for antineutrinos at a mean energy of 3.6 GeV.

  19. Inelastic scattering of hydroxyl radicals with helium and argon by velocity-map imaging.

    PubMed

    Sarma, Gautam; Marinakis, Sarantos; ter Meulen, J J; Parker, David H; McKendrick, Kenneth G

    2012-12-01

    The hydroxyl radical (OH) is one of the most interesting molecules in molecular dynamics. In particular, inelastic collisions of free radicals such as OH are profoundly important in environments ranging from combustion to astrochemistry. However, measuring the velocities of OH molecules in specific internal quantum states has proven to be very difficult. A method that can provide this important information is velocity-map imaging. Although this technique is very widely applicable in principle, it does require a sensitive and selective laser-ionization scheme. Here we show that, under the right conditions, velocity-map imaging can be applied to the study of the inelastic scattering of OH using crossed-molecular-beam methods. We measure fully quantum-state-specified product angular distributions for OH collisions with helium and argon. The agreement between exact close-coupling quantum scattering calculations on ab initio potential energy surfaces and experimental data is generally very satisfactory, except for scattering in the most forward directions.

  20. Expansion of the radioactive ion beam program at Argonne

    NASA Astrophysics Data System (ADS)

    Clark, J. A.

    2011-01-01

    The Argonne Tandem Linear Accelerator System (ATLAS) at Argonne National Laboratory (ANL) provides a wide range of stable ion beams and radioactive beams which have contributed to our understanding of nuclear structure and reactions. Until now, most radioactive ion beams at ATLAS were produced in flight using light-ion reactions such as (p, n), (d, n), (d, p), (d,3He), and (3He,n). Within the next few months, the radioactive ion beam program at ATLAS will acquire much extended, new capabilities with the commissioning of a new facility: the CAlifornium Rare Isotope Breeder Upgrade (CARIBU). CARIBU will supply ion beams of 252Cf fission fragments, which are thermalized in a gas catcher. The singly- and doubly-charged ions extracted from the gas catcher will be mass-separated and either delivered to a low-energy experimental area, or charge bred with a modified ECR source and subsequently reaccelerated by the ATLAS facility. Properties of hundreds of these neutron-rich nuclides will be investigated using ion traps, decay stations, the newly commissioned HELical Orbit Spectrometer (HELIOS), and other available experimental equipment such as Gammasphere and the FMA. HELIOS was constructed to take advantage of rare ion beams, such as those provided by CARIBU, through light-ion transfer reactions in inverse kinematics, and represents a new approach to the study of direct reactions in inverse kinematics which avoids kinematic broadening. Experiments are currently being conducted with HELIOS, and first results with the d(28Si,p) and d(12B,p) reactions have shown excellent energy resolution.

  1. Experimental study of the dynamics of a ruby laser pumped by a CW argon-ion laser

    NASA Technical Reports Server (NTRS)

    Afzal, R. S.; Lin, W. P.; Lawandy, N. M.

    1989-01-01

    A study of the dynamics of a ruby laser pumped by a CW argon-ion laser is presented. The ruby laser is predominantly stable but has two accessible unstable states. One state exhibits chaotic output, while the other results in regular self-pulsing. The conditions needed for instability are discussed and homodyne spectra and temporal maps of the phase-space attractors are obtained. In addition, a numerical simulation of nonlinear beam propagation in ruby is presented that shows that strong deviations from plane-wave behavior exist, and that transverse effects must be incorporated into theoretical models of the instability.

  2. Electron excited multiply charged argon ions studied by means of an energy resolved electron-ion coincidence technique

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Prajapati, Suman; Singh, Bhupendra; Singh, Bhartendu Kumar; Shanker, Rama

    2017-03-01

    Multiply charged argon ions produced from decay of L-shell hole states by impact of a continuous beam of 3.5 keV electrons are studied for the first time using an energy resolved electron-ion coincidence technique. The TOF spectra of argon ions are measured in coincidence with 18-energy selected electrons emitted in a wide energy range (126-242 eV). The coincidence measurement between the energy selected electrons and the correlated ions specifies the individual decay channel for various multiply charged ions. New experimental data are obtained and reported on the correlation probability for production of argon ions with charge states 1+ to 4+ as a function of ejected electrons in the considered energy range. The relative correlation probability of producing different charge state ions and corresponding physical processes involved in their production are presented and discussed. It has been found that the maximum probability for production of Ar2+ ions correlated to ejected Auger electrons in the energy range of 205-209 eV is 100%. No theoretical predictions are available to compare with these results. The present study shows further that not only the auto-ionization and normal Auger transitions but also several other decay processes including Coster-Kronig transitions followed by Auger cascades with a fraction of shake process play important role in producing ions with charge states 1+ to 4+.

  3. Early Clinical Experience With Argon Ion Laser Endarterectomy

    NASA Astrophysics Data System (ADS)

    Eugene, John; Baribeau, Yvon; Ott, Richard A.; McColgan, Stephen J.; Berns, Michael W.

