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Sample records for 3h 4he 16o

  1. An Investigation of 4He+12C and 4He+16O Reactions Using the Cluster Model

    NASA Astrophysics Data System (ADS)

    A. H., Al-Ghamdi; Awad, A. Ibraheem; M. El-Azab, Farid

    2012-07-01

    The α-target semimicroscopic single folding potentials have been derived by folding a composite (repulsive and attractive) effective α-α interaction with the α-cluster distribution density in the target nuclei. The obtained potentials are considered as the real part of the nuclear optical model potentials, while the imaginary parts are phenomenologicaly expressed using the Woods—Saxon form. Nine sets of measured experimental data of the 4He+12C and 4He+16O elastic rainbow scattering over the energy range 80-240 MeV are analyzed using the obtained potentials. The data are successfully reproduced using the extracted potentials. The resulted reaction cross sections are also investigated and compared with the available corresponding data.

  2. Probing for high momentum protons in 4He via the 4He(e,e'p)3 H reaction.

    NASA Astrophysics Data System (ADS)

    Benmokhtar, Fatiha; Iqbal, Sophia; See, Nathalian; Finton, Drew; Aniol, Konrad A.; Ivanov, Martin; Udias, Jose M.; Higinbotham, Douglas; HallA SRC Collaboration Collaboration

    2017-01-01

    The structure and dynamics of 4He can be studied through 4He(e,e'p) coincidence measurements at high momentum transfers. Using the Hall A high resolution spectrometers and a cryogenic 4He target, the short range correlation E07-006 and E08-009 experiments held in Hall A of Jefferson Lab measured the entire range of missing momentum from 0.0 GeV/ c to 0.9 GeV/ c. Experimental cross sections for the 3-body breakup 4He(e,e'p)3 H up to Pmiss = 0.632GeV/ c at xB = 1.24 and Q2 = 2(GeV/c2) are reported. The data are compared to Relativistic Distorted Wave Impulse Approximation (RDWIA) calculations.

  3. Absolute cross section for the reaction /sup 3/H(p,. gamma. /sub 0/)/sup 4/He and a review of /sup 4/He(. gamma. , p/sub 0/)/sup 3/H measurements

    SciTech Connect

    Calarco, J.R.; Hanna, S.S.; Chang, C.C.; Diener, E.M.; Kuhlmann, E.; Fisher, G.A.

    1983-08-01

    Accurate differential cross sections have been measured at 90/sup 0/ for the reaction /sup 3/H(p,..gamma..)/sup 4/He at E/sub p/ = 8.34 and 13.6 MeV. Previously published results for both /sup 3/H(p,..gamma..)/sup 4/He and /sup 4/He(..gamma..,p)/sup 3/H are reviewed and compared with the present data. The theoretical implications of the results are briefly discussed.

  4. Direct measurement of the 4He (12C, 16O) γ reaction cross section near stellar energies

    NASA Astrophysics Data System (ADS)

    Sagara, Kenshi

    2014-09-01

    The 12C+4He-->16O + γ reaction is one of the key reactions in stellar He-burning, but its total cross section at stellar energy (Ecm = 0.3 MeV) has not been measured yet, in spite of many experiments made in the world for about a half century. At Kyushu University Tandem accelerator Laboratory (KUTL), we have been making direct measurement of the 4He (12C, 16O) γ total cross section below Ecm = 2.4 MeV for about 20 years. We have measured the total cross section at Ecm = 2.4, 1.5 and 1.2 MeV. Now we are preparing to measure the cross section at 1.0 MeV. The direct measurement was made from Ecm = 5 MeV down to 1.9 MeV at Ruhr University, Bochum. We use a pulsed 12C beam and a windowless 4He target, and detect all the 16O recoils in a charge state. A usually continuum 12C beam from our tandem accelerator is pulsed by a pre-buncher, a main buncher, and a beam chopper. Our tandem accelerator was designed to be used at the acceleration voltage of 6-10 MV. For the 4He (12C, 16O) γ experiment we need to use it at 1.3-1.8 MV where beam transmission is very low, then we have invented an acceleration-deceleration method for the tandem accelerator. We have developed a blow-in windowless He target based on an original idea. To separate 16O recoils from the 12C beam, we developed a recoil-mass separator. To reject 12C backgrounds, we developed a long-time chopper, and an ionization chamber. Now, we are preparing to measure time-of-flight of 16O recoils and 12C backgrounds. Many original instruments and the experimental results will be presented. Finally we discuss what are necessary for future direct measurement of the 4He (12C, 16O) γ total cross section below 1.0 MeV, down to 0.7 MeV. A dynamitron accelerator and hard-working researchers may be inevitable. The 12C+4He-->16O + γ reaction is one of the key reactions in stellar He-burning, but its total cross section at stellar energy (Ecm = 0.3 MeV) has not been measured yet, in spite of many experiments made in the world

  5. Spin polarization effects in the /sup 3/H(d,n)/sup 4/He fusion reaction

    SciTech Connect

    Conzett, H.E.; Rioux, C.

    1985-06-01

    A recent investigation has shown that the /sup 3/H(d,n)/sup 4/He fusion reaction rate could be enhanced by a factor of 3/2 if the fusion plasma consisted of both polarized deuterons and tritons, forming exclusively the channel-spin S = 3/2, J = 3/2/sup +/ state. This result follows simply from the statistical weights of the quartet S = 3/2 and doublet S = 1/2 initial states, with the assumption of the single J = 3/2/sup +/ reaction amplitude. Since, with a small but nonzero J = 1/2/sup +/ amplitude, the maximum enhancement of the reaction occurs at the peak of the J = 3/2/sup +/ resonance, corresponding to a deuteron lab energy of 107 keV, it is of obvious interest to know what the enhancement would be at the lower energies that are typical of fusion plasmas. We are able to address this question by extending earlier calculations which gave the values of all of the spin-polarization observables at this J = 3/2/sup +/ resonance in both the /sup 3/H(d,n)/sup 4/He and the /sup 3/He(d,p)/sup 4/He reactions.

  6. Ground-state properties of 4He and 16O extrapolated from lattice QCD with pionless EFT

    NASA Astrophysics Data System (ADS)

    Contessi, L.; Lovato, A.; Pederiva, F.; Roggero, A.; Kirscher, J.; van Kolck, U.

    2017-09-01

    We extend the prediction range of Pionless Effective Field Theory with an analysis of the ground state of 16O in leading order. To renormalize the theory, we use as input both experimental data and lattice QCD predictions of nuclear observables, which probe the sensitivity of nuclei to increased quark masses. The nuclear many-body Schrödinger equation is solved with the Auxiliary Field Diffusion Monte Carlo method. For the first time in a nuclear quantum Monte Carlo calculation, a linear optimization procedure, which allows us to devise an accurate trial wave function with a large number of variational parameters, is adopted. The method yields a binding energy of 4He which is in good agreement with experiment at physical pion mass and with lattice calculations at larger pion masses. At leading order we do not find any evidence of a 16O state which is stable against breakup into four 4He, although higher-order terms could bind 16O.

  7. Ab initio many-body calculations of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions.

    PubMed

    Navrátil, Petr; Quaglioni, Sofia

    2012-01-27

    We apply the ab initio no-core shell model combined with the resonating-group method approach to calculate the cross sections of the (3)H(d,n)(4)He and (3)He(d,p)(4)He fusion reactions. These are important reactions for the big bang nucleosynthesis and the future of energy generation on Earth. Starting from a selected similarity-transformed chiral nucleon-nucleon interaction that accurately describes two-nucleon data, we performed many-body calculations that predict the S factor of both reactions. Virtual three-body breakup effects are obtained by including excited pseudostates of the deuteron in the calculation. Our results are in satisfactory agreement with experimental data and pave the way for microscopic investigations of polarization and electron-screening effects, of the (3)H(d,γn)(4)He bremsstrahlung and other reactions relevant to fusion research.

  8. Polarization Transfer in 4He(e-vector,e[prime]p-vector)3H

    SciTech Connect

    Michael Paolone

    2007-10-01

    Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the 4He(e-vector,e[prime]p-vector)3H reaction at a Q2 of 0.8 (GeV/c)2 and 1.3 (GeV/c)2 with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c)2 from both Mainz and Jefferson Lab, in which the measured ratio of polarization-transfer coefficients differs from a fully relativistic DWIA calculation. Preliminary results hint at a possible unexpected Q2 dependence in the polarization transfer coefficient ratio. Final analysis will help constrain FSI models

  9. Quantum Monte Carlo studies of relativistic effects in 3H and 4He

    NASA Astrophysics Data System (ADS)

    Arriaga, A.

    2000-03-01

    Relativistic effects in 3H and 4He have been studied in the context of Relativistic Hamiltonian Dynamics, using Variational Monte Carlo Methods. Relativistic invariance is achieved through Poincaré group algebra, which introduces a boost interaction term defining the first relativistic effect considered. The second consists in the nonlocalities associated with the relativistic kinetic energy operator and with the relativistic one-pion exchange potential (OPEP). These nonlocalities tend to cancel, being the total effect on the binding energy attractive and very small, of the order of 1%. The dominant relativistic effect is due to the boost interaction, whose contribution is repulsive and of the order of 5%. The repulsive term of the nonrelativistic 3-body interaction has to be reduced by 37% so that the optimal triton binding energy is recovered, meaning that around 1/3 of this phenomenological term accounts for relativisitic effects. The changes induced on the wave functions of nuclei by these relativistic effetcs are very small and short ranged. Although the nonlocalities of OPEP, resulting in a reduction of 15%, are cancelled by other relativistic contributions, they may have significant effects on pion exchange currents in nuclei.

  10. Medium Modifications from {sup 4}He(e-vector,e'p-vector){sup 3}H

    SciTech Connect

    Malace, S.; Paolone, M.; Strauch, S.

    2008-10-13

    Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the {sup 4}He(e-vector,e'p-vector){sup 3}H reaction at a Q{sup 2} of 0.8 (GeV/c){sup 2} and 1.3 (GeV/c){sup 2} with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c){sup 2} from both Mainz and Jefferson Lab. The measured ratio of polarization-transfer coefficients differs from a fully relativistic calculation, favoring either the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model or strong charge-exchange final-state interactions. The measured induced polarizations agree well with the fully relativistic calculation and indicate that these strong final-state interactions may not be applicable.

  11. Comparative study of dose distributions and cell survival fractions for 1H, 4He, 12C and 16O beams using Geant4 and Microdosimetric Kinetic model

    NASA Astrophysics Data System (ADS)

    Burigo, Lucas; Pshenichnov, Igor; Mishustin, Igor; Bleicher, Marcus

    2015-04-01

    Depth and radial dose profiles for therapeutic 1H, 4He, 12C and 16O beams are calculated using the Geant4-based Monte Carlo model for Heavy-Ion Therapy (MCHIT). 4He and 16O ions are presented as alternative options to 1H and 12C broadly used for ion-beam cancer therapy. Biological dose profiles and survival fractions of cells are estimated using the modified Microdosimetric Kinetic model. Depth distributions of cell survival of healthy tissues, assuming 10% and 50% survival of tumor cells, are calculated for 6 cm SOBPs at two tumor depths and for different tissues radiosensitivities. It is found that the optimal ion choice depends on (i) depth of the tumor, (ii) dose levels and (iii) the contrast of radiosensitivities of tumor and surrounding healthy tissues. Our results indicate that 12C and 16O ions are more appropriate to spare healthy tissues in the case of a more radioresistant tumor at moderate depths. On the other hand, a sensitive tumor surrounded by more resistant tissues can be better treated with 1H and 4He ions. In general, 4He beam is found to be a good candidate for therapy. It better spares healthy tissues in all considered cases compared to 1H. Besides, the dose conformation is improved for deep-seated tumors compared to 1H, and the damage to surrounding healthy tissues is reduced compared to heavier ions due to the lower impact of nuclear fragmentation. No definite advantages of 16O with respect to 12C ions are found in this study.

  12. Three-Body Calculation of the 4He(3H,γ)7 Li and 4He(3He,γ)7 Be Reactions and Structure of the 7Li and 7Be at Solar Energies

    NASA Astrophysics Data System (ADS)

    Sadeghi, H.; Khalili, H.

    2014-01-01

    The two 3H+4He and 3He+4He fusion reactions at low energies are usually viewed as an approximate external capture process. We study the 4He(3H,γ)7 Li and 4He(3He,γ)7 Be reactions in a cluster model, which can take into account two- and three-body electromagnetic currents, using minimal substitution in the explicit momentum dependence of the two- and three-cluster interactions. Our main goal is to explore how the cross section of the low-energy 3H+4He or 3He+4He capture reactions depends on energy. The astrophysical S-factors for these reactions are calculated at very low energies. We construct the conserved realistic Argonne v18 for two nucleons and Urbana IX or Tucson-Melbourne three-cluster interactions, which are considered for calculation. We also calculate the binding energies and the structural properties of 3H+4He or 3He+4He systems. The binding energies are found to be -37.72 (-36.32) MeV and -39.35 (-37.43) MeV, with (without) three-body interactions for 7Be and 7Li, in satisfactory agreement with other theoretical results and experimental data, respectively.

  13. Precise extraction of the induced polarization in the 4He(e,e'p)3H reaction.

    PubMed

    Malace, S P; Paolone, M; Strauch, S; Albayrak, I; Arrington, J; Berman, B L; Brash, E J; Briscoe, B; Camsonne, A; Chen, J-P; Christy, M E; Chudakov, E; Cisbani, E; Craver, B; Cusanno, F; Ent, R; Garibaldi, F; Gilman, R; Glamazdin, O; Glister, J; Higinbotham, D W; Hyde-Wright, C E; Ilieva, Y; de Jager, C W; Jiang, X; Jones, M K; Keppel, C E; Khrosinkova, E; Kuchina, E; Kumbartzki, G; Lee, B; Lindgren, R; Margaziotis, D J; Meekins, D; Michaels, R; Park, K; Pentchev, L; Perdrisat, C F; Piasetzky, E; Punjabi, V A; Puckett, A J R; Qian, X; Qiang, Y; Ransome, R D; Saha, A; Sarty, A J; Schulte, E; Solvignon, P; Subedi, R R; Tang, L; Tedeschi, D; Tvaskis, V; Udias, J M; Ulmer, P E; Vignote, J R; Wesselmann, F R; Wojtsekhowski, B; Zhan, X

    2011-02-04

    We measured with unprecedented precision the induced polarization P(y) in (4)He(e,e'p)(3)H at Q(2)=0.8 and 1.3  (GeV/c)(2). The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are overestimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin-independent charge-exchange term in the latter calculation.

  14. A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction

    SciTech Connect

    S.P. Malace, M. Paolone, S. Strauch

    2011-01-01

    We measured with unprecedented precision the induced polarization Py in 4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization is indicative of reaction-mechanism effects beyond the impulse approximation. Our results are in agreement with a relativistic distorted-wave impulse approximation calculation but are over-estimated by a calculation with strong charge-exchange effects. Our data are used to constrain the strength of the spin independent charge-exchange term in the latter calculation.

  15. Polarization transfer in the {sup 4}He({rvec e}, e'{rvec p}){sup 3}H reaction

    SciTech Connect

    Sonja Dieterich; et. al

    2001-02-15

    Polarization transfer in the {sup 4}He({rvec e}, e'{rvec p}){sup 3}H reaction at a Q{sup 2} of 0.4 (GeV/c){sup 2} was measured at the Mainz Microtron MAMI. The ratio of the transverse to the longitudinal polarization components of the ejected protons was compared with the same ratio for elastic ep scattering. The results are consistent with a recent fully relativistic calculation which includes a predicted medium modification of the proton form factor based on a quark-meson coupling model.

  16. Polarization Transfer in the {sup 4}He({rvec E},E{prime}{rvec P}){sup 3}H Reaction

    SciTech Connect

    Steffen Strauch

    2003-05-01

    Polarization transfer in the {sup 4}He({rvec E},E{prime}{rvec P}){sup 3}H reaction was measured in Jefferson Lab experiment 93-049. The ratio of the polarization transfer coefficients, (P{prime}{sub x}/P{prime}{sub z}){sub He}, is on average significantly reduced as compared to the same ratio in elastic ep scattering. This is so far unaccounted for by relativistic DWIA calculations, and favors the inclusion of a predicted medium modification of the proton form factor.

  17. Background reduction system of {sup 4}He({sup 12}C,{sup 16}O)gamma at KUTL

    SciTech Connect

    Taniguchi, M.; Sagara, K.; Teranishi, T.; Fujita, K.; Iwabuchi, R.; Gotoh, T.; Nakano, K.; Oba, N.

    2010-06-01

    The C-alpha reaction is one of the most important reactions in astrophysics. At Kyushu University Tandem accelerator Laboratory (KUTL), a high detective efficiency measurement has been made by adopting inverse kinematics: {sup 12}C beam is injected on windowless {sup 4}He gas target. In this experiment, a powerful background reduction system is necessary. We describe the effectiveness of the background system consisting of recoil mass separator, a long time chopper, and new movable slits.

  18. Polarization Transfer in {sup 4}He(e-vector,e{sup '}p-vector){sup 3}H

    SciTech Connect

    Paolone, Michael

    2007-10-26

    Polarization transfer in quasi-elastic nucleon knockout is sensitive to the properties of the nucleon in the nuclear medium, including possible modification of the nucleon form factor and/or spinor. In our recently completed experiment E03-104 at Jefferson Lab we measured the proton recoil polarization in the {sup 4}He(e-vector,e{sup '}p-vector){sup 3}H reaction at a Q{sup 2} of 0.8 (GeV/c){sup 2} and 1.3 (GeV/c){sup 2} with unprecedented precision. These data complement earlier data between 0.4 and 2.6 (GeV/c){sup 2} from both Mainz and Jefferson Lab, in which the measured ratio of polarization-transfer coefficients differs from a fully relativistic DWIA calculation. Preliminary results hint at a possible unexpected Q{sup 2} dependence in the polarization transfer coefficient ratio. Final analysis will help constrain FSI models.

  19. 8Be+8Be and 12C+α breakup states in 16O populated via the 13C(4He,4 α )n reaction

    NASA Astrophysics Data System (ADS)

    Curtis, N.; Almaraz-Calderon, S.; Aprahamian, A.; Ashwood, N. I.; Barr, M.; Bucher, B.; Copp, P.; Couder, M.; Fang, X.; Freer, M.; Goldring, G.; Jung, F.; Lesher, S. R.; Lu, W.; Malcolm, J. D.; Roberts, A.; Tan, W. P.; Wheldon, C.; Ziman, V. A.

    2016-09-01

    The 13C(4He,4 α )n breakup reaction has been studied at beam energies of 27.0, 27.5, and 28.0 MeV. A comparison with previous measurements of the 12C(4He,8Be)8Be excitation function and 12C(16O,4 α )12C breakup channel suggests the Be8gs+Be8gs decay of 16O is observed from a possible 2+ state at 17.3 ±0.2 MeV, a 4+ state at 18.0 ±0.2 MeV, a 2+ or 4+ state at 19.4 ±0.2 MeV, and a 4+ or 6+ state at 21.0 ±0.2 MeV. The 2+ or 4+ assignment for the (19.4 ±0.2 )-MeV state appears to be supported by the relative cross sections expected for resonant and sequential breakup reactions.

  20. Lateral variations of radiobiological properties of therapeutic fields of (1)H, (4)He, (12)C and (16)O ions studied with Geant4 and microdosimetric kinetic model.

    PubMed

    Dewey, Sophie; Burigo, Lucas; Pshenichnov, Igor; Mishustin, Igor; Bleicher, Marcus

    2017-06-27

    As known, in cancer therapy with ion beams the relative biological effectiveness (RBE) of ions changes in the course of their propagation in tissues. Such changes are caused not only by increasing the linear energy transfer (LET) of beam particles with the penetration depth towards the Bragg peak, but also by nuclear reactions induced by beam nuclei leading to the production of various secondary particles. Although the changes of RBE along the beam axis have been studied quite well, much less attention has been paid to the evolution of RBE in the transverse direction, perpendicular to the beam axis. In order to fill this gap, we simulated radiation fields of (1)H, (4)He, (12)C and (16)O nuclei of 20 mm in diameter by means of a Geant4-based Monte Carlo model for heavy-ion therapy connected with the modified microdosimetric kinetic model to describe the response of normal ([Formula: see text] Gy) and early-responding ([Formula: see text] Gy) tissues. Depth and radial distributions of saturation-corrected dose-mean lineal energy, RBE and RBE-weighted dose are investigated for passive beam shaping and active beam scanning. The field of (4)He has a small lateral spread as compared with (1)H field, and it is characterised by a modest lateral variation of RBE suggesting the use of fixed RBE values across the field transverse cross section at each depth. Reduced uncertainties of RBE on the boundary of a (4)He treatment field can be advantageous in a specific case of an organ at risk located in lateral proximity to the target volume. It is found that the lateral distributions of RBE calculated for (12)C and (16)O fields demonstrate fast variations in the radial direction due to changes of dose and composition of secondary fragments in the field penumbra. Nevertheless, the radiation fields of all four projectiles at radii larger than 20 mm can be characterized by a common RBE value defined by tissue radiosensitivity. These findings can help, in particular, in accessing

  1. Lateral variations of radiobiological properties of therapeutic fields of 1H, 4He, 12C and 16O ions studied with Geant4 and microdosimetric kinetic model

    NASA Astrophysics Data System (ADS)

    Dewey, Sophie; Burigo, Lucas; Pshenichnov, Igor; Mishustin, Igor; Bleicher, Marcus

    2017-07-01

    As known, in cancer therapy with ion beams the relative biological effectiveness (RBE) of ions changes in the course of their propagation in tissues. Such changes are caused not only by increasing the linear energy transfer (LET) of beam particles with the penetration depth towards the Bragg peak, but also by nuclear reactions induced by beam nuclei leading to the production of various secondary particles. Although the changes of RBE along the beam axis have been studied quite well, much less attention has been paid to the evolution of RBE in the transverse direction, perpendicular to the beam axis. In order to fill this gap, we simulated radiation fields of 1H, 4He, 12C and 16O nuclei of 20 mm in diameter by means of a Geant4-based Monte Carlo model for heavy-ion therapy connected with the modified microdosimetric kinetic model to describe the response of normal ((α/β)_x-rays=3.8 Gy) and early-responding ((α/β)_x-rays=10 Gy) tissues. Depth and radial distributions of saturation-corrected dose-mean lineal energy, RBE and RBE-weighted dose are investigated for passive beam shaping and active beam scanning. The field of 4He has a small lateral spread as compared with 1H field, and it is characterised by a modest lateral variation of RBE suggesting the use of fixed RBE values across the field transverse cross section at each depth. Reduced uncertainties of RBE on the boundary of a 4He treatment field can be advantageous in a specific case of an organ at risk located in lateral proximity to the target volume. It is found that the lateral distributions of RBE calculated for 12C and 16O fields demonstrate fast variations in the radial direction due to changes of dose and composition of secondary fragments in the field penumbra. Nevertheless, the radiation fields of all four projectiles at radii larger than 20 mm can be characterized by a common RBE value defined by tissue radiosensitivity. These findings can help, in particular, in accessing the transverse

  2. Ab initio study of {sup 2}H(d,{gamma}){sup 4}He, {sup 2}H(d,p){sup 3}H, and {sup 2}H(d,n){sup 4}He reactions and the tensor force

    SciTech Connect

    Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

    2012-11-12

    The {sup 2}H(d,p){sup 3}H, {sup 2}H(d,n){sup 3}He, and {sup 2}H(d,{gamma}){sup 4}He reactions at low energies are studied with realistic nucleon-nucleon interactions in an ab initio approach. The obtained astrophysical S-factors are all in very good agreement with experiment. The most important channels for both transfer and radiative capture are all found to dominate thanks to the tensor force.

  3. The {sup 3}He(e,e'p){sup 2}H and {sup 4}He(e,e'p){sup 3}H reactions at high momentum transfer

    SciTech Connect

    Ford, William P.; Schiavilla, Rocco; Van Orden, J. W.

    2014-03-01

    We present updated calculations for observables in the processes {sup 3}He(e,e'p){sup 2}H, {sup 4}He(e,e'p){sup 3}H and {sup 4}He(e-vector, e'p-vector){sup 3}H. This update entails the implementation of improved nucleon-nucleon (NN) amplitudes to describe final state interactions (FSI) within a Glauber approximation and includes full spin-isospin dependence in the profile operator. In addition, an optical potential, which has also been updated since previous work, is utilized to treat FSI for the {sup 4}He(e,e'p){sup 3}H and {sup 4}He(e-vector, e'p-vector){sup 3}H reactions. The calculations are compared with experimental data and show good agreement between theory and experiment. Comparisons are made between the various approximations in the Glauber treatment, including model dependence due to the NN scattering amplitudes, rescattering contributions, and spin dependence. We also analyze the validity of the Glauber approximation at the kinematics the data is available, by comparing to the results obtained with the optical potential.

  4. Estimating the groundwater residence time in eskers of the Amos region, northern Quebec by 3H-3He and (U-Th/4He) methods

    NASA Astrophysics Data System (ADS)

    Boucher, Christine; Berthot, Laureline; Pinti, Daniele Luigi; Larocque, Marie; Cloutier, Vincent; Blanchette, Daniel; Castro, Maria Clara; Hall, Chris M.

    2013-04-01

    An esker is a long winding ridge of stratified sand and gravel. The eskers of the Amos region (Abitibi-Témiscamingue, Québec) that were deposited during the last deglaciation, are known to be aquifers containing drinking water of exceptional quality. Yet little is known about their hydrologic regime and exchanges with other water sources. A better understanding of these systems is necessary to assess the vulnerability of these aquifers to contaminants and to implement a management plan for these resources. A multi-isotopic study of groundwater in the eskers of the Amos region (Saint-Mathieu-Berry, Barraute and Harricana moraine) was carried out in 2011-2012. Noble gas isotopes, together with major ions chemistry and stable isotopes were used to estimate the residence time of waters, to trace fluid flow paths and to determine the atmospheric temperature at the time of the recharge took place. Measured 3He/4He ratios were primarily used to identify mixing between different water types carrying distinct helium components. The 20Ne/4He vs. 3He/4He relationship shows that waters flowing into eskers have three helium components: atmospheric, tritiogenic 3He-rich and radiogenic 4He-rich. The measured 3He/4He ratios (R) normalized to the atmospheric one (R/Ra) varies between 0.224±0.012 and 1.849±0.036. Most radiogenic 4He-rich mineralized waters are those from fractured basement rocks of Archean age. Freshwater flowing into eskers show mixing between radiogenic helium and tritiogenic 3He. A clear relationship between the well depths, salinity and the 3He/4He ratios suggests that mixing occurs between these two groundwater bodies. Tritium measurements allow the calculation of 3H-3He ages varying from 6.7±1.3 yrs to 9.7±1.3 yrs for waters flowing through the Harricana moraine. Groundwater from Saint-Mathieu de Berry esker ranges from 11.0±2.1 yrs to 32.5±1.6 yrs. The 3H-3He ages plotted against the wells depth show a linear relationship for both, the Saint

  5. Four-body calculation of 4He binding energy and tensor analysing powers for dd → dd and dd → p 3H reactions

    NASA Astrophysics Data System (ADS)

    Fonseca, A. C.

    1990-02-01

    Four-body integral equations are used to calculate the binding energy of 4He as well as dd → dd and dd → p 3H amplitudes using a single term separable nucleon-nucleon potential in channels 1S 0 and 3S 1- 3D 1, together with the energy dependent pole expansion to set up an N term representation of all (3)+1 subamplitudes of interest. The (2)+(2) subamplitudes are treated exactly by convolution. The 4He binding energy is obtained from the exact solution of the equations. In the scattering region first order perturbation theory is used to separate the contribution of the s-wave components of the N-N t-matrix and s- and p-wave three-nucleon channels to the tour-nucleon Kernel, from the contribution of d-wave two- and three-nucleon channel components that result from the tensor-force. Cross sections and analysing powers are calculated using all positive and negative parity four-body amplitudes with total angular momentum J⩽4. Comparison with data is presented.

  6. Polarization transfer in the 4He(e→,e'p→)3H reaction at Q2 = 0.8 and 1.3 (GeV/c)2

    DOE PAGES

    Michael Paolone; Malace, Simona P.

    2010-08-12

    Here, proton recoil polarization was measured in the quasielastic 4He(e→,e'p→)3H reaction at Q2 = 0.8 (GeV/c)2 and 1.3 (GeV/c)2 with unprecedented precision. The polarization-transfer coefficients are found to differ from those of the 1H(e→,e'p→) reaction, contradicting a relativistic distorted-wave approximation, and favoring either the inclusion of medium-modified proton form factors predicted by the quark-meson coupling model or a spin-dependent charge-exchange final-state interaction. For the first time, the polarization-transfer ratio is studied as a function of the virtuality of the proton.

  7. Polarization transfer in the 4He(e,e'p)3H reaction at Q2=0.8 and 1.3 (GeV/c)2.

    PubMed

    Paolone, M; Malace, S P; Strauch, S; Albayrak, I; Arrington, J; Berman, B L; Brash, E J; Briscoe, B; Camsonne, A; Chen, J-P; Christy, M E; Chudakov, E; Cisbani, E; Craver, B; Cusanno, F; Ent, R; Garibaldi, F; Gilman, R; Glamazdin, O; Glister, J; Higinbotham, D W; Hyde-Wright, C E; Ilieva, Y; de Jager, C W; Jiang, X; Jones, M K; Keppel, C E; Khrosinkova, E; Kuchina, E; Kumbartzki, G; Lee, B; Lindgren, R; Margaziotis, D J; Meekins, D; Michaels, R; Park, K; Pentchev, L; Perdrisat, C F; Piasetzky, E; Punjabi, V A; Puckett, A J R; Qian, X; Qiang, Y; Ransome, R D; Saha, A; Sarty, A J; Schulte, E; Solvignon, P; Subedi, R R; Tang, L; Tedeschi, D; Tvaskis, V; Udias, J M; Ulmer, P E; Vignote, J R; Wesselmann, F R; Wojtsekhowski, B; Zhan, X

    2010-08-13

    Proton recoil polarization was measured in the quasielastic 4He(e,e'p)3H reaction at Q{2}=0.8 and 1.3  (GeV/c){2} with unprecedented precision. The polarization-transfer coefficients are found to differ from those of the 1H(e,e'p) reaction, contradicting a relativistic distorted-wave approximation and favoring either the inclusion of medium-modified proton form factors predicted by the quark-meson coupling model or a spin-dependent charge-exchange final-state interaction. For the first time, the polarization-transfer ratio is studied as a function of the virtuality of the proton.

  8. Measurements of thick target neutron yields and shielding studies using beams of 4He, 12C and 16O at 155 MeV/nucleon from the K1200 cyclotron at the National Superconducting Cyclotron Laboratory

    NASA Astrophysics Data System (ADS)

    Britvich, G. I.; Chumakov, A. A.; Ronningen, R. M.; Blue, R. A.; Heilbronn, L. H.

    1999-05-01

    Measurements of neutrons from a thick target of Hevimet were made, using beams of 4He, 12C, and 16O ions at 155 MeV per nucleon. These measurements were made both inside and outside of thick concrete shielding, using Bonner-sphere techniques. Yields, spectra, and spectral integral quantities were obtained. The neutron yields were parameterized, and a Moyer-model approach was taken to estimate the dose-equivalent outside of the thick concrete shielding. The effect of local iron shielding, and the dose equivalent outside of iron roof shielding were also investigated. Finally, two methods to obtain neutron field integral values, the "reconstructed spectra" and "six-spheres" methods, were compared. The measurements and analyses should prove useful to other present or planned medium-energy heavy-ion accelerator facilities.

  9. Absolute measurement of the differential cross section for the reaction sup 4 He(. gamma. , p ) sup 3 H from 63 to 71 MeV

    SciTech Connect

    Jones, R.T.; Jenkins, D.A. ); Debevec, P.T.; Harty, P.D.; Knott, J.E. )

    1991-05-01

    Results are presented from a {sup 4}He photodisintegration experiment performed with quasimonochromatic photons using a large solid-angle detector. The tagged-bremsstrahlung technique gave a reliable absolute normalization. In addition, an unambiguous separation of the proton-triton channel from other photodisintegration channels was achieved. A total cross section of 218{plus minus}8 {mu}b was measured at a mean energy of 67{plus minus}4 MeV and Legendre coefficients up to {ital a}{sub 5} were extracted from the angular distributions.

  10. Polarization transfer in the 4He(e-->,e'p-->)3H reaction up to Q2=2.6 (GeV/c)2.

    PubMed

    Strauch, S; Dieterich, S; Aniol, K A; Annand, J R M; Baker, O K; Bertozzi, W; Boswell, M; Brash, E J; Chai, Z; Chen, J-P; Christy, M E; Chudakov, E; Cochran, A; De Leo, R; Ent, R; Epstein, M B; Finn, J M; Fissum, K G; Forest, T A; Frullani, S; Garibaldi, F; Gasparian, A; Gayou, O; Gilad, S; Gilman, R; Glashausser, C; Gomez, J; Gorbenko, V; Gueye, P L J; Hansen, J O; Higinbotham, D W; Hu, B; Hyde-Wright, C E; Ireland, D G; Jackson, C; de Jager, C W; Jiang, X; Jones, C; Jones, M K; Kellie, J D; Kelly, J J; Keppel, C E; Kumbartzki, G; Kuss, M; LeRose, J J; Livingston, K; Liyanage, N; Malov, S; Margaziotis, D J; Meekins, D; Michaels, R; Mitchell, J H; Nanda, S K; Nappa, J; Perdrisat, C F; Punjabi, V A; Ransome, R D; Roché, R; Rosner, G; Rvachev, M; Sabatie, F; Saha, A; Sarty, A; Udias, J M; Ulmer, P E; Urciuoli, G M; van den Brand, J F J; Vignote, J R; Watts, D P; Weinstein, L B; Wijesooriya, K; Wojtsekhowski, B

    2003-08-01

    We have measured the proton recoil polarization in the 4He(e-->,e(')p-->)4H reaction at Q(2)=0.5, 1.0, 1.6, and 2.6 (GeV/c)(2). The measured ratio of polarization transfer coefficients differs from a fully relativistic calculation, favoring the inclusion of a medium modification of the proton form factors predicted by a quark-meson coupling model. In addition, the measured induced polarizations agree reasonably well with the fully relativistic calculation indicating that the treatment of final-state interactions is under control.

  11. Diffraction dissociation of {sup 7}Li and {sup 7}Be relativistic nuclei on proton targets through the {sup 3}H({sup 3}He)+{sup 4}He channels

    SciTech Connect

    Fetisov, V. N.

    2015-07-15

    For the fragmentation of {sup 7}Li and {sup 7}Be relativistic nuclei (with momenta of, respectively, P = 3 GeV/c and P = 1.6 GeV/c per nucleon) on proton targets through the {sup 3}H({sup 3}He) + {sup 4}He channels, the differential cross sections with respect to the momentum transfer Q to the fragments were calculated on the basis of the cluster version of Akhiezer–Glauber–Sitenko diffraction theory by employing the twobody cluster model for the {sup 7}Li ({sup 3}H + {sup 4}He) and {sup 7}Be ({sup 3}He + {sup 4}He) nuclei. These calculations, performed in the impulse approximation in the interaction of intranuclear clusters with the target nucleus, explained a strong suppression of the cross sections for reactions on protons at Q lower than 100 MeV/c and higher than 350 MeV/c and the observed irregularities in the behavior off the cross section for {sup 7}Li fragmentation on complex track-emulsion nuclei. Cross-section values close to their experimental counterparts were obtained upon setting the coefficient of two-body clustering in the {sup 7}Li and {sup 7}Be nuclei to k ≃ 0.7.

  12. Tensor Force Manifestations in Ab Initio Study of the {sup 2}H(d,{gamma}){sup 4}He, {sup 2}H(d,p){sup 3}H, and {sup 2}H(d,n){sup 3}He Reactions

    SciTech Connect

    Arai, K.; Aoyama, S.; Suzuki, Y.; Descouvemont, P.; Baye, D.

    2011-09-23

    The {sup 2}H(d,p){sup 3}H, {sup 2}H(d,n){sup 3}He, and {sup 2}H(d,{gamma}){sup 4}He reactions are studied at low energies in a multichannel ab initio model that takes into account the distortions of the nuclei. The internal wave functions of these nuclei are given by the stochastic variational method with the AV8{sup '} realistic interaction and a phenomenological three-body force included to reproduce the two-body thresholds. The obtained astrophysical S factors are all in very good agreement with the experiment. The most important channels for both transfer and radiative capture are identified by comparing to calculations with an effective central force. They are all found to dominate thanks to the tensor force.

  13. Method for determination of .sup.18 O/.sup.16 O and .sup.2 H/.sup.1 H ratios and .sup.3 H (tritium) concentrations of xylem waters and subsurface waters using time series sampling

    SciTech Connect

    Smith, Brian; Menchaca, Leticia

    1999-01-01

    A method for determination of .sup.18 O/.sup.16 O and .sup.2 H/.sup.1 H ratios and .sup.3 H concentrations of xylem and subsurface waters using time series sampling, insulating sampling chambers, and combined .sup.18 O/.sup.16 O, .sup.2 H/.sup.1 H and .sup.3 H concentration data on transpired water. The method involves collecting water samples transpired from living plants and correcting the measured isotopic compositions of oxygen (.sup.18 O/.sup.16 O) and hydrogen (.sup.2 H/.sup.1 H and/or .sup.3 H concentrations) to account for evaporative isotopic fractionation in the leafy material of the plant.

  14. Method for determination of {sup 18}O/{sup 16}O and {sup 2}H/{sup 1}H ratios and {sup 3}H (tritium) concentrations of xylem waters and subsurface waters using time-series sampling

    SciTech Connect

    1999-11-09

    This application describes a method for the determination of {sup 18}O/{sup 16}O and {sup 2}H/{sup 1}H ratios and {sup 3}H concentrations of xylem and subsurface waters using time-series sampling, insulating sampling chambers, and combined {sup 18}O/{sup 16}O, {sup 2}H/{sup 1}H and {sup 3}H concentration data on transpired water. The method involves collecting water samples transpired from living plants and correcting the measured isotopic compositions of oxygen ({sup 18}O/{sup 16}O) and hydrogen ({sup 2}H/{sup 1}H and/or {sup 3}H concentrations) to account for evaporative isotopic fractionation in the leafy material of the plant.

  15. Experiments with solid 4He

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.

    2010-08-01

    The possibility of supersolid behavior in 4He was predicted many years ago, but negative experiments in the 1970’s removed motivation for further experimental efforts to explore the possibility until the work of Goodkind’s group renewed attention. Kim and Chan found unambiguous evidence for a period shift in a torsional oscillator filled with solid 4He and this observation and its interpretation have created substantial interest in the study of solid 4He. Here, recent work with an experimental design that allows for superfluid 4He to be in direct contact with solid 4He off the melting curve will be discussed and evidence for the flow of helium atoms through a cell filled with solid 4He, caused by an applied chemical potential difference will be briefly reviewed.

  16. Mobility of solid 4He

    NASA Astrophysics Data System (ADS)

    Day, James

    2005-03-01

    Recent torsional oscillator measurements [1,2] on solid ^4He in the pores of Vycor and in bulk demonstrated non-classical rotational inertia and showed a decrease in period below about 200 mK, suggestive of a transition to a supersolid phase. It becomes interesting to see whether solid ^4He exhibits any of the other unusual flow properties of a superfluid. We have performed capacitive measurements on the mobility of solid ^4He in Vycor. By suddenly increasing the pressure in a cell containing a Vycor sample, we were able to monitor the pressure induced flow of solid ^4He in the pores. Near its melting temperature the solid ^4He does flow in/out of the pores, but the flow rate decreases rapidly with temperature, until no flow is observable below 700 mK. We do not see any flow at temperatures down to 25 mK, implying that either supersolid ^4He in Vycor does not flow in response to a large pressure difference or that superflow occurs at a rate far slower than the critical velocities observed by Kim and Chan. We have also begun work on pressure induced flow of bulk solid ^4He. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC). 1. E. Kim and M.H.W. Chan, Nature 427, 225 (2004). 2. E. Kim and M.H.W. Chan, Science 305, 1941 (2004).

  17. Dipole Resonances in 4He

    SciTech Connect

    Matsumoto, E.; Nakayama, S.; Hayami, R.; Fushimi, K.; Kawasuso, H.; Yasuda, K.; Yamagata, T.; Akimune, H.; Ikemizu, H.; Fujiwara, M.; Yosoi, M.; Nakanishi, K.; Kawase, K.; Hashimoto, H.; Oota, T.; Sagara, K.; Kudoh, T.; Asaji, S.; Ishida, T.; Tanaka, M.

    2007-02-26

    We investigated the analogs of the giant dipole resonance (GDR) and spin-dipole resonance (SDR) of 4He by using the 4He(7Li,7Be) reaction at an incident energy of 455 MeV and at forward scattering angles. The {delta}S=0 and {delta}S=1 spectra for 4He were obtained by measuring the 0.43-MeV 7Be {gamma}-ray in coincidence with the scattered 7Be. From the {delta}S=0 and {delta}S=1 spectra thus obtained, the strength distributions of the GDR and SDR in 4He can be derived and the results are compared with the previous data.

  18. 4He/ 3He thermochronometry

    NASA Astrophysics Data System (ADS)

    Shuster, David L.; Farley, Kenneth A.

    2004-01-01

    Using classical diffusion theory, we present a mathematical technique for the determination of 4He concentration profiles in minerals. This approach should prove useful for constraining the low-temperature cooling histories of individual samples and for correcting (U-Th)/He ages for partial diffusive loss. The calculation assumes that the mineral of interest contains an artificially produced and uniform distribution of 3He obtained by proton irradiation [Shuster et al., Earth Planet. Sci. Lett. 217 (2004) 19-32]. In minerals devoid of natural helium, this isotope allows measurement of He diffusion coefficients; in minerals with measurable radiogenic He, it permits determination of 4He profiles arising during ingrowth and diffusion in nature. The 4He profile can be extracted from stepwise degassing experiments in which the 4He/ 3He ratio is measured. The evolution of the 4He/ 3He ratio as a function of cumulative 3He released can be compared with forward models to constrain the shape of the profile. Alternatively, we present a linear inversion that can be used to directly solve for the unknown 4He distribution. The inversion incorporates a standard regularization technique to filter the influence of random measurement errors on the solution. Using either approach we show that stepwise degassing data can yield robust and high-resolution information on the 4He profile. Profiles of radiogenic He are a sensitive function of the time-Temperate ( t- T) path that a cooling sample experienced. Thus, by step heating a proton-irradiated sample it is possible to restrict the sample's acceptable t- T paths. The sensitivity of this approach was explored by forward-modeling 4He profiles resulting from a range of realistic t- T paths, using apatite as an example. Results indicate that 4He profiles provide rich information on t- T paths, especially when the profiles are coupled with (U-Th)/He cooling ages on the same sample. Samples that experienced only moderate diffusive loss

  19. Ions in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Pang, Tao

    1988-08-01

    A quantum model is proposed to describe the motion of ions in the 4He superfluid. The interaction between the ions and 4He atoms is expressed in terms of the structure factor and quasiparticle operators of the quantum liquid. This model Hamiltonian is solved by a variational scheme. On the basis of the nonparabolic energy-momentum spectum of the dressed ions, an explanation is given for the linear temperature dependence of the ion effective mass observed in the experiments. The study reveals some interesting aspects of the interaction between classical particles and quantum fields.

  20. Superflow in Solid ^4He

    NASA Astrophysics Data System (ADS)

    Saslow, Wayne

    2005-03-01

    Kim and Chan have recently observed Non-Classical Rotational Inertia (NCRI) for solid ^4He in Vycor glass, porous gold, and bulk. Using a microscopic theory where each atom has the same local superfluid velocity (which depends on the microscopic atomic mass density), we show that their low T value of the superfluid fraction, ρs/ρ0 0.015, is consistent with what is known of atomic delocalization in this system. In the macroscopic theory, we explicitly include a lattice mass density ρL distinct from the normal fluid density ρn, thus making the superfluid hydrodynamics consistent with Galilean transformations, which implies that ρ0=ρs+ρn+ρL. We also show that ρL(T)=ρ0(T)-^*s(T), where ρ0(T) is the average mass density and ^*s(T) is computed from the microscopic mass density. This added complexity makes determination of ρn/ρ0 from the measured ρs/ρ0 non-trivial, although an excitation energy of about 0.35 K is relevant as ρn/ρ0 rises from its low temperature value of zero. The macroscopic phase inferred from the observation of NCRI suggests quantum vortices, whose cores must reside between the lattice sites.

  1. Superflow in Solid ^4He.

    NASA Astrophysics Data System (ADS)

    Saslow, Wayne M.

    2004-10-01

    Kim and Chan have recently observed Non-Classical Rotational Inertia (NCRI) for solid ^4He in Vycor glass, gold film, and bulk.^1 Their low T value of the superfluid fraction, ρ_s/ρ_0≈0.015, is consistent with what is known of atomic delocalization in this quantum solid.^2 On including a lattice mass density ρL distinct from the normal fluid density ρn (which is zero at T=0), the superfluid hydrodynamics becomes consistent with Galilean transformations. From its microscopic definition, ρL is temperature dependent. As a consequence, determination of ρ_n/ρ0 from ρ_s/ρ0 is not trivial, although a characteristic excitation energy of about 0.35 K can be estimated. The macroscopic phase inferred from the observation of NCRI suggests quantum vortex lines and quantum vortex rings, which may explain the unusually low critical velocity and certain hysteretic phenomena. 1. E. Kim and M. H. W. Chan, Nature 427, 225 (2004). 2. W. M. Saslow, Phys. Rev. Lett. 36, 1151 (1976).

  2. Experimental dosimetric comparison of (1)H, (4)He, (12)C and (16)O scanned ion beams.

    PubMed

    Tessonnier, T; Mairani, A; Brons, S; Haberer, T; Debus, J; Parodi, K

    2017-05-21

    At the Heidelberg Ion Beam Therapy Center, scanned helium and oxygen ion beams are available in addition to the clinically used protons and carbon ions for physical and biological experiments. In this work, a study of the basic dosimetric features of the different ions is performed in the entire therapeutic energy range. Depth dose distributions are investigated for pencil-like beam irradiation, with and without a modulating ripple filter, focusing on the extraction of key Bragg curve parameters, such as the range, the peak-width and the distal 80%-20% fall-off. Pencil-beam lateral profiles are measured at different depths in water, and parameterized with multiple Gaussian functions. A more complex situation of an extended treatment field is analyzed through a physically optimized spread-out Bragg peak, delivered with beam scanning. The experimental results of this physical beam characterization indicate that helium ions could afford a more conformal treatment and in turn, increased tumor control. This is mainly due to a smaller lateral scattering than with protons, leading to better lateral and distal fall-off, as well as a lower fragmentation tail compared to carbon and oxygen ions. Moreover, the dosimetric dataset can be used directly for comparison with results from analytical dose engines or Monte Carlo codes. Specifically, it was used at the Heidelberg Ion Beam Therapy Center to generate a new input database for a research analytical treatment planning system, as well as for validation of a general purpose Monte Carlo program, in order to lay the groundwork for biological experiments and further patient planning studies.

  3. Experimental dosimetric comparison of 1H, 4He, 12C and 16O scanned ion beams

    NASA Astrophysics Data System (ADS)

    Tessonnier, T.; Mairani, A.; Brons, S.; Haberer, T.; Debus, J.; Parodi, K.

    2017-05-01

    At the Heidelberg Ion Beam Therapy Center, scanned helium and oxygen ion beams are available in addition to the clinically used protons and carbon ions for physical and biological experiments. In this work, a study of the basic dosimetric features of the different ions is performed in the entire therapeutic energy range. Depth dose distributions are investigated for pencil-like beam irradiation, with and without a modulating ripple filter, focusing on the extraction of key Bragg curve parameters, such as the range, the peak-width and the distal 80%-20% fall-off. Pencil-beam lateral profiles are measured at different depths in water, and parameterized with multiple Gaussian functions. A more complex situation of an extended treatment field is analyzed through a physically optimized spread-out Bragg peak, delivered with beam scanning. The experimental results of this physical beam characterization indicate that helium ions could afford a more conformal treatment and in turn, increased tumor control. This is mainly due to a smaller lateral scattering than with protons, leading to better lateral and distal fall-off, as well as a lower fragmentation tail compared to carbon and oxygen ions. Moreover, the dosimetric dataset can be used directly for comparison with results from analytical dose engines or Monte Carlo codes. Specifically, it was used at the Heidelberg Ion Beam Therapy Center to generate a new input database for a research analytical treatment planning system, as well as for validation of a general purpose Monte Carlo program, in order to lay the groundwork for biological experiments and further patient planning studies.

  4. Zircon 4He/3He thermochronometry

    NASA Astrophysics Data System (ADS)

    Tripathy-Lang, Alka; Fox, Matthew; Shuster, David L.

    2015-10-01

    Multiple thermochronometric methods are often required to constrain time-continuous rock exhumation for studying tectonic processes or development of km-scale topography at Earth's surface. Here, we explore 4He/3He thermochronometry of zircon as a method for constraining continuous time-temperature (t-T) paths of individual samples through a temperature range that is complementary to methods such as 40Ar/39Ar thermochronometry of K-feldspar and 4He/3He thermochronometry of apatite. For different cooling rates and diffusion domain size, the temperature sensitivity of zircon 4He/3He thermochronometry ranges from slightly less than 100 °C to slightly greater than 250 °C; a typical sample provides continuous thermal constraints over ∼100 °C within that range. Outside these temperatures, 4He in zircon will either be quantitatively retained or completely lost by volume diffusion. As proof-of-concept, we present stepwise release 4He/3He spectra and associated U and Th concentration maps measured by laser ablation ICP-MS analysis of individual crystal aliquots of Fish Canyon Tuff (FCT) zircon and of a more complex setting in the Sierra Nevada batholith that experienced reheating from a proximal basaltic intrusion, the Little Devil's Postpile (LDP). The FCT zircon 4He/3He release spectra are consistent with a 4He spatial distribution dominated by alpha-ejection from crystal surfaces. The spatial distributions of U and Th measured in the same crystals do not substantially influence 4He/3He release spectra that are predicted for the known thermal history, even when incorporating spatially variable diffusivity due to accumulation of radiation damage. Conversely, the LDP 4He/3He release spectra are strongly influenced by the observed parent nuclide zonation. A three-dimensional (3D) numerical model of 4He production and diffusion, which incorporates crystal geometry, U and Th zonation, and spatially variable He diffusion kinetics, substantially improves the fit between

  5. Exploration of Vacancies in Solid 4^He

    NASA Astrophysics Data System (ADS)

    Clark, Bryan; Ceperley, David

    2006-03-01

    Experiments by Kim and Chan [1] have renewed interest in the understanding of supersolids and whether mechanisms exist in solid ^4He to allow for supersolid-like effects. Ground state vacancies would lead to bose condensation and superfluidity. Using Path Integral Monte Carlo we examine vacancy formation energies, vacancy-vacancy interactions and the effect of vacancies on supersolid behavior in solid ^4He. [1] E. Kim and M. H. Chan, Science 305, 1941 (2004).

  6. Path Integral Simulations of Solid ^4He

    NASA Astrophysics Data System (ADS)

    Ceperley, David

    2006-03-01

    Kim and Chan have found indications that solid ^4He is a supersolid by measuring the period of a torsional oscillator. To understand the state of solid ^4He at low temperature, we [1] have calculated tunnelling frequencies for ring exchanges in bulk solid helium with Path Integral Monte Carlo by finding the free energy of a path that begins with the atoms in one configuration and ends with a permutation of those positions. The exchange frequencies are found to be described by a lattice model which does not show superfluid behavior. However, simulations [2] of ^4He absorbed in Vycor find that ^4He forms a layered structure with the first layer solid-like and highly localized, the second layer disordered with some atoms delocalized and possibly superfluid. This persistent liquid layer mechanism can only be relevant for bulk ^4He in a very disordered crystal. New calculations [3] of the single particle density matrix, (the fourier transform of the momentum distribution) to measure ODLRA will also be discussed. [1] D. M. Ceperley and B. Bernu, Phys. Rev. Letts. 93, 155303(2004).[2] S. A. Khairallah and D. M. Ceperley, Phys. Rev. Letts. 95, 185301 (2005). [3] B. Clark and D. M. Ceperley, unpublished.

  7. Observation of superflow in solid ^4He

    NASA Astrophysics Data System (ADS)

    Kim, Eunseong

    2005-03-01

    At temperatures below 2.176 K, liquid ^4He enters into a superfluid state and flows without any friction. There is strong evidence that Bose-Einstein condensates in dilute gases also exhibit superfluidity. Perhaps it is counter to intuition, but superfluid like behavior is thought possible even in solid helium. We employed a torsional oscillator technique and found evidence of superflow in bulk solid ^4He (1) and solid ^4He confined in porous Vycor glass (2). The effect appears as a drop in the resonant oscillation period as the sample cell is cooled below about 0.2 K. A series of control experiments reveals that the effect is due to irrotational superflow as in superfluid helium. The supersolid fraction in the low temperature limit is about 1%. It has a ``universal'' temperature dependence that is different from that of the superfluid transition in liquid and different from that of a weakly interacting Bose gas. The supersolid fraction is strongly attenuated with increasing oscillation speed, indicating that the critical velocity is extremely low. (1) E. Kim and M. H. W. Chan, Science 305, 1941 (2004) (2) E. Kim and M. H. W. Chan, Nature 425, 227 (2004)

  8. The Momentum Distribution of Liquid ^4{He}

    NASA Astrophysics Data System (ADS)

    Prisk, T. R.; Bryan, M. S.; Sokol, P. E.; Granroth, G. E.; Moroni, S.; Boninsegni, M.

    2017-07-01

    In this paper, we report a high-resolution neutron Compton scattering study of liquid ^4{He} under milli-Kelvin temperature control. To interpret the scattering data, we performed Quantum Monte Carlo calculations of the atomic momentum distribution and final state effects for the conditions of temperature and density considered in the experiment. There is excellent agreement between the observed scattering and ab initio calculations of its lineshape at all temperatures. We also used model fit functions to obtain from the scattering data empirical estimates of the average atomic kinetic energy and Bose condensate fraction. These quantities are also in excellent agreement with ab initio calculations. We conclude that contemporary Quantum Monte Carlo methods can furnish accurate predictions for the properties of Bose liquids, including the condensate fraction, close to the superfluid transition temperature.

  9. The Annealing Process in Solid 4He

    NASA Astrophysics Data System (ADS)

    Rittner, Ann Sophie C.; Reppy, John D.

    2007-09-01

    We have used a torsional oscillator with square cross section and a resonance frequency of 185 Hz to confirm the nonclassical rotational inertia (NCRI) discovered by Kim and Chan (Nature 427:225, 2004; Science 305:1941, 2004). We have also found a strong correlation between the NCRI signal and a high dissipation Q -1 of 4×10-6 of the oscillation above the transition temperature. Here, we present preliminary results of the annealing process in 4He at a pressure of 26 bar. When holding the temperature constant above 1 K we have observed a immediate rise in the period and a slow decay of the dissipation. The equilibrium value of Q -1 decreases with increasing temperature.

  10. Entanglement area law in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Herdman, C. M.; Roy, P.-N.; Melko, R. G.; Maestro, A. Del

    2017-06-01

    Area laws were first discovered by Bekenstein and Hawking, who found that the entropy of a black hole grows proportional to its surface area, and not its volume. Entropy area laws have since become a fundamental part of modern physics, from the holographic principle in quantum gravity to ground-state wavefunctions of quantum matter, where entanglement entropy is generically found to obey area law scaling. As no experiments are currently capable of directly probing the entanglement area law in naturally occurring many-body systems, evidence of its existence is based on studies of simplified qualitative theories. Using new exact microscopic numerical simulations of superfluid 4He, we demonstrate for the first time an area law scaling of entanglement entropy in a real quantum liquid in three dimensions. We validate the fundamental principle that the area law originates from correlations local to the entangling boundary, and present an entanglement equation of state showing how it depends on the density of the superfluid.

  11. Deeply Virtual Compton Scattering off 4He

    NASA Astrophysics Data System (ADS)

    Joosten, Sylvester; CLAS Collaboration

    2015-10-01

    The European Muon Collaboration (EMC) observed the first signs of a modification of the partonic structure of the nucleon when present in a nuclear medium. The precise nature of these effects, as well as their underlying cause, is yet to be determined. The generalized parton distribution (GPD) framework provides a powerful tool to study the partonic structure of nucleons inside a nucleus. Hard exclusive leptoproduction of a real photon off a nucleon, deeply virtual Compton scattering (DVCS), is presently considered the cleanest experimental access to the GPDs, through the Compton form factors (CFFs). This is especially the case for scattering off the spin-zero helium nucleus, where only a single CFF contributes to the process. The real and imaginary parts of this CFF can be constrained through the beam-spin asymmetry (BSA). We will present the first measurements of the DVCS process off 4He using the CEBAF 6 GeV polarized electron beam and the CLAS detector at JLab. The CLAS detector was supplemented with an inner electromagnetic calorimeter for photons produced at small angles, as well as a radial time projection chamber (RTPC) to detect low-energy recoil nuclei. This setup allowed for a clean measurement of the BSA in both the coherent and incoherent channels.

  12. Effective two-body model for spectra of clusters of H 2 ,H 3 ,3He, and 4He with 4He, and H 2 -4He scattering

    NASA Astrophysics Data System (ADS)

    Fraser, P. R.; Massen-Hane, K.; Kadyrov, A. S.; Amos, K.; Bray, I.; Canton, L.

    2017-07-01

    Four light-mass nuclei are considered by an effective two-body clusterization method: 7Li as 3H+4He ,7Be as 3He+4He ,8Be as 4He+4He , and 6Li as 2H+4He . The low-energy spectra of the first three are determined from single-channel Lippmann-Schwinger equations. For the last, two uncoupled sets of equations are considered: those involving the 3S1 and those of the posited 1S0 states of H 2 . Low-energy elastic scattering cross sections are calculated from the same H 2 +4He Hamiltonian, for many angles and energies for which data are available. While some of these systems may be more fully described by many-body theories, this work establishes that a large amount of data may be explained by these two-body clusterizations.

  13. The breakup of (16)O and its astrophysical implications

    NASA Astrophysics Data System (ADS)

    Bryan, Diane Carol

    1998-07-01

    The feasibility of using the breakup of 16O to obtain information about the 12C(/alpha,/gamma)16O radiative capture reaction has been studied in a series of experiments performed at the Nuclear Structure Research Laboratory at the University of Rochester. The 16O breakup fragments-12C and 4He-were identified using a new focal-plane detector capable of identifying these fragments down to a relative energy of 50 keV. The relative energy spectra obtained from 16O breakup on a 58Ni target are dominated by sequential breakup from 9.85 MeV, and 10.36 MeV excited states in 16O. There is also some evidence of breakup at relative energies below 1 MeV. Interpretation of this low energy yield in terms of E2 Coulomb excitation leads to a value of SE2=346 keV b at Erel=0.828 MeV after making a correction for the contribution due to nuclear breakup. This suggests that the rate of the 12C(/alpha,/gamma)16O reaction at astrophysical energies is much higher than is presently accepted, which would have an enormous impact on stellar nucleosynthesis.

  14. Coupled Dynamics for Superfluid (4) {He} 4 He in a Channel

    NASA Astrophysics Data System (ADS)

    Khomenko, D.; Mishra, P.; Pomyalov, A.

    2017-06-01

    We study the coupled dynamics of normal and superfluid components of superfluid ^4{He} in a channel considering the counterflow turbulence with laminar normal component. In particular, we calculated profiles of the normal velocity, the mutual friction, the vortex line density and other flow properties and compared them to the case where the dynamic of the normal component is "frozen." We have found that the coupling between the normal and superfluid components leads to flattening of the normal velocity profile, increasingly more pronounced with temperature, as the mutual friction, and therefore, coupling becomes stronger. The commonly measured flow properties also change when the coupling between the two components is taken into account.

  15. Adsorption of 4He on a Single C60

    NASA Astrophysics Data System (ADS)

    Szybisz, L.; Urrutia, I.

    2004-01-01

    The adsorption of $^4$He inside and outside a single fullerene C$_{60}$ is studied. A physisorption potential is proposed. The energetics and structural features of C$_{60}$-$^4$He$_N$ clusters are investigated. Particular attention is paid to the growth of the highly pronounced layered density profile. The evolution towards bulk liquid and surface thickness at the free interface are discussed.

  16. Dielectric Measurements of Solid ^4He in Vycor

    NASA Astrophysics Data System (ADS)

    Day, James; Beamish, John

    2004-03-01

    It is well established that confinement in pores suppresses the freezing of liquids, including helium. Pressures greater than about 36 bar are required in order to freeze ^4He in the small pores of vycor glass. Recent torsional oscillator measurements^1 at pressures around 60 bar, where the ^4He is expected to be completely solid at low temperatures, showed a decrease in period below about 175 mK, suggesting the possibility of decoupling of a 'supersolid' phase of ^4He. We have made capacitive measurements of the pressure and density of ^4He in vycor. Solidification in the pores was easily detected from the resulting change in the ^4He density. At a pressure of about 40 bar, freezing began at 1.64 K and was accompanied by a 2% density increase. Cooling the solid ^4He/vycor system below 20 mK did not reveal any unexpected capacitance changes that might indicate that helium was entering or leaving the pores. With a capacitance resolution better than 1 ppm, a ^4He density change of 0.01% would have been detected. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC). 1. E Kim and MHW Chan (Nature, to be published)

  17. Supersolidity of Solid ^4He Confined in 25 Angstrom Nanopores

    NASA Astrophysics Data System (ADS)

    Shirahama, Keiya; Yoshimura, Hitomi; Shibayama, Yoshiyuki

    2009-03-01

    There has been growing consensus that dislocations play an important role on the supersolid behaviors observed in torsional oscillator experiments for solid ^4He. When solid He is confined in nanopores, dislocations may not exist, or even if they exist their motion is suppressed, and supersolidity should therefore be greatly modified. Study of solid 4He in confined geometries may therefore give an important clue to elucidate the mechanism of supersolidity. Earlier studies of solid 4He in Vycor by Kim and Chan [1] found no difference in the supersolid behaviors from bulk solid. We have performed torsional oscillator experiments for solid 4He in a porous Gelsil glass that has nanopores of 25 angstroms in diameter. We have observed an increase in oscillator frequency indicating supersolidity below 200 mK. This result suggests that the existence of dislocations is not a necessary condition for supersolidity. [1] E. Kim, M. H. W. Chan, Nature 427, (2004) 225.

  18. Liquid 4He Adsorbed Films on Very Attractive Substrates

    NASA Astrophysics Data System (ADS)

    Urrutia, Ignacio; Szybisz, Leszek

    Adsorbed films of liquid 4He are analized, in the framework of Density functionals Theories (DF). In these systems, when the substrate becomes increasingly attractive, the thin films of 4He approaches the quasi-bidimensional limit. We study this strongly attractive substrate regime with two DF, the Orsay-Trento (OT) and a recent Hybrid proposal (Hyb), focusing in the energy behavior. It is showed that OT does not reproduce the correct limiting energy curve, and it implies that this functional could not provide reliable results for very strongly attractive substrates like Graphite (Gr). In other hand, with the Hyb DF, the correct energy behavior is found for the adsorption energy of 4He on Gr. These results show that OT should not be applied to quasi 2D (confinement) situations, and that Hyb DF provides a much more realistic description.

  19. Liquid 4He Adsorbed Films on Very Attractive Substrates

    NASA Astrophysics Data System (ADS)

    Urrutia, Ignacio; Szybisz, Leszek

    2006-09-01

    Adsorbed films of liquid 4He are analized, in the framework of Density Functional Theories (DF). In these systems, when the substrate becomes increasingly attractive, the thin films of 4He approaches the quasi-bidimensional limit. We study this strongly attractive substrate regime with two DF, the Orsay-Trento (OT) and a recent Hybrid proposal (Hyb), focusing in the energy behavior. It is showed that OT does not reproduce the correct limiting energy curve, and it implies that this functional could not provide reliable results for very strongly attractive substrates like Graphite (Gr). In other hand, with the Hyb DF, the correct energy behavior is found for the adsorption energy of 4He on Gr. These results show that OT should not be applied to quasi 2D (confinement) situations, and that Hyb DF provides a much more realistic description.

  20. Meson Spectroscopy in Coherent Production off 4 He with CLAS

    NASA Astrophysics Data System (ADS)

    Torayev, Bayram; CLAS Collaboration

    2015-04-01

    Meson spectroscopy requires disentanglement of states with different quantum numbers that decay to the same final states, as well as separation of meson-bayron and purely mesonic states. Coherent scattering off 4 He uniquely aids both by providing a spin and iso-spin zero target, simplifying partial wave analysis, and an unmodified recoil nucleus, eliminating background from bayron resonances . At Jefferson Lab, we conducted the first experiment for meson spectroscopy using coherent quasi-real photo-production on 4 He. This took place in Hall-B in 2009, using a 6 GeV electron beam and the CLAS detector. A new radial time projection chamber with high pressure gaseous target detects low-energy recoil 4 He nuclei. In this talk, status of the analysis and the first look on coherently produced mesonic final states will be presented.

  1. The measurement of 4He photodisintegration with MAIKo active target

    NASA Astrophysics Data System (ADS)

    Murata, M.; Adachi, S.; Akimune, H.; Furuno, T.; Kawabata, T.; Tsumura, M.

    2017-06-01

    The phtodisintegration reactions of 4He nuclei i.e., 4He(γ,pt) and 4He(γ,3He)n, play crucial roles for the nucleosynthesis in the universe, but the result of previous experimental studys show sizable discrepancies. We performed the measurement of these reactions with the TPC-based MAIKo active target. The MAIKo active target enable us to detect, the sensitivity for the low energy decay particles emitted to full solid angle. The mearsurement were carried out at the New SUBARU synchrotron radiation facility, and the qusi-monoquromatic pulsed photon beam were irradiated on MAIKo. The data analysis has been partially done. The number of true events were counted by tracking of recorded images, and the total flux of photon beams was determined by the analysis of the spectrum recorded by the NaI beam monitor.

  2. Quantum stereodynamics of the 18O +16O16O16O18O +16O exchange reaction at low collision energy

    NASA Astrophysics Data System (ADS)

    Privat, Erwan; Guillon, Grégoire; Honvault, Pascal

    2017-10-01

    We present a quantum study of stereodynamics of the 18O +16O16O (v = 0, j = 1) →16O18O (v‧ = 0,j‧) +16O exchange reaction at a collision energy Ecoll = 0.01eV . Polarization moments of the reactants have been computed and stereodynamical portraits have been generated. The results show that the reactant preferred relative orientations are strongly dependent on the scattering angle and on the product rotational states.

  3. Proton polarization from π+ absorption in 4He

    NASA Astrophysics Data System (ADS)

    Aclander, J.; MayTal-Beck, S.; Altman, A.; Ashery, D.; Hahn, H.; Moinester, M. A.; Rahav, A.; Feltham, A.; Jones, G.; Pavan, M.; Sevior, M.; Hutcheon, D.; Ottewell, D.; Smith, G. R.; Niskanen, J. A.

    1993-02-01

    The polarization of protons resulting from π+ absorption in 4He was measured at bombarding energies of 120 MeV and 250 MeV. Events arising from absorption in a quasi-deuteron were analysed by using kinematical constraints. The apparatus was tested by measuring the polarization of protons resulting from π +d→ overline→pp . Differences observed between polarization measured for pion absorption in the deuteron and in quasi-deuterons inside 3He and 4He suggest that the density of the absorbing nucleon pair affects this observable. There is however a large discrepancy between the experimental results and theoretical predictions.

  4. Pion Absorption in 3, 4He and πN Resonances

    NASA Astrophysics Data System (ADS)

    Orphanos, L.; Källne, J.; Altemus, R.; Gugelot, P. C.; McCarthy, J. S.; Minehart, R. C.; Gram, P. A. M.; Höistad, B.; Morris, C. L.; Wadlinger, E. A.; Perdrisat, C.

    1981-06-01

    The cross sections of 3,4He(π-,n)2,3H have been measured at 285, 428, 525, and 575 MeV, extending the information on the energy dependence beyond the region previously known (50-300 MeV). The cross sections beyond the region of the Δ resonance are found to decrease less rapidly than that of the elementary πd-->pp process. This energy dependence suggests that pion absorption in a nucleus is associated with π+N (off-shell) scattering which includes I=12 πN resonances that are strongly suppressed in πd-->pp.

  5. Capillary condensation of 4He in cylindrical pores

    NASA Astrophysics Data System (ADS)

    Urrutia, Ignacio; Szybisz, Leszek

    2004-10-01

    The adsorption of superfluid 4He confined into cylindrical pores of alkali metals is illustrated by looking at the case of Na. A density functional formalism is utilized for the theoretical description. The energetics and density profiles are determined as a function of the radius of cylinders and the filling fraction. These results are compared with those provided by a simple model recently proposed.

  6. The ^4He Trimer as an Efimov System: Latest Developments

    NASA Astrophysics Data System (ADS)

    Kolganova, E. A.; Motovilov, A. K.; Sandhas, W.

    2017-03-01

    Kolganova et al. (Few-Body Syst 51:249, 2011) reviewed the results that demonstrate the Efimov nature of the ^4He three-atom system. The present note represents an extension of that survey to the time period which passed since its publication.

  7. Stability and Spectra of Small 3He-4He Clusters

    NASA Astrophysics Data System (ADS)

    Navarro, J.; Fantoni, S.; Guardiola, R.; Zuker, A.

    Diffusion Monte Carlo calculations have been systematically performed to analyze the stability of small mixed 3He-4He clusters, as well as their excitation spectra. The picture that emerges is that of systems with strong shell effects whose binding and excitation energies are essentially determined by the monopole properties of an effective Hamiltonian.

  8. Transverse Ultrasound Measurements in 4He Single Crystals

    NASA Astrophysics Data System (ADS)

    Syshchenko, O.; Beamish, J.

    2008-02-01

    Recently, Kim and Chan (Science 305:1941, 2004; Phys. Rev. Lett. 97:115302, 2006) have reported an anomalous decoupling transition of solid 4He in a torsional oscillator measurement, and interpret their results as evidence for non-classical rotational inertia and a possible supersolid phase of 4He. The detailed nature and properties of such a “supersolid” state in 4He are still far from being clear, although there are clues from experiments involving 3He impurities, different sample cell geometries, annealing effects and grain boundary flow. Defects produced during crystal growth or deformation (e.g. dislocations) may affect supersolidity, or even produce it, and they are expected to have significant impact on the elastic properties of the solid. The supersolid fraction could also decouple from the lattice and produce a decrease in the transverse sound speed. We have begun the experiments in this laboratory to study such effects, measuring the velocity and attenuation of transverse ultrasound at 10 MHz in 4He single crystals grown at constant pressure.

  9. Analysis of 4He+40Ca and 4He+44Ti scattering using different optical model potentials

    NASA Astrophysics Data System (ADS)

    Ibraheem, Awad A.

