WorldWideScience

Sample records for low-energy spin fluctuations

  1. Low-energy spin fluctuations in the non-Fermi-liquid compound YbRh2Si2

    Directory of Open Access Journals (Sweden)

    O. Stockert et al

    2007-01-01

    Full Text Available We report on inelastic neutron scattering experiments on YbRh2Si2 powder to study the low-energy spin dynamics at temperatures between T=0.8 and 22 K. The low-energy magnetic response is quasielastic. However, it exhibits an unusual form not modelled by a simple relaxation rate yielding a Lorentzian lineshape, but can satisfactorily be described by a phenomenological model involving a distribution of relaxation rates. The lower bound of the relaxation rates varies roughly linear with temperature indicating a pronounced slowing down of the critical modes above the antiferromagnetic ordering temperature TNapprox70 mK.

  2. Spin fluctuations and the

    Directory of Open Access Journals (Sweden)

    V.M. Loktev

    2008-09-01

    Full Text Available We analyze the spectral properties of a phenomenological model for a weakly doped two-dimensional antiferromagnet, in which the carriers move within one of the two sublattices where they were introduced. Such a constraint results in the free carrier spectra with the maxima at k=(± π/2 , ± π/2 observed in some cuprates. We consider the spectral properties of the model by taking into account fluctuations of the spins in the antiferromagnetic background. We show that such fluctuations lead to a non-pole-like structure of the single-hole Green's function and these fluctuations can be responsible for some anomalous "strange metal" properties of underdoped cuprates in the nonsuperconducting regime.

  3. Glassy low-energy spin fluctuations and anisotropy gap in La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, A. T.; Chang, J.; Christensen, Niels Bech

    2013-01-01

    between the ordering temperature TN ≃ Tc inferred from elastic neutron scattering and the freezing temperature Tf ≃ 11 K obtained from muon spin rotation studies. The magnetic field independence of the observed excitation spectrum as well as the observation of a partial suppression of magnetic spectral...

  4. Vacuum fluctuations of $\\overline{q}q$ and values of low-energy constants

    CERN Document Server

    Descotes, S

    2000-01-01

    We discuss the influence of the vacuum fluctuations of \\bar{q}q pairs on low-energy constants and condensates. The analysis of the Goldstone boson masses and decay constants shows that the three-flavour condensate and some low-energy constants are very sensitive to the value of L_6, which measures the Zweig-rule violation in the scalar channel. A chiral sum rule based on experimental data in this channel is used to constrain L_6, confirming a significant decrease between the two- and the three-flavor condensates.

  5. The surface magnetization study of Cr2O3 by spin polarized low energy electron microscopy

    Science.gov (United States)

    Cao, Shi; Wu, Ning; Zhang, Xin; N'diaye, Alpha; Chen, Gong; Schmid, Andreas; Echtenkamp, Will; Lauter, Valeria; Binek, Christian; Dowben, Peter

    2014-03-01

    The boundary magnetization at the surface of a Cr2O3 single crystal has been demonstrated by using spin-polarized low-energy electron microscopy (SPLEEM), indicating net surface spin polarization. This work shows that the placement of Cr2O3 single crystal in the single domain state, will result in net Cr2O3 spin polarization at the boundary, even in the presence of a gold overlayer. There are indications that the spin-polarized low-energy electron microscopy (SPLEEM) contrast for the two polarizations states is different. In addition, the boundary magnetization protected by the symmetry exists despite of the surface roughness/softness which was studied by the non-spin neutron reflectometry and low energy electron diffraction. Unoccupied surface oxygen sites and chromium sites are possible mechanism contributing to the surface ``softness,'' which will be discussed.

  6. Spin fluctuations in 3d paramagnetic metals

    Science.gov (United States)

    Wysocki, Aleksander; Kutepov, Andrey; Antropov, Vladimir

    Spin fluctuations (SFs) in 3d paramagnetic metals were investigated using the linear response formalism within the time dependent density functional theory. An efficient scheme of frequency integration using the Matsubara technique has been implemented and tested. The SFs spectrum in 3d paramagnets is analyzed in real and reciprocal spaces as a function of frequency and temperature. For all materials the SFs are characterized by the coexistence of low and high energy branches which originate from different regions of the Brillouin zone. The low-energy ones can be measured by neutron scattering experiments while the high-energy SFs appear to be more localized. Further, we studied the nature of square of fluctuating magnetic moment in these materials. This work was supported, in part, by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy (DOE), and by the Office of Basic Energy Science, Division of Materials Science and Engineering. The research was performed at Ames Laboratory, which is operated for the U.S. DOE by Iowa State University under contract # DE-AC02-07CH11358.

  7. Proceedings of RIKEN BNL Resarch Center Workshop: Fluctuations, Correlations and RHIC Low Energy Runs

    Energy Technology Data Exchange (ETDEWEB)

    Karsch, F.; Kojo, T.; Mukherjee, S.; Stephanov, M.; Xu, N.

    2011-10-27

    Most of our visible universe is made up of hadronic matter. Quantum Chromodynamics (QCD) is the theory of strong interaction that describes the hadronic matter. However, QCD predicts that at high enough temperatures and/or densities ordinary hadronic matter ceases to exist and a new form of matter is created, the so-called Quark Gluon Plasma (QGP). Non-perturbative lattice QCD simulations shows that for high temperature and small densities the transition from the hadronic to the QCD matter is not an actual phase transition, rather it takes place via a rapid crossover. On the other hand, it is generally believed that at zero temperature and high densities such a transition is an actual first order phase transition. Thus, in the temperature-density phase diagram of QCD, the first order phase transition line emanating from the zero temperature high density region ends at some higher temperature where the transition becomes a crossover. The point at which the first order transition line turns into a crossover is a second order phase transition point belonging to three dimensional Ising universality class. This point is known as the QCD Critical End Point (CEP). For the last couple of years the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has been performing experiments at lower energies in search of the elusive QCD CEP. In general critical behaviors are manifested through appearance of long range correlations and increasing fluctuations associated with the presence of mass-less modes in the vicinity of a second order phase transition. Experimental signatures of the CEP are likely to be found in observables related to fluctuations and correlations. Thus, one of the major focuses of the RHIC low energy scan program is to measure various experimental observables connected to fluctuations and correlations. On the other hand, with the start of the RHIC low energy scan program, a flurry of activities are taking place to provide solid theoretical

  8. Electric probe for spin transition and fluctuation

    Science.gov (United States)

    Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'diaye, Alpha T.; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Tserkovnyak, Yaroslov; Qiu, Z. Q.; Saitoh, Eiji

    Spin fluctuation and transition have always been one of central topics of magnetism and condense matter science. To probe them, neutron scatterings have been used as powerful tools. A part of neutrons injected into a sample is scattered by spin fluctuation inside the sample. This process transcribes the spin fluctuation onto scattering intensity, which is commonly represented by dynamical magnetic susceptibility of the sample and is maximized at magnetic phase transitions. Importantly, a neutron carries spin without electric charge, and it thus can bring spin into a sample without being disturbed by electric energy: an advantage of neutrons, although large facilities such as a nuclear reactor is necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop micro probe for spin fluctuation and transition; not only a neutron beam, spin current is also a flux of spin without an electric charge and its transport reflects spin fluctuation in a sample. We demonstrate detection of anti-ferromagnetic transition in ultra-thin CoO films via frequency dependent spin-current transmission measurements.

  9. Low Energy Properties of the Random Spin-1/2 Ferromagnetic-Antiferromagnetic Heisenberg Chain

    OpenAIRE

    Hida, Kazuo

    1996-01-01

    The low energy properties of the spin-1/2 random Heisenberg chain with ferromagnetic and antiferromagnetic interactions are studied by means of the density matrix renormalization group (DMRG) and real space renormalization group (RSRG) method for finite chains. The results of the two methods are consistent with each other. The deviation of the gap distribution from that of the random singlet phase and the formation of the large-spin state is observed even for relatively small systems. For a s...

  10. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-07-15

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

  11. Spin fluctuations and high-temperature superconductivity in cuprates

    Science.gov (United States)

    Plakida, Nikolay M.

    2016-12-01

    To describe the cuprate superconductors, models of strongly correlated electronic systems, such as the Hubbard or t - J models, are commonly employed. To study these models, projected (Hubbard) operators have to be used. Due to the unconventional commutation relations for the Hubbard operators, a specific kinematical interaction of electrons with spin and charge fluctuations emerges. The interaction is induced by the intraband hopping with a coupling parameter of the order of the kinetic energy of electrons W which is much larger than the antiferromagnetic exchange interaction J induced by the interband hopping. This review presents a consistent microscopic theory of spin excitations and superconductivity for cuprates where these interactions are taken into account within the Hubbard operator technique. The low-energy spin excitations are considered for the t-J model, while the electronic properties are studied using the two-subband extended Hubbard model where the intersite Coulomb repulsion V and electron-phonon interaction are taken into account.

  12. Anisotropic spin fluctuations in metallic erbium

    Energy Technology Data Exchange (ETDEWEB)

    Waeppling, R.; Hartmann, O.; Harris, S.; Karlsson, E. (Uppsala Univ., Dept. of Physics (Sweden)); Kalvius, G.M.; Asch, L.; Kratzer, A. (Physik Dept., Technische Univ. Muenchen, Garching (Germany)); Dalmas de Reotier, P.; Yaouanc, A. (CENG/DRFMC/LIH, 38 - Grenoble (France))

    1993-02-01

    From a [mu]SR study of metallic erbium single crystals, the presence of anisotropic spin correlations in the paramagnetic state at temperatures well above T[sub N] has been detected. The temperature dependence of the depolarization rate of the muon precession signal gives a dynamical critical exponent of 0.15(3) for the fluctuations of the magnetic field component at the muon site that is parallel with the c-axis. For magnetic field components perpendicular to the c-axis there are no indications of slowing down of fluctuations due to the onset of spin correlations on approaching T[sub N]. (orig.).

  13. Spin fluctuation theory of itinerant electron magnetism

    CERN Document Server

    Takahashi, Yoshinori

    2013-01-01

    This volume shows how collective magnetic excitations determine most of  the magnetic properties of itinerant electron magnets. Previous theories were mainly restricted to the Curie-Weiss law temperature dependence of magnetic susceptibilities. Based on the spin amplitude conservation idea including the zero-point fluctuation amplitude, this book shows that the entire temperature and magnetic field dependence of magnetization curves, even in the ground state, is determined by the effect of spin fluctuations. It also shows that the theoretical consequences are largely in agreement with many experimental observations. The readers will therefore gain a new comprehensive perspective of their unified understanding of itinerant electron magnetism.

  14. Low-Energy Effective Theories of Quantum Link and Quantum Spin Models

    CERN Document Server

    Schlittgen, B

    2001-01-01

    Quantum spin and quantum link models provide an unconventional regularization of field theory in which classical fields arise via dimensional reduction of discrete variables. This D-theory regularization leads to the same continuum theories as the conventional approach. We show this by deriving the low-energy effective Lagrangians of D-theory models using coherent state path integral techniques. We illustrate our method for the $(2+1)$-d Heisenberg quantum spin model which is the D-theory regularization of the 2-d O(3) model. Similarly, we prove that in the continuum limit a $(2+1)$-d quantum spin model with $SU(N)_L\\times SU(N)_R\\times U(1)_{L=R}$ symmetry is equivalent to the 2-d principal chiral model. Finally, we show that $(4+1)$-d SU(N) quantum link models reduce to ordinary 4-d Yang-Mills theory.

  15. Analytic model for low energy excitation states and phase transitions in spin-ice systems

    Science.gov (United States)

    López-Bara, F. I.; López-Aguilar, F.

    2017-04-01

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole–antipole pairs, possibly having Bose–Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  16. Love triangles, quantum fluctuations and spin jam

    Science.gov (United States)

    Lee, Seung-Hun

    When magnetic moments are interacting with each other in a situation resembling that of complex love triangles, called frustration, a large set of states that are energetically equivalent emerge. This leads to exotic spin states such as spin liquid and spin ice. Recently, we presented evidence for the existence of a topological glassy state, that we call spin jam, induced by quantum fluctuations. The case in point is SrCr9pGa12-9pO19 (SCGO(p)), a highly frustrated magnet, in which the magnetic Cr ions form a quasi-two-dimensional triangular system of bi-pyramids. This system has been an archetype in search for exotic spin states. Understanding the nature of the state has been a great intellectual challenge. Our new experimental data and theoretical spin jam model provide for the first time a coherent understanding of the phenomenon. Furthermore, the findings strongly support the possible existence of purely topological glassy states. Reference:

  17. Low-Energy Charge and Spin Dynamics in Quantum Confined Systems

    Science.gov (United States)

    Rice, William D.

    Condensed matter systems exhibit a variety of dynamical phenomena at low energy scales, from gigahertz (GHz) to terahertz (THz) frequencies in particular, arising from complex interplay between charge, spin, and lattice. A large number of collective and elementary excitations in solids occur in this frequency range, which are further modified and enriched by scattering, interactions, and disorder. Recent advancements in spectroscopic methods for probing low-energy dynamics allow us to investigate novel aspects of charge and spin dynamics in solids. In this dissertation work, we used direct current (DC) conductivity, GHz, THz, and mid-infrared (MIR) techniques to provide significant new insights into interaction and disorder effects in low-dimensional systems. Specifically, we have studied temperature-dependent magnetoresistance (MR) and electron spin resonance (ESR) in single-wall carbon nanotubes (SWCNTs), intra-exciton scattering in InGaAs quantum wells, and high-field MIR-induced band gaps in graphene. Temperature-dependent resistance and MR were measured in an ensemble of SWCNTs from 0.3 to 350 K. The resistance temperature behavior followed a 3D variable range hopping (VRH) behavior from 0.3 to ˜100 K. A positive MR was observed at temperatures above 25 K and could be fit with a spin-dependent VRH model; negative MR was seen at low temperatures. In the GHz regime, the ESR linewidth for SWCNTs was observed to narrow by as much as 50% as the temperature was increased from 3 to 300 K, a phenomenon known as motional narrowing, suggesting that we are detecting the ESR of hopping spins. From the linewidth change versus temperature, we find the hopping frequency to be 285 GHz. For excitons in InGaAs quantum wells, we demonstrate the manipulation of intra-excitonic populations using intense, narrow-band THz pulses. The THz radiation temporarily quenches the 1s emission, which is then followed by an enhancement and subsequent decay of 2s emission. After the quenching

  18. Direct observation of low energy nuclear spin excitations in HoCrO3 by high resolution neutron spectroscopy.

    Science.gov (United States)

    Chatterji, T; Jalarvo, N; Kumar, C M N; Xiao, Y; Brückel, Th

    2013-07-17

    We have investigated low energy nuclear spin excitations in the strongly correlated electron compound HoCrO3. We observe clear inelastic peaks at E = 22.18 ± 0.04 μeV in both energy loss and gain sides. The energy of the inelastic peaks remains constant in the temperature range 1.5-40 K at which they are observed. The intensity of the inelastic peak increases at first with increasing temperature and then decreases at higher temperatures. The temperature dependence of the energy and intensity of the inelastic peaks is very unusual compared to that observed in other Nd, Co, V and also simple Ho compounds. Huge quasielastic scattering appears at higher temperatures presumably due to the fluctuating electronic moments of the Ho ions that get increasingly disordered at higher temperatures. The strong quasielastic scattering may also originate in the first Ho crystal-field excitations at about 1.5 meV.

  19. Anomalous magnetic fluctuations in superconducting Sr2RuO4 revealed by 101Ru nuclear spin-spin relaxation

    Science.gov (United States)

    Manago, Masahiro; Yamanaka, Takayoshi; Ishida, Kenji; Mao, Zhiqiang; Maeno, Yoshiteru

    2016-10-01

    We carried out 101Ru nuclear quadrupole resonance (NQR) measurement on superconducting (SC) Sr2RuO4 under zero magnetic field (H =0 ) and found that the nuclear spin-spin relaxation rate 1 /T2 is enhanced in the SC state. The 1 /T2 measurement in the SC state under H =0 is effective for detecting slow magnetic fluctuations parallel to the quantized axis of the nuclear spin. Our results indicate that low-energy magnetic fluctuations perpendicular to the RuO2 plane emerge when the superconductivity sets in, which is consistent with the previous 17O-NQR result that the nuclear spin-lattice relaxation rate 1 /T1 of the in-plane O site exhibits anomalous behavior in the SC state. The enhancement of the magnetic fluctuations in the SC state is unusual and suggests that the fluctuations are related to the unconventional SC pairing. We suggest that this phenomenon is a consequence of the spin degrees of freedom of the spin-triplet pairing.

  20. Effects of impurities and vortices on the low-energy spin excitations in high-Tc materials

    DEFF Research Database (Denmark)

    Andersen, Brian Møller; Graser, S.; Schmid, M.

    2011-01-01

    We review a theoretical scenario for the origin of the spin-glass phase of underdoped cuprate materials. In particular it is shown how disorder in a correlated d-wave superconductor generates a magnetic phase by inducing local droplets of antiferromagnetic order which eventually merge and form a ...... disorder and/or applied magnetic fields lead to a slowing down of the dynamical spin fluctuations in agreement with neutron scattering and muon spin rotation (mSR) experiments....

  1. Magnetism of epitaxial Tb films on W(110) studied by spin-polarized low-energy electron microscopy

    Science.gov (United States)

    Prieto, J. E.; Chen, Gong; Schmid, A. K.; de la Figuera, J.

    2016-11-01

    Thin epitaxial films of Tb metal were grown on a clean W(110) substrate in ultrahigh vacuum and studied in situ by low-energy electron microscopy. Annealed films present magnetic contrast in spin-polarized low-energy electron microscopy. The energy dependence of the electron reflectivity was determined and a maximum value of its spin asymmetry of about 1% was measured. The magnetization direction of the Tb films is in-plane. Upon raising the temperature, no change in the domain distribution is observed, while the asymmetry in the electron reflectivity decreases when approaching the critical temperature, following a power law ˜(1-T /TC) β with a critical exponent β of 0.39.

  2. Magnetism of metals in the dynamic spin-fluctuation theory

    Science.gov (United States)

    Melnikov, N. B.; Reser, B. I.

    2016-12-01

    We overview new developments in spin-fluctuation theory, which describes magnetic properties of ferromagnetic metals at finite temperatures. We present a detailed analysis of the underlying techniques and compare numerical results with experiment.

  3. Low energy nuclear spin excitations in Ho metal investigated by high resolution neutron spectroscopy.

    Science.gov (United States)

    Chatterji, Tapan; Jalarvo, Niina

    2013-04-17

    We have investigated the low energy excitations in metallic Ho by high resolution neutron spectroscopy. We found at T = 3 K clear inelastic peaks in the energy loss and energy gain sides, along with the central elastic peak. The energy of this low energy excitation, which is 26.59 ± 0.02 μeV at T = 3 K, decreased continuously and became zero at TN ≈ 130 K. By fitting the data in the temperature range 100-127.5 K with a power law we obtained the power-law exponent β = 0.37 ± 0.02, which agrees with the expected value β = 0.367 for a three-dimensional Heisenberg model. Thus the energy of the low energy excitations can be associated with the order parameter.

  4. Low Energy Tests of the Standard Model with Spin Degrees of Freedom

    CERN Document Server

    Erler, J

    2007-01-01

    After briefly reviewing the status of the standard model, I will focus mainly on polarized electron scattering and other tests of the weak neutral current. I will also address other low energy tests in which polarization degrees of freedom play a crucial role, including precision muon physics and searches for electric dipole moments.

  5. Universal spin-polarization fluctuations in one-dimensional wires with magnetic impurities

    DEFF Research Database (Denmark)

    Mortensen, Asger; Egues, J.C.

    2002-01-01

    -flip suppresses conductance fluctuations while enhancing spin-polarization fluctuations. More importantly, spin-polarization fluctuations attain a universal value 1/3 for large enough spin-flip strengths. This intrinsic spin-polarization fluctuation may pose a severe limiting factor to the realization of steady...

  6. Low-energy spin dynamics of the s = 1/2 kagome system herbertsmithite.

    Science.gov (United States)

    Nilsen, G J; de Vries, M A; Stewart, J R; Harrison, A; Rønnow, H M

    2013-03-13

    The low-energy (ε = ħω kagome candidate herbertsmithite are probed in the presence of magnetic fields up to 2.5 T. The zero-field spectra reveal a very weak continuum of scattering at T = 10 K and a broad inelastic peak centred at ε(max) = 0.2 meV at lower temperatures, T kagome planes and moments in the kagome layers.

  7. Effect of transverse vibrations of fissile nuclei on the angular and spin distributions of low-energy fission fragments

    Science.gov (United States)

    Bunakov, V. E.; Kadmensky, S. G.; Lyubashevsky, D. E.

    2016-05-01

    It is shown that A. Bohr's classic theory of angular distributions of fragments originating from low-energy fission should be supplemented with quantum corrections based on the involvement of a superposition of a very large number of angular momenta L m in the description of the relative motion of fragments flying apart along the straight line coincidentwith the symmetry axis. It is revealed that quantum zero-point wriggling-type vibrations of the fissile system in the vicinity of its scission point are a source of these angular momenta and of high fragment spins observed experimentally.

  8. Spin clusters and low-energy excitations in rare earth kagome systems

    Science.gov (United States)

    Hoch, M. J. R.

    2017-01-01

    The rare earth kagome systems R3Ga5SiO14 (R = Nd or Pr), which are weakly frustrated antiferromagnets, do not exhibit long-range order at temperatures down to 40 mK as revealed by neutron scattering. The neutron experiments provide evidence for the emergence at low temperatures of correlated spins in nanoscale cluster regions with magnetic field-dependent correlation lengths. A variety of techniques have been used to determine the magnetic and thermal properties of these systems. In particular, high-field electron spin resonance (ESR), nuclear magnetic resonance (NMR) and muon spin resonance (μSR) experiments have established that dynamic correlation of spins remains significant at temperatures well above 1 K. ESR provides evidence for spin wave excitations in spin clusters and the spectra have been interpreted using a Heisenberg model approach. While Nd3+ (J = 9/2) is a Kramers ion Pr3+ (J = 4) is not. This difference leads to contrasts in the magnetic properties of the two systems. This review surveys the information that has been obtained on the properties of these kagome materials over the past decade.

  9. Progressive slowing down of spin fluctuations in underdoped LaFeAsO$_{1-x}$F$_x$

    OpenAIRE

    Hammerath, F.; Gräfe, U; Kühne, H.; Kuhns, P. L.; Reyes, A. P.; Lang, G.; Wurmehl, S.; Büchner, B.; Carretta, P.; Grafe, H. -J.

    2013-01-01

    The evolution of low-energy spin dynamics in the iron-based superconductor LaFeAsO$_{1-x}$F$_x$ was studied over a broad doping, temperature, and magnetic field range (x = 0 - 0.15, T up to 480K, H up to 30T) by means of As nuclear magnetic resonance (NMR). An enhanced spin-lattice relaxation rate divided by temperature, 1/T1T, in underdoped superconducting samples (x = 0.045, 0.05 and 0.075) suggests the presence of antiferromagnetic spin fluctuations, which are strongly reduced in optimally...

  10. Fluctuation-dissipation ratio of the Heisenberg spin glass.

    Science.gov (United States)

    Kawamura, Hikaru

    2003-06-13

    The fluctuation-dissipation (FD) relation of the three-dimensional Heisenberg spin glass with weak random anisotropy is studied by off-equilibrium Monte Carlo simulation. The numerically determined FD ratio exhibits a "one-step-like" behavior, the effective temperature of the spin-glass state being about twice the spin-glass transition temperature, T(eff) approximately 2T(g), irrespective of the bath temperature. The results are discussed in conjunction with the recent experiment by Hérisson and Ocio, and with the chirality scenario of the spin-glass transition.

  11. Nucleon spin-polarisabilities from polarisation observables in low-energy deuteron Compton scattering

    Science.gov (United States)

    Grießhammer, H. W.; Shukla, D.

    2010-11-01

    We investigate the dependence of polarisation observables in elastic deuteron Compton scattering below the pion production threshold on the spin-independent and spin-dependent iso-scalar dipole polarisabilities of the nucleon. The calculation uses Chiral Effective Field Theory ( χ EFT) with dynamical Δ(1232) degrees of freedom in the Small Scale Expansion (SSE) at next-to-leading order. Resummation of the NN intermediate rescattering states and including the Δ induces sizeable effects. The analysis considers cross-sections and the analysing power of linearly polarised photons on an unpolarised target, and cross-section differences and asymmetries of linearly and circularly polarised beams on a vector-polarised deuteron. An intuitive argument helps one to identify kinematics in which one or several polarisabilities do not contribute. Some double-polarised observables are only sensitive to linear combinations of two of the spin-polarisabilities, simplifying a multipole analysis of the data. Spin-polarisabilities can be extracted at photon energies ≳ 100 MeV, after measurements at lower energies of lesssim 70 MeV provide high-accuracy determinations of the spin-independent ones. An interactive Mathematica 7.0 notebook of our findings is available from hgrie@gwu.edu.

  12. Probing current-induced magnetic fields in Au|YIG heterostructures with low-energy muon spin spectroscopy

    Science.gov (United States)

    Aqeel, A.; Vera-Marun, I. J.; Salman, Z.; Prokscha, T.; Suter, A.; van Wees, B. J.; Palstra, T. T. M.

    2017-02-01

    We investigated the depth dependence of current-induced magnetic fields in a bilayer of a normal metal (Au) and a ferrimagnetic insulator (Yttrium Iron Garnet—YIG) by using low energy muon spin spectroscopy (LE-μSR). This allows us to explore how these fields vary from the Au surface down to the buried Au|YIG interface, which is relevant to study physics like the spin-Hall effect. We observed a maximum shift of 0.4 G in the internal field of muons at the surface of Au film which is in close agreement with the value expected for Oersted fields. As muons are implanted closer to the Au|YIG interface, the shift is strongly suppressed, which we attribute to the dipolar fields present at the Au|YIG interface. Combining our measurements with modeling, we show that dipolar fields caused by the finite roughness of the Au|YIG interface consistently explain our observations. Our results, therefore, gauge the limits on the spatial resolution and the sensitivity of LE-μSR to the roughness of the buried magnetic interfaces, a prerequisite for future studies addressing current induced fields caused by the spin-accumulations due to the spin-Hall effect.

  13. Fluctuation dissipation relation in an ageing spin glass

    Energy Technology Data Exchange (ETDEWEB)

    Herisson, D. E-mail: didier.herisson@angstrom.uu.se; Ocio, M

    2004-05-01

    The time autocorrelation of magnetic fluctuations C(t',t) has been measured in a spin glass, and compared with the magnetic response {chi}(t',t). Clearly, we observe a non-linear fluctuation dissipation relation between C and {chi}. A scaling procedure allows us to extrapolate to the limit of long waiting times t', where the {chi}(C) relationship should become independent of t'.

  14. Linear Response Calculations of Spin Fluctuations

    Science.gov (United States)

    Savrasov, S. Y.

    1998-09-01

    A variational formulation of the time-dependent linear response based on the Sternheimer method is developed in order to make practical ab initio calculations of dynamical spin susceptibilities of solids. Using gradient density functional and a muffin-tin-orbital representation, the efficiency of the approach is demonstrated by applications to selected magnetic and strongly paramagnetic metals. The results are found to be consistent with experiment and are compared with previous theoretical calculations.

  15. Universal spin-Hall conductance fluctuations in two dimensions.

    Science.gov (United States)

    Ren, Wei; Qiao, Zhenhua; Wang, Jian; Sun, Qingfeng; Guo, Hong

    2006-08-11

    We report a theoretical investigation on spin-Hall conductance fluctuation of disordered four-terminal devices in the presence of Rashba or/and Dresselhaus spin-orbital interactions in two dimensions. As a function of disorder, the spin-Hall conductance GsH shows ballistic, diffusive, and insulating transport regimes. For given spin-orbit interactions, a universal spin-Hall conductance fluctuation (USCF) is found in the diffusive regime. The value of the USCF depends on the spin-orbit coupling tso but is independent of other system parameters. It is also independent of whether Rashba or Dresselhaus or both spin-orbital interactions are present. When tso is comparable to the hopping energy t, the USCF is a universal number approximately 0.18e/4pi. The distribution of GsH crosses over from a Gaussian distribution in the metallic regime to a non-Gaussian distribution in the insulating regime as the disorder strength is increased.

  16. Charge and spin fluctuations in the density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Gyoerffy, B.L.; Barbieri, A. (Bristol Univ. (UK). H.H. Wills Physics Lab.); Staunton, J.B. (Warwick Univ., Coventry (UK). Dept. of Physics); Shelton, W.A.; Stocks, G.M. (Oak Ridge National Lab., TN (USA))

    1990-01-01

    We introduce a conceptual framework which allow us to treat charge and spin fluctuations about the Local density Approximation (LDA) to the Density Functional Theory (DFT). We illustrate the approach by explicit study of the Disordered Local Moment (DLM) state in Fe above the Curie Temperature {Tc} and the Mott insulating state in MnO. 27 refs., 6 figs.

  17. Temperature dependence of fluctuation time scales in spin glasses

    DEFF Research Database (Denmark)

    Kenning, Gregory G.; Bowen, J.; Sibani, Paolo;

    2010-01-01

    Using a series of fast cooling protocols we have probed aging effects in the spin glass state as a function of temperature. Analyzing the logarithmic decay found at very long time scales within a simple phenomenological barrier model, leads to the extraction of the fluctuation time scale of the s...

  18. The spin Hall effect as a probe of nonlinear spin fluctuations.

    Science.gov (United States)

    Wei, D H; Niimi, Y; Gu, B; Ziman, T; Maekawa, S; Otani, Y

    2012-01-01

    The spin Hall effect and its inverse have key roles in spintronic devices as they allow conversion of charge currents to and from spin currents. The conversion efficiency strongly depends on material details, such as the electronic band structure and the nature of impurities. Here we show an anomaly in the inverse spin Hall effect in weak ferromagnetic NiPd alloys near their Curie temperatures with a shape independent of material details, such as Ni concentrations. By extending Kondo's model for the anomalous Hall effect, we explain the observed anomaly as originating from the second-order nonlinear spin fluctuation of Ni moments. This brings to light an essential symmetry difference between the spin Hall effect and the anomalous Hall effect, which reflects the first-order nonlinear fluctuations of local moments. Our finding opens up a new application of the spin Hall effect, by which a minuscule magnetic moment can be detected.

  19. Low-energy electrodynamics of novel spin excitations in the quantum spin ice Yb₂Ti₂O₇.

    Science.gov (United States)

    Pan, LiDong; Kim, Se Kwon; Ghosh, A; Morris, Christopher M; Ross, Kate A; Kermarrec, Edwin; Gaulin, Bruce D; Koohpayeh, S M; Tchernyshyov, Oleg; Armitage, N P

    2014-09-18

    In condensed matter systems, formation of long-range order (LRO) is often accompanied by new excitations. However, in many geometrically frustrated magnetic systems, conventional LRO is suppressed, while non-trivial spin correlations are still observed. A natural question to ask is then what is the nature of the excitations in this highly correlated state without broken symmetry? Frequently, applying a symmetry breaking field stabilizes excitations whose properties reflect certain aspects of the anomalous state without LRO. Here we report a THz spectroscopy study of novel excitations in quantum spin ice Yb2Ti2O7 under a directed magnetic field. At large positive fields, both right- and left-handed magnon and two-magnon-like excitations are observed. The g-factors of these excitations are dramatically enhanced in the low-field limit, showing a crossover of these states into features consistent with the quantum string-like excitations proposed to exist in quantum spin ice in small fields.

  20. Zero-Point Spin-Fluctuations of Single Adatoms.

    Science.gov (United States)

    Ibañez-Azpiroz, Julen; Dos Santos Dias, Manuel; Blügel, Stefan; Lounis, Samir

    2016-07-13

    Stabilizing the magnetic signal of single adatoms is a crucial step toward their successful usage in widespread technological applications such as high-density magnetic data storage devices. The quantum mechanical nature of these tiny objects, however, introduces intrinsic zero-point spin-fluctuations that tend to destabilize the local magnetic moment of interest by dwindling the magnetic anisotropy potential barrier even at absolute zero temperature. Here, we elucidate the origins and quantify the effect of the fundamental ingredients determining the magnitude of the fluctuations, namely, the (i) local magnetic moment, (ii) spin-orbit coupling, and (iii) electron-hole Stoner excitations. Based on a systematic first-principles study of 3d and 4d adatoms, we demonstrate that the transverse contribution of the fluctuations is comparable in size to the magnetic moment itself, leading to a remarkable ≳50% reduction of the magnetic anisotropy energy. Our analysis gives rise to a comprehensible diagram relating the fluctuation magnitude to characteristic features of adatoms, providing practical guidelines for designing magnetically stable nanomagnets with minimal quantum fluctuations.

  1. Spin jam induced by quantum fluctuations in a frustrated magnet.

    Science.gov (United States)

    Yang, Junjie; Samarakoon, Anjana; Dissanayake, Sachith; Ueda, Hiroaki; Klich, Israel; Iida, Kazuki; Pajerowski, Daniel; Butch, Nicholas P; Huang, Q; Copley, John R D; Lee, Seung-Hun

    2015-09-15

    Since the discovery of spin glasses in dilute magnetic systems, their study has been largely focused on understanding randomness and defects as the driving mechanism. The same paradigm has also been applied to explain glassy states found in dense frustrated systems. Recently, however, it has been theoretically suggested that different mechanisms, such as quantum fluctuations and topological features, may induce glassy states in defect-free spin systems, far from the conventional dilute limit. Here we report experimental evidence for existence of a glassy state, which we call a spin jam, in the vicinity of the clean limit of a frustrated magnet, which is insensitive to a low concentration of defects. We have studied the effect of impurities on SrCr9pGa12-9pO19 [SCGO(p)], a highly frustrated magnet, in which the magnetic Cr(3+) (s = 3/2) ions form a quasi-2D triangular system of bipyramids. Our experimental data show that as the nonmagnetic Ga(3+) impurity concentration is changed, there are two distinct phases of glassiness: an exotic glassy state, which we call a spin jam, for the high magnetic concentration region (p > 0.8) and a cluster spin glass for lower magnetic concentration (p jam is a unique vantage point from which the class of glassy states of dense frustrated magnets can be understood.

  2. Superconducting fluctuations in systems with Rashba-spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Beyl, Stefan [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Orth, Peter P.; Scheurer, Mathias; Schmalian, Joerg [Institut fuer Theorie der Kondensierten Materie, Karlsruher Institut fuer Technologie (Germany)

    2015-07-01

    We investigate the BEC-BCS crossover in a two-dimensional system with Rashba-spin-orbit coupling. To include the effects of phase and amplitude fluctuations of the superconducting order parameter we perform a loop expansion of the effective field theory. We analyze in particular the probability of a low density superconducting quantum phase transition. The theory is relevant to LaAlO{sub 3}/SrTiO{sub 3} interfaces and two-dimensional cold atom systems with synthetic gauge fields.

  3. Antiferromagnetic exchange and spin-fluctuation pairing in cuprate superconductors

    Science.gov (United States)

    Plakida, Nikolay M.

    2006-01-01

    A microscopic theory of superconductivity is formulated within an effective p-d Hubbard model for a CuO2 plane. By applying the Mori-type projection technique, the Dyson equation is derived for the Green functions in terms of Hubbard operators. The antiferromagnetic exchange caused by interband hopping results in pairing of all carries in the conduction subband and high Tc proportional to the Fermi energy. Kinematic interaction in intraband hopping is responsible for the conventional spin-fluctuation pairing. Numerical solution of the gap equation proves the d-wave gap symmetry and defines Tc doping dependence. Oxygen isotope shift and pressure dependence of Tc are also discussed.

  4. Spin-Fluctuation-Induced Non-Fermi-Liquid Behavior with Suppressed Superconductivity in LiFe1 -xCoxAs

    Science.gov (United States)

    Dai, Y. M.; Miao, H.; Xing, L. Y.; Wang, X. C.; Wang, P. S.; Xiao, H.; Qian, T.; Richard, P.; Qiu, X. G.; Yu, W.; Jin, C. Q.; Wang, Z.; Johnson, P. D.; Homes, C. C.; Ding, H.

    2015-07-01

    We study a series of LiFe1 -xCox As compounds with different Co concentrations by transport, optical spectroscopy, angle-resolved photoemission spectroscopy, and nuclear magnetic resonance. We observe a Fermi-liquid to non-Fermi-liquid to Fermi-liquid (FL-NFL-FL) crossover alongside a monotonic suppression of the superconductivity with increasing Co content. In parallel to the FL-NFL-FL crossover, we find that both the low-energy spin fluctuations and Fermi surface nesting are enhanced and then diminished, strongly suggesting that the NFL behavior in LiFe1 -xCox As is induced by low-energy spin fluctuations that are very likely tuned by Fermi surface nesting. Our study reveals a unique phase diagram of LiFe1 -xCox As where the region of NFL is moved to the boundary of the superconducting phase, implying that they are probably governed by different mechanisms.

  5. Temperature Evolution of Spin Fluctuations in FeAs

    Science.gov (United States)

    Podlesnyak, A.; Ehlers, G.; Tóth, S.; Gofryk, K.; Sefat, A. S.

    2015-03-01

    The discovery of superconductivity (SC) in iron pnictides has opened a new stage in SC research. The superconducting state appears in iron pnictides with doping in metallic parent compounds. This is an important difference to the cuprates, which exhibit SC near a correlated insulating state. Therefore, the nature of the magnetism in the simplest iron pnictide - binary FeAs - is of fundamental importance for understanding the interplay between localized and itinerant magnetism and superconductivity in these materials. We use inelastic neutron scattering to map spin wave excitations in the monoarsenide FeAs at temperatures above and below the antiferromagnetic transition TN ~ 70 K. We find magnetic excitation spectrum near the Néel temperature to be strongly different from the spectrum in the ground state. Near the transition temperature, magnetic fluctuations clearly indicate two-dimensional character in an intrinsically three-dimensional (3D) system. On the other hand, at low temperature, spin waves in FeAs are anisotropic 3D, suggesting a crossover from two-dimensional to three-dimensional character. Work at ORNL was sponsored by the US DOE Scientific User Facilities Division, Office of Basic Energy Sciences (AP, GE) and Materials Science and Engineering Division (KG, AS).

  6. Spin polarized low energy electron microscopy of quantum well resonances in Fe films on the Cu-covered W(110) surface.

    Science.gov (United States)

    Wu, Qiang; Altman, M S

    2013-07-01

    Spin polarized low energy electron microscopy has been used to investigate the quantum size effect (QSE) in electron reflectivity from Fe films grown on a pseudomorphic Cu layer on a W(110) surface. Intensity oscillations caused by the QSE as functions of Fe film thickness and incident electron energy identify quantum well resonance conditions in the film. Evaluation of these intensity oscillations using the phase accumulation model provides information on the unoccupied spin polarized band structure in the Fe film above the vacuum level. We also find evidence that the presence of the non-magnetic Cu layer shifts spin polarized quantum well resonances in the Fe layer uniformly downward in energy by 1.1eV compared to Fe/W(110) films without an interface Cu layer, suggesting that the Cu layer gives a small degree of control over the quantum well resonances.

  7. Thermodynamics, geometrical frustration and quantum fluctuations in coupled spin chains

    Directory of Open Access Journals (Sweden)

    J. Sznajd

    2009-01-01

    Full Text Available The linear-perturbation real space renormalization transformation (LPRG is presented and applied to the study of quantum spin chains coupled by interchain interaction (k1 weaker than intrachain one (k. The method is examined in two exact solvable cases: Ising chains on the square and triangular lattices and quantum XY chain. For the Ising model, in the second order in the cumulant epansion, the deviation of the critical temperature from the exact value is less than 1% for 0.5 k>k1>0.15 k, but even in the case of the standard Ising model (k1=k we found the value of Tc which differs by 2% from the exact one. For the quantum XY chain the deviation of the free energy value found by using LPRG from the exact Katsura result is less than 1% for T/J>1, and for rather low temperature T/J=0.08 is about 6%. The LPRG is used to study the effects of interchain frustration on the phase transition in 2D Heisenberg spin chains with easy axis along the z direction. It is shown that contrary to the pure Ising model in systems with in-plane interactions (XY, the interchain frustration does not destroy the finite-temperature transition. However, such a frustration changes the character of the phase transition from Ising-like to, probably, Kosterlitz-Thouless-like. We have also applied the LPRG method to the calculation of the isothermal magnetocaloric coefficient (MT for several spin models in disordered phases. Is is demonstrated that in the presence of antiferromagnetic fluctuations, MT changes sign at some value of the magnetic field. Generally, MT is negative if magnetic field competes with a short-range order, and consequently it can be an indicator of the change in the short-range correlation.

  8. Photoinduced Coherent Spin Fluctuation in Primary Dynamics of Insulator to Metal Transition in Perovskite Cobalt Oxide

    Directory of Open Access Journals (Sweden)

    Arima T.

    2013-03-01

    Full Text Available Coherent spin fluctuation was detected in the photoinduced Mott insulator-metal transition in perovskite cobalt oxide by using 3 optical-cycle infrared pulse. Such coherent spin fluctuation is driven by the perovskite distortion changing orbital gap.

  9. Depth-dependent spin dynamics in thin films of TbPc2 nanomagnets explored by low-energy implanted muons.

    Science.gov (United States)

    Hofmann, Andrea; Salman, Zaher; Mannini, Matteo; Amato, Alex; Malavolti, Luigi; Morenzoni, Elvezio; Prokscha, Thomas; Sessoli, Roberta; Suter, Andreas

    2012-09-25

    We present measurements of the magnetic properties of thin film TbPc(2) single-molecule magnets evaporated on a gold substrate and compare them to those in bulk. Zero-field muon spin relaxation measurements were used to determine the molecular spin fluctuation rate of TbPc(2) as a function of temperature. At low temperature, we find that the fluctuations in films are much faster than in bulk and depend strongly on the distance between the molecules and the Au substrate. We measure a molecular spin correlation time that varies between 1.4 μs near the substrate and 6.6 μs far away from it. We attribute this behavior to differences in the packing of the magnetic cores, which change gradually on the scale of ~10-20 nm away from the TbPc(2)/Au interface.

  10. Emission of correlated electron pairs from Au(111) and Cu(111) surfaces under low-energy electron impact: Contribution of surface states, d-states and spin effects

    Energy Technology Data Exchange (ETDEWEB)

    Samarin, S., E-mail: samar@physics.uwa.edu.au [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia); Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Artamonov, O.M. [Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Guagliardo, P. [Centre for Microscopy, Characterisation and Analysis, UWA, Perth (Australia); Pravica, L. [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia); Baraban, A. [Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Schumann, F.O. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Williams, J.F. [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia)

    2015-01-15

    Highlights: • Spin-polarized two-electron spectroscopy (e,2e) was applied for studying surface states on Cu(111) and Au(111). • Relative (to d-states) contribution of surface states in the (e,2e) spectrum decreases exponentially when primary electron energy increases from 14 to 30 eV. • Spin asymmetry is readily observed in the spectra of Au(111) whereas in the spectra of Cu(111) the spin effect is negligible. - Abstract: The emission of correlated electron pairs excited from surfaces of Au(111) and Cu(111) by low-energy electrons is measured and analyzed. Energy and momentum conservation allows identification of electron pairs involving excitation of electrons from Shockley surface states and from valence d-states. The relative contributions of surface and d-states to the measured spectra of correlated electron pairs is shown to depend on the primary electron energy and is larger from surface states at relatively small primary energies. The use of a spin-polarized incident electron beam highlights the spin effects in producing an electron pair. Measurements show that spin effects are larger for the pair excitation from the valence d-states than for pairs excited from the surface states.

  11. Low-energy electron reflection from Au-passivated Ir(0 0 1) for application in imaging spin-filters

    Energy Technology Data Exchange (ETDEWEB)

    Vasilyev, D.; Tusche, C. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Giebels, F.; Gollisch, H. [Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Feder, R. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Kirschner, J., E-mail: sekrki@mpi-halle.mpg.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, 06099 Halle (Germany)

    2015-02-15

    We describe the principle, the preparation, and the calibration of a spin-polarizing electron mirror in multichannel spin polarimetry. We show data obtained by two independent devices (a goniometer-type LEED set-up and a momentum-microscope set-up) and compare them to the results of a relativistic multiple scattering theory. We also discuss the effects of misalignment and mosaic structure of the crystal. For multi-channel detection we find a 5000-fold increase of efficiency over a single-channel spin-detector. The lifetime of the detector is more than 6 months in ultra-high vacuum.

  12. Low energy spin dynamics of a quantum ferrimagnetic chain, NiCu(pba)(H 2O) 32H 2O

    Science.gov (United States)

    Fujiwara, N.; Hagiwara, M.

    2000-01-01

    Nuclear magnetic resonance (NMR) for 1H nuclei was performed in a Heisenberg chain with alternating spins S=1 and 1/2, NiCu(pba)(H 2O) 32H 2O (pba=1,3-propylenebis (oxamato)) from 4.2 to 280 K. The relaxation rate (1/ T1) is proportional to 1/ H ( H is applied field), whereas the temperature dependence is weak and is almost constant at high temperatures. The temperature and field dependences are investigated on the basis of the spin-wave theory.

  13. Fractional Spin Fluctuations as a Precursor of Quantum Spin Liquids: Majorana Dynamical Mean-Field Study for the Kitaev Model

    Science.gov (United States)

    Yoshitake, Junki; Nasu, Joji; Motome, Yukitoshi

    2016-10-01

    Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that the precursor of quantum spin liquids appears in the spin dynamics in the paramagnetic state over a wide temperature range. Using the cluster dynamical mean-field theory and the continuous-time quantum Monte Carlo method, which are newly developed in the Majorana fermion representation, we calculate the dynamical spin structure factor, relaxation rate in nuclear magnetic resonance, and magnetic susceptibility for the honeycomb Kitaev model whose ground state is a canonical example of the quantum spin liquid. We find that dynamical spin correlations show peculiar temperature and frequency dependence even below the temperature where static correlations saturate. The results provide the experimentally accessible symptoms of the fluctuating fractionalized spins evincing the quantum spin liquids.

  14. High-energy spin-density-wave correlated fluctuations in paramagnetic Cr + 5 at. % V

    Energy Technology Data Exchange (ETDEWEB)

    Werner, S.A. (Missouri Univ., Columbia, MO (United States). Dept. of Physics); Fawcett, E. (Toronto Univ., ON (Canada). Dept. of Physics); Elmiger, M.W.; Shirane, G. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    Measurements of the magnetic fluctuations, termed spin-density-wave (SDW) paramagnons, in the nearly antiferromagnetic alloy Cr + 5 at.%V are extended up in energy to about 80 MeV. These fluctuating spin-spin correlations occur at incommensurate positions, corresponding to the SDW wavevector Q. Their characteristic energy is at least an order of magnitude larger than that of the magnetic fluctuations seen in the paramagnetic phase of pure Cr, but their intensity is more than two orders of magnitude smaller. We find that the dynamic susceptibility decreases by about 50% between temperature T = 10K and 300K.

  15. High-energy spin-density-wave correlated fluctuations in paramagnetic Cr + 5 at. % V

    Energy Technology Data Exchange (ETDEWEB)

    Werner, S.A. [Missouri Univ., Columbia, MO (United States). Dept. of Physics; Fawcett, E. [Toronto Univ., ON (Canada). Dept. of Physics; Elmiger, M.W.; Shirane, G. [Brookhaven National Lab., Upton, NY (United States)

    1992-11-01

    Measurements of the magnetic fluctuations, termed spin-density-wave (SDW) paramagnons, in the nearly antiferromagnetic alloy Cr + 5 at.%V are extended up in energy to about 80 MeV. These fluctuating spin-spin correlations occur at incommensurate positions, corresponding to the SDW wavevector Q. Their characteristic energy is at least an order of magnitude larger than that of the magnetic fluctuations seen in the paramagnetic phase of pure Cr, but their intensity is more than two orders of magnitude smaller. We find that the dynamic susceptibility decreases by about 50% between temperature T = 10K and 300K.

  16. Nanosecond-Timescale Low Energy Switching of In-Plane Magnetic Tunnel Junctions through Dynamic Oersted-Field-Assisted Spin Hall Effect.

    Science.gov (United States)

    Aradhya, S V; Rowlands, G E; Oh, J; Ralph, D C; Buhrman, R A

    2016-10-12

    We investigate fast-pulse switching of in-plane-magnetized magnetic tunnel junctions (MTJs) within 3-terminal devices in which spin-transfer torque is applied to the MTJ by the giant spin Hall effect. We measure reliable switching, with write error rates down to 10(-5), using current pulses as short as just 2 ns in duration. This represents the fastest reliable switching reported to date for any spin-torque-driven magnetic memory geometry and corresponds to a characteristic time scale that is significantly shorter than predicted possible within a macrospin model for in-plane MTJs subject to thermal fluctuations at room temperature. Using micromagnetic simulations, we show that in the three-terminal spin-Hall devices the Oersted magnetic field generated by the pulse current strongly modifies the magnetic dynamics excited by the spin-Hall torque, enabling this unanticipated performance improvement. Our results suggest that in-plane MTJs controlled by Oersted-field-assisted spin-Hall torque are a promising candidate for both cache memory applications requiring high speed and for cryogenic memories requiring low write energies.

  17. Effect of Quantum Fluctuation on Two-Dimensional Spatially Anisotropic Heisenberg Antiferromagnet with Integer Spin

    Institute of Scientific and Technical Information of China (English)

    JI An-Chun; TIAN Guang-Shan

    2006-01-01

    In the present paper, we calculate the Gaussian correction to the critical value Jc⊥ caused by quantum spin fluctuation in a two-dimensional spatially anisotropic Heisenberg antiferromagnet with integer spin S. Previously, someauthors computed this quantity by the mean-field theory based on the Schwinger boson representation of spin operators.However, for S = 1, their result is much less than the one derived by numerical calculations. By taking the effect ofquantum spin fluctuation into consideration, we are able to produce a greatly improved result.

  18. Pressure-induced spin fluctuations and spin reorientation in hexagonal manganites

    Science.gov (United States)

    Kozlenko, D. P.; Kichanov, S. E.; Lee, S.; Park, J.-G.; Savenko, B. N.

    2007-04-01

    The magnetic structures of hexagonal manganites YMnO3 and LuMnO3 have been studied by powder neutron diffraction up to 6 GPa in the temperature range 10-295 K. At ambient pressure, a triangular antiferromagnetic (AFM) state of a Γ1 irreducible representation is stable below TN = 70 K in YMnO3. Upon the application of high pressure, a spin reorientation is induced and the triangular AFM structure evolves from Γ1 to Γ1+Γ2 representations. On the other hand, in LuMnO3 the triangular AFM state of a Γ2 irreducible representation with TNap90 K remains stable over the entire pressure range investigated. The ordered magnetic moment values decrease under pressure with dM/dP = -0.35 μB GPa-1 in YMnO3 and -0.08 μB GPa-1 in LuMnO3. Simultaneously, a considerable increase in diffuse scattering intensity was found in YMnO3, while it was much less pronounced for LuMnO3. Both features indicate the enhancement of spin fluctuations due to geometrical frustration effects and an increase in the volume fraction of the spin-liquid state coexisting with the ordered AFM phase. The characteristic spin correlation length is weakly affected by pressure. The relationship between the pressure-induced behaviour of magnetic structure and the structural characteristics of the quasi-two-dimensional (2D) triangular network formed by Mn and O ions in hexagonal RMnO3 is analysed.