    1989-09-01

    This report describes our progress in the development of argon ion laser endarterectomy for arteriosclerotic cardiovascular disease. Nine patients underwent 10 vascular reconstructions for claudication (6), rest pain (1), and gangrene (2). There was 1 aortoiliac endarterectomy, 6 superficial femoral artery endarterectomies, 1 profunda femoris endarterectomy and 2 popliteal endarterectomies. The reconstructions were 6 cm to 60 cm in length. The operations were performed using low power argon ion laser radiation, 1.0 W. All patients experienced symptomatic relief and had palpable pulses postoperatively. There were no perforations and there were no injuries to surrounding tissues from laser radiation. Surgical complications occurred and these were technical problems that should be eliminated from the operation with further developments. The early clinical results show that laser endarterectomy can be performed for peripheral vascular reconstruction using low power argon ion laser radiation.

  4. The DarkSide-50 liquid argon dark matter search

    NASA Astrophysics Data System (ADS)

    Johnson, Tessa; DarkSide-50 Collaboration

    2017-01-01

    The DarkSide-50 experiment uses three nested detectors to directly search for WIMP dark matter, with the innermost detector a time projection chamber filled with a target of liquid argon (LAr). The unique difference in pulse shape between electron recoils and nuclear recoils in LAr allows for exceptional discrimination of beta and gamma backgrounds. Event discrimination due to pulse shape coupled with the neutron discrimination power of the outer detectors is used to create a background-free environment for the DarkSide-50 WIMP search. Atmospheric argon, including the radioactive 39Ar isotope, was first used to search for WIMPs in a 50-day campaign, and later a search with 70.9 days of livetime was performed with argon extracted from underground wells, reducing the 39Ar isotope by a factor of 1 . 4 ×103 . The status of the experiment will be discussed.

  5. Equation of state of partially ionized argon plasma

    SciTech Connect

    Chen, Q. F.; Zheng, J.; Gu, Y. J.; Chen, Y. L.; Cai, L. C.

    2011-11-15

    The ionization degree, Hugoniots, and equation of state of partially ionized argon plasma were calculated by using self-consistent fluid variational theory for temperature of 6-50 kK and density of 0.05-4.0 g/cm{sup 3}. The corrections of lowering of ionization energy of fluid argon caused by the interactions among all particles of Ar, Ar{sup +}, Ar{sup 2+}, and e have been taken into consideration in terms of the correlation contributions to the chemical potential which is determined self-consistently by the free energy function. The initial density effects of gas argon under shock compression have been discussed. Comparison is performed with available shock-wave experiments and other theoretical calculations.

  6. Summary of potassium/argon dating, 1981. Topical report

    SciTech Connect

    Evans, S.H. Jr.; Brown, F.H.

    1981-09-01

    The analytical results for the last fiscal year effort in potassium/argon dating in support of US Department of Energy programs are summarized. Nearly 100 new dates have been generated. Recalibration of the argon extraction tables resulted in refinement of values for tracer ratios and depletion constants for our two extraction lines. Tracer ratios are ({sup 36}Ar/{sup 38}Ar){sub T} = 0.0308 and 0.0000449; ({sup 40}Ar/{sup 38}Ar){sub T} = 0.0501 and 0.0014 for extraction tables 1 and 2, respectively. Tracer depletion constants are -0.0002250 and -0.0005501 for tables 1 and 2, respectively. Initial values for the argon tracer pipettes are 3.2522 x 10{sup -11} moles and 3.9329 x 10{sup -11} moles for tables 1 and 2, respectively.

  7. On the electric breakdown in liquid argon at centimeter scale

    NASA Astrophysics Data System (ADS)

    Auger, M.; Blatter, A.; Ereditato, A.; Goeldi, D.; Janos, S.; Kreslo, I.; Luethi, M.; von Rohr, C. Rudolf; Strauss, T.; Weber, M. S.

    2016-03-01

    We present a study on the dependence of electric breakdown discharge properties on electrode geometry and the breakdown field in liquid argon near its boiling point. The measurements were performed with a spherical cathode and a planar anode at distances ranging from 0.1 mm to 10.0 mm. A detailed study of the time evolution of the breakdown volt-ampere characteristics was performed for the first time. It revealed a slow streamer development phase in the discharge. The results of a spectroscopic study of the visible light emission of the breakdowns complement the measurements. The light emission from the initial phase of the discharge is attributed to electro-luminescence of liquid argon following a current of drifting electrons. These results contribute to set benchmarks for breakdown-safe design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

  8. Microwave Spectrum and Molecular Structure of the ARGON-(E)-1-CHLORO-1,2-DIFLUOROETHYLENE Complex

    NASA Astrophysics Data System (ADS)

    Marshall, Mark D.; Leung, Helen O.; Tandon, Hannah K.; Messinger, Joseph P.; Mlaver, Eli

    2014-06-01

    Previous studies of argon complexes with fluoroethylenes have revealed a preference for a geometry that maximizes the contact of the argon atom with heavy atoms on the fluoroethylene. We have observed a continuation of this trend when one of the fluorine atoms is replaced by chlorine. The argon-(E)-1-chloro-1,2-difluoroethylene complex provides two competing heavy atom cavities, FCCF and FCCl, and the opportunity to examine whether the number of heavy atoms or the associated increase in polarizability is determinative of structure. The 5.6 -- 18.1 GHz chirped-pulse Fourier transform microwave spectrum of this species provides initial assignments and predictions for spectra obtained in a more sensitive and higher precision Balle-Flygare instrument. Transitions for both the 35Cl and 37Cl isotopologues are observed and analyzed to provide geometric parameters for this non-planar complex. The spectrum is consistent with the argon atom located in the FCCl cavity, and the structure agrees well with ab initio predictions. Comparisons are made with Ar-1-chloro-1-fluoroethylene, (Z)-1-chloro-2-fluoroethylene, and Ar-vinyl chloride. Z. Kisiel, P.W. Fowler, and A.C. Legon, J. Chem. Phys. 95, 2283 (1991).

