WorldWideScience

Sample records for nonlinear electron transport

  1. Nonlinear electron transport in magnetized laser plasmas

    International Nuclear Information System (INIS)

    Kho, T.H.; Haines, M.G.

    1986-01-01

    Electron transport in a magnetized plasma heated by inverse bremsstrahlung is studied numerically using a nonlinear Fokker--Planck model with self-consistent E and B fields. The numerical scheme is described. Nonlocal transport is found to alter many of the transport coefficients derived from linear transport theory, in particular, the Nernst and Righi--Leduc effects, in addition to the perpendicular heat flux q/sub perpendicular/, are substantially reduced near critical surface. The magnetic field, however, remains strongly coupled to the nonlinear q/sub perpendicular/ and, as has been found in hydrosimulations, convective amplification of the magnetic field occurs in the overdense plasma

  2. Nonlinear transport behavior of low dimensional electron systems

    Science.gov (United States)

    Zhang, Jingqiao

    The nonlinear behavior of low-dimensional electron systems attracts a great deal of attention for its fundamental interest as well as for potentially important applications in nanoelectronics. In response to microwave radiation and dc bias, strongly nonlinear electron transport that gives rise to unusual electron states has been reported in two-dimensional systems of electrons in high magnetic fields. There has also been great interest in the nonlinear response of quantum ballistic constrictions, where the effects of quantum interference, spatial dispersion and electron-electron interactions play crucial roles. In this thesis, experimental results of the research of low dimensional electron gas systems are presented. The first nonlinear phenomena were observed in samples of highly mobile two dimensional electrons in GaAs heavily doped quantum wells at different magnitudes of DC and AC (10 KHz to 20 GHz) excitations. We found that in the DC excitation regime the differential resistance oscillates with the DC current and external magnetic field, similar behavior was observed earlier in AlGaAs/GaAs heterostructures [C.L. Yang et al. ]. At external AC excitations the resistance is found to be also oscillating as a function of the magnetic field. However the form of the oscillations is considerably different from the DC case. We show that at frequencies below 100 KHz the difference is a result of a specific average of the DC differential resistance during the period of the external AC excitations. Secondly, in similar samples, strong suppression of the resistance by the electric field is observed in magnetic fields at which the Landau quantization of electron motion occurs. The phenomenon survives at high temperatures at which the Shubnikov de Haas oscillations are absent. The scale of the electric fields essential for the effect, is found to be proportional to temperature in the low temperature limit. We suggest that the strong reduction of the longitudinal resistance

  3. Nonlinear features of the electron temperature gradient mode and electron thermal transport in tokamaks

    International Nuclear Information System (INIS)

    Kaw, P.K.; Singh, R.; Weiland, J.G.

    2001-01-01

    Analytical investigations of several linear and nonlinear features of ETG turbulence are reported. The linear theory includes effects such as finite beta induced electromagnetic shielding, coupling to electron magnetohydrodynamic modes like whistlers etc. It is argued that nonlinearly, turbulence and transport are dominated by radially extended modes called 'streamers'. A nonlinear mechanism generating streamers based on a modulational instability theory of the ETG turbulence is also presented. The saturation levels of the streamers using a Kelvin Helmholtz secondary instability mechanism are calculated and levels of the electron thermal transport due to streamers are estimated. (author)

  4. Nonlinear charge transport in bipolar semiconductors due to electron heating

    International Nuclear Information System (INIS)

    Molina-Valdovinos, S.; Gurevich, Yu.G.

    2016-01-01

    It is known that when strong electric field is applied to a semiconductor sample, the current voltage characteristic deviates from the linear response. In this letter, we propose a new point of view of nonlinearity in semiconductors which is associated with the electron temperature dependence on the recombination rate. The heating of the charge carriers breaks the balance between generation and recombination, giving rise to nonequilibrium charge carriers concentration and nonlinearity. - Highlights: • A new mechanism of nonlinearity of current-voltage characteristic (CVC) is proposed. • The hot electron temperature violates the equilibrium between electrons and holes. • This violation gives rise to nonequilibrium concentration of electrons and holes. • This leads to nonlinear CVC (along with the heating nonlinearity).

  5. Nonlinear charge transport in bipolar semiconductors due to electron heating

    Energy Technology Data Exchange (ETDEWEB)

    Molina-Valdovinos, S., E-mail: sergiom@fisica.uaz.edu.mx [Universidad Autónoma de Zacatecas, Unidad Académica de Física, Calzada Solidaridad esq. Paseo, La Bufa s/n, CP 98060, Zacatecas, Zac, México (Mexico); Gurevich, Yu.G. [Centro de Investigación y de Estudios Avanzados del IPN, Departamento de Física, Av. IPN 2508, México D.F., CP 07360, México (Mexico)

    2016-05-27

    It is known that when strong electric field is applied to a semiconductor sample, the current voltage characteristic deviates from the linear response. In this letter, we propose a new point of view of nonlinearity in semiconductors which is associated with the electron temperature dependence on the recombination rate. The heating of the charge carriers breaks the balance between generation and recombination, giving rise to nonequilibrium charge carriers concentration and nonlinearity. - Highlights: • A new mechanism of nonlinearity of current-voltage characteristic (CVC) is proposed. • The hot electron temperature violates the equilibrium between electrons and holes. • This violation gives rise to nonequilibrium concentration of electrons and holes. • This leads to nonlinear CVC (along with the heating nonlinearity).

  6. Nonlinear trapped electron mode and anomalous heat transport in tokamaks

    International Nuclear Information System (INIS)

    Kaw, P.K.

    1982-01-01

    We take the phenomenological point of view that the anomalous electron thermal conductivity produced by the non-linear trapped electron mode should also influence the stability properties of the mode itself. Using a model equation, we show that this effect makes the mode self-stabilizing. A simple expression for the anomalous thermal conductivity is derived, and its scaling properties are discussed. (orig.)

  7. Nonlinear ion-mixing-mode particle transport in the dissipative trapped electron regime

    International Nuclear Information System (INIS)

    Ware, A.S.; Terry, P.W.

    1993-09-01

    The nonlinear particle transport arising from the convection of nonadiabatic electron density by ion temperature gradient driven turbulence is examined for trapped electron collisionality regimes. The renormalized dissipative nonadiabatic trapped electron phase space density response is derived and used to calculate the nonlinear particle flux along with an ansatz for the turbulently broadened frequency spectrum. In the lower temperature end of this regime, trapped electrons are collisional and all components of the quasilinear particle flux are outward (i.e., in the direction of the gradients). Nonlinear effects can alter the phase between the nonadiabatic trapped electron phase space density and the electrostatic potential, producing inward components in the particle flux. Specifically, both turbulent shifting of the peak of the frequency spectrum and nonlinear source terms in the trapped electron response can give rise to inward components. However, in the dissipative regime these terms are small and the trapped electron response remains dominantly laminar. When the trapped electrons are collisionless, there is a temperature threshold above which the electron temperature gradient driven component of the quasilinear particle flux changes sign and becomes inward. For finite amplitude turbulence, however, turbulent broadening of both the electron collisional resonance and the frequency spectrum removes tills threshold., and the temperature gradient driven component remains outward

  8. Strongly nonlinear electronic transport in Cr-Si composite films

    International Nuclear Information System (INIS)

    Burkov, A.T.; Vinzelberg, H.; Schumann, J.; Nakama, T.; Yagasaki, K.

    2004-01-01

    The phase formation, the resistivity and the thermopower of amorphous Cr 0.15 Si 0.85 , and nanocrystalline CrSi 2 -Si thin film composites have been studied. The films were produced by a magnetron sputtering of a composite target onto unheated substrates with subsequent crystallization of the film at high temperatures. As the film composite develops under the heat treatment from the initial amorphous state into the final polycrystalline material, two percolation thresholds were found. At first, the percolating cluster of nanocrystalline CrSi 2 is formed. However, this cluster is destroyed with further annealing due to crystallization and redistribution of Si. The composite films which are close to this insulating threshold reveal a strongly nonlinear conductivity. The conductivity increases with the current by two orders of magnitude

  9. New evidence and impact of electron transport non-linearities based on new perturbative inter-modulation analysis

    Science.gov (United States)

    van Berkel, M.; Kobayashi, T.; Igami, H.; Vandersteen, G.; Hogeweij, G. M. D.; Tanaka, K.; Tamura, N.; Zwart, H. J.; Kubo, S.; Ito, S.; Tsuchiya, H.; de Baar, M. R.; LHD Experiment Group

    2017-12-01

    A new methodology to analyze non-linear components in perturbative transport experiments is introduced. The methodology has been experimentally validated in the Large Helical Device for the electron heat transport channel. Electron cyclotron resonance heating with different modulation frequencies by two gyrotrons has been used to directly quantify the amplitude of the non-linear component at the inter-modulation frequencies. The measurements show significant quadratic non-linear contributions and also the absence of cubic and higher order components. The non-linear component is analyzed using the Volterra series, which is the non-linear generalization of transfer functions. This allows us to study the radial distribution of the non-linearity of the plasma and to reconstruct linear profiles where the measurements were not distorted by non-linearities. The reconstructed linear profiles are significantly different from the measured profiles, demonstrating the significant impact that non-linearity can have.

  10. Electron transport and nonlinear optical properties of substituted aryldimesityl boranes: a DFT study.

    Directory of Open Access Journals (Sweden)

    Altaf Hussain Pandith

    Full Text Available A comprehensive theoretical study was carried out on a series of aryldimesityl borane (DMB derivatives using Density Functional theory. Optimized geometries and electronic parameters like electron affinity, reorganization energy, frontiers molecular contours, polarizability and hyperpolarizability have been calculated by employing B3PW91/6-311++G (d, p level of theory. Our results show that the Hammett function and geometrical parameters correlates well with the reorganization energies and hyperpolarizability for the series of DMB derivatives studied in this work. The orbital energy study reveals that the electron releasing substituents increase the LUMO energies and electron withdrawing substituents decrease the LUMO energies, reflecting the electron transport character of aryldimesityl borane derivatives. From frontier molecular orbitals diagram it is evident that mesityl rings act as the donor, while the phenylene and Boron atom appear as acceptors in these systems. The calculated hyperpolarizability of secondary amine derivative of DMB is 40 times higher than DMB (1. The electronic excitation contributions to the hyperpolarizability studied by using TDDFT calculation shows that hyperpolarizability correlates well with dipole moment in ground and excited state and excitation energy in terms of the two-level model. Thus the results of these calculations can be helpful in designing the DMB derivatives for efficient electron transport and nonlinear optical material by appropriate substitution with electron releasing or withdrawing substituents on phenyl ring of DMB system.

  11. New evidence and impact of electron transport non-linearities based on new perturbative inter-modulation analysis

    NARCIS (Netherlands)

    van Berkel, M.; Kobayashi, T.; Igami, H.; Vandersteen, Gerd; Hogeweij, G.M.D.; Tanaka, K.; Tamura, N.; Zwart, Hans; Kubo, S.; Ito, S.; Tsuchiya, H.; de Baar, M.R.

    2017-01-01

    A new methodology to analyze non-linear components in perturbative transport experiments is introduced. The methodology has been experimentally validated in the Large Helical Device for the electron heat transport channel. Electron cyclotron resonance heating with different modulation frequencies by

  12. Nonlinear electron transport in InAs/AlGaSb three-terminal ballistic junctions

    International Nuclear Information System (INIS)

    Koyama, M; Inoue, T; Amano, N; Maemoto, T; Sasa, S; Inoue, M

    2008-01-01

    We have fabricated and characterized an InAs/AlGaSb three-terminal ballistic junction device. The fabricated device exhibited nonlinear electron transport properties because of ballistic motion of electrons in this structure that is comparable to the electron mean free path. When the left branch is biased to a finite voltage Vand the right to a voltage of -V (push-pull fashion), negative voltages appeared at the floating central branch regardless of the polarity of the input voltages. In the case of the central branch grounded in push-pull fashion, the clear current rectification effect also observed in the current flow of the central branch at 4.2K to even at 300K

  13. Non-linear gyrokinetic simulations of microturbulence in TCV electron internal transport barriers

    Energy Technology Data Exchange (ETDEWEB)

    Lapillonne, X; Brunner, S; Sauter, O; Villard, L [Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Fable, E; Goerler, T; Jenko, F; Merz, F, E-mail: stephan.brunner@epfl.ch [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)

    2011-05-15

    Using the local (flux-tube) version of the Eulerian code GENE (Jenko et al 2000 Phys. Plasmas 7 1904), gyrokinetic simulations of microturbulence were carried out considering parameters relevant to electron-internal transport barriers (e-ITBs) in the TCV tokamak (Sauter et al 2005 Phys. Rev. Lett. 94 105002), generated under conditions of low or negative shear. For typical density and temperature gradients measured in such barriers, the corresponding simulated fluctuation spectra appears to simultaneously contain longer wavelength trapped electron modes (TEMs, for typically k{sub p}erpendicular{rho}{sub i} < 0.5, k{sub p}erpendicular being the characteristic perpendicular wavenumber and {rho}{sub i} the ion Larmor radius) and shorter wavelength ion temperature gradient modes (ITG, k{sub p}erpendicular{rho}{sub i} > 0.5). The contributions to the electron particle flux from these two types of modes are, respectively, outward/inward and may cancel each other for experimentally realistic gradients. This mechanism may partly explain the feasibility of e-ITBs. The non-linear simulation results confirm the predictions of a previously developed quasi-linear model (Fable et al 2010 Plasma Phys. Control. Fusion 52 015007), namely that the stationary condition of zero particle flux is obtained through the competitive contributions of ITG and TEM. A quantitative comparison of the electron heat flux with experimental estimates is presented as well.

  14. Non-linear gyrokinetic simulations of microturbulence in TCV electron internal transport barriers

    Science.gov (United States)

    Lapillonne, X.; Brunner, S.; Sauter, O.; Villard, L.; Fable, E.; Görler, T.; Jenko, F.; Merz, F.

    2011-05-01

    Using the local (flux-tube) version of the Eulerian code GENE (Jenko et al 2000 Phys. Plasmas 7 1904), gyrokinetic simulations of microturbulence were carried out considering parameters relevant to electron-internal transport barriers (e-ITBs) in the TCV tokamak (Sauter et al 2005 Phys. Rev. Lett. 94 105002), generated under conditions of low or negative shear. For typical density and temperature gradients measured in such barriers, the corresponding simulated fluctuation spectra appears to simultaneously contain longer wavelength trapped electron modes (TEMs, for typically k⊥ρi 0.5). The contributions to the electron particle flux from these two types of modes are, respectively, outward/inward and may cancel each other for experimentally realistic gradients. This mechanism may partly explain the feasibility of e-ITBs. The non-linear simulation results confirm the predictions of a previously developed quasi-linear model (Fable et al 2010 Plasma Phys. Control. Fusion 52 015007), namely that the stationary condition of zero particle flux is obtained through the competitive contributions of ITG and TEM. A quantitative comparison of the electron heat flux with experimental estimates is presented as well.

  15. A Static and Dynamic Investigation of Quantum Nonlinear Transport in Highly Dense and Mobile 2D Electron Systems

    Science.gov (United States)

    Dietrich, Scott

    Heterostructures made of semiconductor materials may be one of most versatile environments for the study of the physics of electron transport in two dimensions. These systems are highly customizable and demonstrate a wide range of interesting physical phenomena. In response to both microwave radiation and DC excitations, strongly nonlinear transport that gives rise to non-equilibrium electron states has been reported and investigated. We have studied GaAs quantum wells with a high density of high mobility two-dimensional electrons placed in a quantizing magnetic field. This study presents the observation of several nonlinear transport mechanisms produced by the quantum nature of these materials. The quantum scattering rate, 1tau/q, is an important parameter in these systems, defining the width of the quantized energy levels. Traditional methods of extracting 1tau/q involve studying the amplitude of Shubnikov-de Haas oscillations. We analyze the quantum positive magnetoresistance due to the cyclotron motion of electrons in a magnetic field. This method gives 1tau/q and has the additional benefit of providing access to the strength of electron-electron interactions, which is not possible by conventional techniques. The temperature dependence of the quantum scattering rate is found to be proportional to the square of the temperature and is in very good agreement with theory that considers electron-electron interactions in 2D systems. In quantum wells with a small scattering rate - which corresponds to well-defined Landau levels - quantum oscillations of nonlinear resistance that are independent of magnetic field strength have been observed. These oscillations are periodic in applied bias current and are connected to quantum oscillations of resistance at zero bias: either Shubnikov-de Haas oscillations for single subband systems or magnetointersubband oscillations for two subband systems. The bias-induced oscillations can be explained by a spatial variation of electron

  16. Electronic and magnetic phase separation in EuB6. Fluctuation spectroscopy and nonlinear transport

    International Nuclear Information System (INIS)

    Amyan, Adham

    2013-01-01

    The main topics of this thesis are electrical, stationary, and time-resolved transport measurements on EuB 6 as well as the further development of measuring methods and analysis procedures of the fluctuation spectroscopy. The first part of this thesis was dedicated to the further development of the already known measuring methods under application of a fast data-acquisition card. The second part deals with the electrical transport properties of EuB 6 and the understanding of the coupling between charge and magnetic degrees of freedom. By means of resistance and nonlinear-transport measurements as well as fluctuation spectroscopy hypotheses of other scientists were systematically verified as well as new knowledge obtained. The magnetoresistance was studied as function of the temperature in small external magnetic fields between 1 mT and 700 mT. Measurements of the third harmonic resistance as function of the temperature show maxima at T MI and T C . Electrical-resistance fluctuations were measured without external magnetic field between 5 and 100 K as well in presence of a magnetic field between 18 K and 32 K. At constant temperature measurements of the spectral power density in external magnetic fields were performed in the temperature range from 18 K to 32 K. Highly resolving measurements of the thermal expansion coefficient showed a very strong coupling of the magnetic (polaronic) degrees of freedom to the crystal lattice.

  17. Nonlinear dynamics and plasma transport

    International Nuclear Information System (INIS)

    Antonsen, T.M. Jr.; Drake, J.F.; Finn, J.M.; Guzdar, P.N.; Hassam, A.B.; Sagdeev, R.Z.

    1992-01-01

    In this paper we summarize the progress made over the last year in three different areas of research: (a) shear flow generation and reduced transport in fluids and plasma, (b) nonlinear dynamics and visualization of 3D flows, and (c) application of wavelet analysis to the study of fractal dimensions in experimental and numerical data

  18. Nonlinear transport of dynamic system phase space

    International Nuclear Information System (INIS)

    Xie Xi; Xia Jiawen

    1993-01-01

    The inverse transform of any order solution of the differential equation of general nonlinear dynamic systems is derived, realizing theoretically the nonlinear transport for the phase space of nonlinear dynamic systems. The result is applicable to general nonlinear dynamic systems, with the transport of accelerator beam phase space as a typical example

  19. Neoclassical transport including collisional nonlinearity.

    Science.gov (United States)

    Candy, J; Belli, E A

    2011-06-10

    In the standard δf theory of neoclassical transport, the zeroth-order (Maxwellian) solution is obtained analytically via the solution of a nonlinear equation. The first-order correction δf is subsequently computed as the solution of a linear, inhomogeneous equation that includes the linearized Fokker-Planck collision operator. This equation admits analytic solutions only in extreme asymptotic limits (banana, plateau, Pfirsch-Schlüter), and so must be solved numerically for realistic plasma parameters. Recently, numerical codes have appeared which attempt to compute the total distribution f more accurately than in the standard ordering by retaining some nonlinear terms related to finite-orbit width, while simultaneously reusing some form of the linearized collision operator. In this work we show that higher-order corrections to the distribution function may be unphysical if collisional nonlinearities are ignored.

  20. Nonlinear dynamics and plasma transport

    International Nuclear Information System (INIS)

    Liu, C.S.; Sagdeev, R.; Antonsen, T.; Drake, J.; Hassma, A.; Guzdar, P.N.

    1995-12-01

    This progress report reports work done on a program in nonlinear dynamical aspects of plasma turbulence and transport funded by DOE from 1992-1995. The purpose of this program has been to promote the utilization of recent pathbreaking developments in nonlinear science in plasma turbulence and transport and to fully utilize the scientific expertise of Russian fusion and plasma community in collaboration with our group to address outstanding fusion theory problems. In the work reported in our progress report, we have studied simple models which are motivated by observation on actual fusion devices. The models focus on the important physical processes without incorporating the complexity of the geometry of real devices. We have also studied linear stability problems which incorporated important physics issues related to geometry involving closed field lines and open field lines. This allows for a deeper analysis and understanding of the system both analytically and numerically. The strong collaboration between the Russian visitors and the US participants has led to a fruitful and strong research program that taps the complementary analytic and numerical capabilities of the two groups. Over the years several distinguished Russian visitors have interacted with various members of the group and set up collaborative work which forms a significant part of proposed research. Dr. Galeev, Director of the Space Research Institute of Moscow and Dr. Novakovskii from the Kurchatov Institute are two such ongoing collaborations. 21 refs

  1. Nonlinear transport of accelerator beam phase space

    International Nuclear Information System (INIS)

    Xie Xi; Xia Jiawen

    1995-01-01

    Based on the any order analytical solution of accelerator beam dynamics, the general theory for nonlinear transport of accelerator beam phase space is developed by inverse transformation method. The method is general by itself, and hence can also be applied to the nonlinear transport of various dynamic systems in physics, chemistry and biology

  2. Paleoclassical electron heat transport

    International Nuclear Information System (INIS)

    Callen, J.D.

    2005-01-01

    Radial electron heat transport in low collisionality, magnetically-confined toroidal plasmas is shown to result from paleoclassical Coulomb collision processes (parallel electron heat conduction and magnetic field diffusion). In such plasmas the electron temperature equilibrates along magnetic field lines a long length L, which is the minimum of the electron collision length and a maximum effective half length of helical field lines. Thus, the diffusing field lines induce a radial electron heat diffusivity M ≅ L/(πR 0q ) ∼ 10 >> 1 times the magnetic field diffusivity η/μ 0 ≅ ν e (c/ω p ) 2 . The paleoclassical electron heat flux model provides interpretations for many features of 'anomalous' electron heat transport: magnitude and radial profile of electron heat diffusivity (in tokamaks, STs, and RFPs), Alcator scaling in high density plasmas, transport barriers around low order rational surfaces and near a separatrix, and a natural heat pinch (or minimum temperature gradient) heat flux form. (author)

  3. Nonlinear transport theory in the metal with tunnel barrier

    Science.gov (United States)

    Zubov, E. E.

    2018-02-01

    Within the framework of the scattering matrix formalism, the nonlinear Kubo theory for electron transport in the metal with a tunnel barrier has been considered. A general expression for the mean electrical current was obtained. It significantly simplifies the calculation of nonlinear contributions to the conductivity of various hybrid structures. In the model of the tunnel Hamiltonian, all linear and nonlinear contributions to a mean electrical current are evaluated. The linear approximation agrees with results of other theories. For effective barrier transmission ?, the ballistic transport is realised with a value of the Landauer conductivity equal to ?.

  4. Nonlinear transport processes in tokamak plasmas. I. The collisional regimes

    International Nuclear Information System (INIS)

    Sonnino, Giorgio; Peeters, Philippe

    2008-01-01

    An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear ('Onsager') transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlueter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for Joint European Torus (JET) plasmas are also reported. It is found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor that may be of the order 10 2 . The nonlinear classical coefficients exceed the neoclassical ones by a factor that may be of order 2. For JET, the discrepancy between experimental and theoretical results for the electron losses is therefore significantly reduced by a factor 10 2 when the nonlinear contributions are duly taken into account but, there is still a factor of 10 2 to be explained. This is most likely due to turbulence. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain unaltered. The low-collisional regimes, i.e., the plateau and the banana regimes, are analyzed in the second part of this work

  5. Nonlinear Ballistic Transport in an Atomically Thin Material.

    Science.gov (United States)

    Boland, Mathias J; Sundararajan, Abhishek; Farrokhi, M Javad; Strachan, Douglas R

    2016-01-26

    Ultrashort devices that incorporate atomically thin components have the potential to be the smallest electronics. Such extremely scaled atomically thin devices are expected to show ballistic nonlinear behavior that could make them tremendously useful for ultrafast applications. While nonlinear diffusive electron transport has been widely reported, clear evidence for intrinsic nonlinear ballistic transport in the growing array of atomically thin conductors has so far been elusive. Here we report nonlinear electron transport of an ultrashort single-layer graphene channel that shows quantitative agreement with intrinsic ballistic transport. This behavior is shown to be distinctly different than that observed in similarly prepared ultrashort devices consisting, instead, of bilayer graphene channels. These results suggest that the addition of only one extra layer of an atomically thin material can make a significant impact on the nonlinear ballistic behavior of ultrashort devices, which is possibly due to the very different chiral tunneling of their charge carriers. The fact that we observe the nonlinear ballistic response at room temperature, with zero applied magnetic field, in non-ultrahigh vacuum conditions and directly on a readily accessible oxide substrate makes the nanogap technology we utilize of great potential for achieving extremely scaled high-speed atomically thin devices.

  6. Improved electron transport layer

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides: a method of preparing a coating ink for forming a zinc oxide electron transport layer, comprising mixing zinc acetate and a wetting agent in water or methanol; a coating ink comprising zinc acetate and a wetting agent in aqueous solution or methanolic solution......; a method of preparing a zinc oxide electron transporting layer, which method comprises: i) coating a substrate with the coating ink of the present invention to form a film; ii) drying the film; and iii) heating the dry film to convert the zinc acetate substantially to ZnO; a method of preparing an organic...... photovoltaic device or an organic LED having a zinc oxide electron transport layer, the method comprising, in this order: a) providing a substrate bearing a first electrode layer; b) forming an electron transport layer according to the following method: i) coating a coating ink comprising an ink according...

  7. Electronic transport properties

    International Nuclear Information System (INIS)

    Young, W.H.

    1985-01-01

    The theory of the electron transport properties of liquid alkali metals is described. Conductivity coefficients, Boltzmann theory, Ziman theory, alkali form factors, Ziman theory and alkalis, Faber-Ziman alloy theory, Faber-Ziman theory and alkali-alkali methods, status of Ziman theory, and other transport properties, are all discussed. (UK)

  8. Nonlinear acceleration of transport criticality problems

    International Nuclear Information System (INIS)

    Park, H.; Knoll, D.A.; Newman, C.K.

    2011-01-01

    We present a nonlinear acceleration algorithm for the transport criticality problem. The algorithm combines the well-known nonlinear diffusion acceleration (NDA) with a recently developed, Newton-based, nonlinear criticality acceleration (NCA) algorithm. The algorithm first employs the NDA to reduce the system to scalar flux, then the NCA is applied to the resulting drift-diffusion system. We apply a nonlinear elimination technique to eliminate the eigenvalue from the Jacobian matrix. Numerical results show that the algorithm reduces the CPU time a factor of 400 in a very diffusive system, and a factor of 5 in a non-diffusive system. (author)

  9. Hydrodynamic approach to electronic transport in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Narozhny, Boris N. [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation); Gornyi, Igor V. [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe (Germany); Ioffe Physical Technical Institute, St. Petersburg (Russian Federation); Mirlin, Alexander D. [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Institute of Nanotechnology, Karlsruhe Institute of Technology, Karlsruhe (Germany); Petersburg Nuclear Physics Institute, St. Petersburg (Russian Federation); Schmalian, Joerg [Institute for Theoretical Condensed Matter Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Institute for Solid State Physics, Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2017-11-15

    The last few years have seen an explosion of interest in hydrodynamic effects in interacting electron systems in ultra-pure materials. In this paper we briefly review the recent advances, both theoretical and experimental, in the hydrodynamic approach to electronic transport in graphene, focusing on viscous phenomena, Coulomb drag, non-local transport measurements, and possibilities for observing nonlinear effects. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Non-linear spin transport in magnetic semiconductor superlattices

    International Nuclear Information System (INIS)

    Bejar, Manuel; Sanchez, David; Platero, Gloria; MacDonald, A.H.

    2004-01-01

    The electronic spin dynamics in DC-biased n-doped II-VI semiconductor multiquantum wells doped with magnetic impurities is presented. Under certain range of electronic doping, conventional semiconductor superlattices present self-sustained oscillations. Magnetically doped wells (Mn) present large spin splittings due to the exchange interaction. The interplay between non-linear interwell transport, the electron-electron interaction and the exchange between electrons and the magnetic impurities produces interesting time-dependent features in the spin polarization current tuned by an external magnetic field

  11. Nonlinear Electron Waves in Strongly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens

    1980-01-01

    Weakly nonlinear dispersive electron waves in strongly magnetized plasma are considered. A modified nonlinear Schrodinger equation is derived taking into account the effect of particles resonating with the group velocity of the waves (nonlinear Landau damping). The possibility of including the ion...... dynamics in the analysis is also demonstrated. As a particular case the authors investigate nonlinear waves in a strongly magnetized plasma filled wave-guide, where the effects of finite geometry are important. The relevance of this problem to laboratory experiments is discussed....

  12. Enhancing Thermoelectric Performance Using Nonlinear Transport Effects

    Science.gov (United States)

    Jiang, Jian-Hua; Imry, Yoseph

    2017-06-01

    We study nonlinear transport effects on the maximum efficiency and power for both inelastic and elastic thermoelectric generators. The former device refers to phonon-assisted hopping in double quantum dots, while the latter device is represented by elastic tunneling through a single quantum dot. We find that nonlinear thermoelectric transport can lead to enhanced efficiency and power for both types of devices. A comprehensive survey of various quantum-dot energy, temperature, and parasitic heat conduction reveals that the nonlinear transport-induced improvements of the maximum efficiency and power are overall much more significant for inelastic devices than for elastic devices, even for temperature biases as small as Th=1.2 Tc (Th and Tc are the temperatures of the hot and cold reservoirs, respectively). The underlying mechanism is revealed as due to the fact that, unlike the Fermi distribution, the Bose distribution is not bounded when the temperature bias increases. A large flux density of absorbed phonons leads to a great enhancement of the electrical current, output power, and energy efficiency, dominating over the concurrent increase of the parasitic heat current. Our study reveals that nonlinear transport effects can be a useful tool for improving thermoelectric performance.

  13. Test particles dynamics in the JOREK 3D non-linear MHD code and application to electron transport in a disruption simulation

    Science.gov (United States)

    Sommariva, C.; Nardon, E.; Beyer, P.; Hoelzl, M.; Huijsmans, G. T. A.; van Vugt, D.; Contributors, JET

    2018-01-01

    In order to contribute to the understanding of runaway electron generation mechanisms during tokamak disruptions, a test particle tracker is introduced in the JOREK 3D non-linear MHD code, able to compute both full and guiding center relativistic orbits. Tests of the module show good conservation of the invariants of motion and consistency between full orbit and guiding center solutions. A first application is presented where test electron confinement properties are investigated in a massive gas injection-triggered disruption simulation in JET-like geometry. It is found that electron populations initialised before the thermal quench (TQ) are typically not fully deconfined in spite of the global stochasticity of the magnetic field during the TQ. The fraction of ‘survivors’ decreases from a few tens down to a few tenths of percent as the electron energy varies from 1 keV to 10 MeV. The underlying mechanism for electron ‘survival’ is the prompt reformation of closed magnetic surfaces at the plasma core and, to a smaller extent, the subsequent reappearance of a magnetic surface at the edge. It is also found that electrons are less deconfined at 10 MeV than at 1 MeV, which appears consistent with a phase averaging effect due to orbit shifts at high energy.

