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Sample records for low-energy pion-pion scattering

  1. Low energy pion-pion elastic scattering in the Sakai-Sugimoto model

    SciTech Connect

    Parthasarathy, R.; Viswanathan, K. S.

    2008-06-01

    We have considered the holographic large N{sub c} QCD model proposed by Sakai and Sugimoto and evaluated the non-Abelian DBI-action on the D8-brane up to ({alpha}{sup '}){sup 4} terms. Restricting to the pion sector, these corrections give rise to four derivative contact terms for the pion field. We derive the Weinberg's phenemenological Lagrangian. The coefficients of the four derivative terms are determined in terms of g{sub YM}{sup 2}. The low energy pion-pion scattering amplitudes are evaluated. Numerical results are presented with the choice of M{sub KK}=0.94 GeV and N{sub c}=11. The results are compared with the amplitudes calculated using the experimental phase shifts. The agreement with the experimental data is found to be satisfactory.

  2. Determination of SU(2) chiral perturbation theory low energy constants from a precise description of pion-pion scattering threshold parameters

    NASA Astrophysics Data System (ADS)

    Nebreda, J.; Peláez, J. R.; Ríos, G.

    2013-09-01

    We determine the values of the one- and two-loop low energy constants appearing in the SU(2) Chiral Perturbation Theory calculation of pion-pion scattering. For this we use a recent and precise sum rule determination of some scattering lengths and slopes that appear in the effective range expansion. In addition we provide sum rules for these coefficients up to third order in the expansion. Our results when using only the scattering lengths and slopes of the S, P, D, and F waves are consistent with previous determinations but seem to require higher order contributions if they are to accommodate the third order coefficients of the effective range expansion.

  3. Low energy scattering with a nontrivial pion

    SciTech Connect

    Fariborz, Amir H.

    2007-12-01

    An earlier calculation in a generalized linear sigma model showed that the well-known current algebra formula for low energy pion-pion scattering held even though the massless Nambu Goldstone pion contained a small admixture of a two-quark two-antiquark field. Here we turn on the pion mass and note that the current algebra formula no longer holds exactly. We discuss this small deviation and also study the effects of a SU(3) symmetric quark mass type term on the masses and mixings of the eight SU(3) multiplets in the model. We calculate the s-wave scattering lengths, including the beyond current algebra theorem corrections due to the scalar mesons, and observe that the effect of the scalar mesons is to improve the agreement with experiment. In the process, we uncover the way in which linear sigma models give controlled corrections (due to the presence of scalar mesons) to the current algebra scattering formula. Such a feature is commonly thought to exist only in the nonlinear sigma model approach.

  4. Effect of coupled channels of the multi-channel pion-pion scattering in two-pion transitions of the Υ mesons

    NASA Astrophysics Data System (ADS)

    Surovtsev, Yurii S.; Bydžovský, Petr; Gutsche, Thomas; Kamiński, Robert; Lyubovitskij, Valery E.; Nagy, Miroslav

    2015-11-01

    The effect of isoscalar S-wave processes ππ → ππ,KK¯,ηη is considered in the analysis of data (from the ARGUS, CLEO, CUSB, Crystal Ball, Belle, BABAR collaborations) on the bottomonia decays — Υ(mS) → Υ(nS)ππ (m > n,m = 2, 3, 4, 5,n = 1, 2, 3). It is shown that the dipion mass spectra of these decays are explained by the unified mechanism related to the contribution of the multichannel ππ scattering in the final states of these reactions. Since in the analysis the multichannel ππ-scattering amplitudes did not change in comparison with the ones in our combined analysis of data on the multichannel ππ scattering and on the charmonia decays — J/ψ → ϕ(ππ,KK¯) and ψ(2S) → J/ψ(ππ) (from the Crystal Ball, DM2, Mark II, Mark III, and BES II) — the results confirm all our earlier conclusions on the scalar mesons.

  5. Simulation of low-energy ion scattering

    NASA Astrophysics Data System (ADS)

    Langelaar, M. H.; Breeman, M.; Mijiritskii, A. V.; Boerma, D. O.

    A new simulation program `MATCH' has been developed for a detailed analysis of low-energy ion scattering (LEIS) and recoiling data. Instead of performing the full calculation of the three-dimensional trajectories through the sample from the ion source towards the detector, incoming trajectories as well as reversed-time outgoing trajectories are calculated, separately. Finally, these trajectories are matched to obtain the yield. The program has been tested for spectra and azimuthal scans of scattering and recoiling events of various sample species in different scattering geometries.

  6. Low energy Skyrmion-Skyrmion scattering

    SciTech Connect

    Gisiger, T.; Paranjape, M.B. )

    1994-07-15

    We study the scattering of two Skyrmions at low energy and large separation. We use the method proposed by Manton for truncating the degrees of freedom of the system from infinite to a manageable finite number. This corresponds to identifying the manifold consisting of the union of the low energy critical points of the potential along with the gradient flow curves joining these together and by positing that the dynamics is restricted here. The kinetic energy provides an induced metric on this manifold while restricting the full potential energy to the manifold defines a potential. The low energy dynamics is now constrained to these finite number of degrees of freedom. For a large separation of the two Skyrmions the manifold is parametrized by the variables of the product ansatz. We find the interaction between two Skyrmions coming from the induced metric, which was independently found by Schroers. We find that the static potential is actually negligible in comparison to this interaction. Thus to lowest order, at large separation, the dynamics reduces to geodesic motion on the manifold. We consider the scattering to first order in the interaction using the perturbative method of Lagrange and find that the dynamics in the no spin or charge exchange sector reduces to the Kepler problem.

  7. Low energy Skyrmion-Skyrmion scattering

    NASA Astrophysics Data System (ADS)

    Gisiger, T.; Paranjape, M. B.

    1994-07-01

    We study the scattering of two Skyrmions at low energy and large separation. We use the method proposed by Manton for truncating the degrees of freedom of the system from infinite to a manageable finite number. This corresponds to identifying the manifold consisting of the union of the low energy critical points of the potential along with the gradient flow curves joining these together and by positing that the dynamics is restricted here. The kinetic energy provides an induced metric on this manifold while restricting the full potential energy to the manifold defines a potential. The low energy dynamics is now constrained to these finite number of degrees of freedom. For a large separation of the two Skyrmions the manifold is parametrized by the variables of the product ansatz. We find the interaction between two Skyrmions coming from the induced metric, which was independently found by Schroers. We find that the static potential is actually negligible in comparison to this interaction. Thus to lowest order, at large separation, the dynamics reduces to geodesic motion on the manifold. We consider the scattering to first order in the interaction using the perturbative method of Lagrange and find that the dynamics in the no spin or charge exchange sector reduces to the Kepler problem.

  8. Computational Study of Low Energy Nuclear Scattering

    NASA Astrophysics Data System (ADS)

    Salazar, Justin; Hira, Ajit; Brownrigg, Clifton; Pacheco, Jose

    2013-04-01

    We continue our interest in the interactions between different nuclear species with a computational study of the scattering of the low-energy nuclei of H through F atoms ( Z<=9 ) from Palladium and other metals. First, a FORTRAN computer program was developed to compute stopping cross sections and scattering angles in Pd and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 10 to 140kev. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies have potential applications in nuclear physics and in nuclear medicine.

  9. Low-energy pion-nucleon scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Ai, Li; Kaufmann, W. B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.

  10. Low-energy pion-nucleon scattering

    SciTech Connect

    Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}

  11. Low Energy Electron Scattering from Fuels

    NASA Astrophysics Data System (ADS)

    Lopes, M. C. A.; Silva, D. G. M.; Bettega, M. H. F.; da Costa, R. F.; Lima, M. A. P.; Khakoo, M. A.; Winstead, C.; McKoy, V.

    2012-11-01

    In order to understand and optimize processes occurring during the ignition of plasma and its consequences in post-discharge for an internal combustion engine, especially considering the spark plug, we have produced in this work some basic information necessary to modeling spark ignition in alcohol- fuelled engines. Total cross sections of electron scattering by methanol and ethanol molecules in the energy range from 60 to 500 eV are reported, using the linear transmission method based on the Beer-Lambert law to first approximation. Aditionally to that, measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering were also discussed, for impact energies of 1, 2, 5, 10, 15, 20, 30, 50, and 100 eV and for scattering angles of 5°-130°. The measurements were obtained using the relative flow method with an aperture source, and calculations using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons.

  12. Parity violation in low-energy neutron-deuteron scattering

    SciTech Connect

    Song, Young-Ho; Gudkov, Vladimir; Lazauskas, Rimantas

    2011-01-15

    Parity-violating effects for low-energy elastic neutron deuteron scattering are calculated for Desplanques, Donoghue, and Holstein (DDH) and effective field theory types of weak potentials in a distorted-wave Born approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The resulting relation between physical observables and low-energy constants can be used to fix low-energy constants from experiments. Potential model dependencies of parity-violating effects are discussed.

  13. Neutron Radii from Low Energy Pion Scattering.

    NASA Astrophysics Data System (ADS)

    Gyles, William

    Recent electron scattering measurements and muonic atom studies have allowed precise determinations of the charge distributions of nuclei. Measurements of the neutron distributions, however, have not progressed to this degree of sophistication, largely because of the uncertainties in the hadron-nucleus interaction. Charge distribution measurements provide good tests of nuclear structure calculations, but measurements of neutron distributions will provide independent constraints on these calculations and the potentials used. In this experiment, (pi)('-) differential cross section ratios were measured on pairs of isotopes (('36)S,('32)S), (('34)S,('32)S) with 50 MeV pions and (('26)Mg,('24)Mg) with 45 MeV pions. Absolute differential cross sections were also measured for ('32)S and ('24)Mg. Magnetic spectro -meters were used to collect the data. The cross section ratios were compared to optical model calcula-tions in which the parameters of a Fermi function representing the neutron distribution of the larger isotope of each pair were varied. The rms radius difference between the two isotopes producing the best fit was found to be independent of the details of the optical potential used, as long as the potential produced a fit to the absolute cross sections. The neutron distribution of the larger isotope was also rep-resented as a Fermi function modified by a sum of spherical Bessel functions, the coefficients of which were allowed to vary. The results for the rms radius differences were consistent with the Fermi function fits, except for ('34)S-('32)S, where the results differed by a full standard deviation. The rms radius differences found for the sulfur isotopes agreed with the results of shell-model calculations by Hodgson (Str82,Hod83). The extracted rms radius difference of the magnesium isotopes was one standard deviation less than the shell-model prediction. The results for the Fermi function fits, Fourier Bessell fits and the single particle potential (SPP

  14. Low-energy scattering of electrons and positrons in liquids

    NASA Technical Reports Server (NTRS)

    Schrader, D. M.

    1990-01-01

    The scattering of low energy electrons and positrons is described for the liquid phase and compared and contrasted with that for the gas phase. Similarities as well as differences are noted. The loci of scattering sites, called spurs in the liquid phase, are considered in detail. In particular, their temporal and spatial evolution is considered from the point of view of scattering. Two emphases are made: one upon the stochastic calculation of the distribution of distances required for slowing down to thermal velocities, and the other upon the calculation of cross sections for energy loss by means of quantum mechanics.

  15. Scattering of low-energy neutrinos on atomic shells

    NASA Astrophysics Data System (ADS)

    Babič, Andrej; Šimkovic, Fedor

    2015-10-01

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold.

  16. Scattering of low-energy neutrinos on atomic shells

    SciTech Connect

    Babič, Andrej; Šimkovic, Fedor

    2015-10-28

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold.

  17. Low-energy electron scattering by formic acid

    SciTech Connect

    Trevisan, C. S.; Orel, A. E.; Rescigno, T. N.

    2006-10-15

    We report the results of fixed-nuclei complex Kohn variational calculations of elastic electron scattering by formic acid, HCOOH. Momentum transfer and angular differential cross sections for incident electron energies ranging from 0.1 to 15 eV are presented and compared to available experimental data. The low-energy behavior of the cross section is analyzed and found to be consistent with the existence of a virtual state.

  18. Rashba scattering in the low-energy limit

    NASA Astrophysics Data System (ADS)

    Hutchinson, Joel; Maciejko, Joseph

    2016-06-01

    We study potential scattering in a two-dimensional electron gas with Rashba spin-orbit coupling in the limit that the energy of the scattering electron approaches the bottom of the lower spin-split band. Focusing on two spin-independent circularly symmetric potentials, an infinite barrier and a delta-function shell, we show that scattering in this limit is qualitatively different from both scattering in the higher spin-split band and scattering of electrons without spin-orbit coupling. The scattering matrix is purely off-diagonal with both off-diagonal elements equal to one, and all angular momentum channels contribute equally; the differential cross section becomes increasingly peaked in the forward and backward scattering directions; the total cross section exhibits quantized plateaus. These features are independent of the details of the scattering potentials, and we conjecture them to be universal. Our results suggest that Rashba scattering in the low-energy limit becomes effectively one-dimensional.

  19. Resonance formation in low energy electron scattering from uracil

    NASA Astrophysics Data System (ADS)

    Mašín, Zdeněk; Gorfinkiel, Jimena D.

    2014-05-01

    We present detailed ab initio results for resonance formation in low energy electron scattering from uracil obtained with the R-matrix method. We identify a larger number of resonances than any previous theoretical study. Most of these resonances have core-excited shape character and appear to be associated to the ring structure of the molecule. Their link to DEA spectra and to the resonances present in electron scattering from pyrimidine are discussed. Contribution to the Topical Issue "Electron and Positron Induced Processes", edited by Michael Brunger, Radu Campeanu, Masamitsu Hoshino, Oddur Ingólfsson, Paulo Limão-Vieira, Nigel Mason, Yasuyuki Nagashima and Hajime Tanuma.

  20. Low-Energy Neutron Scattering from Heavy Nuclei

    NASA Astrophysics Data System (ADS)

    Horton, Christopher Adams

    Fast neutron inelastic scattering cross sections for the 44.9-keV level in ^{238} U and the 49.4-keV level in ^{232 }Th, and the elastic scattering cross sections of ^{209}Bi and ^{232}Th have been measured using the neutron time-of-flight technique, at an incident neutron energy of 127 keV at six scattering angles from 45 ^circ to 122.5^circ . Neutrons were produced by the ^7 Li(p,n)^7Be reaction. A detector using two photomultiplier tubes in fast coincidence was built for these low-energy measurements. The detector efficiency was determined by comparison with that of a ^{235}U fission chamber. Special attention was paid to determining the efficiency near the ^7Li(p,n)^7Be reaction threshold. The spectrum unfolding included the removal of tails on the peaks which were assumed to be exponential functions. The inelastic peaks were stripped from the elastic peaks by using the shape of the bismuth elastic peak as a standard. Corrections for neutron attenuation were computed analytically. Corrections for multiple scattering were determined using a Monte Carlo method. Results were normalized to the ^{238}U differential elastic scattering cross sections and angular distributions. The angular distributions and integrated cross sections are compared with the ENDF/B-VI evaluation cross sections and with results at similar energies from previous measurements. The use of iron neutron filters for measuring cross sections at low energies is also discussed.

  1. Theoretical Study of Low Energy Scattering from Metal Nuclei.

    NASA Astrophysics Data System (ADS)

    Gomez, Bernadette; Hira, Ajit; Duran, Joe; Jaramillo, Danelle

    2015-04-01

    We continue our interest in the interactions between different nuclear species with a computational study of the scattering of the low-energy nuclei of H through F atoms (Z <= 9 ) from Silver, Palladium and other metals. Recent work has shown that neutron scattering can be used to record holographic images of materials. We have developed a FORTRAN computer program to compute stopping cross sections and scattering angles in Ag and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 50 to 210 keV. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies have potential applications in nuclear physics and in nuclear medicine.

  2. Elastic positron-cadmium scattering at low energies

    SciTech Connect

    Bromley, M. W. J.; Mitroy, J.

    2010-05-15

    The elastic and annihilation cross sections for positron-cadmium scattering are reported up to the positronium-formation threshold (at 2.2 eV). The low-energy phase shifts for the elastic scattering of positrons from cadmium were derived from the bound and pseudostate energies of a very large basis configuration-interaction calculation of the e{sup +}-Cd system. The s-wave binding energy is estimated to be 126{+-}42 meV, with a scattering length of A{sub scat}=(14.2{+-}2.1)a{sub 0}, while the threshold annihilation parameter, Z{sub eff}, was 93.9{+-}26.5. The p-wave phase shift exhibits a weak shape resonance that results in a peak Z{sub eff} of 91{+-}17 at a collision energy of about 490{+-}50 meV.

  3. Virtual Compton scattering off the nucleon at low energies

    SciTech Connect

    Scherer, S.; Korchin, A.Y.; Koch, J.H.

    1996-08-01

    We investigate the low-energy behavior of the four-point Green{close_quote}s function {Gamma}{sup {mu}{nu}} describing virtual Compton scattering off the nucleon. Using Lorentz invariance, gauge invariance, and crossing symmetry, we derive the leading terms of an expansion of the operator in the four-momenta {ital q} and {ital q}{sup {prime}} of the initial and final photon, respectively. The model-independent result is expressed in terms of the electromagnetic form factors of the free nucleon, i.e., on-shell information which one obtains from electron-nucleon scattering experiments. Model-dependent terms appear in the operator at {ital O}({ital q}{sub {alpha}}{ital q}{sub {beta}}{sup {prime}}), whereas the orders {ital O}({ital q}{sub {alpha}}{ital q}{sub {beta}}) and {ital O}({ital q}{sub {alpha}}{sup {prime}}{ital q}{sub {beta}}{sup {prime}}) are contained in the low-energy theorem for {Gamma}{sup {mu}{nu}}, i.e., no new parameters appear. We discuss the leading terms of the matrix element and comment on the use of on-shell equivalent electromagnetic vertices in the calculation of {open_quote}{open_quote}Born terms{close_quote}{close_quote} for virtual Compton scattering. {copyright} {ital 1996 The American Physical Society.}

  4. Computational Study of Low Energy Nuclear Scattering from Metal Nuclei

    NASA Astrophysics Data System (ADS)

    Jaramillo, Danelle; Hira, Ajit; Pacheco, Jose; Salazar, Justin

    2014-03-01

    We continue our interest in the interactions between different nuclear species with a computational study of the scattering of the low-energy nuclei of H through F atoms (Z <= 9) from Palladium, Nickel and other metals. First, a FORTRAN computer program was developed to compute stopping cross sections and scattering angles in Pd and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 10 to 140 keV. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies have potential applications in nuclear physics and in nuclear medicine.

  5. Elastic scattering of low-energy electrons from toluene

    NASA Astrophysics Data System (ADS)

    Sakaamini, Ahmad; Hargreaves, L. R.; Khakoo, M. A.; Pastega, D. F.; Bettega, M. H. F.

    2016-04-01

    Theoretical and normalized experimental differential, momentum transfer, and integral cross sections for vibrationally elastic scattering of low-energy electrons from toluene (C6H5C H3 ) are presented. The differential cross sections are measured at incident energies from 1 to 20 eV and scattering angles from 15° to 130°. The calculated cross sections are obtained using the Schwinger multichannel method with pseudopotentials in the static-exchange plus polarization approximation. Comparisons are made between the present theory and measurements with earlier available measurements. In general, the agreement between the theory and the experiment is very good. We also discuss the resonance spectra of toluene, where we find three π* shape resonances whose locations agree well with the experiment. In addition, we compare the cross sections of toluene and benzene, since the former can be considered as a benzene derivative by the substitution of a hydrogen in benzene by a C H3 group in toluene.

  6. Low-Energy Elastic Electron Scattering by Atomic Oxygen

    NASA Technical Reports Server (NTRS)

    Zatsarinny O.; Bartschat, K.; Tayal, S. S.

    2006-01-01

    The B-spline R-matrix method is employed to investigate the low-energy elastic electron scattering by atomic oxygen. Flexible non-orthogonal sets of radial functions are used to construct the target description and to represent the scattering functions. A detailed investigation regarding the dependence of the predicted partial and total cross sections on the scattering model and the accuracy of the target description is presented. The predicted angle-integrated elastic cross sections are in good agreement with experiment, whereas significant discrepancies are found in the angle-differential elastic cross sections near the forward direction. .The near-threshold results are found to strongly depend on the treatment of inner-core short-range correlation effects in the target description, as well as on a proper account of the target polarizability. A sharp increase in the elastic cross sections below 1 eV found in some earlier calculations is judged to be an artifact of an unbalanced description of correlation in the N-electron target structure and the (N+l)-electron-collision problems.

  7. Low-Energy Electron Scattering by Sugarcane Lignocellulosic Biomass Molecules

    NASA Astrophysics Data System (ADS)

    Oliveira, Eliane; Sanchez, Sergio; Bettega, Marcio; Lima, Marco; Varella, Marcio

    2012-06-01

    The use of second generation (SG) bioethanol instead of fossil fuels could be a good strategy to reduce greenhouse gas emissions. However, the efficient production of SG bioethanol has being a challenge to researchers around the world. The main barrier one must overcome is the pretreatment, a very important step in SG bioethanol aimed at breaking down the biomass and facilitates the extraction of sugars from the biomass. Plasma-based treatment, which can generate reactive species, could be an interesting possibility since involves low-cost atmospheric-pressure plasma. In order to offer theoretical support to this technique, the interaction of low-energy electrons from the plasma with biomass is investigated. This study was motived by several works developed by Sanche et al., in which they understood that DNA damage arises from dissociative electron attachment, a mechanism in which electrons are resonantly trapped by DNA subunits. We will present elastic cross sections for low-energy electron scattering by sugarcane biomass molecules, obtained with the Schwinger multichannel method. Our calculations indicate the formation of π* shape resonances in the lignin subunits, while a series of broad and overlapping σ* resonances are found in cellulose and hemicellulose subunits. The presence of π* and σ* resonances could give rise to direct and indirect dissociation pathways in biomass. Then, theoretical resonance energies can be useful to guide the plasma-based pretreatment to break down specific linkages of interest in biomass.

  8. Low-energy electron scattering by carbon tetrachloride

    NASA Astrophysics Data System (ADS)

    Moreira, Giseli M.; Souza Barbosa, Alessandra; Pastega, Diego F.; Bettega, Márcio H. F.

    2016-02-01

    In this work we report calculated integral and differential elastic cross sections for the scattering of low-energy electrons by CCl4. We employ the Schwinger multichannel method with pseudopotentials to compute the cross sections in the static-exchange and static-exchange plus polarization approximations for energies up to 15 eV. We report two shape resonances located at 0.75 eV and 8 eV belonging to the T 2 and E symmetries of the T d group respectively. We also look at the s-wave contribution to the integral cross section and find no evidence of the presence of a Ramsauer-Townsend minimum. We compare our calculated cross sections with available experimental and theoretical results and find that in general the agreement is good.

  9. Inelastic pion scattering by /sup 13/C at low energies

    SciTech Connect

    Mitchell, J.H.

    1987-03-01

    Angular distributions for inelastically scattered pions were obtained for several states in /sup 13/C at an incident energy of 65 MeV. The data include results from both ..pi../sup +/ and ..pi../sup -/ measurements. In addition, ..pi../sup -/ measurements were made at T/sub ..pi../ = 50 MeV at one angle to give a two point fixed-q excitation function. The data are compared to theory and the data of others. As might be expected, medium corrections are shown to be considerably more important at low energies than at resonance. This is true for inelastic transitions of multipolarity 0,2 and 3. Parameters derived from an analysis of elastic pion scattering and SCX data also provide an adequate description of the inelastic transitions. The charge asymmetry in the cross sections for the 9/2/sup +/ state that was seen at resonance persists at these energies. This result is consistent with an impulse approximation treatment of the spin-flip amplitude. This is true even though the incoming energy of the pions is far below the range where the validity of an impulse treatment is expected. 65 refs., 45 figs.

  10. Low-energy electron scattering by cellulose and hemicellulose components.

    PubMed

    de Oliveira, Eliane M; da Costa, Romarly F; Sanchez, Sergio d'A; Natalense, Alexandra P P; Bettega, Márcio H F; Lima, Marco A P; Varella, Márcio T do N

    2013-02-01

    We report elastic integral, differential and momentum transfer cross sections for low-energy electron scattering by the cellulose components β-D-glucose and cellobiose (β(1 → 4) linked glucose dimer), and the hemicellulose component β-D-xylose. For comparison with the β forms, we also obtain results for the amylose subunits α-D-glucose and maltose (α(1 → 4) linked glucose dimer). The integral cross sections show double peaked broad structures between 8 eV and 20 eV similar to previously reported results for tetrahydrofuran and 2-deoxyribose, suggesting a general feature of molecules containing furanose and pyranose rings. These broad structures would reflect OH, CO and/or CC σ* resonances, where inspection of low-lying virtual orbitals suggests significant contribution from anion states. Though we do not examine dissociation pathways, these anion states could play a role in dissociative electron attachment mechanisms, in case they were coupled to the long-lived π* anions found in lignin subunits [de Oliveira et al., Phys. Rev. A, 2012, 86, 020701(R)]. Altogether, the resonance spectra of lignin, cellulose and hemicellulose components establish a physical-chemical basis for electron-induced biomass pretreatment that could be applied to biofuel production. PMID:23247550

  11. Deconstruction and elastic ππ scattering in Higgsless models

    NASA Astrophysics Data System (ADS)

    Chivukula, R. Sekhar; Simmons, Elizabeth H.; He, Hong-Jian; Kurachi, Masafumi; Tanabashi, Masaharu

    2007-02-01

    We study elastic pion-pion scattering in global linear moose models and apply the results to a variety of Higgsless models in flat and anti-de Sitter (AdS) space using the equivalence theorem. In order to connect the global moose to Higgsless models, we first introduce a block-spin transformation which corresponds, in the continuum, to the freedom to perform coordinate transformations in the Higgsless model. We show that it is possible to make an “f-flat” deconstruction in which all of the f-constants fj of the linear moose model are identical; the phenomenologically relevant f-flat models are those in which the coupling constants of the groups at either end of the moose are small—corresponding to the global linear moose. In studying pion-pion scattering, we derive various sum rules, including one analogous to the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin (KSRF) relation, and use them in evaluating the low-energy and high-energy forms of the leading elastic partial-wave scattering amplitudes. We obtain elastic unitarity bounds as a function of the mass of the lightest KK mode and discuss their physical significance.

  12. Deconstruction and elastic {pi}{pi} scattering in Higgsless models

    SciTech Connect

    Chivukula, R. Sekhar; Simmons, Elizabeth H.; He, Hong-Jian; Kurachi, Masafumi; Tanabashi, Masaharu

    2007-02-01

    We study elastic pion-pion scattering in global linear moose models and apply the results to a variety of Higgsless models in flat and anti-de Sitter (AdS) space using the equivalence theorem. In order to connect the global moose to Higgsless models, we first introduce a block-spin transformation which corresponds, in the continuum, to the freedom to perform coordinate transformations in the Higgsless model. We show that it is possible to make an 'f-flat' deconstruction in which all of the f-constants f{sub j} of the linear moose model are identical; the phenomenologically relevant f-flat models are those in which the coupling constants of the groups at either end of the moose are small--corresponding to the global linear moose. In studying pion-pion scattering, we derive various sum rules, including one analogous to the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin (KSRF) relation, and use them in evaluating the low-energy and high-energy forms of the leading elastic partial-wave scattering amplitudes. We obtain elastic unitarity bounds as a function of the mass of the lightest KK mode and discuss their physical significance.

  13. Isospin breaking in low-energy pion-nucleon scattering

    SciTech Connect

    Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

    1995-05-08

    We have analyzed low-energy pion-nucleon data for isospin invariance by comparing charge-exchange amplitudes derived from charge-exchange data with those predicted from recent {pi}{sup {plus_minus}}{ital p} elastic data through the application of isospin invariance. A discrepancy of the order of 7% is observed beyond the contributions of the {pi}{sup {plus_minus}}{ital p} Coulomb interaction and the hadronic mass differences.

  14. Low energy neutron deuteron scattering to N3LO

    NASA Astrophysics Data System (ADS)

    Margaryan, Arman; Vanasse, Jared; Springer, Roxanne

    2015-10-01

    We calculate the next-to-next-to-next-to-leading order (N3LO) nd scattering amplitude in the framework of nonrelativistic pionless effective field theory (EFTπ/). This theory is only valid when the typical momentum exchange in the scattering is smaller then the mass of the pion. The power counting parameter for EFTπ/ is the ratio Q/Λπ /, where Q is the typical momentum exchange in the scattering and Λπ / is the EFTπ/ breakdown scale, Λπ / scattering at leading order requires summing an infinite set of diagrams. The first nonzero polarization-dependent observables occur at N2LO. At N3LO new 2-body forces appear, which introduce four new EFTπ/ coefficients. These coefficients are fixed by the 3PJ and 1P1 phase shifts of NN scattering. We find that these terms have an important impact. The results of this calculation at N3LO will be important for understanding spin polarization observables in nd scattering, in particular the longstanding Ay puzzle. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics, under Award Number DE-FG02-05ER41368.

  15. Low energy scattering phase shifts for meson-baryon systems

    NASA Astrophysics Data System (ADS)

    Detmold, William; Nicholson, Amy N.

    2016-06-01

    In this work, we calculate meson-baryon scattering phase shifts in four channels using lattice QCD methods. From a set of calculations at four volumes, corresponding to spatial sizes of 2, 2.5, 3, and 4 fm, and a pion mass of mπ˜390 MeV , we determine the scattering lengths and effective ranges for these systems at the corresponding quark masses. We also perform the calculation at a lighter quark mass, mπ˜230 MeV , on the largest volume. Using these determinations, along with those in previous work, we perform a chiral extrapolation of the scattering lengths to the physical point after correcting for the effective range contributions using the multivolume calculations performed at mπ˜390 MeV .

  16. Low-energy elastic differential scattering of He/++/ by He.

    NASA Technical Reports Server (NTRS)

    Lam, S. K.; Doverspike, L. D.; Champion, R. L.

    1973-01-01

    Experimental results are developed for the relative elastic differential scattering of He(++) by He for collision energies in the range 4 equal to or less than E equal to or less than 75 eV. In the analysis of the data, semiclassical considerations are utilized, assuming that the dynamics of the scattering is governed solely by the B and E states of He2(++). It is shown that existing ab initio calculations for the intermolecular potentials predict differential cross sections which are not in particularly good agreement with the experimental data.

  17. Low-energy positron and electron scattering from nitrogen dioxide

    NASA Astrophysics Data System (ADS)

    Chiari, Luca; Zecca, Antonio; García, Gustavo; Blanco, Francisco; Brunger, M. J.

    2013-12-01

    Total cross section (TCS) measurements for positron scattering from nitrogen dioxide (NO2) are presented in the energy range 0.2-40 eV. The TCS, the elastic integral and differential cross sections, and the integral cross section accounting of all the inelastic processes (including positronium formation) have also been computed using the independent atom model with screening corrected additivity rule (IAM-SCAR) for incident energies from 1 to 1000 eV. A qualitative level of agreement is found between the present TCS experiment and theory at the common energies. As no previous measurements or calculations for positron-NO2 scattering exist in the literature, we also computed the TCS for electron collisions with NO2 employing the IAM-SCAR method. A comparison of those results to the present positron cross sections and the earlier electron-impact data and calculations is provided. To investigate the role that chemical substitution plays in positron scattering phenomena, we also compare the present positron-NO2 data with the TCSs measured at the University of Trento for positron scattering from N2O and CO2.

  18. Resonances in low-energy positron-alkali scattering

    NASA Technical Reports Server (NTRS)

    Horbatsch, M.; Ward, S. J.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    Close-coupling calculations were performed with up to five target states at energies in the excitation threshold region for positron scattering from Li, Na and K. Resonances were discovered in the L = 0, 1 and 2 channels in the vicinity of the atomic excitation thresholds. The widths of these resonances vary between 0.2 and 130 MeV. Evidence was found for the existence of positron-alkali bound states in all cases.

  19. Low-energy Scattering of Positronium by Atoms

    NASA Technical Reports Server (NTRS)

    Ray, Hasi

    2007-01-01

    The survey reports theoretical studies involving positronium (Ps) - atom scattering. Investigations carried out in last few decades have been briefly reviewed in this article. A brief description of close-coupling approximation (CCA), the first-Born approximation (FBA) and the Born-Oppenheimer approximation (BOA) for Ps-Atom systems are made. The CCA codes of Ray et a1 [1-6] are reinvestigated using very fine mesh-points to search for resonances. The article advocates the need for an extended basis set & a systematic study using CCAs.

  20. Elastic Scattering of Low-Energy Electrons byTetrahydrofuran

    SciTech Connect

    Trevisan, Cynthia S.; Orel, Ann E.; Rescigno, Thomas N.

    2006-05-09

    We present the results of ab initio calculations for elasticelectron scattering by tetrahydrofuran (THF) using the complex Kohnvariational method. We carried out fixed-nuclei calculations at theequilibrium geometry of the target molecule for incident electronenergies up to 20 eV. The calculated momentum transfer cross sectionsclearly reveal the presence of broad shape resonance behavior in the 8-10eV energy range, in agreement with recent experiments. The calculateddifferential cross sections at 20 eV, which include the effects of thelong-range electron-dipole interaction, are alsofound to be in agreementwith the most recent experimental findings.

  1. Predicting reaction observables from back-scattering measurements in low-energy heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Diaz-Torres, A.; Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.; Gomes, P. R. S.; Lenske, H.

    2016-01-01

    A simplified, reliable and useful method, based on reaction theory, for calculating a number of integrated and differential cross sections in low-energy heavy-ion collisions is presented. Simplified formulae provide predictions of reaction, capture and elastic-scattering differential cross sections, using experimental information about elastic and quasi-elastic back-scattering excitation functions.

  2. Low-energy 6He scattering in a microscopic model

    NASA Astrophysics Data System (ADS)

    Descouvemont, P.

    2016-03-01

    A microscopic version of the continuum discretized coupled channel (CDCC) method is used to investigate 6He scattering on 27Al,58Ni,120Sn, and 208Pb at energies around the Coulomb barrier. The 6He nucleus is described by an antisymmetric 6-nucleon wave function, defined in the resonating group method. The 6He continuum is simulated by square-integrable positive-energy states. The model is based only on well-known nucleon-target potentials and therefore does not depend on any adjustable parameter. I show that experimental elastic cross sections are fairly well reproduced. The calculation suggests that breakup effects increase for high-mass targets. For a light system such as 6He+27Al , breakup effects are small, and a single-channel approximation provides fair results. This property is explained by a very simple model, based on the sharp cutoff approximation for the scattering matrix. I also investigate the 6He-target optical potentials, which confirm that breakup channels are more important when the mass increases. At large distances, polarization effects increase the Coulomb barrier and provide a long-tail absorption component in the imaginary part of the nucleus-nucleus interaction.

  3. Low energy elastic electron scattering from CF3Br molecules.

    PubMed

    Hargreaves, L R; Brunton, J R; Maddern, T M; Brunger, M J

    2015-03-28

    CF3Br is a potentially valuable precursor molecule for generating beams of gas phase Br radicals suitable for electron collisions studies. However, the utility of CF3Br for this purpose depends critically on the availability of sound scattering cross sections to allow the contribution of the precursor to be isolated within the total scattering signal. To this end, here we present elastic differential cross section (DCS) measurements for CF3Br at incident energies between 15 and 50 eV. Comparison of these DCSs to those from the only other available experimental study [Sunohara et al., J. Phys. B: At., Mol. Opt. Phys. 36, 1843 (2003)] and a Schwinger multichannel with pseudo potentials (SMCPPs) calculation [Bettega et al., J. Phys. B: At., Mol. Opt. Phys. 36, 1263 (2003)] shows generally a very good accord. Integral elastic and momentum transfer cross sections, derived from our DCSs, are also found to be in quite good agreement with the SMCPP results. PMID:25833582

  4. Low-energy elastic electron scattering from furan

    SciTech Connect

    Khakoo, M. A.; Muse, J.; Ralphs, K.; Costa, R. F.; Bettega, M. H. F.; Lima, M. A. P.

    2010-06-15

    We report normalized experimental and theoretical differential cross sections for elastic electron scattering by C{sub 4}H{sub 4}O (furan) molecules from a collaborative project between several Brazilian theoretical groups and an experimental group at California State Fullerton, USA. The measurements are obtained by using the relative flow method with helium as the standard gas and a thin aperture target gas collimating source. The relative flow method is applied without the restriction imposed by the relative flow pressure condition on helium and the unknown gas. The experimental data were taken at incident electron energies of 1, 1.5, 1.73, 2, 2.7, 3, 5, 7, 10, 20, 30, and 50 eV and covered the angular range between 10 deg. and 130 deg. The measurements verify observed {pi}* shape resonances at 1.65{+-}0.05eV and 3.10{+-}0.05 eV scattering energies, in good agreement with the transmission electron data of Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004)]. Furthermore, the present results also indicated both resonances dominantly in the d-wave channel. The differential cross sections are integrated in the standard way to obtain integral elastic cross sections and momentum transfer cross sections. The calculations employed the Schwinger multichannel method with pseudopotentials and were performed in the static-exchange and in the static-exchange plus polarization approximations. The calculated integral and momentum transfer cross sections clearly revealed the presence of two shape resonances located at 1.95 and 3.56 eV and ascribed to the B{sub 1} and A{sub 2} symmetries of the C{sub 2v} point group, respectively, in very good agreement with the experimental findings. Overall agreement between theory and experiment regarding the differential, momentum transfer, and integral cross sections is very good, especially for energies below 10 eV.

  5. On triplet low-energy parameters of nucleon-nucleon scattering

    SciTech Connect

    Babenko, V. A.; Petrov, N. M.

    2006-09-15

    Triplet low-energy parameters of neutron-proton scattering, including high-order shape parameters, are calculated on the basis of approximating the effective-range function k cot {delta}{sub t} by polynomials and rational functions with the aid of the latest experimental data on phase shifts from the SAID nucleon-nucleon database. With the resulting values of the low-energy parameters, a good description of phase shifts over a broad energy interval is obtained by using the effective-range expansion featuring a small number of terms. The properties of the deuteron that were calculated on the basis of the values found for the triplet low-energy parameters of scattering agree very well with experimental values. The triplet low-energy parameters and the properties of the deuteron that were obtained here by using present-day data from the SAID database differ markedly from the analogous results obtained for data of the Nijmegen group. Possible reasons behind this discrepancy are discussed. Highly precise new approximate formulas for determining the shape parameter v{sub 2} are proposed and are shown to be efficient in calculations. The effective-range expansion for the D wave is considered, and preliminary results of calculations of low-energy scattering parameters for this case are obtained.

  6. Measurements of ultra-low-energy electron scattering cross sections of atoms and molecules

    SciTech Connect

    Kitajima, M.; Shigemura, K.; Kurokawa, M.; Odagiri, T.; Kato, H.; Hoshino, M.; Tanaka, H.; Ito, K.

    2014-03-05

    A new experimental technique for the total cross section measurements of ultra-low energy electron collisions with atoms and molecules utilizing the synchrotron radiation is presented. The technique employs a combination of the penetrating field technique and the threshold photoionization of rare gas atoms using the synchrotron radiation as an electron source in order to produce a high resolution electron beam at very low energy. Absolute total cross sections for electron scattering from He, Ne, Ar, Kr, and Xe in the energy region from extremely low electron energy to 20 eV are presented.

  7. Universality of entanglement creation in low-energy two-dimensional scattering

    SciTech Connect

    Weder, Ricardo

    2013-10-15

    We prove that the entanglement created in the low-energy scattering of two particles in two dimensions is given by a universal coefficient that is independent of the interaction potential. This is strikingly different from the three dimensional case, where it is proportional to the total scattering cross section. Before the collision the state is a product of two normalized Gaussians. We take the purity as the measure of the entanglement after the scattering. We give a rigorous computation, with error bound, of the leading order of the purity at low-energy. For a large class of potentials, that are not-necessarily spherically symmetric, we prove that the low-energy behavior of the purity, P, is universal. It is given by P=1−1/((ln(σ/ħ)){sup 2}) E, where σ is the variance of the Gaussians and the entanglement coefficient, E, depends only on the masses of the particles and not on the interaction potential. There is a strong dependence of the entanglement in the difference of the masses. The minimum is when the masses are equal, and it increases strongly with the difference of the masses. -- Highlights: •The entanglement in low-energy scattering in two dimensions is universal. It is independent of the potential. •We take the purity as the measure of entanglement. •We give a rigorous computation of the leading order of the purity at low energy. •The created entanglement depends strongly on the masses of the particles. •It takes its minimum for equal masses and it increases strongly with the difference of the masses.

  8. Low-energy theorems for nucleon-nucleon scattering at Mπ=450 MeV

    NASA Astrophysics Data System (ADS)

    Baru, V.; Epelbaum, E.; Filin, A. A.

    2016-07-01

    We apply the low-energy theorems to analyze the recent lattice QCD results for the two-nucleon system at a pion mass of Mπ≃450 MeV obtained by the NPLQCD Collaboration. We find that the binding energies of the deuteron and dineutron are inconsistent with the low-energy behavior of the corresponding phase shifts within the quoted uncertainties and vice versa. Using the binding energies of the deuteron and dineutron as input, we employ the low-energy theorems to predict the phase shifts and extract the scattering length and the effective range in the S31 and S10 channels. Our results for these quantities are consistent with those obtained by the NPLQCD Collaboration from effective field theory analyses but are in conflict with their determination based on the effective-range approximation.

  9. Study of Low Energy Electron Inelastic Scattering Mechanisms Using Spin Sensitive Techniques

    NASA Astrophysics Data System (ADS)

    Hsu, Hongbing

    1995-01-01

    Spin sensitive electron spectroscopies were used to study low energy electron inelastic scattering from metal surfaces and thin films. In these experiments, a beam of spin polarized electrons from a GaAs source is directed on the sample surface, and the spin polarization and intensity are measured as a function of energy loss and scattering angle by a Mott electron polarimeter coupled with a concentric hemispherical energy analyzer. Systematic studies of the angular dependence of inelastically scattered electrons were conducted on a Cu(100) surface, and Mo/Cu(100), non-magnetized Fe/Cu(100), and Co/Cu(100) films. The polarization and intensity of scattered electrons were measured as function of energy loss and scattering angle. Further studies were also conducted on Ag(100) surface and amorphous Cu/Ag(100) films. From the experimental results, the angular distributions of dipole and impact scattered electrons can be determined individually and both are found to peak in the specular scattering direction. Preliminary studies were conducted on magnetized Co/Cu(100) films. The spin dependent scattering intensity asymmetry was measured, with a clearly observable peak at energy loss of ~1 eV, which coincides with the band splitting. The polarizations of secondary electrons produced by an unpolarized primary beam were also measured. The polarizations can be related to the band polarization of magnetized cobalt films.

  10. Comprehensive study of the surface peak in charge-integrated low-energy ion scattering spectra

    SciTech Connect

    Draxler, M.; Gruber, R.; Bauer, P.; Beikler, R.; Taglauer, E.; Schmid, K.; Ermolov, S. N.

    2003-08-01

    Low-energy ion scattering is very surface sensitive if scattered ions are analyzed. By time-of-flight (TOF) techniques, the neutral and the charge-integrated spectra (ions plus neutrals) are obtained, which yield information about deeper layers. It is well known that charge integrated spectra may exhibit a surface peak which is more pronounced for heavier projectiles, e.g., Ne ions. Aiming at a more profound physical understanding of this surface peak, we performed TOF experiments and computer simulations for H, He, and Ne projectiles scattered from a polycrystalline copper target. Measurements were done in the range of 1-9 keV for a scattering angle of 129 degree sign under UHV conditions. The simulations were performed using the MARLOWE code for the given experimental parameters and a polycrystalline target. In the experiments, a pronounced surface peak was observed at low energies, which fades away at higher energies. This peak is quantitatively reproduced by the simulation. Several atomic layers may contribute to the surface peak, depending on the energy. Analyzing the contributions of the individual outermost atomic layers, one finds that the binary collisions of the projectiles with atoms in the first and the second layer yield a narrow energy distribution, while the contribution from the deeper layers is dominated by multiple scattering and therefore exhibits a very broad energy spectrum. It is shown that the appearance of a more or less pronounced surface peak is due to the relative contributions of single scattering and multiple scattering and thus depends on the projectile energy and mass.

  11. Low-energy p-d scattering and {sup 3}He in pionless effective field theory

    SciTech Connect

    Koenig, Sebastian; Hammer, H.-W.

    2011-06-15

    We calculate low-energy proton-deuteron scattering in the framework of pionless effective field theory. In the quartet channel, we calculate the elastic scattering phase shift up to next-to-next-to-leading order in the power counting. In the doublet channel, we perform a next-to-leading-order calculation. We obtain good agreement with the available phase-shift analyses down to the scattering threshold. The phase shifts in the region of nonperturbative Coulomb interactions are calculated by using an optimized integration mesh. Moreover, the Coulomb contribution to the {sup 3}He-{sup 3}H binding energy difference is evaluated in first-order perturbation theory. We comment on the implications of our results for the power counting of subleading three-body forces.

  12. Low-energy theorems for nucleon-nucleon scattering at unphysical pion masses

    NASA Astrophysics Data System (ADS)

    Baru, V.; Epelbaum, E.; Filin, A. A.; Gegelia, J.

    2015-07-01

    The longest-range part of the nuclear force from the one-pion exchange governs the energy dependence of the scattering amplitude in the near-threshold region and imposes correlations between the coefficients in the effective range expansion. These correlations may be regarded as low-energy theorems and are known to hold to a high accuracy in the neutron-proton 3S1 partial wave. We generalize the low-energy theorems to the case of unphysical pion masses and provide results for the correlations between the coefficients in the effective range expansion in this partial wave for pion masses up to Mπ˜400 MeV . We discuss the implications of our findings for the available and upcoming lattice-quantum-chromodynamics simulations of two-nucleon observables.

  13. Carrier scattering processes and low energy phonon spectroscopy in hybrid perovskites crystals

    NASA Astrophysics Data System (ADS)

    Even, Jacky; Paofai, Serge; Bourges, Philippe; Letoublon, Antoine; Cordier, Stéphane; Durand, Olivier; Katan, Claudine

    2016-03-01

    Despite the wealth of research conducted the last three years on hybrid organic perovskites (HOP), several questions remain open including: to what extend the organic moiety changes the properties of the material as compared to allinorganic (AIP) related perovskite structures. To ultimately reach an answer to this question, we have recently introduced two approaches that were designed to take the stochastic molecular degrees of freedom into account, and suggested that the high temperature cubic phase of HOP and AIP is an appropriate reference phase to rationalize HOP's properties. In this paper, we recall the main concepts and discuss more specifically the various possible couplings between charge carriers and low energy excitations such as acoustic and optical phonons. As available experimental or simulated data on low energy excitations are limited, we also present preliminary neutron scattering and ultrasonic measurements obtained and freshly prepared single crystals of CH3NH3PbBr3.

  14. A phenomenological study of photon production in low energy neutrino nucleon scattering

    SciTech Connect

    Jenkins, James P; Goldman, Terry J

    2009-01-01

    Low energy photon production is an important background to many current and future precision neutrino experiments. We present a phenomenological study of t-channel radiative corrections to neutral current neutrino nucleus scattering. After introducing the relevant processes and phenomenological coupling constants, we will explore the derived energy and angular distributions as well as total cross-section predictions along with their estimated uncertainties. This is supplemented throughout with comments on possible experimental signatures and implications. We conclude with a general discussion of the analysis in the context of complimentary methodologies. This is based on a talk presented at the DPF 2009 meeting in Detroit MI.

  15. Nuclear inelastic scattering of heme proteins: from iron ligand vibrations to low energy protein modes

    NASA Astrophysics Data System (ADS)

    Moeser, Beate; Janoschka, Adam; Wolny, Juliusz A.; Filipov, Igor; Chumakov, Aleksandr I.; Walker, F. Ann; Schünemann, Volker

    2012-03-01

    The binding of the signal molecule nitric oxide (NO) to the NO transporter protein Nitrophorin 2 (NP2) from the bloodsucking insect Rhodnius prolixus has been characterized by Mössbauer spectroscopy as well as nuclear forward scattering (NFS) and nuclear inelastic scattering (NIS). A striking feature of the vibrational spectrum obtained from NP2-NO is a vibration at 594 cm - 1. This mode is assigned to a Fe-NO stretching mode via simulation of the NIS data by density functional theory (DFT) coupled with molecular mechanics (MM) methods. At frequencies below 100 cm - 1 collective motions like heme doming occur which could explain spectroscopic features observed by NIS at these low energies.

  16. Resonant charge transfer in low-energy ion scattering: Information depth in the reionization regime.

    PubMed

    Primetzhofer, D; Spitz, M; Taglauer, E; Bauer, P

    2011-11-01

    Time-Of-Flight Low-energy ion scattering (TOF-LEIS) experiments were performed for He(+) ions scattered from Cu(100) and Cu(0.5)Au(0.5)(100). Probabilities for resonant neutralization and reionization in close collisions were deduced in a wide energy range. To learn about the information depth in LEIS, in a next step ion spectra were analyzed for polycrystalline Cu samples. The relative yield of backscattered projectiles, which have undergone distinct charge exchange processes, was calculated. Results indicate a strong contribution to the ion yield that origins from particles reionized in a close collision in deeper layers when experiments are performed at energies where reionization is prominent. The surface sensitivity of the ion signal at different energies is quantified. Based on these results, the total ion spectrum was quantitatively modelled by two consistent, but different approaches. PMID:22053118

  17. Low-energy electron scattering from DNA including structural water and base-pair irregularities

    SciTech Connect

    Caron, Laurent; Sanche, Leon; Tonzani, Stefano; Greene, Chris H.

    2009-07-15

    Elastic scattering of low-energy (0-13 eV) electrons from more realistic models of a DNA base-pair decamer is studied using multiple-scattering theory and T matrices obtained from ab initio R-matrix calculations. The models include two types of irregularities usually found in cellular DNA: base-pair mismatch and structural water molecules. Furthermore, we include in our calculation inelastic collisions. It is found that the basic interference patterns observed in the ideal and nonideal (i.e., more realistic) decamers are similar but have different amplitudes and are shifted in energy. Substantial inelastic losses, interestingly, cause pronounced local resonances, which could have an important influence in DNA strand breaks.

  18. Proton-proton, pion-proton and pion-pion diffractive collisions at ultrahigh energies

    NASA Astrophysics Data System (ADS)

    Anisovich, V. V.; Nikonov, K. V.; Nikonov, V. A.; Nyiri, J.

    2014-05-01

    The LHC energies are those at which the asymptotic regime in hadron-hadron diffractive collisions (pp, πp, ππ) might be switched on. Based on results of the Dakhno-Nikonov eikonal model which is a generalization of the Good-Walker eikonal approach for a continuous set of channels, we present a picture for transformation of the constituent quark mode to the black disk one. In the black disk mode (√ {s} >= 10 TeV), we have a growth of the logarithm squared type for total and elastic cross-sections, σtot ln2 s and σel ln2 s and (τ = q⊥2&sigma_; tot)-scaling for diffractive scattering and diffractive dissociation of hadrons. The diffractive dissociation cross-section grows as σD ln s, σDD ln s, and their relative contribution tends to zero: σD/σtot → 0, σDD/σtot → 0. Asymptotic characteristics of diffractive and total cross-sections are universal, and this results in the asymptotical equality of cross-sections for all types of hadrons (the Gribov universality). The energy scale for switching on the asymptotic mode is estimated for different processes.

  19. On the importance of full-dimensionality in low-energy molecular scattering calculations

    PubMed Central

    Faure, Alexandre; Jankowski, Piotr; Stoecklin, Thierry; Szalewicz, Krzysztof

    2016-01-01

    Scattering of H2 on CO is of great importance in astrophysics and also is a benchmark system for comparing theory to experiment. We present here a new 6-dimensional potential energy surface for the ground electronic state of H2-CO with an estimated uncertainty of about 0.6 cm−1 in the global minimum region, several times smaller than achieved earlier. This potential has been used in nearly exact 6-dimensional quantum scattering calculations to compute state-to-state cross-sections measured in low-energy crossed-beam experiments. Excellent agreement between theory and experiment has been achieved in all cases. We also show that the fully 6-dimensional approach is not needed with the current accuracy of experimental data since an equally good agreement with experiment was obtained using only a 4-dimensional treatment, which validates the rigid-rotor approach widely used in scattering calculations. This finding, which disagrees with some literature statements, is important since for larger systems full-dimensional scattering calculations are currently not possible. PMID:27333870

  20. On the importance of full-dimensionality in low-energy molecular scattering calculations.

    PubMed

    Faure, Alexandre; Jankowski, Piotr; Stoecklin, Thierry; Szalewicz, Krzysztof

    2016-01-01

    Scattering of H2 on CO is of great importance in astrophysics and also is a benchmark system for comparing theory to experiment. We present here a new 6-dimensional potential energy surface for the ground electronic state of H2-CO with an estimated uncertainty of about 0.6 cm(-1) in the global minimum region, several times smaller than achieved earlier. This potential has been used in nearly exact 6-dimensional quantum scattering calculations to compute state-to-state cross-sections measured in low-energy crossed-beam experiments. Excellent agreement between theory and experiment has been achieved in all cases. We also show that the fully 6-dimensional approach is not needed with the current accuracy of experimental data since an equally good agreement with experiment was obtained using only a 4-dimensional treatment, which validates the rigid-rotor approach widely used in scattering calculations. This finding, which disagrees with some literature statements, is important since for larger systems full-dimensional scattering calculations are currently not possible. PMID:27333870

  1. Density functional theory for low-energy electron-molecule scattering

    NASA Astrophysics Data System (ADS)

    Burke, Kieron; Wasserman, Adam

    2004-09-01

    Time-dependent density functional theory (TDDFT) is becoming popular as an approach to time-dependent electronic problems[1]. In the weak field regime, TDDFT predicts electronic transition frequencies and optical spectra of atoms, molecules, clusters, and solids, with an accuracy comparable to high-level wavefunction calculations at a fraction of the computational cost[2]. For large systems, TDDFT is the method of choice. Given the importance of correlation effects in low-energy electron-molecule scattering, extracting scattering amplitudes from TDDFT appears desirable. I will review this background, and outline how this can be done[3]. Detailed results will be shown by Wasserman in another talk. [1] Time-Dependent Density Functional Theory, M.A.L. Marques and E.K.U. Gross, Annu. Rev. Phys. Chem. 55, 427 (2004). [2] Time-dependent density functional theory in quantum chemistry, F. Furche and K. Burke, to appear in 1st vol. of Annu. Rev. of Computational Chemistry (2004) [3] Electron-molecule scattering from time-dependent density functional theory A. Wasserman, N.T. Maitra, and K. Burke, submitted (see http:dft.rutgers.edu/pubs/publist.html).

  2. Low-energy elastic electron scattering from isobutanol and related alkyl amines

    NASA Astrophysics Data System (ADS)

    Fedus, Kamil; Navarro, C.; Hargreaves, L. R.; Khakoo, M. A.; Silva, F. M.; Bettega, M. H. F.; Winstead, C.; McKoy, V.

    2014-09-01

    Normalized experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from isobutanol (C4H9OH ) are presented. The differential cross sections are measured at incident energies from 1 to 100 eV and scattering angles from 5∘ to 130∘. These cross sections are compared to earlier experimental and theoretical results for isobutanol and n-butanol, as well as to results for smaller alcohols and for alkanes. Further comparisons are made with calculated cross sections for isobutylamine (C4H9NH2) and for smaller amines, including ethylamine (C2H5NH2), dimethylamine (CH3NHCH3), the two C3H7NH2 isomers n-propylamine and isopropylamine, and ethylene diamine (NH2C2H4NH2). The calculated cross sections are obtained using the Schwinger multichannel method. The comparisons illuminate the role of molecular structure in determining the angular distribution of resonantly scattered electrons.

  3. Low-energy neutral-current neutrino scattering on {sup 128,130}Te isotopes

    SciTech Connect

    Tsakstara, V.; Kosmas, T. S.

    2011-05-15

    Differential, total, and cumulative cross section calculations for neutral current neutrino scattering on {sup 128,130}Te isotopes are performed in the context of the quasiparticle random phase approximation by utilizing realistic two-nucleon forces. These isotopes are the main contents of detectors of ongoing experiments with multiple neutrino physics goals (COBRA and CUORE at Gran Sasso), including potential low-energy astrophysical neutrino (solar, supernova, geoneutrinos) detection. The incoming neutrino energy range adopted in our calculations ({epsilon}{sub {nu}{<=}1}00 MeV) covers the low-energy {beta}-beam neutrinos and the pion-muon stopped neutrino beams existing or planned to be conducted at future neutron spallation sources. The aim of these facilities is to measure neutrino-nucleus cross sections at low and intermediate neutrino energies with the hope of shedding light on open problems in neutrino-induced reactions on nuclei and neutrino astrophysics. Such probes motivate theoretical studies on weak responses of various nuclear systems; thus the evaluated cross sections may be useful in this direction.

  4. Virtual compton scattering at low energy and the generalized polarizabilities of the nucleon

    SciTech Connect

    Helene Fonvieille

    2003-10-01

    We present a particular kind of (e, e' p) experiments, which has opened a new field of investigation of nucleon structure in the last ten years. The exclusive photon electroproduction process p(e, e' p){gamma} is used to study Virtual Compton Scattering (VCS) off the proton: {gamma}*p {yields} {gamma}p. In the low energy domain, this process gives access to new observables called the Generalized Polarizabilities. They are fundamental properties of the nucleon, characterizing the deformation of its internal structure under an applied electromagnetic field. Dedicated experiments have been performed at MAMI, Jefferson Lab and MIT-Bates. This contribution summarizes the results obtained so far and future prospects in the field.

  5. Low-energy extensions of the eikonal approximation to heavy-ion scattering

    SciTech Connect

    Aguiar, C.E.; Aguiar, C.E.; Zardi, F.; Vitturi, A.