  9. Argon-pumped tunable dye laser therapy for facial port-wine stain hemangiomas in adults--a new technique using small spot size and minimal power

    SciTech Connect

    Scheibner, A.; Wheeland, R.G.

    1989-03-01

    A low power, argon-pumped tunable dye laser was used to deliver yellow light of 577 nm. Individual blood vessels within port-wine stain hemangiomas were treated with a 0.1-mm beam of light using 8 X magnification. This technique permits excellent resolution of facial and nuchal port-wine stain hemangiomas in adults without the adverse complications of textural change, permanent pigmentation abnormality, or hypertrophic scarring.

  10. Properties of radio-frequency heated argon confined uranium plasmas

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

  11. Study on electron beam in a low energy plasma focus

    SciTech Connect

    Khan, Muhammad Zubair; Ling, Yap Seong; San, Wong Chiow

    2014-03-05

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  12. Experimental Studies of Ion Beam Neutralization: Preliminary Results

    SciTech Connect

    Ding, N.; Polansky, J.; Downey, R.; Wang, J.

    2011-05-20

    A testing platform is designed to study ion beam neutralization in the mesothermal, collisionless region. In the experimental setup, argon neutrals were ionized in a microwave cavity and accelerated by a plasma lens system which was biased to 2500 V above the system ground. Electrons were boiled off from two hot tungsten filaments to neutralize the ion beam. The plasma is diagnosed using Langmuir probe and Faraday probe. A 3-D traversing system and a complete data acquisition loop were developed to efficiently measure 3-D beam profile. Preliminary measurements of beam profiles are presented for different operating conditions.

  13. High-spin nuclear structure studies with radioactive ion beams

    SciTech Connect

    Baktash, C.

    1992-12-31

    Two important developments in the sixties, namely the advent of heavy-ion accelerators and fabrication of Ge detectors, opened the way for the experimental studies of nuclear properties at high angular momentum. Addition of a new degree of freedom, namely spin, made it possible to observe such fascinating phenomena as occurrences and coexistence of a variety of novel shapes, rise, fall and occasionally rebirth of nuclear collectivity, and disappearance of pairing correlations. Today, with the promise of development of radioactive ion beams (RIB) and construction of the third-generation Ge-detection systems (GAMMASPHERE and EUROBALL), the authors are poised to explore new and equally fascinating phenomena that have been hitherto inaccessible. With the addition of yet another dimension, namely the isospin, they will be able to observe and verify predictions for exotic shapes as varied as rigid triaxiality, hyperdeformation and triaxial octupole shapes, or to investigate the T = 0 pairing correlations. In this paper, they shall review, separately for neutron-deficient and neutron-rich nuclei, these and a few other new high-spin physics opportunities that may be realized with RIB. Following this discussion, they shall present a list of the beam species, intensities and energies that are needed to fulfill these goals. The paper will conclude with a description of the experimental techniques and instrumentations that are required for these studies.

  14. The Dynamical Dipole Radiation in Dissipative Collisions with Exotic Beams

    NASA Astrophysics Data System (ADS)

    di Toro, M.; Colonna, M.; Rizzo, C.; Baran, V.

    Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium nuclear interaction in regions away from saturation. In this work we present a selection of reaction observables in dissipative collisions particularly sensitive to the isovector part of the interaction, i.e. to the symmetry term of the nuclear Equation of State (EoS). At low energies the behavior of the symmetry energy around saturation influences dissipation and fragment production mechanisms. We will first discuss the recently observed Dynamical Dipole Radiation, due to a collective neutron-proton oscillation during the charge equilibration in fusion and deep-inelastic collisions. We will review in detail all the main properties, yield, spectrum, damping and angular distributions, revealing important isospin effects. Reactions induced by unstable 132Sn beams appear to be very promising tools to test the sub-saturation Isovector EoS. Predictions are also presented for deep-inelastic and fragmentation collisions induced by neutron rich projectiles. The importance of studying violent collisions with radioactive beams at low and Fermi energies is finally stressed.

  15. Cartesian beams.

    PubMed

    Bandres, Miguel A; Gutiérrez-Vega, Julio C

    2007-12-01

    A new and very general beam solution of the paraxial wave equation in Cartesian coordinates is presented. We call such a field a Cartesian beam. The complex amplitude of the Cartesian beams is described by either the parabolic cylinder functions or the confluent hypergeometric functions, and the beams are characterized by three parameters that are complex in the most general situation. The propagation through complex ABCD optical systems and the conditions for square integration are studied in detail. Applying the general expression of the Cartesian beams, we also derive two new and meaningful beam structures that, to our knowledge, have not yet been reported in the literature. Special cases of the Cartesian beams are the standard, elegant, and generalized Hermite-Gauss beams, the cosine-Gauss beams, the Lorentz beams, and the fractional order beams.

  16. Cryogenic Tests of the ATLAS Liquid Argon Calorimeter

    NASA Astrophysics Data System (ADS)

    Bremer, J.; Chalifour, M.; Fabre, C.; Gonidec, A.; Passardi, G.