  14. Nonlinear acceleration of SN transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Fichtl, Erin D [Los Alamos National Laboratory; Warsa, James S [Los Alamos National Laboratory; Calef, Matthew T [Los Alamos National Laboratory

    2010-12-20

    The use of nonlinear iterative methods, Jacobian-Free Newton-Krylov (JFNK) in particular, for solving eigenvalue problems in transport applications has recently become an active subject of research. While JFNK has been shown to be effective for k-eigenvalue problems, there are a number of input parameters that impact computational efficiency, making it difficult to implement efficiently in a production code using a single set of default parameters. We show that different selections for the forcing parameter in particular can lead to large variations in the amount of computational work for a given problem. In contrast, we present a nonlinear subspace method that sits outside and effectively accelerates nonlinear iterations of a given form and requires only a single input parameter, the subspace size. It is shown to consistently and significantly reduce the amount of computational work when applied to fixed-point iteration, and this combination of methods is shown to be more efficient than JFNK for our application.

  15. Electron acoustic nonlinear structures in planetary magnetospheres

    Science.gov (United States)

    Shah, K. H.; Qureshi, M. N. S.; Masood, W.; Shah, H. A.

    2018-04-01

    In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized ( r , q ) distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized ( r , q ) distribution. It has been found that the flatness parameter r , tail parameter q , and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.

  16. Electron dynamics with radiation and nonlinear wigglers

    International Nuclear Information System (INIS)

    Jowett, J.M.

    1986-06-01

    The physics of electron motion in storage rings is described by supplementing the Hamiltonian equations of motion with fluctuating radiation reaction forces to describe the effects of synchrotron radiation. This leads to a description of radiation damping and quantum diffusion in single-particle phase-space by means of Fokker-Planck equations. For practical purposes, most storage rings remain in the regime of linear damping and diffusion; this is discussed in some detail with examples, concentrating on longitudinal phase space. However special devices such as nonlinear wigglers may permit the new generation of very large rings to go beyond this into regimes of nonlinear damping. It is shown how a special combined-function wiggler can be used to modify the energy distribution and current profile of electron bunches

  17. Nonlinear neoclassical transport in toroidal edge plasmas

    International Nuclear Information System (INIS)

    Fueloep, T.; Helander, P.

    2001-01-01

    In conventional neoclassical theory, the density and temperature gradients are not allowed to be as steep as frequently observed in the tokamak edge. In this paper the theory of neoclassical transport in a collisional, impure plasma is extended to allow for steeper profiles than normally assumed. The dynamics of highly charged impurity ions then becomes nonlinear, which affects the transport of all species. As earlier found in the banana regime, when the bulk plasma gradients are large the impurity ions undergo a poloidal redistribution, which reduces their parallel friction with the bulk ions and suppresses the neoclassical ion particle flux. The neoclassical confinement is thus improved in regions with large radial gradients. When the plasma is collisional and the gradients are large, the impurities accumulate on the inboard side of the torus

  18. Nonlinearity in structural and electronic materials

    International Nuclear Information System (INIS)

    Bishop, A.R.; Beardmore, K.M.; Ben-Naim, E.

    1997-01-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project strengthens a nonlinear technology base relevant to a variety of problems arising in condensed matter and materials science, and applies this technology to those problems. In this way the controlled synthesis of, and experiments on, novel electronic and structural materials provide an important focus for nonlinear science, while nonlinear techniques help advance the understanding of the scientific principles underlying the control of microstructure and dynamics in complex materials. This research is primarily focused on four topics: (1) materials microstructure: growth and evolution, and porous media; (2) textures in elastic/martensitic materials; (3) electro- and photo-active polymers; and (4) ultrafast photophysics in complex electronic materials. Accomplishments included the following: organization of a ''Nonlinear Materials'' seminar series and international conferences including ''Fracture, Friction and Deformation,'' ''Nonequilibrium Phase Transitions,'' and ''Landscape Paradigms in Physics and Biology''; invited talks at international conference on ''Synthetic Metals,'' ''Quantum Phase Transitions,'' ''1996 CECAM Euroconference,'' and the 1995 Fall Meeting of the Materials Research Society; large-scale simulations and microscopic modeling of nonlinear coherent energy storage at crack tips and sliding interfaces; large-scale simulation and microscopic elasticity theory for precursor microstructure and dynamics at solid-solid diffusionless phase transformations; large-scale simulation of self-assembling organic thin films on inorganic substrates; analysis and simulation of smoothing of rough atomic surfaces; and modeling and analysis of flux pattern formation in equilibrium and nonequilibrium Josephson junction arrays and layered superconductors

  19. Transport processes in magnetically confined plasmas in the nonlinear regime.

    Science.gov (United States)

    Sonnino, Giorgio

    2006-06-01

    A field theory approach to transport phenomena in magnetically confined plasmas is presented. The thermodynamic field theory (TFT), previously developed for treating the generic thermodynamic system out of equilibrium, is applied to plasmas physics. Transport phenomena are treated here as the effect of the field linking the thermodynamic forces with their conjugate flows combined with statistical mechanics. In particular, the Classical and the Pfirsch-Schluter regimes are analyzed by solving the thermodynamic field equations of the TFT in the weak-field approximation. We found that, the TFT does not correct the expressions of the ionic heat fluxes evaluated by the neoclassical theory in these two regimes. On the other hand, the fluxes of matter and electronic energy (heat flow) is further enhanced in the nonlinear Classical and Pfirsch-Schluter regimes. These results seem to be in line with the experimental observations. The complete set of the electronic and ionic transport equations in the nonlinear Banana regime, is also reported. A paper showing the comparison between our theoretic results and the experimental observations in the JET machine is currently in preparation.

  20. Weakly nonlinear electron plasma waves in collisional plasmas

    DEFF Research Database (Denmark)

    Pecseli, H. L.; Rasmussen, J. Juul; Tagare, S. G.

    1986-01-01

    The nonlinear evolution of a high frequency plasma wave in a weakly magnetized, collisional plasma is considered. In addition to the ponderomotive-force-nonlinearity the nonlinearity due to the heating of the electrons is taken into account. A set of nonlinear equations including the effect...

  1. Conditioner for a helically transported electron beam

    International Nuclear Information System (INIS)

    Wang, Changbiao.

    1992-05-01

    The kinetic theory is developed to investigate a conditioner for a helically transported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron's relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value

  2. Integral representation of nonlinear heat transport

    International Nuclear Information System (INIS)

    Kishimoto, Y.; Mima, K.; Haines, M.G.

    1985-07-01

    The electron distribution function in a plasma with steep temperature gradient is obtained from a Fokker-Planck equation by Green's function method. The formula describes the nonlocal effects on thermal transport over the range, λ e /L e /L → 0. As an example, the heat wave is analyzed numerically by the integral formula and it is found that the previous simulation results are well reproduced. (author)

  3. Monte Carlo Transport for Electron Thermal Transport

    Science.gov (United States)

    Chenhall, Jeffrey; Cao, Duc; Moses, Gregory

    2015-11-01

    The iSNB (implicit Schurtz Nicolai Busquet multigroup electron thermal transport method of Cao et al. is adapted into a Monte Carlo transport method in order to better model the effects of non-local behavior. The end goal is a hybrid transport-diffusion method that combines Monte Carlo Transport with a discrete diffusion Monte Carlo (DDMC). The hybrid method will combine the efficiency of a diffusion method in short mean free path regions with the accuracy of a transport method in long mean free path regions. The Monte Carlo nature of the approach allows the algorithm to be massively parallelized. Work to date on the method will be presented. This work was supported by Sandia National Laboratory - Albuquerque and the University of Rochester Laboratory for Laser Energetics.

  4. Nonlinear wavenumber of an electron plasma wave

    International Nuclear Information System (INIS)

    Vidmar, P.J.; Malmberg, J.H.; Starke, T.P.

    1976-01-01

    The wavenumber of a large-amplitude electron plasma wave propagating on a collisionless plasma column is measured. The wavenumber is shifted from that of a small-amplitude wave of the same frequency. This nonlinear wavenumber shift, deltak/subr/, depends on position, frequency, and initial wave amplitude, Phi. The observed spatial oscillations of deltak/subr/ agree qualitatively with recent theories. Experimentally deltak/subr/proportionalk/subi/S (Phi) rootPhi where k/subi/ is the linear Landau damping coefficient, S (Phi) equivalentk/subi/(Phi)/k/subi/, and k/subi/(Phi) is the initial damping coefficient which depends on Phi

  5. Molecular electronic junction transport

    DEFF Research Database (Denmark)

    Solomon, Gemma C.; Herrmann, Carmen; Ratner, Mark

    2012-01-01

    Whenasinglemolecule,oracollectionofmolecules,isplacedbetween two electrodes and voltage is applied, one has a molecular transport junction. We discuss such junctions, their properties, their description, and some of their applications. The discussion is qualitative rather than quantitative, and f...

  6. Electronic and magnetic phase separation in EuB{sub 6}. Fluctuation spectroscopy and nonlinear transport; Elektronische und magnetische Phasenseparation in EuB{sub 6}. Fluktuationsspektroskopie und nichtlinearer Transport

    Energy Technology Data Exchange (ETDEWEB)

    Amyan, Adham

    2013-07-09

    The main topics of this thesis are electrical, stationary, and time-resolved transport measurements on EuB{sub 6} as well as the further development of measuring methods and analysis procedures of the fluctuation spectroscopy. The first part of this thesis was dedicated to the further development of the already known measuring methods under application of a fast data-acquisition card. The second part deals with the electrical transport properties of EuB{sub 6} and the understanding of the coupling between charge and magnetic degrees of freedom. By means of resistance and nonlinear-transport measurements as well as fluctuation spectroscopy hypotheses of other scientists were systematically verified as well as new knowledge obtained. The magnetoresistance was studied as function of the temperature in small external magnetic fields between 1 mT and 700 mT. Measurements of the third harmonic resistance as function of the temperature show maxima at T{sub MI} and T{sub C}. Electrical-resistance fluctuations were measured without external magnetic field between 5 and 100 K as well in presence of a magnetic field between 18 K and 32 K. At constant temperature measurements of the spectral power density in external magnetic fields were performed in the temperature range from 18 K to 32 K. Highly resolving measurements of the thermal expansion coefficient showed a very strong coupling of the magnetic (polaronic) degrees of freedom to the crystal lattice.

  7. A nonlinear bounce kinetic equation for trapped electrons

    International Nuclear Information System (INIS)

    Gang, F.Y.

    1990-03-01

    A nonlinear bounce averaged drift kinetic equation for trapped electrons is derived. This equation enables one to compute the nonlinear response of the trapped electron distribution function in terms of the field-line projection of a potential fluctuation left-angle e -inqθ φ n right-angle b . It is useful for both analytical and computational studies of the nonlinear evolution of short wavelength (n much-gt 1) trapped electron mode-driven turbulence. 7 refs

  8. Nonlinear neoclassical transport in toroidal edge plasmas

    International Nuclear Information System (INIS)

    Fueloep, T.

    2002-01-01

    Edge plasma processes play a critical role for the global confinement of the plasma in a tokamak. In the edge region, where impurity ions are abundant and the temperature and density gradients are large, the assumptions of standard neoclassical theory break down. This paper reviews recent extensions of neoclassical theory to treat this problem, in particular our own work, which focuses on the nonlinear aspects of transport in a plasma with heavy impurity ions. In this theory, the pressure and temperature gradients are allowed to be steeper than in conventional theory neoclassical theory, so that the friction force between the bulk ions and heavy impurities is comparable to the parallel impurity pressure gradient. The impurity ions are then found to undergo a spontaneous rearrangement on each flux surface. This reduces their parallel friction with the bulk ions and causes the neoclassical ion flux to become a non-monotonic function of the gradients for plasma parameters typical of the tokamak edge. Thus, the neoclassical confinement is improved in regions where the gradients are large, such as in the edge pedestal. (orig.)

  9. Excess electron transport in cryoobjects

    International Nuclear Information System (INIS)

    Eshchenko, D.G.; Storchak, V.G.; Brewer, J.H.; Cottrell, S.P.; Cox, S.F.J.

    2003-01-01

    Experimental results on excess electron transport in solid and liquid phases of Ne, Ar, and solid N 2 -Ar mixture are presented and compared with those for He. Muon spin relaxation technique in frequently switching electric fields was used to study the phenomenon of delayed muonium formation: excess electrons liberated in the μ + ionization track converge upon the positive muons and form Mu (μ + e - ) atoms. This process is shown to be crucially dependent upon the electron's interaction with its environment (i.e., whether it occupies the conduction band or becomes localized in a bubble of tens of angstroms in radius) and upon its mobility in these states. The characteristic lengths involved are 10 -6 -10 -4 cm, the characteristic times range from nanoseconds to tens microseconds. Such a microscopic length scale sometimes enables the electron spend its entire free lifetime in a state which may not be detected by conventional macroscopic techniques. The electron transport processes are compared in: liquid and solid helium (where electron is localized in buble); liquid and solid neon (where electrons are delocalized in solid and the coexistence of localized and delocalized electrons states was found in liquid recently); liquid and solid argon (where electrons are delocalized in both phases); orientational glass systems (solid N 2 -Ar mixtures), where our results suggest that electrons are localized in orientational glass. This scaling from light to heavy rare gases enables us to reveal new features of excess electron localization on microscopic scale. Analysis of the experimental data makes it possible to formulate the following tendency of the muon end-of-track structure in condensed rare gases. The muon-self track interaction changes from the isolated pair (muon plus the nearest track electron) in helium to multi-pair (muon in the vicinity of tens track electrons and positive ions) in argon

  10. Nonlinear fiber optics formerly quantum electronics

    CERN Document Server

    Agrawal, Govind

    1995-01-01

    The field of nonlinear fiber optics has grown substantially since the First Edition of Nonlinear Fiber Optics, published in 1989. Like the First Edition, this Second Edition is a comprehensive, tutorial, and up-to-date account of nonlinear optical phenomena in fiber optics. It synthesizes widely scattered research material and presents it in an accessible manner for students and researchers already engaged in or wishing to enter the field of nonlinear fiber optics. Particular attention is paid to the importance of nonlinear effects in the design of optical fiber communication systems. This is

  11. XXIII International Conference on Nonlinear Dynamics of Electronic Systems

    CERN Document Server

    Stoop, Ruedi; Stramaglia, Sebastiano

    2017-01-01

    This book collects contributions to the XXIII international conference “Nonlinear dynamics of electronic systems”. Topics range from non-linearity in electronic circuits to synchronisation effects in complex networks to biological systems, neural dynamics and the complex organisation of the brain. Resting on a solid mathematical basis, these investigations address highly interdisciplinary problems in physics, engineering, biology and biochemistry.

  12. Nonlinear theory of the free-electron laser

    International Nuclear Information System (INIS)

    Chian, A.C.-L.; Padua Brito Serbeto, A. de.

    1984-01-01

    A theory of Raman free-electron laser using a circularly polarized electromagnetic pump is investigated. Coupled wave equations that describe both linear and nonlinear evolution of stimulated Raman scattering are derived. The dispersion relation and the growth rate for the parametric instability are obtained. Nonlinear processes that may lead to saturation of the free-electron laser are discussed. (Author) [pt

  13. Electron thermal transport in tokamak: ETG or TEM turbulences?

    International Nuclear Information System (INIS)

    Lin, Z.; Chen, L.; Nishimura, Y.; Qu, H.; Hahm, T.S.; Lewandowski, J.; Rewoldt, G.; Wang, W.X.; Diamond, P.H.; Holland, C.; Zonca, F.; Li, Y.

    2005-01-01

    This paper reports progress on numerical and theoretical studies of electron transport in tokamak including: (1) electron temperature gradient turbulence; (2) trapped electron mode turbulence; and (3) a new finite element solver for global electromagnetic simulation. In particular, global gyrokinetic particle simulation and nonlinear gyrokinetic theory find that electron temperature gradient (ETG) instability saturates via nonlinear toroidal couplings, which transfer energy successively from unstable modes to damped modes preferably with longer poloidal wavelengths. The electrostatic ETG turbulence is dominated by nonlinearly generated radial streamers. The length of streamers scales with the device size and is much longer than the distance between mode rational surfaces or electron radial excursions. Both fluctuation intensity and transport level are independent of the streamer size. These simulations with realistic plasma parameters find that the electron heat conductivity is much smaller than the experimental value and in contrast with recent findings of flux-tube simulations that ETG turbulence is responsible for the anomalous electron thermal transport in fusion plasmas. The nonlinear toroidal couplings represent a new paradigm for the spectral cascade in plasma turbulence. (author)

  14. On nonequilibrium many-body systems III: nonlinear transport theory

    International Nuclear Information System (INIS)

    Luzzi, R.; Vasconcellos, A.R.; Algarte, A.C.S.

    1986-01-01

    A nonlinear transport theory for many-body systems arbitrarily away from equilibrium, based on the nonequilibrium statistical operator (NSO) method, is presented. Nonlinear transport equations for a basis set of dynamical quantities are derived using two equivalent treatments that may be considered far reaching generalizations of the Hilbert-Chapman-Enskog method and Mori's generalized Langevin equations method. The first case is considered in some detail and the general characteristics of the theory are discussed. (Author) [pt

  15. Ballistic transport and electronic structure

    NARCIS (Netherlands)

    Schep, Kees M.; Kelly, Paul J.; Bauer, Gerrit E.W.

    1998-01-01

    The role of the electronic structure in determining the transport properties of ballistic point contacts is studied. The conductance in the ballistic regime is related to simple geometrical projections of the Fermi surface. The essential physics is first clarified for simple models. For real

  16. Electron transport code theoretical basis

    International Nuclear Information System (INIS)

    Dubi, A.; Horowitz, Y.S.

    1978-04-01

    This report mainly describes the physical and mathematical considerations involved in the treatment of the multiple collision processes. A brief description is given of the traditional methods used in electron transport via Monte Carlo, and a somewhat more detailed description, of the approach to be used in the presently developed code

  17. Nonlinear Electron Acoustic Waves in Dissipative Plasma with Superthermal Electrons

    Science.gov (United States)

    El-Hanbaly, A. M.; El-Shewy, E. K.; Kassem, A. I.; Darweesh, H. F.

    2016-01-01

    The nonlinear properties of small amplitude electron-acoustic ( EA) solitary and shock waves in a homogeneous system of unmagnetized collisionless plasma consisted of a cold electron fluid and superthermal hot electrons obeying superthermal distribution, and stationary ions have been investigated. A reductive perturbation method was employed to obtain the Kadomstev-Petviashvili-Burgers (KP-Brugers) equation. Some solutions of physical interest are obtained. These solutions are related to soliton, monotonic and oscillatory shock waves and their behaviour are shown graphically. The formation of these solutions depends crucially on the value of the Burgers term and the plasma parameters as well. By using the tangent hyperbolic (tanh) method, another interesting type of solution which is a combination between shock and soliton waves is obtained. The topology of phase portrait and potential diagram of the KP-Brugers equation is investigated.The advantage of using this method is that one can predict different classes of the travelling wave solutions according to different phase orbits. The obtained results may be helpful in better understanding of waves propagation in various space plasma environments as well as in inertial confinement fusion laboratory plasmas.

  18. Excess electron transport in cryoobjects

    CERN Document Server

    Eshchenko, D G; Brewer, J H; Cottrell, S P; Cox, S F J

    2003-01-01

    Experimental results on excess electron transport in solid and liquid phases of Ne, Ar, and solid N sub 2 -Ar mixture are presented and compared with those for He. Muon spin relaxation technique in frequently switching electric fields was used to study the phenomenon of delayed muonium formation: excess electrons liberated in the mu sup + ionization track converge upon the positive muons and form Mu (mu sup + e sup -) atoms. This process is shown to be crucially dependent upon the electron's interaction with its environment (i.e., whether it occupies the conduction band or becomes localized in a bubble of tens of angstroms in radius) and upon its mobility in these states. The characteristic lengths involved are 10 sup - sup 6 -10 sup - sup 4 cm, the characteristic times range from nanoseconds to tens microseconds. Such a microscopic length scale sometimes enables the electron spend its entire free lifetime in a state which may not be detected by conventional macroscopic techniques. The electron transport proc...

  19. Magnetic-field asymmetry of nonlinear thermoelectric and heat transport

    International Nuclear Information System (INIS)

    Hwang, Sun-Yong; Sánchez, David; López, Rosa; Lee, Minchul

    2013-01-01

    Nonlinear transport coefficients do not obey, in general, reciprocity relations. We here discuss the magnetic-field asymmetries that arise in thermoelectric and heat transport of mesoscopic systems. Based on a scattering theory of weakly nonlinear transport, we analyze the leading-order symmetry parameters in terms of the screening potential response to either voltage or temperature shifts. We apply our general results to a quantum Hall antidot system. Interestingly, we find that certain symmetry parameters show a dependence on the measurement configuration. (paper)

  20. Relativistic electron beam acceleration by cascading nonlinear Landau damping of electromagnetic waves in a plasma

    International Nuclear Information System (INIS)

    Sugaya, R.; Ue, A.; Maehara, T.; Sugawa, M.

    1996-01-01

    Acceleration and heating of a relativistic electron beam by cascading nonlinear Landau damping involving three or four intense electromagnetic waves in a plasma are studied theoretically based on kinetic wave equations and transport equations derived from relativistic Vlasov endash Maxwell equations. Three or four electromagnetic waves excite successively two or three nonresonant beat-wave-driven relativistic electron plasma waves with a phase velocity near the speed of light [v p =c(1-γ -2 p ) 1/2 , γ p =ω/ω pe ]. Three beat waves interact nonlinearly with the electron beam and accelerate it to a highly relativistic energy γ p m e c 2 more effectively than by the usual nonlinear Landau damping of two electromagnetic waves. It is proved that the electron beam can be accelerated to more highly relativistic energy in the plasma whose electron density decreases temporally with an appropriate rate because of the temporal increase of γ p . copyright 1996 American Institute of Physics

  1. Nonlinear structure formation in ion-temperature-gradient driven drift waves in pair-ion plasma with nonthermal electron distribution

    Science.gov (United States)

    Razzaq, Javaria; Haque, Q.; Khan, Majid; Bhatti, Adnan Mehmood; Kamran, M.; Mirza, Arshad M.

    2018-02-01

    Nonlinear structure formation in ion-temperature-gradient (ITG) driven waves is investigated in pair-ion plasma comprising ions and nonthermal electrons (kappa, Cairns). By using the transport equations of the Braginskii model, a new set of nonlinear equations are derived. A linear dispersion relation is obtained and discussed analytically as well as numerically. It is shown that the nonthermal population of electrons affects both the linear and nonlinear characteristics of the ITG mode in pair-ion plasma. This work will be useful in tokamaks and stellarators where non-Maxwellian population of electrons may exist due to resonant frequency heating, electron cyclotron heating, runaway electrons, etc.

  2. Renormalization-group approach to nonlinear radiation-transport problems

    International Nuclear Information System (INIS)

    Chapline, G.F.

    1980-01-01

    A Monte Carlo method is derived for solving nonlinear radiation-transport problems that allows one to average over the effects of many photon absorptions and emissions at frequencies where the opacity is large. This method should allow one to treat radiation-transport problems with large optical depths, e.g., line-transport problems, with little increase in computational effort over that which is required for optically thin problems

  3. Bound electron nonlinearity beyond the ionization threshold

    OpenAIRE

    Wahlstrand, J. K.; Zahedpour, S.; Bahl, A.; Kolesik, M.; Milchberg, H. M.

    2018-01-01

    Although high field laser-induced ionization is a fundamental process underlying many applications, there have been no absolute measurements of the nonlinear polarizability of atoms and molecules in the presence of ionization. Such information is crucial, for example, for understanding the propagation of high intensity ultrashort pulses in matter. Here, we present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, ni...

  4. Nonlinear bounce resonances between magnetosonic waves and equatorially mirroring electrons

    Science.gov (United States)

    Chen, Lunjin; Maldonado, Armando; Bortnik, Jacob; Thorne, Richard M.; Li, Jinxing; Dai, Lei; Zhan, Xiaoya

    2015-08-01

    Equatorially mirroring energetic electrons pose an interesting scientific problem, since they generally cannot resonate with any known plasma waves and hence cannot be scattered down to lower pitch angles. Observationally it is well known that the flux of these equatorial particles does not simply continue to build up indefinitely, and so a mechanism must necessarily exist that transports these particles from an equatorial pitch angle of 90° down to lower values. However, this mechanism has not been uniquely identified yet. Here we investigate the mechanism of bounce resonance with equatorial noise (or fast magnetosonic waves). A test particle simulation is used to examine the effects of monochromatic magnetosonic waves on the equatorially mirroring energetic electrons, with a special interest in characterizing the effectiveness of bounce resonances. Our analysis shows that bounce resonances can occur at the first three harmonics of the bounce frequency (nωb, n = 1, 2, and 3) and can effectively reduce the equatorial pitch angle to values where resonant scattering by whistler mode waves becomes possible. We demonstrate that the nature of bounce resonance is nonlinear, and we propose a nonlinear oscillation model for characterizing bounce resonances using two key parameters, effective wave amplitude à and normalized wave number k~z. The threshold for higher harmonic resonance is more strict, favoring higher à and k~z, and the change in equatorial pitch angle is strongly controlled by k~z. We also investigate the dependence of bounce resonance effects on various physical parameters, including wave amplitude, frequency, wave normal angle and initial phase, plasma density, and electron energy. It is found that the effect of bounce resonance is sensitive to the wave normal angle. We suggest that the bounce resonant interaction might lead to an observed pitch angle distribution with a minimum at 90°.

  5. Microtearing Instabilities and Electron Transport in the NSTX Spherical Tokamak

    International Nuclear Information System (INIS)

    Wong, K.L.; Kaye, S.; Mikkelsen, D.R.; Krommes, J.A.; Hill, K.; Bell, R.; LeBlanc, B.

    2007-01-01

    We report a successful quantitative account of the experimentally determined electron thermal conductivity χ e in a beam-heated H mode plasma by the magnetic fluctuations from microtearing instabilities. The calculated χ e based on existing nonlinear theory agrees with the result from transport analysis of the experimental data. Without using any adjustable parameter, the good agreement spans the entire region where there is a steep electron temperature gradient to drive the instability

  6. Nonlinear electrostatic solitary waves in electron-positron plasmas

    Science.gov (United States)

    Lazarus, I. J.; Bharuthram, R.; Moolla, S.; Singh, S. V.; Lakhina, G. S.

    2016-02-01

    The generation of nonlinear electrostatic solitary waves (ESWs) is explored in a magnetized four component two-temperature electron-positron plasma. Fluid theory is used to derive a set of nonlinear equations for the ESWs, which propagate obliquely to an external magnetic field. The electric field structures are examined for various plasma parameters and are shown to yield sinusoidal, sawtooth and bipolar waveforms. It is found that an increase in the densities of the electrons and positrons strengthen the nonlinearity while the periodicity and nonlinearity of the wave increases as the cool-to-hot temperature ratio increases. Our results could be useful in understanding nonlinear propagation of waves in astrophysical environments and related laboratory experiments.

  7. Electron transport and shock ignition

    Energy Technology Data Exchange (ETDEWEB)

    Bell, A R; Tzoufras, M, E-mail: t.bell1@physics.ox.ac.uk [Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

    2011-04-15

    Inertial fusion energy (IFE) offers one possible route to commercial energy generation. In the proposed 'shock ignition' route to fusion, the target is compressed at a relatively low temperature and then ignited using high intensity laser irradiation which drives a strong converging shock into the centre of the fuel. With a series of idealized calculations we analyse the electron transport of energy into the target, which produces the pressure responsible for driving the shock. We show that transport in shock ignition lies near the boundary between ablative and heat front regimes. Moreover, simulations indicate that non-local effects are significant in the heat front regime and might lead to increased efficiency by driving the shock more effectively and reducing heat losses to the plasma corona.

  8. Research on nonlinearity effect of secondary electron multiplier

    International Nuclear Information System (INIS)

    Wei Xingjian; Liao Junsheng; Deng Dachao; Yu Chunrong; Yuan Li

    2007-01-01

    The nonlinearity of secondary electron multiplier (SEM) of a thermal ionization mass spectrometer has been researched by using UTB-500 uranium isotope reference material and multi-collecting technique. The results show that the nonlinearity effect of SEM exists in the whole ion counting range, and there is an extreme point of the nonlinearity when the ion counting rate is about 20000 cps. The deviation between measured value of the extreme point and the reference value of the reference sample can be up to 3%, and the nonlinearity obeys logarithm linearity law on both sides of extreme point. A kind of mathematics model of nonlinearity calibration has been put forward. Using this model, the nonlinearity of SEM of TIMS can be calibrated. (authors)

  9. Electron transport in quantum dots

    CERN Document Server

    2003-01-01

    When I was contacted by Kluwer Academic Publishers in the Fall of 200 I, inviting me to edit a volume of papers on the issue of electron transport in quantum dots, I was excited by what I saw as an ideal opportunity to provide an overview of a field of research that has made significant contributions in recent years, both to our understanding of fundamental physics, and to the development of novel nanoelectronic technologies. The need for such a volume seemed to be made more pressing by the fact that few comprehensive reviews of this topic have appeared in the literature, in spite of the vast activity in this area over the course of the last decade or so. With this motivation, I set out to try to compile a volume that would fairly reflect the wide range of opinions that has emerged in the study of electron transport in quantum dots. Indeed, there has been no effort on my part to ensure any consistency between the different chapters, since I would prefer that this volume instead serve as a useful forum for the...

  10. Achromatic and isochronous electron beam transport for tunable free electron lasers

    International Nuclear Information System (INIS)

    Bengtsson, J.; Kim, K.J.

    1991-09-01

    We have continued the study of a suitable electron beam transport line, which is both isochronous and achromatic, for the free electron laser being designed at Lawrence Berkeley Laboratory. A refined version of the beam transport optics is discussed that accommodates two different modes of FEL wavelength tuning. For the fine tuning involving a small change of the electron beam energy, sextupoles are added to cancel the leading nonlinear dispersion. For the main tuning involving the change of the undulator gap, a practical solution of maintaining the beam matching condition is presented. Calculation of the higher order aberrations is facilitated by a newly developed code. 11 refs., 4 figs., 3 tabs

  11. Paleoclassical transport explains electron transport barriers in RTP and TEXTOR

    NARCIS (Netherlands)

    Hogeweij, G. M. D.; Callen, J.D.

    2008-01-01

    The recently developed paleoclassical transport model sets the minimum level of electron thermal transport in a tokamak. This transport level has proven to be in good agreement with experimental observations in many cases when fluctuation-induced anomalous transport is small, i.e. in (near-) ohmic

  12. Electronic transport in bilayer graphene

    International Nuclear Information System (INIS)

    Koshino, Mikito

    2009-01-01

    We present theoretical studies on the transport properties and localization effects of bilayer graphene. We calculate the conductivity by using the effective mass model with the self-consistent Born approximation, in the presence and absence of an energy gap opened by the interlayer asymmetry. We find that, in the absence of the gap, the minimum conductivity approaches the universal value by increasing the disorder potential, and the value is robust in the strong disorder regime where mixing with high-energy states is considerable. The gap-opening suppresses the conductivity over a wide energy range, even in the region away from the gap.We also study the localization effects in the vicinity of zero energy in bilayer graphene. We find that the states are all localized in the absence of the gap, while the gap-opening causes a phase transition analogous to the quantum Hall transition, which is accompanied by electron delocalization.