  19. Spin-density correlations in the dynamic spin-fluctuation theory: Comparison with polarized neutron scattering experiments

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, N.B., E-mail: melnikov@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Reser, B.I., E-mail: reser@imp.uran.ru [Miheev Institute of Metal Physics, Ural Branch of Russian Academy of Sciences, Ekaterinburg 620990 (Russian Federation); Paradezhenko, G.V., E-mail: gparadezhenko@cs.msu.su [Lomonosov Moscow State University, Moscow 119991 (Russian Federation)

    2016-08-01

    To study the spin-density correlations in the ferromagnetic metals above the Curie temperature, we relate the spin correlator and neutron scattering cross-section. In the dynamic spin-fluctuation theory, we obtain explicit expressions for the effective and local magnetic moments and spatial spin-density correlator. Our theoretical results are demonstrated by the example of bcc Fe. The effective and local moments are found in good agreement with results of polarized neutron scattering experiment over a wide temperature range. The calculated short-range order is small (up to 4 Å) and slowly decreases with temperature.

  20. One-dimensional spinon spin currents

    Science.gov (United States)

    Hirobe, Daichi; Sato, Masahiro; Kawamata, Takayuki; Shiomi, Yuki; Uchida, Ken-Ichi; Iguchi, Ryo; Koike, Yoji; Maekawa, Sadamichi; Saitoh, Eiji

    2017-01-01

    Quantum spin fluctuation in a low-dimensional or frustrated magnet breaks magnetic ordering while keeping spin correlation. Such fluctuation has been a central topic in magnetism because of its relevance to high-Tc superconductivity and topological states. However, utilizing such spin states has been quite difficult. In a one-dimensional spin-1/2 chain, a particle-like excitation called a spinon is known to be responsible for spin fluctuation in a paramagnetic state. Spinons behave as a Tomonaga-Luttinger liquid at low energy, and the spin system is often called a quantum spin chain. Here we show that a quantum spin chain generates and carries spin current, which is attributed to spinon spin current. This is demonstrated by observing an anisotropic negative spin Seebeck effect along the spin chains in Sr2CuO3. The results show that spin current can flow even in an atomic channel owing to long-range spin fluctuation.

  1. Low-energy singlet sector in the spin-1/2 J 1- J 2 Heisenberg model on a square lattice

    Science.gov (United States)

    Aktersky, A. Yu.; Syromyatnikov, A. V.

    2016-12-01

    Based on a special variant of the plaquette expansion, an operator is constructed whose eigenvalues give the low-energy singlet spectrum of a spin-1/2 Heisenberg antiferromagnet on a square lattice with nearest-heighbor and frustrating next-nearest-neighbor exchange couplings J 1 and J 2. It is well known that a nonmagnetic phase arises in this model for 0.4 ≲ J 2/ J 1 ≲ 0.6, sandwiched by two Néel ordered phases. In agreement with previous results, we observe a first-order quantum phase transition (QPT) at J 2 ≈ 0.64 J 1 from the non-magnetic phase to the Néel one. A large gap (≳ 0.4 J 1) is found in the singlet spectrum for J 2 < 0.64 J 1, which excludes a gapless spin-liquid state for 0.4 ≲ J 2/ J 1 ≲ 0.6 and the deconfined quantum criticality scenario for the QPT to another Néel phase. We observe a first-order QPT at J 2 ≈ 0.55 J 1, presumably between two nonmagnetic phases.

  2. Itinerant ferromagnetism in actinide 5 f -electron systems: Phenomenological analysis with spin fluctuation theory

    Science.gov (United States)

    Tateiwa, Naoyuki; Pospíšil, Jiří; Haga, Yoshinori; Sakai, Hironori; Matsuda, Tatsuma D.; Yamamoto, Etsuji

    2017-07-01

    We have carried out an analysis of magnetic data in 69 uranium, 7 neptunium, and 4 plutonium ferromagnets with the spin fluctuation theory developed by Takahashi [Y. Takahashi, J. Phys. Soc. Jpn. 55, 3553 (1986), 10.1143/JPSJ.55.3553]. The basic and spin fluctuation parameters of the actinide ferromagnets are determined and the applicability of the spin fluctuation theory to actinide 5 f system has been discussed. Itinerant ferromagnets of the 3 d transition metals and their intermetallics follow a generalized Rhodes-Wohlfarth relation between peff/ps and TC/T0 , viz., peff/ps∝(TC/T0) -3 /2 . Here, ps, peff, TC, and T0 are the spontaneous and effective magnetic moments, the Curie temperature, and the width of spin fluctuation spectrum in energy space, respectively. The same relation is satisfied for TC/T0theory. The deviation from the theoretical relation may be due to several other effects not included in the spin fluctuation theory such as the crystalline electric field effect on the 5 f electrons from ligand atoms. The value of the spontaneous magnetic moment ps increases linearly as a function of TC/T0 in the uranium and neptunium ferromagnets below (TC/T0)kink=0.32 ±0.02 , where a kink structure appears in relation between the two quantities. ps increases more weakly above (TC/T0)kink. A possible interpretation with the TC/T0 dependence of ps is given.

  3. Temperature dependence of fluctuation time scales in spin glasses

    DEFF Research Database (Denmark)

    Kenning, Gregory G.; Bowen, J.; Sibani, Paolo

    2010-01-01

    a generalized Arrhenius law. We discuss the hypothesis that, upon cooling to a measuring temperature within the spin glass state, there is a range of dynamically in-equivalent configurations in which the system can be trapped, and check within a numerical barrier model simulation, that this  leads to sub...

  4. Effects of magnetohydrodynamics matter density fluctuations on the solar neutrino resonant spin-flavor precession

    CERN Document Server

    Reggiani, N; Colonia, J H; De Holanda, P C

    1998-01-01

    Taking into account the stringent limits from helioseismology observations on possible matter density fluctuations described by magnetohydrodynamics theory, we find the corresponding time variations of solar neutrino survival probability due to the resonant spin-flavor precession phenomenon with amplitude of order O(10%). We discuss the physics potential of high statistics real time experiments, like as Superkamiokande, to observe the effects of such magnetohydrodynamics fluctuations on their data. We conclude that these observations could be thought as a test of the resonant spin-flavor precession solution to the solar neutrino anomaly.

  5. $1/f$ fluctuations in spinning-particle motions around Schwarzschild black hole

    CERN Document Server

    Koyama, H; Konishi, T; Kiuchi, Kenta; Konishi, Tetsuro; Koyama, Hiroko

    2007-01-01

    We study the properties of chaos in spinning-particle motions in Schwarzschild spacetime. We characterize the chaos in the motions using the power spectrum. We discover that the power spectrum shows not only white noise but also $1/f$-type fluctuation, depending on the value of the spin and the angular momentum of the test particle. We obtain the phase diagram for the properties of the chaos. Furthermore, we suggest that the origin of the $1/f$ fluctuations is the ``stagnant motions,'' itinerating among regular orbits (tori).

  6. Disappearance of Static Magnetic Order and Evolution of Spin Fluctuations in Fe1+ SexTe1−x

    Energy Technology Data Exchange (ETDEWEB)

    Xu, G.; Xu, Z.; Wen, J.; Jie, Q.; Lin, Z.; Li, Q.; Chi, S.; Singh, D.K.; Gu, G.; Tranquada, J.M.

    2010-09-29

    We report neutron-scattering studies on static magnetic orders and spin excitations in the Fe-based chalcogenide system Fe{sub 1+{delta}}Se{sub x}Te{sub 1-x} with different Fe and Se compositions. Short-range static magnetic order with an in-plane wave vector near the (0.5,0) (using the two-Fe unit cell), together with strong low-energy magnetic excitations is found in all nonsuperconducting samples for Se doping up to 45%. When the static order disappears and bulk superconductivity emerges, the spectral weight of the magnetic excitations shifts to the region of reciprocal space near the in-plane wave vector (0.5, 0.5), corresponding to 'collinear' spin correlations. Our results suggest that there is a strong correlation between superconductivity and the character of the magnetic order/fluctuations in this system. Excess Fe appears to be important for stabilizing the magnetic order that competes with superconductivity.

  7. Fluctuation Bounds For Interface Free Energies in Spin Glasses

    Science.gov (United States)

    Arguin, L.-P.; Newman, C. M.; Stein, D. L.; Wehr, J.

    2014-07-01

    We consider the free energy difference restricted to a finite volume for certain pairs of incongruent thermodynamic states (if they exist) in the Edwards-Anderson Ising spin glass at nonzero temperature. We prove that the variance of this quantity with respect to the couplings grows proportionally to the volume in any dimension greater than or equal to two. As an illustration of potential applications, we use this result to restrict the possible structure of Gibbs states in two dimensions.

  8. Probing spin fluctuations in the paramagnetic phase of EuTiO3 by muon spin rotation techniques

    Science.gov (United States)

    Guguchia, Zurab; Keller, Hugo; Shengelaya, Alexander; Kohler, Jurgen; Bussmann-Holder, Annette; Max-Planck-Institut Für Festkörperforschung Collaboration; Department of Physics, Tbilisi State University Collaboration; Paul-Scherrer Institute, Switzerland Collaboration; Superconductivity and magnetism Group, Physik-Institut der Universität Zürich Team

    2014-03-01

    The muon spin rotation (μSR) technique was used to search for theoretically predicted spin fluctuations in EuTiO3 (ETO) deep in the paramagnetic phase. ETO is a perovskite with cubic structure above TS=282 K, followed by a tetragonal phase below TS and shows antiferromagnetic (AFM) ordering at TN=5.7 K. A strong spin-lattice coupling exists at low temperatures. Even though it is not apparent that this spin-lattice coupling continues to high temperatures, model calculations predict a strong paramagnon-phonon coupling at elevated temperatures. In order to test these predictions, μSR studies on ETO have been performed at temperatures above and below TS. While the AFM phase is clearly observed in the μSR signal, a finite signal remains also in the paramagnetic phase, following closely the temperature dependence of the zone boundary soft mode. This unusual finding demonstrates that spin fluctuations are present deep in the paramagnetic phase and are tied to the soft zone boundary mode. This work was partly supported by the Swiss Nationa l Science Foundation and the SCOPES grant No. IZ73Z0_128242.

  9. Spin-Fluctuation-Induced Non-Fermi-Liquid Behavior with Suppressed Superconductivity in LiFe_{1−x}Co_{x}As

    Directory of Open Access Journals (Sweden)

    Y. M. Dai

    2015-09-01

    Full Text Available We study a series of LiFe_{1−x}Co_{x}As compounds with different Co concentrations by transport, optical spectroscopy, angle-resolved photoemission spectroscopy, and nuclear magnetic resonance. We observe a Fermi-liquid to non-Fermi-liquid to Fermi-liquid (FL-NFL-FL crossover alongside a monotonic suppression of the superconductivity with increasing Co content. In parallel to the FL-NFL-FL crossover, we find that both the low-energy spin fluctuations and Fermi surface nesting are enhanced and then diminished, strongly suggesting that the NFL behavior in LiFe_{1−x}Co_{x}As is induced by low-energy spin fluctuations that are very likely tuned by Fermi surface nesting. Our study reveals a unique phase diagram of LiFe_{1−x}Co_{x}As where the region of NFL is moved to the boundary of the superconducting phase, implying that they are probably governed by different mechanisms.

  10. Unconventional normal-state spin dynamics in underdoped high-Tc cuprates as a fingerprint of spiral correlations of localized spins and dual localized/itinerant nature of spin fluctuations

    Science.gov (United States)

    Onufrieva, F.

    2017-03-01

    The paper is motivated by the observation of unusual and not well understood spin dynamics in low- and moderately doped high-Tc cuprates as well as by the discovery in these materials of a static incommensurate order for doping exceeding the insulator-metal boundary in the phase diagram. We develop a microscopic approach that allows us to treat accurately the quantum fluctuations in the spiral state developing upon doping the Mott-Neel insulator. We show that the spiral order of localized spins induces an off-diagonal order of mobile charges and a gap Δ ∝|Q | in their spectrum (Q is the spiral incommensurability wave vector defined with respect to QAF). Due to the dynamic spin-charge interaction the latter gap produces a feedback effect consisting in the appearence of a gap in the coherent spin excitation spectrum. As a result, the characteristic energy ωc=Δ appears, in the spin excitation spectra. It separates two components with qualitatively different behavior-above ωc, spin excitations are magnonlike and have an upward dispersion, below it, they are of the relaxation type and have a slight downward dispersion. The form of the dispersion is close to the form observed experimentally (by inelastic neutron scattering), which can be characterized as OPEN-hour-glass shaped or Y -shaped. There is no qualitative difference between the spin dynamics in the normal and SC states as far as doping is relatively low. There is no resonance. Other important features, including the incommensurability and uniaxial anisotropy of the low-energy spin excitations and the doping dependencies of the characteristic energy and wave vectors, are also close to those observed experimentally in low-doped cuprates. We show that the static spiral state becomes unstable at the critical doping nc. We show also that adopting the hypothesis about the presence of finite-energy spiral correlations in the paramagnetic state above nc and based on the results obtained for the static spiral state

  11. Spin-fluctuation-mediated pairing symmetry on the metallic kagome lattice

    Energy Technology Data Exchange (ETDEWEB)

    Kang Jing; Yu Shunli; Li Jianxin [Department of Physics and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Yao Zijian [Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Pokfulam Road (Hong Kong)

    2011-05-04

    We study the magnetic properties and the superconducting pairing mediated by spin fluctuations on the metallic kagome lattice by using the Hubbard model and the fluctuation exchange approximation. It is found that the spin susceptibility is caused by the nesting of the renormalized Fermi surface. We point out that superconductivity will be favored in the spin-singlet channel and may be more easily realized around 25% hole doping. We find an evolution of the pairing state from a d-wave-like symmetry, described by the E{sub 2g} representation of the group D{sub 6h} at low dopings, to that described by the A{sub 2g} representation at heavy hole dopings.

  12. Strength and scales of itinerant spin fluctuations in 3 d paramagnetic metals

    Science.gov (United States)

    Wysocki, Aleksander L.; Kutepov, Andrey; Antropov, Vladimir P.

    2016-10-01

    The full spin density fluctuations (SDF) spectra in 3 d paramagnetic metals are analyzed from first principles using the linear response technique. Using the calculated complete wave vector and energy dependence of the dynamic spin susceptibility, we obtain the most important, but elusive, characteristic of SDF in solids: on-site spin correlator (SC). We demonstrate that the SDF have a mixed character consisting of interacting collective and single-particle excitations of similar strength spreading continuously over the entire Brillouin zone and a wide energy range up to femtosecond time scales. These excitations cannot be adiabatically separated and their intrinsically multiscale nature should always be taken into account for a proper description of metallic systems. Overall, in all studied systems, despite the lack of local moment, we found a very large SC resulting in an effective fluctuating moment of the order of several Bohr magnetons.

  13. Time-Correlated Structure in Spin Fluctuations in Pulsars

    CERN Document Server

    Price, Steve; Shore, Steve; Nice, David

    2012-01-01

    We study statistical properties of stochastic variations in pulse arrival times, timing noise, in radio pulsars using a new analysis method applied in the time domain. The method proceeds in two steps. First, we subtract low-frequency wander using a high-pass filter. Second, we calculate the discrete correlation function of the filtered data. As a complementary method for measuring correlations, we introduce a statistic that measures the dispersion of the data with respect to the data translated in time. The analysis methods presented here are robust and of general usefulness for studying arrival time variations over timescales approaching the average sampling interval. We apply these methods to timing data for 32 pulsars. In two radio pulsars, PSRs B1133+16 and B1933+16, we find that fluctuations in arrival times are correlated over timescales of 10 - 20 d with the distinct signature of a relaxation process. Though this relaxation response could be magnetospheric in origin, we argue that damping between the ...

  14. Low-energy magnetic fluctuations in U(Ru{sub 1-x}Rh{sub x}){sub 2}Si{sub 2}(x=<0.02)

    Energy Technology Data Exchange (ETDEWEB)

    Yokoyama, M. [Faculty of Science, Ibaraki University, Mito 310-8512 (Japan)]. E-mail: makotti@mx.ibaraki.ac.jp; Matsuda, K. [Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Amitsuka, H. [Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Tenya, K. [Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Aso, N. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Tokai 319-1106 (Japan); Yoshizawa, H. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Tokai 319-1106 (Japan)

    2007-03-15

    Inelastic neutron scattering experiments were performed on U(Ru{sub 1-x}Rh{sub x}){sub 2}Si{sub 2} with x=0 and 0.02 in order to investigate the variations of the antiferromagnetic (AF) fluctuations with doping Rh. We have found that the energy of the magnetic excitation observed at Q=(1,0,0) in the hidden order (HO) phase markedly decreases from {approx}2.6meV(x=0) to {approx}0(x=0.02) with increasing x. In addition, the staggered susceptibility {chi}{sub Q} estimated from the inelastic peak develops in the HO phase at x=0.02, while it is suppressed at x=0. These results indicate that the AF fluctuation in the HO phase is significantly enhanced with doping Rh.

  15. Finite-dimensional colored fluctuation-dissipation theorem for spin systems

    CERN Document Server

    Nicolis, Stam; Tranchida, Julien

    2016-01-01

    When nano-magnets are coupled to random external sources, their magnetization becomes a random variable, whose properties are defined by an induced probability density, that can be reconstructed from its moments, using the Langevin equation, for mapping the noise to the dynamical degrees of freedom. When the spin dynamics is discretized in time, a general fluctuation-dissipation theorem, valid for non-Markovian noise, can be established, even when zero modes are present. We discuss the subtleties that arise, when Gilbert damping is present and the mapping between noise and spin degrees of freedom is non--linear.

  16. Finding new superconductors: the spin-fluctuation gateway to high Tc and possible room temperature superconductivity.

    Science.gov (United States)

    Pines, David

    2013-10-24

    We propose an experiment-based strategy for finding new high transition temperature superconductors that is based on the well-established spin fluctuation magnetic gateway to superconductivity in which the attractive quasiparticle interaction needed for superconductivity comes from their coupling to dynamical spin fluctuations originating in the proximity of the material to an antiferromagnetic state. We show how lessons learned by combining the results of almost three decades of intensive experimental and theoretical study of the cuprates with those found in the decade-long study of a strikingly similar family of unconventional heavy electron superconductors, the 115 materials, can prove helpful in carrying out that search. We conclude that, since Tc in these materials scales approximately with the strength of the interaction, J, between the nearest neighbor local moments in their parent antiferromagnetic state, there may not be a magnetic ceiling that would prevent one from discovering a room temperature superconductor.

  17. The role of spin fluctuations in the anomalous anisotropy of MnBi

    Science.gov (United States)

    Barker, Joseph; Mryasov, Oleg

    2016-12-01

    MnBi is unusual for having a magnetic anisotropy energy which increases with temperature. Recent theoretical works have studied how the lattice effects the anisotropy. However, the role of spin fluctuations has been hitherto overlooked, even though this is the primary mechanism for the temperature dependence of anisotropy in magnetic materials. We have created a model of MnBi including all anisotropy terms which are indicated from experiments and theory. Parameterizing based on experimental measurements we used the Callen-Callen theory to calculate the temperature dependence of the magnetic anisotropy due to spin fluctuations. An excellent agreement is found with experiments, across the entire temperature range. Our results indicate the driving force to be the competition between in-plane single ion and out of plane two-ion anisotropies.

  18. Link between spin fluctuations and electron pairing in copper oxide superconductors.

    Science.gov (United States)

    Jin, K; Butch, N P; Kirshenbaum, K; Paglione, J; Greene, R L

    2011-08-03

    Although it is generally accepted that superconductivity is unconventional in the high-transition-temperature copper oxides, the relative importance of phenomena such as spin and charge (stripe) order, superconductivity fluctuations, proximity to a Mott insulator, a pseudogap phase and quantum criticality are still a matter of debate. In electron-doped copper oxides, the absence of an anomalous pseudogap phase in the underdoped region of the phase diagram and weaker electron correlations suggest that Mott physics and other unidentified competing orders are less relevant and that antiferromagnetic spin fluctuations are the dominant feature. Here we report a study of magnetotransport in thin films of the electron-doped copper oxide La(2 - x)Ce(x)CuO(4). We show that a scattering rate that is linearly dependent on temperature--a key feature of the anomalous normal state properties of the copper oxides--is correlated with the electron pairing. We also show that an envelope of such scattering surrounds the superconducting phase, surviving to zero temperature when superconductivity is suppressed by magnetic fields. Comparison with similar behaviour found in organic superconductors strongly suggests that the linear dependence on temperature of the resistivity in the electron-doped copper oxides is caused by spin-fluctuation scattering.

  19. Quantum and thermal fluctuations in a Raman spin-orbit-coupled Bose gas

    Science.gov (United States)

    Chen, Xiao-Long; Liu, Xia-Ji; Hu, Hui

    2017-07-01

    We theoretically study a three-dimensional weakly interacting Bose gas with Raman-induced spin-orbit coupling at finite temperature. By employing a generalized Hartree-Fock-Bogoliubov theory with Popov approximation, we determine a complete finite-temperature phase diagram of three exotic condensation phases (i.e., the stripe, plane-wave, and zero-momentum phases), against both quantum and thermal fluctuations. We find that the plane-wave phase is significantly broadened by thermal fluctuations. The phonon mode and sound velocity at the transition from the plane-wave phase to the zero-momentum phase are thoughtfully analyzed. At zero temperature, we find that quantum fluctuations open an unexpected gap in sound velocity at the phase transition, in stark contrast to the previous theoretical prediction of a vanishing sound velocity. At finite temperature, thermal fluctuations continue to significantly enlarge the gap, and simultaneously shift the critical minimum. For a Bose gas of 87Rb atoms at the typical experimental temperature, T =0.3 T0 , where T0 is the critical temperature of an ideal Bose gas without spin-orbit coupling, our results of gap opening and critical minimum shifting in the sound velocity are qualitatively consistent with the recent experimental observation [Ji et al., Phys. Rev. Lett. 114, 105301 (2015), 10.1103/PhysRevLett.114.105301].

  20. Correlation-Driven Charge and Spin Fluctuations in LaCoO3

    Science.gov (United States)

    Karolak, M.; Izquierdo, M.; Molodtsov, S. L.; Lichtenstein, A. I.

    2015-07-01

    The spin transition in LaCoO3 has been investigated using density-functional theory in combination with dynamical mean-field theory employing continuous time quantum Monte Carlo and exact diagonalization impurity solvers. Calculations on the experimental rhombohedral atomic structure with two Co sites per unit cell show that an independent treatment of the Co atoms results in a ground state with strong charge fluctuations induced by electronic correlations. Each atom shows a contribution from either a d5 or a d7 state in addition to the main d6 state. These states play a relevant role in the spin transition which can be understood as a low spin-high spin (LS-HS) transition with significant contributions (˜10 % ) to the LS and HS states of d5 and d7 states, respectively. We report spectra as well as optical conductivity data for all cases. A thermodynamic analysis reveals a significant kinetic energy gain through introduction of charge fluctuations, which in addition to the potential energy reduction lowers the total energy of the system.

  1. Light scattering in a medium with fluctuating gyrotropy: Application to spin-noise spectroscopy

    Science.gov (United States)

    Kozlov, G. G.; Ryzhov, I. I.; Zapasskii, V. S.

    2017-04-01

    The spin-noise signal in the Faraday-rotation-based detection technique can be considered equally correctly either as a manifestation of the spin-flip Raman effect or as a result of light scattering in the medium with fluctuating gyrotropy. In this paper, we present rigorous description of the signal formation process upon heterodyning of the field scattered due to fluctuating gyrotropy. Along with conventional single-beam experimental arrangement, we consider here a more complicated, but more informative, two-beam configuration that implies the use of an auxiliary light beam passing through the same scattering volume and delivering additional scattered light to the detector. We show that the signal in the spin-noise spectroscopy (SNS) arising due to heterodyning of the scattered field is formed only by the scattered field components the wave vectors of which coincide with those of the probe field. Therefore, in principle, the detected signal in SNS can be increased by increasing overlap of the two fields in the momentum space. We also show that, in the two-beam geometry of SNS, contribution of the auxiliary (tilted) beam to the detected signal is produced only by the region of overlap between the two beams in real space and can be expressed analytically as the Fourier transform of the spatial correlation function of the gyrotropy at the difference of their wave vectors. These features of the two-beam geometry can be used for tomographic measurements in spin systems (a more sophisticated version of three-dimensional tomography proposed earlier) and for studying spatial spin correlations by means of noise spectroscopy.

  2. Magnetic ordering in tetragonal FeS: Evidence for strong itinerant spin fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, K.D.; Refson, K.; Bone, S.; Qiao, R.; Yang, W.; Liu, Z.; Sposito, G.

    2010-11-01

    Mackinawite is a naturally occurring layer-type FeS mineral important in biogeochemical cycles and, more recently, in the development of microbial fuel cells. Conflicting results have been published as to the magnetic properties of this mineral, with Moessbauer spectroscopy indicating no magnetic ordering down to 4.2 K but density functional theory (DFT) predicting an antiferromagnetic ground state, similar to the Fe-based high-temperature superconductors with which it is isostructural and for which it is known that magnetism is suppressed by strong itinerant spin fluctuations. We investigated this latter possibility for mackinawite using photoemission spectroscopy, near-edge x-ray absorption fine structure spectroscopy, and DFT computations. Our Fe 3{sub s} core-level photoemission spectrum of mackinawite showed a clear exchange-energy splitting (2.9 eV) consistent with a 1 {micro}{sub B} magnetic moment on the Fe ions, while the Fe L-edge x-ray absorption spectrum indicated rather delocalized Fe 3{sub d} electrons in mackinawite similar to those in Fe metal. Our DFT computations demonstrated that the ground state of mackinawite is single-stripe antiferromagnetic, with an Fe magnetic moment (2.7 {micro}{sub B}) that is significantly larger than the experimental estimate and has a strong dependence on the S height and lattice parameters. All of these trends signal the existence of strong itinerant spin fluctuations. If spin fluctuations prove to be mediators of electron pairing, we conjecture that mackinawite may be one of the simplest Fe-based superconductors.

  3. Zitterbewegung with spin-orbit coupled ultracold atoms in a fluctuating optical lattice

    Science.gov (United States)

    Argonov, V. Yu; Makarov, D. V.

    2016-09-01

    The dynamics of non-interacting ultracold atoms with artificial spin-orbit coupling is considered. Spin-orbit coupling is created using two moving optical lattices with orthogonal polarizations. Our main goal is to study influence of lattice noise on Rabi oscillations. Special attention is paid to the phenomenon of the Zitterbewegung being trembling motion caused by Rabi transitions between states with different velocities. Phase and amplitude fluctuations of lattices are modelled by means of the two-dimensional stochastic Ornstein-Uhlenbeck process, also known as harmonic noise. In the the noiseless case the problem is solved analytically in terms of the momentum representation. It is shown that lattice noise significantly extends duration of the Zitterbewegung as compared to the noiseless case. This effect originates from noise-induced decoherence of Rabi oscillations.

  4. Theory of spin-fluctuation induced superconductivity in iron-based superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Junhua [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    In this dissertation we focus on the investigation of the pairing mechanism in the recently discovered high-temperature superconductor, iron pnictides. Due to the proximity to magnetic instability of the system, we considered short-range spin fluctuations as the major mediating source to induce superconductivity. Our calculation supports the magnetic fluctuations as a strong candidate that drives Cooper-pair formation in this material. We find the corresponding order parameter to be of the so-called ss-wave type and show its evolution with temperature as well as the capability of supporting high transition temperature up to several tens of Kelvin. On the other hand, our itinerant model calculation shows pronounced spin correlation at the observed antiferromagnetic ordering wave vector, indicating the underlying electronic structure in favor of antiferromagnetic state. Therefore, the electronic degrees of freedom could participate both in the magnetic and in the superconducting properties. Our work shows that the interplay between magnetism and superconductivity plays an important role to the understanding of the rich physics in this material. The magnetic-excitation spectrum carries important information on the nature of magnetism and the characteristics of superconductivity. We analyze the spin excitation spectrum in the normal and superconducting states of iron pnictides in the magnetic scenario. As a consequence of the sign-reversed gap structure obtained in the above, a spin resonance mode appears below the superconducting transition temperature. The calculated resonance energy, scaled with the gap magnitude and the magnetic correlation length, agrees well with the inelastic neutron scattering (INS) measurements. More interestingly, we find a common feature of those short-range spin fluctuations that are capable of inducing a fully gapped ss state is the momentum anisotropy with elongated span along the direction transverse to the antiferromagnetic momentum

  5. The spinning dancer illusion and spontaneous brain fluctuations: an fMRI study.

    Science.gov (United States)

    Bernal, Byron; Guillen, Magno; Marquez, Juan Camilo

    2014-01-01

    The brain activation associated with the Spinning Dancer Illusion, a cognitive visual illusion, is not entirely known. Inferences from other study modalities point to the involvement of the dorso-parieto-occipital areas in the spontaneous switchings of perception in other bistable non-kinetic illusions. fMRI is a mature technique used to investigate the brain responses associated with mental changes. Resting-state fMRI is a novel technique that may help ascertain the effects of spontaneous brain changes in the top-down regulation of visual perception. The purpose of this report is to describe the brain activation associated with the subjective illusory changes of perception of a kinetic bistable stimulus. We hypothesize that there is a relationship between the perception phases with the very slow cortical spontaneous fluctuations, recently described. A single normal subject who was trained to produce voluntarily perception phase switches underwent a series of fMRI studies whose blocks were either defined post-hoc or accordingly with a predefined timeline to assess spontaneous and voluntarily evoked visual perception switches, respectively. Correlation of findings with resting-state fMRI and independent component analysis of the task series was sought. Phases of the rotation direction were found associated with right parietal activity. Independent component analysis of the task series and their comparison with basal resting-state components suggest that this activity is related to one of the very slow spontaneous brain fluctuations. The spontaneous fluctuations of the cortical activity may explain the subjective changes in perception of direction of the Spinning Dancer Illusion. This observation is a proof-of-principle, suggesting that the spontaneous brain oscillations may influence top-down sensory regulation.

  6. Modeling Spin Fluctuations and Magnetic Excitations from Time-Dependent Density Functional Theory

    Science.gov (United States)

    Gorni, Tommaso; Timrov, Iurii; Dal Corso, Andrea; Baroni, Stefano

    Harnessing spin fluctuations and magnetic excitations in materials is key in many fields of technology, spanning from memory devices to information transfer and processing, to name but a few. A proper understanding of the interplay between collective and single-particle spin excitations is still lacking, and it is expected that first-principle simulations based on TDDFT may shed light on this interplay, as well as on the role of important effects such as relativistic ones and related magnetic anisotropies. All the numerical approaches proposed so far to tackle this problem are based on the computationally demanding solution of the Sternheimer equations for the response orbitals or the even more demanding solution of coupled Dyson equations for the spin and charge susceptibilities. The Liouville-Lanczos approach to TDDFT has already proven to be a valuable alternative, the most striking of its features being the avoidance of sums over unoccupied single-particle states and the frequency-independence of the main numerical bottleneck. In this work we present an extension of this methodology to magnetic systems and its implementation in the Quantum ESPRESSO distribution, together with a few preliminary results on the magnon dispersions in bulk Fe.

  7. Interplay of spin gap and nanoscopic quantum fluctuations in intermetallic CeCu{sub 2}Ge{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.K.

    2014-05-01

    Neutron scattering measurements are used to elucidate interplay of the field-induced spin gap and the quantum fluctuations in archetypal heavy electron system CeCu{sub 2}Ge{sub 2}. A spin gap of Δ=0.56 meV is found to develop near the field-induced quantum critical state at H{sub c}≃8 T-driven by fluctuations of the long range antiferromagnetic order parameter. The superconducting transition temperature in many magnetic superconductors is found to exhibit one-to-one correspondence with the spin gap. In this regard, the demonstration of an interplay of the spin gap with the nanoscopic dynamic correlation provides new arena to explore direct relation between the quantum critical behavior and the unconventional superconductivity, especially in heavy electrons systems.

  8. Disappearance of static magnetic order and evolution of spin fluctuations in Fe1+δSexTe1-x

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhijun [Brookhaven National Lab. (BNL), Upton, NY (United States); City College of New York, NY (United States); Wen, Jinsheng [Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., Stony Brook, NY (United States); Xu, Guangyong [Brookhaven National Lab. (BNL), Upton, NY (United States); Jie, Qing [Brookhaven National Lab. (BNL), Upton, NY (United States); Lin, Zhiwei [Brookhaven National Lab. (BNL), Upton, NY (United States); Li, Qiang [Brookhaven National Lab. (BNL), Upton, NY (United States); Chi, Songxue [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Univ. of Maryland, College Park, MD (United States); Singh, D. K. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Univ. of Maryland, College Park, MD (United States); Gu, Genda [Brookhaven National Lab. (BNL), Upton, NY (United States); Tranquada, John M. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2010-09-29

    We report neutron-scattering studies on static magnetic orders and spin excitations in the Fe-based chalcogenide system Fev Se1+δ Te1-x with different Fe and Se compositions. Short-range static magnetic order with an in-plane wave vector near the (0.5,0) (using the two-Fe unit cell), together with strong low-energy magnetic excitations is found in all nonsuperconducting samples for Se doping up to 45%. When the static order disappears and bulk superconductivity emerges, the spectral weight of the magnetic excitations shifts to the region of reciprocal space near the in-plane wave vector (0.5, 0.5), corresponding to “collinear” spin correlations. Our results suggest that there is a strong correlation between superconductivity and the character of the magnetic order/fluctuations in this system. Excess Fe appears to be important for stabilizing the magnetic order that competes with superconductivity.

  9. Fluctuation-dissipation relation in a spin glass in the non-stationary regime

    Energy Technology Data Exchange (ETDEWEB)

    Herisson, D.; Ocio, M

    2003-05-01

    We present the first experimental determination of the time autocorrelation C(t',t) of magnetization in the non-stationary regime of a spin glass. Quantitative comparison with the corresponding response, the magnetic susceptibility {chi}(t',t), is made possible by the use of a new experimental setup allowing both measurements in the same conditions. Clearly, we observe a non-linear fluctuation-dissipation relation between C and {chi}, depending weakly on the waiting time t'. Following theoretical developments on mean-field models, and lately on short range ones, it is predicted that in the limit of long times, the {chi}(C) relationship should become independent on t'. A scaling procedure allows us to extrapolate to the limit of long waiting times.

  10. Strong charge and spin fluctuations in La2O3Fe2Se2

    Science.gov (United States)

    Jin, Guangxi; Wang, Yilin; Dai, Xi; Ren, Xinguo; He, Lixin

    2016-08-01

    The electronic structure and magnetic properties of the strongly correlated material La2O3Fe2Se2 are studied by using both the density-functional theory plus U (DFT +U ) method and the DFT plus Gutzwiller (DFT + G) variational method. The ground-state magnetic structure of this material obtained with DFT +U is consistent with recent experiments with an appropriate U parameter, but its band gap is significantly overestimated by DFT +U , even with a small Hubbard U value. In contrast, the DFT + G method yields a band gap of 0.1-0.2 eV, in excellent agreement with experiment. Detailed analysis shows that the electronic and magnetic properties of La2O3Fe2Se2 are strongly affected by charge and spin fluctuations which are missing in the DFT +U method.

  11. Pressure dependence of critical temperature of bulk FeSe from spin fluctuation theory

    Science.gov (United States)

    Hirschfeld, Peter; Kreisel, Andreas; Wang, Yan; Tomic, Milan; Jeschke, Harald; Jacko, Anthony; Valenti, Roser; Maier, Thomas; Scalapino, Douglas

    2013-03-01

    The critical temperature of the 8K superconductor FeSe is extremely sensitive to pressure, rising to a maximum of 40K at about 10GPa. We test the ability of the current generation of fluctuation exchange pairing theories to account for this effect, by downfolding the density functional theory electronic structure for each pressure to a tight binding model. The Fermi surface found in such a procedure is then used with fixed Hubbard parameters to determine the pairing strength using the random phase approximation for the spin singlet pairing vertex. We find that the evolution of the Fermi surface captured by such an approach is alone not sufficient to explain the observed pressure dependence, and discuss alternative approaches. PJH, YW, AK were supported by DOE DE-FG02-05ER46236, the financial support of MT, HJ, and RV from the DFG Schwerpunktprogramm 1458 is kindly acknowledged.

  12. Phenomenological approach to spin fluctuations in itinerant magnets and superconductors from ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Ortenzi, Luciano

    2013-10-17

    In this thesis I study the interplay between magnetism and superconductivity in itinerant magnets and superconductors. I do this by applying a semiphenomenological method to four representative compounds. In particular I use the discrepancies (whenever present) between density functional theory (DFT) calculations and the experiments in order to construct phenomenological models which explain the magnetic, superconducting and optical properties of four representative systems. I focus my attention on the superconducting and normal state properties of the recently discovered APt3P superconductors, on superconducting hole-doped CuBiSO, on the optical properties of LaFePO and finally on the ferromagnetic-paramagnetic transition of Ni3Al under pressure. At the end I present a new method which aims to describe the effect of spin fluctuations in itinerant magnets and superconductors that can be used to monitor the evolution of the electronic structure from non magnetic to magnetic in systems close to a quantum critical point.

  13. Ti3CrCu4: A possible 2-D ferromagnetic spin fluctuating system

    Directory of Open Access Journals (Sweden)

    S. K. Dhar

    2016-05-01

    Full Text Available Ti3CrCu4 is a new ternary compound which crystallizes in the tetragonal Ti3Pd5 structure type. The Cr atoms form square nets in the a-b plane (a = 3.124 Å which are separated by an unusually large distance c = 11.228 Å along the tetragonal axis, thus forming a -2-D Cr-sublattice. The paramagnetic susceptibility is characterized by a low effective moment, μeff = 1.1 μB, a low paramagnetic Curie temperature θP (below 7 K and a temperature independent χ0 = 6.7 x 10−4 emu/mol. The magnetization at 1.8 K increases rapidly with field nearly saturating to 0.2 μB/f.u. The zero field heat capacity C/T shows an upturn below 7 K (∼190 mJ/mol K2 at ∼0.1K which is suppressed in applied magnetic fields and interpreted as suggesting the presence of spin fluctuations. The resistivity at low temperatures shows non-Fermi liquid behavior. Overall, the experimental data thus reveal an unusual magnetic state in Ti3CrCu4, which likely has its origin in the layered nature of the Cr sub-lattice and ferromagnetic spin fluctuations. Density functional theoretical calculations reveal a sharp Cr density of states peak just above the Fermi level, indicating the propensity of Ti3CrCu4 to become magnetic.

  14. Neutron scattering study of charge fluctuations and spin fluctuations in optimally doped YBa{sub 2}Cu{sub 3}O{sub 6.95}

    Energy Technology Data Exchange (ETDEWEB)

    Pintschovius, Lothar; Endoh, Yasuo; Reznik, Dmitry; Hiraka, H.; Tranquada, John; Reichardt, Winfried; Bourges, Philippe; Sidis, Yvan; Uchiyama, Hiroshi; Masui, T.; Tajima, Setsuko

    2004-10-01

    Inelastic neutron scattering investigations on optimally doped YBCO revealed a very pronounced temperature dependence of the Cu-O in-plane bond-stretching vibrations along the (0 1 0)-direction: a downward shift of spectral weight with decreasing temperature by at least 10 meV in a narrow range of wave vectors halfway to the zone boundary. The temperature evolution starts around 200 K, well above the superconducting transition temperature. This phonon anomaly provides strong evidence for large electron-phonon coupling. It also indicates an incipient charge density wave instability within the CuO{sub 2} planes reminiscent of dynamical charge stripes. The magnetic fluctuations have been investigated in great detail on the same sample. Incommensurate spin fluctuations have been observed for energies both below and above the energy of the resonance peak at E=41 meV. However, the dispersive nature of these fluctuations as well as their apparent isotropy in the basal plane speak against an interpretation of the spin fluctuation spectrum in the framework of the classical stripe phase picture.

  15. Oscillations at low energies

    CERN Document Server

    Dwyer, D A

    2015-01-01

    A concise summary of the "Oscillation at low energies" parallel session at the 2014 Neutrino Oscillation Workshop is provided. Plans to use man-made neutrinos and antineutrinos to determine the neutrino mass hierarchy, search for sterile neutrinos, and to observe coherent neutrino-nucleus scattering were discussed. Potential measurements of solar neutrinos, supernova neutrinos, and geoneutrinos are also summarized.

  16. Neutron scattering studies of two-dimensional antiferromagnetic spin fluctuations in insulating and superconducting S = ½ systems

    DEFF Research Database (Denmark)

    Christensen, Niels Bech

    polarized multimagnon excitations is discovered at energies above the single-magnon branch. At low energies, the findings are well described bylinear spin wave theory. At high energies, linear spin wave theory fails and instead the data are very well accounted for by state-of-the-art Quantum Monte Carlo......Time-of-flight and polarized triple axis neutron scattering is used to probe the spin excitations of Cu(DCOO)_2_·_4D_2O and La_2_-_xSr_xCuO_4. The first part of the thesis contains an investigation of the excitation spectrum of the square lattice S = 1/2Heisenberg antiferromagnet Cu(DCOO)_2_·_4D_2O...

  17. Local Spin Density Approximation Solution for Spinel LiV2O4: Spin Fluctuation as a Possible Role for Heavy Fermion

    Institute of Scientific and Technical Information of China (English)

    谭明秋; 陶向明

    2001-01-01

    We report on a self-consistent full-potential linear muffin tin orbital band-structure calculation for the heavy fermion (HF) compound LiV2O4. It is found that a stable local spin density approximation solution for LiV2O4 is lower in total energy than the local density approximation calculation. We speculate that the mechanism responsible for HF properties in LiV2O4 might be of spin fluctuation type and is different from the Kondo mechanism in conventional 4f and 5f HF compounds.

  18. The robustness of the quantum spin Hall effect to the thickness fluctuation in HgTe quantum wells

    Institute of Scientific and Technical Information of China (English)

    Guo Huai-Ming; Zhang Xiang-Lin; Feng Shi-Ping

    2012-01-01

    The quantum spin Hall effect (QSHE) was first realized in HgTe quantum wells (QWs),which remain the only known two-dimensional topological insulator so far.In this paper,we have systematically studied the effect of the thickness fluctuation of HgTe QWs on the QSHE.We start with the case of constant mass with random distributions,and reveal that the disordered system can be well described by a virtual uniform QW with an effective mass when the number of components is small.When the number is infinite and corresponds to the real fluctuation,we find that the QSHE is not only robust,but also can be generated by relatively strong fluctuation.Our results imply that the thickness fluctuation does not cause backscattering,and the QSHE is robust to it.

  19. Spin 1/2 systems perturbed by fluctuating, arbitrary fields; relaxation and frequency shifts, a new approach to Redfield theory

    CERN Document Server

    Golub, Robert

    2014-01-01

    The usual approach to considerations of apin relaxation and frequency shifts due to fluctuating fields is through the density matrix Slichter. Here we treat the problem of the influence of fluctuating fields on a spin 1/2 system based on direct solution of the Schroedinger equation in contrast to the usual treatment. Our results are seen to be in agreement with the known results in the literature McGregor, Slichter, Red2, CSH, as they must, but our derivation directly from the Schroedinger equation allows us to see the role of the necessary assumptions in a somewhat clearer way.

  20. Low-energy neutrinos

    CERN Document Server

    Ludhova, Livia

    2016-01-01

    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 feld of solar neutrinos, geoneutrinos, and the search for sterile neutrino with artifcial neutrino sources is provided here; other neutrino sources, as for example reactor or high-energy neutrinos, are described elsewhere. For each of these three felds, the present-day motivation and open questions, as well as the latest experimental results and future perspectives are discussed.

  1. Low Energy Hadron Physics

    CERN Document Server

    Pennington, Michael R

    2000-01-01

    Ask a group of particle theorists about low energy hadron physics and they will say that this is a subject that belongs to the age of the dinosaurs. However, it is GeV physics that controls the outcome of every hadronic interaction at almost every energy. Confinement of quarks and gluons (and any other super-constituents) means that it is the femto-universe that determines what experiments detect. What we have to learn at the start of the 21st century is discussed.

  2. Low Energy Nuclear Reactions?

    CERN Document Server

    CERN. Geneva; Faccini, R.

    2014-01-01

    After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

  3. Classical evolution of quantum fluctuations in spin-like systems: squeezing and entanglement

    Energy Technology Data Exchange (ETDEWEB)

    Klimov, A B [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410, Guadalajara, Jalisco (Mexico); Espinoza, P [Departamento de Ciencias Basicas, Universidad de Guadalajara, Enrique Diaz de Leon 1, 47460, Lagos de Moreno, Jalisco (Mexico)

    2005-06-01

    It is shown that the quantum dynamics of spin coherent states governed by quadratic spin-like Hamiltonians, in the large spin limit, is well described in terms of evolution along classical trajectories on the two-dimensional sphere. Two non-linear effects: (a) spin squeezing and (b) spin entanglement are analysed using the Wigner function approach in the quasiclassical limit and numerically compared with the exact solution.

  4. Extra Low ENergy Antiproton

    CERN Multimedia

    To produce dense antiproton beams at very low energies (110 keV), it has been proposed to install a small decelerator ring between the existing AD ring and the experimental area. Phase-space blowup during deceleration is compensated by electron cooling such that the final emittances are comparable to the 5MeV beam presently delivered by the AD. An immediate consequence is a significant increase in the number of trapped antiprotons at the experiments as outlined in the proposal CERN/SPSC-2009-026; SPCS-P-338. This report describes the machine parameters and layout of the proposal ELENA (Extra Low ENergy Antiproton)ring also gives an approximate estimate of cost and manpower needs. Since the initial estimate, published in 2007 (CERN-AB-2007-079), the ELENA design has evolved considerably. This is due to a new location in the AD hall to acommodate for the possibility of another experimental zone, as suggested by the SPCS, and also due to improvements in the ring optics and layout. The cost estimate that is prese...

  5. Spin fluctuations and excitations in a 2D xy-ferromagnet: CoCl/sub 2/ in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wiesler, D.G.; Zabel, H.

    1989-01-01

    We have investigated by neutron scattering the spin fluctuations and excitations in the stage 2 CoCl/sub 2/ -- graphite intercalation compound. This compound has easy-plane anisotropy and sufficiently weak interplanar interaction to qualify as a test material for Kosterlitz-Thouless-Berezinsky type phase transitions. We have carried out quasi-elastic scattering measurements to determine the temperature variation of the spin correlation length /xi/ above the two dimensional ordering transition. We have also probed the dependence on wave vector and temperature of the inelastic scattering cross section, consisting of both a central peak, associated with vortex diffusion, and spin wave, which become strongly damped above the transition temperature. 15 refs., 5 figs.

  6. The fluctuations of the spin state of 3d-ions near the ``triple point''

    Science.gov (United States)

    Zhitlukhina, E. S.; Lamonova, K. V.; Orel, S. M.; Pashkevich, Yu. G.

    2012-10-01

    The spin states of 3d ions placed in an arbitrarily distorted coordination complex are investigated within the semiempirical modified crystal-field theory. A scheme for constructing spin-state diagrams is presented. Spin-state diagrams are obtained for transition metal ions with electron configurations 3d4, 3d5, and 3d6 placed in a pyramidal environment. The spin-state diagrams for all configurations studied display so-called "triple points", i.e., regions where the spin states are mixed in equal proportions. The spin-state evolution of a five-coordinated Co3+ ion in the layered rare-earth cobaltite GdBaCo2O5.5 is studied. It is found that the intermediate spin state of the Co3+ ion is stabilized by the apex oxygen displacement along the pyramidal axis.

  7. Inside bluetooth low energy

    CERN Document Server

    Gupta, Naresh

    2013-01-01

    Bluetooth Low Energy (LE) is one of the latest enhancement to Bluetooth technology and, as the name suggests, it is aimed at ultra low power devices, such as heart rate monitors, thermometers, and sensors. Due to very low power consumption, devices compliant with this standard can operate for several years on coin cell batteries without the need for recharging. This cutting-edge book helps you understand the whats , whys , and hows of Bluetooth LE. It includes a broad view of the technology, identifies the various building blocks, and explains how they come together. You also find discussions on Bluetooth basics, providing the background information needed to master Bluetooth LE.The book explains the architecture of Bluetooth LE stack and the functionality provided by each of the layers. You find expert guidance in setting up your own system in a quick and efficient manner with inexpensive, easily available hardware and just a couple of PCs running Linux. This unique volume features two chapters that are dedi...

  8. Spin fluctuations and structural modifications in frustrated multiferroics RMnO3 (R=Y, Lu) at high pressure

    Science.gov (United States)

    Kozlenko, D. P.; Kichanov, S. E.; Lukin, E. V.; Lee, S.; Park, J.-G.; Savenko, B. N.

    2010-06-01

    The crystal and magnetic structures of hexagonal manganites YMnO3 and LuMnO3 have been studied by powder neutron diffraction up to 6 GPa in the temperature range of 10-300 K. At ambient pressure, a triangular antiferromagnetic (AFM) state of a Γ1 irreducible representation is stable below T N=70 K in YMnO3. Upon application of high pressure, a spin-reorientation was observed and the triangular AFM structure evolves from Γ1 to Γ1+Γ2 representation symmetry. In LuMnO3, the triangular AFM state of a Γ2 symmetry with T N ≈ 95 K remains stable in the investigated pressure range. The ordered Mn magnetic moment is suppressed at high pressure and low temperature, with much more pronounced effects for YMnO3, indicating enhanced spin fluctuations due to stronger magnetic frustration of the triangular lattice under higher pressure. The relationship between the evolution of spin fluctuations and in-plane Mn-O bonds under pressure is analyzed.

  9. Decoherence and fluctuation dynamics of the quantum dot nuclear spin bath probed by nuclear magnetic resonance

    Science.gov (United States)

    Chekhovich, Evgeny A.

    2017-06-01

    Dynamics of nuclear spin decoherence and nuclear spin flip-flops in self-assembled InGaAs/GaAs quantum dots are studied experimentally using optically detected nuclear magnetic resonance (NMR). Nuclear spin-echo decay times are found to be in the range 1-4 ms. This is a factor of ~3 longer than in strain-free GaAs/AlGaAs structures and is shown to result from strain-induced quadrupolar effects that suppress nuclear spin flip-flops. The correlation times of the flip-flops are examined using a novel frequency-comb NMR technique and are found to exceed 1 s, a factor of ~1000 longer than in strain-free structures. These findings complement recent studies of electron spin coherence and reveal the paradoxical dual role of the quadrupolar effects in self-assembled quantum dots: large increase of the nuclear spin bath coherence and at the same time significant reduction of the electron spin-qubit coherence. Approaches to increasing electron spin coherence are discussed. In particular the nanohole filled GaAs/AlGaAs quantum dots are an attractive option: while their optical quality matches the self-assembled dots the quadrupolar effects measured in NMR spectra are a factor of 1000 smaller.

  10. Neutron scattering studies of two-dimensional antiferromagnetic spin fluctuations in insulating and superconducting S = 1/2 systems

    Energy Technology Data Exchange (ETDEWEB)

    Bech Christensen, N

    2005-01-01

    Time-of-flight and polarized triple axis neutron scattering is used to probe the spin excitations of Cu(DCOO){sub 2}x4D{sub 2}O and La{sub 2-x}Sr{sub x}CuO{sub 4}. The first part of the thesis contains an investigation of the excitation spectrum of the square lattice S = 1/2 Heisenberg antiferromagnet Cu(DCOO){sub 2}4D{sub 2}O. Along the antiferromagnetic zone boundary a pronounced intensity variation is found for the dominant single-magnon excitations. This variation tracks an already known zone boundary dispersion. Using polarization analysis to separate the components of the excitation spectrum, a continuum of longitudinally polarized multimagnon excitations is discovered at energies above the single-magnon branch. At low energies, the findings are well described by linear spin wave theory. At high energies, linear spin wave theory fails and instead the data are very well accounted for by state-of-the-art Quantum Monte Carlo computations. In the second part of the thesis, the spin excitation spectra of the high temperature superconductors La{sub 1.90}Sr{sub 0.10}CuO{sub 4} and La{sub 1.84}Sr{sub 0.16}Cu characterized. The main discovery is that the excitations are dispersive at both doping levels. The dispersion strongly resembles that seen in other high-T{sub c} superconductors. The presence of dispersive excitations does not require superconductivity to exist. For La{sub 1.84}Sr{sub 0.16}CuO{sub 4}, but not for La{sub 1.90}Sr{sub 0.10}CuO{sub 4}, the onset superconductivity gives rise to a spectral weight shift which displays qualitative and quantitative similarities to the resonance mode observed in other high-T{sub c} superconductors. (au)

  11. Superconductivity in FeSe Thin Films Driven by the Interplay between Nematic Fluctuations and Spin-Orbit Coupling

    Science.gov (United States)

    Kang, Jian; Fernandes, Rafael M.