    2006-04-01

    The ATLAS liquid argon calorimeter consists of the barrel and two end-cap detectors housed in three independent cryostats filled with a total volume of 78 m3 of liquid argon. During cool-down the temperature differences in the composite structure of the detectors must be kept within strict limits to avoid excessive mechanical stresses and relative displacements. During normal operation the formation of gas bubbles, which are detrimental to the functioning of the detector, must be prevented and temperature gradients of less than 0.7 K across the argon bath are mandatory due to the temperature dependence of the energy measurements. Between April 2004 and May 2005 the barrel (120 t) and one end-cap (219 t) underwent qualification tests at the operating temperature of 87.3 K using a dedicated test facility at ground level. These tests provided a validation of the cooling methods to be adopted in the final underground configuration. In total 6.9 GJ and 15.7 GJ were extracted from the calorimeters and a temperature uniformity of the argon bath of less than 0.4 K was achieved.

  17. Pion Charge Exchange Cross Section on Liquid Argon

    NASA Astrophysics Data System (ADS)

    Nelson, Kevin; LArIAT (FNAL T-1034) Collaboration

    2017-01-01

    The observation of neutrino oscillations allows charge parity violation to be probed in the neutrino sector. Detectors with high calorimetric energy resolution and high spatial resolution will provide precise measurements of neutrino oscillations. By measuring small π+/- cross sections for individual interaction channels, specifically charge exchange, we will make a measurement in the first of its kind on liquid Argon and demonstrate the physics capabilities of a relatively new detector technology: the Liquid Argon Time Projection Chamber (LAr TPC). This analysis will report on the thin slab cross section measurement technique and the Monte Carlo cross section measurements in the energy range of 0.2 - 1.0 GeV. This analysis is the first iteration in classifying charge exchange events from a sample of incident pions, and it aims to identify events in which a π0 was produced without any charged pions leaving the interaction vertex. We will also report on the methodology and efficiency of this algorithm in identifying particles and their interactions in liquid argon. This analysis will inform a future measurement of the π+/- charge exchange cross section on liquid argon. This work was supported in part by the National Science Foundation under Grant No. PHY-1359364.

  18. Thermophysical properties of multi-shock compressed dense argon

    SciTech Connect

    Chen, Q. F. Zheng, J.; Gu, Y. J.; Chen, Y. L.; Cai, L. C.; Shen, Z. J.

    2014-02-21

    In contrast to the single shock compression state that can be obtained directly via experimental measurements, the multi-shock compression states, however, have to be calculated with the aid of theoretical models. In order to determine experimentally the multiple shock states, a diagnostic approach with the Doppler pins system (DPS) and the pyrometer was used to probe multiple shocks in dense argon plasmas. Plasma was generated by a shock reverberation technique. The shock was produced using the flyer plate impact accelerated up to ∼6.1 km/s by a two-stage light gas gun and introduced into the plenum argon gas sample, which was pre-compressed from the environmental pressure to about 20 MPa. The time-resolved optical radiation histories were determined using a multi-wavelength channel optical transience radiance pyrometer. Simultaneously, the particle velocity profiles of the LiF window was measured with multi-DPS. The states of multi-shock compression argon plasma were determined from the measured shock velocities combining the particle velocity profiles. We performed the experiments on dense argon plasmas to determine the principal Hugonoit up to 21 GPa, the re-shock pressure up to 73 GPa, and the maximum measure pressure of the fourth shock up to 158 GPa. The results are used to validate the existing self-consistent variational theory model in the partial ionization region and create new theoretical models.

  19. Supersonic Argon Flow In An Arc Plasma Source

    SciTech Connect

    Izrar, B.; Dudeck, M.; Andre, P.; Elchinger, M. F.; Aubreton, J.

    2006-01-15

    The plasma properties inside a D.C. arc-jet operating with argon is analysed by means of a continuum description taking into account non equilibrium ionization processes and dissipative effects. The relaxation of the different physical processes inside the nozzle and the evolution of the Mach number are aanalysed.

  20. Optical emission spectroscopy of argon and hydrogen-containing plasmas

    NASA Astrophysics Data System (ADS)

    Siepa, Sarah; Danko, Stephan; Tsankov, Tsanko V.; Mussenbrock, Thomas; Czarnetzki, Uwe

    2015-09-01

    Optical emission spectroscopy (OES) on neutral argon is applied to investigate argon, hydrogen and hydrogen-silane plasmas. The spectra are analyzed using an extensive collisional-radiative model (CRM), from which the electron density and the electron temperature (or mean energy) can be calculated. The CRM also yields insight into the importance of different excited species and kinetic processes. The OES measurements are performed on pure argon plasmas at intermediate pressure. Besides, hydrogen and hydrogen-silane plasmas are investigated using argon as a trace gas. Especially for the gas mixture discharges, CRMs for low and high pressure differ substantially. The commonly used line-ratio technique is found to lose its sensitivity for gas mixture discharges at higher pressure. A solution using absolutely calibrated line intensities is proposed. The effect of radiation trapping and the shape of the electron energy distribution function on the results are discussed in detail, as they have been found to significantly influence the results. This work was supported by the Ruhr University Research School PLUS, funded by Germany's Excellence Initiative [DFG GSC 98/3].

  1. Ion energy distribution functions of low energy beams formed by wire extraction electrodes

    SciTech Connect

    Tokumura, S.; Kasuya, T.; Vasquez, M. Jr.; Maeno, S.; Wada, M.