  13. Bound-Electron Nonlinearity Beyond the Ionization Threshold

    Science.gov (United States)

    Wahlstrand, J. K.; Zahedpour, S.; Bahl, A.; Kolesik, M.; Milchberg, H. M.

    2018-05-01

    We present absolute space- and time-resolved measurements of the ultrafast laser-driven nonlinear polarizability in argon, krypton, xenon, nitrogen, and oxygen up to ionization fractions of a few percent. These measurements enable determination of the strongly nonperturbative bound-electron nonlinear polarizability well beyond the ionization threshold, where it is found to remain approximately quadratic in the laser field, a result normally expected at much lower intensities where perturbation theory applies.

  14. Nonlinear transport properties of non-ideal systems

    International Nuclear Information System (INIS)

    Pavlov, G A

    2009-01-01

    The theory of nonlinear transport is elaborated to determine the Burnett transport properties of non-ideal multi-element plasma and neutral systems. The procedure for the comparison of the phenomenological conservation equations of a continuous dense medium and the microscopic equations for dynamical variable operators is used for the definition of these properties. The Mori algorithm is developed to derive the equations of motion of dynamical value operators of a non-ideal system in the form of the generalized nonlinear Langevin equations. In consequence, the microscopic expressions of transport coefficients corresponding to second-order thermal disturbances (temperature, mass velocity, etc) have been found in the long wavelength and low frequency limits

  15. New nonlinear methods for linear transport calculations

    International Nuclear Information System (INIS)

    Adams, M.L.

    1993-01-01

    We present a new family of methods for the numerical solution of the linear transport equation. With these methods an iteration consists of an 'S N sweep' followed by an 'S 2 -like' calculation. We show, by analysis as well as numerical results, that iterative convergence is always rapid. We show that this rapid convergence does not depend on a consistent discretization of the S 2 -like equations - they can be discretized independently from the S N equations. We show further that independent discretizations can offer significant advantages over consistent ones. In particular, we find that in a wide range of problems, an accurate discretization of the S 2 -like equation can be combined with a crude discretization of the S N equations to produce an accurate S N answer. We demonstrate this by analysis as well as numerical results. (orig.)

  16. Nonlinear electron magnetohydrodynamics physics. IV. Whistler instabilities

    International Nuclear Information System (INIS)

    Urrutia, J. M.; Stenzel, R. L.; Strohmaier, K. D.

    2008-01-01

    A very large low-frequency whistler mode is excited with magnetic loop antennas in a uniform laboratory plasma. The wave magnetic field exceeds the ambient field causing in one polarity a field reversal, and a magnetic topology resembling that of spheromaks in the other polarity. These propagating ''whistler spheromaks'' strongly accelerate the electrons and create non-Maxwellian distributions in their toroidal current ring. It is observed that the locally energized electrons in the current ring excite new electromagnetic instabilities and emit whistler modes with frequencies unrelated to the applied frequency. Emissions are also observed from electrons excited in X-type neutral lines around the antenna. The properties of the excited waves such as amplitudes, frequency spectra, field topologies, propagation, polarization, growth, and damping have been investigated. The waves remain linear (B wave 0 ) and convert a small part of the electron kinetic energy into wave magnetic energy (B wave 2 /2μ 0 e )

  17. Electron transport in wurtzite InN

    Indian Academy of Sciences (India)

    InN transport; mobility; energy and momentum relaxation; impurity scattering. ... future generation solar cell because the nitride alloys can cover the whole ... We apply the ensemble Monte Carlo method to investigate the electron transport in.

  18. Nonlinear electron-phonon heat exchange

    International Nuclear Information System (INIS)

    Woods, L.M.; Mahan, G.D.

    1998-01-01

    A calculation of the energy exchange between phonons and electrons is done for a metal at very low temperatures. We consider the energy exchange due to two-phonon processes. Second-order processes are expected to be important at temperatures less than 1 K. We include two different second-order processes: (i) the Compton-like scattering of phonons, and (ii) the electron-dual-phonon scattering from the second-order electron-phonon interaction. It is found that the Compton-like process contains a singular energy denominator. The singularity is removed by introducing quasiparticle damping. For pure metals we find that the energy exchange depends upon the lifetime of the electrons and it is proportional to the temperature of the lattice as T L 8 . The same calculation is performed for the electron-dual-phonon scattering and it is found that the temperature dependence is T L 9 . The results can be applied to quantum dot refrigerators. copyright 1998 The American Physical Society

  19. Phonon limited electronic transport in Pb

    Science.gov (United States)

    Rittweger, F.; Hinsche, N. F.; Mertig, I.

    2017-09-01

    We present a fully ab initio based scheme to compute electronic transport properties, i.e. the electrical conductivity σ and thermopower S, in the presence of electron-phonon interaction. We explicitly investigate the \

  20. Investigations of the role of nonlinear couplings in structure formation and transport regulation in plasma turbulence

    Science.gov (United States)

    Holland, Christopher George

    Studies of nonlinear couplings and dynamics in plasma turbulence are presented. Particular areas of focus are analytic studies of coherent structure formation in electron temperature gradient turbulence, measurement of nonlinear energy transfer in simulations of plasma turbulence, and bispectral analysis of experimental and computational data. The motivation for these works has been to develop and expand the existing theories of plasma transport, and verify the nonlinear predictions of those theories in simulation and experiment. In Chapter II, we study electromagnetic secondary instabilities of electron temperature gradient turbulence. The growth rate for zonal flow generation via modulational instability of electromagnetic ETG turbulence is calculated, as well as that for zonal (magnetic) field generation. In Chapter III, the stability and saturation of streamers in ETG turbulence is considered, and shown to depend sensitively upon geometry and the damping rates of the Kelvin-Helmholtz mode. Requirements for a credible theory of streamer transport are presented. In addition, a self-consistent model for interactions between ETG and ITG (ion temperature gradient) turbulence is presented. In Chapter IV, the nonlinear transfer of kinetic and internal energy is measured in simulations of plasma turbulence. The regulation of turbulence by radial decorrelation due to zonal flows and generation of zonal flows via the Reynolds stress are explicitly demonstrated, and shown to be symmetric facets of a single nonlinear process. Novel nonlinear saturation mechanisms for zonal flows are discussed. In Chapter V, measurements of fluctuation bicoherence in the edge of the DIII-D tokamak are presented. It is shown that the bicoherence increases transiently before a L-H transition, and decays to its initial value after the barrier has formed. The increase in bicoherence is localized to the region where the transport barrier forms, and shows strong coupling between well

  1. Electron and Phonon Transport in Molecular Junctions

    DEFF Research Database (Denmark)

    Li, Qian

    Molecular electronics provide the possibility to investigate electron and phonon transport at the smallest imaginable scale, where quantum effects can be investigated and exploited directly in the design. In this thesis, we study both electron transport and phonon transport in molecular junctions....... The system we are interested in here are π-stacked molecules connected with two semi-infinite leads. π-stacked aromatic rings, connected via π-π electronic coupling, provides a rather soft mechanical bridge while maintaining high electronic conductivity. We investigate electron transport...... transmission at the Fermi energy. We propose and analyze a way of using π   stacking to design molecular junctions to control heat transport. We develop a simple model system to identify optimal parameter regimes and then use density functional theory (DFT) to extract model parameters for a number of specific...

  2. Nonlinearly-enhanced energy transport in many dimensional quantum chaos

    KAUST Repository

    Brambila, D. S.; Fratalocchi, Andrea

    2013-01-01

    By employing a nonlinear quantum kicked rotor model, we investigate the transport of energy in multidimensional quantum chaos. This problem has profound implications in many fields of science ranging from Anderson localization to time reversal of classical and quantum waves. We begin our analysis with a series of parallel numerical simulations, whose results show an unexpected and anomalous behavior. We tackle the problem by a fully analytical approach characterized by Lie groups and solitons theory, demonstrating the existence of a universal, nonlinearly-enhanced diffusion of the energy in the system, which is entirely sustained by soliton waves. Numerical simulations, performed with different models, show a perfect agreement with universal predictions. A realistic experiment is discussed in two dimensional dipolar Bose-Einstein-Condensates (BEC). Besides the obvious implications at the fundamental level, our results show that solitons can form the building block for the realization of new systems for the enhanced transport of matter.

  3. Nonlinearly-enhanced energy transport in many dimensional quantum chaos

    KAUST Repository

    Brambila, D. S.

    2013-08-05

    By employing a nonlinear quantum kicked rotor model, we investigate the transport of energy in multidimensional quantum chaos. This problem has profound implications in many fields of science ranging from Anderson localization to time reversal of classical and quantum waves. We begin our analysis with a series of parallel numerical simulations, whose results show an unexpected and anomalous behavior. We tackle the problem by a fully analytical approach characterized by Lie groups and solitons theory, demonstrating the existence of a universal, nonlinearly-enhanced diffusion of the energy in the system, which is entirely sustained by soliton waves. Numerical simulations, performed with different models, show a perfect agreement with universal predictions. A realistic experiment is discussed in two dimensional dipolar Bose-Einstein-Condensates (BEC). Besides the obvious implications at the fundamental level, our results show that solitons can form the building block for the realization of new systems for the enhanced transport of matter.

  4. Importance of space-time fluctuations and non-linearities for the transport inside insulating glasses

    International Nuclear Information System (INIS)

    Ladieu, F.

    2003-07-01

    This work deals with transport in insulating glasses. In such solids, the discrete translational symmetry is lost, which means that the plane wave analysis is not a priori the right 'starting point'. As a result, the transport is more difficult to handle, and a huge amount of works have been devoted to many aspects of transport in disordered systems, especially since the seventies. Here we focus on three specific questions: (i) the heat transport in glasses submitted to micro-beams and the associated irreversible vaporization; (ii) the electronic d.c. transport, below 1 Kelvin, in Mott-Anderson insulators, i.e. in 'electron glasses' where both disorder and electron-electron interactions are relevant; (iii) the low frequency dielectric constant in 'structural glasses' (i.e. 'ordinary glasses') which, below 1 Kelvin, is both universal (i.e. independent on the chemical composition) and very different of that of crystals. For each topic, we present both original experiments and the new theoretical concepts that we have elaborated so as to understand the main experimental features. Eventually, it appears that, in any case, transport in insulating glasses is strongly dominated by quite a small part of the 'glass-applied field' ensemble and that the nonlinear response is a relevant tool to get informations on this 'sub-part' which dominates the transport in the whole system. (author)

  5. Linear and Nonlinear Theories of Cosmic Ray Transport

    International Nuclear Information System (INIS)

    Shalchi, A.

    2005-01-01

    The transport of charged cosmic rays in plasmawave turbulence is a modern and interesting field of research. We are mainly interested in spatial diffusion parallel and perpendicular to a large scale magnetic field. During the last decades quasilinear theory was the standard tool for the calculation of diffusion coefficients. Through comparison with numerical simulations we found several cases where quasilinear theory is invalid. On could define three major problems of transport theory. I will demonstrate that new nonlinear theories which were proposed recently can solve at least some to these problems

  6. Nonlinear magnetic electron tripolar vortices in streaming plasmas.

    Science.gov (United States)

    Vranjes, J; Marić, G; Shukla, P K

    2000-06-01

    Magnetic electron modes in nonuniform magnetized and unmagnetized streaming plasmas, with characteristic frequencies between the ion and electron plasma frequencies and at spatial scales of the order of the collisionless skin depth, are studied. Two coupled equations, for the perturbed (in the case of magnetized plasma) or self-generated (for the unmagnetized plasma case) magnetic field, and the temperature, are solved in the strongly nonlinear regime and stationary traveling solutions in the form of tripolar vortices are found.

  7. Structure, Electronic and Nonlinear Optical Properties of Furyloxazoles and Thienyloxazoles

    International Nuclear Information System (INIS)

    Dagli, Ozlem; Gok, Rabia; Bahat, Mehmet; Ozbay, Akif

    2016-01-01

    Geometry optimization, electronic and nonlinear optical properties of isomers of furyloxazole and thienyloxazole molecules are carried out at the B3LYP/6-311++G(2d,p) level. The conformational analysis of 12 compounds have been studied as a function of torsional angle between rings. Electronic and NLO properties such as dipole moment, energy gap, polarizability and first hyperpolarizability were also calculated. (paper)

  8. Applied nonlinear optics in the journal 'Quantum Electronics'

    International Nuclear Information System (INIS)

    Grechin, Sergei G; Dmitriev, Valentin G; Chirkin, Anatolii S

    2011-01-01

    A brief historical review of the experimental and theoretical works on nonlinear optical frequency conversion (generation of harmonics, up- and down-conversion, parametric oscillation), which have been published in the journal 'Quantum Electronics' for the last 40 years, is presented.

  9. Electron transport properties in InAs four-terminal ballistic junctions under weak magnetic fields

    International Nuclear Information System (INIS)

    Koyama, M.; Fujiwara, K.; Amano, N.; Maemoto, T.; Sasa, S.; Inoue, M.

    2009-01-01

    We report on the electron transport properties based on ballistic electrons under magnetic fields in four-terminal ballistic junctions fabricated on an InAs/AlGaSb heterostructure. The four-terminal junction structure is composed of two longitudinal stems with two narrow wires slanted with 30 degree from the perpendicular axis. The electron focusing peak was obtained with the bend resistance measurement. Then it was investigated the nonlinear electron transport property of potential difference between longitudinal stems due to ballistic electrons with applying direct current from narrow wires. Observed nonlinearity showed clear rectification effects which have negative polarity regardless of input voltage polarity. Although this nonlinearity was qualitatively changed due to the Lorentz force under magnetic fields, the degradation of ballistic effects on nonlinear properties were observed when the current increased to higher strength. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Coupled electron-photon radiation transport

    International Nuclear Information System (INIS)

    Lorence, L.; Kensek, R.P.; Valdez, G.D.; Drumm, C.R.; Fan, W.C.; Powell, J.L.

    2000-01-01

    Massively-parallel computers allow detailed 3D radiation transport simulations to be performed to analyze the response of complex systems to radiation. This has been recently been demonstrated with the coupled electron-photon Monte Carlo code, ITS. To enable such calculations, the combinatorial geometry capability of ITS was improved. For greater geometrical flexibility, a version of ITS is under development that can track particles in CAD geometries. Deterministic radiation transport codes that utilize an unstructured spatial mesh are also being devised. For electron transport, the authors are investigating second-order forms of the transport equations which, when discretized, yield symmetric positive definite matrices. A novel parallelization strategy, simultaneously solving for spatial and angular unknowns, has been applied to the even- and odd-parity forms of the transport equation on a 2D unstructured spatial mesh. Another second-order form, the self-adjoint angular flux transport equation, also shows promise for electron transport

  11. Application of Chebyshev Formalism to Identify Nonlinear Magnetic Field Components in Beam Transport Systems

    Energy Technology Data Exchange (ETDEWEB)

    Spata, Michael [Old Dominion Univ., Norfolk, VA (United States)

    2012-08-01

    An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a beam-based technique for characterizing the extent of the nonlinearity of the magnetic fields of a beam transport system. Horizontally and vertically oriented pairs of air-core kicker magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the beam orbit relative to the unperturbed reference orbit. Fourier decomposition of the position data at eight different points along the beamline was then used to measure the amplitude of these frequencies. For a purely linear transport system one expects to find solely the frequencies that were applied to the kickers with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. Chebyshev polynomials and their unique properties allow one to directly quantify the magnitude of the nonlinearity with the minimum error. A calibration standard was developed using one of the sextupole magnets in a CEBAF beamline. The technique was then applied to a pair of Arc 1 dipoles and then to the magnets in the Transport Recombiner beamline to measure their multipole content as a function of transverse position within the magnets.

  12. Anomalous Transport of Cosmic Rays in a Nonlinear Diffusion Model

    Energy Technology Data Exchange (ETDEWEB)

    Litvinenko, Yuri E. [Department of Mathematics, University of Waikato, P. B. 3105, Hamilton 3240 (New Zealand); Fichtner, Horst; Walter, Dominik [Institut für Theoretische Physik IV, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44780 Bochum (Germany)

    2017-05-20

    We investigate analytically and numerically the transport of cosmic rays following their escape from a shock or another localized acceleration site. Observed cosmic-ray distributions in the vicinity of heliospheric and astrophysical shocks imply that anomalous, superdiffusive transport plays a role in the evolution of the energetic particles. Several authors have quantitatively described the anomalous diffusion scalings, implied by the data, by solutions of a formal transport equation with fractional derivatives. Yet the physical basis of the fractional diffusion model remains uncertain. We explore an alternative model of the cosmic-ray transport: a nonlinear diffusion equation that follows from a self-consistent treatment of the resonantly interacting cosmic-ray particles and their self-generated turbulence. The nonlinear model naturally leads to superdiffusive scalings. In the presence of convection, the model yields a power-law dependence of the particle density on the distance upstream of the shock. Although the results do not refute the use of a fractional advection–diffusion equation, they indicate a viable alternative to explain the anomalous diffusion scalings of cosmic-ray particles.

  13. Self-focusing of electron bunches in a nonlinear plasma

    International Nuclear Information System (INIS)

    Krasovitskii, V.B.; Osmolovsky, S.I.

    1994-01-01

    The phenomena of self-focusing of previously bunched electron beam in hot nonlinear plasma with the frequency which less than the plasma one is studied. It is established that influence of the Miller's force nonlinearity of the plasma don't leads to self-focusing breaking. However in the case of a dense beam, the appearance strong resonant electric field is followed by the change of the sign of the plasma dielectric constant to positive at the beam axis. But the dielectric constant remain negative at the outer of the beam

  14. Nonlinear optics with coherent free electron lasers

    Science.gov (United States)

    Bencivenga, F.; Capotondi, F.; Mincigrucci, R.; Cucini, R.; Manfredda, M.; Pedersoli, E.; Principi, E.; Simoncig, A.; Masciovecchio, C.

    2016-12-01

    We interpreted the recent construction of free electron laser (FELs) facilities worldwide as an unprecedented opportunity to bring concepts and methods from the scientific community working with optical lasers into the domain of x-ray science. This motivated our efforts towards the realization of FEL-based wave-mixing applications. In this article we present new extreme ultraviolet transient grating (X-TG) data from vitreous SiO2, collected using two crossed FEL pulses (photon frequency 38 eV) to generate the X-TG and a phase matched optical probing pulse (photon frequency 3.1 eV). This experiment extends our previous investigation, which was carried out on a nominally identical sample using a different FEL photon frequency (45 eV) to excite the X-TG. The present data are featured by a peak intensity of the X-TG signal substantially larger than that previously reported and by slower modulations of the X-TG signal at positive delays. These differences could be ascribed to the different FEL photon energy used in the two experiments or to differences in the sample properties. A systematic X-TG study on the same sample as a function of the FEL wavelength is needed to draw a consistent conclusion. We also discuss how the advances in the performance of the FELs, in terms of generation of fully coherent photon pulses and multi-color FEL emission, may push the development of original experimental strategies to study matter at the femtosecond-nanometer time-length scales, with the unique option of element and chemical state specificity. This would allow the development of advanced experimental tools based on wave-mixing processes, which may have a tremendous impact in the study of a large array of phenomena, ranging from nano-dynamics in complex materials to charge and energy transfer processes.

  15. Nonlinear theory of trapped electron temperature gradient driven turbulence in flat density H-mode plasmas

    International Nuclear Information System (INIS)

    Hahm, T.S.

    1990-12-01

    Ion temperature gradient turbulence based transport models have difficulties reconciling the recent DIII-D H-mode results where the density profile is flat, but χ e > χ i in the core region. In this work, a nonlinear theory is developed for recently discovered ion temperature gradient trapped electron modes propagating in the electron diamagnetic direction. This instability is predicted to be linearly unstable for L Ti /R approx-lt κ θ ρ s approx-lt (L Ti /R) 1/4 . They are also found to be strongly dispersive even at these long wavelengths, thereby suggesting the importance of the wave-particle-wave interactions in the nonlinear saturation phase. The fluctuation spectrum and anomalous fluxes are calculated. In accordance with the trends observed in DIII-D, the predicted electron thermal diffusivity can be larger than the ion thermal diffusivity. 17 refs., 3 figs

  16. Nonlinear closure relations theory for transport processes in nonequilibrium systems

    International Nuclear Information System (INIS)

    Sonnino, Giorgio

    2009-01-01

    A decade ago, a macroscopic theory for closure relations has been proposed for systems out of Onsager's region. This theory is referred to as the thermodynamic field theory (TFT). The aim of this work was to determine the nonlinear flux-force relations that respect the thermodynamic theorems for systems far from equilibrium. We propose a formulation of the TFT where one of the basic restrictions, namely, the closed-form solution for the skew-symmetric piece of the transport coefficients, has been removed. In addition, the general covariance principle is replaced by the De Donder-Prigogine thermodynamic covariance principle (TCP). The introduction of TCP requires the application of an appropriate mathematical formalism, which is referred to as the entropy-covariant formalism. By geometrical arguments, we prove the validity of the Glansdorff-Prigogine universal criterion of evolution. A new set of closure equations determining the nonlinear corrections to the linear ('Onsager') transport coefficients is also derived. The geometry of the thermodynamic space is non-Riemannian. However, it tends to be Riemannian for high values of the entropy production. In this limit, we recover the transport equations found by the old theory. Applications of our approach to transport in magnetically confined plasmas, materials submitted to temperature, and electric potential gradients or to unimolecular triangular chemical reactions can be found at references cited herein. Transport processes in tokamak plasmas are of particular interest. In this case, even in the absence of turbulence, the state of the plasma remains close to (but, it is not in) a state of local equilibrium. This prevents the transport relations from being linear.

  17. Ballistic electron transport in mesoscopic samples

    International Nuclear Information System (INIS)

    Diaconescu, D.

    2000-01-01

    In the framework of this thesis, the electron transport in the ballistic regime has been studied. Ballistic means that the lateral sample dimensions are smaller than the mean free path of the electrons, i.e. the electrons can travel through the whole device without being scattered. This leads to transport characteristics that differ significantly from the diffusive regime which is realised in most experiments. Making use of samples with high mean free path, features of ballistic transport have been observed on samples with sizes up to 100 μm. The basic device used in ballistic electron transport is the point contact, from which a collimated beam of ballistic electrons can be injected. Such point contacts were realised with focused ion beam (FIB) implantation and the collimating properties were analysed using a two opposite point contact configuration. The typical angular width at half maximum is around 50 , which is comparable with that of point contacts defined by other methods. (orig.)

  18. Fluid transport due to nonlinear fluid-structure interaction

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1997-01-01

    This work considers nonlinear fluid-structure interaction for a vibrating pipe containing fluid. Transverse pipe vibrations will force the fluid to move relative to the pipe creating unidirectional fluid flow towards the pipe end. The fluid flow induced affects the damping and the stiffness...... of the pipe. The behavior of the system in response to lateral resonant base excitation is analysed numerically and by the use of a perturbation method (multiple scales). Exciting the pipe in the fundamental mode of vibration seems to be most effective for transferring energy from the shaker to the fluid......, whereas higher modes of vibration can be used to transport fluid with pipe vibrations of smaller amplitude. The effect of the nonlinear geometrical terms is analysed and these terms are shown to affect the response for higher modes of vibration. Experimental investigations show good agreement...

  19. Nonlinear mechanisms for drift wave saturation and induced particle transport

    International Nuclear Information System (INIS)

    Dimits, A.M.; Lee, W.W.

    1989-12-01

    A detailed theoretical study of the nonlinear dynamics of gyrokinetic particle simulations of electrostatic collisionless and weakly collisional drift waves is presented. In previous studies it was shown that, in the nonlinearly saturated phase of the evolution, the saturation levels and especially the particle fluxes have an unexpected dependence on collisionality. In this paper, the explanations for these collisionality dependences are found to be as follows: The saturation level is determined by a balance between the electron and ion fluxes. The ion flux is small for levels of the potential below an E x B-trapping threshold and increases sharply once this threshold is crossed. Due to the presence of resonant electrons, the electron flux has a much smoother dependence on the potential. In the 2-1/2-dimensional (''pseudo-3D'') geometry, the electrons are accelerated away from the resonance as they diffuse spatially, resulting in an inhibition of their diffusion. Collisions and three-dimensional effects can repopulate the resonance thereby increasing the value of the particle flux. 30 refs., 32 figs., 2 tabs

  20. Nonlinear dynamic of interaction of the relativistic electron beam with plasma

    International Nuclear Information System (INIS)

    Dorofeenko, V.G.; Krasovitskii, V.B.; Osmolovsky, S.I.

    1994-01-01

    Quasi-transverse instability of thin relativistic electron beam in a dense plasma is studied numerically and analytically in a broad range of the frequency of the beam modulation and external longitudinal magnetic field. It is shown that the nonlinear stage of solution depends on the increment of the instability. It is permitted to classify possible nonlinear solutions and also to determine optimal regimes of the modulation for transport of beam along magnetic field in a plasma without substantial radial divergence. Numerical calculations show, that injection of the bunches with parameters, corresponding nonlinear regime of the beam's instability, in neutrally-charged plasma permits to output on the stationary regime without loss of particles

  1. Electron transport chains of lactic acid bacteria

    NARCIS (Netherlands)

    Brooijmans, R.J.W.

    2008-01-01

    Lactic acid bacteria are generally considered facultative anaerobic obligate fermentative bacteria. They are unable to synthesize heme. Some lactic acid bacteria are unable to form menaquinone as well. Both these components are cofactors of respiratory (electron transport) chains of prokaryotic

  2. Nonlinear electron-acoustic rogue waves in electron-beam plasma system with non-thermal hot electrons

    Science.gov (United States)

    Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.

    2014-11-01

    The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, non-thermal hot electrons obeying a non-thermal distribution, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles on the electron beam and energetic population parameter are discussed. The results of the present investigation may be applicable in auroral zone plasma.

  3. Nonlinear behaviors of a bounded electron beam-plasma system

    International Nuclear Information System (INIS)

    Iizuka, Satoru; Saeki, Koichi; Sato, Noriyoshi; Hatta, Yoshisuke

    1985-01-01

    Nonlinear developments of a bounded electron beam-plasma system including stationary electrons are investigated experimentally. A stable double layer is formed as a result of ion trapping in a growing negative potential dip induced by the Pierce instability above the current regime of the Buneman instability. In the in-between regime of the Buneman and Pierce instabilities, energetic ions are observed. This effective ion heating is caused by ion detrapping due to double-layer disruption, being consistent with computer simulation. (author)

  4. Nonlinear acceleration of S_n transport calculations

    International Nuclear Information System (INIS)

    Fichtl, Erin D.; Warsa, James S.; Calef, Matthew T.

    2011-01-01

    The use of nonlinear iterative methods, Jacobian-Free Newton-Krylov (JFNK) in particular, for solving eigenvalue problems in transport applications has recently become an active subject of research. While JFNK has been shown to be effective for k-eigenvalue problems, there are a number of input parameters that impact computational efficiency, making it difficult to implement efficiently in a production code using a single set of default parameters. We show that different selections for the forcing parameter in particular can lead to large variations in the amount of computational work for a given problem. In contrast, we employ a nonlinear subspace method that sits outside and effectively accelerates nonlinear iterations of a given form and requires only a single input parameter, the subspace size. It is shown to consistently and significantly reduce the amount of computational work when applied to fixed-point iteration, and this combination of methods is shown to be more efficient than JFNK for our application. (author)

  5. Non-linear absorption for concentrated solar energy transport

    Energy Technology Data Exchange (ETDEWEB)

    Jaramillo, O. A; Del Rio, J.A; Huelsz, G [Centro de Investigacion de Energia, UNAM, Temixco, Morelos (Mexico)

    2000-07-01

    In order to determine the maximum solar energy that can be transported using SiO{sub 2} optical fibers, analysis of non-linear absorption is required. In this work, we model the interaction between solar radiation and the SiO{sub 2} optical fiber core to determine the dependence of the absorption of the radioactive intensity. Using Maxwell's equations we obtain the relation between the refractive index and the electric susceptibility up to second order in terms of the electric field intensity. This is not enough to obtain an explicit expression for the non-linear absorption. Thus, to obtain the non-linear optical response, we develop a microscopic model of an harmonic driven oscillators with damp ing, based on the Drude-Lorentz theory. We solve this model using experimental information for the SiO{sub 2} optical fiber, and we determine the frequency-dependence of the non-linear absorption and the non-linear extinction of SiO{sub 2} optical fibers. Our results estimate that the average value over the solar spectrum for the non-linear extinction coefficient for SiO{sub 2} is k{sub 2}=10{sup -}29m{sup 2}V{sup -}2. With this result we conclude that the non-linear part of the absorption coefficient of SiO{sub 2} optical fibers during the transport of concentrated solar energy achieved by a circular concentrator is negligible, and therefore the use of optical fibers for solar applications is an actual option. [Spanish] Con el objeto de determinar la maxima energia solar que puede transportarse usando fibras opticas de SiO{sub 2} se requiere el analisis de absorcion no linear. En este trabajo modelamos la interaccion entre la radiacion solar y el nucleo de la fibra optica de SiO{sub 2} para determinar la dependencia de la absorcion de la intensidad radioactiva. Mediante el uso de las ecuaciones de Maxwell obtenemos la relacion entre el indice de refraccion y la susceptibilidad electrica hasta el segundo orden en terminos de intensidad del campo electrico. Esto no es

  6. Effects of electron-electron interactions on electronic transport in disordered systems

    International Nuclear Information System (INIS)

    Foley, Simon Timothy

    2002-01-01

    This thesis is concerned with the role of electron-electron interactions on electronic transport in disordered systems. We first consider a novel non-linear sigma model in order to microscopically treat the effects of disorder and electronic interaction. We successfully reproduce the perturbative results for the zero-bias anomaly and the interaction correction to the conductivity in a weakly disordered system, and discuss possible directions for future work. Secondly we consider the fluctuations of the dephasing rate for a closed diffusive and quantum dot system. Using the Keldysh technique we derive an expression for the inelastic scattering rate with which we self-consistently obtain the fluctuations in the dephasing rate. For the diffusive regime we find the relative fluctuations is given by F ∼ (L φ /L) 2 /g 2 , where g is the dimensionless conductance, L φ is the dephasing length and L is the sample size. For the quantum dot regime we find a perturbative divergence due to the presence of the zero mode. By mapping divergent diagrams to those for the two-level correlation function, we conjecture the existence of an exact relation between the two. Finally we discuss the consequences of this relation. (author)

  7. Electron transport effects in ion induced electron emission

    Energy Technology Data Exchange (ETDEWEB)

    Dubus, A. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium)]. E-mail: adubus@ulb.ac.be; Pauly, N. [Universite Libre de Bruxelles, Service de Metrologie Nucleaire (CP 165/84), 50 av. FD Roosevelt, B-1050 Brussels (Belgium); Roesler, M. [Karl-Pokern-Str. 12, D-12587 Berlin (Germany)

    2007-03-15

    Ion induced electron emission (IIEE) is usually described as a three-step process, i.e. electron excitation by the incident projectile, electron transport (and multiplication) and electron escape through the potential barrier at the surface. In many cases, the first step of the process has been carefully described. The second step of the process, i.e. electron transport and multiplication, has often been treated in a very rough way, a simple decreasing exponential law being sometimes used. It is precisely the aim of the present work to show the importance of a correct description of electron transport and multiplication in a theoretical calculation of IIEE. A short overview of the electron transport models developed for IIEE is given in this work. The so-called 'Infinite medium slowing-down model' often used in recent works is evaluated by means of Monte Carlo simulations. In particular, the importance of considering correctly the semi-infinite character of the medium and the boundary condition at the vacuum-medium interface is discussed. Quantities like the electron escape depth are also briefly discussed. This evaluation has been performed in the particular case of protons (25keV

  8. The Electron Transport Chain: An Interactive Simulation

    Science.gov (United States)

    Romero, Chris; Choun, James

    2014-01-01

    This activity provides students an interactive demonstration of the electron transport chain and chemiosmosis during aerobic respiration. Students use simple, everyday objects as hydrogen ions and electrons and play the roles of the various proteins embedded in the inner mitochondrial membrane to show how this specific process in cellular…

  9. Phonon limited electronic transport in Pb

    DEFF Research Database (Denmark)

    Rittweger, Florian; Hinsche, Nicki Frank; Mertig, Ingrid

    2017-01-01

    We present a fully ab initio based scheme to compute electronic transport properties, i.e. the electrical conductivity σ and thermopower S, in the presence of electron-phonon interaction. We explicitly investigate the k-dependent structure of the Éliashberg spectral function, the coupling strength...