    2016-09-01

    Elastic scattering of 4He+40Ca and 4He+44Ti reactions at backward angles has been analyzed using two differentmodels, microscopic and semimicroscopic folding potentials. The derived real potentials supplemented with phenomenological Woods-Saxon imaginary potentials, provide good agreement with the experimental data at energy E c.m. = 21.8 MeV without need to renormalize the potentials. Coupledchannels calculations are used to extract the inelastic scattering cross section to the low-lying state 2+ (1.083 MeV) of 44Ti. The deformation length is obtained and compared with the electromagnetic measurement values as well as those obtained from previous studies.

  10. Generalized Rotational Susceptibility Studies of Solid 4He

    NASA Astrophysics Data System (ADS)

    Gadagkar, V.; Pratt, E. J.; Hunt, B.; Yamashita, M.; Graf, M. J.; Balatsky, A. V.; Davis, J. C.

    2012-11-01

    Using a novel SQUID-based torsional oscillator (TO) technique to achieve increased sensitivity and dynamic range, we studied TO's containing solid 4He. Below ˜250 mK, the TO resonance frequency f increases and its dissipation D passes through a maximum as first reported by Kim and Chan. To achieve unbiased analysis of such 4He rotational dynamics, we implemented a new approach based upon the generalized rotational susceptibility χ{4He}^{ - 1}(ω,T). Upon cooling, we found that equilibration times within f( T) and D( T) exhibit a complex synchronized ultraslow evolution toward equilibrium indicative of glassy freezing of crystal disorder conformations which strongly influence the rotational dynamics. We explored a more specific χ{4He}^{ -1}(ω,tau(T)) with τ( T) representing a relaxation rate for inertially active microscopic excitations. In such models, the characteristic temperature T ∗ at which df/ dT and D pass simultaneously through a maximum occurs when the TO angular frequency ω and the relaxation rate are matched: ωτ( T ∗)=1. Then, by introducing the free inertial decay (FID) technique to solid 4He TO studies, we carried out a comprehensive map of f( T, V) and D( T, V) where V is the maximum TO rim velocity. These data indicated that the same microscopic excitations controlling the TO motions are generated independently by thermal and mechanical stimulation of the crystal. Moreover, a measure for their relaxation times τ( T, V) diverges smoothly everywhere without exhibiting a critical temperature or velocity, as expected in ωτ=1 models. Finally, following the observations of Day and Beamish, we showed that the combined temperature-velocity dependence of the TO response is indistinguishable from the combined temperature-strain dependence of the 4He shear modulus. Together, these observations imply that ultra-slow equilibration of crystal disorder conformations controls the rotational dynamics and, for any given disorder conformation, the

  11. Elastic scattering of ^4He by ^6Li at E(^4He) = 24, 25, and 26 MeV

    NASA Astrophysics Data System (ADS)

    Bartosz, E. E.; Cathers, P. D.; Kemper, K. W.; Maréchal, F.; Rusek, K.

    1998-11-01

    A previous optical model analysis of the elastic scattering of ^4He by ^6Li at E(^4He) = 18.5 MeV (P. V. Green, K. W. Kemper, P. L. Kerr, K. Mohajeri, E. G. Myers, D. Robson, K. Rusek and I. J. Thompson, Phys. Rev. C 53) 2862 (1996)., as well as a cluster-folded continuum- discretized coupled channels analysis (K. Rusek, P. V. Green, P. L. Kerr, and K. W. Kemper, Phys. Rev. C 56) 1895 (1997)., resulted in a good description of the data set, but the optical model analysis yielded a poor description of the 25 MeV elastic scattering data measured at the same time. New elastic and inelastic scattering angular distribution cross sections are reported for ^4He + ^6Li at E(^4He) = 24, 25 and 26 MeV. Three energies were used to rule out anomalous scattering at 25 MeV. The results of a cluster-folded continuum- discretized coupled channels analysis similar to that used with the 18.5 MeV data are presented for the three new data sets at 24, 25, and 26 MeV.

  12. Laser pumped (4)He magnetometer with light shift suppression.

    PubMed

    Lin, Zaisheng; Wang, He; Peng, Xiang; Wu, Teng; Guo, Hong

    2016-11-01

    We report a laser-pumped (4)He atomic magnetometer with light shift suppression through the atomic sensor itself. A linearly polarized light is used to optically align the (4)He metastable atoms and we monitor the magneto-optical double resonance (MODR) signals produced by the left- and right-circularly orthogonal components. It is shown that light shift leads to the atomic alignment to orientation conversion effect, and thus, the difference between the two MODR signals. One of these two MODR signals is locked at the Larmor frequency and is used to measure the ambient magnetic field, while the differential signal is, simultaneously, fed back to suppress the light shift. The scheme could be of the advantage to the design of compact magnetometers by reducing the systematic errors due to light shift.

  13. Sodium dimers on the surface of liquid {sup 4}He

    SciTech Connect

    Ancilotto, F.; DeToffol, G.; Toigo, F.

    1995-12-01

    We have studied the structure of a sodium dimer interacting with liquid {sup 4}He. We calculated the equilibrium configuration and binding energy of a Na{sub 2} molecule solvated in a bulk liquid {sup 4}He ``bubble`` and near the liquid-vapor interface ``dimple`` by using a density-functional approach. We find that the solvated molecule is a metastable state, while the the lowest energy bound state occurs when the molecule lies flat on the surface of the liquid. The binding energy for the ``erect`` dimer is only {similar_to}1 K higher than the flat dimer, with no potential energy barrier between the two orientations, implying relatively free rotations of the molecule on the surface. The small effects of the liquid environment on the vibrational properties of the dimer are investigated.

  14. Nuclear polarization corrections to the μ4He+ Lamb shift.

    PubMed

    Ji, C; Nevo Dinur, N; Bacca, S; Barnea, N

    2013-10-04

    Stimulated by the proton radius conundrum, measurements of the Lamb shift in various light muonic atoms are planned at PSI. The aim is to extract the rms charge radius with high precision, limited by the uncertainty in the nuclear polarization corrections. We present an ab initio calculation of the nuclear polarization for μ(4)He(+) leading to an energy correction in the 2S-2P transitions of δ(pol)(A)=-2.47 meV ±6%. We use two different state-of-the-art nuclear Hamiltonians and utilize the Lorentz integral transform with hyperspherical harmonics expansion as few-body methods. We take into account the leading multipole contributions, plus Coulomb, relativistic, and finite-nucleon-size corrections. Our main source of uncertainty is the nuclear Hamiltonian, which currently limits the attainable accuracy. Our predictions considerably reduce the uncertainty with respect to previous estimates and should be instrumental to the μ(4)He(+) experiment planned for 2013.

  15. Action-at-a-distance in confined superfluid 4-HE

    NASA Astrophysics Data System (ADS)

    Thomson, Stephen R. D.

    Previous measurements of the superfluid density for 4He revealed effects at distances much larger than the correlation length. The first study in this thesis was to systematically examine the length scale over which these effects can manifest via confining the 4He in a Corbino geometry. The Corbino geometry consists of two concentric 268 nm planar regions connected via a 34 nm film above a ring of width W. This width W is varied from 4 micrometers up to 100 micrometers in different experimental cells. Two new effects in the superfluid fraction were found: one is hydrodynamic and the other is a shift in the transition temperature as a function of ring width. A second study examined planar films. This revealed that overall scaling fails while the critical temperature can be scaled.

  16. Decoupling NCRI from shear modulus changes in solid ^4He

    NASA Astrophysics Data System (ADS)

    West, Joshua T.; Chan, Moses H. W.

    2008-03-01

    Day and Beamish report a significant increase in the shear modulus of solid ^4He [1] below 250 mK with temperature dependence similar to the non-classical rotational inertia (NCRI) response seen in torsional oscillator measurements [2]. Finite element calculations show that stiffening of the solid ^4He could mimic very small NCRI signals [3]. We have constructed a one-piece, welded oscillator which is designed to minimize the effect from stiffening of the solid helium. Preliminary data will be presented. [1] J. Day and J. R. Beamish, arXiv:0709.4666v1 (2007). [2] E. Kim and M. H. W. Chan, Science 305, 1941 (2004). [3] A. C. Clark and M. H. W. arXiv:0711.3619v1 (2007).

  17. Overview on Solid 4He and the Issue of Supersolidity

    NASA Astrophysics Data System (ADS)

    Chan, M. H. W.; Hallock, R. B.; Reatto, L.

    2013-09-01

    Here we provide an overview of the status of the field of solid 4He with a focus on the recent theoretical and experimental activities stimulated by the 2004 experiments of Kim and Chan. The overview attempts to place the experimental and theoretical work in context, to respect the historical flow of the field and discuss our present understanding of the question of supersolidity in 4He. The possibility of supersolidity in cold atoms and in other systems is also addressed. Special issues of the Journal of Low Temperature Physics (168(3/4), 2012; 169(3/4), 2012), in addition to this issue, have been devoted to this subject and this overview is meant to accompany those issues of the journal.

  18. Bose-Einstein condensation in liquid 4He under pressure

    SciTech Connect

    Glyde, Henry R; Omar Diallo, Souleymane; Azuah, Richard T; Kirichek, Oleg; Taylor, Jon W.

    2011-01-01

    We present neutron scattering measurements of Bose-Einstein condensation, the atomic momen- tum distribution and Final State effects in liquid 4He under pressure. The condensate fraction at low temperature is found to decrease from n0 = 7.25 0.75% at SVP (p 0) to n0 = 3.2 0.75% at pressure p = 24 bar. This indicates an n0 = 3.0% in the liquid at the liquid/solid co-existence line (p = 25.3 bar). The atomic momentum distribution n(k) has high occupation of low k states and differs significantly from a Gaussian (e.g. a classical n(k)). Both n(k) and the Final state function broaden with increasing pressure, reflecting the increased localization of the 4He in space under increased pressure.

  19. 4He Versus 3He Josephson Effect: Vibration Decoherence

    SciTech Connect

    Pereverzev, Sergey V.

    2006-09-07

    Several on-going experiments searching for the Josephson effect in 4He close to the {lambda}-transition employ experimental cells with a weak link in the form of an array of submicron holes, with the size of the array and the cell dimensions very close to those used for 3He-B. In the same environment, the 4He experiment is more prone to decoherence by mechanical vibrations. The problem is due to the shift of the maximum of the vibration response of the experiment to low frequencies (0.1 Hz or less) and to the increase of the power spectrum density of the seismic velocities with decreasing frequency in this frequency range. To avoid decoherence, one needs to lower the cut-off frequency of the vibration isolation or to use an array with a larger open area. The latter option is briefly discussed.

  20. Low-energy inelastic neutrino reactions on 4He.

    PubMed

    Gazit, Doron; Barnea, Nir

    2007-05-11

    The inelastic scattering of neutrino off 4He is calculated microscopically at energies typical for core-collapse supernova environment. The calculation is carried out with the Argonne V18 nucleon-nucleon potential and the Urbana IX three-nucleon force. Full final state interaction is included via the Lorentz integral transform method. The contribution of axial meson exchange currents to the cross sections is taken into account from effective field theory of nucleons and pions to order O(Q3).

  1. Momentum distributions in hcp, bcc, and liquid /sup 4/He

    SciTech Connect

    Sokol, P.E.; Simmons, R.O.; Price, D.L.; Hilleke, R.O.

    1984-05-01

    Using Deep Inelastic Neutron Scattering we have measured the nuclear momentum distribution in hcp, bcc and liquid /sup 4/He at constant density over a temperature range 0.96K < T < 4.0K. We find no temperature dependence of the momentum distribution in the hcp solid or the liquid. We also find no difference between the hcp, bcc and liquid phases. The average kinetic energy per atom is lower than the best present theories predict.

  2. NOVEL CONCEPTS FOR ISOTOPIC SEPARATION OF 3HE/4HE

    SciTech Connect

    Roy, L.; Nigg, H.; Watson, H.

    2012-09-04

    The research outlined below established theoretical proof-of-concept using ab initio calculations that {sup 3}He can be separated from {sup 4}He by taking advantage of weak van der Waals interactions with other higher molecular weight rare gases such as xenon. To the best of our knowledge, this is the only suggested method that exploits the physical differences of the isotopes using a chemical interaction.

  3. Observation and optimization of 4He atomic polarization spectroscopy.

    PubMed

    Wu, Teng; Peng, Xiang; Gong, Wei; Zhan, Yuanzhi; Lin, Zaisheng; Luo, Bin; Guo, Hong

    2013-03-15

    Polarization spectroscopy in (4)He around 1083 nm is observed and optimized with a distributed feedback fiber laser and is applied for frequency stabilization. In order to improve the accuracy and long-term stability of the frequency-locking performance, a power stabilization module is added, and the dependences of the peak-to-peak amplitude and frequency difference (width) of the polarization spectroscopy signal on various pump and probe powers are investigated.

  4. The 4He(π+,π-) reaction at low energies

    NASA Astrophysics Data System (ADS)

    Chaos Collaboration; Gräter, J.; Bilger, R.; Clement, H.; Meier, R.; Wagner, G. J.; Friedman, E.; Schepkin, M.; Amaudruz, P. A.; Felawka, L.; Ottewell, D.; Smith, G. R.; Ambardar, A.; Hofman, G. J.; Kermani, M.; Tagliente, G.; Bonutti, F.; Camerini, P.; Grion, N.; Rui, R.; Hong, P.; Mathie, E. L.; Tacik, R.; Clark, J.; Sevior, M. E.; Patarakin, O.

    1998-02-01

    Using the CHAOS spectrometer at TRIUMF the total cross sections and outgoing pion momentum distributions for the 4He(π+,π-) reaction were measured for π+ kinetic energies from 70 to 130 MeV. At energies around 100 MeV the total cross sections show an excess by a factor 3 over conventional model calculations which could be ascribed to a contribution from a hypothetical d' dibaryon.

  5. Inchworm Driving of 4He Crystals in Superfluid

    NASA Astrophysics Data System (ADS)

    Yoshida, Taichi; Tachiki, Akira; Nomura, Ryuji; Okuda, Yuichi

    2017-07-01

    A 4He quantum crystal can be grown from a superfluid liquid extremely quickly owing to the high crystallization rate at sufficiently low temperatures. Such crystals are readily deformed by an applied force as the result of the crystal-superfluid phase transition but, to date, the remotely controlled movement of highly deformable 4He crystals has yet to be demonstrated. The present work attempted to move 4He crystals using inchworm driving, a technique that is employed to impart motion to classical solid objects based on the difference between static and dynamic friction forces. Using a plate oscillating with a sawtooth-like non-symmetric motion 100 times over the span of 1.0 s, it was found possible to move a 4He crystal on the plate in a superfluid at 0.3 K. However, the observed behavior was quite different from the ordinary inchworm driving of a classical object. Initially, one side of the crystal was seen to stick on the plate, and the crystal did not move for 0.6 s but rather deformed appreciably. After this deformation, the entire body of the crystal began to move, but the distance traversed was one order of magnitude larger than expected from the oscillation amplitude. This peculiar behavior is specific to this quantum crystal. The initial lack of motion can possibly be explained by pinning and depinning of the contact line on the substrate plate, while the extent of motion is attributed to the crystal-superfluid transition, namely crystallization on one side and melting on the other, assisted by superflow induced during the oscillation process.

  6. Measurement of the SOC State Specific Heat in 4He

    NASA Astrophysics Data System (ADS)

    Chatto, A. R.; Lee, R. A. M.; Duncan, R. V.; Day, P. K.; Goodstein, D. L.

    2006-09-01

    When a heat flux Q is applied downward through a sample of liquid 4He near the lambda transition, the helium self organizes such that the gradient in temperature matches the gravity induced gradient in Tλ. All the helium in the sample is then at the same reduced temperature tSOC = TSOC-Tλ/Tλ and the helium is said to be in the Self-Organized Critical (SOC) state. We have made preliminary measurements of the 4He SOC state specific heat, C∇T(T(Q)). Despite having a cell height of 2.54 cm, our results show no difference between C∇T and the zero-gravity 4He specific heat results of the Lambda Point Experiment (LPE) [J.A. Lipa et al., Phys. Rev. B, 68, 174518 (2003)] over the range 250 to 450 nK below the transition. There is no gravity rounding because the entire sample is at the same reduced temperature tSOC(Q). Closer to Tλ the SOC specific heat falls slightly below LPE, reaching a maximum at approximately 50 nK below Tλ, in agreement with theoretical predictions [R. Haussmann, Phys. Rev. B, 60, 12349 (1999)].

  7. Cross-checking groundwater age by 4He and 14C dating in a granite, Tono area, central Japan

    NASA Astrophysics Data System (ADS)

    Hasegawa, Takuma; Nakata, Kotaro; Tomioka, Yuichi; Goto, Kazuyuki; Kashiwaya, Koki; Hama, Katsuhiro; Iwatsuki, Teruki; Kunimaru, Takanori; Takeda, Masaki

    2016-11-01

    Groundwater dating was performed simultaneously by the 4He and 14C methods in granite of the Tono area in central Japan. Groundwater was sampled at 30 packed-off sections of six 1000-m boreholes. 4He concentrations increased and 14C concentrations decreased along a groundwater flow path on a topographic gradient. 4He ages were calculated by using the in situ 4He production rate derived from the porosity, density, and U and Th content of the rock, neglecting external flux. 14C ages were calculated with a noncorrected model in which the initial 14C content was 100 percent of the modern radiocarbon level (Co = 100 pmC), a statistical model using the average 14C content of tritium-bearing samples (Co = 46.4 pmC), and a δ13C model based on the isotopic mass balance. Although the absolute 14C ages calculated by the models were different, the relative 14C ages were almost identical. The relative 14C ages were considered reliable because dissolved inorganic carbon has no significant geochemical reactions in granite. The relation between the 4He ages and the noncorrected 14C ages was [4He age] = 1.15 [14C age] + 7200 (R2 = 0.81), except in the discharge area. The slope of this relation was equivalent to unity, which indicates that the 4He accumulation rate is confirmed by the relative 14C ages. Moreover, the accumulated 3He/4He ratio was equivalent to that derived from the 6Li(α,n)3H reaction in granite. These results show that the accumulated He is of crustal origin, produced in situ without external flux, except in the discharge area. The intercept value of 7200 a implies that the 14C concentrations were diluted due to geochemical reactions. Tritium-bearing samples supported this result. Simultaneous measurements make it feasible to estimate the accumulation rate of 4He and initial dilution of 14C, which cannot be done with a single method. Cross-checking groundwater dating has the potential to provide more reliable groundwater ages. The circulation time of the

  8. Hyperspherical coupled channel calculations of energy and structure of 4He-4He-Li+ and its isotopic combinations

    NASA Astrophysics Data System (ADS)

    Liu, Min-min; Wu, Meng-Shan; Han, Hui-li; Shi, Ting-yun

    2016-07-01

    The ground state vibrational energy and spatial features of 4He-4He-Li+ and its triatomic isotopic complexes are studied using the slow variable discretization (SVD) method in the hyperspherical coordinates for the zero total angular momentum. Our results show that the dominant structure of the system is an isosceles triangle with the shorter side associated with the two Li+-He distances using the sum-of-potential approximation. Corrections caused by the induced dipole-induced dipole interactions on the He atoms are also investigated. The effects are seen to be small and have a minor influence on the binding energy and the structure of present system. The results are also compared with the full ab initio calculations including all the three-body interactions and information of three-body corrections is obtained.

  9. Erratum: The Primordial Abundance of 4He: An Update

    NASA Astrophysics Data System (ADS)

    Olive, Keith A.; Skillman, Evan; Steigman, Gary

    1997-11-01

    In the paper ``The Primordial Abundance of 4He: An Update'' by Keith A. Olive, Evan Skillman, and Gary Steigman (ApJ, 483, 788 [1997]), Evan Skillman's and Gary Steigman's names were interchanged, giving each the wrong address. The correct order of the authors is Keith A. Olive, Evan Skillman, and Gary Steigman; Evan Skillman's address is School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, and Gary Steigman's address is Department of Physics and Astronomy, The Ohio State University, Columbus, OH 43210.

  10. SiO 2: chlorophyll gels under 4He irradiation

    NASA Astrophysics Data System (ADS)

    Rickards, J.; García, J. M.; García, M. R.; Ramírez, E.; López, K.

    1997-05-01

    SiO 2 gels doped with chlorophyll extracted from natural leaves were exposed to different fluences of a 3-MeV 4He beam from the Instituto de Física Pelletron Accelerator. Optical absorption, emission and excitation spectra were measured as a function of fluence in the interval (0-2.5) × 10 14 cm -2. Slight increases in both emission and excitation spectra at small fluences were observed. For larger fluences a characteristic exponential-type decay was produced due to degradation of the organic molecules. The data were fitted with a Lorentzian curve. A discussion of possible mechanisms is given in terms of the irradiation parameters.

  11. Once more on the superfluid 4He (in Ukrainian)

    NASA Astrophysics Data System (ADS)

    Vakarchuk, I. O.

    Through the solution of motion equations for the density fluctuations of the many-particle system expressions for the energy spectrum, structural factor and free energy have been found. At the temperature Tto 0 K they yield the results of Bogoliubov theory and at high temperatures they tend to the corresponding expressions for the classical systems in the random phases approximation. The contribution of the non-linear fluctuations has also been taken into account. The obtained expressions are conducive to the study of λ-transition in liquid ^4He.

  12. Vacancy distribution in a rotating solid 4He

    NASA Astrophysics Data System (ADS)

    Pushkarov, D. I.

    2012-03-01

    Vacancy distribution is considered in a rotating solid 4He immersed in a superfluid helium-II. Vacancies are considered as a quasiparticle gas of vacancions with a gap dispersion law. It is shown that the radial distribution depends on Poisson's ratio and practically not on Young's modulus. The treatment is based on a nonlinear theory unifying the elasticity theory equations and a Boltzmann-type transport equation valid for arbitrary angular velocities. The situation simulates, in a sense, the Kim and Chan rotational experiments where nonclassical inertia was observed. The model cannot be applied to solid 3He. We do not presuppose in this work any supersolid fraction.

  13. Homogeneous nucleation of crystalline order in superdense liquid 4He

    NASA Astrophysics Data System (ADS)

    Pederiva, F.; Ferrante, A.; Fantoni, S.; Reatto, L.

    1995-09-01

    We present the results of a numerical crystallization experiment in 4He performed with the shadow wave function and the variational Monte Carlo method. The experiment consists in Monte Carlo simulations starting from liquidlike configurations of the atoms at a density well above the melting point. The system presents spontaneous nucleation of crystalline seeds, proving the spontaneous symmetry-breaking property of the shadow wave function. The final configurations display a face-centered-cubic structure grown preferentially by \\{111\\} planes, accompanied by stacking disorder.

  14. Optical investigation of impurities in superfluid {sup 4}He

    SciTech Connect

    Tabbert, B.; Guenther, H.; Putlitz, G. zu

    1997-12-01

    This review is devoted to optical studies of foreign particles in superfluid {sup 4}He. Starting with single excess electrons, helium ions and metastable helium atoms, various methods for the implantation of these species into the quantum fluid are summarized. Continuing with neutral and charged atoms, molecules, and clusters implantation techniques like laser ablation, gas discharges, or atomic beams are discussed. The implanted particles act as micro-probes for the liquid helium and form complex defect structures-known as bubbles and snowballs. The behavior of the impurities, their defect structures in the liquid, and their optical spectra are discussed. The treatment is mainly focused on the manifold of atoms and ions from nearly all groups of the periodic table of elements which became available for optical experiments in liquid {sup 4}He in the recent ten years. It includes theoretical description of the impurities by the standard bubble model (SBM). Extensions and limitations of the SBM are discussed regarding non-radiative transitions and the dynamic Jahn-Teller effect. The review is concluded by a discussion of applications of `the presented experimental methods such as spin physics and motion studies in liquid helium.

  15. Primordial 4He constraints on inelastic macro dark matter revisited

    NASA Astrophysics Data System (ADS)

    Jacobs, David M.; Allwright, Gwyneth; Mafune, Mpho; Manikumar, Samyukta; Weltman, Amanda

    2016-11-01

    At present, the best model for the evolution of the cosmos requires that dark matter make up approximately 25% of the energy content of the Universe. Most approaches to explain the microscopic nature of dark matter, to date, have assumed its composition to be of intrinsically weakly interacting particles; however, this need not be the case to have consistency with all extant observations. Given decades of inconclusive evidence to support any dark matter candidate, there is strong motivation to consider alternatives to the standard particle scenario. One such example is macro dark matter, a class of candidates (macros) that could interact strongly with the particles of the Standard Model, have large masses and physical sizes, and yet behave as dark matter. Macros that scatter completely inelastically could have altered the primordial production of the elements, and macro charge-dependent constraints have been obtained previously. Here we reconsider the phenomenology of inelastically interacting macros on the abundance of primordially produced 4He and revise previous constraints by also taking into account improved measurements of the primordial 4He abundance. The constraints derived here are limited in applicability to only leptophobic macros that have a surface potential V (RX)≳0.5 MeV . However, an important conclusion from our analysis is that even neutral macros would likely affect the abundance of the light elements. Therefore, constraints on that scenario are possible and are currently an open question.

  16. A more precise atomic mass of ^4He : Ongoing reduction of uncertainties for the UW-PTMS

    NASA Astrophysics Data System (ADS)

    Pinegar, David; Zafonte, Steven; van Liew van Dyck, Seth, Jr.

    2004-05-01

    Using a Penning trap mass spectrometer (PTMS), the atomic mass of ^4He has been found to be 4 002 603 254.153(64) nu (an uncertainty of 16 ppt). This number agrees well with the previous two best measurements of the ^4He mass(S. Brunner, et al., Eur. Phys. J. D 15), 181-188 (2001). (T. Fritioff, et al., Eur. Phys. J. D 15), 141--143, (2001).. In addition to giving a precise atomic mass of the α-particle, ^4He can now be used as a convenient reference ion by less precise mass spectrometers. For our measurement, the cyclotron frequencies of ^12C^6+ and ^4H^2+ ions were compared, using a Penning ion trap with an extremely stable (less than 2 ppt/h of drift) magnetic field. While many aspects of our experiment have been previously described (as for the recent ^16O result, at 10 ppt unceratinty(R. S. Van Dyck, Jr., S. L. Zafonte, and P. B. Schwinberg, Hyp. Interact. 132), 163--175, (2001), and references.), we will present several techniques and changes to the apparatus that have improved the accuracy of our machine by about an order of magnitude in recent years.

  17. Ab initio many-body calculations of nucleon-4He scattering with three-nucleon forces

    DOE PAGES

    Hupin, Guillaume; Langhammer, Joachim; Navratil, Petr; ...

    2013-11-27

    We extend the ab initio no-core shell model/resonating-group method to include three-nucleon (3N) interactions for the description of nucleon-nucleus collisions. We outline the formalism, give algebraic expressions for the 3N-force integration kernels, and discuss computational aspects of two alternative implementations. The extended theoretical framework is then applied to nucleon-4He elastic scattering using similarity-renormalization-group (SRG)-evolved nucleon-nucleon plus 3N potentials derived from chiral effective field theory. We analyze the convergence properties of the calculated phase shifts and explore their dependence upon the SRG evolution parameter. We include up to six excited states of the 4He target and find significant effects from themore » inclusion of the chiral 3N force, e.g., it enhances the spin-orbit splitting between the 3/2– and 1/2– resonances and leads to an improved agreement with the phase shifts obtained from an accurate R-matrix analysis of the five-nucleon experimental data. As a result, we find remarkably good agreement with measured differential cross sections at various energies below the d+3H threshold, while analyzing powers manifest larger deviations from experiment for certain energies and angles.« less

  18. Quantized Vortex State in hcp Solid 4He

    NASA Astrophysics Data System (ADS)

    Kubota, Minoru

    2012-11-01

    The quantized vortex state appearing in the recently discovered new states in hcp 4He since their discovery (Kim and Chan, Nature, 427:225-227, 2004; Science, 305:1941, 2004) is discussed. Special attention is given to evidence for the vortex state as the vortex fluid (VF) state (Anderson, Nat. Phys., 3:160-162, 2007; Phys. Rev. Lett., 100:215301, 2008; Penzev et al., Phys. Rev. Lett., 101:065301, 2008; Nemirovskii et al., arXiv:0907.0330, 2009) and its transition into the supersolid (SS) state (Shimizu et al., arXiv:0903.1326, 2009; Kubota et al., J. Low Temp. Phys., 158:572-577, 2010; J. Low Temp. Phys., 162:483-491, 2011). Its features are described. The historical explanations (Reatto and Chester, Phys. Rev., 155(1):88-100, 1967; Chester, Phys. Rev. A, 2(1):256-258, 1970; Andreev and Lifshitz, JETP Lett., 29:1107-1113, 1969; Leggett, Phys. Rev. Lett., 25(22), 1543-1546, 1970; Matsuda and Tsuneto, Prog. Theor. Phys., 46:411-436, 1970) for the SS state in quantum solids such as solid 4He were based on the idea of Bose Einstein Condensation (BEC) of the imperfections such as vacancies, interstitials and other possible excitations in the quantum solids which are expected because of the large zero-point motions. The SS state was proposed as a new state of matter in which real space ordering of the lattice structure of the solid coexists with the momentum space ordering of superfluidity. A new type of superconductors, since the discovery of the cuprate high T c superconductors, HTSCs (Bednorz and Mueller, Z. Phys., 64:189, 1986), has been shown to share a feature with the vortex state, involving the VF and vortex solid states. The high T c s of these materials are being discussed in connection to the large fluctuations associated with some other phase transitions like the antiferromagnetic transition in addition to that of the low dimensionality. The supersolidity in the hcp solid 4He, in contrast to the new superconductors which have multiple degrees of freedom of

  19. Dislocation Structure and Mobility in hcp ^{4}He.

    PubMed

    Landinez Borda, Edgar Josué; Cai, Wei; de Koning, Maurice

    2016-07-22

    Using path-integral Monte Carlo simulations, we assess the core structure and mobility of the screw and edge basal-plane dislocations in hcp ^{4}He. Our findings provide key insights into recent interpretations of giant plasticity and mass flow junction experiments. First, both dislocations are dissociated into nonsuperfluid Shockley partial dislocations separated by ribbons of stacking fault, suggesting that they are unlikely to act as one-dimensional channels that may display Lüttinger-liquid-like behavior. Second, the centroid positions of the partial cores are found to fluctuate substantially, even in the absence of applied shear stresses. This implies that the lattice resistance to motion of the partial dislocations is negligible, consistent with the recent experimental observations of giant plasticity. Further results indicate that both the structure of the partial cores and the zero-point fluctuations play a role in this extreme mobility.

  20. Experimental investigation of cavitation in superfluid [sup 4]He

    SciTech Connect

    Pettersen, M.S.; Balibar, S. ); Maris, H.J. )

    1994-05-01

    We present the results of experiments to study cavitation in liquid [sup 4]He at negative pressures. A focused sound wave is used to generate a negative pressure in a small region of the liquid, and the cavitation is detected by light scattering. We have studied the cavitation as a function of the temperature and static pressure applied to the liquid. We are able to observe the statistical nature of the cavitation process, and to determine the nucleation barrier and the attempt frequency. The results for the attempt frequency are lower than expected for homogeneous nucleation. We discuss the possibility that the nucleation is occurring on quantized vortices. The tensile strength at constant pressure decreases slowly with increasing temperature in the range 0.8 to 1.5 K, drops rapidly as the temperature approaches the [lambda] point, and then decreases slowly above [ital T][sub [lambda

  1. Pressure and density of vacancies in solid [sup 4]He

    SciTech Connect

    Bukman, D.J. ); van Leeuwen, J.M.J. )

    1994-01-01

    Crystals of [sup 4]He contain vacancies that move around by a quantum-mechanical hopping process. The density and pressure of these vacancies can be experimentally studied. The accuracy of the experiments is high enough to detect the effect of the Bose statistics of the vacancies. In this paper we examine the effect of the hard-core repulsion between the vacancies, which should also have a measurable effect on their behavior. We set up a virial expansion for a lattice gas of hard-core particles, and calculate the second virial coefficient. It turns out that the vacancies behave as ideal Bose particles at low temperatures, but that the hard-core interaction makes them behave more and more like fermions as the temperature increases.

  2. Fluidization of granular media wetted by liquid 4He.

    PubMed

    Huang, K; Sohaili, M; Schröter, M; Herminghaus, S

    2009-01-01

    We explore experimentally the fluidization of vertically agitated polymethylmethacrylate spheres wetted by liquid 4He . By controlling the temperature around the lambda point, we change the properties of the wetting liquid from a normal fluid (helium I) to a superfluid (helium II). For wetting by helium I, the critical acceleration for fluidization (Gamma_{c}) shows a steep increase close to the saturation of the vapor pressure in the sample cell. For helium II wetting, Gamma_{c} starts to increase at about 75% saturation, indicating that capillary bridges are enhanced by the superflow of the unsaturated helium film. Above saturation, Gamma_{c} enters a plateau regime where the capillary force between particles is independent of the bridge volume. The plateau value is found to vary with temperature and shows a peak at 2.1K , which we attribute to the influence of the specific heat of liquid helium.

  3. Dynamics of photoexcited Ba(+) cations in (4)He nanodroplets.

    PubMed

    Leal, Antonio; Zhang, Xiaohang; Barranco, Manuel; Cargnoni, Fausto; Hernando, Alberto; Mateo, David; Mella, Massimo; Drabbels, Marcel; Pi, Martí

    2016-03-07

    We present a joint experimental and theoretical study on the desolvation of Ba(+) cations in (4)He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba(+) cations and Ba(+)Hen exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba(+) Hen exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba(+). In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba(+) cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba(+) cations or exciplexes, even when relaxation pathways to lower lying states are included.

  4. Dislocation Structure and Mobility in hcp 4He

    NASA Astrophysics Data System (ADS)

    Landinez Borda, Edgar Josué; Cai, Wei; de Koning, Maurice

    2016-07-01

    Using path-integral Monte Carlo simulations, we assess the core structure and mobility of the screw and edge basal-plane dislocations in hcp 4He. Our findings provide key insights into recent interpretations of giant plasticity and mass flow junction experiments. First, both dislocations are dissociated into nonsuperfluid Shockley partial dislocations separated by ribbons of stacking fault, suggesting that they are unlikely to act as one-dimensional channels that may display Lüttinger-liquid-like behavior. Second, the centroid positions of the partial cores are found to fluctuate substantially, even in the absence of applied shear stresses. This implies that the lattice resistance to motion of the partial dislocations is negligible, consistent with the recent experimental observations of giant plasticity. Further results indicate that both the structure of the partial cores and the zero-point fluctuations play a role in this extreme mobility.

  5. Neutron response function characterization of 4He scintillation detectors

    DOE PAGES

    Kelley, Ryan P.; Rolison, Lucas M.; Lewis, Jason M.; ...

    2015-04-15

    Time-of-flight measurements were conducted to characterize the neutron energy response of pressurized 4He fast neutron scintillation detectors for the first time, using the Van de Graaff generator at Ohio University. The time-of-flight spectra and pulse height distributions were measured. This data was used to determine the light output response function, which was found to be linear at energies below 3.5 MeV. The intrinsic efficiency of the detector as a function of incident energy was also calculated: the average efficiency up to 10 MeV was 3.1%, with a maximum efficiency of 6.6% at 1.05 MeV. Furthermore, these results will enable developmentmore » of neutron spectrum unfolding algorithms for neutron spectroscopy applications with these detectors.« less

  6. Investigating Superfluid ^4He Using Commercially Available Quartz Tuning Forks

    NASA Astrophysics Data System (ADS)

    Wiman, Joshua; Deserio, Robert; Sullivan, Neil; Lee, Yoonseok

    2010-03-01

    Mechanical oscillators such as vibrating wire oscillators, torsional oscillators, and acoustic transducers have been widely used to measure the properties of cryogenic liquids. Commercial quartz tuning forks, which can be found in almost every electronic device, have shown promise as viscometers and thermometers for low temperature experiments. These devices are inexpensive, easy to install, and insensitive to magnetic fields. Before a fork can be used, it must be calibrated against a hydrodynamic model. We measured changes in the frequency and width of the fork's resonance response in superfluid ^4He down to 1.5 K. Analysis of the tuning fork's response as a function of temperature shows that its behavior is well-described by the hydrodynamic model for superfluid helium. We will also discuss our future plans.

  7. Dynamics of photoexcited Ba+ cations in 4He nanodroplets

    NASA Astrophysics Data System (ADS)

    Leal, Antonio; Zhang, Xiaohang; Barranco, Manuel; Cargnoni, Fausto; Hernando, Alberto; Mateo, David; Mella, Massimo; Drabbels, Marcel; Pi, Martí

    2016-03-01

    We present a joint experimental and theoretical study on the desolvation of Ba+ cations in 4He nanodroplets excited via the 6p ← 6s transition. The experiments reveal an efficient desolvation process yielding mainly bare Ba+ cations and Ba+Hen exciplexes with n = 1 and 2. The speed distributions of the ions are well described by Maxwell-Boltzmann distributions with temperatures ranging from 60 to 178 K depending on the excitation frequency and Ba+ Hen exciplex size. These results have been analyzed by calculations based on a time-dependent density functional description for the helium droplet combined with classical dynamics for the Ba+. In agreement with experiment, the calculations reveal the dynamical formation of exciplexes following excitation of the Ba+ cation. In contrast to experimental observation, the calculations do not reveal desolvation of excited Ba+ cations or exciplexes, even when relaxation pathways to lower lying states are included.

  8. Theoretical modeling of electron mobility in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Aitken, Frédéric; Bonifaci, Nelly; von Haeften, Klaus; Eloranta, Jussi

    2016-07-01

    The Orsay-Trento bosonic density functional theory model is extended to include dissipation due to the viscous response of superfluid 4He present at finite temperatures. The viscous functional is derived from the Navier-Stokes equation by using the Madelung transformation and includes the contribution of interfacial viscous response present at the gas-liquid boundaries. This contribution was obtained by calibrating the model against the experimentally determined electron mobilities from 1.2 K to 2.1 K along the saturated vapor pressure line, where the viscous response is dominated by thermal rotons. The temperature dependence of ion mobility was calculated for several different solvation cavity sizes and the data are rationalized in the context of roton scattering and Stokes limited mobility models. Results are compared to the experimentally observed "exotic ion" data, which provides estimates for the corresponding bubble sizes in the liquid. Possible sources of such ions are briefly discussed.

  9. Dynamics of Laser Ablation in Superfluid ^4{He}

    NASA Astrophysics Data System (ADS)

    Buelna, X.; Popov, E.; Eloranta, J.

    2017-02-01

    Pulsed laser ablation of metal targets immersed in superfluid ^4{He} is visualized by time-resolved shadowgraph photography and the products are analyzed by post-experiment atomic force microscopy (AFM) measurements. The expansion dynamics of the gaseous ablation half-bubble on the target surface appears underdamped and follows the predicted behavior for the thermally induced bubble growth mechanism. An inherent instability of the ablation bubble appears near its maximum radius and no tightly focused cavity collapse or rebound events are observed. During the ablation bubble retreat phase, the presence of sharp edges in the target introduces flow patterns that lead to the creation of large classical vortex rings. Furthermore, on the nanometer scale, AFM data reveal that the metal nanoparticles created by laser ablation are trapped in spherical vortex tangles and quantized vortex rings present in the non-equilibrium liquid.

  10. Coherent Propagation of Elementary Excitations in Solid ^4He

    NASA Astrophysics Data System (ADS)

    Goodkind, John M.; Ho, Pei-Chun

    1998-03-01

    We have measured the interaction of heat pulses and acoustic pulses propagating along orthogonal paths in solid ^4He with small amounts of ^3He impurities. The interaction is revealed as a variation of the acoustic attenuation, alpha, and velocity, v, as a function of the delay between launching of the heat pulses and the acoustic pulses. alpha and v pass through extreema at delay times corresponding to the relative propagation velocities of the acoustic waves and the excitations created by the heat pulses. The propagation velocities of the various excitations, determined in this way, are between 50 and 150 m/sec and they increase with decreasing temperature. There are two distinct peaks and a long tail at temperatures above about 500 mK indicating that more than one mode is propagating. The peak effect occurs at a different delay time for alpha than for v at temperatures near the attenuation peak (PC HO, I. P. Bindloss, and J. M. Goodkind, J. Low Temp. Phys., November 1997), providing further evidence for more than one type of propagating mode. The sign of the effect reverses as T is decreased and the change of alpha is of opposite sign to that expected from the equilibrium T dependence of alpha. We will discuss the relation of this phenomenon to previous indications of propagating modes in solid ^4He (G.A. Lengua and J. M. Goodkind, J. Low Temp. Phys., 79), 251 (1990)and to the possible Bose-Einstein condensation (PC HO, I. P. Bindloss, and J. M. Goodkind, J. Low Temp. Phys., November 1997).

  11. Thermal conductivity and torsional oscillations of solid 4He

    NASA Astrophysics Data System (ADS)

    Brazhnikov, M. Yu.; Zmeev, D. E.; Golov, A. I.

    2012-11-01

    Polycrystalline samples of hcp 4He of molar volume Vm = 19.5 cm3 with small amount of 3He impurities were grown in an annular container by the blocked-capillary method. Three concentrations of 3He, x3, were studied: isotopically purified 4He with the estimated x3 < 10-10, commercial `well-grade' helium with x3 ˜ 3.10-7 and a mixture with x3 = 2.5.10-6. Torsional oscillations at two frequencies, 132.5 and 853.6 Hz, and thermal conductivity were investigated before and after annealing. The solid helium under investigation was located not only in the annular container but also in the axial fill line inside two torsion rods and dummy bob of the double-frequency torsional oscillator. The analysis of the frequency shifts upon loading with helium and changing temperatures of different parts of the oscillator suggests that the three techniques probe the properties of solid helium in three different locations: the two different torsion modes respond to the changes of the shear modulus of solid helium in either of the two torsion rods while the thermal conductivity probes the phonon mean free path in solid helium inside the annular container. The temperature and width of the torsional anomaly increase with increasing frequency and x3. The phonon mean free path increases with increasing x3. Annealing typically resulted in an increased phonon mean free path but often in little change in the torsional oscillator response. While the magnitude of the torsional anomaly and phonon mean free path can be very different in different samples, no correlation was found between them.

  12. Parity-Violating Neutron Spin Rotation in n-4He

    NASA Astrophysics Data System (ADS)

    Sarsour, Murad; NSR Collaboration

    2016-09-01

    The neutron spin rotation (NSR) collaboration used parity-violating spin rotation of transversely polarized neutrons transmitted through a 0.5 m liquid helium target to constrain weak coupling constants between nucleons. While consistent with theoretical expectation, the upper limit set by this measurement on the rotation angle, d ϕ/dz = [+1.7 +/- 9.1(stat.) +/-1.4(sys.)] ×10-7 rad/m, is limited by statistical uncertainties. The NSR collaboration is preparing a new measurement to improve this statistically-limited result by about an order of magnitude. In addition to using the new high-flux NG-C beam at the National Institute of Standards and Technology (NIST) Center for Neutron Research, the apparatus is being upgraded to take advantage of the larger-area and more divergent NG-C beam. In addition, significant improvements have been made to the cryogenic design and the 3He ion chamber. Details of these improvements and readiness of the upgraded apparatus will be discussed and the current theoretical and experimental status of d ϕ/dz in n-4He will be reviewed. This work was supported in part by NSF-PHY-1068712 and DE-SC0010443.

  13. Critical behavior of liquid {sup 4}He at negative pressures

    SciTech Connect

    Campbell, C.E.; Folk, R.; Krotscheck, E.

    1996-10-01

    The authors examine the equation of state of liquid {sup 4}He at negative pressures close to the spinodal density {rho}{sub s} where the hydrodynamic speed of sound vanishes. The non-analytic behavior of the equation of state and the speed of sound in the vicinity of the spinodal density are calculated in two and in three dimensions; they find for the speed of sound the non-analytic behavior mc{sub s}{sup 2} {approximately} ({rho}-{rho}{sub s}){sup 2/5} in three dimensions and mc{sub s}{sup 2} {approximately} [({rho}-{rho}{sub s})/{vert_bar}ln({rho}-{rho}{sub s}){vert_bar}]{sup 1/2} in two dimensions. The authors then examine the low density regime numerically, using a semianalytic microscopic theory. It is found that non-analytic exponents are visible only in a negligible density regime around the spinodal point. Estimates for the spinodal densities, and the range of critical fluctations are provided.

  14. PROTON-4He Elastic Scattering at ~ 1 GeV

    NASA Astrophysics Data System (ADS)

    Khan, Z. A.; Singh, Minita

    Based on the (spin-independent) Sugar-Blanckenbecler eikonal expansion for the T-matrix, we parametrize the (spin-dependent) NN amplitude (SNN) which successfully describes the pp and pn elastic scattering observables at ~ 1 GeV up to the available momentum transfers. Using SNN, we calculate the differential cross-section, polarization, and spin-rotation function of ~ 1 GeV protons on 4He within the framework of the Glauber model. The analysis also includes the phase variation in the NN amplitude. It is found that the use of SNN, in comparision with the usually parametrized one-term amplitude, improves the agreement with the experimental data. The introduction of a global phase variation provides only a slight improvement over the results with a constant phase. However, if we allow different phases in the central- and spin-dependent parts of the NN amplitude, the agreement with the polarization data improves further without affecting the differential cross-section results.

  15. Superfluidity of Grain Boundaries in Solid ^4He

    NASA Astrophysics Data System (ADS)

    Prokofiev, Nikolay; Pollet, Lode; Boninsegni, Massimo; Kuklov, Anatoly; Svistunov, Boris; Troyer, Matthias

    2007-03-01

    Superfluid grain boundaries (GB) were proposed as a plausible scenario of the effect discovered by Kim and Chan, and have now been experimentally observed (at the melting point) by Sasaki, Ishiguro, Caupin, Maris, and Balibar [Science 313, 1098 (2006)]. We report results of large-scale quantum Monte Carlo simulations (up to 14000 atoms) of GB in ^4He crystals at the melting pressure, as well as deep inside the solid phase. We find that generically GB are superfluid, with transition temperatures about ˜ 1 K--0.5 K (we estimate the maximum Tc at about 1.50(5) K). At the melting point, the density of particles in the GB is slightly higher than that of a crystal and the GB width is about 3 interatomic spacings. We also observe insulating grain boundaries which typically occur at special orientations of the two crystallites. By simulating GB in direct contact with the superfluid liquid and observing that the system of two liquid-solid and one solid-solid interfaces is mechanically stable we prove that the phenomenon of GB-superfluidity is not related to the close vicinity of the melting line.

  16. Dynamical α -cluster model of 16O

    NASA Astrophysics Data System (ADS)

    Halcrow, C. J.; King, C.; Manton, N. S.

    2017-03-01

    We calculate the low-lying spectrum of the 16O nucleus using an α -cluster model which includes the important tetrahedral and square configurations. Our approach is motivated by the dynamics of α -particle scattering in the Skyrme model. We are able to replicate the large energy splitting that is observed between states of identical spin but opposite parities. We also provide a novel interpretation of the first excited state of 16O and make predictions for the energies of 6- states that have yet to be observed experimentally.

  17. Thermal properties of {sup 4}He surfaces and interfaces

    SciTech Connect

    Clements, B.E.; Krotscheck, E. |; Tymczak, C.J.

    1997-05-01

    A first-principle quantum statistical mechanical theory is used to study the properties of thick liquid {sup 4}He films absorbed to the weakly binding substrates: Li, Na, and Cs. Values for the liquid-gas and solid-liquid surface energies are determined. By fitting, at long wavelengths, the film`s lowest energy mode with the standard expression for the ripplon energy, which depends on the liquid-gas surface energy, the authors obtain excellent agreement with the liquid-vacuum surface energy from recent experiments and also the one previously extracted from quantum liquid droplet calculations. The full spectrum of excitations for wave vectors less than 0.50 {Angstrom}{sup {minus}1} is calculated using a dynamical correlated basis function theory developed in earlier work, which includes multi-phonon scattering processes. Particle currents and transition densities are used to elucidate the nature of the excitations. At a coverage of 0.40 {Angstrom}{sup {minus}2}, the lowest mode shows no significant substrate dependence, and is recognized as being a ripplon propagating in the liquid film at the liquid-gas surface. A new effect is observed for the Cs substrate; the second lowest mode is qualitatively different than found on the other substrates and is identified as interfacial ripplon. In the other substrates the second mode is a volume mode altered somewhat by the high density inner liquid layers. The linewidths of these modes are also calculated. The dynamic excitations provide the input for the thermodynamic theory and the effects on the free energy, heat capacity, and thermal surface broadening of these films are studied as function of the nature of the excitations, the number of modes, and variations in the substrate potentials.

  18. Heavy-ion versus 3He/4He fusion-fission reactions: Angular momentum dependence of dissipation in nuclear fission

    NASA Astrophysics Data System (ADS)

    Ye, W.

    2011-09-01

    The stochastic Langevin model is employed to study dissipation properties in fission in the 16O + 181Ta →197Tl system by analyzing prescission neutron yields measured in this reaction. It has been found that the 197Tl nuclei undergo fission that is not in accordance with the standard Bohr-Wheeler statistical theory. A detailed comparison with previously published work in which fission excitation functions measured in 3,4He + 197Au →200,201Tl are shown to be in excellent agreement with the fission width formula predicted by the traditional models of nuclear fission suggests that nuclear dissipation strength may have an angular momentum dependence in addition to the known deformation and temperature dependence. Implications for the basic understanding of the observed abnormal rise in prescission particles at high energy and the need for further experimental confirmations are discussed.

  19. Experiments on Rogue Waves in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Efimov, Viktor; McClintock, Peter; Ganshin, Andrei; Kolmakov, German; Mezhov-Deglin, Leonid

    2010-05-01

    We describe an experimental and theoretical study of nonlinear wave interactions in superfluid helium and report the observation of rogue waves. Rogue waves (or freak waves, or killer waves, or extreme waves) have long been recognized by sailors as a menace to shipping and are believed to have been responsible for the unexplained losses of vessels of all sizes, including e.g. 22 super-carriers between 1968 and 1994 [1, 2]. Rogue waves on the ocean are rare, and are much higher (and steeper) than all the other waves around them. They seem to appear from nowhere and subsequently to disappear without trace [3]. Following the famous 'New Year wave' measured by instruments on the Draupner North Sea oil rig at the beginning of 1995, the existence of oceanic rogue waves is no longer in doubt. There have been several suggestions about possible mechanisms for the creation of rogue waves. These include the combined effects of wind and currents, and the focusing effects associated with the profile of the ocean floor and nearby shorelines. Where rogue waves appear in deep water far from any shore, which they sometimes do, it seems likely that they must evolve through nonlinear interactions within the 'noisy background" of smaller wind-blown waves [4]. Rogue waves have been modeled theoretically, especially by exploiting the special properties of the nonlinear Schrödinger equation. They have been sought experimentally and/or studied in large wave tanks [5], optical systems [6, 7], and superfluid 4He [8]. Our experimental system consists of high intensity second sound (temperature-entropy) waves within a resonant cavity filled with superfluid 4He at 2.1 K. Under steady state conditions, with a constant oscillatory driving force at the resonant frequency, the second sound waves are turbulent and fluxes of energy flow towards both high and low frequencies. It is found that rogue waves appear under the nonequilibrium conditions that prevail shortly after the drive has been

  20. Secondary radiation measurements for particle therapy applications: prompt photons produced by 4He, 12C and 16O ion beams in a PMMA target

    NASA Astrophysics Data System (ADS)

    Mattei, I.; Bini, F.; Collamati, F.; De Lucia, E.; Frallicciardi, P. M.; Iarocci, E.; Mancini-Terracciano, C.; Marafini, M.; Muraro, S.; Paramatti, R.; Patera, V.; Piersanti, L.; Pinci, D.; Rucinski, A.; Russomando, A.; Sarti, A.; Sciubba, A.; Solfaroli Camillocci, E.; Toppi, M.; Traini, G.; Voena, C.; Battistoni, G.

    2017-02-01

    Charged particle beams are used in particle therapy (PT) to treat oncological patients due to their selective dose deposition in tissues with respect to the photons and electrons used in conventional radiotherapy. Heavy (Z  >  1) PT beams can additionally be exploited for their high biological effectiveness in killing cancer cells. Nowadays, protons and carbon ions are used in PT clinical routines. Recently, interest in the potential application of helium and oxygen beams has been growing. With respect to protons, such beams are characterized by their reduced multiple scattering inside the body, increased linear energy transfer, relative biological effectiveness and oxygen enhancement ratio. The precision of PT demands online dose monitoring techniques, crucial to improving the quality assurance of any treatment: possible patient mis-positioning and biological tissue changes with respect to the planning CT scan could negatively affect the outcome of the therapy. The beam range confined in the irradiated target can be monitored thanks to the neutral or charged secondary radiation emitted by the interactions of hadron beams with matter. Among these secondary products, prompt photons are produced by nuclear de-excitation processes, and at present, different dose monitoring and beam range verification techniques based on prompt-γ detection are being proposed. It is hence of importance to perform γ yield measurement in therapeutic-like conditions. In this paper we report on the yields of prompt photons produced by the interaction of helium, carbon and oxygen ion beams with a poly-methyl methacrylate (PMMA) beam stopping target. The measurements were performed at the Heidelberg Ion-Beam Therapy Center (HIT) with beams of different energies. An LYSO scintillator, placed at {{60}\\circ} and {{90}\\circ} with respect to the beam direction, was used as the photon detector. The obtained γ yields for the carbon ion beams are compared with results from the literature, while no other results from helium and oxygen beams have been published yet. A discussion on the expected resolution of a slit camera detector is presented, demonstrating the feasibility of a prompt-γ-based monitoring technique for PT treatments using helium, carbon and oxygen ion beams.

  1. Secondary radiation measurements for particle therapy applications: prompt photons produced by (4)He, (12)C and (16)O ion beams in a PMMA target.

    PubMed

    Mattei, I; Bini, F; Collamati, F; De Lucia, E; Frallicciardi, P M; Iarocci, E; Mancini-Terracciano, C; Marafini, M; Muraro, S; Paramatti, R; Patera, V; Piersanti, L; Pinci, D; Rucinski, A; Russomando, A; Sarti, A; Sciubba, A; Solfaroli Camillocci, E; Toppi, M; Traini, G; Voena, C; Battistoni, G

    2017-02-21

    Charged particle beams are used in particle therapy (PT) to treat oncological patients due to their selective dose deposition in tissues with respect to the photons and electrons used in conventional radiotherapy. Heavy (Z  >  1) PT beams can additionally be exploited for their high biological effectiveness in killing cancer cells. Nowadays, protons and carbon ions are used in PT clinical routines. Recently, interest in the potential application of helium and oxygen beams has been growing. With respect to protons, such beams are characterized by their reduced multiple scattering inside the body, increased linear energy transfer, relative biological effectiveness and oxygen enhancement ratio. The precision of PT demands online dose monitoring techniques, crucial to improving the quality assurance of any treatment: possible patient mis-positioning and biological tissue changes with respect to the planning CT scan could negatively affect the outcome of the therapy. The beam range confined in the irradiated target can be monitored thanks to the neutral or charged secondary radiation emitted by the interactions of hadron beams with matter. Among these secondary products, prompt photons are produced by nuclear de-excitation processes, and at present, different dose monitoring and beam range verification techniques based on prompt-γ detection are being proposed. It is hence of importance to perform γ yield measurement in therapeutic-like conditions. In this paper we report on the yields of prompt photons produced by the interaction of helium, carbon and oxygen ion beams with a poly-methyl methacrylate (PMMA) beam stopping target. The measurements were performed at the Heidelberg Ion-Beam Therapy Center (HIT) with beams of different energies. An LYSO scintillator, placed at [Formula: see text] and [Formula: see text] with respect to the beam direction, was used as the photon detector. The obtained γ yields for the carbon ion beams are compared with results from the literature, while no other results from helium and oxygen beams have been published yet. A discussion on the expected resolution of a slit camera detector is presented, demonstrating the feasibility of a prompt-γ-based monitoring technique for PT treatments using helium, carbon and oxygen ion beams.

  2. 4 He adsorption on a 3He-plated graphite surface

    NASA Astrophysics Data System (ADS)

    Kwon, Yongkyung; Ahn, Jeonghwan

    Path-integral Monte Carlo (PIMC) calculations have been performed for 4He atoms on top of the 3He first layer on graphite. For this we ignore Fermi statistics of solidified 3He adatoms while Bose statistics of 4He atoms are fully incorporated. We first find that the first 3He layer exhibits a 7/12 commensurate solid structure at the areal density of 0.111 Å-2, which turns out to be identical to the experimental value for its completion density. Additional adsorption of 4He atoms above the complete first 3He layer is found to sustain the underlying 3He commensurate structure and the second 4He layer is observed to display the 4/7 commensurate structure with respect to the first-layer commensurate 3He solid at the areal density of 0.0636 Å-2. Furthermore, it is found that the 4/7 commensurate structure of the second-layer 4He atoms can be formed above a mixture of the first-layer 3He and 4He atoms on graphite. These PIMC results suggest that the 4/7 commensurate structure of the second-layer 4He atoms on graphite, whose existence on top of the first 4He layer has long been in dispute, may be realized on a 3He-plated graphite surface. This could lead to a new approach to observe two-dimensional supersolidity in 4He on graphite.

  3. 4He as a dating groundwater tool in a shallow crystalline aquifer : evidence of mixing of young (<70 y) and old (< 10Ky) waters components

    NASA Astrophysics Data System (ADS)

    Labasque, Thierry; Chatton, Eliot; Guillou, Aurélie; Aquilina, Luc; Fourré, Elise; Vergnaud, Virginie

    2017-04-01

    Groundwater dating methods have been widely used since decades for studying subsurface water hydrological and hydrochemical processes. Estimation of groundwater residence time is essential for resource preservation, contaminant studies or groundwater recharge rates and flow velocities assessments. Due to the complexity of groundwater flow, the joint use of several environmental tracers has been often promoted as they offer integrative information on the structure of complex aquifers. Anthropogenic gas tracers as CFC, SF6, 85Kr, 36Cl or 3H have been widely used to study shallow groundwaters with residence time of less than 70 yrs. For longer groundwater residence time (100- x1000 yr), 39Ar, 14C, 36Cl and 4He have been used. 4He can cover an age range of 100 to thousands years. The main difficulty is to estimate the production rate through U and Th decay and the others fluxes : atmosphere, crust and mantellic. In many cases U-Th production is not sufficient to explain the 4He concentrations observed in the aquifer. Other 4He fluxes can then be estimated through the use of other tracers: 14C, 36Cl or modeling. Fracturing may also enhance 4He concentrations in groundwater. We present here the evaluation of 4He in a crystalline fractured aquifer in the Northwest of France (H+ national hydrogeological network), in order to investigate the range of groundwater residence time in this complex shallow aquifer. Previous studies on this aquifer reveal mixing between young (<70 yrs) and old waters (>1000 yrs) (Ayraud et al., 2008). The Helium radiogenic production rate is then evaluated through in situ production (U, Th) and calibration with CFC and 14C. Apparent ages are compared and uncertainties discussed. 4He proves to be a valuable tool for better understanding water mixing in shallow crystalline aquifers. Ayraud, V. et al. Compartmentalization of physical and chemical properties in hard-rock aquifers deduced from chemical and groundwater age analyses. Appl. Geochemistry

  4. Microwave Spectrum of 12C16O

    NASA Astrophysics Data System (ADS)

    Tashkun, S. A.; Mikhailenko, S. N.

    2010-06-01

    12C16O microwave spectrum of the 0-0,1-1,2-2, and 3-3 bands up to J=50 will be presented. The spectrum was calculated from an experimental dataset of energy levels. Calculated frequencies are given together with 99% confidence intervals. Comparison of the spectrum with microwave data containing in spectroscopic databanks will be discussed. This work was supported by CRDF (USA) Grant RUG1-2954-TO-09 and by RFBR. Grant 09-05-92508. S.A. Tashkun, T.I. Velichko, S.N. Mikhailenko, JQSRT, in press (2010).

  5. Anisotropic superfluidity of {sup 4}He on a C{sub 36} fullerene molecule

    SciTech Connect

    Park, Sungjin; Kim, Byeongjoon; Kwon, Yongkyung

    2015-09-14

    We have performed path-integral Monte Carlo calculations to study the adsorption of {sup 4}He atoms on two different C{sub 36} isomers with the D{sub 6h} and the D{sub 2d} symmetries. The radial {sup 4}He density distributions reveal layer-by-layer growth with the first layer being located at a distance of ∼5.5 Å from the C{sub 36} molecular center and the second layer at ∼8.3 Å. From the angular density profiles of {sup 4}He, we find different quantum states as the number of {sup 4}He adatoms N varies. For N = 20, we observe commensurate solid structures on both D{sub 6h} and D{sub 2d} isomers, where each of 8 hexagon and 12 pentagon centers of the fullerene surfaces is occupied by a single {sup 4}He atom. The second-layer promotion starts beyond N = 38 on both isomers, where a compressible incommensurate structure is observed on the D{sub 6h} isomer and another commensurate structure on D{sub 2d}. Between N = 20 and N = 38, the {sup 4}He monolayer on D{sub 6h} shows several distinct rings of delocalized {sup 4}He atoms along with strongly anisotropic superfluid responses at low temperatures, while isotropic but weak superfluid responses are observed in the {sup 4}He layer on D{sub 2d}.

  6. Elastic Form Factors of 3,4He up to Large Q2

    SciTech Connect

    Kees De Jager

    2007-09-10

    Elastic electron scattering off $^3$He and $^4$He has recently been studied at forward and backward scattering angles in Hall A at JLab. The results will provide accurate data on the elastic form factors, charge and magnetic for $^3$He and charge only for $^4$He, up to squared momentum transfer $Q^2$-values of 3.2 GeV$^2$.

  7. An important source of 4He (and 3He) in diamonds

    NASA Astrophysics Data System (ADS)

    Lal, D.

    1989-12-01

    A large data base has recently accumulated on the concentrations of helium isotopes in diamonds mined from various regions. It was noted earlier (Ozima et al. (1985) [1]; Lal et al. (1989) [2]) that the frequency distribution of the 4He concentrations is a fairly narrow one, whereas that of 3He concentrations is a broad one with no pronounced peaks. The ratios 3He/ 4He , on the other hand show a broad maximum around 2 R a ( R a equals atmospheric 3He/ 4He ratio, = 1.40 × 10 -6) with a slow decrease over two orders of magnitude on either side. Does this imply that the diamonds sample a wide variety of helium reservoirs having a range of 3He/ 4He ratios but somehow attain similar 4He concentrations? We propose that in a majority of the diamonds studied, 4He is primarily due to implantation of radiogenic alpha particles from the host material after emplacement in the crust, usually kimberlite, and that the concentrations of 4He in diamonds often get appreciably altered by this process. Thus the 4He trapped in the diamond at the time of its crystallization is usually overwhelmed by the implanted helium and the measured 3He/ 4He ratios do not generally correspond to any "sources" in the mantle. However, the implanted 4He resides in the outer 16 μm of the diamond, and the intrinsic 4He and 3He/ 4He ratios in the diamond can be studied if its outer layers are removed. The wider implications of diamond being the "target" material for nuclear reaction products from the host material are discussed. Radiogenic 3He produced in the host material is also implanted in the diamond, but this contribution is small on a gross basis. However, since the depth of implantation of 3He is greater than that of 4He, some of the very high 3He/ 4He ratios observed in diamonds could be due to the "implantation" of radiogenic 3He. The radiogenic reactions in the host material can also contribute to appreciable 21Ne in diamonds.

  8. Nuclear georeactor origin of oceanic basalt 3He/4He, evidence, and implications

    PubMed Central

    Herndon, J. Marvin

    2003-01-01

    Nuclear georeactor numerical simulation results yield substantial 3He and 4He production and 3He/4He ratios relative to air (RA) that encompass the entire 2-SD (2σ) confidence level range of tabulated measured 3He/4He ratios of basalts from along the global spreading ridge system. Georeactor-produced 3He/4He ratios are related to the extent of actinide fuel consumption at time of production and are high near the end of the georeactor lifetime. Georeactor numerical simulation results and the observed high 3He/4He ratios measured in Icelandic and Hawaiian oceanic basalts indicate that the demise of the georeactor is approaching. Within the present level of uncertainty, one cannot say precisely when georeactor demise will occur, whether in the next century, in a million years, or in a billion years from now. PMID:12615991

  9. Nuclear georeactor origin of oceanic basalt 3He/4He, evidence, and implications.

    PubMed

    Herndon, J Marvin

    2003-03-18

    Nuclear georeactor numerical simulation results yield substantial (3)He and (4)He production and (3)He(4)He ratios relative to air (R(A)) that encompass the entire 2-SD (2sigma) confidence level range of tabulated measured (3)He(4)He ratios of basalts from along the global spreading ridge system. Georeactor-produced (3)He(4)He ratios are related to the extent of actinide fuel consumption at time of production and are high near the end of the georeactor lifetime. Georeactor numerical simulation results and the observed high (3)He(4)He ratios measured in Icelandic and Hawaiian oceanic basalts indicate that the demise of the georeactor is approaching. Within the present level of uncertainty, one cannot say precisely when georeactor demise will occur, whether in the next century, in a million years, or in a billion years from now.

  10. T(T,2n)4He and 3He(3He,2p)4He: The Reaction Mechanism from Solar Energies to 10 MeV

    NASA Astrophysics Data System (ADS)

    Bacher, A. D.; Brune, C. R.; Sayre, D. B.; Hale, G. M.; Frenje, J. A.; Gatu Johnson, M.

    2016-03-01

    We have studied the energy dependence of the reaction mechanism of the T(t,2n)4He reaction at stellar energies and of its charge symmetric analog reaction 3He(3He,2p)4He at energies up 10 MeV. We find that the reaction mechanism changes dramatically over this energy range in part due to the interference of the two identical fermions in the three-body final state. This contribution is dedicated to the memory of Tom Tombrello, my Ph.D. advisor at Cal Tech, who died in 2014.

  11. Searching for ^16^O^18^O.

    NASA Astrophysics Data System (ADS)

    Marechal, P.; Pagani, L.; Langer, W. D.; Castets, A.

    1997-02-01

    After our first tentative detection of the molecular oxygen ^16^O^18^O isotopomer obtained during the winter '92/93 (Pagani et al. 1993), we attempted to confirm our results by making a deep search in other sources and in other positions in L134N. We have not been able to confirm the original detection in any other place in L134N but we obtain good upper limits towards NGC 2264(IRS2), TMC2, OMC3 and L134N (4', -1') and (5.2', -1) which give an O_2_/CO ratio upper limit near 0.1 -- the lowest yet obtained toward galactic sources -- instead of 0.3-0.4 as predicted by gas phase chemical equilibrium models. As our sample consists of eight cold or lukewarm dark clouds, the low abundance of O_2_ with respect to CO seems to be a general characteristic of dark clouds.

  12. Isovector dipole resonances in {sup 4}He and neutrino-heating in supernova

    SciTech Connect

    Nakayama, S.; Matsumoto, E.; Fushimi, K.; Hayami, R.; Suzuki, T.; Yamagata, T.; Akimune, H.; Ikemizu, H.; Fujiwara, M.; Hashimoto, H.; Kawase, K.; Nakanishi, K.; Oota, T.; Yosoi, M.; Greenfield, M. B.; Kudoh, T.; Sagara, K.; Tanaka, M.

    2010-06-01

    We studied transition strengths to isovector dipole resonances (GDR-1-bar , SDR-1-bar , and SDR-2-bar ) in {sup 4}He by using the {sup 4}He({sup 7}Li,{sup 7}Begamma) reaction at 455 MeV and by comparing with shell-model calculations, in order to estimate cross sections of {sup 4}He for reactions induced by neutrinos emitting from a thermalized neutrino-sphere in the type-II supernova. Excitation of the SDR was dominant in the neutrino-heating of {sup 4}He. The {sup 4}He-excitation via neutral-current reactions of nu{sub m}u{sub ,t}au and nu-bar{sub m}u{sub ,t}au was found to be one order of magnitude stronger than that via charged-current reactions of nu{sub e} and nu-bar{sub e}. The total energy-weighted cross section {sub N} for neutrino-induced neutral-current reactions on {sup 4}He was found to amount to about 1.0x10{sup -40} MeVcentre dotcm{sup 2} which is comparable to those used in the previous simulations. The neutrino-heating effect of {sup 4}He is small in the type-II supernova explosion.

  13. Radiogenic 4He as a conservative tracer in buried-valley aquifers

    USGS Publications Warehouse

    Van Der Hoven, S. J.; Wright, R.E.; Carstens, D.A.; Hackley, Keith C.

    2005-01-01

    [1] The accumulation of 4He in groundwater can be a powerful tool in hydrogeologic investigations. However, the use of 4He often suffers from disagreement or uncertainty related to in situ and external sources of 4He. In situ sources are quantified by several methods, while external sources are often treated as calibration parameters in modeling. We present data from direct laboratory measurements of 4He release from sediments and field data of dissolved 4He in the Mahomet Aquifer, a well-studied buried-valley aquifer in central Illinois. The laboratory-derived accumulation rates (0.13-0.91 ??cm3 STP kgwater-1 yr-1) are 1-2 orders of magnitude greater than the accumulation rates based on the U and Th concentrations of the sediments (0.004-0.009 ??cm3 STP kgwater-1 yr -1). The direct measurement of accumulation rates are more consistent with dissolved concentrations of 4He in the groundwater. We suggest that the direct measurement method is applicable in a variety of hydrogeologic settings. The patterns of accumulation of 4He are consistent with the conceptual model of flow in the aquifer based on hydraulic and geochemical evidence and show areas where in situ production and external sources of 4He are dominant. In the southwestern part of the study area, Ne concentrations are less than atmospheric solubility, indicating gases have been lost from the groundwater. Available evidence indicates that the gases are lost as groundwater passes by pockets of CH4 in glacial deposits overlying the aquifer. However, the external flux from the underlying bedrock appears to dominate the accumulation of radiogenic 4He in the aquifer in the southwestern part of the study area, and the loss or gain of helium as groundwater passes through the overlying sediments is minor in comparison. Copyright 2005 by the American Geophysical Union.

  14. Interlayer correlation between two 4He monolayers adsorbed on both sides of α -graphyne

    NASA Astrophysics Data System (ADS)

    Ahn, Jeonghwan; Park, Sungjin; Lee, Hoonkyung; Kwon, Yongkyung

    2015-07-01

    Path-integral Monte Carlo calculations have been performed to study the 4He adsorption on both sides of a single α -graphyne sheet. For investigation of the interlayer correlation between the upper and the lower monolayers of 4He adatoms, the 4He-substrate interaction is described by the sum of the 4He-C interatomic pair potentials for which we use both Lennard-Jones and Yukawa-6 anisotropic potentials. When the lower 4He layer is a C4 /3 commensurate solid, the upper-layer 4He atoms are found to form a kagome lattice structure at a Mott-insulating density of 0.0706 Å-2 and a commensurate solid at an areal density of 0.0941 Å-2 for both substrate potentials. The correlation between upper- and lower-layer pseudospins, which were introduced in Kwon et al. [Phys. Rev. B 88, 201403(R) (2013)], 10.1103/PhysRevB.88.201403 for two degenerate configurations of three 4He atoms in a hexagonal cell, depends on the substrate potential used; with the substrate potential based on the anisotropic Yukawa-6 pair potentials, the Ising pseudospins of both 4He layers are found to be antiparallel to each other whereas the parallel and antiparallel pseudospin alignments between the two 4He layers are nearly degenerate with the Lennard-Jones potentials. This is attributed to the difference in the interlayer distance, which is ˜4 Å with the Yukawa-6 substrate potential but as large as ˜4.8 Å with the Lennard-Jones potential.