    2012-02-15

    The two-electrode extractor system made of 0.1 mm diameter tungsten wires separated by 0.7 mm has formed an argon ion beam with 50 V extraction potential. Energy spreads of the extracted beams were typically less than 2 eV when the beam current density was low. The beam intensity rapidly decreased as the distance between the extractor and the beam detector increased, indicating space charge limited transport of the beam. Problems associated with the emittance measurements are also discussed.

  2. Measuring the Fusion Cross-Section of 18,19 O + 12 C with Low-Intensity Beams at Energies Near and Below the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy; Vadas, Justin; Schmidt, Jon; Singh, Varinderjit; Hudan, Sylvie; Desouza, Romualdo; Baby, Lagy; Kuvin, Sean; Wiedenhover, Ingo; Umar, Sait; Oberacker, Volker

    2015-04-01

    Fusion of neutron-rich light nuclei has been proposed as a heat source that triggers an X-ray superburst in the crust of an accreting neutron star. To investigate this hypothesis the total fusion cross-section for beams of low-intensity, neutron-rich nuclei (<105 ions/s) on light targets has been measured at energies near and below the Coulomb barrier. Evaporation residues, resulting from the fusion of oxygen and 12 C nuclei, were identified by their energy and Time-of-flight. Using this technique, the fusion excitation function was measured in the sub-barrier domain down to the 2 mb level. Comparison of the measured fusion excitation function with the predictions of a density constrained TDHF model reveals that the experimental data exhibit a smaller decrease in cross-section with decreasing energy than is theoretically predicted. This difference can be interpreted as a larger tunneling probability for the experimental data as compared to the theoretical predictions. To determine if this difference increases in magnitude with decreasing incident energy improvements have been implemented to enable measurement of the fusion cross-section to an even lower level. Supported by the US DOE under Grand No. DEFG02-88ER-40404.

  3. Conversion of an atomic to a molecular argon ion and low pressure argon relaxation

    NASA Astrophysics Data System (ADS)

    M, N. Stankov; A, P. Jovanović; V, Lj Marković; S, N. Stamenković

    2016-01-01

    The dominant process in relaxation of DC glow discharge between two plane parallel electrodes in argon at pressure 200 Pa is analyzed by measuring the breakdown time delay and by analytical and numerical models. By using the approximate analytical model it is found that the relaxation in a range from 20 to 60 ms in afterglow is dominated by ions, produced by atomic-to-molecular conversion of Ar+ ions in the first several milliseconds after the cessation of the discharge. This conversion is confirmed by the presence of double-Gaussian distribution for the formative time delay, as well as conversion maxima in a set of memory curves measured in different conditions. Finally, the numerical one-dimensional (1D) model for determining the number densities of dominant particles in stationary DC glow discharge and two-dimensional (2D) model for the relaxation are used to confirm the previous assumptions and to determine the corresponding collision and transport coefficients of dominant species and processes. Project supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No. ON171025).

  4. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for...

  5. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for...

  6. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for...

  7. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for...

  8. 21 CFR 874.4490 - Argon laser for otology, rhinology, and laryngology.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Argon laser for otology, rhinology, and laryngology. 874.4490 Section 874.4490 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND... Argon laser for otology, rhinology, and laryngology. (a) Identification. The argon laser device for...

  9. Atmospheric argon contamination of ocean island basalt olivine phenocrysts

    NASA Astrophysics Data System (ADS)

    Parley, K. A.; Craig, H.

    1994-06-01

    40Ar/ 36Ar and helium and argon concentrations have been repeatedly measured on olivine phenocrysts in a single tholeiitic basalt (PIN-12) from the Juan Fernandez hotspot. Forty olivine splits were analyzed by crushing of bulk samples or laser fusion of single crystals. The measured 40Ar/ 36Ar ratios span a very large range (400-7700) and are consistent with binary mixing of two argon components. Unlike argon, helium in repeated measurements of this single basalt flow has a reproducible isotopic ratio, 17 times the air 3He/ 4He value. It is unlikely that such large variations in 40Ar/ 36Ar represent microscale mantle heterogeneity. Rather the results indicate highly variable mixing proportions of a mantle-derived radiogenic argon component ( 40Ar/ 36Ar ≫ 7700) and an isotopically air-like endmember that is almost certainly an atmospheric contaminant. This air-like constituent cannot be removed by physical and chemical treatments of the olivines. Analysis of individual crystals by laser fusion shows that both the radiogenic and the contaminant components are in fluid inclusions. Siting of the contaminant in inclusions requires the addition of airderived noble gases to hotspot magmas prior to or during emplacement, a process that may occur by assimilation of altered crust during crustal storage or, alternatively, by direct addition of air or seawater to the magma. In either case the olivines must continue to trap argon, presumably by fracture annealing and/or bubble enclosure, after the contaminating event. If atmospheric contamination is a general phenomenon, the 40Ar/ 36Ar composition of olivines (and possibly of basalt glasses as well) must be only a lower limit for the mantle source ratio. With the exception of helium, the other noble gases may be similarly compromised. Our results support contentions that lavas with near-atmospheric noble gas compositions reflect severe atmospheric contamination, rather than the air-like signature of an undegassed primitive