  10. Conditioner for a helically transported electron beam

    International Nuclear Information System (INIS)

    Wang, C.

    1992-05-01

    The kinetic theory is developed to investigate a conditioner for a helically imported electron beam. Linear expressions for axial velocity spread are derived. Numerical simulation is used to check the theoretical results and examine nonlinear aspects of the conditioning process. The results show that in the linear regime the action of the beam conditioner on a pulsed beam mainly depends on the phase at which the beam enters the conditioner and depends only slightly on the operating wavelength. In the nonlinear regime, however, the action of the conditioner strongly depends on the operating wavelength and only slightly upon the entrance phase. For a properly chosen operating wavelength, a little less than the electron's relativistic cyclotron wavelength, the conditioner can decrease the axial velocity spread of a pulsed beam down to less than one-third of its initial value

  11. Monte Carlo electron/photon transport

    International Nuclear Information System (INIS)

    Mack, J.M.; Morel, J.E.; Hughes, H.G.

    1985-01-01

    A review of nonplasma coupled electron/photon transport using Monte Carlo method is presented. Remarks are mainly restricted to linerarized formalisms at electron energies from 1 keV to 1000 MeV. Applications involving pulse-height estimation, transport in external magnetic fields, and optical Cerenkov production are discussed to underscore the importance of this branch of computational physics. Advances in electron multigroup cross-section generation is reported, and its impact on future code development assessed. Progress toward the transformation of MCNP into a generalized neutral/charged-particle Monte Carlo code is described. 48 refs

  12. Electron transport in heterogeneous media

    International Nuclear Information System (INIS)

    Falcao, Rossana Cavalieri

    1992-05-01

    In this work it is presented a model to calculate dose enhancement in the vicinity of plane interfaces irradiated by therapeutic electron beams. The proposed model is based on an approximation of the Boltzmann Equation. The solutions presented to the equation are exact on its angular dependency, making it possible to observe that at low Z/high Z interfaces the dose enhancement is due to an increase of the backscattering. For the inverse situation a decrease of the backscattering can be observed. Calculations have been made for some tissue-metal interfaces irradiated by 13 MeV electron beam. The dose perturbations in tissue were obtained and the results were compared with experimental data as well as Monte Carlo simulations. In both cases the agreement found was very good. (author)

  13. Taking an electron-magnon duality shortcut from electron to magnon transport

    Science.gov (United States)

    Mook, Alexander; Göbel, Börge; Henk, Jürgen; Mertig, Ingrid

    2018-04-01

    The quasiparticles in insulating magnets are the charge-neutral magnons, whose magnetic moments couple to electromagnetic fields. For collinear easy-axis magnets, this coupling can be mapped elegantly onto the scenario of charged particles in electromagnetic fields. From this mapping we obtain equations of motion for magnon wave packets equal to those of electron wave packets in metals. Thus, well-established electronic transport phenomena can be carried over to magnons: this duality shortcut facilitates the discussion of magnon transport. We identify the magnon versions of normal and anomalous Hall, Nernst, Ettingshausen, and Righi-Leduc effects. They are discussed for selected types of easy-axis magnets: ferromagnets, antiferromagnets, and ferrimagnets. Besides a magnon Wiedemann-Franz law and the magnon counterpart of the negative magnetoresistance of electrons in Weyl semimetals, we predict that certain low-symmetry ferrimagnets exhibit a nonlinear version of the anomalous magnon Hall-effect family.

  14. Effect of doping on the electron transport in polyfluorene

    Energy Technology Data Exchange (ETDEWEB)

    Bajpai, Manisha, E-mail: mansa83@gmail.com [Soft Materials Research Laboratory, Centre of Material Sciences, Institute of Interdisciplinary Studies, University of Allahabad, Allahabad, 211002 (India); Department of Physics, Banaras Hindu University, Varanasi-221005 (India); Srivastava, Ritu [Physics for Energy Harvesting Division, National Physical Laboratory (Council of Scientific and Industrial Research), Dr K. S. Krishnan Road, New Delhi 110012 (India); Dhar, Ravindra [Soft Materials Research Laboratory, Centre of Material Sciences, Institute of Interdisciplinary Studies, University of Allahabad, Allahabad, 211002 (India); Tiwari, R. S. [Department of Physics, Banaras Hindu University, Varanasi-221005 (India)

    2016-05-06

    In this paper, electron transport of pure and DMC doped polyfluorne (PF) films have been studied at various doping concentrations. Pure films show space charge limited conduction with field and temperature dependent mobility. The J–V characteristics of doped PF were ohmic at low voltages due to thermally released carriers from dopant states. At higher voltages the current density increases nonlinearly due to field dependent mobility and carrier concentration thereby filling of tail states of HOMO of the host. The conductivity of doped films were analyzed using the Unified Gaussian Disorder Model (UGDM). The carrier concentration obtained from the fitting show a non-linear dependence on doping concentration which may be due to a combined effect of thermally activated carrier generation and increased carrier mobility.

  15. Electron-temperature-gradient-driven drift waves and anomalous electron energy transport

    International Nuclear Information System (INIS)

    Shukla, P.K.; Murtaza, G.; Weiland, J.

    1990-01-01

    By means of a kinetic description for ions and Braginskii's fluid model for electrons, three coupled nonlinear equations governing the dynamics of low-frequency short-wavelength electrostatic waves in the presence of equilibrium density temperature and magnetic-field gradients in a two-component magnetized plasma are derived. In the linear limit a dispersion relation that admits new instabilities of drift waves is presented. An estimate of the anomalous electron energy transport due to non-thermal drift waves is obtained by making use of the saturated wave potential, which is deduced from the mixing-length hypothesis. Stationary solutions of the nonlinear equations governing the interaction of linearly unstable drift waves are also presented. The relevance of this investigation to wave phenomena in space and laboratory plasmas is pointed out. (author)

  16. Nonlinear interplay of TEM and ITG turbulence and its effect on transport

    Science.gov (United States)

    Merz, F.; Jenko, F.

    2010-05-01

    The dominant source of anomalous transport in fusion plasmas on ion scales is turbulence driven by trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. While the individual properties of each of these two instabilities and the corresponding microturbulence have been examined in detail in the past, the effects of a coexistence of the two modes and the phenomena of transitions between the TEM and ITG dominated regimes are not well studied. In many experimental situations, the temperature and density gradients support both microinstabilities simultaneously, so that transitional regimes are important for a detailed understanding of fusion plasmas. In this paper, this issue is addressed, using the gyrokinetic code GENE for a detailed investigation of the dominant and subdominant linear instabilities and the corresponding nonlinear system. A simple quasilinear model based on eigenvalue computations is presented which is shown to reproduce important features of the nonlinear TEM-ITG transition.

  17. Plasma channels for electron beam transport

    International Nuclear Information System (INIS)

    Schneider, R.F.; Smith, J.R.; Moffatt, M.E.; Nguyen, K.T.; Uhm, H.S.

    1988-01-01

    In recent years, there has been much interest in transport of intense relativistic electron beams using plasma channels. These channels are formed by either: ionization of an organic gas by UV photoionization or electron impact ionization of a low pressure gas utilizing a low energy (typically several hundred volts) electron gun. The second method is discussed here. As their electron gun, the authors used a 12 volt lightbulb filament which is biased to -400 volts with respect to the grounded 15 cm diameter drift tube. The electrons emitted from the filament are confined by an axial magnetic field of --100 Gauss to create a plasma channel which is less than 1 cm in radius. The channel density has been determined with Langmuir probes and the resulting line densities were found to be 10 11 to 10 12 per cm. When a multi-kiloamp electron beam is injected onto this channel, the beam space charge will eject the plasma electrons leaving the ions behind to charge neutralize the electron beam, hence allowing the beam to propagate. In this work, the authors performed experimental studies on the dynamics of the plasma channel. These include Langmuir probe measurements of a steady state (DC) channel, as well as time-resolved Langmuir probe studies of pulsed channels. In addition they performed experimental studies of beam propagation in these plasma channels. Specifically, they observed the behavior of current transport in these channels. Detailed results of beam transport and channel studies are presented

  18. Innovative electron transport methods in EGS5

    International Nuclear Information System (INIS)

    Bielajew, A.F.; Wilderman, S.J.

    2000-01-01

    The initial formulation of a Monte Carlo scheme for the transport of high-energy (>≅ 100 keV) electrons was established by Berger in 1963. Calling his method the 'condensed history theory', Berger combined the theoretical results of the previous generation of research into developing approximate solutions of the Boltzmann transport equation with numerical algorithms for exploiting the power of computers to permit iterative, piece-wise solution of the transport equation in a computationally intensive but much less approximate fashion. The methods devised by Berger, with comparatively little modification, provide the foundation of all present day Monte Carlo electron transport simulation algorithms. Only in the last 15 years, beginning with the development and publication of the PRESTA algorithm, has there been a significant revisitation of the problem of simulating electron transport within the condensed history framework. Research in this area is ongoing, highly active, and far from complete. It presents an enormous challenge, demanding derivation of new analytical transport solutions based on underlying fundamental interaction mechanisms, intuitive insight in the development of computer algorithms, and state of the art computer science skills in order to permit deployment of these techniques in an efficient manner. The EGS5 project, a modern ground-up rewrite of the EGS4 code, is now in the design phase. EGS5 will take modern photon and electron transport algorithms and deploy them in an easy-to-maintain, modern computer language-ANSI-standard C ++. Moreover, the well-known difficulties of applying EGS4 to practical geometries (geometry code development, tally routine design) should be made easier and more intuitive through the use of a visual user interface being designed by Quantum Research, Inc., work that is presented elsewhere in this conference. This report commences with a historical review of electron transport models culminating with the proposal of a

  19. Paleoclassical transport explains electron transport barriers in RTP and TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Hogeweij, G M D [FOM-Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, PO Box 1207, NL-3430 BE Nieuwegein (Netherlands); Callen, J D [University of Wisconsin, Madison, WI 53706-1609 (United States)

    2008-06-15

    The recently developed paleoclassical transport model sets the minimum level of electron thermal transport in a tokamak. This transport level has proven to be in good agreement with experimental observations in many cases when fluctuation-induced anomalous transport is small, i.e. in (near-)ohmic plasmas in small to medium size tokamaks, inside internal transport barriers (ITBs) or edge transport barriers (H-mode pedestal). In this paper predictions of the paleoclassical transport model are compared in detail with data from such kinds of discharges: ohmic discharges from the RTP tokamak, EC heated RTP discharges featuring both dynamic and shot-to-shot scans of the ECH power deposition radius and off-axis EC heated discharges from the TEXTOR tokamak. For ohmically heated RTP discharges the T{sub e} profiles predicted by the paleoclassical model are in reasonable agreement with the experimental observations, and various parametric dependences are captured satisfactorily. The electron thermal ITBs observed in steady state EC heated RTP discharges and transiently after switch-off of off-axis ECH in TEXTOR are predicted very well by the paleoclassical model.

  20. Nonlinear ionic transport through microstructured solid electrolytes: homogenization estimates

    Science.gov (United States)

    Curto Sillamoni, Ignacio J.; Idiart, Martín I.

    2016-10-01

    We consider the transport of multiple ionic species by diffusion and migration through microstructured solid electrolytes in the presence of strong electric fields. The assumed constitutive relations for the constituent phases follow from convex energy and dissipation potentials which guarantee thermodynamic consistency. The effective response is heuristically deduced from a multi-scale convergence analysis of the relevant field equations. The resulting homogenized response involves an effective dissipation potential per species. Each potential is mathematically akin to that of a standard nonlinear heterogeneous conductor. A ‘linear-comparison’ homogenization technique is then used to generate estimates for these nonlinear potentials in terms of available estimates for corresponding linear conductors. By way of example, use is made of the Maxwell-Garnett and effective-medium linear approximations to generate estimates for two-phase systems with power-law dissipation. Explicit formulas are given for some limiting cases. In the case of threshold-type behavior, the estimates exhibit non-analytical dilute limits and seem to be consistent with fields localized in low energy paths.

  1. Punchets: nonlinear transport in Hamiltonian pump-ratchet hybrids

    Science.gov (United States)

    Dittrich, Thomas; Medina Sánchez, Nicolás

    2018-02-01

    ‘Punchets’ are hybrids between ratchets and pumps, combining a spatially periodic static potential, typically asymmetric under space inversion, with a local driving that breaks time-reversal invariance, and are intended to model metal or semiconductor surfaces irradiated by a collimated laser beam. Their crucial feature is irregular driven scattering between asymptotic regions supporting periodic (as opposed to free) motion. With all binary spatio-temporal symmetries broken, scattering in punchets typically generates directed currents. We here study the underlying nonlinear transport mechanisms, from chaotic scattering to the parameter dependence of the currents, in three types of Hamiltonian models, (i) with spatially periodic potentials where only in the driven scattering region, spatial and temporal symmetries are broken, and (ii), spatially asymmetric (ratchet) potentials with a driving that only breaks time-reversal invariance. As more realistic models of laser-irradiated surfaces, we consider (iii), a driving in the form of a running wave confined to a compact region by a static envelope. In this case, the induced current can even run against the direction of wave propagation, drastically evidencing its nonlinear nature. Quantizing punchets is indicated as a viable research perspective.

  2. Model Comparison for Electron Thermal Transport

    Science.gov (United States)

    Moses, Gregory; Chenhall, Jeffrey; Cao, Duc; Delettrez, Jacques

    2015-11-01

    Four electron thermal transport models are compared for their ability to accurately and efficiently model non-local behavior in ICF simulations. Goncharov's transport model has accurately predicted shock timing in implosion simulations but is computationally slow and limited to 1D. The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. uses multigroup diffusion to speed up the calculation. Chenhall has expanded upon the iSNB diffusion model to a higher order simplified P3 approximation and a Monte Carlo transport model, to bridge the gap between the iSNB and Goncharov models while maintaining computational efficiency. Comparisons of the above models for several test problems will be presented. This work was supported by Sandia National Laboratory - Albuquerque and the University of Rochester Laboratory for Laser Energetics.

  3. Kinetic theory of nonlinear transport phenomena in complex plasmas

    International Nuclear Information System (INIS)

    Mishra, S. K.; Sodha, M. S.

    2013-01-01

    In contrast to the prevalent use of the phenomenological theory of transport phenomena, a number of transport properties of complex plasmas have been evaluated by using appropriate expressions, available from the kinetic theory, which are based on Boltzmann's transfer equation; in particular, the energy dependence of the electron collision frequency has been taken into account. Following the recent trend, the number and energy balance of all the constituents of the complex plasma and the charge balance on the particles is accounted for; the Ohmic loss has also been included in the energy balance of the electrons. The charging kinetics for the complex plasma comprising of uniformly dispersed dust particles, characterized by (i) uniform size and (ii) the Mathis, Rumpl, and Nordsieck power law of size distribution has been developed. Using appropriate expressions for the transport parameters based on the kinetic theory, the system of equations has been solved to investigate the parametric dependence of the complex plasma transport properties on the applied electric field and other plasma parameters; the results are graphically illustrated.

  4. Nonlinear dynamics of resonant electrons interacting with coherent Langmuir waves

    Science.gov (United States)

    Tobita, Miwa; Omura, Yoshiharu

    2018-03-01

    We study the nonlinear dynamics of resonant particles interacting with coherent waves in space plasmas. Magnetospheric plasma waves such as whistler-mode chorus, electromagnetic ion cyclotron waves, and hiss emissions contain coherent wave structures with various discrete frequencies. Although these waves are electromagnetic, their interaction with resonant particles can be approximated by equations of motion for a charged particle in a one-dimensional electrostatic wave. The equations are expressed in the form of nonlinear pendulum equations. We perform test particle simulations of electrons in an electrostatic model with Langmuir waves and a non-oscillatory electric field. We solve equations of motion and study the dynamics of particles with different values of inhomogeneity factor S defined as a ratio of the non-oscillatory electric field intensity to the wave amplitude. The simulation results demonstrate deceleration/acceleration, thermalization, and trapping of particles through resonance with a single wave, two waves, and multiple waves. For two-wave and multiple-wave cases, we describe the wave-particle interaction as either coherent or incoherent based on the probability of nonlinear trapping.

  5. Electron transport through monovalent atomic wires

    DEFF Research Database (Denmark)

    Lee, Y. J.; Brandbyge, Mads; Puska, M. J.

    2004-01-01

    at the chain determine the conductance. As a result, the conductance for noble-metal chains is close to one quantum of conductance, and it oscillates moderately so that an even number of chain atoms yields a higher value than an odd number. The conductance oscillations are large for alkali-metal chains......Using a first-principles density-functional method we model electron transport through linear chains of monovalent atoms between two bulk electrodes. For noble-metal chains the transport resembles that for free electrons over a potential barrier whereas for alkali-metal chains resonance states...... and their phase is opposite to that of noble-metal chains....

  6. Epitaxial graphene electronic structure and transport

    International Nuclear Information System (INIS)

    De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N; Stroscio, Joseph A; Haddon, Robert; Piot, Benjamin; Faugeras, Clement; Potemski, Marek; Moon, Jeong-Sun

    2010-01-01

    Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.

  7. Computational methods of electron/photon transport

    International Nuclear Information System (INIS)

    Mack, J.M.

    1983-01-01

    A review of computational methods simulating the non-plasma transport of electrons and their attendant cascades is presented. Remarks are mainly restricted to linearized formalisms at electron energies above 1 keV. The effectiveness of various metods is discussed including moments, point-kernel, invariant imbedding, discrete-ordinates, and Monte Carlo. Future research directions and the potential impact on various aspects of science and engineering are indicated

  8. Low energy electron transport in furfural

    OpenAIRE

    Lozano, Ana I.; Krupa, K.; Ferreira da Silva, F.; Limao-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, D. B.; Brunger, M. J.; García, Gustavo

    2017-01-01

    We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulat...

  9. Nonlinear electromagnetic waves in a degenerate electron-positron plasma

    Energy Technology Data Exchange (ETDEWEB)

    El-Labany, S.K., E-mail: skellabany@hotmail.com [Department of Physics, Faculty of Science, Damietta University, New Damietta (Egypt); El-Taibany, W.F., E-mail: eltaibany@hotmail.com [Department of Physics, College of Science for Girls in Abha, King Khalid University, Abha (Saudi Arabia); El-Samahy, A.E.; Hafez, A.M.; Atteya, A., E-mail: ahmedsamahy@yahoo.com, E-mail: am.hafez@sci.alex.edu.eg, E-mail: ahmed_ateya2002@yahoo.com [Department of Physics, Faculty of Science, Alexandria University, Alexandria (Egypt)

    2015-08-15

    Using the reductive perturbation technique (RPT), the nonlinear propagation of magnetosonic solitary waves in an ultracold, degenerate (extremely dense) electron-positron (EP) plasma (containing ultracold, degenerate electron, and positron fluids) is investigated. The set of basic equations is reduced to a Korteweg-de Vries (KdV) equation for the lowest-order perturbed magnetic field and to a KdV type equation for the higher-order perturbed magnetic field. The solutions of these evolution equations are obtained. For better accuracy and searching on new features, the new solutions are analyzed numerically based on compact objects (white dwarf) parameters. It is found that including the higher-order corrections results as a reduction (increment) of the fast (slow) electromagnetic wave amplitude but the wave width is increased in both cases. The ranges where the RPT can describe adequately the total magnetic field including different conditions are discussed. (author)

  10. Comparison of transient electron heat transport in LHD helical and JT-60U tokamak plasmas

    International Nuclear Information System (INIS)

    Inagaki, S.; Ida, K.; Tamura, N.; Shimozuma, T.; Kubo, S.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Ohkubo, K.; Takenaga, H.; Isayama, A.; Takizuka, T.; Kamada, Y.; Miura, Y.

    2005-01-01

    Transient transport experiments are performed in plasmas with and without Internal Transport Barrier (ITB) on LHD and JT-60U. The dependence of χ e on electron temperature, T e , and electron temperature gradient, ∇T e , is analyzed by an empirical non-linear heat transport model. In plasmas without ITB, two different types of non-linearity of the electron heat transport are observed from cold/heat pulse propagation. The χ e depends on T e and ∇T e in JT-60U, while the ∇T e dependence is weak in LHD. Inside the ITB region, there is no or weak ∇T e dependence both in LHD and JT-60U. A cold pulse growing driven by the negative T e dependence of χ e is observed inside the ITB region (LHD) and near the boundary of the ITB region (JT-60U). (author)

  11. Long-term evolution of electron distribution function due to nonlinear resonant interaction with whistler mode waves

    Science.gov (United States)

    Artemyev, Anton V.; Neishtadt, Anatoly I.; Vasiliev, Alexei A.

    2018-04-01

    Accurately modelling and forecasting of the dynamics of the Earth's radiation belts with the available computer resources represents an important challenge that still requires significant advances in the theoretical plasma physics field of wave-particle resonant interaction. Energetic electron acceleration or scattering into the Earth's atmosphere are essentially controlled by their resonances with electromagnetic whistler mode waves. The quasi-linear diffusion equation describes well this resonant interaction for low intensity waves. During the last decade, however, spacecraft observations in the radiation belts have revealed a large number of whistler mode waves with sufficiently high intensity to interact with electrons in the nonlinear regime. A kinetic equation including such nonlinear wave-particle interactions and describing the long-term evolution of the electron distribution is the focus of the present paper. Using the Hamiltonian theory of resonant phenomena, we describe individual electron resonance with an intense coherent whistler mode wave. The derived characteristics of such a resonance are incorporated into a generalized kinetic equation which includes non-local transport in energy space. This transport is produced by resonant electron trapping and nonlinear acceleration. We describe the methods allowing the construction of nonlinear resonant terms in the kinetic equation and discuss possible applications of this equation.

  12. Understanding charge transport in molecular electronics.

    Science.gov (United States)

    Kushmerick, J J; Pollack, S K; Yang, J C; Naciri, J; Holt, D B; Ratner, M A; Shashidhar, R

    2003-12-01

    For molecular electronics to become a viable technology the factors that control charge transport across a metal-molecule-metal junction need to be elucidated. We use an experimentally simple crossed-wire tunnel junction to interrogate how factors such as metal-molecule coupling, molecular structure, and the choice of metal electrode influence the current-voltage characteristics of a molecular junction.

  13. Filamentous bacteria transport electrons over centimetre distances

    DEFF Research Database (Denmark)

    Pfeffer, Christian; Larsen, Steffen; Song, Jie

    2012-01-01

    across centimetre-wide zones. Here we present evidence that the native conductors are long, filamentous bacteria. They abounded in sediment zones with electric currents and along their length they contained strings with distinct properties in accordance with a function as electron transporters. Living...

  14. Electronic transport in torsional strained Weyl semimetals

    Science.gov (United States)

    Soto-Garrido, Rodrigo; Muñoz, Enrique

    2018-05-01

    In a recent paper (Muñoz and Soto-Garrido 2017 J. Phys.: Condens. Matter 29 445302) we have studied the effects of mechanical strain and magnetic field on the electronic transport properties in graphene. In this article we extended our work to Weyl semimetals (WSM). We show that although the WSM are 3D materials, most of the analysis done for graphene (2D material) can be carried out. In particular, we studied the electronic transport through a cylindrical region submitted to torsional strain and external magnetic field. We provide exact analytical expressions for the scattering cross section and the transmitted electronic current. In addition, we show the node-polarization effect on the current and propose a recipe to measure the torsion angle from transmission experiments.

  15. The effect of electron-electron interaction induced dephasing on electronic transport in graphene nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Kahnoj, Sina Soleimani; Touski, Shoeib Babaee [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Pourfath, Mahdi, E-mail: pourfath@ut.ac.ir, E-mail: pourfath@iue.tuwien.ac.at [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Institute for Microelectronics, TU Wien, Gusshausstrasse 27–29/E360, 1040 Vienna (Austria)

    2014-09-08

    The effect of dephasing induced by electron-electron interaction on electronic transport in graphene nanoribbons is theoretically investigated. In the presence of disorder in graphene nanoribbons, wavefunction of electrons can set up standing waves along the channel and the conductance exponentially decreases with the ribbon's length. Employing the non-equilibrium Green's function formalism along with an accurate model for describing the dephasing induced by electron-electron interaction, we show that this kind of interaction prevents localization and transport of electrons remains in the diffusive regime where the conductance is inversely proportional to the ribbon's length.

  16. Electronic Transport in Two-Dimensional Materials

    Science.gov (United States)

    Sangwan, Vinod K.; Hersam, Mark C.

    2018-04-01

    Two-dimensional (2D) materials have captured the attention of the scientific community due to the wide range of unique properties at nanometer-scale thicknesses. While significant exploratory research in 2D materials has been achieved, the understanding of 2D electronic transport and carrier dynamics remains in a nascent stage. Furthermore, because prior review articles have provided general overviews of 2D materials or specifically focused on charge transport in graphene, here we instead highlight charge transport mechanisms in post-graphene 2D materials, with particular emphasis on transition metal dichalcogenides and black phosphorus. For these systems, we delineate the intricacies of electronic transport, including band structure control with thickness and external fields, valley polarization, scattering mechanisms, electrical contacts, and doping. In addition, electronic interactions between 2D materials are considered in the form of van der Waals heterojunctions and composite films. This review concludes with a perspective on the most promising future directions in this fast-evolving field.

  17. Fast electron transport in shaped solid targets

    International Nuclear Information System (INIS)

    Anle Lei; Cao, L.H.; He, X.T.; Zhang, W.Y.; Tanaka, K.A.; Kodama, R.; Mima, K.; Nakamura, T.; Normatsu, T.; Yu, W.

    2010-01-01

    Complete text of publication follows. The scheme of fast ignition fusion energy relies on the ultra-intense ultra-short (UIUS) laser energy transport into the compressed core plasma. One solution is to insert a hollow cone in the fuel shell to block the UIUS laser from the coronal plasma, thus allowing it to reach the core plasma. The cone not only can guide the UIUS laser to its tip, but can play important roles in the specific cone-in-shell target designed for FI. It was found in a PIC simulation that the cone can guide the fast electrons generated at the inner wall to propagate along the wall surface toward its tip, which would increase the energy density at the tip and might enhance the heating of the core plasma. Surface guiding of fast electrons with planar foil targets has been demonstrated experimentally. However, the guided fast electrons will mix the electrons generated ahead by the laser light with a planar target, and hence one cannot experimentally quantitatively validate the guide of the fast electrons. We investigate the cone guiding of fast electrons with an inverse cone target. We found a novel surface current of fast electrons propagating along the cone wall. The fast electrons generated at the planar outer tip of the inverse cone are guided and confined to propagate along the inverse cone wall to form a surface current by induced transient electric and magnetic fields associated with the current itself. Once departing from the source at the outer tip, this surface current of fast electrons is 'clean', neither experiencing the interacting laser light nor mixing fast electrons ahead, unlike those in cone or planar targets. This surface current in the inverse cone may explicitly give the capability of the guide of fast electron energy by the cone wall. The guiding and confinement of fast electrons is of important for fast ignition in inertial confinement fusion and several applications in high energy density science.

  18. Theoretical investigations of molecular wires: Electronic spectra and electron transport

    Science.gov (United States)

    Palma, Julio Leopoldo

    The results of theoretical and computational research are presented for two promising molecular wires, the Nanostar dendrimer, and a series of substituted azobenzene derivatives connected to aluminum electrodes. The electronic absorption spectra of the Nanostar (a phenylene-ethynylene dendrimer attached to an ethynylperylene chromophore) were calculated using a sequential Molecular Dynamics/Quantum Mechanics (MD/QM) method to perform an analysis of the temperature dependence of the electronic absorption process. We modeled the Nanostar as a series of connected units, and performed MD simulations for each chromophore at 10 K and 300 K to study how the temperature affected the structures and, consequently, the spectra. The absorption spectra of the Nanostar were computed using an ensemble of 8000 structures for each chromophore. Quantum Mechanical (QM) ZINDO/S calculations were performed for each conformation in the ensemble, including 16 excited states, for a total of 128,000 excitation energies. The spectral intensity was then scaled linearly with the number of conjugated units. Our calculations for both the individual chromophores and the Nanostar, are in good agreement with experiments. We explain in detail the effects of temperature and the consequences for the absorption process. The second part of this thesis presents a study of the effects of chemical substituents on the electron transport properties of the azobenzene molecule, which has been proposed recently as a component of a light-driven molecular switch. This molecule has two stable conformations (cis and trans) in its electronic ground state, with considerable differences in their conductance. The electron transport properties were calculated using first-principles methods combining non-equilibrium Green's function (NEGF) techniques with density functional theory (DFT). For the azobenzene studies, we included electron-donating groups and electron-withdrawing groups in meta- and ortho-positions with

  19. Charge transport through DNA based electronic barriers

    Science.gov (United States)

    Patil, Sunil R.; Chawda, Vivek; Qi, Jianqing; Anantram, M. P.; Sinha, Niraj

    2018-05-01

    We report charge transport in electronic 'barriers' constructed by sequence engineering in DNA. Considering the ionization potentials of Thymine-Adenine (AT) and Guanine-Cytosine (GC) base pairs, we treat AT as 'barriers'. The effect of DNA conformation (A and B form) on charge transport is also investigated. Particularly, the effect of width of 'barriers' on hole transport is investigated. Density functional theory (DFT) calculations are performed on energy minimized DNA structures to obtain the electronic Hamiltonian. The quantum transport calculations are performed using the Landauer-Buttiker framework. Our main findings are contrary to previous studies. We find that a longer A-DNA with more AT base pairs can conduct better than shorter A-DNA with a smaller number of AT base pairs. We also find that some sequences of A-DNA can conduct better than a corresponding B-DNA with the same sequence. The counterions mediated charge transport and long range interactions are speculated to be responsible for counter-intuitive length and AT content dependence of conductance of A-DNA.