    1997-09-01

    We discuss different schemes devised to extend the eikonal approximation to the regime of low bombarding energies (below 50 MeV per nucleon) in heavy-ion collisions. From one side we consider the first- and second-order corrections derived from Wallace{close_quote}s expansion. As an alternative approach we examine the procedure of accounting for the distortion of the eikonal straight-line trajectory by shifting the impact parameter to the corresponding classical turning point. The two methods are tested for different combinations of colliding systems and bombarding energies, by comparing the angular distributions they provide with the exact solution of the scattering problem. We find that the best results are obtained with the shifted trajectories, the Wallace expansion showing a slow convergence at low energies, in particular for heavy systems characterized by a strong Coulomb field. {copyright} {ital 1997} {ital The American Physical Society}

  6. Direct observation of space charge dynamics by picosecond low-energy electron scattering

    NASA Astrophysics Data System (ADS)

    Cirelli, C.; Hengsberger, M.; Dolocan, A.; Over, H.; Osterwalder, J.; Greber, T.

    2009-01-01

    The transient electric field governing the dynamics of space charge is investigated by time- and energy-resolved low-energy electron scattering. The space charge above a copper target is produced by high-intensity femtosecond laser pulses. The pump-probe experiment has a measured temporal resolution of better than 35 ps at 55 eV probe electron energy. The probe electron acceleration due to space charge is reproduced within a 3-dimensional non-relativistic model, which determines an effective number of electrons in the space charge cloud and its initial diameter. Comparison of the simulations with the experiments indicates a Coulomb explosion, which is consistent with transients in the order of 1 ns, the terminal kinetic energy of the cloud and the thermoemission currents predicted by the Richardson-Dushman formula.

  7. Virtual Compton Scattering at low energy and the generalized polarizabilities of the nucleon

    SciTech Connect

    Helene Fonvieille

    2003-05-01

    Virtual Compton Scattering (VCS) {gamma}*p {yields} {gamma}p at low CM energy gives access to the Generalized Polarizabilities of the nucleon. These observables generalize the concept of electromagnetic polarizabilities to the case of a virtual photon. Dedicated VCS experiments have been performed at MAMI, Jefferson Lab and MIT-Bates. The experimental status is reviewed, including analysis methods and physics results. The measurement of absolute (ep {yields} ep{gamma}) cross sections allows the extraction of the two unpolarized VCS structure functions P{sub LL}-P{sub TT}/{epsilon} and P{sub LT}, which are combinations of the Generalized Polarizabilities of the proton. Future prospects in the field of VCS at low energy are also presented.

  8. Low energy electron-molecule scattering using the R-matrix method

    NASA Astrophysics Data System (ADS)

    Gorfinkiel, Jimena

    2014-10-01

    The study of electron-molecule collisions continues to attract significant interest stimulated, in no small part, by the need for collisional data to model a number of physical environments and applied processes (e.g. the modelling of focused electron beam induced deposition and the description of the interaction of radiation with biological matter). This need for electron scattering data (cross sections but also information on the temporary negative ions, TNI, that can be formed) has motivated the renewed development of theoretical methodology and their computational implementation. I will present the latest developments in the study of low energy electron scattering from molecules and molecular clusters using the R-matrix method. Recent calculations on electron collisions with biologically relevant molecules have shed light on the formation of core-excited TNI these larger targets. The picture that emerges is much more complex than previously thought. I will discuss some examples as well as current and future developments of the methodology and software in order to provide more accurate collisional data (in particular cross sections) for bigger targets. In collaboration with Zdenek Masin, The Open University. This work was partially supported by EPSRC.

  9. Surface structure and composition determination by low-energy electron scattering and Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Sun, Jiebing

    This thesis reports on surface and surface alloy structural and compositional determination with low-energy electron scattering and Monte Carlo simulations. Low-energy electron diffraction (LEED) technique and the newly developed low-energy electron microscopy (LEEM) IV technique are used to measure the electron scattering intensity spectra and dynamical multiple scattering analysis is performed to optimize the surface structural and non-structural parameters via comparison between the experimental spectra and calculated ones. My work focuses on the following four surface systems. (111), (110) and (001) surface structures of the semimetal bismuth are determined with LEED. The unreconstructed (1x1) structure is revealed for all three surfaces. The interlayer spacings for several outermost layers are resolved. All results agree with those obtained by first-principles calculations. The Debye temperatures for the Bi(111) and Bi(110) surface are found to be lower than that of the Bi bulk. In conjunction with the LEED technique, scanning tunneling microscopy (STM) observation is performed on the Bi(001) surface. Surface topology images show dominant bilayer steps and no single layer step. The newly developed LEEM-IV technique is used to investigate the PdCu surface alloy on the substrate Cu(001). Studies include quantifying the temporal evolution of Pd concentration on the Cu(001) terrace, mapping the 3D heterogeneous surface chemical composition, and identifying a step-overgrowth thin film growth mechanism. It is found that, at the initial deposition stages, Pd atoms reside in the second layer at the sample temperature of 473 K, and the Pd concentration increases exponentially with time. The heterogeneous structure and composition near the steps are found to be a result of the step-overgrowth. We highlight the LEEM-IV technique which provides a high lateral resolution at surfaces. We demonstrate a 3D profile of Pd concentration in the surface region by using the LEEM

  10. Low-energy positron scattering from DNA nucleobases: the effects from permanent dipoles

    NASA Astrophysics Data System (ADS)

    Franz, Jan; Gianturco, Francesco Antonio

    2014-10-01

    Ab initio quantum calculations for low-energy positron scattering from gas-phase isolated molecular nucleobases which are part of the DNA structure are presented and discussed over the range of 1 eV to 25 eV. The calculations report the integral cross sections (ICSs) and the momentum-transfer cross sections (MTCSs) for Adenine, Guanine, Thymine and Cytosine. The calculations show very clearly the important role of the dominant long-range interaction between the positron projectile and the permanent dipole-moments of the target molecules in deciding the relative sizes of the ICSs and MTCSs for the present series of molecules. Such results confirm the largely repulsive interaction between positron and DNA bases, which is nevertheless producing very large cross sections and marked deflection functions from the latter molecules. Contribution to the Topical Issue "Nano-scale Insights into Ion-beam Cancer Therapy", edited by Andrey V. Solov'yov, Nigel Mason, Paulo Limão-Vieira and Malgorzata Smialek-Telega.

  11. Surface analysis of zeolites: An XPS, variable kinetic energy XPS, and low energy ion scattering study

    NASA Astrophysics Data System (ADS)

    Bare, Simon R.; Knop-Gericke, Axel; Teschner, Detre; Hävacker, Michael; Blume, Raoul; Rocha, Tulio; Schlögl, Robert; Chan, Ally S. Y.; Blackwell, N.; Charochak, M. E.; ter Veen, Rik; Brongersma, Hidde H.

    2016-06-01

    The surface Si/Al ratio in a series of zeolite Y samples has been obtained using laboratory XPS, synchrotron (variable kinetic energy) XPS, and low energy ion scattering (LEIS) spectroscopy. The non-destructive depth profile obtained using variable kinetic energy XPS is compared to that from the destructive argon ion bombardment depth profile from the lab XPS instrument. All of the data indicate that the near surface region of both the ammonium form and steamed Y zeolites is strongly enriched in aluminum. It is shown that when the inelastic mean free path of the photoelectrons is taken into account the laboratory XPS of aluminosilicates zeolites does not provide a true measurement of the surface stoichiometry, while variable kinetic energy XPS results in a more surface sensitive measurement. A comprehensive Si/Al concentration profile as a function of depth is developed by combining the data from the three surface characterization techniques. The LEIS spectroscopy reveals that the topmost atomic layer is further enriched in Al compared to subsequent layers.

  12. The influence of inner-shell electron promotion on charge exchange processes in low energy ion scattering from surfaces

    NASA Astrophysics Data System (ADS)

    Ting Li; MacDonald, R. J.

    1997-11-01

    The influence of inner-shell electron promotion on charge exchange in low energy (1-7 keV) Ne + ions scattered from the Cu (1 0 0), Ni (1 0 0) and Fe (1 1 0) surfaces has been studied systematically. The yield of Ne + ion scattered from these surfaces has been measured as a function of incident ion energy under various scattering geometries. The relative Ne + ion fraction, which is proportional to the normalised ion yield divided by the differential scattering cross section, is studied and an empirical formula for relative ion fraction has been extracted. The formula combines the charge exchanges along the incoming trajectory, during the close encounter, and along the outgoing trajectory into one simple expression. It can be concluded that inner-shell electron excitations during close encounters contribute significantly to the charge exchange in the scattering systems studied in this work.

  13. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3

    SciTech Connect

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; Gehring, P. M.; Stock, C.; Matsuda, Masaaki; Winn, Barry L.; Gu, Genda; Shapiro, Stephen M.; Birgeneau, R. J.; Ushiyama, T.; Yanagisawa, Y.; Tomioka, Y.; Ito, T.; Xu, Guangyong

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in this multiferroic material are coupled.

  14. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3

    DOE PAGESBeta

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; Gehring, P. M.; Stock, C.; Matsuda, Masaaki; Winn, Barry L.; Gu, Genda; Shapiro, Stephen M.; Birgeneau, R. J.; et al

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in thismore » multiferroic material are coupled.« less

  15. Low energy excitations in iridates studied with Resonant Inelastic X-ray Scattering

    NASA Astrophysics Data System (ADS)

    Liu, Xuerong

    2013-03-01

    In the iridium oxides, the strong spin-orbit coupling (SOC) of the 5d iridium electrons entangles the orbital and spin degrees of freedom, providing opportunities for exotic magnetic states with highly anisotropic exchange interactions. At the same time, the spatially extended 5d electrons are expected to have much stronger hybridization with the oxygen 2p orbitals, comparing with that in 3d transition element compounds. Both factors make crystal symmetry and local environment crucial in determining the electronic and magnetic properties of the iridates. We present here our resonant inelastic X-ray scattering (RIXS) studies of a number of octahedrally coordinated iridates with special structures, exploring these effects. In particular, for the 1-D spin 1/2 chain compound, Sr3CuIrO6, the wavefunction of the hole in the t2g manifold was reconstructed based on the RIXS spectra. Our results show that it is significantly modified from the isotropic shape expected for Jeff = 1 / 2 states in the strong SOC limit, due to the distortion of the oxygen octahedral cage. This distortion is comparable to, or smaller than, that present in most iridates and thus this work emphasizes the importance of local symmetry for the iridate families. Further, the magnetic excitations of this material were also measured. A large gap of ~30 meV, was found, comparable to the magnetic dispersion bandwidth. This is in contrast to the gapless dispersion expected for linear chain with isotropic Heisenberg exchange interaction. We also studied Na4Ir3O8 which has a hyperkagome lattice, and is a candidate quantum spin liquid. Here, a low energy continuum is observed below the d-d excitations. Optical conductivity measurements performed on the same sample and polarization dependence of the RIXS signal suggest that these excitations are magnetic in origin, agreeing with the spin-liquid state prediction. The work at Brookhaven was supported by the U.S. Department of Energy, Division of Materials Science

  16. Low-energy ionization yield in liquid argon for a coherent neutrino-nucleus scatter detector

    NASA Astrophysics Data System (ADS)

    Foxe, Michael P.

    ~ 4 e-- per keVr at 8 keVr. For gaseous Ar, the nuclear ionization quench factor is predicted to be ~ 0.13 at 10 keVr, which is the upper limit on this quantity obtained from the atomic collision model. In order to confidently apply the predictions of the ionization yield model, several experiments have been carried out for its validation. A single-phase Ar detector is used to both understand the processes occurring in the amplification region of a dual-phase Ar detector and to measure the nuclear ionization quench factor (ratio of the ionization signal produced in a nuclear recoil compared to that produced in an electron recoil of equal energy) in gaseous Ar. Using a portable neutron generator based on the 7Li(p,n)7 Be reaction, the nuclear ionization quench factor at 13 keVr was measured in gaseous Ar to be 0:138--0:012, which is in good agreement with the predictions of the ionization yield model. The absolute ionization yield was not measurable in gaseous Ar, because single ionization electron sensitivity has not been achieved in the single-phase Ar detector. The Gamma or Neutron Argon Recoils Resulting in Liquid Ionization (G/NARRLI) detector is a dual-phase Ar detector, which was developed to measure the ionization yield at energies below 10 keVr. While operating the G/NARRLI detector, high purity was achieved, extending the electron lifetime to ≈ 100 -- 200 micros. The ultimate sensitivity was achieved by detecting the single ionization electron peak. Detection of the single electron peak allowed absolutely calibrated spectroscopy to be performed using 55Fe to produce a 6 keV peak and 37Ar to produce a peak at 2.822 keV and a low-energy peak at 270 eV. Spectroscopic detection of the 270 eV peak represents the lowest energy measured to date in a dual-phase Ar detector. The electron yields for the 55Fe and 37Ar sources were used for the validation of the electron transport code, which was in good agreement with the modeling results. An effort was made to

  17. Crystal effects in the neutralization of He+ ions in the low energy ion scattering regime.

    PubMed

    Primetzhofer, D; Markin, S N; Juaristi, J I; Taglauer, E; Bauer, P

    2008-05-30

    Investigating possible crystal effects in ion scattering from elemental surfaces, measurements of the positive ion fraction P+ are reported for He+ ions scattered from single and polycrystalline Cu surfaces. In the Auger neutralization regime, the ion yield is determined by scattering from the outermost atomic layer. For Cu(110) P+ exceeds that for polycrystalline Cu by up to a factor of 2.5, thus exhibiting a strong crystal effect. It is much less pronounced at higher energies, i.e., in the reionization regime. However, there a completely different angular dependence of the ion yield is observed for poly- and single crystals, due to massive subsurface contributions in nonchanneling directions. PMID:18518602

  18. Inelastic scattering measurements of low energy x-ray photons by organics, soil, water, wood, and metals

    NASA Astrophysics Data System (ADS)

    Paki Amouzou, P.; Gertsenshteyn, M.; Jannson, T.; Shnitser, P.; Savant, G.

    2006-08-01

    The angular distribution of the inelastic scattering of photons at low energies (<=80 KeV) has been measured in organic material, soil, rocks, wood, steel sheet, and water. The measurements have been performed under air inside an X-ray shield cabinet using X-rays tube as a photon source and a thermoelectrically cooled CdTe detector. Measurements have been taken for both single and combined materials. The contributions of inelastic scattering of photons for the lower Z material in a given configuration have been extracted. The measured signal is primarily Compton scattering. The measured inelastic scattering contributions were compared with the calculated inelastic scattering cross sections according to the Klein-Nishina theory, updated to include a practical energy distribution of an X-ray tube beam. Relatively good agreement was found for all targets under investigation. The slight discrepancy is attributed to photoelectric effect and sample configuration. Present results may act as a guide for optimization of X-ray imaging sensors and in particular of those based on lobster eye X-ray optics suitable for cargo inspection, improvised explosives detection, non-destructive evaluation, and medical imaging.

  19. Lattice calculation of Delta isospin = 3/2 kaon decays to pion pion decay amplitude with interacting two pions

    NASA Astrophysics Data System (ADS)

    Kim, Changhoan

    We report the results of a calculation of the K → pipi matrix elements of the DeltaI = 3/2 operators. Relying on the 3-flavor effective Hamiltonian, we calculate the low energy contribution to the matrix elements in quenched lattice QCD with the DBW2 action using domain wall fermions, while the high energy contribution is included in the Wilson coefficients. In order to generate interacting pipi states with non-zero relative momentum in lattice, we apply anti-periodic boundary conditions on pions. Since only the magnitude of the overlap of our interpolating operators with the initial and final state is determined, we can calculate only the magnitude of the matrix elements. From the comparison with the experimental result, however, we find some degree of discrepancy. This discrepancy might be ascribed to the unphysical kinematics we choose in this report.

  20. Low-Energy Parameters of the Nucleon-Nucleon Scattering and Deuteron Properties, Electromagnetic Interactions with Bound Systems

    NASA Astrophysics Data System (ADS)

    Shebeko, A.; Dubovik, E.

    2013-08-01

    One more application of the method of unitary clothing transformations (UCT's) in the theory of nucleon-nucleon ( N - N) interaction has been presented. We have extended our previous analysis (Dubovik and Shebeko in Few-Body Syst 48:109-142, 2010) of the N - N scattering below the pion production threshold to treat the neutron-proton ( n - p) scattering at low energies and the deuteron static properties. Our calculations of deuteron magnetic and quadrupole moments have been carried out in the framework of a gauge independent description of electromagnetic (EM) interactions with nuclei (bound systems) using the clothed particle representation of the Hamiltonian, the boost and EM current density operators for the n-p system.

  1. Scattering of Low Energy Electrons and Positrons from Hydrogenic Systems and Applications

    NASA Technical Reports Server (NTRS)

    Bhatia, Anand K.

    2007-01-01

    While the electron scatters from the target, the target no longer stays in its original form. One of the first methods to take into account the distortion of the target at low incident energies is the method of polarized orbitals. In this method the wave function for the process is written using the first-order perturbation theory and the equation for the scattering function is derived from the Schradinger equation. This method has been very successful in calculating the phase shifts and therefore the cross sections at various energies. The total wave function can be used to calculate photoionization cross sections. The disadvantage of this approach is that the method is not variational and therefore does not provide bounds on the phase shifts. These difficulties can be overcome by using the Feshbach projection operator formalism. This approach has been employed for the scattering of electrons and positrons from targets. Results of various calculations will be discussed.

  2. Gravitational scattering in the ADD model at high and low energies

    NASA Astrophysics Data System (ADS)

    Gustafson, G.; Sjödahl, M.

    2008-01-01

    Gravitational scattering in the ADD model is considered at both sub- and transplanckian energies using a common formalism. By keeping a physical cut-off in the KK tower associated with virtual KK exchange, such as the cut-off implied by a finite brane width, troublesome divergences are removed from the calculations in both energy ranges. The scattering behavior depends on three different energy scales: the fundamental Planck mass, the collision energy and the inverse brane width. The result for energies low compared to the effective cut-off (inverse brane width) is a contact-like interaction. At high energies the gravitational scattering associated with the extra dimensional version of Newton’s law is recovered.

  3. Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

    SciTech Connect

    Dzhumagulova, K. N. Shalenov, E. O.; Ramazanov, T. S.

    2015-08-15

    Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

  4. Very low-energy total cross sections and the experimental scattering length for the positron-xenon system

    NASA Astrophysics Data System (ADS)

    Zecca, Antonio; Chiari, Luca; Trainotti, Emanuele; Brunger, Michael J.

    2012-04-01

    We report total cross-section (TCS) results for low-energy positron scattering from the noble gas xenon. A comparison with previous measurements shows a good level of accord with the recent results of the ANU group (2011 New J. Phys. 13 125004). Very good qualitative agreement is also found with the convergent close-coupling (CCC) calculation of Fursa and Bray (2012 New J. Phys. 14 035002) over most of the common energies. By using the shape of the CCC results as a guide, we also extrapolate our measured cross sections to very low energy. With the aid of the CCC theory, we therefore derive the first experimental estimate for the positron-xenon scattering length of a = -99.2 ± 18.4 au. This value is found to be consistent with the CCC-based estimate and also with those of some other theories. This result supports the existence of a positron-xenon virtual state at a positron energy ɛ = (1.4 ± 0.6) × 10-3 eV.

  5. Unified dispersive approach to real and virtual photon-photon scattering at low energy

    NASA Astrophysics Data System (ADS)

    Moussallam, B.

    2013-09-01

    Previous representations of pion-pair production amplitudes by two real photons at low energy, which combine dispersion theoretical constraints with elastic unitarity, chiral symmetry and soft-photon constraints are generalised to the case where one photon is virtual. The constructed amplitudes display explicitly the dependence on the ππ phase-shifts, on pion form factors and on pion polarisabilities. They apply both for space-like and time-like virtualities despite the apparent overlap of the left- and right-hand cuts, by implementing a definition of resonance exchange amplitudes complying with analyticity and consistent limiting prescriptions for the energy variables. Applications are made to the pion generalised polarisabilies, to vector-meson radiative decays, and to the σγ electromagnetic form factor. Finally, an evaluation of the contribution of γππ states in the hadronic vacuum polarisation to the muon g-2 is given, which should be less model dependent than previous estimates.

  6. Trajectory analysis of low-energy and hyperthermal ions scattered from Cu(110)

    SciTech Connect

    McEachern, R. L.; Goodstein, D. M.; Cooper, B. H.

    1989-05-15

    We have investigated the trajectories of Na/sup +/ ions scattered from the Cu(110) surface in the <1/bar 1/0> and <001> azimuths for a range of incident energies from 56 eV to 4 keV. Our goal is to explain the trends observed in the energy spectra and determine what types of trajectories contribute to these spectra. Using the computer program SAFARI, we have performed simulations with trajectory analyses for 100-, 200-, and 400-eV scattering. We show results from the 100-eV simulations in both azimuths and compare them with the experimental data. The simulated energy spectra are in excellent agreement with the data. Ion trajectories and impact parameter plots from the simulations are used to determine the relative importance of different types of ion--surface-atom collisions. The simulations have shown that the striking differences observed in comparing the <1/bar 1/0> and <001> spectra are mostly due to ions which scatter from second-layer atoms. This system exhibits strong focusing onto the second-layer atoms by the first-layer rows, and the focusing is very sensitive to the spacing between the rows. At the lower beam energies, scattering from the second layer dominates the measured spectra.

  7. Trajectory analysis of low-energy and hyperthermal ions scattered from Cu(110)

    SciTech Connect

    McEachern, R.L.; Goodstein, D.M.; Cooper, B.H.

    1989-05-15

    Trajectories of Na{sup +} ions scattered from the Cu(110) surface in the <1 1bar 0> and <001> azimuths were studied for a range of incident energies from 56 eV to 4 keV. The goal is to explain the trends observed in the energy spectra and determine what types of trajectories contribute to these spectra. Using the computer program SAFARI, simulations were performed with trajectory analyses for 100-, 200-, and 400-eV scattering. We show results from the 100-eV simulations in both azimuths and compare them with the experimental data. The simulated energy spectra are in excellent agreement with the data. Ion trajectories and impact parameter plots from the simulations are used to determine the relative importance of different types of ion-surface-atom collisions. The simulations have shown that the striking differences observed in comparing the <1 1bar 0> and <001> spectra are mostly due to ions which scatter from second-layer atoms. This system exhibits strong focusing onto the second-layer atoms by the first-layer rows, and the focusing is very sensitive to the spacing between the rows. At the lower beam energies, scattering from the second layer dominates the measured spectra.

  8. High precision elastic α scattering on the even-odd 115In nucleus at low energies

    NASA Astrophysics Data System (ADS)

    Kiss, G. G.; Szücs, T.; Mohr, P.; Fülöp, Zs; Gyürky, Gy; Halász, Z.; Soha, R. F.; Somorjai, E.; Ornelas, A.; Galaviz, D.; Yalçın, C.; Güray, R. T.; Özkan, N.

    2016-01-01

    Elastic alpha scattering cross sections on the even-odd 115In nucleus have been measured at energies Elab. = 16.15 MeV and 19.50 MeV. The high precision experimental data are used to derive the parameters of a local a nucleus optical potential.

  9. Single-collision approximation for p{sup 3}-He elastic scattering at low energy

    SciTech Connect

    Abusini, M.

    2009-06-15

    A theoretical approach to studying four-body reactions of p{sup 3}-He elastic scattering that takes consistently into account the single-collision mechanism is reported. The theoretical results obtained by this method were compared with experimental data, and the agreement is found to be quite satisfactory.

  10. Importance of nonresonant scattering in low-energy dissociative electron attachment to molecular hydrogen.

    PubMed

    Rabli, Djamal; Morrison, Michael A

    2006-07-01

    A central premise of nearly all theories of dissociative electron attachment is that this process is resonance driven. Neglect of nonresonant scattering, although appropriate for electron-molecule systems with narrow (long-lived) resonances, is problematic for the e-H2 system, which has one of the broadest known resonances. Using the nonadiabatic phase-matrix method we have found that at energies from threshold to 6 eV contributions from nonresonant scattering to cross sections to dissociative attachment to in its ground vibrational and electronic state exceed 60%. Comparison of theoretical and experimental cross sections argue strongly for further efforts to resolve the considerable remaining discrepancies over this most elementary rearrangement process. PMID:16907375

  11. Backward scattering of low-energy antiprotons by highly charged and neutral uranium: Coulomb glory

    SciTech Connect

    Maiorova, A. V.; Telnov, D. A.; Shabaev, V. M.; Tupitsyn, I. I.; Plunien, G.; Stoehlker, T.

    2007-09-15

    Collisions of antiprotons with He-, Ne-, Ni-like, bare, and neutral uranium are studied theoretically for scattering angles close to 180 deg. and antiproton energies in the interval from 100 eV to 10 keV. We investigate the Coulomb glory effect which is caused by a screening of the Coulomb potential of the nucleus and results in a prominent maximum of the differential cross section in the backward direction at some energies of the incident particle. We found that for larger numbers of electrons in the ion the effect becomes more pronounced and shifts to higher energies of the antiproton. On the other hand, a maximum of the differential cross section in the backward direction can also be found in the scattering of antiprotons on a bare uranium nucleus. The latter case can be regarded as a manifestation of the screening property of the vacuum-polarization potential in nonrelativistic collisions of heavy particles.

  12. Isospin breaking corrections to low-energy π-K scattering

    NASA Astrophysics Data System (ADS)

    Nehme, A.; Talavera, P.

    2002-03-01

    We evaluate the matrix elements for the processes π0K0-->π0K0 and π-K+-->π0K0 in the presence of isospin breaking terms at leading and next-to-leading order. As a direct application the relevant combination of the S-wave scattering lengths involved in the pion-kaon atom lifetime is determined. We discuss the sensitivity of the results with respect to the input parameters.

  13. Implications of unitarity for low-energy W+/-L, ZL scattering

    NASA Astrophysics Data System (ADS)

    Durand, Loyal; Johnson, James M.; Maher, Peter N.

    1991-07-01

    We investigate the partial-wave scattering of longitudinally polarized W+/- and Z bosons for energies MW<< √s <

  14. Limits on low energy photon-photon scattering from an experiment on magnetic vacuum birefringence

    SciTech Connect

    Bregant, M.; Cantatore, G.; Della Valle, F.; Lozza, V.; Milotti, E.; Raiteri, G.; Zavattini, E.; Carusotto, S.; Polacco, E.; Cimino, R.; Di Domenico, G.; Zavattini, G.; Gastaldi, U.; Ruoso, G.; Karuza, M.

    2008-08-01

    Experimental bounds on induced vacuum magnetic birefringence can be used to improve present photon-photon scattering limits in the electronvolt energy range. Measurements with the Polarizzazione del Vuoto con Laser apparatus [E. Zavattini et al., Phys. Rev. D 77, 032006 (2008)] at both {lambda}=1064 and 532 nm lead to bounds on the parameter A{sub e}, describing nonlinear effects in QED, of A{sub e}{sup (1064)}<6.6x10{sup -21} T{sup -2}-1064 nm and A{sub e}{sup (532)}<6.3x10{sup -21} T{sup -2}-532 nm, respectively, at 95% confidence level, compared to the predicted value of A{sub e}=1.32x10{sup -24} T{sup -2}. The total photon-photon scattering cross section may also be expressed in terms of A{sub e}, setting bounds for unpolarized light of {sigma}{sub {gamma}}{sub {gamma}}{sup (1064)}<4.6x10{sup -62} m{sup 2} and {sigma}{sub {gamma}}{sub {gamma}}{sup (532)}<2.7x10{sup -60} m{sup 2}. Compared to the expected QED scattering cross section these results are a factor of {approx_equal}2x10{sup 7} higher and represent an improvement of a factor about 500 on previous bounds based on ellipticity measurements and of a factor of about 10{sup 10} on bounds based on direct stimulated scattering measurements.

  15. Elastic scattering of low-energy electrons by 1,4-dioxane

    SciTech Connect

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2014-05-14

    We report calculated cross sections for elastic collisions of low-energy-electrons with 1,4-dioxane. Our calculations employed the Schwinger multichannel method with pseudopotentials and were carried out in the static-exchange and static-exchange plus polarization approximations for energies up to 30 eV. Our results show the presence of three shape resonances belonging to the B{sub u}, A{sub u}, and B{sub g} symmetries and located at 7.0 eV, 8.4 eV, and 9.8 eV, respectively. We also report the presence of a Ramsauer-Townsend minimum located at around 0.05 eV. We compare our calculated cross sections with experimental data and R-matrix and independent atom model along with the additivity rule corrected by using screening coefficients theoretical results for 1,4-dioxane obtained by Palihawadana et al. [J. Chem. Phys. 139, 014308 (2013)]. The agreement between the present and the R-matrix theoretical calculations of Palihawadana et al. is relatively good at energies below 10 eV. Our calculated differential cross sections agree well with the experimental data, showing only some discrepancies at higher energies.

  16. Elastic scattering of low-energy electrons by 1,4-dioxane

    NASA Astrophysics Data System (ADS)

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2014-05-01

    We report calculated cross sections for elastic collisions of low-energy-electrons with 1,4-dioxane. Our calculations employed the Schwinger multichannel method with pseudopotentials and were carried out in the static-exchange and static-exchange plus polarization approximations for energies up to 30 eV. Our results show the presence of three shape resonances belonging to the Bu, Au, and Bg symmetries and located at 7.0 eV, 8.4 eV, and 9.8 eV, respectively. We also report the presence of a Ramsauer-Townsend minimum located at around 0.05 eV. We compare our calculated cross sections with experimental data and R-matrix and independent atom model along with the additivity rule corrected by using screening coefficients theoretical results for 1,4-dioxane obtained by Palihawadana et al. [J. Chem. Phys. 139, 014308 (2013)]. The agreement between the present and the R-matrix theoretical calculations of Palihawadana et al. is relatively good at energies below 10 eV. Our calculated differential cross sections agree well with the experimental data, showing only some discrepancies at higher energies.

  17. Modelization For Electromagnetic Electron Scattering at Low Energies for Radiotherapy applications.

    NASA Astrophysics Data System (ADS)

    Nazaryan, Vahagn; Gueye, Paul

    2006-03-01

    Since release of the GEANT4 particle simulation toolkit in 2003, there has been a growing interest in its applications to medical physics. The applicability of GEANT4 to radiotherapy has been a subject of several investigations in recent years, and it was found to be of great use. Its low-energy model allows for electromagnetic interaction simulations down to 250 eV. The electron physics data are obtained from the Lawrence Livermore National Laboratory's Evaluated Electron Data Library (EEDL). At very lower energies (below 10 MeV), some of the tabulated data in EEDL have big uncertainties (more than 50%), and rely on various extrapolations to energy regions where there is no experimental data. We have investigated the variations of these cross-section data to radiotherapy applications. Our study suggests a strong need for better theoretical models of electron interactions with matter at these energies, and the necessity of new and more reliable experimental data. The progress towards such theoretical model will be presented.

  18. QED radiative corrections to low-energy Møller and Bhabha scattering

    NASA Astrophysics Data System (ADS)

    Epstein, Charles S.; Milner, Richard G.

    2016-08-01

    We present a treatment of the next-to-leading-order radiative corrections to unpolarized Møller and Bhabha scattering without resorting to ultrarelativistic approximations. We extend existing soft-photon radiative corrections with new hard-photon bremsstrahlung calculations so that the effect of photon emission is taken into account for any photon energy. This formulation is intended for application in the OLYMPUS experiment and the upcoming DarkLight experiment but is applicable to a broad range of experiments at energies where QED is a sufficient description.

  19. Low energy elastic electron scattering from CF{sub 3}Br molecules

    SciTech Connect

    Hargreaves, L. R.; Brunton, J. R.; Maddern, T. M.; Brunger, M. J.

    2015-03-28

    CF{sub 3}Br is a potentially valuable precursor molecule for generating beams of gas phase Br radicals suitable for electron collisions studies. However, the utility of CF{sub 3}Br for this purpose depends critically on the availability of sound scattering cross sections to allow the contribution of the precursor to be isolated within the total scattering signal. To this end, here we present elastic differential cross section (DCS) measurements for CF{sub 3}Br at incident energies between 15 and 50 eV. Comparison of these DCSs to those from the only other available experimental study [Sunohara et al., J. Phys. B: At., Mol. Opt. Phys. 36, 1843 (2003)] and a Schwinger multichannel with pseudo potentials (SMCPPs) calculation [Bettega et al., J. Phys. B: At., Mol. Opt. Phys. 36, 1263 (2003)] shows generally a very good accord. Integral elastic and momentum transfer cross sections, derived from our DCSs, are also found to be in quite good agreement with the SMCPP results.

  20. Spin wave excitations in low-energy electron scattering off Fe surfaces

    NASA Astrophysics Data System (ADS)

    Vernoy, Michael; Hopster, Herbert

    2002-03-01

    For the last two decades, SPEELS has been instrumental in the investigation of Stoner excitations in ferromagnets. By analyzing the spin of both the scattered electron beam and the incident beam, so called “complete” experiments were performed [1,2]. By eliminating the spin analysis of the scattered beam it has become possible to examine short wavelength spin wave excitations [3]. We constructed a 127 degree cylindrical deflector spectrometer with an analyzer rotatable to 70 degrees. The polarized electron beam is produced by a negative electron affinity GaAs photocathode. Initial data were taken with a primary beam energy of 20 V at a resolution of 50 meV FWHM on thick Fe/GaAs films. Spin asymmetries show the Stoner continuum as noted in the previous complete experiments as well as an additional feature in the 100-300 meV energy loss region. Angle dependent data will be presented. [1] J. Kirschner, Phys. Rev. Lett. 55, 973 (1985). [2] D. L. Abraham and H. Hopster, Phys. Rev. Lett. 59, 2333 (1987). [3] M. Plihal, D. L. Mills, and J. Kirschner, Phys. Rev. Lett. 82, 2579 (1999).

  1. Low-energy electron elastic scattering cross sections for excited Au and Pt atoms

    NASA Astrophysics Data System (ADS)

    Felfli, Zineb; Eure, Amanda R.; Msezane, Alfred Z.; Sokolovski, Dmitri

    2010-05-01

    Electron elastic total cross sections (TCSs) and differential cross sections (DCSs) in both impact energy and scattering angle for the excited Au and Pt atoms are calculated in the electron impact energy range 0 ⩽ E ⩽ 4.0 eV. The cross sections are found to be characterized by very sharp long-lived resonances whose positions are identified with the binding energies of the excited anions formed during the collisions. The recent novel Regge-pole methodology wherein is embedded through the Mulholland formula the electron-electron correlations is used together with a Thomas-Fermi type potential incorporating the crucial core-polarization interaction for the calculations of the TCSs. The DCSs are evaluated using a partial wave expansion. The Ramsauer-Townsend minima, the shape resonances and the binding energies of the excited Au - and Pt - anions are extracted from the cross sections, while the critical minima are determined from the DCSs.

  2. Low-energy photodetachment of Ga- and elastic electron scattering from neutral Ga

    NASA Astrophysics Data System (ADS)

    Wang, Kedong; Zatsarinny, Oleg; Bartschat, Klaus

    2016-08-01

    We present a comprehensive study of the photodetachment of the negative gallium ion and elastic electron scattering from neutral Ga for photon and electron energies ranging from threshold to 12 eV. The calculations are carried out with the B -spline R -matrix method. A multiconfiguration Hartree-Fock method with nonorthogonal term-dependent orbitals is employed to generate accurate initial- and final-state wave functions. The close-coupling expansions include the 4 s 24 p n l (k l ) bound and continuum states of Ga and the 4 s -excited autoionizing states 4 s 4 p2 . The calculated photodetachment and elastic cross sections exhibit prominent resonance features. In order to clarify the origin of these resonances, the contributions of the major ionization channels to the partial cross sections are analyzed in detail.

  3. Curve crossing for low-energy elastic scattering of He/+/ by Ne.

    NASA Technical Reports Server (NTRS)

    Bobbio, S. M.; Doverspike, L. D.; Champion, R. L.

    1973-01-01

    The perturbation seen in the experimental differential elastic-scattering cross section for the 40-eV He/+/ + Ne system has been attributed to a single crossing of two intermolecular potential-energy curves. A new theoretical treatment of the curve-crossing problem, namely, that of Delos and Thorson, is employed to obtain the crossing probabilities and phases associated with the crossing. These are determined by utilizing ab initio potentials involved in the crossing and are further used in a partial-wave calculation of the cross section, which is compared with our experiment. The origin of the oscillatory structure observed in the differential cross section is discussed in semiclassical terms by defining the problem in terms of two pseudo-deflection-functions. A rainbow effect is shown to be related to a particular feature (a maximum rather than a minimum) of these deflection functions.

  4. Measurement of the beam-recoil polarization in low-energy virtual Compton scattering from the proton

    NASA Astrophysics Data System (ADS)

    Doria, L.; Janssens, P.; Achenbach, P.; Ayerbe Gayoso, C.; Baumann, D.; Bensafa, I.; Benali, M.; Beričič, J.; Bernauer, J. C.; Böhm, R.; Bosnar, D.; Correa, L.; D'Hose, N.; Defaÿ, X.; Ding, M.; Distler, M. O.; Fonvieille, H.; Friedrich, J.; Friedrich, J. M.; Laveissière, G.; Makek, M.; Marroncle, J.; Merkel, H.; Mihovilovič, M.; Müller, U.; Nungesser, L.; Pasquini, B.; Pochodzalla, J.; Postavaru, O.; Potokar, M.; Ryckbosch, D.; Sánchez Majos, S.; Schlimme, B. S.; Seimetz, M.; Širca, S.; Tamas, G.; Van de Vyver, R.; Van Hoorebeke, L.; Van Overloop, A.; Walcher, Th.; Weinriefer, M.; A1 Collaboration

    2015-11-01

    Double-polarization observables in the reaction e ⃗p →e'p ⃗'γ have been measured at Q2=0.33 (GeV/c ) 2 . The experiment was performed at the spectrometer setup of the A1 Collaboration using the 855 MeV polarized electron beam provided by the Mainz Microtron (MAMI) and a recoil proton polarimeter. From the double-polarization observables the structure function PLT ⊥ is extracted for the first time, with the value (-15.4 ±3 .3(stat .)-2.4+1.5(syst.)) GeV-2 , using the low-energy theorem for virtual Compton scattering. This structure function provides a hitherto unmeasured linear combination of the generalized polarizabilities of the proton.

  5. Surface segregation at the binary alloy CuAu (100) studied by low-energy ion scattering

    NASA Astrophysics Data System (ADS)

    Beikler, Robert; Taglauer, Edmund

    2016-01-01

    We present results from an experimental study of segregation at the CuAu (100) surface. It is shown that Au enrichment in the top surface layer persists up to temperatures far beyond the bulk order-disorder transition temperature. From the gradual desegregation at higher temperatures a segregation energy of - 0.30 eV was determined. Our results are in quantitative agreement with calculations by Tersoff predicting oscillatory concentration depth profiles with decreasing amplitudes at higher temperatures. For the layer selective surface analysis we used low-energy He+ and Na+ scattering. Data interpretation and quantification were supported by numerical simulations with the MARLOWE code to which we had added the special features of trajectory resolved analysis and anisotropic thermal vibrations of surface atoms.

  6. Low energy positron interactions with uracil—Total scattering, positronium formation, and differential elastic scattering cross sections

    SciTech Connect

    Anderson, E. K.; Boadle, R. A.; Machacek, J. R.; Makochekanwa, C.; Sullivan, J. P.; Chiari, L.; Buckman, S. J.; Brunger, M. J.; Garcia, G.; Blanco, F.; Ingolfsson, O.

    2014-07-21

    Measurements of the grand total and total positronium formation cross sections for positron scattering from uracil have been performed for energies between 1 and 180 eV, using a trap-based beam apparatus. Angular, quasi-elastic differential cross section measurements at 1, 3, 5, 10, and 20 eV are also presented and discussed. These measurements are compared to existing experimental results and theoretical calculations, including our own calculations using a variant of the independent atom approach.

  7. Low-Energy Excitations in the Second LL: Fundamental Insights from Inelastic Light Scattering

    NASA Astrophysics Data System (ADS)

    Wurstbauer, Ursula; Pinczuk, Aron; Levy, Antonio L.; Watson, John; Mondal, Sumit; Manfra, Michael J.; West, Ken; Pfeiffer, Loren

    2014-03-01

    The competition between quantum phases that dictates the physics in the second Landau level (SLL) results in striking phenomena. Our work explores this fascinating interaction physics by measurements of low-lying neutral excitation modes in the SLL from resonant inelastic light scattering experiments. We focus here on the marked differences of the low-lying collective excitation spectra of the even-denominator state at ν=5/2 with those in the range 5/2> ν>2. Filling factor 5/2 is characterized by the presence of gapped modes, a spin mode exactly at EZ and the absence of a continuum of low-lying excitations. In contrast, a continuum of low-lying excitations and gapped modes are coexistent at ν=2+1/3, 2+3/8 and 2+2/5 and the spin-modes appear significantly below EZ. All observed modes weakens with smallest variations in filling factor substantiating the transition from an incompressible quantum Hall fluid to compressible states. Supported by NSF and AvH.

  8. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    SciTech Connect

    Ghosh, Avijit Ray, Debasis

    2015-03-15

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  9. Low energy electronic excitations and fano resonance in K doped C 60 from Raman scattering excited at 1.16 eV

    NASA Astrophysics Data System (ADS)

    Danieli, R.; Denisov, V. N.; Ruani, G.; Zamboni, R.; Taliani, C.; Zakhidov, A. A.; Ugawa, A.; Imaeda, K.; Yakushi, K.; Inokuchi, H.; Kikuchi, K.; Ikemoto, I.; Suzuki, S.; Achiba, Y.

    1992-01-01

    We present a Raman scattering study of pristine and K doped C 60 at various doping levels by exciting in the near-IR at 1.16 eV. The normal metallic state of K 3C 60 is characterized by a broad scattering background and by the resonance of low energy phonons in the range of 250-500 cm -1. We assign the broad background to an electronic Raman scattering due to low energy electronic excitations. This spectral feature is indicative of an anomalous normal state behaviour and is similar to the case of high temperature ceramic superconductors. In the overdoped K 6C 60 the squashing mode at 278 cm -1 shows a Fano resonance with the electronic scattering associated with localized electronic excitations which are characteristic of isolated regions of K 3C 60 into the matrix of K 6C 60 as a result of inhomogeneous doping. The Fano resonance indicates a specific electron-phonon coupling of this Jahn-Teller mode with low energy excitations and suggests that the symmetry of this electronic excitation is h g (i.e. the same of the coupled phonon mode). We discuss the nature of the anomalous electronic Raman scattering in terms of scattering from low energy excitations involving a low lying singlet band resulting from electron correlation and/or dynamical J-T distortion caused by the squashing mode.

  10. Probing ultrathin film continuity and interface abruptness with x-ray photoelectron spectroscopy and low-energy ion scattering

    SciTech Connect

    Zhang, Wenyu; Nahm, Rambert K.; Engstrom, James R.; Ma, Paul F.

    2013-11-15

    The authors have examined ultrathin (≤10 Å) tantalum nitride (TaN{sub x}) thin films deposited by atomic layer deposition (ALD) on three surfaces relevant to interconnect layers in microelectronic devices: thermally grown SiO{sub 2}; a Cu thin film grown by physical vapor deposition, and a carbon-doped SiO{sub 2} porous low-κ thin film. The authors have employed ex situ angle-resolved x-ray photoelectron spectroscopy (ARXPS), low-energy ion scattering spectroscopy (LEISS), and atomic force microscopy (AFM) to determine the continuity of these thin films, and by implication, the abruptness of the thin film/substrate interface. On SiO{sub 2} and low-κ, the authors find similar results: both ARXPS and AFM indicate that smooth, uniform thin films are deposited, consistent with nearly layer-by-layer growth of TaN{sub x} on these surfaces. Examination of these films using LEISS reveals that while the 10 Å TaN{sub x} thin films are continuous, the 5 Å TaN{sub x} thin films are not continuous and may possess on the order of ∼10% exposed substrate in the form of small subnanometer inclusions. On Cu, the situation is quite different. The TaN{sub x} thin films on these surfaces are not continuous, and our results point to a mixed layer of TaN{sub x} and Cu forming during ALD. In all cases, if one were to rely solely on results from ARXPS, the picture would be incomplete as the results from LEISS are ultimately decisive concerning thin film continuity.

  11. Precise determination of the low-energy hadronic contribution to the muon g -2 from analyticity and unitarity: An improved analysis

    NASA Astrophysics Data System (ADS)

    Ananthanarayan, B.; Caprini, Irinel; Das, Diganta; Imsong, I. Sentitemsu

    2016-06-01

    The two-pion low-energy contribution to the anomalous magnetic moment of the muon, aμ≡(g -2 )μ/2 , expressed as an integral over the modulus squared of the pion electromagnetic form factor, brings a relatively large contribution to the theoretical error, since the low accuracy of experimental measurements in this region is amplified by the drastic increase of the integration kernel. We derive stringent constraints on the two-pion contribution by exploiting analyticity and unitarity of the pion electromagnetic form factor. To avoid the poor knowledge of the modulus of this function, we use instead its phase, known with high precision in the elastic region from Roy equations for pion-pion scattering via the Fermi-Watson theorem. Above the inelastic threshold we adopt a conservative integral condition on the modulus, determined from data and perturbative QCD. Additional high precision data on the modulus in the range 0.65-0.71 GeV, obtained from e+e- annihilation and τ -decay experiments, are used to improve the predictions on the modulus at lower energies by means of a parametrization-free analytic extrapolation. The results are optimal for a given input and do not depend on the unknown phase of the form factor above the inelastic threshold. The present work improves a previous analysis based on the same technique, including more experimental data and employing better statistical tools for their treatment. We obtain for the contribution to aμ from below 0.63 GeV the value (133.258 ±0.723 )×10-10 , which amounts to a reduction of the theoretical error by about 6 ×10-11 .

  12. Low-energy electron scattering from CO. 2: Ab-initio study using the frame-transformation theory

    NASA Technical Reports Server (NTRS)

    Chandra, N.

    1976-01-01

    The Wigner-Eisenbud R matrix method has been combined with the frame transformation theory to study electron scattering from molecular systems. The R matrix, calculated at the boundary point of the molecular core radius, has been transformed to the space frame in order to continue the solution of the scattering equations in the outer region where rotational motion of the nuclei is taken into account. This procedure has been applied to a model calculation of thermal energy electron scattering from CO.

  13. Angular and charge state distributions of highly charged ions scattered during low energy surface-channeling interactions with Au(110)

    SciTech Connect

    Meyer, F.W.; Folkerts, L.; Schippers, S.

    1994-10-01

    The authors have measured scattered projectile angular and charge state distributions for 3.75 keV/amu O{sup q+} (3 {le} q {le} 8) and 1.2 keV/amu Ar{sup 1+} (3 {le} q {le} 14) ions grazingly incident along the [110] and [100] directions of a Au(110) single crystal target. Scattered projectile angular distribution characteristic of surface channeling are observed. For both incident species, the dominant scattered charge fraction is neutral, which varies only by a few percent as a function of incident charge state. Significant O{sup {minus}} formation is observed, which manifests a distinct velocity threshold. For incident Ar projectiles with open L-shells, the positive scattered charge fractions, while always less than about 10%, increase linearly with increasing number of initial L-shell vacancies.

  14. Spin-exchange optically pumped polarized 3He target for low-energy charged particle scattering experiments

    NASA Astrophysics Data System (ADS)

    Katabuchi, T.; Buscemi, S.; Cesaratto, J. M.; Clegg, T. B.; Daniels, T. V.; Fassler, M.; Neufeld, R. B.; Kadlecek, S.

    2005-03-01

    We have constructed, tested, and calibrated a polarized He3 target system which facilitates p-He3 elastic scattering at proton energies as low as 2MeV. This system consists of a target cell placed in a uniform B field inside a scattering chamber and an external optical pumping station utilizing Rb spin exchange. Computer-controlled valves allow polarized He3 gas to be transferred quickly between the optical pumping station and the spherical Pyrex target cell, which has Kapton film covering apertures for the passing beam and the scattering particles. The magnetic field required to maintain He3 polarization in the target cell is created with a compact, shielded sine-theta coil. Target gas polarimetry is accomplished using nuclear magnetic resonance and calibrated using the known analyzing power of α-He3 scattering.

  15. Polarization effects in low-energy electron scattering from silane molecules in an exact static-exchange model

    SciTech Connect

    Jain, A. )

    1991-07-01

    We have investigated the effects of various model polarization potentials in low-energy (below 15 eV) electron-SiH{sub 4} collisions in which electron-exchange correlation is treated exactly via an iterative procedure. Two models of the parameter-free polarization potential are employed; one, the {ital V}{sub pol}{sup JT} potential, introduced by Jain and Thompson (J. Phys. B 15, L631 (1982)), is based on the polarized-orbital theory; the other, the correlation-polarization potential {ital V}{sub pol}{sup CP}, first proposed by O'Connel and Lane (Phys. Rev. A 27, 1893 (1983)), is given as a density functional. In this low-energy region, the differential as well as integral cross sections are greatly influenced by such short-range-correlation and long-range-polarization interactions. We found that a local parameter-free model to mimic charge-distortion effects is quite successful if it is determined under the polarized-orbital-type approach rather than based on density-functional theory.

  16. Determination of low-energy parameters of neutron-proton scattering on the basis of modern experimental data from partial-wave analyses

    SciTech Connect

    Babenko, V. A. Petrov, N. M.

    2007-04-15

    The triplet and singlet low-energy parameters in the effective-range expansion for neutron-proton scattering are determined by using the latest experimental data on respective phase shifts from the SAID nucleon-nucleon database. The results differ markedly from the analogous parameters obtained on the basis of the phase shifts of the Nijmegen group and contradict the parameter values that are presently used as experimental ones. The values found with the aid of the phase shifts from the SAID nucleon-nucleon database for the total cross section for the scattering of zero-energy neutrons by protons, {sigma}{sub 0} = 20.426 b, and the neutron-proton coherent scattering length, f = -3.755 fm, agree perfectly with experimental cross-section values obtained by Houk, {sigma}{sub 0} = 20.436 {+-} 0.023 b, and experimental scattering-length values obtained by Houk and Wilson, f = -3.756 {+-} 0.009 fm, but they contradict cross-section values of {sigma}{sub 0} = 20.491 {+-} 0.014 b according to Dilg and coherent-scattering-length values of f = -3.7409 {+-} 0.0011 fm according to Koester and Nistler.

  17. Low-energy reactive ion scattering as a probe of surface femtochemical reaction: H+ and H- formation on ionic compound surfaces

    NASA Astrophysics Data System (ADS)

    Souda, R.; Suzuki, T.; Kawanowa, H.; Asari, E.

    1999-01-01

    Capture and loss of valence electrons during low-energy (50-500 eV) proton scattering from some alkali-halide surfaces such as LiCl, NaCl, and KF have been investigated in comparison with those from the TiO2(110) and Cs-adsorbed Si(100) surfaces. The primary H+ ion survives neutralization when scattered from the highly ionized target species existing on the surface. For H- ion formation, a close atomic encounter with individual target ions is found to be important; the H- ion is formed more efficiently on the cationic site than on the anionic site despite the fact that the valence electron is spacially localized on the latter. This is because the charge state of scattered hydrogen is determined during a transient chemisorption state and amphoteric hydrogen tends to be coordinated negatively (positively) on the cationic site (the anionic site). The final charge state of scattered hydrogen is fixed at a certain bond-breaking distance (˜5.0 a.u.) from the surface where the well-defined atomic orbital of hydrogen evolves. The competing nonlocal resonance tunneling is suppressed at the ionic-compound surfaces due to the existence of a large band gap, so that hydrogen is scattered without losing the memory of such a transient chemisorption state.

  18. Low-energy positron scattering from gas-phase tetrahydrofuran: A quantum treatment of the dynamics and a comparison with experiments

    SciTech Connect

    Franz, J.; Gianturco, F. A.

    2013-11-28

    In this paper we report new quantum calculations of the dynamics for low-energy positrons interacting with gaseous molecules of tetrahydrofuran. The new quantum scattering cross sections are differential and integral cross sections at collision energies between 1.0 and 25.0 eV and include a careful treatment of the additional effects on the scattering process brought about by the permanent dipole moment of the target molecule. The present results are compared with an extensive range of measured data, both for the angular distributions and for the elastic integral cross sections and agree remarkably well with all findings. The new calculated quantities reported here also show the importance of correcting the experimental integral cross sections for the angular discrimination in the forward direction.

  19. Determination of {sup 16}O and {sup 18}O sensitivity factors and charge-exchange processes in low-energy ion scattering

    SciTech Connect

    Tellez, H.; Chater, R. J.; Fearn, S.; Symianakis, E.; Kilner, J. A.; Brongersma, H. H.

    2012-10-08

    Quantitative analysis in low-energy ion scattering (LEIS) requires an understanding of the charge-exchange processes to estimate the elemental sensitivity factors. In this work, the neutralization of He{sup +} scattered by {sup 18}O-exchanged silica at energies between 0.6 and 7 keV was studied. The process is dominated by Auger neutralization for E{sub i} < 0.8 keV. An additional mechanism starts above the reionization threshold. This collision-induced neutralization becomes the dominant mechanism for E{sub i} > 2 keV. The ion fractions P{sup +} were determined for Si and O using the characteristic velocity method to quantify the surface density. The {sup 18}O/{sup 16}O sensitivity ratio indicates an 18% higher sensitivity for the heavier O isotope.

  20. Low-energy dispersion of dynamic charge stripes in La1.75Sr0.25NiO4 observed with inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Zhong, Ruidan; Tranquada, John; Gu, Genda; Reznik, Dmitry; Winn, Barry

    The dynamic stripe correlations have been the subject of intense research, owing to the possible links with high-Tc superconductivity. In light of a recently published, direct observation of charge-stripe fluctuations in La2-xSrxNiO4 using inelastic neutron scattering, we did a follow-up neutron experiment on a x=0.25 sample to characterize the low-energy dispersion of these dynamic charge stripes using the HYSPEC instrument at the Spallation Neutron Source. The scattering signals are collected in the vicinity of a charge-order peak with a large wave vector (4.4, 3, 0), where dynamic spin-stripe correlations are negligible. Mapping the low-energy charge-stripe fluctuations in a wide temperature range, we observe a finite dispersion along the stripe-modulation direction at T >=160K where the charge stripes become disordered, while the steep dispersion in the orthogonal direction is not resolved. Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-SC00112704.

  1. Faddeev calculations of the K¯NN system with a chirally motivated K¯N interaction. I. Low-energy K-d scattering and antikaonic deuterium

    NASA Astrophysics Data System (ADS)

    Shevchenko, N. V.; Révai, J.

    2014-09-01

    A chirally-motivated coupled-channel K¯N potential, reproducing all low-energy experimental data on K-p scattering and kaonic hydrogen and suitable for using in accurate few-body calculations, was constructed. The potential was used for calculations of low-energy amplitudes of elastic K-d scattering using Faddeev-type Alt-Grassberger-Sandhas (AGS) equations with coupled K¯NN and πΣN channels. A complex K--d potential reproducing the three-body K-d amplitudes was constructed and used for calculation of the 1s level shift and the width of kaonic deuterium. The predicted shift ΔE1sK-d˜-830 eV and width Γ1sK-d≈1055 eV are close to our previous results obtained with phenomenological K ¯N potentials. No quasi-bound states in the K-d system were found.

  2. Adsorption of Iodine and Potassium on Bi2Sr2CaCu2O8+δ Investigated by Low Energy Alkali Ion Scattering

    SciTech Connect

    Gu, G.D.; Gann, R.D.; Cao, J.X.; Wu, R.Q.; Wen, J.; Xu, Z.; Gu, G.D.; Yarmoff, J.A.

    2010-01-01

    The adsorption of K and I on the surface of the high-T{sub c} cuprate BSCCO-2212 is investigated with low-energy (0.8 to 2 keV) Na{sup +} ion scattering and density functional theory (DFT). Samples were cleaved in ultrahigh vacuum and charge-resolved spectra of the scattered ions were collected with time-of-flight. The spectra contain a single peak representing Na scattered from Bi, as the clean surfaces are terminated by BiO. The neutralization of scattered Na depends on the local potential above the target site, and the angular dependence indicates that the clean surface has an inhomogeneous potential. Neutralization is dependent on the coverage of I, but independent of K adsorption. DFT suggests high-symmetry sites for the adsorption of both I and K, and that the potential above the Bi sites is altered by I by an amount consistent with the experimental findings, while the potential is not affected by K adsorption. DFT also enables an experimental determination of the 'freezing distance,' which is the effective point beyond which charge exchange does not occur, to be 1.6 {+-} 0.1 {angstrom} from the outermost Bi layer.

  3. Near shot-noise limited hyperspectral stimulated Raman scattering spectroscopy using low energy lasers and a fast CMOS array.

    PubMed

    Rock, William; Bonn, Mischa; Parekh, Sapun H

    2013-07-01

    We demonstrate near shot-noise limited hyperspectral stimulated Raman scattering (SRS) spectroscopy using oscillator-only excitation conditions. Using a fast CMOS camera synchronized to an acousto-optic modulator and subtracting subsequent frames acquired at up to 1 MHz frame rates, we demonstrate demodulation and recovery of the SRS spectrum. Surprisingly, we observe that the signal-to-noise of SRS spectra is invariant at modulation frequencies down to 2.5 kHz. Our approach allows for a direct comparison of SRS with coherent anti-Stokes Raman scattering (CARS) spectroscopy under identical experimental conditions. Our findings suggest that hyperspectral SRS imaging with shot-noise limited performance at biologically compatible excitation energies is feasible after minor modifications to fast frame-rate CMOS array technology. PMID:23842298

  4. Possibilities of studying the structure of halo nuclei in reactions of quasifree proton scattering at low energies

    SciTech Connect

    Zuyev, S. V. Kasparov, A. A.; Konobeevski, E. S.