  10. Argon metastable dynamics and lifetimes in a direct current microdischarge

    SciTech Connect

    Stefanović, Ilija; Kuschel, Thomas; Schröter, Sandra; Böke, Marc

    2014-09-21

    In this paper we study the properties of a pulsed dc microdischarge with the continuous flow of argon. Argon metastable lifetimes are measured by tunable diode laser absorption spectroscopy (TDLAS) and are compared with calculated values which yield information about excitation and de-excitation processes. By increasing the gas flow-rate about 5 times from 10 to 50 sccm, the Ar{sup m} lifetime increases from 1 to 5 μs due to the reduction of metastable quenching with gas impurities. Optical emission spectroscopy reveals nitrogen and water molecules as the main gas impurities. The estimated N₂ density [N₂]=0.1% is too low to explain the measured metastable lifetimes. Water impurity was found to be the main de-excitation source of argon metastable atoms due to high quenching coefficients. The water impurity level of [H₂O]=0.15% to 1% is sufficient to bring calculated metastable lifetimes in line with experiments. The maximum value of water content in the discharge compared to the argon atoms is estimated to approximately 6%, due to the large surface to volume ratio of the microdischarge. The current pulse releases the water molecules from the electrode surface and they are either re-adsorbed in the time between 0.4 ms for [H₂O]=1% and 2.6 ms for [H₂O]=0.15% or pumped out of the discharge with the speed equal to the gas flow-rate. Depending on its partial pressure, the water impurity re-adsorption time is of the order of magnitude or less then the argon gas residence time.

  11. Development of a Silicon Carbide Molecular Beam Nozzle for Simulation Planetary Flybys and Low-Earth Orbit

    NASA Technical Reports Server (NTRS)

    Patrick, E. L.; Earle, G. D.; Kasprzak, W. T.; Mahaffy, Paul R.

    2008-01-01

    From commercial origins as a molybdenum molecular beam nozzle, a ceramic nozzle of silicon carbide (SiC) was developed for space environment simulation. The nozzle is mechanically stable under extreme conditions of temperature and pressure. A heated, continuous, supersonically-expanded hydrogen beam with a 1% argon seed produced an argon beam component of nearly 4 km/s, with an argon flux exceeding 1x1014 /cm2.s. This nozzle was part of a molecular beam machine used in the Atmospheric Experiments Branch at NASA Goddard Space Flight Center to characterize the performance of the University of Texas at Dallas Ram Wind Sensor (RWS) aboard the Air Force Communications/Navigation Outage Forecasting System (C/NOFS) launched in the Spring of 2008.

  12. Nuclear Structure Studies with Radioactive Ion Beams in the Mass A = 80 Region

    NASA Astrophysics Data System (ADS)

    Galindo-Uribarri, A.; Padilla-Rodal, E.; Batchelder, J. C.; Beene, J. R.; Lagergren, K. B.; Mueller, P. E.; Radford, D. C.; Stracener, D. W.; Urrego-Blanco, J. P.; Varner, R. L.; Yu, C.-H.

    2009-03-01

    An experimental program to measure spectroscopic properties of neutron-rich nuclei in the A = 80 region is underway at the Holifield Radioactive Ion Beam Facility. Our approach has been to get a comprehensive picture of the shell structure in this region by studying a series of properties of low lying states (E(2+), B(E2), g-factors and quadrupole moments). The beams, instrumentation and techniques developed specifically for this purpose have allowed us to systematically study the behavior of these observables along isotopic and isotonic chains using both stable and radioactive nuclei under almost identical experimental conditions. We have developed many techniques and detectors for in-beam gamma spectroscopy with radioactive ion beams. Most of the detectors can be used individually or in combination. Generally these detector systems have very large efficiencies. We give examples of their use from three recent experiments; namely, Coulomb excitation of n-rich nuclei along the N = 50 shell closure, the static quadrupole moment of the first 2+ in 78Ge and g-factor measurements of n-rich isotopes near N = 50.

  13. Evidence for Argon Content in Pure Oxygen from Thermal Data

    NASA Astrophysics Data System (ADS)

    Steur, Peter P. M.; Yang, Inseok; Pavese, Franco

    2017-02-01

    Since many years it is known that argon impurities in oxygen change the temperature of the oxygen triple point by +12 K{\\cdot }mol^{-1} (positive, while most impurities decrease the temperature) without any effect on the melting range of this transition, for the impurity concentrations usually encountered in nominally pure gases. It has been hypothesized that thermal measurements on the α -β solid-to-solid transition at 23.8 K or the β -γ solid-to-solid transition at 43.8 K may give reliable evidence regarding the argon content. However, such measurements require very long times for full completion of each transition (with prohibitive costs if liquid helium is used) and for the α -β solid-to-solid transition the heat pulse method cannot be applied reliably. The availability of closed-cycle refrigerators permits the first obstacle to be surmounted. The automatic system earlier developed at INRIM during the EU Multicells project and used extensively for the project on the isotopic effect in neon is perfectly suited for such measurements. Thus, the uncertainties of the temperature measurements are similar to those obtained previously (of the order of 0.1 mK or less). Three argon-in-oxygen mixtures were prepared gravimetrically and certified at KRISS, just as was previously done for the work on the neon isotopic compositions. Results of continuous-current measurements on the α -β solid-to-solid transition, along with the triple-point data obtained with the heat pulse method, are presented for one cell with a known doped argon content, to be compared with similar data from a cell with oxygen of very high purity. In addition, some preliminary data for the β -γ solid-to-solid transition are given. The measurements on the mixture with the highest argon content, about 1002 μmol{\\cdot } mol^{-1}, imply a (linear) sensitivity of (116 ± 7) K{\\cdot }mol^{-1} for the α -β transition. This sensitivity may be different at much lower argon contents, and follow