  20. Disorder and electronic transport in graphene

    International Nuclear Information System (INIS)

    Mucciolo, E R; Lewenkopf, C H

    2010-01-01

    In this review, we provide an account of the recent progress in understanding electronic transport in disordered graphene systems. Starting from a theoretical description that emphasizes the role played by band structure properties and lattice symmetries, we describe the nature of disorder in these systems and its relation to transport properties. While the focus is primarily on theoretical and conceptual aspects, connections to experiments are also included. Issues such as short- versus long-range disorder, localization (strong and weak), the carrier density dependence of the conductivity, and conductance fluctuations are considered and some open problems are pointed out. (topical review)

  1. Nonlinear transport in semiconducting polymers at high carrier densities.

    Science.gov (United States)

    Yuen, Jonathan D; Menon, Reghu; Coates, Nelson E; Namdas, Ebinazar B; Cho, Shinuk; Hannahs, Scott T; Moses, Daniel; Heeger, Alan J

    2009-07-01

    Conducting and semiconducting polymers are important materials in the development of printed, flexible, large-area electronics such as flat-panel displays and photovoltaic cells. There has been rapid progress in developing conjugated polymers with high transport mobility required for high-performance field-effect transistors (FETs), beginning with mobilities around 10(-4) cm(2) V(-1) s(-1) to a recent report of 1 cm(2) V(-1) s(-1) for poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). Here, the electrical properties of PBTTT are studied at high charge densities both as the semiconductor layer in FETs and in electrochemically doped films to determine the transport mechanism. We show that data obtained using a wide range of parameters (temperature, gate-induced carrier density, source-drain voltage and doping level) scale onto the universal curve predicted for transport in the Luttinger liquid description of the one-dimensional 'metal'.

  2. Low energy electron transport in furfural

    Science.gov (United States)

    Lozano, Ana I.; Krupa, Kateryna; Ferreira da Silva, Filipe; Limão-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, Darryl B.; Brunger, Michael J.; García, Gustavo

    2017-09-01

    We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed.

  3. Sub-electron transport in single-electron-tunneling arrays

    Science.gov (United States)

    Kaplan, Daniel; Sverdlov, Viktor; Korotkov, Alexander; Likharev, Konstantin

    2002-03-01

    We have analyzed quasi-continuous charge transport in two-dimensional tunnel junction arrays with a special distribution of background charges, providing a complete suppression of Coulomb blockade thresholds of tunneling between any pair of islands. Numerical simulations show that at low currents the dc I-V curve is indeed linear, while the shot noise is strongly suppressed and approaches 1/N of the Schottky value (where N is the array length). Thus both conditions of quasi-continuous transport, formulated earlier by Matsuoka and Likharev (Phys. Rev. B, v57, 15613, 1998), are satisfied. At higher fields the electron-hole pair production begins, and shot noise grows sharply. At higher voltages still, the array enters the "plasma" regime (with nearly balanced number of electrons and holes) and the Fano factor drops to 1/N once again. We have studied the resulting shot noise peak in detail, and concluded that its physics is close to that of critical opalescence.

  4. Relativistic nonlinear waves of cyclotron in electron and electron-ion plasmas

    International Nuclear Information System (INIS)

    Bruno, R.

    1981-12-01

    Dispersion relations for electron-cyclotron and ion-cyclotron waves are examined in two models of plasmas, the first propagating in fluent electronic plasmas (''streaming'') as well as in fluent electron-ionic plasmas, and the last in fluent electron-ionic plasmas. The identification of the propagation modes is realized with the aid of a special technique of polinomial expantion of the dispersion relation in the limit of large frequencies and short wavelenghts. The analisys so developed on these dispersion relations for fluent plasmas show that: (i) the wave amplitudes are frequency dependent; (ii) the ''resonances'' frequencies of the respective estationary plasmas must be re-examined with the relations between wave amplitudes and the propagation frequencies near these frequencies; (iii) the electric field amplitudes for the non-linear waves of electron-cyclotron and ion-cyclotron go to zero in the limits of the respective cyclotron frequencies in both fluent plasma models. (M.W.O.) [pt

  5. Electronic transport in methylated fragments of DNA

    International Nuclear Information System (INIS)

    Almeida, M. L. de; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L.; Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.; Moura, F. A. B. F. de; Lyra, M. L.

    2015-01-01

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics

  6. Electronic transport in methylated fragments of DNA

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, M. L. de; Oliveira, J. I. N.; Lima Neto, J. X.; Gomes, C. E. M.; Fulco, U. L., E-mail: umbertofulco@gmail.com; Albuquerque, E. L. [Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN (Brazil); Freire, V. N. [Departamento de Física, Universidade Federal do Ceará, 60455-760 Fortaleza, CE (Brazil); Caetano, E. W. S. [Instituto Federal de Educação, Ciência e Tecnologia do Ceará, 60040-531 Fortaleza, CE (Brazil); Moura, F. A. B. F. de; Lyra, M. L. [Instituto de Física, Universidade Federal de Alagoas, 57072-900 Maceió-AL (Brazil)

    2015-11-16

    We investigate the electronic transport properties of methylated deoxyribonucleic-acid (DNA) strands, a biological system in which methyl groups are added to DNA (a major epigenetic modification in gene expression), sandwiched between two metallic platinum electrodes. Our theoretical simulations apply an effective Hamiltonian based on a tight-binding model to obtain current-voltage curves related to the non-methylated/methylated DNA strands. The results suggest potential applications in the development of novel biosensors for molecular diagnostics.

  7. Electron stopping powers for transport calculations

    International Nuclear Information System (INIS)

    Berger, M.J.

    1988-01-01

    The reliability of radiation transport calculations depends on the accuracy of the input cross sections. Therefore, it is essential to review and update the cross sections from time to time. Even though the main interest of the author's group at NBS is in transport calculations and their applications, the group spends almost as much time on the analysis and preparation of cross sections as on the development of transport codes. Stopping powers, photon attenuation coefficients, bremsstrahlung cross sections, and elastic-scattering cross sections in recent years have claimed attention. This chapter deals with electron stopping powers (with emphasis on collision stopping powers), and reviews the state of the art as reflected by Report 37 of the International Commission on Radiation Units and Measurements

  8. Linear and nonlinear dynamics of electron temperature gradient mode in non-Maxwellian plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Zakir, U.; Qamar, A. [Institute of Physics and Electronics, University of Peshawar, Peshawar (Pakistan); Haque, Q. [Theoretical Plasma Physics Division, PINSTECH, Islamabad (Pakistan); National Centre for Physics, Islamabad (Pakistan)

    2013-05-15

    The effect of non-Maxwellian distributed ions on electron temperature gradient mode is investigated. The linear dispersion relation of η{sub e}−mode is obtained which shows that the behavior of this mode changes in the presence of superthermal ions. The growth rate of η{sub e}−mode driven linear instability is found and is observed to modify due to nonthermal ions. However, it is found that this leaves the electron energy transport coefficient unchanged. In the nonlinear regime, a dipolar vortex solution is derived which indicates that the dynamic behavior of the vortices changes with the inclusion of kappa distributed ions. The importance of present study with respect to space and laboratory plasmas is also pointed out.

  9. Recent developments in discrete ordinates electron transport

    International Nuclear Information System (INIS)

    Morel, J.E.; Lorence, L.J. Jr.

    1986-01-01

    The discrete ordinates method is a deterministic method for numerically solving the Boltzmann equation. It was originally developed for neutron transport calculations, but is routinely used for photon and coupled neutron-photon transport calculations as well. The computational state of the art for coupled electron-photon transport (CEPT) calculations is not as developed as that for neutron transport calculations. The only production codes currently available for CEPT calculations are condensed-history Monte Carlo codes such as the ETRAN and ITS codes. A deterministic capability for production calculations is clearly needed. In response to this need, we have begun the development of a production discrete ordinates code for CEPT calculations. The purpose of this paper is to describe the basic approach we are taking, discuss the current status of the project, and present some new computational results. Although further characterization of the coupled electron-photon discrete ordinates method remains to be done, the results to date indicate that the discrete ordinates method can be just as accurate and from 10 to 100 times faster than the Monte Carlo method for a wide variety of problems. We stress that these results are obtained with standard discrete ordinates codes such as ONETRAN. It is clear that even greater efficiency can be obtained by developing a new generation of production discrete ordinates codes specifically designed to solve the Boltzmann-Fokker-Planck equation. However, the prospects for such development in the near future appear to be remote

  10. Status of electron transport in MCNP trademark

    International Nuclear Information System (INIS)

    Hughes, H.G.

    1997-01-01

    The latest version of MCNP, the Los Alamos Monte Carlo transport code, has now been officially released. MCNP4B has been sent to the Radiation Safety Information Computational Center (RSICC), in Oak Ridge, Tennessee, which is responsible for the further distribution of the code within the US. International distribution of MCNP is done by the Nuclear Energy Agency (ECD/NEA), in Paris, France. Readers with access to the World-Wide-Web should consult the MCNP distribution site http://www-xdiv.lanl.gov/XTM/mcnp/about.html for specific information about contacting RSICC and OECD/NEA. A variety of new features are available in MCNP4B. Among these are differential operator perturbations, cross-section plotting capabilities, enhanced diagnostics for transport in repeated structures and lattices, improved efficiency in distributed-memory multiprocessing, corrected particle lifetime and lifespan estimators, and expanded software quality assurance procedures and testing, including testing of the multigroup Boltzmann-Fokker-Planck capability. New and improved cross section sets in the form of ENDF/B-VI evaluations have also been recently released and can be used in MCNP4B. Perhaps most significant for the interests of this special session, the electron transport algorithm has been improved, especially in the collisional energy-loss straggling and the angular-deflection treatments. In this paper, the author concentrates on a fairly complete documentation of the current status of the electron transport methods in MCNP

  11. Fused electron deficient semiconducting polymers for air stable electron transport

    KAUST Repository

    Onwubiko, Ada

    2018-01-23

    Conventional semiconducting polymer synthesis typically involves transition metal-mediated coupling reactions that link aromatic units with single bonds along the backbone. Rotation around these bonds contributes to conformational and energetic disorder and therefore potentially limits charge delocalisation, whereas the use of transition metals presents difficulties for sustainability and application in biological environments. Here we show that a simple aldol condensation reaction can prepare polymers where double bonds lock-in a rigid backbone conformation, thus eliminating free rotation along the conjugated backbone. This polymerisation route requires neither organometallic monomers nor transition metal catalysts and offers a reliable design strategy to facilitate delocalisation of frontier molecular orbitals, elimination of energetic disorder arising from rotational torsion and allowing closer interchain electronic coupling. These characteristics are desirable for high charge carrier mobilities. Our polymers with a high electron affinity display long wavelength NIR absorption with air stable electron transport in solution processed organic thin film transistors.

  12. Fused electron deficient semiconducting polymers for air stable electron transport

    KAUST Repository

    Onwubiko, Ada; Yue, Wan; Jellett, Cameron; Xiao, Mingfei; Chen, Hung-Yang; Ravva, Mahesh Kumar; Hanifi, David A.; Knall, Astrid-Caroline; Purushothaman, Balaji; Nikolka, Mark; Flores, Jean-Charles; Salleo, Alberto; Bredas, Jean-Luc; Sirringhaus, Henning; Hayoz, Pascal; McCulloch, Iain

    2018-01-01

    Conventional semiconducting polymer synthesis typically involves transition metal-mediated coupling reactions that link aromatic units with single bonds along the backbone. Rotation around these bonds contributes to conformational and energetic disorder and therefore potentially limits charge delocalisation, whereas the use of transition metals presents difficulties for sustainability and application in biological environments. Here we show that a simple aldol condensation reaction can prepare polymers where double bonds lock-in a rigid backbone conformation, thus eliminating free rotation along the conjugated backbone. This polymerisation route requires neither organometallic monomers nor transition metal catalysts and offers a reliable design strategy to facilitate delocalisation of frontier molecular orbitals, elimination of energetic disorder arising from rotational torsion and allowing closer interchain electronic coupling. These characteristics are desirable for high charge carrier mobilities. Our polymers with a high electron affinity display long wavelength NIR absorption with air stable electron transport in solution processed organic thin film transistors.

  13. Fused electron deficient semiconducting polymers for air stable electron transport.

    Science.gov (United States)

    Onwubiko, Ada; Yue, Wan; Jellett, Cameron; Xiao, Mingfei; Chen, Hung-Yang; Ravva, Mahesh Kumar; Hanifi, David A; Knall, Astrid-Caroline; Purushothaman, Balaji; Nikolka, Mark; Flores, Jean-Charles; Salleo, Alberto; Bredas, Jean-Luc; Sirringhaus, Henning; Hayoz, Pascal; McCulloch, Iain

    2018-01-29

    Conventional semiconducting polymer synthesis typically involves transition metal-mediated coupling reactions that link aromatic units with single bonds along the backbone. Rotation around these bonds contributes to conformational and energetic disorder and therefore potentially limits charge delocalisation, whereas the use of transition metals presents difficulties for sustainability and application in biological environments. Here we show that a simple aldol condensation reaction can prepare polymers where double bonds lock-in a rigid backbone conformation, thus eliminating free rotation along the conjugated backbone. This polymerisation route requires neither organometallic monomers nor transition metal catalysts and offers a reliable design strategy to facilitate delocalisation of frontier molecular orbitals, elimination of energetic disorder arising from rotational torsion and allowing closer interchain electronic coupling. These characteristics are desirable for high charge carrier mobilities. Our polymers with a high electron affinity display long wavelength NIR absorption with air stable electron transport in solution processed organic thin film transistors.

  14. Electron Transport Properties of Ge nanowires

    Science.gov (United States)

    Hanrath, Tobias; Khondaker, Saiful I.; Yao, Zhen; Korgel, Brian A.

    2003-03-01

    Electron Transport Properties of Ge nanowires Tobias Hanrath*, Saiful I. Khondaker, Zhen Yao, Brian A. Korgel* *Dept. of Chemical Engineering, Dept. of Physics, Texas Materials Institute, and Center for Nano- and Molecular Science and Technology University of Texas at Austin, Austin, Texas 78712-1062 e-mail: korgel@mail.che.utexas.edu Germanium (Ge) nanowires with diameters ranging from 6 to 50 nm and several micrometer in length were grown via a supercritical fluid-liquid-solid synthesis. Parallel electron energy loss spectroscopy (PEELS) was employed to study the band structure and electron density in the Ge nanowires. The observed increase in plasmon peak energy and peak width with decreasing nanowire diameter is attributed to quantum confinement effects. For electrical characterization, Ge nanowires were deposited onto a patterned Si/SiO2 substrate. E-beam lithography was then used to form electrode contacts to individual nanowires. The influence of nanowire diameter, surface chemistry and crystallographic defects on electron transport properties were investigated and the comparison of Ge nanowire conductivity with respect to bulk, intrinsic Ge will be presented.

  15. Non-linear phenomena in electronic systems consisting of coupled single-electron oscillators

    International Nuclear Information System (INIS)

    Kikombo, Andrew Kilinga; Hirose, Tetsuya; Asai, Tetsuya; Amemiya, Yoshihito

    2008-01-01

    This paper describes non-linear dynamics of electronic systems consisting of single-electron oscillators. A single-electron oscillator is a circuit made up of a tunneling junction and a resistor, and produces simple relaxation oscillation. Coupled with another, single electron oscillators exhibit complex behavior described by a combination of continuous differential equations and discrete difference equations. Computer simulation shows that a double-oscillator system consisting of two coupled oscillators produces multi-periodic oscillation with a single attractor, and that a quadruple-oscillator system consisting of four oscillators also produces multi-periodic oscillation but has a number of possible attractors and takes one of them determined by initial conditions

  16. Study of nonlinear electron-acoustic solitary and shock waves in a dissipative, nonplanar space plasma with superthermal hot electrons

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jiu-Ning, E-mail: hanjiuning@126.com; He, Yong-Lin; Luo, Jun-Hua; Nan, Ya-Gong; Han, Zhen-Hai; Dong, Guang-Xing [College of Physics and Electromechanical Engineering, Hexi University, Zhangye 734000 (China); Duan, Wen-Shan [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Li, Jun-Xiu [College of Civil Engineering, Hexi University, Zhangye 734000 (China)

    2014-01-15

    With the consideration of the superthermal electron distribution, we present a theoretical investigation about the nonlinear propagation of electron-acoustic solitary and shock waves in a dissipative, nonplanar non-Maxwellian plasma comprised of cold electrons, superthermal hot electrons, and stationary ions. The reductive perturbation technique is used to obtain a modified Korteweg-de Vries Burgers equation for nonlinear waves in this plasma. We discuss the effects of various plasma parameters on the time evolution of nonplanar solitary waves, the profile of shock waves, and the nonlinear structure induced by the collision between planar solitary waves. It is found that these parameters have significant effects on the properties of nonlinear waves and collision-induced nonlinear structure.

  17. Understanding of flux-limited behaviors of heat transport in nonlinear regime

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Yangyu, E-mail: yangyuhguo@gmail.com [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics and CNMM, Tsinghua University, Beijing 100084 (China); Jou, David, E-mail: david.jou@uab.es [Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Catalonia (Spain); Wang, Moran, E-mail: mrwang@tsinghua.edu [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics and CNMM, Tsinghua University, Beijing 100084 (China)

    2016-01-28

    The classical Fourier's law of heat transport breaks down in highly nonequilibrium situations as in nanoscale heat transport, where nonlinear effects become important. The present work is aimed at exploring the flux-limited behaviors based on a categorization of existing nonlinear heat transport models in terms of their theoretical foundations. Different saturation heat fluxes are obtained, whereas the same qualitative variation trend of heat flux versus exerted temperature gradient is got in diverse nonlinear models. The phonon hydrodynamic model is proposed to act as a standard to evaluate other heat flux limiters because of its more rigorous physical foundation. A deeper knowledge is thus achieved about the phenomenological generalized heat transport models. The present work provides deeper understanding and accurate modeling of nonlocal and nonlinear heat transport beyond the diffusive limit. - Highlights: • Exploring flux-limited behaviors based on a categorization of existing nonlinear heat transport models. • Proposing phonon hydrodynamic model as a standard to evaluate heat flux limiters. • Providing accurate modeling of nonlocal and nonlinear heat transport beyond the diffusive limit.

  18. Common-User Land Transportation Management in the Layered, Non-Linear, Non-Contiguous Battlefield

    National Research Council Canada - National Science Library

    Strobel, Lawrence E

    2005-01-01

    .... Current multinational counterinsurgency warfare occurs in a layered, non-linear, non-contiguous battle space, making management of ground transportation assets even more critical than in conventional warfare...

  19. Electronic and transport properties of kinked graphene

    DEFF Research Database (Denmark)

    Rasmussen, Jesper Toft; Gunst, Tue; Bøggild, Peter

    2013-01-01

    Local curvature, or bending, of a graphene sheet is known to increase the chemical reactivity presenting an opportunity for templated chemical functionalisation. Using first-principles calculations based on density functional theory (DFT), we investigate the reaction barrier reduction for the ads......Local curvature, or bending, of a graphene sheet is known to increase the chemical reactivity presenting an opportunity for templated chemical functionalisation. Using first-principles calculations based on density functional theory (DFT), we investigate the reaction barrier reduction...... for the adsorption of atomic hydrogen at linear bends in graphene. We find a significant barrier lowering (≈15%) for realistic radii of curvature (≈20 Å) and that adsorption along the linear bend leads to a stable linear kink. We compute the electronic transport properties of individual and multiple kink lines......, and demonstrate how these act as efficient barriers for electron transport. In particular, two parallel kink lines form a graphene pseudo-nanoribbon structure with a semimetallic/semiconducting electronic structure closely related to the corresponding isolated ribbons; the ribbon band gap translates...

  20. Replacing Electron Transport Cofactors with Hydrogenases

    KAUST Repository

    Laamarti, Rkia

    2016-12-01

    Enzymes have found applications in a broad range of industrial production processes. While high catalytic activity, selectivity and mild reaction conditions are attractive advantages of the biocatalysts, particularly costs arising from required cofactors pose a sever limitation. While cofactor-recycling systems are available, their use implies constraints for process set-up and conditions, which are a particular problem e.g. for solid-gas-phase reactions. Several oxidoreductases are able to directly exchange electrons with electrodes. Hence, the co-immobilization of both, an electron-utilizing and an electron-generating oxidoreductase on conductive nanoparticles should facilitate the direct electron flow from an enzymatic oxidation to a reduction reaction circumventing redox-cofactors requirements. In such a set-up, hydrogenases could generate and provide electrons directly form gaseous hydrogen. This thesis describes the co-immobilization of the oxygen tolerant hydrogenases from C. eutropha or C. metallidurans and cytochrome P450BM3 as test system. Conductive material in the form of carbon nanotubes (CNT) serves as a suitable support. A combination of the hydrogenase and the catalytic domain of P450BM3 immobilized on carbon nanotubes were tested for the oxidation of lauric acid in the presence of hydrogen instead of an electron-transport cofactor. The GC-MS analysis reveals the conversion of 4% of lauric acid (LA) into three products, which correspond to the hydroxylated lauric acid in three different positions with a total turnover (TON) of 34. The product distribution is similar to that obtained when using the wildtype P450BM3 with the nicotinamide adenine dinucleotide phosphate (NADPH) cofactor. Such electronic coupling couldn’t be achieved for the conversion of other substrates such as propane and cyclohexane, probably due to the high uncoupling rate within the heme-domain of cytochrome P450BM3 when unnatural substrates are introduced.

  1. Simulations of Electron Transport in Laser Hot Spots

    International Nuclear Information System (INIS)

    Brunner, S.; Valeo, E.

    2001-01-01

    Simulations of electron transport are carried out by solving the Fokker-Planck equation in the diffusive approximation. The system of a single laser hot spot, with open boundary conditions, is systematically studied by performing a scan over a wide range of the two relevant parameters: (1) Ratio of the stopping length over the width of the hot spot. (2) Relative importance of the heating through inverse Bremsstrahlung compared to the thermalization through self-collisions. As for uniform illumination [J.P. Matte et al., Plasma Phys. Controlled Fusion 30 (1988) 1665], the bulk of the velocity distribution functions (VDFs) present a super-Gaussian dependence. However, as a result of spatial transport, the tails are observed to be well represented by a Maxwellian. A similar dependence of the distributions is also found for multiple hot spot systems. For its relevance with respect to stimulated Raman scattering, the linear Landau damping of the electron plasma wave is estimated for such VD Fs. Finally, the nonlinear Fokker-Planck simulations of the single laser hot spot system are also compared to the results obtained with the linear non-local hydrodynamic approach [A.V. Brantov et al., Phys. Plasmas 5 (1998) 2742], thus providing a quantitative limit to the latter method: The hydrodynamic approach presents more than 10% inaccuracy in the presence of temperature variations of the order delta T/T greater than or equal to 1%, and similar levels of deformation of the Gaussian shape of the Maxwellian background

  2. Electron transport in doped fullerene molecular junctions

    Science.gov (United States)

    Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

    The effect of doping on the electron transport of molecular junctions is analyzed in this paper. The doped fullerene molecules are stringed to two semi-infinite gold electrodes and analyzed at equilibrium and nonequilibrium conditions of these device configurations. The contemplation is done using nonequilibrium Green’s function (NEGF)-density functional theory (DFT) to evaluate its density of states (DOS), transmission coefficient, molecular orbitals, electron density, charge transfer, current, and conductance. We conclude from the elucidated results that Au-C16Li4-Au and Au-C16Ne4-Au devices behave as an ordinary p-n junction diode and a Zener diode, respectively. Moreover, these doped fullerene molecules do not lose their metallic nature when sandwiched between the pair of gold electrodes.

  3. Low energy electron transport in furfural

    International Nuclear Information System (INIS)

    Lozano, A.I.; Garcia, G.; Krupa, K.; Ferreira da Silva, F.; Limao-Vieira, P.; Blanco, F.; Munoz, A.; Jones, D.B.; Brunger, M.J.

    2017-01-01

    The cyclic configuration of the furfural molecule is similar to the 5-membered ring structure constituting the sugar units of the DNA helix, hence its importance in biology. In this paper, we report on an initial investigation into the transport of electrons through a gas cell containing 1 mtorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed

  4. Electronic transport properties of (fluorinated) metal phthalocyanine

    KAUST Repository

    Fadlallah, M M; Eckern, U; Romero, A H; Schwingenschlö gl, Udo

    2015-01-01

    The magnetic and transport properties of the metal phthalocyanine (MPc) and F16MPc (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ag) families of molecules in contact with S–Au wires are investigated by density functional theory within the local density approximation, including local electronic correlations on the central metal atom. The magnetic moments are found to be considerably modified under fluorination. In addition, they do not depend exclusively on the configuration of the outer electronic shell of the central metal atom (as in isolated MPc and F16MPc) but also on the interaction with the leads. Good agreement between the calculated conductance and experimental results is obtained. For M = Ag, a high spin filter efficiency and conductance is observed, giving rise to a potentially high sensitivity for chemical sensor applications.

  5. Electronic transport properties of phenylacetylene molecular junctions

    International Nuclear Information System (INIS)

    Liu Wen; Cheng Jie; Yan Cui-Xia; Li Hai-Hong; Wang Yong-Juan; Liu De-Sheng

    2011-01-01

    Electronic transport properties of a kind of phenylacetylene compound— (4-mercaptophenyl)-phenylacetylene are calculated by the first-principles method in the framework of density functional theory and the nonequilibrium Green's function formalism. The molecular junction shows an obvious rectifying behaviour at a bias voltage larger than 1.0 V. The rectification effect is attributed to the asymmetry of the interface contacts. Moreover, at a bias voltage larger than 2.0 V, which is not referred to in a relevant experiment [Fang L, Park J Y, Ma H, Jen A K Y and Salmeron M 2007 Langmuir 23 11522], we find a negative differential resistance phenomenon. The negative differential resistance effect may originate from the change of the delocalization degree of the molecular orbitals induced by the bias. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  6. Electronic transport properties of (fluorinated) metal phthalocyanine

    KAUST Repository

    Fadlallah, M M

    2015-12-21

    The magnetic and transport properties of the metal phthalocyanine (MPc) and F16MPc (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ag) families of molecules in contact with S–Au wires are investigated by density functional theory within the local density approximation, including local electronic correlations on the central metal atom. The magnetic moments are found to be considerably modified under fluorination. In addition, they do not depend exclusively on the configuration of the outer electronic shell of the central metal atom (as in isolated MPc and F16MPc) but also on the interaction with the leads. Good agreement between the calculated conductance and experimental results is obtained. For M = Ag, a high spin filter efficiency and conductance is observed, giving rise to a potentially high sensitivity for chemical sensor applications.

  7. Tracing the transition of a macro electron shuttle into nonlinear response

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chulki [Sensor System Research Center, Korea Institute of Science and Technology, Seoul 136791 (Korea, Republic of); Prada, Marta [I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstr. 9, Hamburg 20355 (Germany); Qin, Hua [Key Laboratory of Nanodevices, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, 398 Ruoshui Road, Industrial Park, Suzhou City, Jiangsu 215123 (China); Kim, Hyun-Seok [Division of Electronics and Electrical Engineering, Dongguk University-Seoul, 100715 Seoul (Korea, Republic of); Blick, Robert H., E-mail: rblick@physnet.uni-hamburg.de [Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin-53706 (United States); Center for Hybrid Nanostructures, Universität Hamburg, Jungiusstr. 11c, Hamburg 20355 (Germany); Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Dr. Madison, Wisconsin-53706 (United States)

    2015-02-09

    We present a study on a macroscopic electron shuttle in the transition from linear to nonlinear response. The shuttle consists of a classical mechanical pendulum situated between two capacitor plates. The metallic pendulum enables mechanical transfer of electrons between the plates, hence allowing to directly trace electron shuttling in the time domain. By applying a high voltage to the plates, we drive the system into a controlled nonlinear response, where we observe period doubling.

  8. Electron thermal energy transport research based on dynamical relationship between heat flux and temperature gradient

    International Nuclear Information System (INIS)

    Notake, Takashi; Inagaki, Shigeru; Tamura, Naoki

    2008-01-01

    In the nuclear fusion plasmas, both of thermal energy and particle transport governed by turbulent flow are anomalously enhanced more than neoclassical levels. Thus, to clarify a relationship between the turbulent flow and the anomalous transports has been the most worthwhile work. There are experimental results that the turbulent flow induces various phenomena on transport processes such as non-linearity, transition, hysteresis, multi-branches and non-locality. We are approaching these complicated problems by analyzing not conventional power balance but these phenomena directly. They are recognized as dynamical trajectories in the flux and gradient space and must be a clue to comprehend a physical mechanism of arcane anomalous transport. Especially, to elucidate the mechanism for electron thermal energy transport is critical in the fusion plasma researches because the burning plasmas will be sustained by alpha-particle heating. In large helical device, the dynamical relationships between electron thermal energy fluxes and electron temperature gradients are investigated by using modulated electron cyclotron resonance heating and modern electron cyclotron emission diagnostic systems. Some trajectories such as hysteresis loop or line segments with steep slope which represent non-linear property are observed in the experiment. (author)

  9. Electron thermal transport in tokamak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Konings, J A

    1994-11-30

    The process of fusion of small nuclei thereby releasing energy, as it occurs continuously in the sun, is essential for the existence of mankind. The same process applied in a controlled way on earth would provide a clean and an abundant energy source, and be the long term solution of the energy problem. Nuclear fusion requires an extremely hot (10{sup 8} K) ionized gas, a plasma, that can only be maintained if it is kept insulated from any material wall. In the so called `tokamak` this is achieved by using magnetic fields. The termal insulation, which is essential if one wants to keep the plasma at the high `fusion` temperature, can be predicted using basic plasma therory. A comparison with experiments in tokamaks, however, showed that the electron enery losses are ten to hundred times larger than this theory predicts. This `anomalous transport` of thermal energy implies that, to reach the condition for nuclear fusion, a fusion reactor must have very large dimensions. This may put the economic feasibility of fusion power in jeopardy. Therefore, in a worldwide collaboration, physicists study tokamak plasmas in an attempt to understand and control the energy losses. From a scientific point of view, the mechanisms driving anomalous transport are one of the challenges in fudamental plasma physics. In Nieuwegein, a tokamak experiment (the Rijnhuizen Tokamak Project, RTP) is dedicated to the study of anomalous transport, in an international collaboration with other laboratories. (orig./WL).

  10. Dynamics of electron wave packet in a disordered chain with delayed nonlinear response

    International Nuclear Information System (INIS)

    Zhu Hongjun; Xiong Shijie

    2010-01-01

    We investigate the dynamics of one electron wave packet in a linear chain with random on-site energies and a nonadiabatic electron-phonon interaction which is described by a delayed cubic nonlinear term in the time-dependent Schroedinger equation. We show that in the regime where the wave packet is delocalized in the case with only the delayed nonlinearity, the wave packet becomes localized when the disorder is added and the localization is enhanced by increasing the disorder. In the regime where the self-trapping phenomenon occurs in the case with only the delayed nonlinearity, by adding the disorder the general dynamical features of the wave packet do not change if the nonlinearity parameter is small, but the dynamics shows the subdiffusive behavior if the nonlinearity parameter is large. The numerical results demonstrate complicated wave packet dynamics of systems with both the disorder and nonlinearity.