    2015-07-15

    The possibility of experimentally studying the structure of halo nuclei in reactions induced by quasifree proton scattering on clusters of these nuclei is considered. Quasifree proton scattering on {sup 6}He, {sup 4}He, {sup 4}n, {sup 2}n, and n clusters in inverse kinematics is considered for the example of the {sup 8}He nucleus. Angular and energy distributions of secondaries are obtained for various representations of the cluster structure of the {sup 8}He nucleus. It is clearly shown that, in the angular and energy distributions of secondaries, one can single out regions that receive dominant contributions from reactions on specific clusters and which correspond to concrete cluster configurations of halo nuclei. Possible relevant experiments are proposed.

  5. Monte Carlo study of coherent scattering effects of low-energy charged particle transport in Percus-Yevick liquids

    NASA Astrophysics Data System (ADS)

    Tattersall, W. J.; Cocks, D. G.; Boyle, G. J.; Buckman, S. J.; White, R. D.

    2015-04-01

    We generalize a simple Monte Carlo (MC) model for dilute gases to consider the transport behavior of positrons and electrons in Percus-Yevick model liquids under highly nonequilibrium conditions, accounting rigorously for coherent scattering processes. The procedure extends an existing technique [Wojcik and Tachiya, Chem. Phys. Lett. 363, 381 (2002), 10.1016/S0009-2614(02)01177-6], using the static structure factor to account for the altered anisotropy of coherent scattering in structured material. We identify the effects of the approximation used in the original method, and we develop a modified method that does not require that approximation. We also present an enhanced MC technique that has been designed to improve the accuracy and flexibility of simulations in spatially varying electric fields. All of the results are found to be in excellent agreement with an independent multiterm Boltzmann equation solution, providing benchmarks for future transport models in liquids and structured systems.

  6. How low-energy weak reactions can constrain three-nucleon forces and the neutron-neutron scattering length.

    PubMed

    Gårdestig, A; Phillips, D R

    2006-06-16

    We show that chiral symmetry and gauge invariance enforce relations between the short-distance physics that occurs in a number of electroweak and pionic reactions on light nuclei. Within chiral perturbation theory, this is manifested via the appearance of the same axial isovector two-body contact term in pi(-)d --> nngamma, p-wave pion production in NN collisions, tritium beta decay, pp fusion, nud scattering, and the hep reaction. Using a Gamow-Teller matrix element obtained from calculations of pp fusion as input, we compute the neutron spectrum obtained in pi(-)d --> nngamma. With the short-distance physics in this process controlled from pp --> de(=)nu(e), the theoretical uncertainty in the nn scattering length extracted from pi(-)d --> nngamma is reduced by a factor larger than 3, to approximately < or = 0.05 fm. PMID:16803373

  7. Geometries and focal properties of two electron-lens systems useful in low-energy electron or ion scattering

    NASA Technical Reports Server (NTRS)

    Chutjian, A.

    1979-01-01

    Geometries and focal properties are given for two types of electron-lens system commonly needed in electron scattering. One is an electron gun that focuses electrons from a thermionic emitter onto a fixed point (target) over a wide range of final energies. The other is an electron analyzer system that focuses scattered electrons of variable energy onto a fixed position (e.g., the entrance plane of an analyzer) at fixed energy with a zero final beam angle. Analyzer-system focusing properties are given for superelastically, elastically, and inelastically scattered electrons. Computer calculations incorporating recent accurate tube-lens focal properties are used to compute lens voltages, locations and diameters of all pupils and windows, filling factors, and asymptotic rays throughout each lens system. Focus voltages as a function of electron energy and energy change are given, and limits of operation of each system discussed. Both lens systems have been in routine use for several years, and good agreement has been consistently found between calculated and operating lens voltages.

  8. Low-Energy Grazing Ion-Scattering from Alkali-Halide Surfaces: A Novel Approach to C-14 Detection

    SciTech Connect

    Meyer, Fred W; Galutschek, Ernst; Hotchkis, Michael

    2009-01-01

    Carbon-14 labeled compounds are widely used in the pharmaceutical industry, e.g., as tracers to determine the fate of these compounds in vivo. Conventional accelerator mass spectrometry (AMS) is one approach that offers sufficiently high sensitivity to avoid radiological waste and contamination issues in such studies, but requires large, expensive facilities that are usually not solely dedicated to this task. At the ORNL Multicharged Ion Research Facility (MIRF) we are exploring a small size, low cost alternative to AMS for biomedical 14C tracer studies that utilizes ECR-ion-source-generated keV-energy-range multicharged C beams grazingly incident on an alkali halide target, where efficient negative ion production by multiple electron capture takes place. By using C ion charge states of +3 or higher, the molecular isobar interference at mass 14, e.g. 12CH2 and 13CH, is eliminated. The negatively charged ions in the beam scattered from the alkali halide surface are separated from other scattered charge states by two large acceptance ({approx}15 msr) stages of electrostatic analysis. The N-14 isobar interference is thus removed, since N does not support a stable negative ion. Initial results for C-14 detection obtained using C-14 enriched CO2 from ANSTO will be described.

  9. Low-energy tail of the giant dipole resonance in Mo98 and Mo100 deduced from photon-scattering experiments

    NASA Astrophysics Data System (ADS)

    Rusev, G.; Schwengner, R.; Dönau, F.; Erhard, M.; Grosse, E.; Junghans, A. R.; Kosev, K.; Schilling, K. D.; Wagner, A.; Bečvář, F.; Krtička, M.

    2008-06-01

    Dipole-strength distributions in the nuclides Mo98 and Mo100 up to the neutron-separation energies have been studied in photon-scattering experiments at the bremsstrahlung facility of the Forschungszentrum Dresden-Rossendorf. To determine the dipole-strength distributions up to the neutron-emission thresholds, statistical methods were developed for the analysis of the measured spectra. The measured spectra of scattered photons were corrected for detector response and atomic background by simulations using the code GEANT3. Simulations of γ-ray cascades were performed to correct the intensities of the transitions to the ground state for feeding from higher-lying levels and to determine their branching ratios. The photoabsorption cross sections obtained for Mo98 and Mo100 from the present (γ,γ') experiments are combined with (γ,n) data from literature, resulting in a photoabsorption cross section covering the range from 4 to about 15 MeV of interest for network calculations in nuclear astrophysics. Novel information about the low-energy tail of the giant dipole resonance and its energy dependence is derived. The photoabsorption cross sections deduced from the present photon-scattering experiments are compared with existing data from neutron capture and He3-induced reactions.

  10. Coulomb suppression in the low-energy p-p elastic scattering via the Trojan Horse Method

    SciTech Connect

    Tumino, A.; Spitaleri, C.; Rapisarda, G. G.; Cherubini, S.; Crucilla, V.; Gulino, M.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Romano, S.; Sergi, M. L.; Mukhamedzhanov, A.; Campajola, L.; Elekes, Z.; Fueloep, Zs.; Gyuerky, G.; Kiss, G. G.; Somorjai, E.; Gialanella, L.

    2010-11-24

    We present here an important test of the main feature of the Trojan Horse Method (THM), namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. This is done by measuring the THM p-p elastic scattering via the p+d{yields}p+p+n reaction at 4.7 and 5 MeV, corresponding to a p-p relative energy ranging from 80 to 670 keV. In contrast to the on-energy-shell (OES) case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum due to the suppression of the Coulomb amplitude. This is confirmed by the half-off-energy shell (HOES) calculations and strengthened by the agreement with the calculated OES nuclear cross sections.

  11. Band effects on inelastic scattering of low-energy ions from metallic and ionic surfaces: A formalism beyond the adiabatic molecular-orbitals calculation

    NASA Astrophysics Data System (ADS)

    García, Evelina A.; Goldberg, E. C.

    1998-03-01

    Charge exchange and inelastic excitation processes have been analyzed in the scattering of low-energy He+ from metallic and ionic surfaces. An Anderson-like Hamiltonian is proposed, where the parameters are defined taking into account the electronic band structure of the surface as well as the atomic nature of the interaction between the projectile and the target atoms. The time-dependent collisional process is solved by using a Green-function formalism, which allows us to calculate not only the charge-state probabilities but also the one-electron interband excitations in the solid. Competitive effects of the hybridizations among the localized state at the projectile site and the localized and extended surface states are contemplated. In this way we can explain the observed energy dependences of the neutralization probability, as well as the occurrence of energy-loss processes due to the excitation of valence and core surface electrons induced by the collision.

  12. Low-energy elastic and inelastic scattering of electrons from SO2 using the R -matrix method

    NASA Astrophysics Data System (ADS)

    Gupta, Monika; Baluja, K. L.

    2006-04-01

    R -matrix method is used to calculate elastic differential, integral, and momentum transfer cross sections for electron- SO2 collision. The electron-impact excitation cross sections for first seven low-lying electronic excited states of SO2 molecule from the ground state of SO2 molecule have been calculated for the first time. Sixteen low-lying electronic states of SO2 molecule are included in the close coupling expansion of the wave function of the entire scattering system, which have vertical excitation energies up to 10.51eV . Configuration-interaction (CI) wave functions are used to calculate these excitation energies. In our CI model, we keep the core 14 electrons frozen in doubly occupied molecular orbitals 1a1 , 2a1 , 3a1 , 4a1 , 1b1 , 1b2 , 2b2 and the remaining 18 electrons span the relevant active space: 5a1 , 6a1 , 7a1 , 8a1 , 9a1 , 2b1 , 3b1 , 3b2 , 4b2 , 5b2 , 6b2 , and 1a2 . Our calculated dipole moment of the ground state of SO2 at its equilibrium geometry is 0.79a.u. , which is in reasonable agreement with the corresponding experimental value 0.64a.u. Our calculations detect one bound SO2- state (B12) at the equilibrium geometry of SO2 molecule. Both shape as well as core-excited shape resonances have been identified in the present work and are correlated with the experimental results on dissociative electron attachment study. A detailed analysis of resonances is provided. Cross sections are reported for the electron impact energy range 0-15eV . All cross section calculations are performed in the fixed-nuclei approximation at the experimental equilibrium geometry of the ground state of SO2 molecule. We have also investigated dependence of resonances on the geometry of SO2 molecule to probe the possible pathways for dissociation of resulting negative ion upon electron attachment. We have excellent agreement of differential, elastic integral, and momentum transfer cross sections calculated in the 16-state R -matrix approximation with the available

  13. Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

    SciTech Connect

    Kyriakou, Ioanna; Emfietzoglou, Dimitris; Garcia-Molina, Rafael; Abril, Isabel; Kostarelos, Kostas

    2011-09-01

    The effect of bulk and surface excitations to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes (MWNTs) is studied using the dielectric formalism. Calculations are based on a semiempirical dielectric response function for MWCNTs determined by means of a many-pole plasmon model with parameters adjusted to available experimental spectroscopic data under theoretical sum-rule constrains. Finite-size effects are considered in the context of electron gas theory via a boundary correction term in the plasmon dispersion relations, thus, allowing a more realistic extrapolation of the electronic excitation spectrum over the whole energy-momentum plane. Energy-loss differential and total inelastic scattering cross sections as a function of electron energy and distance from the surface, valid over the energy range {approx}50-30,000 eV, are calculated with the individual contribution of bulk and surface excitations separated and analyzed for the case of normally incident and escaping electrons. The sensitivity of the results to the various approximations for the spatial dispersion of the electronic excitations is quantified. Surface excitations are shown to have a strong influence upon the shape and intensity of the energy-loss differential cross section in the near surface region whereas the general notion of a spatially invariant inelastic mean free path inside the material is found to be of good approximation.

  14. Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kyriakou, Ioanna; Emfietzoglou, Dimitris; Garcia-Molina, Rafael; Abril, Isabel; Kostarelos, Kostas

    2011-09-01

    The effect of bulk and surface excitations to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes (MWNTs) is studied using the dielectric formalism. Calculations are based on a semiempirical dielectric response function for MWCNTs determined by means of a many-pole plasmon model with parameters adjusted to available experimental spectroscopic data under theoretical sum-rule constrains. Finite-size effects are considered in the context of electron gas theory via a boundary correction term in the plasmon dispersion relations, thus, allowing a more realistic extrapolation of the electronic excitation spectrum over the whole energy-momentum plane. Energy-loss differential and total inelastic scattering cross sections as a function of electron energy and distance from the surface, valid over the energy range ˜50-30,000 eV, are calculated with the individual contribution of bulk and surface excitations separated and analyzed for the case of normally incident and escaping electrons. The sensitivity of the results to the various approximations for the spatial dispersion of the electronic excitations is quantified. Surface excitations are shown to have a strong influence upon the shape and intensity of the energy-loss differential cross section in the near surface region whereas the general notion of a spatially invariant inelastic mean free path inside the material is found to be of good approximation.

  15. In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

    NASA Astrophysics Data System (ADS)

    Coloma Ribera, R.; van de Kruijs, R. W. E.; Sturm, J. M.; Yakshin, A. E.; Bijkerk, F.

    2016-08-01

    In vacuo high-sensitivity low energy ion scattering (HS-LEIS) has been used to investigate the initial growth stages of DC sputtered Ru on top of Si, SiN, and SiO2. The high surface sensitivity of this technique allowed an accurate determination of surface coverages and thicknesses required for closing the Ru layer on all three substrates. The Ru layer closes (100% Ru surface signal) at about 2.0, 3.2, and 4.7 nm on top of SiO2, SiN, and Si, respectively. In-depth Ru concentration profiles can be reconstructed from the Ru surface coverages when considering an error function like model. The large intermixing (4.7 nm) for the Ru-on-Si system is compared to the reverse system (Si-on-Ru), where only 0.9 nm intermixing occurs. The difference is predominantly explained by the strong Si surface segregation that is observed for Ru-on-Si. This surface segregation effect is also observed for Ru-on-SiN but is absent for Ru-on-SiO2. For this last system, in vacuo HS-LEIS analysis revealed surface oxygen directly after deposition, which suggests an oxygen surface segregation effect for Ru-on-SiO2. In vacuo XPS measurements confirmed this hypothesis based on the reaction of Ru with oxygen from the SiO2, followed by oxygen surface segregation.

  16. Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Delichere, P.

    1996-12-01

    Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminates, obtained by sol-gel techniques, with a different amount of sodium, and R equal to 2.1 and 6.1 respectively. LEIS experiments and electron microscopy demonstrate a different location of alkali metal ions in the first two series: in the Na-Pd/SiO{sub 2} catalysts sodium is distributed in a way which is not uniform on the support and on the palladium metal, which is partly decorated with Na ions, whereas in the Pd/natural-pumice series the palladium surface is sodium-free. The results on the third series of catalysts, Pd/model pumice, are not definitive on the basis of the LEIS and TEM analyses, but by FTIR study of CO and CO{sub 2} adsorption, the decoration of palladium by sodium ions could be excluded. The results confirm the importance of the alkali metal ion location in alkali-promoted palladium catalysts and open new possibilities in the design of palladium-supported catalysts by a better control of promoter location. 18 refs., 5 figs., 2 tabs.

  17. High-Spin Gamma-Ray Spectroscopy in BISMUTH-198, Superdeformation in GOLD-191, and Multi-Photon Resonances in Low Energy Positron-Electron Scattering

    NASA Astrophysics Data System (ADS)

    Vo, Duc Ta.

    1993-01-01

    The properties of low-and high-spin levels in ^{198}Bi have been studied with the ^{181}Ta(^ {22}Ne,5n)^{198}Bi reaction at 116 MeV and 120 MeV bombarding energies. Levels along and near the yrast lines, including one isomer, were established up to spin J ~ 30hbar. The main configurations of these states are suggested to be pi h_{9/2} coupled to the known excited states in ^{197 }Pb. A sequence of states built on the excitation of the odd proton (coupled to one, two, or three quasi neutron-holes) was observed. In addition, at least two collective bands were observed. These two bands are backbending bands and are suggested to be oblate collective structures built on oblate proton and possibly neutron states. A superdeformed (SD) band was observed for the first time in an Au isotope. The reaction used was ^{11}B + ^{186 }W, demonstrating that very light ions can be used to populate SD bands at high angular momentum. The band is assigned to ^{191}Au. The gamma-ray energies are at the so -called quarter-point energies of the ^{192 }Hg SD band, indicating that the ^ {191}Au SD band is "identical" to that of ^{192}Hg. A search for resonant states in low-energy e ^+e^- scattering through their decay to multi-photon final states was performed using e ^+ from ^{68}Ga sources and a Pb absorber. Energy-sum and invariant mass spectra of coincident 2gamma and 3gamma events were obtained using the 20-element High Energy-Resolution Array (HERA) facility. No evidence for resonant states was found, and upper limits for the partial decay widths of such resonances were established in the energy range from 1.1 to 1.8 MeV.

  18. Design of the Small Angle Neutron Scattering instrument at the Indiana University Low Energy Neutron Source: Applications to the study of nanostructured materials

    NASA Astrophysics Data System (ADS)

    Remmes, Nicholas B.

    The Low Energy Neutron Source (LENS) located at the Indiana University Cyclotron Facility (IUCF) is a prototypical long-pulse accelerator-based neutron source. The Small Angle Neutron Scattering (SANS) instrument is one of several planned instruments at the LENS facility. The SANS instrument is a time-of-flight instrument which utilizes a pinhole collimation system and neutron wavelengths up to 20A giving it a q range from about 0.006A-1 to 0.5A-1 with a maximum divergence at the sample of about +/-8mrad. The neutron flux on the sample at the anticipated 8kW mode of operation is anticipated to be greater than 2 x 104n/s.cm 2. The design, calibration, and testing of the LENS SANS instrument is discussed, including Monte-Carlo simulations and analytical calculations used to optimize the collimation design, the placement and design of the pulse-overlap chopper system, and other aspects of the instrument's geometry. The expected resolution, count rates, and other general performance parameters of the instrument are presented and, where possible, compared with experimental results. SANS measurements of a family of tripodal organo-silicon dendrimer molecules using the IPNS SAND and the NCNR NG3 SANS instruments are presented. Variations in the scattering curves are compared for solutions of the dendrimers at multiple concentrations in d-heptane, d-DCM, and d-toluene. Models of both the particle form factor and the structure factor are presented. The measurements suggest a distinct difference between the size and behavior of the highest generation dendrimer in two of the solvents (d-DCM and d-toluene) as compared to a third (d-heptane). Additionally, the dendrimer molecules appear to be forming short chains in solution. A brief study of iron oxide magnetic nanoparticles is also presented. This study includes a presentation of the magnetic measurements of the nanoparticles using a SQUID magnetometer. The measurements indicate contributions by a larger dispersion of

  19. Measurement of the Generalized Polarizabilities of the Proton in Virtual Scattering at Q2=0.92 and 1.76 GeV2: I. Low Energy Expansion Analysis

    SciTech Connect

    Stephanie Jaminion; Natalie Degrande; Geraud Laveissiere; Christophe Jutier; Luminita Todor; Rachele Di Salvo; L. Van Hoorebeke

    2003-12-01

    Virtual Compton Scattering is studied at the Thomas Jefferson National Accelerator Facility at low Center-of-Mass energies, below pion threshold. Following the Low Energy Theorem for the ep {yields} ep gamma process, we obtain values for the two structure functions Pll-Ptt/epsilon and Plt at four-momentum transfer squared Q2=0.92 and 1.76 GeV2.

  20. Inelastic neutron scattering studies on the incommensurate-to-commensurate transformation of low energy magnetic excitations in Fe1 + δ - y(Ni / Cu) y Te1 - x Sex

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Schneeloch, John; Zhao, Yang; Matsuda, Masaaki; Ku, Wei; Liu, Xuerong; Gu, Genda; Lee, D.-H.; Birgeneau, R. J.; Tranquada, J. M.; Xu, Guangyong

    2013-03-01

    We have performed a series of neutron scattering and magnetization measurements on Fe1 + δ - y(Ni / Cu) y Te1 - x Sex system to study the interplay between magnetism and superconductivity. Both non-superconducting and superconducting samples with Tc 8 ~15K are studied. The low energy magnetic excitations of all samples at T > >Tc consist of two incommensurate vertical columns. They change to a distinctly different U-shaped dispersion at T >Tc for the superconducting samples and the transition temperature depend on the composition. On the other hand, for all non-superconducting samples, there is no clear temperature dependence, and the low energy magnetic excitations remain two columns for temperatures down to 1.5 K. Work is supported by the Office of Basic Energy Sciences, DOE.

  1. The calculation of the contributions to low energy e+H2 scattering from sigma u+ and Pion u symmetries using the Kohn variational method

    NASA Technical Reports Server (NTRS)

    Armour, E. A. G.; Baker, D. J.; Plummer, M.

    1990-01-01

    Above incident energies of about 2 eV, the contribution to the total cross section in positron+H2 scattering from the sigma g+ symmetry is insufficient to account for the experimental value. Calculations carried out of the lowest partial waves of sigma u+ symmetry and Pion u symmetry using the Kohn variational method are described. The contributions to the total cross section from the two equivalent partial waves of Pion u symmetry significantly reduce the discrepancy with experiment up to incident energies of 4 to 5 eV. Comparisons are made with recent R-matrix calculations performed by Danby and Tennyson.

  2. Momentum-transfer, differential and spin-exchange cross sections in the elastic scattering of low-energy electrons by heavy alkali-metal atoms.

    NASA Astrophysics Data System (ADS)

    Bahrim, Cristian; Thumm, Uwe; Fabrikant, Ilya I.

    2000-06-01

    Based on the relativistic Dirac R-matrix method, we analyze various angle-dependent cross sections for electron scattering by Rb, Cs and Fr targets at energies below 3 eV. We show our angle-dependent and total spin-exchange cross sections for scattering of non-polarized (or polarized) electrons by polarized (or non-polarized) Rb, Cs and Fr targets, and we compare them with available experimental data (B. Jaduszliwer, N.D. Bhaskar, and B. Bederson Phys.Rev. A 14), 162 (1976).. The influence of relativistic effects is discussed. From the energy and angular dependence analysis of the differential cross section, we obtain clear evidence of the Cs^-(^3F^o) shape resonance at 1.528 eV, in excellent agreement with accurate experiments (W. Gehenn and E. Reichert, J.Phys. B 10), 3105 (1977).. We compare our electron momentum-transfer cross section with available data obtained in swarm experiments for Rb (Y. Nakamura, Trans. IEE of Japan 102-A), 23 (1982). and Cs (H.T. Saelee and J. Lucas, J.Phys. D 12), 1275 (1979)..

  3. Low energy supersymmetry phenomenology

    SciTech Connect

    Baer, H.; Chen, C.H.; Bartl, A.; Feng, J.; Fujii, K.; Gunion, J.; Kamon, T.; Lopez, J.L.; Kao, C.

    1995-04-01

    The authors summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, they evaluate the capabilities of various e{sup +}e{sup {minus}}, p{bar p} and pp colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, they discuss capabilities of future facilities to disentangle the anticipated spectrum of super-particles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. The authors then comment upon the complementarity of proposed hadron and e{sup +}e{sup {minus}} machines for a comprehensive study of low energy supersymmetry.

  4. Low energy supersymmetry phenomenology

    SciTech Connect

    Baer, H.; Chen, C.H.; Bartl, A.

    1995-03-01

    The authors summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, they evaluate the capabilities of various e{sup +}e{sup {minus}}, p{anti p} and pp colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, they discuss capabilities of future facilities to disentangle the anticipated spectrum of superparticles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. They comment upon the complementarity of proposed hadron and e{sup +}e{sup {minus}} machines for a comprehensive study of low energy supersymmetry.

  5. LOW ENERGY COUNTING CHAMBERS

    DOEpatents

    Hayes, P.M.

    1960-02-16

    A beta particle counter adapted to use an end window made of polyethylene terephthalate was designed. The extreme thinness of the film results in a correspondingly high transmission of incident low-energy beta particles by the window. As a consequence, the counting efficiency of the present counter is over 40% greater than counters using conventional mica end windows.

  6. Low energy antiproton beams

    NASA Astrophysics Data System (ADS)

    Klapisch, R.

    1992-04-01

    It was the invention of stochastic cooling by S. Van Meer that has allowed antiproton beams to become a powerful tool for the physicist. As a byproduct of the high energy proton-antiproton collider, a versatile low-energy facility, LEAR has been operating at CERN since 1984. The facility and its characteristics will be described as well as examples of its use for studying fundamental properties of the antiproton and for topics in atomic, nuclear and particle Physics.

  7. Low-energy positron scattering by pyrimidine

    NASA Astrophysics Data System (ADS)

    Barbosa, Alessandra Souza; Pastega, Diego F.; Bettega, Márcio H. F.

    2015-12-01

    This work reports elastic integral and differential cross sections for positron collisions with pyrimidine, for energies up to 20 eV. The cross sections were computed with the Schwinger multichannel method in the static plus polarization approximation. We also employed the Born closure procedure to account for the long range potential due to the permanent dipole moment of the molecule. Our results are compared with the experimental total cross section of Zecca et al. [J. Phys. B 43, 215204 (2010)], the experimental grand-total, quasi-elastic integral and differential cross section of Palihawadana et al. [Phys. Rev. A 88, 12717 (2013)]. We also compare our results with theoretical integral and differential cross sections obtained by Sanz et al. [Phys. Rev. A 88, 62704 (2013)] with the R-matrix and the independent atom model with screening-corrected additivity rule methods, and with the results computed by Franz and Gianturco [Phys. Rev. A 88, 042711 (2013)] using model correlation-polarization potentials. The agreement between the theory and the experiment is encouraging.

  8. Low-energy positron scattering by pyrimidine

    SciTech Connect

    Barbosa, Alessandra Souza; Pastega, Diego F.; Bettega, Márcio H. F.

    2015-12-28

    This work reports elastic integral and differential cross sections for positron collisions with pyrimidine, for energies up to 20 eV. The cross sections were computed with the Schwinger multichannel method in the static plus polarization approximation. We also employed the Born closure procedure to account for the long range potential due to the permanent dipole moment of the molecule. Our results are compared with the experimental total cross section of Zecca et al. [J. Phys. B 43, 215204 (2010)], the experimental grand-total, quasi-elastic integral and differential cross section of Palihawadana et al. [Phys. Rev. A 88, 12717 (2013)]. We also compare our results with theoretical integral and differential cross sections obtained by Sanz et al. [Phys. Rev. A 88, 62704 (2013)] with the R-matrix and the independent atom model with screening-corrected additivity rule methods, and with the results computed by Franz and Gianturco [Phys. Rev. A 88, 042711 (2013)] using model correlation-polarization potentials. The agreement between the theory and the experiment is encouraging.

  9. Hard elastic scattering in QCD: Leading behavior

    SciTech Connect

    Botts, J.F.

    1989-01-01

    The author derives the asymptotic behavior of elastic meson-meson and baryon-baryon scattering at high energy and large angle t/s {approximately} O(1). The results organize both Sudakov and nonleading logarithmic corrections to independent (Landshoff) scatterings of valence quarks. He shows how to separate these contributions systematically from single scattering contributions, in a manner which suggests that the complete amplitudes should be computable perturbatively down to the dimensional counting power, in terms of hadronic wave functions. In the final chapter, the perturbative asymptotic amplitude and differential cross section for elastic pion-pion scattering is calculated numerically. For various choices of pion wave function and running coupling, the onset of power law behavior, d{sigma}/dt {approximately} s{sup {minus}5.8}, was observed. The dependence in d{sigma}/dt on the cutoff in gluon momentum, chosen to be O({Lambda}{sub QCD}/Q), was observed to be sharp for ln(s/1GeV{sup 2}) less than 1. Very small oscillations in d{sigma}/dt appear in physically realizable energies, but these are cutoff dependent, and their interpretation unclear. Higher twist effects were estimated to be roughly {approximately}15% for 2 < ln(s/1GeV{sup 2}) < 10.

  10. Low-energy neutrinos

    NASA Astrophysics Data System (ADS)

    Ludhova, Livia

    2016-05-01

    There exist several kinds of sources emitting neutrinos in the MeV energy range. These low-energy neutrinos from different sources can be often detected by the same multipurpose detectors. The status-of-art of the field of solar neutrinos, geoneutrinos, and the search for sterile neutrino with artificial neutrino sources is provided here; other neutrino sources, as for example reactor or high-energy neutrinos, are described elsewhere. For each of these three fields, the present-day motivation and open questions, as well as the latest experimental results and future perspectives are discussed.

  11. Bag-model quantum chromodynamics for hyperons at low energy

    NASA Astrophysics Data System (ADS)

    Weber, H. J.; Maslow, J. N.

    1980-09-01

    In a non-perturbative bag model framework, gluon exchange which mediates quark exchange scattering in conjunction with quark interchange is shown to be the basis of the OBE interactions of hyperons at low energy.

  12. Low energy spin excitations in chromium metal

    SciTech Connect

    Pynn, R.; Azuah, R.T.; Stirling, W.G.; Kulda, J.

    1997-12-31

    Neutron scattering experiments with full polarization analysis have been performed with a single crystal of chromium to study the low-energy spin fluctuations in the transverse spin density wave (TSDW) state. A number of remarkable results have been found. Inelastic scattering observed close to the TSDW satellite positions at (1 {+-} {delta},0,0) does not behave as expected for magnon scattering. In particular, the scattering corresponds to almost equally strong magnetization fluctuations both parallel and perpendicular to the ordered moments of the TSDW phase. As the Neel temperature is approached from below, scattering at the commensurate wavevector (1,0,0) increases in intensity as a result of critical scattering at silent satellites (1,0, {+-} {delta}) being included within the spectrometer resolution function. This effect, first observed by Sternlieb et al, does not account for all of the inelastic scattering around the (1,0,0) position, however, Rather, there are further collective excitations, apparently emanating from the TSDW satellites, which correspond to magnetic fluctuations parallel to the ordered TSDW moments. These branches have a group velocity that is close to that of (1,0,0) longitudinal acoustic (LA) phonons, but assigning their origin to magneto-elastic scattering raises other unanswered questions.

  13. Ginsparg-Wilson pions scattering in a sea of staggered quarks

    NASA Astrophysics Data System (ADS)

    Chen, Jiunn-Wei; O'Connell, Donal; van de Water, Ruth; Walker-Loud, André

    2006-04-01

    We calculate isospin 2 pion-pion scattering in chiral perturbation theory for a partially quenched, mixed action theory with Ginsparg-Wilson valence quarks and staggered sea quarks. We point out that for some scattering channels, the power-law volume dependence of two-pion states in nonunitary theories such as partially quenched or mixed action QCD is identical to that of QCD. Thus one can extract infinite-volume scattering parameters from mixed action simulations. We then determine the scattering length for both 2 and 2+1 sea quarks in the isospin limit. The scattering length, when expressed in terms of the pion mass and the decay constant measured on the lattice, has no contributions from mixed valence-sea mesons, thus it does not depend upon the parameter, CMix, that appears in the chiral Lagrangian of the mixed theory. In addition, the contributions which nominally arise from operators appearing in the mixed action O(a2mq) Lagrangian exactly cancel when the scattering length is written in this form. This is in contrast to the scattering length expressed in terms of the bare parameters of the chiral Lagrangian, which explicitly exhibits all the sicknesses and lattice spacing dependence allowed by a partially quenched mixed action theory. These results hold for both 2 and 2+1 flavors of sea quarks.

  14. Ginsparg-Wilson pions scattering in a sea of staggered quarks

    SciTech Connect

    Chen, J.-W.; O'Connell, Donal; Van de Water, Ruth; Walker-Loud, Andre

    2006-04-01

    We calculate isospin 2 pion-pion scattering in chiral perturbation theory for a partially quenched, mixed action theory with Ginsparg-Wilson valence quarks and staggered sea quarks. We point out that for some scattering channels, the power-law volume dependence of two-pion states in nonunitary theories such as partially quenched or mixed action QCD is identical to that of QCD. Thus one can extract infinite-volume scattering parameters from mixed action simulations. We then determine the scattering length for both 2 and 2+1 sea quarks in the isospin limit. The scattering length, when expressed in terms of the pion mass and the decay constant measured on the lattice, has no contributions from mixed valence-sea mesons, thus it does not depend upon the parameter, C{sub Mix}, that appears in the chiral Lagrangian of the mixed theory. In addition, the contributions which nominally arise from operators appearing in the mixed action O(a{sup 2}m{sub q}) Lagrangian exactly cancel when the scattering length is written in this form. This is in contrast to the scattering length expressed in terms of the bare parameters of the chiral Lagrangian, which explicitly exhibits all the sicknesses and lattice spacing dependence allowed by a partially quenched mixed action theory. These results hold for both 2 and 2+1 flavors of sea quarks.

  15. Modulation of low-energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Sari, J. W.

    1975-01-01

    The relation between the diffusion coefficient of cosmic rays in the solar wind and the power spectrum of interplanetary magnetic field fluctuations, established in recent theories, is tested directly for low energy protons (below 80 MeV). In addition, an attempt is made to determine whether the particles are scattered by magnetic field discontinuities or by fluctuations between discontinuities. Predictions of a perturbation solution of the Fokker-Planck equation are compared with observations of the cosmic ray radial gradient. It is found that at energies between 40 and 80 MeV, galactic cosmic ray protons respond to changes in the predicted diffusion coefficients (i.e., the relationship under consideration holds at these low energies). The relation between changes in the proton flux and modulation parameters is best when the contribution of discontinuities is subtracted, which means that scattering is caused by fluctuations between discontinuities. There appears to be no distinct relation between changes in the modulation parameters and changes in the intensity of 20 to 40 MeV protons.

  16. Low Energy Schools in Ireland

    ERIC Educational Resources Information Center

    Heffernan, Martin

    2004-01-01

    Out of a commitment to reducing carbon dioxide emissions, Ireland's Department of Education and Science has designed and constructed two low energy schools, in Tullamore, County Offaly, and Raheen, County Laois. With energy use in buildings responsible for approximately 55% of the CO[subscript 2] released into the atmosphere and a major…

  17. Beam lifetime and limitations during low-energy RHIC operation

    SciTech Connect

    Fedotov, A.V.; Bai, M.; Blaskiewicz, M.; Fischer, W.; Kayran, D.; Montag, C.; Satogata, T.; Tepikian, S.; Wang, G.

    2011-03-28

    The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam {gamma} = 6.1 and {gamma} = 4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.

  18. Low energy neutrinos in Super-Kamiokande

    NASA Astrophysics Data System (ADS)

    Sekiya, Hiroyuki

    2016-05-01

    Super-Kamiokande (SK), a 50 kton water Cherenkov detector, observes 8B solar neutrinos via neutrino-electron elastic scattering. The analysis threshold was successfully lowered to 3.5 MeV (recoil electron kinetic energy) in SK-IV. To date SK has observed solar neutrinos for 18 years. An analysis regarding possible correlations between the solar neutrino flux and the 11 year solar activity cycle is shown. With large statistics, SK searches for distortions of the solar neutrino energy spectrum caused by the MSW resonance in the core of the sun. SK also searches for a day/night solar neutrino flux asymmetry induced by the matter in the Earth. The Super-Kamiokande Gd (SK-Gd) project is the upgrade of the SK detector via the addition of water-soluble gadolinium (Gd) salt. This modification will enable it to efficiently identify low energy anti-neutrinos. SK-Gd will pursue low energy physics currently inaccessible to SK due to backgrounds. The most important will be the world’s first observation of the diffuse supernova neutrino background. The main R&D program towards SK-Gd is EG ADS: a 200 ton, fully instrumented tank built in a new cavern in the Kamioka mine.

  19. The Low Energy Neutrino Factory

    SciTech Connect

    Bross, Alan; Geer, Steve; Ellis, Malcolm; Fernandez Martinez, Enrique; Li, Tracey; Pascoli, Silvia; Mena, Olga

    2010-03-30

    We show that a low energy neutrino factory with a baseline of 1300 km and muon energy of 4.5 GeV has an excellent physics reach. The results of our optimisation studies demonstrate that such a setup can have remarkable sensitivity to theta{sub 13} and delta for sin{sup 2}(2theta{sub 13})>10{sup -4}, and to the mass hierarchy for sin{sup 2}(2theta{sub 13})>10{sup -3}. We also illustrate the power of the unique combination of golden and platinum channels accessible to the low energy neutrino factory. We have considered both a 20 kton totally active scintillating detector and a 100 kton liquid argon detector as possible detector technologies, finding that a liquid argon detector with very good background rejection can produce sensitivity to theta{sub 13} and delta with that of the International Design Study neutrino factory.

  20. Physics with low energy hadrons

    SciTech Connect

    Guttierez, G.; Littenberg, L.

    1997-10-01

    The prospects for low energy hadron physics at the front end of a muon collider (FMC) are discussed. The FMC, as conceived for the purposes of this workshop, is pretty close to a classical idea of a koan factory. There is an order of magnitude advantage of the FMC front end over the AGS for K{sup {minus}} and {anti p} production below 5 GeV/c.

  1. Atomic ionization by neutrinos at low energies

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-Pang

    2016-05-01

    It is well-known that neutrino-electron scattering at low recoil energies provides sensitivity gain in constraining neutrinos’ magnetic moments and their possible milli-charges. However, in detectors with sub-keV thresholds, the binding effects of electrons become significant. In this talk, we present our recent works of applying ab initio calculations to germanium ionization by neutrinos at low energies. Compared with the conventional differential cross section formulae that were used to derive current experimental bounds, our results with less theoretical uncertainties set a more reliable bound on the neutrino magnetic moment and a more stringent bound on the neutrino milli-charge with current reactor antineutrino data taken from germanium detectors.

  2. Diffuse Galactic low energy gamma ray continuum emission

    NASA Technical Reports Server (NTRS)

    Skibo, J. G.; Ramaty, R.

    1993-01-01

    We investigate the origin of diffuse low-energy Galactic gamma-ray continuum down to about 30 keV. We calculate gamma-ray emission via bremsstrahlung and inverse Compton scattering by propagating an unbroken electron power law injection spectrum and employing a Galactic emmissivity model derived from COSB observations. To maintain the low energy electron population capable of producing the observed continuum via bremsstrahlung, a total power input of 4 x 10 exp 41 erg/s is required. This exceeds the total power supplied to the nuclear cosmic rays by about an order of magnitude.

  3. Spectroscopy of Light Nuclei with Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Lombardo, I.; Dell'Aquila, D.; Vigilante, M.

    2016-07-01

    We discuss new results concerning the investigation of the 19F(p,α 0)16O and 10B(p,α 0)7Be reactions at low energies. Both reactions are important for the nuclear spectroscopy of the formed compound nucleus, i.e. 20Ne and 11C respectively, and play a role in nuclear astrophysics. For the 10B(p,α 0)7Be case, a comprehensive analysis of our reaction data and other scattering data points out the possible presence of an unreported state in 11C at Ex ≈ 9.36 MeV. For the 19F(p,α 0)16O case, the study of the low energy angular distributions testifies the role played by low energy resonances in the S-factor, leading to an enhanced reaction rate at stellar energies.

  4. Low energy p p physics

    SciTech Connect

    Amsler, C.; Crowe, K. . Inst. fuer Physik; Lawrence Berkeley Lab., CA )

    1989-02-01

    A detailed investigation of proton-antiproton interactions at low energy has become feasible with the commissioning of the LEAR facility in 1983. We shall shortly review the status of {bar p}p annihilation at rest and the physics motivations for second generation experiments with the Crystal Barrel detector. This type of detector would be adequate for the study of both Kp and {bar p}p interactions on an extracted beam of the KAON Factory. We shall conclude with a few remarks on the physics opportunities with {bar p}'s at the KAON Factory which, in our opinion, will not be covered by the present LEAR facility. 11 refs., 10 figs., 2 tabs.

  5. Analysis of low energy electrons

    NASA Technical Reports Server (NTRS)

    Sharp, R. D.

    1973-01-01

    Simultaneous observations of low energy electrons in the plasma sheet and in the auroral zone were analyzed. Data from the MIT plasma experiment on the OGO-3 satellite and from the Lockheed experiment on the OV1-18 satellite were processed and compared. The OV1-18 carried thirteen magnetic electron spectrometers designed to measure the intensity, angular, and energy distributions of the auroral electrons and protons in the energy range below 50 keV. Two computer programs were developed for reduction of the OV1-18 data. One program computed the various plasma properties at one second intervals as a function of Universal Time and pitch angle; the other program produced survey plots showing the outputs of the various detectors on the satellite as a function of time on a scale of approximately 100 seconds per cm. The OV1-18 data exhibit the high degree of variability associated with substorm controlled phenomena.

  6. Low-Energy Proton Testing Methodology

    NASA Technical Reports Server (NTRS)

    Pellish, Jonathan A.; Marshall, Paul W.; Heidel, David F.; Schwank, James R.; Shaneyfelt, Marty R.; Xapsos, M.A.; Ladbury, Raymond L.; LaBel, Kenneth A.; Berg, Melanie; Kim, Hak S.; Phan, Anthony; Friendlich, M.R.; Rodbell, Kenneth P.; Hakey, Mark C.; Dodd, Paul E.; Reed, Robert A.; Weller, Robert A.; Mendenhall, Marcus H.; Sierawski, B.D.

    2009-01-01

    Use of low-energy protons and high-energy light ions is becoming necessary to investigate current-generation SEU thresholds. Systematic errors can dominate measurements made with low-energy protons. Range and energy straggling contribute to systematic error. Low-energy proton testing is not a step-and-repeat process. Low-energy protons and high-energy light ions can be used to measure SEU cross section of single sensitive features; important for simulation.

  7. Low-Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Wiedenbeck, M. E.; ACE/CRIS Collaboration

    2002-12-01

    Cosmic rays with energies below about 10 GeV/nucleon have been measured with high precision as a result of experiments on the HEAO, Ulysses, and ACE spacecrafts. The observations provide energy spectra, elemental abundances, and isotopic composition for elements up through Z=30. They include both stable and radioactive nuclides that are synthesized in stars or are produced by nuclear fragmentation during diffusion at high energies through interstellar medium. From these data one obtains a rather detailed picture of the origin of low-energy cosmic rays. For refractory species, the cosmic-ray source composition closely resembles that of the Sun, suggesting that cosmic rays are accelerated from a well-mixed sample of interstellar matter. A chemical fractionation process has depleted the abundances of volatile elements relative to refractories. Using various radioactive clock isotopes it has been shown that particle acceleration occurs at least 105 years after supernova nucleosynthesis and that the accelerated particles diffuse in the Galaxy for approximately 15 Myr after acceleration. Energy spectra and secondary-to-primary ratios are reasonably well accounted for by models in which particles gain the bulk of their energy in a single encounter with a strong shock. Among the large number of species that have been measured, 22Ne stands out as the only nuclide with an abundance that is clearly much different than solar. To test models proposed to account for this anomaly, the data are being analyzed for predicted smaller effects on abundances of other nuclides. In addition to providing a detailed understanding of the origin and acceleration of low-energy cosmic rays, these data are providing constraints on the chemical evolution of interstellar matter. This work was supported by NASA at Caltech (under grant NAG5-6912), JPL, NASA/GSFC, and Washington U.

  8. Low energy overlineKN interaction in nuclear matter

    NASA Astrophysics Data System (ADS)

    Waas, T.; Kaiser, N.; Weise, W.

    1996-02-01

    We investigate the low-energy overlineKN interaction in nuclear matter including Pauli blocking, Fermi motion and binding effects. We use a coupled-channel approach based on the Chiral SU(3) Effective Lagrangian which describes all available low energy data of the coupled overlineKN, πΣ, πΛ system. Due to the dynamics of the Λ (1405) resonance we find a strong non-linear density dependence of the K -p scattering amplitude in nuclear matter. The real part of the K -p scattering length changes sign already at a small fraction of nuclear matter density, less than 0.2 po. This may explain the striking behaviour of the K - -nuclear optical potential found in the analysis of kaonic atom data.

  9. Low-energy structures in strong-field ionization

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Nam, Chang Hee; Kim, Kyung Taec

    2016-04-01

    We show that the Gabor transform provides a convenient tool allowing one to study the origin of the low-energy structures (LES) in the process of the strong-field ionization. The classical trajectories associated with the stationary points of the Gabor transform enable us to explicate the role of the forward scattering process in forming LES. Our approach offers a fully quantum mechanical description of LES, which can also be applied for other strong-field processes.

  10. Intense low energy positron beams

    SciTech Connect

    Lynn, K.G.; Jacobsen, F.M.

    1993-12-31

    Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e{sup +} beams exist producing of the order of 10{sup 8} {minus} 10{sup 9} e{sup +}/sec. Several laboratories are aiming at high intensity, high brightness e{sup +} beams with intensities greater than 10{sup 9} e{sup +}/sec and current densities of the order of 10{sup 13} {minus} 10{sup 14} e{sup +} sec{sup {minus}} {sup 1}cm{sup {minus}2}. Intense e{sup +} beams can be realized in two ways (or in a combination thereof) either through a development of more efficient B{sup +} moderators or by increasing the available activity of B{sup +} particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e{sup +} collisions with atoms and molecules. Within solid state physics high intensity, high brightness e{sup +} beams are in demand in areas such as the re-emission e{sup +} microscope, two dimensional angular correlation of annihilation radiation, low energy e{sup +} diffraction and other fields. Intense e{sup +} beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies.

  11. Low energy effective string cosmology

    SciTech Connect

    Copeland, E.J.; Lahiri, A.; Wands, D. )

    1994-10-15

    We give the general analytic solutions derived from the low energy string effective action for four-dimensional Friedmann-Robertson-Walker models with a dilaton and antisymmetric tensor field, considering both long and short wavelength modes of the [ital H] field. The presence of a homogeneous [ital H] field significantly modifies the evolution of the scale factor and dilaton. In particular it places a lower bound on the allowed value of the dilaton. The scale factor also has a lower bound but our solutions remain singular as they all contain regions where the spacetime curvature diverges signalling a breakdown in the validity of the effective action. We extend our results to the simplest Bianchi type I metric in higher dimensions with only two scale factors. We again give the general analytic solutions for long and short wavelength modes for the [ital H] field restricted to the three-dimensional space, which produces an anisotropic expansion. In the case of [ital H] field radiation (wavelengths within the Hubble length) we obtain the usual four-dimensional radiation-dominated FRW model as the unique late time attractor.

  12. Low-Energy Sputtering Research

    NASA Technical Reports Server (NTRS)

    Ray, P. K.; Shutthanandan, V.

    1999-01-01

    An experimental study is described to measure low-energy (less than 600 eV) sputtering yields of molybdenum with xenon ions using Rutherford backscattering spectroscopy (RBS) and secondary neutral mass spectroscopy (SNMS). An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 (micro)A/sq cm. For RBS measurements, the sputtered material was collected on a thin aluminum strip which was mounted on a semi-circular collector plate. The target was bombarded with 200 and 500 eV xenon ions at normal incidence. The differential sputtering yields were measured using the RBS method with 1 MeV helium ions. The differential yields were fitted with a cosine fitting function and integrated with respect to the solid angle to provide the total sputtering yields. The sputtering yields obtained using the RBS method are in reasonable agreement with those measured by other researchers using different techniques. For the SNMS measurements, 150 to 600 eV xenon ions were used at 50deg angle of incidence. The SNMS spectra were converted to sputtering yields for perpendicular incidence by normalizing SNMS spectral data at 500 eV with the yield measured by Rutherford backscattering spectrometry. Sputtering yields as well as the shape of the yield-energy curve obtained in this manner are in reasonable agreement with those measured by other researchers using different techniques. Sputtering yields calculated by using two semi-spherical formulations agree reasonably well with measured data. The isotopic composition of secondary ions were measured by bombarding copper with xenon ions at energies ranging from 100 eV to 1.5 keV. The secondary ion flux was found to be enriched in heavy isotopes at low incident ion energies. The heavy isotope enrichment was observed to decrease with increasing impact energy. Beyond 700 eV, light isotopes were sputtered preferentially with the enrichment remaining nearly constant.

  13. Towards Low Energy Atrial Defibrillation

    PubMed Central

    Walsh, Philip; Kodoth, Vivek; McEneaney, David; Rodrigues, Paola; Velasquez, Jose; Waterman, Niall; Escalona, Omar

    2015-01-01

    transcutaneous power transfer and sensing of ICI during cardioversion are evidenced as key to the advancement of low-energy atrial defibrillation. PMID:26404298

  14. Towards Low Energy Atrial Defibrillation.

    PubMed

    Walsh, Philip; Kodoth, Vivek; McEneaney, David; Rodrigues, Paola; Velasquez, Jose; Waterman, Niall; Escalona, Omar

    2015-01-01

    transcutaneous power transfer and sensing of ICI during cardioversion are evidenced as key to the advancement of low-energy atrial defibrillation. PMID:26404298

  15. Potential for luminosity improvement for low-energy RHIC operation

    SciTech Connect

    Fedotov A. V.

    2012-05-20

    At the Brookhaven National Laboratory, a physics program, motivated by the search of the QCD phase transition critical point, requires operation of the Relativistic Heavy Ion Collider (RHIC) with heavy ions at very low beam energies corresponding to 2.5-20 GeV/n. Several physics runs were already successfully performed at these low energies. However, the luminosity is very low at lowest energies of interest (< 10 GeV/n) limited by the intra-beam scattering and space-charge, as well as by machine nonlinearities. At these low energies, electron cooling could be very effective in counteracting luminosity degradation due to the IBS, while it is less effective against other limitations. Overall potential luminosity improvement for low-energy RHIC operation from cooling is summarized for various energies, taking into account all these limitations as well as beam lifetime measured during the low-energy RHIC runs. We also explore a possibility of further luminosity improvement under the space-charge limitation.

  16. pi+- p differential cross sections at low energies

    SciTech Connect

    H. Denz; P. Amaudruz; J.T. Brack; J. Breitschopf; P. Camerini; J.L. Clark; H. Clement; L. Felawka; E. Fragiacomo; E.F. Gibson; N. Grion; G.J. Hofman; B. Jamieson; E.L. Mathie; R. Meier; G. Moloney; D. Ottewell; O. Patarakin; J.D. Patterson; M.M. Pavan; S. Piano; K. Raywood; R.A. Ristinen; R. Rui; M.E. Sevior; G.R. Smith; J. Stahov; R. Tacik; G.J. Wagner; F. von Wrochem; D.M. Yeomans

    2005-12-03

    Differential cross sections for pi- p and pi+ p elastic scattering were measured at five energies between 19.9 and 43.3 MeV. The use of the CHAOS magnetic spectrometer at TRIUMF, supplemented by a range telescope for muon background suppression, provided simultaneous coverage of a large part of the full angular range, thus allowing very precise relative cross section measurements. The absolute normalization was determined with a typical accuracy of 5 %. This was verified in a simultaneous measurement of muon proton elastic scattering. The measured cross sections show some deviations from phase shift analysis predictions, in particular at large angles and low energies. From the new data we determine the real part of the isospin forward scattering amplitude.

  17. Low Energy X-Ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Woodruff, Wayne R.

    1981-10-01

    A subkilovolt spectrometer has been produced to permit high-energy-resolution, time-dependent x-ray intensity measurements. The diffracting element is a curved mica (d=9.95Å) crystal. To preclude higher order (n≳1) diffractions, a carbon x-ray mirror that reflects only photons with energies less than ˜1.1 keV is utilized ahead of the diffracting element. The nominal energy range of interest is 800 to 900 eV. The diffracted photons are detected by a gold-surfaced photoelectric diode designed to have a very good frequency response, and whose current is recorded on an oscilloscope. A thin, aluminum light barrier is placed between the diffracting crystal and the photoelectric diode detector to keep any UV generated on or scattered by the crystal from illuminating the detector. High spectral enegy resolution is provided by many photocathodes between 8- and 50-eV wide placed serially along the diffracted x-ray beam at the detector position. The spectrometer was calibrated for energy and energy dispersion using the Ni Lα1,2 lines produced in the LLNL IONAC accelerator and in third order using a molybdenum target x-ray tube. For the latter calibration the carbon mirror was replaced by one surfaced with rhodium to raise the cut-off energy to about 3 keV. The carbon mirror reflection dependence on energy was measured using one of our Henke x-ray sources. The curved mica crystal diffraction efficiency was measured on our Low-Energy X-ray (LEX) machine. The spectrometer performs well although some changes in the way the x-ray mirror is held are desirable.

  18. Low energy x-ray spectrometer

    SciTech Connect

    Woodruff, W.R.

    1981-06-05

    A subkilovolt spectrometer has been produced to permit high-energy-resolution, time-dependent x-ray intensity measurements. The diffracting element is a curved mica (d = 9.95A) crystal. To preclude higher order (n > 1) diffractions, a carbon x-ray mirror that reflects only photons with energies less than approx. 1.1 keV is utilized ahead of the diffracting element. The nominal energy range of interest is 800 to 900 eV. The diffracted photons are detected by a gold-surface photoelectric diode designed to have a very good frequency response, and whose current is recorded on an oscilloscope. A thin, aluminium light barrier is placed between the diffracting crystal and the photoelectric diode detector to keep any uv generated on or scattered by the crystal from illuminating the detector. High spectral energy resolution is provided by many photocathodes between 8- and 50-eV wide placed serially along the diffracted x-ray beam at the detector position. The spectrometer was calibrated for energy and energy dispersion using the Ni L..cap alpha../sub 1/ /sub 2/ lines produced in the LLNL IONAC accelerator and in third order using a molybdenum target x-ray tube. For the latter calibration the carbon mirror was replaced by one surfaced with rhodium to raise the cut-off energy to about 3 keV. The carbon mirror reflection dependence on energy was measured using one of our Henke x-ray sources. The curved mica crystal diffraction efficiency was measured on our Low-Energy x-ray (LEX) machine. The spectrometer performs well although some changes in the way the x-ray mirror is held are desirable. 16 figures.

  19. Low-energy multiple-Coulomb scattering in thick foils

    SciTech Connect

    Morrill, S.M.

    1984-01-01

    Angular and energy distributions were taken using proton and ..cap alpha..-particle beams of energies 2 to 10 MeV incident on a variety of thick foils. Foils were chosen from commonly used materials and to span the periodic table. Foil thicknesses were chosen which resulted in approximately 20-60% energy losses. The lower-energy experiments were done using the Brigham Young University 4-MeV Van de Graaff accelerator while the higher-energy experiments were performed using the Triangle Universities Nuclear Laboratory (TUNL) tandem Van de Graaff. Angular distributions are characterized by the angles at which the distribution had dropped to the 1/e, 1/10, and 1/100 points of their initial values. Energy distributions are characterized by the mean energy and the width of the energy-straggling distribution of the emerging particle. Comparisons are made to the appropriate theories including the angular distribution theory of Nigam, Sundaresan, and Wu (NSW), and the straggling theory of Bethe. Improvements to the NSW method by using an effective energy and effective nuclear charge are discussed.

  20. Low-Energy Multiple-Coulomb Scattering in Thick Foils.

    NASA Astrophysics Data System (ADS)

    Morrill, Steven M.

    Angular and energy distributions were taken using proton and alpha-particle beams of energies 2--10 MeV incident on a variety of thick foils. Foils were chosen from commonly used materials and to span the periodic table. Foil thicknesses were chosen which resulted in approximately 20--60% energy losses. The lower-energy experiments were done using the Brigham Young University 4-MeV Van de Graaff accelerator while the higher-energy experiments were performed using the Triangle Universities Nuclear Laboratory (TUNL) tandem Van de Graaff. Angular distributions were characterized by the angles at which the distribution had dropped to the 1/e, 1/10, and 1/100 points of their initial values. Energy distributions were characterized by the mean energy and the width of the energy straggling distribution of the emerging particle. Comparisons were made to the appropriate theories including the angular distribution theory of Nigam, Sundaresan, and Wu (NSW), and the straggling theory of Bethe. Improvements to the NSW method by using an effective energy and effective nuclear charge were discussed.

  1. Single track nanodosimetry of low energy electrons

    NASA Astrophysics Data System (ADS)

    Bantsar, A.; Grosswendt, B.; Pszona, S.; Kula, J.

    2009-02-01

    Auger-electron-emitting radionuclides (for instance, 125I) with a predominant energy spectrum below 3 keV are an active area of research towards the clinical application of radiopharmaceuticals. Hence, the necessity for an adequate description of the effects of radiation by low-energy electrons on nanometric biological targets seems to be unquestionable. Experimental nanodosimetry for low-energy electrons has been accomplished with a device named JET COUNTER. The present paper describes, for the first time, nanodosimetric experiments in nanometer-sized cavities of nitrogen using low energy electrons ranging from 100 eV to 2 keV.

  2. Electromagnetic production of vector mesons at low energies

    SciTech Connect

    Oh, Y.; Titov, A. I.; Lee, T.-S. H.

    2000-05-17

    The authors have investigated exclusive photoproduction of light vector mesons ({omega}, {rho} and {phi}) on the nucleon at low energies. In order to explore the questions concerning the so-called missing nucleon resonances, they first establish the predictions from a model based on the Pomeron and meson exchange mechanisms. They have also explored the contributions due to the mechanisms involving s- and u-channel intermediate nucleon state. Some discrepancies found at the energies near threshold and large scattering angles suggest a possibility of using this reaction to identify the nucleon resonances.

  3. Development of multichannel low-energy neutron spectrometer.

    PubMed

    Arikawa, Y; Nagai, T; Abe, Y; Kojima, S; Sakata, S; Inoue, H; Utsugi, M; Iwasa, Y; Murata, T; Sarukura, N; Nakai, M; Shiraga, H; Fujioka, S; Azechi, H

    2014-11-01

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments. PMID:25430304

  4. Modelling low-energy electron-molecule capture processes.

    PubMed

    Dashevskaya, E I; Litvin, I; Nikitin, E E; Troe, J

    2008-03-01

    Cross sections and rate coefficients for capture of low-energy electrons with polar and polarizable target molecules are calculated in the framework of Fabrikant and Hotop's extended version of the Vogt-Wannier model and an extension of this approach is given in the present article. Analytical approximations are derived in order to facilitate the application to experiments. A comparison with a selection of experimental electron attachment rate coefficients provides insight into the competition between anion formation through electron capture and scattering processes which do not follow this pathway. PMID:18292861

  5. Development of multichannel low-energy neutron spectrometer

    SciTech Connect

    Arikawa, Y. Nagai, T.; Abe, Y.; Kojima, S.; Sakata, S.; Inoue, H.; Utsugi, M.; Iwasa, Y.; Sarukura, N.; Nakai, M.; Shiraga, H.; Fujioka, S.; Azechi, H.; Murata, T.