    2016-11-01

    The origin of the high-temperature superconducting state observed in FeSe thin films, whose phase diagram displays no sign of magnetic order, remains a hotly debated topic. Here we investigate whether fluctuations arising due to the proximity to a nematic phase, which is observed in the phase diagram of this material, can promote superconductivity. We find that nematic fluctuations alone promote a highly degenerate pairing state, in which both s -wave and d -wave symmetries are equally favored, and Tc is consequently suppressed. However, the presence of a sizable spin-orbit coupling or inversion symmetry breaking at the film interface lifts this harmful degeneracy and selects the s -wave state, in agreement with recent experimental proposals. The resulting gap function displays a weak anisotropy, which agrees with experiments in monolayer FeSe and intercalated Li1 -x(OH )xFeSe .

  12. Ferromagnetic Spin Fluctuation and Unconventional Superconductivity in Rb2Cr3As3 Revealed by 75As NMR and NQR

    Science.gov (United States)

    Yang, J.; Tang, Z. T.; Cao, G. H.; Zheng, Guo-qing

    2015-10-01

    We report 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) studies on the superconductor Rb2Cr3As3 with a quasi-one-dimensional crystal structure. Below T ˜100 K , the spin-lattice relaxation rate (1 /T1 ) divided by temperature, 1 /T1T , increases upon cooling down to Tc=4.8 K , showing a Curie-Weiss-like temperature dependence. The Knight shift also increases with decreasing temperature. These results suggest ferromagnetic spin fluctuation. In the superconducting state, 1 /T1 decreases rapidly below Tc without a Hebel-Slichter peak, and follows a T5 variation below T ˜3 K , which points to unconventional superconductivity with point nodes in the gap function.

  13. Features in Quasi-particle Excitations and Tunnelling Spectra due to Coupling to Spin Fluctuations in High-Tc Cuprates

    Institute of Scientific and Technical Information of China (English)

    赵力; 李建新; 龚昌德; 赵柏儒

    2002-01-01

    In a self-consistent mean-field treatment of the two-dimensional t - t' - J model, we theoretically examine thecoupling of in-plane quasi-particles to the antiferromagnetic spin fluctuations in high-Tc superconductors, whichrenormalizes the fermionic self-energy. We reproduce the characteristic peak,lip-hump structure observed notonly in angle-resolved photoemission spectroscopy, but also in superconductor-insulator-normal metal junctionsand scanning tunnelling microscopy experiments. We consider the evolution of this structure with doping. Itis shown that this kind of coupling can account for many anomalous properties of high-Tc superconductors insuperconducting states.

  14. The fluctuating gap model

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Xiaobin

    2011-01-15

    The quasi-one-dimensional systems exhibit some unusual phenomenon, such as the Peierls instability, the pseudogap phenomena and the absence of a Fermi-Dirac distribution function line shape in the photoemission spectroscopy. Ever since the discovery of materials with highly anisotropic properties, it has been recognized that fluctuations play an important role above the three-dimensional phase transition. This regime where the precursor fluctuations are presented can be described by the so called fluctuating gap model (FGM) which was derived from the Froehlich Hamiltonian to study the low energy physics of the one-dimensional electron-phonon system. Not only is the FGM of great interest in the context of quasi-one-dimensional materials, liquid metal and spin waves above T{sub c} in ferromagnets, but also in the semiclassical approximation of superconductivity, it is possible to replace the original three-dimensional problem by a directional average over effectively one-dimensional problem which in the weak coupling limit is described by the FGM. In this work, we investigate the FGM in a wide temperature range with different statistics of the order parameter fluctuations. We derive a formally exact solution to this problem and calculate the density of states, the spectral function and the optical conductivity. In our calculation, we show that a Dyson singularity appears in the low energy density of states for Gaussian fluctuations in the commensurate case. In the incommensurate case, there is no such kind of singularity, and the zero frequency density of states varies differently as a function of the correlation lengths for different statistics of the order parameter fluctuations. Using the density of states we calculated with non-Gaussian order parameter fluctuations, we are able to calculate the static spin susceptibility which agrees with the experimental data very well. In the calculation of the spectral functions, we show that as the correlation increases, the

  15. Entanglement and Extreme Spin Squeezing for a Fluctuating Number of Indistinguishable Particles

    CERN Document Server

    Hyllus, Philipp; Smerzi, Augusto; Toth, Geza

    2012-01-01

    We extend the criteria for $k$-particle entanglement from the spin squeezing parameter presented in [A.S. S{\\o}rensen and K. M{\\o}lmer, Phys. Rev. Lett. {\\bf 86}, 4431 (2001)] to systems with a fluctating number of particles. We also discuss how other spin squeezing inequalities can be generalized to this situation. Further, we give an operational meaning to the bounds for cases where the individual particles cannot be addressed. As a by-product, this allows us to show that in spin squeezing experiments with cold gases the particles are typically distinguishable in practise. Our results justify the application of the S{\\o}rensen-M{\\o}lmer bounds in recent experiments on spin squeezing in Bose-Einstein condensates.

  16. Correlation driven charge and spin fluctuations in LaCoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Karolak, Michael [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg, Am Hubland, 97074 Wuerzburg (Germany); Izquierdo, Manuel [European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); Synchrotron Soleil, L' Orme des Merisiers St-Aubin, BP-48, 91192, Gif-sur-Yvette (France); Institut fuer Theoretische Physik, Universitaet Hamburg, Jungiusstrasse 9, 20355 Hamburg (Germany); Molodtsov, Serguei L. [European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg (Germany); Institute of Experimental Physics, Technische Universitaet Bergakademie Freiberg, 09599 Freiberg (Germany); ITMO University, Kronverkskiy pr. 49, 197101 St. Petersburg (Russian Federation); Lichtenstein, Alexander I. [Institut fuer Theoretische Physik, Universitaet Hamburg, Jungiusstrasse 9, 20355 Hamburg (Germany)

    2015-07-01

    The spin transition in LaCoO{sub 3} has been investigated within the DFT+DMFT formalism using continuous time quantum Monte Carlo. Calculations on the experimental rhombohedral atomic structure with two Co sites per unit cell show that an independent treatment of the Co atoms results in a ground state with charge imbalance induced by electronic correlations. Each atom shows a contribution from either a d{sup 5} or a d{sup 7} state in addition to the main d{sup 6} state. These charged states play a relevant role in the spin transition which can be understood as a low spin-high spin (LS-HS) transition with significant contributions (∝ 10%) to the LS and HS states of d{sup 5} and d{sup 7} states. A thermodynamic analysis reveals that the introduction of charge imbalance significantly lowers the total energy of the system.

  17. NMR investigation of spin fluctuations in the itinerant-electron magnetic compound Sr1 -xCaxCo2P2

    Science.gov (United States)

    Imai, Masaki; Michioka, Chishiro; Ueda, Hiroaki; Yoshimura, Kazuyoshi

    2017-02-01

    We took P31 NMR measurements of mainly paramagnetic phase Sr1 -xCaxCo2P2 (0 ≤x ≤0.5 ) to reveal the itinerant-electron metamagnetic transition, and of its magnetically ordered phase (0.7 ≤x ≤1 ), and characterized their spin fluctuations by estimating the spin fluctuation parameter T0 corresponding to the width of the spin fluctuation in the spectrum in frequency space. SrCo2P2 has a quasi-two-dimensional uncollapsed tetragonal (ucT) cell without interlayer P-P bonds, whereas CaCo2P2 has a three-dimensional collapsed tetragonal (cT) cell with P-P bonds. The a b -in-plane component of T0 is much larger than the out-of-plane component in SrCo2P2 . As x increases from 0 to 0.5, the in-plane component of T0 decreases proportionally with the metamagnetic transition field. In the antiferromagnetic cT phase (0.7 ≤x ≤1 ), T0 is constant and spin fluctuations show an isotropic character in contrast to their behavior in the paramagnetic ucT phase (0 ≤x ≤0.5 ). These results indicate that the in-plane spin fluctuations due to the quasi-two-dimensional crystal structure play a significant role in the metamagnetic transition of this system.

  18. Anomalous influence of spin fluctuations on the heat capacity and entropy in a strongly correlated helical ferromagnet MnSi

    Science.gov (United States)

    Povzner, A. A.; Volkov, A. G.; Nogovitsyna, T. A.

    2017-02-01

    The influence of spin fluctuations on the thermodynamic properties of a helical ferromagnet MnSi has been investigated in the framework of the Hubbard model with the electronic spectrum determined from the first-principles LDA + U + SO calculation, which is extended taking into account the Hund coupling and the Dzyaloshinskii-Moriya antisymmetric exchange. It has been shown that the ground state of the magnetic material is characterized by large zero-point fluctuations, which disappear at the temperature T* (< T c is the temperature of the magnetic phase transition). In this case, the entropy abruptly increases, and a lambdashaped anomaly appears in the temperature dependence of the heat capacity at constant volume ( C V ( T)). In the temperature range T* < T < T c , thermal fluctuations lead to the disappearance of the inhomogeneous magnetization. The competition between the increase in the entropy due to paramagnon excitations and its decrease as a result of the reduction in the amplitude of local magnetic moments, under the conditions of strong Hund exchange, is responsible for in the appearance of a "shoulder" in the dependence C V ( T)).

  19. Effect of Interband Fluctuation on Spin Susceptibility in Molecular Dirac Fermion System α-(BEDT-TTF)2I3

    Science.gov (United States)

    Matsuno, Genki; Kobayashi, Akito

    2017-01-01

    The nontrivial properties of interband spin fluctuations are studied by the random phase approximation in a Hubbard model describing the molecular conductor α-(BEDT-TTF)2I3, where wave functions are based on the four sublattices named A, A', B, and C in a two-dimensional BEDT-TTF molecular plane. It is found that the ferrimagnetic polarization observed by a recent NMR measurement emerges only if there exist cross terms among intra- and inter-band irreducible susceptibility matrix elements in the presence of the on-site Coulomb interaction U. It is also found that the nontrivial sign of the interband components of the spin susceptibility, being negative only for the B sublattice, is closely related to the characteristic phase structure of wave functions in the Dirac fermion system with multisublattices. The negative value of the spin susceptibility on the B sublattice observed in the experiment is associated with this negative interband susceptibility, which comes from the excitations in the gentle-slope region of the energy dispersion connecting the Dirac points with saddle points in the first Brillouin zone.

  20. Two Dimensional Incommensurate Spin Excitations and Lattice Fluctuations in La2 - x Bax CuO4

    Science.gov (United States)

    Wagman, J. J.; Carlo, J. P.; van Gastel, G.; Zhao, Y.; Kallin, A. B.; Mazurek, E.; Dabkowska, H. A.; Savicii, A.; Granroth, G. E.; Yamani, Z.; Tun, Z.; Gaulin, B. D.

    2013-03-01

    'Hour-glass' shaped dispersions of antiferromagnetic (AF) spin fluctuations are a robust feature common to many high temperature superconductors. In 214 cuprates, these phenomena are well known to display a strong dependence on the concentration of holes that are introduced into the copper oxide planes by doping. The incommensurability (IC) of the two dimensional magnetic order in this system is sensitive to hole concentration. Here, we present a series of neutron scattering measurements on single crystals of La2 - x Bax CuO4 (LBCO), with 0 . 035 <= x <= 0 . 095 , a doping range that spans the transition from diagonal to parallel IC ordering wavevectors, and from non-superconducting to superconducting ground states. Our measurements map out the evolution of the spin excitations for energies below ~ 50 meV, and focus on an enhancement in the scattered intensity centered in the 17-20 meV at the AF IC positions. This regime corresponds to the approximate crossing of very dispersive spin excitations and weakly dispersive low lying optic phonons in LBCO. NSERC, Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy

  1. Magnetic fluctuations and correlations in MnSi: Evidence for a chiral skyrmion spin liquid phase

    NARCIS (Netherlands)

    Pappas, C.; Lelièvre-Berna, E.; Bentley, P.; Falus, P.; Fouquet, P.; Farago, B.

    2011-01-01

    We present a comprehensive analysis of high-resolution neutron scattering data involving neutron spin echo spectroscopy and spherical polarimetry, which confirm the first-order nature of the helical transition in MnSi. The experiments reveal the existence of a totally chiral dynamic phase in a very

  2. Three-dimensional multimodal sub-diffraction imaging with spinning-disk confocal microscopy using blinking/ fluctuating probes

    Institute of Scientific and Technical Information of China (English)

    Xuanze Chen[2; Zhiping zeng[2; Hening Wang[1; Peng Xi[1

    2015-01-01

    Three-dimensional imaging cannot be achieved easily using previously developed localization super-resolution techniques. Here, we present a three-dimensional multimodal sub-diffraction imaging technique with spinning-disk (SD) confocal microscopy called 3D-MUSIC, which not only has all the advantages of SD confocal microscopy such as fast imaging speed, high signal-to-noise ratio, and optical-sectioning capability, but also extends its spatial resolution limit along all three dimensions. Both axial and lateral resolution can be improved simul- taneously by virtue of the blinking/fluctuating nature of modified fluorescent probes, exemplified with the quantum dots. Further, super-resolution images with dual modality can be obtained through super-resolution optical fluctuation imaging (SOFI) and bleaching/blinking-assisted localization microscopy (BALM). Therefore, fast super-resolution imaging can be achieved with SD-SOFI by capturing only 100 frames while SD-BaLM yields high-resolution imaging.

  3. Kagome spin ice

    Science.gov (United States)

    Mellado, Paula

    Spin ice in magnetic pyrochlore oxides is a peculiar magnetic state. Like ordinary water ice, these materials are in apparent violation with the third law of thermodynamics, which dictates that the entropy of a system in thermal equilibrium vanishes as its temperature approaches absolute zero. In ice, a "zero-point" entropy is retained down to low temperatures thanks to a high number of low-energy positions of hydrogen ions associated with the Bernal-Fowler ice-rules. Spins in pyrochlore oxides Ho2Ti 2O7 and Dy2Ti2O7 exhibit a similar degeneracy of ground states and thus also have a sizable zero-point entropy. A recent discovery of excitations carrying magnetic charges in pyrochlore spin ice adds another interesting dimension to these magnets. This thesis is devoted to a theoretical study of a two-dimensional version of spin ice whose spins reside on kagome, a lattice of corner-sharing triangles. It covers two aspects of this frustrated classical spin system: the dynamics of artificial spin ice in a network of magnetic nanowires and the thermodynamics of crystalline spin ice. Magnetization dynamics in artificial spin ice is mediated by the emission, propagation and absorption of domain walls in magnetic nanowires. The dynamics shows signs of self-organized behavior such as avalanches. The theoretical model compares favorably to recent experiments. The thermodynamics of the microscopic version of spin ice on kagome is examined through analytical calculations and numerical simulations. The results show that, in addition to the high-temperature paramagnetic phase and the low-temperature phase with magnetic order, spin ice on kagome may have an intermediate phase with fluctuating spins and ordered magnetic charges. This work is concluded with a calculation of the entropy of kagome spin ice at zero temperature when one of the sublattices is pinned by an applied magnetic field and the system breaks up into independent spin chains, a case of dimensional reduction.

  4. Spatial Fluctuations of Loose Spin Coupling in CuMn/Co Multilayers

    Science.gov (United States)

    Saerbeck, T.; Loh, N.; Lott, D.; Toperverg, B. P.; Mulders, A. M.; Rodríguez, A. Fraile; Freeland, J. W.; Ali, M.; Hickey, B. J.; Stampfl, A. P. J.; Klose, F.; Stamps, R. L.

    2011-09-01

    A detailed investigation of magnetic impurity-mediated interlayer exchange coupling observed in Cu0.94Mn0.06/Co multilayers using polarized neutron reflectometry and magnetic x-ray techniques is reported. Excellent descriptions of temperature and magnetic field dependent biquadratic coupling are obtained using a variant of the loose spin model that takes into account the distribution of the impurity Mn ions in three dimensions. Positional disorder of the magnetic impurities is shown to enhance biquadratic coupling via a new contribution J2fluct, leading to a temperature dependent canting of magnetic domains in the multilayer. These results provide measurable effects on RKKY coupling associated with the distribution of impurities within planes parallel to the interfaces.

  5. Quantum scattering at low energies

    DEFF Research Database (Denmark)

    Derezinski, Jan; Skibsted, Erik

    2009-01-01

    For a class of negative slowly decaying potentials, including V(x):=−γ|x|−μ with 0low-energy regime. Using appropriate modifiers of the Isozaki–Kitada type we show that scattering theory is well behaved on the whole continuous spectrum...

  6. Quantum scattering at low energies

    DEFF Research Database (Denmark)

    Derezinski, Jan; Skibsted, Erik

    For a class of negative slowly decaying potentials, including with , we study the quantum mechanical scattering theory in the low-energy regime. Using modifiers of the Isozaki--Kitada type we show that scattering theory is well behaved on the {\\it whole} continuous spectrum of the Hamiltonian...

  7. PCAC and Shadowing of Low Energy Neutrinos

    CERN Document Server

    Kopeliovich, B Z

    2005-01-01

    The Adler relation between reactions initiated by neutrinos and pions is easy to misinterpret as a manifestation of the pion pole dominance. An axial current, however, cannot fluctuate into a pion, but only to heavy axial-vector states, since the lepton current is transverse. This is the miracle of the PCAC hypothesis which dictates a specific conspiracy between the heavy fluctuations, so that all together they mock the pion pole. Indeed, the observed Q^2 dependence of the axial form factor is controlled by the effective mass m_A \\sim 1 GeV, rather than the pion mass. On the contrary, the onset of nuclear shadowing is governed by the small pion mass, rather than by the large axial mass scale. This is in variance with the conventional wisdom which equates the fluctuation lifetime and the coherence time. For the case of axial current they are different by almost two orders of magnitude. As a result, neutrino interactions are shadowed at very low energies of few hundred MeV, while energy of about 10 GeV is neede...

  8. PCAC and shadowing of low energy neutrinos

    Science.gov (United States)

    Kopeliovich, B. Z.

    2005-02-01

    The Adler relation between reactions initiated by neutrinos and pions is easy to misinterpret as a manifestation of the pion pole dominance. An axial current, however, cannot fluctuate into a pion, but only to heavy axial-vector states, since the lepton current is transverse. This is the miracle of the PCAC hypothesis which dictates a specific conspiracy between the heavy fluctuations, so that all together they mock the pion pole. Indeed, the observed Q2 dependence of the axial form factor is controlled by the effective mass m˜1 GeV, rather than the pion mass. On the contrary, the onset of nuclear shadowing is governed by the small pion mass, rather than by the large axial mass scale. This is in variance with the conventional wisdom which equates the fluctuation lifetime and the coherence time. For the case of axial current they are different by almost two orders of magnitude. As a result, neutrino interactions are shadowed at very low energies of few hundred MeV, while energy of about 10 GeV is needed to access nuclear shadowing for the vector current. On the contrary to naive expectations, nuclear absorption enhances, rather than suppresses the cross section of coherent neutrino-production of pions which is the strongest channel (half of the total cross section) in the black disc limit.

  9. Critical Casimir force and its fluctuations in lattice spin models: exact and Monte Carlo results.

    Science.gov (United States)

    Dantchev, Daniel; Krech, Michael

    2004-04-01

    We present general arguments and construct a stress tensor operator for finite lattice spin models. The average value of this operator gives the Casimir force of the system close to the bulk critical temperature T(c). We verify our arguments via exact results for the force in the two-dimensional Ising model, d -dimensional Gaussian, and mean spherical model with 2Monte Carlo simulations for three-dimensional Ising, XY, and Heisenberg models we demonstrate that the standard deviation of the Casimir force F(C) in a slab geometry confining a critical substance in-between is k(b) TD(T) (A/ a(d-1) )(1/2), where A is the surface area of the plates, a is the lattice spacing, and D(T) is a slowly varying nonuniversal function of the temperature T. The numerical calculations demonstrate that at the critical temperature T(c) the force possesses a Gaussian distribution centered at the mean value of the force = k(b) T(c) (d-1)Delta/ (L/a)(d), where L is the distance between the plates and Delta is the (universal) Casimir amplitude.

  10. Low Energy Atomic Photodesorption from Organic Coatings

    Directory of Open Access Journals (Sweden)

    Alessandro Lucchesini

    2016-10-01

    Full Text Available Organic coatings have been widely used in atomic physics during the last 50 years because of their mechanical properties, allowing preservation of atomic spins after collisions. Nevertheless, this did not produce detailed insight into the characteristics of the coatings and their dynamical interaction with atomic vapors. This has changed since the 1990s, when their adsorption and desorption properties triggered a renewed interest in organic coatings. In particular, a novel class of phenomena produced by non-destructive light-induced desorption of atoms embedded in the coating surface was observed and later applied in different fields. Nowadays, low energy non-resonant atomic photodesorption from organic coatings can be considered an almost standard technique whenever large densities of atomic vapors or fast modulation of their concentration are required. In this paper, we review the steps that led to this widespread diffusion, from the preliminary observations to some of the most recent applications in fundamental and applied physics.

  11. Review of Low Energy Neutrinos

    CERN Document Server

    Vergados, J D

    2007-01-01

    Some issues regarding low energy neutrinos are reviewed. We focus on three aspects i)We show that by employing very low energy (a few keV) electron neutrinos, neutrino disappearance oscillations can be investigated by detecting recoiling electrons with low threshold spherical gaseous TPC's. In such an experiment, which is sensitive to the small mixing angle theta13, the novel feature is that the oscillation length is so small that the full oscillation takes place inside the detector. Thus one can determine accurately all the oscillation parameters and, in particular, measure or set a good limit on theta13. ii) Low threshold gaseous TPC detectors can also be used in detecting nuclear recoils by exploiting the neutral current interaction. Thus these robust and stable detectors can be employed in supernova neutrino detection. iii) The lepton violating neutrinoless double decay is investigated focusing on how the absolute neutrino mass can be extracted from the data

  12. The low energy signaling network

    Directory of Open Access Journals (Sweden)

    Filipa dos Santos Tomé

    2014-07-01

    Full Text Available Stress impacts negatively on plant growth and crop productivity, causing extensive losses to agricultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy saving responses. The resulting low energy syndrome (LES includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases SnRK1 and TOR play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments.

  13. Significance of the direct relaxation process in the low-energy spin dynamics of a one-dimensional ferrimagnet NiCu(C 7H 6N 2O 6)(H 2O) 3·2H 2O

    Science.gov (United States)

    Yamamoto, S.

    2000-11-01

    In response to recent nuclear magnetic resonance measurements on a ferrimagnetic chain compound NiCu(C 7H 6N 2O 6)(H 2O) 3·2H 2O [Solid State Commun. 113 (2000) 433], we calculate the nuclear spin-lattice relaxation rate 1/ T1 in terms of a modified spin-wave theory. Emphasizing that the dominant relaxation mechanism arises from the direct (single-magnon) process rather than the Raman (two-magnon) one, we explain the observed temperature and applied-field dependences of 1/ T1. Ferrimagnetic relaxation phenomena are generally discussed and novel ferrimagnets with extremely slow dynamics are predicted.

  14. Effects of exchange interaction and spin-fluctuation on the magnetic and magneto-optic properties of NdF3

    Institute of Scientific and Technical Information of China (English)

    Zhang Guo-Ying; Xia Tian; Zhang Xue-Long; Xue Liu-Ping

    2008-01-01

    The exchange interaction between the electrons in the different magnetic ions and the spin-fluctuation of the magnetic ions exist in the paramagnetic media NdF3. The exchange interaction between the electrons in the different magnetic ions may be equivalent to an effective field Hin that is in direct proportion to the magnetization M. The spin-fluctuation of the magnetic ions leads the coefficient of the effective field to vary with temperature. The effective field is given as Hin = -(0.75+0.22T) × 10-5 M in NdF3. When the secondary crystal field effect is taken into account,the magnetic susceptibility and Verdet constant are calculated for NdF3 by means of the effective field Hin and the applied field He. The calculated results are in agreement with the measured ones.

  15. Low-energy neutrino measurements

    Indian Academy of Sciences (India)

    Davide D'angelo

    2012-10-01

    Low-energy solar neutrino detection plays a fundamental role in understanding both solar astrophysics and particle physics. After introducing the open questions on both fields, we review here the major results of the last two years and expectations for the near future from Borexino, Super-Kamiokande, SNO and KamLAND experiments as well as from upcoming (SNO+) and planned (LENA) experiments. Scintillator neutrino detectors are also powerful antineutrino detectors which can detect neutrinos emitted by the Earth crust and mantle. First measurements of geoneutrinos have occurred which can bring fundamental contribution in understanding the geophysics of the planet.

  16. Low-energy mechanical ventilation

    DEFF Research Database (Denmark)

    Andersen, Claus Wessel; Hviid, Christian Anker

    2014-01-01

    and with as little energy consumption as 41.1 kWh/m2/year including heating and all building services with no use of renewable energy such as PVcells or solar heating. One of the key means of reaching the objectives was to implement mechanical ventilation with low pressure loss and therefore low energy consumption....... The project consists of two buildings, building one is 6 stories high, and building two is 4 stories high. The buildings have a gross area of 50,500 m2 including underground parking. The ventilation and indoor climate concept was to use mechanical ventilation together with mechanical cooling and fanassisted...

  17. Frozen concentration fluctuations in a poly(N-isopropyl acrylamide) gel studied by neutron spin echo and small-angle neutron scattering

    CERN Document Server

    Koizumi, S; Richter, D; Schwahn, D; Faragó, B; Annaka, M

    2002-01-01

    By employing neutron spin echo and small-angle neutron scattering, we determined the structure factor of the frozen concentration fluctuations on nano-length scales in a swollen poly(N-isopropyl acrylamide) gel. The frozen contribution, showing a plateau at the low scattering wavenumber q (0.02 A sup - sup 1), is intimately related to the abnormal butterfly scattering pattern appearing at low q under deformation. (orig.)

  18. The c—Axis Infrared Conductivity of a dx2—y2— Wave Superconductor with the Hopping Assisted by the Spin Fluctuations

    Institute of Scientific and Technical Information of China (English)

    LOUPing; CAOLie-Zhao; 等

    2002-01-01

    A theory of the c-axis infrared conductivity of a dx2-y2- wave superconductor due to the competition between the interlayer direct hopping and the hopping assisted by the spin fluctuations has been developed.The prediction of our theory captures the main feature of the experiment.Thus we argue that the anomalous behavior of the c-axis infrared conductivity of the underdoped cuprates in superconducting state may be properly understood within the theory.

  19. Dynamic density and spin responses of a superfluid Fermi gas in the BCS-BEC crossover: Path integral formulation and pair fluctuation theory

    Science.gov (United States)

    He, Lianyi

    2016-10-01

    We present a standard field theoretical derivation of the dynamic density and spin linear response functions of a dilute superfluid Fermi gas in the BCS-BEC crossover in both three and two dimensions. The derivation of the response functions is based on the elegant functional path integral approach which allows us to calculate the density-density and spin-spin correlation functions by introducing the external sources for the density and the spin density. Since the generating functional cannot be evaluated exactly, we consider two gapless approximations which ensure a gapless collective mode (Goldstone mode) in the superfluid state: the BCS-Leggett mean-field theory and the Gaussian-pair-fluctuation (GPF) theory. In the mean-field theory, our results of the response functions agree with the known results from the random phase approximation. We further consider the pair fluctuation effects and establish a theoretical framework for the dynamic responses within the GPF theory. We show that the GPF response theory naturally recovers three kinds of famous diagrammatic contributions: the Self-Energy contribution, the Aslamazov-Lakin contribution, and the Maki-Thompson contribution. We also show that unlike the equilibrium state, in evaluating the response functions, the linear (first-order) terms in the external sources as well as the induced order parameter perturbations should be treated carefully. In the superfluid state, there is an additional order parameter contribution which ensures that in the static and long wavelength limit, the density response function recovers the result of the compressibility (compressibility sum rule). We expect that the f-sum rule is manifested by the full number equation which includes the contribution from the Gaussian pair fluctuations. The dynamic density and spin response functions in the normal phase (above the superfluid critical temperature) are also derived within the Nozières-Schmitt-Rink (NSR) theory.

  20. Spin fluctuation and small polaron conduction dominated electrical resistivity in La0.875Sr0.125MnO3 manganite nanostructures

    Indian Academy of Sciences (India)

    K K Choudhary; N Gupta; N Kaurav; S Katiyal; S K Ghosh

    2014-08-01

    The anomalous temperature-dependent electrical resistivity ρ() of La0.875Sr0.125MnO3 manganite nanoparticles (particle size 18 nm) is theoretically analysed. ρ() exhibits semiconducting phase in lowtemperature regime (20 < < 53 K), shows a minima near 53 K and increases with at high temperatures (53 < < 170 K). The resistivity in metallic phase ( > 53 K) is theoretically analysed by considering the strong spin-fluctuation effect, which is modelled using Drude–Lorentz type function. In addition to the spin fluctuation-induced contribution, the electron–phonon and electron–electron $ ρe–e() = 2 contributions are also incorporated for complete understanding of experimental data. The contributions to the resistivity by inherent acoustic phonons ( ρac) as well as high-frequency optical phonons ( ρop) were estimated using Bloch–Gruneisen (BG) model of resistivity. It is observed that the resistivity contribution due to electron–electron interaction shows typical quadratic temperature dependence. Spin fluctuation-induced resistivity is dominant over electron–electron and electron–phonon contributions in overall temperature range in the manganite nanoparticles. Resistivity in the semiconducting phase is discussed with small polaron conduction (SPC) model. SPC model consistently retraces the low-temperature resistivity behaviour ( < 53 K). Finally, the theoretically calculated resistivity compared with experimental data is found to be consistent in wide range of temperature.

  1. Low energy gauge unification theory

    CERN Document Server

    Li Tian Jun

    2002-01-01

    Because of the problems arising from the fermion unification in the traditional Grand Unified Theory and the mass hierarchy between the 4-dimensional Planck scale and weak scale, we suggest the low energy gauge unification theory with low high-dimensional Planck scale. We discuss the non-supersymmetric SU(5) model on M sup 4 xS sup 1 /Z sub 2 xS sup 1 /Z sub 2 and the supersymmetric SU(5) model on M sup 4 xS sup 1 /(Z sub 2 xZ sub 2 ')xS sup 1 /(Z sub 2 xZ sub 2 ')xS sup 1 /(Z sub 2 xZ sub 2 '). The SU(5) gauge symmetry is broken by the orbifold projection for the zero modes, and the gauge unification is accelerated due to the SU(5) asymmetric light KK states. In our models, we forbid the proton decay, still keep the charge quantization, and automatically solve the fermion mass problem. We also comment on the anomaly cancellation and other possible scenarios for low energy gauge unification.

  2. Proceedings of the International Workshop on Low Energy Muon Science: LEMS`93

    Energy Technology Data Exchange (ETDEWEB)

    Leon, M. [comp.

    1994-01-01

    This report contains papers on research with low energy muons. Topics cover fundamental electroweak physics; muonic atoms and molecules, and muon catalyzed fusion; muon spin research; and muon facilities. These papers have been indexed and cataloged separately.

  3. Revisiting orbital-fluctuation-mediated superconductivity in LiFeAs: Nontrivial spin-orbit interaction effects on the band structure and superconducting gap function

    Science.gov (United States)

    Saito, Tetsuro; Yamakawa, Youichi; Onari, Seiichiro; Kontani, Hiroshi

    2015-10-01

    The precise gap structure in LiFeAs (Tc=18 K) given by ARPES studies offers significant information that helps us understand the pairing mechanism in iron-based superconductors. The most remarkable characteristic in the LiFeAs gap structure would be that "the largest gap emerges on the tiny hole-pockets around the Z point." This result has been naturally explained in terms of the orbital-fluctuation scenario [T. Saito et al., Phys. Rev. B 90, 035104 (2014)], 10.1103/PhysRevB.90.035104, whereas the opposite result is obtained by the spin-fluctuation scenario. In this paper, we study the gap structure in LiFeAs by taking the spin-orbit interaction (SOI) into account, motivated by the recent ARPES studies that revealed a significant SOI-induced modification of the Fermi surface topology. For this purpose, we construct two possible tight-binding models with finite SOI by referring the band structures given by different ARPES groups. In addition, we extend the gap equation for multiorbital systems with finite SOI, and calculate the gap functions by applying the orbital-spin fluctuation theory. On the basis of both SOI-induced band structures, the main characteristics of the gap structure in LiFeAs are naturally reproduced only in the presence of strong interorbital interactions between (dx z /y z-dx y) orbitals. Thus the experimental gap structure in LiFeAs is a strong evidence for the orbital-fluctuation pairing mechanism.

  4. Enhanced low-energy magnetic excitations via suppression of the itinerancy in Fe0.98-zCuzTe0.5Se0.5

    Science.gov (United States)

    Wen, Jinsheng; Li, Shichao; Xu, Zhijun; Zhang, Cheng; Matsuda, M.; Sobolev, O.; Park, J. T.; Christianson, A. D.; Bourret-Courchesne, E.; Li, Qiang; Gu, Genda; Lee, Dung-Hai; Tranquada, J. M.; Xu, Guangyong; Birgeneau, R. J.

    2013-10-01

    We have performed resistivity and inelastic neutron scattering measurements on three samples of Fe0.98-zCuzTe0.5Se0.5 with z=0, 0.02, and 0.1. It is found that with increasing Cu doping the sample's resistivity deviates progressively from that of a metal. However, in contrast to expectations that replacing Fe with Cu would suppress the magnetic correlations, the low-energy (≤12 meV) magnetic scattering is enhanced in strength, with greater spectral weight and longer dynamical spin-spin correlation lengths. Such enhancements can be a consequence of either enlarged local moments or a slowing down of the spin fluctuations. In either case, the localization of the conduction states induced by the Cu doping should play a critical role. Our results are not applicable to models that treat 3d transition metal dopants simply as effective electron donors.

  5. A schematic model for QCD I Low energy meson states

    CERN Document Server

    Lerma, S; Hess, P O; Civitarese, O; Reboiro, M

    2003-01-01

    A simple model for QCD is presented, which is able to reproduce the meson spectrum at low energy. The model is a Lipkin type model for quarks coupled to gluons. The basic building blocks are pairs of quark-antiquarks coupled to a definite flavor and spin. These pairs are coupled to pairs of gluons with spin zero. The multiplicity problem, which dictates that a given experimental state can be described in various manners, is removed when a particle-mixing interaction is turned on. In this first paper of a series we concentrates on the discussion of meson states at low energy, the so-called zero temperature limit of the theory. The treatment of baryonic states is indicated, also.

  6. Low-Energy Proton Testing Methodology

    Science.gov (United States)

    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 Supergravity Revisited (I)

    CERN Document Server

    Moultaka, Gilbert; Tant, Damien

    2016-01-01

    General forms of the K\\"ahler and superpotenials that lead to consistent low energy broken Supersymmetry originating from $N=1$ Supergravity have been classified and used for model building since more than three decades. We point out the incompleteness of this classification. Focusing in this paper mainly on the case of minimal K\\"ahler potential, we adopt a rigorous approach that retrieves on the one hand the known forms, and demonstrate on the other hand the existence of a whole set of new forms for the superpotential of which we give a complete classification. The latter forms involve a new type of chiral superfields having the unusual property of belonging neither to the hidden sector nor to the conventional observable sector. We argue how new possibilities for model building can arise, comparing the obtained forms with the conventional ones, and discuss the gravity mediation of supersymmetry breaking and the vacuum structure in the presence of the new type of chiral superfields. In the simplest case, we ...

  8. Pressure-Induced Antiferromagnetic Fluctuations in the Pnictide Superconductor FeSe0.5Te0.5: 125Te NMR Study

    Science.gov (United States)

    Shimizu, Yasuhiro; Yamada, Takato; Takami, Tsuyoshi; Niitaka, Seiji; Takagi, Hidenori; Itoh, Masayuki

    2009-12-01

    To investigate the relationship between superconductivity and low-energy spin fluctuations in the iron-based superconductor FeSe0.5Te0.5, we have conducted 125Te NMR measurements at ambient pressure and 2 GPa. As the superconducting transition temperature Tc is increased by applying pressure, the nuclear spin-lattice relaxation rate divided by temperature, 1/T1T, shows the development of antiferromagnetic fluctuations upon lowering temperature toward Tc. This supports the scenario that spin fluctuations promote superconducting pairing. The depressed Knight shift 125K and the absence of a coherence peak in 1/T1 below Tc are consistent with spin-singlet superconducting pairing with an anisotropic order parameter. In the normal metallic state, the comparison between the uniform and dynamic spin susceptibilities suggests the existence of a Fermi level located near the singularity of the band structure.

  9. Low energy housing, Chimo, Steinbach

    Energy Technology Data Exchange (ETDEWEB)

    1984-01-01

    A house was constructed in Steinbach, Manitoba to demonstrate energy efficient residential construction techniques incorporating a cost-effective innovative wall design. Prior to the construction of the home, a computer analysis was made, and recommendations made to improve the techniques used in the design. During the construction of the home, an air leakage test was performed using the infiltrometer. Major objectives of the builder were to construct a wall with a thickness capable of accommodating R-48 (14'') glassfiber batts without constructing two separate walls and to achieve this with less cost, to provide a continuous path of insulation from the wall section into the attic area, to provide level attic insulation to the exterior of the perimeter wall by utilizing a raised heel type roof truss, to locate the house on the lot to give a southern exposure and to demonstrate the effectiveness of using an air-to-air heat exchanger and circulating hot water duct heater instead of other types of heating systems. It is concluded that the majority of the objectives were met in the design and construction of this home. The I-Beam stud walls use less material and are lighter, stronger and easier to erect than conventional double stud walls. The major disadvantage of the design is that vapour barrier installation is more involved and labour intensive. The circulating hot water duct heater, combined with an air-to-air heat exchanger, is recommended as a heating system for low energy homes. 10 figs., 4 tabs., 12 illus.

  10. Towards Low Energy Atrial Defibrillation

    Directory of Open Access Journals (Sweden)

    Philip Walsh

    2015-09-01

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

  11. Limits on dynamically generated spin-orbit coupling: Absence of l =1 Pomeranchuk instabilities in metals

    Science.gov (United States)

    Kiselev, Egor I.; Scheurer, Mathias S.; Wölfle, Peter; Schmalian, Jörg

    2017-03-01

    An ordered state in the spin sector that breaks parity without breaking time-reversal symmetry, i.e., that can be considered dynamically generated spin-orbit coupling, was proposed to explain puzzling observations in a range of different systems. Here, we derive severe restrictions for such a state that follow from a Ward identity related to spin conservation. It is shown that l =1 spin-Pomeranchuk instabilities are not possible in nonrelativistic systems since the response of spin-current fluctuations is entirely incoherent and nonsingular. This rules out relativistic spin-orbit coupling as an emergent low-energy phenomenon. We illustrate the exotic physical properties of the remaining higher-angular-momentum analogs of spin-orbit coupling and derive a geometric constraint for spin-orbit vectors in lattice systems.

  12. Pressure effect on the competition between ferromagnetic and antiferromagnetic spin fluctuations in TmTe investigated by 125Te-NMR

    Science.gov (United States)

    Yamamoto, A.; Wada, S.; Matsumura, T.

    2007-03-01

    To elucidate from a microscopic point of view the initial evolution of spin fluctuations in TmTe from the semiconducting state at ambient pressure with an antiferroquadrupole ordering (TQ=1.8 K) to the intermediate-valence metallic state at high pressures P⩾2 GPa with a ferromagnetic (FM) ordering (TC≃14 K), we have carried out 125Te-NMR study at pressures P=0 and 0.9 GPa. The spin-lattice relaxation rate measurements revealed a pronounced increase of the staggered susceptibility below T*≃14 K, in addition to the Curie-Weiss-type increase of the uniform susceptibility. Below ˜T*, a wipe-out decrease of the NMR intensity and the finding of an unconventional NMR signal around ˜10 MHz that is insensitive to applied field lead to the conclusion that a field-induced short-range FM ordering caused by the competition of FM and antiferromagnetic fluctuations takes place. Pressure of 0.9 GPa hardly affects the anomalous NMR behaviors below ˜T*, leading to speculate that the short-range FM ordering in the semiconducting state shares the origin with the long-range FM ordering at ≃14 K in the high-pressure metallic state.

  13. Effects of antiferro-ferromagnetic phase coexistence and spin fluctuations on the magnetic and related properties of NdCuSi

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sachin, E-mail: gsachin55@gmail.com, E-mail: suresh@phy.iitb.ac.in; Suresh, K. G., E-mail: gsachin55@gmail.com, E-mail: suresh@phy.iitb.ac.in [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400076 (India); Das, A. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Nigam, A. K. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Hoser, A. [Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14-109 Berlin (Germany)

    2015-06-01

    Polycrystalline NdCuSi is found to show co-existence of antiferromagnetic (AFM) and ferromagnetic (FM) phases at low temperatures, as revealed by neutron diffraction data. The coexistence is attributed to the competing exchange interactions and crystal field effect. The compound shows a large, low-field magnetoresistance (MR) of ∼ − 32% at 20 kOe below T{sub N} (3.1 K), which becomes ∼ − 36% at 50 kOe. The MR value at 50 kOe is found to be the highest among the RTX compounds. Magnetocaloric effect (MCE) is also found to show a large value of ∼11 J/kg K close to T{sub N}. Resistivity data show the presence of spin fluctuations, which get suppressed by the applied field. Large MR and MCE in this compound arise due to the coexistence of the two phases. The field dependencies of MR and MCE show quadratic behavior, confirming the presence of spin fluctuations.

  14. Effects of antiferro-ferromagnetic phase coexistence and spin fluctuations on the magnetic and related properties of NdCuSi

    Directory of Open Access Journals (Sweden)

    Sachin Gupta

    2015-06-01

    Full Text Available Polycrystalline NdCuSi is found to show co-existence of antiferromagnetic (AFM and ferromagnetic (FM phases at low temperatures, as revealed by neutron diffraction data. The coexistence is attributed to the competing exchange interactions and crystal field effect. The compound shows a large, low-field magnetoresistance (MR of ∼ − 32% at 20 kOe below TN (3.1 K, which becomes ∼ − 36% at 50 kOe. The MR value at 50 kOe is found to be the highest among the RTX compounds. Magnetocaloric effect (MCE is also found to show a large value of ∼11 J/kg K close to TN. Resistivity data show the presence of spin fluctuations, which get suppressed by the applied field. Large MR and MCE in this compound arise due to the coexistence of the two phases. The field dependencies of MR and MCE show quadratic behavior, confirming the presence of spin fluctuations.

  15. Low energy beam transport for HIDIF

    Science.gov (United States)

    Meusel, O.; Pozimski, J.; Jakob, A.; Lakatos, A.

    2001-05-01

    Low energy beam transport (LEBT) for a heavy ion inertial fusion (HIDIF, I. Hofmann and G. Plass, Report of the European Study Group on Heavy Ion Driven Inertial Fusion for the Period 1995-1998) facility suffers from high space charge forces and high ion mass. Space charge compensation reduces the necessary focusing force of the lenses and the radius of the beam in the LEBT, and therefrom the emittance growth due to aberrations and self fields is reduced. Gabor lenses (D. Gabor, Nature 160 (1947)) providing a stable space charge cloud for focusing and combine strong cylinder symmetric focusing with partly space charge compensation and low emittance growth. A high tolerance against source noise and current fluctuations and reduced investment costs could be other possible advantages. The proof of principle has already been demonstrated (J.A. Palkovic, Measurements on a Gabor lens for Neutralizing and Focusing a 30 keV Proton beam, University of Wisconsin, Madison, 1989; J. Pozimski, P. Groß, R. Dölling and T. Weis, First experimental studies of a Gabor plasma-lens in Frankfurt, Proceedings of the 3rd EPAC Conference, Berlin, 1992). To broaden the experiences and to investigate the realisation of a LEBT concept for the HIDIF injector an experimental program using two Gabor lenses for independent variation of beam radius and envelope angel at RFQ injection was started. Therefrom the first experimental results using a double Gabor lens (DGPL) LEBT system for transporting an high perveance Xe + beam are presented and the results of numerical simulations are shown.

  16. Low energy beam transport for HIDIF

    Energy Technology Data Exchange (ETDEWEB)

    Meusel, O. E-mail: o.meusel@iap.uni-frankfurt.de; Pozimski, J.; Jakob, A.; Lakatos, A

    2001-05-21

    Low energy beam transport (LEBT) for a heavy ion inertial fusion (HIDIF, I. Hofmann and G. Plass, Report of the European Study Group on Heavy Ion Driven Inertial Fusion for the Period 1995-1998) facility suffers from high space charge forces and high ion mass. Space charge compensation reduces the necessary focusing force of the lenses and the radius of the beam in the LEBT, and therefrom the emittance growth due to aberrations and self fields is reduced. Gabor lenses (D. Gabor, Nature 160 (1947)) providing a stable space charge cloud for focusing and combine strong cylinder symmetric focusing with partly space charge compensation and low emittance growth. A high tolerance against source noise and current fluctuations and reduced investment costs could be other possible advantages. The proof of principle has already been demonstrated (J.A. Palkovic, Measurements on a Gabor lens for Neutralizing and Focusing a 30 keV Proton beam, University of Wisconsin, Madison, 1989; J. Pozimski, P. Gross, R. Doelling and T. Weis, First experimental studies of a Gabor plasma-lens in Frankfurt, Proceedings of the 3rd EPAC Conference, Berlin, 1992). To broaden the experiences and to investigate the realisation of a LEBT concept for the HIDIF injector an experimental program using two Gabor lenses for independent variation of beam radius and envelope angel at RFQ injection was started. Therefrom the first experimental results using a double Gabor lens (DGPL) LEBT system for transporting an high perveance Xe{sup +} beam are presented and the results of numerical simulations are shown.

  17. Adiabatic physics of an exchange-coupled spin-dimer system: Magnetocaloric effect, zero-point fluctuations, and possible two-dimensional universal behavior

    Science.gov (United States)

    Brambleby, J.; Goddard, P. A.; Singleton, J.; Jaime, M.; Lancaster, T.; Huang, L.; Wosnitza, J.; Topping, C. V.; Carreiro, K. E.; Tran, H. E.; Manson, Z. E.; Manson, J. L.

    2017-01-01

    We present the magnetic and thermal properties of the bosonic-superfluid phase in a spin-dimer network using both quasistatic and rapidly changing pulsed magnetic fields. The entropy derived from a heat-capacity study reveals that the pulsed-field measurements are strongly adiabatic in nature and are responsible for the onset of a significant magnetocaloric effect (MCE). In contrast to previous predictions we show that the MCE is not just confined to the critical regions, but occurs for all fields greater than zero at sufficiently low temperatures. We explain the MCE using a model of the thermal occupation of exchange-coupled dimer spin states and highlight that failure to take this effect into account inevitably leads to incorrect interpretations of experimental results. In addition, the heat capacity in our material is suggestive of an extraordinary contribution from zero-point fluctuations and appears to indicate universal behavior with different critical exponents at the two field-induced critical points. The data at the upper critical point, combined with the layered structure of the system, are consistent with a two-dimensional nature of spin excitations in the system.

  18. Low Energy Background Spectrum in CDMSlite

    CERN Document Server

    Barker, D

    2016-01-01

    One trend in dark matter direct detection is the development of techniques which will lower experimental thresholds and achieve sensitivity to light mass dark matter particles. In doing so, it is necessary to have an understanding of the low energy spectrum of the major background components. Geant4 has a number of specialized low energy physics processes that can be implemented when simulating an experimental geometry. To understand this low energy region for the Super Cryogenic Dark Matter Search (SuperCDMS), a variety of these models have been simulated and compared against theoretical calculations and SuperCDMS calibration data. Most of the low energy processes include a more complete description of the atomic structure, allowing us to observe the phenomenon of Compton steps in the simulation. An important application of this low energy background modeling is for the SuperCDMS low ionization threshold experiment (CDMSlite). CDMSlite has reached world-leading sensitivities in the search for low mass weakly...

  19. Experimental evidence of Tc enhancement without the influence of spin fluctuations: NMR study on LaFeAsO1 -xHx under a pressure of 3.0 GPa

    Science.gov (United States)

    Kawaguchi, N.; Fujiwara, N.; Iimura, S.; Matsuishi, S.; Hosono, H.

    2016-10-01

    The electron-doped high-transition-temperature (Tc) iron-based pnictide superconductor LaFeAsO1 -xHx has a unique phase diagram: Superconducting double domes are sandwiched by antiferromagnetic phases at ambient pressure and they turn into a single dome with a maximum Tc that exceeds 45 K at a pressure of 3.0 GPa. We studied whether spin fluctuations are involved in increasing Tc under a pressure of 3.0 GPa by using the 75As nuclear magnetic resonance (NMR) technique. The 75As-NMR results for the powder samples show that Tc increases up to 48 K without the influence of spin fluctuations. This fact indicates that spin fluctuations are not involved in raising Tc, which implies that other factors, such as orbital degrees of freedom, may be important for achieving a high Tc of almost 50 K.

  20. Fluctuation relations for spintronics.

    Science.gov (United States)

    López, Rosa; Lim, Jong Soo; Sánchez, David

    2012-06-15

    Fluctuation relations are derived in systems where the spin degree of freedom and magnetic interactions play a crucial role. The form of the nonequilibrium fluctuation theorems relies on the assumption of a local balance condition. We demonstrate that in some cases the presence of magnetic interactions violates this condition. Nevertheless, fluctuation relations can be obtained from the microreversibility principle sustained only at equilibrium as a symmetry of the cumulant generating function for spin currents. We illustrate the spintronic fluctuation relations for a quantum dot coupled to partially polarized helical edge states.

  1. Single track nanodosimetry of low energy electrons

    Energy Technology Data Exchange (ETDEWEB)

    Bantsar, A. [Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Grosswendt, B. [Physikalisch-Technische Bundesanstalt, 38116 Braunschweig (Germany); Pszona, S. [Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland)], E-mail: pszona@ipj.gov; Kula, J. [Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland)

    2009-02-11

    Auger-electron-emitting radionuclides (for instance, {sup 125}I) 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. Single track nanodosimetry of low energy electrons

    Science.gov (United States)

    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.

  3. Low energy ghosts and the Jeans' instability

    Science.gov (United States)

    Gümrükçüoǧlu, A. Emir; Mukohyama, Shinji; Sotiriou, Thomas P.

    2016-09-01

    We show that a massless canonical scalar field minimally coupled to general relativity can become a tachyonic ghost at low energies around a background in which the scalar's gradient is spacelike. By performing a canonical transformation we demonstrate that this low energy ghost can be recast, at the level of the action, in a form of a fluid that undergoes a Jeans-like instability affecting only modes with large wavelength. This illustrates that low energy tachyonic ghosts do not lead to a catastrophic quantum vacuum instability, unlike the usual high-energy ghost degrees of freedom.

  4. Low-energy Planetary Excavator (LPE) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ORBITEC proposes to develop an innovative Low-energy Planetary Excavator (LPE) to excavate in situ regolith, ice-regolith mixes, and a variety of other geologic...