  11. Electron Transport through Porphyrin Molecular Junctions

    Science.gov (United States)

    Zhou, Qi

    The goal of this work is to study the properties that would affect the electron transport through a porphyrin molecular junction. This work contributes to the field of electron transport in molecular junctions in the following 3 aspects. First of all, by carrying out experiments comparing the conductance of the iron (III) porphyrin (protected) and the free base porphyrin (protected), it is confirmed that the molecular energy level broadening and shifting occurs for porphyrin molecules when coupled with the metal electrodes, and this level broadening and shifting plays an important role in the electron transport through molecular junctions. Secondly, by carrying out an in-situ deprotection of the acetyl-protected free base porphyrin molecules, it is found out that the presence of acetyl groups reduces the conductance. Thirdly, by incorporating the Matrix-assisted laser desorption/ionization (MALDI) spectrum and the in-situ deprotection prior to formation of molecular junctions, it allows a more precise understanding of the molecules involved in the formation of molecular junctions, and therefore allows an accurate analysis of the conductance histogram. The molecules are prepared by self-assembly and the junctions are formed using a Scanning Tunneling Microscopy (STM) molecular break junction technique. The porphyrin molecules are characterized by MALDI in solution before self-assembly to a gold/mica substrate. The self-assembled monolayers (SAMs) of porphyrins on gold are characterized by Ultraviolet-visible (UV-Vis) reflection spectroscopy to confirm that the molecules are attached to the substrate. The SAMs are then characterized by Angle-Resolved X-ray photoelectron spectroscopy (ARXPS) to determine the thickness and the average molecular orientation of the molecular layer. The electron transport is measured by conductance-displacement (G-S) experiments under a given bias (-0.4V). The conductance value of a single molecule is identified by a statistical analysis

  12. ECRH and electron heat transport in tokamaks

    International Nuclear Information System (INIS)

    Zou, X.L.; Giruzzi, G.; Dumont, R.J.

    2003-01-01

    It has been observed during the ECRH experiments in tokamaks that the shape of the electron temperature profile in stationary regimes is not very sensitive to the ECRH power deposition i.e. the temperature profile remains peaked at the center even though the ECRH power deposition is off-axis. Various models have been invoked for the interpretation of this profile resilience phenomenon: the inward heat pinch, the critical temperature gradient, the Self-Organized Criticality, etc. Except the pinch effect, all of these models need a specific form of the diffusivity in the heat transport equation. In this work, our approach is to solve a simplified time-dependent heat transport equation analytically in cylindrical geometry. The features of this analytical solution are analyzed, in particular the relationship between the temperature profile resilience and the Eigenmode of the physical system with respect to the heat transport phenomenon. Finally, applications of this analytical solution for the determination of the transport coefficient and the polarization of the EC waves are presented. It has been shown that the solution of the simplified transport equation in a finite cylinder is a Fourier-Bessel series. This series represents in fact a decomposition of the heat source in Eigenmode, which are characterized by the Bessel functions of order 0. The physical interpretation of the Eigenmodes is the following: when the heat source is given by a Bessel function of order 0, the temperature profile has exactly the same form as the source at every time. At the beginning of the power injection, the effectiveness of the temperature response is the same for each Eigenmode, and the response in temperature, having the same form as the source, is local. Conversely, in the later phase of the evolution, the effectiveness of the temperature response for each Eigenmode is different: the higher the order, the lower the effectiveness. In this case the response in temperature appears as

  13. Geometry and transport in a model of two coupled quadratic nonlinear waveguides

    DEFF Research Database (Denmark)

    Stirling, James R.; Bang, Ole; Christiansen, Peter Leth

    2008-01-01

    This paper applies geometric methods developed to understand chaos and transport in Hamiltonian systems to the study of power distribution in nonlinear waveguide arrays. The specific case of two linearly coupled X(2) waveguides is modeled and analyzed in terms of transport and geometry in the pha...

  14. Quantitative comparison of electron temperature fluctuations to nonlinear gyrokinetic simulations in C-Mod Ohmic L-mode discharges

    Energy Technology Data Exchange (ETDEWEB)

    Sung, C., E-mail: csung@physics.ucla.edu [University of California, Los Angeles, Los Angeles, California 90095 (United States); White, A. E.; Greenwald, M.; Howard, N. T. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Mikkelsen, D. R.; Churchill, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Holland, C. [University of California, San Diego, La Jolla, California 92093 (United States); Theiler, C. [Ecole Polytechnique Fédérale de Lausanne, SPC, Lausanne 1015 (Switzerland)

    2016-04-15

    Long wavelength turbulent electron temperature fluctuations (k{sub y}ρ{sub s} < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (k{sub y}ρ{sub s} ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].

  15. Ion age transport: developing devices beyond electronics

    Science.gov (United States)

    Demming, Anna

    2014-03-01

    There is more to current devices than conventional electronics. Increasingly research into the controlled movement of ions and molecules is enabling a range of new technologies. For example, as Weihua Guan, Sylvia Xin Li and Mark Reed at Yale University explain, 'It offers a unique opportunity to integrate wet ionics with dry electronics seamlessly'. In this issue they provide an overview of voltage-gated ion and molecule transport in engineered nanochannels. They cover the theory governing these systems and fabrication techniques, as well as applications, including biological and chemical analysis, and energy conversion [1]. Studying the movement of particles in nanochannels is not new. The transport of materials in rock pores led Klinkenberg to describe an analogy between diffusion and electrical conductivity in porous rocks back in 1951 [2]. And already in 1940, Harold Abramson and Manuel Gorin noted that 'When an electric current is applied across the living human skin, the skin may be considered to act like a system of pores through which transfer of substances like ragweed pollen extract may be achieved both by electrophoretic and by diffusion phenomena' [3]. Transport in living systems through pore structures on a much smaller scale has attracted a great deal of research in recent years as well. The selective transport of ions and small organic molecules across the cell membrane facilitates a number of functions including communication between cells, nerve conduction and signal transmission. Understanding these processes may benefit a wide range of potential applications such as selective separation, biochemical sensing, and controlled release and drug delivery processes. In Germany researchers have successfully demonstrated controlled ionic transport through nanopores functionalized with amine-terminated polymer brushes [4]. The polymer nanobrushes swell and shrink in response to changes in temperature, thus opening and closing the nanopore passage to ionic

  16. Mitochondrial Electron Transport and Plant Stress

    DEFF Research Database (Denmark)

    Rasmusson, Allan G; Møller, Ian Max

    2011-01-01

    Due to the sessile nature of plants, it is crucial for their survival and growth that they can handle a constantly changing, and thus stressful, ambient environment by modifying their structure and metabolism. The central metabolism of plants is characterized by many alternative options...... for metabolic pathways, which allow a wide range of adjustments of metabolic processes in response to environmental variations. Many of the metabolic pathways in plants involve the processing of redox compounds and the use of adenylates. They converge at the mitochondrial electron transport chain (ETC) where...... redox compounds from carbon degradation are used for powering ATP synthesis. The standard ETC contains three sites of energy conservation in complexes I, III, and IV, which are in common with most other eukaryotes. However, the complexity of the plant metabolic system is mirrored in the ETC. In addition...

  17. Electronic transport study in PAMAM dendrimers

    International Nuclear Information System (INIS)

    Vieira, Nirton C.S.; Soares, Demetrio A.W.; Fernandes, Edson G.R.; Queiroz, Alvaro A.A. de

    2005-01-01

    Dendrimers are nanomaterials that have many potential applications in medicine, including diagnosis and therapeutic procedures. Dendrimers are isomolecular polymers, with a very well controlled architecture and a thousand times smaller than cells. Dendrimers containing biocatalysts are of great interest for clinical applications in biosensors because of the way in which their chemical and electric conduction mechanism can be tailored. In this work, the polyamidoamine dendrimer (PAMAM) of generation 4 was synthesized by divergent route and characterized by NMR spectroscopy. The electronic transport properties of PAMAM in a metal-polymer type heterojunction were studied. The electrical conduction mechanism of PAMAM studied in the temperature range of 291-323 K indicates a conduction mechanism thermally activated. (author)

  18. Molecular electronics--resonant transport through single molecules.

    Science.gov (United States)

    Lörtscher, Emanuel; Riel, Heike

    2010-01-01

    The mechanically controllable break-junction technique (MCBJ) enables us to investigate charge transport through an individually contacted and addressed molecule in ultra-high vacuum (UHV) environment at variable temperature ranging from room temperature down to 4 K. Using a statistical measurement and analysis approach, we acquire current-voltage (I-V) characteristics during the repeated formation, manipulation, and breaking of a molecular junction. At low temperatures, voltages accessing the first molecular orbitals in resonance can be applied, providing spectroscopic information about the junction's energy landscape, in particular about the molecular level alignment in respect to the Fermi energy of the electrodes. Thereby, we can investigate the non-linear transport properties of various types of functional molecules and explore their potential use as functional building blocks for future nano-electronics. An example will be given by the reversible and controllable switching between two distinct conductive states of a single molecule. As a proof-of-principle for functional molecular devices, a single-molecule memory element will be demonstrated.

  19. Paradox in a non-linear capacitated transportation problem

    Directory of Open Access Journals (Sweden)

    Dahiya Kalpana

    2006-01-01

    Full Text Available This paper discusses a paradox in fixed charge capacitated transportation problem where the objective function is the sum of two linear fractional functions consisting of variables costs and fixed charges respectively. A paradox arises when the transportation problem admits of an objective function value which is lower than the optimal objective function value, by transporting larger quantities of goods over the same route. A sufficient condition for the existence of a paradox is established. Paradoxical range of flow is obtained for any given flow in which the corresponding objective function value is less than the optimum value of the given transportation problem. Numerical illustration is included in support of theory.

  20. Cross-separatrix Coupling in Nonlinear Global Electrostatic Turbulent Transport in C-2U

    Science.gov (United States)

    Lau, Calvin; Fulton, Daniel; Bao, Jian; Lin, Zhihong; Binderbauer, Michl; Tajima, Toshiki; Schmitz, Lothar; TAE Team

    2017-10-01

    In recent years, the progress of the C-2/C-2U advanced beam-driven field-reversed configuration (FRC) experiments at Tri Alpha Energy, Inc. has pushed FRCs to transport limited regimes. Understanding particle and energy transport is a vital step towards an FRC reactor, and two particle-in-cell microturbulence codes, the Gyrokinetic Toroidal Code (GTC) and A New Code (ANC), are being developed and applied toward this goal. Previous local electrostatic GTC simulations find the core to be robustly stable with drift-wave instability only in the scrape-off layer (SOL) region. However, experimental measurements showed fluctuations in both regions; one possibility is that fluctuations in the core originate from the SOL, suggesting the need for non-local simulations with cross-separatrix coupling. Current global ANC simulations with gyrokinetic ions and adiabatic electrons find that non-local effects (1) modify linear growth-rates and frequencies of instabilities and (2) allow instability to move from the unstable SOL to the linearly stable core. Nonlinear spreading is also seen prior to mode saturation. We also report on the progress of the first turbulence simulations in the SOL. This work is supported by the Norman Rostoker Fellowship.

  1. Electron scattering and transport in liquid argon

    International Nuclear Information System (INIS)

    Boyle, G. J.; Cocks, D. G.; White, R. D.; McEachran, R. P.

    2015-01-01

    The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies

  2. Electron scattering and transport in liquid argon

    Energy Technology Data Exchange (ETDEWEB)

    Boyle, G. J.; Cocks, D. G.; White, R. D. [College of Science, Technology and Engineering, James Cook University, Townsville 4810 (Australia); McEachran, R. P. [Research School of Physical Sciences and Engineering, Australian National University, Canberra ACT 0200 (Australia)

    2015-04-21

    The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.

  3. Consequences of nonlinear heat transport laws on expected plasma profiles

    International Nuclear Information System (INIS)

    Lackner, K.

    1987-03-01

    The expected variation of plasma pressure profiles against changes in power deposition is investigated by using a simple linear heat transport law as well as a quadratic one. Applying the quadratic transport law it can be shown that the stiffening of the resulting profiles is sufficient to understand the experimentally measured phenomenon of 'profile consistence' without further assumptions of nonlocal effects. (orig.) [de

  4. Nonlinear saturation of dissipative trapped ion instability and anomalous transport

    International Nuclear Information System (INIS)

    Sugihara, Masayoshi; Ogasawara, Masatada.

    1977-04-01

    An expression for the turbulent collision frequency is derived by summing up the most dominant terms from each order in the perturbation expansion in order to obtain the nonlinear saturation level of the dissipative trapped ion instability. Numerical calculation shows that the anomalous diffusion coefficient at the saturated state is in good agreement with the result of Kadomtsev and Pogutse when the effect of the magnetic shear is taken into account. (auth.)

  5. Electron non-linearities in Langmuir waves with application to beat-wave experiments

    International Nuclear Information System (INIS)

    Bell, A.R.; Gibbon, P.

    1988-01-01

    Non-linear Langmuir waves are examined in the context of the beat-wave accelerator. With a background of immobile ions the waves in one dimension are subject to the relativistic non-linearity of Rosenbluth, M.N. and Liu, C.S., Phys. Rev. Lett., 1972, 29, 701. In two or three dimensions, other electron non-linearities occur which involve electric and magnetic fields. The quasi-linear equations for these non-linearities are developed and solved numerically in a geometry representative of laser-driven beat waves. (author)

  6. Nonlinear and Nonsymmetric Single-Molecule Electronic Properties Towards Molecular Information Processing.

    Science.gov (United States)

    Tamaki, Takashi; Ogawa, Takuji

    2017-09-05

    This review highlights molecular design for nonlinear and nonsymmetric single-molecule electronic properties such as rectification, negative differential resistance, and switching, which are important components of future single-molecule information processing devices. Perspectives on integrated "molecular circuits" are also provided. Nonlinear and nonsymmetric single-molecule electronics can be designed by utilizing (1) asymmetric molecular cores, (2) asymmetric anchoring groups, (3) an asymmetric junction environment, and (4) asymmetric electrode materials. This review mainly focuses on the design of molecular cores.

  7. Electronic Monitoring Of Storage And Transport Temperatures Of ...

    African Journals Online (AJOL)

    Electronic Monitoring Of Storage And Transport Temperatures Of Thermostable Newcastle ... 22) were monitored during storage and transport from vaccine production laboratory in Temeke, Dar es ... EMAIL FULL TEXT EMAIL FULL TEXT

  8. Replacing Electron Transport Cofactors with Hydrogenases

    KAUST Repository

    Laamarti, Rkia

    2016-01-01

    to directly exchange electrons with electrodes. Hence, the co-immobilization of both, an electron-utilizing and an electron-generating oxidoreductase on conductive nanoparticles should facilitate the direct electron flow from an enzymatic oxidation to a

  9. Power Electronics Packaging Reliability | Transportation Research | NREL

    Science.gov (United States)

    Packaging Reliability Power Electronics Packaging Reliability A photo of a piece of power electronics laboratory equipment. NREL power electronics packaging reliability research investigates the electronics packaging around a semiconductor switching device determines the electrical, thermal, and

  10. Development of an Integrated Nonlinear Aeroservoelastic Flight Dynamic Model of the NASA Generic Transport Model

    Science.gov (United States)

    Nguyen, Nhan; Ting, Eric

    2018-01-01

    This paper describes a recent development of an integrated fully coupled aeroservoelastic flight dynamic model of the NASA Generic Transport Model (GTM). The integrated model couples nonlinear flight dynamics to a nonlinear aeroelastic model of the GTM. The nonlinearity includes the coupling of the rigid-body aircraft states in the partial derivatives of the aeroelastic angle of attack. Aeroservoelastic modeling of the control surfaces which are modeled by the Variable Camber Continuous Trailing Edge Flap is also conducted. The R.T. Jones' method is implemented to approximate unsteady aerodynamics. Simulations of the GTM are conducted with simulated continuous and discrete gust loads..

  11. Monte Carlo simulation of nonlinear reactive contaminant transport in unsaturated porous media

    International Nuclear Information System (INIS)

    Giacobbo, F.; Patelli, E.

    2007-01-01

    In the current proposed solutions of radioactive waste repositories, the protective function against the radionuclide water-driven transport back to the biosphere is to be provided by an integrated system of engineered and natural geologic barriers. The occurrence of several nonlinear interactions during the radionuclide migration process may render burdensome the classical analytical-numerical approaches. Moreover, the heterogeneity of the barriers' media forces approximations to the classical analytical-numerical models, thus reducing their fidelity to reality. In an attempt to overcome these difficulties, in the present paper we adopt a Monte Carlo simulation approach, previously developed on the basis of the Kolmogorov-Dmitriev theory of branching stochastic processes. The approach is here extended for describing transport through unsaturated porous media under transient flow conditions and in presence of nonlinear interchange phenomena between the liquid and solid phases. This generalization entails the determination of the functional dependence of the parameters of the proposed transport model from the water content and from the contaminant concentration, which change in space and time during the water infiltration process. The corresponding Monte Carlo simulation approach is verified with respect to a case of nonreactive transport under transient unsaturated flow and to a case of nonlinear reactive transport under stationary saturated flow. Numerical applications regarding linear and nonlinear reactive transport under transient unsaturated flow are reported

  12. Ab initio calculation of contact effects on electron transport through single molecules by the RTM/NEGF method

    International Nuclear Information System (INIS)

    Hirose, Kenji; Kobayashi, Nobuhiko

    2006-01-01

    Using the recursion-transfer-matrix (RTM) method combined with the nonequilibrium Green's function (NEGF) method, we study the electronic states and current-voltage (I-V) characteristics of atomic-scale nanocontact systems. We find that non-linear behaviors appear in the I-V characteristics even without molecules between electrodes. Such non-linear behaviors emerge when the nanocontacts are not well constructed and the transport properties change from tunneling to ballistic regimes

  13. Electronic transport in graphene; Elektronischer Transport in Graphen

    Energy Technology Data Exchange (ETDEWEB)

    Lohmann, Timm

    2010-06-08

    In 2004 graphene, a monolayer of carbon atoms, has been isolated as the first real two-dimensional solid by the group of A. Geim at the University of Manchester. Graphene's properties have been theoretically investigated since the 1950s. Until the successful preparation by Geim et al., graphene was suspected to be unstable under ambient conditions above 0 K (Mermin-Wagner theorem). Its two dimensionality and hexagonal lattice symmetry cause interesting novel properties and effects. At experimentally relevant energies, graphene has a linear band structure and charge carrier dynamics must be treated using Dirac's equation. Therefore charge carriers in graphene are called ''Dirac fermions''. Beside exotic effects like ''Klein tunneling'' an unconventional quantum Hall effect (QHE) can be observed with a Hall conductance quantized in units of 2e{sup 2}/h, 6e{sup 2}/h, 10e{sup 2}/h, 14e{sup 2}/h. As a starting point for in-depth transport measurements the processing of graphene field effect transistors (GFETs) has been developed and optimized, based on the pioneering work by Novoselov et al. The optimized process provides samples with carrier mobilities up to 16000 cm{sup 2}/Vs and a well defined Hall geometry. These samples are used to investigate external influences on the electronic properties of graphene. Among those influences molecular adsorbates are responsible for various effects of freshly prepared graphene samples e.g. an intrinsic p-doping, a mobility asymmetry of electrons and holes, the so called ''minimal conductivity'' and a field effect hysteresis at room temperature. In collaboration with the group of A. Yacoby (Harvard) density fluctuations in the vicinity of the Dirac point (''electron-hole puddles'') could be observed using a scanning single electron transistor (SSET). These fluctuations might be one reason for the ''minimal conductivity'' at

  14. Electron transport in InAs/AlGaSb ballistic rectifiers

    International Nuclear Information System (INIS)

    Maemoto, Toshihiko; Koyama, Masatoshi; Furukawa, Masashi; Takahashi, Hiroshi; Sasa, Shigehiko; Inoue, Masataka

    2006-01-01

    Nonlinear transport properties of a ballistic rectifier fabricated from InAs/AlGaSb heterostructures are reported. The operation of the ballistic rectifier is based on the guidance of carriers by a square anti-dot structure. The structure was defined by electron beam lithography and wet chemical etching. The DC characteristics and magneto-transport properties of the ballistic rectifier have been measured at 77 K and 4.2 K. Rectification effects relying on the ballistic transport were observed. From the four-terminal resistance measured at low magnetic fields, we also observed magneto-resistance fluctuations corresponding to the electron trajectories and symmetry-breaking electron scattering, which are influenced by the magnetic field strength

  15. Problems of linear electron (polaron) transport theory in semiconductors

    CERN Document Server

    Klinger, M I

    1979-01-01

    Problems of Linear Electron (Polaron) Transport Theory in Semiconductors summarizes and discusses the development of areas in electron transport theory in semiconductors, with emphasis on the fundamental aspects of the theory and the essential physical nature of the transport processes. The book is organized into three parts. Part I focuses on some general topics in the theory of transport phenomena: the general dynamical theory of linear transport in dissipative systems (Kubo formulae) and the phenomenological theory. Part II deals with the theory of polaron transport in a crystalline semicon

  16. A Nonlinear Dynamic Inversion Predictor-Based Model Reference Adaptive Controller for a Generic Transport Model

    Science.gov (United States)

    Campbell, Stefan F.; Kaneshige, John T.

    2010-01-01

    Presented here is a Predictor-Based Model Reference Adaptive Control (PMRAC) architecture for a generic transport aircraft. At its core, this architecture features a three-axis, non-linear, dynamic-inversion controller. Command inputs for this baseline controller are provided by pilot roll-rate, pitch-rate, and sideslip commands. This paper will first thoroughly present the baseline controller followed by a description of the PMRAC adaptive augmentation to this control system. Results are presented via a full-scale, nonlinear simulation of NASA s Generic Transport Model (GTM).

  17. Melatonin and the electron transport chain.

    Science.gov (United States)

    Hardeland, Rüdiger

    2017-11-01

    Melatonin protects the electron transport chain (ETC) in multiple ways. It reduces levels of ·NO by downregulating inducible and inhibiting neuronal nitric oxide synthases (iNOS, nNOS), thereby preventing excessive levels of peroxynitrite. Both ·NO and peroxynitrite-derived free radicals, such as ·NO 2 , hydroxyl (·OH) and carbonate radicals (CO 3 · - ) cause blockades or bottlenecks in the ETC, by ·NO binding to irons, protein nitrosation, nitration and oxidation, changes that lead to electron overflow or even backflow and, thus, increased formation of superoxide anions (O 2 · - ). Melatonin improves the intramitochondrial antioxidative defense by enhancing reduced glutathione levels and inducing glutathione peroxidase and Mn-superoxide dismutase (Mn-SOD) in the matrix and Cu,Zn-SOD in the intermembrane space. An additional action concerns the inhibition of cardiolipin peroxidation. This oxidative change in the membrane does not only initiate apoptosis or mitophagy, as usually considered, but also seems to occur at low rate, e.g., in aging, and impairs the structural integrity of Complexes III and IV. Moreover, elevated levels of melatonin inhibit the opening of the mitochondrial permeability transition pore and shorten its duration. Additionally, high-affinity binding sites in mitochondria have been described. The assumption of direct binding to the amphipathic ramp of Complex I would require further substantiation. The mitochondrial presence of the melatonin receptor MT 1 offers the possibility that melatonin acts via an inhibitory G protein, soluble adenylyl cyclase, decreased cAMP and lowered protein kinase A activity, a signaling pathway shown to reduce Complex I activity in the case of a mitochondrial cannabinoid receptor.

  18. Energy-filtered cold electron transport at room temperature.

    Science.gov (United States)

    Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

    2014-09-10

    Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature.

  19. Power Electronics and Electric Machines Facilities | Transportation

    Science.gov (United States)

    Research | NREL Facilities Power Electronics and Electric Machines Facilities NREL's power electronics and electric machines thermal management experimentation facilities feature a wide range of four researchers in discussion around a piece of laboratory equipment. Power electronics researchers

  20. Electron transport through a diatomic molecule

    International Nuclear Information System (INIS)

    Imran, Muhammad

    2014-01-01

    Electron transport through a diatomic molecular tunnel junction shows wave like interference phenomenon. By using Keldysh non-equilibrium Green's function (NEGF) theory, we have explicitly presented current and differential conductance calculation for a diatomic molecular and two isolated atoms (two atoms having zero hybridization between their energy orbitals) tunnel junctions. In case of a diatomic molecular tunnel junction, Green's function propagators entering into current and differential conductance formula interfere constructively for a molecular anti-bonding state and destructively for bonding state. Consequently, conductance through a molecular bonding state is suppressed, and to conserve current, conductance through anti-bonding state is enhanced. Therefore, current steps and differential conductance peaks amplitude show asymmetric correspondence between molecular bonding and anti-bonding states. Interestingly, for a diatomic molecule, comprising of two atoms of same energy level, these propagators interfere completely destructively for molecular bonding state and constructively for molecular anti-bonding state. Hence under such condition, a single step or a single peak is shown up in current versus voltage or differential conductance versus voltage studies.

  1. The nonlinear carrier transport in a bipolar semiconductor sample

    International Nuclear Information System (INIS)

    Konin, A

    2008-01-01

    A theory of formation of the voltage across a bipolar semiconductor sample due to the current flow accounting for the energy band bending near the semiconductor surfaces is presented. The non-equilibrium space charge layers near the sample surfaces and the boundary conditions in the real metal-semiconductor junction have been taken into account. It is shown that the voltage-current relation of a thin sample at weak injection differs essentially from the classical Ohm's law and becomes nonlinear for certain semiconductor surface parameters. Complex voltage-current relations and the photo-induced electromotive force measurements allow determining the surface recombination rate in the real metal-semiconductor junction and the semiconductor surface potential

  2. Electron transport and improved confinement on Tore Supra

    International Nuclear Information System (INIS)

    Hoang, G.T.; Bourdelle, C.; Garbet, X.; Aniel, T.; Giruzzi, G.; Ottaviani, M.; Horton, W.; Zhu, P.; Budny, R.V.

    2001-01-01

    Magnetic shear is found to play an important role for triggering various improved confinement regimes through the electron channel. A wide database of hot electron plasmas (T e >2T i ) heated by fast wave electron heating (FWEH) is analyzed for electron thermal transport. A critical gradient is clearly observed. It is found that the critical gradient linearly increases with the ratio between local magnetic shear (s) and safety factor (q). The Horton model, based on the electromagnetic turbulence driven by the electron temperature gradient (ETG) mode, is found to be a good candidate for electron transport modeling. (author)

  3. A computer code package for electron transport Monte Carlo simulation

    International Nuclear Information System (INIS)

    Popescu, Lucretiu M.

    1999-01-01

    A computer code package was developed for solving various electron transport problems by Monte Carlo simulation. It is based on condensed history Monte Carlo algorithm. In order to get reliable results over wide ranges of electron energies and target atomic numbers, specific techniques of electron transport were implemented such as: Moliere multiscatter angular distributions, Blunck-Leisegang multiscatter energy distribution, sampling of electron-electron and Bremsstrahlung individual interactions. Path-length and lateral displacement corrections algorithms and the module for computing collision, radiative and total restricted stopping powers and ranges of electrons are also included. Comparisons of simulation results with experimental measurements are finally presented. (author)

  4. Electron heat transport in stochastic magnetic layer

    International Nuclear Information System (INIS)

    Becoulet, M.; Ghendrih, Ph.; Capes, H.; Grosman, A.

    1999-06-01

    Progress in the theoretical understanding of the local behaviour of the temperature field in ergodic layer was done in the framework of quasi-linear approach but this quasi-linear theory was not complete since the resonant modes coupling (due to stochasticity) was neglected. The stochastic properties of the magnetic field in the ergodic zone are now taken into account by a non-linear coupling of the temperature modes. The three-dimension heat transfer modelling in the ergodic-divertor configuration is performed by quasi-linear (ERGOT1) and non-linear (ERGOT2) numerical codes. The formalism and theoretical basis of both codes are presented. The most important effect that can be simulated with non-linear code is the averaged temperature profile flattening that occurs in the ergodic zone and the barrier creation that appears near the separatrix during divertor operation. (A.C.)

  5. Dichotomy of nonlinear systems: Application to chaos control of nonlinear electronic circuit

    International Nuclear Information System (INIS)

    Wang Jinzhi; Duan Zhisheng; Huang Lin

    2006-01-01

    In this Letter a new method of chaos control for Chua's circuit and the modified canonical Chua's electrical circuit is proposed by using the results of dichotomy in nonlinear systems. A linear feedback control based on linear matrix inequality (LMI) is given such that chaos oscillation or hyperchaos phenomenon of circuit systems injected control signal disappear. Numerical simulations are presented to illustrate the efficiency of the proposed method

  6. Power Electronics Thermal Management | Transportation Research | NREL

    Science.gov (United States)

    Power Electronics Thermal Management Power Electronics Thermal Management A photo of water boiling in liquid cooling lab equipment. Power electronics thermal management research aims to help lower the investigates and develops thermal management strategies for power electronics systems that use wide-bandgap

  7. Nonlinear effects and conversion efficiency of free electron laser in compton regime

    International Nuclear Information System (INIS)

    Taguchi, Toshihiro; Mima, Kunioki; Mochizuki, Takayasu

    1980-01-01

    Nonlinear evolutions of free electron laser are analyzed by using quasi-linear theory. By the analysis, the energy conversion rates and the spectral width of the emitted radiations are calculated self-consistently. Moreover, it is found that the energy conversion rate is remarkably improved, when a RF field is applied to reaccelerate electron beam. (author)

  8. Nonequilibrium Transport and the Bernoulli Effect of Electrons in a Two-Dimensional Electron Gas

    Science.gov (United States)

    Kaya, Ismet I.

    2013-02-01

    Nonequilibrium transport of charged carriers in a two-dimensional electron gas is summarized from an experimental point of view. The transport regime in which the electron-electron interactions are enhanced at high bias leads to a range of striking effects in a two-dimensional electron gas. This regime of transport is quite different than the ballistic transport in which particles propagate coherently with no intercarrier energy transfer and the diffusive transport in which the momentum of the electron system is lost with the involvement of the phonons. Quite a few hydrodynamic phenomena observed in classical gasses have the electrical analogs in the current flow. When intercarrier scattering events dominate the transport, the momentum sharing via narrow angle scattering among the hot and cold electrons lead to negative resistance and electron pumping which can be viewed as the analog of the Bernoulli-Venturi effect observed classical gasses. The recent experimental findings and the background work in the field are reviewed.

  9. Nonlinear Transport in Organic Thin Film Transistors with Soluble Small Molecule Semiconductor.

    Science.gov (United States)

    Kim, Hyeok; Song, Dong-Seok; Kwon, Jin-Hyuk; Jung, Ji-Hoon; Kim, Do-Kyung; Kim, SeonMin; Kang, In Man; Park, Jonghoo; Tae, Heung-Sik; Battaglini, Nicolas; Lang, Philippe; Horowitz, Gilles; Bae, Jin-Hyuk

    2016-03-01

    Nonlinear transport is intensively explained through Poole-Frenkel (PF) transport mechanism in organic thin film transistors with solution-processed small molecules, which is, 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene. We outline a detailed electrical study that identifies the source to drain field dependent mobility. Devices with diverse channel lengths enable the extensive exhibition of field dependent mobility due to thermal activation of carriers among traps.

  10. Joint proposal for US/USSR on nonlinear dynamics and plasma transport

    International Nuclear Information System (INIS)

    Antonsen, T.M. Jr.; Drake, J.F.; Finn, J.M.; Guzdar, P.N.; Hassam, A.B.; Sagdeev, R.Z.