    2014-11-15

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments.

  6. Method and apparatus for generating low energy nuclear particles

    DOEpatents

    Powell, J.R.; Reich, M.; Ludewig, H.; Todosow, M.

    1999-02-09

    A particle accelerator generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer and a neutron filter are also used for preferentially degrading the secondary particles into a lower energy range if desired. 18 figs.

  7. Method and apparatus for generating low energy nuclear particles

    DOEpatents

    Powell, James R.; Reich, Morris; Ludewig, Hans; Todosow, Michael

    1999-02-09

    A particle accelerator (12) generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target (14) is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target (14) produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer (44) and a neutron filter (42) are also used for preferentially degrading the secondary particles into a lower energy range if desired.

  8. Effect of the short-range interaction on low-energy collisions of ultracold dipoles

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Jie, Jianwen

    2014-12-01

    We consider the low-energy scattering of two ultracold polarized dipoles with both a short-range interaction (SRI) and a weak dipole-dipole interaction (DDI), which is far away from shape resonances. In previous analytical studies, the scattering amplitude in this system was often calculated via the first-order Born approximation (FBA). Our results show that significant derivations from this approximation can arise in some cases. In these cases, the SRI can significantly modify the interdipole scattering amplitudes even if the scattering amplitudes for the SRI alone are much smaller than the dipolar length of the DDI. We further obtain approximate analytical expressions for these interdipole scattering amplitudes.

  9. The Science of Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Storms, Edmund

    2007-03-01

    The large literature describing the anomalous behavior attributed to cold fusion or low energy nuclear reactions has been critically described in a recently published book. Over 950 publications are evaluated allowing the phenomenon to be understood. A new class of nuclear reactions has been discovered that are able to generate practical energy without significant radiation or radioactivity. Edmund K Storms, The Science of Low Energy Nuclear Reactions, in press (2006). Also see: http://www.lenr-canr.org/StudentsGuide.htm .

  10. Low-energy electron collisions with thiophene

    NASA Astrophysics Data System (ADS)

    da Costa, R. F.; Varella, M. T. do N.; Lima, M. A. P.; Bettega, M. H. F.

    2013-05-01

    We report on elastic integral, momentum transfer, and differential cross sections for collisions of low-energy electrons with thiophene molecules. The scattering calculations presented here used the Schwinger multichannel method and were carried out in the static-exchange and static-exchange plus polarization approximations for energies ranging from 0.5 eV to 6 eV. We found shape resonances related to the formation of two long-lived π* anion states. These resonant structures are centered at the energies of 1.00 eV (2.85 eV) and 2.82 eV (5.00 eV) in the static-exchange plus polarization (static-exchange) approximation and belong to the B1 and A2 symmetries of the C2v point group, respectively. Our results also suggest the existence of a σ* shape resonance in the B2 symmetry with a strong d-wave character, located at around 2.78 eV (5.50 eV) as obtained in the static-exchange plus polarization (static-exchange) calculation. It is worth to mention that the results obtained at the static-exchange plus polarization level of approximation for the two π* resonances are in good agreement with the electron transmission spectroscopy results of 1.15 eV and 2.63 eV measured by Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004), 10.1021/jp048759a]. The existence of the σ* shape resonance is in agreement with the observations of Dezarnaud-Dandiney et al. [J. Phys. B 31, L497 (1998), 10.1088/0953-4075/31/11/004] based on the electron transmission spectra of dimethyl(poly)sulphides. A comparison among the resonances of thiophene with those of pyrrole and furan is also performed and, altogether, the resonance spectra obtained for these molecules point out that electron attachment to π* molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds.

  11. Low Energy Continuum and Lattice Effective Field Theories

    NASA Astrophysics Data System (ADS)

    Elhatisari, Serdar

    In this thesis we investigate several constraints and their impacts on the short-range potentials in the low-energy limits of quantum mechanics.We also present lattice Monte Carlo calculations using the adiabatic projection method. In the first part we consider the constraints of causality and unitarity for the low-energy interactions of particles. We generalize Wigner's causality bound to the case of non-vanishing partial-wave mixing. Specifically we analyze the system of the low-energy interactions between protons and neutrons. We derive a general theorem that non-vanishing partial-wave mixing cannot be reproduced with zero-range interactions without violating causality or unitarity. We also analyze low-energy scattering for systems with arbitrary short-range interactions plus an attractive 1/ralpha tail for alpha ≥ 2. In particular, we focus on the case of alpha = 6 and we derive the constraints of causality and unitarity also for these systems and find that the van derWaals length scale dominates over parameters characterizing the short-distance physics of the interaction. This separation of scales suggests a separate universality class for physics characterizing interactions with an attractive 1{r6 tail. We argue that a similar universality class exists for any attractive potential 1/ralpha for alpha ≥ 2. In the second part of the thesis we present lattice Monte Carlo calculations of fermion-dimer scattering in the limit of zero-range interactions using the adiabatic projection method. The adiabatic projection method uses a set of initial cluster states and Euclidean time projection to give a systematically improvable description of the low-lying scattering cluster states in a finite volume. We use Luscher's finite-volume relations to determine the s-wave, p-wave, and d-wave phase shifts. For comparison, we also compute exact lattice results using Lanczos iteration and continuum results using the Skorniakov-Ter-Martirosian equation. For our Monte Carlo

  12. Sensitivity of low energy neutrino experiments to physics beyond the standard model

    SciTech Connect

    Barranco, J.; Miranda, O. G.; Rashba, T. I.

    2007-10-01

    We study the sensitivity of future low energy neutrino experiments to extra neutral gauge bosons, leptoquarks, and R-parity breaking interactions. We focus on future proposals to measure coherent neutrino-nuclei scattering and neutrino-electron elastic scattering. We introduce a new comparative analysis between these experiments and show that in different types of new physics it is possible to obtain competitive bounds to those of present and future collider experiments. For the cases of leptoquarks and R-parity breaking interactions we found that the expected sensitivity for most of the future low energy experimental setups is better than the current constraints.

  13. Coherent low-energy electron diffraction on individual nanometer sized objects.

    PubMed

    Steinwand, Elvira; Longchamp, Jean-Nicolas; Fink, Hans-Werner

    2011-03-01

    Today's structural biology techniques require averaging over millions of molecules to obtain detailed structural information. Derivation of the molecular structure from a scattering experiment with just one single 3D-molecule imposes major challenges. Coherent and damage-free radiation is needed to ensure sufficient elastic scattering events before destroying the molecule and a means to solve the phase problem is wanted. We have devised such a scheme using coherent low-energy electrons shaped into a collimated beam by an electrostatic microlens. Initial experiments using a carbon nanotube sample demonstrate the feasibility of coherent low-energy electron diffraction on an individual nanometer-sized object. PMID:21353154

  14. Low energy aspects of circular accelerators

    SciTech Connect

    Holmes, S.D.

    1990-12-01

    Performance in circular accelerators can be limited by some of the same sorts of phenomena described by Miller and Wangler in their lectures on low energy behavior in linear accelerators. In general the strength of the perturbation required to degrade performance is reduced in circular accelerators due to the repetitive nature of the orbits. For example, we shall see that space-charge can severely limit performance in circular accelerators even when operating far from the space-charge dominated regime'' as defined in linear accelerators. We will be discussing two particular aspects of low energy operation in circular accelerators -- space-charge and transition. Low energy'' is defined within the context of these phenomena. We shall see that the phenomena are really only relevant in hadron accelerators.

  15. What is a low-energy house?

    SciTech Connect

    Litt, B.R.; Meier, A.K.

    1994-08-01

    Traditionally, a ``low-energy`` house has been one that used little energy for space heating. But space heating typically accounts for less than half of the energy used by new US homes, and for low heating energy homes, space heating is often the third largest end use, behind water heating and appliances, and sometimes behind cooling. Low space heat alone cannot identify a low-energy house. To better understand the determinants of a low-energy house, we collected data on housing characteristics, incremental costs, and energy measurements from energy-efficient houses around the world and in a range of climates. We compare the energy required to provide thermal comfort as well as water heating, and other appliances. We do not have a single definition of a low-energy house, but through comparisons of actual buildings, we show how different definitions and quantitative indicators fail. In comparing the energy use of whole houses, weather normalization can be important, but for cases in which heating or cooling energy is surpassed by other end uses, other normalization methods must be used.

  16. Low-energy Neutrino Astronomy in LENA

    NASA Astrophysics Data System (ADS)

    Wurm, M.; Bick, D.; Enqvist, T.; Hellgartner, D.; Kaiser, M.; Loo, K. K.; Lorenz, S.; Meloni, M.; Meyer, M.; Möllenberg, R.; Oberauer, L.; Soiron, M.; Smirnov, M.; Trzaska, W. H.; Wonsak, B.

    LENA (Low Energy Neutrino Astronomy) is a proposed next-generation neutrino detector based on 50 kilotons of liquid scintillator. The low detection threshold, good energy resolution and excellent background rejection inherent to the liquid-scintillator detectors make LENA a versatile observatory for low-energy neutrinos from astrophysical and terrestrial sources. In the framework of the European LAGUNA-LBNO design study, LENA is also considered as far detector for a very-long baseline neutrino beam from CERN to Pyhäsalmi (Finland). The present contribution gives an overview LENA's broad research program, highlighting the unique capabilities of liquid scintillator for the detection of low-energy neutrinos from astrophysical sources. In particular, it will focus on the precision measurement of the solar neutrino spectrum: The search for time modulations in the 7Be neutrino flux, the determination of the electron neutrino survival probability in the low-energy region of the 8B spectrum and the favorable detection conditions for neutrinos from the CNO fusion cycle.

  17. The Simbol-X Low Energy Detector

    SciTech Connect

    Lechner, Peter

    2009-05-11

    For the Low Energy Detector of Simbol-X a new type of active pixel sensor based on the integrated amplifier DEPFET has been developed. This concept combines large area, scalable pixel size, low noise, and ultra-fast readout. Flight representative prototypes have been processed with a performance matching the Simbol-X specifications and demonstrating the technology readiness.

  18. Low energy strong electroweak sector with decoupling

    SciTech Connect

    Casalbuoni, R.; Dominici, D. |; Deandrea, A.; Gatto, R.; De Curtis, S.; Grazzini, M. |

    1996-05-01

    We discuss possible symmetries of effective theories describing spinless and spin-1 bosons, mainly to concentrate on an intriguing phenomenological possibility: that of a hardly noticeable strong electroweak sector at relatively low energies. Specifically, a model with both vector and axial vector strong interacting bosons may possess a discrete symmetry imposing degeneracy of the two sets of bosons (degenerate BESS model). In such a case its effects at low energies become almost invisible and the model easily passes all low energy precision tests. The reason lies essentially in the fact that the model automatically satisfies decoupling, contrary to models with only vectors. For large mass of the degenerate spin-one bosons the model becomes identical at the classical level to the standard model taken in the limit of infinite Higgs boson mass. For these reasons we have thought it worthwhile to fully develop the model, together with its possible generalizations, and to study the expected phenomenology. For instance, just because of its invisibility at low energy, it is conceivable that degenerate BESS has low mass spin-one states and gives quite visible signals at existing or forthcoming accelerators. {copyright} {ital 1996 The American Physical Society.}

  19. Parity violation in low-energy

    SciTech Connect

    Martin Savage

    2001-12-01

    Parity violation in low-energy nuclear observables is included in the pionless effective field theory. The model-independent relation between the parity-violating asymmetry in polarized np -> d gamma and the non-nucleon part of the deuteron anapole moment is discussed. The asymmetry in np -> d gamma computed with KSW power-counting, and recently criticized by Desplanques, is discussed.

  20. Low energy [bar p] physics at FNAL

    SciTech Connect

    Hsueh, S.Y.

    1992-12-01

    The charmonium formation experiment is the only low energy [bar p] experiment at FNAL. This paper describes the performance of the Fermilab [bar p] Accumulator during fixed target run for the experiment and the planned upgrades. We also discuss the proposal for the direct CP violation search in [bar p] + p [yields] [bar [Lambda

  1. Studies in Low-Energy Nuclear Science

    SciTech Connect

    Carl R. Brune; Steven M. Grimes

    2010-01-13

    This report presents a summary of research projects in the area of low energy nuclear reactions and structure, carried out between March 1, 2006 and October 31, 2009 which were supported by U.S. DOE grant number DE-FG52-06NA26187.

  2. The low energy atmospheric antiproton albedo

    NASA Technical Reports Server (NTRS)

    Cole, J. B.; Ormes, J. F.

    1989-01-01

    The flux of albedo antiprotons in the 100-1000 MeV kinetic energy range produced by the cosmic ray primaries in the atmosphere is calculated. It is shown that this is not a significant background to measurements of the low energy anti-proton cosmic ray flux.

  3. Nuclear Astrophysics and Structure Studies Using Low-energy RI Beams at CRIB

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Hashimoto, T.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kubono, S.

    2010-05-01

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Using the RI beams at CRIB, Many measurements on proton and alpha resonance scatterings, (α,p) reactions, and others were peformed in recent years, mainly for studying astrophysical reactions and exotic nuclear structure. Among them, the results on the 7Be+p and 7Li+α resonance scatterings are presented.

  4. Low-energy neutrino-nucleus interactions and beta-beam neutrino

    SciTech Connect

    Jachowicz, N.; Pandey, V.

    2015-05-15

    We present an overview of neutrino-nucleus scattering at low energies with cross sections obtained within a continuum random phase approximation (CRPA) formalism. We highlight potential applications of beta-beam neutrino experiments for neutrino astrophysics. Our calculations are compared with MiniBooNe data at intermediate energies.

  5. Collisions of low-energy electrons with isopropanol

    SciTech Connect

    Bettega, M. H. F.; Winstead, C.; McKoy, V.; Jo, A.; Gauf, A.; Tanner, J.; Hargreaves, L. R.; Khakoo, M. A.

    2011-10-15

    We report measured and calculated cross sections for elastic scattering of low-energy electrons by isopropanol (propan-2-ol). The experimental data were obtained using the relative flow technique with helium as the standard gas and a thin aperture as the collimating target gas source, which permits use of this method without the restrictions imposed by the relative flow pressure conditions on helium and the unknown gas. The differential cross sections were measured at energies of 1.5, 2, 3, 5, 6, 8, 10, 15, 20, and 30 eV and for scattering angles from 10 deg. to 130 deg. The cross sections were computed over the same energy range employing the Schwinger multichannel method in the static-exchange plus polarization approximation. Agreement between theory and experiment is very good. The present data are compared with previously calculated and measured results for n-propanol, the other isomer of C{sub 3}H{sub 7}OH. Although the integral and momentum transfer cross sections for the isomers are very similar, the differential cross sections show a strong isomeric effect: In contrast to the f-wave behavior seen in scattering by n-propanol, d-wave behavior is observed in the cross sections of isopropanol. These results corroborate our previous observations in electron collisions with isomers of C{sub 4}H{sub 9}OH.

  6. Low energy ion loss at Mars

    NASA Astrophysics Data System (ADS)

    Curry, S.; Liemohn, M.; Fang, X.; Ma, Y.

    2012-04-01

    Current data observations and modeling efforts have indicated that the low-energy pick-up ions on Mars significantly contribute to the overall escape rate. Due to the lack of a dipole magnetic field, the solar wind directly interacts with the dayside upper atmosphere causing particles to be stripped away. In this study, we use a 3-D Monte Carlo test particle simulation with virtual detectors to observe low energy ions (< 50 eV) in the Mars space environment. We will present velocity space distributions that can capture the asymmetric and non-gyrotropic features of particle motion. The effect of different solar conditions will also be discussed with respect to ion fluxes at various spatial locations as well as overall loss in order to robustly describe the physical processes controlling the distribution of planetary ions and atmospheric escape.

  7. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1985-01-01

    The author built and tested a low energy cyclotron for radiocarbon dating similar to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. The author found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. The author shows how a conventional carbon negative ion source located outside the cyclotron magnet, would produce sufficient beam and provide for quick sample changing to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  8. Experimental Measurement of Low Energy Neutrino Interactions

    SciTech Connect

    Scholberg, Kate

    2011-11-23

    Neutrino interactions in the few to few tens of MeV range are of importance for several physics topics, including solar, supernova and reactor neutrinos, as well as future proposed oscillation and Standard Model test experiments. Although interaction cross-sections for some simple targets are well understood, very little experimental data exist for interactions with nuclei. This talk will discuss the motivation for measuring low energy neutrino interactions, the state of knowledge, and possible future strategies.

  9. PHYSICS WITH ULTRA-LOW ENERGY ANTIPROTONS

    SciTech Connect

    M. HOLZSCHEITER

    2001-02-01

    In this report the author describes the current status of the antiproton deceleration (AD) facility at CERN, and highlights the physics program with ultra-low energy antiproton at this installation. He also comments on future possibilities provided higher intensity antiproton beams become available at Fermilab, and review possibilities for initial experiments using direct degrading of high energy antiprotons in material has been developed and proven at CERN.

  10. Maximum Likelihood Analysis of Low Energy CDMS II Germanium Data

    SciTech Connect

    Agnese, R.

    2015-03-30

    We report on the results of a search for a Weakly Interacting Massive Particle (WIMP) signal in low-energy data of the Cryogenic Dark Matter Search experiment using a maximum likelihood analysis. A background model is constructed using GEANT4 to simulate the surface-event background from Pb210decay-chain events, while using independent calibration data to model the gamma background. Fitting this background model to the data results in no statistically significant WIMP component. In addition, we also perform fits using an analytic ad hoc background model proposed by Collar and Fields, who claimed to find a large excess of signal-like events in our data. Finally, we confirm the strong preference for a signal hypothesis in their analysis under these assumptions, but excesses are observed in both single- and multiple-scatter events, which implies the signal is not caused by WIMPs, but rather reflects the inadequacy of their background model.

  11. Materials and neutronic research at the Low Energy Neutron Source

    NASA Astrophysics Data System (ADS)

    Baxter, David V.

    2016-04-01

    In the decade since the Low Energy Neutron Source (LENS) at Indiana University Center for Exploration of Energy and Matter (CEEM) produced its first neutrons, the facility has made important contributions to the international neutron scattering community. LENS employs a 13MeV proton beam at up to 4kW beam power onto one of two Be targets to produce neutrons for research in fields ranging from radiation effects in electronics to studies of the structure of fluids confined in nanoporous materials. The neutron source design at the heart of LENS facilitates relatively rapid hands-on access to most of its components which provides a foundation for a research program in experimental neutronics and affords numerous opportunities for novel educational experiences. We describe in some detail a number of the unique capabilities of this facility.

  12. Low-energy electron-impact ionization of helium

    SciTech Connect

    Schow, E.; Hazlett, K.; Childers, J. G.; Medina, C.; Vitug, G.; Khakoo, M. A.; Bray, I.; Fursa, D. V.

    2005-12-15

    Normalized doubly differential cross sections for the electron-impact ionization of helium at low energies are presented. The data are taken at the incident electron energies of 26.3, 28.3, 30.3, 32.5, 34.3, 36.5, and 40.7 eV and for scattering angles of 10 deg. -130 deg. The measurements involve the use of the moveable target method developed at California State University Fullerton to accurately determine the continuum background in the energy-loss spectra. Normalization of experimental data is made on a relative scale to well-established experimental differential cross sections for excitation of the n=2 manifold of helium and then on an absolute scale to the well-established total ionization cross sections of Shah et al. [J. Phys. B 21, 2751 (1988)]. Comparisons are made with available experimental data and the results of the convergent close-coupling theory.

  13. Low-energy dissociative electron attachment to CF2

    NASA Astrophysics Data System (ADS)

    Chourou, S. T.; Larson, Ã.; Orel, A. E.

    2015-08-01

    We present the results of a theoretical study of dissociative electron attachment (DEA) of low-energy electrons to CF2. We carried out electron scattering calculations using the complex Kohn variational method at the static-exchange and relaxed self-consistent field (SCF) level at the equilibrium geometry and compare our differential cross sections to other results. We then repeated these calculations as a function of the three internal degrees of freedom to obtain the resonance energy surfaces and autoionization widths. We use this data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional wave equation is solved using the multiconfiguration time-dependent Hartree (MCTDH) approach within the local approximation.

  14. Targeting Low-Energy Ballistic Lunar Transfers

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2010-01-01

    Numerous low-energy ballistic transfers exist between the Earth and Moon that require less fuel than conventional transfers, but require three or more months of transfer time. An entirely ballistic lunar transfer departs the Earth from a particular declination at some time in order to arrive at the Moon at a given time along a desirable approach. Maneuvers may be added to the trajectory in order to adjust the Earth departure to meet mission requirements. In this paper, we characterize the (Delta)V cost required to adjust a low-energy ballistic lunar transfer such that a spacecraft may depart the Earth at a desirable declination, e.g., 28.5(white bullet), on a designated date. This study identifies the optimal locations to place one or two maneuvers along a transfer to minimize the (Delta)V cost of the transfer. One practical application of this study is to characterize the launch period for a mission that aims to launch from a particular launch site, such as Cape Canaveral, Florida, and arrive at a particular orbit at the Moon on a given date using a three-month low-energy transfer.

  15. Low-energy generation in nanostructured Si

    NASA Astrophysics Data System (ADS)

    Kuznicki, Zbigniew T.; Meyrueis, Patrick

    2008-04-01

    Solar photon energy can be better used when totally transformed on collectable free-carriers. The conversion of one energetic photon could result in more than one free-carrier pair if a low-energy mechanism is involved. Such PV conversion represents a multistage nonlinear process and requires especially dedicated low-energy centers. A cascade-like progression is induced by the primary/fundamental/interband absorption. As shown by us previously, the corresponding structure can be realized, for example, with nanostructured Si. The experimental devices convert 400 nm photons into collectable primary and secondary free-carriers. The excess carriers can be drawn out into the external electrical circuit even in a multiinterface architecture containing a carrier collection limit. The superficial effect seems to be totally independent of the presence or not of a buried amorphized layer. This is the first simple experimental evidence for low-energy generation. The performance is inversely proportional to the incident light intensity. The thermodynamic limit of conventional photovoltaic conversion is lower than 30%, while in the case of the mechanism reported here, it can be propelled above 60%. An optimization of the effect by a suitable conditioning and annealing should be possible, opening the way to different applications, especially in the areas of nanophotovoltaics and very high efficiency solar cells.

  16. RHIC low energy beam loss projections

    SciTech Connect

    Satogata,T.

    2009-08-01

    For RHIC low-energy operations, we plan to collide Au beams with energies of E = 2:5-10 GeV/u in RHIC. Beams are injected into collision optics, and RHIC runs as a storage ring with no acceleration. At these low energies, observed beam lifetimes are minutes, with measured beam lifetimes of 3.5 min (fast) and 50 min (slow) at E=4.6 GeV/u in the March 2008 test run. With these lifetimes we can operate RHIC as a storage ring to produce reasonable integrated luminosity. This note estimates beam losses and collimator/dump energy deposition in normal injection modes of low energy operation. The main question is whether a normal injection run is feasible for an FY10 10-15 week operations run from a radiation safety perspective. A peripheral question is whether continuous injection operations is feasible from a radiation safety perspective. In continuous injection mode, we fill both rings, then continuously extract and reinject the oldest bunches that have suffered the most beam loss to increase the overall integrated luminosity. We expect to gain a factor of 2-3 in integrated luminosity from continuous injection at lowest energies if implemented[1]. Continuous injection is feasible by FY11 from an engineering perspective given enough effort, but the required extra safety controls and hardware dose risk make it unappealing for the projected luminosity improvement. Low-energy electron cooling will reduce beam losses by at least an order of magnitude vs normal low-energy operations, but low energy cooling is only feasible in the FY13 timescale and therefore beyond the scope of this note. For normal injection low energy estimates we assume the following: (1) RHIC beam total energies are E=2.5-10 GeV/u. (Continuous injection mode is probably unnecessary above total energies of E=7-8 GeV/u.); (2) RHIC operates only as a storage ring, with no acceleration; (3) 110 bunches of about 0.5-1.0 x 10{sup 9} initial bunch intensities (50-100% injection efficiency, likely conservative

  17. Low energy nuclear reactions with RIBRAS, Radioactive Ion Beam in Brasil, system

    NASA Astrophysics Data System (ADS)

    Guimarães, V.; Lépine-Szily, A.; Lichtenthäler, R.; de Faria, P. N.; Barioni, A.; Pires, K. C. C.; Morcelle, V.; Mendes, D. R.; Zamora, J. C.; Morais, M. C.; Condori, R. P.; Benjamim, E. A.; Monteiro, D. S.; Crema, E.; Moro, A. M.; Lubian, J.

    2011-09-01

    RIBRAS, Radioactive Ion beam in Brasil, is a system based on superconducting solenoids which can produce low energy RNB (Radioactive Nuclear Beams) at the University of São Paulo, Brazil. Secondary radioactive beams of light particles such as 6He, 7Be and 8Li have been produced and low energy elastic scattering and transfer reaction experiments have been performed. The recent scientific program using this facility includes elastic scattering and transfer reactions of 6He halo nucleus on 9Be, 27Al, 51V and 120Sn targets and 8Li on 9Be, 12C and 51V targets. The total reaction cross section as a function of energy has been extracted from the elastic scattering data and the role of breakup of weakly bound or exotic nuclei is discussed. Also spectroscopic factors have been obtained from the transfer reactions.

  18. Ab initio calculations on collisions of low energy electrons with polyatomic molecules

    SciTech Connect

    Rescigno, T.N.

    1991-08-01

    The Kohn variational method is one of simplest, and oldest, techniques for performing scattering calculations. Nevertheless, a number of formal problems, as well as practical difficulties associated with the computation of certain required matrix elements, delayed its application to electron--molecule scattering problems for many years. This paper will describe the recent theoretical and computational developments that have made the complex'' Kohn variational method a practical tool for carrying out calculations of low energy electron--molecule scattering. Recent calculations on a number of target molecules will also be summarized. 41 refs., 7 figs.

  19. Nonadiabatic couplings in low-energy collisions of hydrogen ground-state atoms

    SciTech Connect

    Wolniewicz, L.

    2003-10-01

    The effect of nonadiabatic couplings on low-energy s-wave scattering of two hydrogen atoms is investigated. Coupling matrix elements are computed in a wide range of internuclear distances. The resulting scattering equations are numerically unstable and therefore are integrated only approximately. Computations are performed for H, D, and T atoms. The phase shifts in the zero velocity limit are inversely proportional to the nuclear reduced mass {delta}{sub 0}{approx_equal}0.392/{mu}. This leads to infinite scattering lengths.

  20. MILO, a mirror reflectivity code for low-energy x-rays

    SciTech Connect

    Kissel, L.

    1982-09-01

    MILO (MIrror reflectivity code, LOw energy) is an interactive fault-tolerant user-oriented code which calculates low-energy x-ray mirror reflectivity. The code combines user input with previously calculated, complex, atomic scattering factors to produce the unpolarized mirror reflectivity at various values of mirror angle and photon energy. The code can calculate the reflectivity of mirrors composed of pure elements and of homogeneous mixtures of elements. MILO is written in standard, high-machine-independent, FORTRAN 77 (ANSI X3.9-1978).

  1. The low energy booster project status

    SciTech Connect

    Tuttle, G.W.

    1993-05-01

    In order to achieve the required injection momentum, the Superconducting Super Collider (SSC) has an accelerator chain comprised of a Linear Accelerator and three synchrotrons. The Low Energy Booster (LEB) is the first synchrotron in this chain. The LEB project has made significant progress in the development of major subsystems and conventional construction. This paper briefly reviews the performance requirements of the LEB and describes significant achievements in each of the major subsystem areas. Highlighted among these achievements are the LEB foreign collaborations with the Budker Institute of Nuclear Physics (BINP) located in Novosibirsk, Russia.

  2. Low-energy ballistic lunar transfers

    NASA Astrophysics Data System (ADS)

    Parker, Jeffrey S.

    A systematic method is developed that uses dynamical systems theory to model, analyze, and construct low-energy ballistic lunar transfers (BLTs). It has been found that low-energy BLTs may be produced by intersecting the stable manifold of an unstable Earth-Moon three-body orbit with the Earth. A spacecraft following such a trajectory is only required to perform a single maneuver, namely, the Trans-Lunar Injection maneuver, in order to complete the transfer. After the Trans-Lunar Injection maneuver, the spacecraft follows an entirely ballistic trajectory that asymptotically approaches and arrives at the target lunar three-body orbit. Because these orbit transfers require no orbit insertion maneuver at the three-body orbit, the transfers may be used to send spacecraft 25--40% more massive than spacecraft sent to the same orbits via conventional, direct transfers. From the targeted three-body orbits, the spacecraft may transfer to nearly any region within the Earth-Moon system, including any location on the surface of the Moon. The systematic methods developed in this research allow low-energy BLTs to be characterized by six parameters. It has been found that BLTs exist in families, where a family of BLTs consists of transfers whose parameters vary in a continuous fashion from one end of the family to the other. The families are easily identified and studied using a BLT State Space Map (BLT Map). The present research studies BLT Maps and has surveyed a wide variety of BLTs that exist in the observed families. It has been found that many types of BLTs may be constructed between 185-km low Earth parking orbits and lunar three-body orbits that require less than 3.27 km/s and fewer than 120 days of transfer time. Under certain conditions, BLTs may be constructed that require less than 3.2 km/s and fewer than 100 days of transfer time. It has been found that BLTs may implement LEO parking orbits with nearly any combination of altitude and inclination; they may depart from

  3. Annihilation of Low Energy Antiprotons in Hydrogen

    SciTech Connect

    Ovchinnikov, S.Yu.; Macek, J.H.

    2003-08-26

    The cross sections for annihilation of antiprotons in hydrogen are very important for designing the High-Performance Antiproton Trap (HiPAT). When antiprotons are trapped they undergo atomic reactions with background gases which remove them from the trap. First, antiprotons are captured into highly excited bound states by ejecting the bound electrons, then they are radiationally deexcited and, finally, they annihilate by nuclear interaction. An understanding of these process require reliable cross sections for low-energy collisions of antiprotons with atoms. We have developed a theoretical technique for accurate calculations of these cross sections.

  4. Interaction of low energy electrons with platinum surface

    NASA Astrophysics Data System (ADS)

    Borka, D.; Tőkési, K.

    2015-07-01

    We present Monte Carlo simulation of low energy electrons backscattered from platinum (Pt) surface. We take into account both elastic and inelastic collisions during the simulation. For the case of the elastic scattering of electrons by Pt atoms we use the static field approximation with non-relativistic Schrödinger partial wave analysis. For the case of inelastic scattering we use the dielectric response formalism. In our simulations the primary electron energy is 250 eV and the incidence angle of the electron beam with respect to the surface is varied between 1° and 90°. The backscattered electron energy loss distributions for primary and as well for secondary electrons and the distribution of maximum electron penetration depths in the Pt sample were calculated using only the bulk and also the surface dielectric function. We found that the maximum attained depth of the electrons is around 20 Å, i.e. the electrons are at the vicinity of the surface. Therefore we expect that the experimental data will be close to our simulation using surface-excitations modes.

  5. Low Energy Nuclear Reactions: 2007 Update

    NASA Astrophysics Data System (ADS)

    Krivit, Steven B.

    2007-03-01

    This paper presents an overview of low energy nuclear reactions, a subset of the field of condensed matter nuclear science. Condensed matter nuclear science studies nuclear effects in and/or on condensed matter, including low energy nuclear reactions, an entirely new branch of science that gained widespread attention and notoriety beginning in 1989 with the announcement of a previously unrecognized source of energy by Martin Fleischmann and Stanley Pons that came to be known as cold fusion. Two branches of LENR are recognized. The first includes a set of reactions like those observed by Fleischmann and Pons that use palladium and deuterium and yield excess heat and helium-4. Numerous mechanisms have been proposed to explain these reactions, however there is no consensus for, or general acceptance of, any of the theories. The claim of fusion is still considered speculative and, as such, is not an ideal term for this work. The other branch is a wide assortment of nuclear reactions that may occur with either hydrogen or deuterium. Anomalous nuclear transmutations are reported that involve light as well as heavy elements. The significant questions that face this field of research are: 1) Are LENRs a genuine nuclear reaction? 2) If so, is there a release of excess energy? 3) If there is, is the energy release cost-effective?

  6. Low Energy Ion-Molecule Reactions

    SciTech Connect

    James M. Farrar

    2004-05-01

    This objective of this project is to study the dynamics of the interactions of low energy ions important in combustion with small molecules in the gas phase and with liquid hydrocarbon surfaces. The first of these topics is a long-standing project in our laboratory devoted to probing the key features of potential energy surfaces that control chemical reactivity. The project provides detailed information on the utilization of specific forms of incident energy, the role of preferred reagent geometries, and the disposal of total reaction energy into product degrees of freedom. We employ crossed molecular beam methods under single collision conditions, at collision energies from below one eV to several eV, to probe potential surfaces over a broad range of distances and interaction energies. These studies allow us to test and validate dynamical models describing chemical reactivity. Measurements of energy and angular distributions of the reaction products with vibrational state resolution provide the key data for these studies. We employ the crossed beam low energy mass spectrometry methods that we have developed over the last several years.

  7. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1984-12-01

    The measurement of naturally occurring radioisotopes whose half lives are less than a few hundred million years but more than a few years provides information about the temporal behavior of geologic and climatic processes, the temporal history of meteoritic bodies as well as the production mechanisms of these radioisotopes. A new extremely sensitive technique for measuring these radioisotopes at tandem Van de Graaff and cyclotron facilities has been very successful though the high cost and limited availability have been discouraging. We have built and tested a low energy cyclotron for radiocarbon dating similar in size to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. We found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. We show how a conventional carbon negative ion source, located outside the cyclotron magnet, would produce sufficient beam and provide for quick sampling to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  8. Investigation of low-energy electronic response in high-{Tc} superconductor by Raman spectroscopy

    SciTech Connect

    Yamanaka, Akio; Asayama, Nobuo; Furutani, Takashi; Inoue, Kuon; Takekawa, Shunji

    1996-12-31

    Low-energy electronic response due to single-particle excitations has been investigated in high-{Tc} copper-oxide Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} single-crystals by Raman scattering spectroscopy. The authors find that the low-energy electronic response in the superconducting phase depends significantly on polarization configuration. For tetragonal B{sub 1g} the suppression of the low-energy spectral weight of the electronic continuum due to an opening of the superconducting gap occurs abruptly below {Tc}, whereas that of the B{sub 2g}-response shows a gradual temperature dependence. The symmetry-dependent superconducting response is basically consistent with the superconducting order parameter having a nodal structure with X{sup 2}-Y{sup 2} symmetry.

  9. Low Energy Antiproton Experiments - A Review

    SciTech Connect

    Jungmann, Klaus P.

    2005-10-19

    Low energy antiprotons offer excellent opportunities to study properties of fundamental forces and symmetries in nature. Experiments with them can contribute substantially to deepen our fundamental knowledge in atomic, nuclear and particle physics. Searches for new interactions can be carried out by studying discrete symmetries. Known interactions can be tested precisely and fundamental constants can be extracted from accurate measurements on free antiprotons (p-bar's) and bound two- and three-body systems such as antihydrogen (H-bar = p-bare-), the antprotonic helium ion (He++p-bar)+ and the antiprotonic atomcule (He++p-bare-) . The trapping of a single p-bar in a Penning trap, the formation and precise studies of antiprotonic helium ions and atoms and recently the production of H-bar have been among the pioneering experiments. They have led already to precise values for p-bar parameters, accurate tests of bound two- and three-body Quantum Electrodynamics (QED), tests of the CPT theorem and a better understanding of atom formation from their constituents. Future experiments promise more precise tests of the standard theory and have a robust potential to discover new physics. Precision experiments with low energy p-bar's share the need for intense particle sources and the need for time to develop novel instrumentation with all other experiments, which aim for high precision in exotic fundamental systems. The experimental programs - carried out in the past mostly at the former LEAR facility and at present at the AD facility at CERN - would benefit from intense future sources of low energy p-bar's. The highest possible p-bar fluxes should be aimed for at new facilities such as the planned FLAIR facility at GSI in order to maximize the potential of delicate precision experiments to influence model building. Examples of key p-bar experiments are discussed here and compared with other experiments in the field. Among the central issues is their potential to obtain

  10. Low energy dislocation structures in epitaxy

    NASA Technical Reports Server (NTRS)

    Van Der Merwe, Jan H.; Woltersdorf, J.; Jesser, W. A.

    1986-01-01

    The principle of minimum energy was applied to epitaxial interfaces to show the interrelationship beteen misfit, overgrowth thickness and misfit dislocation spacing. The low energy dislocation configurations were presented for selected interfacial geometries. A review of the interfacial energy calculations was made and a critical assessment of the agreement between theory and experiment was presented. Modes of misfit accommodation were presented with emphasis on the distinction between kinetic effects and equilibrium conditions. Two-dimensional and three-dimensional overgrowths were treated together with interdiffusion-modified interfaces, and several models of interfacial structure were treated including the classical and the current models. The paper is concluded by indicating areas of needed investigation into interfacial structure.

  11. Low energy consumption spintronics using multiferroic heterostructures

    NASA Astrophysics Data System (ADS)

    Trassin, Morgan

    2016-01-01

    We review the recent progress in the field of multiferroic magnetoelectric heterostructures. The lack of single phase multiferroic candidates exhibiting simultaneously strong and coupled magnetic and ferroelectric orders led to an increased effort into the development of artificial multiferroic heterostructures in which these orders are combined by assembling different materials. The magnetoelectric coupling emerging from the created interface between the ferroelectric and ferromagnetic layers can result in electrically tunable magnetic transition temperature, magnetic anisotropy or magnetization reversal. The full potential of low energy consumption magnetic based devices for spintronics lies in our understanding of the magnetoelectric coupling at the scale of the ferroic domains. Although the thin film synthesis progresses resulted into the complete control of ferroic domain ordering using epitaxial strain, the local observation of magnetoelectric coupling remains challenging. The ability to imprint ferroelectric domains into ferromagnets and to manipulate those solely using electric fields suggests new technological advances for spintronics such as magnetoelectric memories or memristors.

  12. Low-energy neutrino factory design

    SciTech Connect

    Ankenbrandt, C.; Bogacz, S.A.; Bross, A.; Geer, S.; Johnstone, C.; Neuffer, D.; Popovic, M.; /Fermilab

    2009-07-01

    The design of a low-energy (4 GeV) neutrino factory (NF) is described, along with its expected performance. The neutrino factory uses a high-energy proton beam to produce charged pions. The {pi}{sup {+-}} decay to produce muons ({mu}{sup {+-}}), which are collected, accelerated, and stored in a ring with long straight sections. Muons decaying in the straight sections produce neutrino beams. The scheme is based on previous designs for higher energy neutrino factories, but has an improved bunching and phase rotation system, and new acceleration, storage ring, and detector schemes tailored to the needs of the lower energy facility. Our simulations suggest that the NF scheme we describe can produce neutrino beams generated by {approx} 1.4 x 10{sup 21} {mu}{sup +} per year decaying in a long straight section of the storage ring, and a similar number of {mu}{sup -} decays.

  13. Low energy high pressure miniature screw valve

    DOEpatents

    Fischer, Gary J.; Spletzer, Barry L.

    2006-12-12

    A low energy high pressure screw valve having a valve body having an upper portion and a lower portion, said lower portion of said valve body defining an inlet flow passage and an outlet flow passage traversing said valve body to a valve seat, said upper portion of said valve body defining a cavity at said valve seat, a diaphragm restricting flow between said upper portion of said valve body and said lower portion, said diaphragm capable of engaging said valve seat to restrict fluid communication between said inlet passage and said outlet passage, a plunger within said cavity supporting said diaphragm, said plunger being capable of engaging said diaphragm with said valve seat at said inlet and outlet fluid passages, said plunger being in point contact with a drive screw having threads engaged with opposing threads within said upper portion of said valve body such engagement allowing motion of said drive screw within said valve body.

  14. RHIC low energy tests and initial operations

    SciTech Connect

    Satogata,T.; Ahrens, L.; Bai, M.; Brennan, J.M.; Bruno, D.; Butler, J.; Drees, A.; Fedotov, A.; Fischer, W.; Harvey, M.; Hayes, T.; Jappe, W.; Lee, R.C.; Mackay, W.W.; Malitsky, N.; Marr, G.; Michnoff, R.; Oerter, B.; Pozdeyev, E.; Roser, T.; Severino, F.; Smith, K.; Tepikian, S.; Tsoupas, N.

    2009-05-04

    Future Relativistic Heavy Ion Collider (RHIC) runs, including a portion of FY10 heavy ion operations, will explore collisions at center of mass energies of 5-50 GeV/n (GeV/nucleon). Operations at these energies is motivated by a search for the QCD phase transition critical point. The lowest end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy of {radical} s = 20.8 GeV/n. There are several operational challenges in the RHIC low-energy regime, including harmonic number changes, small longitudinal acceptance, lowered magnet field quality, nonlinear orbit control, and luminosity monitoring. We report on the experience with some of these challenges during beam tests with gold in March 2008, including first RHIC operations at {radical}s = 9.18 GeV/n and first beam experience at {radical}s = 5 GeV/n.

  15. Phenomenological implications of low energy supersymmetry breaking

    SciTech Connect

    Dimopoulos, S. |; Dine, M.; Raby, S.; Thomas, S.; Wells, J.D.

    1996-07-01

    The experimental signatures for low energy supersymmetry breaking are presented. The lightest standard model superpartner is unstable and decays to its partner plus a Goldstino, G. For a supersymmetry breaking scale below a few 1,000 TeV this decay can take place within a detector, leading to very distinctive signatures. If a neutralino is the lightest standard model superpartner it decays by {chi}{sub 1}{sup 0} {r_arrow} {gamma} + G, and if kinematically accessible by {chi}{sub 1}{sup 0} {r_arrow} (Z{sup 0}, h{sup 0}, H{sup 0}, A{sup 0}) + G. These decays can give rise to displaced vertices. Alternately, if a slepton is the lightest standard model superpartner it decays by {tilde l} {r_arrow} l + G. This can be seen as a greater than minimum ionizing charged particle track, possibly with a kink to a minimum ionizing track.

  16. Low-energy neutral-atom spectrometer

    SciTech Connect

    Voss, D.E.; Cohen, S.A.

    1982-04-01

    The design, calibration, and performance of a low energy neutral atom spectrometer are described. Time-of-flight analysis is used to measure the energy spectrum of charge-exchange deuterium atoms emitted from the PLT tokamak plasma in the energy range from 20 to 1000 eV. The neutral outflux is gated on a 1 ..mu..sec time scale by a slotted rotating chopper disc, supported against gravity in vacuum by magnetic levitation, and is detected by secondary electron emission from a Cu-Be plate. The energy dependent detection efficiency has been measured in particle beam experiments and on the tokamak so that the diagnostic is absolutely calibrated, allowing quantitative particle fluxes to be determined with 200 ..mu..sec time resolution. In addition to its present application as a plasma diagnostic, the instrument is capable of making a wide variety of measurements relevant to atomic and surface physics.

  17. Low energy ion-molecule reactions

    SciTech Connect

    Farrar, J.M.

    1993-12-01

    This project is concerned with elucidating the dynamics of elementary ion-molecule reactions at collision energies near and below 1 eV. From measurements of the angular and energy distributions of the reaction products, one can infer intimathe details about the nature of collisions leading to chemical reaction, the geometries and lifetimes of intermediate complexes that govern the reaction dynamics, and the collision energy dependence of these dynamical features. The author employs crossed-beam low energy mass spectrometry technology developed over the last several years, with the focus of current research on proton transfer and hydrogen atom transfer reactions of te O{sup {minus}} ion with species such as HF, H{sub 2}O, and NH{sub 3}.

  18. Particle Settling in Low Energy Turbulence

    NASA Astrophysics Data System (ADS)

    Allen, Rachel; MacVean, Lissa; Tse, Ian; Mazzaro, Laura; Stacey, Mark; Variano, Evan

    2014-11-01

    Particle settling velocities can be altered by turbulence. In turbulence, dense particles may get trapped in convergent flow regions, and falling particles may be swept towards the downward side of turbulent eddies, resulting in enhanced settling velocities. The degree of velocity enhancement may depend on the Stokes number, the Rouse number, and the turbulent Reynolds number. In a homogeneous, isotropic turbulence tank, we tested the effects of particle size and type, suspended sediment concentration, and level of turbulence on the settling velocities of particles typically found in muddy estuaries. Two Acoustic Doppler Velocimeters (ADVs), separated vertically, measured turbulent velocities and suspended sediment concentrations, which yield condition dependent settling velocities, via ∂/á C ñ ∂ t = -∂/∂ z (ws á C ñ + á w ' C ' ñ) . These results are pertinent to fine sediment transport in estuaries, where high concentrations of suspended material are transported and impacted by low energy turbulence.

  19. Low energy particle signature of substorm dipolarization

    SciTech Connect

    Liu, C.; Perez, J.D. ); Moore, T.E.; Chappell, C.R. )

    1994-02-01

    The low energy particle signature of substorm dipolarization is exhibited through a case study of RIMS data on DE-1 at [approximately]2100 MLT, ILAT = 59[degrees][approximately]65[degrees], L = 3.8 [approximately] 5.4 R[sub E], and geocentric distances 2.6[approximately]2.9 R[sub E]. A strong cross-field-line, poleward outflow that lasts for a few minutes with a velocity that reaches at least 50 km/s is correlated with substorm activity evidenced in the AE index and the MAG-1 data. All the major species (H[sup +], He[sup +], O[sup +]) are observed to have the same bulk velocity. The parallel velocities are strongly correlated with the perpendicular velocities. The parallel acceleration is shown to result from the centrifugal force of the ExB drift induced by the dipolarizing perturbation of the magnetic field. 9 refs., 4 figs.

  20. Low energy demonstration accelerator technical area 53

    SciTech Connect

    1996-04-01

    As part of the Department of Energy`s (DOE) need to maintain the capability of producing tritium in support of its historic and near-term stewardship of the nation`s nuclear weapons stockpile, the agency has recently completed a Programmatic Environmental Impact Statement for Tritium Supply and Recycling. The resulting Record of Decision (ROD) determined that over the next three years the DOE would follow a dual-track acquisition strategy that assures tritium production for the nuclear weapon stockpile in a rapid, cost effective, and safe manner. Under this strategy the DOE will further investigate and compare two options for producing tritium: (1) purchase of an existing commercial light-water reactor or irradiation services with an option to purchase the reactor for conversion to a defense facility; and (2) design, build, and test critical components of a system for accelerator production of tritium (APT). The final decision to select the primary production option will be made by the Secretary of Energy in the October 1998 time frame. The alternative not chosen as the primary production method, if feasible, would be developed as a back-up tritium supply source. This Environmental Assessment (EA) analyzes the potential environmental effects that would be expected to occur if the DOE were to design, build, and test critical prototypical components of the accelerator system for tritium production, specifically the front-end low-energy section of the accelerator, at Los Alamos National Laboratory. The Low Energy Demonstration Accelerator (LEDA) would be incrementally developed and tested in five separate stages over the next seven years. The following issues were evaluated for the proposed action: utility demands, air, human health, environmental restoration, waste management, transportation, water, threatened and endangered species, wetlands, cultural resources, and environmental justice.

  1. Low energy AMS of americium and curium

    NASA Astrophysics Data System (ADS)

    Christl, Marcus; Dai, Xiongxin; Lachner, Johannes; Kramer-Tremblay, Sheila; Synal, Hans-Arno

    2014-07-01

    Accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for actinide analyses. While analyses of U and Pu isotopes have already become routine at the ETH Zurich 0.5 MV AMS system "Tandy", there is an increasing demand for highly sensitive analyses of the higher actinides such as Am and Cm for bioassay applications and beyond. In order to extend the actinide capabilities of the compact ETH Zurich AMS system and to develop new, more sensitive bioassay routines, a pilot study was carried out. The aim was to investigate and document the performance and the potential background of Am and Cm analyses with low energy AMS. Our results show that 241Am and Cm isotopes can be determined relative to a 243Am tracer if samples and AMS standards are prepared identically with regard to the matrix elements, in which the sample is dispersed. In this first test, detection limits for Cm and Am isotopes are all in the sub-femtogram range and even below 100 ag for Cm isotopes. In a systematic background study in the mass range of the Cm isotopes, two formerly unknown metastable triply charged Th molecules were found on amu(244) and amu(248). The presence of such a background is not a principal problem for AMS if the stripper pressure is increased accordingly. Based on our first results, we conclude that ultra-trace analyses of Am and Cm isotopes for bioassay are very well possible with low energy AMS.

  2. The Low Energy Effective Area of the Chandra Low Energy Transmission Grating Spectrograph

    NASA Technical Reports Server (NTRS)

    Pease, D.; Drake, J. J.; Johnson, C. O.; Kashya, V.; Ratzlaff, P. W.; Wargelin, B. J.; Brinkman, A. C.; Kaastra, J. S.; vanderMeer, R.; Paerels, F. B.

    2000-01-01

    The Chandra X-ray Observatory was successfully launched on July 23, 1999, and subsequently began an intensive calibration phase. We present the preliminary results from the in-flight calibration of the low energy response of the High Resolution Camera spectroscopic readout (HRC-S) combined with the Low Energy Transmission Grating (LETG) aboard Chandra. These instruments comprise the Low Energy Transmission Grating Spectrograph (LETGS). For this calibration study, we employ a pure hydrogen non-LTE white dwarf emission model (T = 25000 K and log g = 9.0) for comparison with the Chandra observations of Sirius B. The pre-flight calibration of the LETGS effective area only covered wavelengths shortward of 44 A (E less than 277 eV). Our Sirius B analysis shows that the HRC-S quantum efficiency (QE) model assumed for longer wavelengths leads to an overestimate of the effective area by an average factor of about 1.6. We derive a correction to the low energy HRC-S QE model to match the predicted and observed Sirius B spectra over the wavelength range of 44-185 A. We make an independent test of our results by the comparison of a Chandra LETGS observation of HZ 43 with pure hydrogen model atmosphere predictions and find good agreement.

  3. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  4. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  5. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  6. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  7. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  8. Nucleon Spin Structure at Low Energies

    SciTech Connect

    Krebs, H.; Bernard, V.; Meissner, Ulf-G.

    2009-07-27

    We apply chiral effective field theory with explicit DELTA-1232) degrees of freedom to study double virtual Compton scattering at the photon point. Generalized spin polarizabilities are calculated up to order epsilon{sup 3} in the covariant small scale expansion. Systematic inclusion of DELTA degrees of freedom drastically improves the theoretical predictions.

  9. Study on astrophysical reactions using low-energy RI beams

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hidetoshi

    2009-10-01

    In recent years, low-energy RI beams can be produced in a good intensity and they have been used for studying many astrophysical reactions. One of the facilities producing low-energy RI beams is CRIB (CNS Radio-Isotope Beam separator) [1,2], an RI-beam separator of Center for Nuclear Study, University of Tokyo. Taking CRIB as an example, recent improvements on the RI-beam production and experimental results on astrophysical studies are presented. Several experimental approaches have been taken for the studies on astrophysical reactions.The feature of each method are discussed based on real measurements performed at CRIB. One is the direct method, applied for measurements of reactions such as (α,p) [3]. Another is the measurement of proton/alpha resonance scattering using the thick target method in inverse kinematics, by which we can obtain information on the resonances relevant in astrophysical reactions [4,5]. A recent fruitful result was from a measurement of proton resonance scattering using a ^7Be beam [5]. The energy level structure of ^8B, revealed by the experiment, is especially of interest as it is related with the ^7Be(p,γ) ^8B reaction, responsible for the production of ^8B neutrinos in the sun. We successfully determined parameters of resonances in ^8B below 6.7 MeV, which may affect the ^7Be(p,γ)^8B reaction rate at the solar temparature. Indirect methods, such as ANC and the Trojan Horse Method, were also used in some of the measurements.[4pt] [1] S. Kubono et al., Eur. Phys. J. A13 (2002) 217.[0pt] [2] Y. Yanagisawa et al., Nucl. Instrum. Meth. Phys. Res., Sect. A 539 (2005) 74.[0pt] [3] M. Notani et al., Nucl. Phys. A 764 (2004) 113c.[0pt] [4] T. Teranishi et al., Phys. Lett. B 650 (2007) 129.[0pt] [5] H. Yamaguchi et al., Phys. Lett. B 672 (2009) 230.

  10. Experimental studies using a low-energy RI beam separator at CNS

    NASA Astrophysics Data System (ADS)

    Teranishi, T.; Kubono, S.; Shimoura, S.; Notani, M.; Yanagisawa, Y.; Michimasa, S.; Ue, K.; Iwasaki, H.; Kurokawa, M.; Satou, Y.; Morikawa, T.; Saito, A.; Baba, H.; Lee, J. H.; Lee, C. S.; Fülöp, Zs.; Kato, S.

    2003-05-01

    Radioactive-ion (RI) beams of 10C, 14O, 12N and 11C with energies low 10 A MeV were produced by using a low-energy in-flight RI beam separator newly constructed by CNS, University of Tokyo. Using the 12N and 11C beams, some resonance states were identified in the proton elastic scattering 12N+p and 11C+p, respectively.

  11. Alpha-induced reaction studies using low-energy RI beams at CRIB

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Kahl, D.; Hu, J.; Kubono, S.; Hayakawa, S.; Hashimoto, T.

    2012-11-01

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Studies on proton and alpha resonance scatterings, (α, p) reactions, and other types of measurements (β-decay lifetimes etc.) have been performed using RI beams at CRIB, motivated by interests on astrophysical reactions and exotic nuclear structure. Among the studies at CRIB, the measurement of 7Li+α/7Be+α resonant scatterings are presented.

  12. Alpha-induced reaction studies using low-energy RI beams at CRIB

    SciTech Connect

    Yamaguchi, H.; Kahl, D.; Hu, J.; Kubono, S.; Hayakawa, S.; Hashimoto, T.

    2012-11-12

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo. Studies on proton and alpha resonance scatterings, ({alpha}, p) reactions, and other types of measurements ({beta}-decay lifetimes etc.) have been performed using RI beams at CRIB, motivated by interests on astrophysical reactions and exotic nuclear structure. Among the studies at CRIB, the measurement of {sup 7}Li+{alpha}/{sup 7}Be+{alpha} resonant scatterings are presented.

  13. Low energy CMOS for space applications

    NASA Technical Reports Server (NTRS)

    Panwar, Ramesh; Alkalaj, Leon

    1992-01-01

    The current focus of NASA's space flight programs reflects a new thrust towards smaller, less costly, and more frequent space missions, when compared to missions such as Galileo, Magellan, or Cassini. Recently, the concept of a microspacecraft was proposed. In this concept, a small, compact spacecraft that weighs tens of kilograms performs focused scientific objectives such as imaging. Similarly, a Mars Lander micro-rover project is under study that will allow miniature robots weighing less than seven kilograms to explore the Martian surface. To bring the microspacecraft and microrover ideas to fruition, one will have to leverage compact 3D multi-chip module-based multiprocessors (MCM) technologies. Low energy CMOS will become increasingly important because of the thermodynamic considerations in cooling compact 3D MCM implementations and also from considerations of the power budget for space applications. In this paper, we show how the operating voltage is related to the threshold voltage of the CMOS transistors for accomplishing a task in VLSI with minimal energy. We also derive expressions for the noise margins at the optimal operating point. We then look at a low voltage CMOS (LVCMOS) technology developed at Stanford University which improves the power consumption over conventional CMOS by a couple of orders of magnitude and consider the suitability of the technology for space applications by characterizing its SEU immunity.

  14. Novel results on low energy neutrino physics

    NASA Astrophysics Data System (ADS)

    Bellini, Gianpaolo

    2012-07-01

    Many progresses have been achieved in the study of low energy neutrinos from Sun and Earth. In the solar neutrinos the flux from 7Be has been measured with a total error <5% (introducing strong constraints also on the pp flux), while the day/night effect in that energy region has been determined at 1%. The 8B neutrinos have been detected with a threshold down to 3 MeV, while the solar neutrinos flux from pep reaction has been measured together with a stringent limit on CNO. These results give the experimental proof of the neutrino oscillation in vacuum and the validation of the MSW-LMA model in that region, while the day/night allows the isolation of the LMA solution by means of the solar neutrinos only, without the assumption of CPT symmetry. The evidence of the antineutrinos produced within the Earth by radioactive decays is now very robust, but more statistics is needed to clearly estimate the radiogenic contribution to the terrestrial caloric energy.

  15. Low-energy positron interactions with xenon

    NASA Astrophysics Data System (ADS)

    Machacek, J. R.; Makochekanwa, C.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Bellm, S.; Lohmann, B.; Fursa, D. V.; Bray, I.; Mueller, D. W.; Stauffer, A. D.

    2011-12-01

    Low-energy interactions of positrons with xenon have been studied both experimentally and theoretically. The experimental measurements were carried out using a trap-based positron beam with an energy resolution of ˜80 meV, while the theoretical calculations were carried out using the convergent close-coupling method and the relativistic optical potential approach. Absolute values of the grand total, positronium formation and grand total minus positronium formation cross sections are presented over the energy range of 1-60 eV. Elastic differential cross sections (DCS), for selected energies, are also presented both below and above the positronium formation threshold. Fine energy-step measurements of the positronium formation cross section over the energy range of 4.4-8.4 eV, and measurements of the elastic DCS at the energies of 5.33 and 6.64 eV, have been carried out to investigate the ionization threshold regions corresponding to the 2P3/2 and 2P1/2 states of the Xe+ ion. The present results are compared with both experimental and theoretical values from the literature where available.