  5. Low-energy Planetary Excavator (LPE) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ORBITEC is developing an innovative Low-energy Planetary Excavator (LPE) to excavate in situ regolith, ice-regolith mixes, and a variety of other geologic materials...

  6. Monochromatic gamma emitter for low energy quanta

    CERN Document Server

    Tomova, Z R; Mironova, S A

    2004-01-01

    The possibility of creating of a monochromatic gamma emitter of low energy quanta is analyzed. The idea is based on Daning's scheme. Except for purely scientific problems the monochromator is actual for therapy of wide range of diseases.

  7. Low Energy Mission Planning Toolbox Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Low Energy Mission Planning Toolbox is designed to significantly reduce the resources and time spent on designing missions in multi-body gravitational...

  8. The X-ray magnetic dichroism, the sum rule and spin fluctuations on the surface of manganite (LaPrCa)MnO3

    Science.gov (United States)

    Grebennikov, Vladimir I.; Bebenin, Nikolai G.; Zainullina, Rimma I.; Kuepper, Karsten; Kuznetsova, Tatyana V.

    2017-10-01

    The problem of determining the magnitude of the atomic magnetic moments in compounds with rare-earth and transition elements using the X-ray magnetic circular dichroism (XMCD) is investigated. The standard sum rules approach usually gives the moment values by several times smaller than their bulk values obtained from the direct magnetic measurements. We attribute this to the strong spin fluctuations in the surface layer which actually formed the soft XMCD signal. A method of determining the value of the local magnetic moments in the presence of strong fluctuations is proposed. The magnetic interactions in La0.5Pr0.2Ca0.3MnO3 are investigated by x-ray absorption spectroscopy, XMCD and bulk magnetization measurements. The proposed procedure is used to determine the values of atomic magnetic moments of transition and rare-earth elements as well as net magnetization on the surface and in the bulk from experimental Mn L2,3 and Pr M4,5 XMCD spectra.

  9. Optical investigation of BaFe2(As0.77P0.23)2 : Spin-fluctuation-mediated superconductivity under pressure

    Science.gov (United States)

    Uykur, E.; Kobayashi, T.; Hirata, W.; Miyasaka, S.; Tajima, S.; Kuntscher, C. A.

    2017-06-01

    Temperature-dependent reflectivity measurements in the frequency range 75-8000 cm-1 were performed on BaFe2(As0.77P0.23)2 single crystals under pressure up to ˜5 GPa . The obtained optical conductivity spectra have been analyzed to extract the electron-boson spectral density α2F (Ω ) . A sharp resonance peak was observed in α2F (Ω ) upon the superconducting transition, persisting throughout the applied pressure range. The energy and temperature dependences of this peak are consistent with the superconducting gap opening. Furthermore, several similarities with other experimental probes such as inelastic neutron scattering (INS) [D. S. Inosov et al., Nat. Lett. 6, 178 (2010), 10.1038/nphys1483] give evidence for the coupling to a bosonic mode, possibly due to spin fluctuations. Moreover, electronic correlations have been calculated via spectral weight analysis, which revealed that the system stays in the strongly correlated regime throughout the applied pressure range. However, a comparison to the parent compound showed that the electronic correlations are slightly decreased with P doping. The investigation of the phase diagram obtained by our optical study under pressure also revealed the coexistence of the spin-density wave and the superconducting regions, where the coexistence region shifts to the lower pressure range with increasing P content. Moreover, the optimum pressure range, where the highest superconducting transition temperature has been obtained, shows a nonlinear decrease with increasing P content.

  10. Anisotropic spin fluctuations in heavy-fermion superconductor CeCoIn sub 5. In-NQR and Co-NMR studies

    CERN Document Server

    Kawasaki, Y; Yashima, M

    2003-01-01

    We report In-NQR and Co-NMR experiments of CeCoIn sub 5 that undergoes a superconducting transition with a record high T sub c =2.3 K to date among heavy-fermion superconductors. At zero magnetic field, an anomalous temperature (T) dependence of nuclear spin-lattice relaxation rate 1/T sub 1 of sup 1 sup 1 sup 5 In is explained by the relation 1/T sub 1 propor to T centre dot chi sub Q (T) sup 3 sup / sup 4 based on the anisotropic spin-fluctuations model in case of the proximity to an antiferromagnetic (AFM) quantum critical point (QCP). The novel behavior of 1/T sub 1 - T sup 1 sup / sup 4 over a wide T range of T sub c < T < 40 K arises because the staggered susceptibility almost follows the Curie law chi sub Q (T) propor to 1/(T + theta) with theta=0.6 K and hence 1/T sub 1 propor to T/(T + 0.6) sup 3 sup / sup 4 - T sup 1 sup / sup 4 for theta < T. We highlight that the behavior 1/T sub 1 - T sup 1 sup / sup 4 is due to the proximity to the anisotropic AFM QCP relevant with its layered structure...

  11. Inelastic neutron scattering study of a nonmagnetic collapsed tetragonal phase in nonsuperconducting CaFe2As2: evidence of the impact of spin fluctuations on superconductivity in the iron-arsenide compounds.

    Science.gov (United States)

    Soh, J H; Tucker, G S; Pratt, D K; Abernathy, D L; Stone, M B; Ran, S; Bud'ko, S L; Canfield, P C; Kreyssig, A; McQueeney, R J; Goldman, A I

    2013-11-27

    The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in the nonsuperconducting collapsed tetragonal phase of CaFe2As2 via inelastic neutron scattering time-of-flight data, which is consistent with the view that spin fluctuations are a necessary ingredient for unconventional superconductivity in the iron pnictides. We demonstrate that the collapsed tetragonal phase of CaFe2As2 is nonmagnetic, and discuss this result in light of recent reports of high-temperature superconductivity in the collapsed tetragonal phase of closely related compounds.

  12. Dosimetry of Low-Energy Beta Radiation

    DEFF Research Database (Denmark)

    Borg, Jette

    Useful techniques and procedures for derermination of absorbed doses from exposure in a low-energy beta radiation were studied and evaluated. The four techniques included were beta spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical...... low-energy beta radiation field a moderated spectrum from a carbon-14 source was used. The measured responce of a Si(Li) detector to photons (bremsstrahlung) showed fine agreemant with the MC calculated photon response, whereas the difference between measured and MC calculated response to electrons...

  13. Dosimetry of Low-Energy Beta Radiation

    DEFF Research Database (Denmark)

    Borg, Jette

    Useful techniques and procedures for derermination of absorbed doses from exposure in a low-energy beta radiation were studied and evaluated. The four techniques included were beta spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical...... low-energy beta radiation field a moderated spectrum from a carbon-14 source was used. The measured responce of a Si(Li) detector to photons (bremsstrahlung) showed fine agreemant with the MC calculated photon response, whereas the difference between measured and MC calculated response to electrons...

  14. Low energy ion beam assisted growth of metal multilayers

    Science.gov (United States)

    Quan, Junjie

    Vapor deposited metal multilayers have attracted a great deal of interest in recent years because they offer extraordinary strength, hardness, heat resistance, and unexpected new properties like high reflectivity and spin-dependent conductivity. The giant magnetoresistance effects discovered in Fe/Cr artificial superstructures in 1988 stimulated a large number of studies on the electronic transport properties of spintronic materials because of their important applications in highly sensitive magnetic sensors, nonvolatile random access memories, and the data storage industry in general. Magnetic multilayers allow exploitation of unique micromagnetic, magnetooptic, and magnetoelectronic phenomena that cannot be realized using conventional materials. For example, if ferromagnetic layers (such as CoFe) with a thicknesses of 5-7 nm are separated by a non-magnetic spacer (such as Cu or AlOx) of an appropriate thickness (1-3 nm), they can exhibit large changes in their electrical resistance when a magnetic field is applied. These changes are caused mainly by spin-dependent conduction electron scattering at magnetic multilayer interfaces. Many experimental and theoretical works have sought to promote a basic understanding of the effect of atomic structure in thin film multilayers upon spin dependent transport. It has been found that interfacial imperfections, such as interfacial roughness and interlayer mixing, dramatically reduce the properties exploited for spintronic applications. A combination of computer modeling and experiments has been used to discover more effective ways to control the interfacial structures of metal multilayers. Earlier atomic simulations had indicated that it is very important to control adatom energy during deposition in order to improve interface properties. Based on these ideas, this dissertation has investigated the effects of low energy ion assistance during metal multilayer deposition. Using molecular dynamics modeling, the effects of ion

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

    Science.gov (United States)

    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.

  16. Theories of Low Energy Nuclear Transmutations

    CERN Document Server

    Srivastava, Y N; Swain, J

    2012-01-01

    Employing concrete examples from nuclear physics it is shown that low energy nuclear reactions can and have been induced by all of the four fundamental interactions (i) (stellar) gravitational, (ii) strong, (iii) electromagnetic and (iv) weak. Differences are highlighted through the great diversity in the rates and similarity through the nature of the nuclear reactions initiated by each.

  17. Branch II : Neutrino Oscillations at Low Energies

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera, A., E-mail: anatael@in2p3.fr [CNRS/IN2P3. Laboratoire d' Astro-Particule et Cosmologie. 10 rue Alice Domont et Leonie Duquet. Paris. 75205. Cedex 13 (France); Volpe, C., E-mail: volpe@ipno.in2p3.fr [Institut de Physique Nucleaire Orsay and University of Paris XI,CNRS/IN2P3, F-91406 Orsay cedex (France)

    2011-08-15

    We summarize here briefly the experimental and theoretical results presented at the NOW2010 workshop during the parallel session Branch II 'Oscillations at low energies'. The topics have covered open problems and recent advances in solar neutrinos, reactor and geo-neutrinos, as well as neutrinos from core-collapse supernovae.

  18. Studies in Low-Energy Nuclear Science

    Energy Technology Data Exchange (ETDEWEB)

    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.

  19. Low Energy Antiproton Ring experimental area

    CERN Multimedia

    1991-01-01

    The experimental area at the Low Energy Antiproton Ring (LEAR) is seen. This set up was used to slow down antiprotons which had been produced by colliding a proton beam with a solid target. The experiments in the hall then took antiprotons from LEAR to perform antimatter studies. One such experiment, PS210, produced the world's first antihydrogen atoms.

  20. Low-Energy Spectral Features in GRBs

    CERN Document Server

    Briggs, M S

    1996-01-01

    I discuss low-energy lines in gamma-ray bursts. The process of deconvolving gamma-ray spectral data and the steps needed to demonstrate the existence of a line are explained. Previous observations and the current status of the analysis of the BATSE data are described.

  1. Low energy observables with the ATLAS experiment

    CERN Document Server

    Foster, Andrew Geoffrey; The ATLAS collaboration

    2017-01-01

    Recent results in the soft QCD sector of the Standard Model are presented. Measurements of low energy observables were performed with the ATLAS detector at the Large Hadron Collider at CERN. In particular, underlying event, charged particle correlation and diffraction observables are reported and various models of Monte Carlo predictions are compared to the data.

  2. The low energy atmospheric antiproton albedo

    Science.gov (United States)

    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. Low-energy physics of three-orbital impurity model with Kanamori interaction

    Science.gov (United States)

    Horvat, Alen; Žitko, Rok; Mravlje, Jernej

    2016-10-01

    We discuss the low-energy physics of the three-orbital Anderson impurity model with the Coulomb interaction term of the Kanamori form which has orbital SO(3) and spin SU(2) symmetry and describes systems with partially occupied t2 g shells. We focus on the case with two electrons in the impurity that is relevant to Hund's metals. Using the Schrieffer-Wolff transformation we derive an effective Kondo model with couplings between the bulk and impurity electrons expressed in terms of spin, orbital, and orbital quadrupole operators. The bare spin-spin Kondo interaction is much smaller than the orbit-orbit and spin-orbital couplings or is even ferromagnetic. Furthermore, the perturbative scaling equations indicate faster renormalization of the couplings related to orbital degrees of freedom compared to spin degrees of freedom. Both mechanisms lead to a slow screening of the local spin moment. The model thus behaves similarly to the related quantum impurity problem with a larger SU(3) orbital symmetry (Dworin-Narath interaction) where this was first observed. We find that the two problems actually describe the same low-energy physics since the SU(3) symmetry is dynamically established through the renormalization of the splittings between the orbital and quadrupole coupling constants to zero. The perturbative renormalization group results are corroborated with the numerical-renormalization group (NRG) calculations. The dependence of spin Kondo temperatures and orbital Kondo temperatures as a function of interaction parameters, the hybridization, and the impurity occupancy is calculated and discussed.

  4. Correlated impurities and intrinsic spin-liquid physics in the kagome material herbertsmithite

    Science.gov (United States)

    Han, Tian-Heng; Norman, M. R.; Wen, J.-J.; Rodriguez-Rivera, Jose A.; Helton, Joel S.; Broholm, Collin; Lee, Young S.

    2016-08-01

    Low energy inelastic neutron scattering on single crystals of the kagome spin-liquid compound ZnCu3(OD) 6Cl2 (herbertsmithite) reveals antiferromagnetic correlations between impurity spins for energy transfers ℏ ω kagome spins. The low energy fluctuations are characterized by diffuse scattering near wave vectors (100) and (00 3/2 ), which is consistent with antiferromagnetic correlations between pairs of nearest-neighbor Cu impurities on adjacent triangular (Zn) interlayers. The corresponding impurity lattice resembles a simple cubic lattice in the dilute limit below the percolation threshold. Such an impurity model can describe prior neutron, NMR, and specific heat data. The low energy neutron data are consistent with the presence of a small spin gap (Δ ˜0.7 meV ) in the kagome layers, similar to that recently observed by NMR. The ability to distinguish the scattering due to Cu impurities from that of the planar kagome Cu spins provides an important avenue for probing intrinsic spin-liquid physics.

  5. Fractionalized spin-wave continuum in kagome spin liquids

    Science.gov (United States)

    Mei, Jia-Wei; Wen, Xiao-Gang

    Motivated by spin-wave continuum (SWC) observed in recent neutron scattering experiments in Herbertsmithite, we use Gutzwiller-projected wave functions to study dynamic spin structure factor S (q , ω) of spin liquid states on the kagome lattice. Spin-1 excited states in spin liquids are represented by Gutzwiller-projected two-spinon excited wave functions. We investigate three different spin liquid candidates, spinon Fermi-surface spin liquid (FSL), Dirac spin liquid (DSL) and random-flux spin liquid (RSL). FSL and RSL have low energy peaks in S (q , ω) at K points in the extended magnetic Brillouin zone, in contrast to experiments where low energy peaks are found at M points. There is no obviuos contradiction between DSL and neutron scattering measurements. Besides a fractionalized spin (i.e. spin-1/2), spinons in DSL carry a fractionalized crystal momentum which is potentially detectable in SWC in the neutron scattering measurements.

  6. Entanglement creation in low-energy scattering

    Energy Technology Data Exchange (ETDEWEB)

    Weder, Ricardo [Institut National de Recherche en Informatique et en Automatique Paris-Rocquencourt, Projet POEMS, Domaine de Voluceau-Rocquencourt, BP 105, F-78153, Le Chesnay Cedex (France)

    2011-12-15

    We study the entanglement creation in the low-energy scattering of two particles in three dimensions, for a general class of interaction potentials that are not required to be spherically symmetric. The incoming asymptotic state, before the collision, is a product of two normalized Gaussian states. After the scattering, the particles are entangled. We take as a measure of the entanglement the purity of one of them. We provide a rigorous explicit computation, with error bound, of the leading order of the purity at low energy. The entanglement depends strongly on the difference of the masses. It takes its minimum when the masses are equal, and it increases rapidly with the difference of the masses. It is quite remarkable that the anisotropy of the potential gives no contribution to the leading order of the purity, in spite of the fact that entanglement is a second-order effect.

  7. Geant4 Low Energy Electromagnetic Physics

    Institute of Scientific and Technical Information of China (English)

    S.Chauvie; G.Depaola; 等

    2001-01-01

    Geant4 Low Energy Electromagnetic package Provides a precise treatment of electromagnetic interations of particles with matter down to very low energies (250 oV for electrons and photons,<1 keV for hadrons and ions),It includes a veriety of models for the electromagnetic processes of electrons,photons,hadrons and ions,taking into account advance features,such as shell effects and effects due to charge dependence.The comprehensive set of particle types it can handle,the variety of modeling approaches and the extended coverage of energy range make this package a unique tool among Monte Carlo codes on the market,and of relevance to serveral experimental domains in HIEP,astroparticle physics,space science and biomedical studies.

  8. Low-Energy Polymeric Phases of Alanates

    Science.gov (United States)

    Huan, Tran Doan; Amsler, Maximilian; Marques, Miguel A. L.; Botti, Silvana; Willand, Alexander; Goedecker, Stefan

    2013-03-01

    Low-energy structures of alanates are currently known to be described by patterns of isolated, nearly ideal tetrahedral [AlH4] anions and metal cations. We discover that the novel polymeric motif recently proposed for LiAlH4 plays a dominant role in a series of alanates, including LiAlH4, NaAlH4, KAlH4, Mg(AlH4)2, Ca(AlH4)2, and Sr(AlH4)2. In particular, most of the low-energy structures discovered for the whole series are characterized by networks of corner-sharing [AlH6] octahedra, forming wires and/or planes throughout the materials. Finally, for Mg(AlH4)2 and Sr(AlH4)2, we identify two polymeric phases to be lowest in energy at low temperatures.

  9. Gas Electron multipliers for low energy beams

    CERN Document Server

    Arnold, F; Ropelewski, L; Spanggaard, J; Tranquille, G

    2010-01-01

    Gas Electron Multipliers (GEM) find their way to more and more applications in beam instrumentation. Gas Electron Multiplication uses a very similar physical phenomenon to that of Multi Wire Proportional Chambers (MWPC) but for small profile monitors they are much more cost efficient both to produce and to maintain. This paper presents the new GEM profile monitors intended to replace the MWPCs currently used at CERN’s low energy Antiproton Decelerator (AD). It will be shown how GEMs overcome the documented problems of profile measurements with MWPCs for low energy beams, where the interaction of the beam with the detector has a large influence on the measured profile. Results will be shown of profile measurements performed at 5 MeV using four different GEM prototypes, with discussion on the possible use of GEMs at even lower energies needed at the AD in 2013.

  10. Architectural Quality of Low Energy Houses

    DEFF Research Database (Denmark)

    Lauring, Michael; Marsh, Rob

    2008-01-01

    This paper expounds a systematic vocabulary concerning architectural quality in houses in general and low energy houses in particular. The vocabulary consists of nine themes. Inside each theme, examples are given of how to achieve both architectural quality and good environmental performance....... The purpose is to provide a useful tool for communication and argumentation in order to further integrated design of houses with good architecture and good environmental performance. ...

  11. Low Energy Pion-Hyperon Interaction

    CERN Document Server

    Hama, Y

    2001-01-01

    We study the low energy pion-hyperon interaction considering effective non-linear chiral invariant Lagrangians including pions, rho mesons, hyperons and corresponding resonances. Then we calculate the S- and P-wave phase-shifts, total cross sections, angular distributions and polarizations for the momentum in the center-of-mass frame up to k=400 MeV. With these results we discuss the CP violation in the csi-> pi-lambda and omega-> pi-csi weak decays.

  12. Study on low-energy positron polarimetry

    Indian Academy of Sciences (India)

    A Schälicke; G Alexander; R Dollan; K Laihem; T Lohse; S Riemann; P Starovoitov; A Ushakov

    2007-12-01

    A polarised positron source has been proposed for the design of the international linear collider (ILC). In order to optimise the positron beam, a measurement of its degree of polarisation close to the positron creation point is desired. In this contribution, methods for determining the positron polarisation at low energies are reviewed. A newly developed polarisation extension to GEANT4 will provide the basis for further polarimeter investigations.

  13. Architectural Quality of Low Energy Houses

    DEFF Research Database (Denmark)

    Lauring, Michael; Marsh, Rob

    2008-01-01

    This paper expounds a systematic vocabulary concerning architectural quality in houses in general and low energy houses in particular. The vocabulary consists of nine themes. Inside each theme, examples are given of how to achieve both architectural quality and good environmental performance....... The purpose is to provide a useful tool for communication and argumentation in order to further integrated design of houses with good architecture and good environmental performance. ...

  14. EULEB EUropean high quality Low Energy Buildings

    OpenAIRE

    2006-01-01

    ABSTRACT: The EULEB-Project is intended to supply information to architects and engineers throughout Europe and beyond it. Within the EU it will support the new Energy Directive on Buildings through providing design and engineering details of European public high quality buildings with low energy consumption. By providing a CD containing information on architecture, energy consumption and economical efficiency as well as the comfort of these innovative buildings in use, the lac...

  15. Targeting Low-Energy Ballistic Lunar Transfers

    Science.gov (United States)

    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.

  16. Ultra low energy results and their impact to dark matter and low energy neutrino physics

    CERN Document Server

    Bougamont, E; Derre, J; Giomataris, I; Gerbier, G; Gros, M; Magnier, P; Navick, X F; Salin, P; Savvidis, I; Tsiledakis, G; Vergados, J D

    2010-01-01

    We present ultra low energy results taken with the novel Spherical Proportional Counter. The energy threshold has been pushed down to about 25 eV and single electrons are clearly collected and detected. To reach such performance low energy calibration systems have been successfully developed: - A pulsed UV lamp extracting photoelectrons from the inner surface of the detector - Various radioactive sources allowing low energy peaks through fluorescence processes. The bench mark result is the observation of a well resolved peak at 270 eV due to carbon fluorescence which is unique performance for such large-massive detector. It opens a new window in dark matter and low energy neutrino search and may allow detection of neutrinos from a nuclear reactor or from supernova via neutrino-nucleus elastic scattering

  17. Dosimetry of low-energy beta radiation

    Energy Technology Data Exchange (ETDEWEB)

    Borg, J.

    1996-08-01

    Useful techniques and procedures for determination of absorbed doses from exposure in a low-energy {beta} radiation field were studied and evaluated in this project. The four different techniques included were {beta} spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical low-energy {beta} radiation field a moderated spectrum from a {sup 14}C source (E{sub {beta}},{sub max} =156 keV) was chosen for the study. The measured response of a Si(Li) detector to photons (bremsstrahlung) showed fine agreement with the MC calculated photon response, whereas the difference between measured and MC calculated responses to electrons indicates an additional dead layer thickness of about 12 {mu}m in the Si(Li) detector. The depth-dose profiles measured with extrapolation chambers at two laboratories agreed very well, and it was confirmed that the fitting procedure previously reported for {sup 147}Pm depth-dose profiles is also suitable for {beta} radiation from {sup 14}C. An increasing difference between measured and MC calculated dose rates for increasing absorber thickness was found, which is explained by limitations of the EGS4 code for transport of very low-energy electrons (below 10-20 keV). Finally a study of the thermally stimulated exoelectron emission (TSEE) response of BeO thin film dosemeters to {beta} radiation for radiation fields with maximum {beta} energies ranging from 67 keV to 2.27 MeV is reported. For maximum {beta} energies below approximately 500 keV, a decrease in the response amounting to about 20% was observed. It is thus concluded that a {beta} dose higher than about 10 {mu}Gy can be measured with these dosemeters to within 0 to -20% independently of the {beta}energy for E{sub {beta}},{sub max} values down to 67 keV. (au) 12 tabs., 38 ills., 71 refs.

  18. Low energy constraints and scalar leptoquarks⋆

    Directory of Open Access Journals (Sweden)

    Fajfer Svjetlana

    2014-01-01

    Full Text Available The presence of a colored weak doublet scalar state with mass below 1 TeV can provide an explanation of the observed branching ratios in B → D(∗τντ decays. Constraints coming from Z → bb̄, muon g − 2, lepton flavor violating decays are derived. The colored scalar is accommodated within 45 representation of SU(5 group of unification. We show that presence of color scalar can improve mass relations in the up-type quark sector mass. Impact of the colored scalar embedding in 45-dimensional representation of SU(5 on low-energy phenomenology is also presented.

  19. FLSR - The Frankfurt low energy storage ring

    Science.gov (United States)

    Stiebing, K. E.; Alexandrov, V.; Dörner, R.; Enz, S.; Kazarinov, N. Yu.; Kruppi, T.; Schempp, A.; Schmidt Böcking, H.; Völp, M.; Ziel, P.; Dworak, M.; Dilfer, W.

    2010-02-01

    An electrostatic storage ring for low-energy ions with a design energy of 50 keV is presently being set up at the Institut für Kernphysik der Johann Wolfgang Goethe-Universität Frankfurt am Main, Germany (IKF). This new device will provide a basis for new experiments on the dynamics of ionic and molecular collisions, as well as for high precision and time resolved laser spectroscopy. In this article, the design parameters of this instrument are reported.

  20. Extending the Eikonal Approximation to Low Energy

    CERN Document Server

    Capel, Pierre; Ogata, Kazuyuki

    2014-01-01

    E-CDCC and DEA, two eikonal-based reaction models are compared to CDCC at low energy (e.g. 20AMeV) to study their behaviour in the regime at which the eikonal approximation is supposed to fail. We confirm that these models lack the Coulomb deflection of the projectile by the target. We show that a hybrid model, built on the CDCC framework at low angular momenta and the eikonal approximation at larger angular momenta gives a perfect agreement with CDCC. An empirical shift in impact parameter can also be used reliably to simulate this missing Coulomb deflection.

  1. Non-degenerate Low Energy Leptogenesis

    CERN Document Server

    Geng, Chao-Qiang

    2009-01-01

    We study a simple extension of the standard model to tackle the neutrino masses, matter-antimatter asymmetry and dark matter (DM) in the universe, and the lithium problems. In our model, the baryon asymmetry is achieved by the low energy leptogenesis mechanism without requiring any degeneracy of masses, DM is provided by the neutral component of the inert scalar doublet, and the lithium problems are solved by using its negatively charged component. The new particles proposed in the model are within the reach at the future colliders. We also show that our model satisfies the electroweak precision tests.

  2. Low energy behaviour of standard model extensions

    CERN Document Server

    Boggia, Michele; Passarino, Giampiero

    2016-01-01

    The integration of heavy scalar fields is discussed in a class of BSM models, containing more that one representation for scalars and with mixing. The interplay between integrating out heavy scalars and the Standard Model decoupling limit is examined. In general, the latter cannot be obtained in terms of only one large scale and can only be achieved by imposing further assumptions on the couplings. Systematic low-energy expansions are derived in the more general, non-decoupling scenario, including mixed tree-loop and mixed heavy-light generated operators. The number of local operators is larger than the one usually reported in the literature.

  3. Round Gating for Low Energy Block Ciphers

    DEFF Research Database (Denmark)

    Banik, Subhadeep; Bogdanov, Andrey; Regazzoni, Francesco;

    2016-01-01

    Pushed by the pervasive diffusion of devices operated by battery or by the energy harvested, energy has become one of the most important parameter to be optimized for embedded systems. Particularly relevant would be to optimize the energy consumption of security primitives. In this paper we explore...... design techniques for implementing block ciphers in a low energy fashion. We concentrate on round based implementation and we discuss how gating, applied at round level can affect and improve the energy consumption of the most common lightweight block cipher currently used in the internet of things...

  4. Low energy signatures of nonlocal field theories

    Science.gov (United States)

    Belenchia, Alessio; Benincasa, Dionigi M. T.; Martín-Martínez, Eduardo; Saravani, Mehdi

    2016-09-01

    The response of inertial particle detectors coupled to a scalar field satisfying nonlocal dynamics described by nonanalytic functions of the d'Alembertian operator □ is studied. We show that spontaneous emission processes of a low energy particle detector are very sensitive to high-energy nonlocality scales. This allows us to suggest a nuclear physics experiment (˜MeV energy scales) that outperforms the sensitivity of LHC experiments by many orders of magnitude. This may have implications for the falsifiability of theoretical proposals of quantum gravity.

  5. Low energy cyclotron for radiocarbon dating

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Beam diagnostics for low energy beams

    Directory of Open Access Journals (Sweden)

    J. Harasimowicz

    2012-12-01

    Full Text Available Low-energetic ion and antimatter beams are very attractive for a number of fundamental studies. The diagnostics of such beams, however, is a challenge due to low currents down to only a few thousands of particles per second and significant fraction of energy loss in matter at keV beam energies. A modular set of particle detectors has been developed to suit the particular beam diagnostic needs of the ultralow-energy storage ring (USR at the future facility for low-energy antiproton and ion research, accommodating very low beam intensities at energies down to 20 keV. The detectors include beam-profile monitors based on scintillating screens and secondary electron emission, sensitive Faraday cups for absolute intensity measurements, and capacitive pickups for beam position monitoring. In this paper, the design of all detectors is presented in detail and results from beam measurements are shown. The resolution limits of all detectors are described and options for further improvement summarized. Whilst initially developed for the USR, the instrumentation described in this paper is also well suited for use in other low-intensity, low-energy accelerators, storage rings, and beam lines.

  7. The Telescope Array's Low Energy Extension: TALE

    Science.gov (United States)

    Matthews, John

    2009-05-01

    A great deal of information about the sources of ultra high energy cosmic rays exists encoded in the energy spectrum. There are three spectral features in the ultra high energy regime (the second knee, the ankle, and the GZK cut-off). An important composition change also occurs in this energy range. The Telescope Array (TA) is a large area ultra high energy cosmic ray observatory built and operated by groups from the US, Japan, Korea, and Russia. The existing part of the Telescope Array already has good efficiency above the ankle (˜10^18.5 eV). These detectors are already in the field collecting data. The TA Low Energy Extension (TALE) refers to the detectors devoted to the ``low energy'' portion of the spectrum - 10^16.5 - 10^19 eV. The aim of TA/TALE is to understand the origin of cosmic rays and to study their composition over a broad energy range. We will introduce the detector components and discuss the opportunities.

  8. Mechanical generation of spin current

    Directory of Open Access Journals (Sweden)

    Mamoru eMatsuo

    2015-07-01

    Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.

  9. Zn and Ni substitutional effects on spin fluctuations in YBa sub 2 Cu sub 3 O sub 7 by sup 6 sup 3 sup , sup 6 sup 5 Cu NQR

    CERN Document Server

    Han, K S; Mean, B J; Lee, K H; Seo, S W; Lee, M H; Lee, W C

    2000-01-01

    We have prepared Zn- and Ni-substituted YBa sub 2 Cu sub 3 O sub 7 (YBa sub 2 Cu sub 3 sub - sub x M sub x O sub 7 , M=Zn or Ni, x=0.00 approx 0.09) and performed sup 6 sup 3 sup , sup 6 sup 5 Cu nuclear quadrupole resonance (NQR) measurements for the plane site at 300 and 100 K. Substitutional effects on the relaxation rates are markedly different. Both the spin-lattice and the spin-spin relaxation rates decrease for Zn-doped YBCO. However, those increase for Ni-doped YBCO. This contrast in local electronic dynamics provides clear microscopic evidence that Zn forms no local moment while Ni develops a local moment. Consequently, the antiferromagnetic spin fluctuation is suppressed by Zn doping whereas it is preserved by Ni doping. This is also confirmed by the ratio of the sup 6 sup 3 sup , sup 6 sup 5 Cu spin-lattice relaxation rates for the plane coppers.

  10. Low-energy neutrino factory design

    Directory of Open Access Journals (Sweden)

    C. Ankenbrandt

    2009-07-01

    Full Text Available 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 π^{±} decay to produce muons (μ^{±}, 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 ∼1.4×10^{21} μ^{+} per year decaying in a long straight section of the storage ring, and a similar number of μ^{-} decays.

  11. Detection of low energy antimatter with emulsions

    CERN Document Server

    Aghion, S; Ariga, T; Bollani, M; Cas, E Dei; Ereditato, A; Evans, C; Ferragut, R; Giammarchi, M; Pistillo, C; Romé, M; Sala, S; Scampoli, P

    2016-01-01

    Emulsion detectors feature a very high position resolution and consequently represent an ideal device when particle detection is required at the micrometric scale. This is the case of quantum interferometry studies with antimatter, where micrometric fringes have to be measured. In this framework, we designed and realized a new emulsion based detector characterized by a gel enriched in terms of silver bromide crystal contents poured on a glass plate. We tested the sensitivity of such a detector to low energy positrons in the range 10-20 keV. The obtained results prove that nuclear emulsions are highly efficient at detecting positrons at these energies. This achievement paves the way to perform matter-wave interferometry with positrons using this technology.

  12. Low energy ion-molecule reactions

    Energy Technology Data Exchange (ETDEWEB)

    Farrar, J.M. [Univ. of Rochester, NY (United States)

    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}.

  13. Towards a Low Energy Society from me

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen; Christensen, Bente Lis

    The book is based on energy planning research at Technical University of Denmark. With 1980 as a base year, two possible scenarios for future development in Denmark are analysed and described with respect to technology used and life style practised. In a high-energy society the country's energy...... consumption is almost doubled by 2030, and in a low-energy society energy consumption in 2030 can be less than one third of that in the base year. In this updated version a chapter is added dealing with what actually happened over the first 20 years of the scenario period, in which energy consumption stayed...... constant in between the two scenarios. It is analysed what went right with energy savings and what didn't over these passed years. The book is illustrated with drawings and graphs by Claus Deleuran....

  14. LEAR (Low Energy Antiproton Ring), general view.

    CERN Multimedia

    1990-01-01

    When the Antiproton Project was launched in the late 1970s, it was recognized that in addition to the primary purpose of high-energy proton-antiproton collisions in the SPS, there was interesting physics to be done with low-energy antiprotons. In 1982, LEAR was ready to receive antiprotons from the Antiproton Accumulator (AA), via the PS. A year later, delivery of antiprotons to the experiments began, at momenta as low as 100 MeV/c (kinetic energy 5.3 MeV), in an "Ultra-Slow Extraction" mode, dispensing some E9 antiprotons over times counted in hours. For such an achievement, stochastic and electron cooling had to be brought to high levels of perfection.

  15. Bluetooth Low Energy Mesh Networks: A Survey.

    Science.gov (United States)

    Darroudi, Seyed Mahdi; Gomez, Carles

    2017-06-22

    Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues.

  16. Low-energy dynamics of gravitation

    Science.gov (United States)

    Torma, Tibor

    The present status of theories of quantum gravity are reviewed from the low energy point of view. String theory relates classical black-hole type solutions of Einstein- like equations (e.g. axidilaton gravity) to the string vacuum. Several such solutions are proposed and their properties are investigated, including their behavior under supersymmetry transformations. A general feature of all possible quantum theories of gravitation is that they lead to a field theory description at low (as compared to the Planck mass) energies. The theoretical consistency, uniqueness and consequences of such an effective theory are investigated. I show that a power counting theorem allows for the momentum expansion that defines the effective theory even in the presence of large masses. I also show that graviton-graviton scattering is free of potential infrared and collinear divergencies that plague perturbative discussions of Yang-Mills theories.

  17. Bluetooth Low Energy Mesh Networks: A Survey

    Science.gov (United States)

    Darroudi, Seyed Mahdi; Gomez, Carles

    2017-01-01

    Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues. PMID:28640183

  18. Low energy consumption spintronics using multiferroic heterostructures.

    Science.gov (United States)

    Trassin, Morgan

    2016-01-27

    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.

  19. Windows in Low Energy Houses. Size Matters

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Mari-Louise

    2004-06-01

    A generally accepted way of building passive houses has been to have small windows facing north and a large glass facade to the south. This is to minimize losses on the north side while gaining as much solar heat as possible on the south. In spring 2001, twenty terraced houses were built outside Goeteborg partly in this way. The indoor temperature is kept at a comfortable level by passive methods, using solar gains and internal gains from household appliances and occupants. Heat losses are very low, since the building envelope is well insulated and since modern coated triple-glazed windows have been installed. The purpose of this work is to investigate how decreasing the window size facing south and increasing the window size facing north in low energy houses will influence the energy consumption and maximum power needed to keep the indoor temperature between 23 and 26 deg C. Different climates and orientations have been investigated and so have the influence of occupancy and window type. A dynamic building simulation tool, DEROB, has been used and the simulations indicate an extremely low energy demand for the houses. The results show that the size of the energy efficient windows does not have a major influence on the heating demand in winter, but is of relevant signification looking at the cooling need in summer. This indicates that instead of the traditional technique of building passive houses it is possible to enlarge the window area facing north and get better lighting conditions. To decrease the energy need for cooling, there is an optimal window size facing south that is smaller than the original size of the investigated buildings.

  20. Unconstrained Hamiltonian formulation of low energy QCD

    Directory of Open Access Journals (Sweden)

    Pavel Hans-Peter

    2014-04-01

    Full Text Available Using a generalized polar decomposition of the gauge fields into gaugerotation and gauge-invariant parts, which Abelianises the Non-Abelian Gauss-law constraints to be implemented, a Hamiltonian formulation of QCD in terms of gauge invariant dynamical variables can be achieved. The exact implementation of the Gauss laws reduces the colored spin-1 gluons and spin-1/2 quarks to unconstrained colorless spin-0, spin-1, spin-2 and spin-3 glueball fields and colorless Rarita-Schwinger fields respectively. The obtained physical Hamiltonian naturally admits a systematic strongcoupling expansion in powers of λ = g−2/3, equivalent to an expansion in the number of spatial derivatives. The leading-order term corresponds to non-interacting hybridglueballs, whose low-lying spectrum can be calculated with high accuracy by solving the Schrödinger-equation of the Dirac-Yang-Mills quantum mechanics of spatially constant fields (at the moment only for the 2-color case. The discrete glueball excitation spectrum shows a universal string-like behaviour with practically all excitation energy going in to the increase of the strengths of merely two fields, the “constant Abelian fields” corresponding to the zero-energy valleys of the chromomagnetic potential. Inclusion of the fermionic degrees of freedom significantly lowers the spectrum and allows for the study of the sigma meson. Higher-order terms in λ lead to interactions between the hybridglueballs and can be taken into account systematically using perturbation theory in λ, allowing for the study of IR-renormalisation and Lorentz invarianz. The existence of the generalized polar decomposition used, the position of the zeros of the corresponding Jacobian (Gribov horizons, and the ranges of the physical variables can be investigated by solving a system of algebraic equations. Its exact solution for the case of one spatial dimension and first numerical solutions for two and three spatial dimensions indicate

  1. Low energy dynamics of U(1) vortices in systems with cholesteric vacuum structure

    Science.gov (United States)

    Peterson, Adam J.; Shifman, Mikhail; Tallarita, Gianni

    2015-02-01

    We discuss flux tubes in systems with U(1) gauge, and spin-orbit locked SO(3) S + L symmetry. The spin-orbit locking is achieved explicitly in the Lagrangian by introducing a parity violating twist term which causes the spontaneous breaking of SO(3) S + L → SO(2) . Additionally, this term causes a spontaneous breaking of the translational symmetry along a particular direction. Thus, the system appears with a cholesteric vacuum under certain conditions of the parameter space. With this term, the system admits U(1) topologically stable vortices with additional structure in the vortex cores. This added structure leads to additional moduli appearing in the low energy dynamics. We determine these solutions and their low energy theory.

  2. Low energy dynamics of $U(1)$ vortices in systems with cholesteric vacuum structure

    CERN Document Server

    Peterson, Adam; Tallarita, Gianni

    2014-01-01

    We discuss flux tubes in systems with $U(1)$ gauge, and spin-orbit locked $SO(3)_{S+L}$ symmetry. The spin-orbit locking is achieved explicitly in the Lagrangian by introducing a parity violating twist term which causes the spontaneous breaking of $SO(3)_{S+L} \\rightarrow SO(2)$. Additionally, this term causes a spontaneous breaking of the translational symmetry along a particular direction. Thus, the system appears with a cholesteric vacuum under certain conditions of the parameter space. With this term, the system admits $U(1)$ topologically stable vortices with additional structure in the vortex cores. This added structure leads to additional moduli appearing in the low energy dynamics. We determine these solutions and their low energy theory.

  3. Influence of Low-Energy Ion Irradiation on Plasma MembranePermeability of Cells

    Institute of Scientific and Technical Information of China (English)

    ZHANG Dong-Mei; CUI Fu-Zhai; SUN Su-Qin; LIN You-Bo; TIAN Min-Bo; CHEN Guo-Qiang

    2000-01-01

    Effect of low-energy ion irradiation on plasma membrane permeability has been investigated by using electron spin resonance (ESR) spectroscopy of spin probe technique. The investigated system is plumule cells of wheat (Triticum aestivum L.) seeds implanted by 30keV N+ ions. ESR spectra indicated that plasmalemma permeability is sensitive to low-energyion irradiation. Ion irradiations with increasing fluences up to semi-lethal dose lead to gradual increase in plasmalemma permeability of the plumule cells. The possible factors relevant to the changes in membrane permeability are discussed in relation to the changes in the physical state and chemical nature of membranes.

  4. Magnetic Density of States at Low Energy in Geometrically Frustrated Systems

    Science.gov (United States)

    Yaouanc, A.; de Réotier, P. Dalmas; Glazkov, V.; Marin, C.; Bonville, P.; Hodges, J. A.; Gubbens, P. C.; Sakarya, S.; Baines, C.

    2005-07-01

    Using muon-spin-relaxation measurements we show that the pyrochlore compound Gd2Ti2O7, in its magnetically ordered phase below ˜1 K, displays persistent spin dynamics down to temperatures as low as 20 mK. The characteristics of the induced muon relaxation can be accounted for by a scattering process involving two magnetic excitations, with a density of states characterized by an upturn at low energy and a small gap depending linearly on the temperature. We propose that such a density of states is a generic feature of geometrically frustrated magnetic materials.

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

    Science.gov (United States)

    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...

  6. Low energy electron scattering from fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, M. Cristina A.; Silva, Daniel G.M.; Coelho, Rafael F.; Duque, Humberto V.; Santos, Rodrigo R. dos; Ribeiro, Thiago M. [Universidade Federal de Juiz de Fora (UFJF), MG (Brazil). Dept. de Fisica; Yates, Brent; Hong, Ling; Khakoo, Murtadha A. [California State University at Fullerton, CA (US). Physics Department; Bettega, Marcio H.F. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Fisica; Costa, Romarly F. da [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Lima, Marco A.P. [Laboratorio Nacional de Ciencia e Tecnologia do Bioetanol (CTBE/CNPEM), Campinas, SP (Brazil)

    2011-07-01

    Full text. Accurate and precise values of absolute total cross section (TCS) represent important information in many scientific and technological applications. In our case, for example, we are motivated to provide such information for electron-fuel collision processes which are specifically relevant to modeling spark ignition in alcohol-fuelled internal combustion engines. Many electron scattering TCS measurements are presently available for a diverse range of atomic and molecular targets. However, lack of data for important bio-molecular targets still remains. Disagreements between the available TCS data for the alcohols have prompted several studies of electron scattering collision of slow electrons with these molecules which are currently important in applications as bio- fuels. This relevance, which has attracted much attention, has been one of the subjects of a recent collaboration between experimental and theoretical groups in the USA and Brazil. Recently this collaboration reported first measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering by several primary alcohols. In this work we address methanol and ethanol TCSs at low energy range and report additional studies of resonant structure in ethanol using the detection of metastable states produced by electron impact excitation with high energy resolution. We have recently constructed a TCS apparatus in our laboratory at Universidade Federal de Juiz de Fora, Brazil, based on the well-known linear transmission technique. The experimental setup is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the atoms or molecules to be studied at a given pressure. It consists essentially of an electron gun, a gas cell and an electron energy analyzer composed of an array of decelerating electrostatic lenses, a cylindrical dispersive 127o analyzer and a Faraday cup. To our knowledge, there exist

  7. Design of the Proposed Low Energy Ion Collider Ring at Jefferson Lab

    Energy Technology Data Exchange (ETDEWEB)

    Nissen, Edward W. [JLAB; Lin, Fanglei [JLAB; Morozov, Vasiliy [JLAB; Zhang, Yuhong [JLAB

    2013-06-01

    The polarized Medium energy Electron-Ion Collider (MEIC) envisioned at Jefferson Lab will cover a range of center-of-mass energies up to 65 GeV. The present MEIC design could also allow the accommodation of low energy electron-ion collisions (LEIC) for additional science reach. This paper presents the first design of the low energy ion collider ring which is converted from the large ion booster of MEIC. It can reach up to 25 GeV energy for protons and equivalent ion energies of the same magnetic rigidity. An interaction region and an electron cooler designed for MEIC are integrated into the low energy collider ring, in addition to other required new elements including crab cavities and ion spin rotators, for later reuse in MEIC itself. A pair of vertical chicanes which brings the low energy ion beams to the plane of the electron ring and back to the low energy ion ring are also part of the design.

  8. Low frequency spin dynamics in the quantum magnet copper pyrazine dinitrate

    Energy Technology Data Exchange (ETDEWEB)

    Kuehne, H.; Klauss, H.H. [Institut fuer Festkoerperphysik, TU Dresden Dresden (Germany); Institut fuer Physik der Kondensierten Materie, TU Braunschweig (Germany); Guenther, M. [Institut fuer Festkoerperphysik, TU Dresden Dresden (Germany); Grossjohann, S.; Brenig, W. [Institut fuer Theoretische Physik, TU Braunschweig (Germany); Litterst, F.J. [Institut fuer Physik der Kondensierten Materie, TU Braunschweig (Germany); Reyes, A.P.; Kuhns, P.L. [National High Magnetic Field Laboratory, Tallahassee, FL (United States); Turnbull, M.M.; Landee, C.P. [Carlson School of Chemistry and Department of Physics, Clark University, Worcester, MA (United States)

    2010-03-15

    The S = 1/2 antiferromagnetic Heisenberg chain exhibits a magnetic field driven quantum critical point. We study the low frequency spin dynamics in copper pyrazine dinitrate (CuPzN), a realization of this model system of quantum magnetism, by means of {sup 13}C-NMR spectroscopy. Measurements of the nuclear spin-lattice relaxation rate T{sub 1}{sup -} {sup 1} in the vicinity of the saturation field are compared with quantum Monte Carlo calculations of the dynamic structure factor. Both show a strong divergence of low energy excitations at temperatures in the quantum regime. The analysis of the anisotropic T{sub 1}{sup -} {sup 1}-rates and frequency shifts allows one to disentangle the contributions from transverse and longitudinal spin fluctuations for a selective study and to determine the transfer of delocalized spin moments from copper to the neighboring nitrogen atoms. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  9. Low Energy High Brilliance Beam Characterization

    CERN Document Server

    Bähr, J

    2005-01-01

    Low energy high brilliance beam characterization plays an important role for electron sources and injectors of Free Electron Lasers (FELs) and electron linear accelerators as for example the future ILC project. The topic is discussed basing on solutions of the PITZ facility (PhotoInjector Test facility Zeuthen) which are compared with methods applied at other facilities. The properties of an electron beam produced at a laser-driven rf-gun is mainly influenced also by characteristics of the laser beam and the electron gun itself. Therefore aspects of diagnostics will be also discussed for the laser, laser beam line and gun as well. The main properties of the electron beam are transverse and longitudinal phase space and charge as well. The measurement of transverse beam size and position, transverse emittance, charge, beam current, and longitudinal phase space will be discussed in detail. The measurements of the transverse emittance at PITZ is based on a single slit method. The measurement of the longitudinal p...

  10. Low-energy electron scattering from cyanamide

    Science.gov (United States)

    Wang, Kedong; Guo, Shuangcheng; Meng, Ju; Huang, Xiaotian; Wang, Yongfeng

    2016-09-01

    The low-energy electron collisions with cyanamide molecule are investigated by using the UK molecular R -matrix codes for electron energies ranging from 0.01 eV to 10 eV. Three models including static-exchange, static-exchange plus polarization, and close-coupling (CC) approximations are employed to reveal the dynamic interaction. Elastic (integrated and differential), momentum-transfer, and excitation cross sections from the ground state to the three low-lying electron excited states have been presented. Two shape resonances, two core-excited resonances, and two Feshbach resonances are detected in the CC approximation. The role of active space in the target and scattering problem including the resonances is discussed. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. These resonances may be responsible for the fragments observed in a recent experiment of the dissociative electron attachments to cyanamide. Since the cyanamide molecule has a large permanent dipole moment, a Born closure procedure is used to account for the contribution of partial waves higher than l =4 to obtain converged cross sections.

  11. Studies in Low-Energy Nuclear Science

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Low Energy Investigations at Kamioka Observatory

    CERN Document Server

    Sekiya, Hiroyuki

    2013-01-01

    At Kamioka Observatory many activities for low energy rare event search are ongoing. Super-Kamiokande(SK), the largest water Cherenkov neutrino detector, currently continues data taking as the fourth phase of the experiment (SK-IV). In SK-IV, we have upgraded the water purification system and tuned water flow in the SK tank. Consequently the background level was lowered significantly. This allowed SK-IV to derive solar neutrino results down to 3.5MeV energy region. With these data, neutrino oscillation parameters are updated from global fit; $\\Delta m^2_{12}=7.44^{+0.2}_{-0.19}\\times10^{-5} {\\rm eV}^2$, $\\sin^2\\theta_{12}=0.304\\pm0.013$, $\\sin^2\\theta_{13}=0.030^{+0.017}_{-0.015}$. NEWAGE, the directional sensitive dark matter search experiment, is currently operated as "NEWAGE-0.3a" which is a $0.20\\times0.25\\times0.31$ m$^3$ micro-TPC filled with CF4 gas at 152 Torr. Recently we have developed "NEWAGE-0.3b". It was succeeded to lower the operation pressure down to 76 Torr and the threshold down to 50 keV (F...

  13. Exploring Neutrino Mixing with Low Energy Superbeams

    CERN Document Server

    Minakata, H; Minakata, Hisakazu; Nunokawa, Hiroshi

    2001-01-01

    We explore as clearly as possible the features of neutrino oscillation which are relevant for measurements of the CP violating Kobayashi-Maskawa phase delta and the sign of \\Delta m^2_{13}. We focus on the so called low-energy option and discuss principles for optimizing experimental parameters to measure these two quantities simultaneously. Toward the goal, we first formulate a method for obtaining a bird-eye view of the phenomenon of neutrino oscillation by introducing a new powerful tool called the ``CP trajectory diagram in bi-probability space''. It allows us to represent pictorially the three effects separately in a single diagram; effect from genuine CP violation due to the sin delta term, effect from the CP conserving cos delta term, and the fake CP violating effect due to earth matter. By using the CP trajectory diagram we observe that there is a two-fold ambiguity in the determination of delta which is related with the sign of Delta m^2_{13}. We then address the question of what are the promising op...

  14. Optimal Low Energy Earth-Moon Transfers

    Science.gov (United States)

    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.

  15. {mu}SR study of impurity effects on the Cu-spin fluctuations in the overdoped regime of La{sub 2-x}Sr{sub x}Cu{sub 1-y}Zn{sub y}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Risdiana; Adachi, T.; Oki, N.; Yairi, S.; Tanabe, Y.; Omori, K. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Suzuki, T.; Watanabe, I. [Advanced Meson Science Laboratory, Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako 351-0198 (Japan); Koda, A. [Muon Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK-IMSS), 1-1 Oho, Tsukuba 305-0801 (Japan); Higemoto, W. [Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirane, Shirakata, Tokai, Ibaraki 319-1195 (Japan); Koike, Y. [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)], E-mail: koike@teion.apph.tohoku.ac.jp

    2007-09-01

    Zero-field muon-spin-relaxation measurements have been carried out for La{sub 2-x}Sr{sub x}Cu{sub 1-y}Zn{sub y}O{sub 4} (LSCO) with y = 0-0.10 in the overdoped regime up to x = 0.30, in order to investigate whether the dynamical stripe correlations are pinned and stabilized even for the overdoped LSCO or not. It has been found that the Zn-induced slowing down of the Cu-spin fluctuations is weakened with increasing x but takes place in the overdoped regime and disappears at x = 0.30. This suggests that the stripe-pinning model holds good in the whole superconducting regime of LSCO and that there is no quantum critical point at x {approx} 0.19.