  14. Study of Track Ambiguities and Wire Plane Orientation in Single Phase Liquid Argon Time Projection Chambers

    NASA Astrophysics Data System (ADS)

    Bullard, Brendon; Zhang, Chao; Deep Underground Neutrino Experiment Collaboration

    2017-01-01

    The Deep Underground Neutrino Experiment (DUNE) is currently in development and will utilize a ten-kiloton scale liquid argon time projection chamber (LArTPC) to observe neutrinos from a beam produced using protons from the Main Injector at Fermilab. It is difficult to accurately reconstruct tracks traveling nearly parallel to the LArTPC wire planes due to the finite time resolution of the detector and the limitations of using projective wire geometries. Such reconstructed tracks exhibit degeneracy to varying degrees and could have a large enough effect on primary signals and backgrounds to warrant a design change in the DUNE TPCs. We simulated charged current signal and neutral pion decay background events in order to understand the impact on signal efficiency and background rejection in a LArTPC using wire readout planes situated parallel or perpendicular to the neutrino beam. We found that using a perpendicular wire plane significantly reduces the degeneracy problem for both lepton and hadrons. Other aspects of perpendicular TPC design including signal processing are still under study. Department of Energy.

  15. Dose effects on amorphous silicon sputtering by argon ions: A molecular dynamics simulation

    SciTech Connect

    Marques, L.A.; Rubio, J.E.; Jaraiz, M.; Bailon, L.A.; Barbolla, J.J.

    1997-02-01

    We have investigated, using molecular dynamics techniques, the sputtering yield enhancement of amorphous silicon produced by argon ion accumulation within the target. Several amorphous silicon samples, with different argon contents, were bombarded with 1 keV argon ions at normal incidence. To study the influence of the target structure, we considered samples with different argon arrangements, either uniformly distributed or within solid bubbles. We have observed that silicon sputtering yield increases linearly with dose until steady state conditions are reached. This enhancement is produced by the shallow argon atoms through the weakening of Si{endash}Si bonds. We have also observed that argon release takes place even long after the end of the collisional phase, and it is produced by ion-induced desorption and bubble destabilization. This enhanced argon yield determines the dose where target saturation and steady state conditions are reached. {copyright} {ital 1997 American Institute of Physics.}

  16. Data Reduction Processes Using FPGA for MicroBooNE Liquid Argon Time Projection Chamber

    SciTech Connect

    Wu, Jinyuan

    2010-05-26

    MicroBooNE is a liquid Argon time projection chamber to be built at Fermilab for an accelerator-based neutrino physics experiment and as part of the R&D strategy for a large liquid argon detector at DUSEL. The waveforms of the {approx}9000 sense wires in the chamber are continuously digitized at 2 M samples/s - which results in a large volume of data coming off the TPC. We have developed a lossless data reduction scheme based on Huffman Coding and have tested the scheme on cosmic ray data taken from a small liquid Argon time projection chamber, the BO detector. For sense wire waveforms produced by cosmic ray tracks, the Huffman Coding scheme compresses the data by a factor of approximately 10. The compressed data can be fully recovered back to the original data since the compression is lossless. In addition to accelerator neutrino data, which comes with small duty cycle in sync with the accelerator beam spill, continuous digitized waveforms are to be temporarily stored in the MicroBooNE data-acquisition system for about an hour, long enough for an external alert from possible supernova events. Another scheme, Dynamic Decimation, has been developed to compress further the potential supernova data so that the storage can be implemented within a reasonable budget. In the Dynamic Decimation scheme, data are sampled at the full sampling rate in the regions-of-interest (ROI) containing waveforms of track-hits and are decimated down to lower sampling rate outside the ROI. Note that unlike in typical zerosuppression schemes, in Dynamic Decimation, the data in the pedestal region are not thrown away but kept at a lower sampling rate. An additional factor of 10 compression ratio is achieved using the Dynamic Decimation scheme on the BO detector data, making a total compression rate of approximate 100 when the Dynamic Decimation and the Huffman Coding functional blocks are cascaded. Both of the blocks are compiled in low-cost FPGA and their silicon resource usages are low.

  17. Aluminium metallisation of argon and oxygen plasma-modified polycarbonate thin film surfaces

    NASA Astrophysics Data System (ADS)

    Rastomjee, C. S.; Keil, M.; Sotobayashi, H.; Bradshaw, A. M.; Lamont, C. L. A.; Gador, D.; Umbach, E.