  16. Studies in Low-Energy Nuclear Science

    SciTech Connect

    Brune, Carl R; Grimes, Steven M

    2006-03-30

    This report presents a summary of research projects in the area of low energy nuclear reactions and structure, carried out between 1 January 2003 and 31 December 2005 and supported by U.S. DOE grant number DE-FG03-03NA00074. Cross sections measured with high resolution have been subjected to an Ericson theory analysis to infer information about the nuclear level density. Other measurements were made of the spectral shape of particles produced in evaporation processes; these also yield level density information. A major project was the development of a new Hauser-Feshbach code for analyzing such spectra. Other measurements produced information on the spectra of gamma rays emitted in reactions on heavy nuclei and gave a means of refining our understanding of gamma-ray strength functions. Finally,reactions on light nuclei were studied and subjected to an R-matrix analysis. Cross sections fora network of nuclear reactions proceedingthrough a given compound nucleus shouldgreatly constrain the family of allowed parameters. Modifications to the formalism andcomputer code are also discussed.

  17. Low-energy electron collisions with biomolecules

    NASA Astrophysics Data System (ADS)

    Winstead, Carl; McKoy, Vincent

    2012-11-01

    We report recent progress in applying the Schwinger multichannel computational method to the interactions of slow electrons with biomolecules. Calculations on constituents of DNA, including nucleobases, phosphate esters, and models of the backbone sugar, have provided insight into the nature of the low-energy shape resonances, and thereby into possible sites and mechanisms for electron attachment that may lead to strand-breaking. At the same time, more approximate calculations on larger assemblies such as nucleosides and deoxyadenosine monophosphate indicate how the resonance properties of the subunits will or will not persist in DNA itself. We are pursuing a similar strategy for another major class of biomolecules, the proteins, by beginning with fixed-nuclei studies of the constituent amino acids; here we present preliminary results for the simplest amino acid, glycine. We also describe efforts directed at an improved understanding electron collisions with alcohols, which, in addition to basic scientific interest, may prove useful in the modeling of ignition and combustion within biofuel-powered engines.

  18. Optimal Low Energy Earth-Moon Transfers

    NASA Technical Reports Server (NTRS)

    Griesemer, Paul Ricord; Ocampo, Cesar; Cooley, D. S.

    2010-01-01

    The optimality of a low-energy Earth-Moon transfer is examined for the first time using primer vector theory. An optimal control problem is formed with the following free variables: the location, time, and magnitude of the transfer insertion burn, and the transfer time. A constraint is placed on the initial state of the spacecraft to bind it to a given initial orbit around a first body, and on the final state of the spacecraft to limit its Keplerian energy with respect to a second body. Optimal transfers in the system are shown to meet certain conditions placed on the primer vector and its time derivative. A two point boundary value problem containing these necessary conditions is created for use in targeting optimal transfers. The two point boundary value problem is then applied to the ballistic lunar capture problem, and an optimal trajectory is shown. Additionally, the ballistic lunar capture trajectory is examined to determine whether one or more additional impulses may improve on the cost of the transfer.

  19. Low energy beam transport system developments

    NASA Astrophysics Data System (ADS)

    Dudnikov, V.; Han, B.; Stockli, M.; Welton, R.; Dudnikova, G.

    2015-04-01

    For high brightness beam production it is important to preserve the brightness in the low energy beam transport system (LEBT) used to transport and match the ion beams to the next stage of acceleration, usually an RFQ. While electrostatic focusing can be problematic for high current beam transport, reliable electrostatic LEBT operation has been demonstrated with H- beams up to 60 mA. Now, however, it is commonly accepted that an optimal LEBT for high current accelerator applications consists of focusing solenoids with space charge compensation. Two-solenoid LEBTs are successfully used for high current (>100 mA) proton beam transport. Preservation of low emittances (~0.15 π mm-mrad) requires the addition of a heavy gas (Xe, Kr), which causes ~5% of proton loss in a 1 m long LEBT. Similar Xe densities would be required to preserve low emittances of H- beams, but such gas densities cause unacceptably high H- beam losses. A short LEBT with only one short solenoid, movable for RFQ matching, can be used for reduced negative ion stripping. A strong electrostatic-focusing LEBT has been successfully adopted for transport of high current H- beams in the SNS Front End. Some modifications of such electrostatic LEBTs are expected to improve the reliable transport of intense positive and negative ion beams without greatly degrading their low emittances. We concentrate on processes that determine the beam brightness degradation and on their prevention. Proposed improvements to the SNS electrostatic LEBT are discussed.

  20. Oscillations of very low energy atmospheric neutrinos

    SciTech Connect

    Peres, Orlando L. G.; Smirnov, A. Yu.

    2009-06-01

    There are several new features in the production, oscillations, and detection of the atmospheric neutrinos of low energies E < or approx. 100 MeV. The flavor ratio r of muon to electron neutrino fluxes is substantially smaller than 2 and decreases with energy, a significant part of events is due to the decay of invisible muons at rest, etc. Oscillations in a two-layer medium (atmosphere-Earth) should be taken into account. We derive analytical and semianalytical expressions for the oscillation probabilities of these 'sub-sub-GeV' neutrinos. The energy spectra of the e-like events in water Cherenkov detectors are computed, and the dependence of the spectra on the 2-3 mixing angle {theta}{sub 23}, the 1-3 mixing, and the CP-violation phase are studied. We find that variations of {theta}{sub 23} in the presently allowed region change the number of e-like events by about 15%-20% as well as lead to distortion of the energy spectrum. The 1-3 mixing and CP violation can lead to {approx}10% effects. Detailed study of the sub-sub-GeV neutrinos will be possible in future megaton-scale detectors.

  1. Low energy stable plasma calibration facility

    NASA Astrophysics Data System (ADS)

    Frederick-Frost, K. M.; Lynch, K. A.

    2007-07-01

    We have designed and fabricated a low energy plasma calibration facility for testing and calibration of rocket-borne charged-particle detectors and for the investigation of plasma sheath formation in an environment with ionospheric plasma energies, densities, and Debye lengths. We describe the vacuum system and associated plasma source, which was modified from a Naval Research Laboratory design [Bowles et al. Rev. Sci. Instrum. 67, 455 (1996)]. Mechanical and electrical modifications to this cylindrical microwave resonant source are outlined together with a different method of operating the magnetron that achieves a stable discharge. This facility produces unmagnetized plasmas with densities from 1×103/cm3to6×105/cm3, electron temperatures from 0.1to1.7eV, and plasma potentials from 0.5to8V depending on varying input microwave power and neutral gas flow. For the range of input microwave power explored (350-600W), the energy density of the plasma remains constant because of an inverse relationship between density and temperature. This relationship allows a wide range of Debye lengths (0.3-8.4cm) to be investigated, which is ideal for simulating the ionospheric plasma sheaths we explore.

  2. Low energy CMOS for space applications

    NASA Astrophysics Data System (ADS)

    Panwar, Ramesh; Alkalaj, Leon

    The current focus of NASA's space flight programs reflects a new thrust towards smaller, less costly, and more frequent space missions, when compared to missions such as Galileo, Magellan, or Cassini. Recently, the concept of a microspacecraft was proposed. In this concept, a small, compact spacecraft that weighs tens of kilograms performs focused scientific objectives such as imaging. Similarly, a Mars Lander micro-rover project is under study that will allow miniature robots weighing less than seven kilograms to explore the Martian surface. To bring the microspacecraft and microrover ideas to fruition, one will have to leverage compact 3D multi-chip module-based multiprocessors (MCM) technologies. Low energy CMOS will become increasingly important because of the thermodynamic considerations in cooling compact 3D MCM implementations and also from considerations of the power budget for space applications. In this paper, we show how the operating voltage is related to the threshold voltage of the CMOS transistors for accomplishing a task in VLSI with minimal energy. We also derive expressions for the noise margins at the optimal operating point. We then look at a low voltage CMOS (LVCMOS) technology developed at Stanford University which improves the power consumption over conventional CMOS by a couple of orders of magnitude and consider the suitability of the technology for space applications by characterizing its SEU immunity.

  3. New Cooperative Mechanisms of Low-Energy Nuclear Reactions Using Super Low-Energy External Field

    NASA Astrophysics Data System (ADS)

    Gareev, F. A.; Zhidkova, I. E.

    We propose a new mechanism of LENR: cooperative processes in the whole system, nuclei + atoms + condensed matter, can occur at a smaller threshold energies than the corresponding ones on free constituents. The cooperative processes can be induced and enhanced by low-energy external fields. The excess heat is the emission of internal energy and transmutations at LENR are the result of redistribution of inner energy of the whole system.

  4. In-medium nuclear interactions of low-energy hadrons

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Gal, A.

    2007-11-01

    Exotic atoms provide a unique laboratory for studying strong interactions and nuclear medium effects at zero kinetic energy. Experimental and theoretical developments of the last decade in the study of exotic atoms and some related low-energy reactions are reviewed. The exotic atoms considered are of π-,K-,pbar,Σ-, and also the so far unobserved Ξ- atoms. The analysis of these atomic systems consists of fitting density-dependent optical potentials Vopt=t(ρ)ρ to comprehensive sets of data of strong-interaction level shifts, widths and yields across the periodic table. These provide information on the in-medium hadron-nucleon t matrix t(ρ) over a wide range of densities up to central nuclear densities. For pions, the review focuses on the extraction of the πN in-medium s-wave interaction from pionic atoms, which include also the deeply bound π- atomic states recently observed at GSI in isotopes of Sn and Pb. Also included are recent measurements at PSI of elastic scattering of π± on Si, Ca, Ni and Zr at 21.5 MeV. The experimental results are analyzed in the context of chirally motivated π-nuclear potentials, and the evidence for partial restoration of chiral symmetry in dense nuclear matter is critically discussed. For antikaons, we review the evidence from K- atoms, and also from low-energy K-p scattering and reaction data for and against a deepKbar-nucleus potential of 150-200 MeV attraction at nuclear matter density. The case for relatively narrow deeply bound K-atomic states is made, essentially independent of the potential-depth issue. Recent experimental suggestions from KEK and DA ΦNE (Frascati) for signals of Kbar-nuclear deeply bound states are reviewed, and dynamical models for calculating binding energies and widths of Kbar- nuclear states are discussed. For kaons we review the evidence, from K+ total and reaction cross section measurements at the AGS (BNL) on Li, C, Si and Ca at plab=500-700 MeV/c, for significant absorptivity of t

  5. The Low Energy Neutron Source at Indiana University

    NASA Astrophysics Data System (ADS)

    Baxter, David

    2004-03-01

    The National Science Foundation has recently approved funding for construction of LENS (the Low Energy Neutron Source) at Indiana University and construction of this facility has begun. LENS represents a new paradigm for economically introducing neutron scattering into a university or industrial setting. Neutrons are produced in a long-pulse (1ms) mode through (p,n) reactions on a water-cooled Be target and supplied to three instrument beam lines. In this talk we will describe how LENS will use neutrons to fulfill its three-fold mission in education, materials research, and developing novel instrumentation. Of particular interest are the facility's ability to study cryogenic moderators at significantly lower temperatures than is possible at other facilities and the development of instruments that make use of the neutron spin to perform high-precision measurements of momentum transfer without significant collimation of the beam. The potential for these developments to expand significantly the range of problems amenable to exploration with neutron techniques will be discussed.

  6. Maximum Likelihood Analysis of Low Energy CDMS II Germanium Data

    DOE PAGESBeta

    Agnese, R.

    2015-03-30

    We report on the results of a search for a Weakly Interacting Massive Particle (WIMP) signal in low-energy data of the Cryogenic Dark Matter Search experiment using a maximum likelihood analysis. A background model is constructed using GEANT4 to simulate the surface-event background from Pb210decay-chain events, while using independent calibration data to model the gamma background. Fitting this background model to the data results in no statistically significant WIMP component. In addition, we also perform fits using an analytic ad hoc background model proposed by Collar and Fields, who claimed to find a large excess of signal-like events in ourmore » data. Finally, we confirm the strong preference for a signal hypothesis in their analysis under these assumptions, but excesses are observed in both single- and multiple-scatter events, which implies the signal is not caused by WIMPs, but rather reflects the inadequacy of their background model.« less

  7. Low energy electron attachment at sub-meV resolution

    NASA Astrophysics Data System (ADS)

    Kortyna, A.; Howe, P.-T.; Darrach, M.; Chutjian, A.

    2000-06-01

    Single-photon ionization of rare-gas atoms is used to produce low energy electrons for the study of electron attachment to SF_6. Vacuum ultraviolet laser radiation (λ ≈ 92 nm), produced by nonlinear up-conversion techniques and tunable near the Xe^+ ^2P^0_1/2 threshold, intersects a Xe beam to yield photoelectrons that scatter from SF6 target molecules admixed into the same beam. The photoelectron energy, ɛ, is scanned over the range 0 <= ɛ <= 84 meV. A Monte Carlo model of the attachment signal shows that the electron energy distribution width is <100 μeV and that the electron attachment cross section below 5 meV obeys the expected ɛ-1/2 energy dependence without the need to modify the Wigner threshold law. At ɛ = 45 ± 1 meV, a resonant structure reveals the opening of an inelastic attachment channel associated with the ω6 vibrational mode of SF6 whose excitation energy has been measured previously to be 44.0 ± 0.2 meV. Further investigations into the threshold behavior of the electron attachment cross section are underway. This work was carried out at JPL/Caltech and supported through agreement with NASA.

  8. Collisions of low-energy electrons with cyclohexane

    SciTech Connect

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2014-12-28

    We report calculated cross sections for elastic scattering of low-energy electrons by cyclohexane (c-C{sub 6}H{sub 12}). We employed the Schwinger multichannel method implemented with norm-conserving pseudopotentials in the static-exchange and static-exchange plus polarization approximations, for impact energies up to 30 eV. We compare our calculated integral cross section with experimental total cross sections available in the literature. We also compare our calculated differential cross sections (DCSs) with experimental results for benzene and experimental and theoretical results for 1,4-dioxane, in order to investigate the similarities between those molecules under electron collisions. Although benzene is a cyclic six-carbon molecule, as cyclohexane, we found that the differential cross sections of the latter are more similar to those of 1,4-dioxane than those of benzene. These similarities suggest that the geometry may play an important role in the behavior of the DCSs of these molecules. Our integral cross section displays a broad structure at around 8.5 eV, in agreement with the total cross section experimental data of 8 eV and vibrational excitation data of 7.5 eV. The present integral cross section also shows the presence of a Ramsauer-Townsend minimum at around 0.12 eV. In general, our integral cross section shows a qualitative agreement with the experimental total cross section.

  9. Investigation of low energy space plasma

    NASA Technical Reports Server (NTRS)

    Comfort, Richard H.; Horwitz, James L.

    1987-01-01

    An important modification was made in the method for computing ion densities from DE1/RIMS observations, based on the observed relationship between total plasma density and spacecraft potential. An iterative technique was developed to require that this relationship be preserved in all individual observations, not just in the average sense observed. Results of employing this technique were examined closely and are found to generally improve the final densities in terms of agreement with densities obtained from PWI upper hybrid frequency observations. It also has the effect of reducing scatter in the density vs. L profiles.

  10. Offer search deviations from Newton's law of gravity using low-energy neutrons

    NASA Astrophysics Data System (ADS)

    Alexandrov, Yu

    2012-03-01

    Information about the planned experiment at the reactor IBR-2M (installation YuMO) dedicated to finding differs from the Newtonian law of gravitation at small (atomic) distances reported. The experiment is to study the energy dependence of the scattering length on the matter with a very small length of pure nuclear scattering (e.g. by a mixture of isotopes of tungsten), allowing thereby increasing the relative contribution of gravitational scattering. At the concentration of tungsten-186 of about 90% in the mixture, nuclear scattering length may to turn to zero at low energies. Relying on the accuracy of existing experiments it can argued that not Newtonian gravitational scattering can be detected if the scattering length is more than 10-16 or 10-17cm. Estimates show that in the theoretical model associated with the length of the electroweak interaction the amplitude of the gravitational scattering of neutrons in the Born approximation may be in the region from 10-11 to 10-21 cm. The magnitude of usual Newtonian gravitational scattering is 10-32 cm, i.e. significantly less.

  11. Low energy beam transport system developments

    SciTech Connect

    Dudnikov, V.; Han, B.; Stockli, M.; Welton, R.; Dudnikova, G.

    2015-04-08

    For high brightness beam production it is important to preserve the brightness in the low energy beam transport system (LEBT) used to transport and match the ion beams to the next stage of acceleration, usually an RFQ. While electrostatic focusing can be problematic for high current beam transport, reliable electrostatic LEBT operation has been demonstrated with H{sup −} beams up to 60 mA. Now, however, it is commonly accepted that an optimal LEBT for high current accelerator applications consists of focusing solenoids with space charge compensation. Two-solenoid LEBTs are successfully used for high current (>100 mA) proton beam transport. Preservation of low emittances (~0.15 π mm-mrad) requires the addition of a heavy gas (Xe, Kr), which causes ~5% of proton loss in a 1 m long LEBT. Similar Xe densities would be required to preserve low emittances of H{sup −} beams, but such gas densities cause unacceptably high H{sup −} beam losses. A short LEBT with only one short solenoid, movable for RFQ matching, can be used for reduced negative ion stripping. A strong electrostatic-focusing LEBT has been successfully adopted for transport of high current H{sup −} beams in the SNS Front End. Some modifications of such electrostatic LEBTs are expected to improve the reliable transport of intense positive and negative ion beams without greatly degrading their low emittances. We concentrate on processes that determine the beam brightness degradation and on their prevention. Proposed improvements to the SNS electrostatic LEBT are discussed.

  12. Low-Energy Impacts onto Lunar Regolith

    NASA Astrophysics Data System (ADS)

    Seward, L. M.; Colwell, J. E.

    2011-12-01

    Collisions in space are vital to the formation and evolution of planetary bodies such as protoplanetary disks, planetary rings, the Kuiper belt, and the asteroid belt. Low-velocity impacts are common in planetary rings and protoplanetary disks. Saturn ring particles collide at speeds less than 1 m/s throughout most of the main rings, with more energetic collisions occurring in the dynamically stirred F ring. We are conducting a program of laboratory experiments to study low-velocity impacts of 1 to 5 m/s into regolith. We use direct measurement of ejecta mass and high resolution video tracking of ejecta particle trajectories to derive ejecta mass velocity distributions. We wish to characterize and understand the collision parameters that control the outcome of low-velocity impacts into regolith, including impact velocity, impactor mass, target size distribution, regolith depth, and target relative density, and to experimentally determine the functional dependencies of the outcomes of low-velocity collisions (ejecta mass and ejecta velocities) on the controlling parameters of the collision. Our goal is to understand the physics of ejecta production and regolith compaction in low-energy impacts and experimentally validate predictive models for dust flow and deposition. We present results from our ongoing study showing the positive correlation between impact energy and ejecta mass. Our results show that the production of ejecta mass increases as a function of impact kinetic energy. The production of mass also increases as a function of target relative density to a point of maximum ejecta production, beyond which the trend reverses.

  13. Propagation of low energy solar electrons

    NASA Technical Reports Server (NTRS)

    Anderson, K. A.; Mcfadden, J. P.; Lin, R. P.

    1981-01-01

    Two events are reported in which 2-10 keV electrons of solar energy have undergone significant adiabatic mirroring and pitch angle scattering in large scale magnetic structures in the interplanetary medium within a distance of about 0.5 AU from the earth. Electrons of 3 keV, typical of the energies measured, have a speed of about one-tenth of the speed of light, so that their travel time from the sun at 0 deg pitch angle would be about 100 minutes. Their cyclotron radius is about 20 km for a pitch angle of 30 deg, and a field of magnitude of 5 nT, and the cyclotron period is about 7.1 milliseconds. The electrons are scattered by spatial variations in the interplanetary magnetic field. When the spatial variations are convected past a stationary spacecraft by a 500 km/sec solar wind, they are seen as temporal fluctuations at a frequency of about 3 Hz.

  14. Chorus intensity modulation driven by time-varying field-aligned low-energy plasma

    NASA Astrophysics Data System (ADS)

    Nishimura, Y.; Bortnik, J.; Li, W.; Liang, J.; Thorne, R. M.; Angelopoulos, V.; Le Contel, O.; Auster, U.; Bonnell, J. W.

    2015-09-01

    Recent studies have shown that chorus waves are responsible for scattering and precipitating the energetic electrons that drive the pulsating aurora. While some of the chorus intensity modulation events are correlated with <~100 eV electron density modulation, most of the chorus intensity modulation events in the postmidnight sector occur without apparent density changes. Although it is generally difficult to measure evolution of low-energy (<~20 eV) electron fluxes due to constraints imposed by the spacecraft potential and electrostatic analyzer (ESA) energy range limit, we identified using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite data that low-energy ions of ~100 eV show density modulation that is correlated with chorus intensity modulation. Those low-energy ions and electrons are field-aligned with major peaks in 0° (for northern hemisphere winter event) and 180° (for northern hemisphere summer event) pitch angle, indicating that outflowing plasma from the sunlit hemisphere is the source of the low-energy plasma density modulation near the equator. Plasma sheet plasma density, and ambient electric and magnetic fields do not show modulations that are correlated with the chorus intensity modulation. Assuming charge neutrality, the low-energy ions can be used to represent cold plasma density in wave growth rate calculations, and the enhancements of the low-energy plasma density are found to contribute most effectively to chorus linear growth rates. These results suggest that chorus intensity modulation is driven by a feedback process where outflowing plasma due to energetic electron precipitation increases the equatorial density that drives further electron precipitation.

  15. Interaction between Low Energy Ions and the Complicated Organism

    NASA Astrophysics Data System (ADS)

    Yu, Zeng-liang

    1999-12-01

    Low energy ions exist widely in natural world, but people pay a little attention on the interaction between low energy ions and matter, it is even more out of the question of studying on the relation of low energy ions and the complicated organism. The discovery of bioeffect induced by ion implantation has, however, opened a new branch in the field of ion beam application in life sciences. This paper reports recent advances in research on the role of low energy ions in chemical synthesis of the biomolecules and application in genetic modification.

  16. Low-Energy Ballistic Transfers to Lunar Halo Orbits

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2009-01-01

    Recent lunar missions have begun to take advantage of the benefits of low-energy ballistic transfers between the Earth and the Moon rather than implementing conventional Hohmann-like lunar transfers. Both Artemis and GRAIL plan to implement low-energy lunar transfers in the next few years. This paper explores the characteristics and potential applications of many different families of low-energy ballistic lunar transfers. The transfers presented here begin from a wide variety of different orbits at the Earth and follow several different distinct pathways to the Moon. This paper characterizes these pathways to identify desirable low-energy lunar transfers for future lunar missions.

  17. Development of a Low-energy Trigger for VERITAS

    SciTech Connect

    Kildea, J.

    2008-12-24

    During the 2007/2008 observing season a low-energy trigger configuration was developed and tested for VERITAS. The configuration makes uses of the small ({approx}35 m) baseline between two of the VERITAS telescopes and employs a much lower discriminator threshold and tighter coincidence window compared to the standard VERITAS trigger. Five hours of Crab Nebula ON/OFF observations were obtained in low-energy mode and were used to test new low-energy analysis algorithms. We present some details of the VERITAS low-energy trigger and the associated data analysis.

  18. Low-energy calculations for nuclear photodisintegration

    NASA Astrophysics Data System (ADS)

    Deflorian, S.; Efros, V. D.; Leidemann, W.

    2016-03-01

    In the Standard Solar Model a central role in the nucleosynthesis is played by reactions of the kind {}{Z_1}{A_1}{X_1} + {}{Z_2}{A_2}{X_2} to {}{Z_1 + {Z_2}}{A_1 + {A_2}}Y + γ , which enter the proton-proton chains. These reactions can also be studied through the inverse photodisintegration reaction. One option is to use the Lorentz Integral Transform approach, which transforms the continuum problem into a bound state-like one. A way to check the reliability of such methods is a direct calculation, for example using the Kohn Variational Principle to obtain the scattering wave function and then directly calculate the response function of the reaction.

  19. Low-energy positron interactions with krypton

    SciTech Connect

    Makochekanwa, C.; Machacek, J. R.; Jones, A. C. L.; Caradonna, P.; Slaughter, D. S.; McEachran, R. P.; Sullivan, J. P.; Buckman, S. J.; Bellm, S.; Lohmann, B.; Fursa, D. V.; Bray, I.; Mueller, D.W.; Stauffer, A. D.; Hoshino, M.

    2011-03-15

    Cross sections for positron scattering from krypton have been measured with an energy resolution of {approx}60 meV over the energy range 0.5-60 eV. Absolute values of the grand total ({sigma}{sub GT}), positronium formation ({sigma}{sub Ps}), and grand total minus positronium formation ({sigma}{sub GT}-{sigma}{sub Ps},) cross sections are presented. Theoretical estimations of {sigma}{sub GT} and {sigma}{sub GT}-{sigma}{sub Ps} are also performed for this target using the convergent close-coupling method and the relativistic optical potential approach. We also provide experimental and theoretical results for elastic differential cross sections, for selected energies both below and above the Ps threshold. Where available, the present results are compared to both experimental and theoretical values from the literature.

  20. Coherent scattering of cosmic neutrinos

    NASA Technical Reports Server (NTRS)

    Opher, R.

    1974-01-01

    It is shown that cosmic neutrino scattering can be non-negligible when coherence effects previously neglected are taken into account. The coherent neutrino scattering cross section is derived and the neutrino index of refraction evaluated. As an example of coherent neutrino scattering, a detector using critical reflection is described which in principle can detect the low energy cosmic neutrino background allowed by the measured cosmological red shift.

  1. A Germanium Detector with Optimized Compton Veto for High Sensitivity at Low Energy

    SciTech Connect

    Friedrich, S

    2011-11-30

    We have built a prototype germanium detector with a Compton veto that is optimized for high sensitivity in the low-energy range around {approx}100 keV. It is specifically designed to address the problem to directly detect plutonium gamma emissions in spent nuclear fuel by non-destructive assay. This is not possible with current detectors due to the large low-energy background of Compton-scattered high-energy radiation from the fission products, whose gamma flux is at least 6 to 7 orders of magnitude higher than the Pu signal. Our instrument is designed to assess the feasibility to selectively suppress the background in the low-energy region around {approx}100 keV with the strongest Pu X-ray and gamma emissions lines. It employs a thin Ge detector with a large Compton veto directly behind it to suppress the background from forward-scattered radiation by anti-coincidence vetoing. This report summarizes the design considerations and the performance of the instrument.

  2. Very low-energy neutrino interactions

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshio

    2015-05-01

    Neutrino-nucleus reaction cross sections are now evaluated rather accurately by shell-model (SM) or SM+RPA calculations based on recent advances in nuclear structure studies. Due to these achievements, reliable constraints on super-nova neutrino temperatures as well as neutrino oscillation parameters become possible. Supernova neutrino tempeatures are constrained from abundances of elements obtained by using new ν-nucleus reaction cross sections. A possibility of constructing supernova neutrino spectrum from beta-beam measurements is pointed out. Neutrino mass hierarchy and mixing angle θ13 can be determined from abundance ratio of 7Li/11B, which is sensitive to the MSW matter oscillation effects in supernova explosions. Inverted mass hierarchy is shown to be statistically more favored based on a recent analysis of presolar grains. Effects of neutrino-neutrino interactions are also shown to play important roles in r-process nucleosynthesis. Importance and possibilities of direct measurements of ν-induced cross sections on 40Ar and 208Pb are discussed for future supernova neutrino detections. Recent calculations of the cross sections for ν-40Ar are presented. The need for new theoretical evaluations of the cross sections for ν-208Pb is pointed out. Challenges to experiments on coherent elastic scattering are presented.

  3. Very low-energy neutrino interactions

    SciTech Connect

    Suzuki, Toshio

    2015-05-15

    Neutrino-nucleus reaction cross sections are now evaluated rather accurately by shell-model (SM) or SM+RPA calculations based on recent advances in nuclear structure studies. Due to these achievements, reliable constraints on super-nova neutrino temperatures as well as neutrino oscillation parameters become possible. Supernova neutrino tempeatures are constrained from abundances of elements obtained by using new ν-nucleus reaction cross sections. A possibility of constructing supernova neutrino spectrum from beta-beam measurements is pointed out. Neutrino mass hierarchy and mixing angle θ{sub 13} can be determined from abundance ratio of {sup 7}Li/{sup 11}B, which is sensitive to the MSW matter oscillation effects in supernova explosions. Inverted mass hierarchy is shown to be statistically more favored based on a recent analysis of presolar grains. Effects of neutrino-neutrino interactions are also shown to play important roles in r-process nucleosynthesis. Importance and possibilities of direct measurements of ν-induced cross sections on {sup 40}Ar and {sup 208}Pb are discussed for future supernova neutrino detections. Recent calculations of the cross sections for ν-{sup 40}Ar are presented. The need for new theoretical evaluations of the cross sections for ν-{sup 208}Pb is pointed out. Challenges to experiments on coherent elastic scattering are presented.

  4. Low-energy neutron-deuteron reactions with N 3 LO chiral forces

    NASA Astrophysics Data System (ADS)

    Golak, J.; Skibiński, R.; Topolnicki, K.; Witała, H.; Epelbaum, E.; Krebs, H.; Kamada, H.; Meißner, Ulf-G.; Bernard, V.; Maris, P.; Vary, J.; Binder, S.; Calci, A.; Hebeler, K.; Langhammer, J.; Roth, R.; Nogga, A.; Liebig, S.; Minossi, D.

    2014-11-01

    We solve three-nucleon Faddeev equations with nucleon-nucleon and three-nucleon forces derived consistently in the framework of chiral perturbation theory at next-to-next-to-next-to-leading order in the chiral expansion. In this first investigation we include only matrix elements of the three-nucleon force for partial waves with the total two-nucleon (three-nucleon) angular momenta up to 3 (5/2). Low-energy neutron-deuteron elastic scattering and deuteron breakup reaction are studied. Emphasis is put on A y puzzle in elastic scattering and cross sections in symmetric-space-star and neutron-neutron quasi-free-scattering breakup configurations, for which large discrepancies between data and theory have been reported.

  5. Low-energy antiprotons physics and the FLAIR facility

    NASA Astrophysics Data System (ADS)

    Widmann, E.

    2015-11-01

    FLAIR, the Facility for low-energy antiproton and ion research has been proposed in 2004 as an extension of the planned FAIR facility at Darmstadt, Germany. FLAIR was not included into the modularized start version of FAIR, but the recent installation of the CRYRING storage ring at GSI Darmstadt has opened new perspectives for physics with low-energy antiprotons at FAIR.

  6. What is a low-energy house and who cares?

    SciTech Connect

    Litt, B.R.

    1994-12-01

    Most energy analysts view low-energy houses as good things, yet differ in their expectations of what exactly a low energy house is. There are two intertwining threads to this report. The first is an evaluation of 50 buildings that have been claimed to be low-energy residences, for which monitored energy performance data have been collected. These data represent the preliminary effort in the ongoing update of the Buildings Energy-Use Compilation and Analysis (BECA) data base for new residences. The second thread concerns the definition of a low-energy house. After the elements of a definition are presented, their implications for actors involved in providing housing are identified. Several more tractable definitions are applied to the houses in this compilation. The outcomes illustrate ways in which different interests are served by various definitions. Different definitions can yield very different energy rankings. No single definition of a low-energy house is universally applicable.

  7. Low energy analysis of νN→νNγ in the standard model

    NASA Astrophysics Data System (ADS)

    Hill, Richard J.

    2010-01-01

    The production of single photons in low energy (˜1GeV) neutrino scattering off nucleons is analyzed in the standard model. At very low energies, Eν≪GeV, a simple description of the chiral Lagrangian involving baryons and arbitrary SU(2)L×U(1)Y gauge fields is developed. Extrapolation of the process into the ˜1-2GeV region is treated in a simple phenomenological model. Coherent enhancements in compound nuclei are studied. The relevance of single-photon events as a background to experimental searches for νμ→νe is discussed. In particular, single photons are a plausible explanation for excess events observed by the MiniBooNE experiment.

  8. Hyperspherical hidden crossing calculation of Ps formation in low-energy e+-Na collisions

    NASA Astrophysics Data System (ADS)

    Ward, S. J.; Shertzer, J.

    2011-05-01

    The hyperspherical hidden crossing method (HHCM) can provide important insight into scattering processes. Previously, we have used the HHCM to calculate the Ps(1s)-formation cross section in low-energy e+-H and e+-Li collisions. Here we apply the HHCM to low-energy e+-Na collisions. We use the Peach model potential and treat e+e-Na+ as an effective three-body system. We calculate the Ps(1s)-formation cross sections for 0 <= L <= 3 and compare our results with a hyperspherical close-coupling calculation. The HHCM provides an explanation for the small S-wave Ps(1s)-formation cross section. The S-wave Stückelberg phase is close to π for the three collision systems due to destructive interference between the two amplitudes that correspond to different paths leading to Ps(1s) formation.

  9. Thermal transport in amorphous nanostructures: the (enduring) role of low-energy phonons

    NASA Astrophysics Data System (ADS)

    Underwood, Jason

    2014-03-01

    Micromachined amorphous solid structures have proven to be ideal platforms for physicists to challenge their understanding of phonon transport. Such nanostructures have been exploited for early experimental demonstrations of the quantum of thermal conductance. These structures also serve important technological functions. Amorphous silicon nitride (SiNx) nanostructures, in particular, are increasingly critical to the operation of state-of-the-art low temperature detector arrays. Achieving control over which phonon modes propagate in a given structure -- phononics -- is a major goal for engineering better thermoelectric materials, for regulating heat flow in ever-shrinking microprocessors, and for the developing field of caloritronics. At very low temperatures, it is generally accepted that phonons with energy much lower than the Debye energy (i.e., ω <<1013 Hz) dominate thermal transport. At room temperature, the preponderance of higher energy modes is usually reason enough to assume that the low energy modes do not contribute substantially to the overall thermal conductance. While generally true for crystals, the efficient scattering of high-energy phonons in amorphous solids means that the remaining low-energy modes may acquire comparably long mean free paths. Recent measurements of SiNx nanostructures strongly suggest that this bias in mean free paths leads to the result that low-energy phonons may contribute up to 50% of the overall thermal conductance of the structure -- even at room temperature. After a brief review of thermal transport in the low-energy regime, I will discuss these results, as well as other recent experiments where low-energy phonons play an important role.

  10. Precision measurement of quenching factors for low-energy nuclear recoils at TUNL

    NASA Astrophysics Data System (ADS)

    Rich, Grayson; Barbeau, Phil; Howell, Calvin; Karwowski, Hugon

    2014-03-01

    With detector technologies becoming increasingly sensitive to exotic events, a thorough understanding of signal yield as a function of deposited energy is required for appropriate interpretation of results from cutting edge detector systems. Elastic neutron scattering is a probe which has been used to mimic the nuclear recoils which may be produced in detection media by light-WIMP interactions or coherent neutrino-nucleus scattering (CNS). We have built at the Triangle Universities Nuclear Laboratory (TUNL) a facility which produces pulsed, collimated, low-energy, quasi-monoenergetic neutron beams using the 7Li(p,n) reaction, resulting in fluxes of ~ 1 neutrons / (s . cm2) at ~90 cm from the neutron-production target. The first precision results from this facility are reported for ultra-low-energy recoils in NaI(Tl) and CsI(Na) and future plans are outlined, including measurements on candidate materials for a CNS detector that can potentially be fielded at the Spallation Neutron Source of Oak Ridge National Laboratory as a part the Coherent Scatter Initiative (CSI). We discuss the implications of new, precise measurements of quenching factors on neutrino detectors and on current- and next-generation light-WIMP searches, particularly the DAMA experiment.

  11. A method of imaging ultrathin foils with very low energy electrons.

    PubMed

    Müllerová, Ilona; Hovorka, Miloš; Frank, Luděk

    2012-08-01

    We demonstrate the possibility to examine the free-standing foils of thicknesses in units of nm in the scanning low energy electron microscope, using both reflected and transmitted electrons. Very high contrast has been obtained in dependence on the thickness and structure of the foil. A contribution of secondary electrons to the forward scattered electron signal is discussed and a way of suppressing it is presented. Examples of reflected, total transmitted and dark field transmitted electron signal for two graphene-like samples are shown. Dependence of the transmitted signal on the electron energy is observed. PMID:22326390

  12. Integration of the low-energy particle track simulation code in Geant4

    NASA Astrophysics Data System (ADS)

    Arce, Pedro; Muñoz, Antonio; Moraleda, Montserrat; Gomez Ros, José María; Blanco, Fernando; Perez, José Manuel; García, Gustavo

    2015-08-01

    The Low-Energy Particle Track Simulation code (LEPTS) is a Monte Carlo code developed to simulate the damage caused by radiation at molecular level. The code is based on experimental data of scattering cross sections, both differential and integral, and energy loss data, complemented with theoretical calculations. It covers the interactions of electrons and positrons from energies of 10 keV down to 0.1 eV in different biologically relevant materials. In this article we briefly mention the main characteristics of this code and we present its integration within the Geant4 Monte Carlo toolkit.

  13. Reaction dynamics of F+HD-->HF+D at low energies: Resonant tunneling mechanism

    NASA Astrophysics Data System (ADS)

    Lee, Shih-Huang; Dong, Feng; Liu, Kopin

    2002-05-01

    The complete state-resolved differential cross section σ(v',j',θ;Ec), investigated in a crossed-beam scattering study, is presented for the title reaction at six initial collision energies (Ec) which are below or near the barrier energy. At low energies, all reactive flux is gated through a trapped resonance state via a tunneling process. Hence, it serves as a benchmark system for better understanding the reactive resonance phenomenon. In addition to highlighting various resonance fingerprints of experimental observable, the concept of resonant tunneling reaction mechanism is elucidated. Particular emphasis is placed on its distinction from the more conventional transition-state reaction mechanism.

  14. Past, present and future low energy antiproton facilities at CERN

    NASA Astrophysics Data System (ADS)

    Bartmann, W.; Belochitskii, P.; Breuker, H.; Butin, F.; Carli, C.; Eriksson, T.; Maury, S.; Oelert, W.; Pasinelli, S.; Tranquille, G.

    2014-05-01

    Low energy antiprotons are available for physics experiments at CERN since the 1980s and have been used by a large variety of experiments. The Low Energy Antiproton Ring LEAR has been constructed as a complementary use of antiprotons available at that time for high energy physics and delivered beam to experiments mainly using slow extraction. After completion of LEAR exploitation, the Antiproton Decelerator (AD) was constructed (adaptation of the existing Antiproton Collector, AC) to allow for a simpler low energy antiproton scheme (only one accelerator operated with Antiprotons) with fast extraction well suited for trap experiments. The Extra Low ENergy Antiproton ring ELENA is a small synchrotron presently constructed to further decelerate antiprotons from the AD in a controlled manner, and to reduce emittances with the help of an electron cooler to improve the capture efficiencies of existing experiments and allow for additional ones.

  15. Radial Flux Distribution of Low-Energy Neutrons.

    ERIC Educational Resources Information Center

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  16. Biological assessments for the low energy demonstration accelerator, 1996

    SciTech Connect

    Cross, S.

    1997-03-01

    This report discusses the biological impact to the area around the Los Alamos National Laboratory of the Low Energy Demonstration Accelerator. In particular the impact to the soils, water quality, vegetation, and wildlife are discussed.

  17. Surface Passivation and Junction Formation Using Low Energy Hydrogen Implants

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.

    1985-01-01

    New applications for high current, low energy hydrogen ion implants on single crystal and polycrystal silicon grain boundaries are discussed. The effects of low energy hydrogen ion beams on crystalline Si surfaces are considered. The effect of these beams on bulk defects in crystalline Si is addressed. Specific applications of H+ implants to crystalline Si processing are discussed. In all of the situations reported on, the hydrogen beams were produced using a high current Kaufman ion source.

  18. Potential for luminosity improvement for low-energy RHIC operation with long bunches

    SciTech Connect

    Fedotov, A.; Blaskiewicz, M.

    2012-02-10

    Electron cooling was proposed to increase luminosity of the RHIC collider for heavy ion beams at low energies. Luminosity decreases as the square of bunch intensity due to the beam loss from the RF bucket as a result of the longitudinal intra beam scattering (IBS), as well as due to the transverse emittance growth because of the transverse IBS. Both transverse and longitudinal IBS can be counteracted with electron cooling. This would allow one to keep the initial peak luminosity close to constant throughout the store essentially without the beam loss. In addition, the phase-space density of the hadron beams can be further increased by providing stronger electron cooling. Unfortunately, the defining limitation for low energies in RHIC is expected to be the space charge. Here we explore an idea of additional improvement in luminosity, on top of the one coming from just IBS compensation and longer stores, which may be expected if one can operate with longer bunches at the space-charge limit in a collider. This approach together with electron cooling may result in about 10-fold improvement in total luminosity for low-energy RHIC program.

  19. Apparent Low-Energy Scale Invariance in Two-Dimensional Fermi Gases

    NASA Astrophysics Data System (ADS)

    Taylor, Edward

    2013-05-01

    Strongly-interacting systems in two dimensions have occupied a central position in the study of quantum materials. From high temperature superconductors to the Hall effect in two-dimensional electron gases, strong quantum and thermal fluctuations conspire to make this an extremely rich yet poorly-understood regime to work in. Several remarkable and surprising recent experiments in ultracold atomic gases show us that there are puzzles to be understood even in the simplest nontrivial two-dimensional system: a dilute quantum gas with strong s-wave interactions. Amongst these is an experiment that finds an undamped breathing mode oscillating at twice the trap frequency over a wide range of parameters, behaviour nominally associated with scale invariance, even though scale invariance is strictly broken in this system by a finite s-wave scattering length. This apparent scale symmetry is all the more remarkable given that the mean-field BCS theory for the 2D gas predicts an exact low-energy scale invariance, relevant to the low-energy breathing mode, meaning that only quantum and thermal fluctuations can break this low-energy scale symmetry. Understanding why the symmetry breaking is so weak may give insight into how to make reliable theoretical predictions in systems with strong fluctuation effects, where there is no obvious small parameter from which a perturbation expansion can be formulated. Supported by NSF Grant No. DMR-1006532 (Mohit Randeria), NSERC, and the Canadian Institute for Advanced Research.

  20. Photon Strength and the Low-Energy Enhancement

    SciTech Connect

    Wiedeking, M; Bernstein, L A; Krticka, M; Bleuel, D L; Allmond, J M; Basunia, M S; Burke, J T; Fallon, P; Firestone, R B; Goldblum, B L; Hatarik, R; Lake, P T; Lee, I Y; Lesher, S R; Paschalis, S; Petri, M; Phair, L; Scielzo, N D

    2012-02-22

    The ability of atomic nuclei to emit and absorb photons with energy E{sub {gamma}} is known as the photon strength function f(E{sub {gamma}}). It has direct relevance to astrophysical element formation via neutron capture processes due to its central role in nuclear reactions. Studies of f(E{sub {gamma}}) have benefited from a wealth of data collected in neutron capture and direct reactions but also from newly commissioned inelastic photon scattering facilities. The majority of these experimental methods, however, rely on the use of models because measured {gamma}-ray spectra are simultaneously sensitive to both the nuclear level density and f(E{sub {gamma}}). As excitation energy increases towards the particle separation energies, the level density increases rapidly, creating the quasi-continuum. Nuclear properties in this excitation energy region are best characterized using statistical quantities, such as f(E{sub {gamma}}). A point of contention in studies of the quasi-continuum has been an unexpected and unexplained increase in f(E{sub {gamma}}) at low {gamma}-ray energies (i.e. below E{sub {gamma}} {approx}3 MeV) in a subset of light-to-medium mass nuclei. Ideally, a new model-independent experimental technique is required to address questions regarding the existence and origin of this low-energy enhancement in f(E{sub {gamma}}). Here such a model-independent approach is presented for determining the shape of f(E{sub {gamma}}) over a wide range of energies. The method involves the use of coupled high-resolution particle and {gamma}-ray spectroscopy to determine the emission of {gamma} rays from the quasi-continuum in a nucleus with defined excitation energy to individual discrete levels of known spins and parities. This method shares characteristics of two neutron capture-based techniques: the Average Resonance Capture (ARC) and the Two-Step Cascade analysis (TSC). The power of the new technique lies in the additional ability to positively identify primary

  1. A (e,2e +ion) study of low-energy electron-impact ionization of THF

    NASA Astrophysics Data System (ADS)

    Ali, Esam; Ren, Xueguang; Ning, Chuangang; Dorn, Alexander; Madison, Don

    2015-09-01

    We have investigated the Fully Differential Cross Sections (FDCS) for electron impact induced ionization of THF (C4H8O) by low-energy (Eo = 26 eV) for three different orbital states of the highest, next highest, and next-next highest occupied molecular orbitals (HOMO, NHOMO, and Next NHOMO). Theoretical results are compared with experiment for in plane scattering with projectile scattering angles of 15°, 25°, 35°, and 50°. Different theoretical models are examined - the molecular 3 body distorted wave (M3DW), and the distorted wave Born approximation (DWBA), with the effects of the post collision interaction (PCI) treated either exactly or with the Ward-Macek approximations. This work is supported by the US National Science Foundation under Grant No. PHY-1068237 and XSEDE resources provided by the Texas Advanced Computing Center (Grant No. TG-MCA07S029).

  2. Low-energy parameters of neutron-neutron interaction in the effective-range approximation

    SciTech Connect

    Babenko, V. A.; Petrov, N. M.

    2013-06-15

    The effect of the mass difference between the charged and neutral pions on the low-energy parameters of nucleon-nucleon interaction in the {sup 1}S{sub 0} state is studied in the effective-range approximation. On the basis of experimental values of the singlet parameters of neutron-proton scattering and the experimental value of the virtual-state energy for the neutron-neutron systemin the {sup 1}S{sub 0} state, the following values were obtained for the neutron-neutron scattering length and effective range: a{sub nn} = -16.59(117) fm and r{sub nn} = 2.83(11) fm. The calculated values agree well with present-day experimental results.

  3. Origin of Unexpected Low Energy Structure in Photoelectron Spectra Induced by Midinfrared Strong Laser Fields

    SciTech Connect

    Liu Chengpu; Hatsagortsyan, Karen Z.

    2010-09-10

    Using a semiclassical model which incorporates tunneling and Coulomb field effects, the origin of the low-energy structure (LES) in the above-threshold ionization spectrum observed in recent experiments [Blaga et al., Nature Phys. 5, 335 (2009); Quan et al., Phys. Rev. Lett. 103, 093001 (2009).] is identified. We show that the LES arises due to an interplay between multiple forward scattering of an ionized electron and the electron momentum disturbance by the Coulomb field immediately after the ionization. The multiple forward scattering is mainly responsible for the appearance of LES, while the initial disturbance mainly determines the position of the LES peaks. The scaling laws for the LES parameters, such as the contrast ratio and the maximal energy, versus the laser intensity and wavelength are deduced.

  4. Recent results from the TwinSol low-energy RIB facility

    NASA Astrophysics Data System (ADS)

    Becchetti, F. D.; Kolata, J. J.

    2016-06-01

    We report on some of the recent developments and experimental work done at the twin-solenoid low-energy radioactive-ion-beam (RIB) facility TwinSol installed at the U Notre Dame 10 MV FN tandem accelerator. The TwinSol facility is a joint project of the University of Michigan (UM) and the University of Notre Dame (UND), and includes several U.S. and foreign collaborators. A number of significant experiments including RIB-induced transfer reactions, elastic scattering, resonant scattering, and fusion at energies near and well below the Coulomb barrier have been performed with this facility. Several of these as well as future work and upgrades planned will be described.

  5. Design of low energy bunch compressors with space charge effects

    NASA Astrophysics Data System (ADS)

    He, A.; Willeke, F.; Yu, L. H.; Yang, L.; Shaftan, T.; Wang, G.; Li, Y.; Hidaka, Y.; Qiang, J.

    2015-01-01

    In this paper, we explore a method to manipulate low energy electron bunches in a space charge dominated regime, and we use this method to design low energy linac bunch compressors to compress electron bunches in a space charge dominated regime. In the method, we use the space charge effects instead of avoiding them; i.e., we use the space charge forces to generate the required energy chirp instead of the ordinary method which uses the rf accelerating system to generate the chirp. We redefine the concepts of the dispersion function and beta functions in a space charge dominated regime to guide the optimization. Using this method, we study the low energy (5-22 MeV) linac bunch compressor design to produce short (˜150 fs ) and small size (˜30 μ m ) bunches for the electron beam slicing project. The low energy linac bunch compressors work in a space charge dominated regime, and the bunches at the downstream of the gun have a negative energy chirp due to the space charge effects. To provide compression for the negative energy chirped bunch, we design a positive R56 dispersive section using a four-dipole chicane with several quadrupole magnets. We have designed low energy linac bunch compressors with different photocathode rf guns. For example, one linac bunch compressor with the BNL photocathode electron rf gun has achieved a low energy bunch with the 166 fs rms bunch length, 28 and 31 μ m rms beam size in the vertical and horizontal directions, respectively, at 5 MeV with 50 pC charge. Another example with LBNL's very-high frequency gun has achieved a low energy bunch with the 128 fs rms bunch length, 42 and 25 μ m rms beam size in the vertical and horizontal directions, respectively, at 22 MeV with 200 pC charge.

  6. A G/NARRLI Effort. Measuring the Ionization Yield of Low-Energy Nuclear Recoils in Liquid Argon

    SciTech Connect

    Joshi, Tenzing Henry Yatish

    2014-01-01

    Liquid argon has long been used for particle detection due to its attractive drift properties, ample abundance, and reasonable density. The response of liquid argon to lowenergy O(102 -1044 eV) interactions is, however, largely unexplored. Weakly interacting massive particles such as neutrinos and hypothetical dark-matter particles (WIMPs) are predicted to coherently scatter on atomic nuclei, leaving only an isolated low-energy nuclear recoil as evidence. The response of liquid argon to low-energy nuclear recoils must be studied to determine the sensitivity of liquid argon based detectors to these unobserved interactions. Detectors sensitive to coherent neutrino-nucleus scattering may be used to monitor nuclear reactors from a distance, to detect neutrinos from supernova, and to test the predicted behavior of neutrinos. Additionally, direct detection of hypothetical weakly interacting dark matter would be a large step toward understanding the substance that accounts for nearly 27% of the universe. In this dissertation I discuss a small dual-phase (liquid-gas) argon proportional scintillation counter built to study the low-energy regime and several novel calibration and characterization techniques developed to study the response of liquid argon to low-energy O(102 -104 eV) interactions.

  7. Certification of NIST Room Temperature Low-Energy and High-Energy Charpy Verification Specimens

    PubMed Central

    Lucon, Enrico; McCowan, Chris N.; Santoyo, Ray L.

    2015-01-01

    The possibility for NIST to certify Charpy reference specimens for testing at room temperature (21 °C ± 1 °C) instead of −40 °C was investigated by performing 130 room-temperature tests from five low-energy and four high-energy lots of steel on the three master Charpy machines located in Boulder, CO. The statistical analyses performed show that in most cases the variability of results (i.e., the experimental scatter) is reduced when testing at room temperature. For eight out of the nine lots considered, the observed variability was lower at 21 °C than at −40 °C. The results of this study will allow NIST to satisfy requests for room-temperature Charpy verification specimens that have been received from customers for several years: testing at 21 °C removes from the verification process the operator’s skill in transferring the specimen in a timely fashion from the cooling bath to the impact position, and puts the focus back on the machine performance. For NIST, it also reduces the time and cost for certifying new verification lots. For one of the low-energy lots tested with a C-shaped hammer, we experienced two specimens jamming, which yielded unusually high values of absorbed energy. For both specimens, the signs of jamming were clearly visible. For all the low-energy lots investigated, jamming is slightly more likely to occur at 21 °C than at −40 °C, since at room temperature low-energy samples tend to remain in the test area after impact rather than exiting in the opposite direction of the pendulum swing. In the evaluation of a verification set, any jammed specimen should be removed from the analyses. PMID:26958453

  8. New insights gained on mechanisms of low-energy proton-induced SEUs by minimizing energy straggle

    DOE PAGESBeta

    Dodds, Nathaniel Anson; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Martinez, Marino J.; Black, Jeffrey D.; Marshall, P. W.; Reed, R. A.; McCurdy, M. W.; Weller, R. A.; et al

    2015-12-01

    In this study, we present low-energy proton single-event upset (SEU) data on a 65 nm SOI SRAM whose substrate has been completely removed. Since the protons only had to penetrate a very thin buried oxide layer, these measurements were affected by far less energy loss, energy straggle, flux attrition, and angular scattering than previous datasets. The minimization of these common sources of experimental interference allows more direct interpretation of the data and deeper insight into SEU mechanisms. The results show a strong angular dependence, demonstrate that energy straggle, flux attrition, and angular scattering affect the measured SEU cross sections, andmore » prove that proton direct ionization is the dominant mechanism for low-energy proton-induced SEUs in these circuits.« less

  9. New insights gained on mechanisms of low-energy proton-induced SEUs by minimizing energy straggle

    SciTech Connect

    Dodds, Nathaniel Anson; Dodd, Paul E.; Shaneyfelt, Marty R.; Sexton, Frederick W.; Martinez, Marino J.; Black, Jeffrey D.; Marshall, P. W.; Reed, R. A.; McCurdy, M. W.; Weller, R. A.; Pellish, J. A.; Rodbell, K. P.; Gordon, M. S.

    2015-12-01

    In this study, we present low-energy proton single-event upset (SEU) data on a 65 nm SOI SRAM whose substrate has been completely removed. Since the protons only had to penetrate a very thin buried oxide layer, these measurements were affected by far less energy loss, energy straggle, flux attrition, and angular scattering than previous datasets. The minimization of these common sources of experimental interference allows more direct interpretation of the data and deeper insight into SEU mechanisms. The results show a strong angular dependence, demonstrate that energy straggle, flux attrition, and angular scattering affect the measured SEU cross sections, and prove that proton direct ionization is the dominant mechanism for low-energy proton-induced SEUs in these circuits.

  10. A Compton-Vetoed Germanium Detector with Increased Sensitivity at Low Energies

    SciTech Connect

    Friedrich, S; Bates, C; Drury, O B; Burks, M; DiPrete, D

    2012-03-29

    The difficulty to directly detect plutonium in spent nuclear fuel due to the high Compton background of the fission products motivates the design of a Gamma detector with improved sensitivity at low energies. We have built such a detector by operating a thin high-purity Ge detector with a large scintillator Compton veto directly behind it. The Ge detector is thin to absorb just the low-energy Pu radiation of interest while minimizing Compton scattering of high energy radiation from the fission products. The subsequent scintillator is large so that forward scattered photons from the Ge detector interact in it at least once to provide an anti-coincidence veto for the Ge detector. For highest sensitivity, additional material in the line-of-sight is minimized, the radioactive sample is kept thin, and its radiation is collimated. We will discuss the instrument design, and demonstrate the feasibility of the approach with a prototype that employs two large CsI scintillator vetoes. Initial spectra of a thin Cs-137 calibration source show a background suppression of a factor of {approx}2.5 at {approx}100 keV, limited by an unexpectedly thick 4 mm dead layer in the Ge detector.

  11. Characterization of hydrogen binding to tungsten and beryllium surfaces using low energy ion beam analysis

    NASA Astrophysics Data System (ADS)

    Kolasinski, Robert; Whaley, Josh

    2015-11-01

    In this study, we use low energy ion beam analysis to determine how hydrogen interacts with tungsten and beryllium surfaces. The goal of this work is to provide insight into processes that contribute to recycling from plasma-facing surfaces in magnetic fusion devices. Here we have applied low energy ion scattering (LEIS) to enable detection of adsorbed hydrogen at sub-monolayer resolution and to provide isotopic sensitivity. We probe the surfaces of interest with He + and Ne + at energies less than 5 keV to determine the structure and composition of the first few atomic layers. This approach enables us to examine how hydrogen surface concentrations evolve in real time, providing insight into adsorption kinetics. In addition, we have developed a means of determining the hydrogen binding configuration at different temperatures by exploiting mechanisms of ion channeling along surfaces. Using these methods, we have been able to identify hydrogen binding configurations for the W(100) +H, W(110) +H, and Be(0001) +H adsorption systems. We also report on our efforts to more accurately and efficiently model atomic collisions during scattering, key steps needed to extract structural information from LEIS signals. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Prediction of background in low-energy spectrum of Phoswich detector.

    PubMed

    Arun, B; Manohari, M; Mathiyarasu, R; Rajagopal, V; Jose, M T

    2014-12-01

    In vivo monitoring of actinides in occupational workers is done using Phoswich detector by measuring the low-energy X ray and gamma rays. Quantification of actinides like plutonium and americium in the lungs is extremely difficult due to higher background in the low-energy regions, which is from ambient background as well as from the subject. In the latter case, it is mainly due to the Compton scattering of body potassium, which varies person-to-person. Hence, an accurate prediction of subject-specific background counts in the lower-energy regions is an essential element in the in vivo measurement of plutonium and americium. Empirical equations are established for the prediction of background count rate in (239)Pu and (241)Am lower-energy regions, called 'target regions', as a function of count rate in the monitoring region (97-130 keV)/(40)K region in the high-energy spectrum, weight-to-height ratio of the subject (scattering parameter) and the gender. PMID:24300341

  13. IONS (ANURADHA): Ionization states of low energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Biswas, S.; Chakraborti, R.; Cowsik, R.; Durgaprasad, N.; Kajarekar, P. J.; Singh, R. K.; Vahia, M. N.; Yadav, J. S.; Dutt, N.; Goswami, J. N.