  16. E1 and M1 strength functions at low energy

    Directory of Open Access Journals (Sweden)

    Schwengner Ronald

    2017-01-01

    Full Text Available We report photon-scattering experiments using bremsstrahlung at the γELBE facility of Helmholtz-Zentrum Dresden-Rossendorf and using quasi-monoenergetic, polarized γ beams at the HIγS facility of the Triangle Universities Nuclear Laboratory in Durham. To deduce the photoabsorption cross sections at high excitation energy and high level density, unresolved strength in the quasicontinuum of nuclear states has been taken into account. In the analysis of the spectra measured by using bremsstrahlung at γELBE, we perform simulations of statistical γ-ray cascades using the code γDEX to estimate intensities of inelastic transitions to low-lying excited states. Simulated average branching ratios are compared with model-independent branching ratios obtained from spectra measured by using monoenergetic γ beams at HIγS. E1 strength in the energy region of the pygmy dipole resonance is discussed in nuclei around mass 90 and in xenon isotopes. M1 strength in the region of the spin-flip resonance is also considered for xenon isotopes. The dipole strength function of 74Ge deduced from γELBE experiments is compared with the one obtained from experiments at the Oslo Cyclotron Laboratory. The low-energy upbend seen in the Oslo data is interpreted as M1 strength on the basis of shell-model calculations.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. High-Resolution Measurements of Low-Energy Conversion Electrons

    CERN Multimedia

    Gizon, A; Putaux, J

    2002-01-01

    Measurements of low-energy internal conversion electrons have been performed with high energy resolution in some N = 105 odd and odd-odd nuclei using a semi-circular spectrograph associated to a specific tape transport system. These experiments aimed to answer the following questions~: \\begin{itemize} \\item Do M3 isomeric transitions exist in $^{183}$Pt and $^{181}$Os, isotones of $^{184}$Au~? \\item Are the neutron configurations proposed to describe the isomeric and ground states of $^{184}$Au right or wrong~? \\item Does it exist an isomeric state in $^{182}$Ir, isotone of $^{181}$Os, $^{183}$Pt and $^{184}$Au~? \\item What are the spin and parity values of the excited states of $^{182}$Ir~? \\end{itemize} In $^{183}$Pt, the 35.0 keV M3 isomeric transition has been clearly observed and the reduced transition probability has been determined. The deduced hindrance factor is close to that observed in the neighbouring odd-odd $^{184}$Au nucleus. This confirms the neutron configurations previously proposed for the ...

  19. Design of Low-Energy District Heating System for a Settlement with Low-Energy Buildings

    DEFF Research Database (Denmark)

    Tol, Hakan; Svendsen, Svend

    2011-01-01

    velocity and/or max pressure gradient. Since traditional dimensioning methods cause over-dimensioned network, special attention has to be given to lower the dimensions and as a consequence heat loss from the DH network further. In this investigation pipe dimensioning method of low-energy DH system......With the integration of new low-energy buildings the traditional district heating (DH) systems with high operating temperatures will have significantly higher heat loss according to the heat supplied to the district. The relatively higher heat loss could be reduced with low operating temperatures...... was developed with an optimization method in the objective of minimizing heat loss from the network while pressure drop values were kept as the constraints through the DH network. In the dimensioning method also descending pipe dimensions were formed in the branched type DH network by taking into account...

  20. Low energy x-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    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.

  1. Low energy beam transport system developments

    Energy Technology Data Exchange (ETDEWEB)

    Dudnikov, V., E-mail: vadim@muonsinc.com [Muons, Inc., Batavia, IL 60510 (United States); Han, B.; Stockli, M.; Welton, R. [ORNL, Oak Ridge, TN 37831 (United States); Dudnikova, G. [University of Maryland, College Park, MD 3261 (United States); Institute of Computational Technologies SBRAS, Novosibirsk (Russian Federation)

    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.

  2. Spin-disordered superfluid state for spin-1 bosons with fractional spin and statistics

    OpenAIRE

    2002-01-01

    We study a strongly correlated spin-1 Bose gas in 2D space by using the projective construction. A spin-disordered superfluid state is constructed and proposed as a candidate competing with the conventional polar condensate when interaction is antiferromagnetic. This novel state has a non-trivial topological order whose low energy excitations carry fractional spin, charge, and statistics. The spin excitations become gapless only at the edge and are described by level-1 SU(2) Kac-Moody algebra...

  3. European national strategies to move towards very low energy buildings

    DEFF Research Database (Denmark)

    Wittchen, Kim Bjarne; Thomsen, Kirsten Engelund

    difficult. One way of promoting very low energy buildings is by various direct or indirect actions that make these kinds of buildings more attractive. The most popular support for low energy buildings is e.g. loans with low interest rates to finance low energy buildings. This is done either by means...... high energy performance. It is important to stress the need for MS to introduce a national or regional definition of very low energy buildings in their building regulation and to develop a national strategy towards this level of energy performance to become the standard. This market transformation...... the ambition in the EU Action plan - to develop an EU strategy towards very low energy houses. The current recast of the EPBD is an opportunity, which must not be missed to introduce the requirement to MS to define very low energy buildings and a national strategy towards this level of energy performance...

  4. Occupant satisfaction with new low-energy houses

    DEFF Research Database (Denmark)

    Knudsen, Henrik Nellemose; Jensen, Ole Michael; Kristensen, Lars

    2012-01-01

    The development and the erection of low-energy buildings have been intensified in recent years. Still, there are only few studies of the energy performance and occupant satisfaction with living in low-energy houses. A questionnaire survey was therefore carried out among occupants of low-energy ho......The development and the erection of low-energy buildings have been intensified in recent years. Still, there are only few studies of the energy performance and occupant satisfaction with living in low-energy houses. A questionnaire survey was therefore carried out among occupants of low......-energy houses. The purpose was to study occupant satisfaction with new low-energy houses concerning i.a. the perceived indoor climate and the technical installations for heating and ventilation. The survey showed an overall satisfaction with the new low-energy houses, but also that there were problems...... that should be addressed to make low-energy houses more attractive to ordinary people. Problems could be that it was too hot in summer and too cold in winter; that there were initial difficulties with the technical installations and that they were difficult to use. A series of recommendations to increase...

  5. Low-Energy Ballistic Transfers to Lunar Halo Orbits

    Science.gov (United States)

    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.

  6. Magnetic Nanostructures Spin Dynamics and Spin Transport

    CERN Document Server

    Farle, Michael

    2013-01-01

    Nanomagnetism and spintronics is a rapidly expanding and increasingly important field of research with many applications already on the market and many more to be expected in the near future. This field started in the mid-1980s with the discovery of the GMR effect, recently awarded with the Nobel prize to Albert Fert and Peter Grünberg. The present volume covers the most important and most timely aspects of magnetic heterostructures, including spin torque effects, spin injection, spin transport, spin fluctuations, proximity effects, and electrical control of spin valves. The chapters are written by internationally recognized experts in their respective fields and provide an overview of the latest status.

  7. Neutron Scattering Study of Low Energy Magnetic Excitation in FeTeSe System

    Science.gov (United States)

    Xu, Zhijun; Wen, Jinsheng; Schneeloch, John; Matsuda, Masaaki; Christianson, A. D.; Gu, Genda; Zaliznyak, I. A.; Xu, Guangyong; Tranquada, J. M.; Birgeneau, R. J.

    2014-03-01

    We have performed neutron scattering and magnetization/transport measurements on a series of FeTe1-xSex system single crystals to study the interplay between magnetism and superconductivity. Comparing to pure FeTe1-xSex compounds, extra Fe and Ni/Cu doping on Fe-site can change physics properties of these samples, including resistivity, magnetization and superconducting properties. Our neutron scattering studies also show the Fe-site doping change low energy magnetic spectrum, including the magnetic excitations intensity, position and magnetic correlation length in these samples. On the other hand, the temperature dependence of the low energy magnetic fluctuations are also found to be different depending on the composition. This work is supported by the Office of Basic Energy Sciences, DOE.

  8. Odd–even effect in fragment angular momentum in low-energy fission of actinides

    Indian Academy of Sciences (India)

    B S Tomar; R Tripathi; A Goswami

    2007-01-01

    Quantitative explanation for the odd–even effect on fragment angular momenta in the low-energy fission of actinides have been provided by taking into account the single particle spin of the odd proton at the fragment's scission point deformation in the case of odd- fragments along with the contribution from the population of angular momentum bearing collective vibrations of the fissioning nucleus at scission point. The calculated fragment angular momenta have been found to be in very good agreement with the experimental data for fragments in the mass number region of 130–140. The odd–even effect observed in the fragment angular momenta in the low-energy fission of actinides has been explained quantitatively for the first time.

  9. Low-energy-consumption hybrid lasers for silicon photonics

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Ran, Qijiang; Mørk, Jesper

    2012-01-01

    Physics and characteristics of a hybrid vertical-cavity laser that can be an on-chip Si light source with high speed and low energy consumption are discussed.......Physics and characteristics of a hybrid vertical-cavity laser that can be an on-chip Si light source with high speed and low energy consumption are discussed....

  10. Occupant Experiences and Satisfaction with New Low-Energy Houses

    DEFF Research Database (Denmark)

    Knudsen, Henrik Nellemose; Thomsen, Kirsten Engelund; Mørck, Ove

    2013-01-01

    The development and the erection of low-energy buildings have been intensified in recent years. Still, there are only few studies on occupant experiences and satisfaction of living in low-energy houses. A questionnaire survey was therefore carried out in the autumn 2011 among occupants of low......-energy houses that meet the future lower energy requirements of the planned Danish Building Regulations 2015. The purpose was to study experiences and satisfaction among occupants living in new low-energy houses. It included i.a. overall satisfaction, perceived indoor climate and experiences and satisfaction...... with technical installations for heating and ventilation, the ability of regulating the indoor climate, the availability and quality of information and the experienced heat consumption. The survey showed an overall satisfaction with new low-energy houses, but also that there were problems that should...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Coupled Quantum Fluctuations and Quantum Annealing

    Science.gov (United States)

    Hormozi, Layla; Kerman, Jamie

    We study the relative effectiveness of coupled quantum fluctuations, compared to single spin fluctuations, in the performance of quantum annealing. We focus on problem Hamiltonians resembling the the Sherrington-Kirkpatrick model of Ising spin glass and compare the effectiveness of different types of fluctuations by numerically calculating the relative success probabilities and residual energies in fully-connected spin systems. We find that for a small class of instances coupled fluctuations can provide improvement over single spin fluctuations and analyze the properties of the corresponding class. Disclaimer: This research was funded by ODNI, IARPA via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  13. Simulation of indoor environment in low energy housing

    DEFF Research Database (Denmark)

    Vagiannis, Georgios; Knudsen, Henrik N.; Toftum, Jørn;

    The aim of this study was to assess whether low energy consumption in dwellings imposes problems by deteriorating the indoor environment. Several indoor environment parameters were correlated with the energy consumption of low energy houses. One house from a village of low energy houses in Denmark...... was selected and sensitivity analyses were conducted for the importance of occupancy, ventilation, window opening, and heat recovery efficiency. In particular occupancy and venting played significant roles for the indoor environment and energy consumption. It was also shown that with passive measures, but also...... with the installation of a chiller, a comfortable thermal indoor environment could be achieved with only a minor increase in the energy consumption....

  14. Cryostat for Ultra-low-energy Threshold Germanium Spectrometers

    CERN Document Server

    Aalseth, Craig E; Fast, James E; Hossbach, Todd W; Orrell, John L; Overman, Cory T; Vandevender, Brent A

    2012-01-01

    This paper presents progress on the development of a cryostat intended to improve upon the low-energy threshold (below 0.5 keV) of p-type point contact germanium gamma-ray spectrometers. Ultra-low energy thresholds are important in the detection of low-energy nuclear recoils, an event class relevant to both dark matter direct detection and measurement of coherent neutrino-nucleus scattering. The cryostat design, including a thermal and electrical-field model, is given. A prototype cryostat has been assembled and data acquired to evaluate its vacuum and thermal performance.

  15. Spin currents and magnon dynamics in insulating magnets

    Science.gov (United States)

    Nakata, Kouki; Simon, Pascal; Loss, Daniel

    2017-03-01

    Nambu–Goldstone theorem provides gapless modes to both relativistic and nonrelativistic systems. The Nambu–Goldstone bosons in insulating magnets are called magnons or spin-waves and play a key role in magnetization transport. We review here our past works on magnetization transport in insulating magnets and also add new insights, with a particular focus on magnon transport. We summarize in detail the magnon counterparts of electron transport, such as the Wiedemann–Franz law, the Onsager reciprocal relation between the Seebeck and Peltier coefficients, the Hall effects, the superconducting state, the Josephson effects, and the persistent quantized current in a ring to list a few. Focusing on the electromagnetism of moving magnons, i.e. magnetic dipoles, we theoretically propose a way to directly measure magnon currents. As a consequence of the Mermin–Wagner–Hohenberg theorem, spin transport is drastically altered in one-dimensional antiferromagnetic (AF) spin-1/2 chains; where the Néel order is destroyed by quantum fluctuations and a quasiparticle magnon-like picture breaks down. Instead, the low-energy collective excitations of the AF spin chain are described by a Tomonaga–Luttinger liquid (TLL) which provides the spin transport properties in such antiferromagnets some universal features at low enough temperature. Finally, we enumerate open issues and provide a platform to discuss the future directions of magnonics.

  16. Photon Strength and the Low-Energy Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    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

  17. Photon Strength and the Low-Energy Enhancement

    Energy Technology Data Exchange (ETDEWEB)

    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

  18. Method for analysis of low energy backscattering spectra

    Energy Technology Data Exchange (ETDEWEB)

    Hnatowicz, V.; Kvitek, J. (Ceskoslovenska Akademie Ved, Rez. Ustav Jaderne Fyziky); Pelikan, L. (Ceske Vysoke Uceni Technicke, Prague (Czechoslavika). Dept. of Microelectronics); Rybka, V.; Krejci, P. (Tesla, Prague (Czechoslovakia))

    1982-04-15

    An analytical formula is proposed describing the shape of the energy spectra of particles backscattered from samples implanted with heavy impurities. The method is suitable for quantitative evaluation of backscattering spectra measured with low energy ions.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  20. Classification of low energy houses in Danish Building Regulations

    DEFF Research Database (Denmark)

    Rose, Jørgen; Svendsen, Svend

    2005-01-01

    The new Danish Building Regulations (Building Regulations, 2005) introduces the total energy consumption, i.e. energy use for heating, ventilation, cooling and domestic hot water, for buildings as a measure for the energy efficiency of new buildings, i.e. moving away from the former U-value demands....... In addition to the minimum requirements for new buildings, the new Building Regulations also specify requirements for characterizing a building as either low energy building class 1 or low energy building class 2. This paper describes a type-house that is presently being built in Denmark. The type......-house easily meets the requirements for being categorized as a low energy building class 1, and the paper investigates how much U-values can be increased if the type-house were to fulfil the requirements for a low energy building class 2 or a building that just fulfils the minimum demands....

  1. Low-Energy Excitation Spectra in the Excitonic Phase of Cobalt Oxides

    Science.gov (United States)

    Yamaguchi, Tomoki; Sugimoto, Koudai; Ohta, Yukinori

    2017-04-01

    We study the excitonic phase and low-energy excitation spectra of perovskite cobalt oxides. Constructing the five-orbital Hubbard model defined on the three-dimensional cubic lattice for the 3d bands of Pr0.5Ca0.5CoO3, we calculate the excitonic susceptibility in the normal state in the random-phase approximation (RPA) to show the presence of the instability toward excitonic condensation. On the basis of the excitonic ground state with a magnetic multipole obtained in the mean-field approximation, we calculate the dynamical susceptibility of the excitonic phase in the RPA and find that there appear a gapless collective excitation in the spin-transverse mode (Goldstone mode) and a gapful collective excitation in the spin-longitudinal mode (Higgs mode). The experimental relevance of our results is discussed.

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

    Science.gov (United States)

    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.

  3. The MAJORANA Demonstrator Low-Energy Rare Event Search

    Science.gov (United States)

    Wiseman, Clinton; Majorana Collaboration

    2016-09-01

    The extremely low backgrounds of the MAJORANA DEMONSTRATOR neutrinoless double beta decay experiment, combined with the excellent energy resolution of its high-purity germanium (HPGe) detectors, provide an opportunity for a dark matter search at low energy (rare event searches at low energies, including light WIMPs (Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility.

  4. Saturation of low-energy antiproton annihilation on nuclei

    Science.gov (United States)

    Gal, A.; Friedman, E.; Batty, C. J.

    2000-10-01

    Recent measurements of very low-energy (pL0, parallels the recent prediction, for /E<0, that the level widths of /p¯ atoms saturate and, hence, that /p¯ deeply bound atomic states are relatively narrow. Antiproton annihilation cross sections are calculated at pL=57 MeV//c across the periodic table, and their dependence on /Z and /A is classified and discussed with respect to the Coulomb focussing effect at very low energies.

  5. Incommensurate spin ordering and fluctuations in underdoped La{sub 2-x}Ba{sub x}CuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Dunsiger, Sarah [Physics Department E21, Technical University of Munich, Garching (Germany); Zhao, Yang; Gaulin, Bruce; Dabkowska, Hanna [Department of Physics and Astronomy, McMaster University, Hamilton, ON (Canada); Yamani, Zahra; Buyers, William [Canadian Neutron Beam Centre, NRC, Chalk River Laboratories, Chalk River, ON (Canada); Qiu, Yiming; Copley, John [National Institute of Standards and Technology, Gaithersburg, Maryland (United States); Sidis, Yvan; Bourges, Philippe [Laboratoire Leon Brillouin, CEA-Saclay, Gif-sur-Yvette (France)

    2008-07-01

    The diverse magnetic properties of the La{sub 2-x}(Sr,Ba){sub x}CuO{sub 4} transition metal oxides may be tuned in a controllable way by doping with mobile holes. In one interpretation, the holes are believed to organise into correlated static or dynamic stripes. We report the first observation of static incommensurate spin ordering in underdoped La{sub 2-x}Ba{sub x}CuO{sub 4} (x=0.025, 0.05, 0.08) using neutron diffraction. Elastic collinear incommensurate peaks are observed below the superconducting transition (T{sub C}{proportional_to}27 K) in La{sub 2-x}Ba{sub x}CuO{sub 4} (x=0.08). In marked contrast, diagonal satellite peaks have been observed at low temperature in positions rotated by 45 {sup circle} within the (HK0) plane for La{sub 2-x}Ba{sub x}CuO{sub 4} (x{proportional_to}0.025, 0.05). Our neutron scattering results are compared with analogous studies on La{sub 2-x}Sr{sub x}CuO{sub 4} which indicate that such a rotation of the spin structure may be a generic feature of the underdoped La-214 cuprates.

  6. Low-Energy Brane-World Effective Actions and Partial Supersymmetry Breaking

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Matthias

    2003-03-18

    As part of a programme for the general study of the low-energy implications of supersymmetry breaking in brane-world scenarios, we study the nonlinear realization of supersymmetry which occurs when breaking N = 2 to N = 1 supergravity. We consider three explicit realizations of this supersymmetry breaking pattern, which correspond to breaking by one brane, by one antibrane or by two (or more) parallel branes. We derive the minimal field content, the effective action and supersymmetry transformation rules for the resulting N = 1 theory perturbatively in powers of {kappa} = 1/M{sub Planck}. We show that the way the massive gravitino and spin-1 fields assemble into N = 1 multiplets implies the existence of direct brane-brane contact interactions at order {Omicron}({kappa}). This result is contrary to the {Omicron}({kappa}{sup 2}) predicted by the sequestering scenario but in agreement with recent work of Anisimov et al. Our low-energy approach is model independent and is a first step towards determining the low-energy implications of more realistic brane models which completely break all supersymmetries.

  7. Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects

    Science.gov (United States)

    Gotfryd, Dorota; Rusnačko, Juraj; Wohlfeld, Krzysztof; Jackeli, George; Chaloupka, Jiří; Oleś, Andrzej M.

    2017-01-01

    We explore the phase diagram of the Kitaev-Heisenberg model with nearest neighbor interactions on the honeycomb lattice using the exact diagonalization of finite systems combined with the cluster mean field approximation, and supplemented by the insights from analytic approaches: the linear spin-wave and second-order perturbation theories. This study confirms that by varying the balance between the Heisenberg and Kitaev term, frustrated exchange interactions stabilize in this model either one of four phases with magnetic long range order: Néel phase, ferromagnetic phase, and two other phases with coexisting antiferromagnetic and ferromagnetic bonds, zigzag and stripy phase, or one of two distinct spin-liquid phases. Out of these latter disordered phases, the one with ferromagnetic Kitaev interactions has a substantially broader range of stability as the neighboring competing ordered phases, ferromagnetic and stripy, have very weak quantum fluctuations. Focusing on the quantum spin-liquid phases, we study spatial spin correlations and dynamic spin structure factor of the model by the exact diagonalization technique, and discuss the evolution of gapped low-energy spin response across the quantum phase transitions between the disordered spin liquid and phases with long range magnetic order.

  8. Magnetism in the iron-based superconductors: The determination of spin-nematic fluctuations as the primary order parameter and its implications for unconventional superconductivity

    Science.gov (United States)

    Taddei, Keith M.

    With nearly innumerable applications, superconductivity stands as a holy grail in the research of quantum phenomena. Understanding the mechanism that begets the fabled pairing of electrons which leads to zero resistance is the most significant undertaking in order to bring to fruition all of superconductivity's splendor. Yet the interaction which couples electrons in the most promising family of superconductors known as unconventional superconductors, which show the highest Tc's and largest upper critical fields remains a mystery. Intense study over the past several decades on the cuprate superconductors has allowed for the identification of several candidate mechanisms --- cardinal of which is magnetic fluctuations --- however as of yet the question still remains. Recently, the discovery of the iron-based superconductors has provided another fruitful avenue through which this mechanism can be probed. Excitingly in these materials superconductivity not only arises near a magnetic instability - a situation which is expected to be particularly suited for engendering superconductivity should magnetic fluctuations be the pairing mechanism - but also exhibit the microscopic co-existence of the two presumably adversarial phenomena. In the work presented here the powerful techniques of neutron and x-ray diffraction will be used to study two particularly interesting members of this family: the intercalated iron-selenide CsxFe 2--xSe2 and two members of the iron-arsenide 122 family (BaFe2(As1--xPx)2 and Sr1--xNaxFe2As 2). Though isostructural at high temperatures, these two materials behave remarkably differently and the idiosyncratic manifestations of superconductivity and ordered magnetism in either give clues as to how the latter might stabilize the former. The iron-selenides will be shown to exhibit a complex phase space with phase separation leading to stabilization of magnetism and superconductivity in separate phases. The structure, behavior and complex vacancy

  9. Spin-fluctuation mediated superconductivity and magnetic order in the cuprate La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, Astrid Tranum

    High-temperature superconductivity in cuprates emerges as one out of many electronic phases when doping the antiferromagnetic Mott insulator La2CuO4 away from half _lling. The description of the superconducting phase is therefore complicated by intertwined electronic orders that compete...... with superconductivity. However, it is possible that the tendency towards additional ordering phenomena is a necessary condition for unconventional superconductivity to develop. Indeed most superconductors discovered throughout the last 29 years, including also the recently discovered class of iron-based superconductors......, show a very rich electronic phase diagram. A common feature that characterizes both cuprates, heavy fermions, and iron pnictides is the proximity to magnetic order. Therefore, the idea of spin-uctuation mediated pairing is a popular paradigm proposed for unconventional superconductivity. A _ngerprint...

  10. Low energy gauge couplings in grand unified theories and high precision physics

    Energy Technology Data Exchange (ETDEWEB)

    Lynn, B.W. [Stanford Univ., CA (United States). Dept. of Physics]|[Superconducting Super Collider Lab., Dallas, TX (United States)

    1993-09-01

    I generalize the leading log relations between low energy SU(3){sub QCD}, SU(2){sub {rvec I}} and U(l){sub Y} effective gauge couplings to include all one-loop threshold effects of matter fields in oblique vector self energy quantum corrections for both supersymmetric and non-supersymmetric SU(5) grand unified theories. These always involve an exactly conserved current from the unbroken SU(3){sub QCD} {times} U(L){sub QED} subgroup; this fact strongly constrains any non-decoupling of heavy states as well as the generic character of threshold effects. Relations between low energy gauge couplings depend on the details of the spectra of both the superheavy and low mass sectors; I display the common origin of the logs appropriate to superheavy matter states, which can be found with well known renormalization group techniques, and the combination of logs and polynomials appropriate for light matter states, which cannot. Relations between any two or all three low energy effective gauge couplings do not depend on the top quark or standard model Higgs` masses. Neither do they depend on neutral color singlet states such as other neutral color singlet Higgs` or higgsinos, neutrinos, zinos or photinos. Further, they do not depend on degenerate SU(5) matter representations, of either spin 0 or spin 1/2 of any mass; matter representations of SU(5) can affect such relations only if there is mass splitting within them. The b quark splitting from the {tau} and {nu}{sub {tau}} can affect the relation between gauge couplings for {vert_bar}q{sub 2}{vert_bar} {yields} m{sub b}{sup 2} as can hadronic resonances and multi-hadron states for lower {vert_bar}q{sub 2}{vert_bar}. New mass-split representations of light states, such as occur in supersymmetric theories, can also affect such relations.

  11. Low-energy microscopic models for iron-based superconductors: a review

    Science.gov (United States)

    Fernandes, Rafael M.; Chubukov, Andrey V.

    2017-01-01

    The development of sensible microscopic models is essential to elucidate the normal-state and superconducting properties of the iron-based superconductors. Because these materials are mostly metallic, a good starting point is an effective low-energy model that captures the electronic states near the Fermi level and their interactions. However, in contrast to cuprates, iron-based high-T c compounds are multi-orbital systems with Hubbard and Hund interactions, resulting in a rather involved 10-orbital lattice model. Here we review different minimal models that have been proposed to unveil the universal features of these systems. We first review minimal models defined solely in the orbital basis, which focus on a particular subspace of orbitals, or solely in the band basis, which rely only on the geometry of the Fermi surface. The former, while providing important qualitative insight into the role of the orbital degrees of freedom, do not distinguish between high-energy and low-energy sectors and, for this reason, generally do not go beyond mean-field. The latter allow one to go beyond mean-field and investigate the interplay between superconducting and magnetic orders as well as Ising-nematic order. However, they cannot capture orbital-dependent features like spontaneous orbital order. We then review recent proposals for a minimal model that operates in the band basis but fully incorporates the orbital composition and symmetries of the low-energy excitations. We discuss the results of the renormalization group study of such a model, particularly of the interplay between superconductivity, magnetism, and spontaneous orbital order, and compare theoretical predictions with experiments on iron pnictides and chalcogenides. We also discuss the impact of the glide-plane symmetry on the low-energy models, highlighting the key role played by the spin-orbit coupling.

  12. Energy and carbon impact of very low energy building

    Energy Technology Data Exchange (ETDEWEB)

    Dyrboel, Susanne; Eriksen, Kurt Emil (EuroACE (Belgium)). e-mail: susanne.dyrboel@rockwool.com; Engelund Thomsen, Kirsten; Wittchen, Kim B.; Jensen, Ole Michael (Danish Building Research Inst., SBI (Denmark))

    2009-07-01

    The main purpose of the current study is to investigate the impact associated with a wider introduction of very low energy buildings in Europe, especially for EU Member States (MS) which have elaborated plans for the future towards very low energy buildings. In the study, the resulting energy savings and CO{sub 2} emission reduction from buildings constructed as very low energy buildings will be dealt with, taking into account the national energy-mix as well as national interpretation of very low energy buildings. In addition, the study seeks to obtain information on relevant national studies on very low energy buildings, including measures and programmes to promote such buildings and to remove barriers to their future development. In this context, education, training, and the public sector are areas of special interest. In a recent study [1] we gathered a picture of the planned strategies in European countries regarding the implementation of requirements towards very low energy buildings (on passive house level or similar). This paper discusses results from a second survey on potential energy and CO{sub 2} emission reductions if European MS shift towards very low energy buildings. One of the prescribed actions on buildings in the EU Action Plan on Energy Efficiency [2] is for the Commission to develop a strategy for very low energy or passive houses (before 2009) towards a more widespread deployment of these building types by 2015. In the Commission proposal for the Energy Performance of Buildings Directive (EPBD) recast [3] MS will be required to draw up national plans for increasing the number of buildings for which both carbon dioxide emissions and primary energy consumption are low or equal to zero. The MS shall set targets for the minimum percentage which these buildings shall constitute of the total number of buildings in 2020. The targets shall be specified for both new and existing buildings as well as for buildings occupied by public authorities. The

  13. Low energy availability in the marathon and other endurance sports.

    Science.gov (United States)

    Loucks, Anne B

    2007-01-01

    Energy availability is the amount of dietary energy remaining after exercise training for all other metabolic processes. Excessively low energy availability impairs reproductive and skeletal health, although genetics and age may alter an individual's initial conditions and sensitivity when low energy availability is imposed. Many marathon runners and other endurance athletes reduce energy availability either (i) intentionally to modify body size and composition for improving performance; (ii) compulsively in a psychopathological pattern of disordered eating; or (iii) inadvertently because there is no strong biological drive to match energy intake to activity-induced energy expenditure. Inadvertent low energy availability is more extreme when consuming a low fat, high carbohydrate diet. Low energy availability, reproductive disorders, low bone mineral density and stress fractures are more common in female than male athletes. Functional menstrual disorders caused by low energy availability should be diagnosed by excluding diseases that also disrupt menstrual cycles. To determine energy availability (in units of kilocalories or kilojoules per kilogram of fat-free mass), athletes can record their diets and use diet analysis software to calculate energy intake, measure energy expenditure during exercise using a heart monitor and measure fat-free mass using a bioelectrical impedance body composition scale. All are commercially available at consumer prices.

  14. Studies of Fluctuation Processes in Nuclear Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Ayik, Sakir [Tennessee Technological Univ., Cookeville, TN (United States). Dept. of Physics

    2016-04-14

    The standard one-body transport approaches have been extensively applied to investigate heavy-ion collision dynamics at low and intermediate energies. At low energies the approach is the mean-field description of the time-dependent Hartree-Fock (TDHF) theory. At intermediate energies the approach is extended by including a collision term, and its application has been carried out mostly in the semi-classical framework of the Boltzmann-Uhling-Uhlenbeck (BUU) model. The standard transport models provide a good understanding of the average properties of the collision dynamics in terms of the effective interactions in both low and intermediate energies. However, the standard models are inadequate for describing the fluctuation dynamics of collective motion at low energies and disassembling of the nuclear system into fragments at intermediate energies resulting from the growth of density fluctuations in the spinodal region. Our tasks have been to improve the standard transport approaches by incorporating fluctuation mechanisms into the description. There are mainly two different mechanisms for fluctuations: (i) Collisional fluctuations generated by binary nucleon collisions, which provide the dominant mechanism at intermediate energies, and (ii) One-body mechanism or mean-field fluctuations, which is the dominant mechanism at low energies. In the first part of our project, the PI extended the standard transport model at intermediate energies by incorporating collisional mechanism according to the “Generalized Langevin Description” of Mori formalism. The PI and his collaborators carried out a number of applications for describing dynamical mechanism of nuclear multi fragmentations, and nuclear collective response in the semi-classical framework of the approach, which is known as the Boltzmann-Langevin model. In the second part of the project, we considered dynamical description at low energies. Because of the effective Pauli blocking, the collisional dissipation and

  15. Calculation of astrophysical S factor at low energy levels

    Science.gov (United States)

    Andic, Halil Ibrahim; Ozer, Okan

    2017-02-01

    Nuclear reactions are very important for the structure, evolution, nucleosynthesis and various observational manifestations of main-sequence stars, white dwarfs and neutron stars. For astrophysical applications, one needs to know value of S-factor for many reactions at low energies. The experimental measurements of cross-sections at such low energies are essentially not easily available since the Coulomb barrier. Theoretical calculations are model dependent, so that nuclear physics uncertainties of calculated S-factor can be substantial. Using the supersymmetric quantum mechanics one can obtain the supersymmetric partner potential that can vary by several orders of magnitude in the energy range of a given reaction in the calculation of S factor. Since the determination of reaction rates requires accurate values of cross sections at very low energies, then in order to eliminate the main part of the energy dependence of these cross sections one makes use of the astrophysical S-factor in Taylor Expansion series about zero-energy.

  16. Low Energy Analyzing Powers in Pion-Proton Elastic Scattering

    CERN Document Server

    Meier, R; Bilger, R; Van den Brandt, B; Breitschopf, J; Clement, H; Comfort, J R; Denz, H; Erhardt, A; Föhl, K; Friedman, E; Gr"ater, J; Hautle, P; Hofman, G J; Konter, J A; Mango, S; P"atzold, J; Pavan, M M; Wagner, G J; Von Wrochem, F

    2004-01-01

    Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS as well as a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for pi+ p scattering, and at 67.3 and 87.2 MeV for pi- p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

  17. EVOLUTION OF THE CRAB NEBULA IN A LOW ENERGY SUPERNOVA

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Haifeng; Chevalier, Roger A., E-mail: hy4px@virginia.edu, E-mail: rac5x@virginia.edu [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States)

    2015-06-20

    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 (∼10{sup 50} 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. Evolution of the Crab nebula in a low energy supernova

    CERN Document Server

    Yang, Haifeng

    2015-01-01

    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 ($\\sim 10^{50}$ ergs). 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.

  19. Coulomb effects in low-energy nuclear fragmentation

    Science.gov (United States)

    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.

  20. Low Energy Description of Quantum Gravity and Complementarity

    CERN Document Server

    Nomura, Yasunori; Weinberg, Sean J

    2013-01-01

    We propose an explicit framework in which low energy dynamics of quantum gravity is described preserving locality, and yet taking into account the effects that are not captured by the naive global spacetime picture, e.g. those associated with black hole complementarity. Our framework employs a "special relativistic" description of gravity; specifically, gravity is treated as a force measured by the observer tied to the coordinate system associated with a freely falling local Lorentz frame. We explicitly identify regions of spacetime in which low energy local descriptions are applicable as viewed from the freely falling frame; in particular, we identify a surface called the gravitational observer horizon on which the local proper acceleration measured in the observer's coordinates becomes the cutoff (string) scale. This allows for separating clearly between the "low-energy" local physics and "trans-Planckian" intrinsically quantum gravitational (stringy) physics, and allows for developing clear physical pictur...

  1. The Solar Solution: Tracking the Sun with Low Energy Neutrinos

    CERN Document Server

    Hartman, Nicole

    2016-01-01

    As neutrinos become a significant background for projected dark matter experiments, the community will become concerned with determining if events counted in a dark matter experiment are good dark matter candidates or low-energy neutrinos from astrophysical sources. We investigate the feasibility of using neutrino-electron scattering in a terrestrial detector medium as a means to determine the flight direction of the original, low-energy solar neutrino.Using leading-order weak interactions in the Standard Model and constrains from energy and momentum conservation, we developed a simple simulation that suggests that 68% of the time the ejected electron would be within 0.99 radians of the incident neutrino's direction. This suggests that it may be fruitful to pursue low-energy neutrino detection capability that can utilize such ejected electrons.

  2. Coulomb and Nuclear Breakup at Low Energies: Scaling Laws

    Directory of Open Access Journals (Sweden)

    Hussein M. S.

    2013-12-01

    Full Text Available We report on a recent work on the low-energy behavior of the breakup cross section in so far as it has important role in the fusion of weakly bound and halo nuclei at near-barrier energies. We assess the way the nuclear component of this cross section scales with the target mass. In complete accord with previous finding at higher energies we verify that the low energy behavior of the breakup cross section for a given projectile and relative center of mass energy with respect to the Coulomb barrier height scales as the cubic root of the mass number of the target. Surprisingly we find that the Coulomb component of the breakup cross section at these low energies also obeys scaling, but with a linear dependence on the target charge. Our findings are important when planning for experiments involving these exotic nuclei.

  3. Low energy analyzing powers in pion-proton elastic scattering

    Science.gov (United States)

    Meier, R.; Cröni, M.; Bilger, R.; van den Brandt, B.; Breitschopf, J.; Clement, H.; Comfort, J. R.; Denz, H.; Erhardt, A.; Föhl, K.; Friedman, E.; Gräter, J.; Hautle, P.; Hofman, G. J.; Konter, J. A.; Mango, S.; Pätzold, J.; Pavan, M. M.; Wagner, G. J.; von Wrochem, F.

    2004-05-01

    Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for π-p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

  4. Electron polarimetry at low energies in Hall C at JLab

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, D. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia, 23606 (United States)

    2013-11-07

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  5. A Low Energy Intelligent Clustering Protocol for Wireless Sensor Network

    DEFF Research Database (Denmark)

    Li, Qiao; Cui, Lingguo; Zhang, Baihai

    2010-01-01

    LEACH (low-energy adaptive clustering hierarchy) is a well-known self-organizing, adaptive clustering protocol of wireless sensor networks. However it has some shortcomings when it faces such problems as the cluster construction and energy management. In this paper, LEICP (low energy intelligent...... clustering protocol), an improvement of the LEACH protocol is proposed to overcome the shortcomings of LEACH. LEICP aims at balancing the energy consumption in every cluster and prolonging the network lifetime. A fitness function is defined to balance the energy consumption in every cluster according...

  6. Indoor Positioning System based on Bluetooth Low Energy

    OpenAIRE

    2014-01-01

    Bluetooth Low Energy is a new radio interface offered in all new smartphones. In addition to be able to transmit data, BLE can be used to locate things. [ANGLÈS] Bluetooth Low Energy is the new specification of Bluetooth available for all new smartphones. It is a new low power consumption technology aimed to transmit small amount of data. In addition to be able to transmit data, BLE can be used to locate things. iBeacon protocol, which uses BLE, is aimed at that objective with special atte...

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

    Science.gov (United States)

    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. Scattering of low-energy neutrinos on atomic shells

    Energy Technology Data Exchange (ETDEWEB)

    Babič, Andrej [Dept. of Dosimetry and Application of Ionizing Radiation, Czech Technical University, 115 19 Prague, Czech Rep. (Czech Republic); Institute of Experimental and Applied Physics, Czech Technical University, 128 00 Prague (Czech Republic); Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Šimkovic, Fedor [Institute of Experimental and Applied Physics, Czech Technical University, 128 00 Prague (Czech Republic); Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Department of Nuclear Physics and Biophysics, Comenius University, 842 48 Bratislava (Slovakia)

    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.

  9. Superconductivity and spin excitations in orbitally ordered FeSe

    Science.gov (United States)

    Kreisel, Andreas; Mukherjee, Shantanu; Hirschfeld, P. J.; Andersen, B. M.

    We provide a band-structure with low-energy properties consistent with recent photoemission and quantum oscillations measurements on the Fe-based superconductor FeSe, including a mean-field like orbital ordering in the dxz /dyz channel, and show that this model also accounts for the temperature dependence of the measured Knight shift and the spin-relaxation rate. An RPA calculation of the dynamical spin susceptibility yields spin excitations which are peaked at wave vector (π , 0) in the 1-Fe Brillouin zone, with a broad maximum at energies of order a few meV. Furthermore, the superconducting gap structure obtained from spin fluctuation theory exhibits nodes on the electron pockets, consistent with the 'V'-shaped density of states measured by tunneling spectroscopy on this material. The redistribution of spectral weight in the superconducting state creates a (π , 0) ''neutron resonance'' as seen in recent experiments. Comparing to various experimental results, we give predictions for further studies A.K. and B.M.A. acknowledge financial support from a Lundbeckfond fellowship (Grant No. A9318). P.J.H. was partially supported by the Department of Energy under Grant No. DE-FG02-05ER46236.

  10. Magnons, Spin Current and Spin Seebeck Effect

    Science.gov (United States)

    Maekawa, Sadamichi

    2012-02-01

    When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

  11. Critical fluctuations for quantum mean-field models

    Energy Technology Data Exchange (ETDEWEB)

    Fannes, M.; Kossakowski, A.; Verbeure, A. (Univ. Louvain (Belgium))

    1991-11-01

    A Ginzburg-Landau-type approximation is proposed for the local Gibbs states for quantum mean-field models that leads to the exact thermodynamics. Using this approach, the spin fluctuations are computed for some spin-1/2 models. At the critical temperature, the distribution function showing abnormal fluctuations is found explicitly.

  12. Low energy effective Lagrangians in open superstring theory

    Energy Technology Data Exchange (ETDEWEB)

    Medina, Ricardo [Universidade Federal de Itajuba, MG (Brazil). Inst. de Ciencias Exatas

    2008-07-01

    The low energy effective Lagrangian describes the interactions of the massless modes of String Theory. Present work is being done to obtain all alpha'{sup 3} terms (bosonic and fermionic) by means of the known 5-point amplitudes and SUSY.

  13. Mirrored low-energy channel for the MiniXRD

    Science.gov (United States)

    Dutra, E. C.; MacNeil, L. P.; Compton, S. M.; Jacoby, B. A.; Raphaelian, M. L.

    2015-08-01

    X-ray Diodes (XRDs) are currently used for spectroscopic measurements, measuring X-ray flux, and estimating spectral shape of the VUV to soft X-ray spectrum. A niche exists for an inexpensive, robust X-ray diode that can be used for experiments in hostile environments on multiple platforms, including explosively driven experiments that have the potential for destroying the diode during the experiment. A multiple channel stacked filtered array was developed with a small field of view where a wider parallel array could not be used, but filtered channels for energies lower than 1000 eV were too fragile to deploy under normal conditions. To achieve both the robustness and the required low-energy detection ability, we designed a small low-energy mirrored channel with a spectral sensitivity from 30 to 1000 eV. The stacked MiniXRD X-ray diode system design incorporates the mirrored low-energy channel on the front of the stacked filtered channels to allow the system to work within a small field of view. We will present results that demonstrate this is a promising solution for low-energy spectrum measurements.

  14. Low-energy CZT detector array for the ASIM mission

    DEFF Research Database (Denmark)

    Cenkeramaddi, Linga Reddy; Genov, Georgi; Kohfeldt, Anja

    2012-01-01

    In this article we introduce the low-energy CZT (CdZnTe) 16 384-pixel detector array on-board the Atmosphere Space Interaction Monitor (ASIM), funded by the European Space Agency. This detector is a part of the larger Modular X-and Gamma-ray sensor (MXGS). The CZT detector array is sensitive...

  15. Mirrored low-energy channel for the MiniXRD

    Energy Technology Data Exchange (ETDEWEB)

    Dutra, Eric [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); MacNeil, Lawrence [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Raphaelian, Mark [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Compton, Steve; Jacoby, Barry

    2015-10-08

    X-ray Diodes (XRDs) are currently used for spectroscopic measurements, measuring X-ray flux, and estimating spectral shape of the VUV to soft X-ray spectrum. A niche exists for an inexpensive, robust X-ray diode that can be used for experiments in hostile environments on multiple platforms, including explosively driven experiments that have the potential for destroying the diode during the experiment. A multiple channel stacked filtered array was developed with a small field of view where a wider parallel array could not be used, but filtered channels for energies lower than 1000 eV were too fragile to deploy under normal conditions. To achieve both the robustness and the required low-energy detection ability, the researchers designed a small low-energy mirrored channel with a spectral sensitivity from 30 to 1000 eV. The stacked MiniXRD X-ray diode system design incorporates the mirrored low-energy channel on the front of the stacked filtered channels to allow the system to work within a small field of view. We will present results that demonstrate this is a promising solution for low-energy spectrum measurements.

  16. Some Aspects of Low Energy Properties of Nucleons

    OpenAIRE

    Upadhyay, Alka

    2011-01-01

    We conclude that nucleon is a many body complex system whose low-energy behaviour is determined mainly by strong interaction. Non-perturbative approach to QCD, such as QCD sum rule and the QCD based effective theory, and the models such as a statistical model, have a complementary role in exposing different aspects of nucleonic properties.

  17. MEIC Proton Beam Formation with a Low Energy Linac

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuhong [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    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.

  18. Low energy electron microscopy imaging using Medipix2 detector

    NARCIS (Netherlands)

    Sikharulidze, I.; Gastel, van R.; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, van der S.J.

    2011-01-01

    Low Energy Electron Microscopy (LEEM) and Photo-Emission Electron Microscopy (PEEM) predominantly use a combination of microchannel plate (MCP), phosphor screen and optical camera to record images formed by 10–20 keV electrons. We have tested the performance of a LEEM/PEEM instrument with a Medipix2

  19. Compact Measurement Station for Low Energy Proton Beams

    CERN Document Server

    Yildiz, H.

    2017-01-01

    A compact, remote controlled, cost efficient diagnostic station has been developed to measure the charge, the profile and the emittance for low energy proton beams. It has been installed and tested in the proton beam line of the Project Prometheus at SANAEM of the Turkish Atomic Energy Authority.

  20. LOW ENERGY BEAM-GAS SPECTROSCOPY OF HIGHLY IONISED ATOMS

    OpenAIRE

    Desesquelles, J.; DENIS A.; Druetta, M.; Martin, S.

    1989-01-01

    Features of low energy beam-gas spectroscopic source are reviewed and compared to those of other light sources. Measurement techniques are surveyed. They include the study of wavelength of heavy multiply charged ions in visible and u.v. ranges from normal excited states, doubly excited states, high n levels and doubly excited Rydberg levels.

  1. Medipix 2 detector applied to low energy electron microscopy

    NARCIS (Netherlands)

    Gastel, van R.; Sikharulidze, I.; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, van der S.J.

    2009-01-01

    Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy.

  2. Low energy neutron propagation in MCNPX and GEANT4

    CERN Document Server

    Lemrani, R; Gerbier, G; Kudryavtsev, V A; Robinson, M; Spooner, N J C

    2006-01-01

    Simulations of neutron background from rock for underground experiments are presented. Neutron propagation through two types of rock, lead and hydrocarbon material is discussed. The results show a reasonably good agreement between GEANT4, MCNPX and GEANT3 in transporting low-energy neutrons.

  3. Low-energy limit of the extended Linear Sigma Model

    CERN Document Server

    Divotgey, Florian; Giacosa, Francesco; Rischke, Dirk H

    2016-01-01

    The extended Linear Sigma Model (eLSM) is an effective hadronic model based on the linear realization of chiral symmetry $SU(N_f)_L \\times SU(N_f)_R$, with (pseudo)scalar and (axial-)vector mesons as degrees of freedom. In this paper, we study the low-energy limit of the eLSM for $N_f=2$ flavors by integrating out all fields except for the pions, the (pseudo-)Nambu--Goldstone bosons of chiral symmetry breaking. We only keep terms entering at tree level and up to fourth order in powers of derivatives of the pion fields. Up to this order, there are four low-energy coupling constants in the resulting low-energy effective action. We show that the latter is formally identical to Chiral Perturbation Theory (ChPT), after choosing a representative for the coset space generated by chiral symmetry breaking and expanding up to fourth order in powers of derivatives of the pion fields. Two of the low-energy coupling constants of the eLSM are uniquely determined by a fit to hadron masses and decay widths. We find that thei...

  4. Positron impact ionization of atomic hydrogen at low energies

    Indian Academy of Sciences (India)

    K Chakrabarti

    2001-04-01

    Low energy positron impact ionization of atomic hydrogen is studies theoretically using the hyperspherical partial wave method of Das [1] in constant 12, equal energy sharing geometry. The TDCS reveal considerable differences in physics compared to electron impact ionization under the same geometry.

  5. Low-energy house in Sisimiut - Data overview

    DEFF Research Database (Denmark)

    Andersen, Philip Hvidthøft Delff; Rode, Carsten; Madsen, Henrik

    Experiments with persistently exciting heat inputs are a fundamental tool in identification of heat dynamics in buildings. The Low-energy house in Sisimiut, Greenland, provides an advanced experimental setup with frequent measurements of temperatures, heat inputs, and much more. This paper presents...

  6. Catalogue of Radionuclide Low-Energy Electron Spectra (LEES)

    CERN Document Server

    Vylov, T D; Kovalik, A; Yakushev, E A; Mahmoud, M; Novgorodov, A F; Lebedev, N A; Filossofov, D V; Briançon, C; Walen, R J; Coursol, N F; Minkova, A; Petev, P; Dragoun, O; Brabec, V; Inoyatov, A

    2003-01-01

    More than 100 of apparatus low-energy electron spectra from radionuclides with Z=24-95 are collected in the presented LEES Catalogue. These spectra have been recorded in systematical investigations of Auger and internal conversion electrons with the ESA-50 electrostatic spectrometer during past 20 years.

  7. Theoretical approaches to low energy $\\bar{K}N$ interactions

    CERN Document Server

    Cieply, Ales

    2016-01-01

    We provide a direct comparison of modern theoretical approaches based on the SU(3) chiral dynamics and describing the low energy $\\bar{K}N$ data. The model predictions for the $\\bar{K}N$ amplitudes and pole content of the models are discussed.

  8. Low-energy neutrino observation at Super-Kamiokande-III

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Y [Kamioka Observatory, ICRR, University of Tokyo, 456 Higashi-Mozumi, Kamioka-cho, Hida-shi, Gifu 506-1205 (Japan)], E-mail: takeuchi@icrr.u-tokyo.ac.jp

    2008-07-15

    Super-Kamiokande-III (SK-III) has been started its observation in July 2006. The main targets of low-energy neutrinos are the solar neutrinos and the diffuse supernova neutrino background. In this paper, the current status of the solar neutrino observation in SK-III is reported.

  9. Causality and universality in low-energy quantum scattering

    Energy Technology Data Exchange (ETDEWEB)

    Hammer, H.-W., E-mail: hammer@hiskp.uni-bonn.d [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Lee, Dean [Department of Physics, North Carolina State University, Raleigh, NC 27695 (United States); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany)

    2009-11-16

    We generalize Wigner's causality bounds and Bethe's integral formula for the effective range to arbitrary dimension and arbitrary angular momentum. Moreover, we discuss the impact of these constraints on the separation of low- and high-momentum scales and universality in low-energy quantum scattering.

  10. LHC to skip low-energy test runs

    CERN Multimedia

    Cartwright, Jon

    2007-01-01

    "The Large Hadron Collider will not be ready in time to perform a low-energy "engineering run", which was originally scheduled to take place this November, according to an official at CERN. This will leave the operators no chance to gain exerinece with the particle accelerator's steering and detection systems before the high-energy runs begin in spring next year." (1 page)

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

    Science.gov (United States)

    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.

  12. Utilization of low-energy electron accelerators in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byung Cheol [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2003-02-01

    There are more than 20 electron accelerators in Korea. Most of those are installed in factories for heat-resistant cables, heat-shrinkable cables, radial tires, foams, tube/ films, curing, etc. Four low-energy electron accelerators are in operation for research purposes such as polymer modification, purification of flue gas, waste water treatment, modification of semiconductor characteristics, etc. (author)

  13. Low-energy buildings on mainstream market terms

    DEFF Research Database (Denmark)

    Quitzau, Maj-Britt; Elle, Morten; Hoffmann, Birgitte

    2008-01-01

    This paper looks into the challenge of actually implementing energy efficient technologies and concepts in mainstream new build. The aim of the paper is to point out some of the provisos of promoting low-energy buildings on mainstream market terms, emphasising the need to understand forces working...

  14. Dynamical theory of spin relaxation

    Science.gov (United States)

    Field, Timothy R.; Bain, Alex D.