    1998-12-01

    The influence of plasma treatment on the metallisation of polycarbonate surfaces was studied using X-ray absorption spectroscopy (XAFS) and core level X-ray photoelectron spectroscopy (XPS). Thin films of two different molecules were chosen: bis-phenol-A polycarbonate with phenol endgroups (P-PC) prepared ex situ by the spin-coating technique onto MoTe 2{0001}surfaces, and the model compound bis-phenol-A polycarbonate ( n=1) with tert-butyl phenyl endgroups (tBP-PC) evaporated in situ in UHV onto Cu{110}, Ag{100} and Ag{111} surfaces with film thicknesses of up to several monolayers. Surfaces of untreated samples and of samples which were pre-treated with either an inert argon or a reactive oxygen microwave plasma were metallised with Al (evaporated by electron beam heating) at film thicknesses ranging from the sub-monolayer region up to several monolayers. For the untreated surface, XAFS and XPS spectra suggest that the Al reacts with the carbonate groups leading to a breaking of the CO double bonds (and/or a reduction in bond order) as well as formation of Al oxide, Al hydroxide and Al-O-C linkages. A study of the time-dependent oxidation of the evaporated Al leads to the conclusion that Al slowly diffuses to the reactive sites in the first few subsurface layers of the polymer. Argon plasma treatment of samples leads to a reduction in the number of carbonyl groups in the near surface region. After metal deposition a higher ratio of metallic, non-reacted, Al was observed covering the polycarbonate surface and the diffusion rate into the polymer bulk seems to be higher than in the case of the untreated surface. Oxygen plasma treatment leads to the creation of additional CO containing species which also react with the Al in the subsequent metallisation process. Here, the ratio of oxidised Al on the polymer surface is higher than observed for untreated and argon plasma pre-treated polymer surfaces.

  18. ATLAS Liquid Argon Endcap Calorimeter R&D for sLHC

    NASA Astrophysics Data System (ADS)

    Schacht, P.

    2010-04-01

    The performance of the ATLAS liquid argon endcap has been studied for luminosities as expected for the operation at sLHC. The increase of integrated luminosity by a factor of ten has serious consequences for the signal reconstruction, radiation hardness requirements and operations of the forward liquid argon calorimeters. The response has been studied with small modules of the type as built for ATLAS in a very high intensity beam at IHEP/Protvino. The highest intensity obtained was well above the level of energy impact expected for ATLAS at sLHC. The signal processing of the ATLAS Hadronic Endcap Calorimeter employs the concept of 'active pads' which keep the detector capacities at the input of the amplifiers small and thereby achieves a fast rise time of the signal. This concept is realized using highly integrated amplifier and summing chips in GaAs technology. With an increase of luminosity by a factor of ten the safety factor for the radiation hardness is essentially eliminated. Therefore new, more radiation hard technologies have been studied: SiGe bipolar, Si CMOS FET and GaAs FET transistors have been irradiated with neutrons up to an integrated fluence of 2.2 × 1016n/cm2. All technologies exceed the limit required for the radiation hardness for the operation at sLHC of 2 × 1015n/cm2. The temperature dependence of the gain has been studied as well. Here the bipolar technologies - in contrast to CMOS - need an adjustment of the operation point when going from room temperature to liquid nitrogen temperature.

  19. Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon

    DOE PAGES

    Cao, H.

    2015-05-26

    We have measured the scintillation and ionization yield of recoiling nuclei in liquid argon as a function of applied electric field by exposing a dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy pulsed narrow band neutron beam produced at the Notre Dame Institute for Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged to detect and identify neutrons scattered in the TPC and to select the energy of the recoiling nuclei. We also report measurements of the scintillation yields for nuclear recoils with energies from 10.3 to 57.3 keV and for median applied electric fields from 0more » to 970 V/cm. For the ionization yields, we report measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486 V/cm. Furthermore, we report the observation of an anticorrelation between scintillation and ionization from nuclear recoils, which is similar to the anticorrelation between scintillation and ionization from electron recoils. Assuming that the energy loss partitions into excitons and ion pairs from 83mKr internal conversion electrons is comparable to that from 207Bi conversion electrons, we obtained the numbers of excitons (Nex) and ion pairs (Ni) and their ratio (Nex/Ni) produced by nuclear recoils from 16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in LAr-TPC signals due to columnar recombination, a comparison of the light and charge yield of recoils parallel and perpendicular to the applied electric field is presented for the first time.« less

  20. Observed damage during Argon gas cluster depth profiles of compound semiconductors

    SciTech Connect

    Barlow, Anders J. Portoles, Jose F.; Cumpson, Peter J.

    2014-08-07

    Argon Gas Cluster Ion Beam (GCIB) sources have become very popular in XPS and SIMS in recent years, due to the minimal chemical damage they introduce in the depth-profiling of polymer and other organic materials. These GCIB sources are therefore particularly useful for depth-profiling polymer and organic materials, but also (though more slowly) the surfaces of inorganic materials such as semiconductors, due to the lower roughness expected in cluster ion sputtering compared to that introduced by monatomic ions. We have examined experimentally a set of five compound semiconductors, cadmium telluride (CdTe), gallium arsenide (GaAs), gallium phosphide (GaP), indium arsenide (InAs), and zinc selenide (ZnSe) and a high-κ dielectric material, hafnium oxide (HfO), in their response to argon cluster profiling. An experimentally determined HfO etch rate of 0.025 nm/min (3.95 × 10{sup −2} amu/atom in ion) for 6 keV Ar gas clusters is used in the depth scale conversion for the profiles of the semiconductor materials. The assumption has been that, since the damage introduced into polymer materials is low, even though sputter yields are high, then there is little likelihood of damaging inorganic materials at all with cluster ions. This seems true in most cases; however, in this work, we report for the first time that this damage can in fact be very significant in the case of InAs, causing the formation of metallic indium that is readily visible even to the naked eye.