    1987-01-01

    IONS (ANURADHA), the experimental payload designed specifically to determine the ionization states, flux, composition, energy spectra and arrival directions of low energy (10 to 100 MeV/amu) anomalous cosmic ray ions of helium to iron in near-Earth space, had a highly successful flight and operation Spacelab-3 mission. The experiment combines the accuracy of a highly sensitive CR-39 nuclear track detector with active components included in the payload to achieve the experimental objectives. Post-flight analysis of detector calibration pieces placed within the payload indicated no measurable changes in detector response due to its exposure in spacelab environment. Nuclear tracks produced by alpha-particles, oxygen group and Fe ions in low energy anomalous cosmic rays were identified. It is calculated that the main detector has recorded high quality events of about 10,000 alpha-particles and similar number of oxygen group and heavier ions of low energy cosmic rays.

  14. Engaging schools in the science of low-energy buildings.

    PubMed

    Charnley, Fiona; Fleming, Paul; Dowsett, Tony; Fleming, Margaret; Cook, Malcolm; Mill, Greig

    2012-10-01

    This article explores the relationship between the previous UK government's initiative to rebuild and renew secondary schools, and the requirement for improved education for sustainable development in the UK. The documented research utilized a number of mechanisms to engage with pupils in Leicester city schools to increase their awareness, knowledge and understanding of the science and engineering associated with the design and operation of low-energy school buildings. Workshops, discussions with energy and sustainable development experts and inspirational visits to existing low-energy buildings were employed to develop an appreciation for the importance of energy efficiency and best design practice. The results demonstrate an increase in pupils' knowledge and understanding of low-energy school design and additionally a rise in those pupils who are interested in science and would consider it as a career option. PMID:23832564

  15. The problem of low energy particle measurements in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Whipple, E. C., Jr.

    1978-01-01

    The accurate measurement of low energy (less than 100 eV) particle properties in the magnetosphere has been difficult, partly because of the low density of such particles, but more particularly because of spacecraft interference effects. Some early examples of how these phenomena have affected particle measurements on an OGO spacecraft are presented. Data obtained with the UCSD particle detectors on ATS-6 are then presented showing how some of these difficulties have been partially overcome. Future measurements of low energy particles in the magnetosphere can be improved by: (1) improving the low energy resolution of detectors; (2) building electrostatically clean spacecraft; (3) controlling spacecraft potential; and (4) using auxiliary measurements, particularly wave data.

  16. Techniques of absolute low energy x-ray calibration

    SciTech Connect

    Day, R.H.

    1986-01-01

    Recent advances in pulsed plasma research, materials science, and astrophysics have required many new diagnostic instruments for use in the low energy x-ray regime. The characterization of these instruments has provided a challenge to instrument designers and provided the momentum to improve x-ray sources and dosimetry techniques. In this paper, the present state-of-the-art in low energy x-ray characterization techniques is reviewed. A summary is given of low energy x-ray generator technology and dosimetry techniques including a discussion of thin window proportional counters and ionization chambers. A review is included of the widely used x-ray data bases and a sample of ultrasoft x-ray measuring procedures, chopped x-ray source generators, phase sensitive detection of ultralow currents, and angular divergence measurements.

  17. Evolution of the Crab Nebula in a Low Energy Supernova

    NASA Astrophysics Data System (ADS)

    Yang, Haifeng; Chevalier, Roger A.

    2015-06-01

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼1050 erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  18. Low-energy physics of high-temperature superconductors

    SciTech Connect

    Emery, V.J. . Physics Dept.); Kivelson, S.A. . Dept. of Physics)

    1992-01-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the universality'' of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter.

  19. Low-energy physics of high-temperature superconductors

    SciTech Connect

    Emery, V.J.; Kivelson, S.A.

    1992-09-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the ``universality`` of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter.

  20. Coulomb effects in low-energy nuclear fragmentation

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Chun, Sang Y.; Badavi, Francis F.; John, Sarah

    1993-01-01

    Early versions of the Langley nuclear fragmentation code NUCFRAG (and a publicly released version called HZEFRG1) assumed straight-line trajectories throughout the interaction. As a consequence, NUCFRAG and HZEFRG1 give unrealistic cross sections for large mass removal from the projectile and target at low energies. A correction for the distortion of the trajectory by the nuclear Coulomb fields is used to derive fragmentation cross sections. A simple energy-loss term is applied to estimate the energy downshifts that greatly alter the Coulomb trajectory at low energy. The results, which are far more realistic than prior versions of the code, should provide the data base for future transport calculations. The systematic behavior of charge-removal cross sections compares favorably with results from low-energy experiments.

  1. Light element production by low energy nuclei from massive stars

    NASA Technical Reports Server (NTRS)

    Vangioni-Flam, E.; Casse, M.; Ramaty, R.

    1997-01-01

    The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

  2. Low energy particle composition. [cosmic rays produced in solar system

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1975-01-01

    A review is given of current knowledge of low-energy cosmic ray particles produced in the solar system. It is argued that the notion that the sun alone can accelerate particles in the solar system must be abandoned in light of evidence that Jupiter and earth may be sources of observed low-energy particles. Measurements of the composition and energy spectra of low-energy particles during quiet times are examined, emphasizing the abundance of protons and helium and of anomalous N, O, and Ne. The abundance of heavy particles (B, C, N, O, Ne, Ca and Fe) of unknown origin in the earth magnetosphere is examined. Reported observations of Jovian electrons are discussed and solar particle events with anomalous compositions (He-3 rich events and Fe rich events) are treated in detail. Nuclear abundances of solar particles, emphasizing their temporal and spatial variations are considered together with the nature of nuclear reaction products in solar flares.

  3. Feasibility of Electron Cooling for Low-Energy RHIC Operation

    SciTech Connect

    Fedotov,A.; Ben-Zvi, I.; Chang, X.; Kayran, D.; Litvinenko, V.; Pozdeyev, E.; Satogata, T.

    2008-04-01

    A concrete interest in running RHIC at low energies in a range of 2.5-25 GeV/nucleon total energy of a single beam has recently emerged. Providing collisions in this energy range, which in the RHIC case is termed 'low-energy' operation, will help to answer one of the key questions in the field of QCD about existence and location of a critical point on the QCD phase diagram. However, luminosity projections are relatively low for the lowest energy points of interest. Luminosity improvement can be provided with electron cooling applied directly in RHIC at low energies. This report summarizes the expected luminosity improvement with electron cooling, possible technical approaches and various limitations.

  4. A New HOM Water Cooled Absorber for the PEP-II B-factory Low Energy Ring

    SciTech Connect

    Weathersby, Stephen; Kosovsky, Michael; Kurita, Nadine; Novokhatski, Alexander; Seeman, John; /SLAC

    2006-09-05

    At high currents and small bunch lengths beam line components in the PEP-II B-factory experience RF induced heating from higher order RF modes (HOMs) produced by scattered intense beam fields. A design for a passive HOM water cooled absorber for the PEP-II low energy ring is presented. This device is situated near HOM producing beamline components such as collimators and provide HOM damping for dipole and quadrupole modes without impacting beam impedance. We optimized the impedance characteristics of the device through the evaluation of absorber effectiveness for specific modes using scattering parameter and wakefield analysis. Operational results are presented and agree very well with the predicted effectiveness.

  5. Strong flux of low-energy neutrons produced by thunderstorms.

    PubMed

    Gurevich, A V; Antonova, V P; Chubenko, A P; Karashtin, A N; Mitko, G G; Ptitsyn, M O; Ryabov, V A; Shepetov, A L; Shlyugaev, Yu V; Vildanova, L I; Zybin, K P

    2012-03-23

    We report here for the first time about the registration of an extraordinary high flux of low-energy neutrons generated during thunderstorms. The measured neutron count rate enhancements are directly connected with thunderstorm discharges. The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed. PMID:22540588

  6. Modelling low energy electron and positron tracks for biomedical applications

    NASA Astrophysics Data System (ADS)

    Sanz, A. G.; Fuss, M. C.; Roldán, A. M.; Oller, J. C.; Blanco, F.; Limão-Vieira, P.; Brunger, M. J.; Buckman, S. J.; García, G.

    2012-11-01

    In order to incorporate the effect of low energy electrons and positron in radiation damage models, the simulation method proposed here is based on experimental and theoretical cross section data and energy loss spectra we have previously derived. After a summary of the main techniques used to obtain reliable input data, the basis of a Low Energy Particle Track Simulation (LEPTS) procedure is established. Single electron and positron tracks in liquid water are presented and the possibility of using these results to develop tools for nanodosimetry is discussed.

  7. Techniques and methods for the low-energy neutrino detection

    NASA Astrophysics Data System (ADS)

    Ranucci, Gioacchino

    2016-04-01

    Low-energy neutrino physics and astrophysics has been one of the most active field of particle physics research over the past two decades, achieving important and sometimes unexpected results, which have paved the way for a bright future of further exciting studies. The methods, the techniques and the technologies employed for the construction of the many experiments which acted as important players in this area of investigation have been crucial elements to reach the many accumulated physics successes. The topic covered in this review is, thus, the description of the main features of the set of methodologies at the basis of the design, construction and operation of low-energy neutrino detectors.

  8. Low energy antiprotons from supernova exploding in dense clouds

    NASA Technical Reports Server (NTRS)

    Stephens, S. A.; Mauger, B. G.

    1984-01-01

    The antiproton spectrum resulting from a supernova, which exploded inside a dense cloud, is calculated by taking into account all energy loss processes including adiabatic deceleration during the expansion phase. The influence of various energy loss processes on the evolution of the spectrum as the supernova expands is investigated. It is shown that if about 25 percent of the cosmic ray nucleons are from such sources, the observed low energy antiprotons can be explained, provided the effect of solar modulation is not very large. The possibility of obtaining enhanced low energy spectrum by this process is also examined.

  9. A FORTRAN-90 Low-Energy Electron Diffraction program (LEED90 v1.1)

    NASA Astrophysics Data System (ADS)

    Blanco-Rey, Maria; de Andres, Pedro; Held, Georg; King, David A.

    2004-08-01

    We describe a FORTRAN-90 program to compute low-energy electron diffraction I(V) curves. Plane-waves and layer doubling are used to compute the inter-layer multiple-scattering, while the intra-layer multiple-scattering is computed in the standard way expanding the wavefield on a basis of spherical waves. The program is kept as general as possible, in order to allow testing different parts of multiple-scattering calculations. In particular, it can handle non-diagonal t-matrices describing the scattering of non-spherical potentials, anisotropic vibrations, anharmonicity, etc. The program does not use old FORTRAN flavours, and has been written keeping in mind the advantage for parallelism brought forward by FORTRAN-90. Program summaryTitle of program: LEED90 Catalogue number: ADUE Program summary URL:http://cpc.sc.qub.ac.uk/summaries/ADUE Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland. Computers: Alpha ev6-21264 (700 MHz) and Pentium-IV. Operating system: Digital UNIX V5.0 and Linux (Red Hat 8.0). Programming language: FORTRAN-90/95 (Compaq True64 compiler, and Intel Fortran Compiler 7.0 for Linux). High-speed storage required for the test run: minimum 64 Mbytes, it can grow to more depending on the system considered. Disk storage required: None No. of bits in a word: 64 and 32 No. of lines in distributed program, including test data, etc.: 17 953 No. of bytes in distributed program, including test data, etc.: 100 051 Distribution format: tar.gz Nature of problem: We describe the FORTRAN-90 program LEED90 (v1.1) to compute dynamical I(V) curves using layer-doubling. The program has been designed to be able to take, as an option, input from non-diagonal t-matrix, e.g., representing a molecule, temperature corrections for anisotropic/anharmonic vibrations, or non-spherical muffin-tin potentials. Method of solution: The intra-layer multiple-scattering problem is solved by adding self-consistently spherical wave amplitudes

  10. The low-energy ion range in DNA.

    PubMed

    Yu, L D; Kamwanna, T; Brown, I G

    2009-08-21

    In fundamental studies of low-energy ion irradiation effects on DNA, calculation of the low-energy ion range, an important basic physical parameter, is often necessary. However, up to now a unified model and approach for range calculation is still lacking, and reported data are quite divergent and thus unreliable. Here we describe an approach for calculation of the ion range, using a simplified mean-pseudoatom model of the DNA target. Based on ion stopping theory, for the case of low-energy (< or = a few keV) ion implantation into DNA, the stopping falls in the low reduced energy regime, which gives a cube-root energy dependence of the stopping (E(1/3)). Calculation formulas of the ion range in DNA are obtained and presented to unify the relevant calculations. The upper limits of the ion energy as a function of the atomic number of the bombarding ion species are proposed for the low-energy case to hold. Comparison of the results of this approach with the results of some widely used computer simulation codes and with results reported by other groups indicates that the approach described here provides convincing and dependable results. PMID:19652287

  11. Nuclear phenomena in low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B

    2013-09-01

    This is a comment on Storms E (2010) Status of Cold Fusion, Naturwissenschaften 97:861-881. This comment provides the following remarks to other nuclear phenomena observed in low-energy nuclear reactions aside from helium-4 make significant contributions to the overall energy balance; and normal hydrogen, not just heavy hydrogen, produces excess heat. PMID:23949247

  12. MEIC Proton Beam Formation with a Low Energy Linac

    SciTech Connect

    Zhang, Yuhong

    2015-09-01

    The MEIC proton and ion beams are generated, accumulated, accelerated and cooled in a new green-field ion injector complex designed specifically to support its high luminosity goal. This injector consists of sources, a linac and a small booster ring. In this paper we explore feasibility of a short ion linac that injects low-energy protons and ions into the booster ring.

  13. Physics overview of the Fermilab Low Energy Antiproton Facility Workshop

    SciTech Connect

    Chanowitz, M.S.

    1986-05-01

    A physics overview is presented of the Fermilab workshop to consider a possible high flux, low energy antiproton facility that would use cooled antiprotons from the accumulator ring of the Tevatron collider. Two examples illustrate the power of each a facility to produce narrow states at high rates. Physics topics to which such a facility may be applied are reviewed.

  14. Procuring low-energy design and consulting services

    SciTech Connect

    1997-07-01

    This report presents information which aids in the design of low energy building elements. The proven strategies can dramatically reduce a building`s energy consumption for little or no added cost while improving it`s comfort, economy, and environmental performance.

  15. HEAO-1 analysis of Low Energy Detectors (LED)

    NASA Technical Reports Server (NTRS)

    Nousek, John A.

    1992-01-01

    The activities at Penn State University are described. During the period Oct. 1990 to Dec. 1991 work on HEAO-1 analysis of the Low Energy Detectors (LED) concentrated on using the improved detector spectral simulation model and fitting diffuse x-ray background spectral data. Spectral fitting results, x-ray point sources, and diffuse x-ray sources are described.

  16. Isotopic fractionation in low-energy ion implantation

    NASA Astrophysics Data System (ADS)

    Ponganis, K. V.; Graf, T.; Marti, K.

    1997-08-01

    The evolutions of planetary atmospheres and other solar system reservoirs have been affected by a variety of fractionating mechanisms. It has been suggested that one of these mechanisms could be low-energy ion implantation. Bernatowicz and Hagee [1987] showed that Kr and Xe implanted at low energy onto tungsten are fractionated by approximately 1% per amu, favoring the heavy isotopes; we confirm these effects. We have extended these studies to Ar and Ne, using a modified Bayard-Alpert type implanter design of cylindrical symmetry with collector potentials of -40 to -100V, and observe systematically larger mass dependent isotopic fractionation for argon and neon, >=3% per amu and >=4% per amu, respectively. These fractionations scale approximately as Δm/m for all of the noble gases measured, consistent with the findings of Bernatowicz and coworkers. Experimental data at higher energies and predictions by TRIM (Transport of Ions in Matter) code simulations indicate that sticking probabilities may depend upon the mass ratios of projectile and target. Many natural environments for low-energy ion implantation existed in the early solar nebula, such as in dusty plasmas or in the interaction of the bipolar outflow with small grains or in the wind of the early active Sun with accreting planetesimals. Low-energy ions provide viable sources for gas loading onto nebular dust grains; the result is isotopic and elemental fractionation of the projectiles.

  17. Hadronic Interactions from Lattice QCD

    SciTech Connect

    Konstantinos Orginos

    2006-03-19

    In this talk I discuss a few recent results on lattice calculations of scattering lengths in hadronic processes. In particular, I present the scattering length of the pion-pion scattering in the I=2 channel and the nucleon-nucleon {sup 1}S{sub 0} channel and {sup 3}S{sub 1}-{sup 3}D{sub 1} coupled channels.

  18. Effective field theories in the study of KAON(LONG) TO PION+ PION- POSITRON ELECTRON and heavy quark fragmentation

    NASA Astrophysics Data System (ADS)

    Elwood, John Kenneth

    1997-03-01

    This thesis examines several situations in which effective field theories may be used to generate perturbative predictions for nonperturbative phenomena. The decay mode K-long to Pi(plus) Pi(minus) e(plus) e(minus) is analyzed in great detail using chiral perturbation theory, and the form factors for the decay are determined, along with the sizes of various CP violating observables. One of these variables turns out to be quite sizeable, approaching 20% for appropriate cuts on the lepton pair invariant mass. Fragmentation of a c quark to the excited charmed baryon doublet Lambda- c(*) is also studied within the framework of a chiral theory, and various decay distributions are expressed in terms of nonperturbative fragmentation parameters. A perturbative calculation of related fragmentation parameters is also briefly discussed.

  19. Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

    SciTech Connect

    Butorin, S.M.; Guo, J.; Magnuson, M.

    1997-04-01

    Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.

  20. Low-energy universality and scaling of van der Waals forces

    SciTech Connect

    Calle Cordon, A.; Ruiz Arriola, E.

    2010-04-15

    At long distances, interactions between neutral ground-state atoms can be described by the van der Waals potential. In the ultracold regime, atom-atom scattering is dominated by s-waves phase shifts given by an effective range expansion in terms of the scattering length {alpha}{sub 0} and the effective range r{sub 0}. We show that while the scattering length cannot be predicted for these potentials, the effective range is given by the universal low-energy theorem r{sub 0}=A+B/{alpha}{sub 0}+C/{alpha}{sub 0}{sup 2}, where A, B, and C depend on the dispersion coefficients C{sub n} and the reduced diatom mass. We confront this formula to about 100 determinations of r{sub 0} and {alpha}{sub 0} and show why the result is dominated by the leading dispersion coefficient C{sub 6}. Universality and scaling extend much beyond naive dimensional analysis estimates.

  1. Elastic cross sections for low-energy electron collisions with tetrahydropyran

    NASA Astrophysics Data System (ADS)

    Souza Barbosa, Alessandra; Bettega, Márcio H. F.

    2016-02-01

    We report on calculated elastic cross sections for low-energy electron collisions with the cyclic ether tetrahydropyran (C5H10O). The calculations were carried out with the Schwinger multichannel method implemented with norm-conserving pseudopotentials in the static-exchange-polarization approximation for energies up to 20 eV. Our cross sections are compared with previous results obtained for cyclohexane and 1,4-dioxane, since the three molecules present similar structures. The calculated differential cross sections for these three molecules present similarities, except at low scattering angles, where the differential cross sections of tetrahydropyran present a sharp increase due to the permanent dipole moment of the molecule. The similarities observed in the cross sections reveal that the molecular geometry plays an important role in the description of scattering process. We also compared our calculated elastic integral cross section for tetrahydropyran with experimental total cross sections data available in the literature and found a good qualitative agreement between both results. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  2. Numerical simulations for width fluctuations in compound elastic and inelastic scattering at low energies

    SciTech Connect

    Kawano, Toshihiko; Talou, Patrick

    2012-09-18

    The statistical theories - the Hauser-Feshbach model with the width fluctuation correction - play a central role in studying nuclear reactions in the fast energy region, hence the statistical model codes are essential for the nuclear data evaluations nowadays. In this paper, we revisit issues regarding the statistical model calculations in the fast energy range, such as the inclusion of the direct channels, and the energy averaged cross sections using different statistical assumptions. Although they have been discussed for a long time, we need more precise quantitative investigations to understand uncertainties coming from the models deficiencies in the fast energy range. For example, the partition of compound formation cross section into the elastic and inelastic channels depends on the elastic enhancement factor calculated from the statistical models. In addition, unitarity of S-matrix constrains this partition when the direct reactions are involved. Practically some simple assumptions, which many nuclear reaction model codes adopt, may work reasonably for the nuclear data evaluations. However, the uncertainties on the evaluated cross sections cannot go lower than the model uncertainty itself. We perform numerical simulations by generating the resonances using the R-matrix theory, and compare the energy (ensemble) averaged cross sections with the statistical theories, such as the theories of Moldauer, HRTW (Hofmann, Richert, Tepel, and Weidenmueller), KKM (Kawai-Kerman-McVoy), and GOE (Gaussian orthogonal ensemble).

  3. Low-energy electron elastic scattering from Mn, Cu, Zn, Ni, Ag, and Cd atoms

    SciTech Connect

    Felfli, Z.; Msezane, A. Z.; Sokolovski, D.

    2011-05-15

    Electron elastic total cross sections (TCSs) for ground and excited Mn, Cu, Zn, Ni, Ag, and Cd atoms have been investigated in the electron-impact energy range 0 {<=}E{<=} 1 eV. The near-threshold TCSs for both the ground and excited states of these atoms are found to be characterized by Ramsauer-Townsend minima, shape resonances, and extremely sharp resonances corresponding to the formation of stable bound negative ions. The recently developed Regge-pole methodology where the crucial electron-electron correlations are embedded is employed for the calculations. From close scrutiny of the imaginary parts of the complex angular momenta, we conclude that these atoms form stable weakly bound ground and excited negative ions as Regge resonances through slow electron collisions. The extracted electron binding energies from the elastic TCSs of these atoms are contrasted with the available experimental and theoretical values.

  4. Measuring Neutron-Proton Radiative Capture Cross-section at Low Energy

    NASA Astrophysics Data System (ADS)

    Yu, To Chin; Kovash, Michael; Matthews, June; Yang, Hongwei; Yang, Yunjie

    2015-10-01

    The experiment aims to fill in a gap in our data for the cross-section of neutron-proton radiative capture (p(n,d γ)) at energies below 500 keV. Current measurements in this energy range are scarce and inconsistent with theoretical predictions and with each other. A well-determined cross-section of the capture reaction in the low energy range is useful in nuclear physics due to its fundamental nature. The measurement is also of interest in cosmology. Big Bang Nucleosynthesis (BBN), the process by which light elements are formed in early universe, is very sensitive to the p(n,d γ) cross-section in the low energy range. The measurement enables us to put tighter constraints on the theoretical predictions of BBN. We have conducted preliminary measurements in the van de Graaff accelerator facility at the University of Kentucky. Our array of detectors consists of three plastic scintillators to serve as proton targets and deuteron detectors, and five BGO scintillators to detect γ-rays. The combination results in an over-determination of reaction kinematics that discriminates against scattering processes and other backgrounds. We have obtained some early results which show promise for the precise measurement of the p(n,d γ) cross-section.

  5. Extending ion-track lithography to the low-energy ion regime

    SciTech Connect

    Musket, R.G.

    2006-06-01

    Ion tracking and ion-track lithography have been performed almost exclusively using ions with energies near or above the maximum in electronic stopping, which occurs at {approx}1 MeV/amu. In this paper, ion-track lithography using ions with energies well below this maximum is discussed. The results of etching ion tracks created in polycarbonate films by ions with energies just above the anticipated threshold for creating etchable latent tracks with cylindrical geometry have been examined. Low-energy neon and argon ions with 18-60 keV/amu and fluences of {approx}10{sup 8} cm{sup -2} were used to examine the limits for producing useful, etchable tracks in polycarbonate films. By concentrating on the early stages of etching (i.e., {approx}20 nmscattering events were calculated to assess their importance as a function of ion energy. All these results have significant implications with respect to the threshold for formation of etchable tracks and to the use of low-energy ions for lithographic applications of ion tracking.

  6. Extending ion-track lithography to the low-energy ion regime

    SciTech Connect

    Musket, R G

    2005-10-14

    Ion tracking and ion-track lithography have been performed almost exclusively using ions with energies near or above the maximum in electronic stopping, which occurs at {approx}1 MeV/amu. In this paper, ion-track lithography using ions with energies well below this maximum is discussed. The results of etching ion tracks created in polycarbonate films by ions with energies just above the anticipated threshold for creating etchable latent tracks with cylindrical geometry have been examined. Low-energy neon and argon ions with 18-60 keV/amu and fluences of {approx}10{sup 8}/cm{sup 2} were used to examine the limits for producing useful, etchable tracks in polycarbonate films. By concentrating on the early stages of etching (i.e., {approx}20 nm < SEM hole diameter < {approx}100 nm), the energy deposition calculated for the incident ion was correlated with the creation of etchable tracks. The experimental results are discussed with regard to the energy losses of the ions in the polycarbonate films and to the formation of continuous latent tracks through the entire thickness of the films. The probability distributions for large-angle scattering events were calculated to assess their importance as a function of ion energy. All these results have significant implications with respect to the threshold for formation of etchable tracks and to the use of low-energy ions for lithographic applications of ion tracking.

  7. A feasibility study of beam-chopping at low energy for LANSCE

    SciTech Connect

    Tai-Sen Wang; Channell, P.J.; Mottershead, C.T.

    1996-10-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). If a beam-chopping system could be developed for the Los Alamos Meson Physics Facility low-energy beam line, there would be potential to operate the Los Alamos Neutron Scattering Center (LANSCE) at much higher power and duty factor and enable such operation with a radio-frequency quadrapole (RFQ) injector. This would greatly extend the capability of the facility. To accommodate LANSCE operation in the new configuration, a chopped beam must be created in the low-energy transport line before the RFQ. Chopping in this region has never been demonstrated and constitutes the major uncertainty of the proposal and determines the critical path for project completion. This study produces a better understanding of the physics involved in chopping an H-beam in a dilute plasma background, and in transporting a chopped H-beam through a neutralized or partially neutralized plasma channel, as well as an estimate for the optimum neutralization strategy for the beam chopping and transport between the ion source and the RFQ.

  8. Laser pulse duration dependence of the low-energy structure in strong field ionization

    NASA Astrophysics Data System (ADS)

    Lai, Yu Hang; Zhang, Kaikai; Blaga, Cosmin; Xu, Junliang; Agostini, Pierre; Dimauro, Louis; Schmidt, Bruno; Légaré, François; The Ohio State University Team; Institut National de la Recherche Scientifique Team

    2015-05-01

    Low-energy structure (LES) in strong field ionization is a spike-like feature appearing in the low energy part (a few eV) of photoelectron spectra along the laser polarization. It has been observed in rare gas atoms and diatomic molecules. In the classical picture, the formation of LES is due to the Coulomb interaction between the ionized electron and its parent ion via the process of multiple forward scattering, which can happen only if the electron is ionized with a small drift momentum. We have studied the LES in rare gas atoms with few-cycle laser pulses centered at 1800nm. We observed that the LES peak shifts to lower energy as the pulse duration decreases from 5 down to 2 optical cycles, which is in qualitative agreement with classical-trajectory Monte Carlo simulations. Classically, the shift could be attributed to the dependence of the ratio between the field amplitude of the central cycle and the adjacent cycle on the pulse duration. Our data support the classical nature of the LES.

  9. Polycrystalline neutron scattering for Geant4: NXSG4

    NASA Astrophysics Data System (ADS)

    Kittelmann, T.; Boin, M.

    2015-04-01

    An extension to Geant4 based on the nxs library is presented. It has been implemented in order to include effects of low-energy neutron scattering in polycrystalline materials, and is made available to the scientific community.

  10. Low-energy proton increases associated with interplanetary shock waves.

    NASA Technical Reports Server (NTRS)

    Palmeira, R. A. R.; Allum, F. R.; Rao, U. R.

    1971-01-01

    Impulsive increases in the low energy proton flux observed by the Explorer 34 satellite, in very close time association with geomagnetic storm sudden commencements are described. It is shown that these events are of short duration (20-30 min) and occur only during the decay phase of a solar cosmic-ray flare event. The differential energy spectrum and the angular distribution of the direction of arrival of the particles are discussed. Two similar increases observed far away from the earth by the Pioneer 7 and 8 deep-space probes are also presented. These impulsive increases are compared with Energetic Storm Particle events and their similarities and differences are discussed. A model is suggested to explain these increases, based on the sweeping and trapping of low energy cosmic rays of solar origin by the advancing shock front responsible for the sudden commencement detected on the earth.

  11. Integrated control system for low-energy buildings

    SciTech Connect

    Lute, P.J.; van Paassen, D.H.C. )

    1990-01-01

    This paper presents a proposal for an integrated system for the control of lighting, ventilation, and indoor temperature of low-energy buildings. It also presents results of simulations with the proposed control system. The low energy consumption is achieved by using the outdoor climate as much as possible. The building has components, such as shading devices and ventilation windows., to regulate the influence of the outdoor climate on the indoor climate. These components have to be controlled to achieve an acceptable indoor climate throughout the year. Simulations have been done for two types of climate, moderate (Uccle, Belgium) and warm (Carpentras, France). The proposed integrated control system is compared with an on/off control system. The conclusion is that the integrated control system saves energy and provides a good indoor climate. In moderate climates, this can almost be achieved with only passive components. In warmer climates, overheating occurs during the summer because of the outdoor climate.

  12. Steering continuum electron dynamics by low-energy attosecond streaking

    NASA Astrophysics Data System (ADS)

    Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

    2016-08-01

    A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

  13. Three dimensional calculation of flux of low energy atmospheric neutrinos

    NASA Technical Reports Server (NTRS)

    Lee, H.; Bludman, S. A.

    1985-01-01

    Results of three-dimensional Monte Carlo calculation of low energy flux of atmospheric neutrinos are presented and compared with earlier one-dimensional calculations 1,2 valid at higher neutrino energies. These low energy neutrinos are the atmospheric background in searching for neutrinos from astrophysical sources. Primary cosmic rays produce the neutrino flux peaking at near E sub=40 MeV and neutrino intensity peaking near E sub v=100 MeV. Because such neutrinos typically deviate by 20 approximately 30 from the primary cosmic ray direction, three-dimensional effects are important for the search of atmospheric neutrinos. Nevertheless, the background of these atmospheric neutrinos is negligible for the detection of solar and supernova neutrinos.

  14. Low-energy particle population. [in Jupiter magnetosphere

    NASA Technical Reports Server (NTRS)

    Krimigis, S. M.; Roelof, E. C.

    1983-01-01

    A review is conducted of the measurements of the intensities, energy spectra, angular variations, and composition characteristics of the low-energy ion population in and around the Jovian magnetosphere, taking into account data obtained by both Voyager spacecraft. A description is provided of some novel analysis techniques which have been employed to generate density, pressure, composition, and plasma flow profiles in the magnetosphere. The obtained results are compared with data reported in connection with other investigations related to the spacecraft. Attention is given to the Low-Energy Charged Particle investigation, the Voyager 1 and 2 trajectories within 1000 Jupiter radii, and a hot plasma model of the Jovian magnetosphere. The measurement of hot multispecies convected plasmas using energetic particle detectors is also discussed.

  15. Surface modification using low energy ground state ion beams

    NASA Technical Reports Server (NTRS)

    Chutjian, Ara (Inventor); Hecht, Michael H. (Inventor); Orient, Otto J. (Inventor)

    1990-01-01

    A method of effecting modifications at the surfaces of materials using low energy ion beams of known quantum state, purity, flux, and energy is presented. The ion beam is obtained by bombarding ion-generating molecules with electrons which are also at low energy. The electrons used to bombard the ion generating molecules are separated from the ions thus obtained and the ion beam is directed at the material surface to be modified. Depending on the type of ion generating molecules used, different ions can be obtained for different types of surface modifications such as oxidation and diamond film formation. One area of application is in the manufacture of semiconductor devices from semiconductor wafers.

  16. HIGH POWER OPERATIONS AT THE LOW ENERGY DEMONSTRATION ACCELERATOR (LEDA)

    SciTech Connect

    M. DURAN; V. R. HARRIS

    2001-01-01

    Recently, the Low-Energy Demonstration Accelerator (LEDA) portion of the Accelerator Production of Tritium (APT) project reached its 100-mA, 8-hr continuous wave (CW) beam operation milestone. The LEDA accelerator is a prototype of the low-energy front-end of the linear accelerator (linac) that would have been used in an APT plant. LEDA consists of a 75-keV proton injector, 6.7-MeV, 350-MHz CW radio-frequency quadrupole (RFQ) with associated high-power and low-level RF systems, a short high-energy beam transport (HEBT) and high-power (670-kW CW) beam dump. Details of the LEDA design features will be discussed along with the operational health physics experiences that occurred during the LEDA commissioning phase.

  17. Developments in low energy electron beam machinery and processes

    NASA Astrophysics Data System (ADS)

    Nablo, S. V.; Chrusciel, J.; Cleghorn, D. A.; Rangwalla, I.

    2003-08-01

    The engineering and development of a new generation of low energy, high power electron beam equipment is presented. Operating voltages range from 80 to 125 kV at widths to 1.65 m. At 110 kV these systems deliver 1000 Mrad m min -1 at 110 kV. Equipment operating power levels and their impact on reducing equipment size and cost are reviewed. The advantages of electron curing at these reduced operating voltages are described. The principles of the electron beam fluidized bed process for the treatment of powders and particulates in high-speed pneumatic transport are discussed. Typical system performances for polymer dissociation and crosslinking, or for agroproduct disinfestation and disinfection are presented. A process for the sterilization of polymer food containers employing the injection of low energy electrons through the open mouth has been developed. Some of its sterilization capabilities for bottles up to 2 l capacity are described.

  18. Surface conversion techniques for low energy neutral atom imagers

    NASA Technical Reports Server (NTRS)

    Quinn, J. M.

    1995-01-01

    This investigation has focused on development of key technology elements for low energy neutral atom imaging. More specifically, we have investigated the conversion of low energy neutral atoms to negatively charged ions upon reflection from specially prepared surfaces. This 'surface conversion' technique appears to offer a unique capability of detecting, and thus imaging, neutral atoms at energies of 0.01 - 1 keV with high enough efficiencies to make practical its application to low energy neutral atom imaging in space. Such imaging offers the opportunity to obtain the first instantaneous global maps of macroscopic plasma features and their temporal variation. Through previous in situ plasma measurements, we have a statistical picture of large scale morphology and local measurements of dynamic processes. However, with in situ techniques it is impossible to characterize or understand many of the global plasma transport and energization processes. A series of global plasma images would greatly advance our understanding of these processes and would provide the context for interpreting previous and future in situ measurements. Fast neutral atoms, created from ions that are neutralized in collisions with exospheric neutrals, offer the means for remotely imaging plasma populations. Energy and mass analysis of these neutrals provides critical information about the source plasma distribution. The flux of neutral atoms available for imaging depends upon a convolution of the ambient plasma distribution with the charge exchange cross section for the background neutral population. Some of the highest signals are at relatively low energies (well below 1 keV). This energy range also includes some of the most important plasma populations to be imaged, for example the base of the cleft ion fountain.

  19. Exchange and relaxation effects in low-energy radiationless transitions

    NASA Technical Reports Server (NTRS)

    Chen, M. H.; Crasemann, B.; Aoyagi, M.; Mark, H.

    1978-01-01

    The effect on low-energy atomic inner-shell Coster-Kronig and super Coster-Kronig transitions that is produced by relaxation and by exchange between the continuum electron and bound electrons was examined and illustrated by specific calculations for transitions that deexcite the 3p vacancy state of Zn. Taking exchange and relaxation into account is found to reduce, but not to eliminate, the discrepancies between theoretical rates and measurements.

  20. Exotic low-energy separation in 1D quantum liquids

    SciTech Connect

    Carmelo, J.M.P.; Neto, A.H.C.; Campbell, D.K.

    1995-05-01

    We define the low-energy separation of the Hubbard chain in a magnetic field and chemical potential in terms of two {open_quotes}c{close_quotes} and {open_quotes}s{close_quotes} bosonic algebras. This generalizes the usual charge-spin separation, which is recovered in the limit of zero magnetization only. The corresponding pseudoparticle bosonization follows directly from the perturbative character of the pseudoparticle operator basis.

  1. Low energy cosmic ray studies from a lunar base

    NASA Technical Reports Server (NTRS)

    Wiedenbeck, Mark E.

    1990-01-01

    Studies of cosmic ray nuclei with energies less than about 7 GeV/nucleon in low earth orbit are hampered by the geomagnetic field. Even in high inclination orbits these effects can be significant. The lunar surface (or lunar orbit) provides an attractive site for carrying out low energy cosmic ray studies which require large detectors. The rationale and requirements for this type of experiment are described.

  2. Overview of Light Hydrogen-Based Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Miley, George H.; Shrestha, Prajakti J.

    This paper reviews light water and hydrogen-based low-energy nuclear reactions (LENRs) including the different methodologies used to study these reactions and the results obtained. Reports of excess heat production, transmutation reactions, and nuclear radiation emission are cited. An aim of this review is to present a summary of the present status of light water LENR research and provide some insight into where this research is heading.

  3. Heavy Meson Production at a Low-Energy Photon Collider

    SciTech Connect

    Asztalos, S

    2004-04-15

    A low-energy {gamma}{gamma} collider has been discussed in the context of a testbed for a {gamma}{gamma} interaction region at the Next Linear Collider(NLC). We consider the production of heavy mesons at such a testbed using Compton-backscattered photons and demonstrate that their production rivals or exceeds those by BELLE, BABAR or LEP where they are produced indirectly via virtual {gamma}{gamma} luminosities.

  4. Pin diode calibration - beam overlap monitoring for low energy cooling

    SciTech Connect

    Drees, A.; Montag, C.; Thieberger, P.

    2015-09-30

    We were trying to address the question whether or not the Pin Diodes, currently installed approximately 1 meter downstream of the RHIC primary collimators, are suitable to monitor a recombination signal from the future RHIC low energy cooling section. A maximized recombination signal, with the Au+78 ions being lost on the collimator, will indicate optimal Au-electron beam overlap as well as velocity matching of the electron beam in the cooling section.

  5. A study of low-energy type II supernovae

    NASA Astrophysics Data System (ADS)

    Lisakov, Sergey M.; Dessart, Luc; Hillier, D. John; Waldman, Roni; Livne, Eli

    2015-08-01

    All stars with an initial mass greater than 8Msun, but not massive enough to encounter the pair-production instability, eventually form a degenerate core and collapse to form a compact object, either a neutron star or a black hole.At the lower mass end, these massive stars die as red-supergiant stars and give rise to Type II supernovae (SNe). The diversity of observed properties of SNe II suggests a range of progenitor mass, radii, but also explosion energy.We have performed a large grid simulations designed to cover this range of progenitor and explosion properties. Using MESA STAR, we compute a set of massive star models (12-30Msun) from the main sequence until core collapse. We then generate explosions with V1D to produce ejecta with a range of explosion energies and yields. Finally, all ejecta are evolved with CMFGEN to generate multi-band light curves and spectra.In this poster, we focus our attention on the properties of low-energy explosions that give rise to low-luminosity Type II Plateau (II-P) SNe. In particular, we present a detailed study of SN 2008bk, but also include other notorious low-energy SNe II-P like 2005cs, emphasising their non-standard properties by comparing to models that match well events like SN 1999em. Such low-energy explosions, characterised by low ejecta expansion rates, are more suitable for reliable spectral line identifications.Based on our models, we discuss the distinct signatures of low-energy explosions in lower and higher mass models. One important goal is to identify whether there is a progenitor-mass bias leading to such events.

  6. Low energy supersymmetry from the heterotic string landscape.

    PubMed

    Lebedev, Oleg; Nilles, Hans-Peter; Raby, Stuart; Ramos-Sánchez, Saúl; Ratz, Michael; Vaudrevange, Patrick K S; Wingerter, Akin

    2007-05-01

    We study possible correlations between properties of the observable and hidden sectors in heterotic string theory. Specifically, we analyze the case of the Z6-II orbifold compactification which produces a significant number of models with the spectrum of the supersymmetric standard model. We find that requiring realistic features does affect the hidden sector such that hidden sector gauge group factors SU(4) and SO(8) are favored. In the context of gaugino condensation, this implies low energy supersymmetry breaking. PMID:17501559

  7. Modern Theories of Low-Energy Astrophysical Reactions

    SciTech Connect

    Rocco Schiavilla

    2004-02-01

    We summarize recent ab initio studies of low-energy electroweak reactions of astrophysical interest, relevant for both big bang nucleosynthesis and solar neutrino production. The calculational methods include direct integration for np radiative and pp weak capture, correlated hyperspherical harmonics for reactions of A=3,4 nuclei, and variational Monte Carlo for A=6,7 nuclei. Realistic nucleon-nucleon and three-nucleon interactions and consistent current operators are used as input.

  8. Neutrino Physics and Dark Matter Physics with Ultra-Low-Energy Germanium Detector

    SciTech Connect

    Shin-Ted, Lin

    2008-10-10

    The status and plans of the TEXONO Collaboration on the development of ultra-low-energy germanium detectors with sub-keV sensitivities are reported. We survey the scientific goals which include the observation of neutrino-nucleus coherent scattering, the studies of neutrino magnetic moments, as well as the searches of WIMP dark matter. In particular, an energy threshold of 220{+-}10 eV at an efficiency of 50% were achieved with a four-channel prototype detectors each of an active mass of 5 g. New limits were set for WIMPs with mass between 3-6 GeV. The prospects of the realization of full-scale experiments are discussed. This detector technique makes the unexplored sub-keV energy window accessible for new neutrino and dark matter experiments.

  9. Nuclear Astrophysical studies using low-energy RI beams at CRIB

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Wakabayashi, Y.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kurihara, Y.; Kubono, S.; Teranishi, T.; He, J. J.; Kwon, Y. K.; Nishimura, S.; Togano, Y.; Iwasa, N.; Niikura, M.; Khiem, L. H.

    2009-05-01

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo, used for various studies covering nuclear-astrophysical topics. An application of the RI beam at CRIB for the astrophysical studies is a new measurement of the proton resonance scattering on 7Be. The measurement was performed up to the excitation energy of 6.8 MeV, ans the excitation function above 3.5 MeV was successfully measured for the first time, providing important information about the reaction rate of 7Be(p,γ)8B, which is the key reaction in the solar 8B neutrino production. A preliminary result of the 7Be+p experiment is presented.

  10. Reaction studies with low-energy weakly-bound beams at INFN-LNS

    NASA Astrophysics Data System (ADS)

    Di Pietro, A.; Fernandez-Garcia, J. P.; Figuera, P.; Fisichella, M.; Lattuada, M.; Torresi, D.; Zadro, M.

    2016-05-01

    The reaction dynamics of collisions involving halo or weakly bound nuclei, at energies around the Coulomb barrier, can be strongly affected by the structure of such nuclei. Very strong entrance channel effects have been observed on various reaction pocess such as, elastic scattering, fusion and direct reactions when comparing collision induced by the 6He and 11Be halo nuclei with the ones induced by their cores 4He and 10Be. Collisions induced by the stable weakly bound nuclei 6Li, 7Li show also some peculiarities in comparison to the ones induced by well bound nuclei; coupling with the break-up channel is in fact very important in reproducing low energy data. In this contribution an overview of our present understanding of the discussed topic will be given along with the discussion of some new preliminary results.

  11. Low Energy Neutrino and Dark Matter Physics with sub-keV Germanium Detectors

    SciTech Connect

    Singh, L.; Singh, V.; Soma, A. K.; Singh, M. K.; Wong, H. T.

    2011-10-06

    A TEXONO collaboration research program on low energy neutrino and dark matter physics is going on at the Kuo-Sheng Neutrino Laboratory (KSNL). Collaboration main goals are to measure the neutrino-nucleus coherent scattering cross section, neutrino magnetic moments, and the searches of WIMP dark matter. To achieve these goals various prototype detectors and their sub-keV background are under study. A threshold of 220 eV was achieved with prototype detectors at the KSNL. New limits were set for WIMPs with mass between 3-6 GeV. Data are being taken with a 500 g Point Contact Germanium detector, where a threshold of {approx}350 eV was demonstrated. A 20 g ULEGe detector is taking data at CJPL in Sichuan, China.

  12. Low energy properties of the Kondo chain in the RKKY regime

    DOE PAGESBeta

    D. H. Schimmel; Tsvelik, A. M.; Yevtushenko, O. M.

    2016-05-03

    We study the Kondo chain in the regime of high spin concentration where the low energy physics is dominated by the Ruderman–Kittel–Kasuya–Yosida interaction. As has been recently shown (Tsvelik and Yevtushenko 2015 Phys. Rev. Lett. 115 216402), this model has two phases with drastically different transport properties depending on the anisotropy of the exchange interaction. In particular, the helical symmetry of the fermions is spontaneously broken when the anisotropy is of the easy plane type. This leads to a parametrical suppression of the localization effects. In the present paper we substantially extend the previous theory, in particular, by analyzing amore » competition of forward- and backward- scattering, including into the theory short range electron interactions and calculating spin correlation functions. In conclusion, we discuss applicability of our theory and possible experiments which could support the theoretical findings.« less

  13. Low energy dynamics of slender monopoles in non-Abelian superconductor

    NASA Astrophysics Data System (ADS)

    Arai, M.; Blaschke, F.; Eto, M.; Sakai, N.

    2016-01-01

    Low energy dynamics of magnetic monopoles and anti-monopoles in the U(2)c gauge theory is studied in the Higgs (non-Abelian superconducting) phase. The monopoles in this phase are slender ellipsoids, pierced by a vortex string. We investigate scattering of monopole with anti-monopole and find that they do not always decay into radiation, contrary to our naive intuition. They can repel, make bound states (magnetic mesons) or resonances. We point out that some part of solutions in 1 + 3 dimensions can be mapped exactly onto the sine-Gordon system in 1 + 1 dimensions in the first non-trivial order of rigid-body approximation and we provide analytic formulas for such solutions there.

  14. A New Apparatus for Studies of Low Energy Electron Collisions with Nucleotide Molecules

    NASA Astrophysics Data System (ADS)

    Duron, Jessica; Hargreaves, Leigh

    Low-energy electrons, the most copiously produced by-product of radiation cancer therapy, have been shown to be a strong driver of DNA damage in living cells [1]. Quantitative data describing these collisions are presently rare due to technological challenges in performing electron scattering measurements from the nucleobases, e.g. uracil, thymine, guanine, etc. These challenges include the low-vapor pressure of commercial samples (which are powders at room temperature), and the difficulty in making accurate flow measurements from heated gas sources, required to establish the absolute scale of the measured data. Based on techniques pioneered in positron collision physics [2], a new apparatus is presently undergoing commissioning at the California State University Fullerton, which aims to address these issues. We will make the first cross-section measurements for slow (E0 < 30eV) electron collisions with nucleotides. We will report design parameters and ongoing progress in the commissioning of this new experiment.

  15. Low-energy excitations, symmetry breaking and specific heat in YbBiPt

    SciTech Connect

    Robinson, R.A.; Christianson, A.; Nakotte, H. |; Beyermann, W.P.; Canfield, P.C.

    1998-12-31

    The heavy fermion compound YbBiPt has a very large linear coefficient of specific heat {gamma} = 8 Jmol{sup {minus}1} K{sup {minus}2} and this is understood, to first order, in terms of the observed low-energy neutron scattering response. However, at low temperatures, symmetry forbidden splittings at 1 and 2 meV respectively are observed. These levels give good qualitative agreement with the measured specific heat, but poor quantitative agreement. Indeed, the specific heat drops more rapidly with temperature that can be accounted for assuming a temperature-independent density of states. The authors also present new low-temperature crystallographic data, which rule out any significant structural distortions.

  16. Low energy properties of the Kondo chain in the RKKY regime

    NASA Astrophysics Data System (ADS)

    Schimmel, D. H.; Tsvelik, A. M.; Yevtushenko, O. M.

    2016-05-01

    We study the Kondo chain in the regime of high spin concentration where the low energy physics is dominated by the Ruderman–Kittel–Kasuya–Yosida interaction. As has been recently shown (Tsvelik and Yevtushenko 2015 Phys. Rev. Lett. 115 216402), this model has two phases with drastically different transport properties depending on the anisotropy of the exchange interaction. In particular, the helical symmetry of the fermions is spontaneously broken when the anisotropy is of the easy plane type. This leads to a parametrical suppression of the localization effects. In the present paper we substantially extend the previous theory, in particular, by analyzing a competition of forward- and backward- scattering, including into the theory short range electron interactions and calculating spin correlation functions. We discuss applicability of our theory and possible experiments which could support the theoretical findings.

  17. Nuclear Astrophysical studies using low-energy RI beams at CRIB

    SciTech Connect

    Yamaguchi, H.; Wakabayashi, Y.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kurihara, Y.; Kubono, S.; Niikura, M.; Teranishi, T.; He, J. J.; Kwon, Y. K.; Nishimura, S.; Togano, Y.; Iwasa, N.; Khiem, L. H.

    2009-05-04

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo, used for various studies covering nuclear-astrophysical topics. An application of the RI beam at CRIB for the astrophysical studies is a new measurement of the proton resonance scattering on {sup 7}Be. The measurement was performed up to the excitation energy of 6.8 MeV, ans the excitation function above 3.5 MeV was successfully measured for the first time, providing important information about the reaction rate of {sup 7}Be(p,{gamma}){sup 8}B, which is the key reaction in the solar {sup 8}B neutrino production. A preliminary result of the {sup 7}Be+p experiment is presented.

  18. A Low energy neutrino factory for large theta(13)

    SciTech Connect

    Geer, Steve; Mena, Olga; Pascoli, Silvia; /Durham U., IPPP

    2007-01-01

    If the value of {theta}{sub 13} is within the reach of the upcoming generation of long-baseline experiments, T2K and NOvA, they show that a low-energy neutrino factory, with peak energy in the few GeV range, would provide a sensitive tool to explore CP-violation and the neutrino mass hierarchy. They consider baselines with typical length 1000-1500 km. The unique performance of the low energy neutrino factory is due to the rich neutrino oscillation pattern at energies between 1 and 4 GeV at baselines {Omicron}(1000) km. They perform both a semi-analytical study of the sensitivities and a numerical analysis to explore how well this setup can measure {theta}{sub 13}, CP-violation, and determine the type of mass hierarchy and the {theta}{sub 23} quadrant. A low energy neutrino factory provides a powerful tool to resolve ambiguities and make precise parameter determinations, for both large and fairly small values of the mixing parameter {theta}{sub 13}.

  19. Low-energy trions in graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Cheng, H.-C.; Lue, N.-Y.; Chen, Y.-C.; Wu, G. Y.

    2014-06-01

    We investigate, within the envelope function approximation, the low-energy states of trions in graphene quantum dots (QDs). The presence of valley pseudospin in graphene as an electron degree of freedom apart from spin adds convolution to the interplay between exchange symmetry and the electron-electron interaction in the trion, leading to new states of trions as well as a low-energy trion spectrum different from those in semiconductors. Due to the involvement of valley pseudospin, it is found that the low-energy spectrum is nearly degenerate and consists of states all characterized by having an antisymmetric (pseudospin) ⊗ (spin) component in the wave function, with the spin (pseudospin) part being either singlet (triplet) or triplet (singlet), as opposed to the spectrum in a semiconductor whose ground state is known to be nondegenerate and always a spin singlet in the case of X- trions. We investigate trions in the various regimes determined by the competition between quantum confinement and electron-electron interaction, both analytically and numerically. The numerical work is performed within a variational method accounting for electron mass discontinuity across the QD edge. The result for electron-hole correlation in the trion is presented. Effects of varying quantum dot size and confinement potential strength on the trion binding energy are discussed. The "relativistic effect" on the trion due to the unique relativistic type electron energy dispersion in graphene is also examined.

  20. Low-Energy Monte Carlo and W-Values

    NASA Astrophysics Data System (ADS)

    Grosswendt, B.

    Electrons in the low-energy range of about 1 keV or less play an important role in many fields of radiation research for two reasons: firstly, they are created in large numbers during the passage of all kinds of ionizing radiation through matter, and secondly, they have a linear energy transfer comparable to that of low-energy protons and a-particles, and accordingly they are responsible for the greater part of radiation damage observable in any material. A detailed understanding of the action of low-energy electrons in matter therefore is required in many contexts. In the fields of dosimetry, for example, the determination of the absorbed dose in water or the air kerma is great practical importance, but in most experiments only the amount of ionization produced by secondary electrons within the sensitive volume of a dosimeter can be measured. The results of ionization measurements therefore must converted to quantities based on energy absorption or energy transfer, either by calibration or numerically using an appropriate conversion factor. The most frequently used conversion factor is the so-called W-value, which is the mean energy required to produce an ion pair upon complete slowing down of a charged particle. Its relation to the primary particle kinetic energy T, and to the mean n umber N i of ionizations produced (ionization yield), is given by

  1. Electron cooling for low-energy RHIC program

    SciTech Connect

    Fedotov, A.; Ben-Zvi, I.; Chang, X.; Kayran, D.; Litvinenko, V.N.; Pendzick, A.; Satogata, T.

    2009-08-31

    Electron cooling was proposed to increase luminosity of the RHIC collider for heavy ion beam energies below 10 GeV/nucleon. Providing collisions at such energies, termed RHIC 'low-energy' operation, will help to answer one of the key questions in the field of QCD about existence and location of critical point on the QCD phase diagram. The electron cooling system should deliver electron beam of required good quality over energies of 0.9-5 MeV. Several approaches to provide such cooling were considered. The baseline approach was chosen and design work started. Here we describe the main features of the cooling system and its expected performance. We have started design work on a low-energy RHIC electron cooler which will operate with kinetic electron energy range 0.86-2.8 (4.9) MeV. Several approaches to an electron cooling system in this energy range are being investigated. At present, our preferred scheme is to transfer the Fermilab Pelletron to BNL after Tevatron shutdown, and to use it for DC non-magnetized cooling in RHIC. Such electron cooling system can significantly increase RHIC luminosities at low-energy operation.

  2. Enhancement of surface processes with low energy ions

    SciTech Connect

    Chason, E.

    1995-05-01

    Continuing trends in device fabrication towards smaller feature sizes, lower thermal budgets and advanced device structures put greater emphasis on controlling the surface structure and reactivity during processing. Since the evolution of the semiconductor surface during processing is determined by the interaction of multiple surface processes, understanding how to control and modify these processes on the atomic level would enable us to exert greater control over the resulting morphology and composition. Low energy ions represent one method for bringing controlled amounts of energy to the surface to modify surface structure and kinetics. The kinetic energy deposited by the ions can break bonds and displace atoms, creating defect populations significantly in excess of the equilibrium concentration. Consequences of these non-equilibrium conditions include the enhancement of surface kinetic processes, increased surface reactivity and formation of metastable structures and compositions. These effects can be beneficial (ion enhanced mass transport can lead to surface smoothing) or they can be detrimental (residual defects can degrade electrical properties or lead to amorphization). The net results depend on a complex balance that depends on many parameters including ion mass, energy, flux and temperature. In the following section, we review progress both in our fundamental understanding of the production of low-energy ion-induced defects and in the use of low energy ions to enhance surface morphology, stimulate low temperature growth and obtain non-equilibrium structures and compositions.

  3. Colorado School of Mines low energy nuclear physics project

    SciTech Connect

    Cecil, F.E.

    1991-01-02

    A major accomplishment of this project in the past year is the completion of a fairly comprehensive paper describing the survey of radiative capture reactions of protons on light nuclei at low energies. In addition we have completed a preliminary set of measurements of (d,p)/(d,{alpha}) cross section ratios on the charge symmetric nuclei {sup 6}Li and {sup 10}B as a test of the Oppenheimer-Phillips effect. While the {sup 6}Li data remain inconclusive, the {sup 10}B data show solid evidence for the Oppenheimer-Phillips enhancement of the (d,p) reaction relative to the (d,{alpha}) reaction for deuteron bombarding energies below about 100 keV. We have continued our investigation of fusion reaction products from deuterium-metal systems at room temperatures with the startling observation of intense burst of energetic charged particles from deuterium gas loaded thin titaium foils subject to non-equilibrium thermal and electrical conditions. We have completed two projects involving the application of the low energy particle accelerator to material science problems; firstly a study of the transformation of crystalline to amorphous Fe-Zr systems by proton irradiation and secondly the effects of ion bombardment on the critical temperature of YBCO high-temperature superconductors. Finally we have made progress in several instrumentation projects which will be used in some of the up-coming measurements of nuclear cross sections at very low energies.

  4. Can inflation be connected to low energy particle physics?

    SciTech Connect

    Hertzberg, Mark P.

    2012-08-01

    It is an interesting question whether low energy degrees of freedom may be responsible for early universe inflation. To examine this, here we present a simple version of Higgs-inflation with minimal coupling to gravity and a quadratic inflationary potential. This quantitatively differs from the popular non-minimally coupled models, although it is qualitatively similar. In all such models, new heavy fields must enter in order for the theory to be well behaved in the UV. We show that in all cases the Higgs self coupling λ must be quite small in order to integrate out the heavy fields and use the resulting low energy effective field theory of the Higgs to describe inflation. For moderately sized λ, the UV completion is required and will, in general, determine the inflationary regime. We discuss the important issue of the arbitrariness of the Lagrangians used in all these setups by presenting a new class of such models, including a supergravity version. This suggests that the inflationary potential is disconnected from low energy physics.