    2013-02-01

    The dynamics of a spin system is usually calculated using the density matrix. However, the usual formulation in terms of the density matrix predicts that the signal will decay to zero, and does not address the issue of individual spin dynamics. Using stochastic calculus, we develop a dynamical theory of spin relaxation, the origins of which lie in the component spin fluctuations. This entails consideration of random pure states for individual protons, and how these pure states are correctly combined when the density matrix is formulated. Both the lattice and the spins are treated quantum mechanically. Such treatment incorporates both the processes of spin-spin and (finite temperature) spin-lattice relaxation. Our results reveal the intimate connections between spin noise and conventional spin relaxation.

  15. Dynamically induced frustration as a route to a quantum spin ice state in Tb2Ti2O7 via virtual crystal field excitations and quantum many-body effects.

    Science.gov (United States)

    Molavian, Hamid R; Gingras, Michel J P; Canals, Benjamin

    2007-04-13

    The Tb2Ti2O7 pyrochlore magnetic material is attracting much attention for its spin liquid state, failing to develop long-range order down to 50 mK despite a Curie-Weiss temperature thetaCW approximately -14 K. In this Letter we reinvestigate the theoretical description of this material by considering a quantum model of independent tetrahedra to describe its low-temperature properties. The naturally tuned proximity of this system near a Néel to spin ice phase boundary allows for a resurgence of quantum fluctuation effects that lead to an important renormalization of its effective low-energy spin Hamiltonian. As a result, Tb2Ti2O7 is argued to be a quantum spin ice. We put forward an experimental test of this proposal using neutron scattering on a single crystal.

  16. The low-energy effective theory of QCD at small quark masses in a finite volume

    Energy Technology Data Exchange (ETDEWEB)

    Lehner, Christoph

    2010-01-15

    At low energies the theory of quantum chromodynamics (QCD) can be described effectively in terms of the lightest particles of the theory, the pions. This approximation is valid for temperatures well below the mass difference of the pions to the next heavier particles. We study the low-energy effective theory at very small quark masses in a finite volume V. The corresponding perturbative expansion in 1/{radical}(V) is called {epsilon} expansion. At each order of this expansion a finite number of low-energy constants completely determine the effective theory. These low-energy constants are of great phenomenological importance. In the leading order of the {epsilon} expansion, called {epsilon} regime, the theory becomes zero-dimensional and is therefore described by random matrix theory (RMT). The dimensionless quantities of RMT are mapped to dimensionful quantities of the low-energy effective theory using the leading-order lowenergy constants {sigma} and F. In this way {sigma} and F can be obtained from lattice QCD simulations in the '' regime by a fit to RMT predictions. For typical volumes of state-of-the-art lattice QCD simulations, finite-volume corrections to the RMT prediction cannot be neglected. These corrections can be calculated in higher orders of the {epsilon} expansion. We calculate the finite-volume corrections to {sigma} and F at next-to-next-to-leading order in the {epsilon} expansion. We also discuss non-universal modifications of the theory due to the finite volume. These results are then applied to lattice QCD simulations, and we extract {sigma} and F from eigenvalue correlation functions of the Dirac operator. As a side result, we provide a proof of equivalence between the parametrization of the partially quenched low-energy effective theory without singlet particle and that of the super-Riemannian manifold used earlier in the literature. Furthermore, we calculate a special version of the massless sunset diagram at finite volume without

  17. How to Succeed in Low-Energy Housing—Path Creation Analysis of Low-Energy Innovation Projects

    Directory of Open Access Journals (Sweden)

    Pia Pässilä

    2015-07-01

    Full Text Available The low-energy and the nearly zero-energy buildings trend is calling for radical new innovations from the construction industry. This study uses path creation theory to examine two innovation concepts for low-energy housing in Northern Europe with contrasting outcomes—with one being an apparent market success and the other a disappointment. The results highlight two issues behind the success, one of a systemic nature and the other concerning innovation management. First, the development of energy efficiency regulations and the dominant technological trajectory regarding low-energy houses are interdependent. However, it seems that while supporting the trajectory of the innovation developed in the first case, regulators created virtually insurmountable cognitive and normative obstacles to finding alternative technological pathways. Second, the significance of proof of concepts for new innovations cannot be underestimated. The importance of a pilot project rests not only on showcasing and testing the technology, but also on its ability to increase political support, investments, and public awareness. The study implies that low-energy construction seems to be the next great challenge, one where genuine co-operation between the industry, public authorities and academia is a prerequisite for success.

  18. On the determination of low-energy constants for $\\Delta S=1$ transitions

    CERN Document Server

    Giusti, Leonardo; Laine, Mikko; Peña, C; Wennekers, J; Wittig, H

    2005-01-01

    We present our preliminary results for three-point correlation functions involving the operators entering the $\\Delta{S}=1$ effective Hamiltonian with an active charm quark, obtained using overlap fermions in the quenched approximation. This is the first computation carried out for valence quark masses small enough so as to permit a matching to Quenched Chiral Perturbation Theory in the $\\epsilon$-regime. The commonly observed large statistical fluctuations are tamed by means of low-mode averaging techniques, combined with restrictions to individual topological sectors. We also discuss the matching of the resulting hadronic matrix elements to the effective low-energy constants for $\\Delta{S}=1$ transitions. This involves (a) finite-volume corrections which can be evaluated at NLO in Quenched Chiral Perturbation Theory, and (b) the short-distance renormalization of the relevant four-quark operators in discretizations based on the overlap operator. We discuss perturbative estimates for the renormalization facto...

  19. Optimization of the Energy Performance of a Low Energy House Based on Sensitivity Analysis

    Science.gov (United States)

    Sedláková, Anna; Geletka, Vladimír

    2013-11-01

    For buildings with for heating requirements, energy balance is based on the difference between two similarly large numbers (heat gain and heat loss) in which the calculation becomes increasingly sensitive to changes in parameters. The output of the hourly simulation method illustrates the temperature in "free-floating" mode, which unlike the requirement for heating provides better information on the thermal behavior of the building itself in order to model the dynamic response of the object to certain changes in the input data. For the purpose of the evaluation the minimum and maximum acceptable temperature and the area within the boundaries called comfort zone. In this paper a low energy house is evaluated in terms of energy performance and thermal comfort, where some parameters are altered in order to determine its sensitivity to fluctuations. The methodology is based on a sensitivity analysis (SA) and Monte Carlo simulation based on a stochastic random selection. Thermal comfort is evaluated using an adaptive thermal comfort.

  20. Evaluation of Low Energy Pack Ration by Short Term Feeding to Soldiers

    Directory of Open Access Journals (Sweden)

    K.R. Viswanathan

    1991-07-01

    Full Text Available Fifteen soldiers were fed, during intensive training including a patrol operation, on low energy pack(LEP ration for eight days for evaluating the suitability of the LEP ration providing 2100 kcal. Measurements were taken for body weight, skinfold thickness, blood cholesterol and phospholipids, glucose tolerance, and a battery of physical performance tests. Data were compared with another two identical groups of soldiers fed either a normal energy fresh(NEF ration(3631 kcal. The group on LEP ration lost 1.2 kg in body weight while the other two groups maintained their body weight with marginal fluctuations. Besides the slight loss of weight and a transient impairment of glucose tolerance, the subjects on LEP ration showed no other abnormality in any of the parameters studied. The study revealed that the LEP ration was suitable for feeding soldiers for short durations.

  1. Measurement of Low Energy Electronic Recoil Response and Electronic/Nuclear Recoils Discrimination in XENON100

    Science.gov (United States)

    Ye, Jingqiang; Xenon Collaboration

    2017-01-01

    The XENON100 detector uses liquid xenon time projection chamber to search for nuclear recoils(NR) caused by hypothetical Weakly Interacting Massive Particles (WIMPs). The backgrounds are mostly electronic recoils(ER), thus it's crucial to distinguish NR from ER. Using high statistical calibration data from tritiated methane, AmBe and other sources in XENON100, the ER/NR discrimination under different electric fields are measured. The Photon yield and recombination fluctuation of low energy electronic recoils under different fields will also be presented and compared to results from NEST and other experiments, which is crucial to understanding the response of liquid xenon detectors in the energy regime of searching dark matter.

  2. Extraction characteristics of a low-energy ion beam system with a remote plasma chamber

    Energy Technology Data Exchange (ETDEWEB)

    Vasquez, M. R., E-mail: mrvasquez@coe.upd.edu.ph [Department of Mining, Metallurgical, and Materials Engineering, College of Engineering, University of the Philippines, Diliman, Quezon City 1101 (Philippines); Wada, M. [Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321 (Japan)

    2016-02-15

    Low-energy argon beams were extracted from a dual-chamber ion source system. The first chamber is a quartz cylinder where dense inductively coupled plasmas were produced using 13.56 MHz radio frequency (rf) power. The discharge was driven into an adjacent chamber which acts as a reservoir for ion beam extraction using a dual-electrode extractor configuration. Extraction of ions from the second chamber with energies in the 100 eV range was achieved while minimizing fluctuations induced by the rf signal. A custom-built retarding potential analyzer was used to analyze the effectiveness of ion beam transport using the remote plasma chamber. Well-defined beams were extracted between 60 and 100 V extraction potentials at 50–100 W rf powers. An increase in rf power resulted in an increase in average ion energy, increase in ion current density while the energy spread remains constant.

  3. Applications of β-NMR and Low Energy μSR for Interface Engineering

    Science.gov (United States)

    Salman, Zaher

    2016-09-01

    One of the big hopes in material science today is the capability of producing materials and devices which satisfy a list of requirements/functions on demand. Interface engineering is proposed as a route to achieve this aim by growing thin film layered structures of different materials. Generally, the properties of the interfaces in these structures are different from those of the constituent materials. Of particular interest are interfaces between transition metal oxides (TMOs). This important class of materials exhibits a variety of physical properties and ground states including magnetic, superconducting, insulating and conducting. Therefore, heterostructures involving such materials provide a rich and interesting prospect for producing interfaces with physical properties not present, nor predictable, from the constituent materials, and may lead to new technological applications. Here we present applications of low energy beams of spin polarized 8Li and muons to study such interfaces, providing a unique depth resolved measurement of their magnetic properties on the nanometer scale.

  4. Kitaev spin models from topological nanowire networks

    NARCIS (Netherlands)

    Kells, G.; Lahtinen, V.; Vala, J.

    2014-01-01

    We show that networks of superconducting topological nanowires can realize the physics of exactly solvable Kitaev spin models on trivalent lattices. This connection arises from the low-energy theory of both systems being described by a tight-binding model of Majorana modes. In Kitaev spin models the

  5. LENDA, a Low Energy Neutron Detector Array for experiments with radioactive beams in inverse kinematics

    CERN Document Server

    Perdikakis, G; Austin, Sam M; Bazin, D; Caesar, C; Cannon, S; Deaven, J M; Doster, H J; Guess, C J; Hitt, G W; Marks, J; Meharchand, R; Nguyen, D T; Peterman, D; Prinke, A; Scott, M; Shimbara, Y; Thorne, K; Valdez, L; Zegers, R G T

    2011-01-01

    The Low Energy Neutron Detector Array (LENDA) is a neutron time-of-flight (TOF) spectrometer developed at the National Superconducting Cyclotron Lab- oratory (NSCL) for use in inverse kinematics experiments with rare isotope beams. Its design has been motivated by the need to study the spin-isospin response of unstable nuclei using (p, n) charge-exchange reactions at intermediate energies (> 100 MeV/u). It can be used, however, for any reaction study that involves emission of low energy neutrons (150 keV - 10 MeV). The array consists of 24 plastic scintillator bars and is capable of registering the recoiling neutron energy and angle with high detection efficiency. The neutron energy is determined by the time-of-flight technique, while the position of interaction is deduced using the timing and energy information from the two photomultipliers of each bar. A simple test setup utilizing radioactive sources has been used to characterize the array. Results of test measurements are compared with simulations. A neut...

  6. LENDA: A low energy neutron detector array for experiments with radioactive beams in inverse kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Perdikakis, G., E-mail: perdikak@nscl.msu.edu [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Sasano, M.; Austin, Sam M. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Bazin, D. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Caesar, C. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Cannon, S. [Hastings College, Hastings, NE 68901 (United States); Deaven, J.M.; Doster, H.J.; Guess, C.J.; Hitt, G.W. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Marks, J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Meharchand, R. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Joint Institute of Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824 (United States); Nguyen, D.T. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Peterman, D. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); and others

    2012-09-11

    The Low Energy Neutron Detector Array (LENDA) is a neutron time-of-flight (TOF) spectrometer developed at the National Superconducting Cyclotron Laboratory (NSCL) for use in inverse kinematics experiments with rare isotope beams. Its design has been motivated by the need to study the spin-isospin response of unstable nuclei using (p,n) charge-exchange reactions at intermediate energies (>100MeV/u). It can be used, however, for any reaction study that involves emission of low energy neutrons (150 keV to 10 MeV). The array consists of 24 plastic scintillator bars and is capable of registering the recoiling neutron energy and angle with high detection efficiency. The neutron energy is determined by the time-of-flight technique, while the position of interaction is deduced using the timing and energy information from the two photomultipliers of each bar. A simple test setup utilizing radioactive sources has been used to characterize the array. Results of test measurements are compared with simulations. A neutron energy threshold of <150keV, an intrinsic time (position) resolution of {approx} 400 ps ({approx} 6 cm) and an efficiency >20% for neutrons below 4 MeV have been obtained.

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

    Science.gov (United States)

    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.

  8. Low-Energy Electron Beam Direct Writing Equipment

    Science.gov (United States)

    Fuse, Takashi; Ando, Atsushi; Kotsugi, Tadashi; Kinoshita, Hidetoshi; Sugihara, Kazuyoshi

    2007-09-01

    We proposed an electron beam direct writing (EBDW) system capable of high throughput and maskless operation based on a novel concept of using both low-energy electron beam (EB) and character projection (CP) system. We fabricated an EB optical column of low-energy EBDW equipment and obtained a resist pattern. We also investigated the beam blur and line width roughness (LWR) of lines and spaces (L/S) formed on a resist to change various EB current densities and convergence half angles. The obtained results show that a Coulomb interaction effect markedly affects the beam blur in our EB optical column. Thus, we reduce the number of sources caused by LWR and developed photoresists to obtain small LWR L/S patterns for achieving a high throughput.

  9. Space charge compensation in low energy proton beams

    CERN Document Server

    Ismail, A B; Uriot, D; Pichoff, N

    2004-01-01

    High power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully managed. This nonlinear force can generate a high irreversible emittance growth of the beam. To reduce space charge effects, neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the dynamic study. Modelling the beam behaviour in such regime would be a significant contribution to the development of high intensity accelerators. Numerical and experimental study of SCC is in progress on the Saclay High Intensity Proton Injector. Experimental measurements and 2D/3D simulations of proton beam SCC will be presented.

  10. Low-energy (CaCu{2}O{8+δ}.

    Science.gov (United States)

    Plumb, N C; Reber, T J; Koralek, J D; Sun, Z; Douglas, J F; Aiura, Y; Oka, K; Eisaki, H; Dessau, D S

    2010-07-23

    Using low photon energy angle-resolved photoemission, we study the low-energy dispersion along the nodal (π,π) direction in Bi{2}Sr{2}CaCu{2}O{8+δ} as a function of temperature. Less than 10 meV below the Fermi energy, the high-resolution data reveal a novel "kinklike" feature in the electron self-energy that is distinct from the larger well-known kink roughly 70 meV below E{F}. This new kink is strongest below the superconducting critical temperature and weakens substantially at higher temperatures. A corollary of this finding is that the Fermi velocity v{F}, as measured in this low-energy range, varies rapidly with temperature-increasing by almost 30% from 70 to 110 K. The behavior of v{F}(T) appears to shift as a function of doping, suggesting a departure from simple "universality" in the nodal Fermi velocity of cuprates.

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

    Science.gov (United States)

    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.

  12. Antineutron and antiproton nuclear interactions at very low energies

    Science.gov (United States)

    Friedman, E.

    2014-05-01

    Experimental annihilation cross sections of antineutrons and antiprotons at very low energies are compared. Features of Coulomb focusing are observed for pbar annihilation on protons. Direct comparisons for heavier targets are not straightforward due to lack of overlap between targets and energies of experimental results for pbar and nbar. Nevertheless, the annihilation cross sections for nbar on nuclei cannot be described by an optical potential that fits well all the available data on pbar interactions with nuclei. Comparisons made with the help of this potential reveal in the nbar data features similar to Coulomb focusing. Direct comparisons between nbar and pbar annihilations at very low energies would be possible when pbar cross sections are measured on the same targets and at the same energies as the available cross sections for nbar. Such measurements may be possible in the foreseeable future.

  13. Patients with rett syndrome sustain low-energy fractures

    DEFF Research Database (Denmark)

    Roende, Gitte; Ravn, Kirstine; Fuglsang, Kathrine

    2011-01-01

    We present the first case-control study addressing both fracture occurrence and fracture mechanisms in Rett syndrome (RTT). Two previous studies have shown increased fracture risk in RTT. This was also our hypothesis regarding the Danish RTT population. Therefore, we investigated risk factors...... and x-ray evaluations. National register search on fracture diagnoses was done to obtain complete fracture histories. Our results showed that patients with RTT sustained significantly more low-energy fractures from early age compared with controls, even though overall fracture occurrence apparently...... was not increased. Low-energy fractures were significantly associated with less mobility and lack of ambulation. Associations with MECP2 mutations or epilepsy were not demonstrated, contrary to previous findings. Blood biochemistry indicated a possible need for D vitamin supplementation in RTT. Our study casts...

  14. A primer for electroweak induced low-energy nuclear reactions

    Indian Academy of Sciences (India)

    Y N Srivastava; A Widom; L Larsen

    2010-10-01

    Under special circumstances, electromagnetic and weak interactions can induce low-energy nuclear reactions to occur with observable rates for a variety of processes. A common element in all these applications is that the electromagnetic energy stored in many relatively slow-moving electrons can – under appropriate circumstances – be collectively transferred into fewer, much faster electrons with energies sufficient for the latter to combine with protons (or deuterons, if present) to produce neutrons via weak interactions. The produced neutrons can then initiate low-energy nuclear reactions through further nuclear transmutations. The aim of this paper is to extend and enlarge upon various examples analysed previously, present order of magnitude estimates for each and to illuminate a common unifying theme amongst all of them.

  15. Consumer Unit for Low Energy District Heating Net

    DEFF Research Database (Denmark)

    Paulsen, Otto; Fan, Jianhua; Furbo, Simon

    2008-01-01

    A low energy/ low temperature consumer installation is designed and analyzed. The consumer type is a low energy single family house 145 m2 with annual energy consumption in the range of 7000 kWh, incl. domestic hot water in a 2800 degree day climate. The network is an extreme low temperature system...... to reduce heat loss in the network. The consumer’s installation is a unit type with an accumulation tank for smoothing the heat load related to the domestic hot water. The building heat load is delivered by an under-floor heating system. The heavy under-floor heating system is assumed to smooth the room...... heat load on a daily basis, having a flow temperature control based on outdoor climate. The unit is designed for a near constant district heating water flow. The paper describes two concepts. The analyses are based on TRNSYS (Klein et al., 2006) simulation, supplied with laboratory verification...

  16. Radiation processing of liquid with low energy electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Makuuchi, Keizo [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    2003-02-01

    Radiation induced emulsion polymerization, radiation vulcanization of NR latex (RVNRL) and radiation degradation of natural polymers were selected and reviewed as the radiation processing of liquid. The characteristic of high dose rate emulsion polymerization is the occurrence of cationic polymerization. Thus, it can be used for the production of new materials that cannot be obtained by radical polymerization. A potential application will be production of polymer emulsion that can be used as water-borne UV/EB curing resins. The technology of RVNRL by {gamma}-ray has been commercialized. RVNRL with low energy electron accelerator is under development for further vulcanization cost reduction. Vessel type irradiator will be favorable for industrial application. Radiation degradation of polysaccharides is an emerging and promising area of radiation processing. However, strict cost comparison between liquid irradiation with low energy EB and state irradiation with {gamma}-ray should be carried out. (author)

  17. Low-energy supersymmetry breaking and fermion mass hierarchies

    CERN Document Server

    Gherghetta, Tony; Poppitz, E R; Gherghetta, Tony; Jungman, Gerard; Poppitz, Erich

    1995-01-01

    In models with low-energy supersymmetry breaking, an anomalous Abelian horizontal gauge symmetry can simultaneously explain the fermion mass hierarchy and the values of the \\mu and B terms. We construct an explicit model where the anomaly is cancelled by the Green-Schwarz mechanism at the string scale. We show that with our charge assignments, the breaking of the horizontal symmetry generates the correct order of magnitude and correct hierarchy for all Yukawa couplings.

  18. Negative ions as a source of low energy neutral beams

    Energy Technology Data Exchange (ETDEWEB)

    Fink, J.H.

    1980-01-01

    Little consideration has been given to the impact of recent developments in negative ion source technology on the design of low energy neutral beam injectors. However, negative ion sources of improved operating efficiency, higher gas efficiency, and smaller beam divergence will lead to neutral deuterium injectors, operating at less than 100 keV, with better operating efficiencies and more compact layouts than can be obtained from positive ion systems.

  19. Selected Papers on Low-Energy Antiprotons and Possible Applications

    Energy Technology Data Exchange (ETDEWEB)

    Noble, Robert [Fermilab

    1998-09-19

    The only realistic means by which to create a facility at Fermilab to produce large amounts of low energy antiprotons is to use resources which already exist. There is simply too little money and manpower at this point in time to generate new accelerators on a time scale before the turn of the century. Therefore, innovation is required to modify existing equipment to provide the services required by experimenters.

  20. New views on the low-energy side of gravity

    OpenAIRE

    Piazza, Federico

    2009-01-01

    Common wisdom associates all the unraveled and theoretically challenging aspects of gravity with its UV-completion. However, there appear to be few difficulties afflicting the effective framework for gravity already at low energy, that are likely to be detached from the high-energy structure. Those include the black hole information paradox, the cosmological constant problem and the rather involved and fine tuned model building required to explain our cosmological observations. I review some ...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Sustainable Heating/Cooling for Low Energy Buildings

    DEFF Research Database (Denmark)

    Krajčík, M.; Olesen, Bjarne W.; Petráš, D.

    2012-01-01

    Experimental evaluation is one of the means that allow thorough investigation of the indoor environment in a room. Providing that the measurement procedures are correct and that the investigator has the necessary experimental equipment available, experimental measurements can provide results with...... located in a low-energy building. Procedures and indicators that can be successfully used for experimental investigations of indoor environment are described and a sample of measured data is reported....

  3. A Low energy neutrino factory for large theta(13)

    Energy Technology Data Exchange (ETDEWEB)

    Geer, Steve; Mena, Olga; /Fermilab /Rome U. /INFN, Rome; 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}.

  4. Enhancement of surface processes with low energy ions

    Energy Technology Data Exchange (ETDEWEB)

    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.

  5. Improving Indoor Localization Using Bluetooth Low Energy Beacons

    Directory of Open Access Journals (Sweden)

    Pavel Kriz

    2016-01-01

    Full Text Available The paper describes basic principles of a radio-based indoor localization and focuses on the improvement of its results with the aid of a new Bluetooth Low Energy technology. The advantage of this technology lies in its support by contemporary mobile devices, especially by smartphones and tablets. We have implemented a distributed system for collecting radio fingerprints by mobile devices with the Android operating system. This system enables volunteers to create radio-maps and update them continuously. New Bluetooth Low Energy transmitters (Apple uses its “iBeacon” brand name for these devices have been installed on the floor of the building in addition to existing WiFi access points. The localization of stationary objects based on WiFi, Bluetooth Low Energy, and their combination has been evaluated using the data measured during the experiment in the building. Several configurations of the transmitters’ arrangement, several ways of combination of the data from both technologies, and other parameters influencing the accuracy of the stationary localization have been tested.

  6. Ultra-low energy storage ring at FLAIR

    Energy Technology Data Exchange (ETDEWEB)

    Welsch, Carsten P., E-mail: c.p.welsch@liverpool.ac.uk [Cockcroft Institute and the University of Liverpool (United Kingdom); Papash, A. I.; Gorda, O. [Max Planck Institute for Nuclear Physics (Germany); Harasimowicz, J. [Cockcroft Institute and University of Liverpool (United Kingdom); Karamyshev, O.; Karamysheva, G. [Max Planck Institute for Nuclear Physics (Germany); Newton, D. [Cockcroft Institute and University of Liverpool (United Kingdom); Panniello, M. [Max Planck Institute for Nuclear Physics (Germany); Putignano, M.; Siggel-King, M. R. F. [Cockcroft Institute and University of Liverpool (United Kingdom); Smirnov, A. [Max Planck Institute for Nuclear Physics (Germany)

    2012-12-15

    The Ultra-low energy electrostatic Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) will provide cooled beams of antiprotons in the energy range between 300 keV down to 20 keV and possibly less. The USR has been completely redesigned over the past three years. The ring structure is based on a 'split achromat' lattice that allows in-ring experiments with internal gas jet target. Beam parameters might be adjusted in a wide range: from very short pulses in the nanosecond regime to a Coasting beam. In addition, a combined fast and slow extraction scheme was developed that allows for providing external experiments with cooled beams of different time structure. Detailed investigations of the USR, including studies into the ring's long term beam dynamics, life time, equilibrium momentum spread and equilibrium lateral spread during collisions with an internal target were carried out. New tools and beam handling techniques for diagnostics of ultra-low energy ions at beam intensities less than 10{sup 6} were developed by the QUASAR Group. In this paper, progress on the USR project will be presented with an emphasis on the expected beam parameters available to the experiments at FLAIR.

  7. Spin-Stripe Density Varies Linearly With the Hole Content in Single-Layer Bi2+xSr2-xCuO6+y Cuprate Superconductors

    Science.gov (United States)

    Enoki, M.; Fujita, M.; Nishizaki, T.; Iikubo, S.; Singh, D. K.; Chang, S.; Tranquada, J. M.; Yamada, K.

    2013-01-01

    We have performed inelastic neutron scattering measurements on the single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x=0.2, 0.3, 0.4, and 0.5, a doping range that spans the spin-glass to superconducting phase boundary. The doping evolution of low energy spin fluctuations (≲11meV) was found to be characterized by a change in the incommensurate modulation wave vector from the tetragonal [110] to [100]/[010] directions, while maintaining a linear relation between the incommensurability and the hole concentration, δ≈p. In the superconducting regime, the spectral weight is strongly suppressed below ˜4meV. Similarities and differences in the spin correlations between Bi2201 and the prototypical single-layer system La2-xSrxCuO4 are discussed.

  8. Coupling of Spin and Orbital Excitations in the Iron-based Superconductor FeSe0.5Te0.5

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.H.; Xu, G.; Ku, W.; Wen, J.S.; Lee, C.C.: Katayama, N.; Xu, Z.J.; Ji, S.; Lin, Z.W.; Gu, G. D.; Yang, H.-B.; Johnson, P.D.; Pan, Z.-H.; Valla, T.; Fujita, M.; Sato, T.J.; Chang, S.; Yamada, K.; Tranquada, J.M.

    2010-06-14

    We present a combined analysis of neutron scattering and photoemission measurements on superconducting FeSe{sub 0.5}Te{sub 0.5}. The low-energy magnetic excitations disperse only in the direction transverse to the characteristic wave vector (1/2,0,0) whereas the electronic Fermi surface near (1/2,0,0) appears to consist of four incommensurate pockets. While the spin resonance occurs at an incommensurate wave vector compatible with nesting, neither spin-wave nor Fermi-surface-nesting models can describe the magnetic dispersion. We propose that a coupling of spin and orbital correlations is key to explaining this behavior. If correct, it follows that these nematic fluctuations are involved in the resonance and could be relevant to the pairing mechanism.

  9. Coupling of spin and orbital excitations in the iron-based superconductor FeSe0.5Te0.5

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.-H.; Xu, Guangyong; Ku, Wei; Wen, J.S.; Lee, C.C.; Katayama, N.; Xu, Z.J.; Ji, S.; Lin, Z.W.; Gu, G.D.; Yang, H.-B.; Johnson, Peter D.; Pan, Z.-H.; Valla, Tonica; Fujita, M.; Sato, T.J.; Chang, S.; Yamada, K.; Tranquada, John M.

    2010-06-14

    We present a combined analysis of neutron scattering and photoemission measurements on superconducting FeSe{sub 0.5} Te{sub 0.5} . The low-energy magnetic excitations disperse only in the direction transverse to the characteristic wave vector (1/2 ,0,0) whereas the electronic Fermi surface near (1/2 ,0,0) appears to consist of four incommensurate pockets. While the spin resonance occurs at an incommensurate wave vector compatible with nesting, neither spin-wave nor Fermi-surface-nesting models can describe the magnetic dispersion. We propose that a coupling of spin and orbital correlations is key to explaining this behavior. If correct, it follows that these nematic fluctuations are involved in the resonance and could be relevant to the pairing mechanism.

  10. Review of rest gas interaction at very low energies applied to the Extra Low Energy Antiproton ring ELENA

    CERN Document Server

    Carli, C; Karamyshev, O; Welsch, C P

    2014-01-01

    The Extremely Low ENergy Antiproton ring (ELENA) is a small synchrotron equipped with an electron cooler, which shall be constructed at CERN to decelerate antiprotons to energies as low as 100 keV. Scattering of beam particles on rest gas molecules may have a detrimental effect at such low energies and leads to stringent vacuum requirements. Within this contribution scattering of the stored beam on rest gas molecules is discussed for very low beam energies. It is important to carefully distinguish between antiprotons scattered out of the acceptance and lost, and those remaining inside the aperture to avoid overestimation of emittance blow-up. Furthermore, many antiprotons do not interact at all during the time they are stored in ELENA and hence this is not a multiple scattering process

  11. Low-energy effective field theory of superfluid 3He-B and its gyromagnetic and Hall responses

    CERN Document Server

    Fujii, Keisuke

    2016-01-01

    The low-energy physics of a superfluid 3He-B is governed by Nambu-Goldstone bosons resulting from its characteristic symmetry breaking pattern. Here we construct an effective field theory at zero temperature consistent with all available symmetries in curved space, which are the U(1) phase x SU(2) spin x SO(3) orbital gauge invariance and the nonrelativistic general coordinate invariance, up to the next-to-leading order in a derivative expansion. The obtained low-energy effective field theory is capable of predicting gyromagnetic responses of the superfluid 3He-B, such as a magnetization generated by a rotation and an orbital angular momentum generated by a magnetic field, in a model-independent and nonperturbative way. We furthermore show that the stress tensor exhibits a dissipationless Hall viscosity with coefficients uniquely fixed by the orbital angular momentum density, which manifests itself as an elliptical polarization of sound wave with an induced transverse component.

  12. Dissipative Dynamics of Quantum Fluctuations

    CERN Document Server

    Benatti, F; Floreanini, R

    2015-01-01

    One way to look for complex behaviours in many-body quantum systems is to let the number $N$ of degrees of freedom become large and focus upon collective observables. Mean-field quantities scaling as $1/N$ tend to commute, whence complexity at the quantum level can only be inherited from complexity at the classical level. Instead, fluctuations of microscopic observables scale as $1/\\sqrt{N}$ and exhibit collective Bosonic features, typical of a mesoscopic regime half-way between the quantum one at the microscopic level and the classical one at the level of macroscopic averages. Here, we consider the mesoscopic behaviour emerging from an infinite quantum spin chain undergoing a microscopic dissipative, irreversible dynamics and from global states without long-range correlations and invariant under lattice translations and dynamics. We show that, from the fluctuations of one site spin observables whose linear span is mapped into itself by the dynamics, there emerge bosonic operators obeying a mesoscopic dissipa...

  13. Experimental Realization of a Quantum Spin Pump

    DEFF Research Database (Denmark)

    Watson, Susan; Potok, R.; M. Marcus, C.;

    2003-01-01

    We demonstrate the operation of a quantum spin pump based on cyclic radio-frequency excitation of a GaAs quantum dot, including the ability to pump pure spin without pumping charge. The device takes advantage of bidirectional mesoscopic fluctuations of pumped current, made spin......-dependent by the application of an in-plane Zeeman field. Spin currents are measured by placing the pump in a focusing geometry with a spin-selective collector....

  14. Topological Effects on Quantum Phase Slips in Superfluid Spin Transport

    Science.gov (United States)

    Kim, Se Kwon; Tserkovnyak, Yaroslav

    2016-03-01

    We theoretically investigate effects of quantum fluctuations on superfluid spin transport through easy-plane quantum antiferromagnetic spin chains in the large-spin limit. Quantum fluctuations result in the decaying spin supercurrent by unwinding the magnetic order parameter within the easy plane, which is referred to as phase slips. We show that the topological term in the nonlinear sigma model for the spin chains qualitatively differentiates the decaying rate of the spin supercurrent between the integer versus half-odd-integer spin chains. An experimental setup for a magnetoelectric circuit is proposed, in which the dependence of the decaying rate on constituent spins can be verified by measuring the nonlocal magnetoresistance.

  15. Spin Transport by Collective Spin Excitations

    Science.gov (United States)

    Hammel, P. Chris

    We report studies of angular momentum transport in insulating materials. Our measurements reveal efficient spin pumping from high wavevector k spin waves in thin film Y3Fe5O12 (YIG): spin pumping is independent of wavevector up to k ~ 20 μm-1. Optical detection of YIG FMR by NV centers in diamond reveals a role for spin waves in this insulator-to-insulator spin transfer process. Spin transport is typically suppressed by insulating barriers, but we find that fluctuating antiferromagnetic correlations enable efficient spin transport at nm-scale thicknesses in insulating antiferromagnets, even in the absence of long-range order, and that the spin decay length increases with the strength of the antiferromagnetic correlations. This research is supported by the U.S. DOE through Grants DE-FG02-03ER46054 and DE-SC0001304, by the NSF MRSEC program through Grant No. 1420451 and by the Army Research Office through Grant W911NF0910147.

  16. Precise tests of fundamental symmetries at low energies using a {sup 3}He-{sup 129}Xe comagnetometer

    Energy Technology Data Exchange (ETDEWEB)

    Allmendinger, Fabian

    2015-01-21

    Effects of theories beyond the Standard Model would become directly apparent at high energies, which are probably out of reach for colliders. As an alternative, low-energy high-precision measurements of quantities are performed, looking for deviations from the Standard Model (SM) predictions. In this case: Firstly, a small amount of the large effects of quantum gravity at the Planck scale should remain at low energies, which is tested by looking for Lorentz invariance violation in the neutron sector. Secondly, new sources of CP-violation would cause permanent electric dipole moments (EDMs)of particles that are many orders of magnitude larger than the EDMs predicted by the SM. The experimental approach is to measure the free precession of nuclear spin polarized {sup 3}He and {sup 129}Xe atoms in a homogeneous magnetic guiding field of about 400 nT using LT{sub C} SQUIDs as low-noise magnetic flux detectors. This dissertation reports on the search for a CPT and Lorentz invariance violating coupling of the {sup 3}He and {sup 129}Xe nuclear spins to posited background fields. An upper limit on the equatorial component of the background field interacting with the spin of the bound neutron b{sup n} {sub perpendicular} {sub to} <8.4.10{sup -34} GeV (68% C.L.) was obtained. Furthermore, the technical developments and preparations for measurements of the {sup 129}Xe EDM are described.

  17. On Spinning-String Solutions in the Low Energy Regime of String Theory

    OpenAIRE

    "道下, 洋二"

    2009-01-01

    弦理論において弦のさまざまな古典解、特にブラックホール解を熱的統計集団であると考えることは閉じた弦に対してはしばしば行われてきたが、開いた弦の場合も知られているよりもっとさまざまな解が存在して、同様のことが行えないかを考察する。

  18. Developing effective rockfall protection barriers for low energy impacts

    Science.gov (United States)

    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

  19. Absence of Magnetic Dipolar Phase Transition and Evolution of Low-Energy Excitations in PrNb2Al20 with Crystal Electric Field Γ3 Ground State: Evidence from 93Nb-NQR Studies

    Science.gov (United States)

    Kubo, Tetsuro; Kotegawa, Hisashi; Tou, Hideki; Higashinaka, Ryuji; Nakama, Akihiro; Aoki, Yuji; Sato, Hideyuki

    2015-07-01

    We report measurements of bulk magnetic susceptibility and 93Nb nuclear quadrupole resonance (NQR) in the Pr-based caged compound PrNb2Al20. By analyzing the magnetic susceptibility and magnetization, the crystal electric field (CEF) level scheme of PrNb2Al20 is determined to be Γ3(0 K)-Γ4(21.32 K)-Γ5(43.98 K)-Γ1(51.16 K) within the framework of the localized 4f electron picture. The 93Nb-NQR spectra exhibit neither spectral broadening nor spectral shift upon cooling down to 75 mK. The 93Nb-NQR spin-lattice relaxation rate 1/T1 at 5 K depends on the frequency and remains almost constant below 5 K. The frequency dependence of 1/T1 is attributed to the magnetic fluctuation due to the hyperfine-enhanced 141Pr nuclear moment inherent in the nonmagnetic Γ3 CEF ground state. The present NQR results provide evidence that no symmetry-breaking magnetic dipole order occurs down to 75 mK. Also, considering an invariant form of the quadrupole and octupole couplings between a 93Nb nucleus and Pr 4f electrons, Pr 4f quadrupoles and an octupole can couple with a 93Nb nuclear quadrupole moment and nuclear spin, respectively. Together with the results of bulk measurements, the present NQR results suggest that the possibility of a static quadrupole or octupole ordering can be excluded down to 100 mK. At low temperatures below 500 mK, however, the nuclear spin-echo decay rate gradually increases and the decay curve changes from Gaussian decay to Lorentzian decay, suggesting the evolution of a low-energy excitation.

  20. EPIDEMIOLOGICAL STUDY OF LOW ENERGY FRACTURES IN REPUBLIC OF ARMENIA

    Directory of Open Access Journals (Sweden)

    S. Saakyan

    2017-01-01

    Full Text Available Until present no data was available inArmeniain respect of incidence of low energy fractures that are typical of osteoporotic locations which consequently did not allow to evaluate the scope of this problem across the country.Purpose of the study – to identify the incidence of low energy fractures in proximal femur, in distal forearm, in proximal humerus and in distal tibia across population ofArmenia aged 50 years and older.Materials and methods. An observing population study was performed in two regions of Armenia during 2011-2013 where the frequency of selected locations in cases of moderate trauma was identified. During 2011-2012 the information was collected based on traumatology service records adding in 2013 other sources including primary level of healthcare due to observed infrequent applications for medical help in cases of trauma. Results. In 2013 the incidence of proximal femur fractures in men was reported as 136 cases per 100 000 of population aged 50 years and older, in women – 201 cases per 100 000. At the same time only 57.7% of patients with proximal femur fractures were admitted to hospital. Distal forearm fractures incidence in men and women was observed correspondingly 56/100 000 and 176/100 000 cases, proximal humerus fractures – 39/100 000 and 86/100 000 cases and distal tibia fractures – 39/100 000 and 86/100 000 cases. The predicted annual number of proximal femur fracture in Armenia amounts to 2067 cases, distal forearm fractures – 1205, proximal humerus fractures – 640.Conclusion. Epidemiological data that was collected for the first time on low energy fractures incidence confirmed the acute osteoporosis issue inArmenia and revealed the problems in organization of medical care for the group of senior patients with injuries.

  1. RADIATION HAZARD AND PROTECTION OF LOW ENERGY ACCELERATORS

    Institute of Scientific and Technical Information of China (English)

    雷清章

    1994-01-01

    In this paper,the origin and type of radiation hazards as well as the main aspects of radiation protection for low-energy accelerators are discussed in general,and the problems of radiation protection and the experimental results of the operational monitoring of the five accelecrators in the Institute of Nuclear Science and Technology,Sichuan University,namely,one 1.2M cyclofron,two Cockroft-waltons and two Van de Graafts,as well as a powerful electron accelerator for industrial irradiation are described.The discussion and evaluation are made according to the requirments of the national standards GB5172-85.

  2. Low energy electron beams for industrial and environmental applications

    CERN Document Server

    Skarda, Vlad

    2017-01-01

    EuCARD-2 Workshop, 8-9 December 2016, Warsaw, Poland. Organizers: Science and Technology Facilities Council, UK CERN - The European Organization for Nuclear Research, Switzerland, Institute of Nuclear Chemistry and Technology, Poland, Fraunhofer Institute for Electron Beam and Plasma Technology, Germany, Warsaw University of Technology, Poland. An article presents short information about EuCARD-2 Workshop “Low energy electron beams for industrial and environmental applications”, which was held in December 2016 in Warsaw. Objectives, main topics and expected output of meeting are described. List of organizers is included.

  3. Energy performance of the low-energy house in Greenland

    DEFF Research Database (Denmark)

    Kragh, Jesper; Svendsen, Svend

    2005-01-01

    energy gain, efficient ventilation system with heat recovery and solar heating. In this paper the results of a calculation of the energy consumption of low-energy house is presented. The calculation was done using the program BSim2002 [1] and a new weather test reference year based on climatic data...... by ventilation heat recovery (90% efficiency) specially designed for arctic conditions, by using thicker insulation in walls (300 mm) and roof/floor (350 mm), and by using solar hot water heating (3250 kWh/year). The building is intended to enhance sustainability in the building sector in Greenland....

  4. Low-energy features of a 1-tev higgs sector

    CERN Document Server

    Appelquist, Thomas

    1979-01-01

    It seems very likely that the Higgs sector of a spontaneously broken gauge theory could be heavy (M = 1 TeV) and strongly interacting. By exploiting the intimate connection of such theories to nonlinear a models, it is possible to show under quite general conditions what sort of impact the heavy Higgs sector can have on low energy experiments (E << 1 TeV). In this talk, the techniques and results will be summar- ized for an SU(2) gauge theory, The analysis of the Weinberg-Salam and other realistic theories will appear in a forthcoming paper.

  5. Characterization of low energy radioactive beams using direct reactions

    DEFF Research Database (Denmark)

    Johansen, J.G.; Fraser, M.A.; Bildstein, V.

    2013-01-01

    We demonstrate a new technique to determine the beam structure of low energy radioactive beams using coincidence events from a direct reaction. The technique will be described and tested using Geant4 simulations. We use the technique to determine for the first time the width, divergence and energy...... of an accelerated radioactive beam produced at ISOLDE. We use data from an experiment with an 11Be beam incident on a deuteron target producing 10Be from a (d,t) reaction. The T-REX Si detector array was used for particle detection, but the technique is applicable for other setups....

  6. Validation of GPUMCD for low-energy brachytherapy seed dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Hissoiny, Sami; Ozell, Benoit; Despres, Philippe; Carrier, Jean-Francois [Ecole polytechnique de Montreal, Departement de genie informatique et genie logiciel, 2500 chemin de Polytechnique, Montreal, QC, H3T 1J4 (Canada); Departement de radio-oncologie, Centre hospitalier universitaire de Quebec (CHUQ), 11 Cote du Palais, Quebec, QC, G1R 2J6 (Canada); Departement de physique, Universite de Montreal, Montreal, QC (Canada) and Departement de radio-oncologie and Centre de recherche du CHUM, Centre hospitalier de l' Universite de Montreal (CHUM), Montreal, QC, H2L 4M1 (Canada)

    2011-07-15

    Purpose: To validate GPUMCD, a new package for fast Monte Carlo dose calculations based on the GPU (graphics processing unit), as a tool for low-energy single seed brachytherapy dosimetry for specific seed models. As the currently accepted method of dose calculation in low-energy brachytherapy computations relies on severe approximations, a Monte Carlo based approach would result in more accurate dose calculations, taking in to consideration the patient anatomy as well as interseed attenuation. The first step is to evaluate the capability of GPUMCD to reproduce low-energy, single source, brachytherapy calculations which could ultimately result in fast and accurate, Monte Carlo based, brachytherapy dose calculations for routine planning. Methods: A mixed geometry engine was integrated to GPUMCD capable of handling parametric as well as voxelized geometries. In order to evaluate GPUMCD for brachytherapy calculations, several dosimetry parameters were computed and compared to values found in the literature. These parameters, defined by the AAPM Task-Group No. 43, are the radial dose function, the 2D anisotropy function, and the dose rate constant. These three parameters were computed for two different brachytherapy sources: the Amersham OncoSeed 6711 and the Imagyn IsoStar IS-12501. Results: GPUMCD was shown to yield dosimetric parameters similar to those found in the literature. It reproduces radial dose functions to within 1.25% for both sources in the 0.5< r <10 cm range. The 2D anisotropy function was found to be within 3% at r = 5 cm and within 4% at r = 1 cm. The dose rate constants obtained were within the range of other values reported in the literature.Conclusion: GPUMCD was shown to be able to reproduce various TG-43 parameters for two different low-energy brachytherapy sources found in the literature. The next step is to test GPUMCD as a fast clinical Monte Carlo brachytherapy dose calculations with multiple seeds and patient geometry, potentially providing

  7. Early forest fire detection using low-energy hydrogen sensors

    Directory of Open Access Journals (Sweden)

    K. Nörthemann

    2013-11-01

    Full Text Available Most huge forest fires start in partial combustion. In the beginning of a smouldering fire, emission of hydrogen in low concentration occurs. Therefore, hydrogen can be used to detect forest fires before open flames are visible and high temperatures are generated. We have developed a hydrogen sensor comprising of a metal/solid electrolyte/insulator/semiconductor (MEIS structure which allows an economical production. Due to the low energy consumption, an autarkic working unit in the forest was established. In this contribution, first experiments are shown demonstrating the possibility to detect forest fires at a very early stage using the hydrogen sensor.

  8. Use of a streamer chamber for low energy nuclear physics

    Energy Technology Data Exchange (ETDEWEB)

    Van Bibber, K.; Pang, W.; Avery, M.; Bloemhof, E.

    1979-10-01

    A small streamer chamber has been implemented for low energy heavy ion reaction studies at the LBL 88-inch cyclotron. The response of the chamber to light and heavy ions below 35 MeV/nucleon has been examined. The limited sensitivity of light output as a function of ionization works to advantage in recording a wide variety of tracks in the same photograph whose energy loss may vary considerably. Furthermore, as gas targets are attractive for several reasons, we have investigated the suitability of Ar and Xe for use in streamer chambers.

  9. Modelling low energy electron interactions for biomedical uses of radiation

    Energy Technology Data Exchange (ETDEWEB)

    Fuss, M; Garcia, G [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones CientIficas (CSIC), Serrano 113-bis, 28006 Madrid (Spain); Munoz, A; Oller, J C [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avenida Complutense 22, 28040 Madrid (Spain); Blanco, F [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Avenida Complutense s.n., 28040 Madrid (Spain); Limao-Vieira, P [Departamento de Fisica, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Huerga, C; Tellez, M [Hospital Universitario La Paz, paseo de la Castellana 261, 28046 Madrid (Spain); Hubin-Fraskin, M J [Department of Chemistry, University of Liege, 4000 Liege 1 (Belgium); Nixon, K; Brunger, M, E-mail: g.garcia@imaff.cfmac.csic.e [School of Chemistry, Physics and Earth Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia)

    2009-11-15

    Current radiation based medical applications in the field of radiotherapy, radio-diagnostic and radiation protection require modelling single particle interactions at the molecular level. Due to their relevance in radiation damage to biological systems, special attention should be paid to include the effect of low energy secondary electrons. In this study we present a single track simulation procedure for photons and electrons which is based on reliable experimental and theoretical cross section data and the energy loss distribution functions derived from our experiments. The effect of including secondary electron interactions in this model will be discussed.

  10. Matter-Antimatter Asymmetry - Aspects at Low Energy

    CERN Document Server

    Willmann, Lorenz

    2015-01-01

    The apparent dominance of matter over antimatter in our universe is an obvious and puzzling fact which cannot be adequately explained in present physical frameworks that assume matter-antimatter symmetry at the big bang. However, our present knowledge of starting conditions and of known sources of CP violation are both insufficient to explain the observed asymmetry. Therefore ongoing research on matter-antimatter differences is strongly motivated as well as attempts to identify viable new mechanisms that could create the present asymmetry. Here we concentrate on possible precision experiments at low energies towards a resolution of this puzzle.

  11. Low Energy Lorentz Violation from Modified Dispersion at High Energies.

    Science.gov (United States)

    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.

  12. The lowest resonance in QCD from low--energy data

    CERN Document Server

    Ametller, L

    2014-01-01

    We show that a generalization of $su(2)$ Chiral Perturbation Theory, including a perturbative singlet scalar field, converges faster towards the physical value of sensible low--energy observables. The physical mass and width of the scalar particle are obtained through a simultaneous analysis of the pion radius and the gamma gamma -> pi^0 pi^0 cross-section. Both values are statistically consistent with the ones obtained by using Roy equations in pi-pi scattering. In addition we find indications that the photon-photon-singlet coupling is quite small.

  13. GEANT4 simulations for low energy proton computerized tomography

    Energy Technology Data Exchange (ETDEWEB)

    Milhoretto, Edney [Federal University of Technology-Parana, UTFPR, Av. Sete de Setembro 3165, Curitiba-PR (Brazil); Schelin, Hugo R. [Federal University of Technology-Parana, UTFPR, Av. Sete de Setembro 3165, Curitiba-PR (Brazil)], E-mail: schelin@utfpr.edu.br; Setti, Joao A.P.; Denyak, Valery; Paschuk, Sergei A. [Federal University of Technology-Parana, UTFPR, Av. Sete de Setembro 3165, Curitiba-PR (Brazil); Evseev, Ivan G.; Assis, Joaquim T. de; Yevseyeva, O. [Polytechnic Institute/UERJ, Rua Alberto Rangel s/n, N. Friburgo, RJ, Brazil 28630-050 (Brazil); Lopes, Ricardo T. [Nuclear Instr. Lab./COPPE/UFRJ, Av. Horacio Macedo 2030, Rio de Janeiro-RJ (Brazil); Vinagre Filho, Ubirajara M. [Institute of Nuclear Engineering-IEN/CNEN, Rua Helio de Almeida 75, Rio de Janeiro-RJ (Brazil)

    2010-04-15

    This work presents the recent results of computer simulations for the low energy proton beam tomographic scanner installed at the cyclotron CV-28 of IEN/CNEN. New computer simulations were performed in order to adjust the parameters of previous simulation within the first experimental results and to understand some specific effects that affected the form of the final proton energy spectra. To do this, the energy and angular spread of the initial proton beam were added, and the virtual phantom geometry was specified more accurately in relation to the real one. As a result, a more realistic view on the measurements was achieved.

  14. Revisiting \\gamma\\gamma->\\pi^+\\pi^- at low energies

    CERN Document Server

    Gasser, J; Sainio, M E; Gasser, Juerg; Ivanov, Mikhail A.; Sainio, Mikko E.

    2006-01-01

    We complete the recalculation of the available two-loop expressions for the reaction \\gamma\\gamma->\\pi\\pi in the framework of chiral perturbation theory. Here, we present the results for charged pions. The cross section and the values of the dipole polarizabilities agree very well with the earlier calculation, provided the same set of low-energy constants (LECs) is used. With updated values for the LECs at order p^4, we find for the dipole polarizabilities (\\alpha_1-\\beta_1)_{\\pi^\\pm} = (5.7\\pm 1.0) 10^{-4} fm^3, which is in conflict with the experimental result recently reported by the MAMI Collaboration.

  15. Hannover fare[Ultra low energy flats in Hannover, Germany

    Energy Technology Data Exchange (ETDEWEB)

    Bellew, P.; Kauschmann, J. [Atelier Ten (Germany)

    2000-08-01

    This article describes the new ultra-low energy apartments established for Expo 2000 in the Kronsberg residential district on the outskirts of Hannover. Details are given of the concept design placing the blocks back to back and separating them by a covered atrium, the connection of the eight blocks to a mechanical ventilation system with heat recovery, and the unusual 3-skin roof structure with different cavities inflated in winter and summer. The heating and hot water system, the metering of the apartments, and the regulatory framework governing the construction of the buildings are discussed.