  15. Triple oxygen isotopic composition of the high-3He/4He mantle

    NASA Astrophysics Data System (ADS)

    Starkey, N. A.; Jackson, C. R. M.; Greenwood, R. C.; Parman, S.; Franchi, I. A.; Jackson, M.; Fitton, J. G.; Stuart, F. M.; Kurz, M.; Larsen, L. M.

    2016-03-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the Δ17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 × SEM)‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (∼5‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that magmatic oxygen is sourced from the same mantle as other, more incompatible elements and that the intermediate δ18O value is a feature of the high-3He/4He mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source.

  16. Structure and stability of superfluid 4He systems with cylindrical symmetry

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek; Gatica, Silvina M.

    2001-12-01

    The structure and stability of superfluid 4He systems with cylindrical symmetry are studied. Ground-state energies and density profiles are computed by using density-functional approaches. A model to understand the energetics of cylindrical systems is developed by following the main ideas of the Droplet Model utilized to describe spherical clusters. The necessary condition for stability is formulated by imposing a positive longitudinal isothermal compressibility along the principal axis of the cylinder. It is shown that free cylinders of 4He at T=0 K are unstable. As an example of the evolution towards stable systems, results for liquid 4He confined by cylindrical nanopores in Cs are reported.

  17. Tricritical Casimir forces and order parameter profiles in wetting films of ^{3}He-^{4}He mixtures.

    PubMed

    Farahmand Bafi, N; Maciołek, A; Dietrich, S

    2017-03-01

    Tricritical Casimir forces in ^{3}He-^{4}He wetting films are studied, within mean field theory, in terms of a suitable lattice gas model for binary liquid mixtures with short-ranged surface fields. The proposed model takes into account the continuous rotational symmetry O(2) of the superfluid degrees of freedom associated with ^{4}He and it allows, inter alia, for the occurrence of a vapor phase. As a result, the model facilitates the formation of wetting films, which provides a strengthened theoretical framework to describe available experimental data for tricritical Casimir forces acting in ^{3}He-^{4}He wetting films.

  18. Development of a thermodynamic model for a cold cycle 3He-4He dilution refrigerator

    NASA Astrophysics Data System (ADS)

    Mueller, B. W.; Miller, F. K.

    2016-10-01

    A thermodynamic model of a 3He-4He cold cycle dilution refrigerator with no actively-driven mechanical components is developed and investigated. The refrigerator employs a reversible superfluid magnetic pump, passive check valves, a phase separation chamber, and a series of recuperative heat exchangers to continuously circulate 3He-4He and maintain a 3He concentration gradient across the mixing chamber. The model predicts cooling power and mixing chamber temperature for a range of design and operating parameters, allowing an evaluation of feasibility for potential 3He-4He cold cycle dilution refrigerator prototype designs. Model simulations for a prototype refrigerator design are presented.

  19. Tricritical Casimir forces and order parameter profiles in wetting films of 3He-4He mixtures

    NASA Astrophysics Data System (ADS)

    Farahmand Bafi, N.; Maciołek, A.; Dietrich, S.

    2017-03-01

    Tricritical Casimir forces in 3He-4He wetting films are studied, within mean field theory, in terms of a suitable lattice gas model for binary liquid mixtures with short-ranged surface fields. The proposed model takes into account the continuous rotational symmetry O(2) of the superfluid degrees of freedom associated with 4He and it allows, inter alia, for the occurrence of a vapor phase. As a result, the model facilitates the formation of wetting films, which provides a strengthened theoretical framework to describe available experimental data for tricritical Casimir forces acting in 3He-4He wetting films.

  20. Viscosity of liquid {sup 4}He and quantum of circulation: Are they related?

    SciTech Connect

    L’vov, Victor S. E-mail: skrbek@fzu.cz; Skrbek, Ladislav E-mail: skrbek@fzu.cz; Sreenivasan, Katepalli R. E-mail: skrbek@fzu.cz

    2014-04-15

    In the vicinity of the superfluid transition in liquid {sup 4}He, we explore the relation between two apparently unrelated physical quantities—the kinematic viscosity, ν, in the normal state and the quantum of circulation, κ, in the superfluid state. The model developed here leads to the simple relationship ν ≈ κ/6, and links the classical and quantum flow properties of liquid {sup 4}He. We critically examine available data relevant to this relation and find that the prediction holds well at the saturated vapor pressure. Additionally, we predict the kinematic viscosity for liquid {sup 4}He along the λ-line at negative pressures.

  1. The enigmatic high 3He/4He mantle: Characteristics and Origins. (Invited)

    NASA Astrophysics Data System (ADS)

    Jackson, M. G.

    2009-12-01

    Noble gas isotopes measured in some oceanic island basalts (OIBs) exhibit ratios that are associated with the solar wind and the atmosphere of Jupiter, suggesting that the lavas tap portions of an ancient reservoir that still resides in the Earth’s mantle [e.g., 1]. High 3He/4He, as seen in the sources of some OIBs, can therefore serve as a powerful indicator for tracing ancient signatures that have survived in the Earth’s interior. However, the storage mechanisms and reasons for long-term survival of the high 3He/4He signature in the Earth’s convecting mantle are poorly understood. One important observation is that high 3He/4He lavas have 143Nd/144Nd ratios that are higher than chondrites, suggesting that they were derived from a mantle reservoir that suffered ancient depletion. The association of primitive, high 3He/4He with depleted, nonprimitive 143Nd/144Nd in OIBs is not straightforward and a number of models have been developed to resolve this apparent complexity [e.g., 2,3,4,5,6]. It is also becoming apparent that the high 3He/4He reservoir is heterogeneous. High 3He/4He (>30 times atmospheric) lavas from Hawaii, Iceland and Galapagos have more depleted 143Nd/144Nd (0.51294-0.51297) than lavas with similarly high 3He/4He from Samoa (0.51283). In fact, the highest 3He/4He sample from each southern hemisphere high 3He/4He hotspot (FOZO-A, austral) exhibits lower 143Nd/144Nd ratios their northern hemisphere (FOZO-B, boreal) counterparts. The mechanism for this separation is unknown, but it is similar in spatial scale to the DUPAL anomaly, a globe-encircling feature of isotopic enrichment observed primarily in southern hemisphere OIBs. With the exception of Baffin Is. picrites [7], high 3He/4He OIBs also exhibit evidence for Ti, Ta, and Nb (TITAN) enrichment relative to low 3He/4He OIBs. This was interpreted as the result of addition of refractory, rutile-bearing eclogite to a peridotitic high 3He/4He reservoir [8]. This hypothesis is supported by the

  2. Mathematical aspects of quantum fluids. I. Generalized two-cycles of /sup 4/He type

    SciTech Connect

    Kupershmidt, B.A.

    1985-11-01

    It is shown that the two-cocycle involved in the Hamiltonian description of the superfluid /sup 4/He, both nonrotating and rotating, is a particular case of generalized symplectic two-cocycles on semidirect product Lie algebras.

  3. The Triple Oxygen Isotopic Composition of High 3He/4He Mantle

    NASA Astrophysics Data System (ADS)

    Jackson, C.; Parman, S. W.; Starkey, N.; Greenwood, R.; Franchi, I.; Jackson, M. G.; Fitton, J. G.; Stewart, F. M.; Larsen, L. M.

    2015-12-01

    Measurements of Xe isotope ratios in ocean island basalts (OIB) suggest that Earth's mantle accreted heterogeneously, and that compositional remnants of accretion are sampled by modern, high-3He/4He OIB associated with the Icelandic and Samoan plumes [1]. If so, the high-3He/4He source may also have a distinct oxygen isotopic composition from the rest of the mantle. Here, we test if the major elements of the high-3He/4He source preserve any evidence of heterogeneous accretion using measurements of three oxygen isotopes on olivine from a variety of high-3He/4He OIB locations. To high precision, the ∆17O value of high-3He/4He olivines from Hawaii, Pitcairn, Baffin Island and Samoa, are indistinguishable from bulk mantle olivine (Δ17OBulk Mantle - Δ17OHigh 3He/4He olivine = -0.002 ± 0.004 (2 x SEM) ‰). Thus, there is no resolvable oxygen isotope evidence for heterogeneous accretion in the high-3He/4He source. Modelling of mixing processes indicates that if an early-forming, oxygen-isotope distinct mantle did exist, either the anomaly was extremely small, or the anomaly was homogenised away by later mantle convection. The δ18O values of olivine with the highest 3He/4He ratios from a variety of OIB locations have a relatively uniform composition (~5 ‰). This composition is intermediate to values associated with the depleted MORB mantle and the average mantle. Similarly, δ18O values of olivine from high-3He/4He OIB correlate with radiogenic isotope ratios of He, Sr, and Nd. Combined, this suggests that oxygen remains coupled to the more incompatible elements during melt production and migration and that the intermediate δ18O value is a feature of the mantle source. The processes responsible for the δ18O signature of high-3He/4He mantle are not certain, but δ18O-87Sr/86Sr correlations indicate that it may be connected to a predominance of a HIMU-like (high U/Pb) component or other moderate δ18O components recycled into the high-3He/4He source. [1] S

  4. The second law of thermodynamics and entropy-decreasing processes with 4He superflows

    NASA Astrophysics Data System (ADS)

    Yu, Yongle

    2016-10-01

    We review on a recently proposed quantum exception to the second law of thermodynamics (SLT). We emphasize that 4He superflows, like any other forms of flows, shall carry entropy or heat in a thermal environment. Following that, one can use a heterogeneous 4He superflow loop to realize entropy-decreasing processes. We also mention that the heat content of a superflow has an unusual dependence on flow velocity, which is an important factor contributing to the entropy-decreasing processes.

  5. From nonwetting to prewetting: The asymptotic behavior of 4He drops on alkali substrates

    NASA Astrophysics Data System (ADS)

    Barranco, M.; Guilleumas, M.; Hernández, E.; Mayol, R.; Pi, M.; Szybisz, L.

    2003-07-01

    We investigate the spreading of 4He droplets on alkali-metal surfaces at zero temperature, within the frame of finite range density-functional theory. The equilibrium configurations of several 4HeN clusters and their asymptotic trend with increasing particle number N, which can be traced to the wetting behavior of the quantum fluid, are examined for nanoscopic droplets. We discuss the size effects inferring that the asymptotic properties of large droplets correspond to those of the prewetting film.

  6. New Phenomenon of the Hysteresis of 4He in Vycor Glass

    NASA Astrophysics Data System (ADS)

    Jin, Xin; Xu, Xiaonong; Yan, Yong; A, L. Thomson; D, F. Brewer; S, Haynes; N, Sharma

    1992-02-01

    The low temperature part of hysteresis curves of the freezing and melting processes of 4He in vycor glass with the lowest temperature 0.4K were measured, as the pressure ranged from 36.45 to 55.18 (105 Pa). Some novel characteristics of these curves were observed in such high temperature and pressure range. They may result from the existence of superfluid 4He.

  7. Kosterlitz-Thouless transition for 4He films adsorbed to rough surfaces.

    PubMed

    Luhman, D R; Hallock, R B

    2004-08-20

    We report the study of adsorption isotherms of 4He on several well characterized rough CaF2 surfaces using a quartz crystal microbalance technique at 1.672 K. The signature of decoupled mass observed on crossing the Kosterlitz-Thouless transition as a function of 4He film thickness decreases and becomes increasingly difficult to identify as the surface roughness is increased. A peak in the dissipation, indicative of the onset of superfluidity, changes little with roughness.

  8. Gersch-Rodriguez-Smith computation of deep inelastic electron scattering on 4He

    NASA Astrophysics Data System (ADS)

    Viviani, M.; Kievsky, A.; Rinat, A. S.

    2003-03-01

    We compute cross sections for inclusive scattering of high-energy electrons on 4He, based on the two lowest orders of the Gersch-Rodriguez-Smith series. The required one- and two-particle density matrices are obtained from nonrelativistic 4He wave functions using realistic models for the nucleon-nucleon and three-nucleon interaction. The computed results for E=3.6 GeV agree well with the NE3 SLAC-Virginia data.

  9. Resonances in (11)C observed in the (4)He((7)Be, alpha)(7)Be and (4)He((7)Be, p)(10)B reactions

    SciTech Connect

    Freer, M.; Ashwood, N. I.; Curtis, N.; Malcolm, J.; Munoz-Britton, T.; Price, D.; Wheldon, C.; Achouri, N. L.; Demaret, P.; Bardayan, Daniel W; Pain, Steven D; Brown, S.; Catford, W.; Harlin, Christopher W; Thomas, J. S.; Wilson, G.; Chipps, K.; Milin, M.; Raabe, R.; Soic, N.

    2012-01-01

    Measurements of the {sup 4}He({sup 7}Be,{alpha}){sup 7}Be and {sup 4}He({sup 7}Be,p){sup 10}B reactions were performed using {sup 7}Be beam energies of 7.1 and 23 MeV and a helium-4 target, employing the thick target technique. Resonances were observed between E{sub x}({sup 11}C) = 8.6 to 13.8 MeV. An R-matrix analysis was performed to characterize the spins and partial widths. This analysis showed that the observed sequence of states was consistent with that found for {sup 7}Li + {alpha} resonant scattering populating resonances in {sup 11}B. A comparison of the proposed partial widths for decay with the Wigner limit indicates that several of the states are associated with cluster-like structures.

  10. Analysis of {sup 4}He+{sup 40}Ca and {sup 4}He+{sup 44}Ti scattering using different optical model potentials

    SciTech Connect

    Ibraheem, Awad A.

    2016-09-15

    Elastic scattering of {sup 4}He+{sup 40}Ca and {sup 4}He+{sup 44}Ti reactions at backward angles has been analyzed using two different models, microscopic and semimicroscopic folding potentials. The derived real potentials supplemented with phenomenological Woods–Saxon imaginary potentials, provide good agreement with the experimental data at energy E{sub c.m.} = 21.8 MeV without need to renormalize the potentials. Coupled channels calculations are used to extract the inelastic scattering cross section to the low-lying state 2+ (1.083 MeV) of {sup 44}Ti. The deformation length is obtained and compared with the electromagnetic measurement values as well as those obtained from previous studies.

  11. Trojan horse particle invariance studied with the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He reactions

    SciTech Connect

    Pizzone, R. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Bertulani, C.; Mukhamedzhanov, A.; Blokhintsev, L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Kiss, G. G.; Li, C.; Tumino, A.

    2011-04-15

    The Trojan horse nucleus invariance for the binary reaction cross section extracted from the Trojan horse reaction was tested using the quasifree {sup 3}He({sup 6}Li,{alpha}{alpha})H and {sup 3}He({sup 7}Li,{alpha}{alpha}){sup 2}H reactions. The cross sections for the {sup 6}Li(d,{alpha}){sup 4}He and {sup 7}Li(p,{alpha}){sup 4}He binary processes were extracted in the framework of the plane wave approximation. They are compared with direct behaviors as well as with cross sections extracted from previous indirect investigations of the same binary reactions using deuteron as the Trojan horse nucleus instead of {sup 3}He. The very good agreement confirms the applicability of the plane wave approximation which suggests the independence of the binary indirect cross section on the chosen Trojan horse nucleus, at least for the investigated cases.

  12. Titanium Isotopes Link the High 3He/4He Reservoir to Continent Formation

    NASA Astrophysics Data System (ADS)

    Millet, M. A.; Jackson, M. G.; Dauphas, N.; Burton, K. W.; Williams, H. M.; Kurz, M. D.; Doucelance, R.; Smithies, H.; Champion, D. C.; Nowell, G. M.

    2016-12-01

    Elevated 3He/4He ratios found in ocean island basalts (OIB) argue for the survival of an early-formed reservoir (>4.5 Ga) in the Earth's mantle [1]. However, its nature remains debated. A characteristic of high 3He/4He OIBs is their anomalous enrichment in Ti abundance relative to elements of similar incompatibility (Sm and Tb). Here we use a new geochemical tool, the stable isotopes of Titanium, to investigate the origin of Ti enrichment of high 3He/4He OIBs. Recent work [2] has shown that Ti isotopes are a powerful tracer of oxide-melt equilibrium in magmatic systems. Results show that primitive OIB samples from localities associated with low 3He/4He ratios (≤15 R/Ra) have δ49Ti values within error of the mantle (δ49Ti=0.005±0.005 [2]) and chondrite values (+0.004±0.010 [3]) regardless of their Ti anomaly (0.93He/4He ratios (>25R/Ra) display δ49Ti values ranging from mantle-like to enriched in light isotopes (up to -0.065‰±0.005) that are negatively correlated with their Ti/Ti* and uncorrelated to indices of magma differentiation. This indicates that i) elevated Ti/Ti* in high 3He/4He OIBs is a mantle source signature and ii) that the high 3He/4He reservoir is enriched in light isotopes of Ti relative to the BSE. This enrichment in light isotopes is balanced by the heavy δ49Ti values and negative Ti/Ti* of Archean Tonalite-Throndhjemite-Granodiorite samples (TTG) from the Pilbara and Yilgarn Craton (+0.20<δ49Ti<+0.40), a proxy for early-formed, juvenile continental crust. Given the chondritic composition of the Earth's mantle and the inability of the typical mantle lithologies to fractionate Ti isotopes, this implies that the Ti enrichment of the high 3He/4He mantle reservoir is linked to the recycling of residues of partial melting events in the presence of rutile (TiO2), a process that drove continent formation in the Archean and possibly earlier. In addition, since these residues cannot display elevated 3He/4He ratios, it requires the Ti

  13. Elementary Excitations in Solid and Liquid 4He at the Melting Pressure

    NASA Astrophysics Data System (ADS)

    Todoshchenko, I. A.; Alles, H.; Junes, H. J.; Manninen, M. S.; Parshin, A. Y.; Tsepelin, V.

    2008-02-01

    Recent discovery of a nonclassical rotational inertia (NCRI) in solid 4He below 0.2 K by Kim and Chan has revived great interest in the problem of supersolidity and initiated intensive study on the properties of solid 4He. A direct proof that the onset of NCRI corresponds to the supersolid transition would be the observation of a corresponding drop of the entropy of solid 4He below the transition temperature. We have measured the melting pressure of ultrapure 4He in the temperature range from 0.01 to 0.45 K with several single crystals grown at different pressures and with the accuracy of 0.5 μbar. In addition, supplementary measurements of the pressure in liquid 4He at constant volume have been performed, which allowed us to eliminate the contribution of the temperature-dependent properties of the pressure gauge from the measured melting pressure data. With the correction to the temperature-dependent sensitivity of the pressure gauge, the variation of the melting pressure of 4He below 320 mK obeys the pure T 4 law due to phonons with the accuracy of 0.5 μbar, and no sign of the transition is seen (Todoshchenko et al. in JETP Lett. 85:454, 2007). This sets the upper limit of ˜5ṡ10-8 R for a possible excess entropy in high-quality 4He crystals below 320 mK. At higher temperatures the contribution from rotons in the superfluid 4He has been observed. The thermal expansion coefficient of the superfluid 4He has been measured in the range from 0.01 to 0.7 K with the accuracy of ˜10-7 1/K, or by two orders of magnitude better than in previous measurements. The roton contributions to the melting pressure and to the pressure in liquid at a constant volume are consistent and yield the value of 6.8 K for the roton gap, which is very close to the values obtained with other methods. As no contribution due to weakly interacting vacancies to the melting pressure of 4He has been observed, the lower limit of about 5.5 K for their activation energy can be set.

  14. Measurements on the melting curve of ^4He down to 10 mK

    NASA Astrophysics Data System (ADS)

    Alles, Harry

    2007-03-01

    Recent discovery of a nonclassical rotational inertia in solid ^4He below about 0.2 K by Kim and Chan has initiated an intensive study on the properties of solid ^4He. As Kim and Chan have interpreted their observation as the evidence of supersolid behavior, we have decided to measure very accurately the melting curve of ^4He because, as the slope of the melting curve is proportional to the difference in the entropy of the liquid and solid phases, there should be an anomaly at the possible supersolid transition. We have measured the melting curve of ^4He with the accuracy of about 0.5 microbar with ^4He crystals which had various concentration of defects. All our samples showed only the expected T^4 dependence due to phonons without any sign of the supersolid transition in the temperature range of 80400 mK. Below 80 mK we observed a small deviation from T^4 dependence which, however, cannot be attributed to the supersolid transition because our recent measurements with the cell containing liquid sample only suggest that this deviation is by the temperature variation of properties of BeCu membrane of our capacitive pressure gauge. In addition to our published data with ^4He of natural purity [Phys. Rev. Lett. 97, 165302 (2006)] we also report our recent measurements of the melting curve with ultra pure ^4He (0.3 ppb of ^3He impurities). In these measurements we followed optically the shape of the sample crystals which had very good quality.

  15. New light on the intriguing history of superfluidity in liquid (4)He.

    PubMed

    Griffin, Allan

    2009-04-22

    Surprisingly, it was 30 years after the first liquefaction of (4)He in 1908 that the discovery that liquid (4)He is not just a 'cold' liquid was made. Below T = 2.18 K, it is a 'quantum' liquid which exhibits spectacular macroscopic quantum behaviour that can be seen with the naked eye. Since the observation of superfluidity in liquid (4)He is one of the greatest discoveries in modern physics, we present a day-to-day chronology of the tangled events which preceded the seminal discovery of zero viscosity in 1938 by Kapitza in Moscow and by Allen and Misener in Cambridge. On the theory side, London argued in 1938 that the microscopic basis for this new superfluid phase was the forgotten phenomenon of Bose-Einstein condensation (BEC) first suggested by Einstein in 1925. In 1941, Landau developed a very successful theory of superfluid (4)He, but it was not anchored in a microscopic theory of interacting atoms. It took another 20 years for theorists to unify the two seemingly different theories of Landau and London. Experiments on trapped superfluid atomic gases since 1995 have shone new light on superfluid (4)He. In the mid-1930s, London had emphasized that superconductivity in metals and superfluidity in liquid (4)He were similar. Experiments on trapped two-component Fermi gases in the last five years have shown that a Bose condensate is indeed the basis of both of these superfluid phases. This confirms the now famous Bardeen-Cooper-Schrieffer-BEC crossover scenario developed for superfluidity by Leggett and Nozières in the early 1980s but largely ignored until a few years ago. The study of superfluid (4)He will increasingly overlap with strongly interacting dilute quantum gases, perhaps opening up a new era of research on this most amazing liquid.

  16. Breakup effects on alpha spectroscopic factors of 16O

    NASA Astrophysics Data System (ADS)

    Adhikari, S.; Basu, C.; Sugathan, P.; Jhinghan, A.; Behera, B. R.; Saneesh, N.; Kaur, G.; Thakur, M.; Mahajan, R.; Dubey, R.; Mitra, A. K.

    2017-01-01

    The triton angular distribution for the 12C(7Li,t)16O* reaction is measured at 20 MeV, populating discrete states of 16O. Continuum discretized coupled reaction channel calculations are used to to extract the alpha spectroscopic properties of 16O states instead of the distorted wave born approximation theory to include the effects of breakup on the transfer process. The alpha reduced width, spectroscopic factors and the asymptotic normalization constant (ANC) of 16O states are extracted. The error in the spectroscopic factor is about 35% and in that of the ANC about 27%.

  17. Excitation of 0/sup -/ states by /sup 16/O(pp')/sup 16/O inelastic scattering

    SciTech Connect

    Hosono, K.; Fujiwara, M.; Hatanaka, K.; Ikegami, H.; Kondo, M.; Matsuoka, N.; Saito, T.; Matsuki, S.; Ogino, K.; Kato, S.

    1984-08-01

    Differential cross sections and analyzing powers for 0/sup -/ states in /sup 16/O have been measured in inelastic scattering of 65 MeV polarized protons. This is the first observation of both isovector and isoscalar 0/sup +/..-->..0/sup -/ transitions in proton scattering on a particular isotope. Microscopic distorted-wave Born approximations and distorted-wave impulse approximation calculations do not describe very well either experimental cross sections or analyzing powers. It is suggested that more complicated reaction mechanisms and wave functions may be needed to describe these transitions.

  18. Control of the wetting properties of ^{4}He crystals in superfluid.

    PubMed

    Takahashi, T; Minezaki, H; Suzuki, A; Obara, K; Itaka, K; Nomura, R; Okuda, Y

    2016-05-01

    To investigate whether it is possible to control the wetting of ^{4}He crystals on a wall in superfluid, the contact angles of ^{4}He crystals were measured on rough and smooth walls at very low temperatures. A rough wall was prepared in a simple manner in which a commercially available coating agent for car mirrors, which makes the glass surface superhydrophobic, was used to coat a glass plate. The contact angles of ^{4}He crystals were increased by approximately 10^{∘} on the rough wall coated with the agent. Therefore, the increase in the repellency of ^{4}He crystals in superfluid was demonstrated to be possible on a very rough surface. The enhancement of the contact angles and a scanning electron microscopy image of the coated surface both suggest that a Cassie-Baxter state of ^{4}He crystals was realized on the surface; the crystals did not have full contact with the wall, but entrapped superfluid was present beneath the crystals in the hollow parts of the rough wall.

  19. On the origin of (4)He and (40)Ar in natural gold

    NASA Technical Reports Server (NTRS)

    Eugster, O.; Hofmann, B.; Niedermann, S.; Thalmann, CH.

    1993-01-01

    In a first report on our investigations of noble gases in native gold we demonstrated that placer gold contains an excess of radiogenic (4)He and (40)Ar relative to the concentrations expected from in situ decay of U, Th, and K, respectively, during the geologic age of about 30 Ma of the samples. We also showed that the U/Th-(4)He age of 36 Ma of vein-type gold from the Southern Alps agrees with its K-Ar formation age derived from associated muscovite and biotite. We now studied the question of the origin of the (4)He and (40)Ar excesses of placer gold. We conclude that gold contains two components of noble gases, a low-temperature component from fluid inclusions or phases which release noble gases at less than 800 C and a high-temperature component released when gold melts (1064 C). In some samples extremely high U and K concentrations or an unreasonably high formation age would be required to explain the observed (4)He abundances. Thus, trapped (4)He and (40)Ar must be present in gold.

  20. Torsional oscillator studies for possible supersolidity in two-dimensional 4He solid

    NASA Astrophysics Data System (ADS)

    Shibayama, Y.; Fukuyama, H.; Shirahama, K.

    2009-02-01

    The origin of "supersolidity" of solid 4He, which was reported by Kim and Chan, has not yet been clarified. Although Bose-Einstein condensation of zero-point vacancies (ZPVs) was initially considered to be a possible origin, recent studies imply that crystal imperfections in the solid samples are strongly associated with the observed supersolid behaviors. In two-dimensional (2D) 3He system on graphite, on the other hand, a novel phase due to quantum hopping of ZPVs has been found. This suggests that ZPVs form also in 2D 4He solid systems and their quantum hopping results in superfluidity of ZPVs, namely, supersolidity. In order to search for the possible 2D supersolid state, we perform torsional oscillator studies for 4He films adsorbed on graphite. At the 4He coverage of 18.7 nm-2 a positive frequency shift was observed below 300 mK. The size of the shift decreases with increasing the oscillation velocity. This behavior closely resembles to the supersolid behavior of bulk solid 4He.

  1. Improved fission neutron energy discrimination with 4He detectors through pulse filtering

    NASA Astrophysics Data System (ADS)

    Zhu, Ting; Liang, Yinong; Rolison, Lucas; Barker, Cathleen; Lewis, Jason; Gokhale, Sasmit; Chandra, Rico; Kiff, Scott; Chung, Heejun; Ray, Heather; Baciak, James E.; Enqvist, Andreas; Jordan, Kelly A.

    2017-03-01

    This paper presents experimental and computational techniques implemented for 4He gas scintillation detectors for induced fission neutron detection. Fission neutrons are produced when natural uranium samples are actively interrogated by 2.45 MeV deuterium-deuterium fusion reaction neutrons. Fission neutrons of energies greater than 2.45 MeV can be distinguished by their different scintillation pulse height spectra since 4He detectors retain incident fast neutron energy information. To enable the preferential detection of fast neutrons up to 10 MeV and suppress low-energy event counts, the detector photomultiplier gain is lowered and trigger threshold is increased. Pile-up and other unreliable events due to the interrogating neutron flux and background radiation are filtered out prior to the evaluation of pulse height spectra. With these problem-specific calibrations and data processing, the 4He detector's accuracy at discriminating fission neutrons up to 10 MeV is improved and verified with 252Cf spontaneous fission neutrons. Given the 4He detector's ability to differentiate fast neutron sources, this proof-of-concept active-interrogation measurement demonstrates the potential of special nuclear materials detection using a 4He fast neutron detection system.

  2. Quantum dynamics of molecules in 4He nano-droplets: Microscopic superfluidity

    NASA Astrophysics Data System (ADS)

    Dey, S.; Gewali, J. P.; Jha, A. K.; Chhaigte, L.; Jain, Y. S.

    2011-08-01

    High resolution spectroscopy of doped molecules in 4He nano-droplets and clusters gives a signature of superfluidity in microscopic system, termed as microscopic superfluidity. Ro-vibrational spectrum of 4HeN-M clusters is studied with the help of some important observations, revealed from experiments ( viz., localised and orderly arrangement of 4He atoms, although, being free to move in the order of their locations; individual 4He atoms can not be tagged as normal/ superfluid, etc.) and other factors (e.g., consideration that the 4He atoms which happen to fall in the plane of rotation of a molecule, render a equipotential ring and thus, do not take part in rotation; etc.) which effect the rotational and vibrational spectrum of the system. This helps us in successfully explaining the experimental findings which state that the rotational spectrum of clusters have sharp peaks (indicating that the molecule rotates like a free rotor) and moment of inertia and vibrational frequency shift have a non-trivial dependence on N.

  3. On the origin of (4)He and (40)Ar in natural gold

    NASA Technical Reports Server (NTRS)

    Eugster, O.; Hofmann, B.; Niedermann, S.; Thalmann, CH.

    1993-01-01

    In a first report on our investigations of noble gases in native gold we demonstrated that placer gold contains an excess of radiogenic (4)He and (40)Ar relative to the concentrations expected from in situ decay of U, Th, and K, respectively, during the geologic age of about 30 Ma of the samples. We also showed that the U/Th-(4)He age of 36 Ma of vein-type gold from the Southern Alps agrees with its K-Ar formation age derived from associated muscovite and biotite. We now studied the question of the origin of the (4)He and (40)Ar excesses of placer gold. We conclude that gold contains two components of noble gases, a low-temperature component from fluid inclusions or phases which release noble gases at less than 800 C and a high-temperature component released when gold melts (1064 C). In some samples extremely high U and K concentrations or an unreasonably high formation age would be required to explain the observed (4)He abundances. Thus, trapped (4)He and (40)Ar must be present in gold.

  4. Study of 12C(γ, 2α)4He with NewSUBARU laser Compton scattered gamma-ray beam

    NASA Astrophysics Data System (ADS)

    Shima, Tatsushi; Nagai, Yasuki; Miyamoto, Shuji; Amano, Sou; Horikawa, Ken; Mochizuki, Takayasu; Utsunomiya, Hiroaki; Akimune, Hidetoshi

    2010-08-01

    The 16O(γ, 2α)4He reaction cross section was measured in the γ-ray energy range from 16 MeV up to 39 MeV using an active target method and a quasi-monochromatic γ-ray beam provided at the Laboratory of Advanced Science and Technology for Industry (LASTI) of the University of Hyogo. The cross section is found to be rather small in the energy region corresponding to the 2+ and 4+ excited states of the intermediate 8Be nucleus, while it becomes large above the energy corresponding to the 8Be 1- state, being in contrast to the latest result reported by Afanas'ev and Khodyachikh. The present result suggests the cross sections are dominated by the contributions of the 1- states in 12C which are excited with the E1 transition.

  5. Heavy-ion versus {sup 3}He/{sup 4}He fusion-fission reactions: Angular momentum dependence of dissipation in nuclear fission

    SciTech Connect

    Ye, W.

    2011-09-15

    The stochastic Langevin model is employed to study dissipation properties in fission in the {sup 16}O + {sup 181}Ta {yields}{sup 197}Tl system by analyzing prescission neutron yields measured in this reaction. It has been found that the {sup 197}Tl nuclei undergo fission that is not in accordance with the standard Bohr-Wheeler statistical theory. A detailed comparison with previously published work in which fission excitation functions measured in {sup 3,4}He + {sup 197}Au {yields}{sup 200,201}Tl are shown to be in excellent agreement with the fission width formula predicted by the traditional models of nuclear fission suggests that nuclear dissipation strength may have an angular momentum dependence in addition to the known deformation and temperature dependence. Implications for the basic understanding of the observed abnormal rise in prescission particles at high energy and the need for further experimental confirmations are discussed.

  6. New Measurements of the ^4He Abundance in Galactic HII Regions

    NASA Astrophysics Data System (ADS)

    Cioni, M. R.; Cortiglioni, S.; Orsini, M.; Palazzi, E.; Palumbo, G. G. C.; Sorochenko, R. L.; Tsivilev, A. P.

    Preliminary results of the ^4He relative abundance determination from Radio Recombination Lines observations at different frequencies in the Orion, Rosette and W3 HII regions are presented. The Orion HII region has been mapped at both 22 GHz and 36 GHz with the same beamwidth (2 arcmin) using the Medicina and Puschino radio telescopes respectively. The RRLs parameters, together with their variation with frequency and with distance were determined by centering the map on the star theta^1Ori C. Three positions were observed in the Rosette HII region at 8.3 GHz leading to the first detection in this region of the transition He92alpha . The derived ^4He relative abundance is considerably greater than the ones obtained from previous measurements. The W3 HII region was observed at 36 GHz and the ^4He/H value derived was compared with previous measurements performed with higher spatial resolution.

  7. Simultaneous observation of 10 MHz ultra sound in solid ^4He contained in torsional oscillator

    NASA Astrophysics Data System (ADS)

    Hein, Bettina; Goodkind, John; Kojima, Harry

    2012-02-01

    Kim and Chan[1] were motivated in part by an anomalous ultra sound propagation observed by Ho et al.[2] in solid ^4He near 200 mK to carry out torsional oscillator(TO) experiments which led to the discovery of supersolid phenomena. We constructed a 270 Hz TO oscillator which incorporated quartz transducers for simultaneously observing 10 MHz longitudinal ultra sound and torsional oscillation of solid ^4He samples. We are searching for correlation between behaviors in ultra sound propagation and TO response. The length and density of dislocations extracted from ultra sound and the frequency shifts of TO measured in some half a dozen solid ^4He samples have not shown clear correlation.[4pt] [1] E. Kim and M. Chan, Nature 427, 225(2004).[0pt] [2] P. Ho, I. Bindloss and J. Goodkind, JLTP 109, 409(1997).

  8. Study of Supersolidity and Shear Modulus Anomaly of 4He in a Triple Compound Oscillator

    NASA Astrophysics Data System (ADS)

    Mi, Xiao; Mueller, Erich J.; Reppy, John D.

    2012-12-01

    The recently discovered shear modulus anomaly in solid 4He bears a strong similarity to the phenomenon of supersolidity in solid 4He and can lead to the period shift and dissipative signals in torsional oscillator experiments that are nearly identical to the classic NCRI signals observed by Kim and Chan. In the experiments described here, we attempt to isolate the effects of these two phenomena on the resonance periods of torsion oscillators. We have constructed a triple compound oscillator with distinct normal modes. We are able to demonstrate that, for this oscillator, the period shifts observed below 200 mK have their primary origin in the temperature dependence of the shear modulus of the solid 4He sample rather than the formation of a supersolid state.

  9. High-resolution measurement of absolute {alpha}-decay widths in {sup 16}O

    SciTech Connect

    Wheldon, C.; Ashwood, N. I.; Barr, M.; Curtis, N.; Freer, M.; Kokalova, Tz.; Malcolm, J. D.; Spencer, S. J.; Ziman, V. A.; Faestermann, Th.; Kruecken, R.; Wirth, H.-F.; Hertenberger, R.; Lutter, R.; Bergmaier, A.

    2011-06-15

    By using a large-acceptance position-sensitive silicon detector array in coincidence with the high-resolution Munich Q3D spectrograph, unambiguous measurements have been made of the absolute {alpha}-particle decay widths from excited states in {sup 16}O* in the energy range 13.85 to 15.87 MeV. Carbon targets have been bombarded with 42-MeV {sup 6}Li beams to induce {sub 6}{sup 12}C({sub 3}{sup 6}Li, d){sub 8}{sup 16}O* reactions. The deuteron ejectiles were measured in the Q3D and the results gated by {sup 4}He+{sup 12}C breakup products detected in the silicon array, the efficiency of which was modeled using Monte Carlo simulations. By comparing total population and breakup-gated spectra, the following absolute {alpha}-decay widths have been measured with high resolution: {Gamma}{sub {alpha}}0/{Gamma}{sub tot} = 0.87{+-}0.11 (13.980 MeV), 1.04{+-}0.15 (14.302 MeV), 0.92{+-}0.10 (14.399 MeV), 0.59{+-}0.04 (14.815 MeV), 0.88{+-}0.18 (15.785 MeV), and {Gamma}{sub {alpha}}1/{Gamma}{sub tot}=1.14{+-}0.08 (14.660 MeV), 0.46{+-}0.06 (14.815 MeV).

  10. Wetting of planar substrates of rubidium by liquid films of 4He

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek

    2000-11-01

    The wetting of planar solid surfaces of Rb by superfluid 4He films at T=0 K is examined theoretically. The calculations were carried out by (i) using the most elaborated nonlocal density functional known as the Orsay-Trento proposal and (ii) assuming that the helium atoms interact with the substrate via the potential recently worked out by Chizmeshya, Cole, and Zaremba. The asymptotic surface tension was evaluated by applying two different procedures. Our results indicate that films of 4He wet Rb at zero absolute temperature.

  11. JLab measurement of the 4He charge form factor at large momentum transfers.

    PubMed

    Camsonne, A; Katramatou, A T; Olson, M; Sparveris, N; Acha, A; Allada, K; Anderson, B D; Arrington, J; Baldwin, A; Chen, J-P; Choi, S; Chudakov, E; Cisbani, E; Craver, B; Decowski, P; Dutta, C; Folts, E; Frullani, S; Garibaldi, F; Gilman, R; Gomez, J; Hahn, B; Hansen, J-O; Higinbotham, D W; Holmstrom, T; Huang, J; Iodice, M; Jiang, X; Kelleher, A; Khrosinkova, E; Kievsky, A; Kuchina, E; Kumbartzki, G; Lee, B; LeRose, J J; Lindgren, R A; Lott, G; Lu, H; Marcucci, L E; Margaziotis, D J; Markowitz, P; Marrone, S; Meekins, D; Meziani, Z-E; Michaels, R; Moffit, B; Norum, B; Petratos, G G; Puckett, A; Qian, X; Rondon, O; Saha, A; Sawatzky, B; Segal, J; Shabestari, M; Shahinyan, A; Solvignon, P; Subedi, R R; Suleiman, R; Sulkosky, V; Urciuoli, G M; Viviani, M; Wang, Y; Wojtsekhowski, B B; Yan, X; Yao, H; Zhang, W-M; Zheng, X; Zhu, L

    2014-04-04

    The charge form factor of 4He has been extracted in the range 29  fm(-2) ≤ Q2 ≤ 77  fm(-2) from elastic electron scattering, detecting 4He recoil nuclei and electrons in coincidence with the high resolution spectrometers of the Hall A Facility of Jefferson Lab. The measurements have uncovered a second diffraction minimum for the form factor, which was predicted in the Q2 range of this experiment. The data are in qualitative agreement with theoretical calculations based on realistic interactions and accurate methods to solve the few-body problem.

  12. Excimers He2* as tracers of quantum turbulence in 4He in the t = 0 limit.

    PubMed

    Zmeev, D E; Pakpour, F; Walmsley, P M; Golov, A I; Guo, W; McKinsey, D N; Ihas, G G; McClintock, P V E; Fisher, S N; Vinen, W F

    2013-04-26

    We have studied the interaction of metastable 4He2* excimer molecules with quantized vortices in superfluid 4He in the zero temperature limit. The vortices were generated by either rotation or ion injection. The trapping diameter of the molecules on quantized vortices was found to be 96±6  nm at a pressure of 0.1 bar and 27±5  nm at 5.0 bar. We have also demonstrated that a moving tangle of vortices can carry the molecules through the superfluid helium.

  13. Energy dependence of the 4He(π+,π-) total cross section

    NASA Astrophysics Data System (ADS)

    Gräter, J.; Bilger, R.; Clement, H.; Meier, R.; Wagner, G. J.; Friedman, E.; Schepkin, M.; Amaudruz, P. A.; Felawka, L.; Ottewell, D.; Smith, G. R.; Ambardar, A.; Hofman, G. J.; Kermani, M.; Tagliente, G.; Bonutti, F.; Camerini, P.; Grion, N.; Rui, R.; Hong, P.; Mathie, E. L.; Tacik, R.; Clark, J.; Sevior, M. E.; Patarakin, O.

    1998-09-01

    The total cross section of the 4He(π+,π-) reaction was measured for π+ kinetic energies ranging from 70 to 130 MeV using the CHAOS spectrometer at TRIUMF and a liquid 4He target. Around Tπ=90 MeV, total cross sections exceed conventional model predictions by a factor of 3, whereas at Tπ=70 MeV and for Tπ>130 MeV the data are consistent with these calculations. An attempt is made to understand this behavior by assuming the production of the hypothetical d' dibaryon.

  14. Heat Transfer in 3{He}-4{He} Mixtures in Cylindrical Geometry

    NASA Astrophysics Data System (ADS)

    Nemchenko, K.; Rogova, S.; Vikhtinskaya, T.

    2017-05-01

    The paper presents the results of theoretical studies of the transport processes that take place in the newly proposed experiments on study of a vibrating quartz fork in superfluid 3{He}-4{He} mixtures. In addition to known mechanisms of energy loss from a vibrating quartz fork such as first sound radiation or interaction with thermal excitations, two more mechanisms specific for 3{He}-4{He} mixtures are proposed and studied in the paper. The relative contribution of these mechanisms: second sound and effective diffusion, is considered, and experimental conditions under which these mechanisms become effective are discussed.

  15. Theory for supersolid 4He: Vacancy condensation facilitated by a low-energy bound state

    NASA Astrophysics Data System (ADS)

    Dai, Xi

    2006-03-01

    Although both vacancies and interstitials have relatively high activation energies in the normal solid, we propose that a lower energy bound state of a vacancy and an interstitial may facilitate vacancy condensation to give supersolidity in 4He. We use a phenomenological two-band boson lattice model to demonstrate this new mechanism and discuss the possible relevance to the recently observed superfluidlike, nonclassical rotational inertial experiments of Kim and Chan in solid 4He. Some of our results may also be applicable to trapped bosons in optical lattices.

  16. Heat Transfer in 3He -4He Mixtures in Cylindrical Geometry

    NASA Astrophysics Data System (ADS)

    Nemchenko, K.; Rogova, S.; Vikhtinskaya, T.

    2017-02-01

    The paper presents the results of theoretical studies of the transport processes that take place in the newly proposed experiments on study of a vibrating quartz fork in superfluid 3He -4He mixtures. In addition to known mechanisms of energy loss from a vibrating quartz fork such as first sound radiation or interaction with thermal excitations, two more mechanisms specific for 3He -4He mixtures are proposed and studied in the paper. The relative contribution of these mechanisms: second sound and effective diffusion, is considered, and experimental conditions under which these mechanisms become effective are discussed.

  17. Implications of new High 3He/4He Values from the Samoan Hotspot

    NASA Astrophysics Data System (ADS)

    Jackson, M. G.; Kurz, M. D.; Hart, S. R.; Workman, R.

    2005-12-01

    We report new olivine phenocryst helium measurements from Ofu Island, American Samoa; the 3He/4He ratios range from 19.5 to 33.7 times atmospheric (R/Ra), significantly expanding the observed range for Samoa. The highest 3He/4He ratio of 33.7 Ra was measured in olivines from an ankaramite dike. Relatively high helium concentrations (4.4*108 cc/g) in this sample, crushing and fusion measurements, coupled with sampling from a roadcut exposure, all ensure that the isotope ratio is not affected by in situ cosmogenic 3He. A second basaltic dike yielded a 3He/4He ratio of 29.6 Ra, and measurements on 9 other basalt samples from Ofu range from 19.5 to 26.4 Ra. Previous high 3He/4He measurements (~25 Ra) from the Samoan hotspot were also obtained from basaltic dikes, but were from Tutuila Island (Farley et al., 1992). The new high 3He/4He ratios from Samoa are similar in magnitude to the high ratios found at Iceland (~37 Ra) and Hawaii (~35 Ra). However, the Ofu basalts have 87Sr/86Sr > 0.7044, which is significantly more radiogenic than Iceland or Hawaii. The combined Sr-He isotopic data are broadly consistent with mixing between an enriched mantle source (EM2) and the putative common high 3He/4He component (FOZO, as best represented by Baffin Island Picrites, Stuart et al., 2003). Assuming that the overall isotopic variations are produced by mixing processes, we attempt to place constraints on the relative helium concentrations in the FOZO, EM2 and Depleted MORB mantle (DMM) endmembers. In addition to using the shape of the plausible mixing lines, we employ new estimates for the trace element concentrations in the DMM and Samoan EM2 sources (Workman et al., 2004; Workman and Hart, 2005) to get at relative helium concentrations in these reservoirs. We assume that high 3He/4He basalts from the mid-Atlantic ridge North of Iceland (Schilling et al., 1999, and others) are a mixture between DMM and FOZO. We further assume that the N. Iceland ridge-FOZO and Ofu-FOZO mixing

  18. Hexagonal Close-Packed (4) {He} 4 He as Crystalline Multilayered Polytype: An Alternative for `Supersolid' or `Glassy-Like' Phase

    NASA Astrophysics Data System (ADS)

    Chishko, K. A.; Antsygina, T. N.; Poltavskaya, M. I.

    2017-06-01

    We apply the model of a crystalline polytype built of close-packed 2D monoatomic basal planes with triangular lattice to interpret the anomalous thermodynamical and mechanical properties of solid hexagonal close-packed (HCP) ^4{He}. The polytype is a 3D stack of the basal planes, and its structure can be built from the simplest periodic packing (HCP, FCC, 4H, 5H, 6R, \\ldots etc.) up to random stacking fault system (RSFS) totally aperiodic in only c-direction perpendicular to the basal planes. RSFS is a crystal without microscopic translation symmetry along c-axis, i.e., entirely disordered in only one spatial direction. Despite of packing disorder, c-direction remains the crystallographic axis of third order at arbitrary sequence of the 2D plates in the whole stack. In a long-wave limit the HCP polytype can be treated as 3D anisotropic continuum, as a result its phonon spectrum and Helmholtz free energy have been calculated. The temperature dependence of the phonon pressure is calculated theoretically and compared with experimental data. A quantitative agreement between the theory and the experiment is achieved. Mechanical properties of ^4{He} crystals in the framework of the polytype model are briefly discussed.

  19. Indirect Study of the 16O+16O Fusion Reaction Toward Stellar Energies by the Trojan Horse Method

    NASA Astrophysics Data System (ADS)

    Hayakawa, S.; Spitaleri, C.; Burtebayev, N.; Aimaganbetov, A.; Figuera, P.; Fisichella, M.; Guardo, G. L.; Igamov, S.; Indelicato, I.; Kiss, G.; Kliczewski, S.; La Cognata, M.; Lamia, L.; Lattuada, M.; Piasecki, E.; Rapisarda, G. G.; Romano, S.; Sakuta, S. B.; Siudak, R.; Trzcińska, A.; Tumino, A.; Urkinbayev, A.

    2016-05-01

    The 16O+16O fusion reaction is important in terms of the explosive oxygen burning process during late evolution stage of massive stars as well as understanding of the mechanism of low-energy heavy-ion fusion reactions. We aim to determine the excitation function for the most major exit channels, α+28Si and p+31P, toward stellar energies indirectly by the Trojan Horse Method via the 16O(20Ne, α28Si)α and 16O(20Ne, p31P)α three-body reactions. We report preliminary results involving reaction identification, and determination of the momentum distribution of α-16O intercluster motion in the projectile 20Ne nucleus.

  20. Search for anisotropy in the Debye-Waller factor of HCP solid (4)He.

    PubMed

    Barnes, Ashleigh L; Hinde, Robert J

    2016-02-28

    The properties of hexagonal close packed (hcp) solid (4)He are dominated by large atomic zero point motions. An accurate description of these motions is therefore necessary in order to accurately calculate the properties of the system, such as the Debye-Waller (DW) factors. A recent neutron scattering experiment reported significant anisotropy in the in-plane and out-of-plane DW factors for hcp solid (4)He at low temperatures, where thermal effects are negligible and only zero-point motions are expected to contribute. By contrast, no such anisotropy was observed either in earlier experiments or in path integral Monte Carlo (PIMC) simulations of solid hcp (4)He. However, the earlier experiments and the PIMC simulations were both carried out at higher temperatures where thermal effects could be substantial. We seek to understand the cause of this discrepancy through variational quantum Monte Carlo simulations utilizing an accurate pair potential and a modified trial wavefunction which allows for anisotropy. Near the melting density, we find no anisotropy in an ideal hcp (4)He crystal. A theoretical equation of state is derived from the calculated energies of the ideal crystal over a range of molar volumes from 7.88 to 21.3 cm(3), and is found to be in good qualitative agreement with experimental data.

  1. Third sound and stability of 3He-4He mixture films

    SciTech Connect

    Anderson, R. H.; Krotscheck, E.; Miller, M. D.

    2006-09-07

    We study third sound and the interaction between 3He adatoms in two thin 3He-4He mixture films from a first-principles, microscopic theory. Utilizing the variational, hypernetted-chain Euler-Lagrange (HNC-EL) theory as applied to inhomogeneous boson systems, we calculate chemical potentials for both the 4He superfluid film and the physisorbed 3He. Numerical density derivatives of the chemical potentials lead to the sought-after third sound speeds that clearly reflect a layered structure of at least seven oscillations. In this paper, we report third sound on model substrates: Nuclepore, and sodium. We find that the effect of the 3He depends sensitively on the particular 4He film coverage. Our most important result is that, with the addition of 3He, the third sound speed can either increase or decrease. In fact, in some regimes, the added 3He destabilizes the film and can drive ''layering transitions'', leading to fairly complicated geometric structures of the film in which the outermost layer is predicted to consist of phase-separated regions of 3He and 4He.

  2. Dislocation Mobility and Anomalous Shear Modulus Effect in ^4He Crystals

    NASA Astrophysics Data System (ADS)

    Malmi-Kakkada, Abdul N.; Valls, Oriol T.; Dasgupta, Chandan

    2017-02-01

    We calculate the dislocation glide mobility in solid ^4He within a model that assumes the existence of a superfluid field associated with dislocation lines. Prompted by the results of this mobility calculation, we study within this model the role that such a superfluid field may play in the motion of the dislocation line when a stress is applied to the crystal. To do this, we relate the damping of dislocation motion, calculated in the presence of the assumed superfluid field, to the shear modulus of the crystal. As the temperature increases, we find that a sharp drop in the shear modulus will occur at the temperature where the superfluid field disappears. We compare the drop in shear modulus of the crystal arising from the temperature dependence of the damping contribution due to the superfluid field, to the experimental observation of the same phenomena in solid ^4He and find quantitative agreement. Our results indicate that such a superfluid field plays an important role in dislocation pinning in a clean solid ^4He at low temperatures and in this regime may provide an alternative source for the unusual elastic phenomena observed in solid ^4He.

  3. Implanted 3He, 4He, and Xe in further studies of diamonds from Western Australia.

    PubMed

    McConville, P; Reynolds, J H; Epstein, S; Roedder, E

    1991-01-01

    In measurements of the noble gases in additional samples of diamonds from the Argyle and Ellendale lamproites in Western Australia we have failed to encounter any neon-rich stones such as showed solar-like isotopic compositions in earlier work. No neon was detected above the relatively high blank levels in our glass apparatus. White and brown diamonds showed no differences in noble gas content, nor did samples segregated by the color of long-wave UF fluorescence. The rare gas patterns in the 1.2 Ga Argyle pipe are largely consistent with implanted 3He, 4He, and fissiogenic Xe from U/Th in the matrix rock in which the diamonds have been stored for so long. These implanted species are absent in diamonds from the much younger (approximately 20 Ma) Ellendale pipe. We give implantation formulae for several models of inhomogeneously distributed U/Th. Differences in 3He content between pipe and alluvial Argyle samples are consistent with expected cosmogenic production in the latter. An expanded data base for helium and carbon isotopic data on the same samples supports a negative [4He]-delta 13C correlation seen earlier in work from our group, but if the Argyle samples, which contain light carbon, are corrected for implanted 4He, the correlation is considerably weakened. We no longer see an earlier 3He/4He-delta 13C correlation.

  4. Observation of Crossover from Ballistic to Diffusion Regime for Excimer Molecules in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Zmeev, D. E.; Papkour, F.; Walmsley, P. M.; Golov, A. I.; McClintock, P. V. E.; Fisher, S. N.; Guo, W.; McKinsey, D. N.; Ihas, G. G.; Vinen, W. F.

    2013-05-01

    We have measured the temperature dependence of the time of flight of helium excimer molecules {He}2^{*}(a3Σ +u) in superfluid 4He and find that the molecules behave ballistically below ˜100 mK and exhibit Brownian motion above ˜200 mK. In the intermediate temperature range the transport cannot be described by either of the models.

  5. Phase-space analysis of convection in a /sup 3/He - superfluid /sup 4/He solution

    SciTech Connect

    Haucke, H.; Maeno, Y.

    1982-01-01

    Observations have been made on thermal convection below 1K in a dilute solution of /sup 3/He in superfluid /sup 4/He contained in a cylindrical cell of aspect ratio GAMMA = 1.20. Complicated oscillatory phenomena were observed with a high degree of reproducibility using two temperature sensors. Phase-space analysis suggests a description in terms of strange-attractor dynamics.

  6. ^4He Crystals in Reduced Gravity Obtained by Parabolic Flights of a Jet Plane

    NASA Astrophysics Data System (ADS)

    Takahashi, Takuya; Nomura, Ryuji; Okuda, Yuichi

    2016-11-01

    ^4He crystals usually sink to the bottom of the container in a superfluid and are deformed into a flat shape by gravity when their size is much larger than the capillary length of 1 mm. When gravity is reduced to zero, the capillary length diverges and the gravity-flattened crystals are expected to relax into an equilibrium crystal shape determined by the interfacial free energy at low enough temperatures where the relaxation time is very short. We performed a reduced gravity experiment on ^4He crystals at ultralow temperatures by developing a specially designed ^3He-^4He dilution refrigerator compatible with the experimental restrictions in a small jet plane. ^4He crystals relaxed to the equilibrium crystal shape below 600 mK during a reduced gravity period of 20 s produced by a parabolic flight. The equilibrium crystal shape, however, was metastable in most cases, governed by the boundary conditions imposed by the wall. Utilizing acoustic radiation pressure, we deformed the crystal enough to allow it to escape from the metastable shape below 150 mK. After this large deformation, the crystal relaxed to a shape completely different from its initial shape, showing three types of facets, viz., c-, a-, and s-facets, which was concluded to be the lowest energy equilibrium shape.

  7. Superfluid State of 4He on Graphane and Graphene-Fluoride: Anisotropic Roton States

    NASA Astrophysics Data System (ADS)

    Nava, M.; Galli, D. E.; Cole, M. W.; Reatto, L.

    2013-06-01

    We explore the phase behavior of Helium films on two variants of graphene: graphane (graphene coated with H, denoted GH) and graphene-fluoride (GF). A semiempirical interaction with these substrates is used in T=0 K Path Integral Ground State and finite temperature Path Integral Monte Carlo simulations. We predict that 4He forms anisotropic fluid states at low coverage. This behavior differs qualitatively from that on graphite because of the different surface composition, symmetry and spacing of the adsorption sites. The 4He ground state on both substrates is thus a self-bound anisotropic superfluid with a superfluid fraction ρ s / ρ lower than 1 due to the corrugation of the adsorption potential. In the case of GF such corrugation is so large that ρ s / ρ=0.6 at T=0 K and the superfluid is essentially restricted to move in a multiconnected space, along the bonds of a honeycomb lattice. We predict a superfluid transition temperature T≃ 0.25 (1.1) K for 4He on GF (GH). We have studied the elementary excitation spectrum of 4He on GF at equilibrium density finding a phonon-maxon-roton dispersion relation that is strongly anisotropic in the roton region. We conclude that these new platforms for adsorption studies offer the possibility of studying novel superfluid phases of quantum condensed matter.

  8. Velocity of second sound in /sup 3/He-/sup 4/He mixtures: a revision

    SciTech Connect

    Bowley, R.M.

    1988-05-01

    Greywall has recently proposed a new temperature scale for the /sup 3/He melting curve thermometer. A reanalysis of the velocity of second sound in /sup 3/He-/sup 4/He mixtures using the data of Greywall and Paalanen with this new temperature scale shows that the interaction between /sup 3/He quasiparticles is now independent of concentration.

  9. The Quest for Bose-Einstein Condensation in Solid 4He

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.; Azuah, R. T.; Glyde, H. R.

    2011-03-01

    Ever since the seminal torsional oscillator (TO) measurements of Kim and Chan which suggested the existence of a phase transition in solid 4He, from normal to a `supersolid' state below a critical temperature T c = 200 mK, there has been an unprecedented amount of excitement and research activity aimed at better understanding this phase. Despite much work, this remarkable phase has yet to be independently confirmed by conventional scattering techniques, such as neutron scattering. We have carried out a series of neutron scattering measurements, which we here review, aimed at observing Bose-Einstein condensation (BEC) in solid 4He at temperatures below T c . In bulk liquid 4He, the appearance of BEC below T λ signals the onset of superfluidity. The observation of a condensate fraction in the solid would provide an unambiguous confirmation for `supersolidity'. Although, our measurements have not yet revealed a non-zero condensate fraction or algebraic off diagonal long-range order n 0 in solid 4He down to 65 mK, i.e. n 0=(0±0.3)%, our search for BEC and its corollaries continues with improved instrumentation.

  10. Search for supersolid 4He in neutron scattering experiments at ISIS

    NASA Astrophysics Data System (ADS)

    Kirichek, O.

    2009-02-01

    The observation of a non-classical rotation inertia (NCRI) fraction in bulk solid 4He by M. Chan and E. Kim [1, 2] attracted significant interest as a possible manifestation of supersolid state of matter. Despite numerous experimental and theoretical studies inspired by this observation, an explicit explanation for this phenomenon is still missing. Neutron scattering experiments on solid helium may help to shed light on the physical grounds of NCRI and answer the question on whether this phenomenon could be caused by Bose-Einstein Condensation. In this paper we are going to discuss the results obtained in experiments involving neutron scattering on solid 4He. Microscopic quantitative data such as mean kinetic energy, mean square momentum and mean square displacement of helium atoms as well as the lattice parameter have been obtained for the first time for solid 4He in temperature range 70mK - 500 mK. No change was seen in the single atom kinetic energy (within statistical error better than 1%) as well as change in the lattice parameter (within 0.03%). The mean square displacement did not change in the region of expected supersolid transition either. All these results suggest that the NCRI transition is quite different from the superfluid transition in liquid 4He.

  11. Electron screening in the {sup 3}He(d,p){sup 4}He reaction

    SciTech Connect

    Barker, F. C.

    2007-02-15

    A reanalysis of data for the {sup 3}He(d,p){sup 4}He reaction obtained using the Trojan-horse method, together with data from a direct measurement, leads to an electron-screening potential that is not consistent with the adiabatic limit, but it is consistent with a previous value from different data.

  12. Equilibrium shape of (4)He crystal under zero gravity below 200 mK.

    PubMed

    Takahashi, Takuya; Ohuchi, Haruka; Nomura, Ryuji; Okuda, Yuichi

    2015-10-01

    Equilibrium crystal shape is the lowest energy crystal shape that is hardly realized in ordinary crystals because of their slow relaxation. (4)He quantum crystals in a superfluid have been expected as unique exceptions that grow extremely fast at very low temperatures. However, on the ground, gravity considerably deforms the crystals and conceals the equilibrium crystal shape, and thus, gravity-free environment is needed to observe the equilibrium shape of (4)He. We report the relaxation processes of macroscopic (4)He crystals in a superfluid below 200 mK under zero gravity using a parabolic flight of a jet plane. When gravity was removed from a gravity-flattened (4)He crystal, the crystal rapidly transformed into a shape with flat surfaces. Although the relaxation processes were highly dependent on the initial condition, the crystals relaxed to a nearly homothetic shape in the end, indicating that they were truly in an equilibrium shape minimizing the interfacial free energy. Thanks to the equilibrium shape, we were able to determine the Wulff's origin and the size of the c-facet together with the vicinal surface profile next to the c-facet. The c-facet size was extremely small in the quantum crystals, and the facet-like flat surfaces were found to be the vicinal surfaces. At the same time, the interfacial free energy of the a-facet and s-facet was also obtained.

  13. Development of a proof of concept low temperature 4He Superfluid Magnetic Pump

    NASA Astrophysics Data System (ADS)

    Jahromi, Amir E.; Miller, Franklin K.

    2017-03-01

    We describe the development and experimental results of a proof of concept Superfluid Magnetic Pump in this work. This novel low temperature, no moving part pump can replace the existing bellows-piston driven 4He or 3He-4He mixture compressor/circulators used in various sub Kelvin refrigeration systems such as dilution, Superfluid pulse tube, Stirling, or active magnetic regenerative refrigerators. Due to the superior thermal transport properties of sub-Lambda 4He this pump can also be used as a simple circulator to distribute cooling over large surface areas. Our pump was experimentally shown to produce a maximum flow rate of 440 mg/s (averaged over cycle), 665 mg/s (peak) and produced a maximum pressure difference of 2323 Pa using only the more common isotope of helium, 4He. This pump worked in an ;ideal; thermodynamic state: The experimental results matched with the theoretical values predicted by a computer model. Pump curves were developed to map the performance of this pump. This successful demonstration will enable this novel pump to be implemented in suitable sub Kelvin refrigeration systems.

  14. Two-Body Photodisintegration of ^4He into p+t

    NASA Astrophysics Data System (ADS)

    Nasseripour, Rakhsha; Berman, Barry

    2008-10-01

    The two-body photodisintegration of ^4He into a proton and a triton has been studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.35 to 1.55 GeV were incident on a liquid ^4He target. This is the first measurement of the photodisintegration of ^4He above 0.4 GeV. The differential cross sections for the γ^4He-> pt reaction have been measured as a function of photon-beam energy and proton-scattering angle, and are compared with the latest model calculations by Laget [1]. At 0.6-0.8 GeV, our data are in good agreement only with the calculations that include three-body mechanisms, thus confirming their importance. At the same time, the strength of the one-body mechanisms is overestimated at higher energies and at small proton-scattering angles. These results reinforce the conclusion of our previous study of the three-body breakup of ^3He that demonstrated the great importance of three-body mechanisms in the energy region 0.5-0.8 GeV [2]. [1] J.-M. Laget, private communication (2008) [2] S. Niccolai et al., Phys. Rev. C 70, 064003 (2004)

  15. Lieb-Liniger-like model of quantum solvation in CO-4HeN clusters

    NASA Astrophysics Data System (ADS)

    Farrelly, D.; Iñarrea, M.; Lanchares, V.; Salas, J. P.

    2016-05-01

    Small 4He clusters doped with various molecules allow for the study of "quantum solvation" as a function of cluster size. A peculiarity of quantum solvation is that, as the number of 4He atoms is increased from N = 1, the solvent appears to decouple from the molecule which, in turn, appears to undergo free rotation. This is generally taken to signify the onset of "microscopic superfluidity." Currently, little is known about the quantum mechanics of the decoupling mechanism, mainly because the system is a quantum (N + 1)-body problem in three dimensions which makes computations difficult. Here, a one-dimensional model is studied in which the 4He atoms are confined to revolve on a ring and encircle a rotating CO molecule. The Lanczos algorithm is used to investigate the eigenvalue spectrum as the number of 4He atoms is varied. Substantial solvent decoupling is observed for as few as N = 5 4He atoms. Examination of the Hamiltonian matrix, which has an almost block diagonal structure, reveals increasingly weak inter-block (solvent-molecule) coupling as the number of 4He atoms is increased. In the absence of a dopant molecule the system is similar to a Lieb-Liniger (LL) gas and we find a relatively rapid transition to the LL limit as N is increased. In essence, the molecule initially—for very small N—provides a central, if relatively weak, attraction to organize the cluster; as more 4He atoms are added, the repulsive interactions between the identical bosons start to dominate as the solvation ring (shell) becomes more crowded which causes the molecule to start to decouple. For low N, the molecule pins the atoms in place relative to itself; as N increases the atom-atom repulsion starts to dominate the Hamiltonian and the molecule decouples. We conclude that, while the notion of superfluidity is a useful and correct description of the decoupling process, a molecular viewpoint provides complementary insights into the quantum mechanism of the transition from a molecular

  16. Lieb-Liniger-like model of quantum solvation in CO-(4)HeN clusters.

    PubMed

    Farrelly, D; Iñarrea, M; Lanchares, V; Salas, J P

    2016-05-28

    Small (4)He clusters doped with various molecules allow for the study of "quantum solvation" as a function of cluster size. A peculiarity of quantum solvation is that, as the number of (4)He atoms is increased from N = 1, the solvent appears to decouple from the molecule which, in turn, appears to undergo free rotation. This is generally taken to signify the onset of "microscopic superfluidity." Currently, little is known about the quantum mechanics of the decoupling mechanism, mainly because the system is a quantum (N + 1)-body problem in three dimensions which makes computations difficult. Here, a one-dimensional model is studied in which the (4)He atoms are confined to revolve on a ring and encircle a rotating CO molecule. The Lanczos algorithm is used to investigate the eigenvalue spectrum as the number of (4)He atoms is varied. Substantial solvent decoupling is observed for as few as N = 5 (4)He atoms. Examination of the Hamiltonian matrix, which has an almost block diagonal structure, reveals increasingly weak inter-block (solvent-molecule) coupling as the number of (4)He atoms is increased. In the absence of a dopant molecule the system is similar to a Lieb-Liniger (LL) gas and we find a relatively rapid transition to the LL limit as N is increased. In essence, the molecule initially-for very small N-provides a central, if relatively weak, attraction to organize the cluster; as more (4)He atoms are added, the repulsive interactions between the identical bosons start to dominate as the solvation ring (shell) becomes more crowded which causes the molecule to start to decouple. For low N, the molecule pins the atoms in place relative to itself; as N increases the atom-atom repulsion starts to dominate the Hamiltonian and the molecule decouples. We conclude that, while the notion of superfluidity is a useful and correct description of the decoupling process, a molecular viewpoint provides complementary insights into the quantum mechanism of the transition from a

  17. Search for dilute excited states in 16O

    NASA Astrophysics Data System (ADS)

    Ogloblin, A. A.; Danilov, A. N.; Demyanova, A. S.; Goncharov, S. A.; Belyaeva, T. L.

    2016-11-01

    The root mean square radii of 16O in the short-lived 0+ excited states were experimentally deduced for the first time from the analyses of α +16O diffraction scattering. Differential cross sections of the elastic and inelastic α +16O and 16O+16O scattering in the incident energy range from a few MeV/nucleon up to 100 MeV/nucleon were analyzed by the modified diffraction model. No significant radius enhancement in any state in comparison with the ground state was observed. This concerns, in particular, the 15.1-MeV 06+ state of 16O, located in the vicinity of the four-α -particle complete dissociation threshold, for which we did not confirm the "gigantic" size predicted by the α -particle condensation model. This result does not support the idea that 16O in the 06+ state has a dilute structure and can be considered as an analog of the famous 7.65-MeV 02+ Hoyle state of 12C.

  18. Search for supersolidity in solid 4He using multiple-mode torsional oscillators

    PubMed Central

    Eyal, Anna; Mi, Xiao; Talanov, Artem V.; Reppy, John D.

    2016-01-01

    In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid 4He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941–1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid 4He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the 4He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853–856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid 4He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the 4He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state. PMID:27222579

  19. Search for supersolidity in solid 4He using multiple-mode torsional oscillators

    NASA Astrophysics Data System (ADS)

    Eyal, Anna; Mi, Xiao; Talanov, Artem V.; Reppy, John D.

    2016-06-01

    In 2004, Kim and Chan (KC) reported a decrease in the period of torsional oscillators (TO) containing samples of solid 4He, as the temperature was lowered below 0.2 K [Kim E, Chan MHW (2004) Science 305(5692):1941-1944]. These unexpected results constituted the first experimental evidence that the long-predicted supersolid state of solid 4He may exist in nature. The KC results were quickly confirmed in a number of other laboratories and created great excitement in the low-temperature condensed-matter community. Since that time, however, it has become clear that the period shifts seen in the early experiments can in large part be explained by an increase in the shear modulus of the 4He solid identified by Day and Beamish [Day J, Beamish J (2007) Nature 450(7171):853-856]. Using multiple-frequency torsional oscillators, we can separate frequency-dependent period shifts arising from changes in the elastic properties of the solid 4He from possible supersolid signals, which are expected to be independent of frequency. We find in our measurements that as the temperature is lowered below 0.2 K, a clear frequency-dependent contribution to the period shift arising from changes in the 4He elastic properties is always present. For all of the cells reported in this paper, however, there is always an additional small frequency-independent contribution to the total period shift, such as would be expected in the case of a transition to a supersolid state.

  20. Radiative p 16O Capture at Astrophyiscal Energies

    NASA Astrophysics Data System (ADS)

    Dubovichenko, S. B.

    2016-12-01

    Within the framework of the modified potential cluster model with forbidden states and classification of states according to the Young tableaux, the possibility is considered of describing experimental data for the astrophysical S-factor of radiative p 16O capture to the ground state of the 17F nucleus. It is shown that on the basis of E1 transitions from p 16O scattering states to the ground state of 17F in the p 16O channel overall success is achieved in explaining the magnitude of the measured cross sections at astrophysical energies.

  1. Testing the U-Th/4He dating method on carbonates I. Helium diffusion

    NASA Astrophysics Data System (ADS)

    Pinti, D. L.; Ghaleb, B. G.; Sano, Y.; Blanchette, S.; Mathouchanh, E.; Takahata, N.