  5. Monte Carlo calculations of characteristic quantities of low-energy electron irradiation to spacecraft dielectrics

    NASA Astrophysics Data System (ADS)

    Tan, Zhenyu; Dong, Lei; Tang, Fule

    2012-08-01

    The calculations of the characteristic quantities of low-energy electron (⩽20 keV) irradiation to the five typical spacecraft dielectrics, i.e. epoxy, kapton, mylar, polyethylene, and teflon, have been performed by means of Monte Carlo method. These characteristic quantities include the electron backscattering coefficient, the depth distributions of both energy deposition and deposited electrons, and the maximum penetration depth of deposited electrons in the dielectrics. A Monte Carlo model has been specifically constructed for simulating the transport of low-energy electrons in spacecraft dielectrics (organic materials). In this model, the description of the inelastic scattering of energetic electron is based on the dielectric approach developed previously and the Born-Ochkur's exchange correction is included. Especially, the optical energy loss functions of organic materials can be obtained using an empirical evaluation. In addition, the mean cross section based on the Mott model is proposed for calculating the elastic scattering of energetic electrons in organic materials for high simulation efficiency. The constructed Monte Carlo model has been examined by a series of calculations and comparisons with the reported experiments and other theoretical results. For the dielectrics under consideration and in the energy range of E0 ⩽ 20 keV, the calculated electron backscattering coefficients and the extrapolated range of deposited electrons are listed at selected energies in numerical form for convenient use, and an empirical expression of estimating the extrapolated range in the energy range of 1-20 keV is given. The distribution characteristics of both energy deposition and deposited electrons are presented, and it is found that kapton and mylar present the close characteristic quantities for each other, which is of significance for the choice of the dielectrics in design of spacecraft. The characteristic quantity calculations presented in this work are a

  6. Low-energy electron-induced reactions in condensed matter

    NASA Astrophysics Data System (ADS)

    Arumainayagam, Christopher R.; Lee, Hsiao-Lu; Nelson, Rachel B.; Haines, David R.; Gunawardane, Richard P.

    2010-01-01

    The goal of this review is to discuss post-irradiation analysis of low-energy (≤50 eV) electron-induced processes in nanoscale thin films. Because electron-induced surface reactions in monolayer adsorbates have been extensively reviewed, we will instead focus on low-energy electron-induced reactions in multilayer adsorbates. The latter studies, involving nanoscale thin films, serve to elucidate the pivotal role that the low-energy electron-induced reactions play in high-energy radiation-induced chemical reactions in condensed matter. Although electron-stimulated desorption (ESD) experiments conducted during irradiation have yielded vital information relevant to primary or initial electron-induced processes, we wish to demonstrate in this review that analyzing the products following low-energy electron irradiation can provide new insights into radiation chemistry. This review presents studies of electron-induced reactions in nanoscale films of molecular species such as oxygen, nitrogen trifluoride, water, alkanes, alcohols, aldehydes, ketones, carboxylic acids, nitriles, halocarbons, alkane and phenyl thiols, thiophenes, ferrocene, amino acids, nucleotides, and DNA using post-irradiation techniques such as temperature-programmed desorption (TPD), reflection-absorption infrared spectroscopy (RAIRS), X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HREELS), gel electrophoresis, and microarray fluorescence. Post-irradiation temperature-programmed desorption, in particular, has been shown to be useful in identifying labile radiolysis products as demonstrated by the first identification of methoxymethanol as a reaction product of methanol radiolysis. Results of post-irradiation studies have been used not only to identify radiolysis products, but also to determine the dynamics of electron-induced reactions. For example, studies of the radiolysis yield as a function of incident electron energy have shown that dissociative

  7. On the idea of low-energy nuclear reactions in metallic lattices by producing neutrons from protons capturing "heavy" electrons

    NASA Astrophysics Data System (ADS)

    Tennfors, Einar

    2013-02-01

    The present article is a critical comment on Widom and Larsens speculations concerning low-energy nuclear reactions (LENR) based on spontaneous collective motion of protons in a room temperature metallic hydride lattice producing oscillating electric fields that renormalize the electron self-energy, adding significantly to the effective electron mass and enabling production of low-energy neutrons. The frequency and mean proton displacement estimated on the basis of neutron scattering from protons in palladium and applied to the Widom and Larsens model of the proton oscillations yield an electron mass enhancement less than one percent, far below the threshold for the proposed neutron production and even farther below the mass enhancement obtained by Widom and Larsen assuming a high charge density. Neutrons are not stopped by the Coulomb barrier, but the energy required for the neutron production is not low.

  8. AE-C observations of low-energy particles and ionospheric temperatures in the turbulent polar cusp - Evidence for the Kelvin-Helmholtz instability

    NASA Technical Reports Server (NTRS)

    Potemra, T. A.; Bostrom, C. O.; Doering, J. P.; Peterson, W. K.; Hoffman, R. A.; Brace, L. H.

    1978-01-01

    Particle observations at 283 km acquired with the AE-C spacecraft during the large geomagnetic storm of May 16, 1975 indicate that the polar cusp was displaced to 71 deg invariant latitude between 1020 and 1244 MLT. Three regions of low-energy particle fluxes were determined which may be indentified with regions of field-aligned current flow in the dayside auroral zone and cusp. It is suggested that the low-energy electrons are scattered and that their pitch angles are isotropized by magnetic fluctuations associated with the Kelvin-Helmholtz instability caused by shear in the proton flow into the cusp.

  9. Developing effective rockfall protection barriers for low energy impacts

    NASA Astrophysics Data System (ADS)

    Mentani, Alessio; Giacomini, Anna; Buzzi, Olivier; Govoni, Laura; Gottardi, Guido; Fityus, Stephen

    2016-04-01

    Recently, important progresses have been made towards the development of high capacity rockfall barriers (100 kJ - 8000 kJ). The interest of researchers and practitioners is now turning to the development of fences of minor capacity, whose use becomes essential in areas where rockfall events generally have low intensity and the use of high capacity barriers would be accompanied by excessive costs and high environmental impact. Low energy barriers can also provide a cost-effective solution even in areas where high energies events are expected. Results of full-scale tests are vital to any investigation on the behaviour of these structures. An experimental set-up has been developed at The University of Newcastle (AUS), to investigate the response of low energy rockfall barrier prototypes to low energy impacts. The Australian territory, and in particular New South Wales, is in fact characterised by rockfall events of low-to-medium intensity (50 kJ - 500 kJ) and the need of protection structures working within such energy range, is particularly felt [1]. The experiments involved the impact of a test block onto three spans, low energy barrier prototypes, made of steel structural posts, fully fixed at the base, side cables and a steel meshwork constituted by a double twist hexagonal wire net [2]. Test data enabled the development, calibration and assessment of FE models [3], on which non-linear and dynamic analyses have been performed addressing the effect of the block size. Results have shown that the response of the structure is strongly governed by the net. Data from tests conducted on the sole net and on the entire barrier showed in fact a similar trend, different to what typically observed for high capacity barriers, whose behaviour is also led by the presence of uphill cables and brakes. In particular, the numerical analyses have demonstrated a dependence of the net performance on the block size. In particular, a loss of capacity in the order of 50% occurred as the

  10. Interactions and low-energy collisions between an alkali ion and an alkali atom of a different nucleus

    NASA Astrophysics Data System (ADS)

    Rakshit, Arpita; Ghanmi, Chedli; Berriche, Hamid; Deb, Bimalendu

    2016-05-01

    We study theoretically interaction potentials and low-energy collisions between different alkali atoms and alkali ions. Specifically, we consider systems such as X + {{{Y}}}+, where X({{{Y}}}+) is either Li(Cs+) or Cs(Li+), Na(Cs+) or Cs(Na+) and Li(Rb+) or Rb(Li+). We calculate the molecular potentials of the ground and first two excited states of these three systems using a pseudopotential method and compare our results with those obtained by others. We derive ground-state scattering wave functions and analyze the cold collisional properties of these systems for a wide range of energies. We find that, in order to get convergent results for the total scattering cross sections for energies of the order 1 K, one needs to take into account at least 60 partial waves. The low-energy scattering properties calculated in this paper may serve as a precursor for experimental exploration of quantum collisions between an alkali atom and an alkali ion of a different nucleus.

  11. Differential cross sections and escape plots for low-energy solitonic SU(2) BPS magnetic monopole dynamics

    NASA Astrophysics Data System (ADS)

    Temple-Raston, M.; Alexander, D.

    1993-05-01

    We compute the low-energy classical differential scattering cross section for solitonic BPS SU(2) magnetic monopoles using the geodesic approximation to the actual dynamics and 32K virtual parallel processors on a CM2. We compare the classical solitonic differential cross section to the low-energy quantum BPS SU(2) magnetic monopole differential cross section obtained by Schroers. Our numerical experiments suggest that the classical solitonic BPS magnetic monopole differential cross section approximates well the quantum BPS magnetic monopole differential cross section. In particular, the expected quantum interference of identical bosons at scattering angle θ = {π}/{2} (centre-of-mass frame) is not observed numerically, and indeed is contradicted. We argue that the lack of singularities in the two-body configuration space, related to the solitonic qualities of the BPS SU(2) magnetic monopole, is responsible for the agreement observed between the classical solitonic and the quantum mechanical cross sections. We also study the scattering and bounded classical motions of BPS SU(2) dyons and their global structure in phase space by constructing "escape plots". The escape plots contain a surprising amount of structure. The escape plots suggest that the classical dynamics of two BPS SU(2) magnetic monopoles is non-integrable and that there are closed and bounded two-monopole motions with isolated energies.

  12. Low energy electrons in the inner Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Ganushkina, Natalia; Sillanpaa, Ilkka; Dugyagin, Stepan; Pitchford, David; Rodriguez, Juan; Runov, Andrei

    2016-04-01

    The fluxes of electrons with energies < 100 keV are not usually analyzed and modeled in details when studying the electron radiation belts. These fluxes constitute the low energy part of the seed population, which is critically important for radiation belt dynamics. Moreover, energetic electrons with energies less than about 100 keV are responsible for hazardous space-weather phenomena such as surface charging. The electron flux at these energies varies highly with geomagnetic activity and even during quiet-time periods. Significant variations in the low-energy electrons can be seen during isolated substorms, not related to any storm periods. Moreover, electron flux variations depend on the electron energy. Statistical analysis of AMC 12 CEASE II ESA instrument data (5-50 keV) and GOES MAGED data (40, 75, 150 keV) have revealed that electron fluxes increase by the same order of magnitude during isolated substorms with 200 nT of AE index and storm-time substorms with 1200 nT of AE index. If substorms are represented as electromagnetic pulses which transport and accelerate electrons additionally, how are their amplitudes determined, if not related directly to a substorm's strength? Another factor of crucial importance is the specification of boundary conditions in the electron plasma sheet. We developed a new model for electron number density and temperature in the plasma sheet as dependent on solar wind and IMF conditions based on THEMIS data analysis. We present observational and modeling results on low energy electrons in the inner magnetosphere with newly-developed, time-dependent boundary conditions with a special focus on the role of substorms for electron transport and acceleration.

  13. Magnetospheric imaging with low-energy neutral atoms.

    PubMed Central

    McComas, D J; Barraclough, B L; Elphic, R C; Funsten, H O; Thomsen, M F

    1991-01-01

    Global imaging of the magnetospheric charged particle population can be achieved by remote measurement of the neutral atoms produced when magnetospheric ions undergo charge exchange with cold exospheric neutral atoms. Previously suggested energetic neutral atom imagers were only able to measure neutral atoms with energies typically greater than several tens of keV. A laboratory prototype has been built and tested for a different type of space plasma neutral imaging instrument, which allows neutral atoms to be imaged down to <1 keV. Such low-energy measurements provide greater sensitivity for imaging the terrestrial magnetosphere and allow the bulk of the magnetospheric ion distribution, typically centered below 10 keV, to be observed rather than just the high-energy tail of the distribution. The low-energy neutral atom measurements are made possible by utilizing charge state modifications that occur when an initially neutral atom passes through an ultrathin carbon foil. Oxygen, for example, is highly electronegative, and for energies of approximately 10-30 keV, the O- yield is approximately 30%, essentially independent of the charge state of the incident oxygen atom. These ions are energy per charge analyzed, and the UV background is rejected by using an electrostatic analyzer. Imaging of other ion species, such as hydrogen, could also be accomplished by using ultrathin foil-induced charge state modifications. The technique described in this paper provides a method for imaging charge exchange neutrals from the terrestrial magnetosphere and would also have applications for similar imaging in other planetary or cometary environs. The Inner Magnetosphere Imaging Mission, which the National Aeronautics and Space Administration is presently considering, would provide a nearly ideal platform for low-energy neutral atom imaging, and such measurements would substantially enhance the scientific yield of this mission. PMID:11607229

  14. Low energy sputtering of cobalt by cesium ions

    NASA Technical Reports Server (NTRS)

    Handoo, A.; Ray, Pradosh K.

    1989-01-01

    An experimental facility to investigate low energy (less than 500 eV) sputtering of metal surfaces with ions produced by an ion gun is described. Results are reported on the sputtering yield of cobalt by cesium ions in the 100 to 500 eV energy range at a pressure of 1 times 10(exp -6) Torr. The target was electroplated on a copper substrate. The sputtered atoms were collected on a cobalt foil surrounding the target. Co-57 was used as a tracer to determine the sputtering yield.

  15. Development of a spin polarized low energy electron diffraction system.

    PubMed

    Pradeep, A V; Roy, Arnab; Kumar, P S Anil; Kirschner, J

    2016-02-01

    We have designed and constructed a spin polarized low energy electron diffraction system working in the reflected electron pulse counting mode. This system is capable of measuring asymmetries due to spin-orbit and exchange interactions. Photoemission from a strained GaAs/GaAsP super lattice is used as the source of spin polarized electrons. Spin-orbit asymmetry is evaluated for Ir(100) single crystal at various energies. Subsequently, exchange asymmetry has been evaluated on 40 monolayer Fe deposited on Ir(100). This instrument proves to be useful in understanding structure and magnetism at surfaces. PMID:26931865

  16. Low-energy expansion of meson form factors

    NASA Astrophysics Data System (ADS)

    Gasser, J.; Leutwyler, H.

    We calculate the corrections to various low-energy theorems concerning the behaviour of the pseudoscalar meson form factors near t=0. In particular we discuss (i) the Ademollo-Gatto theorem, (ii) Sirlin's relation between the Kl3 form factor ƒ +Kπ (t) and the electromagnetic form factors, (iii) the Callan-Treiman relation, and (iv) the Dashen-Weinstein relation, which connects the slope λ0 of ƒ 0Kπ (t) with the ratio FK/ Fπ. Furthermore, we point out a remarkable isospin breaking effect which is clearly visible in the experimental rates of the decays K +→ π0e +ν, K 0→ π-e +ν.

  17. Low energy argon ion irradiation surface effects on triglycine sulfate

    NASA Astrophysics Data System (ADS)

    Aragó, Carmen; Plaza, José L.; Marqués, Manuel I.; Gonzalo, Julio A.

    2013-09-01

    An experimental study of the effects of low energy (1-2 keV) argon ion (Ar+) irradiation on Triglycine Sulfate (TGS) has been performed. Ferroelectric parameters, such as the Curie temperature TC determined from the dielectric constant peaks ɛ(T), or the remnant polarization Pr, and coercive field Ec, obtained from the hysteresis loops, show interesting differences between samples irradiated in ferroelectric and paraelectric phases, respectively. The radiation damage seems to be superficial, as observed by AFM microscope, and the surface alteration in both phases becomes eventually notorious when the radiation dosage increases.

  18. Internal Conversion Coefficients for Low-Energy Nuclear Transitions

    NASA Astrophysics Data System (ADS)

    Band, I. M.; Trzhaskovskaya, M. B.

    1993-09-01

    Presented here are calculated internal conversion coefficients (ICCs) of gamma rays for 35 observed low-energy nuclear transitions having Eγ ≲ 3 keV. Additionally, the ICCs for 24 high-multipole-order transitions which have been measured extensively are also given. The ICC calculations have been performed using Dirac-Fock electron wave functions, the exchange terms of the Dirac-Fock equations being included wthout any approximations both for the interaction between bound electrons and the interaction between bound and free electrons. Our previous studies have shown that the Dirac-Fock method allows ICC values to be obtained in best agreement with experimental data.

  19. Quantum effects in low-energy photofission of heavy nuclei

    SciTech Connect

    Tsipenyuk, Y.M.; Ostapenko, Y.B.; Smirenkin, G.N.; Soldatov, A.S.

    1984-09-01

    The article is devoted to quantum effects in highly deformed nuclei and the related features of the fission mechanism in the low-energy photofission of heavy nuclei. The following questions are considered: the spectrum of transition states (fission channels), the symmetry of the nuclear configuration in the deformation process, the features of the passage through the barrier due to the existence in the second well of quasistationary states of fissile and nonfissile modes, the isomeric-shelf phenomenon in deep sub-barrier fission, and the relation between the fragment mass distribution and the structure of the fission barrier.

  20. HgI2 low energy beta particle detector

    NASA Technical Reports Server (NTRS)

    Shah, K. S.; Squillante, M. R.; Entine, G.

    1990-01-01

    An HgI2 device structure was designed and tested which allows HgI2 to be used to make low-energy beta-particle detectors. The devices detected tritium beta particles with an efficiency of about 25 percent. A protective encapsulant has been developed which should protect the devices for up to 20 years and will attenuate only a small fraction of the beta particles. It is noted that the devices hold significant promise to provide a practical alternative to liquid scintillation counters and gas flow-through proportional counters.

  1. Experimental limit on low energy antiprotons in the cosmic radiation

    NASA Technical Reports Server (NTRS)

    Streitmatter, R. E.; Stochaj, S. J.; Ormes, J. F.; Golden, R. L.; Stephens, S. A.

    1989-01-01

    Results are reported from the Low Energy Antiproton Experiment (LEAP), a balloon-borne instrument which was flown in August, 1987. No evidence of antiproton fluxes is found in the kinetic energy range of 120 MeV to 360 MeV, at the top of the atmosphere. The 90-percent is found confidence upper limit on the antiproton/proton ratio in this energy range is 3.5 x 10 to the -5th. In particular, this new experiment places an upper limit on the flux almost an order of magnitude below the reported flux of Buffington et al. (1981).

  2. RHIC RF Harmonic Numbers for Low Energy Operations

    SciTech Connect

    Satogata,T.

    2008-05-01

    There have been several test runs of RHIC operations to explore the feasibility of luminosity production at low energies. There is considerable international interest in the possible existence of a QCD phase diagram critical point in the RHIC gold-gold collision energy range of {radical}s{sub NN} = 5-50 GeV[l, 2, 3]. This paper reviews the RF harmonic number constraints for RHIC gold-gold collisions in this energy range, and concludes that optimal simultaneous collisions at both experiments are only feasible when the harmonic number is divisible by 9.

  3. Threshold LET for SEU induced by low energy ions

    SciTech Connect

    McNulty, P.J.; Roche, P.; Palau, J.M.; Gasiot, J.

    1999-12-01

    Simulations to determine the threshold LET as a function of the length of the ion track are consistent with there being two regions of charge collection. In the top layer which contains the depletion region all the charge generated is collected in time to upset the device. In the next layer, 10% to 20% of the charge generated is collected and contributes to upsetting the device. This second layer of partial charge collection may significantly impact the accuracy of SEU predictions involving low-energy neutrons and protons. A simple method of including this contribution in calculations is proposed.

  4. On the anisotropies of interplanetary low-energy proton intensities

    NASA Technical Reports Server (NTRS)

    Pesses, M. E.; Sarris, E. T.

    1975-01-01

    Explorer 35 proton anisotropic flux data (proton energies between 0.3 and 6.3 MeV) and simultaneous magnetic field measurements were used to supply more information on the propagation characteristics of low-energy protons in the interplanetary medium. During the rising portions of the proton events, large field-aligned anisotropies were observed. During the decaying part of the proton events, either radial anisotropy or near-isotropy was noticed. In addition, certain observations made during the decaying part of the proton events revealed anisotropies deviating significantly from the radial direction.

  5. Targeting Low-Energy Transfers to Low Lunar Orbit

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.; Anderson, Rodney L.

    2011-01-01

    A targeting scheme is presented to build trajectories from a specified Earth parking orbit to a specified low lunar orbit via a low-energy transfer and up to two maneuvers. The total transfer delta V (velocity) is characterized as a function of the Earth parking orbit inclination and the departure date for transfers to each given low lunar orbit. The transfer delta V (velocity) cost is characterized for transfers constructed to low lunar polar orbits with any longitude of ascending node and for transfers that arrive at the Moon at any given time during a month.

  6. Low energy beam transport in the NSLS UV-FEL

    SciTech Connect

    Zhang, X.; Gallardo, J.C.

    1993-06-01

    A design of the injection low energy transport line for the proposed NSLS UV-FEL is presented. The main concern is to control the beam transverse emittance dilution due to space charge, energy spread and non-linear forces introduced by magnetic elements. The design considerations to optimize the transport line are discussed including the deleterious effects of space charge and energy spread as modeled by the particle code PARMELA. The results from PARMELA are analyzed, and the concept of slice emittance is used to examine the causes of emittance growth.

  7. Low energy beam transport in the NSLS UV-FEL

    SciTech Connect

    Zhang, X.; Gallardo, J.C.

    1993-01-01

    A design of the injection low energy transport line for the proposed NSLS UV-FEL is presented. The main concern is to control the beam transverse emittance dilution due to space charge, energy spread and non-linear forces introduced by magnetic elements. The design considerations to optimize the transport line are discussed including the deleterious effects of space charge and energy spread as modeled by the particle code PARMELA. The results from PARMELA are analyzed, and the concept of slice emittance is used to examine the causes of emittance growth.

  8. Study on electron beam in a low energy plasma focus

    SciTech Connect

    Khan, Muhammad Zubair; Ling, Yap Seong; San, Wong Chiow

    2014-03-05

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device.

  9. Fast self-attenuation determination of low energy gamma lines.

    PubMed

    Haddad, Kh

    2016-09-01

    Linear correlation between self-attenuation factor of 46.5keV ((210)Pb) and the 1764keV, 46.5 counts ratio has been developed in this work using triple superphosphate fertilizer samples. Similar correlation has been also developed for 63.3keV ((238)U). This correlation offers simple, fast, and accurate technique for self-attenuation determination of low energy gamma lines. Utilization of 46.5keV in the ratio has remarkably improved the technique sensitivity in comparison with other work, which used similar concept. The obtained results were used to assess the validity of transmission technique. PMID:27337648

  10. Recombination in liquid xenon for low-energy recoils

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Mei, Dongming; Cubed Collaboration

    2014-09-01

    Detector response to low-energy recoils in sub-keV region is critical to detection of low-mass dark matter particles-WIMPS (Weakly interacting massive particles). The role of electron-ion recombination is important to the interpretation of the relation between ionization yield and scintillation yield, which are in general anti-correlated. Recent experimental results show that ionization yield increases down to keV range. This phenomenon contradicts general understanding for low energy recoils in the keV range in which direct excitation dominates. The explanation is that recombination becomes much less efficient when the track length is smaller than the thermalization distance of electrons. However, recombination rate is also proportional to ionization density, which is very high for keV recoils. To understand how recombination rate behaves for keV recoils, we calculated both initial recombination rate and volume recombination rate for keV recoils in liquid xenon. In this paper, we show the results of the calculated recombination rate as a function of recoil energy for both electronic recoils and nuclear recoils. Detector response to low-energy recoils in sub-keV region is critical to detection of low-mass dark matter particles-WIMPS (Weakly interacting massive particles). The role of electron-ion recombination is important to the interpretation of the relation between ionization yield and scintillation yield, which are in general anti-correlated. Recent experimental results show that ionization yield increases down to keV range. This phenomenon contradicts general understanding for low energy recoils in the keV range in which direct excitation dominates. The explanation is that recombination becomes much less efficient when the track length is smaller than the thermalization distance of electrons. However, recombination rate is also proportional to ionization density, which is very high for keV recoils. To understand how recombination rate behaves for keV recoils

  11. Studies in Low Energy Nuclear Science, Progress Report

    SciTech Connect

    Carl R. Brune; Steven M. Grimes; Thomas N. Massey

    2004-03-01

    OAK-B135 Research in the area of low-energy nuclear science is described. We report on studies of the Z dependence of nuclear level densities, the development of a new Hauser-Feshbach computer code, and plans to measure level densities in nuclei off the line of stability. We also discuss the development of our R-matrix fitting capabilities, including new codes and the application to the C-14 system. Plans for future measurements of the Be-9(alpha,n) and B-11(alpha,n) reactions are discussed.

  12. Straight low energy beam transport for intense uranium beams

    NASA Astrophysics Data System (ADS)

    Xiao, C.; Groening, L.; Vormann, H.; Mickat, S.; Hollinger, R.; Adonin, A.; Orzhekhovskaya, A.; Maier, M.; Al-Omari, H.; Barth, W.; Kester, O. K.; Yaramyshev, S.

    2015-07-01

    A new high current uranium ion source and dedicated Low Energy Beam Transport (LEBT) will be built at the GSI High Current Injector (HSI). This LEBT will be integrated into the existing complex which already comprises two branches. The paper presents the design and dynamics simulation using the TRACE-3D and TRACK code. The simulation results illustrate that this straight LEBT can transport uranium beams over a wide range of space-charge compensation, and can provide 15.4 (14.2) mA U4+ inside of the effective acceptance of the subsequent RFQ assuming the space-charge is compensated to 100% (95%).

  13. Low Energy Lorentz Violation from Modified Dispersion at High Energies.

    PubMed

    Husain, Viqar; Louko, Jorma

    2016-02-12

    Many quantum theories of gravity propose Lorentz-violating dispersion relations of the form ω=|k|f(|k|/M⋆), with recovery of approximate Lorentz invariance at energy scales much below M⋆. We show that a quantum field with this dispersion predicts drastic low energy Lorentz violation in atoms modeled as Unruh-DeWitt detectors, for any f that dips below unity somewhere. As an example, we show that polymer quantization motivated by loop quantum gravity predicts such Lorentz violation below current ion collider rapidities. PMID:26918976

  14. Bosonization of the low energy excitations of Fermi liquids

    SciTech Connect

    Castro Neto, A.H.; Fradkin, E. )

    1994-03-07

    We bosonize the low energy excitations of Fermi liquids in any number of dimensions in the limit of long wavelengths. The bosons are a coherent superposition of electron-hole pairs and are related with the displacements of the Fermi surface in some arbitrary direction. A coherent-state path integral for the bosonized theory is derived and it is shown to represent histories of the shape of the Fermi surface. The Landau theory of Fermi liquids can be obtained from the formalism in the absence of nesting of the Fermi surface and singular interactions. We show that the Landau equation for sound waves is exact in the semiclassical approximation for the bosons.

  15. Development of a spin polarized low energy electron diffraction system

    NASA Astrophysics Data System (ADS)

    Pradeep, A. V.; Roy, Arnab; Kumar, P. S. Anil; Kirschner, J.

    2016-02-01

    We have designed and constructed a spin polarized low energy electron diffraction system working in the reflected electron pulse counting mode. This system is capable of measuring asymmetries due to spin-orbit and exchange interactions. Photoemission from a strained GaAs/GaAsP super lattice is used as the source of spin polarized electrons. Spin-orbit asymmetry is evaluated for Ir(100) single crystal at various energies. Subsequently, exchange asymmetry has been evaluated on 40 monolayer Fe deposited on Ir(100). This instrument proves to be useful in understanding structure and magnetism at surfaces.

  16. Spintronic switches for ultra low energy global interconnects

    SciTech Connect

    Sharad, Mrigank Roy, Kaushik

    2014-05-07

    We present ultra-low energy interconnect design using nano-scale spin-torque (ST) switches for global data-links. Emerging spin-torque phenomena can lead to ultra-low-voltage, high-speed current-mode magnetic-switches. ST-switches can simultaneously provide large trans-impedance gain by employing magnetic tunnel junctions, to convert current-mode signals into large-swing voltage levels. Such device-characteristics can be used in the design of energy-efficient current-mode global interconnects.

  17. Low-energy negative muon interaction with matter

    NASA Astrophysics Data System (ADS)

    Danev, Petar; Adamczak, Andrzej; Bakalov, Dimitar; Mocchiutti, Emiliano; Stoilov, Mihail; Vacchi, Andrea

    2016-03-01

    Using simulated data, obtained with the FLUKA code, we derive empirical regularities about the propagation and stopping of low-energy negative muons in hydrogen and selected solid materials. The results are intended to help the preliminary stages of the set-up design for experimental studies of muon capture and muonic atom spectroscopy. Provided are approximate expressions for the parameters of the the momentum, spatial and angular distribution of the propagating muons. In comparison with the available data on the stopping power and range of muons (with which they agree in the considered energy range) these results have the advantage to also describe the statistical spread of the muon characteristics of interest.

  18. Low-Energy Hot Plasma and Particles in Saturn's Magnetosphere.

    PubMed

    Krimigis, S M; Armstrong, T P; Axford, W I; Bostrom, C O; Gloeckler, G; Keath, E P; Lanzerotti, L J; Carbary, J F; Hamilton, D C; Roelof, E C

    1982-01-29

    The low-energy charged particle instrument on Voyager 2 measured low-energy electrons and ions (energies greater, similar 22 and greater, similar 28 kiloelectron volts, respectively) in Saturn's magnetosphere. The magnetosphere structure and particle population were modified from those observed during the Voyager 1 encounter in November 1980 but in a manner consistent with the same global morphology. Major results include the following. (i) A region containing an extremely hot ( approximately 30 to 50 kiloelectron volts) plasma was identified and extends from the orbit of Tethys outward past the orbit of Rhea. (ii) The low-energy ion mantle found by Voyager 1 to extend approximately 7 Saturn radii inside the dayside magnetosphere was again observed on Voyager 2, but it was considerably hotter ( approximately 30 kiloelectron volts), and there was an indication of a cooler ( < 20 kiloelectron volts) ion mantle on the nightside. (iii) At energies greater, similar 200 kiloelectron volts per nucleon, H(1), H(2), and H(3) (molecular hydrogen), helium, carbon, and oxygen are important constituents in the Saturnian magnetosphere. The presence of both H(2) and H(3) suggests that the Saturnian ionosphere feeds plasma into the magnetosphere, but relative abundances of the energetic helium, carbon, and oxygen ions are consistent with a solar wind origin. (iv) Low-energy ( approximately 22 to approximately 60 kiloelectron volts) electron flux enhancements observed between the L shells of Rhea and Tethys by Voyager 2 on the dayside were absent during the Voyager 1 encounter. (v) Persistent asymmetric pitch-angle distributions of electrons of 60 to 200 kiloelectron volts occur in the outer magnetosphere in conjunction with the hot ion plasma torus. (vi) The spacecraft passed within approximately 1.1 degrees in longitude of the Tethys flux tube outbound and observed it to be empty of energetic ions and electrons; the microsignature of Enceladus inbound was also observed. (vii

  19. A New Polyethylene Scattering Law Determined Using Inelastic Neutron Scattering

    SciTech Connect

    Lavelle, Christopher M; Liu, C; Stone, Matthew B

    2013-01-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S (Q, E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for T =300 K, and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 300 K which are used to improve the scattering law for HDPE. We describe the experimental methods, review some of the past HDPE scattering laws, and compare computations using these models to the measured S (Q, E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the 1 phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  20. Experimental Approach to High-Temperature Stellar Reactions with Low-Energy RI Beams

    NASA Astrophysics Data System (ADS)

    Kubono, S.; Yamaguchi, H.; Amadio, G.; Hayakawa, S.; Wakabayashi, Y.; Kurihara, Y.; He, J. J.; Saito, A.; Fujikawa, H.; Khiem, Le Hong; Niikura, M.; Teranishi, T.; Nishimura, S.; Kato, S.; Lee, C. S.; Kwon, Y. K.; Hahn, I. S.; Kim, A.

    2008-04-01

    The experimental efforts for the stellar reactions under high-temperature and high densities have been made as the major program using the RI beams from the CNS low-energy in-flight RI beam separator (CRIB) of University of Tokyo, in order to understand the evolution of the universe as well as various stellar phenomena. Specifically, two subjects of hydrogen burning are discussed here. One is a reaction study of the pp-chain and the second is of the explosive hydrogen burning, the rp-process. Some s-wave resonances have been identified by the thick target method in the crucial reaction processes in the hydrogen burning. The resonant scattering with the thick target method also succeeded in identifying inelastic resonant scattering, giving proton widths for the first excited state of the target nucleus. This provides very efficiently the reaction rate estimate for the process under high-temperature equilibrium condition. Possibilities of the CRIB facility in near future are also briefly discussed.

  1. Improved convergence in the three-nucleon system at very low energies

    NASA Astrophysics Data System (ADS)

    Grießhammer, Harald W.

    2004-11-01

    Neutron-deuteron scattering in the context of "pion-less" effective field theory at very low energies is investigated to next-to-next-to-leading order. Convergence is improved by fitting the two-nucleon contact interactions to the tail of the deuteron wave-function, a procedure known as Z-parameterisation and extended here to the three-nucleon system. The improvement is particularly striking in the doublet-S-wave (triton) channel, where better agreement to potential-model calculations and better convergence from order to order in the power counting is achieved for momenta as high as ˜120 MeV. Investigating the cut-off dependence of the phase-shifts, one confirms numerically the analytical finding that the first momentum-dependent three-body force enters at N 2LO. The other partial waves converge also substantially faster. Effective-range parameters of the nd-system are determined, e.g., for the quartet-S-wave scattering length a=[6.35±0.02] fm, which compares favourably both in magnitude and uncertainty with recent high-precision potential-model determinations. Differential cross-sections up to E≈15 MeV agree with data.

  2. Studying astrophysical reactions with low-energy RI beams at CRIB

    NASA Astrophysics Data System (ADS)

    Yamaguchi, H.; Kahl, D.; Hayakawa, S.; Sakaguchi, Y.; Wakabayashi, Y.; Hashimoto, T.; Cherubini, S.; Gulino, M.; Spitaleri, C.; Rapisarda, G. G.; La Cognata, M.; Lamia, L.; Romano, S.; Kubono, S.; Iwasa, N.; Teranishi, T.; Kawabata, T.; Kwon, Y. K.; Binh, D. N.; Khiem, L. H.; Duy, N. N.; Kato, S.; Komatsubara, T.; Coc, A.; De Sereville, N.; Hammache, F.; Kiss, G.; Bishop, S.

    2016-05-01

    Studies on nuclear astrophysics, nuclear structure, and other interests have been performed using the radioactive-isotope (RI) beams at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study (CNS), the University of Tokyo. A typical measurement performed at CRIB is the elastic resonant scattering with the inverse kinematics. One recent experiment was on the α resonant scattering with 7Li and 7Be beams. This study is related to the astrophysical 7Li/7Be(α,γ) reactions, important at hot p-p chain and νp-process in supernovae. There have also been measurements based on other experimental methods. The first THM measurement using an RI beam has been performed at CRIB, to study the 18F(p, α)15O reaction at astrophysical energies via the three body reaction 2H(18F, α15O)n. The 18F(p, α) 15O reaction rate is crucial to understand the 511-keV γ-ray production in nova explosion phenomena, and we successfully evaluated the reaction cross section at novae temperature and below experimentally for the first time.

  3. Analysis of the Low-Energy π-p Charge-Exchange Data

    NASA Astrophysics Data System (ADS)

    Matsinos, E.; Rasche, G.

    2013-05-01

    We analyze the charge-exchange (CX) measurements π-p→π0n below pion laboratory kinetic energy of 100 MeV. After the removal of five degrees of freedom from the initial database, we combine it with the truncated π+p database [E. Matsinos and G. Rasche, J. Mod. Phys.3, 1369 (2012)] and fit the ETH model [P. F. A. Goudsmit, H. J. Leisi, E. Matsinos, B. L. Birbrair and A. B. Gridnev, Nucl. Phys. A575, 673 (1994)] to the resulting data. The set of the parameter values of the ETH model, as well as the predictions derived on their basis for the hadronic phase shifts and for the low-energy πN constants, are significantly different from the results obtained in the analysis of the truncated π±p elastic-scattering databases. The main difference in the hadronic phase shifts occurs in ˜ {δ }0+1/2. We discuss the implications of these findings in terms of the violation of the isospin invariance in the hadronic part of the πN interaction. The effect observed amounts to the level of 7-8% in the CX scattering amplitude below 70 MeV. The results and conclusions of this study agree well with those obtained in the mid 1990s, when the isospin invariance was first tested by using πN experimental data, and disagree with the predictions obtained within the framework of the heavy-baryon Chiral-Perturbation Theory.

  4. Optical models from low-energy s-, p- and d-wave cross sections

    SciTech Connect

    Johnson, C.H.

    1984-01-01

    From transmission measurements with good resolution at low energies one can obtain data on the optical model potential (OMP) for individual partical waves by first making a multilevel analysis to isolate the partial waves and then averaging for comparison to the OMP. For each J..pi.. the averaging yields two quantities which are related to the amplitude and phase of the OMP scattering function or, alternatively, to the volume integrals of the real and imaginary potentials. Historically, the experimental average have been represented by the s- and p-wave strength functions, S/sub 0/ and S/sub 1/, and the s-wave scattering radius R'. To make full use of data from modern time-of-flight facilities such as ORELA it is necessary to re-examine the averaging procedure in order to extend it upward both in energy and neutron l-value. This averaging is discussed and applied to data on /sup 30/Si, /sup 32/S, /sup 34/S, /sup 40/Ca, /sup 60/Ni, /sup 86/Kr and /sup 208/Pb. The resulting OMP shows a systematic real potential with some indication of a parity dependence. The imaginary potential shows considerable fluctuations indicating the importance of nuclear structure at neutron eneries below 1 MeV. A coupled channel OMP is also discussed for some of the nulei. 19 references.

  5. Elastic cross sections for low-energy electron collisions with tetrahydropyran

    NASA Astrophysics Data System (ADS)

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2016-02-01

    We report on calculated elastic cross sections for low-energy electron collisions with the cyclic ether tetrahydropyran (C5H10O). The calculations were carried out with the Schwinger multichannel method implemented with norm-conserving pseudopotentials in the static-exchange-polarization approximation for energies up to 20 eV. Our cross sections are compared with previous results obtained for cyclohexane and 1,4-dioxane, since the three molecules present similar structures. The calculated differential cross sections for these three molecules present similarities, except at low scattering angles, where the differential cross sections of tetrahydropyran present a sharp increase due to the permanent dipole moment of the molecule. The similarities observed in the cross sections reveal that the molecular geometry plays an important role in the description of scattering process. We also compared our calculated elastic integral cross section for tetrahydropyran with experimental total cross sections data available in the literature and found a good qualitative agreement between both results.

  6. Low-energy paramagnetic spin fluctuations in the weak itinerant ferromagnet MnSi

    NASA Astrophysics Data System (ADS)

    Ishikawa, Y.; Noda, Y.; Fincher, C.; Shirane, G.

    1982-01-01

    Low-energy paramagnetic excitations in the weak itinerant ferromagnet (WIF) MnSi have been studied by neutron scattering. The observed spectrum has a Lorentzian form (ΓΓ2+ω2) and is clearly separated from excitations in the Stoner continuum. The generalized susceptibility, χ(q), has been obtained by integrating the scattering intensity over energy. It is found that χ(q) depends upon the wave vector q as χ(q)-1=κ2(T)+q2 for q<=0.125(2πa) with κ2(T)=κ20(T-Tc). After extrapolating these results to q=0, it is found that χ(q=0) follows the Curie-Weiss law, suggesting that the observed spin fluctuations correspond to the Moriya-Kawabata (MK) spin fluctuations responsible for the Curie-Weiss dependence of the static susceptibility of a WIF. The linewidth Γ is found to be proportional to qχ(q) as predicted by the MK theory, in contrast with the q2χ(q) relation expected in a Heisenberg system. These results provide the first direct experimental evidence for the existence of MK spin fluctuations in a WIF above Tc.

  7. Rayleigh Scattering.

    ERIC Educational Resources Information Center

    Young, Andrew T.

    1982-01-01

    The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)

  8. Response of plastic scintillators to low-energy photons

    NASA Astrophysics Data System (ADS)

    Peralta, Luis; Rêgo, Florbela

    2014-08-01

    Diagnostic radiology typically uses x-ray beams between 25 and 150 kVp. Plastic scintillation detectors (PSDs) are potentially successful candidates as field dosimeters but careful selection of the scintillator is crucial. It has been demonstrated that they can suffer from energy dependence in the low-energy region, an undesirable dosimeter characteristic. This dependence is partially due to the nonlinear light yield of the scintillator to the low-energy electrons set in motion by the photon beam. In this work, PSDs made of PMMA, PVT or polystyrene were studied for the x-ray beam range 25 to 100 kVp. For each kVp data has been acquired for additional aluminium filtrations of 0.5, 1.0, 2.0 and 4.0 mm. Absolute dose in the point of measurement was obtained with an ionization chamber calibrated to dose in water. From the collected data, detector sensitivities were obtained as function of the beam kVp and additional filtration. Using Monte Carlo simulations relative scintillator sensitivities were computed. For some of the scintillators these sensitivities show strong energy-dependence for beam average energy below 35 keV for each additional filtration but fair constancy above. One of the scintillators (BC-404) has smaller energy-dependence at low photon average energy and could be considered a candidate for applications (like mammography) where beam energy has small span.

  9. The low energy detector of Simbol-X

    NASA Astrophysics Data System (ADS)

    Lechner, P.; Andricek, L.; Briel, U.; Hasinger, G.; Heinzinger, K.; Herrmann, S.; Huber, H.; Kendziorra, E.; Lauf, T.; Lutz, G.; Richter, R.; Santangelo, A.; Schaller, G.; Schnecke, M.; Schopper, F.; Segneri, G.; Strüder, L.; Treis, J.

    2008-07-01

    Simbol-X is a French-Italian-German hard energy X-ray mission with a projected launch in 2014. Being sensitive in the energy range from 500 eV to 80 keV it will cover the sensitivity gap beyond the energy interval of today's telescopes XMM-Newton and Chandra. Simbol-X will use an imaging telescope of nested Wolter-I mirrors. To provide a focal length of 20 m it will be the first mission of two independent mirror and detector spacecrafts in autonomous formation flight. The detector spacecraft's payload is composed of an imaging silicon low energy detector in front of a pixelated cadmium-telluride hard energy detector. Both have a sensitive area of 8 × 8 cm2 to cover a 12 arcmin field of view and a pixel size of 625 × 625 μm2 adapted to the telescope's resolution of 20 arcsec. The additional LED specifications are: high energy resolution, high quantum efficiency, fast readout and optional window mode, monolithic device with 100 % fill factor and suspension mounting, and operation at warm temperature. To match these requirements the low energy detector is composed of 'active macro pixels', combining the large, scalable area of a Silicon Drift Detector and the low-noise, on-demand readout of an integrated DEPFET amplifier. Flight representative prototypes have been processed at the MPI semiconductor laboratory, and the prototype's measured performance demonstrates the technology readiness.

  10. Low-energy control of electrical turbulence in the heart

    NASA Astrophysics Data System (ADS)

    Luther, Stefan; Fenton, Flavio H.; Kornreich, Bruce G.; Squires, Amgad; Bittihn, Philip; Hornung, Daniel; Zabel, Markus; Flanders, James; Gladuli, Andrea; Campoy, Luis; Cherry, Elizabeth M.; Luther, Gisa; Hasenfuss, Gerd; Krinsky, Valentin I.; Pumir, Alain; Gilmour, Robert F.; Bodenschatz, Eberhard

    2011-07-01

    Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves in a heterogeneous anatomical substrate. In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation. Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E) and a characteristic time, τ, for tissue depolarization that obeys the power law τ~Eα. These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques.

  11. Diphoton excess, low energy theorem, and the 331 model

    NASA Astrophysics Data System (ADS)

    Cao, Qing-Hong; Liu, Yandong; Xie, Ke-Pan; Yan, Bin; Zhang, Dong-Ming

    2016-04-01

    We interpret the diphoton anomaly as a heavy scalar H3 in the so-called 331 model. The scalar is responsible for breaking the S U (3 )C⊗S U (3 )L⊗U (1 )X gauge symmetry down to the standard model electroweak gauge group. It mainly couples to the standard model gluons and photons through quantum loops involving heavy quarks and leptons. Those quarks and leptons, together with the SM quarks and leptons, form the fundamental representation of the 331 model. We use the low energy theorem to calculate the effective couplings of H3g g , H3γ γ , H3Z Z , H3W W and H3Z γ . The analytical results can be applied to new physics models satisfying the low energy theorem. We show that the heavy quark and lepton contribution cannot produce enough diphoton pairs. It is crucial to include the contribution of charged scalars to explain the diphoton excess. The extra neutral Z' boson could also explain the 2 TeV diboson excess observed at the LHC Run-I.

  12. New Mechanism of Low Energy Nuclear Reactions Using Superlow

    NASA Astrophysics Data System (ADS)

    Gareev, F. A.; Zhidkova, I. E.

    2006-03-01

    We proposed a new mechanism of LENR (low energy nuclear reactions) cooperative processes in the whole system - nuclei+atoms+condensed matter can occur at smaller threshold than the corresponding ones assoiciated with free constituents. The cooperative processes can be induced and enhanced by (``superlow energy'') external fields. The excess heat is the emission of internal energy, and transmutations from LENR are the result of redistribution of the internal energy of the whole system. A review of possible stimulation mechanisms of LENR is presented. We have concluded that transmutation of nuclei at low energies and excess heat are possible in the framework of the known fundamental physical laws: The universal resonance synchronization principle, and based on it, different enhancement mechanisms of reaction rates are responsible for these processes. The excitation and ionization of atoms may play the role of a trigger for LENR. F.A. Gareev, I.E. Zhidkova, E-print arXiv Nucl-th/0511092 v1 30 Nov 2005. F.A. Gareev, In: FPB-98, Novosibirsk, June 1998, p.92; F.A.Gareev, G.F. Gareeva, in: Novosibirsk, July 2000, p.161. F.A. Gareev, I.E. Zhidkova and Yu.L. Ratis, Preprint JINR P4-2004-68, Dubna, 2004. F.A. Gareev, I.E. Zhidkova, E-print arXiv Nucl-th/0505021 9 May 2005.

  13. Neutrino phenomenology of very low-energy seesaw scenarios

    SciTech Connect

    Gouvea, Andre de; Jenkins, James; Vasudevan, Nirmala

    2007-01-01

    The standard model augmented by the presence of gauge-singlet right-handed neutrinos proves to be an ideal scenario for accommodating nonzero neutrino masses. Among the new parameters of this 'new standard model' are right-handed neutrino Majorana masses M. Theoretical prejudice points to M much larger than the electroweak symmetry breaking scale, but it has recently been emphasized that all M values are technically natural and should be explored. Indeed, M around 1-10 eV can accommodate an elegant oscillation solution to the liquid scintillator neutrino detector (LSND) anomaly, while other M values lead to several observable consequences. We consider the phenomenology of low-energy (M < or approx. 1 keV) seesaw scenarios. By exploring such a framework with three right-handed neutrinos, we can consistently fit all oscillation data--including those from LSND--while partially addressing several astrophysical puzzles, including anomalous pulsar kicks, heavy element nucleosynthesis in supernovae, and the existence of warm dark matter. In order to accomplish all of this, we find that a nonstandard cosmological scenario is required. Finally, low-energy seesaws - regardless of their relation to the LSND anomaly - can also be tested by future tritium beta-decay experiments, neutrinoless double-beta decay searches, and other observables. We estimate the sensitivity of such probes to M.

  14. Development of Low Energy Gap and Fully Regioregular Polythienylenevinylene Derivative

    DOE PAGESBeta

    David, Tanya M. S.; Zhang, Cheng; Sun, Sam-Shajing

    2014-01-01

    Low energy gap and fully regioregular conjugated polymers find its wide use in solar energy conversion applications. This paper will first briefly review this type of polymers and also report synthesis and characterization of a specific example new polymer, a low energy gap, fully regioregular, terminal functionalized, and processable conjugated polymer poly-(3-dodecyloxy-2,5-thienylene vinylene) or PDDTV. The polymer exhibited an optical energy gap of 1.46 eV based on the UV-vis-NIR absorption spectrum. The electrochemically measured highest occupied molecular orbital (HOMO) level is −4.79 eV, resulting in the lowest unoccupied molecular orbital (LUMO) level of −3.33 eV based on optical energy gap. The polymer wasmore » synthesized via Horner-Emmons condensation and is fairly soluble in common organic solvents such as tetrahydrofuran and chloroform with gentle heating. DSC showed two endothermic peaks at 67°C and 227°C that can be attributed to transitions between crystalline and liquid states. The polymer is thermally stable up to about 300°C. This polymer appears very promising for cost-effective solar cell applications.« less

  15. Low Energy Laser Biostimulation: New Prospects For Medical Applications

    NASA Astrophysics Data System (ADS)

    Castel, John C.; Abergel, R. Patrick; Willner, Robert E.; Baumann, James G.

    1987-03-01

    The therapeutic benefits of light-energy is not a new concept to the modern world. Documented applications from ancient times tell of the therapeutic effects of ordinary sun-light to treat such common ailments as painful body joints, wounds, compound fractures and tetanus. The discovery of laser light in the 1960's, opened up new prospects for the medical use of light. Laser light differs from other forms of electromagnetic spectrum in that a single wavelength rather than a spectrum of wavelengths is emitted. Since the early 1970's, low-energy laser radiation has been reported to enhance wound healing rates, reduce edema, and relieve musculoskeletal pain. There is no detectable thermal effect of this laser on the tissue being treated. The effects are considered to occur as a result of photochemical, non thermal effects of the laser beam. Photons are absorbed by the tissue being treated and, in turn, produce positive therapeutic effects such as reduction of pain and edema. Pre-clinical and clinical evaluations are, presently, underway to document the safety and efficacy of low energy laser therapy, which represents a significant advance in the non-invasive treatment of pain.

  16. Mass spectrograph for imaging low-energy neutral atoms

    SciTech Connect

    Ghielmetti, A.G.; Shelley, E.G.; Fuselier, S.A. ); Wurz, P.; Bochsler, P. . Physikalisches Inst.); Herrero, F.A.; Smith, M.F. . NASA Goddard Space Flight Center); Stephen, T.S. . Physics Dept.)

    1994-02-01

    The authors describe an instrument concept for measuring low-energy neutral H and O atoms with kinetic energies ranging from about 10 eV to several hundred. The instrument makes use of a low work function surface to convert neutral atoms to negative ions. These ions are then accelerated away from the surface and brought to an intermediate focus by a large aperture lens. After deflection in a spherical electrostatic analyzer, the ions are postaccelerated to [approximately]25-keV final energy into a carbon-foil time-of-flight mass analyzer. Mass resolution is adequate to resolve H, D, He, and O. Energy and azimuth angle information is obtained by means of position imaging the secondary electrons produced at the carbon foil. A large geometric factor combined with simultaneous angle-energy-mass imaging that eliminates the need for duty cycles provide the necessary high sensitivity. From a spinning spacecraft this instrument is capable of producing a 2-D map of low-energy neutral atom fluxes.

  17. Defect production and recombination during low-energy ion processing

    SciTech Connect

    Kellerman, B.K.; Floro, J.A.; Chason, E.; Brice, D.K.; Picraux, S.T.; White, J.M.

    1994-10-01

    Low-energy ion processing produces damaged, microroughened semiconductor surfaces due to the production of point defects. The authors present a study of point defect production and annealing on the Ge(001)-2x1 surface during low-energy inert ion bombardment as a function of ion energy, ion mass and substrate temperature. Ion-induced surface point defect production was quantified experimentally in real time using in situ Reflection High Energy Electron Diffraction. The observed surface defect yield decreased abruptly around room temperature as the substrate temperature was increased from 175 K to 475 K. The authors have developed Monte Carlo simulations of defect diffusion to model defect recombination both in the bulk and on the surface. Bulk defect production statistics generated by a binary collision simulator, TRIMRC, were coupled with our bulk diffusion simulator to predict the number of ion-induced surface defects. A comparison between the experimental results and the simulation predictions indicated that defects produced in the bulk may represent a significant contribution to the observed surface defect yield and suggested that TRIMRC may overestimate the depth distribution of the defects. The simulations further indicated that the abrupt drop in the experimental yield with increasing substrate temperature does not arise from bulk defect recombination. The Monte Carlo simulations of surface diffusion (applicable to any crystalline surface) support a defect annealing mechanism (at low ion fluxes) that involves surface recombination of defects generated within a single cascade.

  18. Low-energy-state dynamics of entanglement for spin systems

    SciTech Connect

    Jafari, R.

    2010-11-15

    We develop the ideas of the quantum renormalization group and quantum information by exploring the low-energy-state dynamics of entanglement resources of a system close to its quantum critical point. We demonstrate that low-energy-state dynamical quantities of one-dimensional magnetic systems can show a quantum phase transition point and show scaling behavior in the vicinity of the transition point. To present our idea, we study the evolution of two spin entanglements in the one-dimensional Ising model in the transverse field. The system is initialized as the so-called thermal ground state of the pure Ising model. We investigate the evolution of the generation of entanglement with increasing magnetic field. We obtain that the derivative of the time at which the entanglement reaches its maximum with respect to the transverse field diverges at the critical point and its scaling behaviors versus the size of the system are the same as the static ground-state entanglement of the system.

  19. Modeling low energy laser ignition of explosive and pyrotechnic powders

    SciTech Connect

    Glass, M.W.; Merson, J.A.; Salas, F.J.

    1992-01-01

    Laser diode ignition (LDI) of explosives and pyrotechnics is being developed at Sandia National Laboratories as a replacement for low energy hotwire devices. This technology offers significant improvements in device safety due to the insensitivity to electrostatic discharge (ESD) and electromagnetic radiation (EMR). The LDI system incorporates a laser diode source, a fiber optic cable to transmit the laser energy, and the energetic component. The laser energy is volumetrically absorbed by the explosive component causing its temperature to rise to its auto-ignition temperature. Substantial experimental work characterizing the optical ignition mechanism has been undertaken in support of the LDI development work. This work has primarily been focused on the explosive component, CP, 2-(5-cyanotetrazolato) pentaamminecobalt(III) perchlorate, doped with a small amount of carbon black to enhance the laser energy absorptance at the 850 nm wavelength of the laser diode. To support the experimental efforts, numerical modeling of the thermal response of CP to a low energy laser input has been undertaken.

  20. Modeling low energy laser ignition of explosive and pyrotechnic powders

    SciTech Connect

    Glass, M.W.; Merson, J.A.; Salas, F.J.

    1992-07-01

    Laser diode ignition (LDI) of explosives and pyrotechnics is being developed at Sandia National Laboratories as a replacement for low energy hotwire devices. This technology offers significant improvements in device safety due to the insensitivity to electrostatic discharge (ESD) and electromagnetic radiation (EMR). The LDI system incorporates a laser diode source, a fiber optic cable to transmit the laser energy, and the energetic component. The laser energy is volumetrically absorbed by the explosive component causing its temperature to rise to its auto-ignition temperature. Substantial experimental work characterizing the optical ignition mechanism has been undertaken in support of the LDI development work. This work has primarily been focused on the explosive component, CP, 2-(5-cyanotetrazolato) pentaamminecobalt(III) perchlorate, doped with a small amount of carbon black to enhance the laser energy absorptance at the 850 nm wavelength of the laser diode. To support the experimental efforts, numerical modeling of the thermal response of CP to a low energy laser input has been undertaken.

  1. Radiative neutralino production in low energy supersymmetric models

    SciTech Connect

    Basu, Rahul; Sharma, Chandradew; Pandita, P. N.

    2008-06-01

    We study the production of the lightest neutralinos in the radiative process e{sup +}e{sup -}{yields}{chi}-tilde{sub 1}{sup 0}{chi}-tilde{sub 1}{sup 0}{gamma} in low energy supersymmetric models for the International Linear Collider energies. This includes the minimal supersymmetric standard model as well as its extension with an additional chiral Higgs singlet superfield, the nonminimal supersymmetric standard model. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the minimal and nonminimal supersymmetric standard model. We also consider the background to this process coming from the standard model process e{sup +}e{sup -}{yields}{nu}{nu}{gamma}, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) e{sup +}e{sup -}{yields}{nu}-tilde{nu}-tilde*{gamma}, which can be a background to the radiative neutralino production when the sneutrinos decay invisibly. In low energy supersymmetric models radiative production of the lightest neutralinos may be the only channel to study supersymmetric partners of the standard model particles at the first stage of a linear collider, since heavier neutralinos, charginos, and sleptons may be too heavy to be pair produced at a e{sup +}e{sup -} machine with {radical}(s)=500 GeV.

  2. Einstein - Cartan - Dirac theory in the low-energy limit

    NASA Astrophysics Data System (ADS)

    Singh, P.; Ryder, L. H.

    1997-12-01

    We look for manifestations of the effects of torsion in the low-energy limit in the context of Einstein - Cartan - Dirac theory (or any theory of gravity in which the torsion tensor is purely axial). To proceed, we introduce the mathematical law governing the transport of orthonormal bases or tetrads in a spacetime with torsion. This law is applied to compute the metric and connection in a rotating and accelerating frame, or laboratory. A spin-0264-9381/14/12/031/img1 particle is placed in this rotating and accelerating frame and the low-energy limit of the Dirac equation is taken by means of the Foldy - Wouthuysen transformation. In addition to obtaining the Bonse - Wroblewski phase shift due to acceleration, Sagnac-type effects, rotation - spin couplings of the Mashhoon type, redshift of the kinetic energy and the spin - orbit coupling term of Hehl and Ni, we also obtain several interesting and significant terms as a consequence of introducing torsion into spacetime. We give a detailed interpretation of these additional terms and discuss their observability in the light of current well-known experimental techniques.

  3. Low energy charged particles interacting with amorphous solid water layers

    SciTech Connect

    Horowitz, Yonatan; Asscher, Micha

    2012-04-07

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 {mu}A) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 {+-} 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  4. Formation of a high intensity low energy positron string

    NASA Astrophysics Data System (ADS)

    Donets, E. D.; Donets, E. E.; Syresin, E. M.; Itahashi, T.; Dubinov, A. E.