  16. Development of multichannel low-energy neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Arikawa, Y., E-mail: arikawa-y@ile.osaka-u.ac.jp; Nagai, T.; Abe, Y.; Kojima, S.; Sakata, S.; Inoue, H.; Utsugi, M.; Iwasa, Y.; Sarukura, N.; Nakai, M.; Shiraga, H.; Fujioka, S.; Azechi, H. [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka (Japan); Murata, T. [Kumamoto University, 2-40-1 Kurokami, Kumamoto 860-8555 (Japan)

    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.

  17. Two-particle Anderson localization at low energies

    CERN Document Server

    Ekanga, Trésor

    2012-01-01

    We prove exponential spectral localization in a two-particle lattice Anderson model, with a short-range interaction and external random i.i.d. potential, at sufficiently low energies. The proof is based on the multi-particle multi-scale analysis developed earlier by Chulaevsky and Suhov (2009) in the case of high disorder. Our method applies to a larger class of random potentials than in Aizenman and Warzel (2009) where dynamical localization was proved with the help of the fractional moment method.

  18. Combining high-scale inflation with low-energy SUSY

    Energy Technology Data Exchange (ETDEWEB)

    Antusch, Stefan [Basel Univ. (Switzerland). Dept. of Physics; Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut; Dutta, Koushik [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Halter, Sebastian [Max-Planck-Institut fuer Physik, Muenchen (Germany). Werner-Heisenberg-Institut

    2011-12-15

    We propose a general scenario for moduli stabilization where low-energy supersymmetry can be accommodated with a high scale of inflation. The key ingredient is that the stabilization of the modulus field during and after inflation is not associated with a single, common scale, but relies on two different mechanisms. We illustrate this general scenario in a simple example, where during inflation the modulus is stabilized with a large mass by a Kaehler potential coupling to the field which provides the inflationary vacuum energy via its F-term. After inflation, the modulus is stabilized, for instance, by a KKLT superpotential. (orig.)

  19. Plasma focus in the limit of low energy

    Energy Technology Data Exchange (ETDEWEB)

    Silva, P.; Soto, L.; Sylvester, G.; Zambra, M. [Comision Chilena de Energia Nuclear, Casilla 188 D, Santiago (Chile); Bruzzone, H.; Clausse, A.; Moreno, C. [Red Interinstitucional de Plasmas Densos y Magnetizados, PLADEMA (Argentina)

    2002-07-01

    In order to achieve the design of a repetitive neutron pulses source for a substance detector, a single shot very small plasma focus device has been designed and constructed. The plasma focus operates in the limit of low energy (160 nF capacitor bank, 25-50 nH, 30-40 kV, 70-130 J). The design of the electrode was assisted by a simple model of a Mather plasma focus. A neutron yield of 10{sup 4} - 10{sup 5} is expected when the discharge is operated with deuterium. (Author)

  20. Double aberration correction in a low-energy electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Th., E-mail: schmidtt@fhi-berlin.mpg.de [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany); Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Marchetto, H.; Levesque, P.L. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany); Groh, U.; Maier, F. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Preikszas, D. [Technische Universitaet Darmstadt, Angewandte Physik, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Carl Zeiss NTS GmbH, Carl-Zeiss-Strasse 56, D-73447 Oberkochen (Germany); Hartel, P.; Spehr, R. [Technische Universitaet Darmstadt, Angewandte Physik, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Lilienkamp, G. [Technische Universitaet Clausthal, Physikalisches Institut, Leibnizstrasse 4, D-38678 (Germany); Engel, W. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany); Fink, R. [Universitaet Erlangen-Nuernberg, Physikalische Chemie II, Egerlandstrasse 3, D-91058 Erlangen (Germany); Bauer, E. [Technische Universitaet Clausthal, Physikalisches Institut, Leibnizstrasse 4, D-38678 (Germany); Arizona State University, Department of Physics, Tempe, AZ 85287 (United States); Rose, H. [Technische Universitaet Darmstadt, Angewandte Physik, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Umbach, E. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Freund, H.-J. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany)

    2010-10-15

    The lateral resolution of a surface sensitive low-energy electron microscope (LEEM) has been improved below 4 nm for the first time. This breakthrough has only been possible by simultaneously correcting the unavoidable spherical and chromatic aberrations of the lens system. We present an experimental criterion to quantify the aberration correction and to optimize the electron optical system. The obtained lateral resolution of 2.6 nm in LEEM enables the first surface sensitive, electron microscopic observation of the herringbone reconstruction on the Au(1 1 1) surface.

  1. Wavelet modulation: An alternative modulation with low energy consumption

    Science.gov (United States)

    Chafii, Marwa; Palicot, Jacques; Gribonval, Rémi

    2017-02-01

    This paper presents wavelet modulation, based on the discrete wavelet transform, as an alternative modulation with low energy consumption. The transmitted signal has low envelope variations, which induces a good efficiency for the power amplifier. Wavelet modulation is analyzed and compared for different wavelet families with orthogonal frequency division multiplexing (OFDM) in terms of peak-to-average power ratio (PAPR), power spectral density (PSD) properties, and the impact of the power amplifier on the spectral regrowth. The performance in terms of bit error rate and complexity of implementation are also evaluated, and several trade-offs are characterized. xml:lang="fr"

  2. Low Energy Continuum and Lattice Effective Field Theories

    Science.gov (United States)

    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

  3. International development trends in low-energy cements

    Energy Technology Data Exchange (ETDEWEB)

    Stark, J.; Mueller, A.

    1988-04-01

    Besides the currently dominant tendency to increase the proportion of interground additive in cement, the following development trends are internationally emerging in the material composition of so-called low-energy cements with a view to minimizing energy input for cement manufacture: (1) active belite cement with the principal clinker minerals a'C/sub 2/S and C/sub 3/S; (2) belite sulphoaluminate cement (..beta.. C/sub 2/S, C/sub 4/A/sub 3/S); (3) belite sulphoferrite cement (..beta.. C/sub 2/S, C/sub 4/AF, C/sub 4/A/sub 3/S); (4) NTS cement (alinite).

  4. Low-energy cosmic rays in the Orion region

    DEFF Research Database (Denmark)

    Pohl, M.

    1998-01-01

    The recently observed nuclear gamma-ray line emission from the Orion complex implies a high flux of low-energy cosmic rays (LECR) with unusual abundance. This cosmic ray component would dominate the energy density, pressure, and ionising power of cosmic rays, and thus would have a strong impact...... sections, thus it depends only weakly on the LECR spectrum and not on any other parameter. Observations with HEPC will allow us to derive the bremsstrahlung spectrum over the weakly extended gamma-ray emission regions....

  5. Quantum effects at low-energy atom–molecule interface

    Indian Academy of Sciences (India)

    B Deb; A Rakshit; J Hazra; D Chakraborty

    2013-01-01

    The effects of quantum interference in inter-conversion between cold atoms and diatomic molecules are analysed in this study. Within the framework of Fano’s theory, continuum bound anisotropic dressed state formalism of atom–molecule quantum dynamics is presented. This formalism is applicable in photo- and magneto-associative strong-coupling regimes. The significance of Fano effect in ultracold atom–molecule transitions is discussed. Quantum effects at low-energy atom–molecule interface are important for exploring coherent phenomena in hitherto unexplored parameter regimes.

  6. Low-energy K- optical potentials: deep or shallow?

    Science.gov (United States)

    Cieplý, A.; Friedman, E.; Gal, A.; Mareš, J.

    2001-12-01

    The K- optical potential in the nuclear medium is evaluated self consistently from a free-space K-Nt matrix constructed within a coupled-channel chiral approach. The fit of model parameters gives a good description of the low-energy data plus the available K- atomic data. The resulting optical potential is relatively `shallow' in contradiction to the potentials obtained from phenomenological analysis. The calculated (Kstop-,π) hypernuclear production rates are very sensitive to the details of kaonic bound state wave function. The (Kstop-,π) reaction could thus serve as a suitable tool to distinguish between shallow and deep K- optical potentials.

  7. Characterization of a free air ionization chamber for low energies

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Natalia F.; Xavier, Marcos; Vivolo, Vitor; Caldas, Linda V.E., E-mail: nsilva@ipen.br, E-mail: mxavier@ipen.br, E-mail: vivolo@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Free air ionization chambers are used by most primary metrology laboratories as primary standards of the quantities air kerma and exposure in X-ray beams. The free air ionization chamber for low energies of the Calibration Laboratory (LCI) of IPEN showed in a characterization test a problem in the set responsible for the variation of its sensitive volume. After a modification in the support of the micrometers used for the movement of the internal cylinder and the establishment of a new alignment system protocol, the tests were redone. The objective of this work was to present the results obtained in the new condition. (author)

  8. Low-energy electron scattering from molecules, biomolecules and surfaces

    CERN Document Server

    Carsky, Petr

    2011-01-01

    Since the turn of the 21st century, the field of electron molecule collisions has undergone a renaissance. The importance of such collisions in applications from radiation chemistry to astrochemistry has flowered, and their role in industrial processes such as plasma technology and lighting are vital to the advancement of next generation devices. Furthermore, the development of the scanning tunneling microscope highlights the role of such collisions in the condensed phase, in surface processing, and in the development of nanotechnology.Low-Energy Electron Scattering from Molecules, Biomolecule

  9. Restrained Dark $U(1)_d$ at Low Energies

    CERN Document Server

    Correia, F C

    2016-01-01

    We investigate a spontaneously broken $U(1)_d$ gauge symmetry with a muon-specific dark Higgs. Our first goal is to verify how the presence of a new dark Higgs, $\\phi$, and a dark gauge boson, $V$, can simultaneously face the anomalies from the muon magnetic moment and the proton charge radius. Secondly, by assuming that $V$ must decay to an electron-positron pair, we explore the corresponding parameter space determined with the low energy constraints coming from $ K \\to \\mu X$, electron $(g-2)_e$, $K \\to \\mu \

  10. Low-Energy Signatures of Nonlocal Field Theories

    CERN Document Server

    Belenchia, Alessio; Martin-Martinez, Eduardo; Saravani, Mehdi

    2016-01-01

    The response of inertial particle detectors coupled to a scalar field satisfying nonlocal dynamics described by non-analytic functions of the d'Alembertian operator $\\Box$ is studied. We show that spontaneous emission processes of a low energy particle detector are very sensitive to high-energy non-locality scales. This allows us to suggest a nuclear physics experiment ($\\sim$ MeV energy scales) that outperforms the sensitivity of LHC experiments by many orders of magnitude. This may have implications for the falsifiability of theoretical proposals of quantum gravity.

  11. Effective Field Theory for Low-Energy np Systems

    CERN Document Server

    Park, T S

    1998-01-01

    The properties of low-energy neutron-proton systems are studied in an effective field theory where only nucleons figure as relevant degrees of freedom. With a finite momentum cut-off regularization scheme, we show that the large scattering lengths of the np systems do not spoil the convergence of the effective field theory, which turns out to be extremely successful in reproducing, with little cut-off dependence, the deuteron properties, the np 1S0 scattering amplitude and most significantly, the M1 transition amplitude entering into the radiative np capture process.

  12. Assessing the role of the (n, γ f process in the low-energy fission of actinides

    Directory of Open Access Journals (Sweden)

    Talou Patrick

    2016-01-01

    Full Text Available We review the role of the (n, γ f process in the low-energy neutron-induced fission reaction of 239Pu. Recent measurements of the average total γ-ray energy released in this reaction were performed with the Detector for Advanced Neutron Capture Experiments (DANCE at Los Alamos. Significant fluctuations of this quantity in the resonance region below 100 eV can be interpreted by invoking the presence of the indirect (n, γ f process. Modern calculations of the probability for such an event to occur are presented.

  13. Static and dynamic properties of interacting spin-1 bosons in an optical lattice

    Science.gov (United States)

    Natu, Stefan S.; Pixley, J. H.; Das Sarma, S.

    2015-04-01

    We study the physics of interacting spin-1 bosons in an optical lattice using a variational Gutzwiller technique. We compute the mean-field ground state wave function and discuss the evolution of the condensate, spin, nematic, and singlet order parameters across the superfluid-Mott transition. We then extend the Gutzwiller method to derive the equations governing the dynamics of low energy excitations in the lattice. Linearizing these equations, we compute the excitation spectra in the superfluid and Mott phases for both ferromagnetic and antiferromagnetic spin-spin interactions. In the superfluid phase, we recover the known excitation spectrum obtained from Bogoliubov theory. In the nematic Mott phase, we obtain gapped, quadratically dispersing particle and hole-like collective modes, whereas in the singlet Mott phase, we obtain a nondispersive gapped mode, corresponding to the breaking of a singlet pair. For the ferromagnetic Mott insulator, the Gutzwiller mean-field theory only yields particle-hole-like modes but no Goldstone mode associated with long-range spin order. To overcome this limitation, we supplement the Gutzwiller theory with a Schwinger boson mean-field theory which captures superexchange-driven fluctuations. In addition to the gapped particle-hole-like modes, we obtain a gapless quadratically dispersing ferromagnetic spin-wave Goldstone mode. We discuss the evolution of the singlet gap, particle-hole gap, and the effective mass of the ferromagnetic Goldstone mode as the superfluid-Mott phase boundary is approached from the insulating side. We discuss the relevance and validity of Gutzwiller mean-field theories to spinful systems, and potential extensions of this framework to include more exotic physics which appears in the presence of spin-orbit coupling or artificial gauge fields.

  14. High field – low energy muon ionization cooling channel

    Directory of Open Access Journals (Sweden)

    Hisham Kamal Sayed

    2015-09-01

    Full Text Available Muon beams are generated with large transverse and longitudinal emittances. In order to achieve the low emittances required by a muon collider, within the short lifetime of the muons, ionization cooling is required. Cooling schemes have been developed to reduce the muon beam 6D emittances to ≈300  μm-rad in transverse and ≈1–1.5  mm in longitudinal dimensions. The transverse emittance has to be further reduced to ≈50–25  μm-rad with an upper limit on the longitudinal emittance of ≈76  mm in order to meet the high-energy muon collider luminosity requirements. Earlier studies of the transverse cooling of low energy muon beams in high field magnets showed a promising performance, but did not include transverse or longitudinal matching between the stages. In this study we present the first complete design of the high field-low energy ionization cooling channel with transverse and longitudinal matching. The channel design was based on strong focusing solenoids with fields of 25–30 T and low momentum muon beam starting at 135  MeV/c and gradually decreasing. The cooling channel design presented here is the first to reach ≈50 micron scale emittance beam. We present the channel’s optimized design parameters including the focusing solenoid fields, absorber parameters and the transverse and longitudinal matching.

  15. Low energy charged particles interacting with amorphous solid water layers

    Energy Technology Data Exchange (ETDEWEB)

    Horowitz, Yonatan; Asscher, Micha [Institute of Chemistry, Hebrew University of Jerusalem, Edmund J. Safra Campus, Givat-Ram, Jerusalem 91904 (Israel)

    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.

  16. Low energy charged particles interacting with amorphous solid water layers

    Science.gov (United States)

    Horowitz, Yonatan; Asscher, Micha

    2012-04-01

    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 μA) 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.

  17. Passive and low energy research and development: a global view

    Energy Technology Data Exchange (ETDEWEB)

    Balcomb, J.D.

    1984-01-01

    Passive and low energy applications in buildings have become a topic of worldwide interest within the last few years. It has now been demonstrated very clearly that indoor comfort can be maintained with an expenditure of only 10 to 20% of the energy often required by modern buildings. This is accomplished through a combination of conservation measures to minimize the load, passive use of solar energy for heating, natural cooling, and daylighting. The major research emphasis has been on devising mathematical models to characterize heat flow within buildings, on the validation of these models by comparison with test results, and on the subsequent use of the models to investigate the influence of both design parameters and weather on system performance. Design guidelines have been developed, and simplified methods of analysis have been promulgated. Performance has been monitored in test modules, test buildings, and many residential and commercial buildings. The results both confirm good performance and establish the accuracy of model predictions. A significant change in the research picture has been seen in the last 4 years; whereas the major effort was originally in the United States, research is now being conducted in many countries throughout the world as many people have realized that passive and low energy methods are appropriate in virtually every climate and are well suited to economic, convenient, and reliable building construction and operation.

  18. Origin of the Low Energy Structure in Above Threshold Ionization

    CERN Document Server

    Titi, Atef S

    2015-01-01

    We present an ab initio analytic theory to account for both the very low energy structure (VLES) [C. Y. Wu et al., Phys. Rev. Lett. 109, 043001 (2012); W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)], and the low energy structure (LES) [W. Quan et al. Phys. Rev. Lett. 103, 093001 (2009); C.I. Blaga et al., Nat. Phys. 5, 335 2009)] of above threshold ionization. The origin of both VLES and LES lies in a forward scattering mechanism by the Coulomb potential. We parameterize the S matrix in terms of ?, which is the displacement of the the classical motion of an electron in the laser field. When ? = 0, the S matrix is singular, which we attribute to be forward Coulomb scattering without absorption of light quanta. By devising a regularization scheme, the resulting S matrix is non-singular when ? = 0, and the origins of VLES and LES are revealed. We attribute VLES to multiple forward scattering of near-threshold electrons by the Coulomb potential, with no absorption of light quanta, signifying the role of the...

  19. Response of plastic scintillators to low-energy photons.

    Science.gov (United States)

    Peralta, Luis; Rêgo, Florbela

    2014-08-21

    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.

  20. Low energy probes of PeV scale sfermions

    Energy Technology Data Exchange (ETDEWEB)

    Altmannshofer, Wolfgang; Harnik, Roni; Zupan, Jure

    2013-11-27

    We derive bounds on squark and slepton masses in mini-split supersymmetry scenario using low energy experiments. In this setup gauginos are at the TeV scale, while sfermions are heavier by a loop factor. We cover the most sensitive low energy probes including electric dipole moments (EDMs), meson oscillations and charged lepton flavor violation (LFV) transitions. A leading log resummation of the large logs of gluino to sfermion mass ratio is performed. A sensitivity to PeV squark masses is obtained at present from kaon mixing measurements. A number of observables, including neutron EDMs, mu->e transitions and charmed meson mixing, will start probing sfermion masses in the 100 TeV-1000 TeV range with the projected improvements in the experimental sensitivities. We also discuss the implications of our results for a variety of models that address the flavor hierarchy of quarks and leptons. We find that EDM searches will be a robust probe of models in which fermion masses are generated radiatively, while LFV searches remain sensitive to simple-texture based flavor models.

  1. Formation of a high intensity low energy positron string

    Science.gov (United States)

    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.

  2. Personnel Security System using Bluetooth Low Energy (BLE Tag

    Directory of Open Access Journals (Sweden)

    K.Gautham

    2013-04-01

    Full Text Available One of the primary aspects of Personal security is through various user authentication techniques like biometrics, password, Smart Card, etc. We propose to design a personal security authentication system using the commonly available Bluetooth technology. The authentication is done on a fixed device, connected to the web and the identity is provided by a mobile device commonly carried by the person. Almost every cell phone has Bluetooth® transceiver for connecting to a wireless headset or to a host PC. Many new cars have Bluetooth to let you talk hands free while driving. Bluetooth has thus emerged as a pervasive technology. The aim of the paper is to describe a Personnel Security System using Bluetooth Low Energy (BLE Tag which operates on a coin cell battery that will discover all the available low energy devices in the vicinity and keep track of when it entered and when it left the zone. In addition, this tag can also be used as a positioning device by measuring the Received Signal Strength (RSSI value. The initial phase is aimed at designing the hardware for the tag. The second phase is initiated towards programming the tag. The final phase is targeted towards testing the designed hardware module and developing a Personnel Security System.

  3. Low energy electron point source microscopy: beyond imaging.

    Science.gov (United States)

    Beyer, André; Gölzhäuser, Armin

    2010-09-01

    Low energy electron point source (LEEPS) microscopy has the capability to record in-line holograms at very high magnifications with a fairly simple set-up. After the holograms are numerically reconstructed, structural features with the size of about 2 nm can be resolved. The achievement of an even higher resolution has been predicted. However, a number of obstacles are known to impede the realization of this goal, for example the presence of electric fields around the imaged object, electrostatic charging or radiation induced processes. This topical review gives an overview of the achievements as well as the difficulties in the efforts to shift the resolution limit of LEEPS microscopy towards the atomic level. A special emphasis is laid on the high sensitivity of low energy electrons to electrical fields, which limits the structural determination of the imaged objects. On the other hand, the investigation of the electrical field around objects of known structure is very useful for other tasks and LEEPS microscopy can be extended beyond the task of imaging. The determination of the electrical resistance of individual nanowires can be achieved by a proper analysis of the corresponding LEEPS micrographs. This conductivity imaging may be a very useful application for LEEPS microscopes.

  4. Low Energy Laser Biostimulation: New Prospects For Medical Applications

    Science.gov (United States)

    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.

  5. Low-energy control of electrical turbulence in the heart

    Science.gov (United States)

    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.

  6. Low energy nanoemulsification to design veterinary controlled drug delivery devices

    Directory of Open Access Journals (Sweden)

    Thierry F Vandamme

    2010-10-01

    Full Text Available Thierry F Vandamme, Nicolas Anton, University of Strasbourg, Faculty of Pharmacy, Illkirch Cedex, France; UMR CNRS 7199, Laboratoire de Conception et Application de Molécules Bioactives, équipe de Pharmacie Biogalénique, Illkirch Cedex, France,  This work is selected as Controlled Release Society Outstanding Veterinary Paper Award 2010Abstract: The unique properties of nanomaterials related to structural stability and quantum-scale reactive properties open up a world of possibilities that could be exploited to design and to target drug delivery or create truly microscale biological sensors for veterinary applications. We developed cost-saving and solvent-free nanoemulsions. Formulated with a low-energy method, these nanoemulsions can find application in the delivery of controlled amounts of drugs into the beverage of breeding animals (such as poultry, cattle, pigs or be used for the controlled release of injectable poorly water-soluble drugs.Keywords: nanoemulsion, nanomedicine, low-energy emulsification, veterinary, ketoprofen, sulfamethazine

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

    Science.gov (United States)

    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. Very low energy supernovae and their resulting transients

    Science.gov (United States)

    Lovegrove, Elizabeth

    Core-collapse supernovae play a key role in many of astrophysical processes, but the details of how these explosive events work remain elusive. Many questions about the CCSN explosion mechanism and progenitor stars could be answered by either detecting very-low-energy supernovae (VLE SNe) or alternately placing a tight upper bound on their fraction of the CCSN population. However, VLE SNe are by definition dim events. Many VLE SNe result from the failure of the standard CCSN explosion mechanism, meaning that any observable signature must be created by secondary processes either before or during the collapse. In this dissertation I examine alternate means of producing transients in otherwise-failed CCSNe and consider the use of shock breakout flashes to both detect VLE SNe and retrieve progenitor star information. I begin by simulating neutrino-mediated mass loss in CCSNe progenitors to show that a dim, unusual, but still observable transient can be produced. I then simulate shock breakout flashes in VLE SNe for both the purposes of detection as well as extracting information about the exploding star. I discuss particular challenges of modeling shock breakout at low energies and behaviors unique to this regime, in particular the behavior of the spectral temperature. All simulations in this dissertation were done with the CASTRO radiation-hydrodynamic code.

  9. Development of Low Energy Gap and Fully Regioregular Polythienylenevinylene Derivative

    Directory of Open Access Journals (Sweden)

    Tanya M. S. David

    2014-01-01

    Full Text Available 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 was 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.

  10. Materials for Low-Energy Neutron Radiation Shielding

    Science.gov (United States)

    Singleterry, Robert C., Jr.; Thibeault, Sheila A.

    2000-01-01

    Various candidate aircraft and spacecraft materials were analyzed and compared in a low-energy neutron environment using the Monte Carlo N-Particle (MCNP) transport code with an energy range up to 20 MeV. Some candidate materials have been tested in particle beams, and others seemed reasonable to analyze in this manner before deciding to test them. The two metal alloys analyzed are actual materials being designed into or used in aircraft and spacecraft today. This analysis shows that hydrogen-bearing materials have the best shielding characteristics over the metal alloys. It also shows that neutrons above 1 MeV are reflected out of the face of the slab better by larger quantities of carbon in the material. If a low-energy absorber is added to the material, fewer neutrons are transmitted through the material. Future analyses should focus on combinations of scatterers and absorbers to optimize these reaction channels and on the higher energy neutron component (above 50 MeV).

  11. Low Energy Continuum and Lattice Effective Field Theories

    CERN Document Server

    Elhatisari, Serdar

    2014-01-01

    In the first part of the thesis we consider the constraints of causality and unitarity for particles interacting via strictly finite-range interactions. 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 also analyze low-energy scattering for systems with arbitrary short-range interactions plus an attractive $1/r^{\\alpha}$ tail for $\\alpha\\geq2$. 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 der Waals 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 $1/r^{6}$ tail. We argue that a similar universality class exists for any attractive potential $1/r^{\\alpha}$ for $\\alpha\\geq2$. In the second part of ...

  12. Study of chirally motivated low-energy K - optical potentials

    Science.gov (United States)

    Cieplý, A.; Friedman, E.; Gal, A.; Mareš, J.

    2001-12-01

    The K - optical potential in the nuclear medium is evaluated self consistently from a free-space K -N t matrix constructed within a coupled-channel chiral approach to the low-energy K¯N data. The chiral-model parameters are fitted to a select subset of the low-energy data plus the K - atomic data throughout the periodic table. The resulting attractive K - optical potentials are relatively 'shallow', with central depth of the real part about 55 MeV, for a fairly reasonable reproduction of the atomic data with χ2/ N≈2.2. Relatively 'deep' attractive potentials of depth about 180 MeV, which result in other phenomenological approaches with χ2/ N≈1.5, are ruled out within chirally motivated models. Different physical data input is required to distinguish between shallow and deep K - optical potentials. The (K -stop, π) reaction could provide such a test, with exclusive rates differing by over a factor of three for the two classes of potentials. Finally, forward (K -,p) differential cross sections for the production of relatively narrow deeply bound K -nuclear states are evaluated for deep K - optical potentials, yielding values considerably lower than those estimated before.

  13. Low energy recoil detection with a spherical proportional counter

    CERN Document Server

    Savvidis, I; Eleftheriadis, C; Giomataris, I; Papaevangellou, T

    2016-01-01

    We present low energy recoil detection results in the keV energy region, from measurements performed with the Spherical Proportional Counter (SPC). An ${}^{241}Am-{}^{9}{Be}$ fast neutron source is used in order to obtain neutron-nucleus elastic scattering events inside the gaseous volume of the detector. The detector performance in the $keV$ energy region was resolved by observing the $5.9\\ keV$ line of a ${}^{55}Fe$ X-ray source, with energy resolution of $9\\%$ ($\\sigma$). The toolkit GEANT4 was used to simulate the irradiation of the detector by an ${}^{241}Am-{}^{9}{Be}$ source, while SRIM was used to calculate the Ionization Quenching Factor (IQF). The GEANT4 simulated energy deposition spectrum in addition with the SRIM calculated quenching factor provide valuable insight to the experimental results. The performance of the SPC in low energy recoil detection makes the detector a good candidate for a wide range of applications, including Supernova or reactor neutrino detection and Dark Matter (WIMP) searc...

  14. Low energy probes of PeV scale sfermions

    Science.gov (United States)

    Altmannshofer, Wolfgang; Harnik, Roni; Zupan, Jure

    2013-11-01

    We derive bounds on squark and slepton masses in mini-split supersymmetry scenario using low energy experiments. In this setup gauginos are at the TeV scale, while sfermions are heavier by a loop factor. We cover the most sensitive low energy probes including electric dipole moments (EDMs), meson oscillations and charged lepton flavor violation (LFV) transitions. A leading log resummation of the large logs of gluino to sfermion mass ratio is performed. A sensitivity to PeV squark masses is obtained at present from kaon mixing measurements. A number of observables, including neutron EDMs, μ to e transitions and charmed meson mixing, will start probing sfermion masses in the 100 TeV-1000 TeV range with the projected improvements in the experimental sensitivities. We also discuss the implications of our results for a variety of models that address the flavor hierarchy of quarks and leptons. We find that EDM searches will be a robust probe of models in which fermion masses are generated radiatively, while LFV searches remain sensitive to simple-texture based flavor models.

  15. Impact of magnetic fluctuations on lattice excitations in fcc nickel.

    Science.gov (United States)

    Körmann, Fritz; Ma, Pui-Wai; Dudarev, Sergei L; Neugebauer, Jörg

    2016-02-24

    The spin-space averaging formalism is applied to compute atomic forces and phonon spectra for magnetically excited states of fcc nickel. Transverse and longitudinal magnetic fluctuations are taken into account by a combination of magnetic special quasi random structures and constrained spin-density-functional theory. It turns out that for fcc Ni interatomic force constants and phonon spectra are almost unaffected by both kinds of spin fluctuations. Given the computational expense to simulate coupled magnetic and atomic fluctuations, this insight facilitates computational modeling of magnetic alloys such as Ni-based superalloys.

  16. Tissue modeling schemes in low energy breast brachytherapy.

    Science.gov (United States)

    Afsharpour, Hossein; Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

    2011-11-21

    Breast tissue is heterogeneous and is mainly composed of glandular (G) and adipose (A) tissues. The proportion of G versus A varies considerably among the population. The absorbed dose distributions in accelerated partial breast irradiation therapy with low energy photon brachytherapy sources are very sensitive to tissue heterogeneities. Current clinical algorithms use the recommendations of the AAPM TG43 report which approximates the human tissues by unit density water. The aim of this study is to investigate various breast tissue modeling schemes for low energy brachytherapy. A special case of breast permanent seed implant is considered here. Six modeling schemes are considered. Uniform and non-uniform water breast (UWB and NUWB) consider the density but neglect the effect of the composition of tissues. The uniform and the non-uniform G/A breast (UGAB and NUGAB) as well the age-dependent breast (ADB) models consider the effect of the composition. The segmented breast tissue (SBT) method uses a density threshold to distinguish between G and A tissues. The PTV D(90) metric is used for the analysis and is based on the dose to water (D(90(w,m))). D(90(m,m)) is also reported for comparison to D(90(w,m)). The two-month post-implant D(90(w,m)) averaged over 38 patients is smaller in NUWB than in UWB by about 4.6% on average (ranging from 5% to 13%). Large average differences of G/A breast models with TG43 (17% and 26% in UGAB and NUGAB, respectively) show that the effect of the chemical composition dominates the effect of the density on dose distributions. D(90(w,m)) is 12% larger in SBT than in TG43 when averaged. These differences can be as low as 4% or as high as 20% when the individual patients are considered. The high sensitivity of dosimetry on the modeling scheme argues in favor of an agreement on a standard tissue modeling approach to be used in low energy breast brachytherapy. SBT appears to generate the most geometrically reliable breast tissue models in this

  17. Status report on the Low Energy Neutron Source for 2015

    Science.gov (United States)

    Baxter, D. V.; Rinckel, T.

    2016-11-01

    The Low Energy Neutron Source at Indiana University first produced cold neutrons in April of 2005. Ten years after first reaching this milestone, the facility has three instruments in operation on its cold target station, and a second target station is devoted to thermal and fast neutron physics offers capabilities in radiation effects research (single-event effects in electronics) and radiography. Key elements in our success over these last ten years have been the diversity of activities we have been able maintain (which often involves using each of our instruments for multiple different activities), the close relationship we have developed with a number of major sources, and the focus we have had on innovation in neutron instrumentation. In this presentation, we will introduce some of the highlights from our most recent activities, provide an update on some of our technical challenges, and describe some of our ideas for the future.

  18. Effects of heavy sea quarks at low energies.

    Science.gov (United States)

    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.

  19. District Heating in Areas with Low Energy Houses

    DEFF Research Database (Denmark)

    Tol, Hakan Ibrahim

    houses there being considered for renovation to houses of a low-energy class, and due to the existing heat-supply energy infrastructure there being a natural gas grid. The third case study carried out aimed at developing energy conversion systems based on use of renewable energy sources that were...... in Denmark. The second case study was aimed at solving another regional energy planning scheme, one concerned with already existing houses, the heat requirements of which were currently being met by use of a natural gas grid or a conventional high-temperature district heating network. The idea considered...... to study the improvement in efficiency achieved by use of multi-generation systems, (ii) various types of energy conversion systems, such as single-generation, cogeneration, and multi-generation systems, (iii) the long-term storage of heat energy to cope with the mismatch between the energy production from...

  20. Ignitor with stable low-energy thermite igniting system

    Science.gov (United States)

    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.

  1. Physical Mechanism of Nuclear Reactions at Low Energies

    CERN Document Server

    Oleinik, V P; Arepjev, Yu.D

    2002-01-01

    The physical mechanism of nuclear reactions at low energies caused by spatial extension of electron is considered. Nuclear reactions of this type represent intra-electronic processes, more precisely, the processes occurring inside the area of basic localization of electron. Distinctive characteristics of these processes are defined by interaction of the own field produced by electrically charged matter of electron with free nuclei. Heavy nucleus, appearing inside the area of basic localization of electron, is inevitably deformed because of interaction of protons with the adjoining layers of electronic cloud, which may cause nuclear fission. If there occur "inside" electron two or greater number of light nuclei, an attractive force appears between the nuclei which may result in the fusion of nuclei. The intra-electronic mechanism of nuclear reactions is of a universal character. For its realization it is necessary to have merely a sufficiently intensive stream of free electrons, i.e. heavy electric current, an...

  2. Ee-Leach(Low Energy Adaptive Clustering Hierarchy Modified Protocol

    Directory of Open Access Journals (Sweden)

    Nishita Payar,

    2014-05-01

    Full Text Available A wireless sensor network is made by many homogeneous and/or nodes which can sense data and communicate to each other. As energy is a scarce resource in WSN, the main issue is energy efficient routing. Many flat and hierarchical protocols have been projected to enhance the network lifetime. Low Energy Adaptive Clustering Hierarchy (LEACH protocol is a basic energy efficient hierarchical routing protocol in WSN. In LEACH, cluster heads are selected and cluster is formed by joining non cluster head nodes. Member nodes transmit the data to respective cluster head and the cluster head is conscientious to transmit the gathered and aggregated data directly to the base station. This paper examines the performance of the conventional LEACH protocol and gives an enhancement to it for energy efficiency. The proposed protocol considers many parameters like residual energy and distance from base station etc. for cluster head selection and energy efficient routing.

  3. Novel Role of Superfluidity in Low-Energy Nuclear Reactions

    CERN Document Server

    Magierski, Piotr; Wlazłowski, Gabriel

    2016-01-01

    We demonstrate, within symmetry unrestricted time dependent density functional theory, the existence of new effects in low-energy nuclear reactions which originate from superfluidity. The dynamics of the pairing field induces solitonic excitations in the colliding nuclear systems, leading to qualitative changes in the reaction dynamics. The solitonic excitation prevents collective energy dissipation and effectively suppresses capture cross section. We demonstrate how the variations of the total kinetic energy of the fragments can be traced back to the energy stored in the superfluid junction of colliding nuclei. Both contact time and scattering angle in non-central collisions are significantly affected. The modification of the capture cross section and possibilities for its experimental detection are discussed.

  4. Linac4 low energy beam measurements with negative hydrogen ions.

    Science.gov (United States)

    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

    2014-02-01

    Linac4, a 160 MeV normal-conducting H(-) 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(-) 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.

  5. NRV web knowledge base on low-energy nuclear physics

    Science.gov (United States)

    Karpov, V.; Denikin, A. S.; Alekseev, A. P.; Zagrebaev, V. I.; Rachkov, V. A.; Naumenko, M. A.; Saiko, V. V.

    2016-09-01

    Principles underlying the organization and operation of the NRV web knowledge base on low-energy nuclear physics (http://nrv.jinr.ru) are described. This base includes a vast body of digitized experimental data on the properties of nuclei and on cross sections for nuclear reactions that is combined with a wide set of interconnected computer programs for simulating complex nuclear dynamics, which work directly in the browser of a remote user. Also, the current situation in the realms of application of network information technologies in nuclear physics is surveyed. The potential of the NRV knowledge base is illustrated in detail by applying it to the example of an analysis of the fusion of nuclei that is followed by the decay of the excited compound nucleus formed.

  6. Optimization of design parameters of low-energy buildings

    Science.gov (United States)

    Vala, Jiří; Jarošová, Petra

    2017-07-01

    Evaluation of temperature development and related consumption of energy required for heating, air-conditioning, etc. in low-energy buildings requires the proper physical analysis, covering heat conduction, convection and radiation, including beam and diffusive components of solar radiation, on all building parts and interfaces. The system approach and the Fourier multiplicative decomposition together with the finite element technique offers the possibility of inexpensive and robust numerical and computational analysis of corresponding direct problems, as well as of the optimization ones with several design variables, using the Nelder-Mead simplex method. The practical example demonstrates the correlation between such numerical simulations and the time series of measurements of energy consumption on a small family house in Ostrov u Macochy (35 km northern from Brno).

  7. Computer simulations of a low energy proton beam tomograph

    Energy Technology Data Exchange (ETDEWEB)

    Milhoretto, E.; Schelin, H.R.; Setti, J.A.P.; Denyak, V.; Paschuk, S.A.; Basilio, A.C.; Rocha, R.; Ribeiro Junior, S. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil). Curso de Pos-Graduacao em Engenharia Eletrica e Informatica Industrial (CPGEI)]. E-mails: sergei@utfpr.edu.br; edneymilhoretto@yahoo.com; schelin@cpgei.cefetpr.br; Evseev, I.; Yevseyeva, O. [Universidade Estadual do Rio de Janeiro (UERJ), Nova Friburgo, RJ (Brazil)]. E-mail: evseev@iprj.uerj.br; Lopes, R.T. [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graducao em Engenharia (COPPE). Lab. de Instrumentacao Nuclear]. E-mail: ricardo@lin.ufrj.br; Vinagre Filho, U.M. [Instituto de Energia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2007-07-01

    This work presents the recent development of a low energy proton beam tomograph. The proton tomograph prototype (involving UTFPR, UERJ, UFRJ and IEN/CNEN) has been installed and tested at the cyclotron CV-28 of IEN/CNEN. New computer simulations were performed in order to optimize the performance of the scattered proton beam and its aluminum collimator energy losses. The computer code simulates the tomographic measurements with two aluminum collimators (variable aperture from 0.2 mm to 0.4 mm in diameter and variable thickness from 4 mm to 8 mm), a water phantom and a Si(Li) detector. The analysis of the exit beam energy spectra in comparison with a perfectly collimated proton beam made it possible to achieve the best quality of reconstructed tomographic images of water phantom. (author)

  8. Low Energy States in the $SU(N)$ Skyrme Models

    CERN Document Server

    Ioannidou, T A; Zakrzewski, W J

    1998-01-01

    We show that any solution of the SU(2) Skyrme model can be used to give a topologically trivial solution of the SU(4) one. In addition, we extend the method introduced by Houghton et al. and use harmonic maps from S2 to CP(N-1) to construct low energy configurations of the SU(N) Skyrme models. We show that one of such maps gives an exact, topologically trivial, solution of the SU(3) model. We study various properties of these maps and show that, in general, their energies are only marginally higher than the energies of the corresponding SU(2) embeddings. Moreover, we show that the baryon (and energy) densities of the SU(3) configurations with baryon number B=2-4 are more symmetrical than their SU(2) analogues. We also present the baryon densities for the B=5 and B=6 configurations and discuss their symmetries.

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

    CERN Document Server

    Agnese, R; Balakishiyeva, D; Thakur, R Basu; Bauer, D A; Billard, J; Borgland, A; Bowles, M A; Brandt, D; Brink, P L; Bunker, R; Cabrera, B; Caldwell, D O; Cerdeno, D G; Chagani, H; Chen, Y; Cooley, J; Cornell, B; Crewdson, C H; Cushman, P; Daal, M; Di Stefano, P C F; Doughty, T; Esteban, L; Fallows, S; Figueroa-Feliciano, E; Fritts, M; Godfrey, G L; Golwala, S R; Graham, M; Hall, J; Harris, H R; Hertel, S A; Hofer, T; Holmgren, D; Hsu, L; Huber, M E; Jastram, A; Kamaev, O; Kara, B; Kelsey, M H; Kennedy, A; Kiveni, M; Koch, K; Leder, A; Loer, B; Asamar, E Lopez; Mahapatra, R; Mandic, V; Martinez, C; McCarthy, K A; Mirabolfathi, N; Moffatt, R A; Moore, D C; Nelson, R H; Oser, S M; Page, K; Page, W A; Partridge, R; Pepin, M; Phipps, A; Prasad, K; Pyle, M; Qiu, H; Rau, W; Redl, P; Reisetter, A; Ricci, Y; Rogers, H E; Saab, T; Sadoulet, B; Sander, J; Schneck, K; Schnee, R W; Scorza, S; Serfass, B; Shank, B; Speller, D; Upadhyayula, S; Villano, A N; Welliver, B; Wright, D H; Yellin, S; Yen, J J; Young, B A; Zhang, J

    2014-01-01

    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 (CDMS~II) experiment using a maximum likelihood analysis. A background model is constructed using GEANT4 to simulate the surface-event background from $^{210}$Pb decay-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 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. 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.

  10. Low energy vibrational excitations characteristic of superionic glass

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, M. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: nakamura.mitsutaka@jaea.go.jp; Iwase, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Arai, M. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kartini, E. [Industrial Material Division, R and D Center for Materials Science and Technology, BATAN, Serpong, Tangerang 15314 (Indonesia); Russina, M. [Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin (Germany); Yokoo, T. [Institute of Materials Structure Science, KEK, 1-1 Oho, Tsukuba 305-0801 (Japan); Taylor, J.W. [Rutherford Appleton Laboratory, ISIS, Chilton Didcot, Oxon OX11 (United Kingdom)

    2006-11-15

    The mechanism of high ionic conductivity in superionic glass constitutes an unsolved problem in the field of science. Here we performed inelastic neutron scattering measurements of superionic glass system (AgI){sub x}(Ag{sub 2}S){sub x}(AgPO{sub 3}){sub 1-2x} by using MARI spectrometer at ISIS, and found that the Q-dependence of inelastic intensity in the energy region from 1 to 3meV of superionic phase glass shows an excess intensity above Q=1.8A{sup -1} compared with insulator phase. Similar phenomena were also observed in another superionic glass (AgI){sub 0.5}(AgPO{sub 3}){sub 0.5} by using NEAT spectrometer at HMI with high resolution measurement. These results clearly suggest peculiar low energy vibrational excitations should be universal features of superionic glass.

  11. Performance of the Low-energy House in Sisimiut

    DEFF Research Database (Denmark)

    Rode, Carsten; Kragh, Jesper; Borchersen, Egil;

    2009-01-01

    A low-energy house was built in Sisimiut, Greenland in 2004-05 and since its inauguration in April 2005, its performance and operation have been object of study for researchers and students. The house is characterised by a highly insulated building envelope, advanced windows and a ventilation...... auxiliary heat to a room in the building. The paper briefly introduces the design and technology of the house before reporting on the performance results until date. It has been a challenge in some aspects to introduce new technologies which have not been commonly used before in an Arctic environment...... system with heat recovery, which should cut the energy consumption of the building to only half of what in 2006 became the permissible value in the Greenlandic building code. In addition to this, the house is equipped with a solar collector that supplies heat to the domestic hot water system and delivers...

  12. Low-energy lepton violation from supersymmetric flipped SU(5)

    Science.gov (United States)

    Brahm, David E.; Hall, Lawrence J.

    1989-10-01

    We construct a supersymmetric flipped SU(5)⊗U(1) model which violates R parity and electron number at low energies, through a superpotential term (1/2CijkLiLjEck. Rotation of the electron and Higgs superfields makes this term also responsible for charged-lepton masses. The model employs a missing-partners mechanism for the Higgs fields and a seesaw mechanism for the neutrinos. It correctly predicts the approximate electron mass and several mass relations, as well as numerical values for the grand unification scale and the Cijk coefficients. The electron-neutrino Majorana mass is close to experimental limits, and provides constraints. Interesting Z0 decays are predicted: e.g., Z0-->e-μ+e+μ- with invariant-mass peaks in the (e,μ) channels.

  13. Low-energy Variety of Asymmetric SUSY Flavor Structure

    CERN Document Server

    Inoue, K; Yoshioka, K; Inoue, Kenzo; Kojima, Kentaro; Yoshioka, Koichi

    2007-01-01

    In this letter we study the low-energy phenomenology and cosmological implications of supersymmetric grand unified theory with asymmetric flavor structure, which is suggested by the recent observation of fermion masses and mixing angles. The predictions of the scenario are rather dependent on a Yukawa parameter fixed by group-theoretical argument. A reduced value of the parameter gives a resolution to the sign problem of supersymmetric Higgs mass \\mu, with which the theory becomes simultaneously consistent with the experimental data of bottom/tau mass ratio, flavor-changing rare decay of bottom quark, and the muon anomalous magnetic moment. The relic abundance of the lightest superparticle as cold dark matter of the universe is also investigated in light of the three-years WMAP result. A new source of flavor violation is found in the D-term induced scalar masses, that is a distinctive signature of the generation asymmetry.

  14. Low-energy Coulomb excitation of Sr,9896 beams

    Science.gov (United States)

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

    2016-11-01

    The structure of neutron-rich Sr,9896 nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E 2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N =60 , giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.

  15. The nuclear structure and low-energy reactions (NSLER) collaboration

    Science.gov (United States)

    Dean, D. J.; NSLER Collaboration

    2006-09-01

    The long-term vision of the Nuclear Structure and Low-Energy Reactions (NSLER) collaboration is to arrive at a comprehensive and unified description of nuclei and their reactions that is grounded in the interactions between the constituent nucleons. For this purpose, we will develop a universal energy density functional for nuclei and replace current phenomenological models of nuclear structure and reactions with a well-founded microscopic theory that will deliver maximum predictive power with minimal uncertainties that are well quantified. Nuclear structure and reactions play an essential role in the science to be investigated at rare isotope facilities, and in nuclear physics applications to the Science-Based Stockpile Stewardship Program, next-generation reactors, and threat reduction. We anticipate an expansion of the computational techniques and methods we currently employ, and developments of new treatments, to take advantage of petascale architectures and demonstrate the capability of the leadership class machines to deliver new science heretofore impossible.

  16. First evidence of low energy enhancement in Ge isotopes

    Directory of Open Access Journals (Sweden)

    Renstrøm T.

    2015-01-01

    Full Text Available The γ-strength functions and level densities of 73,74Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ∼1-13 MeV for 74Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ∼3MeV towards lower γ energies. The obtained data show that both 73,74Ge display an increase in strength at low γ energies.

  17. Profitable solutions in low energy homes; Loennsomme varmeloesninger i lavenergiboliger

    Energy Technology Data Exchange (ETDEWEB)

    Axell, Monica; Ruud, Svein; Nylund, Hilde Karin

    2011-07-01

    Various combinations of technical installations for three different building bodies is compared to a calculation model. Both the energy consequences for action on climate change on the screen, a requirement in the regulations and life cycle costs are assessed for Swedish climate zones. The combination of geothermal heat, heat recovery and effective climate monitor will, not surprisingly, provide the best solution for the total energy needs. At the same time, this study shows that there is a need to develop heat pumps as a product. Existing solutions on the Swedish market is either too big, too expensive, or both to be cost-efficient solutions for a low-energy villas in Norway. (AG)

  18. The CERN Low Energy Antiproton Ring (LEAR) project

    CERN Document Server

    Lefèvre, P; Plass, G

    1980-01-01

    The idea to add to the CERN Antiproton Accumulator (AA) a facility for experiments with dense and pure beams of low energy antiprotons has received enthusiastic support from many members of the physics community. After conceptual studies done since 1977 the following scheme was authorized in May 1980: Small batches of cooled antiprotons will be skimmed off from the AA at regular intervals, decelerated in the CERN PS and transferred into a small storage ring (LEAR). In its first stage LEAR will work as a beam stretcher providing a high duty cycle spill of 10/sup 6/ p/s into an experimental area. Future options (not yet authorized) foresee internal jet targets together with cooling, co-rotating beams of p and H, proton antiproton colliding beams, fast extraction with slowing down of p's to rest. A storage ring to fulfil this variety of tasks has to combine some unusual machine features which are summarized in the present report. (6 refs).

  19. Low Energy Cosmic Rays and the Disturbed Magnetosphere

    CERN Document Server

    Kudela, K

    2013-01-01

    Low energy galactic cosmic rays as well as particles accelerated to high energies either at the solar surface or in the interplanetary medium have access to the atmosphere above a given position on the Earth depending upon the state of the magnetosphere. The interpretation of the cosmic ray anisotropy, deduced from the neutron monitor (NM) network, must assume the variability of the magnetospheric configuration. Along with a short review of changes of the geomagnetic cutoffs in the disturbed magnetosphere reported in the earlier papers, we present the results of computations of transmissivity function and asymptotic directions for selected points on the ground and for a low altitude polar orbiting satellite as well. The computations, based on different available models of geomagnetic field of external sources are performed for quiet time periods and for strong geomagnetic disturbances occurred in 2003 and 2004.

  20. Opportunistic Sensor Data Collection with Bluetooth Low Energy.

    Science.gov (United States)

    Aguilar, Sergio; Vidal, Rafael; Gomez, Carles

    2017-01-23

    Bluetooth Low Energy (BLE) has gained very high momentum, as witnessed by its widespread presence in smartphones, wearables and other consumer electronics devices. This fact can be leveraged to carry out opportunistic sensor data collection (OSDC) in scenarios where a sensor node cannot communicate with infrastructure nodes. In such cases, a mobile entity (e.g., a pedestrian or a vehicle) equipped with a BLE-enabled device can collect the data obtained by the sensor node when both are within direct communication range. In this paper, we characterize, both analytically and experimentally, the performance and trade-offs of BLE as a technology for OSDC, for the two main identified approaches, and considering the impact of its most crucial configuration parameters. Results show that a BLE sensor node running on a coin cell battery can achieve a lifetime beyond one year while transferring around 10 Mbit/day, in realistic OSDC scenarios.

  1. The Construction of Affordable Low Energy Prefabricated Housing in Denmark

    DEFF Research Database (Denmark)

    Vibæk, Kasper Sánchez; Beim, Anne

    2013-01-01

    Can prefabrication contribute to the development of high performance homes? To answer this question, this chapter defines high performance in more broadly inclusive terms, acknowledging the technical, architectural, social and economic conditions under which energy consumption and production occur....... Consideration of all these factors is a precondition for a truly integrated practice and as this chapter demonstrates, innovative project delivery methods founded on the manufacturing of prefabricated buildings contribute to the production of high performance homes that are cost effective to construct, energy...... efficient to operate and valuable for building communities. Herein discussed are two successful examples of low energy prefabricated housing projects built in Copenhagen Denmark, which embraced both the constraints and possibilities offered by prefabrication....

  2. Linac4 Low Energy Beam Measurements with Negative Hydrogen

    CERN Document Server

    Scrivens, R; Crettiez, O; Dimov, V; Gerard, D; Granemann Souza, E; Guida, R; Hansen, J; Lallement, J B; Lettry, J; Lombardi, A; Midttun, O; Pasquino, C; Raich, U; Riffaud, B; Roncarolo, F; Valerio-Lizarraga, C A; Wallner, J; Yarmohammadi Satri, M; Zickler, T

    2014-01-01

    Linac4, a 160 MeV normal-conducting H- 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 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- 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.