    2012-12-01

    Corals and other carbonates, such as speleothems, are important climatic-change proxies which need to be precisely dated for paleoclimatic reconstructions. Yet, U-Th disequilibrium method is applicable up to ca. 500 ka old carbonates. Calcite is difficult to date precisely by U-Pb method because of the low U amounts often found and difficulties in correcting for the common lead. Radiogenic 4He produced by decay of 238U and 235U incorporated into carbonates is a potential chronometer of Quaternary, and possibly Tertiary, corals and speleothems. However, several limitations exist for this method, related to the few data on the He diffusion [1] and on the alpha recoil effect in carbonate minerals. We decided to measure 4He by step heating in carbonate samples dated previously by U-Th disequilibrium: a coral (Scleractinia) from Cape Verde dated at 125 ka; a stalagmite from Patagonia dated at 128 ka; and two hydrothermal travertines from the Ziz Valley in Morocco with ages ≥ 500 ka. A one cm3 of each sample was cut by saw, crushed, washed and sieved to 80-100μm and 100-125μm fractions. Crushed samples (0.5 to 1 gram) were loaded in a vacuum crucible and 4He extracted by step heating. Previous step heating experiments on a sub-Arctic flowstone suggested that 4He is mainly released between 400 and 600°C [2]. However, the first coral sample heated at 100°C steps, showed a release pattern profile with 4He mainly released between 200 and 400°C. Measured 4He amount of 2.05 x 10-8 (±0.03% 1σ) ccSTP/g and U content of 2.7 ppm yield a U-4He age of 62.5 ka, lower than that obtained by U-Th disequilibrium. Data were not precise enough to calculate diffusion parameters using the Arrhenius diagram. The second step-heating pyrolysis of the coral using 50°C-steps indicated that all 4He is released between 250 and 350°C. The measured 4He amount was 2.27 x 10-8 (±0.04% 1σ) ccSTP/g, yielding an age of 83 ka, again lower compared to that obtained by U-Th disequilibrium. The

  2. Airy structure in 16O+14C nuclear rainbow scattering

    NASA Astrophysics Data System (ADS)

    Ohkubo, S.; Hirabayashi, Y.

    2015-08-01

    The Airy structure in 16 O +14 C rainbow scattering is studied with an extended double-folding (EDF) model that describes all the diagonal and off-diagonal coupling potentials derived from the microscopic realistic wave functions for 16 O by using a density-dependent nucleon-nucleon force. The experimental angular distributions at EL=132 , 281, and 382.2 MeV are well reproduced by the calculations. By studying the energy evolution of the Airy structure, the Airy minimum around θ =76∘ in the angular distribution at EL=132 MeV is assigned as the second-order Airy minimum A 2 in contrast to the recent literature which assigns it as the third order A 3 . The Airy minima in the 90∘ excitation function is investigated in comparison with well-known 16 O +16 O and 12 C +12 C systems. Evolution of the Airy structure into the molecular resonances with the 16 O +14 C cluster structure in the low-energy region around Ec .m .=30 MeV is discussed. It is predicted theoretically for the first time for a non-4 N 16O +14 C system that Airy elephants in the 90∘ excitation function are present.

  3. High-power closed-cycle 4He cryostat with top-loading sample exchange

    NASA Astrophysics Data System (ADS)

    Piegsa, F. M.; van den Brandt, B.; Kirch, K.

    2017-10-01

    We report on the development of a versatile cryogen-free laboratory cryostat based upon a commercial pulse tube cryocooler. It provides enough cooling power for continuous recondensation of circulating 4He gas at a condensation pressure of approximately 250 mbar. Moreover, the cryostat allows for exchange of different cryostat-inserts as well as fast and easy ;wet; top-loading of samples directly into the 1 K pot with a turn-over time of less than 75 min. Starting from room temperature and using a 4He cryostat-insert, a base temperature of 1.0 K is reached within approximately seven hours and a cooling power of 250 mW is established at 1.24 K.

  4. Apatite 4He/3He and (U-Th)/He evidence for an ancient Grand Canyon.

    PubMed

    Flowers, R M; Farley, K A

    2012-12-21

    The Grand Canyon is one of the most dramatic features on Earth, yet when and why it was carved have been controversial topics for more than 150 years. Here, we present apatite (4)He/(3)He thermochronometry data from the Grand Canyon basement that tightly constrain the near-surface cooling history associated with canyon incision. (4)He/(3)He spectra for eastern Grand Canyon apatites of differing He date, radiation damage, and U-Th zonation yield a self-consistent cooling history that substantially validates the He diffusion kinetic model applied here. Similar data for the western Grand Canyon provide evidence that it was excavated to within a few hundred meters of modern depths by ~70 million years ago (Ma), in contrast to the conventional model in which the entire canyon was carved since 5 to 6 Ma.

  5. Multiple critical velocities in oscillatory flow of superfluid 4He due to quartz tuning forks

    NASA Astrophysics Data System (ADS)

    Schmoranzer, D.; Jackson, M. J.; Tsepelin, V.; Poole, M.; Woods, A. J.; Človečko, M.; Skrbek, L.

    2016-12-01

    We report recent investigations into the transition to turbulence in superfluid 4He, realized experimentally by measuring the drag forces acting on two custom-made quartz tuning forks with fundamental resonances at 6.5 kHz and 55.5 kHz, in the temperature range 10 mK to 2.17 K. In pure superfluid in the zero temperature limit, three distinct critical velocities were observed with both tuning forks. We discuss the significance of all critical velocities and associate the third critical velocity reported here with the development of large vortical structures in the flow, which thus starts to mimic turbulence in classical fluids. The interpretation of our results is directly linked to previous experimental work with oscillators such as tuning forks, grids, and vibrating wires, focusing on the behavior of purely superfluid 4He at very low temperatures.

  6. WORM ALGORITHM PATH INTEGRAL MONTE CARLO APPLIED TO THE 3He-4He II SANDWICH SYSTEM

    NASA Astrophysics Data System (ADS)

    Al-Oqali, Amer; Sakhel, Asaad R.; Ghassib, Humam B.; Sakhel, Roger R.

    2012-12-01

    We present a numerical investigation of the thermal and structural properties of the 3He-4He sandwich system adsorbed on a graphite substrate using the worm algorithm path integral Monte Carlo (WAPIMC) method [M. Boninsegni, N. Prokof'ev and B. Svistunov, Phys. Rev. E74, 036701 (2006)]. For this purpose, we have modified a previously written WAPIMC code originally adapted for 4He on graphite, by including the second 3He-component. To describe the fermions, a temperature-dependent statistical potential has been used. This has proven very effective. The WAPIMC calculations have been conducted in the millikelvin temperature regime. However, because of the heavy computations involved, only 30, 40 and 50 mK have been considered for the time being. The pair correlations, Matsubara Green's function, structure factor, and density profiles have been explored at these temperatures.

  7. Efficient (3)He/(4)He separation in a nanoporous graphenylene membrane.

    PubMed

    Qu, Yuanyuan; Li, Feng; Zhao, Mingwen

    2017-08-16

    Helium-3 is a precious noble gas, which is essential in many advanced technologies such as cryogenics, isotope labeling and nuclear weapons. The current imbalance of (3)He demand and supply shortage leads to the search for an efficient membrane with high performance for (3)He separation. In this study, based on first-principles calculations, we demonstrated that highly efficient (3)He harvesting can be achieved in a nanoporous graphenylene membrane with industrially-acceptable selectivity and permeance. The quantum tunneling effect leads to (3)He harvesting with high efficiency via kinetic sieving. Both the quantum tunneling effect and zero-point energy (ZPE) determine the (3)He/(4)He separation via thermally-driven equilibrium sieving, where the ZPE effect dominates efficient (3)He/(4)He separation between two reservoirs. The quantum effects revealed in this work suggest that the nanoporous graphenylene membrane is promising for efficient (3)He harvesting that can be exploited for industrial applications.

  8. Rayleigh-Taylor instability of crystallization waves at the superfluid-solid 4He interface.

    PubMed

    Burmistrov, S N; Dubovskii, L B; Tsymbalenko, V L

    2009-05-01

    At the superfluid-solid 4He interface there exist crystallization waves having much in common with gravitational-capillary waves at the interface between two normal fluids. The Rayleigh-Taylor instability is an instability of the interface which can be realized when the lighter fluid is propelling the heavier one. We investigate here the analogs of the Rayleigh-Taylor instability for the superfluid-solid 4He interface. In the case of a uniformly accelerated interface the instability occurs only for a growing solid phase when the magnitude of the acceleration exceeds some critical value independent of the surface stiffness. For the Richtmyer-Meshkov limiting case of an impulsively accelerated interface, the onset of instability does not depend on the sign of the interface acceleration. In both cases the effect of crystallization wave damping is the reduction in the perturbation growth rate of the Taylor unstable interface.

  9. Observation of Nonclassical Rotational Inertia in Bulk Solid ^4He Confined to a Cylindrical Cavity

    NASA Astrophysics Data System (ADS)

    Shirahama, Keiya; Kondo, Motoshi; Takada, Shunichi; Shibayama, Yoshiyuki

    2006-03-01

    Recent observation of nonclassical rotational inertia (NCRI) in solid ^4He by Kim and Chan has attracted great interest in physics of supersolid, and motivated a number of theoretical studies. However, there have been surprisingly few experiments to pursuit the nature of their observation. Thus, we have begun a torsional oscillator experiment for bulk solid ^4He. In order to study the effects of sample geometry and crystal quality, we employ a cylindrical cell, 8 mm high and 8 mm in diameter, which is mounted on an aluminum alloy torsion rod. The resonant torsion frequency is about 1750 Hz, which is 2 ˜5 times the frequencies in the Kim and Chan's experiments. In a preliminary experiment we have observed an increase in the frequency below about 250 mK, indicating the existence of NCRI. The frequency shift shows a substantial driving amplitude dependence, which is also consistent with the previous observation.

  10. Effect of ^3He impurity on the supersolid transition of ^4He

    NASA Astrophysics Data System (ADS)

    Kim, E.; Xia, J. S.; West, J. T.; Lin, X.; Chan, M. H. W.

    2007-03-01

    The supersolid phase of ^4He was reported by a series of torsional oscillator experiments [1]. One of the most striking features of the supersolid transition is the intriguing ^3He impurity effect. The addition of an extremely small amount of ^3He impurity broadens the transition and enhances the transition temperature Tc. This effect is very different from that in helium film and that in `bulk' superfluid helium. We have studied the influence of ^3He impurity on the supersolid transition systematically by progressively diluting isotopically-pure ^4He (^3He impurity less than 2ppb) with ^3He. The transition temperature is monotonically enhanced with increasing ^3He concentration and the supersolid fraction shows a broad maximum around 0.2 ppm. [1] E. Kim and M. H. W. Chan, Science 305, 1941 (2004); Nature 425, 227 (2004); J. Low Temp. Phys. 138, 859 (2005); Phys. Rev. Lett. 97, 115302 (2006).

  11. AC Calorimetry Study of Possible Bose-Einstein Condensation in Solid ^4He

    NASA Astrophysics Data System (ADS)

    Clark, Anthony C.; Kim, Eunseong; Ganshin, Andrey; Chan, Moses H. W.

    2004-03-01

    Recent torsional oscillator measurements on solid ^4He grown inside vycor glass suggest the possible existence of a supersolid state of matter below 200mK.^1 If the onset of the supersolid can be considered as a BEC transition, then there should be an associated heat capacity signature. Ideal Bose gas theory indicates that this feature should be measurable for the observed supersolid fraction. We are currently in the process of conducting heat capacity measurements on solid ^4He confined in vycor glass in the temperature range of interest. The heat capacity is measured using an AC technique. Solid helium samples are prepared using a blocked capillary method, resulting in final pressures ranging from 40 to 70 bars. This work is supported by NSF Grant DMR 0207071. 1. E. Kim and M.H.W. Chan, to be published in Nature.

  12. Effect of ^3He impurity on the supersolid transition of ^4He

    NASA Astrophysics Data System (ADS)

    Kim, Eunseong; Chan, Moses H. W.

    2006-03-01

    The supersolid phase of ^4He was revealed by a series of torsional oscillator experiments.[1] One of the most intriguing features of the supersolid transition is the broadening of the transition and the enhancement of Tc by the addition of extremely small amount of ^3He impurity. This effect is very different from that in superfluid film and that in `bulk' superfluid helium. We have investigated the^ influence of ^3He on the supersolid transition by systematically diluting isotopically-pure ^4He (^3He impurity less than 0.3ppb) with ^3He. [1] E. Kim and M. H. W. Chan, Science 305, 1941 (2004); Nature 425, 227 (2004); J. Low Temp. Phys. 138, 859 (2005)

  13. Nuclear structure corrections for μ4He+ and μ3He+ spectroscopy

    NASA Astrophysics Data System (ADS)

    Nevo Dinur, Nir; Ji, Chen; Hernandez, Oscar; Bacca, Sonia; Barnea, Nir

    2016-09-01

    The proton charge radius was recently determined from muonic hydrogen spectroscopy with tenfold improved precision but 7 . 9 σ disagreement with the accepted value, leading to the ``proton radius puzzle''. To further investigate, and to obtain precise radii, these measurements were repeated in μ4He+ and μ3He+. This may also shed light on the discrepancy between isotope-shift measurements of the 4He -3He radius difference. However, the precision of radii determined from the muonic experiments is limited by the uncertainties in the nuclear structure corrections. We present first ab-initio calculations of these corrections that reduced the uncertainties from 20 % to the few percent goal. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This work was supported in parts by the Natural Sciences and Engineering Research Council (Grant Number SAPIN-2015-00031).

  14. Prediction of reentrant wetting of [sup 3]He-[sup 4]He mixtures on cesium

    SciTech Connect

    Pettersen, M.S. ); Saam, W.F. )

    1993-02-01

    The authors examine the effect of [sup 3]He impurities on the wetting behavior of [sup 4]He on cesium, predicting a phase diagram which includes reentrant wetting transitions. This phase diagram is shown to be very sensitive to effects such as a theoretically predicted bound state of [sup 3]He at the liquid-cesium interface, and the contact angle may be sensitive to interesting temperature dependences of the helium-cesium surface tension resulting from surface rotons or Rayleigh waves.

  15. SANS study of phase separation in solid {sup 3}He-{sup 4}He

    SciTech Connect

    Koster, J.P.; Nagler, S.E.; Adams, E.D.; Wignall, G.D.

    1994-12-31

    Small angle neutron scattering has been used to study phase separation in a quantum alloy, solid {sup 3}He{sub x}-{sup 4}He{sub 1{minus}x}. The onset of phase separation is marked by a dramatic increase in the measured scattering. A simple interpretation of the results suggests that the late-stage phase separation kinetics are dominated by an increase in the concentration of {sup 3}He atoms in preexisting precipitate regions.

  16. Specific heat of 4He confined to 9869 Å planar geometry

    NASA Astrophysics Data System (ADS)

    Kimball, Mark O.; Gasparini, Francis M.

    2000-07-01

    We report new data for 4He confined between two silicon wafers spaced 9869 Å apart. This spacing complements a series of previous measurements which now span a factor of 20 between the smallest and largest confinements. These new data allow us to further check scaling predictions. We find, as reported with previous data, that the present data scale well except near the heat capacity maximum, and below into the superfluid region.

  17. Solution of the five-body η4He problem with separable pole expansion method

    NASA Astrophysics Data System (ADS)

    Fix, A.; Kolesnikov, O.

    2017-09-01

    The Alt-Grassberger-Sandhas equations for the five-body η - 4 N problem are solved for the case of the driving ηN and NN potentials limited to s-waves. Separable expansion of the transition amplitudes in all different subsystems is employed to convert the five-body equations into the effective two-body form. Numerical results are presented for the η4 He scattering length.

  18. Production of {sup 4}He and tritium from Be in the COBRA-1A2 irradiation

    SciTech Connect

    Greenwood, L.R.

    1998-03-01

    The production of {sup 4}He and tritium has been calculated for beryllium irradiated in the COBRA-1A2 experiment in the Experimental Breeder Reactor II. Reaction rates were based on adjusted neutron spectra determined from reactor dosimetry measurements at three different elevations in the region of the beryllium capsules. Equations are given so that gas production can be calculated for any specific capsule elevation.

  19. Sperrylite (PtAs2) as a 190Pt-4He geochronometer

    NASA Astrophysics Data System (ADS)

    Yakubovich, O. V.; Mochalov, A. G.; Sluzhenikin, S. F.

    2015-05-01

    The high stability of radiogenic He in natural conductive nonmetals is firstly shown for the example of sperrylite (PtAs2). The urgency of its study is explained by the abundance of Pt sulfarsenides, in particular, sperrilite in many PGE deposits. The 190Pt-4He age of sperrylite from the famous Kondyor (AyanMaya region) and Oktyabrsky (Norilsk region) PGE deposits was determined for the first time: 122 ± 6 and 242 ± 12 Ma, respectively.

  20. Linear Response of One-Dimensional Liquid ^4{He} to External Perturbations

    NASA Astrophysics Data System (ADS)

    Motta, M.; Bertaina, G.; Vitali, E.; Galli, D. E.; Rossi, M.

    2016-11-01

    We study the response of one-dimensional liquid ^4{He} to weak perturbations relying on the dynamical structure factor, S(q,ω ) , recently obtained via ab-initio techniques (Bertaina et al. in Phys Rev Lett 116:135302, 2016). We evaluate the drag force, F_v , experienced by an impurity moving along the system with velocity v and the static response function, χ (q) , describing the density modulations induced by a periodic perturbation with wave vector q.

  1. Wave Turbulence in Superfluid {sup 4}He: Energy Cascades and Rogue Waves in the Laboratory

    SciTech Connect

    Efimov, V. B.; Ganshin, A. N.; McClintock, P. V. E.; Kolmakov, G. V.; Mezhov-Deglin, L. P.

    2008-11-13

    Recent work on second sound acoustic turbulence in superfluid {sup 4}He is reviewed. Observations of forward and inverse energy cascades are described. The onset of the inverse cascade occurs above a critical driving energy and it is accompanied by giant waves that constitute an acoustic analogue of the rogue waves that occasionally appear on the surface of the ocean. The theory of the phenomenon is outlined and shown to be in good agreement with the experiments.

  2. The nucleation of vortices in superfluid [sup 4]He: Answers and questions

    SciTech Connect

    Avenel, O.; Ihas G.G. ); Varoquaux, E. )

    1993-12-01

    The velocity threshold for phase slips, v[sub c], has been measured in ultra-pure [sup 4]He and ultra-dilute [sup 3]He-[sup 4]He mixtures, down to a temperature of 15 mK. These experiments have revealed a crossover from a temperature-dependent regime above [approximately]150 mK to a plateau of v[sub c] below in ultra-pure [sup 4]He. Concentrations of [sup 3]He impurities as low as a few parts in 10[sup [minus]9] greatly affect the plateau regime, causing v[sub c] to decrease markedly at low temperature. These observations are interpreted in the framework of the nucleation, either thermally activated or by quantum tunnelling, of vortices in the appropriate shape of half-rings. These vortices form on wall asperities at local velocities u[sub s] estimated to be [approximately]22 m/s in these experiments. The half-ring model is shown to yield a critical velocity of the same magnitude but leaves many basic questions unanswered.

  3. Aging of solid 4He under torsional oscillation at low temperatures

    NASA Astrophysics Data System (ADS)

    Gumann, P.; Kojima, H.

    2013-10-01

    Observations have been made to reveal unusual aging behavior in solid 4He samples contained in a torsional oscillator. Oscillation of samples is initiated at a given oscillator drive amplitude near 100 mK. After the samples are cooled to a measurement temperature, they are "aged" for a waiting time, tw, between 15 min and 25 h. The drive amplitude is then halved and subsequent variation in the oscillator response amplitude, A(t), and frequency are monitored as time t elapses. When the measurement temperature is lower than Ts = 40 mK, A(t) shows unusual behavior: A(t) initially undershoots to less than half of the original value, partially recovers exponentially and eventually continues to increase logarithmically. The amount of undershoot, partial recovery magnitude and the rate of logarithmic increase all show aging effect with logarithmic dependence on tw. When the measurement temperature is greater than Ts, the above unusual behavior in A(t) disappears. If solid 4He cooled below Ts behaved analogously to spin glasses, A(t/tw) would be independent of tw. Such behavior of A(t/tw) is not observed. Origin of the unusual aging behavior in solid 4He is not yet clear. Motion of dislocation lines is discussed as a possible origin.

  4. Observation of a Dislocation-Related Interfacial Friction Mechanism in Mobile Solid 4He

    NASA Astrophysics Data System (ADS)

    Eyal, Anna; Livne, Ethan; Polturak, Emil

    2016-04-01

    We report a study of the temperature and stress dependence of the friction associated with a relative motion of crystallites of solid 4He in contact with each other. A situation where such motion exists emerges spontaneously during a disordering of a single crystal contained inside an annular sample space of a torsional oscillator (TO). Under the torque applied by the oscillating walls of the TO these crystallites move relative to each other, generating measurable dissipation at their interface. We studied this friction between 0.5 and 1.8 K in solid samples grown from commercially pure 4He and from a 100 ppm 3He-4He mixture. The data were analyzed by modeling the TO as a driven harmonic oscillator. In this model, an analysis of the resonant frequency and amplitude of the TO yields the temperature dependence of the friction coefficient. By fitting the data to specific forms, we found that over our temperature range, the dominant friction mechanism associated with the interfacial motion of the crystallites results from climb of individual dislocations. The characteristic energy scale associated with this friction can be 3 or 6 K, depending on the sample. The motion of the solid in the presence of such friction can perhaps be described as the low limit of "slip-stick" motion.

  5. On the lateral dose profile of (4)He beams in water.

    PubMed

    Embriaco, A; Bellinzona, V E; Fontana, A; Rotondi, A

    2017-08-01

    We investigate the possibility to improve the accuracy of the lateral dose profile for (4)He beams with a novel approach, by extending an already validated model for proton beams to heavier ions. The full Molière theory for the Coulomb multiple scattering is applied to the case of (4)He beams, with a complete separation of the electromagnetic and of the nuclear contributions in the calculation of the total dose. The latter is described with only three free parameters. The accuracy of the results compared with Monte Carlo predictions already validated with experimental data is comparable with other studies at low energy, but improves by a factor 2 at high energy. In addition the found solution is more stable with respect to (multi-) Gaussian and other parameterizations. This result makes this method of interest for applications to Treatment Planning Systems (TPS) in ion beam therapy. We propose a model, named MONETα (MOdel of ioN dosE for Therapy for α), for the calculation of the lateral dose of (4)He beams in water that allows fast and accurate dose calculations by requiring a small data base of parameters as input. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  6. Rotational structure of small 4He clusters seeded with HF, HCl, and HBr molecules.

    PubMed

    Ramilowski, Jordan A; Mikosz, Aleksandra A; Farrelly, David; Fajín, José Luis Cagide; Fernandez, Berta

    2007-12-13

    Diffusion Monte Carlo calculations are performed for ground and excited rotational states of HX(4He)N, complexes with N4He nanodroplet will be smaller than that observed for HF, despite HF's having the largest (by far) gas-phase rotational constant of the three molecules. This suggests that the specifics of the solvation dynamics of a molecule in a 4He cluster are the result of a delicate interplay between the magnitude of the gas-phase rotational constant of the molecule and the anisotropic contributions to the atom-molecule potential energy.

  7. Observation of Non-Classical Rotational Inertia in Bulk Solid 4He

    NASA Astrophysics Data System (ADS)

    Kondo, Motoshi; Takada, Shunichi; Shibayama, Yoshiyuki; Shirahama, Keiya

    2007-09-01

    In recent torsional oscillator experiments by Kim and Chan (KC), a decrease of rotational inertia has been observed in solid 4He in porous materials (Kim, E., Chan, M.H.W. in Nature 427:225, 2004; J. Low Temp. Phys. 138:859, 2005) and in a bulk annular channel (Kim, E., Chan, M.H.W. in Science 305:1941, 2004). This observation strongly suggests the existence of “non-classical rotational inertia” (NCRI), i.e. superflow, in solid 4He. In order to study such a possible “supersolid” phase, we perform torsional oscillator experiments for cylindrical solid 4He samples. We have observed decreases in rotational inertia below 200 mK for two solid samples (pressures P=4.1 and 3.0 MPa). The observed NCRI fraction at 70 mK is 0.14%, which is about 1/3 of the fraction observed in the annulus by KC. Our observation is the first experimental confirmation of the possible supersolid finding by KC.

  8. Muon Capture on ^3H

    NASA Astrophysics Data System (ADS)

    Golak, Jacek; Skibiński, Roman; Witała, Henryk; Topolnicki, Kacper; Kamada, Hiroyuki; Nogga, Andreas; Marcucci, Laura E.

    2017-01-01

    The μ ^- + ^3H → ν _μ + n + n + n capture reaction is studied under full inclusion of final-state interactions with the AV18 nucleon-nucleon potential and the Urbana IX three-nucleon force. We employ the single nucleon weak current operator comprising the dominant relativistic corrections to obtain first estimates of the total capture rates based on realistic forces. Our results are compared with older theoretical predictions.

  9. Apatite 4He/3He thermochronometry evidence for an ancient Grand Canyon, Colorado Plateau, USA

    NASA Astrophysics Data System (ADS)

    Flowers, R. M.; Farley, K. A.

    2012-12-01

    The very existence of Grand Canyon inspires questions about why canyons are carved, how drainage systems and landscapes evolve, and how these processes relate to the elevation gain of plateaus. Yet when and why Grand Canyon was carved have been extraordinarily controversial for more than 150 years. Over the last several decades, the dominant view for the origin of the canyon is one of rapid incision at 5-6 Ma, when detritus derived from the upstream reaches of the Colorado River system appeared in Grand Wash Trough at the Colorado River's western exit from the Colorado Plateau. The absence of such diagnostic deposits prior to 6 Ma has been used to argue that Grand Canyon was not yet excavated (e.g., Karlstrom et al., 2008). However, a variety of data hint at a more ancient age for part or all of the canyon, and it has been proposed that a smaller drainage basin in largely carbonate lithologies could explain the absence of pre-6 Ma Colorado River clastics in Grand Wash Trough even if a significant Grand Canyon were present. Most recently, apatite (U-Th)/He (AHe) thermochronometry data from western Grand Canyon were used to infer excavation of this area to within several hundred meters of its modern depth by ca. 70 Ma (Wernicke, 2011), an interpretation in direct conflict with the young canyon model. The unexpected implications of the initial Grand Canyon AHe work motivated the apatite 4He/3He and U-Th zonation study presented here. Apatite 4He/3He thermochronometry provides information about the spatial distribution of radiogenic 4He in an apatite crystal that can better constrain a sample's cooling history. A key premise of AHe and 4He/3He spectra interpretation is that the He kinetic model used is accurate. We first investigate whether differing 4He/3He spectra for apatites of variable AHe date, radiation damage, and U-Th zonation from eastern Grand Canyon yield mutually consistent thermal history results using the RDAAM kinetic model, which must be true if the

  10. Commensurate-incommensurate solid transition in the 4He monolayer on a single γ-graphyne sheet

    NASA Astrophysics Data System (ADS)

    Kwon, Yongkyung; Ahn, Jeonghwan

    2014-03-01

    We have performed path-integral Monte Carlo calculations to study 4He adsorption on γ-graphyne. Assuming the 4He-substrate interaction described by a pairwise sum of empirical helium-carbon interatomic potentials, we find that unlike α-graphyne, a single sheet of γ-graphyne is not permeable to 4He atoms despite its large surface area. One-dimensional density distribution shows layer-by-layer growth of 4He on γ-graphyne. Partially-filled 4He monolayers are found to exhibit different commensurate structures depending on the helium coverage; it shows a C2/2 commensurate structure at the areal density of 0.0491 Å-2, a C3/2 structure at 0.0736 Å-2, and a C4/2 structure at 0.0982 Å-2. After going through various domain structures, the 4He monolayer is completed at the areal density of 0.115 Å-2 where 4He adatoms form an incommensurate triangular solid. Possible superfluid response of the 4He monolayer on γ-graphyne is now under investigation.

  11. Three-body interactions and the elastic constants of hcp solid (4)He.

    PubMed

    Barnes, Ashleigh L; Hinde, Robert J

    2017-09-21

    The effect of three-body interactions on the elastic properties of hexagonal close packed solid (4)He is investigated using variational path integral (VPI) Monte Carlo simulations. The solid's nonzero elastic constants are calculated, at T = 0 K and for a range of molar volumes from 7.88 cm(3)/mol to 20.78 cm(3)/mol, from the bulk modulus and the three pure shear constants C0, C66, and C44. Three-body interactions are accounted for using our recently reported perturbative treatment based on the nonadditive three-body potential of Cencek et al. Previous studies have attempted to account for the effect of three-body interactions on the elastic properties of solid (4)He; however, these calculations have treated zero point motions using either the Einstein or Debye approximations, which are insufficient in the molar volume range where solid (4)He is characterized as a quantum solid. Our VPI calculations allow for a more accurate treatment of the zero point motions which include atomic correlation. From these calculations, we find that agreement with the experimental bulk modulus is significantly improved when three-body interactions are considered. In addition, three-body interactions result in non-negligible differences in the calculated pure shear constants and nonzero elastic constants, particularly at higher densities, where differences of up to 26.5% are observed when three-body interactions are included. We compare to the available experimental data and find that our results are generally in as good or better agreement with experiment as previous theoretical investigations.

  12. Three-body interactions and the elastic constants of hcp solid 4He

    NASA Astrophysics Data System (ADS)

    Barnes, Ashleigh L.; Hinde, Robert J.

    2017-09-01

    The effect of three-body interactions on the elastic properties of hexagonal close packed solid 4He is investigated using variational path integral (VPI) Monte Carlo simulations. The solid's nonzero elastic constants are calculated, at T = 0 K and for a range of molar volumes from 7.88 cm3/mol to 20.78 cm3/mol, from the bulk modulus and the three pure shear constants C0, C66, and C44. Three-body interactions are accounted for using our recently reported perturbative treatment based on the nonadditive three-body potential of Cencek et al. Previous studies have attempted to account for the effect of three-body interactions on the elastic properties of solid 4He; however, these calculations have treated zero point motions using either the Einstein or Debye approximations, which are insufficient in the molar volume range where solid 4He is characterized as a quantum solid. Our VPI calculations allow for a more accurate treatment of the zero point motions which include atomic correlation. From these calculations, we find that agreement with the experimental bulk modulus is significantly improved when three-body interactions are considered. In addition, three-body interactions result in non-negligible differences in the calculated pure shear constants and nonzero elastic constants, particularly at higher densities, where differences of up to 26.5% are observed when three-body interactions are included. We compare to the available experimental data and find that our results are generally in as good or better agreement with experiment as previous theoretical investigations.

  13. Variational calculation of 4He tetramer ground and excited states using a realistic pair potential

    NASA Astrophysics Data System (ADS)

    Hiyama, E.; Kamimura, M.

    2012-02-01

    We calculated the 4He trimer and tetramer ground and excited states with the LM2M2 potential using our Gaussian expansion method for ab initio variational calculations of few-body systems. The method has been extensively used for a variety of three-, four-, and five-body systems in nuclear physics and exotic atomic and molecular physics. The trimer (tetramer) wave function is expanded in terms of symmetric three- (four-) body Gaussian basis functions, ranging from very compact to very diffuse, without assumption of any pair correlation function. The calculated results for the trimer ground and excited states are in excellent agreement with values reported in the literature. The binding energies of the tetramer ground and excited states are obtained as 558.98 and 127.33 mK (0.93 mK below the trimer ground state), respectively. We found that precisely the same shape of the short-range correlation (rij≲4 Å) in the dimer appears in the ground and excited states of the trimer and tetramer. The overlap function between the trimer excited state and the dimer ground state and that between the tetramer excited state and the trimer ground state are almost proportional to the dimer wave function in the asymptotic region (up to ˜1000 Å). Also, the pair correlation functions of trimer and tetramer excited states are almost proportional to the squared dimer wave function. We then propose a model which predicts the binding energy of the first excited state of 4HeN (N≥3) measured from the 4HeN-1 ground state to be nearly (N)/(2(N-1))B2 where B2 is the dimer binding energy.

  14. Heat Capacity of Superfluid (sup 4)He in the Presence of a Heat Current Near T

    NASA Technical Reports Server (NTRS)

    Chui, Talso C. P.; Goodstein, David L.; Harter, Alexa W.; Mukhopadhyay, Ranjan

    1996-01-01

    The thermodynamic theory of superfluid helium in the presence of a heat current is presented. We show that there is a thermodynamic relation between the heat capacity and the expression ps(W), which describes the depression of the superfluid density with the counterflow velocity W. Using this relation we show that the heat capacity of superfluid super4He in the presence of a heat current diverges at a depressed lambda transition temperature, suggesting the possibility of a new second order phase transition where the superfluid wave function is not the order parameter.

  15. Electro-Weak Transitions of 4He Using Realistic Nuclear Interactions

    NASA Astrophysics Data System (ADS)

    Horiuchi, Wataru; Suzuki, Yasuyuki; Sato, Toru

    In this contribution we discuss electro-weak induced transitions involving 4He. The wave function of the ground state is obtained accurately using an explicitly correlated basis with a realistic nuclear interaction. Four-body final states are expressed in a superposition of many basis functions which contain important configurations for the low-lying transition strength. Resonant and continuum states are treated properly in the complex scaling method. The discussion is mainly focused on the electric dipole strength. Also, we mention those transitions induced by the weak interactions which are important for a neutrino-nucleus reaction.

  16. Head-on Collisions of Xe Atoms Against Superfluid ^4 He Nanodroplets

    NASA Astrophysics Data System (ADS)

    Coppens, François; Leal, Antonio; Barranco, Manuel; Halberstadt, Nadine; Pi, Marti

    2016-11-01

    We study the head-on collision of a heliophilic xenon atom with a superfluid ^4 He droplet made of 1000 atoms. At variance with the findings for a heliophobic cesium atom of a similar atomic weight, it is found that the xenon atom has to hit the droplet with a large kinetic energy in order to get across it without being captured. When it is not captured, the xenon impurity does not emerge as a bare atom; instead, due to its heliophilic character it carries away some helium atoms.

  17. Spatially Extended Avalanches in a Hysteretic Capillary Condensation System: Superfluid {sup {bold 4}}He in Nuclepore

    SciTech Connect

    Lilly, M.P.; Wootters, A.H.; Hallock, R.B.

    1996-11-01

    Capacitive studies of hysteretic capillary condensation of superfluid {sup 4}He in Nuclepore have shown that the initial draining of the pores occurs over a small range of the chemical potential with avalanches present as groups of pores drain. In the work reported here, the avalanches in this system are shown to be nonlocal events which involve pores distributed at low density across the entire sample. The nonlocal avalanche behavior is shown to be enabled by the presence of a superfluid film connection among the pores. {copyright} {ital 1996 The American Physical Society.}

  18. 4He Implantation in Natural Diamond: Implications for Apatite (U-Th)/He Thermochronometry

    NASA Astrophysics Data System (ADS)

    Phillips, D.; Kohn, B. P.; Gleadow, A. J.; Harris, J. W.

    2007-12-01

    Current apatite (U-Th)/He thermochronometry protocols correct for ejection of α-particles from grain margins. However, the potential for implantation of 4He into apatite grains, from primary or secondary actinide minerals, has received more limited attention. Evidence for significant natural α-fluxes in the near- surface environment is provided by surface feature and He abundance studies on diamond. Intense α- damage induces a green colour centre in diamond, enabling visual assessment of natural α-implantation doses. Diamonds with transparent green coats and/or green spots occur in most primary and detrital diamond deposits worldwide, indicating that α-implantation rates into upper crustal minerals may be more significant than previously envisaged. Experiments on transparent green-coated natural diamonds reveal implanted αHe concentrations up to 0.015 cc/g, attributed to secondary uranium phases deposited by circulating groundwater (Shelkov et al., 1998). Implantation of similar α-dosages into apatite grains would increase (U-Th)/He ages by up to several hundred percent, dependent on α-dose rate, grain dimensions and actinide content. Investigation of actinide-rich granites in Australia has revealed the common juxtaposition of apatite and actinide phases such as monazite and zircon. In addition, secondary actinide-bearing phases (e.g. uraninite) are observed along joints, fractures, miarolitic cavities and weathering fronts, thus providing additional α-sources. These results demonstrate that (U-Th)/He thermochronometry analyses of apatite, particularly from actinide-rich, weathered granites and sediments, need to evaluate the potential for 4He implantation in the near-surface environment. Insight into the extent of this problem may be achievable through multiple analyses of single grains, in situ laser probe analyses, 4He/3He step-heating experiments, abrasion of grains and/or complementary apatite fission track analyses. Reference: Shelkov, D

  19. Head-on Collisions of Xe Atoms Against Superfluid (4) 4 He Nanodroplets

    NASA Astrophysics Data System (ADS)

    Coppens, François; Leal, Antonio; Barranco, Manuel; Halberstadt, Nadine; Pi, Marti

    2017-06-01

    We study the head-on collision of a heliophilic xenon atom with a superfluid ^4He droplet made of 1000 atoms. At variance with the findings for a heliophobic cesium atom of a similar atomic weight, it is found that the xenon atom has to hit the droplet with a large kinetic energy in order to get across it without being captured. When it is not captured, the xenon impurity does not emerge as a bare atom; instead, due to its heliophilic character it carries away some helium atoms.

  20. Cross section of 3He( 3He,2p) 4He measured near the Gamow peak

    NASA Astrophysics Data System (ADS)

    Itahashi, T.; Kudomi, N.; Yoshida, S.; Kume, K.; Komori, M.; Ohsumi, H.

    2003-06-01

    We measured the cross section of 3He( 3He,2p) 4He in the energy region of 30-50 keV center of mass energy by using the OCEAN facility. The resulting astrophysical S-factors are in agreement with the existing data and their total errors are as good as those of the previous experiment. For further study we tried the measurements at lower energies than E cm = 30 keV. It will require running times of one month with more improvements such as background reduction and steady operation of the detection system.

  1. An ultracold, optically trapped mixture of 87Rb and metastable 4He atoms

    NASA Astrophysics Data System (ADS)

    Flores, Adonis Silva; Mishra, Hari Prasad; Vassen, Wim; Knoop, Steven

    2017-02-01

    We report on the realization of an ultracold (<25 μK) mixture of rubidium (87Rb) and metastable triplet helium (4He) in an optical dipole trap. Our scheme involves laser cooling in a dual-species magneto-optical trap, simultaneous MW- and RF-induced forced evaporative cooling in a quadrupole magnetic trap, and transfer to a single-beam optical dipole trap. We observe long trapping lifetimes for the doubly spin-stretched spin-state mixture and measure much shorter lifetimes for other spin-state combinations. We discuss prospects for realizing quantum degenerate mixtures of alkali-metal and metastable helium atoms.

  2. Heat Capacity of Superfluid (sup 4)He in the Presence of a Heat Current Near T

    NASA Technical Reports Server (NTRS)

    Chui, Talso C. P.; Goodstein, David L.; Harter, Alexa W.; Mukhopadhyay, Ranjan

    1996-01-01

    The thermodynamic theory of superfluid helium in the presence of a heat current is presented. We show that there is a thermodynamic relation between the heat capacity and the expression ps(W), which describes the depression of the superfluid density with the counterflow velocity W. Using this relation we show that the heat capacity of superfluid super4He in the presence of a heat current diverges at a depressed lambda transition temperature, suggesting the possibility of a new second order phase transition where the superfluid wave function is not the order parameter.

  3. Communication: Nucleation of quantized vortex rings in {sup 4}He nanodroplets

    SciTech Connect

    Mateo, David; Leal, Antonio; Barranco, Manuel; Pi, Martí; Hernando, Alberto; Cargnoni, Fausto; Mella, Massimo; Zhang, Xiaohang; Drabbels, Marcel

    2014-04-07

    Whereas most of the phenomena associated with superfluidity have been observed in finite-size helium systems, the nucleation of quantized vortices has proven elusive. Here we show using time-dependent density functional simulations that the solvation of a Ba{sup +} ion created by photoionization of neutral Ba at the surface of a {sup 4}He nanodroplet leads to the nucleation of a quantized ring vortex. The vortex is nucleated on a 10 ps timescale at the equator of a solid-like solvation structure that forms around the Ba{sup +} ion. The process is expected to be quite general and very efficient under standard experimental conditions.

  4. Properties of 4He and 6Li with improved chiral EFT interactions

    NASA Astrophysics Data System (ADS)

    Maris, P.; Binder, S.; Calci, A.; Epelbaum, E.; Furnstahl, R. J.; Golak, J.; Hebeler, K.; Kamada, H.; Krebs, H.; Langhammer, J.; Liebig, S.; Meißner, U.-G.; Minossi, D.; Nogga, A.; Potter, H.; Roth, R.; Skibiński, R.; Topolnicki, K.; Vary, J. P.; Witala, H.

    2016-03-01

    We present recent results for 4He and 6Li obtained with improved NN interactions derived from chiral effective field theory up to N4LO. The many-body calculations are performed order-by-order in the chiral expansion. At N3LO and N4LO additional renormalization using the Similarity Renormalization Group is adopted to improve numerical convergence of the many-body calculations. We discuss results for the ground state energies, as well as the magnetic moment and the low-lying spectrum of 6Li.

  5. New Precision Measurement of the 3He(4He,γ) 7Be Cross Section

    NASA Astrophysics Data System (ADS)

    Singh, B. S.; Hass, M.; Nir-El, Y.; Haquin, G.

    2004-12-01

    The 3He(4He,γ) 7Be reaction plays an important role in determining the high energy solar neutrino flux and in understanding the abundances of primordial 7Li. This Letter reports a new precision measurement of the cross sections of this direct capture reaction, determined by measuring the ensuing 7Be activity in the region of Ec.m.=420 to 950keV. Various recent theoretical fits to our data result in a consistent extrapolated value of S34(0)=0.53(2)(1) keV b.

  6. Survey of A asymmetries in semi-exclusive electron scattering on 4He and 12C

    NASA Astrophysics Data System (ADS)

    Protopopescu, D.; Hersman, F. W.; Holtrop, M.; Adams, G.; Ambrozewicz, P.; Anciant, E.; Anghinolfi, M.; Asavapibhop, B.; Asryan, G.; Audit, G.; Auger, T.; Avakian, H.; Bagdasaryan, H.; Ball, J. P.; Barrow, S.; Battaglieri, M.; Beard, K.; Bektasoglu, M.; Bellis, M.; Benmouna, N.; Berman, B. L.; Bertozzi, W.; Bianchi, N.; Biselli, A. S.; Boiarinov, S.; Bonner, B. E.; Bouchigny, S.; Bradford, R.; Branford, D.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Butuceanu, C.; Calarco, J. R.; Carman, D. S.; Carnahan, B.; Cetina, C.; Chen, S.; Cole, P. L.; Coleman, A.; Cords, D.; Corvisiero, P.; Crabb, D.; Crannell, H.; Cummings, J. P.; Debruyne, D.; De Sanctis, E.; DeVita, R.; Degtyarenko, P. V.; Dennis, L.; Dharmawardane, K. V.; Dhuga, K. S.; Djalali, C.; Dodge, G. E.; Doughty, D.; Dragovitsch, P.; Dugger, M.; Dytman, S.; Dzyubak, O. P.; Egiyan, H.; Egiyan, K. S.; Elouadrhiri, L.; Empl, A.; Eugenio, P.; Fatemi, R.; Feuerbach, R. J.; Forest, T. A.; Funsten, H.; Gavalian, G.; Gilad, S.; Gilfoyle, G. P.; Giovanetti, K. L.; Girard, P.; Gordon, C. I. O.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guillo, M.; Guler, N.; Guo, L.; Gyurjyan, V.; Hadjidakis, C.; Hakobyan, R. S.; Hardie, J.; Heddle, D.; Hicks, K.; Hleiqawi, I.; Hu, J.; Hyde-Wright, C. E.; Ingram, W.; Ireland, D.; Ito, M. M.; Jenkins, D.; Joo, K.; Juengst, H. G.; Kelley, J. H.; Kellie, J. D.; Khandaker, M.; Kim, K. Y.; Kim, K.; Kim, W.; Klein, A.; Klein, F. J.; Klimenko, A. V.; Klusman, M.; Kossov, M.; Kramer, L. H.; Kuhn, S. E.; Kuhn, J.; Lachniet, J.; Laget, J. M.; Langheinrich, J.; Lawrence, D.; Lee, T.; Li, Ji; Livingston, K.; Lukashin, K.; Manak, J. J.; Marchand, C.; McAleer, S.; McLauchlan, S. T.; McNabb, J. W. C.; Mecking, B. A.; Melone, J. J.; Mestayer, M. D.; Meyer, C. A.; Mikhailov, K.; Minehart, R.; Mirazita, M.; Miskimen, R.; Morand, L.; Morrow, S. A.; Muccifora, V.; Mueller, J.; Mutchler, G. S.; Napolitano, J.; Nasseripour, R.; Nelson, S. O.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Niczyporuk, B. B.; Niyazov, R. A.; Nozar, M.; O'Rielly, G. V.; Osipenko, M.; Ostrovidov, A.; Park, K.; Pasyuk, E.; Peterson, G.; Philips, S. A.; Pivnyuk, N.; Pocanic, D.; Pogorelko, O.; Polli, E.; Pozdniakov, S.; Preedom, B. M.; Price, J. W.; Prok, Y.; Qin, L. M.; Raue, B. A.; Riccardi, G.; Ricco, G.; Ripani, M.; Ritchie, B. G.; Ronchetti, F.; Rosner, G.; Rossi, P.; Rowntree, D.; Rubin, P. D.; Ryckebusch, J.; Sabatié, F.; Sabourov, K.; Salgado, C.; Santoro, J. P.; Sapunenko, V.; Schumacher, R. A.; Serov, V. S.; Sharabian, Y. G.; Shaw, J.; Simionatto, S.; Skabelin, A. V.; Smith, E. S.; Smith, L. C.; Sober, D. I.; Spraker, M.; Stavinsky, A.; Stepanyan, S.; Stokes, B. E.; Stoler, P.; Strauch, S.; Taiuti, M.; Taylor, S.; Tedeschi, D. J.; Thoma, U.; Thompson, R.; Tkabladze, A.; Todor, L.; Tur, C.; Ungaro, M.; Vineyard, M. F.; Vlassov, A. V.; Wang, K.; Weinstein, L. B.; Weller, H.; Weygand, D. P.; Whisnant, C. S.; Williams, M.; Wolin, E.; Wood, M. H.; Yegneswaran, A.; Yun, J.; Zana, L.; Zhang, B.; CLAS Collaboration

    2005-02-01

    Single spin azimuthal asymmetries A were measured at Jefferson Lab using 2.2 and 4.4 GeV longitudinally polarised electrons incident on 4He and 12C targets in the CLAS detector. A is related to the imaginary part of the longitudinal-transverse interference and in quasifree nucleon knockout it provides an unambiguous signature for final state interactions (FSI). Experimental values of A were found to be below 5%, typically |A|⩽3% for data with good statistical precision. Optical model in eikonal approximation (OMEA) and relativistic multiple-scattering Glauber approximation (RMSGA) calculations are shown to be consistent with the measured asymmetries.

  7. Oceanic lavas sampling the high 3He/4He mantle reservoir: Primitive, depleted, or re-enriched?

    NASA Astrophysics Data System (ADS)

    Garapic, G.; Mallik, A.; Dasgupta, R.; Jackson, M. G.

    2014-12-01

    Helium isotopes are used as a tracer for primitive reservoirs that have persisted in the Earth's mantle. Basalts erupted at several intraplate oceanic islands, including Hawaii, Iceland, Galapagos and Samoa, have hosted the highest 3He/4He ratios (> 30 Ra, where Ra is atmospheric 3He/4He ratio) globally that are far in excess of the 3He/4He typical of the upper mantle sampled at mid-ocean ridges (8 Ra). These lavas have been suggested to be melts of a primitive, or possibly slightly depleted, mantle reservoir, i.e., either fertile or a depleted peridotite. We report evidence for geochemical enrichment in the high 3He/4He mantle sampled by lavas with the highest 3He/4He from Hawaii, Samoa and possibly Galapagos. The titanium concentrations in high 3He/4He lavas from Samoa are too high to be explained by melts of a mantle peridotite, even at infinitesimally small degrees of melting, and the elevated Ti corresponds to elevated Pb-isotopic ratios. The highest 3He/4He lavas from Loihi, Hawaii have Ti concentrations that are too high to be melts of primitive mantle peridotite at the degrees of melt extraction proposed for those ocean islands. Thus, Ti-rich material must have been added to the high 3He/4He mantle reservoir, and this material is likely to be recycled mafic crust similar to MORB-like eclogite, which is consistent with the elevated Pb-isotopic ratios. We show that fractionation corrected, major element compositions of high 3He/4He alkalic lavas can be satisfactorily modeled by melting and melt-rock interaction scenario in a fertile peridotite-MORB-eclogite hybrid system. Primitive peridotitic and recycled eclogitic reservoirs are suggested to be intimately associated in the deepest mantle and far from being primitive, the high 3He/4He lavas may sample a mantle source that hosts a component of recycled oceanic crust.

  8. 16O + 16O molecular structures of positive- and negative-parity superdeformed bands in 34S

    NASA Astrophysics Data System (ADS)

    Taniguchi, Yasutaka

    2016-05-01

    The structures of excited states in 34S are investigated using the antisymmetrized molecular dynamics and generator coordinate method(GCM). The GCM basis wave functions are calculated via energy variation with a constraint on the quadrupole deformation parameter β. By applying the GCM after parity and angular momentum projections, the coexistence of two positive- and one negative-parity super de formed(SD) bands are predicted, and low-lying states and other deformed bands are obtained. The SD bands have structures of 16O + 16O + two valence neutrons in molecular orbitals around the two 16O cores in a cluster picture. The configurations of the two valence neutrons are δ2 and π2 for the positive-parity SD bands and π1δ1 for the negative parity SD band.

  9. Missing Lead and High 3He/4He in Ancient Sulfides Associated with Continental Crust Formation

    PubMed Central

    Huang, Shichun; Lee, Cin-Ty A.; Yin, Qing-Zhu

    2014-01-01

    Major terrestrial reservoirs have Pb isotopes more radiogenic than the bulk silicate Earth. This requires a missing unradiogenic Pb reservoir, which has been argued to reside in the lower continental crust or dissolved in the core. Chalcophile element studies indicate that continent formation requires the formation of sulfide-bearing mafic cumulates in arcs. Because Pb, but not U, partitions into sulfides, we show that continent formation must have simultaneously generated time-integrated unradiogenic Pb reservoirs composed of sulfide-bearing cumulates, now recycled back into the mantle or stored deep in the continental lithosphere. The generation of such cumulates could also lead to coupled He-Pb isotopic systematics because 4He is also produced during U-Th-Pb decay. Here, we show that He may be soluble in sulfide melts, such that sulfide-bearing cumulates would be enriched in both Pb and He relative to U and Th, “freezing” in He and Pb isotopes of the ambient mantle at the time of sulfide formation. This implies that ancient sulfide-bearing cumulates would be characterized by unradiogenic Pb and He isotopes (high-3He/4He). These primitive signatures are usually attributed to primordial, undifferentiated mantle, but in this case, they are the very imprint of mantle differentiation via continent formation. PMID:24937103

  10. Stability of free planar films of liquid 4He at T=0 K

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek

    1997-11-01

    The stability of planar films of liquid 4He at T=0 K without a supporting potential is investigated. For this purpose, the third-sound velocity, c3, is examined within the framework of two different theoretical descriptions: (i) the correlated-basis functions theory in conjunction with the hypernetted-chain approximation and (ii) the nonlocal density functional theory. All the calculations yield negative values of c23. In particular, the behavior of the chemical potential as a function of the coverage provides convincing evidence in favor of the instability of all the analyzed free films. Furthermore, the analysis of the trend of thick films leads to the plausible conjecture that free planar films with finite coverage would be always unstable. The conclusion of the present work matches well with the nonwetting phenomenon of Rb and Cs substrates by a liquid 4He film at T=0 K and with the hydrodynamic prediction that a free semi-infinite system with a flat surface is unstable.

  11. Spin-polarized hydrogen adsorbed on the surface of superfluid {sup 4}He

    SciTech Connect

    Marín, J. M.; Boronat, J.; Markić, L. Vranješ

    2013-12-14

    The experimental realization of a thin layer of spin-polarized hydrogen H↓ adsorbed on top of the surface of superfluid {sup 4}He provides one of the best examples of a stable, nearly two-dimensional (2D) quantum Bose gas. We report a theoretical study of this system using quantum Monte Carlo methods in the limit of zero temperature. Using the full Hamiltonian of the system, composed of a superfluid {sup 4}He slab and the adsorbed H↓ layer, we calculate the main properties of its ground state using accurate models for the pair interatomic potentials. Comparing the results for the layer with the ones obtained for a strictly 2D setup, we analyze the departure from the 2D character when the density increases. Only when the coverage is rather small the use of a purely 2D model is justified. The condensate fraction of the layer is significantly larger than in 2D at the same surface density, being as large as 60% at the largest coverage studied.

  12. Inrared Spectroscopy and Tunneling Dynamics of the Vinyl Radical in ^{4}He Nanodroplets

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Liang, Tao; Obi, Emmanuel I.; Douberly, Gary E.

    2013-06-01

    The vinyl radical has been trapped in ^{4}He nanodroplets and probed with infrared laser spectroscopy in the CH stretch region between 2850 and 3200 cm^{-1}. The assigned band origins for the CH{_2} symmetric (ν{_3}), CH{_2} antisymmetric (ν{_2}), and lone α-CH stretch (ν{_1}) vibrations are in good agreement with previously reported full-dimensional vibrational configuration interaction calculations. For all three bands, a-type and b-type transitions are observed from the lowest symmetry allowed roconvibrational state of each nuclear spin isomer, which allows for a determination of the tunneling splittings in both the ground and excited vibrational levels. Comparisons to gas phase millimeter-wave rotation-tunneling and high-resolution jet-cooled infrared spectra reveal that the effect of the ^{4}He solvent is to reduce the ground and ν{_3} excited state tunneling splittings by ≈20%. This solvent-induced modification of the tunneling dynamics can be reasonably accounted for by assuming either an ≈2.5% increase in the effective barrier height along the tunneling coordinate or an ≈5% increase in the effective reduced mass of the tunneling particles. A. R. Sharma, B. J. Braams, S. Carter, B. C. Shepler, and J. M. Bowman, J. Chem. Phys. {130}, 174301 2009 K. Tanaka, M. Toshimitsu, K. Harada, and T. Tanaka, J. Chem. Phys. {120}, 3604 2004 F. Dong, M. Roberts, and D. J. Nesbitt, J. Chem. Phys. {128}, 044305 (2008)

  13. Excitations in a thin liquid {sup 4}He film from inelastic neutron scattering

    SciTech Connect

    Clements, B.E. |; Godfrin, H.; Krotscheck, E. |; Lauter, H.J.; Leiderer, P.; Passiouk, V. |; Tymczak, C.J.

    1996-05-01

    We perform a thorough analysis of the experimental dynamic structure function measured by inelastic neutron scattering for a low-temperature ({ital T}=0.65 K) four-layer liquid {sup 4}He film. The results are interpreted in light of recent theoretical calculations of the (nonvortex) excitations in thin liquid Bose films. The experimental system consists of four outer liquid layers, adsorbed to two solid inner {sup 4}He layers, which are themselves adsorbed to a graphite substrate. Relatively intense surface (ripplon) and bulklike modes are observed. The analysis of the experimental data gives strong evidence for still other modes and supports the long-standing theoretical predictions of layerlike modes (layer phonons) associated with excitations propagating primarily within the liquid layers comprising the film. The results of the analysis are consistent with the occurrence of level crossings between modes, and the existence of a layer modes for which the theory predicts will propagate in the vicinity of the solid-liquid interface. The theory and experiment agree on the detailed nature of the ripplon; its dispersion at low momenta, its fall off in intensity at intermediate momenta, and the level crossings at high momentum. Similar to experiment, the theory yields an intense mode in the maxon-roton region which is intrepreted as the formation of the bulklike excitation. {copyright} {ital 1996 The American Physical Society.}

  14. Conceptual design of 4He film suppressor in Still of Dilution Refrigerator

    NASA Astrophysics Data System (ADS)

    Bidhan Chandra, Mandal; Das, Nisith Kr

    2017-02-01

    The capacity of a dilution refrigerator in terms of its cooling power and base temperature is primarily governed by the flow rate of the isotopic mixture of helium. In the process of circulation of gas mixture, geometrical configuration of 3He distillation chamber (Still) maintained at a temperature of around 0.7 K plays a significant role in controlling the flow rate. We have already employed a still in our existing dilution refrigerator, however, a new conceptual design is presented here and it is envisaged that this novel design will improve the gas circulation efficiency. Even though, thermodynamic conditions are major issues in eliminating unwanted 4He film as compared to 3He molecules, this design based on a new geometry is likely to enhance the pressure and the temperature at the still that helps in burning out the super-fluid 4He film. The conceptual design of film suppressor and its relevance in the recently commissioned indigenous dilution refrigerator at Variable Energy Cyclotron Centre is presented in this paper.

  15. Capture of Xe and Ar atoms by quantized vortices in (4)He nanodroplets.

    PubMed

    Coppens, François; Ancilotto, Francesco; Barranco, Manuel; Halberstadt, Nadine; Pi, Martí

    2017-09-04

    We present a computational study, based on time-dependent Density Functional theory, of the real-time interaction and trapping of Ar and Xe atoms in superfluid (4)He nanodroplets either pure or hosting quantized vortex lines. We investigate the phase-space trajectories of the impurities for different initial conditions and describe in detail the complex dynamics of the droplets during the capture of the impurities. We show that the interaction of the incoming atom with the vortex core induces large bending and twisting excitations of the vortex core lines, including the generation of helical Kelvin waves propagating along the vortex core. We have also calculated the stationary configurations of a (4)He droplet hosting a 6-vortex array whose cores are filled with Ar atoms. As observed in recent experiments, we find that doping adds substantial rigidity to the system, such that the doped vortex array remains stable, even at low values of the angular velocities where the undoped vortices would otherwise be pushed towards the droplet surface and be expelled.

  16. Hysteretic behavior in torsional oscillator experiments & de Gennes, Bean and Livingston effect in hcp 4He

    NASA Astrophysics Data System (ADS)

    Kubota, Minoru; Ueda, Hiroaki; Yagi, Masahiko; Shimizu, Nobutaka; Rogacki, Kris.; Inoue, Kazuo

    2014-03-01

    Recent reports on the absence of supersolid signal in 4He in Vycor as well as reports on effects of the sample elasticity to torsional oscillator (TO) experiments caused people to ask if supersolid may not exist. There are recent activities to check such questions more quantitatively. We revisit our TO study, which was performed on relatively small number of bulk hcp 4He samples, but under quite different conditions as under DC rotation as well as under wide range of AC excitation Vac with extremely high stability. We proposed a transition at Tc = 75(~ 60) mK well below the onset temperature of the anomaly around 500 mK in the same sample. The transition at Tc was detected by three independent methods. Namely, the hysteresis appears below this Tc when AC excitation was changed under a certain sequence. We analyzed the maximum period shift across the hysteretic loop as a function of Vac. This quantity appears abruptly below Tc and surprisingly its T dependence coincides with that of the extra energy dissipation rotational velocity Omega linear slope under DC rotation, also below Tc. We discuss that the maximum is caused by de Gennes, Bean and Livingston effect, which is a quantized vortices effect known for superconductors. The third Tc detection is given by a jump in the log Vac linear dependence of the period shift. Authors acknowledge support from ISSP, Univ. Tokyo.

  17. Superfluidity, Bose-Einstein condensation and dimensions of liquid 4He in nanopores

    NASA Astrophysics Data System (ADS)

    Vranješ Markić, Leandra; Glyde, Henry

    Path integral Monte Carlo (PIMC) calculations of the superfluid fraction, ρS / ρ , and the one-body density matrix (OBDM) (Bose-Einstein condensation (BEC)) of liquid 4He confined in nanopores are presented. The goal is to determine the effective dimensions of the liquid in the nanopore. We simulate a cylinder of liquid of diameter dL surrounded by 5 Åof inert solid 4He in a nanopore of diameter d; d = dL + 10 Å. The PIMC ρS (T) / ρ and OBDM scales as a 1D Luttinger Liquid at extremely small liquid pore diameters only, dL = 6 Åwhere the liquid atoms form a 1D line at the center of the pore. In the range 8 <=dL <= 22 Åthe PIMC ρS (T) / ρ scales as a 2D liquid. In this dL range the liquid fills the pores in cylindrical layers. There is a cross over from 2D to 3D scaling at larger dL ~= 22 Å. In the range 8 <=dL <= 22 Å, the TC predicted using the Kosterlitz-Thouless 2D scaling criterion of the OBDM agrees well with the TC obtained from ρS (T) / ρ . Superflow observed in pores of diameter (18 < d < 32 Å) is apparently standard static superflow with the low TC arising from its 2D character. Supported by Office of Basic Energy Sciences, USDOE, ER46680.

  18. Giant isochoric compressibility of solid 4He: The bistability of superclimbing dislocations

    NASA Astrophysics Data System (ADS)

    Kuklov, A. B.

    2015-10-01

    A significant accumulation of matter in solid 4He observed during a superflow event, dubbed the giant isochoric compressibility (or the syringe effect), is discussed within the model of dislocations with superfluid core. It is shown that solid 4He in contact with a superfluid reservoir can develop a bistability with respect to the syringe fraction, with the threshold for the bias by chemical potential determined by a typical free length of dislocations with superfluid core. The main implications of this effect are hysteresis and strongly nonlinear dynamical behavior leading to growth, proliferation, and possibly exiting from a crystal of superclimbing dislocations. Three major channels for such dynamics are identified: (i) injection and inflation of the prismatic loops from the boundary, (ii) Bardeen-Herring generation of the loops in the bulk, and (iii) helical instability of the screw dislocations. It is argued that the syringe instability may have already been observed in the experiments on the superflow through solid Helium-4. Several testable predictions for the time and the bias dependencies of the dynamics are suggested.

  19. First viscosity of dilute3He-4He mixtures below 0.6 K

    NASA Astrophysics Data System (ADS)

    Um, Chung-In; Yoo, Sahng-Kyoon; Lee, Soo-Young; George, Thomas F.; Pandey, Lakshmi N.

    1994-01-01

    Starting with the Boltzmann transport equation, the first viscosity of dilute3He-4He mixtures for various3He concentrations x is evaluated up to around T ≅ 0.6 K by including the contribution from three-phonon processes (3PP) in the anomalous elementary excitation spectrum of liquid4He. Due to 3PP, the characteristic time τη for3He viscosity at high temperatures, i.e., T⩾2TF where TF is the3He Fermi temperature, is evaluated as 5 × 10-12/xT, which is smaller than the value estimated by Rosenbaum et al. This is interpolated with τη in the degenerate (quantum) region, T≪TF. The obtained viscosities are in better agreement with experimental results than those of Baym and Saam, whose theory does not include 3PP. However, at very low concentrations there exists a discrepancy between the present theory and experiments, so that an alternate treatment should be considered.

  20. Intertwined superfluid and density wave order in two-dimensional 4He

    NASA Astrophysics Data System (ADS)

    Nyéki, Ján; Phillis, Anastasia; Ho, Andrew; Lee, Derek; Coleman, Piers; Parpia, Jeevak; Cowan, Brian; Saunders, John

    2017-02-01

    Superfluidity is a manifestation of the operation of the laws of quantum mechanics on a macroscopic scale. The conditions under which superfluidity becomes manifest have been extensively explored experimentally in both quantum liquids (liquid 4He being the canonical example) and ultracold atomic gases, including as a function of dimensionality. Of particular interest is the hitherto unresolved question of whether a solid can be superfluid. Here we report the identification of a new state of quantum matter with intertwined superfluid and density wave order in a system of two-dimensional bosons subject to a triangular lattice potential. Using a torsional oscillator we have measured the superfluid response of the second atomic layer of 4He adsorbed on the surface of graphite, over a wide temperature range down to 2 mK. Superfluidity is observed over a narrow range of film densities, emerging suddenly and subsequently collapsing towards a quantum critical point. The unusual temperature dependence of the superfluid density in the limit of zero temperature and the absence of a clear superfluid onset temperature are explained, self-consistently, by an ansatz for the excitation spectrum, reflecting density wave order, and a quasi-condensate wavefunction breaking both gauge and translational symmetry.

  1. Search for new evidence of superfluidity in solid ^4He by phonon propagation

    NASA Astrophysics Data System (ADS)

    Aoki, Yuki; Kojima, Harry

    2007-03-01

    The phonon propagation generated by heat pulse has been studied in solid ^4He under pressure between 25 and 56 bar to search for a sign of supersolid behavior at temperatures down to 40 mK. Response to input heat pulses are detected by a titanium film superconducting edge bolometer separated by a 4.5 mm thick solid ^4He from the heater. According to theoretical studies, a new fourth sound-like mode is expected to emerge in the supersolid state. The sensitivity of our bolometer has been improved from an earlier version by an order of magnitude by changing the film structure for the purpose of searching for a small temperature deviation signal accompanying the fourth sound-like propagation mode. The response of the bolometer to heat pulse was measured in different quality solid samples which had been grown with different cooling rates during solidification. The detected response signal has not revealed any identifiable signature of a new mode within a temperature excursion of about δT = 5 μK from the background signal shape. An estimated superflow velocity corresponding to the temperature excursion is greater than the critical velocity observed by Kim and Chan. Our detection sensitivity must be further increased before a definitive conclusion on the fourth sound-like mode can be made.

  2. Premelting Induced Decoupling as a cause of Nonclassical Rotational Inertia in Solid ^4He

    NASA Astrophysics Data System (ADS)

    Wettlaufer, J. S.; Dash, J. G.

    2005-03-01

    Recent reports by Kim and Chan describe the observation of nonclassical rotational inertia in solid ^4He, which is taken to demonstrate superfluidity of the solid. This exciting possibility was noted as a long standing speculation, based on the hypothesis of Bose-Einstein condensation of zero-point vacancies. Here we suggest an alternative explanation of the experiment: decoupling of the solid from the wall of the container by grain boundary premelting. However, the premelting in question is not at ordinary grain boundaries, but at the interface between the bulk solid and dense adsorbed layers at the container wall. The dense layers, due strong adsorption forces, are responsible for nonzero wetting angles between solid ^4He and copper and glass walls; the contacting surface in question more nearly resembles the interface between two different materials. In view of the sensitivity of premelting to the crystal structure of the solid, and the density difference between the solid and the adsorbed layers at the wall, we propose that premelting occurs at that interface. The reduction in the latent heat of fusion with decreasing temperature enhances the film thickness, which we calculate as function of the parameters of the Lennard-Jones potential to be nearly four atomic layers at the experimental temperatures of 175 mK.

  3. High-relief glacial landscape evolution constrained by apatite 4He/3He thermochronometry

    NASA Astrophysics Data System (ADS)

    Shuster, D. L.; Sanders, J. W.; Cuffey, K. M.

    2009-12-01

    Apatite 4He/3He thermochronometry of bedrock samples collected from high-relief and heavily glaciated terrain near Milford Sound in Fiordland, New Zealand reveals clear differences between the cooling histories of high and low elevation samples. Across the region, the youngest apatite (U-Th)/He ages ~1 million years (Ma) generally occur at cirque floor elevations (~500-700 m elevation) rather than at sea level where (U-Th)/He ages approach ~2 Ma. Thermal histories constrained by 4He/3He thermochronometry of three vertically oriented samples collected along the headwall of a ~1100 meter deep cirque indicate that since ~1 Ma ago: (i) rocks presently located near the cirque rim (~1720 m elevation) have resided at temperatures <25 oC, while (ii) rocks at the floor of the cirque (~575 m elevation) continuously cooled from ~75-110 oC to the present surface temperature. These thermal histories indicate that most of the cirque relief developed over the last ~1 Ma and/or the sub-surface thermal field was highly perturbed during that time interval over an ~1 km horizontal scale. We will interpret sample cooling histories in conjunction with a 3-D model of subsurface temperature evolution in response to changes in topography. The goal is to constrain the rates and patterns of glacial valley development over the Quaternary.

  4. Is there a stable commensurate solid phase in the second 4He layer on graphite? - path integral Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Ahn, Jeonghwan; Lee, Hoonkyung; Kwon, Yongkyung

    2015-03-01

    Existence of a stable commensurate structure in the second 4He layer on graphite has been a subject of intensive experimental and theoretical studies because of its implication in the possible realization of two-dimensional supersolidity. Earlier path-integral Monte Carlo (PIMC) calculations of Pierce and Manousakis predicted a stable C4/7 commensurate structure above the first-layer 4He atoms fixed at triangular lattice sites, but Corboz et al. later showed that no commensurate phase was stable when quantum dynamics of the first-layer 4He atoms was incorporated in the PIMC calculations. On the other hand, recent heat capacity measurements of Nakamura et al. provided a strong evidence for a commensurate solid in the second 4He layer over an extended density range. Motivated by this, we have performed new PIMC calculations for the second helium layer on graphite. Unlike previous PIMC calculations where a laterally-averaged one-dimensional substrate potential was used, we here employ an anisotropic 4He-graphite potential described by a sum of the 4He-C pair potentials. With this fully-corrugated substrate potential we make more accurate description of quantum dynamics of the first-layer 4He atoms and analyze its effects on the phase diagram of the second layer.

  5. Dissociation of relativistic {sup 7}Be nuclei through the {sup 3}He+{sup 4}He channel on a proton target

    SciTech Connect

    Alexandrov, Yu. A.; Peresadko, N. G. Gerasimov, S. G.; Dronov, V. A.; Pisetskaya, A. V.; Fetisov, V. N.; Kharlamov, S. P.; Shesterkina, L. N.

    2015-05-15

    The differential cross section for the interaction of {sup 7}Be nuclei with protons was measured in the momentum-transfer region extending up to a value of 0.5 GeV/c at which {sup 7}Be decay to {sup 3}He and {sup 4}He fragments was not accompanied by the emergence of other charged particles. In the momentum-transfer region extending up to about 100 MeV/c, the cross section is strongly suppressed in just the same way as in the case of the dissociation of {sup 7}Li nuclei on a proton target through the {sup 3}H+{sup 4}He channel. The total reaction cross section is 10 ± 4 mb. The mean transverse-momentum transfer in observed events is 233 ± 6 MeV/c, the dispersion of its distribution being about 63 MeV/c. The interactions in question were detected in photoemulsion irradiated with {sup 7}Be nuclei originating from a charge-exchange process involving {sup 7}Li nuclei accelerated to the momentum of 1.7 GeV/c per nucleon at the nuclotron of the Joint Institute for Nuclear Research (Dubna)

  6. Communication: Unraveling the {sup 4}He droplet-mediated soft-landing from ab initio-assisted and time-resolved density functional simulations: Au@{sup 4}He{sub 300}/TiO{sub 2}(110)

    SciTech Connect

    Lara-Castells, María Pilar de Aguirre, Néstor F.; Stoll, Hermann; Mitrushchenkov, Alexander O.; Mateo, David; Pi, Martí

    2015-04-07

    An ab-initio-based methodological scheme for He-surface interactions and zero-temperature time-dependent density functional theory for superfluid {sup 4}He droplets motion are combined to follow the short-time collision dynamics of the Au@{sup 4}He{sub 300} system with the TiO{sub 2}(110) surface. This composite approach demonstrates the {sup 4}He droplet-assisted sticking of the metal species to the surface at low landing energy (below 0.15 eV/atom), thus providing the first theoretical evidence of the experimentally observed {sup 4}He droplet-mediated soft-landing deposition of metal nanoparticles on solid surfaces [Mozhayskiy et al., J. Chem. Phys. 127, 094701 (2007) and Loginov et al., J. Phys. Chem. A 115, 7199 (2011)].