    1991-01-01

    This report discusses: convection-driven flow in plasma and fluids; particle transport and rotation damping by sound wave propagation along stochastic magnetic field lines; acceleration of charge article in a magnetic field by electromagnetic and electrostatic waves, lagrangian particle transport in time-dependent 20 flows; fast dynamo; 3D flows will stagnation points and vortices; Edge-localized modes in Tokamaks; and code development for nonlinear analysis and visualization. (LP)

  11. Coupled Particle Transport and Pattern Formation in a Nonlinear Leaky-Box Model

    Science.gov (United States)

    Barghouty, A. F.; El-Nemr, K. W.; Baird, J. K.

    2009-01-01

    Effects of particle-particle coupling on particle characteristics in nonlinear leaky-box type descriptions of the acceleration and transport of energetic particles in space plasmas are examined in the framework of a simple two-particle model based on the Fokker-Planck equation in momentum space. In this model, the two particles are assumed coupled via a common nonlinear source term. In analogy with a prototypical mathematical system of diffusion-driven instability, this work demonstrates that steady-state patterns with strong dependence on the magnetic turbulence but a rather weak one on the coupled particles attributes can emerge in solutions of a nonlinearly coupled leaky-box model. The insight gained from this simple model may be of wider use and significance to nonlinearly coupled leaky-box type descriptions in general.

  12. Magnetic turbulent electron transport in a reversed field pinch

    International Nuclear Information System (INIS)

    Schoenberg, K.; Moses, R.

    1990-01-01

    A model of magnetic turbulent electron transport is presented. The model, based on the thermal conduction theory of Rechester and Rosenbluth, entails a Boltzmann description of electron dynamics in the long mean-free-path limit and quantitatively describes the salient features of superthermal electron measurements in the RFP edge plasma. Included are predictions of the mean superthermal electron energy, current density, and power flux asymmetry. A discussion of the transport model, the assumptions implicit in the model, and the relevance of this work to more general issue of magnetic turbulent transport in toroidal systems is presented. 32 refs., 3 figs

  13. Electron transport chain in a thermotolerant yeast.

    Science.gov (United States)

    Mejía-Barajas, Jorge A; Martínez-Mora, José A; Salgado-Garciglia, Rafael; Noriega-Cisneros, Ruth; Ortiz-Avila, Omar; Cortés-Rojo, Christian; Saavedra-Molina, Alfredo

    2017-04-01

    Yeasts capable of growing and surviving at high temperatures are regarded as thermotolerant. For appropriate functioning of cellular processes and cell survival, the maintenance of an optimal redox state is critical of reducing and oxidizing species. We studied mitochondrial functions of the thermotolerant Kluyveromyces marxianus SLP1 and the mesophilic OFF1 yeasts, through the evaluation of its mitochondrial membrane potential (ΔΨ m ), ATPase activity, electron transport chain (ETC) activities, alternative oxidase activity, lipid peroxidation. Mitochondrial membrane potential and the cytoplasmic free Ca 2+ ions (Ca 2+ cyt) increased in the SLP1 yeast when exposed to high temperature, compared with the mesophilic yeast OFF1. ATPase activity in the mesophilic yeast diminished 80% when exposed to 40° while the thermotolerant SLP1 showed no change, despite an increase in the mitochondrial lipid peroxidation. The SLP1 thermotolerant yeast exposed to high temperature showed a diminution of 33% of the oxygen consumption in state 4. The uncoupled state 3 of oxygen consumption did not change in the mesophilic yeast when it had an increase of temperature, whereas in the thermotolerant SLP1 yeast resulted in an increase of 2.5 times when yeast were grown at 30 o , while a decrease of 51% was observed when it was exposed to high temperature. The activities of the ETC complexes were diminished in the SLP1 when exposed to high temperature, but also it was distinguished an alternative oxidase activity. Our results suggest that the mitochondria state, particularly ETC state, is an important characteristic of the thermotolerance of the SLP1 yeast strain.

  14. Large time behaviour of oscillatory nonlinear solute transport in porous media

    NARCIS (Netherlands)

    Duijn, van C.J.; Zee, van der S.E.A.T.M.

    2018-01-01

    Oscillations in flow occur under many different situations in natural porous media, due to tidal, daily or seasonal patterns. In this paper, we investigate how such oscillations in flow affect the transport of an initially sharp solute front, if the solute undergoes nonlinear sorption and,

  15. Electron acceleration during the decay of nonlinear Whistler waves in low-beta electron-ion plasma

    International Nuclear Information System (INIS)

    Umeda, Takayuki; Saito, Shinji; Nariyuki, Yasuhiro

    2014-01-01

    Relativistic electron acceleration through dissipation of a nonlinear, short-wavelength, and monochromatic electromagnetic whistler wave in low-beta plasma is investigated by utilizing a one-dimensional fully relativistic electromagnetic particle-in-cell code. The nonlinear (large-amplitude) parent whistler wave decays through the parametric instability which enhances electrostatic ion acoustic waves and electromagnetic whistler waves. These waves satisfy the condition of three-wave coupling. Through the decay instability, the energy of electron bulk velocity supporting the parent wave is converted to the thermal energy perpendicular to the background magnetic field. Increase of the perpendicular temperature triggers the electron temperature anisotropy instability which generates broadband whistler waves and heats electrons in the parallel direction. The broadband whistler waves are inverse-cascaded during the relaxation of the electron temperature anisotropy. In lower-beta conditions, electrons with a pitch angle of about 90° are successively accelerated by inverse-cascaded whistler waves, and selected electrons are accelerated to over a Lorentz factor of 10. The result implies that the nonlinear dissipation of a finite-amplitude and short-wavelength whistler wave plays an important role in producing relativistic nonthermal electrons over a few MeV especially at lower beta plasmas.

  16. Electron transport in the presence of a Coulomb field

    International Nuclear Information System (INIS)

    Burgdoerfer, J.; Gibbons, J.

    1990-01-01

    We analyze the modifications of the transport behavior of electrons in dense media due to the presence of a strong Coulomb field generated by an ion moving initially in close phase-space correlation with the electrons. These modifications play a profound role in convoy electron emission in ion-solid collisions. The transport behavior is studied within the framework of a classical phase-space master equation. The nonseparable master equation is solved numerically using test-particle discretization and Monte Carlo sampling. In the limit of vanishing Coulomb forces the master equation becomes separable and can be reduced to standard one-dimensional kinetic equations for free-electron transport that can be solved exactly. The comparison to free-electron transport is used to gauge both the reliability of test-particle discretization and the significance of Coulomb distortion of the distribution functions. Applications to convoy-electron emission are discussed

  17. Nonlinear screening effect in an ultrarelativistic degenerate electron-positron gas

    International Nuclear Information System (INIS)

    Tsintsadze, N. L.; Rasheed, A.; Shah, H. A.; Murtaza, G.

    2009-01-01

    Nonlinear screening process in an ultrarelativistic degenerate electron-positron gas has been investigated by deriving a generalized nonlinear Poisson equation for the electrostatic potential. In the simple one-dimensional case, the nonlinear Poisson equation leads to Debye-like (Coulomb-like) solutions at distances larger (less) than the characteristic length. When the electrostatic energy is larger than the thermal energy, this nonlinear Poisson equation converts into the relativistic Thomas-Fermi equation whose asymptotic solution in three dimensions shows that the potential field goes to zero at infinity much more slowly than the Debye potential. The possibility of the formation of a bound state in electron-positron plasma is also indicated. Further, it is investigated that the strong spatial fluctuations of the potential field may reduce the screening length and that the root mean square of this spatial fluctuating potential goes to zero for large r rather slowly as compared to the case of the Debye potential.

  18. Tokamak electron heat transport by direct numerical simulation of small scale turbulence

    International Nuclear Information System (INIS)

    Labit, B.

    2002-10-01

    In a fusion machine, understanding plasma turbulence, which causes a degradation of the measured energy confinement time, would constitute a major progress in this field. In tokamaks, the measured ion and electron thermal conductivities are of comparable magnitude. The possible sources of turbulence are the temperature and density gradients occurring in a fusion plasma. Whereas the heat losses in the ion channel are reasonably well understood, the origin of the electron losses is more uncertain. In addition to the radial velocity associated to the fluctuations of the electric field, electrons are more affected than ions by the magnetic field fluctuations. In experiments, the confinement time can be conveniently expressed in terms of dimensionless parameters. Although still somewhat too imprecise, these scaling laws exhibit strong dependencies on the normalized pressure β or the normalized Larmor radius, ρ * . The present thesis assesses whether a tridimensional, electromagnetic, nonlinear fluid model of plasma turbulence driven by a specific instability can reproduce the dependence of the experimental electron heat losses on the dimensionless parameters β and ρ * . The investigated interchange instability is the Electron Temperature Gradient driven one (ETG). The model is built by using the set of Braginskii equations. The developed simulation code is global in the sense that a fixed heat flux is imposed at the inner boundary, leaving the gradients free to evolve. From the nonlinear simulations, we have put in light three characteristics for the ETG turbulence: the turbulent transport is essentially electrostatic; the potential and pressure fluctuations form radially elongated cells called streamers; the transport level is very low compared to the experimental values. The thermal transport dependence study has shown a very small role of the normalized pressure, which is in contradiction with the Ohkama's formula. On the other hand, the crucial role of the

  19. Adiabatic theory of nonlinear electron cyclotron resonance heating

    International Nuclear Information System (INIS)

    Kotel'nikov, I.A.; Stupakov, G.V.

    1989-01-01

    Plasma heating at electron frequency by an ordinary wave propagating at right angle to unidirectional magnetic field is treated. Injected microwave power is assumed to be so large that relativistic change of electron gyrofrequency during one flight thorugh the wave beam is much greater than inverse time of flight. The electron motion in the wave field is described using Hamiltonian formalism in adiabatic approximation. It is shown that energy coupling from the wave to electrons is due to a bifurcation of electron trajectory which results in a jumpm of the adiabatic invariant. The probability of bifurcational transition from one trajectory to another is calculated analytically and is used for the estimation of the beam power absorbed in plasma. 6 refs.; 2 figs

  20. Effects of Collisionality on the Nonlinear Characteristics of Boundary Turbulence and Blob/hole Transport in Tokamak Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.; Yasuaki, K., E-mail: lijq@energy.kyoto-u.ac.jp [Kyoto University, Kyoto (Japan); Cheng, J.; Longwen, Y.; Jiaqi, D. [Southwestern Institute of Physics, Chengdu (China)

    2012-09-15

    Full text: Blob/hole dynamics near tokamak separatrix is of striking importance in determining the boundary transport. Based on simulations using an extended 2-region (edge/SOL) fluid model, we found that blob/hole dynamics are sensitively influenced by the plasma collisionality, i.e., ion-electron and ion-neutral collisions. Namely, the holes are enhanced in highly collisional edge whereas the blobs are weakened at the SOL, causing larger particle convection. These blob/hole dynamics are closely correlated with potential dipoles. The trends are experimentally evidenced on the HL-2A tokamak. Moreover, as the neutral-ion collision increases, the blobs at the SOL tend to develop into streamers propagating outwards with reduced amplitude while the holes inwards are suppressed, showing a key role in nonlinear structure regulation and resultant transport suppression. Results suggest that adjusting the plasma collisionality by fueling, e.g., gas puffing, could serve as a method to nonlinearly select turbulent structures, i.e., blobs, holes or streamers, to access the control of boundary transport. (author)

  1. Stereocomplex micelle from nonlinear enantiomeric copolymers efficiently transports antineoplastic drug

    Science.gov (United States)

    Wang, Jixue; Shen, Kexin; Xu, Weiguo; Ding, Jianxun; Wang, Xiaoqing; Liu, Tongjun; Wang, Chunxi; Chen, Xuesi

    2015-05-01

    Nanoscale polymeric micelles have attracted more and more attention as a promising nanocarrier for controlled delivery of antineoplastic drugs. Herein, the doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (PDM/DOX), poly(L-lactide)-based micelle (PLM/DOX), and stereocomplex micelle (SCM/DOX) from the equimolar mixture of the enantiomeric four-armed poly(ethylene glycol)-polylactide (PEG-PLA) copolymers were successfully fabricated. In phosphate-buffered saline (PBS) at pH 7.4, SCM/DOX exhibited the smallest hydrodynamic diameter ( D h) of 90 ± 4.2 nm and the slowest DOX release compared with PDM/DOX and PLM/DOX. Moreover, PDM/DOX, PLM/DOX, and SCM/DOX exhibited almost stable D hs of around 115, 105, and 90 nm at above normal physiological condition, respectively, which endowed them with great potential in controlled drug delivery. The intracellular DOX fluorescence intensity after the incubation with the laden micelles was different degrees weaker than that incubated with free DOX · HCl within 12 h, probably due to the slow DOX release from micelles. As the incubation time reached to 24 h, all the cells incubated with the laden micelles, especially SCM/DOX, demonstrated a stronger intracellular DOX fluorescence intensity than free DOX · HCl-cultured ones. More importantly, all the DOX-loaded micelles, especially SCM/DOX, exhibited potent antineoplastic efficacy in vitro, excellent serum albumin-tolerance stability, and satisfactory hemocompatibility. These encouraging data indicated that the loading micelles from nonlinear enantiomeric copolymers, especially SCM/DOX, might be promising in clinical systemic chemotherapy through intravenous injection.

  2. Power Electronics and Electric Machines Publications | Transportation

    Science.gov (United States)

    Research | NREL and Electric Machines Publications Power Electronics and Electric Machines Publications NREL and its partners have produced many papers and presentations related to power electronics and from power electronics and electric machines research are available to the public. Photo by Pat Corkery

  3. Multi-level nonlinear diffusion acceleration method for multigroup transport k-Eigenvalue problems

    International Nuclear Information System (INIS)

    Anistratov, Dmitriy Y.

    2011-01-01

    The nonlinear diffusion acceleration (NDA) method is an efficient and flexible transport iterative scheme for solving reactor-physics problems. This paper presents a fast iterative algorithm for solving multigroup neutron transport eigenvalue problems in 1D slab geometry. The proposed method is defined by a multi-level system of equations that includes multigroup and effective one-group low-order NDA equations. The Eigenvalue is evaluated in the exact projected solution space of smallest dimensionality, namely, by solving the effective one- group eigenvalue transport problem. Numerical results that illustrate performance of the new algorithm are demonstrated. (author)

  4. Nonlinear 2D convection and enhanced cross-field plasma transport near the MHD instability threshold

    International Nuclear Information System (INIS)

    Pastukhov, V.P.; Chudin, N.V.

    2003-01-01

    Results of theoretical study and computer simulations of nonlinear 2D convection induced by a convective MHD instability near its threshold in FRC-like non-paraxial magnetic confinement system are presented. An appropriate closed set of weakly nonideal reduced MHD equations is derived to describe the self-consistent plasma dynamics. It is shown that the convection forms nonlinear large scale stochastic vortices (convective cells), which tend to restore and to maintain the marginally stable pressure pro e and result in an essentially nonlocal enhanced heat transport. A large amount of data on the structure of the nascent convective flows is obtained and analyzed. The computer simulations of long time plasma evolutions demonstrate such features of the resulting anomalous transport as pro e consistency, L-H transition, external transport barrier, pinch of impurities, etc. (author)

  5. Nonlinear theory for the parametric instability with comparable electron and ion temperatures

    International Nuclear Information System (INIS)

    Oberman, C.

    1972-01-01

    The basic linear theory of the parametric instability driven by a pump E 0 sin ω 0 t oscillating near the electron plasma frequency is reviewed. An expression is derived for the temporal nonlinear development of the fluctuation spectrum of the excited waves. For plasma with comparable electron and ion temperatures nonlinear Landau damping of electron plasma waves on ions provides the dominant nonlinearity. The steady state solutions are examined both analytically and numerically in the limit when the spontaneous emission term is small. The characteristics of the plasma wave spectrum agrees well with the general features of ionospheric observations. The enhanced dissipation rate of the pump due to the presence of the fluctuations agrees with laboratory observations. (U.S.)

  6. Nonlinear interaction of powerful short electromagnetic pulses with an electron plasma

    International Nuclear Information System (INIS)

    Rao, N.N.; Yu, M.Y.; Shukla, P.K.

    1990-01-01

    The nonlinear interaction of powerful short electromagnetic pulses with a plasma consisting of two groups of electrons and immobile ions has been studied. It is shown that the interaction is governed by a nonlinear equation for the electromagnetic wave envelope and a driven nonlinear equation for the low-frequency electron fluctuations. The driver for the latter depends explicitly on the spatio-temporal evolution of the electromagnetic wave flux. It is found that, depending on the cold-to-hot electron density ratio, the localized pulse can propagate with sub- as well as supersonic velocities accompanied by compressional or rarefactional density perturbations. The conditions of existence for the different types of solitary pulses are obtained. The present investigation may be relevant to the study of wave-plasma interaction devices such as inertial fusion confinement as well as to ionospheric modification experiments. (author)

  7. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field

    International Nuclear Information System (INIS)

    Wang, C.; Wang, F.; Cao, J. C.

    2014-01-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation

  8. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field.

    Science.gov (United States)

    Wang, C; Wang, F; Cao, J C

    2014-09-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

  9. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C., E-mail: cwang@mail.sim.ac.cn; Wang, F.; Cao, J. C., E-mail: jccao@mail.sim.ac.cn [Key Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China)

    2014-09-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

  10. Analytical treatment of the nonlinear electron cloud effect and the combined effects with beam-beam and space charge nonlinear forces in storage rings

    International Nuclear Information System (INIS)

    Gao Jie

    2009-01-01

    In this paper we treat first some nonlinear beam dynamics problems in storage rings, such as beam dynamic apertures due to magnetic multipoles, wiggles, beam-beam effects, nonlinear space charge effect, and then nonlinear electron cloud effect combined with beam-beam and space charge effects, analytically. This analytical treatment is applied to BEPC II. The corresponding analytical expressions developed in this paper are useful both in understanding the physics behind these problems and also in making practical quick hand estimations. (author)

  11. Robust transport by multiple motors with nonlinear force–velocity relations and stochastic load sharing

    International Nuclear Information System (INIS)

    Kunwar, Ambarish; Mogilner, Alexander

    2010-01-01

    Transport by processive molecular motors plays an important role in many cell biological phenomena. In many cases, motors work together to transport cargos in the cell, so it is important to understand the mechanics of the multiple motors. Based on earlier modeling efforts, here we study effects of nonlinear force–velocity relations and stochastic load sharing on multiple motor transport. We find that when two or three motors transport the cargo, then the nonlinear and stochastic effects compensate so that the mechanical properties of the transport are robust. Similarly, the transport is insensitive to compliance of the cargo-motor links. Furthermore, the rate of movement against moderate loads is not improved by increasing the small number of motors. When the motor number is greater than 4, correlations between the motors become negligible, and the earlier analytical mean-field theory of the multiple motor transport holds. We predict that the effective diffusion of the cargo driven by the multiple motors under load increases by an order of magnitude compared to that for the single motor. Finally, our simulations predict that the stochastic effects are responsible for a significant dispersion of velocities generated by the 'tug-of-war' of the multiple opposing motors

  12. Nonlinear waves in reaction-diffusion systems: The effect of transport memory

    International Nuclear Information System (INIS)

    Manne, K. K.; Hurd, A. J.; Kenkre, V. M.

    2000-01-01

    Motivated by the problem of determining stress distributions in granular materials, we study the effect of finite transport correlation times on the propagation of nonlinear wave fronts in reaction-diffusion systems. We obtain results such as the possibility of spatial oscillations in the wave-front shape for certain values of the system parameters and high enough wave-front speeds. We also generalize earlier known results concerning the minimum wave-front speed and shape-speed relationships stemming from the finiteness of the correlation times. Analytic investigations are made possible by a piecewise linear representation of the nonlinearity. (c) 2000 The American Physical Society

  13. Nonlinear waves in reaction-diffusion systems: The effect of transport memory

    Science.gov (United States)

    Manne, K. K.; Hurd, A. J.; Kenkre, V. M.

    2000-04-01

    Motivated by the problem of determining stress distributions in granular materials, we study the effect of finite transport correlation times on the propagation of nonlinear wave fronts in reaction-diffusion systems. We obtain results such as the possibility of spatial oscillations in the wave-front shape for certain values of the system parameters and high enough wave-front speeds. We also generalize earlier known results concerning the minimum wave-front speed and shape-speed relationships stemming from the finiteness of the correlation times. Analytic investigations are made possible by a piecewise linear representation of the nonlinearity.

  14. Novel phenomena in one-dimensional non-linear transport in long quantum wires

    International Nuclear Information System (INIS)

    Morimoto, T; Hemmi, M; Naito, R; Tsubaki, K; Park, J-S; Aoki, N; Bird, J P; Ochiai, Y

    2006-01-01

    We have investigated the non-linear transport properties of split-gate quantum wires of various channel lengths. In this report, we present results on a resonant enhancement of the non-linear conductance that is observed near pinch-off under a finite source-drain bias voltage. The resonant phenomenon exhibits a strong dependence on temperature and in-plane magnetic field. We discuss the possible relationship of this phenomenon to the spin-polarized manybody state that has recently been suggested to occur in quasi-one dimensional systems

  15. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    Energy Technology Data Exchange (ETDEWEB)

    Haynes, Christopher T., E-mail: c.t.haynes@qmul.ac.uk; Burgess, David; Sundberg, Torbjorn [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Camporeale, Enrico [Multiscale Dynamics, Centrum Wiskunde and Informatica (CWI), Amsterdam (Netherlands)

    2015-01-15

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  16. Chaos in Electronic Circuits: Nonlinear Time Series Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Wheat, Jr., Robert M. [Kennedy Western Univ., Cheyenne, WY (United States)

    2003-07-01

    Chaos in electronic circuits is a phenomenon that has been largely ignored by engineers, manufacturers, and researchers until the early 1990’s and the work of Chua, Matsumoto, and others. As the world becomes more dependent on electronic devices, the detrimental effects of non-normal operation of these devices becomes more significant. Developing a better understanding of the mechanisms involved in the chaotic behavior of electronic circuits is a logical step toward the prediction and prevention of any potentially catastrophic occurrence of this phenomenon. Also, a better understanding of chaotic behavior, in a general sense, could potentially lead to better accuracy in the prediction of natural events such as weather, volcanic activity, and earthquakes. As a first step in this improvement of understanding, and as part of the research being reported here, methods of computer modeling, identifying and analyzing, and producing chaotic behavior in simple electronic circuits have been developed. The computer models were developed using both the Alternative Transient Program (ATP) and Spice, the analysis techniques have been implemented using the C and C++ programming languages, and the chaotically behaving circuits developed using “off the shelf” electronic components.

  17. Extracellular Electron Transport Coupling Biogeochemical Processes Centimeters

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Fossing, Henrik; Christensen, Peter Bondo

    2010-01-01

    of the oxygen uptake in laboratory incubations of initially homogenized and stabilized sediment. Using microsensors and process rate measurements we further investigated the effect of the electric currents on sediment biogeochemistry. Dissolved sulfide readily donated electrons to the networks and could...... confirmed the depth range of the electric communication and indicated donation of electrons directly from organotrophic bacteria. The separation of oxidation and reduction processes created steep pH gradients eventually causing carbonate precipitation at the surface. The results indicate that electron...... exchanging organisms have major biogeochemical importance as they allow widely separated electron donors and acceptors to react with one another....

  18. Quantum electronics and Moscow State University's Khokhlov-Akhmanov school of coherent and nonlinear optics

    International Nuclear Information System (INIS)

    Makarov, V.A.

    2004-01-01

    The aim of the report is to describe the history of the Moscow University Coherent and Nonlinear Optics School headed by R.V. Khokhlov and S.A. Akhmanov being a part of the history of the Russian efforts to investigate into quantum electronics. The reports describes briefly the most significant results of the mentioned School activity, in particular, thermonuclear reactions initiated by laser pulses in plasma; the procedure to accelerate electrons up to 1 GeV using the present-day lasers; the nonlinear-optical analogues of the Faraday and the Kerr effects [ru

  19. Molecular electronics: some views on transport junctions and beyond.

    Science.gov (United States)

    Joachim, Christian; Ratner, Mark A

    2005-06-21

    The field of molecular electronics comprises a fundamental set of issues concerning the electronic response of molecules as parts of a mesoscopic structure and a technology-facing area of science. We will overview some important aspects of these subfields. The most advanced ideas in the field involve the use of molecules as individual logic or memory units and are broadly based on using the quantum state space of the molecule. Current work in molecular electronics usually addresses molecular junction transport, where the molecule acts as a barrier for incoming electrons: This is the fundamental Landauer idea of "conduction as scattering" generalized to molecular junction structures. Another point of view in terms of superexchange as a guiding mechanism for coherent electron transfer through the molecular bridge is discussed. Molecules generally exhibit relatively strong vibronic coupling. The last section of this overview focuses on vibronic effects, including inelastic electron tunneling spectroscopy, hysteresis in junction charge transport, and negative differential resistance in molecular transport junctions.

  20. Fast electron generation and transport in a turbulent, magnetized plasma

    International Nuclear Information System (INIS)

    Stoneking, W.R.

    1994-05-01

    The nature of fast electron generation and transport in the Madison Symmetric Torus (MST) reversed field pinch (RFP) is investigated using two electron energy analyzer (EEA) probes and a thermocouple calorimeter. The parallel velocity distribution of the fast electron population is well fit by a drifted Maxwellian distribution with temperature of about 100 eV and drift velocity of about 2 x 10 6 m/s. Cross-calibration of the EEA with the calorimeter provides a measurement of the fast electron perpendicular temperature of 30 eV, much lower than the parallel temperature, and is evidence that the kinetic dynamo mechanism (KDT) is not operative in MST. The fast electron current is found to match to the parallel current at the edge, and the fast electron density is about 4 x 10 11 cm -3 independent of the ratio of the applied toroidal electric field to the critical electric field for runaways. First time measurements of magnetic fluctuation induced particle transport are reported. By correlating electron current fluctuations with radial magnetic fluctuations the transported flux of electrons is found to be negligible outside r/a∼0.9, but rises the level of the expected total particle losses inside r/a∼0.85. A comparison of the measured diffusion coefficient is made with the ausilinear stochastic diffusion coefficient. Evidence exists that the reduction of the transport is due to the presence of a radial ambipolar electric field of magnitude 500 V/m, that acts to equilibrate the ion and electron transport rates. The convective energy transport associated with the measured particle transport is large enough to account for the observed magnetic fluctuation induced energy transport in MST

  1. Tunneling explains efficient electron transport via protein junctions.

    Science.gov (United States)

    Fereiro, Jerry A; Yu, Xi; Pecht, Israel; Sheves, Mordechai; Cuevas, Juan Carlos; Cahen, David

    2018-05-15

    Metalloproteins, proteins containing a transition metal ion cofactor, are electron transfer agents that perform key functions in cells. Inspired by this fact, electron transport across these proteins has been widely studied in solid-state settings, triggering the interest in examining potential use of proteins as building blocks in bioelectronic devices. Here, we report results of low-temperature (10 K) electron transport measurements via monolayer junctions based on the blue copper protein azurin (Az), which strongly suggest quantum tunneling of electrons as the dominant charge transport mechanism. Specifically, we show that, weakening the protein-electrode coupling by introducing a spacer, one can switch the electron transport from off-resonant to resonant tunneling. This is a consequence of reducing the electrode's perturbation of the Cu(II)-localized electronic state, a pattern that has not been observed before in protein-based junctions. Moreover, we identify vibronic features of the Cu(II) coordination sphere in transport characteristics that show directly the active role of the metal ion in resonance tunneling. Our results illustrate how quantum mechanical effects may dominate electron transport via protein-based junctions.

  2. The theory and simulation of relativistic electron beam transport in the ion-focused regime

    International Nuclear Information System (INIS)

    Swanekamp, S.B.; Holloway, J.P.; Kammash, T.; Gilgenbach, R.M.

    1992-01-01

    Several recent experiments involving relativistic electron beam (REB) transport in plasma channels show two density regimes for efficient transport; a low-density regime known as the ion-focused regime (IFR) and a high-pressure regime. The results obtained in this paper use three separate models to explain the dependency of REB transport efficiency on the plasma density in the IFR. Conditions for efficient beam transport are determined by examining equilibrium solutions of the Vlasov--Maxwell equations under conditions relevant to IFR transport. The dynamic force balance required for efficient IFR transport is studied using the particle-in-cell (PIC) method. These simulations provide new insight into the transient beam front physics as well as the dynamic approach to IFR equilibrium. Nonlinear solutions to the beam envelope are constructed to explain oscillations in the beam envelope observed in the PIC simulations but not contained in the Vlasov equilibrium analysis. A test particle analysis is also developed as a method to visualize equilibrium solutions of the Vlasov equation. This not only provides further insight into the transport mechanism but also illustrates the connections between the three theories used to describe IFR transport. Separately these models provide valuable information about transverse beam confinement; together they provide a clear physical understanding of REB transport in the IFR

  3. Nonlinear spin fluctuations in the Fermi liquid of itinerant electron ferromagnets

    International Nuclear Information System (INIS)

    Solontsov, A.; Lacroix, C.

    2003-01-01

    A microscopic derivation of nonlinear equations of magnetic dynamics for itinerant ferromagnets is presented within the electron Fermi liquid model accounting for both long-range Coulomb and short-range interactions of quasiparticles, which founds the basis for the phenomenological description of nonlinear spin fluctuations (SF) using the Ginsburg-Landau formalism. Crystal lattice is shown to play a significant role screening the long-range Coulomb interaction and affecting magnetic dynamics. The spectrum of longitudinal SF with account of nonlinear mode-mode coupling is shown to result from an interplay of quasielastic SF and inelastic excitations near the magnon frequencies, both having mainly the nonlinear nature and arising due to their emission (absorption) by magnons

  4. Transport of runaway and thermal electrons due to magnetic microturbulence

    International Nuclear Information System (INIS)

    Mynick, H.E.; Strachan, J.D.

    1981-01-01

    The ratio of the runaway electron confinement to thermal electron energy confinement is derived for tokamaks where both processes are determined by free streaming along stochastic magnetic field lines. The runaway electron confinement is enhanced at high runaway electron energies due to phase averaging over the magnetic perturbations when the runaway electron drift surfaces are displaced from the magnetic surfaces. Comparison with experimental data from LT-3, Ormak, PLT, ST, and TM-3 indicates that magnetic stochasticity may explain the relative transport rates of runaways and thermal electron energy

  5. Electron transport in quantum wires: possible current instability mechanism

    International Nuclear Information System (INIS)

    Sablikov, V.A.

    2001-01-01

    The electrons nonlinear and dynamic transition in quantum wires connecting the electron reservoirs, are studies with an account of the Coulomb interaction distribution of electron density between the reservoirs and the wire. It is established that there exist two processes, leading to electrical instability in such structure. One of them is expressed in form of multistability of the charge accumulated in the wire, and negative differential conductivity. The other one is connected with origination of negative dynamic conductivity in the narrow frequency range near the resonance frequency of the charge waves on the wire length [ru

  6. Temperature gradient driven electron transport in NSTX and Tore Supra

    International Nuclear Information System (INIS)

    Horton, W.; Wong, H.V.; Morrison, P.J.; Wurm, A.; Kim, J.H.; Perez, J.C.; Pratt, J.; Hoang, G.T.; LeBlanc, B.P.; Ball, R.