  3. Low-energy house in Sisimiut - Measurement equipment

    Energy Technology Data Exchange (ETDEWEB)

    Hvidthoeft Delff Andersen, P.; Rode, C.; Madsen, Henrik

    2013-08-15

    This paper documents the measurement equipment in a low-energy house in Sisimiut, Greenland. Detailed measurements are being taken on energy consumption, indoor temperatures, floor heating, ventilation, open/closed state of doors and windows, and indoors climate. Equipped with a central control unit, experiments can be designed in order to study heat dynamics of the building. It is described how to plan and execute such experiments in one apartment in the building. The building also features both a solar thermal system and extra buffer tank facilitating testing of storage strategies on the power generated by the solar thermal system. A weather station equipped with thermometer, pyranometer and anemometer is installed on the building as well. Finally, it is described how to retrieve data from an SQL server which is configured to take monthly backups. R functions have been implemented to fetch and prepare the data for time series analysis. Examples are given on the use of these. (Author)

  4. Linac4 low energy beam measurements with negative hydrogen ions

    Energy Technology Data Exchange (ETDEWEB)

    Scrivens, R., E-mail: richard.scrivens@cern.ch; 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. [CERN, 1211 Geneva 23 (Switzerland)

    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.

  5. Triton Electric Form Factor at Low-Energies

    CERN Document Server

    Sadeghi, H

    2009-01-01

    Making use of the Effective Field Theory(EFT) expansion recently developed by the authors, we compute the charge form factor of triton up to next-to-next-to-leading order (N$^2$LO). The three-nucleon forces(3NF) is required for renormalization of the three-nucleon system and it effects are predicted for process and is qualitatively supported by available experimental data. We also show that, by including higher order corrections, the calculated charge form factor and charge radius of $^3$H are in satisfactory agreement with the experimental data and the realistic Argonne $v_{18}$ two-nucleon and Urbana IX potential models calculations. This method makes possible a high precision few-body calculations in nuclear physics. Our result converges order by order in low energy expansion and also cut-off independent.

  6. A New Instrument Design for Imaging Low Energy Neutral Atoms

    Science.gov (United States)

    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.

  7. Low energy neutral atom imaging: Remote observations of the magnetosphere

    Energy Technology Data Exchange (ETDEWEB)

    Funsten, H.O.; McComas, D.J.; Scime, E.E.; Moore, K.R.

    1995-02-01

    Recent developments in detection of neutral atom imaging should enable imaging the global structure and dynamics of the terrestrial magnetosphere. The inherent technical challenge of imaging low energy neutral atoms (LENAs) with energy < 30 keV is their separation from the tremendous UV background, to which LENA detectors are sensitive, without loss of information of LENA trajectory and energy. Three instrument concepts for separating LENAs from the background UV are presented: LENA charge conversion via transmission through an ultrathin carbon foil and subsequent electrostatic deflection, EUV grating polarizers and attenuators, and high frequency shutters. Each of these concepts can be mated to a detector section that provides both LENA imaging capability and coincidence/time-of-flight.

  8. Low-energy antinucleon-nucleus interaction revisited

    Science.gov (United States)

    Friedman, E.

    2015-08-01

    Annihilation cross sections of antiprotons and antineutrons on the proton between 50 and 400 MeV/c show Coulomb focusing below 200 MeV/c and almost no charge-dependence above 200 MeV/c. Similar comparisons for heavier targets are not possible for lack of overlap between nuclear targets studied with and beams. Interpolating between -nucleus annihilation cross sections with the help of an optical potential to compare with -nucleus annihilation cross sections reveal unexpected features of Coulomb interactions in the latter. Direct comparisons between -nucleus and -nucleus annihilations at very low energies could be possible if cross sections are measured on the same targets and at the same energies as the available cross sections for . Such measurements may be feasible in the foreseeable future.

  9. Oxidation of nickel surfaces by low energy ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Saric, Iva [Faculty of Civil Engineering, University of Rijeka (Croatia); Center for Micro and Nano Sciences and Technologies, University of Rijeka (Croatia); Peter, Robert; Kavre, Ivna; Badovinac, Ivana Jelovica; Petravic, Mladen [Center for Micro and Nano Sciences and Technologies, University of Rijeka (Croatia); Department of Physics, University of Rijeka (Croatia)

    2016-03-15

    We have studied formation of oxides on Ni surfaces by low energy oxygen bombardment using X-ray photoemission spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Different oxidation states of Ni ions have been identified in XPS spectra measured around Ni 2p and O 1s core-levels. We have compared our results with thermal oxidation of Ni and shown that ion bombardment is more efficient in creating thin oxide films on Ni surfaces. The dominant Ni-oxide in both oxidation processes is NiO (Ni{sup 2+} oxidation state), while some Ni{sub 2}O{sub 3} contributions (Ni{sup 3+} oxidation state) are still present in all oxidised samples. The oxide thickness of bombarded Ni samples, as determined by SIMS, was shown to be related to the penetration depth of oxygen ions in Ni.

  10. Opportunistic Sensor Data Collection with Bluetooth Low Energy

    Science.gov (United States)

    Aguilar, Sergio; Vidal, Rafael; Gomez, Carles

    2017-01-01

    Bluetooth Low Energy (BLE) has gained very high momentum, as witnessed by its widespread presence in smartphones, wearables and other consumer electronics devices. This fact can be leveraged to carry out opportunistic sensor data collection (OSDC) in scenarios where a sensor node cannot communicate with infrastructure nodes. In such cases, a mobile entity (e.g., a pedestrian or a vehicle) equipped with a BLE-enabled device can collect the data obtained by the sensor node when both are within direct communication range. In this paper, we characterize, both analytically and experimentally, the performance and trade-offs of BLE as a technology for OSDC, for the two main identified approaches, and considering the impact of its most crucial configuration parameters. Results show that a BLE sensor node running on a coin cell battery can achieve a lifetime beyond one year while transferring around 10 Mbit/day, in realistic OSDC scenarios. PMID:28124987

  11. Modeling energy flexibility of low energy buildings utilizing thermal mass

    DEFF Research Database (Denmark)

    Foteinaki, Kyriaki; Heller, Alfred; Rode, Carsten

    2016-01-01

    the load shifting potential of an apartment of a low energy building in Copenhagen is assessed, utilizing the heat storage capacity of the thermal mass when the heating system is switched off for relieving the energy system. It is shown that when using a 4-hour preheating period before switching off...... of the external envelope and the thermal capacity of the internal walls as the main parameters that affect the load shifting potential of the apartment....... to match the production patterns, shifting demand from on-peak hours to off-peak hours. Buildings could act as flexibility suppliers to the energy system, through load shifting potential, provided that the large thermal mass of the building stock could be utilized for energy storage. In the present study...

  12. Modeling of human movement monitoring using Bluetooth Low Energy technology.

    Science.gov (United States)

    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.

  13. Bluetooth low energy: wireless connectivity for medical monitoring.

    Science.gov (United States)

    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.

  14. Low-energy nuclear reactions in crystal structures

    Science.gov (United States)

    Bagulya, A. V.; Dalkarov, O. D.; Negodaev, M. A.; Rusetskii, A. S.

    2017-09-01

    Results of studying low-energy nuclear reactions at the HELIS facility (LPI) are presented. Investigations of yields from DD reactions in deuterated crystal structures at deuteron energies of 10 to 25 keV show a considerable enhancement effect. It is shown that exposure of the deuterated targets to the H+ (proton) and Ne+ beams with energies from 10 to 25 keV and an X-ray beam with the energy of 20 to 30 keV stimulates DD reaction yields. For the CVD diamond target, it is shown that its orientation with respect to the deuteron beam affects the neutron yield. The D+ beam is shown to cause much higher heat release in the TiDx target than the H+ and Ne+ beams, and this heat release depends on the deuterium concentration in the target and the current density of the deuteron beam.

  15. NRV web knowledge base on low-energy nuclear physics

    Science.gov (United States)

    Karpov, A. V.; Denikin, A. S.; Naumenko, M. A.; Alekseev, A. P.; Rachkov, V. A.; Samarin, V. V.; Saiko, V. V.; Zagrebaev, V. I.

    2017-07-01

    The paper describes the principles of organization and operation of the NRV web knowledge base on low-energy nuclear physics (http://nrv.jinr.ru/) which integrates a large amount of digitized experimental data on the properties of nuclei and nuclear reaction cross sections with a wide range of computational programs for modeling of nuclear properties and various processes of nuclear dynamics which work directly in the browser of a remote user. The paper also gives an overview of the current situation in the field of application of network information technologies in nuclear physics. The features of the NRV knowledge base are illustrated in detail on the example of the analysis of nucleon transfer reactions within the distorted wave Born approximation.

  16. Low energy ion beam dynamics of NANOGAN ECR ion source

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sarvesh, E-mail: sarvesh@iuac.res.in; 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.

  17. The rising cost of low-energy-density foods.

    Science.gov (United States)

    Monsivais, Pablo; Drewnowski, Adam

    2007-12-01

    Consuming lower-energy-density foods is one recommended strategy for management of body weight. This cross-sectional study used retail food prices to test the hypothesis that low-energy-density foods are not only more costly per kilocalorie, but have increased disproportionately in price as compared to high-energy-density foods. For a list of 372 foods and beverages belonging to a food frequency questionnaire database, retail prices were obtained from major supermarket chains in the Seattle, WA, metropolitan area in 2004 and 2006. Energy density of all items was calculated and prices were expressed as $/100 g edible portion and as $/1,000 kcal. Foods were stratified by quintiles of energy density and the differences in energy cost and in percent price change were tested using analyses of variance. High-energy-density foods provided the most dietary energy at least cost. Energy cost of foods in the bottom quintile of energy density, beverages excluded, was $18.16/1,000 kcal as compared to only $1.76/1,000 kcal for foods in the top quintile. The 2-year price change for the least energy-dense foods was +19.5%, whereas the price change for the most energy-dense foods was -1.8%. The finding that energy-dense foods are not only the least expensive, but also most resistant to inflation, may help explain why the highest rates of obesity continue to be observed among groups of limited economic means. The sharp price increase for the low-energy-density foods suggests that economic factors may pose a barrier to the adoption of more healthful diets and so limit the impact of dietary guidance.

  18. Restrained dark U (1 )d at low energies

    Science.gov (United States)

    Correia, Fagner C.; Fajfer, Svjetlana

    2016-12-01

    We investigate a spontaneously broken U (1 )d gauge symmetry with a muon-specific dark Higgs. Our first goal is to verify how the presence of a new dark Higgs, ϕ , and a dark gauge boson, V , can simultaneously face the anomalies from the muon magnetic moment and the proton charge radius. Second, by assuming that V must decay to an electron-positron pair, we explore the corresponding parameter space determined with the low-energy constraints coming from K →μ X , electron (g -2 )e, K →μ νμe+e-, K →μ νμμ+μ-, and τ →ντμ νμe+e-. We focus on the scenario where the V mass is below ˜2 mμ and the ϕ mass runs from few MeV to 250 MeV, with V -photon mixing of the order ˜O (10-3). Among weak process at low energies, we check the influence of the new light vector on kaon decays as well as on the scattering e+e-→μ+μ-e+e- and discuss the impact of the dark Higgs on e+e-→μ+μ-μ+μ-. Finally, we consider contributions of the V -photon mixing in the decays π0→γ e+e-, η →γ e+e-, ρ →π e+e-, K*→K e+e-, and ϕ (1020 )→η e+e-.

  19. Spin foams without spins

    Science.gov (United States)

    Hnybida, Jeff

    2016-10-01

    We formulate the spin foam representation of discrete SU(2) gauge theory as a product of vertex amplitudes each of which is the spin network generating function of the boundary graph dual to the vertex. In doing so the sums over spins have been carried out. The boundary data of each n-valent node is explicitly reduced with respect to the local gauge invariance and has a manifest geometrical interpretation as a framed polyhedron of fixed total area. Ultimately, sums over spins are traded for contour integrals over simple poles and recoupling theory is avoided using generating functions.

  20. Quantum annealing with manufactured spins.

    Science.gov (United States)

    Johnson, M W; Amin, M H S; Gildert, S; Lanting, T; Hamze, F; Dickson, N; Harris, R; Berkley, A J; Johansson, J; Bunyk, P; Chapple, E M; Enderud, C; Hilton, J P; Karimi, K; Ladizinsky, E; Ladizinsky, N; Oh, T; Perminov, I; Rich, C; Thom, M C; Tolkacheva, E; Truncik, C J S; Uchaikin, S; Wang, J; Wilson, B; Rose, G

    2011-05-12

    Many interesting but practically intractable problems can be reduced to that of finding the ground state of a system of interacting spins; however, finding such a ground state remains computationally difficult. It is believed that the ground state of some naturally occurring spin systems can be effectively attained through a process called quantum annealing. If it could be harnessed, quantum annealing might improve on known methods for solving certain types of problem. However, physical investigation of quantum annealing has been largely confined to microscopic spins in condensed-matter systems. Here we use quantum annealing to find the ground state of an artificial Ising spin system comprising an array of eight superconducting flux quantum bits with programmable spin-spin couplings. We observe a clear signature of quantum annealing, distinguishable from classical thermal annealing through the temperature dependence of the time at which the system dynamics freezes. Our implementation can be configured in situ to realize a wide variety of different spin networks, each of which can be monitored as it moves towards a low-energy configuration. This programmable artificial spin network bridges the gap between the theoretical study of ideal isolated spin networks and the experimental investigation of bulk magnetic samples. Moreover, with an increased number of spins, such a system may provide a practical physical means to implement a quantum algorithm, possibly allowing more-effective approaches to solving certain classes of hard combinatorial optimization problems.

  1. Magneto-elastic artificial neurons with extremely low energy dissipation

    Science.gov (United States)

    Biswas, Ayan K.; Al-Rashid, Md Mamun; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-03-01

    We present a detailed analysis of artificial step transfer function neurons and binary weight synapses implemented with magneto-tunneling junctions whose soft layers are magnetostrictive nanomagnets switched with voltage generated mechanical strain. These devices are more energy-efficient than CMOS-based neurons or so-called spin neurons that are based on magnets switched with spin-polarized current. We studied their switching dynamics using stochastic Landau-Lifshitz-Gilbert simulations for two different geometries (elliptical and cylindrical) of the magnetostrictive nanomagnet. Our study revealed that while the step transition (firing) of the magnetic neuron is always very sharp at 0 K, the threshold is significantly broadened at room temperature, regardless of geometry and regardless of whether the magnet is switched with strain or spin-polarized current. While this could preclude some applications, the extreme energy-efficiency of these neurons makes them nearly ideal for use in certain types of neuromorphic computation. This work is supported by the NSF under grant ECCS-1124714 and CCF-1216614.

  2. Ultra Low Energy Switching of Ferromagnet with Perpendicular Anisotropy on Topological Insulator by Voltage Controlled Magnetic Anisotropy

    Science.gov (United States)

    Ghosh, Bahniman; Pramanik, Tanmoy; Dey, Rik; Roy, Urmimala; Register, Leonard; Banerjee, Sanjay

    2015-03-01

    We propose and demonstrate, through simulation, an ultra low energy memory device on a topological insulator thin film. The device consists of a thin layer of Fe deposited on the surface of a topological insulator, Bi2Se3. The top surface of Fe is covered with MgO so that the ferromagnetic layer has perpendicular anisotropy. Current is passed on the surface of the topological insulator which switches the magnetization of the Fe ferromagnet through strong exchange interaction, between electrons contributing to the surface current on the Bi2Se3 and the d electrons in the ferromagnet, and spin transfer torque due to shunting of current through the ferromagnet. Voltage controlled magnetic anisotropy enables ultra low energy switching. Our micromagnetic simulations, predict switching time of the order of 2.4 ns and switching energy of the order of 0.16 fJ for a ferromagnetic bit with thermal stability of 90 kBT. The proposed structure combines the advantages of both large spin torque from topological insulators and those of perpendicular anisotropy materials. This work is supported by NRI SWAN and NSF NASCENT Center.

  3. Spin-orbit mediated control of spin qubits

    DEFF Research Database (Denmark)

    Flindt, Christian; Sørensen, A.S; Flensberg, Karsten

    2006-01-01

    We propose to use the spin-orbit interaction as a means to control electron spins in quantum dots, enabling both single-qubit and two-qubit operations. Very fast single-qubit operations may be achieved by temporarily displacing the electrons. For two-qubit operations the coupling mechanism is based...... on a combination of the spin-orbit coupling and the mutual long-ranged Coulomb interaction. Compared to existing schemes using the exchange coupling, the spin-orbit induced coupling is less sensitive to random electrical fluctuations in the electrodes defining the quantum dots....

  4. Neutron Scattering Study of Low Energy Magnetic Excitation in superconducting Te-vapor annealed under-doped FeTeSe

    Science.gov (United States)

    Xu, Zhijun; Yi, Ming; Xu, Guangyong; Shneeloch, J. A.; Matsuda, Masaaki; Chi, Songxue; Gu, Genda; Tranquada, J. M.; Birgeneau, R. J.

    To study the interplay between magnetism and superconductivity, we have performed neutron scattering and magnetization measurements on a Te vapor annealed single crystal Fe1 +yTe0.8Se0.2 (Tc~13K) sample. Te vapor annealed process is found to reduce/remove the excess Fe in the as-grown sample and make the under-doped originally non-superconducting sample become good superconducting sample. Our neutron scattering studies show both spin gap and spin resonance found in the Te vapor annealed superconducting sample. Comparing to commensurate spin resonance in as-grown optimal-doped sample, the spin resonance of Te annealed sample only shows up at the clearly incommensurate positions. The temperature and energy dependence of low energy magnetic excitations are also measured in the sample. This work is supported by the Office of Basic Energy Sciences, DOE.

  5. Softness and Amplitudes' Positivity for Spinning Particles

    CERN Document Server

    Bellazzini, Brando

    2016-01-01

    We derive positivity bounds for scattering amplitudes of particles with arbitrary spin using unitarity, analyticity and crossing symmetry. The bounds imply the positivity of certain low-energy coefficients of the effective action that controls the dynamics of the light degrees of freedom. We show that low-energy amplitudes strictly softer than $O(p^4)$ do not admit unitary ultraviolet completions unless the theory is free. This enforces a bound on the energy growth of scattering amplitudes in the region of validity of the effective theory. We discuss explicit examples including the Goldstino from spontaneous supersymmetry breaking, and the theory of a spin-1/2 fermion with a shift symmetry.

  6. Low energy class 1 typehouses according to the Danish building regulations

    DEFF Research Database (Denmark)

    Rose, Jørgen; Kragh, Jesper; Svendsen, Svend

    2008-01-01

    In 2005 the Danish Building regulations introduced two low energy classes for buildings in addition to tightened minimum requirements. The low energy class 1 and low energy class 2 correspond to total energy use, i.e. energy use for heating, ventilation, cooling and domestic hot water, as 50...

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

    Science.gov (United States)

    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

  8. Quantum-spin-liquid states in the two-dimensional kagome antiferromagnets ZnxCu4-x(OD)6Cl2.

    Science.gov (United States)

    Lee, S-H; Kikuchi, H; Qiu, Y; Lake, B; Huang, Q; Habicht, K; Kiefer, K

    2007-11-01

    A three-dimensional system of interacting spins typically develops static long-range order when it is cooled. If the spins are quantum (S=1/2), however, novel quantum paramagnetic states may appear. The most highly sought state among them is the resonating-valence-bond state, in which every pair of neighbouring quantum spins forms an entangled spin singlet (valence bonds) and these singlets are quantum mechanically resonating among themselves. Here we provide an experimental indication for such quantum paramagnetic states existing in frustrated antiferromagnets, Zn(x)Cu(4-x)(OD)(6)Cl(2), where the S=1/2 magnetic Cu2+ moments form layers of a two-dimensional kagome lattice. We find that in Cu(4)(OD)(6)Cl(2), where distorted kagome planes are weakly coupled, a dispersionless excitation mode appears in the magnetic excitation spectrum below approximately 20 K, whose characteristics resemble those of quantum spin singlets in a solid state, known as a valence-bond solid, that breaks translational symmetry. Doping with non-magnetic Zn2+ ions reduces the distortion of the kagome lattice, and weakens the interplane coupling but also dilutes the magnetic occupancy of the kagome lattice. The valence-bond-solid state is suppressed, and for ZnCu(3)(OD)(6)Cl(2), where the kagome planes are undistorted and 90% occupied by the Cu2+ ions, the low-energy spin fluctuations become featureless.

  9. Knot spinning

    OpenAIRE

    Friedman, Greg

    2004-01-01

    This is an introduction to the construction of higher-dimensional knots by spinning methods. Simple spinning of classical knots was introduced by E. Artin in 1926, and several generalizations have followed. These include twist spinning, superspinning or p-spinning, frame spinning, roll spinning, and deform spinning. We survey these constructions and some of their most important applications, as well as some newer hybrids due to the author. The exposition, meant to be accessible to a broad aud...

  10. Magnetic fluctuations in heavy-fermion metals

    DEFF Research Database (Denmark)

    Mason, T.E.; Petersen, T.; Aeppli, G.

    1995-01-01

    , the nature of the antiferromagnetic order and magnetic fluctuations is qualitatively quite different. UPd2Al3 resembles a rare earth magnetic system with coupling of the 4f electrons to the conduction electrons manifested in a broadening of otherwise conventional spin wave excitations. This is in marked...

  11. Magnetic fluctuations in UNi4B

    DEFF Research Database (Denmark)

    Mentink, S.A.M.; Mason, T.E.; Buyers, W.J.L.;

    1997-01-01

    We investigate the magnetic fluctuation spectrum of the geometrically frustrated antiferromagnetic compound UNi4B, which partially orders below T-N = 20 K. An overdamped spin excitation is observed at the AF wave vector around 2.4 meV. Low-frequency, weakly Q-dependent inelastic scattering...

  12. Statistical Treatment of Low-Energy Nuclear Level Schemes

    Institute of Scientific and Technical Information of China (English)

    M.Gholami; M.Kildir; A.N.Behkami

    2007-01-01

    The level density parameter and the back shift energy E1 are determined for nuclei with A-values across the whole periodic table from fits to complete level schemes at low excitation energy near the neutron binding energies.We find that the energy back shift E1 shows complicated behavior and depends on the type of the nucleus,even-even,odd mass,and odd-odd.The spin cut-off factor has also been investigated for nuclei mentioned above.The results arecompared with the previous results and different experimental data on level densities.

  13. Very Low Energy Electron Scattering from Ozone and Chlorine Dioxide

    Science.gov (United States)

    Gulley, R. J.; Field, T. A.; Steer, W. A.; Mason, N. J.; Ziesel, J. P.; Lunt, S. L.; Field, D.

    1998-10-01

    Total cross-sections are reported for the scattering of electrons from ozone (O_3) and chlorine dioxide (OClO) for energies in the range of 9 meV to 10 eV. The measurements were made in transmission experiments using a synchrotron photoionization apparatus with an energy resolution in the incident electron beam of ~ 3.5 meV (FWHM). The cross section for O3 shows strong rotational scattering at low energy, through the presence of the permanent dipole moment of O_3. Superposed on this strong scattering signal, there is evidence of a weak structure around 50 meV associated with dissociative attachment. A shape resonance, known from earlier work at ~ 4 meV, is also observed. Electron scattering from OClO is dominated by rotationally inelastic scattering decreasing from a peak at essentially zero eV to an energy of 40 meV, where p-wave attachment becomes more important, peaking at 50--60 meV and extending to several hundred meV.

  14. Automation of variable low-energy positron beam experiments

    CERN Document Server

    Jayapandian, J; Amarendra, G; Venugopal-Rao, G; Purniah, B; Viswanathan, B

    2000-01-01

    By exploiting the special BIOS interrupt (INT 1CH) of PC in conjunction with a compatible high-voltage controller card and menu-driven control program, we report here the automation of variable low-energy positron beam experiments. The beam experiment consists of monitoring the Doppler broadening lineshape parameters corresponding to the annihilation 511 keV gamma-ray at various positron beam implantation energies. The variation and monitoring of the sample high voltage, which determines positron beam energy, is carried out using a controller add-on card coupled to a 0-30 kV high-voltage unit. The design features of this controller card are discussed. This controller card is housed in a PC, which also houses a multichannel analyser (MCA) card. The MCA stores the Doppler energy spectrum of the annihilation gamma-ray. The interactive control program, written in Turbo C, carries out the assigned tasks. The design features of the automation and results are presented.

  15. Review of lattice results concerning low-energy particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Colangelo, G.; Leutwyler, H.; Wenger, U. [Universitaet Bern, Albert Einstein Center for Fundamental Physics, Institut fuer Theoretische Physik, Bern (Switzerland); Duerr, S. [Bergische Universitaet Wuppertal, Wuppertal (Germany); Forschungszentrum Juelich, Juelich Supercomputing Centre, Juelich (Germany); Juettner, A.; Necco, S. [CERN, Physics Department, TH Unit, Geneva 23 (Switzerland); Lellouch, L. [Centre de Physique Theorique, Marseille (France); Lubicz, V. [Universita Roma Tre (Italy); INFN, Dipartimento di Fisica, Rome (Italy); Sachrajda, C.T. [University of Southampton, School of Physics and Astronomy, Southampton (United Kingdom); Simula, S. [INFN, Sezione di Roma Tre, Rome (Italy); Vladikas, A. [Universita di Roma Tor Vergata (Italy); INFN, Sezione di Tor Vergata, Rome (Italy); Wittig, H. [University of Mainz, Institut fuer Kernphysik (Germany); Helmholtz Institute Mainz, Mainz (Germany)

    2011-07-15

    We review lattice results relevant for pion and kaon physics with the aim of making them easily accessible to the particle physics community. Specifically, we review the determination of the light-quark masses, the form factor f{sub +}(0), relevant for the semileptonic K{yields}{pi} transition at zero momentum transfer as well as the ratio f{sub K} /f{sub {pi}} of decay constants and discuss the consequences for the elements V{sub us} and V{sub ud} of the CKM matrix. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2){sub L} x SU(2){sub R} and SU(3){sub L} x SU(3){sub R} Chiral Perturbation Theory and review the determination of the B{sub K} parameter of neutral kaon mixing. We introduce quality criteria and use these when forming averages. Although subjective and imperfect, these criteria may help the reader to judge different aspects of current lattice computations. Our main results are summarized in Sect. 1.2, but we stress the importance of the detailed discussion that underlies these results and constitutes the bulk of the present review. (orig.)

  16. On the low energy end of the QCD spectrum

    CERN Document Server

    Leutwyler, H

    2008-01-01

    The energy gap of QCD is now understood very well. There is no doubt that the expansion in powers of the two lightest quark masses does represent a very useful tool for the analysis of the low energy structure. Concerning the expansion in powers of m_s, however, the current situation leaves much to be desired. While some of the lattice results indicate, for instance, that the violations of the Okubo-Iizuka-Zweig rule in the quark condensate and in the decay constants are rather modest, others point in the opposite direction. I am confident that the dust will settle soon, so that the effective coupling constants that govern the dependence of the various quantities of physical interest on m_s can be determined, to next-to-next-to-leading order of the chiral expansion. The range of validity of ChPT can be extended by means of dispersive methods. The properties of the physical states occurring in the spectrum of QCD below KKbar threshold can reliably be investigated on this basis. In particular, as shown only rat...

  17. Oxidation of polyethylene implanted with low energy magnesium ions

    Energy Technology Data Exchange (ETDEWEB)

    Deslandes, Alec, E-mail: acd@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Sydney (Australia); Ionescu, Mihail, E-mail: mio@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Sydney (Australia); Karatchevtseva, Inna, E-mail: ikm@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Sydney (Australia); Siegele, Rainer, E-mail: rns@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Sydney (Australia); Cohen, David D., E-mail: dcz@ansto.gov.au [Australian Nuclear Science and Technology Organisation, Sydney (Australia)

    2013-07-15

    The oxidation of polyethylene implanted with low energy, i.e. 25–50 keV, Mg ions to fluences from 5 × 10{sup 12}–5 × 10{sup 16} ions/cm{sup 2} was studied. Rutherford back-scattering spectroscopy showed all implanted samples gained oxygen but the distribution did not match that of the implanted Mg. An increase in carbon content was also observed for the near-surface region. Depth profiles of hydrogen were obtained via elastic recoil detection analysis, showing that hydrogen was lost throughout and beyond the range of the Mg ions, producing unsaturated and chemically active sites available for oxidation. Fourier-transform infrared spectroscopy revealed the formation of carbon–oxygen bonding such as carbonyl groups, but showed no evidence of oxidised magnesium. Raman spectroscopy showed disordered and graphitic carbon bonding configurations were created by the irradiation, but no evidence of oxidised magnesium. The implantation of films to high fluence produced a carbonized surface-layer that made the irradiated polymer more resistant to oxidation.

  18. The low-energy program of the MAJORANA DEMONSTRATOR

    Science.gov (United States)

    Massarczyk, Ralph; MAJORANA Collaboration

    2017-01-01

    The MAJORANA Collaboration constructed an ultra-low background, modular high-purity Ge detector array to search for neutrinoless double-beta decay in 76Ge. Located at the 4850-ft level of the Sanford Underground Research Facility, the DEMONSTRATOR detector assembly has the goal to show that it is possible to achieve background rates necessary for future ton-scale experiments. The ultra-clean assembly in combination with low-noise p-type point contact detectors allows measurements with thresholds in the keV range. The talk will give an overview of the low-energy physics and recent achievements made since the completed DEMONSTRATOR array started data taking in mid 2016. Recent results from campaign will be presented, including new limits on bosonic dark matter interaction rates. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics Program of the National Science Foundation, and the Sanford Underground Research Facility. We acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program.

  19. Review of lattice results concerning low-energy particle physics

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, S. [Kyoto University, Yukawa Institute for Theoretical Physics, Kyoto (Japan); Aoki, Y. [Nagoya University, Kobayashi-Maskawa Institute for the Origin of Particles and the Universe (KMI), Nagoya (Japan); Brookhaven National Laboratory, RIKEN BNL Research Center, Upton, NY (United States); Bernard, C. [Washington University, Department of Physics, Saint Louis, MO (United States); Blum, T. [Brookhaven National Laboratory, RIKEN BNL Research Center, Upton, NY (United States); University of Connecticut, Physics Department, Storrs, CT (United States); Colangelo, G.; Leutwyler, H.; Necco, S.; Wenger, U. [Institut fuer theoretische Physik, Universitaet Bern, Albert Einstein Center for Fundamental Physics, Bern (Switzerland); Della Morte, M. [University of Southern Denmark, CP3-Origins and Danish IAS, Odense M (Denmark); IFIC (CSIC), Paterna (Spain); Duerr, S. [Bergische Universitaet Wuppertal, Wuppertal (Germany); Juelich Supercomputing Center, Juelich (Germany); El-Khadra, A.X. [University of Illinois, Department of Physics, Urbana, IL (United States); Fukaya, H.; Onogi, T. [Osaka University, Department of Physics, Osaka (Japan); Horsley, R. [University of Edinburgh, School of Physics, Edinburgh (United Kingdom); Juettner, A.; Sachrajda, C.T. [University of Southampton, School of Physics and Astronomy, Southampton (United Kingdom); Kaneko, T. [High Energy Accelerator Research Organization (KEK), Ibaraki (Japan); Laiho, J. [University of Glasgow, SUPA, Department of Physics and Astronomy, Glasgow (United Kingdom); Syracuse University, Department of Physics, Syracuse, New York (United States); Lellouch, L. [Aix-Marseille Universite, CNRS, CPT, UMR 7332, Marseille (France); Universite de Toulon, CNRS, CPT, UMR 7332, La Garde (France); Lubicz, V. [Universita Roma Tre, Dipartimento di Matematica e Fisica, Rome (Italy); Sezione di Roma Tre, INFN, Rome (Italy); Lunghi, E. [Indiana University, Physics Department, Bloomington, IN (United States); Pena, C. [Universidad Autonoma de Madrid, Instituto de Fisica Teorica UAM/CSIC and Departamento de Fisica Teorica, Madrid (Spain); Sharpe, S.R. [University of Washington, Physics Department, Seattle, WA (United States); Simula, S. [Sezione di Roma Tre, INFN, Rome (Italy); Sommer, R. [NIC rate at DESY, Zeuthen (Germany); Water, R.S.V. de [Fermi National Accelerator Laboratory, Batavia, IL (United States); Vladikas, A. [Universita di Roma Tor Vergata, INFN, Sezione di Tor Vergata, c/o Dipartimento di Fisica, Rome (Italy); Wittig, H. [University of Mainz, PRISMA Cluster of Excellence, Institut fuer Kernphysik and Helmholtz Institute Mainz, Mainz (Germany); Collaboration: FLAG Working Group

    2014-09-15

    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 lightquark masses, the form factor f{sub +}(0), arising in semileptonic K → π transition at zero momentum transfer, as well as the decay-constant ratio f{sub K}/f{sub π} of decay constants and its consequences for the CKM matrix elements V{sub us} and V{sub ud}. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of SU(2){sub L} x SU(2){sub R} andSU(3)L{sub L} x SU(3){sub 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, we focus here 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 α{sub s}. (orig.)

  20. Low energy electron interactions with complex biological targets

    Science.gov (United States)

    Orlando, Thomas

    2012-10-01

    The low energy (1-25 eV) electron-induced damage of DNA oligomers have been examined both theoretically and experimentally. Specifically, elastic scattering of 5-30 eV electrons within B-DNA 5'-CCGGCGCCGG-3' and A-DNA 5'-CGCGAATTCGCG-3' sequences has been calculated using the separable representation of a free-space electron propagator and a curved wave multiple scattering formalism. The disorder brought about by the surrounding water and helical base stacking leads to featureless amplitude build-up of elastically scattered electrons on the sugars and phosphate groups for all energies between 5-30 eV. However, some constructive interference features arising from diffraction were revealed when examining the structural waters within the major groove. We correlated these scattering features with measured DNA single and double strand breaks. Compound resonance states involving interfacial water and excitation energies > 5 eV seem to be required for lethal double strand breaks. We have recently extended this work to excitation energies below 5 eV by examining the damage using Raman-microscopy and scanning electrostatic force microscopy. Very efficient damage via single strand breaks is observed below 5 eV excitation energies. This involves π* negative ion resonances that are initially localized on the bases but transferred to the σ* states of the sugar-phosphate bond. The efficacies of these channels depend upon the base-pair sequences as well as the presence of water.

  1. Photon strength and the low-energy enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Wiedeking, M. [iThemba LABS, P.O. Box 722, Somerset West 7129 (South Africa); Bernstein, L. A.; Bleuel, D. L.; Burke, J. T.; Hatarik, R.; Lesher, S. R.; Scielzo, N. D. [Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Krtička, M. [Faculty of Mathematics and Physics, Charles University, V Holešovickách 2, Prague 8 (Czech Republic); Allmond, J. M. [Department of Physics, University of Richmond, Virginia 23173 (United States); Basunia, M. S.; Fallon, P.; Firestone, R. B.; Lake, P. T.; Lee, I-Y.; Paschalis, S.; Petri, M.; Phair, L. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Goldblum, B. L. [Department of Nuclear Engineering, University of California, Berkeley, California 94720 (United States)

    2014-08-14

    Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in {sup 95}Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted on an event-by-event basis. The results are presented and compared to {sup 95}Mo photon strength function data measured at the University of Oslo.

  2. Strong interactions and electromagnetism in low-energy hadron physics

    Energy Technology Data Exchange (ETDEWEB)

    Kubis, B.

    2002-10-01

    In the present work, we study various aspects of the entanglement of the strong and electromagnetic interactions as it is manifest in low-energy hadron physics. In the framework of chiral perturbation theory, two aspects are investigated: the test of the structure of baryons as probed by external electromagnetic currents, and the modification of reactions mediated by the strong interactions in the presence of internal (virtual) photons. In the first part of this work, we study the electromagnetic form factors of nucleons and the ground state baryon octet, as well as strangeness form factors of the nucleon. Emphasis is put on the comparison of a new relativistic scheme for the calculation of loop diagrams to the heavy-baryon formalism, and on the convergence of higher-order corrections in both schemes. The new scheme is shown to yield both a phenomenologically more successful description of the data and better convergence behaviour. In the second part, we study isospin violation in pion-kaon scattering as mediated by virtual photon effects and the light quark mass difference. This investigation is of particular importance for the extraction of scattering lengths from measurements of lifetime and energy levels in pion-kaon atoms. The isospin breaking corrections are shown to be small and sufficiently well under control. (orig.)

  3. Wettability Modification of Nanomaterials by Low-Energy Electron Flux

    Directory of Open Access Journals (Sweden)

    Torchinsky I

    2009-01-01

    Full Text Available Abstract Controllable modification of surface free energy and related properties (wettability, hygroscopicity, agglomeration, etc. of powders allows both understanding of fine physical mechanism acting on nanoparticle surfaces and improvement of their key characteristics in a number of nanotechnology applications. In this work, we report on the method we developed for electron-induced surface energy and modification of basic, related properties of powders of quite different physical origins such as diamond and ZnO. The applied technique has afforded gradual tuning of the surface free energy, resulting in a wide range of wettability modulation. In ZnO nanomaterial, the wettability has been strongly modified, while for the diamond particles identical electron treatment leads to a weak variation of the same property. Detailed investigation into electron-modified wettability properties has been performed by the use of capillary rise method using a few probing liquids. Basic thermodynamic approaches have been applied to calculations of components of solid–liquid interaction energy. We show that defect-free, low-energy electron treatment technique strongly varies elementary interface interactions and may be used for the development of new technology in the field of nanomaterials.

  4. Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

    Energy Technology Data Exchange (ETDEWEB)

    Stratton, J. Chris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Singer, Brett C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    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.

  5. Addressing Kitchen Contaminants for Healthy, Low-Energy Homes

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Molecular ion sources for low energy semiconductor ion implantation (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Hershcovitch, A., E-mail: hershcovitch@bnl.gov [Brookhaven National Laboratory, Upton, New York 11973 (United States); Gushenets, V. I.; Bugaev, A. S.; Oks, E. M.; Vizir, A.; Yushkov, G. Yu. [High Current Electronics Institute, Siberian Branch of Russian Academy of Sciences, Tomsk 634055 (Russian Federation); Seleznev, D. N.; Kulevoy, T. V.; Kozlov, A.; Kropachev, G. N.; Kuibeda, R. P.; Minaev, S. [Institute for Theoretical and Experimental Physics, Moscow 117218 (Russian Federation); Dugin, S.; Alexeyenko, O. [State Scientific Center of the Russian Federation State Research Institute for Chemistry and Technology of Organoelement Compounds, Moscow (Russian Federation)

    2016-02-15

    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 (C{sub 4}H{sub 12}B{sub 10}O{sub 4}) 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 4PH{sub 3} = P{sub 4} + 6H{sub 2}; generated molecular phosphorous in a pure gaseous process was then injected into the HCEI Calutron-Bernas ion source, from which P{sub 4}{sup +} ion beams were extracted. Results from devices and some additional concepts are described.

  7. Low-energy buildings: Bioclimatic improvements appropriate to Belgrade

    Directory of Open Access Journals (Sweden)

    MiloradoviĆ Nenad

    2006-01-01

    Full Text Available Buildings consume around 40% of the total world energy and bioclimatic architecture may achieve energy savings for heating and air conditioning purposes. The geometric shape of a building membrane, its compactness aerodynamics and orientation, building aggregation, the level of isolation as well as the layout and size of windows are all determining for the energy performance of a building. In this paper it is presented an optimized configuration for the low-energy construction basis of a building, which reduces energy exchange with surroundings. Such layout, with specific south-eastern orientation (because of "košava" wind influence is suitable for Belgrade constructions. Here is also presented an example of dense structures, which can be developed in urban areas. Above all, the advantage of such layout of the base is in its compactness, whereas south-eastern orientation allows for opportune heating of a building in the morning hours it increases its aerodynamics (by which it reduces ventilation loss for heating, and represents a compromise solution for winter and summer energy requirements.

  8. Review of lattice results concerning low energy particle physics

    CERN Document Server

    Colangelo, Gilberto; Juttner, Andreas; Lellouch, Laurent; Leutwyler, Heinrich; Lubicz, Vittorio; Necco, Silvia; Sachrajda, Christopher T; Simula, Silvano; Vladikas, Anastassios; Wenger, Urs; Wittig, Hartmut

    2011-01-01

    We review lattice results relevant for pion and kaon physics with the aim of making them easily accessible to the particle physics community. Specifically, we review the determination of the light-quark masses, the form factor f_+(0), relevant for the semileptonic K -> pi transition at zero momentum transfer as well as the ratio f_K/f_pi of decay constants and discuss the consequences for the elements V_{us} and V_{ud} of the CKM matrix. 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 B_K parameter of neutral kaon mixing. We introduce quality criteria and use these when forming averages. Although subjective and imperfect, these criteria may help the reader to judge different aspects of current lattice computations. Our main results are summarized in section 1.2, but we stress the importance of the detailed discussion that underlies these results and constitute...

  9. Neutrino Phenomenology of Very Low-Energy Seesaws

    CERN Document Server

    De Gouvêa, A; Vasudevan, N; 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 LSND anomaly, while other M values lead to several observable consequences. We consider the phenomenology of low energy seesaw scenarios with M less than and equal to approximately 1 keV. 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 wa...

  10. Low energy, high power hydrogen neutral beam for plasma heating

    Energy Technology Data Exchange (ETDEWEB)

    Deichuli, P.; Davydenko, V.; Ivanov, A., E-mail: ivanov@inp.nsk.su; Mishagin, V.; Sorokin, A.; Stupishin, N. [Budker Institute of Nuclear Physics, Prospect Lavrentieva 11, 630090 Novosibirsk (Russian Federation); Korepanov, S.; Smirnov, A. [Tri Alpha Energy, Inc., Foothill Ranch, California 92610 (United States)

    2015-11-15

    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.

  11. ECR ion source based low energy ion beam facility

    Indian Academy of Sciences (India)

    P Kumar; G Rodrigues; U K Rao; C P Safvan; D Kanjilal; A Roy

    2002-11-01

    Mass analyzed highly charged ion beams of energy ranging from a few keV to a few MeV plays an important role in various aspects of research in modern physics. In this paper a unique low energy ion beam facility (LEIBF) set up at Nuclear Science Centre (NSC) for providing low and medium energy multiply charged ion beams ranging from a few keV to a few MeV for research in materials sciences, atomic and molecular physics is described. One of the important features of this facility is the availability of relatively large currents of multiply charged positive ions from an electron cyclotron resonance (ECR) source placed entirely on a high voltage platform. All the electronic and vacuum systems related to the ECR source including 10 GHz ultra high frequency (UHF) transmitter, high voltage power supplies for extractor and Einzel lens are placed on a high voltage platform. All the equipments are controlled using a personal computer at ground potential through optical fibers for high voltage isolation. Some of the experimental facilities available are also described.

  12. Low-energy lepton violation from supersymmetric flipped SU(5)

    Energy Technology Data Exchange (ETDEWEB)

    Brahm, D.E.; Hall, L.J. (Physics Department, University of California, Berkeley, California 94720 (US) Theoretical Physics Group, Lawrence Berkeley Laboratory, 1 Cyclotron Road, Berkeley, California 94720)

    1989-10-01

    We construct a supersymmetric flipped SU(5){direct product}U(1) model which violates {ital R} parity and electron number at low energies, through a superpotential term (1/2{ital C}{sup {ital ijk}}L{sub i}L{sub j}E{sub k}{sup c}). Rotation of the electron and Higgs superfields makes this term also responsible for charged-lepton masses. The model employs a missing-partners mechanism for the Higgs fields and a seesaw mechanism for the neutrinos. It correctly predicts the approximate electron mass and several mass relations, as well as numerical values for the grand unification scale and the {ital C}{sup {ital ijk}} coefficients. The electron-neutrino Majorana mass is close to experimental limits, and provides constraints. Interesting {ital Z}{sup 0} decays are predicted: e.g., {ital Z}{sup 0}{r arrow}e{sup {minus}}{mu}{sup +}e{sup +}{mu}{sup {minus}} with invariant-mass peaks in the ({ital e},{mu}) channels.

  13. Homestake result, sterile neutrinos and low energy solar neutrino experiments

    CERN Document Server

    De Holanda, P C

    2003-01-01

    The large mixing (LMA) MSW solution predicts ~2-sigma higher Ar-production rate, Q_{Ar}, than the Homestake result. Also there is no apparent upturn of the spectrum (R=N_obs/N_SSM) at low energies in SNO and Super-Kamiokande (SK). Both these facts can be explained if a light, \\Delta m^2_{01} ~ (2 - 20)10^{-5} eV^2, sterile neutrino exists which mixes very weakly with active neutrinos: sin^2 2\\alpha ~ (10^{-5} - 10^{-3}). We perform both the analytical and numerical study of conversion effects in the system of two active neutrinos with the LMA parameters and one weakly mixed sterile neutrino. The presence of sterile neutrino leads to a dip in the survival probability in the intermediate energy range E = (0.5 - 5) MeV thus suppressing the Be, or/and pep, CNO as well as B neutrino fluxes. Apart from diminishing Q_{Ar} it leads also to decrease of the Ge-production rate and may lead to decrease of the BOREXINO signal and CC/NC ratio at SNO. Future studies of the solar neutrinos by SNO, SK, BOREXINO and KamLAND as...

  14. Low-energy radioactive ion beam production of 22Mg

    Science.gov (United States)

    Duy, N. N.; Kubono, S.; Yamaguchi, H.; Kahl, D.; Wakabayashi, Y.; Teranishi, T.; Iwasa, N.; Kwon, Y. K.; Khiem, L. H.; Kim, Y. H.; Song, J. S.; Hu, J.; Ayyad, Y.

    2013-09-01

    The 22Mg nucleus plays an important role in nuclear astrophysics, specially in the 22Mg(α,p)25Al and proton capture 22Mg(p,γ)23Al reactions. It is believed that 22Mg is a waiting point in the αp-process of nucleosynthesis in novae. We proposed a direct measurement of the 22Mg+α resonance reaction in inverse kinematics using a radioactive ion (RI) beam. A 22Mg beam of 3.73 MeV/u was produced at CRIB (Center for Nuclear Study (CNS) low-energy RI Beam) facility of the University of Tokyo located at RIKEN (Japan) in 2011. In this paper we present the results about the production of the 22Mg beam used for the direct measurement of the scattering reaction 22Mg(α,α)22Mg, and the stellar reaction 22Mg(α,p)25Al in the energy region concerning an astrophysical temperature of T9=1-3 GK.

  15. Performance of the ETH gas ionization chamber at low energy

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, A.M., E-mail: arnold.mueller@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH-Zurich, Schafmattstrasse 20, CH-8093 Zurich (Switzerland); Doebeli, M.; Suter, M.; Synal, H.-A. [Laboratory of Ion Beam Physics, ETH-Zurich, Schafmattstrasse 20, CH-8093 Zurich (Switzerland)

    2012-09-15

    The performance of gas ionization chambers (GIC) for the detection of low energy ions has been considerably improved in the past years by the use of silicon nitride entrance windows and low noise preamplifiers. This has led to an increased use of high resolution GICs in the fields of accelerator mass spectrometry and ion beam analysis. This development and the underlying physical principles are reviewed and the latest technical status of such devices is summarized. A detailed study on energy resolution and pulse height defect is presented with projectiles covering a wide particle mass range (H, {sup 9}Be, {sup 13}C, {sup 27}Al, {sup 35}Cl, {sup 127}I, {sup 232}Th) with energies between 0.1 and 2.2 MeV. The dependence of energy resolution and charge output per unit particle energy on the nuclear charge of the projectile is investigated and parametrized. SRIM calculations of ionizing energy loss considerably differ from these experimental findings. For 1 MeV particles discrepancies up to 50% are observed. The performance of GICs and their practical use is compared to that of solid state detectors. The potential for further improvement of the technology and its fields of application are assessed.

  16. Low-energy gamma ray attenuation characteristics of aviation fuels

    Science.gov (United States)

    Singh, Jag J.; Shen, Chih-Ping; Sprinkle, Danny R.

    1990-01-01

    Am241 (59.5 keV) gamma ray attenuation characteristics were investigated in 270 aviation fuel (Jet A and Jet A-1) samples from 76 airports around the world as a part of world wide study to measure the variability of aviation fuel properties as a function of season and geographical origin. All measurements were made at room temperature which varied from 20 to 27 C. Fuel densities (rho) were measured concurrently with their linear attenuation coefficients (mu), thus providing a measure of mass attenuation coefficient (mu/rho) for the test samples. In 43 fuel samples, rho and mu values were measured at more than one room temperature, thus providing mu/rho values for them at several temperatures. The results were found to be independent of the temperature at which mu and rho values were measured. It is noted that whereas the individual mu and rho values vary considerably from airport to airport as well as season to season, the mu/rho values for all samples are constant at 0.1843 + or - 0.0013 cu cm/gm. This constancy of mu/rho value for aviation fuels is significant since a nuclear fuel quantity gauging system based on low energy gamma ray attenuation will be viable throughout the world.

  17. Low-energy Antikaon Interaction with Nuclei: The AMADEUS Challenge

    CERN Document Server

    Marton, Johann; Bellotti, Giovanni; Berucci, Carolina; Bosnar, Dimitri; Bragadireanu, Mario; Curceanu, Catalina; Clozza, Alberto; Cargnelli, Michael; Butt, Aslan; Del Grande, Raffaele; Fabbietti, Laura; Fiorini, Carlo; Ghio, Francesco; Guaraldo, Carlo; Iliescu, Mihai; Sandri, Paolo Levi; Pietreanu, Dorel; Piscicchia, Kristian; Vidal, Antonio Romero; Scordo, Alessandro; Shi, Hexi; Sirghi, Diana; Sirghi, Florin; Tucakovic, Ivana; Doce, Oton Vazquez; Widmann, Eberhard; Zmeskal, Johann

    2016-01-01

    The low-energy strong interaction of antikaons (K-) with nuclei has many facets and rep- resents a lively and challenging research ?eld. It is interconnected to the peculiar role of strangeness, since the strange quark is rather light, but still much heavier than the up and down quarks. Thus, when strangeness is involved one has to deal with spontaneous and explicit symmetry breaking in QCD. It is well known that the antikaon interaction with nucleons is attractive, but how strong ? Is the interaction strong enough to bind nucleons to form kaonic nuclei and, if so, what are the properties (binding energy, decay width)? There are controversial indications for such bound states and new results are expected to come soon. The existence of antikaon mediated bound states might have important consequences since it would open the possibility for the formation of cold baryonic matter of high density which might have a severe impact in astrophysics for the understanding of the composi- tion of compact (neutron) stars. ...

  18. A new look at low-energy nuclear reaction research.

    Science.gov (United States)

    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.

  19. Analysis of Latency Performance of Bluetooth Low Energy (BLE) Networks

    Science.gov (United States)

    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

  20. Seeking to Improve Low Energy Neutral Atom Detection in Space

    Science.gov (United States)

    Shappirio, M.; Coplan, M.; Chornay, D.; Collier, M.; Herrero, F.; Ogilvie, K.; Williams, E.

    2007-01-01

    The detection of energetic neutral atoms allows for the remote examination of the interactions between plasmas and neutral populations in space. Before these neutral atoms can be measured, they must first be converted to ions. For the low energy end of this spectrum, interaction with a conversion surface is often the most efficient method to convert neutrals into ions. It is generally thought that the most efficient surfaces are low work functions materials. However, by their very nature, these surfaces are highly reactive and unstable, and therefore are not suitable for space missions where conditions cannot be controlled as they are in a laboratory. We therefore are looking to optimize a stable surface for conversion efficiency. Conversion efficiency can be increased either by changing the incident angle of the neutral particles to be grazing incidence and using stable surfaces with high conversion efficiencies. We have examined how to increase the angle of incidence from -80 degrees to -89 degrees, while maintaining or improving the total active conversion surface area without increasing the overall volume of the instrument. We are developing a method to micro-machine silicon, which will reduce the volume to surface area ratio by a factor of 60. We have also examined the material properties that affect the conversion efficiency of the surface for stable surfaces. Some of the parameters we have examined are work function, smoothness, and bond structure. We find that for stable surfaces, the most important property is the smoothness of the surface.