  7. Spectroscopic Parameters for Ozone and its Isotopes: Current Status, Prospects for Improvement, and the Identification of 16O16O17O and O-16O-16O-17 and O-16O-17O-16 Lines in Infrared Ground-Based and Stratospheric Solar Absorption Spectra

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Flaud, J.-M.; Goldman, A.; Perrin, A.; Camy-Peyret, C.; Smith, M. A. H.; Devi, V. Malathy; Benner, D. C.; Barbe, A.; Stephens, T. M.; hide

    1998-01-01

    We describe the updates to the spectroscopic parameters of ozone and its isotopes in the 1996 HITRAN compilation. Recent published studies not included in HITRAN are also summarized. Finally, we report the identification of infrared lines of the v(sub 3) bands of O-16O-16O-17 and O-16O-17O-16 in high-resolution solar spectra recorded by stratospheric balloon-borne and ground-based Fourier transform spectrometers.

  8. Nonlinear Ultrasound Propagation in Solid ^4{He} Compared with Shear Modulus Experiments

    NASA Astrophysics Data System (ADS)

    Iwasa, Izumi; Kojima, Harry

    2016-10-01

    Ultrasound attenuation (α ) and velocity (V) at 9.6 MHz are measured in polycrystalline hcp ^4{He} . The ultrasound signal above 200 mK is linear and understood in terms of resonant vibration of dislocation segments pinned between network nodes with an average pinning length of 3.7 μ m, much shorter than 59 μ m estimated from a shear modulus measurement. Dramatic changes in α and V are observed below 200 mK. The changes are strongly dependent on temperature and are nonlinear and hysteretic. These effects result from pinning of dislocations by ^3{He} impurities (nominal concentration of 0.3 ppm). The dislocation damping constant due to thermal phonons, the binding energy between dislocation and ^3{He} , and the average network pinning length obtained from the ultrasound data are compared with those from the shear modulus experiments.

  9. Curvature effects on the surface thickness and tension at the free interface of 4He systems

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek; Urrutia, Ignacio

    2003-08-01

    The thickness W and the surface energy σA at the free interface of superfluid 4He are studied. Results of calculations carried out using density functionals for cylindrical and spherical systems are presented in a unified way, including a comparison with the behavior of planar slabs. It is found that for large species W is independent of the geometry. The obtained values of W are compared with prior theoretical results and experimental data. Experimental data favor results evaluated by adopting finite range approaches. The behavior of σA and WσA exhibits overshoots similar to that found previously for the central density, and the trend of these observables towards their asymptotic values is examined.

  10. Decoupling of first sound from second sound in dilute 3He-superfluid 4He mixtures

    NASA Astrophysics Data System (ADS)

    Riekki, T. S.; Manninen, M. S.; Tuoriniemi, J. T.

    2016-12-01

    Bulk superfluid helium supports two sound modes: first sound is an ordinary pressure wave, while second sound is a temperature wave, unique to superfluid systems. These sound modes do not usually exist independently, but rather variations in pressure are accompanied by variations in temperature, and vice versa. We studied the coupling between first and second sound in dilute 3He -superfluid 4He mixtures, between 1.6 and 2.2 K, at 3He concentrations ranging from 0% to 11%, under saturated vapor pressure, using a quartz tuning fork oscillator. Second sound coupled to first sound can create anomalies in the resonance response of the fork, which disappear only at very specific temperatures and concentrations, where two terms governing the coupling cancel each other, and second sound and first sound become decoupled.

  11. Dynamics of {sup 3}He impurities in {sup 4}He films

    SciTech Connect

    Clements, B.E. |; Krotscheck, E. |; Saarela, M.

    1995-08-01

    Using a microscopic variational theory the authors calculate the binding energy of {sup 3}He impurities in films of {sup 4}He absorbed to a graphite substrate. Without adjustable parameters, they obtain excellent agreement with the experimental binding energies for the ground state of the {sup 3}He impurity. To calculate excited states, they then introduce a time-dependent variational wave function. In that way, the impurity acquires a hydrodynamic effective mass for its motion parallel to the surface due to hydrodynamic backflow. Excited states have a finite lifetime. When these effects are included, both the energy of the first excited state of the impurity, and the effective mass of the ground state, also agree well with experimental data.

  12. Disappearance of Roton Propagation in Superfluid {sup 4}He at T{sub {lambda}}

    SciTech Connect

    Svensson, E.C.; Montfrooij, W.; de Schepper, I.M.

    1996-11-01

    Using neutron scattering, we determine the dynamic structure factor {ital S}({ital q},{nu}) of liquid {sup 4}He for the roton wave number {ital q}=2.0{sup {minus}1} as a function of frequency {nu} at constant density 0.1715 gcm{sup {minus}3} and for ten temperatures in the range 1.08{le}{ital T}{le}2.00 K, primarily near the superfluid transition temperature {ital T}{sub {lambda}}=1.9202 K. The {lambda} transition is marked by a complete softening of the roton mode and a rapid decrease in lifetime. This change is continuous with temperature, and we find no evidence for a new mode appearing as one enters the superfluid phase, as has been proposed on the basis of theoretical considerations. {copyright} {ital 1996 The American Physical Society.}

  13. Experimental study of nanofluidics and phase transitions of normal and superfluid 4He

    NASA Astrophysics Data System (ADS)

    Velasco, Angel Enriques

    This thesis addresses the experimental results of two different research topics. The first is the experimental work of pressure driven flows in the smallest, single nanotubes ever investigated. The nanotube boundary conditions and slip lengths from argon, nitrogen, water, and helium experiments were analyzed and compared to macroscopic boundary conditions. The second research topic discusses the work on ellipsometric and quartz microbalance measurements of the 2D superfluid phase diagram of 4He on alkali substrates. Ellipsometric results of sodium on HOPG provide the first evidence of the existence of the 2D critical point on an intermediate strength substrate. Pressure driven flows through single nanopores and microtubes were measured with a calibrated mass spectrometer with pressure drops up to 30 Atm. The nanopores were between 30 nm to 600 nm in diameter and etched in mica and PET membranes of several microns thickness. Microtubes several inches long of fused quartz and nickel material were tested with diameters between 1.8 micron and 25 micron. For 4He and argon gas we observed the flow transition between the free molecular and continuum regimes at 293 K and 77 K. No discrepancy between the macroscopic theory and the 30 nm nanopore data was found. Because of the exceptionally low viscosity of gaseous helium the laminar-turbulent transition could also be observed within these submicron channels. The small viscosity of 4He was too small to dampen inertial effects at a Reynolds number of 2000. In addition to single phase gas flows, our experimental technique also allows us to investigate flows in which the nano or micro scale pipe is either partially or completely filled with liquids. The position of the intrinsic liquid/vapor interface was important for understanding this type of flow. Strong evaporation and cooling at the liquid-vapor interface can lead to freezing for conventional fluids such as nitrogen and water, which in turn leads to complex intermittent

  14. Elementary excitations and a collective mode in hcp sup 4 He

    SciTech Connect

    Lengua, G.A.; Goodkind, J.M. )

    1990-06-01

    We have measured the velocity and attenuation of sound at 10, 30, and 50 MHz in solid {sup 4}He at higher purity, lower density, and lower acoustic power than have been measured previously. At 10 MHz the velocity varies as T{sup 4}, as would be expected for a very high quality crystal with remarkable low dislocation density. The temperature dependence of the attenuation reveals coupling to thermally activated excitations that are consistent with vacancies measured in other work. However, in our work the activation energy is {approximately}0.7 K so that their concentration is sufficiently high to require Bose statistics. At 30 and 50 MHz, an unexpected, additional resonant behavior was observed.

  15. Anisotropic Formation of Quantum Turbulence Generated by a Vibrating Wire in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Yano, H.; Ogawa, K.; Chiba, Y.; Obara, K.; Ishikawa, O.

    2016-12-01

    To investigate the formation of quantum turbulence in superfluid 4He, we have studied the emission of vortex rings with a ring size of larger than 38 μm in diameter from turbulence generated by a vibrating wire. The emission rate of vortex rings from a turbulent region remains low until the beginning of high-rate emissions, suggesting that some of the vortex lines produced by the wire combine to form a vortex tangle, until an equilibrium is established between the rate of vortex line combination with the tangle and dissociation. The formation times of equilibrium turbulence are proportional to ɛ^{-1.2} and ɛ^{-0.6} in the directions perpendicular and parallel to the vibrating direction of the generator, respectively, indicating the anisotropic formation of turbulence. Here, ɛ is the generation power of the turbulence. This power dependence may be associated with the characteristics of quantum turbulence with a constant energy flux.

  16. Magnetic field dependent transverse spin diffusion constant in 3He- 4He solutions

    NASA Astrophysics Data System (ADS)

    Owers-Bradley, J. R.; Child, A.; Bowley, R. M.

    1994-02-01

    The transverse spin diffusion constant of 3He- 4He solutions has been measured by pulsed nmr in magnetic fields of 2.18T and 8.8T for 3He concentrations of 0.5%, 1.0% and 3.8%. For the higher concentrations the diffusion constant at 8.8T is smaller than at 2.18T for the lowest temperatures used. The effect is largest for the 3.8% solution (a reduction by 1.7 at 15mK), but is too small to be measurable for the 0.5% solution. These results are compared to measurements of Candela et al. for pure 3He, and to the theory of Jeon and Mullin.

  17. Response functions of imaging plates to photons, electrons and 4He particles.

    PubMed

    Bonnet, T; Comet, M; Denis-Petit, D; Gobet, F; Hannachi, F; Tarisien, M; Versteegen, M; Aléonard, M M

    2013-10-01

    Imaging plates from Fuji (BAS-SR, MS, and TR types) are phosphor films routinely used in ultra high intensity laser experiments. However, few data are available on the absolute IP response functions to ionizing particles. We have previously measured and modeled the IP response functions to protons. We focus here on the determination of the responses to photons, electrons, and (4)He particles. The response functions are obtained on an energy range going from a few tens of keV to a few tens of MeV and are compared to available data. The IP sensitivities to the different ionizing particles demonstrate a quenching effect depending on the particle stopping power.

  18. Microscopic approach to critical behavior in 3He-4He mixtures. Effective Hamiltonian and instability

    NASA Astrophysics Data System (ADS)

    Singh, K. K.; Goswami, Partha

    1984-03-01

    A system of weakly interacting bosons and fermions is used as a model to develop a theory of critical behavior of 3He-4He mixtures. The fermion amplitudes and the short-wavelength boson amplitudes are eliminated from the problem within the framework of perturbation theory. The resulting effective boson Hamiltonian possesses interesting features. It implies an instability of the mixture and of its λ line when certain conditions are fulfilled. The coefficients associated with the quartic and six-operator terms of the effective Hamiltonian have properties characteristic of the classical Landau model often used to discuss tricritical behavior. The condition of stability derived for the mixture agrees with an earlier result of Cohen and Leeuwen for the degenerate phase but is in disagreement with their results for the nondegenerate phase.

  19. Magnetocardiography measurements with 4He vector optically pumped magnetometers at room temperature

    NASA Astrophysics Data System (ADS)

    Morales, S.; Corsi, M. C.; Fourcault, W.; Bertrand, F.; Cauffet, G.; Gobbo, C.; Alcouffe, F.; Lenouvel, F.; Le Prado, M.; Berger, F.; Vanzetto, G.; Labyt, E.

    2017-09-01

    In this paper, we present a proof of concept study which demonstrates for the first time the possibility of recording magnetocardiography (MCG) signals with 4He vector optically pumped magnetometers (OPM) operated in a gradiometer mode. Resulting from a compromise between sensitivity, size and operability in a clinical environment, the developed magnetometers are based on the parametric resonance of helium in a zero magnetic field. Sensors are operated at room temperature and provide a tri-axis vector measurement of the magnetic field. Measured sensitivity is around 210 f T (√Hz)-1 in the bandwidth (2 Hz; 300 Hz). MCG signals from a phantom and two healthy subjects are successfully recorded. Human MCG data obtained with the OPMs are compared to reference electrocardiogram recordings: similar heart rates, shapes of the main patterns of the cardiac cycle (P/T waves, QRS complex) and QRS widths are obtained with both techniques.

  20. Stationary convection in dilute solutions of 3He in superfluid 4He

    PubMed Central

    Warkentin, P. A.; Haucke, H. J.; Lucas, P.; Wheatley, J. C.

    1980-01-01

    Two symmetric, convecting steady states have been observed in a novel cell of unity aspect ratio and studied over a range of temperature for two concentrations of 3He in superfluid 4He. An existing theory due to Parshin has been related to the conditions necessary for convection in this system, defining a Rayleigh number closely analogous to that of a classical one-component Bénard system. Values of this Rayleigh number at the onset of convection calculated from experimental data are found to have little temperature dependence, with an average value near that for a classical one-component fluid in this geometry. The Prandtl number is small and temperature dependent, with a smallest calculated value of 0.05. PMID:16592932

  1. Russell Donnelly's last legacy: Pursuing grid turbulence in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Ihas, Gary; Yang, Jihee

    2015-11-01

    Quantum turbulence, a tangle of quantized vortex lines in a superfluid, may hold significant keys to understanding all types of turbulence. Russell Donnelly pioneered this line of research, beginning with studies of grid turbulence probed by second sound. The apparatus built by Russell and his students, with significant up-grades, is now being used at the University of Florida to continue his work on decaying grid turbulence in superfluid 4He. The Oregon work used a 1cm wide square channel, while the Florida work has been in both 1 cm and 5 cm square channels. The larger channel allows detailed study of the increase in eddy size before saturation at the channel walls during the decay process. Power law fits of the turbulence decay in time allow comparison with theory, work intended to be Russell Donnelly's last experiment. Supported in part by US NSF #1007937.

  2. Microscopic optical model calculations of 4He, 12C-nucleus absorption cross sections

    NASA Technical Reports Server (NTRS)

    Dubey, R. R.; Khandelwal, G. S.; Cucinotta, F. A.; Wilson, J. W.

    1996-01-01

    Calculations of absorption cross sections using a microscopic first-order optical potential for heavy-ion scattering are compared with experiments. In-medium nucleon-nucleon (NN) cross sections were used to calculate the two-body scattering amplitude. A medium-modified first-order optical potential was obtained for heavy-ion scattering using the in-medium two-body scattering amplitude. A partial wave expansion of the Lippmann-Schwinger equation in momentum space was used to calculate the absorption cross sections for various systems. The results are presented for the absorption cross sections for 4He-nucleus and 12C-nucleus scattering systems and are compared with the experimental values in the energy range 18-83A MeV. The use of the in-medium NN cross sections is found to result in significant reduction of the free space absorption cross sections in agreement with experiment.

  3. A predictive theory for elastic scattering and recoil of protons from 4He

    DOE PAGES

    Hupin, Guillaume; Quaglioni, Sofia; Navratil, Petr

    2014-12-08

    Low-energy cross sections for elastic scattering and recoil of protons from 4He nuclei (also known as α particles) are calculated directly by solving the Schrodinger equation for five nucleons interacting through accurate two- and three-nucleon forces derived within the framework of chiral effective field theory. Precise knowledge of these processes at various proton backscattering/recoil angles and energies is needed for the ion-beam analysis of numerous materials, from the surface layers of solids, to thin films, to fusion-reactor materials. Indeed, the same elastic scattering process, in two different kinematic configurations, can be used to probe the concentrations and depth profiles ofmore » either hydrogen or helium. Furthermore, we compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among data sets and can be used to predict these cross sections when measurements are not available.« less

  4. A two-stage 3He- 4He fridge for bolometric photometry

    NASA Astrophysics Data System (ADS)

    Maiani, T.; de Bernardis, P.; De Petris, M.; Granata, S.; Masi, S.; Orlando, A.; Aquilini, E.; Cardoni, P.; Martinis, L.; Scaramuzzi, F.

    1999-09-01

    We describe the design, construction and performance of a double stage 3He- 4He refrigerator, built to cool down a multiband bolometric photometer at the MITO telescope. The fridge was optimized to work without external pumps, with the main cryostat providing a 4.2 K thermostat at sea level and a 4.0 K one at high mountain pressure conditions. The measured ultimate temperature of the fridge is 290 mK, with a hold time of 81 h. The external heat input on the cold flange is ˜35 μW, with the main bath at 4.0 K. The recycle time is 8 h with a heat input on the thermostat during recycling of ˜6800 J. The cryostat can operate without any relevant changes to performance tilted down to 50° from the vertical position, as needed at the telescope focal plane.

  5. Response functions of imaging plates to photons, electrons and {sup 4}He particles

    SciTech Connect

    Bonnet, T.; Denis-Petit, D.; Gobet, F.; Hannachi, F.; Tarisien, M.; Versteegen, M.; Aléonard, M. M.

    2013-10-15

    Imaging plates from Fuji (BAS-SR, MS, and TR types) are phosphor films routinely used in ultra high intensity laser experiments. However, few data are available on the absolute IP response functions to ionizing particles. We have previously measured and modeled the IP response functions to protons. We focus here on the determination of the responses to photons, electrons, and {sup 4}He particles. The response functions are obtained on an energy range going from a few tens of keV to a few tens of MeV and are compared to available data. The IP sensitivities to the different ionizing particles demonstrate a quenching effect depending on the particle stopping power.

  6. Rapid glacial erosion at 1.8 Ma revealed by 4He/3He thermochronometry.

    PubMed

    Shuster, David L; Ehlers, Todd A; Rusmoren, Margaret E; Farley, Kenneth A

    2005-12-09

    Alpine glaciation and river incision control the topography of mountain ranges, but their relative contributions have been debated for years. Apatite 4He/3He thermochronometry tightly constrains the timing and rate of glacial erosion within one of the largest valleys in the southern Coast Mountains of British Columbia, Canada. Five proximate samples require accelerated denudation of the Klinaklini Valley initiating 1.8 +/- 0.2 million years ago (Ma). At least 2 kilometers of overlying rock were removed from the valley at >/=5 millimeters per year, indicating that glacial valley deepening proceeded >/=6 times as fast as erosion rates before approximately 1.8 Ma. This intense erosion may be related to a global transition to enhanced climate instability approximately 1.9 Ma.

  7. Phase separation in dilute solutions of 3He in solid 4He

    NASA Astrophysics Data System (ADS)

    Huan, C.; Yin, L.; Xia, J. S.; Candela, D.; Cowan, B. P.; Sullivan, N. S.

    2017-03-01

    We report the results of studies of the phase separation of solid solutions of dilute concentrations of 3He in 4He. The temperatures and the kinetics of the phase separation were determined from NMR experiments for 3He concentrations 1.6 ×10-5

  8. 4He-induced L X-ray production cross sections in Pt and Bi

    NASA Astrophysics Data System (ADS)

    Ouziane, S.; Amokrane, A.; Toumert, I.; Nourreddine, A.

    2009-05-01

    L shell X-ray production cross sections for 4He on Pt and Bi are measured at 2.0, 2.3 and 3.0 MeV. Good agreement is found with the available data of Balsamo et al. [A. Balsamo, N. De Cesare, F. Murolo, E. Perillo, G. Spadaccini, M. Vigilante, J. Phys. B: Atom. Mol. Opt. Phys. 32 (1999) 5699]. The results are compared with those of theoretical calculations using the ECPSSR model [W. Brandt, G. Lapicki, Phys. Rev. A 23 (1981) 1717]. The difference already observed at low incident ion energy between ECPSSR calculations and measured data for the L β and L γ lines clearly appears in this work.

  9. Multifragmentation of Au induced by 14.6 GeV {sup 4}He

    SciTech Connect

    Grabez, B.; Dragic, A.

    2006-11-15

    The multifragmentation reaction channel was investigated in 14.6 GeV {sup 4}He+Au interactions. The experimental setup enabled event-by-event analysis. An internal correlation study suggests a nearly simultaneous emission of fragments. The velocities (V{sub c.m.}) of the center-of-mass system of correlated fragments were calculated. The transverse component of V{sub c.m.} with respect to the beam direction has higher values than the longitudinal one, which corresponds to large recoil angles of the source. The angular distributions of fragments are sideways peaked. The peak angle is dependent on the atomic number of fragment and multiplicity. Our results show that the heaviest fragment in one event corresponds, on average, to the largest emission angle, the second heaviest fragment corresponds to the second largest emission angle, and so on.

  10. Superfluidlike Mass Flow Through 8  μm Thick Solid ^{4}He Samples.

    PubMed

    Shin, Jaeho; Kim, Duk Y; Haziot, Ariel; Chan, Moses H W

    2017-06-09

    We report the observation of superfluidlike mass flow through coin-shaped 8  μm thick solid ^{4}He samples sandwiched between superfluid leads. Mass flow is found from the melting pressure to at least 30 bar with a concomitant decrease in the onset temperature from 1 to 0.25 K. The mass-flow rate is found to be sample dependent and can be enhanced by thermal annealing. The flow rate decreases with temperature and decays nearly exponentially with the pressure of the samples. The dissipation associated with the mass flow decreases with temperature and becomes superfluidlike near 0.1 K. In contrast to earlier studies on centimeter-thick samples, we do not see a sharp cutoff in the mass-flow rate at low temperature.

  11. Low-Temperature Heat Capacity of 4 He Films on Graphite

    NASA Astrophysics Data System (ADS)

    Morishita, Masashi

    2017-02-01

    Heat capacities of 4 He films have been measured at rather low temperatures between 2 and 80 mK and at areal densities between 2 and 24 nm^{-2} . These areal densities correspond to a monolayer fluid and third-layer fluid. For monolayer films, the results do not contradict previous measurements carried out at high temperatures. On the other hand, at some areal densities, small and broad but definite bumps, whose origin has not yet been understood, have been observed around 15 mK. Between 13 and 24 nm^{-2} , the measured heat capacities above 40 mK are proportional to T2 and hardly change with areal density. These behaviors suggest that the second atomic layer does not solidify before the third-layer promotion, at least not into a commensurate solid, such as the so-called 4/7 phase.

  12. Detailed study of nonlinear wave front distortion of focused sound in superfluid4He

    NASA Astrophysics Data System (ADS)

    Sasaki, Yasuo; Kishi, Hidenobu; Karaki, Koichi; Okuda, Yuichi

    1995-02-01

    We have investigated a nonlinear phenomenon which appears in a focused sound in superfluid4He under pressure higher than 18 atm. Wave front distortion of the focused ultrasound by nonlinear effect was obtained by the Fourier transform of the transducer output as a function of the defocusing length. The wave was found to suffer discontinuous wave front distortion for the input power above a certain value. This distortion is well represented by the picture that a second wave whose phase is shifted by approx. π develops, and interferes with the original wave. The amplitude of this second wave decreases suddenly as the pressure is lowered below 18 atm and the nonlinear wave front distortion also disappears. The possible mechanism of this second wave generation are discussed.

  13. Streaming flow due to a quartz tuning fork oscillating in normal and superfluid 4He

    NASA Astrophysics Data System (ADS)

    Duda, D.; La Mantia, M.; Skrbek, L.

    2017-07-01

    We visualize the streaming flow due to a rapidly oscillating quartz tuning fork, in both normal He I and superfluid He II, by following the flow-induced motions of relatively small particles suspended in the liquid. Over the investigated temperature range, between 1.2 and 2.3 K, at the experimentally probed length scales, the streaming patterns observed in He II appear identical to those seen in He I and are very similar to those reported to occur in water, outside the Stokes boundary layer. The outcome strongly supports the view that, at scales larger than the quantum length scale of the flow, the mean distance between quantized vortices, mechanically forced turbulent coflows of He II behave classically, due to the dynamical locking of the two components of superfluid 4He by the action of the mutual friction force.

  14. Measurements of the lifetimes of electron bubbles in large size selected 4HeN- droplets

    NASA Astrophysics Data System (ADS)

    Fárník, Michal; Samelin, Björn; Toennies, J. Peter

    1999-05-01

    The lifetimes of electron bubbles in large size selected 4HeN- droplets have been measured in a molecular beam experiment to lie between 2ṡ10-3 and 0.2 s in droplets with sizes between N≈105 and 107 atoms, respectively. The dependence of the lifetimes on the electric fields used to size select the droplets, on the energies of the incident electrons, and on the infrared radiation emitted from the apparatus walls were investigated and taken into account. The experimental lifetimes are many orders of magnitude smaller than predicted by earlier theories but consistent with a recent theory published by the authors in Phys. Rev. Lett. 81, 3892 (1998).

  15. Alumina shunt for precooling a cryogen-free 4He or 3He refrigerator

    NASA Astrophysics Data System (ADS)

    Uhlig, Kurt

    2016-10-01

    In this technical report a cryogen-free 1 K cryostat is described where the pot of the 4He refrigeration unit is precooled by the 2nd stage of a pulse tube cryocooler (PTC) from room temperature to T ∼ 3 K via a shunt made from sintered alumina (SA); the total mass of the 1 K stage is 3.5 kg. SA has high thermal conductivity at high temperatures; but below ∼50 K the thermal conductivity drops rapidly, almost following a T3-law. This makes SA an interesting candidate for the construction of a thermal shunt, especially as the heat capacity of metals drops by several orders of magnitude in the temperature range from 300 K to 3 K. At the base temperature of the PTC, the heat conduction of the shunt is so small that the heat leak into the 1 K stage is negligible.

  16. Relaxation dynamics of spindodal decomposition in superfluid ^3He-^4He mixtures

    NASA Astrophysics Data System (ADS)

    Chay, Terrence Y.; Goldenfeld, Nigel; Bauer, Gregory H.; Ceperley, David M.

    1998-03-01

    We study the dynamics of the Hohenberg-Nelson system(P.C. Hohenberg and David R. Halperin, Phys. Rev. B 20):2665 (1979). for ^3He-^4He mixtures after a quench using a mesoscopic cell dynamical systems (CDS) model. The spinodal region is characterized by maximal growth at a single nonzero wave vector which scales with time. Because CDS exploits universality to avoid taking Δ x and Δ t to infinitesimals, rapid simulations are possible on large systems making it an ideal way to find such scaling behavior. Using thermodynamic properties obtained from experiement and exactly calculated from path integral monte carlo studies, one can obtain the workable CDS phenomenological parameters to do time evolution studies of large-scale mixtures.

  17. Shadow wave-function variational calculations of crystalline and liquid phases of 4He

    NASA Astrophysics Data System (ADS)

    Vitiello, S. A.; Runge, K. J.; Chester, G. V.; Kalos, M. H.

    1990-07-01

    A new class of variational wave functions for boson systems, shadow wave functions, is used to investigate the properties of solid and liquid 4He. The wave function is translationally invariant and symmetric under particle interchange. In principle, the calculations for the crystalline phase do not require the use of any auxiliary lattice. Using the Metropolis Monte Carlo algorithm, we show that the additional variational degrees of freedom in the wave function lower the energy significantly. This wave function also allows the crystalization of an equilibrated liquid phase when a crystalline seed is used. The pair correlation function and structure factor S(k) are determined in the liquid phase. The condensate fraction is calculated as well. Results are given for the single-particle distribution function around the lattice positions in the solid phase.

  18. Probing Liquid ^4He with Quartz Tuning Forks Using a Novel Multifrequency Lock-in Technique

    NASA Astrophysics Data System (ADS)

    Bradley, D. I.; Haley, R. P.; Kafanov, S.; Noble, M. T.; Pickett, G. R.; Tsepelin, V.; Vonka, J.; Wilcox, T.

    2016-09-01

    We report on a novel technique to measure quartz tuning forks, and possibly other vibrating objects, in a quantum fluid using a multifrequency lock-in amplifier. The multifrequency technique allows to measure the resonance curve of a vibrating object much faster than a conventional single frequency lock-in amplifier technique. Forks with resonance frequencies of 12 kHz and 16 kHz were excited and measured electro-mechanically either at a single frequency or at up to 40 different frequencies simultaneously around the same mechanical mode. The response of each fork was identical for both methods and validates the use of the multifrequency lock-in technique to probe properties of liquid helium at low fork velocities. Using both methods we measured the resonance frequency and drag of two 25-μ m-wide quartz tuning forks immersed in liquid ^4He in the temperature range from 4.2 K to 1.5 K at saturated vapour pressure. The damping and shift of resonance frequency experienced by both tuning forks at low velocities are well described by hydrodynamic contributions in the framework of the two-fluid model. The sensitivity of the 25-μ m-wide tuning forks is larger compared to similar 75-μ m-wide forks and in combination with the faster multifrequency lock-in technique could be used to improve thermometry in liquid ^4He. The multifrequency technique could also be used for studies of the onset of non-linear phenomena such as quantum turbulence and cavitation in superfluids.

  19. Phonon-roton modes of liquid 4He beyond the roton in MCM-41

    SciTech Connect

    Azuah, Richard T; Omar Diallo, Souleymane; Adams, Mark A.; Kirichek, Oleg; Glyde, Henry R

    2013-01-01

    We present neutron scattering measurements of the phonon-roton (P-R) mode of superfluid 4He confined in 47 A MCM-41 at T = 0.5 K at wave vectors, Q, beyond the roton wave vector (QR = 1.92 A-1). Measurements beyond the roton require access to high wave vectors (up to Q = 4 A-1) with excellent energy resolution and high statistical precision. The present results show for the first time that at T = 0.5 K the P-R mode in MCM-41 extends out to wave-vector Q 3.6 A-1 with the same energy and zero width (within precision) as observed in bulk superfluid 4He. Layer modes in the roton region are also observed. Specifically, the P-R mode energy, !Q, increases with Q for Q > QR and reaches a plateau at a maximum energy !Q = 2 where is the roton energy, = 0.74 0.01 meV in MCM-41. This upper limit means the P-R mode decays to two rotons when its energy exceeds 2 . It also means that the P-R mode does not decay to two layers modes. If the P-R could decay to two layer modes, !Q would plateau at a lower energy, !Q = 2 L where L = 0.60 meV is the energy of the roton like minimum of the layer mode. The observation of the P-R mode with energy up to 2 shows that the P-R mode and the layer modes are independent modes with apparently little interaction between them.

  20. Path Integral Monte Carlo Study Confirms a Highly Ordered Snowball in 4He Nanodroplets Doped with an Ar+ Ion

    NASA Astrophysics Data System (ADS)

    Tramonto, F.; Salvestrini, P.; Nava, M.; Galli, D. E.

    2015-07-01

    By means of the Path Integral Monte Carlo method, we have performed a detailed microscopic study of 4He nanodroplets doped with an argon ion, Ar, at K. We have computed density profiles, energies, dissociation energies, and characterized the local order around the ion for nanodroplets with a number of 4He atoms ranging from 10 to 64 and also 128. We have found the formation of a stable solid structure around the ion, a "snowball", consisting of three concentric shells in which the 4He atoms are placed at the vertices of platonic solids: the first inner shell is an icosahedron (12 atoms); the second one is a dodecahedron with 20 atoms placed on the faces of the icosahedron of the first shell; the third shell is again an icosahedron composed of 12 atoms placed on the faces of the dodecahedron of the second shell. The "magic numbers" implied by this structure, 12, 32, and 44 helium atoms, have been observed in a recent experimental study (Bartl et al., J Phys Chem A 118:8050, 2014) of these complexes; the dissociation energy curve computed in the present work shows jumps in correspondence with those found in the nanodroplets abundance distribution measured in that experiment, strengthening the agreement between theory and experiment. The same structures were predicted in Galli et al. (J Phys Chem A 115:7300, 2011) in a study regarding Na+@4He when ; a comparison between Ar+@4He and Na+@4He complexes is also presented.

  1. Near-monolayer 3-4He films: Two superfluid transitions and the 3He effective mass and binding energy

    NASA Astrophysics Data System (ADS)

    Wang, Xingwu; Gasparini, Francis M.

    1988-12-01

    We have measured the mass loading on a torsional oscillator of mixture films of 3He and 4He at coverages near one active atomic layer of 4He. These measurements yield information about the superfluid transition of 4He and the effective mass and binding energy of 3He. Unlike the situation with submonolayer and multilayer films, where the superfluid transition takes place at a single temperature, we observe for these films a transition in two steps. This confirms a report some time ago of a similar observation by Bishop and Reppy. By comparing the mass loading at T=0 of pure 4He films with that of mixtures, we obtain the 3He effective mass which can be compared with results from the specific heat. We find, in particular, that the effective mass has a maximum as a function of 4He thickness with correct asymptotic values for infinite and zero thickness limits. This maximum coincides very nearly with the thickness of 4He at which the transition into the superfluid state takes place in two steps. In the submonolayer region the effective mass agrees with a density dependence one might expect as an extension of the theory of Pandharipande and Itoh for three-dimensional mixtures. We believe such theory should be able to be done for the two-dimensional case.

  2. The CW-CRDS spectra of the 16O/18O isotopologues of ozone between 5930 and 6340 cm-1—Part 3: 16O18O18O and 18O16O18O

    NASA Astrophysics Data System (ADS)

    De Backer, M.-R.; Barbe, A.; Starikova, E.; Tyuterev, Vl. G.; Mondelain, D.; Kassi, S.; Campargue, A.

    2013-09-01

    Our systematic investigation of the high sensitivity CW-Cavity Ring Down Spectra of 16O/18O ozone isotopologues at high vibrational excitation continues with the study of the 16O18O18O and 18O16O18O species. The first two papers of this series were devoted to the analysis of the same four bands of the 16O16O18O and 16O18O16O species in the 5930-6340 cm-1domain. Here, after a brief reminder of relevant experiment and theory, we report the analyses of two bands of 16O18O18O, vibrationally assigned as 2ν2+5ν3 and 2ν1+2ν2+3ν3_2 and three bands of 18O16O18O, assigned to 2ν1+2ν2+3ν3_1, 5ν1+ν3 and 3ν1+ν2+3ν3.They correspond to the highest vibration excitations observed so far for the 16O18O18O and 18O16O18O isotopologues. Altogether for the two new bands of 16O18O18O, 1214 rovibrational transitions were assigned up to Jmax=29 and for the three new bands of 18O16O18O, 948 rovibrational transitions were assigned up to Jmax=27. Observed line positions were fitted with root-mean squares deviations ranging from 0.005 to 0.011 cm-1, using effective Hamiltonian models accounting for dark state perturbations. The derived band centres and rotational constants are in good agreement with new theoretical calculations from the molecular potential function. The corresponding lists of 3365 lines are provided as Supplementary material.

  3. Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid (4)He.

    PubMed

    Mateo, David; Eloranta, Jussi; Williams, Gary A

    2015-02-14

    The interaction of a number of impurities (H2, Ag, Cu, Ag2, Cu2, Li, He3 (+), He(*) ((3)S), He2 (∗) ((3)Σu), and e(-)) with quantized rectilinear vortex lines in superfluid (4)He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He(*).

  4. Inclusive electron scattering from 2H,3He, and 4He

    NASA Astrophysics Data System (ADS)

    Dytman, S. A.; Bernstein, A. M.; Blomqvist, K. I.; Pavel, T. J.; Quinn, B. P.; Altemus, R.; McCarthy, J. S.; Mechtel, G. H.; Ueng, T. S.; Whitney, R. R.

    1988-08-01

    We present new results for inclusive electron scattering in 2H, 3He, and 4He in order to test the reaction mechanism for quasielastic scattering as a function of nuclear density. Radiative corrections are applied to the cross section data and Rosenbluth separations are made for three-momentum transfer (q) between 300 and 600 MeV/c. The A and q dependencies of the data are discussed for the quasielastic peak and the region between the quasielastic peak and the Δ resonance peak (dip region). Comparisons are shown between the data and models based on a quasielastic reaction mechanism. The models give a reasonable representation of the peak at q~500 MeV/c, but the longitudinal data for the helium isotopes are significantly suppressed with respect to the quasielastic predictions at q<400 MeV/c. None of the calculations predict the rapid rise with q and A in the transverse strength in the dip region seen in the data. A significant breakdown of the quasielastic picture is seen in the data as A increases from 2 to 4.

  5. Simultaneous Oscillation of Annular Solid ^4He Samples at Two Mode Frequencies in Compound Torsion Pendulum

    NASA Astrophysics Data System (ADS)

    Keiderling, Michael C.; Kojima, Harry

    2009-03-01

    We have extended our studies on the non-classical behavior of solid ^4He contained in compound torsional oscillator (TO) cell below 1 K. Our unique TO design allows observations on the identical sample at two distinct frequencies(f1=493 and f2=1165 Hz). The sample was grown by blocked capillary method in an annular cell(id = 8.0 mm, od = 10.0 mm, height = 9.0 mm). We focus here on experiments in which the two modes are excited simultaneously. While keeping the drive of f2 mode at a very low level, the drive of f1 mode was varied from high to low levels to produce substantial variations in the non-classical rotation inertia fraction (NCRIf). When the NCRIf seen by f1 mode is reduced by 89, 91 and 94 % at 9.7, 23.5 and 56.5 mK, respectively, the NCRIf seen by f2 mode (driven at low level) is reduced by 62, 68 and 80 %. The discrepancies and their temperature dependence in the observed reductions in NCRIf are not yet understood. Similar Measurements with the roles of the drive levels of the modes reversed as well as the changes in the dissipation of the torsional oscillator during the simultaneous drive will be reported.

  6. Interaction of ultrasound with elementary excitations of hcp sup 4 He

    SciTech Connect

    Lengua, G.A.

    1988-01-01

    The author has made high-resolution measurements of the velocity and attenuation of longitudinal sound at 10, 30 and 50 MHz in extremely high quality {sup 4}He crystals at low densities. The 10 MHz data show the characteristic effects of as broad vacancy wave band. The vacancy wave-phonon relaxation time appears to be temperature independent, suggesting the vacancy waves are correlated. The author found that the vacancy formation energy approaches zero at the minimum in the melting curve, and at the melting temperature as well. The 30 and 50 MHz data have this same behavior, but in addition show the effects of some resonant coupling. The form of the coupling suggests another traveling wave, possibly second sound on the vacancy gas. This may be a sign that the system is supersolid. The higher frequencies also showed signs of Akheiser attenuation. Below 150 mK, an attenuation peak occurs as well. The velocity in this region decreases with decreasing temperature. These may be a consequence of a relaxation effect.

  7. Investigation of Grid Turbulence in Superfluid 4He with Improved Measurement Technique

    NASA Astrophysics Data System (ADS)

    Yang, Jihee; Ihas, Gary G.

    Quantum turbulence(QT), a tangle of quantized vorticity in a macroscopically correlated quantum fluid, can have many analogous aspects to classical turbulence. Understanding QT can give us insights into classical turbulence as well as fluids in general. We generate QT by pulling a grid through a 4.6 cm x 4.6 cm cross-section channel in superfluid 4He. Second sound, a temperature/entropy wave, is used to monitor vorticity, ω. A resonant technique with high (3000) Q increases greatly the sensitivity of the measurement, but it requires a phase and amplitude locked tracking system which adheres to the resonant peak independent of frequency shifts. According to theories, the vorticity decays as ω ~ t- 11 / 10 or ω ~ t- 17 / 14 when the energy containing eddies are growing. When they saturate at the channel size, the vorticity begins decaying as ω ~ t3/2. These different decaying regions are examined in this large channel and compared to previous experiments that have been performed in 1 cm2 square channels. US NSF DMR#1007937.

  8. Operator evolution for ab initio electric dipole transitions of 4He

    DOE PAGES

    Schuster, Micah D.; Quaglioni, Sofia; Johnson, Calvin W.; ...

    2015-07-24

    A goal of nuclear theory is to make quantitative predictions of low-energy nuclear observables starting from accurate microscopic internucleon forces. A major element of such an effort is applying unitary transformations to soften the nuclear Hamiltonian and hence accelerate the convergence of ab initio calculations as a function of the model space size. The consistent simultaneous transformation of external operators, however, has been overlooked in applications of the theory, particularly for nonscalar transitions. We study the evolution of the electric dipole operator in the framework of the similarity renormalization group method and apply the renormalized matrix elements to the calculationmore » of the 4He total photoabsorption cross section and electric dipole polarizability. All observables are calculated within the ab initio no-core shell model. Furthermore, we find that, although seemingly small, the effects of evolved operators on the photoabsorption cross section are comparable in magnitude to the correction produced by including the chiral three-nucleon force and cannot be neglected.« less

  9. One-Dimensional Liquid ^{4}He: Dynamical Properties beyond Luttinger-Liquid Theory.

    PubMed

    Bertaina, G; Motta, M; Rossi, M; Vitali, E; Galli, D E

    2016-04-01

    We compute the zero-temperature dynamical structure factor of one-dimensional liquid ^{4}He by means of state-of-the-art quantum Monte Carlo and analytic continuation techniques. By increasing the density, the dynamical structure factor reveals a transition from a highly compressible critical liquid to a quasisolid regime. In the low-energy limit, the dynamical structure factor can be described by the quantum hydrodynamic Luttinger-liquid theory, with a Luttinger parameter spanning all possible values by increasing the density. At higher energies, our approach provides quantitative results beyond the Luttinger-liquid theory. In particular, as the density increases, the interplay between dimensionality and interaction makes the dynamical structure factor manifest a pseudo-particle-hole continuum typical of fermionic systems. At the low-energy boundary of such a region and moderate densities, we find consistency, within statistical uncertainties, with predictions of a power-law structure by the recently developed nonlinear Luttinger-liquid theory. In the quasisolid regime, we observe a novel behavior at intermediate momenta, which can be described by new analytical relations that we derive for the hard-rods model.

  10. Third Sound Measurements of Superfluid 4He Films on Multiwall Carbon Nanotubes Below 1 K

    NASA Astrophysics Data System (ADS)

    Menachekanian, Emin; Iaia, Vito; Li, Andrew; Chen, Bob; Williams, Gary

    2014-03-01

    Third sound is studied for superfluid films of 4He adsorbed on multiwall carbon nanotubes of average diameter 12 Angstroms packed into an annular resonator. The third sound is generated with mechanical oscillation of the cell, and detected with carbon bolometers. A filling curve at temperatures near 250 mK shows oscillations in the third sound velocity, with maxima at the completion of the third and fourth atomic layers. The ``dead'' layer appears to be close to two atomic layers, about one layer thinner than previously found for flat graphite surfaces. We attribute this weaker binding to the effect of the cylindrical geometry on the van der Waals potential, the repulsive surface tension forces from the high curvature, and the lower density of the tubes compared to graphite. At the completion of the third layer there is a sudden reduction of the superfluid onset temperature, and then a recovery back to the Kosterlitz-Thouless linear dependence, forming re-entrant superfluidity. In a small region around 2.5 layers there is very anomalous behavior in the low-temperature variation of the third sound velocity, which is found to increase linearly with temperature. This could be related to changes in the gas-liquid coexistence at this intermediate fill. Work supported in part by the Nation Science Foundation, Grant DMR 0906467.

  11. Spectral shifts and helium configurations in 4He(N)-tetracene clusters.

    PubMed

    Whitley, Heather D; DuBois, Jonathan L; Whaley, K Birgitta

    2009-09-28

    Spectral shifts of electronic transitions of tetracene in helium droplets are investigated in a theoretical study of (4)He(N)-tetracene clusters with 1 < or = N < or = 150. Utilizing a pairwise interaction for the S(0) state of tetracene with helium that is extended by semiempirical terms to construct a potential for the S(1) state of tetracene with helium, the spectral shift is calculated from path integral Monte Carlo calculations of the helium equilibrium properties with tetracene in the S(0) and S(1) states at T = 0 and at T = 0.625 K. The calculated spectral shifts are in quantitative agreement with available experimental measurements for small values of N (< or = 8) at T approximately 0.4 K and show qualitative agreement for larger N (10-20). The extrapolated value of the spectral shift in large droplets (N approximately 10(4)) is approximately 90% of the experimentally measured value. We find no evidence of multiple configurations of helium for any cluster size for either the S(0) or S(1) state of tetracene. These results suggest that the observed spectral splitting of electronic transitions of tetracene in large helium droplets is not due to the coexistence of static metastable helium densities, unlike the situation previously analyzed for the phthalocyanine molecule.

  12. Transport in very dilute solutions of 3He in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baym, Gordon; Beck, D. H.; Pethick, C. J.

    2013-07-01

    Motivated by a proposed experimental search for the electric dipole moment of the neutron (nEDM) utilizing neutron-3He capture in a dilute solution of 3He in superfluid 4He, we derive the transport properties of dilute solutions in the regime where the 3He are classically distributed and rapid 3He-3He scatterings keep the 3He in equilibrium. Our microscopic framework takes into account phonon-phonon, phonon-3He, and 3He-3He scatterings. We then apply these calculations to measurements by Rosenbaum [J. Low Temp. Phys.JLTPAC0022-229110.1007/BF00655864 16, 131 (1974)] and by Lamoreaux [Europhys. Lett.EULEEJ0295-507510.1209/epl/i2002-00408-4 58, 718 (2002)] of dilute solutions in the presence of a heat flow. We find satisfactory agreement of theory with the data, serving to confirm our understanding of the microscopics of the helium in the future nEDM experiment.

  13. Applicability of Density Functional Theory to Model Molecular Solvation in Superfluid 4He

    NASA Astrophysics Data System (ADS)

    Isojärvi, Teemu; Lehtovaara, Lauri; Eloranta, Jussi

    2006-09-01

    Density functional theory (DFT) has been extensively applied to model solvation of atomic and molecular species ("impurities") in superfluid helium. The interaction between the impurity and the surrounding liquid may range from purely repulsive (e.g. alkali metal atoms and most diatomic excimers) to deeply bound potentials (e:g. aromatic compounds). In order to apply DFT to model processes relevant to low temperature chemistry in superfluid 4He, it is essential to obtain the limits of applicability of the theory. For purely repulsive potentials, the spatial gradient of the liquid density remains small and DFT is expected to produce accurate results. This has been verified previously by comparing DFT results to quantum Monte Carlo calculations. For strong binding potentials, however, DFT fails since the individual He atoms tend to localize about the potential minimum. The present work tests the accuracy of DFT between the weakly and strongly bound regimes. This is done by comparing DFT and quantum Monte Carlo (diffusion Monte Carlo) results for various realistic model potentials with varying degree of binding.

  14. Dynamics of He2∗ triplet state excimer bubbles in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Eloranta, J.

    2007-02-01

    Time-dependent density functional theory calculations for bulk superfluid 4He were carried out to model dynamics around He2∗ excimers after optical excitation from the 3a to 3d state. The liquid dynamics occurring after a sudden change in the helium-liquid interaction results in interfacial dynamics, which can be divided into three different modes: (1) non-linear processes yielding shock and solitonic progressions, (2) fast interfacial dynamics related to thinning of the liquid-gas interface that occurs within few picoseonds and (3) slow spherical breathing motion of the liquid-gas interface with recursion times up to 110 ps. The long-range repulsive tail ( R > 12 Å) in the He-He2∗ interaction is found to play an important role in determining the recursion time of the solvent cavity breathing mode. As energy differences of just few wavenumbers in this region are sufficient to produce large changes in the recursion time, none of the pair potentials derived from the first principles could reproduce the experimental data [V.A. Benderskii, J. Eloranta, R. Zadoyan, V.A. Apkarian, J. Chem. Phys. 117 (2002) 1201]. Therefore it is concluded that the pump-probe experiments measure energy differences that are not possible to calculate using the current electronic structure methods. The results obtained from the density functional theory calculations are consistent with the proposed experimental scheme.

  15. 4He+n+n continuum within an ab initio framework

    DOE PAGES

    Romero-Redondo, Carolina; Quaglioni, Sofia; Navratil, Petr; ...

    2014-07-16

    In this study, the low-lying continuum spectrum of the 6He nucleus is investigated for the first time within an ab initio framework that encompasses the 4He+n+n three-cluster dynamics characterizing its lowest decay channel. This is achieved through an extension of the no-core shell model combined with the resonating-group method, in which energy-independent nonlocal interactions among three nuclear fragments can be calculated microscopically, starting from realistic nucleon-nucleon interactions and consistent ab initio many-body wave functions of the clusters. The three-cluster Schrödinger equation is solved with three-body scattering boundary conditions by means of the hyperspherical-harmonics method on a Lagrange mesh. Using amore » soft similarity-renormalization-group evolved chiral nucleon-nucleon potential, we find the known Jπ = 2+ resonance as well as a result consistent with a new low-lying second 2+ resonance recently observed at GANIL at ~2.6 MeV above the He6 ground state. We also find resonances in the 2–, 1+, and 0– channels, while no low-lying resonances are present in the 0+ and 1– channels.« less

  16. Excited Rotational States in Doped {4} He Clusters: a Diffusion Monte Carlo Analysis

    NASA Astrophysics Data System (ADS)

    Coccia, Emanuele

    2017-03-01

    We report an extension of diffusion Monte Carlo (DMC) to the calculation of the molecular rotational energies by means of the generalized, symmetry-adapted, imaginary-time correlation functions (SAITCFs) originally introduced in the reptation quantum Monte Carlo (RQMC) framework (Škrbić in J Phys Chem A 111:12749, 2007). We studied the a-type and b-type rotational lines of the CO(4 He)N clusters with N= 1-8 that correlate, in the dimer limit, with the end-over-end and free-rotor transitions. We compare the SAITCF-DMC results with accurate DVR (for the dimer case), RQMC and other DMC data, and with reference experimental findings (Surin in Phys Rev Lett 101:233401, 2008). A good agreement is generally found, but a systematic underestimation of the SAITCF-DMC rotational energies of the b-type series is observed. Sources of inaccuracy in our theoretical approach and in the computational protocol are discussed and analyzed in detail.

  17. Finite-size-scaling analysis of a simulation of the 4He superfluid transition

    NASA Astrophysics Data System (ADS)

    Pollock, E. L.; Runge, Karl J.

    1992-08-01

    Several finite-size scaling techniques are applied to path-integral simulations of the superfluid transition in three-dimensional (3D) 4He at low pressure. The twist free energy shows a linear increase with periodic cell length below the transition temperature, which it predicts as 2.19+/-0.02 K. (The experimental value is 2.172 K.) Fitting the superfluid fraction to the scaled form Lρs(t,L)/ρ=Q(L1/νt), t=(T-Tc)/Tc, gives Tc=2.17+/-0.05 K and the correlation-length exponent ν=0.72+/-0.1 (experimentally 0.67). The universal constant (ħ2ρ/mkTc)Q(0)=0.50+/-0.02 found here compares well with the value 0.49+/-0.01 from recent 3D XY model simulations. Additional analyses that include corrections to scaling are found to yield values for Tc in agreement with the above estimates. A phenomenological renormalization analysis suggests the superfluid density exponent υ=(1.0-1.3)ν, consistent with the Josephson relation.

  18. Time-resolved study of laser initiated shock wave propagation in superfluid 4He

    NASA Astrophysics Data System (ADS)

    Garcia, Allan; Buelna, Xavier; Popov, Evgeny; Eloranta, Jussi

    2016-09-01

    Intense shock waves in superfluid 4He between 1.7 and 2.1 K are generated by rapidly expanding confined plasma from laser ablation of a metal target immersed in the liquid. The resulting shock fronts in the liquid with initial velocities up to ca. Mach 10 are visualized by time-resolved shadowgraph photography. These high intensity shocks decay within 500 ns into less energetic shock waves traveling at Mach 2, which have their lifetime in the microsecond time scale. Based on the analysis using the classical Rankine-Hugoniot theory, the shock fronts created remain in the solid phase up to 1 μs and the associated thermodynamic state appears outside the previously studied region. The extrapolated initial shock pressure of 0.5 GPa is comparable to typical plasma pressures produced during liquid phase laser ablation. A secondary shock originating from fast heat propagation on the metal surface is also observed and a lower limit estimate for the heat propagation velocity is measured as 7 × 104 m/s. In the long-time limit, the high intensity shocks turn into liquid state waves that propagate near the speed of sound.

  19. Stopping power of 1H and 4He in lithium niobate

    NASA Astrophysics Data System (ADS)

    Barradas, N. P.; Marques, J. G.; Alves, E.

    2014-08-01

    Lithium niobate is an important material for applications in bulk optoelectronics and integrated optics devices. Ion beam analysis methods are often used to study this material. However, to our knowledge a single study has been presented in 1996 on measurement of stopping powers in LiNbO3 at velocities usual in ion beam analysis, for protons and deuterons near the stopping power maximum. The results were 15% lower than the values calculated from the elemental Li, Nb and O stopping powers then available together with the Bragg rule. In practice, all ion beam analysis studies of LiNbO3 still use the Bragg rule. We have used a bulk method, previously developed by us and applied successfully to other systems, to determine experimentally the stopping power of lithium niobate for 1H and 4He ions in the energy range 0.3-2.3 MeV. The results of our measurements and bulk method analysis are presented and discussed in the context of currently available stopping power calculations.

  20. Direct simulation Monte Carlo study of quantum effects on the spherical expansion of 4He

    NASA Astrophysics Data System (ADS)

    Koura, Katsuhisa

    1999-10-01

    Quantum effects on the translational nonequilibrium at low temperatures in a spherical expansion of 4He from room temperature are studied using the direct simulation Monte Carlo method to make a comparison with the experimental measurements along the axis of a helium free jet expansion. The quantum-mechanical scattering cross sections are obtained by a quantum phase-shift calculation for the Lennard-Jones and more elaborate Hartree-Fock dispersion potentials. It is shown that the parallel and perpendicular kinetic temperatures are higher and lower, respectively, for the quantum-mechanical scattering than for the classical-mechanical scattering. A comparison with the parallel temperature determined by fitting the ellipsoidal velocity distribution function to the measured spectral profiles indicates that the parallel kinetic temperature for the quantum-mechanical scattering is higher than the measured temperature, with which the parallel kinetic temperature for the classical-mechanical scattering is fortuitously in better agreement. Because both the parallel and perpendicular velocity distribution functions appreciably deviate from Maxwellians and the Maxwellian (half-width) fit temperatures are lower than the kinetic temperatures, the discrepancy between the quantum-mechanical and measured parallel temperatures may partly be resolved by the difference between the kinetic and fitting temperatures.

  1. Fluid pinch-off in superfluid and normal {sup 4}He

    SciTech Connect

    Burton, J. C.; Rutledge, J. E.; Taborek, P.

    2007-03-15

    We present frames from high-speed videos of the pinch-off of liquid {sup 4}He droplets. The temperature of the fluid droplets ranged from 1.33 K to 4.8 K, and the size of the drops was proportional to the temperature-dependent capillary length. We observed no qualitative difference between pinch-off in the normal and superfluid states. In both cases, the shape of the fluid in the final stages of pinch-off resembles a cone piercing a sphere, which is typical of other low-viscosity fluids. The evolution of the minimum neck radius r{sub min} can be characterized by power laws r{sub min}{proportional_to}{tau}{sup n}, where {tau} is the time remaining until pinch-off occurs. In the regime near pinch-off, the data from image analysis are consistent with n=2/3. The data at the beginning of the pinch process when the neck is of the order of the capillary length are also described by n=2/3, but with a different proportionality factor. There is an intermediate crossover regime characterized by n=2/5.

  2. Copper dimer interactions on a thermomechanical superfluid {sup 4}He fountain

    SciTech Connect

    Popov, Evgeny; Eloranta, Jussi

    2015-05-28

    Laser induced fluorescence imaging and frequency domain excitation spectroscopy of the copper dimer (B{sup 1}Σ{sub g}{sup +}←X{sup 1}Σ{sub u}{sup +}) in thermomechanical helium fountain at 1.7 K are demonstrated. The dimers penetrate into the fountain provided that their average propagation velocity is ca. 15 m/s. This energy threshold is interpreted in terms of an imperfect fountain liquid-gas interface, which acts as a trap for low velocity dimers. Orsay-Trento density functional theory calculations for superfluid {sup 4}He are used to characterize the dynamics of the dimer solvation process into the fountain. The dimers first accelerate towards the fountain surface and once the surface layer is crossed, they penetrate into the liquid and further slow down to Landau critical velocity by creating a vortex ring. Theoretical lineshape calculations support the assignment of the experimentally observed bands to Cu{sub 2} solvated in the bulk liquid. The vibronic progressions are decomposed of a zero-phonon line and two types of phonon bands, which correlate with solvent cavity interface compression (t < 200 fs) and expansion (200 < t < 500 fs) driven by the electronic excitation. The presented experimental method allows to perform molecular spectroscopy in bulk superfluid helium where the temperature and pressure can be varied.

  3. Homogeneous 3 He- 4 He solid solutions in the pre-separation region

    NASA Astrophysics Data System (ADS)

    Antsygina, T. N.; Lisunov, A. A.; Maidanov, V. A.; Rubanskyi, V. Y.; Rubets, S. P.; Rudavskii, E. Ya.; Chishko, K. A.

    2011-10-01

    Temperature dependences of the pressure P( T) in homogeneous solid 3He- 4He mixtures have been studied experimentally in the wide range of concentrations (35.0%, 62.0%, 68.3%, 74.1%, 75.0%, and 89.3% 3He) above and below the equilibrium phase separation temperature Ts. An anomalous behaviour of the pressure in the vicinity of Ts is found for all investigated samples. With decreasing temperature, as Ts is approached, the pressure increases instead of expected reduction due to decrease in the phonon contribution ( Pph∼T4). Such an increase in pressure continues in the metastable region below Ts until the mixture separates. Theoretical interpretation of the observed effects based on a rigorous thermodynamic approach is proposed. The found experimentally pressure behaviour can be described only with the consistent account for fluctuations in the impurity subsystem which near Ts dominates over phonon contribution into the pressure. The obtained theoretical results are in good quantitative agreement with the experimental data. Density fluctuations in the concentrated mixtures give rise to a spontaneous formation of impuriton nano-clusters containing several hundreds of atoms. The fluctuation can be rigorously interpreted as a nucleus of the second phase in the pre-separated homogeneous solid mixture. The estimated size of the fluctuation nano-clusters agrees with the corresponding value for second phase nuclei obtained from the Lifshits-Slesov phenomenological theory of homogeneous nucleation.

  4. Tentative explanation of the anomalies in the Kapitza resistance between solids and liquid 4He II

    NASA Astrophysics Data System (ADS)

    Goldschvartz, J. M.

    More than 40 years after Kapitza's discovery of a discontinuity in the temperature between solids and liquid 4He II, called thermal boundary resistance or Kapitza resistance, the anomalies found in the measurements of this resistance, especially within the range 2-1 K, are still alive and no experimentally demonstrable explanation entirely satisfactory for those anomalies has been found. Based upon experiments with solid superleaks which showed that the pores, smaller than 10 nm, are empty above the onset temperature of the superleaks, it is suggested that filling with the superfluid of eventual pores or defects in the solid boundary, could provide the clue to explain those anomalies. A variation of the real contact area and, consequently, a variation of the phononic heat transfer, would take place until those pores or defects on the solid surface are totally filled with the liquid by the action of the thermomechanical effect. However, no prediction is possible due to the fact that the random geometry of the defects is unknown.

  5. Improvement of the Spatial Amplitude Isotropy of a ^4He Magnetometer Using a Modulated Pumping Beam

    NASA Astrophysics Data System (ADS)

    Chéron, B.; Gilles, H.; Hamel, J.; Moreau, O.; Noël, E.

    1997-08-01

    Optically pumped magnetometers are scalar magnetometers. Contrary to vectoriel magnetometers, they measure the total magnetic field whatever the direction of the sensor. However, for some orientations of the magnetometer with respect to the magnetic field direction, the resonant signal vanishes and the measurement is impossible. In this paper we present a simple solution to reduce the amplitude spatial anisotropy and apply it to a ^4He magnetometer developed in our Laboratory. Les magnétomètres à pompage optique sont des magnétomètres scalaires. Contrairement aux magnétomètres vectoriels, ils mesurent le module du champ magnétique quelle que soit l'orientation du capteur dans l'espace. Cependant, pour certaines orientations du magnétomètre par rapport à la direction du champ à mesurer, l'amplitude du signal de résonance s'annule et la mesure devient impossible. Dans cet article, nous présentons une solution simple pour réduire l'anisotropie spatiale d'amplitude et nous l'appliquons à un magnétomètre à hélium-4 développé dans notre Laboratoire.

  6. Observations on non-classical behavior of solid 4He with compound torsional oscillator

    NASA Astrophysics Data System (ADS)

    Keiderling, M. C.; Aoki, Y.; Kojima, H.

    2009-02-01

    The response of oscillating hcp solid 4He samples was studied with a unique compound torsional oscillator a dummy mass and a sample (cylindrical or annular) container connected by two torsion rods. Identical solid sample could be probed within the same apparatus at two different frequencies (~ 0.5 and 1.2 kHz) separately or simultaneously. The apparent onset of the non-classical rotational inertia (NCRI) occurred at a higher temperature in the higher frequency mode. The peak in dissipation of the higher mode also occurred at higher temperature. Surprisingly, the mechanical dissipation was significantly greater in the lower mode. When the lower mode was driven at high levels to induce "critical state" in the sample and the higher mode was simultaneously driven at a low level for probing, the critical state seen in the lower mode did not entirely appear. Conversely, if a critical state was induced by the higher mode, it also did not appear in the lower mode. These preliminary results are contrary to the simple expectation from identifying the critical state as indication of suppressed superfluid density.

  7. Absolute Charge Exchange Cross Sections for ^3He^2+ Collisions with ^4He and H_2

    NASA Astrophysics Data System (ADS)

    Mawhorter, R. J.; Greenwood, J.; Smith, S. J.; Chutjian, A.

    2002-05-01

    The JPL charge exchange beam-line(J.B. Greenwood, et al., Phys. Rev A 63), 062707 (2001) was modified to increase the forward acceptance angle and enable the measurement of total charge-exchange cross sections for slow, light, highly-charged ion collisions with neutral targets(R. E. Olson and M. Kimura, J. Phys. B 15), 4231 (1982). Data are presented for single charge exchange cross sections for ^3He^2+ nuclei scattered by ^4He and H2 in the energy range 0.33-4.67 keV/amu. For both targets there is good agreement with Kusakabe, et al.(T. Kusakabe, et al., J. Phys. Soc. Japan 59), 1218 (1990). Angular collection is studied by a comparison with differential measurements(D. Bordenave-Montesquieu and R. Dagnac, J. Phys. B 27), 543 (1994), as well as with earlier JPL results(J.B. Greenwood, et al., Ap. J. 533), L175 (2000), ibid. 529, 605 (2000) using heavier projectiles and targets. This work was carried out at JPL/Caltech, and was supported through contract with NASA. RJM thanks the NRC for a Senior Associateship at JPL.

  8. Precision measurement of the n-4He scattering length using neutron interferometry

    NASA Astrophysics Data System (ADS)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Black, T. C.; Shahi, C. B.; Wietfeldt, F. E.

    2010-11-01

    The NIST neutron interferometer and optics facility (NIOF) is currently performing a precision measurement of the n-4He scattering length to less than 0.3% relative uncertainty. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons entering the interferometer are Bragg diffracted in the blades to produce two spatially separate yet coherent beam paths much like an optical Mach-Zehnder interferometer. A sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths. This phase difference is directly related to the sample's scattering length. Neutron scattering lengths are one parameter that can be predicted using advanced theoretical models describing two and three nucleon interactions. In an effort to provide tests and/or benchmarks of these theoretical models, the NIOF has already performed precision measurements of neutron scattering lengths to less than 1% relative uncertainty in several low Z gases: H, D, 3He, and polarized 3He. A preliminary result of this work will be given.

  9. /sup 2/H, /sup 3,4/He(p,p') and /sup 3,4/He(p,d') continuum yields for 100 and 150 MeV protons

    SciTech Connect

    Wesick, J.S.; Roos, P.G.; Chant, N.S.; Chang, C.C.; Nadasen, A.; Rees, L.; Yoder, N.R.; Cowley, A.A.; Mills, S.J.; Jacobs, W.W.

    1985-11-01

    The continuum cross sections and analyzing powers from the /sup 2/H, /sup 3,4/He(p,p') and /sup 3,4/He(p,d') reactions were measured for 98.7 and 149.3 MeV polarized protons in the angular range 17.5/sup 0/ to 60/sup 0/. The /sup 2/H and /sup 3/He data show strong quasifree contributions with more ambiguous results for /sup 4/He. These data are compared with distorted-wave impulse approximation calculations based on quasifree nucleon and deuteron knockout. Overall, the agreement between theory and experiment is moderately good. However, some significant discrepancies are observed and corrections to the simple model are discussed.

  10. Optimizing the modified microdosimetric kinetic model input parameters for proton and 4He ion beam therapy application

    NASA Astrophysics Data System (ADS)

    Mairani, A.; Magro, G.; Tessonnier, T.; Böhlen, T. T.; Molinelli, S.; Ferrari, A.; Parodi, K.; Debus, J.; Haberer, T.

    2017-06-01

    Models able to predict relative biological effectiveness (RBE) values are necessary for an accurate determination of the biological effect with proton and 4He ion beams. This is particularly important when including RBE calculations in treatment planning studies comparing biologically optimized proton and 4He ion beam plans. In this work, we have tailored the predictions of the modified microdosimetric kinetic model (MKM), which is clinically applied for carbon ion beam therapy in Japan, to reproduce RBE with proton and 4He ion beams. We have tuned the input parameters of the MKM, i.e. the domain and nucleus radii, reproducing an experimental database of initial RBE data for proton and He ion beams. The modified MKM, with the best fit parameters obtained, has been used to reproduce in vitro cell survival data in clinically-relevant scenarios. A satisfactory agreement has been found for the studied cell lines, A549 and RENCA, with the mean absolute survival variation between the data and predictions within 2% and 5% for proton and 4He ion beams, respectively. Moreover, a sensitivity study has been performed varying the domain and nucleus radii and the quadratic parameter of the photon response curve. The promising agreement found in this work for the studied clinical-like scenarios supports the usage of the modified MKM for treatment planning studies in proton and 4He ion beam therapy.

  11. Used fuel storage monitoring using novel 4He scintillation fast neutron detectors and neutron energy discrimination analysis

    NASA Astrophysics Data System (ADS)

    Kelley, Ryan P.

    With an increasing quantity of spent nuclear fuel being stored at power plants across the United States, the demand exists for a new method of cask monitoring. Certifying these casks for transportation and long-term storage is a unique dilemma: their sealed nature lends added security, but at the cost of requiring non-invasive measurement techniques to verify their contents. This research will design and develop a new method of passively scanning spent fuel casks using 4He scintillation detectors to make this process more accurate. 4He detectors are a relatively new technological development whose full capabilities have not yet been exploited. These detectors take advantage of the high 4He cross section for elastic scattering at fast neutron energies, particularly the resonance around 1 MeV. If one of these elastic scattering interactions occurs within the detector, the 4He nucleus takes energy from the incident neutron, then de-excites by scintillation. Photomultiplier Tubes (PMTs) at either end of the detector tube convert this emitted light into an electrical signal. The goal of this research is to use the neutron spectroscopy features of 4He scintillation detectors to maintain accountability of spent fuel in storage. This project will support spent fuel safeguards and the detection of fissile material, in order to minimize the risk of nuclear proliferation and terrorism.

  12. First-principles modeling of quantum nuclear effects and atomic interactions in solid 4He at high pressure

    NASA Astrophysics Data System (ADS)

    Cazorla, Claudio; Boronat, Jordi

    2015-01-01

    We present a first-principles computational study of solid 4He at T =0 K and pressures up to ˜160 GPa. Our computational strategy consists in using van der Waals density functional theory (DFT-vdW) to describe the electronic degrees of freedom in this material, and the diffusion Monte Carlo (DMC) method to solve the Schrödinger equation describing the behavior of the quantum nuclei. For this, we construct an analytical interaction function based on the pairwise Aziz potential that closely matches the volume variation of the cohesive energy calculated with DFT-vdW in dense helium. Interestingly, we find that the kinetic energy of solid 4He does not increase appreciably with compression for P ≥85 GPa. Also, we show that the Lindemann ratio in dense solid 4He amounts to 0.10 almost independently of pressure. The reliability of customary quasiharmonic DFT (QH DFT) approaches in describing quantum nuclear effects in solids is also studied. We find that QH DFT simulations, although provide a reasonable equation of state in agreement with experiments, are not able to reproduce correctly these critical effects in compressed 4He. In particular, we disclose huge discrepancies of at least ˜50 % in the calculated 4He kinetic energies using both the QH DFT and present DFT-DMC methods.

  13. 4He in Bahamas Carbonates: A Link between Dust Export and North African Mega-droughts over the Last Millennium

    NASA Astrophysics Data System (ADS)

    Bhattacharya, A.; Mukhopadhyay, S.; Maloof, A. C.; Williams, E. R.; Evan, A. T.

    2014-12-01

    4He is a well-established proxy of aeolian input. 4He measurements in carbonate mud from the north-western Andros Islands in the Bahamas and soil samples from North Africa provide a record of the broad trends in dust export to the Bahamas over the past millennium. The 4He-based dust record provides evidence that mineral dust export from the Sahara-Sahel region of North Africa increased during the second half of the 20th century, in association with the multi-decadal droughts that affected the Sahel region during this interval. Furthermore, the 4He-based dust export rates to the Bahamas are linked to broad scale wet and dry cycles in North Africa over the past millennium with high 4He fluxes are associated with mega-droughts of this period, suggesting that centennial patterns of dust export to the Caribbean could have been linked to persistent droughts in the recent past. We will compare the dust record in relation to existing high-resolution geochemical proxy observations of sub-Saharan aridity and dust emission/export patterns from terrestrial, lacustrine and marine environments as well as satellite and station based observations. (The Helium analysis was conducted in the noble gas laboratory at Harvard University)

  14. Spatial distribution and temporal variation of 3He/ 4He in hot spring gas released from Unzen volcanic area, Japan

    NASA Astrophysics Data System (ADS)

    Notsu, K.; Nakai, S.; Igarashi, G.; Ishibashi, J.; Mori, T.; Suzuki, M.; Wakita, H.

    2001-11-01

    Following the first phreatic explosion on 17 November 1990, hot spring gases were collected periodically over the next 10 years for 3He/ 4He isotopic ratio and chemical analyses from three hot springs (Obanma, Unzen and Shimabara) located around Unzen volcano, Japan. The 3He/ 4He ratios, although showing some scatter at each site, show an increase from west to east (Obama4He ratios at Shimabara and Unzen after 1990 were significantly higher than the single values for the 1983 sample ( Marty et al., 1989), possibly due to an additional supply of magmatic helium related to the recent post-1990 volcanic activity. The 3He/ 4He ratio at Shimabara hot spring increased slightly after November 1990, reaching a maximum value in July 1992, and decreasing later. This suggests that magmatic helium with relatively high 3He/ 4He ratios took about one year to travel 5 km from beneath Fugendake volcanic cone to Shimabara hot spring site, because the magma effusion rate (and magma degassing rate) reached a maximum in June 1991.