    2004-05-01

    The possibility of a high intensity low energy positron beam production is discussed. The proposed Positron String Trap (PST) is based on the principles and technology of the Electron String Ion Source (ESIS) developed in JINR during the last decade. A linear version of ESIS has been used successfully for the production of intense highly charged ion beams of various elements. Now the Tubular Electron String Ion Source (TESIS) concept is under study and this opens really new promising possibilities in physics and technology. In this report, we discuss the application of the tubular-type trap for the storage of positrons cooled to the cryogenic temperatures of 0.05 meV. It is intended that the positron flux at the energy of 1-5 eV, produced by the external source, is injected into the Tubular Positron Trap which has a similar construction as the TESIS. Then the low energy positrons are captured in the PST Penning trap and are cooled down because of their synchrotron radiation in the strong (5-10 T) applied magnetic field. It is expected that the proposed PST should permit storing and cooling to cryogenic temperature of up to 5×109 positrons. The accumulated cooled positrons can be used further for various physics applications, for example, antihydrogen production.

  5. TOPICAL REVIEW: RBE of low energy electrons and photons

    NASA Astrophysics Data System (ADS)

    Nikjoo, Hooshang; Lindborg, Lennart

    2010-05-01

    Relative biological effectiveness (RBE) compares the severity of damage induced by a radiation under test at a dose D relative to the reference radiation Dx for the same biological endpoint. RBE is an important parameter in estimation of risk from exposure to ionizing radiation (IR). The present work provides a review of the recently published data and the knowledge of the RBE of low energy electrons and photons. The review presents RBE values derived from experimental data and model calculations including cell inactivation, chromosome aberration, cell transformation, micronuclei formation and induction of double-strand breaks. Biophysical models, including physical features of radiation track, and microdosimetry parameters are presented, analysed and compared with experimental data. The biological effects of low energy electrons and photons are of particular interest in radiation biology as these are strongly absorbed in micrometer and sub-micrometer layers of tissue. RBE values not only depend on the electron and photon energies but also on the irradiation condition, cell type and experimental conditions.

  6. Variations of Low-energy Ion Distributions Measured in the Heliosheath

    SciTech Connect

    Decker, R. B.; Roelof, E. C.; Hill, M. E.; Krimigis, S. M.

    2010-12-30

    This report is an update of low-energy ion intensities and angular distributions measured recently by the Low Energy Charged Particle instruments on the Voyager 1 and 2 spacecraft in the inner heliosheath.

  7. Summary of low-energy aspects of QCD and medium-energy hadron parallel sessions

    SciTech Connect

    McClelland, J.B.

    1991-01-01

    Two sessions were organized dealing with low energy aspects of QCD. The first dealt with the issue of QCD dibaryons. The second session centered on mostly low-energy tests of QCD. This report discusses experiments dealing with these sessions.

  8. Deep absorbing porphyrin small molecule for high-performance organic solar cells with very low energy losses.

    PubMed

    Gao, Ke; Li, Lisheng; Lai, Tianqi; Xiao, Liangang; Huang, Yuan; Huang, Fei; Peng, Junbiao; Cao, Yong; Liu, Feng; Russell, Thomas P; Janssen, René A J; Peng, Xiaobin

    2015-06-17

    We designed and synthesized the DPPEZnP-TEH molecule, with a porphyrin ring linked to two diketopyrrolopyrrole units by ethynylene bridges. The resulting material exhibits a very low energy band gap of 1.37 eV and a broad light absorption to 907 nm. An open-circuit voltage of 0.78 V was obtained in bulk heterojunction (BHJ) organic solar cells, showing a low energy loss of only 0.59 eV, which is the first report that small molecule solar cells show energy losses <0.6 eV. The optimized solar cells show remarkable external quantum efficiency, short circuit current, and power conversion efficiency up to 65%, 16.76 mA/cm(2), and 8.08%, respectively, which are the best values for BHJ solar cells with very low energy losses. Additionally, the morphology of DPPEZnP-TEH neat and blend films with PC61BM was studied thoroughly by grazing incidence X-ray diffraction, resonant soft X-ray scattering, and transmission electron microscopy under different fabrication conditions. PMID:26035342

  9. Bulk NaI(Tl) scintillation low energy events selection with the ANAIS-0 module

    NASA Astrophysics Data System (ADS)

    Cuesta, C.; Amaré, J.; Cebrián, S.; García, E.; Ginestra, C.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; de Solórzano, A. Ortiz; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

    2014-11-01

    Dark matter particles scattering off target nuclei are expected to deposit very small energies in form of nuclear recoils (below 100 keV). Because of the low scintillation efficiency for nuclear recoils as compared to electron recoils, in most of the scintillating targets considered in the search for dark matter, the region below 10 keVee (electron equivalent energy) concentrates most of the expected dark matter signal. For this reason, very low energy threshold (at or below 2 keVee) and very low background are required to be competitive in the search for dark matter with such detection technique. This is the case of Annual modulation with NaI Scintillators (ANAIS), which is an experiment to be carried out at the Canfranc Underground Laboratory. A good knowledge of the detector response function for real scintillation events in the active volume, a good characterization of other anomalous or noise event populations contributing in that energy range, and the development of convenient filtering procedures for the latter are mandatory in order to achieve the required low background at such a low energy. In this work we present the characteristics of different types of events observed in large size NaI(Tl) detectors, and the event-type identification techniques developed. Such techniques allow distinguishing among events associated with bulk NaI scintillation, and events related to muon interactions in the detectors or shielding, photomultiplier origin events, and analysis event fakes. We describe the specific protocols developed to build bulk scintillation events spectra from the raw data and we apply them to data obtained with one of the ANAIS prototypes, ANAIS-0. Nuclear recoil type events were also explored using data from a neutron calibration; however pulse shape cuts were found not to be effective to discriminate them from electron recoil events. The effect of the filtering procedures developed in this nuclear recoils population has been analyzed in order to

  10. Low-energy ion implantation: Large mass fractionation of argon

    NASA Technical Reports Server (NTRS)

    Ponganis, K. V.; Graf, TH.; Marti, K.

    1993-01-01

    The isotropic signatures of noble gases in the atmospheres of the Earth and other planets are considerably evolved when compared to signatures observed in the solar wind. The mechanisms driving the evolution of planetary volatiles from original compositions in the solar accretion disk are currently poorly understood. Modeling of noble-gas compositional histories requires knowledge of fractionating processes that may have operated through the evolutionary stages. Since these gases are chemically inert, information on noble-gas fractionation processes can be used as probes. The importance of understanding these processes extends well beyond 'noble-gas planetology.' Trapped argon acquired by low-energy implantation (approximately less than 100 eV) into solids is strongly mass fractionated (approximately greater than or equal to 3 percent/amu). This has potential implications for the origin and evolution of terrestrial planet atmospheres.

  11. Quantifying Low Energy Proton Damage in Multijunction Solar Cells

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Burke, Edward A.; Walters, Robert J.; Warner, Jeffrey H.; Summers, Geoffrey P.; Lorentzen, Justin R.; Morton, Thomas L.; Taylor, Steven J.

    2007-01-01

    An analysis of the effects of low energy proton irradiation on the electrical performance of triple junction (3J) InGaP2/GaAs/Ge solar cells is presented. The Monte Carlo ion transport code (SRIM) is used to simulate the damage profile induced in a 3J solar cell under the conditions of typical ground testing and that of the space environment. The results are used to present a quantitative analysis of the defect, and hence damage, distribution induced in the cell active region by the different radiation conditions. The modelling results show that, in the space environment, the solar cell will experience a uniform damage distribution through the active region of the cell. Through an application of the displacement damage dose analysis methodology, the implications of this result on mission performance predictions are investigated.

  12. Effects of heavy sea quarks at low energies.

    PubMed

    Bruno, Mattia; Finkenrath, Jacob; Knechtli, Francesco; Leder, Björn; Sommer, Rainer

    2015-03-13

    We present a factorization formula for the dependence of light hadron masses and low energy hadronic scales on the mass M of a heavy quark: apart from an overall mass-independent factor Q, ratios such as r_{0}(M)/r_{0}(0) are computable in perturbation theory at large M. The perturbation theory part is stable concerning different loop orders. Our nonperturbative Monte Carlo results obtained in a model calculation, where a doublet of heavy quarks is decoupled, match quantitatively to the perturbative prediction. Upon taking ratios of different hadronic scales at the same mass, the perturbative function drops out and the ratios are given by the decoupled theory up to M^{-2} corrections. We verify-in the continuum limit-that the sea quark effects of quarks with masses around the charm mass are very small in such ratios. PMID:25815925

  13. Hierarchical fuzzy control of low-energy building systems

    SciTech Connect

    Yu, Zhen; Dexter, Arthur

    2010-04-15

    A hierarchical fuzzy supervisory controller is described that is capable of optimizing the operation of a low-energy building, which uses solar energy to heat and cool its interior spaces. The highest level fuzzy rules choose the most appropriate set of lower level rules according to the weather and occupancy information; the second level fuzzy rules determine an optimal energy profile and the overall modes of operation of the heating, ventilating and air-conditioning system (HVAC); the third level fuzzy rules select the mode of operation of specific equipment, and assign schedules to the local controllers so that the optimal energy profile can be achieved in the most efficient way. Computer simulation is used to compare the hierarchical fuzzy control scheme with a supervisory control scheme based on expert rules. The performance is evaluated by comparing the energy consumption and thermal comfort. (author)

  14. Ignitor with stable low-energy thermite igniting system

    DOEpatents

    Kelly, Michael D.; Munger, Alan C.

    1991-02-05

    A stable compact low-energy igniting system in an ignitor utilizes two components, an initiating charge and an output charge. The initiating charge is a thermite in ultra-fine powder form compacted to 50-70% of theoretical maximum density and disposed in a cavity of a header of the ignitor adjacent to an electrical ignition device, or bridgewire, mounted in the header cavity. The initiating charge is ignitable by operation of the ignition device in a hot-wire mode. The output charge is a thermite in high-density consoladated form compacted to 90-99% of theoretical maximum density and disposed adjacent to the initiating charge on an opposite end thereof from the electrical ignition device and ignitable by the initiating charge. A sleeve is provided for mounting the output charge to the ignitor header with the initiating charge confined therebetween in the cavity.

  15. ULTRA-LOW-ENERGY HIGH-CURRENT ION SOURCE

    SciTech Connect

    Anders, Andre; Yushkov, Georgy Yu.; Baldwin, David A.

    2009-11-20

    The technical objective of the project was to develop an ultra-low-energy, high-intensity ion source (ULEHIIS) for materials processing in high-technology fields including semiconductors, micro-magnetics and optics/opto-electronics. In its primary application, this ion source can be incorporated into the 4Wave thin-film deposition technique called biased target ion-beam deposition (BTIBD), which is a deposition technique based on sputtering (without magnetic field, i.e., not the typical magnetron sputtering). It is a technological challenge because the laws of space charge limited current (Child-Langmuir) set strict limits of how much current can be extracted from a reservoir of ions, such as a suitable discharge plasma. The solution to the problem was an innovative dual-discharge system without the use of extraction grids.

  16. Modeling of human movement monitoring using Bluetooth Low Energy technology.

    PubMed

    Mokhtari, G; Zhang, Q; Karunanithi, M

    2015-01-01

    Bluetooth Low Energy (BLE) is a wireless communication technology which can be used to monitor human movements. In this monitoring system, a BLE signal scanner scans signal strength of BLE tags carried by people, to thus infer human movement patterns within its monitoring zone. However to the extent of our knowledge one main aspect of this monitoring system which has not yet been thoroughly investigated in literature is how to build a sound theoretical model, based on tunable BLE communication parameters such as scanning time interval and advertising time interval, to enable the study and design of effective and efficient movement monitoring systems. In this paper, we proposed and developed a statistical model based on Monte-Carlo simulation, which can be utilized to assess impacts of BLE technology parameters in terms of latency and efficiency, on a movement monitoring system, and can thus benefit a more efficient system design. PMID:26737430

  17. Contamination control and plume assessment of low-energy thrusters

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1993-01-01

    Potential contamination of a spacecraft cryogenic surface by a xenon (Xe) ion generator was evaluated. The analysis involves the description of the plume exhausted from the generator with its relative component fluxes on the spacecraft surfaces, and verification of the conditions for condensation, adsorption, and sputtering at those locations. The data describing the plume fluxes and their effects on surfaces were obtained from two sources: the tests carried out with the Xe generator in a small vacuum chamber to indicate deposits and sputter on monitor slides; and the extensive tests with a mercury (Hg) ion thruster in a large vacuum chamber. The Hg thruster tests provided data on the neutrals, on low-energy ion fluxes, on high-energy ion fluxes, and on sputtered materials at several locations within the plume.

  18. Low energy neutral atoms in the earth's magnetosphere: Modeling

    SciTech Connect

    Moore, K.R.; McComas, D.J.; Funsten, H.O.; Thomsen, M.F.

    1992-01-01

    Detection of low energy neutral atoms (LENAs) produced by the interaction of the Earth's geocorona with ambient space plasma has been proposed as a technique to obtain global information about the magnetosphere. Recent instrumentation advances reported previously and in these proceedings provide an opportunity for detecting LENAs in the energy range of <1 keV to {approximately}50 keV. In this paper, we present results from a numerical model which calculates line of sight LENA fluxes expected at a remote orbiting spacecraft for various magnetospheric plasma regimes. This model uses measured charge exchange cross sections, either of two neural hydrogen geocorona models, and various empirical modes of the ring current and plasma sheet to calculate the contribution to the integrated directional flux from each point along the line of sight of the instrument. We discuss implications for LENA imaging of the magnetosphere based on these simulations. 22 refs.

  19. Low Dose, Low Energy 3d Image Guidance during Radiotherapy

    NASA Astrophysics Data System (ADS)

    Moore, C. J.; Marchant, T.; Amer, A.; Sharrock, P.; Price, P.; Burton, D.

    2006-04-01

    Patient kilo-voltage X-ray cone beam volumetric imaging for radiotherapy was first demonstrated on an Elekta Synergy mega-voltage X-ray linear accelerator. Subsequently low dose, reduced profile reconstruction imaging was shown to be practical for 3D geometric setup registration to pre-treatment planning images without compromising registration accuracy. Reconstruction from X-ray profiles gathered between treatment beam deliveries was also introduced. The innovation of zonal cone beam imaging promises significantly reduced doses to patients and improved soft tissue contrast in the tumour target zone. These developments coincided with the first dynamic 3D monitoring of continuous body topology changes in patients, at the moment of irradiation, using a laser interferometer. They signal the arrival of low dose, low energy 3D image guidance during radiotherapy itself.

  20. Scintillation Efficiency of Liquid Xenon for Low Energy Nuclear Recoils

    NASA Astrophysics Data System (ADS)

    Wongjirad, Taritree; Ni, Kaixuan; Manzur, Angel; Kastens, Louis; McKinsey, Daniel

    2008-04-01

    In early 2006, the XENON and ZEPLIN collaborations announced highly stringent upper limits on the WIMP-nucleon cross-section. However, the dominant systematic uncertainty in these limits is due to the uncertainty in the nuclear recoil scintillation efficiency (NRSE) for liquid xenon. The NRSE is defined as the amount of scintillation produced by nuclear recoils, divided by the amount of scintillation produced by electron recoils, per unit energy. Though the NRSE has been measured by several groups, its value at the low energies most important for the liquid xenon WIMP searches has a large uncertainty. Furthermore, the NRSE may vary with the strength of the electric field in the liquid xenon. In an attempt to reduce these uncertainties, we have measured the NRSE down to 5 keV nuclear recoil energy for various electric fields.

  1. Bluetooth low energy: wireless connectivity for medical monitoring.

    PubMed

    Omre, Alf Helge

    2010-03-01

    Electronic wireless sensors could cut medical costs by enabling physicians to remotely monitor vital signs such as blood pressure, blood glucose, and blood oxygenation while patients remain at home. According to the IDC report "Worldwide Bluetooth Semiconductor 2008-2012 Forecast," published November 2008, a forthcoming radio frequency communication ("wireless connectivity") standard, Bluetooth low energy, will link wireless sensors via radio signals to the 70% of cell phones and computers likely to be fitted with the next generation of Bluetooth wireless technology, leveraging a ready-built infrastructure for data transmission. Analysis of trends indicated by this data can help physicians better manage diseases such as diabetes. The technology also addresses the concerns of cost, compatibility, and interoperability that have previously stalled widespread adoption of wireless technology in medical applications. PMID:20307407

  2. Quantum Aspects of Low-Energy Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Furman, W.

    2011-10-01

    A helicity representation for fission product channels with correctly defined parity is used to describe neutron induced fission with arbitrary spin density matrix in ingoing channel. Recently obtained data for ROT effect in binary fission give evidence for high accuracy of the helicity representation just at scission. A general expression for differential cross-section of (n,f)-reaction is obtained. In the framework of multilevel, many channel R-matrix theory the reduced S-matrix for JΠK effective channels rigorously derived. These channels include fission modes in natural way. Theoretical analysis of experimentally observed P-even and P-odd interference effects in low energy nuclear fission allows one to make some essential conclusions on basic mechanism of the process.

  3. A New Instrument Design for Imaging Low Energy Neutral Atoms

    NASA Technical Reports Server (NTRS)

    Keller, John W.; Collier, Michael R.; Chornay, Dennis; Rozmarynowski, Paul; Getty, Stephanie; Cooper, John F.; Smith, Billy

    2007-01-01

    The MidSTAR-2 satellite, to be built at the US Naval Academy as a follow-on to the successful MidSTAR-1 satellite (http://web.ew.usna.edu/midstar/), will launch in 2011 and carry three Goddard Space Flight Center (GSFC) experiments developed under Goddard's Internal Research and Development (IRAD) program. One of these GSFC instruments, the Miniature Imager for Neutral Ionospheric atoms and Magnetospheric Electrons (MINI-ME) builds on the heritage of the Goddard-developed Low-Energy Neutral Atom (LENA) imager launched on the IMAGE spacecraft in 2000. MINI-ME features a Venetian-blind conversion surface assembly that improves both light rejection and conversion efficiency in a smaller and lighter package than LENA making this an highly effective instrument for viewing solar wind charge exchange with terrestrial and planetary exospheres. We will describe the MINI-ME prototyping effort and its science targets.

  4. The low energy spectra of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Bussard, R. W.; Lamb, F. K.

    1982-01-01

    The implications of observed gamma-ray burst spectra for the physical conditions and geometries of the sources are examined. It is noted that an explanation of the continua in terms of optically thin thermal bremsstrahlung requires a relatively large area but a fairly shallow depth. On the other hand, a spectrum similar to that observed could be produced by rapid flickering of sources with less extreme geometries if each flicker emits a Comptonized thermal spectrum. Either field inhomogeneities or plasma motions are required to interpret the low energy features as cyclotron extinction. An alternative explanation is photoelectric absorption by heavy atoms; this requires a field strength high enough to make one-photon electron positron annihilation possible. Observational tests of these possibilities are proposed

  5. Molecular ion sources for low energy semiconductor ion implantation (invited).

    PubMed

    Hershcovitch, A; Gushenets, V I; Seleznev, D N; Bugaev, A S; Dugin, S; Oks, E M; Kulevoy, T V; Alexeyenko, O; Kozlov, A; Kropachev, G N; Kuibeda, R P; Minaev, S; Vizir, A; Yushkov, G Yu

    2016-02-01

    Smaller semiconductors require shallow, low energy ion implantation, resulting space charge effects, which reduced beam currents and production rates. To increase production rates, molecular ions are used. Boron and phosphorous (or arsenic) implantation is needed for P-type and N-type semiconductors, respectively. Carborane, which is the most stable molecular boron ion leaves unacceptable carbon residue on extraction grids. A self-cleaning carborane acid compound (C4H12B10O4) was synthesized and utilized in the ITEP Bernas ion source resulting in large carborane ion output, without carbon residue. Pure gaseous processes are desired to enable rapid switch among ion species. Molecular phosphorous was generated by introducing phosphine in dissociators via 4PH3 = P4 + 6H2; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P4(+) ion beams were extracted. Results from devices and some additional concepts are described. PMID:26932065

  6. Molecular Ion Beam Transportation for Low Energy Ion Implantation

    SciTech Connect

    Kulevoy, T. V.; Kropachev, G. N.; Seleznev, D. N.; Yakushin, P. E.; Kuibeda, R. P.; Kozlov, A. V.; Koshelev, V. A.; Hershcovitch, A.; Johnson, B. M.; Gushenets, V. I.; Oks, E. M.; Polozov, S. M.; Poole, H. J.

    2011-01-07

    A joint research and development of steady state intense boron ion sources for 100's of electron-volt ion implanters has been in progress for the past five years. Current density limitation associated with extracting and transporting low energy ion beams result in lower beam currents that in turn adversely affects the process throughput. The transport channel with electrostatic lenses for decaborane (B{sub 10}H{sub 14}) and carborane (C{sub 2}B{sub 10}H{sub 12}) ion beams transportation was developed and investigated. The significant increase of ion beam intensity at the beam transport channel output is demonstrated. The transport channel simulation, construction and experimental results of ion beam transportation are presented.

  7. An intense low energy muon source for the muon collider

    SciTech Connect

    Taqqu, D.

    1996-05-01

    A scheme for obtaining an intense source of low energy muons is described. It is based on the production of pions in a high field magnetic bottle trap. By ensuring efficient slowing down and extraction of the decay muons an intense intermediate energy muon beam is obtained. For the specific case of negative muons a novel technique called frictional accumulation provides efficient conversion into a 10 keV{mu}{sup {minus}} beam whose emittance is then reduced in a configuration providing extended frictional cooling. The result is a beam of very small transverse and longitudinal emittance that can be used together with an equivalent {mu}{sup +} beam as compact intense muon source for the {mu}{sup +}{mu}{sup {minus}} collider. A final luminosity around 10{sup 34} cm{sup {minus}2}s{sup {minus}1} is expected to be obtained at 2 TeV. {copyright} {ital 1996 American Institute of Physics.}

  8. HIGH INTENSITY LOW-ENERGY POSITRON SOURCE AT JEFFERSON

    SciTech Connect

    Serkan Golge, Bogdan Wojtsekhowski, Branislav Vlahovic

    2012-07-01

    We present a novel concept of a low-energy e{sup +} source with projected intensity on the order of 10{sup 10} slow e{sup +}/s. The key components of this concept are a continuous wave e{sup -} beam, a rotating positron-production target, a synchronized raster/anti-raster, a transport channel, and extraction of e{sup +} into a field-free area through a magnetic plug for moderation in a cryogenic solid. Components were designed in the framework of GEANT4-based (G4beamline) Monte Carlo simulation and TOSCA magnetic field calculation codes. Experimental data to demonstrate the effectiveness of the magnetic plug is presented.

  9. Low-Energy Ions from Laser-Cooled Atoms

    NASA Astrophysics Data System (ADS)

    Shayeganrad, G.; Fioretti, A.; Guerri, I.; Tantussi, F.; Ciampini, D.; Allegrini, M.; Viteau, M.; Fuso, F.

    2016-05-01

    We report the features of an ion source based on two-color photoionization of a laser-cooled cesium beam outsourced from a pyramidal magneto-optical trap. The ion source operates in continuous or pulsed mode. At acceleration voltages below 300 V, it delivers some ten ions per bunch with a relative energy spread Δ Urms/U ≃0.032 , as measured through the retarding field-energy-analyzer approach. Space-charge effects are negligible thanks to the low ion density attained in the interaction volume. The performances of the ion beam in a configuration using focused laser beams are extrapolated on the basis of the experimental results. Calculations demonstrate that our low-energy and low-current ion beam can be attractive for the development of emerging technologies requiring the delivery of a small amount of charge, down to the single-ion level and its eventual focusing in the 10-nm range.

  10. Flux tube spectra from approximate integrability at low energies

    SciTech Connect

    Dubovsky, S. Flauger, R.; Gorbenko, V.

    2015-03-15

    We provide a detailed introduction to a method we recently proposed for calculating the spectrum of excitations of effective strings such as QCD flux tubes. The method relies on the approximate integrability of the low-energy effective theory describing the flux tube excitations and is based on the thermodynamic Bethe ansatz. The approximate integrability is a consequence of the Lorentz symmetry of QCD. For excited states, the convergence of the thermodynamic Bethe ansatz technique is significantly better than that of the traditional perturbative approach. We apply the new technique to the lattice spectra for fundamental flux tubes in gluodynamics in D = 3 + 1 and D = 2 + 1, and to k-strings in gluodynamics in D = 2 + 1. We identify a massive pseudoscalar resonance on the worldsheet of the confining strings in SU(3) gluodynamics in D = 3 + 1, and massive scalar resonances on the worldsheet of k = 2.3 strings in SU(6) gluodynamics in D = 2 + 1.

  11. Subtalar dislocation secondary to a low energy injury.

    PubMed

    McKeag, Philip; Lyske, Jonathan; Reaney, Jonathan; Thompson, Neville

    2015-01-01

    An 18-year-old young man presented with an ankle injury, after landing on a supinated right foot following jumping while playing football. A plain X-ray revealed a medial subtalar dislocation. Despite obvious ankle deformity, the surrounding skin remained intact. Closed reduction of the subtalar joint was successfully performed under general anaesthesia in theatre. A CT of the ankle, after reduction, demonstrated a non-displaced fracture of the neck of the talus; no osteochondral defect was observed. This was successfully managed conservatively, with immobilisation of the ankle, in a non-weight bearing cast for 6 weeks. This case highlights that subtalar dislocation may follow a low-energy mechanism and that such injuries can be managed without open reduction. PMID:25650063

  12. Molecular ion sources for low energy semiconductor ion implantation (invited)

    NASA Astrophysics Data System (ADS)

    Hershcovitch, A.; Gushenets, V. I.; Seleznev, D. N.; Bugaev, A. S.; Dugin, S.; Oks, E. M.; Kulevoy, T. V.; Alexeyenko, O.; Kozlov, A.; Kropachev, G. N.; Kuibeda, R. P.; Minaev, S.; Vizir, A.; Yushkov, G. Yu.

    2016-02-01

    Smaller semiconductors require shallow, low energy ion implantation, resulting space charge effects, which reduced beam currents and production rates. To increase production rates, molecular ions are used. Boron and phosphorous (or arsenic) implantation is needed for P-type and N-type semiconductors, respectively. Carborane, which is the most stable molecular boron ion leaves unacceptable carbon residue on extraction grids. A self-cleaning carborane acid compound (C4H12B10O4) was synthesized and utilized in the ITEP Bernas ion source resulting in large carborane ion output, without carbon residue. Pure gaseous processes are desired to enable rapid switch among ion species. Molecular phosphorous was generated by introducing phosphine in dissociators via 4PH3 = P4 + 6H2; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P4+ ion beams were extracted. Results from devices and some additional concepts are described.

  13. Linac4 low energy beam measurements with negative hydrogen ions

    SciTech Connect

    Scrivens, R. Bellodi, G.; Crettiez, O.; Dimov, V.; Gerard, D.; Granemann Souza, E.; Guida, R.; Hansen, J.; Lallement, J.-B.; Lettry, J.; Lombardi, A.; Midttun, Ø.; Pasquino, C.; Raich, U.; Riffaud, B.; Roncarolo, F.; Valerio-Lizarraga, C. A.; Wallner, J.; Yarmohammadi Satri, M.; Zickler, T.

    2014-02-15

    Linac4, a 160 MeV normal-conducting H{sup −} linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H{sup −} beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  14. Effects of low-energy electrons on DNA constituents: effective cross sections for condensed thymidine

    NASA Astrophysics Data System (ADS)

    Panajotovic, Radmila

    2009-05-01

    Since the first experiments of low-energy electron scattering from condensed DNA [1] have been performed, the interest in studying low-energy electron-biomolecule interactions has been increasing. Knowledge of effective cross sections for single- and double-strand breaks of DNA and for vibrational and electronic excitation of nucleic bases and nucleosides are opening the door to better understanding of effects of radiation on live tissue and possibly indicating interaction pathways leading to gene mutations and cancer. The strong variation of effective cross sections for DNA single-strand breaks with incident electron energy and the resonant enhancement at 1 eV suggested that considerable damage is inflicted by very low-energy electrons to DNA, and indicates the important role of π* shape resonances in the bond-breaking process. However, the complexity of DNA, even if studied as a short single-strand chain, imposes a need to perform measurements on its isolated constituents, such as nucleic bases and nucleosides. Thymidine is one of the most important nucleosides of DNA and an important component of antiviral compounds. In the condensed phase, thymidine's 2'-deoxyribose ring is in the pentose sugar ring form, which is a true conformation of this nucleoside in DNA. Results from High-Resolution Electron Energy Loss [2] study of monomolecular films of thymidine will be discussed and the presence of resonances in the effective cross sections at incident energy below 5 eV will be commented as a possible indication of the dissociative electron attachment. In addition, results on the resonance structures in the effective cross sections for electronic excitations for the incident electron energy from 1.5 to 12 eV will be discussed as a possible pathway for strand brakes in DNA. [4pt] [1] Boudaiffa B, Cloutier P, Hunting D, Huels M A and Sanche L 2002 Rad. Res. 157 227-234[0pt] [2] Panajotovic R, Martin F, Cloutier P, Hunting, D, and Sanche L, 2006 Rad.Res. 165 452

  15. Low energy ion beam dynamics of NANOGAN ECR ion source

    NASA Astrophysics Data System (ADS)

    Kumar, Sarvesh; Mandal, A.

    2016-04-01

    A new low energy ion beam facility (LEIBF) has been developed for providing the mass analyzed highly charged intense ion beams of energy ranging from a few tens of keV to a few MeV for atomic, molecular and materials sciences research. The new facility consists of an all permanent magnet 10 GHz electron cyclotron resonance (ECR) ion source (NANOGAN) installed on a high voltage platform (400 kV) which provides large currents of multiply charged ion beams. Higher emittance at low energy of intense ion beam puts a tremendous challenge to the beam optical design of this facility. The beam line consists of mainly the electrostatic quadrupoles, an accelerating section, analyzing cum switching magnet and suitable beam diagnostics including vacuum components. The accelerated ion beam is analyzed for a particular mass to charge (m/q) ratio as well as guided to three different lines along 75°, 90° and 105° using a large acceptance analyzing cum switching magnet. The details of transverse beam optics to all the beam lines with TRANSPORT and GICOSY beam optics codes are being described. Field computation code, OPERA 3D has been utilized to design the magnets and electrostatic quadrupoles. A theoretical estimation of emittance for optimized geometry of ion source is given so as to form the basis of beam optics calculations. The method of quadrupole scan of the beam is used to characterize the emittance of the final beam on the target. The measured beam emittance increases with m/q ratios of various ion beams similar to the trend observed theoretically.

  16. Transcanalicular laser dacryocystorhinostomy using low energy 810 nm diode laser

    PubMed Central

    Gupta, Sanjiv K.; Kumar, Ajai; Agarwal, Swati; Pandey, Paritosh

    2012-01-01

    Background: Hypertrophic scarring may be a cause of failure after transcanalicular laser dacryocystorhinostomy (DCR) surgery. This hypertrophic scarring results from tissue charring and excessive coagulation, which may be caused by the high laser energy. We have evaluated the use of low energy settings to prevent hypertrophic scarring, for a successful outcome. Aims: To perform and evaluate transcanalicular laser DCR using low energy 810 nm diode laser. Design: Interventional, non-comparative, case series. Materials and Methods: Patients with nasolacrimal duct obstruction and chronic dacryocystitis, who needed DCR, and were fit for surgery under local anesthesia, were recruited to undergo transcanalicular laser DCR using a 810 nm diode laser. The outcome was measured by the patency of the lacrimal passage, as indicated by the relief in the symptoms and the patency on syringing at the last follow-up. The surgical time and surgical complications were noted. Statistical Analysis Used: Descriptive analysis. Results: The study included 94 patients. The average age was 30.1 years (range 15 - 69 years). Seventy (74.4%) patients were female. Eight patients had failed external DCR. Per-operative patency of the passage was obtained in all the patients. Average surgical time was seven minutes (5 – 18 minutes). At the end of the study period of one year, a successful outcome was seen in 85 patients (90.5%). There were eight patients of previous failed DCR surgeries, and six of them achieved a cure at the end of follow-up. Conclusions: Transcanalicular Laser DCR can be safely performed using a low power 810 nm diode laser. The surgery is elegant, minimally invasive, allows fast rehabilitation, and has an excellent success rate. PMID:23439888

  17. Low-Energy Impacts onto Lunar Regolith Simulant

    NASA Astrophysics Data System (ADS)

    Seward, Laura M.; Colwell, J.; Mellon, M.; Stemm, B.

    2012-10-01

    Low-Energy Impacts onto Lunar Regolith Simulant Laura M. Seward1, Joshua E. Colwell1, Michael T. Mellon2, and Bradley A. Stemm1, 1Department of Physics, University of Central Florida, Orlando, Florida, 2Southwest Research Institute, Boulder, Colorado. Impacts and cratering in space play important roles in the formation and evolution of planetary bodies. Low-velocity impacts and disturbances to planetary regolith are also a consequence of manned and robotic exploration of planetary bodies such as the Moon, Mars, and asteroids. We are conducting a program of laboratory experiments to study low-velocity impacts of 1 to 5 m/s into JSC-1 lunar regolith simulant, JSC-Mars-1 Martian regolith simulant, and silica targets under 1 g. We use direct measurement of ejecta mass and high-resolution video tracking of ejecta particle trajectories to derive ejecta mass velocity distributions. Additionally, we conduct similar experiments under microgravity conditions in a laboratory drop tower and on parabolic aircraft with velocities as low as 10 cm/s. We wish to characterize and understand the collision parameters that control the outcome of low-velocity impacts into regolith, including impact velocity, impactor mass, target shape and size distribution, regolith depth, target relative density, and crater depth, and to experimentally determine the functional dependencies of the outcomes of low-velocity collisions (ejecta mass and ejecta velocities) on the controlling parameters of the collision. We present results from our ongoing study showing the positive correlation between impact energy and ejecta mass. The total ejecta mass is also dependent on the packing density (porosity) of the regolith. We find that ejecta mass velocity fits a power-law or broken power-law distribution. Our goal is to understand the physics of ejecta production and regolith compaction in low-energy impacts and experimentally validate predictive models for dust flow and deposition. We will present our

  18. Synthesis of sputtered thin films in low energy ion beams

    NASA Astrophysics Data System (ADS)

    Howson, R. P.

    1997-01-01

    Magnetron sputtering is a process which gives a highly energetic depositing species. The growing film can be further bombarded with ions of the heavy gas used for sputtering by directing a plasma of it onto the surface. This can be done quite simply by using an unbalanced magnetron. The immersion of an insulating or isolated substrate-film combination in this plasma leads to a self-bias of around 30 V appearing on it's surface and a bombardment of low energy ions of the sputtering gas of several milli-amps per square centimetre. If the residual gas contains a reactive component, to form a compound film, then the gas is made much more reactive and less is needed to form the stoichiometric film. This can take place in a continuously operating system made stable using partial pressure control of the reactive gas with plasma emission monitoring or something similar. It can also be operated when the process of deposition is separated in time from the process of reaction and is repeated to build the film. We have called this process successive-plasma-anodisation (SPA) and it can be achieved by mechanically transferring the substrate between two magnetrons, one to deposit the metal film and one, which is unbalanced, to provide an oxygen plasma. It can also be operated by pulsing the reactive gas under carefully controlled conditions. Examples are given of the synthesis of compound films using low energy ion bombardment with these techniques and it is demonstrated that excellent films of a large range of oxides and nitrides can be made.

  19. Response of BC418 Plastic Scintillator to Low Energy Protons

    NASA Astrophysics Data System (ADS)

    Daub, B. H.; Henzl, V.; Kovash, M. A.; Matthews, J. L.; Miller, Z. W.; Shoniyozov, K.; Yang, H.

    2012-10-01

    The response of fast plastic scintillators is unknown for proton energies below approximately 300 keV. The response of BC418 plastic scintillator to protons from 100 keV to 3.6 MeV was measured using elastic scattering of neutrons at the University of Kentucky and at the Los Alamos Neutron Science Center. At Kentucky, protons of precise energies from a Van de Graaff accelerator impinged on a thin LiF target to produce neutrons in narrow energy bands. At Los Alamos, neutrons were produced from a tungsten spallation source and their energies determined by time of flight. In both experiments a coincidence was detected between the recoiling proton in the plastic scintillator and the elastically scattered neutron in a liquid scintillator. The energy of the recoil proton is determined by the elastic scattering kinematics, with the scattered neutron energy precisely determined by time of flight. The results are compared with previous measurements of the response of similar plastic scintillators in the energy region where they overlap.

  20. Low energy electron impact vibrational excitation of acetylene

    NASA Astrophysics Data System (ADS)

    Patra, Sigma; Hargreaves, Leigh; Khakoo, Murtadha

    2016-05-01

    Experimental differential cross sections for the vibration excitation of the four fundamental modes of acetylene at low incident electron energies from 1 eV to 20 eV and scattering angles of 10o to 130o will be presented. The results will be compared to results available in the literature. Funded by NSF-AMOP-RUI Grant.

  1. Low-energy photons in high-energy photon fields--Monte Carlo generated spectra and a new descriptive parameter.

    PubMed

    Chofor, Ndimofor; Harder, Dietrich; Willborn, Kay; Rühmann, Antje; Poppe, Björn

    2011-09-01

    The varying low-energy contribution to the photon spectra at points within and around radiotherapy photon fields is associated with variations in the responses of non-water equivalent dosimeters and in the water-to-material dose conversion factors for tissues such as the red bone marrow. In addition, the presence of low-energy photons in the photon spectrum enhances the RBE in general and in particular for the induction of second malignancies. The present study discusses the general rules valid for the low-energy spectral component of radiotherapeutic photon beams at points within and in the periphery of the treatment field, taking as an example the Siemens Primus linear accelerator at 6 MV and 15 MV. The photon spectra at these points and their typical variations due to the target system, attenuation, single and multiple Compton scattering, are described by the Monte Carlo method, using the code BEAMnrc/EGSnrc. A survey of the role of low energy photons in the spectra within and around radiotherapy fields is presented. In addition to the spectra, some data compression has proven useful to support the overview of the behaviour of the low-energy component. A characteristic indicator of the presence of low-energy photons is the dose fraction attributable to photons with energies not exceeding 200 keV, termed P(D)(200 keV). Its values are calculated for different depths and lateral positions within a water phantom. For a pencil beam of 6 or 15 MV primary photons in water, the radial distribution of P(D)(200 keV) is bellshaped, with a wide-ranging exponential tail of half value 6 to 7 cm. The P(D)(200 keV) value obtained on the central axis of a photon field shows an approximately proportional increase with field size. Out-of-field P(D)(200 keV) values are up to an order of magnitude higher than on the central axis for the same irradiation depth. The 2D pattern of P(D)(200 keV) for a radiotherapy field visualizes the regions, e.g. at the field margin, where changes of

  2. Elastic electron scattering by ethyl vinyl ether

    SciTech Connect

    Khakoo, M. A.; Hong, L.; Kim, B.; Winstead, C.; McKoy, V.

    2010-02-15

    We report measured and calculated results for elastic scattering of low-energy electrons by ethyl vinyl ether (ethoxyethene), a prototype system for studying indirect dissociative attachment processes that may play a role in DNA damage. The integral cross section displays the expected {pi}{sup *} shape resonance. The agreement between the calculated and measured cross sections is generally good.

  3. Electromagnetic Form Factors of the Nucleon and Compton Scattering

    SciTech Connect

    Charles Hyde-Wright; Cornelis De Jager

    2004-12-01

    We review the experimental and theoretical status of elastic electron scattering and elastic low-energy photon scattering (with both real and virtual photons) from the nucleon. As a consequence of new experimental facilities and new theoretical insights, these subjects are advancing with unprecedented precision. These reactions provide many important insights into the spatial distributions and correlations of quarks in the nucleon.

  4. Enhancement of Compton scattering by an effective coupling constant

    SciTech Connect

    Barbiellini, Bernardo; Nicolini, Piero

    2011-08-15

    A robust thermodynamic argument shows that a small reduction of the effective coupling constant {alpha} of QED greatly enhances the low-energy Compton-scattering cross section and that the Thomson scattering length is connected to a fundamental scale {lambda}. A discussion provides a possible quantum interpretation of this enormous sensitivity to changes in the effective coupling constant {alpha}.

  5. Recent advances in Multi-Channel Algebraic Scattering

    SciTech Connect

    Karataglidis, S.; Fraser, P. R.; Amos, K.; Canton, L.; Pisent, G.; Svenne, J. P.; Knijff, D. van der

    2011-10-28

    For coupled-channel descriptions of low-energy nucleon-induced interactions involving nuclei with particle-unstable exited states, it is necessary to include the widths of the target states. How those widths may affect the elastic scattering cross sections is examined within the framework of the Multi-Channel Algebraic Scattering (MCAS) method.

  6. Development of deterministic transport methods for low energy neutrons for shielding in space

    NASA Technical Reports Server (NTRS)

    Ganapol, Barry

    1993-01-01

    Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade. The ENDF/B V database is used to generate the total and scattering cross sections for neutrons in

  7. Testing SO(10)-inspired leptogenesis with low energy neutrino experiments

    SciTech Connect

    Bari, Pasquale Di; Riotto, Antonio E-mail: Antonio.Riotto@cern.ch

    2011-04-01

    We extend the results of a previous analysis of ours showing that, when both heavy and light flavour effects are taken into account, successful minimal (type I + thermal) leptogenesis with SO(10)-inspired relations is possible. Barring fine tuned choices of the parameters, these relations enforce a hierarchical RH neutrino mass spectrum that results into a final asymmetry dominantly produced by the next-to-lightest RH neutrino decays (N{sub 2} dominated leptogenesis). We present the constraints on the whole set of low energy neutrino parameters. Allowing a small misalignment between the Dirac basis and the charged lepton basis as in the quark sector, the allowed regions enlarge and the lower bound on the reheating temperature gets relaxed to values as low as ∼ 10{sup 10} GeV. It is confirmed that for normal ordering (NO) there are two allowed ranges of values for the lightest neutrino mass: m{sub 1} ≅ (1−5) × 10{sup −3} eV and m{sub 1} ≅ (0.03−0.1) eV. For m{sub 1}∼<0.01 eV the allowed region in the plane θ{sub 13}-θ{sub 23} is approximately given by θ{sub 23}∼<49°+0.65 (θ{sub 13}−5°), while the neutrinoless double beta decay effective neutrino mass falls in the range m{sub ee} = (1−3) × 10{sup −3} eV for θ{sub 13} = (6°−11.5°). For m{sub 1}∼>0.01 eV, one has quite sharply m{sub ee} ≅ m{sub 1} and an upper bound θ{sub 23}∼<46°. These constraints will be tested by low energy neutrino experiments during next years. We also find that inverted ordering (IO), though quite strongly constrained, is not completely ruled out. In particular, we find approximately θ{sub 23} ≅ 43°+12° log (0.2 eV/m{sub 1}), that will be fully tested by future experiments.

  8. Low-energy theory for the graphene twist bilayer

    NASA Astrophysics Data System (ADS)

    Weckbecker, D.; Shallcross, S.; Fleischmann, M.; Ray, N.; Sharma, S.; Pankratov, O.

    2016-01-01

    The graphene twist bilayer represents the prototypical system for investigating the stacking degree of freedom in few-layer graphenes. The electronic structure of this system changes qualitatively as a function of angle, from a large-angle limit in which the two layers are essentially decoupled—with the exception of a 28-atom commensuration unit cell for which the layers are coupled on an energy scale of ≈8 meV —to a small-angle strong-coupling limit. Despite sustained investigation, a fully satisfactory theory of the twist bilayer remains elusive. The outstanding problems are (i) to find a theoretically unified description of the large- and small-angle limits, and (ii) to demonstrate agreement between the low-energy effective Hamiltonian and, for instance, ab initio or tight-binding calculations. In this article, we develop a low-energy theory that in the large-angle limit reproduces the symmetry-derived Hamiltonians of Mele [Phys. Rev. B 81, 161405 (2010), 10.1103/PhysRevB.81.161405], and in the small-angle limit shows almost perfect agreement with tight-binding calculations. The small-angle effective Hamiltonian is that of Bistritzer and MacDonald [Proc. Natl. Acad. Sci. (U.S.A.) 108, 12233 (2011), 10.1073/pnas.1108174108], but with the momentum scale Δ K , the difference of the momenta of the unrotated and rotated special points, replaced by a coupling momentum scale g(c )=8/π √{3 }a sinθ/2 . Using this small-angle Hamiltonian, we are able to determine the complete behavior as a function of angle, finding a complex small-angle clustering of van Hove singularities in the density of states (DOS) that after a "zero-mode" peak regime between 0 .90°<θ <0 .15° limits θ <0 .05° to a DOS that is essentially that of a superposition DOS of all bilayer stacking possibilities. In this regime, the Dirac spectrum is entirely destroyed by hybridization for -0.25

  9. Four-nucleon potential due to exchange of pions

    SciTech Connect

    Robilotta, M.R.

    1985-03-01

    A four-body force due to the exchange of pions has been derived by means of It includes effects corresponding to pion-pion scattering, pion production, and pion-nucleon rescattering. The strength parameters of this four-body potential are typically one order of magnitude smaller than those of the two-pion-exchange three-body force.

  10. A new look at low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B; Marwan, Jan

    2009-10-01

    This paper presents a new look at low-energy nuclear reaction research, a field that has developed from one of the most controversial subjects in science, "cold fusion." Early in the history of this controversy, beginning in 1989, a strong polarity existed; many scientists fiercely defended the claim of new physical effects as well as a new process in which like-charged atomic nuclei overcome the Coulomb barrier at normal temperatures and pressures. Many other scientists considered the entire collection of physical observations-along with the hypothesis of a "cold fusion"--entirely a mistake. Twenty years later, some people who had dismissed the field in its entirety are considering the validity of at least some of the reported experimental phenomena. As well, some researchers in the field are wondering whether the underlying phenomena may be not a fusion process but a neutron capture/absorption process. In 2002, a related tabletop form of thermonuclear fusion was discovered in the field of acoustic inertial confinement fusion. We briefly review some of this work, as well. PMID:19809695

  11. Fragmentation efficiencies of peptide ions following low energy collisional activation

    NASA Astrophysics Data System (ADS)

    Summerfield, Scott G.; Gaskell, Simon J.

    1997-11-01

    Low energy fragmentations of protonated peptides in the gas phase are generally attributed to charge-directed processes. The extent and location of peptide backbone fragmentation is accordingly influenced by the extent to which charge is sequestered on amino acid side-chains. We describe systematic studies of the efficiencies of decomposition of peptide ions to assess in particular the influence of the presence of basic amino acid residues and of the protonation state. In a set of analogues containing two arginine, two histidine or two lysine residues, the extent of fragmentation of [M + 2H]2+ ions decreases with increased basicity, reflecting decreased backbone protonation. The collisionally activated dissociation of multiply protonated melittin ions shows an increase in fragmentation efficiency with higher charge state (using activation conditions which are similar for each charge state). For a single charge state, acetylation of primary amine groups increases fragmentation efficiency, consistent with the reduction in basicity of lysine side-chains. Conversion of arginine residues to the less basic dimethylpyrimidylornithine, however, decreases fragmentation efficiency, suggesting more effective sequestering of ionizing protons; the effect may be attributable to a disfavouring of proton-bridged structures but this hypothesis requires further study. Preliminary data for the decompositions of [M- 2H]2- ions derived from peptides containing two acidic residues suggest that the sequestration of charge away from the backbone is again detrimental to efficient fragmentation. Apparently diagnostic cleavages adjacent to aspartic acid residues are observed.

  12. Milagro: A low energy threshold extensive air shower array

    NASA Astrophysics Data System (ADS)

    Sinnis, Gus

    1995-07-01

    Observations of gamma-ray bursts, active galactic nuclei, and radio pulsars by CGRO have revolutionized our view of the cosmos. Sources may pop into existence for a few milliseconds never to appear again and galaxies can change their luminosity by an order of magnitude within a few days. In addition to these space-based measurements, there have been at least 2 sources detected at even higher energies, ~1 TeV, using earth-bound detectors. To date, ground-based detectors of high-energy gamma rays with energy thresholds low enough to make credible detections have all had narrow fields of view and low duty factors. While these detectors are well suited to perform detailed studies of selected sources, they can not perform surveys of the entire sky with adequate sensitivity in a reasonable amount of time. We have designed a new type of ground-based gamma-ray detector with a low energy threshold, ~250 GeV, large aperture (~1 sr), and a duty factor greater than 90%-Milagro.

  13. Low energy, high power hydrogen neutral beam for plasma heating

    NASA Astrophysics Data System (ADS)

    Deichuli, P.; Davydenko, V.; Ivanov, A.; Korepanov, S.; Mishagin, V.; Smirnov, A.; Sorokin, A.; Stupishin, N.

    2015-11-01

    A high power, relatively low energy neutral beam injector was developed to upgrade of the neutral beam system of the gas dynamic trap device and C2-U experiment. The ion source of the injector produces a proton beam with the particle energy of 15 keV, current of up to 175 A, and pulse duration of a few milliseconds. The plasma emitter of the ion source is produced by superimposing highly ionized plasma jets from an array of four arc-discharge plasma generators. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase the efficiency and improve the uniformity of the plasma emitter. Multi-slit grids with 48% transparency are fabricated from bronze plates, which are spherically shaped to provide geometrical beam focusing. The focal length of the Ion Optical System (IOS) is 3.5 m and the initial beam diameter is 34 cm. The IOS geometry and grid potentials were optimized numerically to ensure accurate beam formation. The measured angular divergences of the beam are ±0.01 rad parallel to the slits and ±0.03 rad in the transverse direction.

  14. Optical intraday variability studies of 10 low energy peaked blazars

    NASA Astrophysics Data System (ADS)

    Rani, Bindu; Gupta, Alok C.; Joshi, U. C.; Ganesh, S.; Wiita, Paul J.

    2011-05-01

    We have carried out optical (R band) intraday variability (IDV) monitoring of a sample of 10 bright low energy peaked blazars (LBLs). 40 photometric observations, of an average of ˜4 h each, were made between 2008 September and 2009 June using two telescopes in India. Measurements with good signal-to-noise ratios were typically obtained within 1-3 min, allowing the detection of weak, fast variations using N-star differential photometry. We employed both structure function and discrete correlation function analysis methods to estimate any dominant time-scales of variability and found that in most of the cases any such time-scales were longer than the duration of the observation. The calculated duty cycle of IDV in LBLs during our observing run is ˜52 per cent, which is low compared to many earlier studies; however, the relatively short periods for which each source was observed can probably explain this difference. We briefly discuss possible emission mechanisms for the observed variability.

  15. Options for Production Staging for a Low Energy Neutrino Factory

    SciTech Connect

    Berg J. S.

    2011-10-26

    A low energy neutrino factory (LENF) is defined, for the purpose of this report, to accelerate a muon beam to a total energy in the range of 10-14 GeV, and store it in a decay ring directing a resulting neutrino beam to a detector 2200-2300 km distant. The machine should be ultimately capable of producing 10{sup 21} decays toward that detector per year of 10{sup 7} s. We consider such a neutrino factory to be the accelerator defined in the Interim Design Report (IDR) of the International Design Study for the Neutrino Factory (IDS-NF), modified to remove the final stage of acceleration, possibly modifying the remaining acceleration stages to adjust the final energy, and replacing the decay ring with one designed for the lower energy and shorter baseline. We discuss modifications to that design which would reduce the cost of the machine at the price of a reduction in neutrino production, down to as low as 10{sup 20} decays per year. These modifications will not preclude eventually upgrading the machine to the full production of 10{sup 21} decays per year. The eventual cost of a machine which achieves the full production through a series of lower-production stages should not exceed the cost of a machine which is immediately capable of the full production by more than a small fraction of the cost difference between the full production machine and the lowest production stage.

  16. Review of lattice results concerning low-energy particle physics

    SciTech Connect

    Aoki, S.; Aoki, Y.; Bernard, C.; Blum, T.; Colangelo, G.; Della Morte, M.; Dürr, S.; El-Khadra, A. X.; Fukaya, H.; Horsley, R.; Jüttner, A.; Kaneko, T.; Laiho, J.; Lellouch, L.; Leutwyler, H.; Lubicz, V.; Lunghi, E.; Necco, S.; Onogi, T.; Pena, C.; Sachrajda, C. T.; Sharpe, S. R.; Simula, S.; Sommer, R.; Van de Water, R. S.; Vladikas, A.; Wenger, U.; Wittig, H.

    2014-09-01

    We review lattice results related to pion, kaon, D- and B-meson physics with the aim of making them easily accessible to the particle physics community. More specifically, we report on the determination of the light-quark masses, the form factor f+(0), arising in semileptonic K -> pi transition at zero momentum transfer, as well as the decay constant ratio fK/fpi of decay constants and its consequences for the CKM matrix elements Vus and Vud. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2)LxSU(2)R and SU(3)LxSU(3)R Chiral Perturbation Theory and review the determination of the BK parameter of neutral kaon mixing. The inclusion of heavy-quark quantities significantly expands the FLAG scope with respect to the previous review. Therefore, for this review, we focus on D- and B-meson decay constants, form factors, and mixing parameters, since these are most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. In addition we review the status of lattice determinations of the strong coupling constant alpha_s.

  17. Dose controlled low energy electron irradiator for biomolecular films

    NASA Astrophysics Data System (ADS)

    Kumar, S. V. K.; Tare, Satej T.; Upalekar, Yogesh V.; Tsering, Thupten

    2016-03-01

    We have developed a multi target, Low Energy Electron (LEE), precise dose controlled irradiator for biomolecular films. Up to seven samples can be irradiated one after another at any preset electron energy and dose under UHV conditions without venting the chamber. In addition, one more sample goes through all the steps except irradiation, which can be used as control for comparison with the irradiated samples. All the samples are protected against stray electron irradiation by biasing them at -20 V during the entire period, except during irradiation. Ethernet based communication electronics hardware, LEE beam control electronics and computer interface were developed in house. The user Graphical User Interface to control the irradiation and dose measurement was developed using National Instruments Lab Windows CVI. The working and reliability of the dose controlled irradiator has been fully tested over the electron energy range of 0.5 to 500 eV by studying LEE induced single strand breaks to ΦX174 RF1 dsDNA.

  18. Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

    SciTech Connect

    Stratton, J. Chris; Singer, Brett C.

    2014-01-01

    Cooking and cooking burners emit pollutants that can adversely affect indoor air quality in residences and significantly impact occupant health. Effective kitchen exhaust ventilation can reduce exposure to cooking-related air pollutants as an enabling step to healthier, low-energy homes. This report identifies barriers to the widespread adoption of kitchen exhaust ventilation technologies and practice and proposes a suite of strategies to overcome these barriers. The recommendations have been vetted by a group of industry, regulatory, health, and research experts and stakeholders who convened for two web-based meetings and provided input and feedback to early drafts of this document. The most fundamental barriers are (1) the common misconception, based on a sensory perception of risk, that kitchen exhaust when cooking is unnecessary and (2) the lack of a code requirement for kitchen ventilation in most US locations. Highest priority objectives include the following: (1) Raise awareness among the public and the building industry of the need to install and routinely use kitchen ventilation; (2) Incorporate kitchen exhaust ventilation as a requirement of building codes and improve the mechanisms for code enforcement; (3) Provide best practice product and use-behavior guidance to ventilation equipment purchasers and installers, and; (4) Develop test methods and performance targets to advance development of high performance products. A specific, urgent need is the development of an over-the-range microwave that meets the airflow and sound requirements of ASHRAE Standard 62.2.

  19. Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

    SciTech Connect

    Stratton, J. Chris; Singer, Brett C.

    2014-01-01

    Cooking and cooking burners emit pollutants that can adversely affect indoor air quality in residences and significantly impact occupant health. Effective kitchen exhaust ventilation can reduce exposure to cooking-related air pollutants as an enabling step to healthier, low-energy homes. This report by Lawrence Berkeley National Laboratory identifies barriers to the widespread adoption of kitchen exhaust ventilation technologies and practice and proposes a suite of strategies to overcome these barriers. The recommendations have been vetted by a group of industry, regulatory, health, and research experts and stakeholders who convened for two meetings and provided input and feedback to early drafts of this document. The most fundamental barriers are (1) the common misconception, based on a sensory perception of risk, that kitchen exhaust when cooking is unnecessary and (2) the lack of a code requirement for kitchen ventilation in most U.S. locations. Highest priority objectives include the following: (1) Raise awareness among the public and the building industry of the need to install and routinely use kitchen ventilation; (2) Incorporate kitchen exhaust ventilation as a requirement of building codes and improve the mechanisms for code enforcement; (3) Provide best practice product and use-behavior guidance to ventilation equipment purchasers and installers, and; (4) Develop test methods and performance targets to advance development of high performance products. A specific, urgent need is the development of an over-the-range microwave that meets the airflow and sound requirements of ASHRAE Standard 62.2.

  20. Analysis of latency performance of bluetooth low energy (BLE) networks.

    PubMed

    Cho, Keuchul; Park, Woojin; Hong, Moonki; Park, Gisu; Cho, Wooseong; Seo, Jihoon; Han, Kijun

    2015-01-01

    Bluetooth Low Energy (BLE) is a short-range wireless communication technology aiming at low-cost and low-power communication. The performance evaluation of classical Bluetooth device discovery have been intensively studied using analytical modeling and simulative methods, but these techniques are not applicable to BLE, since BLE has a fundamental change in the design of the discovery mechanism, including the usage of three advertising channels. Recently, there several works have analyzed the topic of BLE device discovery, but these studies are still far from thorough. It is thus necessary to develop a new, accurate model for the BLE discovery process. In particular, the wide range settings of the parameters introduce lots of potential for BLE devices to customize their discovery performance. This motivates our study of modeling the BLE discovery process and performing intensive simulation. This paper is focused on building an analytical model to investigate the discovery probability, as well as the expected discovery latency, which are then validated via extensive experiments. Our analysis considers both continuous and discontinuous scanning modes. We analyze the sensitivity of these performance metrics to parameter settings to quantitatively examine to what extent parameters influence the performance metric of the discovery processes. PMID:25545266