  15. The algebraic cluster model: Structure of 16O

    NASA Astrophysics Data System (ADS)

    Bijker, R.; Iachello, F.

    2017-01-01

    We discuss an algebraic treatment of four-body clusters which includes both continuous and discrete symmetries. In particular, tetrahedral configurations with Td symmetry are analyzed with respect to the energy spectrum, transition form factors and B (EL) values. It is concluded that the low-lying spectrum of 16O can be described by four α particles at the vertices of a regular tetrahedron, not as a rigid structure but rather a more floppy structure with relatively large rotation-vibration interactions and Coriolis forces.

  16. Effects of {Delta}-isobar degrees of freedom on the reactions {sup 3}He(n,{gamma}){sup 4}He and {sup 3}He(p,e{sup +}{nu}{sub e}){sup 4}He at low-energy

    SciTech Connect

    Schiavilla, R.

    1991-12-31

    The cross sections of the radiative {sup 3}He(n,{gamma}){sup 4}He and weak {sup 3}He(p,e{sup +}{nu}{sub e}){sup 4}He capture reactions at thermal neutron and keV proton energies have been calculated with the Variational Monte Carlo method. The ground state and low-energy continuum wave functions have been determined variationally from a realistic Hamiltonian, and include both nucleon and {Delta}-isobar degrees of freedom. The electroweak transition operator contains one- and two-body components in the N + {Delta} Hilbert space.

  17. Effects of. Delta. -isobar degrees of freedom on the reactions sup 3 He(n,. gamma. ) sup 4 He and sup 3 He(p,e sup +. nu. sub e ) sup 4 He at low-energy

    SciTech Connect

    Schiavilla, R.

    1991-01-01

    The cross sections of the radiative {sup 3}He(n,{gamma}){sup 4}He and weak {sup 3}He(p,e{sup +}{nu}{sub e}){sup 4}He capture reactions at thermal neutron and keV proton energies have been calculated with the Variational Monte Carlo method. The ground state and low-energy continuum wave functions have been determined variationally from a realistic Hamiltonian, and include both nucleon and {Delta}-isobar degrees of freedom. The electroweak transition operator contains one- and two-body components in the N + {Delta} Hilbert space.

  18. Depth profiling Li in electrode materials of lithium ion battery by 7Li(p,γ)8Be and 7Li(p,α)4He nuclear reactions

    NASA Astrophysics Data System (ADS)

    Sunitha, Y.; Kumar, Sanjiv

    2017-06-01

    A proton induced γ-ray emission method based on 7Li(p,γ)8Be proton capture reaction and a nuclear reaction analysis method involving 7Li(p,α)4He reaction are described for depth profiling Li in the electrode materials, graphite and lithium cobalt oxide for example, of a Li-ion battery. Depth profiling by 7Li(p,γ)8Be reaction is accomplished by the resonance at 441 keV and involves the measurement of 14.6 and 17.6 MeV γ-rays, characteristic of the reaction, by a NaI(Tl) detector. The method has a detection sensitivity of ˜0.2 at% and enables profiling up to a depth ≥20 μm with a resolution of ≥150 nm. The profiling to a fairly large depth is facilitated by the absence of any other resonance up to 1800 keV proton energy. The reaction has substantial off-resonance cross-sections. A procedure is outlined for evaluating the off-resonance yields. Interferences from fluorine and aluminium are major limitation of this depth profiling methodology. The depth profile measurement by 7Li(p,α)4He reaction, on the other hand, utilises 2-3 MeV protons and entails the detection of α-particles at 90° or 150° angles. The reaction exhibits inverse kinematics at 150°. This method, too, suffers interference from fluorine due to the simultaneous occurrence of 19F(p,α)16O reaction. Kinematical considerations show that the interference is minimal at 90° and thus is the recommended angle of detection. The method is endowed with a detection sensitivity of ˜0.1 at%, a depth resolution of ˜100 nm and a probing depth of about 30 μm in the absence and 5-8 μm in the presence of fluorine in the material. Both methods yielded comparable depth profiles of Li in the cathode (lithium cobalt oxide) and the anode (graphite) of a Li-ion battery.

  19. On the Transition from Potential Flow to Turbulence Around a Microsphere Oscillating in Superfluid ^4{He}

    NASA Astrophysics Data System (ADS)

    Niemetz, M.; Hänninen, R.; Schoepe, W.

    2017-05-01

    The flow of superfluid ^4{He} around a translationally oscillating sphere, levitating without mechanical support, can either be laminar or turbulent, depending on the velocity amplitude. Below a critical velocity v_c that scales as ω ^{1/2} and is temperature independent below 1 K, the flow is laminar (potential flow). Below 0.5 K, the linear drag force is caused by ballistic phonon scattering that vanishes as T^4 until background damping, measured in the empty cell, becomes dominant for T < 0.1 K. Increasing the velocity amplitude above v_c leads to a transition from potential flow to turbulence, where the large turbulent drag force varies as (v^2 - v_c^2). In a small velocity interval Δ v {/} v_c ≤ 3% above v_c, the flow is unstable below 0.5 K, switching intermittently between both patterns. From time series recorded at constant temperature and driving force, the lifetimes of both phases are analyzed statistically. We observe metastable states of potential flow which, after a mean lifetime of 25 min, ultimately break down due to vorticity created by natural background radioactivity. The lifetimes of the turbulent phases have an exponential distribution, and the mean increases exponentially with Δ v^2. We investigate the frequency at which the vortex rings are shed from the sphere. Our results are compared with recent data of other authors on vortex shedding by moving a laser beam through a Bose-Einstein condensate. Finally, we show that our observed transition to turbulence belongs to the class of "supertransient chaos" where lifetimes of the turbulent states increase faster than exponentially.

  20. Second-sound studies of coflow and counterflow of superfluid {sup 4}He in channels

    SciTech Connect

    Varga, Emil; Skrbek, L.; Babuin, Simone

    2015-06-15

    We report a comprehensive study of turbulent superfluid {sup 4}He flow through a channel of square cross section. We study for the first time two distinct flow configurations with the same apparatus: coflow (normal and superfluid components move in the same direction), and counterflow (normal and superfluid components move in opposite directions). We realise also a variation of counterflow with the same relative velocity, but where the superfluid component moves while there is no net flow of the normal component through the channel, i.e., pure superflow. We use the second-sound attenuation technique to measure the density of quantised vortex lines in the temperature range 1.2 K ≲ T ≲ T{sub λ} ≈ 2.18 K and for flow velocities from about 1 mm/s up to almost 1 m/s in fully developed turbulence. We find that both the steady-state and temporal decay of the turbulence significantly differ in the three flow configurations, yielding an interesting insight into two-fluid hydrodynamics. In both pure superflow and counterflow, the same scaling of vortex line density with counterflow velocity is observed, L∝V{sub cf}{sup 2}, with a pronounced temperature dependence; in coflow instead, the vortex line density scales with velocity as L ∝ V{sup 3/2} and is temperature independent; we provide theoretical explanations for these observations. Further, we develop a new promising technique to use different second-sound resonant modes to probe the spatial distribution of quantised vortices in the direction perpendicular to the flow. Preliminary measurements indicate that coflow is less homogeneous than counterflow/superflow, with a denser concentration of vortices between the centre of the channel and its walls.

  1. Infrared spectroscopy and tunneling dynamics of the vinyl radical in 4He nanodroplets

    NASA Astrophysics Data System (ADS)

    Raston, Paul L.; Liang, Tao; Douberly, Gary E.

    2013-05-01

    The vinyl radical has been trapped in 4He nanodroplets and probed with infrared laser spectroscopy in the CH stretch region between 2850 and 3200 cm-1. The assigned band origins for the CH2 symmetric (ν3), CH2 antisymmetric (ν2), and lone α-CH stretch (ν1) vibrations are in good agreement with previously reported full-dimensional vibrational configuration interaction computations [A. R. Sharma, B. J. Braams, S. Carter, B. C. Shepler, and J. M. Bowman, J. Chem. Phys. 130, 174301 (2009)], 10.1063/1.3120607. For all three bands, a-type and b-type transitions are observed from the lowest symmetry allowed roconvibrational state of each nuclear spin isomer, which allows for a determination of the tunneling splittings in both the ground and excited vibrational levels. Comparisons to gas phase millimeter-wave rotation-tunneling [K. Tanaka, M. Toshimitsu, K. Harada, and T. Tanaka, J. Chem. Phys. 120, 3604-3618 (2004)], 10.1063/1.1642583 and high-resolution jet-cooled infrared spectra [F. Dong, M. Roberts, and D. J. Nesbitt, J. Chem. Phys. 128, 044305 (2008)], 10.1063/1.2816704 reveal that the He solvent effect is to reduce the ground and ν3 excited state tunneling splittings by ≈20%. This solvent-induced modification of the tunneling dynamics can be reasonably accounted for by assuming either a ≈2.5% increase in the effective barrier height along the tunneling coordinate or a ≈5% increase in the effective reduced mass of the tunneling particles.

  2. On the Transition from Potential Flow to Turbulence Around a Microsphere Oscillating in Superfluid ^4{He}

    NASA Astrophysics Data System (ADS)

    Niemetz, M.; Hänninen, R.; Schoepe, W.

    2017-01-01

    The flow of superfluid ^4{He} around a translationally oscillating sphere, levitating without mechanical support, can either be laminar or turbulent, depending on the velocity amplitude. Below a critical velocity v_c that scales as ω ^{1/2} and is temperature independent below 1 K, the flow is laminar (potential flow). Below 0.5 K, the linear drag force is caused by ballistic phonon scattering that vanishes as T^4 until background damping, measured in the empty cell, becomes dominant for T < 0.1 K. Increasing the velocity amplitude above v_c leads to a transition from potential flow to turbulence, where the large turbulent drag force varies as (v^2 - v_c^2) . In a small velocity interval Δ v {/} v_c ≤ 3 % above v_c , the flow is unstable below 0.5 K, switching intermittently between both patterns. From time series recorded at constant temperature and driving force, the lifetimes of both phases are analyzed statistically. We observe metastable states of potential flow which, after a mean lifetime of 25 min, ultimately break down due to vorticity created by natural background radioactivity. The lifetimes of the turbulent phases have an exponential distribution, and the mean increases exponentially with Δ v^2 . We investigate the frequency at which the vortex rings are shed from the sphere. Our results are compared with recent data of other authors on vortex shedding by moving a laser beam through a Bose-Einstein condensate. Finally, we show that our observed transition to turbulence belongs to the class of "supertransient chaos" where lifetimes of the turbulent states increase faster than exponentially.

  3. T(t,2n)4He Neutron Spectrum from Inertial Confinement Implosions

    NASA Astrophysics Data System (ADS)

    McNabb, Dennis; Bacher, Andy; Brune, Carl; Caggiano, Jac; Gatu-Johnson, Maria; Sayre, Dan; ICF Stellar Rates Team

    2013-10-01

    Measurements of the T(t,2n)4He reaction (TT) have been conducted using high-purity tritium, gas-filled capsules in ICF implosions at the NIF and OMEGA facilities. Neutron spectra were measured using two instruments: the neutron-time-of-flight (nTOF) and the Magnetic Recoil Spectrometer. The nTOF spectra represent a significant improvement in energy resolution and statistics over previous measurements, and afford the first definitive observation of a small, narrow peak starting at the 9.44 MeV endpoint resulting from sequential decay through the ground state of 5He at low reaction energies Ecm < 100 keV. However, most of the TT reaction produces a broad neutron spectrum from 0-9.5 MeV. To describe the spectrum, an R-matrix model that accounts for interferences from fermion symmetry and intermediate states has been developed. This model can describe the entire spectrum via sequential decay through l = 1 states in 5He, which differs from previous interpretations. Work is in collaboration with V. Yu Glebov, R. Hatarik, D. L. Bleuel, D. T. Casey, C. J. Cerjan, M. J. Eckart, R. J. Fortner, J. A. Frenje, G. P. Grim, C. Hagmann, J. P. Knauer, J. L. Kline, J. M. McNaney, J. M. Mintz, M. J. Moran, A. Nikroo, T. Phillips, J. E. Pino, B. A. Remington, D. P. Rowley, D. H. Schneider, V. A. Smalyuk, W. Stoeffl, R. E. Tipton, S. V. Weber, C. B. Yeamans, C. K. Li, M. J.-E. Manuel, D. D. Meyerhofer, R. D. Petrasso, P. B. Radha, T. C. Sangster, N. Sinenian, F. H. Seguin, and A. B. Zylstra.

  4. The reflection of low energy phonons at the free surface of liquid4He. I. Theory

    NASA Astrophysics Data System (ADS)

    Baddar, H.; Edwards, D. O.

    1996-09-01

    The scattering of a low energy phonon at the free surface of liquid4He at finite temperature is discussed in relation to the reflection measurements in the accompanying paper (II). If not specularly reflected, the phonon may be inelastically scattered, with the emission or absorption of a single ripplon, or it may be absorbed with the emission of two ripplons. The inelastic scattering produces deviations from ideal specular reflection that depend logarithmically on the angular sensitivity of the measurement. For the experiment described in II, the predicted deviations due to scattering and absorption are roughly equal and too small (˜5×10-4) to be measured. In addition, there should be a small broadening (less than 1 ° in angle) of the reflected image of the phonon source due to phonon decay in the bulk liquid. This was calculated from the curvature of the phonon spectrum measured by Rugar and Foster. Phonon decay also determines the distribution of the incident phonon beam with respect to energy. From the known decay rate, the average incident phonon energy in our experiment is calculated to be ˜0.5 K. We also discuss the attenuation of surface second sound due to the inelastic scattering and absorption of thermal phonons at the surface. We find that two ripplon absorption is the dominant effect. Below ˜0.7 K, the attenuation due to phonons is probably just small enough for pure ripplon surface sound to exist in a narrow range of low frequencies. To show this, we have recalculated the ripplon lifetime using the 3-ripplon interaction as recently revised by Roche et al. The results for the ripplon lifetime are displayed in a simple scaling format.

  5. Interaction of ions, atoms, and small molecules with quantized vortex lines in superfluid {sup 4}He

    SciTech Connect

    Mateo, David; Eloranta, Jussi; Williams, Gary A.

    2015-02-14

    The interaction of a number of impurities (H{sub 2}, Ag, Cu, Ag{sub 2}, Cu{sub 2}, Li, He{sub 3}{sup +}, He{sup *} ({sup 3}S), He{sub 2}{sup ∗} ({sup 3}Σ{sub u}), and e{sup −}) with quantized rectilinear vortex lines in superfluid {sup 4}He is calculated by using the Orsay-Trento density functional theory (DFT) method at 0 K. The Donnelly-Parks (DP) potential function binding ions to the vortex is combined with DFT data, yielding the impurity radius as well as the vortex line core parameter. The vortex core parameter at 0 K (0.74 Å) obtained either directly from the vortex line geometry or through the DP potential fitting is smaller than previously suggested but is compatible with the value obtained from re-analysis of the Rayfield-Reif experiment. All of the impurities have significantly higher binding energies to vortex lines below 1 K than the available thermal energy, where the thermally assisted escape process becomes exponentially negligible. Even at higher temperatures 1.5-2.0 K, the trapping times for larger metal clusters are sufficiently long that the previously observed metal nanowire assembly in superfluid helium can take place at vortex lines. The binding energy of the electron bubble is predicted to decrease as a function of both temperature and pressure, which allows adjusting the trap depth for either permanent trapping or to allow thermally assisted escape. Finally, a new scheme for determining the trapping of impurities on vortex lines by optical absorption spectroscopy is outlined and demonstrated for He{sup *}.

  6. 190Pt-4He age of PGE ores in the Alkaline-Ultramafic Kondyor Massif (Khabarovsk District, Russia)

    NASA Astrophysics Data System (ADS)

    Mochalov, A. G.; Yakubovich, O. V.; Bortnikov, N. S.

    2016-08-01

    A new 190Pt-4He method for dating isoferroplatinum has been developed at the Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences. Here we publish the first results of dating of isoferroplatinum from the main mineralogical and geochemical types of PGE mineralization in dunite. The obtained 190Pt-4He age of isoferroplatinum is 129 ± 6 Ma. The gained 190Pt-4He age of isoferroplatinum specimens of different genesis (magmatic, fluid-metamorphogenic, and metasomatic) from the Kondyor Massif indicates that the PGM mineralization took place synchronously and successively with evolution of primarily picrite, followed by subalkaline and alkaline melts of the Mesozoic tectonic-magmatic activation of the Aldan Shield.

  7. Measurements of the strong-interaction widths of the kaonic 3He and 4He 2p levels

    PubMed Central

    Bazzi, M.; Beer, G.; Bombelli, L.; Bragadireanu, A.M.; Cargnelli, M.; Curceanu (Petrascu), C.; dʼUffizi, A.; Fiorini, C.; Frizzi, T.; Ghio, F.; Guaraldo, C.; Hayano, R.S.; Iliescu, M.; Ishiwatari, T.; Iwasaki, M.; Kienle, P.; Levi Sandri, P.; Longoni, A.; Marton, J.; Okada, S.; Pietreanu, D.; Ponta, T.; Rizzo, A.; Romero Vidal, A.; Sbardella, E.; Scordo, A.; Shi, H.; Sirghi, D.L.; Sirghi, F.; Tatsuno, H.; Tudorache, A.; Tudorache, V.; Vazquez Doce, O.; Wünschek, B.; Widmann, E.; Zmeskal, J.

    2012-01-01

    The kaonic 3He and 4He X-rays emitted in the 3d→2p transitions were measured in the SIDDHARTA experiment. The widths of the kaonic 3He and 4He 2p states were determined to be Γ2p(He3)=6±6(stat.)±7 (syst.) eV, and Γ2p(He4)=14±8 (stat.)±5 (syst.) eV, respectively. Both results are consistent with the theoretical predictions. The width of kaonic 4He is much smaller than the value of 55±34 eV determined by the experiments performed in the 70ʼs and 80ʼs, while the width of kaonic 3He was determined for the first time. PMID:22876000

  8. The First Measurement of Cross Section for the 7Be(n, α)4He Reaction at the Cosmological Energy

    NASA Astrophysics Data System (ADS)

    Takeda, Tomoya; Kawabata, Takahiro; Furono, Tatsuya; Ichikawa, Masaya; Iwasa, Naohito; Kanada-En'yo, Yoshiko; Koshikawa, Ami; Kubono, Shigeru; Miyawaki, Eisuke; Morimoto, Takahiro; Murata, Motoki; Nanamura, Takuya; Nishimura, Shunji; Shikata, Yuki; Takahashi, Yu; Tsumura, Miho; Watanabe, Ken

    The cross section for the 4He(α, n)7Be reaction was measured at low energies between Eα = 38.50 and 39.64 MeV to solve the cosmological lithium problem. On the basis of the detailed balance principle, the cross section for the 7Be(n, α)4He reaction was obtained at Ec.m. = 0.20-0.81 MeV close to the Big Bang nucleosynthesis (BBN) energy window for the first time. The obtained cross sections are significantly smaller than the theoretical estimation used in the BBN calculations. The present results suggest the 7Be(n, α)4He reaction rate is not large enough to solve the cosmological lithium problem.

  9. Excitation function for 4He(π+,pp)2H two-nucleon absorption across the Δ resonance

    NASA Astrophysics Data System (ADS)

    Breuer, H.; Khayat, M. G.; Adimi, F.; Flanders, B. S.; Khandaker, M. A.; Roos, P. G.; Zhang, D.; Bauer, Th. S.; Konijn, J.; de Laat, C. T. A. M.; Kyle, G. S.; Mukhopadhyay, S.; Wang, M.; Tacik, T.

    1994-05-01

    Angular distributions and total cross sections for the 4He(π+,pp)2H reaction have been measured with small relative uncertainties at incident energies of T+π=64, 87, 114, 162, 217, 278, and 327 MeV. The results strongly support the quasideuteron absorption model for pion absorption on two nucleons, which is found to contribute only ~=50% to the total absorption cross section near the Δ resonance. All essential reaction channels of pion absorption near the Δ resonance on heavier nuclei seem to be present in 4He, but not in 3He. Any nuclear-density-related increase of pion absorption in 4He relative to 2H is <50% and no binding energy effect is found.

  10. Suppression of Freezing and Emergence of a Novel Ordered State in 4He Confined in a Nano - porous Material

    SciTech Connect

    Yamamoto, K.; Shibayama, Y.; Shirahama, K.

    2006-09-07

    Confinement of 4He in a porous material with nanometer - size pores suppresses both the freezing and superfluidity. In our previous investigation of superfluid density of 4He confined in a porous Gelsil glass which has pores of 2.5 nm in diameter, it was demonstrated that the superfluidity is greatly suppressed by pressurization. In order to explore the overall P - T phase diagram, we study the liquid - solid coexistence line. The freezing pressure is elevated up to about 3.4 MPa and independent of temperature below 1.3 K. Along with the previous measurement of superfluid density these features indicate that a nonsuperfluid phase exists next to the solid phase. The flat freezing curve indicates that this nonsuperfluid phase has small entropy as well as that of solid. Therefore the nonsuperfluid phase is possibly a novel ordered state, in which the global phase coherence is destroyed by strong correlation between 4He atoms and/or by random potential.

  11. Search of Superfluidity of Solid 4He in a Porous Vycor Glass by Means of the Ultrasound Technique

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Fukazawa, S.; Taniguchi, J.; Suzuki, M.; Shirahama, K.

    2006-09-01

    Kim and Chan have reported that solid 4He shows a reduction of the rotational moment of inertia below 0.2 K, which suggests an onset of superfluidity. Ultrasound should be sensitive to mass decoupling caused by superfluidity. If a superfluid component exists, the sound velocity of a porous material filled with solid 4He could increase. We have carried out ultrasonic measurements for a porous Vycor glass filled with solid 4He. Since the reported "critical velocity" is very low, we have adopted a continuous wave resonance technique which realizes the oscillating velocity less than 1 × 10-7 m/s. The resolution of the sound velocity is 10-5 for small oscillating velocities, and is enough to detect the expected mass decoupling. Although the present experimental conditions are rather limited, no signature of supersolid has been observed.

  12. Search for {sup 3}He and {sup 4}He in Arata-Style Palladium Cathodes I: A Negative Result

    SciTech Connect

    Clarke, W. Brian

    2001-09-15

    The {sup 3}He and {sup 4}He concentrations in 2- to 6-mg samples of palladium-black from the interior of Arata-style cathodes were investigated using a tungsten wire furnace on-line to an ultrahigh sensitivity static mass spectrometer. The detection limit of the mass spectrometer was {approx}10{sup 4} atoms {sup 3}He and 10{sup 8} atoms {sup 4}He, and the mass resolution of 1 part in 620 was sufficient to cleanly resolve {sup 3}He from H{sub 3} and HD. Three specimens of palladium-black (A, B, and C) were from hollow Pd cathodes that had generated excess heat in D{sub 2}O electrolysis experiments carried out by Arata and Zhang in their laboratory. One specimen of Pd-black (D) had not been used in any electrolysis experiment. A total of twelve samples, three from each specimen, were analyzed. The {sup 3}He and {sup 4}He concentrations were variable as if due to sample inhomogeneity. Two samples (C-1 and B-1) showed apparent {sup 4}He of 4.4 x 10{sup 9} atoms/mg and 6.6 x 10{sup 9} atoms/mg, respectively, and three (A-3, B-2, and D-3) showed excess {sup 3}He from 77 to 1096 x 10{sup 3} atoms/mg relative to the atmospheric {sup 3}He/{sup 4}He ratio. Seven samples showed no apparent excess of {sup 3}He or {sup 4}He. Five samples of the aluminum foil used to wrap Pd-black samples were also analyzed and gave mean values of 13 {+-} 18 x 10{sup 3} atoms/mg and 1.50 {+-} 0.66 x 10{sup 9} atoms/mg for {sup 3}He and {sup 4}He, respectively. The values for Al and Pd-black are comparable to the 1978 results of Mamyrin, Khabarin, and Yudenich, who examined helium isotopes in many ordinary metals and other materials including Al and Pd. At present, there is no evidence for the very much larger concentrations (10{sup 16} to 10{sup 17} atoms/mg) of {sup 3}He and {sup 4}He that Arata and Zhang claim to have detected in similar specimens of Pd-black from Pd cathodes subjected to D{sub 2}O electrolysis.

  13. Pole approximation validation in the study of the {sup 6}Li(d,{alpha}){sup 4}He reaction

    SciTech Connect

    Pizzone, R. G.; Kiss, G. G.; Spitaleri, C.; Lamia, L.; Cherubini, S.; La Cognata, M.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Burjan, V.; Hons, Z.; Kroha, V.; Mrazek, J.; Piskor, S.; Li, C.; Tumino, A.

    2010-11-24

    The Trojan Horse Method (THM) was applied to the {sup 3}He+{sup 6}Li interaction in order to investigate the quasi-free {sup 6}Li(d,{alpha}){sup 4}He reaction. The experiment was performed at 17 MeV at the Cyclotron Institute of the Czech Academy of Science. The extracted {sup 6}Li(d,{alpha}){sup 4}He quasi-free cross-section was compared with the behavior of direct data. A good agreement between data sets shows up throughout the energy range investigated, providing a very important validity test of the pole approximation for the THM above the Coulomb barrier.

  14. Precision Measurement of the Rovibrational Energy-Level Structure of ^{4}He^{+}_{2}

    NASA Astrophysics Data System (ADS)

    Semeria, Luca; Jansen, Paul; Agner, Josef A.; Schmutz, Hansjürg; Merkt, Frederic

    2017-06-01

    He_{2}^{+} is a three-electron system for which highly accurate ab initio calculations are possible. The latest calculations of the rovibrational energies of He_{2}^{+} by Tung et al. have a reported accuracy of 120 MHz, although they do not include relativistic and quantum electrodynamics (QED) effects. We determined the rovibrational structure of ^{4}He^{+}_{2} from measurements of the Rydberg spectrum of metastable a ^3Σ_u^+ He_{2} (He^{*}_{2} hereafter) and Rydberg-series extrapolation using multichannel quantum-defect-theory. He^{*}_{2} molecules are produced in supersonic beams with velocities tunable down to about 100 m/s by combining a cryogenic supersonic-beam source with a multistage Zeeman decelerator. They are then excited to high-np Rydberg states by single-photon excitation. In the experiments, we use a pulsed uv laser system, with a near Fourier-transform-limited bandwidth of 150 MHz. The Zeeman deceleration reduces the systematic uncertainty arising from a possible Doppler shift and greatly simplifies the spectral assignment because of its spin-rotational state selectivity. Results will be presented on the rotational structure of the lowest three vibrational levels of He^{+}_{2}. The unprecedented accuracy that we have obtained for the v^{+}=0 rotational intervals of He_{2}^{+} enables the quantification of the relativistic and QED corrections by comparison with the results of Tung et al.^a W.-C. Tung, M. Pavanello and L. Adamowicz, J. Chem. Phys., 136, 104309, 2012. C. Jungen, Elements of Quantum Defect Theory, in : Handbook of High-resolution Spectroscopy, 2001. D. Sprecher, J. Liu, T. Krähenmann, M. Schäfer, and F. Merkt, J. Chem. Phys., 140, 064304, 2014. A. W. Wiederkehr, S. D. Hogan, M. Andrist, H. Schmutz, B. Lambillotte, J. A. Agner, and F. Merkt., J. Chem. Phys., 135, 214202, 2011. M. Motsch, P. Jansen, J. A. Agner, H. Schmutz, and F. Merkt, Phys. Rev. A, 89, 043420, 2014. P. Jansen, L. Semeria, L. E. Hofer, S. Scheidegger, J. A. Agner

  15. Spectroscopic information of 6Li from elastic scattering of deuterons, 3He and 4He by 6Li

    NASA Astrophysics Data System (ADS)

    Amar, A.

    2014-07-01

    The elastic scattering of deuterons, 3He and 4He on 6Li at different incident energies have been analyzed in the framework of the optical model (OM) using ECIS88 as well as SPI GENOA codes. The optical potential parameters were extracted in the phenomenological treatment. A good agreement between theoretical and experimental differential cross-sections was obtained in whole angular range. Parameters for real part of potential have been also calculated microscopically with double-folding model for the d, 3He and 4He scattering, respectively, using DFPOT code. The elastic transfer mechanism has been studied by coupled reaction channel (CRC) method using FRESCO code. Spectroscopic amplitudes of 6Li ≡ t + 3He and 6Li ≡ α + d configurations have been extracted from d, 3He and 4He scattering on 6Li at wide energy range. A comparison between spectroscopic amplitudes obtained from deuteron and α elastically scattering from 6Li has been made. The extracted spectroscopic amplitudes of 6Li ≡ 4He + d(SF = SA2) from 6Li(d, 6Li)d and 6Li(α, 6Li)α are not the same as expected theoretically.

  16. Prediction of stable C7 /12 and metastable C4 /7 commensurate solid phases for 4He on graphite

    NASA Astrophysics Data System (ADS)

    Ahn, Jeonghwan; Lee, Hoonkyung; Kwon, Yongkyung

    2016-02-01

    Using a substrate potential described by a pairwise sum of empirical 4He-C interatomic potentials, we have performed path-integral Monte Carlo calculations for 4He adatoms on graphite. It is found that a second-layer commensurate structure is not stable above an incommensurate first-layer triangular solid. This is consistent with the conclusion of the previous theoretical study of Corboz et al. [Phys. Rev. B 78, 245414 (2008), 10.1103/PhysRevB.78.245414] that was based on a laterally averaged one-dimensional potential. On the other hand, we observe a new stable C7 /12 commensurate solid in the first 4He layer at the areal density of 0.111 Å-2, which is close to the second-layer promotion density. This high-density commensurate solid exhibits a √{12 }×√{12 } structure registered to the graphite surface that is not disrupted by the development of the second 4He layer. Furthermore, a second-layer 4/7 commensurate structure relative to the first-layer C7 /12 solid is found to be at least metastable, opening the possibility of two-dimensional supersolidity.

  17. Observation of two-dimensional classical wave localization: third sound on superfluid 4He films on a disordered substrate.

    PubMed

    Luhman, D R; Herrmann, J C; Hallock, R B

    2005-05-06

    We present the results of measurements of the propagation of third sound waves on superfluid 4He adsorbed to two-dimensional ordered and disordered substrates. In the disordered case we compare the experimental results to theoretical predictions of classical wave localization in such systems and conclude that classical wave localization is present in our system.

  18. Ultra-High Sensitivity Techniques for the Determination of 3 He /4 He Abundances in Helium by Accelerator Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Mumm, H. P.; Huber, M.; Bauder, W.; Abrams, N.; Deibel, C.; Huffer, C.; Huffman, P.; Schelhammer, K.; Janssens, R.; Jiang, C.; Scott, R.; Pardo, R.; Rehm, K.; Vondrasek, R.; Swank, C.; O'Shaughnessy, C.; Paul, M.; Yang, L.

    2017-01-01

    We report the development of an Accelerator Mass Spectrometry technique to measure the 3He/4He isotopic ratio using a radio frequency (RF) discharge source and the ATLAS facility at Argonne National Laboratory. Control over 3He/4He ratio in helium several orders of magnitude lower than natural abundance is critical for neutron lifetime and source experiments using liquid helium. Due to low ultimate beam currents, the ATLAS accelerator and beam line were tuned using a succession of species of the same M/q. A unique RF source was developed for the experiment due to large natural 3He backgrounds. Analog H_3 + and DH + molecular ions are eliminated by dissociation via a gold stripper foil near the detector. The stripped ions were dispersed in a magnetic spectrograph and 3He2 + ions counted in the focal plane detector. This technique is sensitive to 3 He /4 He ratios in the regime of 10-12 with backgrounds that appear to be below 10-14. The techniques used to reduce the backgrounds and remaining outstanding problems will be presented along with results from measurements on high purity 4He samples.

  19. Path integral Monte Carlo simulation of global and local superfluidity in liquid 4He reservoirs separated by nanoscale apertures

    NASA Astrophysics Data System (ADS)

    Volkoff, Tyler; Kwon, Yongkyung; Whaley, K. Birgitta

    2016-10-01

    We present a path integral Monte Carlo study of the global superfluid fraction and local superfluid density in cylindrically symmetric reservoirs of liquid 4He separated by nanoaperture arrays. The superfluid response to both translations along the axis of symmetry (longitudinal response) and rotations about the cylinder axis (transverse response) are computed, together with radial and axial density distributions that reveal the microscopic inhomogeneity arising from the combined effects of the confining external potential and the 4He-4He interatomic potentials. We make a microscopic determination of the length scale of decay of superfluidity at the radial boundaries of the system by analyzing the local superfluid density distribution to extract a displacement length that quantifies the superfluid mass displacement away from the boundary. We find that the longitudinal superfluid response is reduced in reservoirs separated by a septum containing sufficiently small apertures compared to a cylinder with no intervening aperture array, for all temperatures below Tλ. For a single aperture in the septum, a significant drop in the longitudinal superfluid response is seen when the aperture diameter is made smaller than twice the empirical temperature-dependent 4He healing length, consistent with the formation of a weak link between the reservoirs. Increasing the diameter of a single aperture or the number of apertures in the array results in an increase of the superfluid density toward the expected bulk value.

  20. The helium flux from the continents and ubiquity of low-3He/4He recycled crust and lithosphere

    NASA Astrophysics Data System (ADS)

    Day, James M. D.; Barry, Peter H.; Hilton, David R.; Burgess, Ray; Pearson, D. Graham; Taylor, Lawrence A.

    2015-03-01

    New helium isotope and trace-element abundance data are reported for pyroxenites and eclogites from South Africa, Siberia, and the Beni Bousera Massif, Morocco that are widely interpreted to form from recycled oceanic crustal protoliths. The first He isotope data are also presented for Archaean peridotites from the Kaapvaal (South Africa), Slave (Canada), and Siberian cratons, along with recently emplaced off-craton peridotite xenoliths from Kilbourne Hole, San Carlos (USA) and Vitim (Siberia), to complement existing 3He/4He values obtained for continental and oceanic peridotites. Helium isotope compositions of peridotite xenoliths vary from 7.3 to 9.6 RA in recently (<10 kyr) emplaced xenoliths, to 0.05 RA in olivine from cratonic peridotite xenoliths of the 1179 Ma Premier kimberlite, South Africa. The helium isotope compositions of the peridotites can be explained through progressive sampling of 4He produced from radiogenic decay of U and Th in the mineral lattice in the older emplaced peridotite xenoliths. Ingrowth of 4He is consistent with generally higher 4He concentrations measured in olivine from older emplaced peridotite xenoliths relative to those from younger peridotite xenoliths. Collectively, the new data are consistent with pervasive open-system behaviour of He in peridotite xenoliths from cratons, mobile belts and tectonically-active regions. However, there is probable bias in the estimate of the helium isotope composition of the continental lithospheric mantle (6.1 ± 2.1 RA), since previously published databases were largely derived from peridotite xenoliths from non-cratonic lithosphere, or phenocrysts/xenocrysts obtained within continental intraplate alkaline volcanics that contain a contribution from asthenospheric sources. Using the new He isotope data for cratonic peridotites and assuming that significant portions (>50%) of the Archaean and Proterozoic continental lithospheric mantle are stable and unaffected by melt or fluid infiltration on

  1. The interstellar chemistry of C3H and C3H2 isomers

    NASA Astrophysics Data System (ADS)

    Loison, Jean-Christophe; Agúndez, Marcelino; Wakelam, Valentine; Roueff, Evelyne; Gratier, Pierre; Marcelino, Núria; Reyes, Dianailys Nuñez; Cernicharo, José; Gerin, Maryvonne

    2017-10-01

    We report the detection of linear and cyclic isomers of C3H and C3H2 towards various starless cores and review the corresponding chemical pathways involving neutral (C3Hx with x = 1,2) and ionic (C3Hx+ with x = 1,2,3) isomers. We highlight the role of the branching ratio of electronic dissociative recombination (DR) reactions of C3H2+ and C3H3+ isomers, showing that the statistical treatment of the relaxation of C3H* and C3H2* produced in these DR reactions may explain the relative c,l-C3H and c,l-C3H2 abundances. We have also introduced in the model the third isomer of C3H2 (HCCCH). The observed cyclic-to-linear C3H2 ratio varies from 110 ± 30 for molecular clouds with a total density of about 1 × 104 molecules cm-3 to 30 ± 10 for molecular clouds with a total density of about 4 × 105 molecules cm-3, a trend well reproduced with our updated model. The higher ratio for molecular clouds with low densities is determined mainly by the importance of the H + l-C3H2 → H + c-C3H2 and H + t-C3H2 → H + c-C3H2 isomerization reactions.

  2. Enhancing the branching ratios in the dissociation channels for O16O16O18 molecule by designing optimum laser pulses: A study using stochastic optimization

    NASA Astrophysics Data System (ADS)

    Talukder, Srijeeta; Sen, Shrabani; Shandilya, Bhavesh K.; Sharma, Rahul; Chaudhury, Pinaki; Adhikari, Satrajit

    2015-10-01

    We propose a strategy of using a stochastic optimization technique, namely, simulated annealing to design optimum laser pulses (both IR and UV) to achieve greater fluxes along the two dissociating channels (O18 + O16O16 and O16 + O16O18) in O16O16O18 molecule. We show that the integrated fluxes obtained along the targeted dissociating channel is larger with the optimized pulse than with the unoptimized one. The flux ratios are also more impressive with the optimized pulse than with the unoptimized one. We also look at the evolution contours of the wavefunctions along the two channels with time after the actions of both the IR and UV pulses and compare the profiles for unoptimized (initial) and optimized fields for better understanding the results that we achieve. We also report the pulse parameters obtained as well as the final shapes they take.

  3. Enhancing the branching ratios in the dissociation channels for O(16)O(16)O(18) molecule by designing optimum laser pulses: A study using stochastic optimization.

    PubMed

    Talukder, Srijeeta; Sen, Shrabani; Shandilya, Bhavesh K; Sharma, Rahul; Chaudhury, Pinaki; Adhikari, Satrajit

    2015-10-14

    We propose a strategy of using a stochastic optimization technique, namely, simulated annealing to design optimum laser pulses (both IR and UV) to achieve greater fluxes along the two dissociating channels (O(18) + O(16)O(16) and O(16) + O(16)O(18)) in O(16)O(16)O(18) molecule. We show that the integrated fluxes obtained along the targeted dissociating channel is larger with the optimized pulse than with the unoptimized one. The flux ratios are also more impressive with the optimized pulse than with the unoptimized one. We also look at the evolution contours of the wavefunctions along the two channels with time after the actions of both the IR and UV pulses and compare the profiles for unoptimized (initial) and optimized fields for better understanding the results that we achieve. We also report the pulse parameters obtained as well as the final shapes they take.

  4. The isotopic ratios 17O/ 16O and 18O/ 16O in molecular oxygen and their significance in biogeochemistry

    NASA Astrophysics Data System (ADS)

    Luz, Boaz; Barkan, Eugeni

    2005-03-01

    Recently, a new method has been introduced for the estimation of photosynthetic oxygen production from the triple isotope composition (δ 17O and δ 18O) of dissolved O 2 in the ocean and of air O 2 in ice cores. This method is based on the deviations ( 17Δ) from mass dependent respiratory fractionation, the major process affecting the isotopic composition of air O 2. To apply this method, the slope in the 17O/ 16O vs. 18O/ 16O relationship used for 17Δ calculation must be known with high accuracy. Using numerical simulations and closed system experiments, we show how the respiratory slope is manifested in the 17Δ of O 2 in situations where respiration is the only process affecting oxygen isotopic composition (kinetic slope), and in systems in steady state between photosynthesis and respiration (steady state slope). The slopes of the fractionation line in these two cases are different, and the reasons of this phenomenon are discussed. To determine the kinetic respiratory slope for the dominant O 2 consumers in aquatic systems, we have conducted new experiments using a wide range of organisms and conditions and obtained one universal value (0.5179 ± 0.0006) in ln(δ 17O + 1) vs. ln(δ 18O + 1) plots. It was also shown that the respiratory fractionations under light and dark are identical within experimental error. We discuss various marine situations and conclude that the kinetic slope 0.518 should be used for calculating 17Δ of dissolved O 2. In contrast, a steady state fractionation slope should be used in global mass balance calculations of triple isotope ratios of O 2 in air records of ice cores.

  5. Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of {sup 4}He nanodroplets on surfaces: {sup 4}He/graphene

    SciTech Connect

    Lara-Castells, María Pilar de; Stoll, Hermann; Civalleri, Bartolomeo; Causà, Mauro; Voloshina, Elena; Mitrushchenkov, Alexander O.; Pi, Martí

    2014-10-21

    In this work we propose a general strategy to calculate accurate He–surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on {sup 4}He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of {sup 4}He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the {sup 4}He nanodroplet, the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.

  6. Communication: A combined periodic density functional and incremental wave-function-based approach for the dispersion-accounting time-resolved dynamics of 4He nanodroplets on surfaces: 4He/graphene

    NASA Astrophysics Data System (ADS)

    de Lara-Castells, María Pilar; Stoll, Hermann; Civalleri, Bartolomeo; Causà, Mauro; Voloshina, Elena; Mitrushchenkov, Alexander O.; Pi, Martí

    2014-10-01

    In this work we propose a general strategy to calculate accurate He-surface interaction potentials. It extends the dispersionless density functional approach recently developed by Pernal et al. [Phys. Rev. Lett. 103, 263201 (2009)] to adsorbate-surface interactions by including periodic boundary conditions. We also introduce a scheme to parametrize the dispersion interaction by calculating two- and three-body dispersion terms at coupled cluster singles and doubles and perturbative triples (CCSD(T)) level via the method of increments [H. Stoll, J. Chem. Phys. 97, 8449 (1992)]. The performance of the composite approach is tested on 4He/graphene by determining the energies of the low-lying selective adsorption states, finding an excellent agreement with the best available theoretical data. Second, the capability of the approach to describe dispersionless correlation effects realistically is used to extract dispersion effects in time-dependent density functional simulations on the collision of 4He droplets with a single graphene sheet. It is found that dispersion effects play a key role in the fast spreading of the 4He nanodroplet, the evaporation-like process of helium atoms, and the formation of solid-like helium structures. These characteristics are expected to be quite general and highly relevant to explain experimental measurements with the newly developed helium droplet mediated deposition technique.

  7. Possible Explanation of {sup 4}He Production in a Pd/D{sub 2} System by the TNCF Model

    SciTech Connect

    Kozima, Hideo; Ohta, Masayuki; Fujii, Mitsutaka; Arai, Kunihito; Kudoh, Hitoshi

    2001-07-15

    Experimental data showing generation of {sup 4}He from a Pd sheet-D{sub 2} gas system observed by E. Botta et al. are analyzed by the trapped neutron catalyzed fusion (TNCF) model. The proposed mechanism of {sup 4}He generation is not the direct d-d reaction but the reactions between the trapped neutron and a Pd isotope, n-{sub 46}{sup A}Pd reactions, with a supplemental assumption, decrease of threshold energies for (n,{alpha}) reactions of {sub 46}{sup A}Pd in solids. The arbitrary parameter n{sub n}, the density of the trapped neutron, of the model is determined to be {approx}10{sup 12} cm{sup -3}, which is consistent with values determined in analyses of data in various events in the cold fusion phenomenon.

  8. Excitation functions for complete-fusion and transfer reactions in {sup 4}He interaction with {sup 197}Au nuclei

    SciTech Connect

    Kulko, A. A.; Demekhina, N. A.; Kalpakchieva, R.; Muzychka, Yu. A.; Penionzhkevich, Yu. E.; Rassadov, D. N.; Skobelev, N. K.; Testov, D. A.

    2007-04-15

    Excitation functions are measured for the fusion reactions {sup 197}Au({sup 4}He, xn){sup 201-xn}Tl that are induced by alpha-particle interaction with gold nuclei in the energy range 14-36 MeV and in which x neutrons (0 {<=} x {<=} 3) are evaporated. The stack-activation technique was used to record and separate reaction products. Experimental data on the fusion reactions followed by evaporation of one to three neutrons agree with results of previous studies. For the radiative-capture reaction {sup 197}Au({sup 4}He,{gamma}){sup 201}Tl, the upper limit on the cross section proved to be much lower. The excitation functions for the reactions subjected to measurements are compared with the results of calculations based on the statistical model and with the results of an experiment performed previously in a {sup 6}He beam.

  9. Excitation functions for complete-fusion and transfer reactions in 4He interaction with 197Au nuclei

    NASA Astrophysics Data System (ADS)

    Kulko, A. A.; Demekhina, N. A.; Kalpakchieva, R.; Muzychka, Yu. A.; Penionzhkevich, Yu. E.; Rassadov, D. N.; Skobelev, N. K.; Testov, D. A.

    2007-04-01

    Excitation functions are measured for the fusion reactions 197Au(4He, xn)201-xn Tl that are induced by alpha-particle interaction with gold nuclei in the energy range 14 36 MeV and in which x neutrons (0 ≤ x ≤ 3) are evaporated. The stack-activation technique was used to record and separate reaction products. Experimental data on the fusion reactions followed by evaporation of one to three neutrons agree with results of previous studies. For the radiative-capture reaction 197Au(4He,γ)201Tl, the upper limit on the cross section proved to be much lower. The excitation functions for the reactions subjected to measurements are compared with the results of calculations based on the statistical model and with the results of an experiment performed previously in a 6He beam.

  10. Fragmentation of 120 and 200 MeV u(-1)(4)He ions in water and PMMA targets.

    PubMed

    Rovituso, M; Schuy, C; Weber, U; Brons, S; Cortés-Giraldo, M A; La Tessa, C; Piasetzky, E; Izraeli, D; Schardt, D; Toppi, M; Scifoni, E; Krämer, M; Durante, M

    2017-02-21

    Recently, the use of (4)He particles in cancer radiotherapy has been reconsidered as they potentially represent a good compromise between protons and (12)C ions. The first step to achieve this goal is the development of a dedicated treatment planning system, for which basic physics information such as the characterization of the beam lateral scattering and fragmentation cross sections are required. In the present work, the attenuation of (4)He primary particles and the build-up of secondary charged fragments at various depths in water and polymethyl methacrylate were investigated experimentally for 120 and 200 MeV u(-1) beams delivered by the synchrotron at the Heidelberg Ion-Beam Therapy Center, Heidelberg. Species and isotope identification was accomplished combining energy loss and time-of-flight measurements. Differential yields and energy spectra of all fragments types were recorded between 0° and 20° with respect to the primary beam direction.

  11. Fragmentation of 120 and 200 MeV u-1 4He ions in water and PMMA targets

    NASA Astrophysics Data System (ADS)

    Rovituso, M.; Schuy, C.; Weber, U.; Brons, S.; Cortés-Giraldo, M. A.; La Tessa, C.; Piasetzky, E.; Izraeli, D.; Schardt, D.; Toppi, M.; Scifoni, E.; Krämer, M.; Durante, M.

    2017-02-01

    Recently, the use of 4He particles in cancer radiotherapy has been reconsidered as they potentially represent a good compromise between protons and 12C ions. The first step to achieve this goal is the development of a dedicated treatment planning system, for which basic physics information such as the characterization of the beam lateral scattering and fragmentation cross sections are required. In the present work, the attenuation of 4He primary particles and the build-up of secondary charged fragments at various depths in water and polymethyl methacrylate were investigated experimentally for 120 and 200 MeV u-1 beams delivered by the synchrotron at the Heidelberg Ion-Beam Therapy Center, Heidelberg. Species and isotope identification was accomplished combining energy loss and time-of-flight measurements. Differential yields and energy spectra of all fragments types were recorded between 0° and 20° with respect to the primary beam direction.

  12. Motion of a helical vortex filament in superfluid 4He under the extrinsic form of the local induction approximation

    NASA Astrophysics Data System (ADS)

    Van Gorder, Robert A.

    2013-08-01

    Very recently, Shivamoggi ["Vortex motion in superfluid 4He: Reformulation in the extrinsic vortex-filament coordinate space," Phys. Rev. B 84, 012506 (2011)], 10.1103/PhysRevB.84.012506 studied the extrinsic form of the local induction approximation (LIA) for the motion of a Kelvin wave on a vortex filament in superfluid 4He, and obtained some results in a cubic approximation. Presently, we study the motion of helical vortex filaments in superfluid 4He under the exact fully nonlinear LIA considered in potential form by Van Gorder ["Fully nonlinear local induction equation describing the motion of a vortex filament in superfluid 4He," J. Fluid Mech. 707, 585 (2012)], 10.1017/jfm.2012.308 and obtained from the Biot-Savart law through the equations of Hall and Vinen ["The rotation of liquid helium II. I. Experiments on the propagation of second sound in uniformly rotating helium II," Proc. R. Soc. London, Ser. A 238, 204 (1956)], 10.1098/rspa.1956.0214 including superfluid friction terms. Nonlinear dispersion relations governing the helical Kelvin wave on such a vortex filament are derived in exact form, from which we may exactly calculate the phase and group velocity of the Kelvin wave. With this, we classify the motion of a helical Kelvin wave on a vortex filament under the LIA. The dispersion relations and results, which follow are exact in nature, in contrast to most results in the literature, which are usually numerical approximations. As such, our results accurately capture the qualitative behavior of the Kelvin waves under the LIA. Extensions to other frameworks are discussed.

  13. Quasifree Lambda, Sigma^0, and Sigma^- electroproduction from 1,2H, 3,4He, and Carbon

    SciTech Connect

    F. Dohrmann; A. Ahmidouch; C.S. Armstrong; J. Arrington; R. Asaturyan; S. Avery; K. Bailey; H. Bitao; H. Breuer; D.S. Brown; R. Carlini; J. Cha; N. Chant; E. Christy; A. Cochran; L. Cole; J. Crowder; S. Danagoulian; M. Elaasar; R. Ent; H. Fenker; Y. Fujii; L. Gan; K. Garrow; D.F. Geesaman; P. Gueye; K. Hafidi; W. Hinton; H. Juengst; C. Keppel; Y. Liang; J.H. Liu; A. Lung; D. Mack; P. Markowitz; J. Mitchell; T. Miyoshi; H. Mkrtchyan; S.K. Mtingwa; B. Mueller; G. Niculescu; I. Niculescu; D. Potterveld; B.A. Raue; P.E. Reimer; J. Reinhold; J. Roche; M. Sarsour; Y. Sato; R.E. Segel; A. Semenov; S. Stepanyan; V. Tadevosyan; S. Tajima; L. Tang; A. Uzzle; S. Wood; H. Yamaguchi; C. Yan; L. Yuan; B. Zeidman; M. Zeier; B. Zihlmann

    2007-07-30

    Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He, 4He, and Carbon targets has been measured at Jefferson Laboratory. The quasifree angular distributions of Lambda and Sigma hyperons were determined at Q^2= 0.35(GeV/c)^2 and W= 1.91GeV. Electroproduction on hydrogen was measured at the same kinematics for reference.

  14. Production of {sup 4}He, {sup 3}He, and tritium from Be irradiated in FFTF-MOTA-2B

    SciTech Connect

    Greenwood, L.R.

    1998-03-01

    The production of {sup 4}He, {sup 3}He, and tritium has been calculated for beryllium irradiated in the Materials Open Test Assembly (MOTA)-2B experiment in the Fast Flux Test Facility (FFTF). Reaction rates were based on adjusted neutron spectra determined from reactor dosimetry measurements at seven different elevations in the irradiation assembly. Equations are given so that gas production, dpa, and neutron fluences can be calculated for any specific elevation in the MOTA-2B assembly.

  15. Are high 3He/4He ratios in oceanic basalts an indicator of deep-mantle plume components?

    USGS Publications Warehouse

    Meibom, A.; Anderson, D.L.; Sleep, Norman H.; Frei, R.; Chamberlain, C.P.; Hren, M.T.; Wooden, J.L.

    2003-01-01

    The existence of a primordial, undegassed lower mantle reservoir characterized by high concentration of 3He and high 3He/4He ratios is a cornerstone assumption in modern geochemistry. It has become standard practice to interpret high 3He/4He ratios in oceanic basalts as a signature of deep-rooted plumes. The unfiltered He isotope data set for oceanic spreading centers displays a wide, nearly Gaussian, distribution qualitatively similar to the Os isotope (187Os/188 Os) distribution of mantle-derived Os-rich alloys. We propose that both distributions are produced by shallow mantle processes involving mixing between different proportions of recycled, variably aged radiogenic and unradiogenic domains under varying degrees of partial melting. In the case of the Re-Os isotopic system, radiogenic mid-ocean ridge basalt (MORB)-rich and unradiogenic (depleted mantle residue) endmembers are constantly produced during partial melting events. In the case of the (U+Th)-He isotope system, effective capture of He-rich bubbles during growth of phenocryst olivine in crystallizing magma chambers provides one mechanism for 'freezing in' unradiogenic (i.e. high 3He/4He) He isotope ratios, while the higher than chondritic (U+Th)/He elemental ratio in the evolving and partially degassed MORB melt provides the radiogenic (i.e. low 3He/4He) endmember. If this scenario is correct, the use of He isotopic signatures as a fingerprint of plume components in oceanic basalts is not justified. Published by Elsevier Science B.V.

  16. The structure of mixed {sup 3}He-{sup 4}He droplets doped with OCS: A density functional approach

    SciTech Connect

    Leal, Antonio; Mateo, David; Pi, Martí; Barranco, Manuel; Navarro, Jesús

    2013-11-07

    We have investigated the structure and energetics of mixed {sup 3}He-{sup 4}He droplets doped with a carbonyl sulfide molecule within a density functional approach considering a small but finite temperature of 0.1 K. The molecule is treated as an external field to which the helium droplet is attached. The energetics and appearance of these droplets are discussed for selected numbers of helium atoms, identifying the first magic numbers of the fermionic component.

  17. Measurement of the sup 3 He( n ,. gamma. ) sup 4 He cross section at thermal neutron energies

    SciTech Connect

    Wolfs, F.L.H.; Freedman, S.J.; Nelson, J.E. ); Dewey, M.S.; Greene, G.L. )

    1989-12-18

    We have measured the cross section for radiative capture of thermal neutrons on {sup 3}He. The measured cross section of 54{plus minus}6 {mu}b is used to estimate the astrophysical {ital S} factor for the reaction {sup 3}He({ital p},{ital e}{sup +}{nu}){sup 4}He which gives rise to high-energy neutrinos from the Sun.

  18. 142Nd/144Nd inferences on the nature and origin of the source of high 3He/4He magmas

    NASA Astrophysics Data System (ADS)

    de Leeuw, G. A. M.; Ellam, R. M.; Stuart, F. M.; Carlson, R. W.

    2017-08-01

    High-precision measurements of 142Nd/144Nd in picrites from the Baffin Bay region that contain the highest 3He/4He ratios yet measured in terrestrial mantle-derived rocks are indistinguishable from the value measured in the terrestrial standard and other modern mantle-derived rocks. The Baffin Island lavas are distinguished from other hotspot lavas by their unusually high 3He/4He and 182W/184W ratios, but their Sr, 142Nd, 143Nd, Hf, and Pb isotopic signatures overlap the values measured in North Atlantic MORB. These features imply either that the mantle source region of high 3He/4He magmas carries the lithophile isotopic signatures of incompatible element depletion, or that the He isotope signature of this source is decoupled from the lithophile isotope tracers in the magmas. The coupled 142Nd-143Nd data are consistent with the magma source acquiring the incompatible element depletion during, or shortly after, Earth formation if the bulk-Earth has a 142Nd/144Nd ratio more similar to the average measured for enstatite chondrites than modern terrestrial rocks. If Earth's initial 142Nd/144Nd was higher than the average of enstatite chondrites, the data are consistent with the traditional interpretation that the depleted-mantle reservoir was formed through the extraction of an incompatible-element-rich reservoir, such as continental crust, after the circa 4 Ga extinction of 146Sm. This explanation, however, fails to account for the high 3He/4He. The Nd isotopic composition of the picrites could reflect a dominant contribution from the incompatible element depleted source of North Atlantic MORB, overprinted by a small (10-20%) contribution from a mantle source with He concentrations at least ten times higher than the depleted mantle along with W isotopic compositions substantially higher than typical of mantle-derived rocks.

  19. Secondary radiation measurements for particle therapy applications: nuclear fragmentation produced by (4)He ion beams in a PMMA target.

    PubMed

    Marafini, M; Paramatti, R; Pinci, D; Battistoni, G; Collamati, F; De Lucia, E; Faccini, R; Frallicciardi, P M; Mancini-Terracciano, C; Mattei, I; Muraro, S; Piersanti, L; Rovituso, M; Rucinski, A; Russomando, A; Sarti, A; Sciubba, A; Solfaroli Camillocci, E; Toppi, M; Traini, G; Voena, C; Patera, V

    2017-02-21

    Nowadays there is a growing interest in particle therapy treatments exploiting light ion beams against tumors due to their enhanced relative biological effectiveness and high space selectivity. In particular promising results are obtained by the use of (4)He projectiles. Unlike the treatments performed using protons, the beam ions can undergo a fragmentation process when interacting with the atomic nuclei in the patient body. In this paper the results of measurements performed at the Heidelberg Ion-Beam Therapy center are reported. For the first time the absolute fluxes and the energy spectra of the fragments-protons, deuterons, and tritons-produced by (4)He ion beams of 102, 125 and 145 MeV u(-1) energies on a poly-methyl methacrylate target were evaluated at different angles. The obtained results are particularly relevant in view of the necessary optimization and review of the treatment planning software being developed for clinical use of (4)He beams in clinical routine and the relative bench-marking of Monte Carlo algorithm predictions.

  20. Secondary radiation measurements for particle therapy applications: nuclear fragmentation produced by 4He ion beams in a PMMA target

    NASA Astrophysics Data System (ADS)

    Marafini, M.; Paramatti, R.; Pinci, D.; Battistoni, G.; Collamati, F.; De Lucia, E.; Faccini, R.; Frallicciardi, P. M.; Mancini-Terracciano, C.; Mattei, I.; Muraro, S.; Piersanti, L.; Rovituso, M.; Rucinski, A.; Russomando, A.; Sarti, A.; Sciubba, A.; Solfaroli Camillocci, E.; Toppi, M.; Traini, G.; Voena, C.; Patera, V.

    2017-02-01

    Nowadays there is a growing interest in particle therapy treatments exploiting light ion beams against tumors due to their enhanced relative biological effectiveness and high space selectivity. In particular promising results are obtained by the use of 4He projectiles. Unlike the treatments performed using protons, the beam ions can undergo a fragmentation process when interacting with the atomic nuclei in the patient body. In this paper the results of measurements performed at the Heidelberg Ion-Beam Therapy center are reported. For the first time the absolute fluxes and the energy spectra of the fragments—protons, deuterons, and tritons—produced by 4He ion beams of 102, 125 and 145 MeV u-1 energies on a poly-methyl methacrylate target were evaluated at different angles. The obtained results are particularly relevant in view of the necessary optimization and review of the treatment planning software being developed for clinical use of 4He beams in clinical routine and the relative bench-marking of Monte Carlo algorithm predictions.

  1. A direct measurement of the 6Li(n,t)4He cross section at sub-thermal neutron energy

    NASA Astrophysics Data System (ADS)

    Yue, A.; Dewey, M.; Gilliam, D.; Nico, J.; Greene, G.; Laptev, A.

    2014-09-01

    The thermal neutron capture cross section for the 6Li(n,t)4He reaction is an important neutron cross section standard. Yet few measurements of it have been performed and the ENDF/B-VII recommended value of (938 . 5 +/- 1 . 3) b is based heavily on measurements performed at higher energies. The first absolute, direct measurement of the 6Li(n,t)4He cross section at sub-thermal neutron energy has been performed at the NIST Center for Neutron Research. An alpha-gamma counter was used to measure the absolute neutron fluence of a monoenergetic neutron beam to sub-0.1% precision. The alpha-gamma counter used a thick, totally absorbing target of 10B-enriched boron carbide. The rate of absorbed neutrons was determined by counting the 478 keV 10B(n, γ)7Li gamma rays with calibrated high-purity germanium detectors. Simultaneously, the absolute rate of neutron-induced charged particles was measured for three thin 6Li targets of known density with a defined solid-angle counter. Using the known density of the 6Li targets and measurements of the rate of charged particles from the 6Li targets, the fluence of the neutron beam, and the energy of the neutron beam, we determine the 6Li(n,t)4He cross section at En = 3 . 3 meV to 0.3% uncertainty.

  2. Effect of three-body interactions on the zero-temperature equation of state of HCP solid 4He

    NASA Astrophysics Data System (ADS)

    Barnes, Ashleigh L.; Hinde, Robert J.

    2017-03-01

    Previous studies have pointed to the importance of three-body interactions in high density 4He solids. However the computational cost often makes it unfeasible to incorporate these interactions into the simulation of large systems. We report the implementation and evaluation of a computationally efficient perturbative treatment of three-body interactions in hexagonal close packed solid 4He utilizing the recently developed nonadditive three-body potential of Cencek et al. This study represents the first application of the Cencek three-body potential to condensed phase 4He systems. Ground state energies from quantum Monte Carlo simulations, with either fully incorporated or perturbatively treated three-body interactions, are calculated in systems with molar volumes ranging from 21.3 cm3/mol down to 2.5 cm3/mol. These energies are used to derive the zero-temperature equation of state for comparison against existing experimental and theoretical data. The equations of state derived from both perturbative and fully incorporated three-body interactions are found to be in very good agreement with one another, and reproduce the experimental pressure-volume data with significantly better accuracy than is obtained when only two-body interactions are considered. At molar volumes below approximately 4.0 cm3/mol, neither two-body nor three-body equations of state are able to accurately reproduce the experimental pressure-volume data, suggesting that below this molar volume four-body and higher many-body interactions are becoming important.

  3. STUDY OP THE 12C(α, γ)16O REACTION BY BREAKUP OF A 16O -BEAM AT 100 MeV/A

    NASA Astrophysics Data System (ADS)

    Tatischeff, V.; Kiener, J.; Aguer, P.; Angulo-Perez, C.; Bogaert, G.; Coc, A.; Disdier, D.; Ichihara, T.; Kraus, L.; Lefebvre, A.; Linck, I.; Mittig, W.; Motobayashi, T.; Oliveira, F.; Roussel-Chomaz, P.; Stephan, C.; Thibaud, J. P.

    We present some preliminary calculations on cross sections for the breakup of 16O around 100 MeV/A with emphasis on the effect of nuclear breakup on the angular distributions. Underlying the results of these calculations, the possibilities and problems of extracting the astrophysical S-factor for the 12C(α, γ)16O reaction at very low energies are discussed. Some considerations on the experimental conditions for a 16O breakup experiment aiming at this astrophysical information, are given.

  4. C3H8 and C3H4 in Titan's atmosphere

    NASA Technical Reports Server (NTRS)

    Maguire, W. C.; Hanel, R. A.; Jennings, D. E.; Kunde, V. G.; Samuelson, R. E.

    1981-01-01

    Four bands of propane C3H8 and two of methyl acetylene C3H4 have been identified in the Voyager IR spectrum of Titan. Stratospheric abundances of 2 x 10 to the -5 for C3H8 and 3 x 10 to the -8 for C3H4 have been determined for the mid-latitude region. A feature at 1,154/cm, previously assigned solely to CH3D, is now identified at least in part due to C3H8.

  5. Static and thermodynamic properties of low-density supercritical 4He-breakdown of the Feynman-Hibbs approximation.

    PubMed

    Kowalczyk, Piotr; Brualla, Lorenzo; Gauden, Piotr A; Terzyk, Artur P

    2009-10-28

    We study the applicability of the semiclassical Feynman and Hibbs (FH) (second-order or fourth-order) effective potentials to the description of the thermodynamic properties of quantum fluids at finite temperatures. First, we use path integral Monte Carlo (PIMC) simulations to estimate the thermodynamic/static properties of our model quantum fluid, i.e. low-density 4He at 10 K. With PIMC we obtain the experimental equation of state, the single-particle mean kinetic energy, the single-particle density matrix and the single-particle momentum distribution of this system at low densities. We show that our PIMC results are in full agreement with experimental data obtained with deep inelastic neutron scattering at high momentum transfers (D. Colognesi, C. Andreani, R. Senesi, Europhys. Lett., 2000, 50, 202). As expected, in this region of the 4He phase diagram, quantum effects modify the width of the single-particle momentum distribution but do not alter its Gaussian shape. Knowing the exact values of density, pressure and single-particle mean kinetic energy for our model quantum fluid, we investigate the limitations of the semiclassical FH effective potentials. We show that commonly used 'short-time' approximations to the high-temperature density matrix due to Feynman and Hibbs can only be applied in a very limited range of the 4He phase diagram. We found that FH effective potentials reproduce the experimental densities of 4He at 10 K for Lambda/a < 0.45 (Lambda = 2.73 A denotes the thermal de Broglie wavelength, a = rho(-1/3) is the mean nearest-neighbor distance in the fluid and rho denotes fluid density). Moreover, semiclassical FH effective potentials are able to correctly predict the single-particle mean kinetic energy of 4He at 10 K in a very limited range of fluid densities, i.e.Lambda/a < 0.17. We show that the ad hoc application of the semiclassical FH effective potentials for the calculation of the thermodynamic properties of dense liquid-like para

  6. Production of thin targets by implantation for the measurement of the 16O + 16O elastic scattering below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Silva, H.; Cruz, J.; Sánchez-Benítez, A. M.; Santos, C.; Luís, H.; Fonseca, M.; Jesus, A. P.

    2017-09-01

    In recent decades, the processes of fusion of 16O were studied both theoretically and experimentally. However, the theoretical calculations are unable to fit both elastic scattering cross sections and fusion S-factors. The use of 16O thin transmission targets is required to measure the elastic forward scattering 16O + 16O reaction. The areal density of the target must be high to maximize the reaction products yields, but not so high as to allow a correct calculation of the effective beam energy. Besides this, the target must withstand beam interactions without noticeable deterioration, and contaminants must be minimal. In this study, the production of thin targets is performed with an innovative technique. Beam characterization and preliminary spectrum for the elastic scattering are also presented, showing the suitability of these targets for the proposed reaction.

  7. Peculiarities of the 16O(α, α) 16O 3.045 Me V resonance scattering and its application to investigation of oxygen in silicon

    NASA Astrophysics Data System (ADS)

    Soroka, V. I.; Artsimovich, M. V.; Lobach, I. Yu.; Mogilnik, I. F.; Pavlovich, V. N.; Tokarevsky, V. V.; Kudriavtsev, E. M.; Romanjuk, B. N.

    1993-11-01

    The elastic scattering of alpha particles by oxygen in the vicinity of the 3.045 MeV resonance was studied with the aim of its use in nuclear microanalysis. The 16O(α, α) 16O resonance scattering was used to investigate the theoretically predicted effect of resonant laser-induced diffusion of impurities in crystals and to determine the lattice site location of oxygen in silicon using the channelling technique.

  8. Multichannel study of the {sup 13}C({alpha},n){sup 16}O and {sup 16}O(n,{gamma}){sup 17}O reactions

    SciTech Connect

    Dufour, M.; Descouvemont, P.

    2005-07-01

    The {sup 13}C({alpha},n){sup 16}O reaction is investigated in a microscopic two-cluster model with an effective interaction recently developed for transfer reactions. The wave functions are defined in the generator coordinate method. The basis includes all {sup 13}C+{alpha} and {sup 16}O+n channels with {sup 13}C and {sup 16}O described in the p shell. Particle-hole excitations in the sd shell are also taken into account in order to include the {sup 16}O(3{sup -})+n channel. The {sup 17}O spectroscopy is in good agreement with experiment. In particular, the width of the astrophysically relevant 1/2{sub 2}{sup +} state is well reproduced ({gamma}=121 keV as compared to the experimental value {gamma}=124{+-}12 keV). The calculation of the {sup 13}C({alpha},n){sup 16}O S factor shows the importance of the 3/2{sub 3}{sup +} resonance, and provides S(0.2 MeV)=2.1x10{sup 6} MeV b, slightly lower than the NACRE recommended value (2.5x10{sup 6} MeV b). The same model is applied to the {sup 16}O(n,{gamma}){sup 17}O radiative-capture reaction at thermal and astrophysical energies.

  9. Photodisintegration of /sup 3/H and /sup 3/He. [Threshold to 25 MeV

    SciTech Connect

    Faul, D.D.

    1980-09-01

    The photoneutron cross sections for /sup 3/H and /sup 3/He have been measured from threshold to approx. 25 MeV with monoenergetic photons from the annihilation in flight of fast positrons at the LLL Electron-Positron Linear Accelerator facility. These reactions include the two-body breakup of /sup 3/H and the three-body breakup of both /sup 3/H and /sup 3/He; these measurements for /sup 3/H are the first to span the energy region across the peaks of the cross sections. An efficient BF/sub 3/-tube-and-paraffin neutron detector and high-pressure gaseous samples of several moles each (the activity of the /sup 3/H sample was approx. 200,000 Ci) were employed in these measurements. Measurements on /sup 16/O and /sup 2/H also were performed to verify the absolute cross-section scale. The results, when compared with each other and with results for the two-body breakup cross section for /sup 3/He from the literature, show that the two-body breakup cross sections for /sup 3/H and /sup 3/He have nearly the same shape, but the one for /sup 3/He lies lower in magnitude; the three-body breakup cross section for /sup 3/He lies higher in magnitude and is broader in the peak region and also rises less sharply from threshold than that for /sup 3/H; and these measured differences between the cross sections for the breakup modes largely compensate in their sum, so that the total photon absorption cross sections for /sup 3/H and /sup 3/He are nearly the same in both size and shape at energies near and above their peaks. Theoretical results from the literature disagree with the experimental results to a certain extent over the entire photon-energy region for which the photoneutron cross sections were measured. 50 figures, 7 tables.

  10. Analysis of the scintillation mechanism in a pressurized {sup 4}He fast neutron detector using pulse shape fitting

    SciTech Connect

    Kelley, R.P. Ray, H.; Jordan, K.A.; Murer, D.

    2015-03-15

    An empirical investigation of the scintillation mechanism in a pressurized {sup 4}He gas fast neutron detector was conducted using pulse shape fitting. Scintillation signals from neutron interactions were measured and averaged to produce a single generic neutron pulse shape from both a {sup 252}Cf spontaneous fission source and a (d,d) neutron generator. An expression for light output over time was then developed by treating the decay of helium excited states in the same manner as the decay of radioactive isotopes. This pulse shape expression was fitted to the measured neutron pulse shape using a least-squares optimization algorithm, allowing an empirical analysis of the mechanism of scintillation inside the {sup 4}He detector. A further understanding of this mechanism in the {sup 4}He detector will advance the use of this system as a neutron spectrometer. For {sup 252}Cf neutrons, the triplet and singlet time constants were found to be 970 ns and 686 ns, respectively. For neutrons from the (d,d) generator, the time constants were found to be 884 ns and 636 ns. Differences were noted in the magnitude of these parameters compared to previously published data, however the general relationships were noted to be the same and checked with expected trends from theory. Of the excited helium states produced from a {sup 252}Cf neutron interaction, 76% were found to be born as triplet states, similar to the result from the neutron generator of 71%. The two sources yielded similar pulse shapes despite having very different neutron energy spectra, validating the robustness of the fits across various neutron energies.

  11. Analysis of the scintillation mechanism in a pressurized 4He fast neutron detector using pulse shape fitting

    NASA Astrophysics Data System (ADS)

    Kelley, R. P.; Murer, D.; Ray, H.; Jordan, K. A.

    2015-03-01

    An empirical investigation of the scintillation mechanism in a pressurized 4He gas fast neutron detector was conducted using pulse shape fitting. Scintillation signals from neutron interactions were measured and averaged to produce a single generic neutron pulse shape from both a 252Cf spontaneous fission source and a (d,d) neutron generator. An expression for light output over time was then developed by treating the decay of helium excited states in the same manner as the decay of radioactive isotopes. This pulse shape expression was fitted to the measured neutron pulse shape using a least-squares optimization algorithm, allowing an empirical analysis of the mechanism of scintillation inside the 4He detector. A further understanding of this mechanism in the 4He detector will advance the use of this system as a neutron spectrometer. For 252Cf neutrons, the triplet and singlet time constants were found to be 970 ns and 686 ns, respectively. For neutrons from the (d,d) generator, the time constants were found to be 884 ns and 636 ns. Differences were noted in the magnitude of these parameters compared to previously published data, however the general relationships were noted to be the same and checked with expected trends from theory. Of the excited helium states produced from a 252Cf neutron interaction, 76% were found to be born as triplet states, similar to the result from the neutron generator of 71%. The two sources yielded similar pulse shapes despite having very different neutron energy spectra, validating the robustness of the fits across various neutron energies.

  12. High pressure line shapes of the Rb D1 and D2 lines for 4He and 3He collisions

    NASA Astrophysics Data System (ADS)

    Miller, Wooddy S.; Rice, Christopher A.; Hager, Gordon D.; Rotondaro, Mathew D.; Berriche, Hamid; Perram, Glen P.

    2016-11-01

    Line shapes for the Rb D1 (51/2 2S ↔ 51/2 2P) and D2 (51/2 2S ↔ 53/2 2P) transitions with 4He and 3He collisions at pressures of 500-15,000 Torr and temperatures of 333-533 K have been experimentally observed and compared to predictions from the Anderson-Talman theory. The ground X1/2 + 2Σ and excited A1/2 + 2Π, A3/2 2Π, and B1/2 + 2Σ potential energy surfaces required for the line shape predictions have been calculated using a one-electron pseudo-potential technique. The observed collision induced shift rates for 4He are dramatically higher for the D1 line, 4.60±0.12 MHz/Torr, than the D2 line, 0.20±0.14 MHz/Torr. The asymmetry is somewhat larger for the D1 line and has the same sign as the shifting rate. The 3He broadening rate for the D2 line is 4% larger than the 4He rate, and 14% higher for the D1 line, reflecting the higher relative speed. The calculated broadening rates are systematically larger than the observed rates by 1.1-3.2 MHz/Torr and agree within 14%. The primary focus of the current work is to characterize the high pressure line shapes, focusing on the non-Lorentzian features far from line center. In the far wing, the cross-section decreases by more than 4 orders of magnitude, with a broad, secondary maximum in the D2 line near 735 nm. The potentials do not require empirical modification to provide excellent quantitative agreement with the observations. The dipole moment variation and absorption Boltzmann factor is critical to obtaining strong agreement in the wings.

  13. Model-independent analysis of Airy structures in the {sup 16}O+{sup 12}C and {sup 16}O+{sup 16}O elastic scattering differential cross sections at 13-22 MeV/nucleon

    SciTech Connect

    Korda, V. Yu.; Molev, A. S.; Klepikov, V. F.; Korda, L. P.

    2009-02-15

    We present the results of the model-independent analysis of Airy structures in the {sup 16}O+{sup 12}C and {sup 16}O+{sup 16}O elastic scattering differential cross sections at 13-22 MeV/nucleon. The analysis has been performed with help of a procedure based on the application of the evolutionary algorithm, which enables us to extract the nuclear part of the scattering matrix S{sub N}(l) as a complex function of angular momentum directly from the scattering data. Contrary to the commonly used model approaches, our procedure gives the better fits and leads to the S{sub N}(l) representations defined by the moduli and the nuclear phases exhibiting smooth monotonic dependencies on l.

  14. Adsorption of superfluid 4He films on planar heavy-alkali metals studied with the Orsay-Trento density functional

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek

    2003-04-01

    The wetting of planar surfaces of alkali metals (Cs, Rb, K, and Na) by superfluid 4He films at T=0 K is theoretically studied. Calculations have been carried out by using the Orsay-Trento nonlocal density functional and the adsorption potential of Chizmeshya-Cole-Zaremba. Surface tensions and contact angles are determined for several approximations. We find that the conclusion on the wetting of an Rb substrate is sensible to the gradient-gradient term in the functional and the softness of the He-metal interaction.

  15. Analysis of states in {sup 13}C populated in {sup 9}Be + {sup 4}He resonant scattering

    SciTech Connect

    Freer, M.; Ashwood, N. I.; Curtis, N.; Kokalova, Tz.; Wheldon, C.; Di Pietro, A.; Figuera, P.; Fisichella, M.; Scuderi, V.; Torresi, D.; Grassi, L.; Jelavic Malenica, D.; Koncul, M.; Mijatovic, T.; Prepolec, L.; Skukan, N.; Soic, N.; Szilner, S.; Tokic, V.; Milin, M.

    2011-09-15

    Measurements of {sup 9}Be + {alpha} resonant scattering have been performed using the thick-target approach with a {sup 4}He gas volume and a large-area silicon strip detector. {sup 9}Be beam energies in the range 12 to 21.4 MeV were used to measure the {sup 13}C excitation energy spectrum between 13.2 and 16.2 MeV. An R-matrix analysis has been performed to characterize the spins and widths of {sup 13}C resonances, some of which have been proposed to be associated with a 3{alpha}+n molecular band.

  16. Relationship between 3He/4He ratios and subduction of the Philippine Sea plate beneath southwest Japan

    NASA Astrophysics Data System (ADS)

    Umeda, Koji; Kusano, Tomohiro; Asamori, Koichi; McCrank, Glen F.

    2012-10-01

    Regional and local variations in mantle helium provide insight into the coupling of mantle-crust tectonics, and heat and/or mass transfer from the Earth's interior. In order to further elucidate the geographic distribution of3He/4He ratios in southwest Japan, the data from a total of 924 sites were compiled and synthesized. These include data from 48 additional hot spring and drinking water well sites on the northern Kyushu Island and in the northern Chugoku region. There appears to be good correlation between variations in helium isotope ratios and the geophysical evidence used to determine the configuration of the subducting Philippine Sea plate (PHS). Seismological studies reveal that the leading edge of the aseismic slab does not extend to the northern Chugoku region nor to the Osaka Bay area, where gas samples with significantly elevated 3He/4He ratios occur. This is consistent with a mantle-derived helium in these areas, from melts and/or mantle fluids ascribed to upwelling asthenosphere without being hindered by the descending PHS slab. In contrast, gas samples in the regions where the overriding crust comes into direct contact with the subducting PHS are dominated by radiogenic helium derived from the crust because of the absence of a mantle wedge, the most plausible source of mantle helium. Owing to the abrupt changes in the seismicity and focal mechanisms of intraplate earthquakes, the PHS is considered to have slab tears beneath the Kii Channel and/or the eastern Kii Peninsula oriented in a NW-SE direction. However, the lenear alignment of anomalously high3He/4He ratios does not appear to be NW-SE trending along the assumed slab tears but rather forms an broad, ENE-WSW trending zone between the tears where low-frequency events occur. The emanation of gas with elevated3He/4He ratios in the central peninsula can be explained by the upward mobilization of mantle volatiles derived from the mantle wedge above the PHS and/or transferred from the hydrated slab

  17. Parity-violating electron scattering from 4He and the strange electric form factor of the nucleon.

    PubMed

    Aniol, K A; Armstrong, D S; Averett, T; Benaoum, H; Bertin, P Y; Burtin, E; Cahoon, J; Cates, G D; Chang, C C; Chao, Y-C; Chen, J-P; Choi, Seonho; Chudakov, E; Craver, B; Cusanno, F; Decowski, P; Deepa, D; Ferdi, C; Feuerbach, R J; Finn, J M; Frullani, S; Fuoti, K; Garibaldi, F; Gilman, R; Glamazdin, A; Gorbenko, V; Grames, J M; Hansknecht, J; Higinbotham, D W; Holmes, R; Holmstrom, T; Humensky, T B; Ibrahim, H; de Jager, C W; Jiang, X; Kaufman, L J; Kelleher, A; Kolarkar, A; Kowalski, S; Kumar, K S; Lambert, D; LaViolette, P; LeRose, J; Lhuillier, D; Liyanage, N; Margaziotis, D J; Mazouz, M; McCormick, K; Meekins, D G; Meziani, Z-E; Michaels, R; Moffit, B; Monaghan, P; Munoz-Camacho, C; Nanda, S; Nelyubin, V; Neyret, D; Paschke, K D; Poelker, M; Pomatsalyuk, R; Qiang, Y; Reitz, B; Roche, J; Saha, A; Singh, J; Snyder, R; Souder, P A; Subedi, R; Suleiman, R; Sulkosky, V; Tobias, W A; Urciuoli, G M; Vacheret, A; Voutier, E; Wang, K; Wilson, R; Wojtsekhowski, B; Zheng, X

    2006-01-20

    We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q2 = 0.091 GeV2 . From these data, for the first time, the strange electric form factor of the nucleon G(E)s can be isolated. The measured asymmetry of A(PV) = (6.72 +/- 0.84(stat) +/- 0.21(syst) x 10(-6) yields a value of G(E)s = -0.038 +/- 0.042(stat) +/- 0.010(syst), consistent with zero.

  18. Quadrupole contributions to 10,11B + 16O elastic scattering

    NASA Astrophysics Data System (ADS)

    Parks, L. A.; Stanley, D. P.; Courtney, L. H.; Kemper, K. W.

    1980-01-01

    Elastic scattering angular distributions have been measured for the systems 10B + 16O at EL=33.7, 41.6, and 49.5 MeV and 11B + 16O at EL=41.6 and 49.5 MeV. The 10B and 11B data are oscillatory and similar for angles less than 50° c.m. For angles greater than 50° c.m., the oscillations in the 10B data are damped and the data stop decreasing with increasing angle. Elastic scattering angular distributions have been calculated for 10,11B + 16O with the coupling to the ground-state quadrupole moment included explicitly. Potentials which describe the scattering are extracted with the double folding model. It is found that the quadrupole coupling is necessary to explain the difference in 10B and 11B scattering from 16O. NUCLEAR REACTIONS 16O (10B, 10B) 16O, EL=33.7, 41.6, and 49.5 MeV, 16O (11B, 11B) 16O, EL=41.6 and 49.5 MeV. Measured σ(θ), deduced Woods-Saxon, and double-folding model parameters. Coupled channels calculations for the ground-state quadrupole moment contributions.

  19. Existence of an 16O-rich gaseous reservoir in the solar nebula.

    PubMed

    Krot, Alexander N; McKeegan, Kevin D; Leshin, Laurie A; MacPherson, Glenn J; Scott, Edward R D

    2002-02-08

    Carbonaceous chondrite condensate olivine grains from two distinct petrographic settings, calcium-aluminum-rich inclusion (CAI) accretionary rims and amoeboid olivine aggregates (AOAs), are oxygen-16 (16O) enriched at the level previously observed inside CAIs. This requires that the gas in the nebular region where these grains condensed was 16O-rich. This contrasts with an 16O-poor gas present during the formation of chondrules, suggesting that CAIs and AOAs formed in a spatially restricted region of the solar nebula containing 16O-rich gas. The 16O-rich gas composition may have resulted either from mass-independent isotopic chemistry or from evaporation of regions with enhanced dust/gas ratios, possibly in an X-wind environment near the young Sun.

  20. Wetting of potassium surfaces by superfluid 4He: A study using variational properties of the chemical potential

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek

    2000-08-01

    The wetting of planar surfaces of K by superfluid 4He films at T=0 K is theoretically studied. In order to examine the consistency of numerical results, new variational properties of the chemical potential μ are derived. Two substrate-adsorbate interactions are analyzed: (a) the standard ``3-9'' one and (b) the more elaborated potential recently proposed by Chizmeshya, Cole, and Zaremba (CCZ). New results calculated within the framework of two different nonlocal density functionals (namely, those known as the Orsay-Paris and Orsay-Trento formalisms) are reported. It is demonstrated that the numerical solutions obtained from the theoretical equations verify with high accuracy the derived variational conditions. The main output of this investigation is the finding that, for both analyzed adsorption potentials, thick enough helium films exhibit a positive square of the third-sound velocity. The wetting of a potassium substrate by superfluid 4He at T=0 K suggested by experimental data is guaranteed in the case of the recent CCZ potential.

  1. Hexagonal Close-Packed ^4{He} as Crystalline Multilayered Polytype: An Alternative for `Supersolid' or `Glassy-Like' Phase

    NASA Astrophysics Data System (ADS)

    Chishko, K. A.; Antsygina, T. N.; Poltavskaya, M. I.

    2017-01-01

    We apply the model of a crystalline polytype built of close-packed 2D monoatomic basal planes with triangular lattice to interpret the anomalous thermodynamical and mechanical properties of solid hexagonal close-packed (HCP) ^4{He} . The polytype is a 3D stack of the basal planes, and its structure can be built from the simplest periodic packing (HCP, FCC, 4H, 5H, 6R, ldots etc.) up to random stacking fault system (RSFS) totally aperiodic in only c-direction perpendicular to the basal planes. RSFS is a crystal without microscopic translation symmetry along c-axis, i.e., entirely disordered in only one spatial direction. Despite of packing disorder, c-direction remains the crystallographic axis of third order at arbitrary sequence of the 2D plates in the whole stack. In a long-wave limit the HCP polytype can be treated as 3D anisotropic continuum, as a result its phonon spectrum and Helmholtz free energy have been calculated. The temperature dependence of the phonon pressure is calculated theoretically and compared with experimental data. A quantitative agreement between the theory and the experiment is achieved. Mechanical properties of ^4{He} crystals in the framework of the polytype model are briefly discussed.

  2. Measurement of the Fast Neutron Response for {sup 4}He Scintillation Detectors Using a Coincidence Scattering Method

    SciTech Connect

    Kelley, R.P.; Lewis, J.M.; Murer, D.; Enqvist, A.; Jordan, K.A.

    2015-07-01

    Previous work has measured the neutron response of pressurized {sup 4}He scintillation detectors, however these studies only examine the response as a function of incident neutron energy. Since the detection mechanism in {sup 4}He detectors is elastic scattering, and the interacting neutron will only deposit a fraction of its incident kinetic energy in the detector gas, an examination of the response of the detector output to deposited energy is necessary to transform these detectors into instruments for neutron spectrometry. Using a combined time-of-flight (TOF) and coincidence scattering method, this paper further characterizes the {sup 4}He light response to fast neutrons by examining the scintillation light yield as a function of deposited energy, measuring the light response up to 5 MeV. These {sup 4}He detectors are simple in design, and are manufactured by Arktis Radiation Detectors in several sizes. The specific model used in this experiment had an active volume 20 cm long with an inner diameter of 4.4 cm, giving a total active volume of 304 cm{sup 3}. The key components include the active volume, filled with 150 bar of helium-4 gas, and photomultiplier tubes (PMTs) mounted at either end of the active volume. The detector body is made of stainless steel. The detector response was experimentally measured using a two-detector coincidence arrangement with a {sup 252}Cf source. Two {sup 4}He detectors were vertically mounted, and the source was placed at a horizontal distance from the center of the bottom detector, forming a right angle. By requiring coincidence between the two detectors, it was confirmed that each neutron interacting in the second (top) detector must first have undergone a scattering interaction in the first (bottom) detector, and the time-of-flight (TOF) technique could then be used to determine the energy of the neutron as it traveled between the two detectors by the difference in time between the two detector events. More importantly, with

  3. Unified description of 6Li structure and deuterium-4He dynamics with chiral two- and three-nucleon forces

    DOE PAGES

    Hupin, Guillaume; Quaglioni, Sofia; Navratil, Petr

    2015-05-29

    Here, we provide a unified ab initio description of the 6Li ground state and elastic scattering of deuterium (d) on 4He (α) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of 6Li. The calculation reproduces the empirical binding energy of 6Li, yielding an asymptotic D- to S-state ratio of the 6Li wave function in the d+α configuration of –0.027, in agreement with a determination from 6Li–4He elastic scattering, but overestimates the excitation energy of the 3+more » state by 350 keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the 2H(α,γ)6Li radiative capture, responsible for the big-bang nucleosynthesis of 6Li.« less

  4. Unified description of ^{6}Li structure and deuterium-^{4}He dynamics with chiral two- and three-nucleon forces.

    PubMed

    Hupin, Guillaume; Quaglioni, Sofia; Navrátil, Petr

    2015-05-29

    We provide a unified ab initio description of the ^{6}Li ground state and elastic scattering of deuterium (d) on ^{4}He (α) using two- and three-nucleon forces from chiral effective field theory. We analyze the influence of the three-nucleon force and reveal the role of continuum degrees of freedom in shaping the low-lying spectrum of ^{6}Li. The calculation reproduces the empirical binding energy of ^{6}Li, yielding an asymptotic D- to S-state ratio of the ^{6}Li wave function in the d+α configuration of -0.027, in agreement with a determination from ^{6}Li-^{4}He elastic scattering, but overestimates the excitation energy of the 3^{+} state by 350 keV. The bulk of the computed differential cross section is in good agreement with data. These results endorse the application of the present approach to the evaluation of the ^{2}H(α,γ)^{6}Li radiative capture, responsible for the big-bang nucleosynthesis of ^{6}Li.

  5. Anomalous nonlinear attenuation of ultrasound in solid 4He in a torsional oscillator below 200 mK

    NASA Astrophysics Data System (ADS)

    Iwasa, I.; Goodkind, J. M.; Kojima, H.

    2014-12-01

    In order to elucidate the ultra-low temperature behavior of solid 4He, simultaneous measurements of longitudinal ultrasound (US) and torsional oscillation have been made. Changes in attenuation and velocity of US at 10 MHz have been measured in polycrystalline hcp 4He samples (0.3 or 20 ppm of 3He impurity) grown in a 1 kHz torsional oscillator (TO). In a 0.3 ppm 3He sample, the US attenuation and velocity were found to depend on the US drive voltage at temperatures below 70 mK where the anomalies in the TO frequency and dissipation were also observed. The US attenuation at low T (10 mK) decreased monotonically as the drive voltage was decreased but then remained small and constant as the drive voltage was increased again. The US velocity change at low T was negative with respect to the high-T (400 mK) value, contrary to the positive sign expected from the known variation in the shear modulus. In a 20 ppm 3He sample, both the US and TO anomalies shifted to 150 mK. The amplitude dependence and hysteresis of US attenuation were related to pinning of dislocations by 3He impurities, and nonlinear spatial variations of the amplitude of US pulses were derived.

  6. Frequency-dependent Study of Ultrapure Solid 4He by Using Rigid Double-pendulum Torsional Oscillator

    NASA Astrophysics Data System (ADS)

    Choi, Jaewon; Shin, Jaeho; Kim, Eunseong

    2015-03-01

    The physical origin of the period drop found in the torsional oscillator (TO) containing solid 4He was previously interpreted as the appearance of supersolidity. The current consensus is that the increase in the shear modulus leads to the period anomaly. Further studies show that the stiffening effect in TO can be amplified if a TO is not properly designed to be ``rigid.'' In this study, we designed a rigid double-pendulum TO. High purity solid 4He sample (0.6ppb) was grown by the block capillary method. The resonant period of TO starts to decrease from the empty cell data at 80mK. The ratio of the resonant period changes to the total mass loading are 3 . 8 ×10-5 and 2 . 6 ×10-4 for 1st and 2nd mode, respectively. Unlike recent experiment, we could not found a frequency-independent period drop. The upper bound for the putative supersolid fraction is less than 4 ×10-6 . The dissipation peak accompanied with the period drop was also analyzed with Cole-Cole plot and ωτ plot. We conclude that major contribution for the anomalous TO responses comes from the elastic effect.

  7. Onset of nanoscale dissipation in superfluid 4He at zero temperature: Role of vortex shedding and cavitation

    NASA Astrophysics Data System (ADS)

    Ancilotto, Francesco; Barranco, Manuel; Eloranta, Jussi; Pi, Martí

    2017-08-01

    Two-dimensional flow past an infinitely long cylinder of nanoscopic radius in superfluid 4He at zero temperature is studied using time-dependent density-functional theory. The calculations reveal two distinct critical phenomena for the onset of dissipation: (i) vortex-antivortex pair shedding from the periphery of the moving cylinder, and (ii) the appearance of cavitation in the wake, which possesses similar geometry to that observed experimentally for fast-moving micrometer-scale particles in superfluid 4He. The formation of cavitation bubbles behind the cylinder is accompanied by a sudden jump in the drag exerted on the moving cylinder by the fluid. Vortex pairs with the same circulation are occasionally emitted in the form of dimers, which constitute the building blocks for the Benard-von Karman vortex street structure observed in classical turbulent fluids and Bose-Einstein condensates. The cavitation-induced dissipation mechanism should be common to all superfluids that are self-bound and have a finite surface tension, which include the recently discovered self-bound droplets in ultracold Bose gases. These systems would provide an ideal testing ground for further exploration of this mechanism experimentally.

  8. Analytic Calculation of Temperature Error in Sidewall Thermometry Measurements near T_λ in ^4He Thermal Conductivity Cells

    NASA Astrophysics Data System (ADS)

    Zofka, M.; Boyd, S. T. P.; Kenkre, V. M.; Duncan, R. V.

    1996-03-01

    We report results of a simple analytical calculation of heat flow in a ^4He thermal conductivity cell. The cell has two isothermal anvils which are coaxial with the gravitational field. A coaxial cylindrical shell, or sidewall, of thermal conductivity 20 mWcm-1K-1, is between the two anvils and is sealed to them. ^4He is confined inside the vessel formed by the sidewall and the two anvils. We model the temperature field T in the sidewall. Kapitza boundary resistance is set constant. T in the helium column is approximated by the 1-d analytic solution. We model the error of sidewall thermometry Δ T as the temperature difference between the helium and the outer surface of the sidewall at a height z_probe. When the superfluid interface is well below z_probe, Δ T is very small. As the superfluid interface moves up in the cell, we find that Δ T increases sharply over a range of about 0.6 mm to a maximum value, then decreases slowly over about 2 cm to a relatively constant offset when the superfluid interface is well above z_probe. For a heat flux of Q=10-7 Wcm-2, Δ T maximizes at about 40 nK, and goes to a constant value of about 20 nK. We find Δ T to increase strongly with Q.

  9. Asymmetry in melting and growth relaxation of 4He crystals in superfluid after manipulation by acoustic radiation pressure

    NASA Astrophysics Data System (ADS)

    Nomura, Ryuji; Abe, Haruka; Okuda, Yuichi

    2017-02-01

    The relaxation dynamics of the crystal–superfluid interface of 4He after deformation induced by acoustic radiation pressure was investigated for various crystal orientations. The melting relaxation after growth was approximately 10 times slower than the growth relaxation after melting for vicinal surfaces and facets, while both relaxation times were consistent with each other for rough surfaces. The asymmetry in the time constant between the melting and growth of vicinal surfaces and facets can be qualitatively explained as the effect of superflow induced by local rapid interface motion, such as a quick rounding of facet edges of the 4He crystal. Rough surfaces move more isotropically and no significant local rapid interface motion is induced; therefore, their relaxation is likely to be symmetric with a minimal effect of superflow. While the growth relaxation was simply back to the initial shape in a single stage, the melting relaxation was much more complex with multiple stages and the exhibition of various anomalous shapes depending on temperature. Anomalous shapes such as needle-like shapes during melting have a larger curvature and higher energy and thus should have disappeared more quickly than the growth shape with a smaller curvature, but they were considerably stable and disappeared slowly. This counter-intuitive asymmetry suggests the significant role of superflow in the relaxation process.

  10. Transition from a 2D Degenerate Bose Liquid to 3D Superfluid in 4He Films Formed in Nanopores

    NASA Astrophysics Data System (ADS)

    Matsushita, Taku; Hieda, Mitsunori; Toda, Ryo; Inagaki, Shinji; Wada, Nobuo

    2017-10-01

    The phase transition mechanism in a new dimensional condition was studied for the 4He film formed in 3D nanopore where pores of 2.7 nm diameter are connected in 3D with a period of 5.5 nm. In the case of a very low superfluid onset temperature TSF at a low coverage, a sharp and large peak of the specific heat indicates the typical 3D transition of the 4He film. This is understood by comparing the relative lengths among the 3D and 2D mean atomic distances and the 3D connection length of the film. When the coverage is increased, these length relations are changed to a new dimensional condition. We observed a sharp peak at TSF of the 3D transition up to 1.1 K. For a thick film, we also observed a hump at TB, which is higher than TSF. The hump is attributed to a phase change to a 2D degenerate state with a finite amplitude but without a long range order in the phase of superfluid order parameters. This indicates a new type of transition at TSF from the 2D degenerate state to the 3D superfluid, which is essentially different from the Kosterlitz-Thouless transition.

  11. Analysis and theoretical modeling of the 18O enriched carbon dioxide spectrum by CRDS near 1.35 μm: (I) 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2

    NASA Astrophysics Data System (ADS)

    Kassi, S.; Karlovets, E. V.; Tashkun, S. A.; Perevalov, V. I.; Campargue, A.

    2017-01-01

    The room temperature absorption spectrum of 18O enriched carbon dioxide has been recorded by very high-sensitivity Cavity Ring Down spectroscopy between 6977 and 7918 cm-1 (1.43-1.26 μm). The achieved sensitivity (noise equivalent absorption αmin 8×10-11 cm-1) has allowed for the detection of more than 8600 lines belonging to 166 bands of eleven carbon dioxide isotopologues. Line intensities of the weakest observed transitions are on the order of 2×10-30 cm/molecule. In this first part, we present the results relative to the 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2 isotopologues. Their absorption lines were rovibrationally assigned on the basis of the predictions of their respective effective Hamiltonian model. Overall 5476 lines were measured and assigned to 93 bands. Forty nine of them, all belonging to 16O12C18O and 16O12C17O, are reported for the first time. The studied spectral region is formed by ΔP=10-12 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The spectroscopic parameters of 58 bands of 16O12C18O and 16O12C17O were determined from a fit of the measured line positions. An inter- and an intrapolyad resonance perturbation were identified and analyzed in the 16O12C18O spectrum. The comparison with the line positions and line intensities included in the AMES line list is discussed. Global fits of the line intensities were performed in order to (i) improve the ΔP=10 and 11 sets of the effective dipole moment parameters of 16O12C18O and the ΔP=11 set of parameters of 16O12C17O and (ii) derive for the first time the ΔP=10 and 12 parameters of 16O12C17O and 16O12C18O, respectively.

  12. 3H/3He ages, CFC ages and He isotopes in the fractured bedrock of the Mirror Lake Basin, NH

    NASA Astrophysics Data System (ADS)

    Torgersen, T.; Stute, M.; Drenkard, S.; Schlosser, P.; Busenberg, E.; Plummer, N.; Shapiro, A.

    2001-05-01

    Tritium/3He and CFC (chlorofluorocarbon) analyses were conducted on groundwater samples from the fractured bedrock and the overlying drift of Mirror Lake watershed in central New Hampshire. These groundwaters have a significant terrigenic helium component that increases with depth. The 3He/4He ratio of the terrigenic helium indicates the presence of two groundwater types. Where terrigenic sources of 3He are no more than 10 times the 3He signal produced by 3H decay (tritiogenic 3He), 3H/3He ages can be calculated. However, drift age profiles cannot be interpreted as recharge rates because the 2D, 2-layer coupled bedrock/drift system violates the simple homogeneous 1D conditions necessary to interpret age profiles as recharge rates. Secondly, while some agreement is seen between 3H/3He ages and CFC ages, the reconstruction of the 1963 'bomb' 3H peak yields a maximum that is significantly less (1/10) than expected. This apparent loss of 3H is cannot be attributed to dispersion or dual hydraulic conductivity but is consistent with the models of dual porosity. The data also demonstrate that '3H/3Hetri calibrated 4He ages' are invalid and cannot be used to extend the 'age' information contained in He isotope analysis. The results of this study again demonstrate that tracers have an important role in the calibration and definition of flow models for complex groundwater systems. However, it is suggested that tracers should be routinely inserted into groundwater flow models to determine (I) which tracers are best suited to the problem and (ii) where to sample for tracers to best differentiate among model possibilities as well as which parameters constitute the best descriptions of the groundwater system. Such coupling of multiple tracers and flow models at the earliest stages will provide the highest probability for determining the best flow model.

  13. Assessing the use of 3H-3He dating to determine the subsurface transit time of cave drip waters.

    PubMed

    Kluge, Tobias; Wieser, Martin; Aeschbach-Hertig, Werner

    2010-09-01

    (3)H-(3)He measurements constitute a well-established method for the determination of the residence time of young groundwater. However, this method has rarely been applied to karstified aquifers and in particular to drip water in caves, despite the importance of the information which may be obtained. Besides the determination of transfer times of climate signals from the atmosphere through the epikarst to speleothems as climate archives, (3)H-(3)He together with Ne, Ar, Kr, Xe data may also help to give new insights into the local hydrogeology, e.g. the possible existence of a perched aquifer above a cave. In order to check the applicability of (3)H-(3)He dating to cave drips, we collected drip water samples from three adjacent caves in northwestern Germany during several campaigns. The noble gas data were evaluated by inverse modelling to obtain recharge temperature and excess air, supporting the calculation of the tritiogenic (3)He and hence the (3)H-(3)He age. Although atmospheric noble gases were often found to be close to equilibrium with the cave atmosphere, several drip water samples yielded an elevated (3)He/(4)He ratio, providing evidence for the accumulation of (3)He from the decay of (3)H. No significant contribution of radiogenic (4)He was found, corresponding to the low residence times mostly in the range of one to three years. Despite complications during sampling, conditions of a perched aquifer could be confirmed by replicate samples at one drip site. Here, the excess air indicator ΔNe was about 10 %, comparable to typical values found in aquifers in mid-latitudes. The mean (3)H-(3)He age of 2.1 years at this site presumably refers to the residence time in the perched aquifer and is lower than the entire transit time of 3.4 years estimated from the tritium data.

  14. Frequency-dependent study of solid 4He contained in a rigid double-torus torsional oscillator

    NASA Astrophysics Data System (ADS)

    Choi, Jaewon; Shin, Jaeho; Kim, Eunseong

    2015-10-01

    The rigid double-torus torsional oscillator (TO) is constructed to reduce any elastic effects inherent to complicated TO structures, allowing explicit probing for a genuine supersolid signature. We investigated the frequency- and temperature-dependent response of the rigid double-torus TO containing solid 4He with 0.6-ppb 3He and 300-ppb 3He . We did not find evidence to support the frequency-independent contribution proposed to be a property of supersolid helium. The frequency-dependent contribution which comes from the simple elastic effect of solid helium coupled to the TO is essentially responsible for the entire response. The magnitude of the period drop is linearly proportional to f2, indicating that the responses observed in this TO are mostly caused by the overshoot of "soft" solid helium against the wall of the torus. Dissipation of the rigid TO is vastly suppressed compared to that of nonrigid TOs.

  15. Acceptance Studies for 4He(e,e'p)X Reaction up to High Missing Energies and Momenta

    NASA Astrophysics Data System (ADS)

    Finton, Drew; Benmokhtar, Fatiha

    2014-03-01

    Data collected from the Helium-4 target in Hall A at Thomas Jefferson National Accelerator Facility (TJNAF) in Newport News, Virginia, was analyzed using the object-oriented data analysis software ROOT and used to create Missing Energy Spectra for Missing Momenta ranging from 150 MeV/c to 755 MeV/c for 4He(e,e'p)X reaction channels. Jefferson Lab is a continuous electron beam accelerator facility, and Hall A contains two high resolution spectrometers as well as the cryogenic Helium-4 target. Acceptance cuts were made to six measured variables to remove background noise, and then applied to produce a Missing Energy Spectrum showing two- and three-body break up channels as well as pion electro-production energy threshold. The analysis of these missing energy spectra will be used to understand the contributions of one-, two-, and three-body interactions.

  16. Electric breakdown and ionization detection in normal liquid and superfluid 4He for the SNA nEDM experiment

    NASA Astrophysics Data System (ADS)

    Karcz, Maciej

    A new experiment to search for the neutron electric dipole moment (nEDM) is under construction at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The SNS nEDM experiment is a national collaboration spanning over 20 universities and laboratories with more than 100 physicists and engineers contributing to the research and development. The search for a nEDM is a precision test of time reversal symmetry in particle physics, in the absence of a discovery, the SNS nEDM experiment seeks to improve the present limit on the nEDM value by two orders of magnitude. A non-zero value of the nEDM would help to explain the asym- metry between matter and anti-matter in the universe by providing an additional source of charge conjugation and parity symmetry violation, a necessary ingredient in the theory of baryogenesis in the early universe. The nEDM experiment will measure the Larmor precession frequency of neutrons by detecting scintillation from neutron capture by a dilute concentration of 3He inside a bath of superfluid 4He. Neutron capture by 3He is spin-dependent and the magnetic moments of the neutron and the 3He nucleus are comparable. A direct measurement of the precession frequency of polarized 3He and scintillation from neutron capture allows for the relative precession frequencies of 3He and the neutron to be determined. The experiment will then look for changes in the relative precession of 3He and neutrons under the influence of strong electric fields. 3He has negligible EDM and therefore any deviation due to an applied electric field would be from a nEDM. The nEDM experiment will need to apply strong electric fields inside superfluid (SF) 4He and it was necessary to investigate the ability of SF 4He to sustain electric fields. An experiment to study electric breakdown in superfluid 4He was constructed at the Indiana University Center for Exploration of Energy and Matter (CEEM). The experiment studied the electric breakdown behavior of liquid

  17. Parity-Violating Electron Scattering from {sup 4}He and the Strange Electric Form Factor of the Nucleon

    SciTech Connect

    Aniol, Konrad; Armstrong, David; Averett, Todd; Benaoum, Hachemi; Bertin, Pierre; Burtin, Etienne; Cahoon, Jason; Cates, Gordon; Chang, C; Chao, Yu-Chiu; Chen, Jian-Ping; Choi, Seonho; Chudakov, Eugene; Craver, Brandon; Cusanno, Francesco; Decowski, Piotr; Deepa, Deepa; Ferdi, Catherine; Feuerbach, Robert; Finn, John; Frullani, Salvatore; Fuoti, Kirsten; Garibaldi, Franco; Gilman, Ronald; Glamazdin, Oleksandr; Gorbenko, V; Grames, Joseph; Hansknecht, John; Higinbotham, Douglas; Holmes, Richard; Holmstrom, Timothy; Humensky, Thomas; Ibrahim, Hassan; Jager, Cornelis De; Jiang, Xiaodong; Kaufman, Lisa; Kelleher, Aidan; Kolarkar, Ameya; Kowalski, Stanley; Kumar, Krishna; Lambert, Daniel; Laviolette, Peter; LeRose, John; Lhuillier, David; Liyanage, Nilanga; Margaziotis, Demetrius; Mazouz, Malek; McCormick, Kathy; Meekins, David; Meziani, Zein-Eddine; Michaels, Robert; Moffit, Bryan; Monaghan, Peter; Camacho, Carlos Munoz; Nanda, Sirish; Nelyubin, Vladimir; Neyret, Damien; Paschke, Kent; Poelker, Benard; Pomatsalyuk, Roman; Qiang, Yi; Reitz, Bodo; Roche, Julie; Saha, Arunava; Singh, Jaideep; Snyder, Ryan; Souder, Paul; Subedi, Ramesh; Suleiman, Riad; Sulkosky, Vincent; Tobias, William; Urciuoli, Guido; Vacheret, Antonin; Voutier, Eric; Wang, Kebin; Wilson, R; Wojtsekhowski, Bogdan; Zheng, Xiaochao

    2005-06-01

    We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 4}He at an average scattering angle {theta}{sub lab} = 5.7 degrees and a four-momentum transfer Q{sup 2} = 0.091 GeV{sup 2}. From these data, for the first time, the strange electric form factor of the nucleon G{sub E}{sup s} can be isolated. The measured asymmetry of A{sub PV} = 6.72 {+-} 0.84 (stat) {+-} 0.21 (syst) parts per million yields a value of G{sub E}{sup s} = -0.038 {+-} 0.042 (stat) {+-} 0.010 (syst), consistent with zero.

  18. Increase in the primordial 4He yield in the two-doublet four-neutrino mixing scheme

    NASA Astrophysics Data System (ADS)

    Abazajian, Kevork; Fuller, George M.; Shi, Xiangdong

    2000-11-01

    We assess the effects on big bang nucleosynthesis (BBN) of lepton number generation in the early universe resulting from the two-doublet four-neutrino mass-mixing scheme. It has been argued that this neutrino mass-mixing arrangement gives the most viable fit to the existing data. We study full 4×4 mixing matrices and show how possible symmetries in these can affect the BBN 4He abundance yields. Though there is as yet no consensus on the reliability of BBN calculations with neutrino flavor mixing, we show that, in the case where the sign of the lepton number asymmetry is unpredictable, BBN considerations may pick out specific relationships between mixing angles. In particular, reconciling the observed light element abundances with a ν¯μ⇌ν¯e oscillation interpretation of LSND would allow unique new constraints on the neutrino mixing angles in this model.

  19. Ratios of 15N/12C and 4He/12C inclusive electroproduction cross sections in the nucleon resonance region

    SciTech Connect

    Peter Bosted; Robert Fersch

    2007-12-14

    The ratio of inclusive electron scattering cross sections for 15N/12C was determined in the kinematic range 0.8<2 GeV and 0.2<1 GeV2 using 2.285 GeV electrons and the CLAS detector at Jefferson Lab. The ratio exhibits only slight resonance structure, as predicted by a phenomenological model, and also by quark-hadron duality. Within the super-scaling quasi-elastic model, slight evidence is found for a 1 MeV lower effective nucleon binding energy in 15N than in 12C. Ratios of 4He/12C using 1.6 to 2.5 GeV electrons are in good agreement with the phenomenological model.

  20. Parity-Violating Electron Scattering from {sup 4}He and the Strange Electric Form Factor of the Nucleon

    SciTech Connect

    Aniol, K.A.; Margaziotis, D.J.; Armstrong, D.S.; Averett, T.; Finn, J.M.; Holmstrom, T.; Kelleher, A.; Moffit, B.; Sulkosky, V.; Benaoum, H.; Holmes, R.; Souder, P.A.; Bertin, P.Y.; Ferdi, C.

    2006-01-20

    We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 4}He at an average scattering angle <{theta}{sub lab}>=5.7 deg. and a four-momentum transfer Q{sup 2}=0.091 GeV{sup 2}. From these data, for the first time, the strange electric form factor of the nucleon G{sub E}{sup s} can be isolated. The measured asymmetry of A{sub PV}=(6.72{+-}0.84{sub (stat)}{+-}0.21{sub (syst)})x10{sup -6} yields a value of G{sub E}{sup s}=-0.038{+-}0.042{sub (stat)}{+-}0.010{sub (syst)}, consistent with zero.

  1. Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

    SciTech Connect

    Gong, W.; Peng, X. Li, W.; Guo, H.

    2014-07-15

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  2. Frequency stabilization of a 1083 nm fiber laser to 4He transition lines with optical heterodyne saturation spectroscopies

    NASA Astrophysics Data System (ADS)

    Gong, W.; Peng, X.; Li, W.; Guo, H.

    2014-07-01

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable 4He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10-12@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  3. Knockout of proton-neutron pairs from 16O with electromagnetic probes

    NASA Astrophysics Data System (ADS)

    Middleton, D. G.; Annand, J. R. M.; Barbieri, C.; Giusti, C.; Grabmayr, P.; Hehl, T.; MacGregor, I. J. D.; Martin, I.; McGeorge, J. C.; Moschini, F.; Pacati, F. D.; Schwamb, M.; Watts, D.

    2010-02-01

    After recent improvements to the Pavia model of two-nucleon knockout from 16O with electromagnetic probes the calculated cross-sections are compared to experimental data from such reactions. Comparison with data from a measurement of the 16O (e,e’ pn) reaction cross-section shows much better agreement between the experimental data and the results of the theoretical model than was previously observed. In a comparison with recent data from a measurement of the 16O ( γ ,pn) reaction cross-section the model over-predicts the measured cross-section at low missing momentum.

  4. Low-energy R -matrix fits for the 6Li(d ,α ) 4HeS factor

    NASA Astrophysics Data System (ADS)

    Grineviciute, J.; Lamia, L.; Mukhamedzhanov, A. M.; Spitaleri, C.; La Cognata, M.

    2015-01-01

    Background: Information about the 6Li(d ,α ) 4He reaction rates of astrophysical interest can be obtained by extrapolating direct data to lower energies, or by indirect methods. The indirect Trojan horse method, as well as various R -matrix and polynomial fits to direct data, estimate electron screening energies much larger than the adiabatic limit. Calculations that include the subthreshold resonance estimate smaller screening energies. Purpose: Obtain the 6Li(d,α ) 4He reaction R -matrix parameters and the bare astrophysical S factor for energies relevant to the stellar plasmas by fitting R -matrix formulas for the subthreshold resonances to the S -factor data above 60 keV. Methods: The bare S factor is calculated using the single- and the two-level R -matrix formulas for the closest to the threshold 0+ and 2+ subthreshold states at 22.2 ,20.2 , and 20.1 MeV. The electron screening potential U e is then obtained by fitting it as a single parameter to the low-energy data. The calculations are also done by fitting U e simultaneously with other parameters. Results: The low-energy S factor is dominated by the 2+ subthreshold resonance at 22.2 MeV. The influence of the other two subthreshold states is small. The resultant electron screening is smaller than the adiabatic value. The fits that neglect the electron screening above 60 keV produce a significantly smaller electron screening potential. The calculations show a large ambiguity associated with a choice of the initial channel radius. Conclusions: The R -matrix fits do not show a significantly larger Ue than predicted by the atomic physics models. The R -matrix best fit provides U e=149.5 eV and Sb(0 ) =21.7 MeV b.

  5. 16O+12C resonances within the strong absorption region for Ec.m.>23 MeV

    NASA Astrophysics Data System (ADS)

    Jachcinski, C. M.; Braun-Munzinger, P.; Berkowitz, G. M.; Freifelder, R. H.; Gai, M.; Renner, T. R.; Uhlhorn, C. D.

    1980-07-01

    Excitation functions for 12C(16O, 16O)12C elastic and inelastic scattering have been measured in the energy range 23<=Ec.m.<=32 MeV. Two strong structures at Ec.m.=25.5 and 29.6 MeV are observed in the 12C + 16O(3-,6.13 MeV) exit channel; angular correlation measurements at these energies suggest spin assignments of 15- and 16+, respectively. NUCLEAR REACTIONS 12C(16O, 16O*)12C*; Ec.m.=23-32 MeV, θc.m.(16O)=130°-155° measured σ(E) angular correlations.

  6. Correlation of gold in siliceous sinters with {3He}/{4He} in hot spring waters of Yellowstone National Park

    NASA Astrophysics Data System (ADS)

    Fournier, Robert O.; Kennedy, B. Mack; Aoki, Masahiro; Thompson, J. Michael

    1994-12-01

    temperatures may contain waters with different [H2S] and [Au]. The [H2S] in a subsurface reservoir water is difficult to assess on the basis of analyses of hot spring waters because of uncertainties about steam loss during fluid ascent. However, the same processes that result in low [H2S] in reservoir waters also tend to result in decreases in the ratio of {3He}/{4He(R)} dissolved in that water. Values of R relative to this ratio in air (Ra) attain values > 15 in YNP thermal waters. To date, all of the thermal waters at YNP that have {R}/{Ra} values <9 have been found to deposit sinters with relatively low gold concentrations. These include all of the thermal waters that discharge from 180-215°C reservoirs at Upper, Midway, and Lower Geyser Basins within the western part of the Yellowstone caldera, and thermal waters at Norris Geyser Basin, outside the Yellowstone caldera, where some of the waters flow directly to the surface from a reservoir where the temperature is about 300°C. A high {3He}/{4He} ratio in thermal water discharged at the surface does not guarantee high gold concentrations in the sinter deposited by this water. Boiling with loss of steam (the gas phase takes a separate route to the surface) during rapid upflow from the shallowest reservoir to the surface decreases the [H2S] and total He dissolved in the residual liquid without appreciably changing the {3He}/{4He} ratio. This is because the isotopic composition of the He of the initial bulk fluid is unchanged and there is too little time for much radiogenic 4He to build back into the liquid during this rapid ascent from the near-surface reservoir. However, if boiling with phase separation and loss of steam occurs deep in the system, the {3He}/{4He} ratio in the residual liquid, now depleted in H2S and total He, will be susceptible to dilution with radiogenic 4He that is acquired during the longer residence time underground. Some or all of the Au that comes out of solution when an initial gold bisulfide

  7. Correlation of gold in siliceous sinters with 3He 4He in hot spring waters of Yellowstone National Park

    USGS Publications Warehouse

    Fournier, R.O.; Kennedy, B.M.; Aoki, M.; Thompson, J.M.

    1994-01-01

    temperatures may contain waters with different [H2S] and [Au]. The [H2S] in a subsurface reservoir water is difficult to assess on the basis of analyses of hot spring waters because of uncertainties about steam loss during fluid ascent. However, the same processes that result in low [H2S] in reservoir waters also tend to result in decreases in the ratio of 3He 4He(R) dissolved in that water. Values of R relative to this ratio in air (Ra) attain values > 15 in YNP thermal waters. To date, all of the thermal waters at YNP that have R Ra values <9 have been found to deposit sinters with relatively low gold concentrations. These include all of the thermal waters that discharge from 180-215??C reservoirs at Upper, Midway, and Lower Geyser Basins within the western part of the Yellowstone caldera, and thermal waters at Norris Geyser Basin, outside the Yellowstone caldera, where some of the waters flow directly to the surface from a reservoir where the temperature is about 300??C. A high 3He 4He ratio in thermal water discharged at the surface does not guarantee high gold concentrations in the sinter deposited by this water. Boiling with loss of steam (the gas phase takes a separate route to the surface) during rapid upflow from the shallowest reservoir to the surface decreases the [H2S] and total He dissolved in the residual liquid without appreciably changing the 3He 4He ratio. This is because the isotopic composition of the He of the initial bulk fluid is unchanged and there is too little time for much radiogenic 4He to build back into the liquid during this rapid ascent from the near-surface reservoir. However, if boiling with phase separation and loss of steam occurs deep in the system, the 3He 4He ratio in the residual liquid, now depleted in H2S and total He, will be susceptible to dilution with radiogenic 4He that is acquired during the longer residence time underground. Some or all of the Au that comes out of solution when an initial gold bisulfide complex breaks

  8. Adrenergic receptor and catecholamine distribution in rat cerebral cortex: binding studies with [3H]prazosin, [3H]idazoxan and [3H]dihydroalprenolol.

    PubMed

    Diop, L; Brière, R; Grondin, L; Reader, T A

    1987-02-03

    The tritiated adrenergic antagonists [3H]dihydroalprenolol ([3H]DHA; beta-receptors), [3H]prazosin ([3H]PRZ; alpha 1-receptors), and [3H]idazoxan ([3H]IDA; alpha 2-receptors) were used to determine the distribution of these sites in 5 defined areas of the adult rat cerebral cortex. The highest density of [3H]PRZ binding was found in the prefrontal cortex, with a lower and homogeneous distribution for the frontal, parietal, occipital and temporal areas. The [3H]IDA binding sites were fairly uniform for all areas, except for the temporal cortex where it was very dense. In contrast, beta-adrenoceptors labelled by [3H]DHA were very homogeneous for all the regions examined. The functional significance of the distribution of alpha 1, alpha 2 and beta-adrenoceptors is discussed in relation to the catecholamine innervation and monoamine contents measured by high performance liquid chromatography.

  9. Comparison of the effectiveness of exposure to low LET helium particles (4He) and gamma rays (137Cs) on the disruption of cognitive performance

    USDA-ARS?s Scientific Manuscript database

    Rats were exposed to either Helium (4He) particles (1000 MeV/n; 0.1 – 10 cGy; head-only) or Cesium 137Cs gamma rays (50 – 400 cGy; whole body) and the effects of irradiation on cognitive performance evaluated. The results indicated that exposure to doses of 4He particles as low as 0.1 cGy disrupted...

  10. [3H]Ethynylbicycloorthobenzoate ([3H]EBOB) binding in recombinant GABAA receptors.

    PubMed

    Yagle, Monica A; Martin, Michael W; de Fiebre, Christopher M; de Fiebre, NancyEllen C; Drewe, John A; Dillon, Glenn H

    2003-12-01

    Ethynylbicycloorthobenzoate (EBOB) is a recently developed ligand that binds to the convulsant site of the GABAA receptor. While a few studies have examined the binding of [3H]EBOB in vertebrate brain tissue and insect preparations, none have examined [3H]EBOB binding in preparations that express known configurations of the GABAA receptor. We have thus examined [3H]EBOB binding in HEK293 cells stably expressing human alpha1beta2gamma2 and alpha2beta2gamma2 GABAA receptors, and the effects of CNS convulsants on its binding. The ability of the CNS convulsants to displace the prototypical convulsant site ligand, [35S]TBPS, was also assessed. Saturation analysis revealed [3H]EBOB binding at a single site, with a K(d) of approximately 9 nM in alpha1beta2gamma2 and alpha2beta2gamma2 receptors. Binding of both [3H]EBOB and [35S]TBPS was inhibited by dieldrin, lindane, tert-butylbicycloorthobenzoate (TBOB), PTX, TBPS, and pentylenetetrazol (PTZ) at one site in a concentration-dependent fashion. Affinities were in the high nM to low microM range for all compounds except PTZ (low mM range), and the rank order of potency for these convulsants to displace [3H]EBOB and [35S]TBPS was the same. Low [GABA] stimulated [3H]EBOB binding, while higher [GABA] (greater than 10 microM) inhibited [3H]EBOB binding. Overall, our data demonstrate that [3H]EBOB binds to a single, high affinity site in alpha1beta2gamma2 and alpha2beta2gamma2 GABAA receptors, and modulation of its binding is similar to that seen with [35S]TBPS. [3H]EBOB has a number of desirable traits that may make it preferable to [35S]TBPS for analysis of the convulsant site of the GABAA receptor.

  11. Cross Section Measurements of 12C+16O Fusion Reaction at Stellar Energies

    NASA Astrophysics Data System (ADS)

    Tan, Wanpeng; Fang, X.; Beard, M.; Gilardy, G.; Jung, H.; Liu, Q.; Lyons, S.; Robertson, D.; Setoodehnia, K.; Seymour, C.; Stech, E.; Vande Kolk, B.; Wiescher, M.; de Souza, R.; Hudan, S.; Singh, V.; Tang, X.; Uberseder, E.

    2016-09-01

    12C+16O is one of the three fusion reactions (12C+12C, 12C+16O, and 16O+16O) that play an important role at the late stage of stellar evolution in massive stars. The previous meassurements of its cross section at low energies rely on the singles measurements of either gamma rays or charged particles. New measurement was conducted for the 12C+16O reaction at Ecm = 3.64 - 4.93 MeV with the detection of both gammas and charged particles using the high intensity St ANA accelerator at the University of Notre Dame. The protons and alphas from the fusion evaporation were measured by a large area silicon strip detector array (SAND) while the gamma rays were detected by one large volume HPGe detector right after the target. Statistical model calculation were employed to interpret the experimental results. This provided a more reliable extrapolation for the 12C+16O fusion cross section, reducing substantially the uncertainty for stellar model simulations. This work was supported by the National Science Foundation through Grant Numbers PHY-1068192 and PHY-1419765 and the Joint Institute for Nuclear Astrophysics under Grant No. PHY-0822648.

  12. Construction of a newly designed small-size mass spectrometer for helium isotope analysis: toward the continuous monitoring of (3)he/(4)he ratios in natural fluids.

    PubMed

    Bajo, Ken-Ichi; Sumino, Hirochika; Toyoda, Michisato; Okazaki, Ryuji; Osawa, Takahito; Ishihara, Morio; Katakuse, Itsuo; Notsu, Kenji; Igarashi, George; Nagao, Keisuke

    2012-01-01

    The construction of a small-size, magnetic sector, single focusing mass spectrometer (He-MS) for the continuous, on-site monitoring of He isotope ratios ((3)He/(4)He) is described. The instrument is capable of measuring (4)He/(20)Ne ratios dissolved in several different types of natural fluids of geochemical interest, such as groundwater and gas from hot springs, volcanoes and gas well fields. The ion optics of He-MS was designed using an ion trajectory simulation program "TRIO," which permits the simultaneous measurement of (3)He and (4)He with a double collector system under a mass resolution power (M/ΔM) of >700. The presently attained specifications of He-MS are; (1) a mass resolving power of ca. 430, sufficient to separate (3)He(+) from interfering ions, HD(+) and H3 (+), (2) ultra-high vacuum conditions down to 3×10(-8) Pa, and (3) a sufficiently high sensitivity to permit amounts of (3)He to be detected at levels as small as 10(-13) cm(3) STP (3×10(6) atoms). Long term stability for (3)He/(4)He analysis was examined by measuring the (3)He/(4)He standard gas (HESJ) and atmospheric He, resulting in ∼3% reproducibility and ≤5% experimental error for various amounts of atmospheric He from 0.3 to 2.3×10(-6) cm(3) STP introduced into the instrument. A dynamic range of measurable (3)He/(4)He ratios with He-MS is greater than 10(3) which was determined by measuring various types of natural fluid samples from continental gas (with a low (3)He/(4)He ratio down to 2×10(-8)) to volcanic gas (with a high (3)He/(4)He ratio up to 3×10(-5)). The accuracy and precision of (3)He/(4)He and (4)He/(20)Ne ratios were evaluated by comparing the values with those measured using well established noble gas mass spectrometers (modified VG5400/MS-III and -IV) in our laboratory, and were found to be in good agreement within analytical errors. Usefulness of the selective extraction of He from water/gas using a high permeability of He through a silica glass wall at high

  13. Construction of a Newly Designed Small-Size Mass Spectrometer for Helium Isotope Analysis: Toward the Continuous Monitoring of 3He/4He Ratios in Natural Fluids

    PubMed Central

    Bajo, Ken-ichi; Sumino, Hirochika; Toyoda, Michisato; Okazaki, Ryuji; Osawa, Takahito; Ishihara, Morio; Katakuse, Itsuo; Notsu, Kenji; Igarashi, George; Nagao, Keisuke

    2012-01-01

    The construction of a small-size, magnetic sector, single focusing mass spectrometer (He-MS) for the continuous, on-site monitoring of He isotope ratios (3He/4He) is described. The instrument is capable of measuring 4He/20Ne ratios dissolved in several different types of natural fluids of geochemical interest, such as groundwater and gas from hot springs, volcanoes and gas well fields. The ion optics of He-MS was designed using an ion trajectory simulation program “TRIO,” which permits the simultaneous measurement of 3He and 4He with a double collector system under a mass resolution power (M/ΔM) of >700. The presently attained specifications of He-MS are; (1) a mass resolving power of ca. 430, sufficient to separate 3He+ from interfering ions, HD+ and H3+, (2) ultra-high vacuum conditions down to 3×10−8 Pa, and (3) a sufficiently high sensitivity to permit amounts of 3He to be detected at levels as small as 10−13 cm3 STP (3×106 atoms). Long term stability for 3He/4He analysis was examined by measuring the 3He/4He standard gas (HESJ) and atmospheric He, resulting in ∼3% reproducibility and ≤5% experimental error for various amounts of atmospheric He from 0.3 to 2.3×10−6 cm3 STP introduced into the instrument. A dynamic range of measurable 3He/4He ratios with He-MS is greater than 103 which was determined by measuring various types of natural fluid samples from continental gas (with a low 3He/4He ratio down to 2×10−8) to volcanic gas (with a high 3He/4He ratio up to 3×10−5). The accuracy and precision of 3He/4He and 4He/20Ne ratios were evaluated by comparing the values with those measured using well established noble gas mass spectrometers (modified VG5400/MS-III and -IV) in our laboratory, and were found to be in good agreement within analytical errors. Usefulness of the selective extraction of He from water/gas using a high permeability of He through a silica glass wall at high temperature (700°C) is demonstrated. PMID:24349910

  14. Characterization of helium diffusion behavior from continuous heating experiments: Sample screening and identification of multiple 4He components

    NASA Astrophysics Data System (ADS)

    McDannell, K. T.; Idleman, B. D.; Zeitler, P. K.

    2015-12-01

    Old, slowly cooled apatites often yield overdispersed helium ages due to factors such as parent zonation, He implantation, radiation damage, crystal defects, and fluid inclusions. Careful mineral selection and many replicate analyses can mitigate the impact of some of these effects. However, this approach adds unnecessary costs in time and resources when dating well-behaved apatites and is generally ineffective at identifying the root cause of age dispersion and providing suitable age corrections for poorly behaved samples. We assess a new technique utilizing static-gas measurement during continuous heating as a means to rapidly screen apatite samples. In about the time required for a conventional total-gas analysis, this method can discriminate between samples showing the volume-diffusion behavior expected for apatite and those showing anomalous release patterns, inconsistent with their use in thermochronologic applications. This method may also have the potential to quantify and discriminate between the radiogenic and extraneous 4He fractions released by a sample. Continuously heated samples that outgas by volume diffusion during a linear heating schedule should produce a characteristic sigmoidal 4He fractional loss profile, with the exact shape and position of these profiles (in loss vs. heating time space) controlled by sample kinetics, grain size, and heating rate. Secondary factors such as sample zoning and alpha-loss distribution have a relatively minor impact on such profiles. Well-behaved examples such as the Durango standard and other apatites with good age reproducibility show the expected smooth, sigmoidal gas release with complete exhaustion by temperatures predicted for volume diffusion using typical apatite kinetics (e.g., by ~900˚C for linear heating at 20˚C/minute). In contrast, "bad actor" samples that do not replicate well show significant degrees of helium release deferred to higher temperatures. We report on screening results for a range of

  15. On the K- 4He → Λπ- 3He resonant and non-resonant processes

    NASA Astrophysics Data System (ADS)

    Piscicchia, K.; Wycech, S.; Curceanu, C.

    2016-10-01

    The ongoing data analyses by the AMADEUS/KLOE-2 Collaboration on the 2004-2005 KLOE data revive studies of the K ‾ nuclear absorption at low energies. The aim is to study K ‾ interactions at subthreshold energies and to search for signals of K ‾ meson nuclear states. In this paper the spectrum of the K- 4He → Λπ- 3He reaction is discussed. One - calculable - mode of decay involves P-wave intermediate Σ (1385) resonance. Another mode involves S-wave KN → Λπ amplitude which may be extracted from the experimental results. Comparison of these two allows a check of subthreshold extrapolations of multichannel K ‾ N S-wave interaction models. Given the established significance of the P wave interaction in the K ‾ N system presented here, the obtained spectra will serve for the AMADEUS/KLOE-2 data analysis, in order to properly extract the subthreshold non-resonant transition amplitude.

  16. Effect of an intermediate bcc phase on the evolution of superfluid inclusions in an hcp 3He-4He matrix

    NASA Astrophysics Data System (ADS)

    Birchenko, A. P.; Mihin, N. P.; Neoneta, A. S.; Rudavskii, E. Ya.; Fysun, Ya. Yu.

    2016-09-01

    Pulsed NMR is used to study the evolution of liquid inclusions formed in an hcp matrix during rapid cooling of a 3He-4He solution containing 1.05% 3He. The diffusion coefficient of 3He in the liquid inclusions as they evolve is measured by a spin echo technique with two probe pulses. The measurements were made at 1.67 K, which corresponds to the region of the bcc phase in the phase diagram, and at 1.38 K, where the bcc phase is absent. It is found that during the evolution in both cases, the liquid inclusions are smaller than the diffusion length and diffusion is restricted. The measured coefficient of restricted diffusion made it possible to determine the characteristic size of the inclusions. In the first case, during the evolution of the liquid inclusions an intermediate bcc phase in the form of dendrites develops and separates the liquid inclusions into a mass of fine droplets. Because of the rapid growth of the bcc phase, the size of the droplets decreases rapidly and the process ends with the disappearance of the bcc phase and the formation of an amorphous state. The results derived from the measured diffusion coefficient correlate with the behavior of the spin-lattice relaxation time in this kind of system. In the second case, at a lower temperature, the bcc phase does not develop and the evolution of the liquid inclusions is accompanied by a very slow reduction in their size until their complete solidification.

  17. Simultaneous measurements of the torsional oscillator and shear modulus of solid 4He diluted with various 3He concentration

    NASA Astrophysics Data System (ADS)

    Shin, Jaeho; Choi, Wonsuk; Choi, Jaewon; Jang, Seong; Shirahama, Keiya; Kim, Eunseong

    2013-03-01

    In 2004, Kim and Chan observed the non-classical rotational inertia (NCRI) of solid helium-4 by using a torsional oscillator (TO). Below 200mK, the resonance period of solid helium dropped, which was originally interpreted as the mass decoupling of the fraction of solid helium. Recently, anomalous increase in the shear modulus of solid helium was found and showed striking similarity in temperature, frequency, 3He concentration, and drive dependence to those of the NCRI. To understand the connection between the NCRI and the shear modulus anomaly, we simultaneously measure the change in the resonance frequency and the stiffness of solid helium below 200mK. The torsion cell contains a pair of the concentric piezoelectric transducers (PZT) which defines an annular channel for the simultaneous measurements. We will report the interference between the motion of the TO at resonance and AC motion of the PZT in solid 4He with different 3He concentration. We gratefully acknowledge the financial support by the National Research Foundation of Korea through the Creative Research Initiatives.

  18. Two-nucleon absorption of π+ in 4He at T+π=114 and 162 MeV

    NASA Astrophysics Data System (ADS)

    Adimi, F.; Breuer, H.; Flanders, B. S.; Khandaker, M. A.; Khayat, M. G.; Roos, P. G.; Zhang, D.; Bauer, Th. S.; Konijn, J.; de Laat, C. T. A. M.; Kyle, G. S.; Mukhopadhyay, S.; Wang, M.; Tacik, R.

    1992-06-01

    Differential and integrated cross sections for the reaction 4He(π+,pp) at Tπ=114 and 162 MeV are reported. These are the first results for this reaction using a large solid angle detector covering ~=55% of 4π sr. Directly measured integrated cross sections for absorption on two-nucleon pairs are σabs=25.7+/-1.8 mb at 114 MeV and σabs=21.0+/-1.5 mb at 162 MeV. These cross sections, when corrected by a factor of 1.4 final state interaction effects, account for about 50% of the total absorption cross section for all final-state reaction channels at both energies. The data are compared with Monte Carlo simulations of the reaction process using a quasideuteron absorption model for the two-nucleon absorption process in a plane wave impulse approximation. The consequences for the extraction of the two-nucleon absorption cross section by imposing different conditions on the data are explored.

  19. A "high 4He/3He" mantle material detected under the East Pacific Rise (15°4'N)

    NASA Astrophysics Data System (ADS)

    Mougel, Berengere; Moreira, Manuel; Agranier, Arnaud

    2015-03-01

    We investigate in details helium isotope data reported in Mougel et al. (2014) for 14 basaltic samples collected on the East Pacific Rise by submersible (15°4'N) where the ridge interacts with the Mathematician seamounts. Samples locations are separated by only few hundred meters across a 15 km along-axis profile. The data reveal a strong geochemical variability that has never been observed at such high spatial resolution for helium isotope compositions. Moreover, they reveal an unusually high 4He/3He mantle component also characterized by unradiogenic lead, atypical in oceanic basalts. He-Pb systematics suggests a mixture between a nonradiogenic lead and radiogenic helium pyroxenitic component, recycled from the deep continental lithosphere and the ambient peridotitic mantle. The He isotope difference between these two end-members can be interpreted as a time evolution of two distinct mantle sources after a slight (U + Th)/3He fractionation, likely due to some ancient degassing during the formation of deep continental pyroxenites.

  20. Quantum interferences in the photodissociation of Cl2(B) in superfluid helium nanodroplets ((4)He)N.

    PubMed

    Vilà, Arnau; González, Miguel; Mayol, Ricardo

    2015-12-28

    Quantum interferences are probably one of the most fascinating phenomena in chemical physics and, particularly, in reaction dynamics, where they are often very elusive from an experimental perspective. Here, we have theoretically investigated, using a hybrid method recently proposed by us, the dynamics of the formation of confinement quantum interferences in the photodissociation of a Cl2 molecule (B ← X electronic excitation) embedded in a superfluid helium nanodroplet of different sizes (50-500 (4)He atoms), which is to the best of our knowledge the first time that this type of interference is described in reaction dynamics. Thus, we have widely extended a recent contribution of our group, where interferences were not the main target, identifying the way they are formed and lead to the production of strongly oscillating velocity distributions in the Cl dissociating atoms, and also paying attention to the energy transfer processes involved. This probably corresponds to a rather general behavior in the photodissociation of molecules in helium nanodroplets. We hope that the present study will encourage the experimentalists to investigate this captivating phenomenon, although the technical difficulties involved are very high.

  1. Evaluation of L-shell X-ray production cross sections by impact of {sup 4}He{sup +} ions

    SciTech Connect

    Miranda, J.

    2013-07-03

    A database of published L-subshell X-ray production cross sections due to the impact of {sup 4}He{sup +} ions on several elements is compiled. In order to evaluate the data, they are compared with theoretical calculations using the ECPSSR theory (which modifies the Plane Wave Born Approximation) and its corrections, such as Multiple Ionization of the target atom (MI), United Atom (UA), and Intra-shell coupling (IS) models. It was found that the theory does not predict reliably the experimental results for all elements and energy ranges. Furthermore, a possible universal scaling for the xray production cross sections of the L{sub {alpha}}(L{sub 3}M{sub 4}+L{sub 3}M{sub 5}) and the L{sub {gamma}}(L{sub 2}N{sub 4}+L{sub 1}N{sub 2}+L{sub 1}N{sub 3}+L{sub 1}O{sub 3}+L{sub 1}O{sub 2}+L{sub 2}N{sub 1}+L{sub 2}O{sub 4}) lines is proposed, based on reduced velocity parameters {xi}{sub L}{sup R} and {xi}{sub L1,2}{sup R}, respectively. This scaling seems to be useful for the L{sub {alpha}} experimental points and not so good for the L{sub {gamma}} line, suggesting that more extensive theoretical studies in this direction should be followed.

  2. Mutual interactions between objects oscillating in isotopically pure superfluid 4He in the T → 0 limit

    NASA Astrophysics Data System (ADS)

    Garg, D.; Efimov, V. B.; Giltrow, M.; McClintock, P. V. E.; Skrbek, L.

    2012-11-01

    We report the results of experiments to explore interactions between physically separated oscillating objects in isotopically pure superfluid 4He at T ˜ 10 mK. The investigations focused mainly on 32 kHz quartz tuning forks, but also consider a nearby 1 kHz oscillating grid. The low-drive linewidth (LDL) and resonant frequency fd of a detector fork were monitored while the maximum velocity of a transmitter fork, separated from the detector by a few mm, was varied over a wide range. Clear evidence was found for mutual interactions between the two forks, and for the influence of the grid on the forks. Monitoring the detector's LDL and fd provides evidence for a generator critical velocity in the range 0.3<υc1<1.0 cm/s for onset of the detector responses, in addition to a second critical velocity υc2˜13 cm/s probably corresponding to the production of quantum turbulence at the generator. The results are discussed, but are not yet fully understood.

  3. Uptake of [3H]-nicotine and [3H]-noradrenaline by cultured chromaffin cells.

    PubMed Central

    Ceña, V.; García, A. G.; Montiel, C.; Sánchez-García, P.

    1984-01-01

    Three day-old cultured bovine adrenal chromaffin cells incubated at room temperature with Krebs-HEPES solution containing different concentrations of [3H]-nicotine, took up and retained increasing amounts of the drug by a mechanism that did not saturate. Concentrations of cold nicotine as high as 100 microM did not alter the amount of [3H]-nicotine retained by cells. Imipramine, cocaine, tetracaine or mecamylamine, at concentrations (10 microM) that blocked the catecholamine secretory effects of nicotine completely, did not modify the uptake of [3H]-nicotine. Both imipramine and cocaine drastically inhibited [3H]-noradrenaline uptake by cells in a concentration-dependent manner (IC50S of 0.08 and 1 microM, respectively). These data indicate that the secretory effects of nicotine are not coupled to its previous uptake into cells, and are evidence in favour of a site of action for nicotine located in or at the surface of the chromaffin cell membrane. PMID:6704577

  4. Comparisons of longitudinal and lateral dose profiles and relative biological effectiveness for DNA double strand breaks among 1H, 4He and 12C beams

    NASA Astrophysics Data System (ADS)

    Lin, Yu-Shen; Chao, Tsi-Chian; Hong, Ji-Hong; Tung, Chuan-Jong

    2017-08-01

    Monte Carlo FLUKA and MCDS codes were used to study 1H, 4He and 12C ion beams with similar ranges in water phantom. The longitudinal and lateral dose profiles and the relative biological effectiveness (RBE) were investigated. Simulations were performed with particular emphasis in the vicinity of the Bragg peak (BP). The impact of individual nuclear fragments created by the primary beams was examined. Comparisons were made for the BP width, lateral dose profile width, and RBE value at different depths in the phantom. RBE values for the induction of DNA double-strand breaks were estimated, particularly in the vicinity of the BP. Results showed that 12C beam had the narrowest BP width, smallest lateral dose profile, and largest RBE value, followed by 4He and 1H beams. However, the differences between 4He and 12C were smaller than those between 1H and 4He. It also showed that the influence of nuclear fragments was significant for 12C beam, moderate for 4H beam, and minor for 1H beam. This influence was important for 12C at depths beyond the BP. Our results suggest that 4He beam is also a promising option for cancer therapy.

  5. An Experimental Study on What Controls the Ratios of 18O/16O and 17O/16O of O2 During Microbial Respiration

    NASA Astrophysics Data System (ADS)

    Stolper, D. A.; Ward, B. B.; Fischer, W. W.; Bender, M. L.

    2015-12-01

    18O/16O and 17O/16O ratios of atmospheric and dissolved oceanic O2 are key biogeochemical tracers of total photosynthesis and respiration on global to local length scales and glacial/interglacial time scales (Luz et al., 1999). Critical to the use of these ratios as biogeochemical tracers is knowledge of how they are affected by production, consumption, and transport of O2. We present new measurements of O2 respiration by E. coli and N. oceanus, an ammonia oxidizing bacterium, to test three assumptions of isotopically enabled models of the O2 cycle: (i) laboratory-measured respiratory 18O/16O isotope effects (18α) of microorganisms are constant under all experimental and natural conditions (e.g., temperature and growth rate); (ii) the respiratory 'mass law' relationship between 18O/16O and 17O/16O [17α = (18α)β] is universal; and (iii) 18α and β for aerobic ammonia and organic carbon oxidation are identical. For E. coli, we find that both 18α and β are variable. From 37°C to 15°C, 18α varies linearly with temperature from 17 to 14‰, and β varies linearly from 0.513 to 0.508. 18α and β do not appear to vary with growth rate (as tested using different carbon sources). Both 18α and β are lower than previous observations for bacteria: 18α = 17-20‰ (Kiddon et al., 1993) and β = 0.515 (Luz and Barkan, 2005). We were able to simulate the observed temperature dependence of 18α and β using a model of respiration with two isotopically discriminating steps: O2 binding to cytochrome bo oxidase (the respiratory enzyme) and reduction of O2 to H2O. Finally, initial results on N. oceanus suggest it has similar values for 18α and β as previously studied aerobic bacteria that consume organic carbon, providing the first support for assumption (iii). Based on these results, isotopically constrained biogeochemical models of O2 cycling may need to consider a temperature dependence for 18α and β for microbial respiration. For example, these results may

  6. Long-distance correlation-length effects and hydrodynamics of 4He films in a Corbino geometry

    NASA Astrophysics Data System (ADS)

    Thomson, Stephen R. D.; Perron, Justin K.; Gasparini, Francis M.

    2016-09-01

    Previous measurements of the superfluid density ρs and specific heat for 4He have identified effects that are manifest at distances much larger than the correlation length ξ3 D [Perron et al., Nat. Phys. 6, 499 (2010), 10.1038/nphys1671; Perron and Gasparini, Phys. Rev. Lett. 109, 035302 (2012), 10.1103/PhysRevLett.109.035302; Perron et al., Phys. Rev. B 87, 094507 (2013), 10.1103/PhysRevB.87.094507]. We report here measurements of the superfluid density which are designed to explore this phenomenon further. We determine the superfluid fraction ρs/ρ from the resonance of 34-nm films of varying widths 4 ≤W ≤100 μ m . The films are formed across a Corbino ring separating two chambers where a thicker 268-nm film is formed. This arrangement is realized using lithography and direct Si-wafer bonding. We identify two effects in the behavior of ρs/ρ : one is hydrodynamic, for which we present an analysis, and the other is a correlation-length effect which manifests as a shift in the transition temperature Tc relative to that of a uniform 34-nm film uninfluenced by proximity effects. We find that one can collapse both ρs/ρ and the quality factor of the resonance onto universal curves by shifting Tc as Δ Tc˜W-ν . This scaling is a surprising result on two counts: it involves a very large length scale W relative to the magnitude of ξ3 D and the dependence on W is not what is expected from correlation-length finite-size scaling which would predict Δ Tc˜W-1 /ν .

  7. The Breakdown of Superfluidity in Liquid 4He V. Measurement of the Landau Critical Velocity for Roton Creation

    NASA Astrophysics Data System (ADS)

    Ellis, T.; McClintock, P. V. E.

    1985-08-01

    We report a precise experimental determination of the Landau critical velocity vL for roton creation in HeII. The technique used was based on measurements of the drift velocity, {v}, of negative ions through isotopically pure liquid 4He at ca. 80 m K, under the infleunce of weak electric fields, E, for pressures, P, within the range 13 <= P <= 25 bar. It relied on the use of the equation ({v}-vL) propto E1/3, which is believed to correspond to the creation of rotons occurring predominantly in pairs and which fitted the experimental data to very high precision for E > 500 V m-1. At lower values of E, however, small deviations from this equation were observed. These are tentatively attributed, not to the predicted onset of single-roton emission, but to a novel form of ion-vortex scattering. The values of vL(P) deduced from the measurements of {v}(E) at various pressures for E > 500 V m-1 agree to within 1.5% with theoretical predictions based on Landau's excitation model of HeII, incorporating accepted numerical values of the roton parameters. The observed pressure dependence of vL(P) is significantly stronger than that predicted; however, a discrepancy that appears to point towards the decreasing accuracy with which the roton parameters are known at high pressures. The modulus of the matrix element |Vk_{0,k0}| characterizing roton-pair emission has also been deduced and is found to decrease rapidly with falling pressure. A linear extrapolation of the data suggests that |Vk_{0,k0}| falls to zero at P ≈ 3 bar (1 bar = 105 Pa).

  8. Transverse spin diffusion and spin rotation in very dilute, spin-polarized 3-4He mixtures

    NASA Astrophysics Data System (ADS)

    Candela, D.; McAllaster, D. R.; Wei, L.-J.

    1991-10-01

    We report measurements of the transverse-spin-diffusion coefficient D⊥ and the spin-rotation parameter Ωτ⊥ for two very dilute 3-4He mixtures (x3=1.82×10-3 and 6.26×10-4) spin polarized by an 8-T magnetic field. Brute-force spin polarization up to 40% was achieved at the lowest temperature, 6 mK. We find that Ωτ⊥ increases monotonically as the temperature is reduced through the Fermi temperature TF, in disagreement with the only previous experiment but in good agreement with recent theory. Unlike the earlier experiment, which measured spin echoes, the present experiments employed a spin-wave technique that avoids nonlinear excitation of the spin field. We compare our results with the recent calculations of Jeon and Mullin for spin transport in dilute gases with arbitrary polarization and degeneracy. The best fit to the data is obtained by scaling the quasiparticle interaction V(q) proposed by Ebner by a modest factor, 1.07. The corresponding s-wave scattering length is a=-1.21 Å. Good agreement is found for Ωτ⊥(T) at both concentrations and all temperatures, and for D⊥/Ωτ⊥(T) apart from the lower concentration at T<20 mK. The discrepancy in D⊥/Ωτ⊥ at the lowest temperatures and x3 could be explained by an unanticipated polarization dependence or by modification of the spin-wave boundary condition by processes occurring at the interface between the mixture and the silica cavity wall.

  9. Exciplexes with ionic dopants: stability, structure, and experimental relevance of M(+)((2)P)(4)He(n) (M = Sr, Ba).

    PubMed

    Mella, Massimo; Cargnoni, Fausto

    2014-08-21

    M(+)((2)P)(4)Hen species, possibly involved in the post (2)P ← (2)S excitation dynamics of Sr(+) and Ba(+) in cold (4)He gas or droplets, are studied employing both high level ab initio calculations to determine the potential energy curves (PEC) and diffusion Monte Carlo (DMC) to obtain information on their ground state structure and energetics. PEC for the excited M(+)((2)P)He dimers were obtained using MRCI calculations with extended basis sets. Potential energy surfaces (PES) for M(+)((2)P)Hen were built with the DIM model including spin-orbit coupling via a perturbative procedure. DMC simulations indicated several exciplexes (n > 2) to be stable against He dissociation whatever the ion state, a finding that is at variance with what was previously suggested for Ba(+)((2)P1/2) due to the repulsive nature of the interaction potential obtained in [ Phys. Rev. A 2004 , 69 , 042505 ]. Our results, instead, support the suggestion made in [J. Chem. Phys. 2012, 137, 051102] for the existence of Ba(+)((2)P1/2)Hen exciplexes emitted following the excitation of the barium cation solvated into He droplets. In the (2)P1/2 state, the Ba ion also shows a peculiar behavior as a function of n with respect to the location and binding strength of the attached He atoms compared to Sr(+). Although the latter forms the usual equatorial He ring, Ba(+) deviates from this geometry for 1 ≤ n ≤ 4, with the radial distribution functions strongly depending on the number of solvent atoms. Finally, a putative species is proposed to explain the emission band at 523 nm that follows D1 or D2 excitation of Ba(+) in superfluid bulk helium.

  10. Human epididymis protein 4 (HE4) plays a key role in ovarian cancer cell adhesion and motility

    SciTech Connect

    Lu, Renquan; Sun, Xinghui; Xiao, Ran; Zhou, Lei; Gao, Xiang; Guo, Lin

    2012-03-09

    Highlights: Black-Right-Pointing-Pointer We generated stable transduced HE4 overexpression and knockdown cells. Black-Right-Pointing-Pointer HE4 was associated with EOC cell adhesion and motility. Black-Right-Pointing-Pointer HE4 might have some effects on activation of EGFR-MAPK signaling pathway. Black-Right-Pointing-Pointer HE4 play an important role in EOC tumorigenicity. -- Abstract: Human epididymis protein 4 (HE4) is a novel and specific biomarker for epithelial ovarian cancer (EOC). We previously demonstrated that serum HE4 levels were significantly elevated in the majority of EOC patients but not in subjects with benign disease or healthy controls. However, the precise mechanism of HE4 protein function is unknown. In this study, we generated HE4-overexpressing SKOV3 cells and found that stably transduced cells promoted cell adhesion and migration. Knockdown of HE4 expression was achieved by stable transfection of SKOV3 cells with a construct encoding a short hairpin DNA directed against the HE4 gene. Correspondingly, the proliferation and spreading ability of HE4-expressed cells were inhibited by HE4 suppression. Mechanistically, impaired EGFR and Erk1/2 phosphorylation were observed in cells with HE4 knockdown. The phosphorylation was restored when the knockdown cells were cultured in conditioned medium containing HE4. Moreover, in vivo tumorigenicity showed that HE4 suppression markedly inhibited the growth of tumors. This suggests that expression of HE4 is associated with cancer cell adhesion, migration and tumor growth, which can be related to its effects on the EGFR-MAPK signaling pathway. Our results provide evidence of the cellular and molecular mechanisms that may underlie the motility-promoting role of HE4 in EOC progression. The role of HE4 as a target for gene-based therapy might be considered in future studies.

  11. Measurement of the cross section for the 4He(α, n)7Be reaction as a possible solution to the cosmological lithium problem

    NASA Astrophysics Data System (ADS)

    Kawabata, T.; Furuno, T.; Ichikawa, M.; Iwasa, N.; Kanada-En'yo, Y.; Koshikawa, A.; Kubono, S.; Miyawaki, E.; Morimoto, T.; Murata, M.; Nanamura, T.; Nishimura, S.; Shikata, Y.; Takahashi, Y.; Takeda, T.; Tsumura, M.; Watanabe, K.

    2017-06-01

    The cross section for the 4He(α,n)7Be reaction was measured at low energies between Eα = 38.50 and 39.64 MeV motivated by the cosmological lithium problem. On the basis of the detailed balance principle, the cross section for the 7Be(n,α)4He reaction was obtained at Ec.m. = 0.20-0.81 MeV close to the Big Bang nucleosynthesis (BBN) energy window for the first time. The obtained cross sections are significantly smaller than the theoretical estimation widely used in the BBN calculations. The present results suggest the 7Be(n,α)4He reaction rate is not large enough to solve the cosmological lithium problem.

  12. Some thoughts on a simple mechanism for the [sup 2]H + [sup 2]H [yields] [sup 4]He cold fusion reaction

    SciTech Connect

    Park, A.E.

    1993-11-01

    A speculative mechanism for the creation of [sup 4]He using cold fusion is proposed. The nuclear transformation can be made by the fusion of two excited rotating ground states of deuterium into a highly excited rotating ground state of [sup 4]He. Under compression and relatively stable conditions, the formation of such a bound, stretched-out pnnp state of [sup 4]He would be favored (with respect to Coulomb repulsion) over other nuclear ground states without as much angular momentum. The reaction likely occurs at the surface of palladium. A more descriptive name for this reaction is compressed-rotational-shielded (CRS) fusion. Potential experimental conditions for enhancing the initiation of CRS fusion are discussed. 8 refs., 2 figs.

  13. Bare-nucleus astrophysical factor of the {sup 3}He(d,p){sup 4}He reaction via the 'Trojan horse' method

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Tumino, A.; Cherubini, S.; Lamia, L.; Musumarra, A.; Pizzone, R.G.; Rinollo, A.; Romano, S.; Typel, S.; Rolfs, C.; Schuermann, D.; Strieder, F.

    2005-12-15

    The {sup 3}He(d,p){sup 4}He reaction has been studied from E{sub c.m.}=600 keV down to astrophysical energies by means of the 'Trojan horse' method using the {sup 6}Li({sup 3}He,p{alpha}){sup 4}He three-body reaction at E{sub lab}=5 and 6 MeV. Coincidence spectra were measured in kinematic conditions favoring the quasifree {sup 3}He+{sup 2}H process. The bare astrophysical factor S{sub b}(E) for the {sup 3}He(d,p){sup 4}He reaction was extracted from the three-body cross section in the modified plane-wave Born approximation. Comparison with the S{sub b} extrapolation from the free two-body data is presented. The independent estimate of the screening potential as obtained with the present work seems to confirm the theoretical adiabatic limit.

  14. Observation of Spin-Dependent Charge Symmetry Breaking in ΛN Interaction: Gamma-Ray Spectroscopy of _{Λ}^{4}He.

    PubMed

    Yamamoto, T O; Agnello, M; Akazawa, Y; Amano, N; Aoki, K; Botta, E; Chiga, N; Ekawa, H; Evtoukhovitch, P; Feliciello, A; Fujita, M; Gogami, T; Hasegawa, S; Hayakawa, S H; Hayakawa, T; Honda, R; Hosomi, K; Hwang, S H; Ichige, N; Ichikawa, Y; Ikeda, M; Imai, K; Ishimoto, S; Kanatsuki, S; Kim, M H; Kim, S H; Kinbara, S; Koike, T; Lee, J Y; Marcello, S; Miwa, K; Moon, T; Nagae, T; Nagao, S; Nakada, Y; Nakagawa, M; Ogura, Y; Sakaguchi, A; Sako, H; Sasaki, Y; Sato, S; Shiozaki, T; Shirotori, K; Sugimura, H; Suto, S; Suzuki, S; Takahashi, T; Tamura, H; Tanabe, K; Tanida, K; Tsamalaidze, Z; Ukai, M; Yamamoto, Y; Yang, S B

    2015-11-27

    The energy spacing between the spin-doublet bound state of _{Λ}^{4}He(1^{+},0^{+}) was determined to be 1406±2±2  keV, by measuring γ rays for the 1^{+}→0^{+} transition with a high efficiency germanium detector array in coincidence with the ^{4}He(K^{-},π^{-})_{Λ}^{4}He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus _{Λ}^{4}H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the 0^{+} ground state but is vanishingly small in the 1^{+} excited state, demonstrating that the ΛN CSB interaction has spin dependence.

  15. Evidence of tensor interactions in 16O observed via (p,d) reaction

    NASA Astrophysics Data System (ADS)

    Ong, H. J.; Tanihata, I.; Tamii, A.; Myo, T.; Ogata, K.; Fukuda, M.; Hirota, K.; Ikeda, K.; Ishikawa, D.; Kawabata, T.; Matsubara, H.; Matsuta, K.; Mihara, M.; Naito, T.; Nishimura, D.; Ogawa, Y.; Okamura, H.; Ozawa, A.; Pang, D. Y.; Sakaguchi, H.; Sekiguchi, K.; Suzuki, T.; Taniguchi, M.; Takashina, M.; Toki, H.; Yasuda, Y.; Yosoi, M.; Zenihiro, J.

    2014-03-01

    We measured the differential cross sections of the 16O(p,d) reaction populating the ground state and several low-lying excited states in 15O using 198-, 295- and 392-MeV proton beams at the Research Center for Nuclear Physics (RCNP), Osaka University, to study the effect of the tensor interactions in 16O. Dividing the cross sections for each excited state by the one for the ground state and comparing the ratios over a wide range of momentum transfer, we found a marked enhancement of the ratio for the positive-parity state(s). The observation is consistent with large components of high-momentum neutrons in the ground-state configurations of 16O due possibly to the tensor interactions.

  16. Effect of tensor interactions in 16O studied via (p,d) reaction

    NASA Astrophysics Data System (ADS)

    Ong, H. J.; Tanihata, I.; Tamii, A.; Myo, T.; Ogata, K.; Fukuda, M.; Hirota, K.; Ikeda, K.; Ishikawa, D.; Kawabata, T.; Matsubara, H.; Matsuta, K.; Mihara, M.; Naito, T.; Nishimura, D.; Ogawa, Y.; Ozawa, A.; Pang, D. Y.; Sakaguchi, H.; Sekiguchi, K.; Suzuki, T.; Taniguchi, M.; Takashina, M.; Toki, H.; Yasuda, Y.; Yosoi, M.; Zenihiro, J.

    2014-12-01

    The differential cross sections of the 16O(p,d) reaction populating the ground state and several low-lying excited states in 15O were measured using 198-, 295- and 392-MeV proton beams at the Research Center for Nuclear Physics (RCNP), Osaka University, to study the effect of the tensor interactions in 16O. Dividing the cross sections for each excited state by the one for the ground state and comparing the ratios over a wide range of momentum transfer, we found a marked enhancement of the ratio for the positive-parity state(s). The observation is consistent with large components of high-momentum neutrons in the ground-state configurations of 16O due possibly to the tensor interactions.

  17. Pion-induced nucleon knockout reactions on 16O and 18O

    NASA Astrophysics Data System (ADS)

    Piasetzky, E.; Altman, A.; Lichtenstadt, J.; Yavin, A. I.; Ashery, D.; Bertl, W.; Felawka, L.; Walter, H. K.; Schlepütz, F. W.; Powers, K. J.; Winter, R. G.; Pluym, J. V. D.

    1982-12-01

    The (π+, π+p), (π-, π-p), and (π-, π-n) reactions on 16O and 18O were studied at 165 MeV by coincidence measurements of the outgoing particles. The cross sections for the (π-, π-n) reaction is larger on 18O than on 16O, whereas those for the (π+, π+p) and the (π-, π-p) reactions are smaller, most likely because of the coupling between the absorption and the scattering channels. NUCLEAR REACTIONS (π+/-, π+/-p) (π-, π-n) coin. Measurements on 16O18O E=165 MeV; deduced coupling between the absorption and the scattering channels.

  18. Using 81Kr-age of groundwater in the Guarani Aquifer, Brazil, to constrain estimates of continental degassing flux of 4He

    NASA Astrophysics Data System (ADS)

    Aggarwal, P. K.; Matsumoto, T.; Sturchio, N. C.; Chang, H. K.; Gastmans, D.; Lu, Z.; Jiang, W.; Müller, P.; Yokochi, R.; Han, L.; Klaus, P.; Torgersen, T.

    2013-12-01

    Continental degassing flux of helium is the dominant component of dissolved helium in deep groundwater together with that produced in-situ in the aquifer. A reliable estimate of the degassing flux is critical to the use of 4He as a dating tool in groundwater studies. The degassing flux is also important for understanding fluid and heat transport in the mantle and the rust. An independent tracer of groundwater age is required in order to deconvolute the two signals of the external, degassing flux and in situ production. Estimates of degassing flux mostly have relied upon shorter-lived radionuclides such as 14C and tritium and the resulting flux estimates have a significant variability (Torgersen, 2010). In the Guarani Aquifer in Brazil, an effective crustal 4He degassing flux into the aquifer was estimated from 81Kr ages ranging from about 70 Ka to 570 Ka. We then used the model framework of Toregesen and Ivey (1985), modified to include a diffusive reduction of originally uniform crustal helium flux from basement rocks through a thick sedimentary layer beneath the aquifer, to calculate a distribution of radiogenic 4He within the aquifer. With this framework, we obtain 4He ages that are consistent with ages based on 81Kr and 14C, and with a crustal degassing flux equivalent to that estimated from U and Th contents in the crust. The model framework for the Guarani Aquifer is also applied to data from other deep aquifers in Africa and Australia and our results suggest that the continental flux of 4He may be uniform, at least in stable continental areas. Additionally, a reliable estimate of the 4He degassing flux also helps to constrain the surficial discharge of deep groundwater.

  19. A method for investigation of the D(4He, γ)6Li reaction in the Ultralow energy region under a high background

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Dudkin, G. N.; Krylov, A. R.; Gazi, S.; Huran, J.; Nechaev, B. A.; Padalko, V. N.; Sadovsky, A. B.; Tuleushev, Yu. Zh.; Filipowicz, M.; Philippov, A. V.

    2016-07-01

    The cosmological lithium problem, that is, a noticeable discrepancy between the predicted and observed abundances of lithium, is in conflict with the Standard Big Bang Nucleosynthesis model. For example, the abundance of 7Li is 2-4 times smaller than predicted by the Standard Big Bang Nucleosynthesis. As to the abundance of 6Li, recent more accurate optical investigations have yielded only the upper limit on the 6Li/7Li ratio, which makes the problem of 6Li abundance and accordingly of disagreement with the Standard Big Bang Nucleosynthesis predictions less acute. However, experimental study of the D(4He, γ)6Li reaction cross section is still of current importance because there is a theoretical approach predicting its anomalously large value in the region of energies below the Standard Big Bang Nucleosynthesis energy. The work is dedicated to the measurement of the cross section for the D(4He, γ)6Li reaction proceeding in zirconium deuteride at the incident 4He+ion energy of 36 keV. The experiment is performed at a pulsed Hall plasma accelerator with an energy spread of 20% FWHM. A method for direct measurement of the background from the reaction chain D(4He, 4He)D→D(D, n)3He→(n, γ) and/or (n, n‧γ) ending with activation of the surrounding material by neutrons is proposed and implemented in the work. An upper limit on the D(4He, γ)6Li reaction cross section σ≤7·10-36 cm2 at the 90% confidence level is obtained.

  20. Differential binding of /sup 3/H-imipramine and /sup 3/H-mianserin in rat cerebral cortex

    SciTech Connect

    Dumbrille-Ross, A.; Tang, S.W.; Coscina, D.V.

    1981-11-16

    Drug competition profiles, effect of raphe lesion, and sodium dependency of the binding of two antidepressant drugs /sup 3/H-imipramine and /sup 3/H-mianserin to rat cerebral cortex homogenate were compared to examine whether the drugs bound to a common ''antidepressant receptor.'' Of the neurotransmitters tested, only serotonin displaced binding of both /sup 3/H-imipramine and /sup 3/H-mianserin. /sup 3/H-Mianserin binding was potently displaced by serotonin S/sub 2/ antagonists and exhibited a profile similar to that of /sup 3/H-spiperone binding. In the presence of the serotonin S/sub 2/ antagonist spiperone, antihistamines (H/sub 1/) potently displaced /sup 3/H-mianserin binding. /sup 3/H-Imipramine binding was displaced potently by serotonin uptake inhibitors. The order of potency of serotonergic drugs in displacing /sup 3/H-imipramine binding was not similar to their order in displacing /sup 3/H-spiperone or -3H-serotonin binding. Prior midbrain raphe lesions greatly decreased the binding of /sup 3/H-imipramine but did not alter binding of /sup 3/H-mianserin. Binding of /sup 3/H-imipramine but not /sup 3/H-mianserin was sodium dependent. These results show that /sup 3/H-imipramine and /sup 3/H-mianserin bind to different receptors. /sup 3/H-Imipramine binds to a presynaptic serotonin receptor which is probably related to a serotonin uptake recognition site, the binding of which is sodium dependent. /sup 3/H-Mianserin binds to postsynaptic receptors, possibly both serotonin S/sub 2/ and histamine H/sub 1/ receptors, the binding of which is sodium independent.

  1. New determination of 12C(α,γ)16O reaction rate

    NASA Astrophysics Data System (ADS)

    Oulebsir, N.

    2015-12-01

    The reaction 12C(α,γ)16O was investigated through the direct α-transfer reaction (7Li,t) at 28 and 34 MeV incident energies. We determined the reduced α-widths of the sub-threshold 2+ and 1- states of 16O from the DWBA analysis of the transfer reaction 12C(7Li,t)16O performed at two incident energies. The obtained result for the 2+ and 1- sub-threshold resonances as introduced in the R-matrix fitting of radiative capture and elastic-scattering data to determine the E2 and E1 S-factor from 0.01MeV to 4.2MeV in the center-of-mass energy. After determining the astrophysic factor of 12C(α,γ)16O S(E) with Pierre Descouvement code, I determined numerically the new reaction rate of this reaction at a different stellar temperature (0.06 Gk-2 GK). The 12C(α,γ)16O reaction rate at T9 = 0.2 is [7.21-2.25+2.15] × 10-15 cm3 s-1 mol-1. Some comparisons and discussions about our new 12C(α,γ)16O reaction rate are presented. The agreements of the reaction rate below T9 = 2 between our results and with those proposed by NACRE indicate that our results are reliable, and they could be included in the astrophysical reaction rate network.

  2. Angular Distributions for 3,4 Lambda H Bound States in the 3,4 He(e,e'K+) reaction

    SciTech Connect

    Dohrmann, Frank; Ahmidouch, Abdellah; Armstrong, Christopher; Arrington, John; Asaturyan, Razmik; Avery, Steven; Bailey, Kevin; Hu, Bitao; Breuer, Herbert; Brown, Daniel; Carlini, Roger; Cha, Jinseok; Chant, Nicholas; Christy, Michael; Cochran, Anthony; Cole, Leon; Crowder, J.; Danagoulian, Samuel; Elaasar, Mostafa; Ent, Rolf; Fenker, Howard; Fujii, Yu; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Hafidi, Kawtar; Hinton, Wendy; Juengst, Henry; Keppel, Cynthia; Liang, Yongguang; Liu, Jinghua; Lung, Allison; Mack, David; Markowitz, Pete; Mitchell, Joseph; Miyoshi, Toshinobu; Mkrtchyan, Hamlet; Mtingwa, Sekazi; Mueller, Robert; Niculescu, Gabriel; Niculescu, Maria-Ioana; Potterveld, David; Raue, Brian; Reimer, Paul; Reinhold, Joerg; Roche, Julie; Sarsour, Murad; Sato, Yoshinori; Segel, Ralph; Semenov, Andrei; Stepanyan, Samuel; Tadevosyan, Vardan; Tajima, Shigeyuki; Tang, Liguang; Uzzle, Alicia; Wood, Stephen; Yamaguchi, Hiroshi; Yan, Chen; Yuan, Lulin; Zeidman, Benjamin; Zeier, Markus; Zihlmann, Benedikt

    2004-12-01

    The 3Lambda H and 4Lambda H hypernuclear bound states have been observed for the first time in kaon electroproduction on 3,4He targets. The production cross sections have been determined at Q**2= 0.35 GeV**2 and W= 1.91 GeV. For either hypernucleus the nuclear form factor is determined by comparing the angular distribution of the 3,4He(e,e'K+)3,4Lambda H processes to the elementary cross section 1H(e,e'K+) Lambda on the free proton, measured during the same experiment.

  3. Interaction of Hydrogen Atoms with Helium Films: Sticking Probabilities for H on 3He and 4He, and the Binding Energy of H on 3He

    NASA Astrophysics Data System (ADS)

    Jochemsen, R.; Morrow, M.; Berlinsky, A. J.; Hardy, W. N.

    1981-09-01

    Magnetic resonance at 1420 MHz in zero magnetic field and for 0.064He. The binding energy for H on liquid 3He is found to be 0.42+/-0.05 K, and the sticking probabilities are 0.035 for H on 4He and 0.016 for H on 3He.

  4. Theory for supersolid 4He : Vacancy condensation facilitated by a low-energy bound state of a vacancy and an interstitial

    NASA Astrophysics Data System (ADS)

    Dai, Xi; Ma, Michael; Zhang, Fu-Chun

    2005-10-01

    Although both vacancies and interstitials have relatively high activation energies in the normal solid, we propose that a lower energy bound state of a vacancy and an interstitial may facilitate vacancy condensation to give supersolidity in 4He . We use a phenomenological two-band boson lattice model to demonstrate this new mechanism and discuss the possible relevance to the recently observed superfluidlike, nonclassical rotational inertial experiments of Kim and Chan in solid 4He . Some of our results may also be applicable to trapped bosons in optical lattices.

  5. Double Folding Potential of Different Interaction Models for 16O + 12C Elastic Scattering

    NASA Astrophysics Data System (ADS)

    Hamada, Sh.; Bondok, I.; Abdelmoatmed, M.

    2016-12-01

    The elastic scattering angular distributions for 16O + 12C nuclear system have been analyzed using double folding potential of different interaction models: CDM3Y1, CDM3Y6, DDM3Y1 and BDM3Y1. We have extracted the renormalization factor N r for the different concerned interaction models. Potential created by BDM3Y1 model of interaction has the shallowest depth which reflects the necessity to use higher renormalization factor. The experimental angular distributions for 16O + 12C nuclear system in the energy range 115.9-230 MeV exhibited unmistakable refractive features and rainbow phenomenon.

  6. Measurement and extrapolation of total cross sections of 12C+16O fusion at stellar energies

    NASA Astrophysics Data System (ADS)

    Fang, Xiao

    Carbon burning and oxygen burning in massive stars (M ≥ 8M[special character omitted]) are important burning phases in late stellar evolution following helium burning. They determined the nucleosynthesis phases and the initial matter distribution. Hydrostatic burning of 12C and 16O at lower temperatures remains an important feature. The critical reactions are the 12C+12C, 12C+ 16O and 16O+16O fusion processes. Extensive effort, both experimentally and theoretically, has been invested in the determination of the reaction rates for all reaction channels. Despite this effort, there remain large uncertainties in the predicted results that rely primarily on the extrapolation of the data into the Gamow range. The predicted results depend sensitively on the adopted model parameters, hindrance effects, and the possibility of resonances at relevant energies. The astrophysical important energy range of the 12C+12C fusion reaction spans from 1.0 MeV to 3.0 MeV. However, its cross section has not been determined with enough precision, despite numerous studies, due to the extremely low reaction cross sections and the large experimental background. The 12C+16O is difficult for experimental measurement due to the same reason. To allow measurements of the 12C+ 12C and 12C+16O fusions at astrophysical energies, a large-area silicon strip detector array was developed. The total cross section of the 12C+16O fusion has been measured at low energies using the St Ana 5MV accelerator at the University of Notre Dame. A high-intensity oxygen beam was produced impinging on a thick ultra-pure graphite target. Protons and gamma-rays have been measured simultaneously in the center-of-mass energy range of 3.64 to 4.93 MeV, using silicon and HPGe detectors. Statistical model calculations were employed to interpret the experimental results. This provides a more reliable extrapolation for the 12C+16O fusion cross section reducing substantially the uncertainty for stellar model simulations.

  7. New measurements and phase shift analysis of p16O elastic scattering at astrophysical energies

    NASA Astrophysics Data System (ADS)

    Dubovichenko, Sergey; Burtebayev, Nassurlla; Dzhazairov-Kakhramanov, Albert; Zazulin, Denis; Kerimkulov, Zhambul; Nassurlla, Marzhan; Omarov, Chingis; Tkachenko, Alesya; Shmygaleva, Tatyana; Kliczewski, Stanislaw; Sadykov, Turlan

    2017-01-01

    The results of new experimental measurements of p16O elastic scattering in the energy range of 0.6-1.0 MeV at angles of 40°-160° are given. Phase shift analysis of p16O elastic scattering was made using these and other experimental data on differential cross sections in excitation functions and angular distributions at energies of up to 2.5 MeV. Supported by the Ministry of Education and Science of the Republic of Kazakhstan (0073/PCF-IS-MES)

  8. New Astrophysical Reaction Rate for the 12C(α, γ)16O Reaction

    NASA Astrophysics Data System (ADS)

    An, Zhen-Dong; Ma, Yu-Gang; Fan, Gong-Tao; Li, Yong-Jiang; Chen, Zhen-Peng; Sun, Ye-Ying

    2016-01-01

    A new astrophysical reaction rate for 12C(α, γ)16O has been evaluated on the basis of a global R-matrix fitting to the available experimental data. The reaction rates of 12C(α, γ)16O for stellar temperatures between 0.04 ≤ T9 ≤ 10 are provided in a tabular form and by an analytical fitting expression. At T9 = 0.2, the reaction rate is (7.83 ± 0.35) × 1015 cm3 mol-1 s-1, where stellar helium burning occurs.

  9. Isotopic effects in the ( π±, 2N) reactions on 16O and 18O

    NASA Astrophysics Data System (ADS)

    Altman, A.; Ashery, D.; Piasetzky, E.; Lichtenstadt, J.; Yavin, A. I.; Bertl, W.; Felawka, L.; Walter, H. K.; Powers, R. J.; Winter, R. G.; v. d. Pluym, J.

    1984-09-01

    The ( π+, 2p), ( π+, pn) and ( π-, pn) reactions on 16O and 18O were studied at 165 MeV. The cross section for the ( π+, 2p) reaction on 18O is larger than that for 16O be only 5% ± 3%, while the total π+ absorption cross section is larger by 17% ± 5%. This supports the assumption that two-nucleon absorption occurs mainly on nucleons in the same shell. It is further concluded that Δ++n → pp is not only absorption mechanism that couples strongly to the nucleon knock out reactions.

  10. True absorption and scattering of pions on 16O and 18O

    NASA Astrophysics Data System (ADS)

    Navon, I.; Piasetzky, E.; Ashery, D.; Altman, A.; Azuelos, G.; Schlepütz, F. W.; Walter, H. K.

    1980-10-01

    The inclusive pion inelastic scattering and true absorption cross sections on 16O and 18O were measured at 165 MeV for π± and at 315 MeV for π+. The results show large effects of the two neutrons in 18O on the absorption and inelastic scattering cross sections at the resonance energy. In particular, the inelastic scattering of π+ from 18O is considerably smaller than from 16O and this effect is attributed to the coupling between the reaction channels.

  11. Inelastic pion double charge exchange on /sup 16/O at 240 MeV

    SciTech Connect

    Mischke, R.E.; Blomberg, A.; Gram, P.A.M.; Jansen, J.; Zichy, J.; Bolger, J.; Boschitz, E.; Ingram, C.H.Q.; Proebstle, G.

    1980-05-05

    The deep-inelastic double-charge-exchange reaction /sup 16/O(..pi../sup +/,..pi../sup -/) has been measured at 50/sup 0/, 85/sup 0/, and 130/sup 0/ with 240-MeV incident pions. The doubly differential cross section is peaked at low outgoing pion energies, as is expected from a double-scattering process, and is nearly isotropic. The integrated cross section is 5.8 +- 0.9 mb. The shape of the differential cross section suggests that the low-energy tail in /sup 16/O(..pi../sup +/,..pi../sup +prime/) scattering at the same energy also arises from double scattering.

  12. Spectral linelist of HD16O molecule based on VTT calculations for atmospheric application

    NASA Astrophysics Data System (ADS)

    Voronin, B. A.

    2014-11-01

    Three version line-list of dipole transition for isotopic modification of water molecule HD16O are presented. Line-lists have been created on the basis of VTT calculations (Voronin, Tennyson, Tolchenov et al. MNRAS, 2010) by adding air- and self-broadening coefficient, and temperature exponents for HD16O-air case. Three cut-of values for the line intensities were used: 1e-30, 1e-32 and 1e-35 cm/molecule. Calculated line-lists are available on the site ftp://ftp.iao.ru/pub/VTT/VTT-296/.

  13. Differential effects of triethyllead on synaptosomal [3H]dopamine vs. [3H]acetylcholine and [3H]gamma-aminobutyric acid release.

    PubMed

    Minnema, D J; Cooper, G P; Schamer, M M

    1991-01-01

    In vitro exposure to tetraethyllead (Et4Pb, 10 microM) did not alter the release of [3H] dopamine (DA), [3H]acetylcholine (ACh), or [3H]gamma-aminobutyric acid (GABA) from superfused synaptosomes isolated from rat brain striatum, hippocampus, and cortex, respectively. On the other hand, a concentration-dependent increase in the spontaneous release of these transmitters was observed following exposure to triethyllead (Et3Pb, 0.1-10 microM). The magnitude of 1 microM Et3Pb-induced [3H]DA release was 5-fold greater than that observed for [3H]ACh or [3H]GABA release. Removal of [Ca2+]e did not alter the Et3Pb-induced increase in the release of these three transmitter substances, nor did Et3Pb alter synaptosomal 45Ca efflux. EtePb-induced [3H]ACh and [3H]GABA release, but not [3H]DA release, was blocked by lowering [Na+]e from 140 to 50 mM. Similarly, the release of [3H]ACh and [3H]GABA, but not [3H]DA, induced by either Na,K-ATPase inhibition or veratridine (a Na(+)-ionophore), was attenuated by lowering [Na+]e from 140 to 50 mM. However, Et3Pb did not inhibit isolated synaptic membrane Na,K-ATPase, nor did the magnitude or temporal patterns of Et3Pb-induced transmitter release resemble transmitter release induced by Na,K-ATPase inhibition. Et3Pb and veratridine, but not Na,K-ATPase inhibition, produced an increase in synaptosomal [3H] deoxyglucose phosphate (dGluP) efflux, suggesting that both compounds increase membrane permeability. A Et3Pb-induced increase in membrane permeability is further supported by electrophysiological studies using the frog neuromuscular junction in which Et3Pb was found to reduce both the input resistance and membrane potential of muscle cells. As with [3H]ACh and [3H]GABA release, the Et3Pb-induced increase in synaptosomal [3H]dGluP efflux was attenuated by lowering [Na+]e.(ABSTRACT TRUNCATED AT 250 WORDS)

  14. Macroscopic quantum phenomena in interacting bosonic systems: Josephson flow in liquid 4He and multimode Schrodinger cat states

    NASA Astrophysics Data System (ADS)

    Volkoff, Tyler James

    In this dissertation, I analyze certain problems in the following areas: 1) quantum dynamical phenomena in macroscopic systems of interacting, degenerate bosons (Parts II, III, and V), and 2) measures of macroscopicity for a large class of two-branch superposition states in separable Hilbert space (Part IV). Part I serves as an introduction to important concepts recurring in the later Parts. In Part II, a microscopic derivation of the effective action for the relative phase of driven, aperture-coupled reservoirs of weakly-interacting condensed bosons from a (3 + 1)D microscopic model with local U(1) gauge symmetry is presented. The effective theory is applied to the transition from linear to sinusoidal current vs. phase behavior observed in recent experiments on liquid 4He driven through nanoaperture arrays. Part III discusses path-integral Monte Carlo (PIMC) numerical simulations of quantum hydrodynamic properties of reservoirs of He II communicating through simple nanoaperture arrays. In addition to calculating the local superfluid density in these systems, new estimators for hydrodynamic observables and novel methods for extracting the length scale characterizing the decay of superfluidity at the system boundary from PIMC data are introduced with the aim of exploring the mechanism of superfluid weak-link formation in nanoscale containers. Part IV consists of an analysis of macroscopicity measures for a large class of Schrodinger cat states of N-mode photonic systems. For cat states of this class, it is shown that a well-known measure of superposition size based on the optimal distinguishability of the branches and another based on metrological usefulness of the superposition relative to its branches agree (i.e., designate the same superpositions as macroscopic) when the inner product of the branches of the superposition is sufficiently small. For certain superpositions in this class, a technique is presented for deriving a state-specific metrological

  15. Search for the enhancement of the thermal expansion coefficient of superfluid 4HE Near T_Lambada by a heat current

    NASA Technical Reports Server (NTRS)

    Liu, Y.; Israelsson, U.; Larson, M.

    2001-01-01

    Presentation on the transition in 4He in the presence of a heat current (Q) provides an ideal system for the study of phase transitions under non-equlibrium, dynamical conditions. Many physical properties become nonlinear and Q-dependant near the transition temperature, T_Lambada.

  16. Search for the enhancement of the thermal expansion coefficient of superfluid 4HE Near T_Lambada by a heat current

    NASA Technical Reports Server (NTRS)

    Liu, Y.; Israelsson, U.; Larson, M.

    2001-01-01

    Presentation on the transition in 4He in the presence of a heat current (Q) provides an ideal system for the study of phase transitions under non-equlibrium, dynamical conditions. Many physical properties become nonlinear and Q-dependant near the transition temperature, T_Lambada.

  17. Probing the repulsive core of the nucleon-nucleon interaction via the (4)He(e,e'pN) triple-coincidence reaction.

    PubMed

    Korover, I; Muangma, N; Hen, O; Shneor, R; Sulkosky, V; Kelleher, A; Gilad, S; Higinbotham, D W; Piasetzky, E; Watson, J W; Wood, S A; Aguilera, P; Ahmed, Z; Albataineh, H; Allada, K; Anderson, B; Anez, D; Aniol, K; Annand, J; Armstrong, W; Arrington, J; Averett, T; Badman, T; Baghdasaryan, H; Bai, X; Beck, A; Beck, S; Bellini, V; Benmokhtar, F; Bertozzi, W; Bittner, J; Boeglin, W; Camsonne, A; Chen, C; Chen, J-P; Chirapatpimol, K; Cisbani, E; Dalton, M M; Daniel, A; Day, D; de Jager, C W; De Leo, R; Deconinck, W; Defurne, M; Flay, D; Fomin, N; Friend, M; Frullani, S; Fuchey, E; Garibaldi, F; Gaskell, D; Gilman, R; Glamazdin, O; Gu, C; Gueye, P; Hamilton, D; Hanretty, C; Hansen, J-O; Hashemi Shabestari, M; Holmstrom, T; Huang, M; Iqbal, S; Jin, G; Kalantarians, N; Kang, H; Khandaker, M; LeRose, J; Leckey, J; Lindgren, R; Long, E; Mammei, J; Margaziotis, D J; Markowitz, P; Marti Jimenez-Arguello, A; Meekins, D; Meziani, Z; Michaels, R; Mihovilovic, M; Monaghan, P; Munoz Camacho, C; Norum, B; Nuruzzaman; Pan, K; Phillips, S; Pomerantz, I; Posik, M; Punjabi, V; Qian, X; Qiang, Y; Qiu, X; Rakhman, A; Reimer, P E; Riordan, S; Ron, G; Rondon-Aramayo, O; Saha, A; Schulte, E; Selvy, L; Shahinyan, A; Sirca, S; Sjoegren, J; Slifer, K; Solvignon, P; Sparveris, N; Subedi, R; Tireman, W; Wang, D; Weinstein, L B; Wojtsekhowski, B; Yan, W; Yaron, I; Ye, Z; Zhan, X; Zhang, J; Zhang, Y; Zhao, B; Zhao, Z; Zheng, X; Zhu, P; Zielinski, R

    2014-07-11

    We studied simultaneously the (4)He(e,e'p), (4)He(e,e'pp), and (4)He(e,e'pn) reactions at Q(2)=2(GeV/c)(2) and x(B)>1, for an (e,e'p) missing-momentum range of 400 to 830  MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum, in a region where the nucleon-nucleon (NN) force is expected to change from predominantly tensor to repulsive. The abundance of neutron-proton pairs is reduced as the nucleon momentum increases beyond ∼500  MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum. Our data are compared with calculations of two-nucleon momentum distributions in (4)He and discussed in the context of probing the elusive repulsive component of the NN force.

  18. Probing the Repulsive Core of the Nucleon-Nucleon Interaction via the 4He(e,e`pN) Triple-Coincidence Reaction

    DOE PAGES

    Korover, Igor; Muangma, Navaphon; Hen, Or; ...

    2014-07-01

    We studied simultaneously the 4He(e,e'p), 4He(e,e'pp), and 4He(e,e'pn) reactions at Q2=2 [GeV/c]2 and xB >1, for a (e,e'p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A=2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum in a region where the nucleon-nucleon force is expected to change from predominantly tensor to repulsive. Neutron-proton pairs dominate the high-momentum tail ofmore » the nucleon momentum distributions, but their abundance is reduced as the nucleon momentum increases beyond ~500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum in the range we studied. Our data are compared with ab-initio calculations of two-nucleon momentum distributions in 4He.« less

  19. Calculation of photo-nuclear reaction cross sections for 16O

    NASA Astrophysics Data System (ADS)

    Arasoglu, Ali; Faruk Ozdemir, Omer

    2015-07-01

    Because of the high thermal expansion coefficient of uranium, the fuel used in nuclear power plants is usually in the form of UO2 which has ceramic structure and small thermal expansion coefficient. UO2 include one uranium atom and two oxygen atoms. After fission progress, total energy values of emitted gamma are about 14 MeV. This gamma energy may cause transmutation of 16O isotopes. Transmutation of 16O isotopes changes physical properties of nuclear fuel. Due to above explanations, it is very important to calculate photo-nuclear reaction cross sections of 16O. In this study; for (γ,p), (γ,np), (γ,n) and (γ,2n) reactions of 16O, photo-nuclear reaction cross-sections were calculated using different models for pre-equilibrium and equilibrium effects. Taking incident gamma energy values up to 40 MeV, Hybrid and Cascade Exciton Models were used for pre-equilibrium calculations and Weisskopf-Ewing (Equilibrium) Model was used for equilibrium model calculations. Calculation results were compared with experimental and theoretical data. While experimental results were obtained from EXFOR, TENDL-2013, JENDL/PD-2004 and ENDF/B VII.1 data base were used to get theoretical results.

  20. Angular correlation measurements for 4-{alpha} decaying states in {sup 16}O

    SciTech Connect

    Wuosmaa, A.H.; Back, B.B.; Betts, R.R.

    1995-08-01

    Previous measurements of the {sup 12}C({sup 12}C,{sup 8}Be){sup 16}O{sup *}(4 {alpha}) reaction identified discrete levels in {sup 16}O which decay by breakup into 4 {alpha} particles through a number of different decay sequences, including {sup 16}O{sup *} {yields} {sup 8}Be + {sup 8}Be and {alpha} + {sup 12}C (O{sub 2}{sup +}). These states are observed in a range of excitation energies where resonances are observed in inelastic {alpha} + {sup 12}C scattering leading to the {sup 8}Be + {sup 8}Be and {alpha} + {sup 12}C final states. These resonances were associated with 4 {alpha}-particle chain configurations in {sup 16}O. Should the states populated in the {sup 12}C + {sup 12}C reaction possess this same extended structure, it would serve as an important piece of evidence supporting the idea that even more deformed structures are formed in the {sup 24}Mg compound system. In order to more firmly make this association, it is important to determine the spins of the states populated in the {sup 12}C + {sup 12}C reaction.

  1. Isotope 18 O 16 O Ratio Measurements of Water Vapor by use of Photoacoustic Spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsumi, Yutaka; Kishigami, Masahiro; Tanaka, Noriyuki; Kawasaki, Masahiro; Inoue, Gen

    1998-09-01

    We applied a photoacoustic spectroscopy technique to isotope ratio measurements of 16 O and 18 O in water-vapor samples, using a pulsed tunable dye laser pumped by a Nd:YAG laser. The fourth overtone bands (4 OH ) of water molecules near 720 nm were investigated. We identified the absorption lines of H 2 16 O and H 2 18 O in the photoacoustic spectra that we measured by using an 18 O-enriched water sample and the HITRAN database. We measured the difference in the 18 O 16 O isotope ratios for normal distilled water and Antarctic ice, using the photoacoustic method. The value obtained for the difference between the two samples is 18 O 32 16 , where the indicated deviation was a 1 value among 240-s measurements, whereas the value measured with a conventional isotope mass spectrometer was 18 O 28 2 . This method is demonstrated to have the potential of a transportable system for in situ and quick measurements of the H 2 18 O H 2 16 O ratio in the environment.

  2. A comparison of groundwater dating with 81Kr, 36Cl and 4He in four wells of the Great Artesian Basin, Australia

    NASA Astrophysics Data System (ADS)

    Lehmann, B. E.; Love, A.; Purtschert, R.; Collon, P.; Loosli, H. H.; Kutschera, W.; Beyerle, U.; Aeschbach-Hertig, W.; Kipfer, R.; Frape, S. K.; Herczeg, A.; Moran, J.; Tolstikhin, I. N.; Gröning, M.

    2003-06-01

    The isotopic ratios 81Kr/Kr and 36Cl/Cl and the 4He concentrations measured in groundwater from four artesian wells in the western part of the Great Artesian Basin (GAB) in Australia are discussed. Based on radioactive decay along a water flow path the 81Kr/Kr ratios are directly converted to groundwater residence times. Results are in a range of 225-400 kyr with error bars in the order of 15% primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement. Additional uncertainties from subsurface production and/or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude. These 81Kr ages are then used to calibrate the 36Cl and the 4He dating methods. Based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining Bulldog shale the in situ flux of thermal neutrons and the corresponding 3He/ 4He and 36Cl/Cl ratios are calculated. From a comparison of: (i) the 3He/ 4He ratios measured in the groundwater samples with the calculated in situ ratios in rocks and (ii) the measured δ 37Cl ratios with the 4He concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and/or mixing. Based on this 'working hypothesis' the 36Cl transport equation in groundwater is solved taking into account: (i) radioactive decay, (ii) subsurface production in the sandstone aquifer (with an in situ 36Cl/Cl ratio of 6×10 -15) and (iii) addition of chloride from a source in the confining shale (with a 36Cl/Cl ratio of 13×10 -15). Lacking better information it is assumed that the chloride concentration increased linearly with time from an (unknown) initial value Ci to its measured present value C= Ci+ Ca, where Ca represents the (unknown) amount of chloride added from subsurface sources. Using the 81Kr ages of the four groundwater samples and a

  3. Large and unexpected enrichment in stratospheric 16O13C18O and its meridional variation

    PubMed Central

    Yeung, Laurence Y.; Affek, Hagit P.; Hoag, Katherine J.; Guo, Weifu; Wiegel, Aaron A.; Atlas, Elliot L.; Schauffler, Sue M.; Okumura, Mitchio; Boering, Kristie A.; Eiler, John M.

    2009-01-01

    The stratospheric CO2 oxygen isotope budget is thought to be governed primarily by the O(1D)+CO2 isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO2 isotopologue 16O13C18O, in concert with 18O and 17O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric 16O13C18O, observed as proportions in the polar vortex that are higher than in any naturally derived CO2 sample to date. We show, through photochemical experiments, that lower 16O13C18O proportions observed in the midlatitudes are determined primarily by the O(1D)+CO2 isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher 16O13C18O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O(1D)+CO2. We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO2 or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric 16O13C18O enrichments may impose additional isotopic constraints on biosphere–atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change. PMID:19564595

  4. Determination of the delta(18O/16O)of Water: RSIL Lab Code 489

    USGS Publications Warehouse

    Revesz, Kinga; Coplen, Tyler

    2008-01-01

    The purpose of the technique described by the Reston Stable Isotope Laboratory (RSIL) lab code 489 is to present a method to determine the delta(180/160), abbreviated as delta-180, of water. This delta-18O measurement of water also is a component of National Water Quality Laboratory (NWQL in USGS) schedules 1142 and 1172. Water samples are loaded into glass sample containers on a vacuum manifold to equilibrate gaseous CO2 at constant temperature (25 deg C) with water samples. After loading water samples on the vacuum manifold, air is evacuated through capillary to avoid evaporation, and CO2 is added. The samples are shaken to increase the equilibration rate of water and CO2. When isotopic equilibrium has been attained, an aliquot of CO2 is extracted sequentially from each sample container, separated from water vapor by means of a dry ice trap, and introduced into a dual-inlet isotope-ratio mass spectrometer (DI-IRMS) for determination of the delta-18O value. There is oxygen isotopic fractionation between water and CO2, but it is constant at constant temperature. The DI-IRMS is a DuPont double-focusing mass spectrometer. It has a double collector. One ion beam passes through a slit in a forward collector and is collected in the rear collector. The other ion beams are collected in the front collector. The instrument is capable of measuring mass/charge (m/z) 44 and 45 or 44 and 46 by changing the ion-accelerating voltage under computer control. The ion beams from these m/z values are as follows: m/z 44=CO2=12C16O16O, m/z 45=CO2=13C16O16O primarily, and m/z 46 = CO2=12C16O18O primarily. The data acquisition and control software calculates delta-18O values.

  5. Large and unexpected enrichment in stratospheric 16O13C18O and its meridional variation.

    PubMed

    Yeung, Laurence Y; Affek, Hagit P; Hoag, Katherine J; Guo, Weifu; Wiegel, Aaron A; Atlas, Elliot L; Schauffler, Sue M; Okumura, Mitchio; Boering, Kristie A; Eiler, John M

    2009-07-14

    The stratospheric CO(2) oxygen isotope budget is thought to be governed primarily by the O((1)D)+CO(2) isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO(2) isotopologue (16)O(13)C(18)O, in concert with (18)O and (17)O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric (16)O(13)C(18)O, observed as proportions in the polar vortex that are higher than in any naturally derived CO(2) sample to date. We show, through photochemical experiments, that lower (16)O(13)C(18)O proportions observed in the midlatitudes are determined primarily by the O((1)D)+CO(2) isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher (16)O(13)C(18)O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O((1)D)+CO(2). We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO(2) or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric (16)O(13)C(18)O enrichments may impose additional isotopic constraints on biosphere-atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change.

  6. Astrophysical S-factor of T(4He, γ)7Li reaction at E cm = 15.7 keV

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Dudkin, G. N.; Emets, E. G.; Filipowicz, M.; Krylov, A. R.; Nechaev, B. A.; Nurkin, A.; Padalko, V. N.; Philippov, A. V.; Sadovsky, A. B.

    2017-07-01

    The astrophysical S-factor of the reaction T(4He, γ)7Li is measured for the first time at the center of mass energy E cm = 15.7 keV, lower than the energy range of the Standard Big Bang Nucleosynthesis (SBBN) model. The experiment is performed on a Hall pulsed accelerator (TPU, Tomsk). An acceleration pulse length of 10 μs allows one to suppress the background of cosmic radiation and the ambient medium by five orders of magnitude. A beam intensity of 5 × 1014 4He+ ions per pulse allows one to measure an extremely low reaction yield. The yield of γ-quanta with the energies E γ 0 = 2483.7 keV and E γ 1 = 2006.1 keV is registered by NaI(Tl) detectors with the efficiency ɛ = 0.331 ± 0.026. A method for direct measurement of the background from the chain of reactions T(4He, 4He)T→T(T, 2 n)X→( n, γ) and/or ( n, n'γ) which ends by neutron activation of materials surrounding the target is proposed and implemented in this study. The value of the astrophysical S-factor of the reaction T(4He, γ)7Li S αt ( E cm = 15.7 keV) = 0.091 ± 0.032 keV b provides the choice from the set of experimental data for the astrophysical S αt -factor in favor of experimental data [4] with S αt ( E cm = 0) = 0.1067 ± 0.0064 keV b.

  7. Elastic scattering of {sup 16}O+{sup 16}O at energies E/A between 5 and 8 MeV

    SciTech Connect

    Nicoli, M. P.; Haas, F.; Freeman, R. M.; Aissaoui, N.; Beck, C.; Elanique, A.; Nouicer, R.; Morsad, A.; Szilner, S.; Basrak, Z.

    1999-12-01

    The elastic scattering of {sup 16}O+{sup 16}O has been measured at nine energies between E{sub lab}=75 and 124 MeV. The data cover up to 100 degree sign in the c.m. and can be described in terms of phenomenological and folding model potentials which reproduce the main features observed. In agreement with studies at higher energies in this and similar systems, refractive effects are present in the angular distributions at all energies. In particular, the passage of Airy minima through 90 degree sign at E{sub c.m.}=40, 47.5, and 62 MeV explains the deep minima observed in the excitation function. The real part of the optical potential is found to vary very little with energy over the studied interval, but the imaginary part shows a rapid change in its shape at incident energy about 90 MeV. Nonetheless, the energy dependence of the volume integral of the real and imaginary parts is in agreement with dispersion relation predictions. (c) 1999 The American Physical Society.

  8. Evolving model-free scattering matrix via evolutionary algorithm: {sup 16}O-{sup 16}O elastic scattering at 350 MeV

    SciTech Connect

    Korda, V.Yu.; Molev, A.S.; Korda, L.P.

    2005-07-01

    We present a new procedure that enables us to extract a scattering matrix S(l) as a complex function of angular momentum directly from the scattering data without any a priori model assumptions implied. The key ingredient of the procedure is the evolutionary algorithm with diffused mutation that evolves the population of the scattering matrices by means of their smooth deformations from the primary arbitrary analytical S(l) shapes to the final ones, giving high-quality fits to the data. Because of the automatic monitoring of the scattering-matrix derivatives, the final S(l) shapes are monotonic and do not have any distortions. For the {sup 16}O-{sup 16}O elastic-scattering data at 350 MeV, we show the independence of the final results of the primary S(l) shapes. Contrary to other approaches, our procedure provides an excellent fit by the S(l) shapes that support the 'rainbow' interpretation of the data under analysis.

  9. The 3H(d,γ)5He Reaction for Ec.m. ≤ 300 keV

    NASA Astrophysics Data System (ADS)

    Parker, C. E.; Brune, C. R.; Massey, T. N.; O'Donnell, J. E.; Richard, A. L.; Sayre, D. B.

    2016-03-01

    The 3H(d, γ)5He reaction has been measured using a 500-keV pulsed deuteron beam incident on a stopping titanium tritide target at Ohio University's Edwards Accelerator Laboratory. The time-of-flight (TOF) technique has been used to distinguish the γ-rays from neutrons detected in the bismuth germinate (BGO) γ-ray detector. A stilbene scintillator and an NE-213 scintillator have been used to detect the neutrons from the 3H(d, n)4He reaction using both the pulse-shape discrimination and TOF techniques. A newly-designed target holder with a silicon surface barrier detector to simultaneously measure α-particles to normalize the neutron count was incorporated for subsequent measurements. The γ-rays have been measured at laboratory angles of 0°, 45°, 90°, and 135°. Information about the γ-ray energy distribution for the unbound ground state and first excited state of 5He can be obtained experimentally by comparing the BGO data to Monte Carlo simulations. The 3H(d, γ)/3H(d, n) branching ratio has also been determined.

  10. Comparison of (/sup 3/H)nicotine and (/sup 3/H)acetylcholine binding in mouse brain: regional distribution

    SciTech Connect

    Sershen, H.; Reith, M.E.; Hashim, A.; Lajtha, A.

    1985-06-01

    In a continuing study of nicotine binding sites, the authors determined the relative amount of nicotine binding and acetylcholine binding in various brain regions of C57/BL and of DBA mice. Although midbrain showed the highest and cerebellum the lowest binding for both (/sup 3/H)nicotine and (/sup 3/H)acetylcholine, the ratio of nicotine to acetylcholine binding showed a three-fold regional variation. Acetylcholine inhibition of (/sup 3/H)nicotine binding indicated that a portion of nicotine binding was not inhibited by acetylcholine. These results indicate important differences between the binding of (+/-)-(/sup 3/H)nicotine and that of (/sup 3/H)acetylcholine.

  11. Infiltration of river water to a shallow aquifer investigated with 3H/ 3He, noble gases and CFCs

    NASA Astrophysics Data System (ADS)

    Beyerle, U.; Aeschbach-Hertig, W.; Hofer, M.; Imboden, D. M.; Baur, H.; Kipfer, R.

    1999-09-01

    Noble gas isotopes ( 3He, 4He, Ne, Ar, Kr, Xe), tritium ( 3H), chlorofluorocarbons (CFCs) and dissolved oxygen (O 2) were seasonally measured in a small groundwater system recharged by infiltration of river water at Linsental, northeastern Switzerland. All Groundwater samples contained an excess of atmospheric noble gases ('excess air') usually with an elemental composition equal to air. The concentrations of atmospheric noble gases in the groundwater were used to calculate the excess air component and the water temperature at recharge. The noble gas temperatures (NGTs) in the boreholes close to the river vary seasonally, however, the average NGT of all samples lies close to the mean annual temperature of the river water. Groundwater ages were calculated using the tritium/helium-3 ( 3H/ 3He) dating method. The water ages of the samples obtained near the river depend on the amount of recently infiltrated river water and are young during times of active river discharge. In contrast, the mean water age of about 3 years of the deep aquifer remained nearly constant over the sampling period. The observed CFC-11 (CFCl 3) and CFC-12 (CF 2Cl 2) concentrations are significantly higher than the atmospheric equilibrium concentrations and therefore CFCs do not provide any direct information on the residence time of the groundwater. Nevertheless, the CFC excess in the groundwater shows a linear increase with the 3H/ 3He age. Additionally, both accumulation of radiogenic He ( 4He rad) and O 2 consumption are strongly correlated with residence time. All these correlations can be interpreted either in terms of mixing of recently infiltrated river water with older groundwater or in terms of accumulation/consumption rates.

  12. Binding of [3H]-prazosin and [3H]-dihydroergocryptine to rat cardiac alpha-adrenoceptors.

    PubMed Central

    Guicheney, P.; Meyer, P.

    1981-01-01

    1 [3H]-prazosin binds specifically to a single class of alpha-adrenoceptors in rat cardiac membranes (KD25 degrees C = 0.2 nM). 2 That these receptors are of the alpha 1-type was indicated by competition studies, i.e. alpha 1-antagonists such as prazosin and (2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1, 4-benzodioxane (WB 4101) were more potent than the alpha 2-antagonists, yohimbine and piperoxan in inhibiting [3H]-prazosin binding. 3 A comparative study of [3H]-prazosin binding and [3H]-dihydroergocryptine binding to cardiac membranes showed that both [3H]-prazosin and [3H]-dihydroergocryptine (at low concentrations) bind to alpha 2-adrenoceptors, while [3H]-dihydroergocryptine (at higher concentrations) also binds to another class of sites. PMID:6269682

  13. High performance cobalt-free Cu1.4Mn1.6O4 spinel oxide as an intermediate temperature solid oxide fuel cell cathode

    NASA Astrophysics Data System (ADS)

    Zhen, Shuying; Sun, Wang; Li, Peiqian; Tang, Guangze; Rooney, David; Sun, Kening; Ma, Xinxin

    2016-05-01

    In this work Cu1.4Mn1.6O4 (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu+/Cu2+ and Mn3+/Mn4+ couples exist in the CMO sample, and a maximum conductivity of 78 S cm-1 is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc2O3 stabilized ZrO2 (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm2 at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm-2 at 800 °C under H2 (3% H2O) as the fuel and ambient air as the oxidant. These results indicate that Cu1.4Mn1.6O4 is a superior and promising cathode material for IT-SOFCs.

  14. Asthenosphere-lithosphere interactions in Western Saudi Arabia: Inferences from 3He/4He in xenoliths and lava flows from Harrat Hutaymah

    NASA Astrophysics Data System (ADS)

    Konrad, Kevin; Graham, David W.; Thornber, Carl R.; Duncan, Robert A.; Kent, Adam J. R.; Al-Amri, Abdullah M.

    2016-04-01

    Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed 3He/4He, and He, CO2 and trace element concentrations in minerals separated from xenoliths and lava flows from Harrat Hutaymah, supplemented with reconnaissance He isotope data from several other volcanic fields (Harrat Al Birk, Harrat Al Kishb and Harrat Ithnayn). Harrat Hutaymah is young (< 850 ka) and the northeasternmost of the volcanic fields. There is a remarkable homogeneity of 3He/4He trapped within most xenoliths, with a weighted mean of 7.54 ± 0.03 RA (2σ, n = 20). This homogeneity occurs over at least eight different xenolith types (including spinel lherzolite, amphibole clinopyroxenite, olivine websterite, clinopyroxenite and garnet websterite), and encompasses ten different volcanic centers within an area of ~ 2500 km2. The homogeneity is caused by volatile equilibration between the xenoliths and fluids derived from their host magma, as fluid inclusions are annealed during the infiltration of vapor-saturated magmas along crystalline grain boundaries. The notable exceptions are the anhydrous spinel lherzolites, which have a lower weighted mean 3He/4He of 6.8 ± 0.3 RA (2σ, n = 2), contain lower concentrations of trapped He, and have a distinctly depleted light rare earth element signature. 3He/4He values of ~ 6.8 RA are also commonly found in spinel lherzolites from harrats Ithnayn, Al Birk, and from Zabargad Island in the Red Sea. Olivine from non-xenolith-bearing lava flows at Hutaymah spans the He isotope range of the xenoliths. The lower 3He/4He in the anhydrous spinel lherzolites appears to be tied to remnant Proterozoic lithosphere prior to metasomatic fluid overprinting. Elevated 3He/4He in the western harrats has been observed only at Rahat (up to 11.8 RA; Murcia et al., 2013), a

  15. Analogs of the giant dipole and spin-dipole resonances in {sup 4}He and in {alpha} clusters of {sup 6,7}Li studied by the {sup 4}He,{sup 6,7}Li({sup 7}Li,{sup 7}Be{gamma}) reactions

    SciTech Connect

    Nakayama, S.; Matsumoto, E.; Fushimi, K.; Hayami, R.; Kawasuso, H.; Yasuda, K.; Yamagata, T.; Akimune, H.; Ikemizu, H.; Asaji, S.; Ishida, T.; Kudoh, T.; Sagara, K.; Fujiwara, M.; Hashimoto, H.; Kawase, K.; Nakanishi, K.; Oota, T.; Yosoi, M.; Greenfield, M. B.

    2008-07-15

    We studied analogs of the giant dipole resonance (GDR) and spin-dipole resonance (SDR) in {sup 4}He and in the {alpha} clusters of {sup 6,7}Li via the ({sup 7}Li,{sup 7}Be{gamma}) reactions on {sup 4}He, {sup 6}Li, and {sup 7}Li at an incident energy of 455 MeV and at a scattering angle of 0 deg. by measuring spin-nonflip and spin-flip spectra. The reaction Q-values for the analogs of the GDR and SDR in the {alpha} clusters of {sup 6,7}Li were found to be more negative than those in {sup 4}He by 2.0{+-}0.5 MeV. The ratios of the cross section for the analog of the GDR to that for the analog of the SDR in {sup 4}He and in the {alpha} clusters of {sup 6}Li and {sup 7}Li were found to be the same within errors, 0.5{+-}0.1. The cross sections for the analogs of the GDR as well as those for the analogs of the SDR in the {alpha} clusters of {sup 6,7}Li were 0.6{approx}0.8 times smaller than those in {sup 4}He. These results suggest that excitations of {alpha} clusters embedded in nuclei are suppressed as compared with excitations of free {alpha} particles.

  16. One-two step transfer observed in 16O+11B nuclear system

    NASA Astrophysics Data System (ADS)

    Hamada, Sh.; Burtebayev, N.

    2015-06-01

    The angular distribution measurements for 16O ion beam elastically scattered from 11B target of thickness 32.9μg/cm2 at energy 22.4 MeV had been performed in the cyclotron DC-60 INP NNC RK. The previous measurements for 16O+11B nuclear system at energies 27, 30, 32.5 and 35 MeV showed an increase in the differential cross-section at backward angles due to the contribution of cluster transfer. Such transfer process could not be described in terms of optical model (OM); it could be described within the framework of distorted wave Born approximation method implemented in FRESCO code. Both one (5Li) and two-step transfer (proton transfer followed by Alpha transfer) were taken into considerations. We have extracted the spectroscopic amplitude (SA) for the configuration 16O→11B+5Li.

  17. The gamma 1 and gamma 3 bands of (16)O3: Line positions and intensities

    NASA Technical Reports Server (NTRS)

    Flaud, J.-M.; Camy-Peyret, C.; Devi, V. Malathy; Rinsland, C. P.; Smith, M. A. H.

    1988-01-01

    Using 0.005/cm-resolution Fourier transform spectra of samples of ozone, the gamma 1 and gamma 3 bands of (16)O3 have been reanalyzed to obtain accurate line positions and an extended set of upper state rotational levels (J up to 69, K sub a up to 20). Combined with the available microwave data, these upper state rotational levels were satisfactorily fitted using a Hamiltonian which takes explicitly into account the strong Coriolis interaction affecting the rotational levels of these two interacting states. In addition, 350 relative line intensities were measured from which the rotational expansions of the transition moment operators for the gamma 1 and gamma 3 states have been deduced. Finally, a complete listing of line positions, intensities, and lower state energies of the gamma 1 and gamma 3 bands of (16)O3 has been generated.

  18. Spectroscopy of {sup 16}O Using {alpha}+{sup 12}C Resonant Scattering in Inverse Kinematics

    SciTech Connect

    Ashwood, N. I.; Freer, M.; Bloxham, T. R.; Curtis, N.; Haigh, P. J.; Price, D. L.; Achouri, N. L.; Catford, W. N.; Harlin, C. W.; Patterson, N. P.; Thomas, J. S.; Soic, N.

    2009-08-26

    A measurement of the {alpha}({sup 12}C,{alpha}){sup 12}C reaction has been performed using resonant scattering with a gas target. Beam energies of 46, 51, 56 and 63 MeV were used to populate resonances in the excitation energy range of 11.6 to 22.9 MeV in {sup 16}O. The angular distributions of the elastic scattering were measured at zero degrees using an array of segmented silicon strip detectors with a minimum range of 0 deg. to 30 deg. in the centre of mass. The spins of 8 resonances between 14.1 and 18.5 MeV were obtained, confirming spin assignments made using elastic scattering in normal kinematics. An R-matrix analysis of the data was performed which indicates that the present understanding of {sup 16}O in this region is good, but not complete.

  19. Two-neutron stripping in ({sup 18}O, {sup 16}O) and (t,p) reactions

    SciTech Connect

    Cavallaro, M.; Agodi, A.; Carbone, D.; Cunsolo, A.; Bondì, M.; Cappuzzello, F.; Nicolosi, D.; Tropea, S.; Borello-Lewin, T.; Rodrigues, M. R. D.; De Napoli, M.; Garcia, V. N.

    2014-11-11

    The {sup 12}C({sup 18}O,{sup 16}O){sup 14}C reactions has been investigated at 84 MeV incident energy. The charged ejectiles produced in the reaction have been momentum analyzed and identified by the MAGNEX magnetic spectrometer. Q-value spectra have been extracted with an energy resolution of 160 keV (Full Width at Half Maximum) and several known bound and resonant states of {sup 14}C have been identified up to 15 MeV. In particular, excited states with dominant 2p - 4h configuration are the most populated. The absolute values of the cross sections have been extracted showing a striking similarity with those measured for the same transitions by (t,p) reactions. This indicates that the effect of the {sup 16}O core is negligible in the reaction mechanism.

  20. Effect of Tensor Interactions in 16O Studied via (p,d) Reaction

    NASA Astrophysics Data System (ADS)

    Ong, H. J.; Tanihata, I.; Tamii, A.; Myo, T.; Ogata, K.; Fukuda, M.; Hirota, K.; Ikeda, K.; Ishikawa, D.; Kawabata, T.; Matsubara, H.; Matsuta, K.; Mihara, M.; Naito, T.; Nishimura, D.; Ogawa, Y.; Ozawa, A.; Pang, D. Y.; Sakaguchi, H.; Sekiguchi, K.; Suzuki, T.; Taniguchi, M.; Takashina, M.; Toki, H.; Yasuda, Y.; Yosoi, M.; Zenihiro, J.

    We report a study on the effect of the tensor interactions in 16O via the (p,d) reaction using proton beams at 198, 295, and 392 MeV at the Research Center for Nuclear Physics (RCNP), Osaka University. Differential cross sections populating the ground state and several low-lying excited states in 15O were measured. Dividing the cross sections for each excited state by the one for the ground state and comparing the ratios over a wide range of momentum transfer, we found a marked enhancement of the ratio for the 5/2+ and/or 1/2+ state(s). The observation indicates large components of high-momentum neutrons in the ground-state configurations of 16O due possibly to the tensor interactions.