    2005-01-01

    Electron thermal fluxes are derived from the power balance for Tore Supra (TS) and NSTX discharges with centrally deposited fast wave electron heating. Measurements of the electron temperature and density profiles, combined with ray tracing computations of the power absorption profiles, allow detailed interpretation of the thermal flux versus temperature gradient. Evidence supporting the occurrence of electron temperature gradient turbulent transport in the two confinement devices is found. With control of the magnetic rotational transform profile and the heating power, internal transport barriers are created in TS and NSTX discharges. These partial transport barriers are argued to be a universal feature of transport equations in the presence of invariant tori that are intrinsic to non-monotonic rotational transforms in dynamical systems

  7. Electronic and vibrational hopping transport in boron carbides

    International Nuclear Information System (INIS)

    Emin, D.

    1991-01-01

    General concepts of hopping-type transport and localization are reviewed. Disorder, electronic correlations and atomic displacements, effects ignored in electronic band structure calculations, foster localization of electronic charge carriers. Examples are given that illustrate the efficacy of these effects in producing localization. This introduction is followed by a brief discussion of the relation between hopping-type transport and localization. The fundamentals of the formation, localization, and hopping transport of small polarons and/or bipolarons is then described. Electronic transport in boron carbides is presented as an example of the adiabatic hopping of small bipolarons. Finally, the notion of vibrational hopping is introduced. The high-temperature thermal diffusion in boron carbides is presented as a potential application of this idea

  8. Nonequilibrium electron transport through quantum dots in the Kondo regime

    DEFF Research Database (Denmark)

    Wölfle, Peter; Paaske, Jens; Rosch, Achim

    2005-01-01

    Electron transport at large bias voltage through quantum dots in the Kondo regime is described within the perturbative renormalization group extended to nonequilibrium. The conductance, local magnetization, dynamical spin susceptibility and local spectral function are calculated. We show how...

  9. Transport of electrons in lead oxide studied by CELIV technique

    International Nuclear Information System (INIS)

    Semeniuk, O; Juska, G; Oelerich, J O; Jandieri, K; Baranovskii, S D; Reznik, A

    2017-01-01

    Although polycrystalline lead oxide (PbO) has a long history of application in optoelectronics and imaging, the transport mechanism for electrons in this material has not yet been clarified. Using the photo-generated charge extraction by linear increasing voltage (photo-CELIV) technique, we provide the temperature- and field-dependences of electron mobility in poly-PbO. It is found that electrons undergo dispersive transport, i.e. their mobility decreases in the course of time. Multiple trapping of electrons from the conduction band into the developed band tail is revealed as the dominant transport mechanism. This differs dramatically from the dispersive transport of holes in the same material, dominated by topological factors and not by energy disorder. (paper)

  10. Electron-lattice Interaction and Nonlinear Excitations in Cuprate Structures

    International Nuclear Information System (INIS)

    Paulsen, J.; Eschrig, H.; Drechsler, S.L.; Malek, J.

    1995-01-01

    A low temperature lattice modulation of the chains of the YBa 2 Cu 3 O 7 is considered by deriving a Hamiltonian of electron-lattice interaction from density-functional calculations for deformed lattice and solving it for the groundstate. Hubbard-type Coulomb interaction is included. The obtained groundstate is a charge-density-wave state with a pereodicity of four lattice constants and a gap for one-electron excitations of about 1eV, sensitively depending on parameters of the Hamiltonian. There are lots of polaronic and solitonic excitations with formation energies deep in the gap, which can pin the Fermi level and thus produce again metallicity of the chain. They might also contribute to pairing of holes in adjacent CuO 2 -planes. (author)

  11. Simulation of electron thermal transport in H-mode discharges

    International Nuclear Information System (INIS)

    Rafiq, T.; Pankin, A. Y.; Bateman, G.; Kritz, A. H.; Halpern, F. D.

    2009-01-01

    Electron thermal transport in DIII-D H-mode tokamak plasmas [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] is investigated by comparing predictive simulation results for the evolution of electron temperature profiles with experimental data. The comparison includes the entire profile from the magnetic axis to the bottom of the pedestal. In the simulations, carried out using the automated system for transport analysis (ASTRA) integrated modeling code, different combinations of electron thermal transport models are considered. The combinations include models for electron temperature gradient (ETG) anomalous transport and trapped electron mode (TEM) anomalous transport, as well as a model for paleoclassical transport [J. D. Callen, Nucl. Fusion 45, 1120 (2005)]. It is found that the electromagnetic limit of the Horton ETG model [W. Horton et al., Phys. Fluids 31, 2971 (1988)] provides an important contribution near the magnetic axis, which is a region where the ETG mode in the GLF23 model [R. E. Waltz et al., Phys. Plasmas 4, 2482 (1997)] is below threshold. In simulations of DIII-D discharges, the observed shape of the H-mode edge pedestal is produced when transport associated with the TEM component of the GLF23 model is suppressed and transport given by the paleoclassical model is included. In a study involving 15 DIII-D H-mode discharges, it is found that with a particular combination of electron thermal transport models, the average rms deviation of the predicted electron temperature profile from the experimental profile is reduced to 9% and the offset to -4%.

  12. Electron Transport in Quantum Dots and Heat Transport in Molecules

    DEFF Research Database (Denmark)

    Kirsanskas, Gediminas

    Since the invention of the transistor in 1947 and the development of integrated circuits in the late 1950’s, there was a rapid progress in the development and miniaturization of the solid state devices and electronic circuit components. This miniaturization raises a question “How small do we have...

  13. Electronic transport and lasing in microstructures

    International Nuclear Information System (INIS)

    Lax, M.

    1992-01-01

    We consider the interaction of hot carriers with hot phonons in a quantum well. Transport is considered in the transverse direction and tunneling through the well barriers. Time-dependent transport effects down to the femto-second regime are included, as are strong and/or microwave fields, with negative resistance effects. Resonant tunneling assisted by phonon relaxation and infra-red radiation will be explored. The limitations on transmission of information due to partition noise, as influenced by the design of semiconductor feedback lasers will be considered. The use of light scattering and decision theory to detect shell-like aerosols is examined

  14. Contribution of Higher-Order Dispersion to Nonlinear Electron-Acoustic Solitary Waves in a Relativistic Electron Beam Plasma System

    International Nuclear Information System (INIS)

    Zahran, M.A.; El-Shewy, E.K.

    2008-01-01

    The nonlinear properties of solitary wave structures are reported in an unmagnetized collisionless plasma comprising of cold relativistic electron fluid, Maxwellian hot electrons, relativistic electron beam, and stationary ions. The Korteweg--de Vries (KdV) equation has been derived using a reductive perturbation theory. As the wave amplitude increases, the width and velocity of the soliton deviate from the prediction of the KdV equation i.e. the breakdown of the KdV approximation. On the other hand, to overcome this weakness we extend our analysis to obtain the KdV equation with fifth-order dispersion term. The solution of the resulting equation has been obtained

  15. Hot electrons in superlattices: quantum transport versus Boltzmann equation

    DEFF Research Database (Denmark)

    Wacker, Andreas; Jauho, Antti-Pekka; Rott, S.

    1999-01-01

    A self-consistent solution of the transport equation is presented for semiconductor superlattices within different approaches: (i) a full quantum transport model based on nonequilibrium Green functions, (ii) the semiclassical Boltzmann equation for electrons in a miniband, and (iii) Boltzmann...

  16. Optimal perturbations for nonlinear systems using graph-based optimal transport

    Science.gov (United States)

    Grover, Piyush; Elamvazhuthi, Karthik

    2018-06-01

    We formulate and solve a class of finite-time transport and mixing problems in the set-oriented framework. The aim is to obtain optimal discrete-time perturbations in nonlinear dynamical systems to transport a specified initial measure on the phase space to a final measure in finite time. The measure is propagated under system dynamics in between the perturbations via the associated transfer operator. Each perturbation is described by a deterministic map in the measure space that implements a version of Monge-Kantorovich optimal transport with quadratic cost. Hence, the optimal solution minimizes a sum of quadratic costs on phase space transport due to the perturbations applied at specified times. The action of the transport map is approximated by a continuous pseudo-time flow on a graph, resulting in a tractable convex optimization problem. This problem is solved via state-of-the-art solvers to global optimality. We apply this algorithm to a problem of transport between measures supported on two disjoint almost-invariant sets in a chaotic fluid system, and to a finite-time optimal mixing problem by choosing the final measure to be uniform. In both cases, the optimal perturbations are found to exploit the phase space structures, such as lobe dynamics, leading to efficient global transport. As the time-horizon of the problem is increased, the optimal perturbations become increasingly localized. Hence, by combining the transfer operator approach with ideas from the theory of optimal mass transportation, we obtain a discrete-time graph-based algorithm for optimal transport and mixing in nonlinear systems.

  17. Study of Electron Transport and Amplification in Diamond

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Zvi, Ilan [Stony Brook Univ., NY (United States); Muller, Erik [Stony Brook Univ., NY (United States)

    2015-01-05

    The development of the Diamond Amplified Photocathode (DAP) has produced significant results under our previous HEP funded efforts both on the fabrication of working devices and the understanding of the underlying physics governing its performance. The results presented here substantiate the use of diamond as both a secondary electron amplifier for high-brightness, high-average-current electron sources and as a photon and particle detector in harsh radiation environments. Very high average current densities (>10A/cm2) have been transported through diamond material. The transport has been measured as a function of incident photon energy and found to be in good agreement with theoretical models. Measurements of the charge transport for photon energies near the carbon K-edge (290 eV for sp3 bonded carbon) have provided insight into carrier loss due to diffusion; modeling of this aspect of charge transport is underway. The response of diamond to nanosecond x-ray pulses has been measured; in this regime the charge transport is as expected. Electron emission from hydrogenated diamond has been measured using both electron and x-ray generated carriers; a gain of 178 has been observed for electron-generated carriers. The energy spectrum of the emitted electrons has been measured, providing insight into the electron affinity and ultimately the thermal emittance. The origin of charge trapping in diamond has been investigated for both bulk and surface trapping

  18. A correlation electron cyclotron emission diagnostic and the importance of multifield fluctuation measurements for testing nonlinear gyrokinetic turbulence simulations.

    Science.gov (United States)

    White, A E; Schmitz, L; Peebles, W A; Carter, T A; Rhodes, T L; Doyle, E J; Gourdain, P A; Hillesheim, J C; Wang, G; Holland, C; Tynan, G R; Austin, M E; McKee, G R; Shafer, M W; Burrell, K H; Candy, J; DeBoo, J C; Prater, R; Staebler, G M; Waltz, R E; Makowski, M A

    2008-10-01

    A correlation electron cyclotron emission (CECE) diagnostic has been used to measure local, turbulent fluctuations of the electron temperature in the core of DIII-D plasmas. This paper describes the hardware and testing of the CECE diagnostic and highlights the importance of measurements of multifield fluctuation profiles for the testing and validation of nonlinear gyrokinetic codes. The process of testing and validating such codes is critical for extrapolation to next-step fusion devices. For the first time, the radial profiles of electron temperature and density fluctuations are compared to nonlinear gyrokinetic simulations. The CECE diagnostic at DIII-D uses correlation radiometry to measure the rms amplitude and spectrum of the electron temperature fluctuations. Gaussian optics are used to produce a poloidal spot size with w(o) approximately 1.75 cm in the plasma. The intermediate frequency filters and the natural linewidth of the EC emission determine the radial resolution of the CECE diagnostic, which can be less than 1 cm. Wavenumbers resolved by the CECE diagnostic are k(theta) < or = 1.8 cm(-1) and k(r) < or = 4 cm(-1), relevant for studies of long-wavelength turbulence associated with the trapped electron mode and the ion temperature gradient mode. In neutral beam heated L-mode plasmas, core electron temperature fluctuations in the region 0.5 < r/a < 0.9, increase with radius from approximately 0.5% to approximately 2%, similar to density fluctuations that are measured simultaneously with beam emission spectroscopy. After incorporating "synthetic diagnostics" to effectively filter the code output, the simulations reproduce the characteristics of the turbulence and transport at one radial location r/a = 0.5, but not at a second location, r/a = 0.75. These results illustrate that measurements of the profiles of multiple fluctuating fields can provide a significant constraint on the turbulence models employed by the code.

  19. Computer codes for three dimensional mass transport with non-linear sorption

    International Nuclear Information System (INIS)

    Noy, D.J.

    1985-03-01

    The report describes the mathematical background and data input to finite element programs for three dimensional mass transport in a porous medium. The transport equations are developed and sorption processes are included in a general way so that non-linear equilibrium relations can be introduced. The programs are described and a guide given to the construction of the required input data sets. Concluding remarks indicate that the calculations require substantial computer resources and suggest that comprehensive preliminary analysis with lower dimensional codes would be important in the assessment of field data. (author)

  20. Sustainability of transport structures - some aspects of the nonlinear reliability assessment

    Science.gov (United States)

    Pukl, Radomír; Sajdlová, Tereza; Strauss, Alfred; Lehký, David; Novák, Drahomír

    2017-09-01

    Efficient techniques for both nonlinear numerical analysis of concrete structures and advanced stochastic simulation methods have been combined in order to offer an advanced tool for assessment of realistic behaviour, failure and safety assessment of transport structures. The utilized approach is based on randomization of the non-linear finite element analysis of the structural models. Degradation aspects such as carbonation of concrete can be accounted in order predict durability of the investigated structure and its sustainability. Results can serve as a rational basis for the performance and sustainability assessment based on advanced nonlinear computer analysis of the structures of transport infrastructure such as bridges or tunnels. In the stochastic simulation the input material parameters obtained from material tests including their randomness and uncertainty are represented as random variables or fields. Appropriate identification of material parameters is crucial for the virtual failure modelling of structures and structural elements. Inverse analysis using artificial neural networks and virtual stochastic simulations approach is applied to determine the fracture mechanical parameters of the structural material and its numerical model. Structural response, reliability and sustainability have been investigated on different types of transport structures made from various materials using the above mentioned methodology and tools.

  1. Suppressing electron turbulence and triggering internal transport barriers with reversed magnetic shear in the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, J. L. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Bell, R.; Guttenfelder, W.; Hammett, G. W.; Kaye, S. M.; LeBlanc, B.; Mikkelsen, D. R. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Candy, J. [General Atomics, San Diego, California 92186 (United States); Smith, D. R. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Yuh, H. Y. [Nova Photonics Inc., Princeton, New Jersey 08540 (United States)

    2012-05-15

    The National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] can achieve high electron plasma confinement regimes that are super-critically unstable to the electron temperature gradient driven (ETG) instability. These plasmas, dubbed electron internal transport barriers (e-ITBs), occur when the magnetic shear becomes strongly negative. Using the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)], the first nonlinear ETG simulations of NSTX e-ITB plasmas reinforce this observation. Local simulations identify a strongly upshifted nonlinear critical gradient for thermal transport that depends on magnetic shear. Global simulations show e-ITB formation can occur when the magnetic shear becomes strongly negative. While the ETG-driven thermal flux at the outer edge of the barrier is large enough to be experimentally relevant, the turbulence cannot propagate past the barrier into the plasma interior.

  2. Memory function formalism applied to electronic transport in disordered systems

    International Nuclear Information System (INIS)

    Cunha Lima, I.C. da

    1984-01-01

    Memory function formalism is briefly reviewed and applied to electronic transport using the projection operator technique. The resistivity of a disordered 2-D electron gas under strong magnetic field is obtained in terms of force-force correlation function. (Author) [pt

  3. Full radius linear and nonlinear gyrokinetic simulations for tokamaks and stellarators: Zonal flows, applied E x B flows, trapped electrons and finite beta

    International Nuclear Information System (INIS)

    Villard, L.; Allfrey, S.J.; Bottino, A.

    2003-01-01

    The aim of this paper is to report on recent advances made on global gyrokinetic simulations of Ion Temperature Gradient modes (ITG) and other microinstabilities. The nonlinear development and saturation of ITG modes and the role of E x B zonal flows are studied with a global nonlinear δ f formulation that retains parallel nonlinearity and thus allows for a check of the energy conservation property as a means to verify the quality of the numerical simulation. Due to an optimised loading technique the conservation property is satisfied with an unprecedented quality well into the nonlinear stage. The zonal component of the perturbation establishes a quasi-steady state with regions of ITG suppression, strongly reduced radial energy flux and steepened effective temperature profile alternating with regions of higher ITG mode amplitudes, larger radial energy flux and flattened effective temperature profile. A semi-Lagrangian approach free of statistical noise is proposed as an alternative to the nonlinear δf formulation. An ASDEX-Upgrade experiment with an Internal Transport Barrier (ITB) is analysed with a global gyrokinetic code that includes trapped electron dynamics. The weakly destabilizing effect of trapped electron dynamics on ITG modes in an axisymmetric bumpy configuration modelling W7-X is shown in global linear simulations that retain the full electron dynamics. Finite β effects on microinstabilities are investigated with a linear global spectral electromagnetic gyrokinetic formulation. The radial global structure of electromagnetic modes shows a resonant behaviour with rational q values. (author)

  4. Transport of secondary electrons and reactive species in ion tracks

    Science.gov (United States)

    Surdutovich, Eugene; Solov'yov, Andrey V.

    2015-08-01

    The transport of reactive species brought about by ions traversing tissue-like medium is analysed analytically. Secondary electrons ejected by ions are capable of ionizing other molecules; the transport of these generations of electrons is studied using the random walk approximation until these electrons remain ballistic. Then, the distribution of solvated electrons produced as a result of interaction of low-energy electrons with water molecules is obtained. The radial distribution of energy loss by ions and secondary electrons to the medium yields the initial radial dose distribution, which can be used as initial conditions for the predicted shock waves. The formation, diffusion, and chemical evolution of hydroxyl radicals in liquid water are studied as well. COST Action Nano-IBCT: Nano-scale Processes Behind Ion-Beam Cancer Therapy.

  5. Exponential discontinuous numerical scheme for electron transport in the continuous slowing down approximation

    International Nuclear Information System (INIS)

    Prinja, A.K.

    1997-01-01

    A nonlinear discretization scheme in space and energy, based on the recently developed exponential discontinuous method, is applied to continuous slowing down dominated electron transport (i.e., in the absence of scattering.) Numerical results for dose and charge deposition are obtained and compared against results from the ONELD and ONEBFP codes, and against exact results from an adjoint Monte Carlo code. It is found that although the exponential discontinuous scheme yields strictly positive and monotonic solutions, the dose profile is considerably straggled when compared to results from the linear codes. On the other hand, the linear schemes produce negative results which, furthermore, do not damp effectively in some cases. A general conclusion is that while yielding strictly positive solutions, the exponential discontinuous method does not show the crude cell accuracy for charged particle transport as was apparent for neutral particle transport problems

  6. Thermal Transport in Diamond Films for Electronics Thermal Management

    Science.gov (United States)

    2018-03-01

    AFRL-RY-WP-TR-2017-0219 THERMAL TRANSPORT IN DIAMOND FILMS FOR ELECTRONICS THERMAL MANAGEMENT Samuel Graham Georgia Institute of Technology MARCH... ELECTRONICS THERMAL MANAGEMENT 5a. CONTRACT NUMBER FA8650-15-C-7517 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61101E 6. AUTHOR(S) Samuel...seeded sample (NRL 010516, Die A5). The NCD membrane and Al layer thicknesses, tNCD, were measured via transmission electron microscopy (TEM). The

  7. Kinetic Theory of Electronic Transport in Random Magnetic Fields

    Science.gov (United States)

    Lucas, Andrew

    2018-03-01

    We present the theory of quasiparticle transport in perturbatively small inhomogeneous magnetic fields across the ballistic-to-hydrodynamic crossover. In the hydrodynamic limit, the resistivity ρ generically grows proportionally to the rate of momentum-conserving electron-electron collisions at large enough temperatures T . In particular, the resulting flow of electrons provides a simple scenario where viscous effects suppress conductance below the ballistic value. This new mechanism for ρ ∝T2 resistivity in a Fermi liquid may describe low T transport in single-band SrTiO3 .

  8. Runaway electron transport studies in the HL-1M tokamak

    International Nuclear Information System (INIS)

    Zheng Yongzhen; Qi Changwei; Ding Xuantong; Li Wenzhong

    2002-01-01

    The transport of runaway electrons in a hot plasma has been studied in four experiments, which provide the runaway diffusivity D r The first experiment obtained runaway electrons using a steady state approach for values of the runaway confinement time τ r , deduced from hard X-ray bremsstrahlung spectra. In the second experiment, diffusion has been interpreted in terms of the magnetic fluctuation, from which a electron thermal diffusivity can be deduced. Runaway electro diffusion coefficient is determined by intrinsic magnetic fluctuations, rather than electrostatic fluctuations because of the high energy involved. The results presented here demonstrate the efficiency of using runaway transport techniques for determining intrinsic magnetic fluctuations

  9. Multidimensional electron-photon transport with standard discrete ordinates codes

    International Nuclear Information System (INIS)

    Drumm, C.R.

    1995-01-01

    A method is described for generating electron cross sections that are compatible with standard discrete ordinates codes without modification. There are many advantages of using an established discrete ordinates solver, e.g. immediately available adjoint capability. Coupled electron-photon transport capability is needed for many applications, including the modeling of the response of electronics components to space and man-made radiation environments. The cross sections have been successfully used in the DORT, TWODANT and TORT discrete ordinates codes. The cross sections are shown to provide accurate and efficient solutions to certain multidimensional electronphoton transport problems

  10. A ballistic transport model for electronic excitation following particle impact

    Science.gov (United States)

    Hanke, S.; Heuser, C.; Weidtmann, B.; Wucher, A.

    2018-01-01

    We present a ballistic model for the transport of electronic excitation energy induced by keV particle bombardment onto a solid surface. Starting from a free electron gas model, the Boltzmann transport equation (BTE) is employed to follow the evolution of the temporal and spatial distribution function f (r → , k → , t) describing the occupation probability of an electronic state k → at position r → and time t. Three different initializations of the distribution function are considered: i) a thermal distribution function with a locally and temporally elevated electron temperature, ii) a peak excitation at a specific energy above the Fermi level with a quasi-isotropic distribution in k-space and iii) an anisotropic peak excitation with k-vectors oriented in a specific transport direction. While the first initialization resembles a distribution function which may, for instance, result from electronic friction of moving atoms within an ion induced collision cascade, the peak excitation can in principle result from an autoionization process after excitation in close binary collisions. By numerically solving the BTE, we study the electronic energy exchange along a one dimensional transport direction to obtain a time and space resolved excitation energy distribution function, which is then analyzed in view of general transport characteristics of the chosen model system.

  11. Unconventional aspects of electronic transport in delafossite oxides

    Science.gov (United States)

    Daou, Ramzy; Frésard, Raymond; Eyert, Volker; Hébert, Sylvie; Maignan, Antoine

    2017-12-01

    The electronic transport properties of the delafossite oxides ? are usually understood in terms of two well-separated entities, namely the triangular ? and (? layers. Here, we review several cases among this extensive family of materials where the transport depends on the interlayer coupling and displays unconventional properties. We review the doped thermoelectrics based on ? and ?, which show a high-temperature recovery of Fermi-liquid transport exponents, as well as the highly anisotropic metals ?, ?, and ?, where the sheer simplicity of the Fermi surface leads to unconventional transport. We present some of the theoretical tools that have been used to investigate these transport properties and review what can and cannot be learned from the extensive set of electronic structure calculations that have been performed.

  12. Diffusion tensor in electron swarm transport

    International Nuclear Information System (INIS)

    Makabe, T.; Mori, T.

    1983-01-01

    Expression for the diffusion tensor of the electron (or light ion) swarm is presented from the higher-order expansion of the velocity distribution in the Boltzmann equation in hydrodynamic stage. Derived diffusion coefficients for the transverse and longitudinal directions include the additional terms representative of the curvature effect under the action of an electric field with the usual-two-term expressions. Numerical analysis is given for the electron swarm in model gases having the momentum transfer cross section Qsub(m)(epsilon)=Q 0 epsilon sup(beta) (β=0, 1/2, 1) using the present theory. As the result, appreciable degree of discrepancy appears between the transverse diffusion coefficient defined here and the conventional expression with increasing of β in Qsub(m). (Author)

  13. Theory of nonlinear harmonic generation in free-electron lasers with helical wigglers

    International Nuclear Information System (INIS)

    Geloni, G.; Saldin, E.; Schneidmiller, E.; Yurkov, M.

    2007-05-01

    CoherentHarmonicGeneration (CHG), and in particularNonlinearHarmonicGeneration (NHG), is of importance for both short wavelength Free-Electron Lasers (FELs), in relation with the achievement of shorter wavelengths with a fixed electron-beam energy, and high-average power FEL resonators, in relation with destructive effects of higher harmonics radiation on mirrors. In this paper we present a treatment of NHG from helical wigglers with particular emphasis on the second harmonic. Our study is based on an exact analytical solution of Maxwell's equations, derived with the help of a Green's function method. In particular, we demonstrate that nonlinear harmonic generation (NHG) fromhelicalwigglers vanishes on axis. Our conclusion is in open contrast with results in literature, that include a kinematical mistake in the description of the electron motion. (orig.)

  14. Vibrationally coupled electron transport through single-molecule junctions

    Energy Technology Data Exchange (ETDEWEB)

    Haertle, Rainer

    2012-04-26

    Single-molecule junctions are among the smallest electric circuits. They consist of a molecule that is bound to a left and a right electrode. With such a molecular nanocontact, the flow of electrical currents through a single molecule can be studied and controlled. Experiments on single-molecule junctions show that a single molecule carries electrical currents that can even be in the microampere regime. Thereby, a number of transport phenomena have been observed, such as, for example, diode- or transistor-like behavior, negative differential resistance and conductance switching. An objective of this field, which is commonly referred to as molecular electronics, is to relate these transport phenomena to the properties of the molecule in the contact. To this end, theoretical model calculations are employed, which facilitate an understanding of the underlying transport processes and mechanisms. Thereby, one has to take into account that molecules are flexible structures, which respond to a change of their charge state by a profound reorganization of their geometrical structure or may even dissociate. It is thus important to understand the interrelation between the vibrational degrees of freedom of a singlemolecule junction and the electrical current flowing through the contact. In this thesis, we investigate vibrational effects in electron transport through singlemolecule junctions. For these studies, we calculate and analyze transport characteristics of both generic and first-principles based model systems of a molecular contact. To this end, we employ a master equation and a nonequilibrium Green's function approach. Both methods are suitable to describe this nonequilibrium transport problem and treat the interactions of the tunneling electrons on the molecular bridge non-perturbatively. This is particularly important with respect to the vibrational degrees of freedom, which may strongly interact with the tunneling electrons. We show in detail that the resulting

  15. Suppressing Electron Turbulence and Triggering Internal Transport Barriers with Reversed Magnetic Shear in the National Spherical Torus Experiment

    Science.gov (United States)

    Peterson, Jayson Luc

    2011-10-01

    Observations in the National Spherical Torus Experiment (NSTX) have found electron temperature gradients that greatly exceed the linear threshold for the onset for electron temperature gradient-driven (ETG) turbulence. These discharges, deemed electron internal transport barriers (e-ITBs), coincide with a reversal in the shear of the magnetic field and with a reduction in electron-scale density fluctuations, qualitatively consistent with earlier gyrokinetic predictions. To investigate this phenomenon further, we numerically model electron turbulence in NSTX reversed-shear plasmas using the gyrokinetic turbulence code GYRO. These first-of-a-kind nonlinear gyrokinetic simulations of NSTX e-ITBs confirm that reversing the magnetic shear can allow the plasma to reach electron temperature gradients well beyond the critical gradient for the linear onset of instability. This effect is very strong, with the nonlinear threshold for significant transport approaching three times the linear critical gradient in some cases, in contrast with moderate shear cases, which can drive significant ETG turbulence at much lower gradients. In addition to the experimental implications of this upshifted nonlinear critical gradient, we explore the behavior of ETG turbulence during reversed shear discharges. This work is supported by the SciDAC Center for the Study of Plasma Microturbulence, DOE Contract DE-AC02-09CH11466, and used the resources of NCCS at ORNL and NERSC at LBNL. M. Ono et al., Nucl. Fusion 40, 557 (2000).

  16. Importance of space-time fluctuations and non-linearities for the transport inside insulating glasses; Importance des fluctuations spatio-temporelles et des non linearites pour le transport dans les verres isolants

    Energy Technology Data Exchange (ETDEWEB)

    Ladieu, F

    2003-07-01

    This work deals with transport in insulating glasses. In such solids, the discrete translational symmetry is lost, which means that the plane wave analysis is not a priori the right 'starting point'. As a result, the transport is more difficult to handle, and a huge amount of works have been devoted to many aspects of transport in disordered systems, especially since the seventies. Here we focus on three specific questions: (i) the heat transport in glasses submitted to micro-beams and the associated irreversible vaporization; (ii) the electronic d.c. transport, below 1 Kelvin, in Mott-Anderson insulators, i.e. in 'electron glasses' where both disorder and electron-electron interactions are relevant; (iii) the low frequency dielectric constant in 'structural glasses' (i.e. 'ordinary glasses') which, below 1 Kelvin, is both universal (i.e. independent on the chemical composition) and very different of that of crystals. For each topic, we present both original experiments and the new theoretical concepts that we have elaborated so as to understand the main experimental features. Eventually, it appears that, in any case, transport in insulating glasses is strongly dominated by quite a small part of the 'glass-applied field' ensemble and that the nonlinear response is a relevant tool to get informations on this 'sub-part' which dominates the transport in the whole system. (author)

  17. Modelling transport in single electron transistor

    International Nuclear Information System (INIS)

    Dinh Sy Hien; Huynh Lam Thu Thao; Le Hoang Minh

    2009-01-01

    We introduce a model of single electron transistor (SET). Simulation programme of SET is used as the exploratory tool in order to gain better understanding of process and device physics. This simulator includes a graphic user interface (GUI) in Matlab. The SET was simulated using GUI in Matlab to get current-voltage (I-V) characteristics. In addition, effects of device capacitance, bias, temperature on the I-V characteristics were obtained. In this work, we review the capabilities of the simulator of the SET. Typical simulations of the obtained I-V characteristics of the SET are presented.

  18. Angular dependent transport of auroral electrons in the upper atmosphere

    International Nuclear Information System (INIS)

    Lummerzheim, D.; Rees, M.H.

    1989-01-01

    The transport of auroral electrons through the upper atmosphere is analyzed. The transport equation is solved using a discrete ordinate method including elastic and inelastic scattering of electrons resulting in changes of pitch angle, and degradation in energy as the electrons penetrate into the atmosphere. The transport equation is solved numerically for the electron intensity as a function of altitude, pitch angle, and energy. In situ measurements of the pitch angle and energy distribution of precipitating electrons over an auroral arc provide boundary conditions for the calculation. The electron spectra from various locations over the aurora present a variety of anisotropic pitch angle distributions and energy spectra. Good agreement is found between the observed backscattered electron energy spectra and model predictions. Differences occur at low energies (below 500 eV) in the structure of the pitch angle distribution. Model calculations were carried out with various different phase functions for elastic and inelastic collisions to attempt changing the angular scattering, but the observed pitch angle distributions remain unexplained. We suggest that mechanisms other than collisional scattering influence the angular distribution of auroral electrons at or below 300 km altitude in the low energy domain. (author)

  19. Fast electron transport study for inertial confinement fusion

    International Nuclear Information System (INIS)

    Touati, Michael

    2015-01-01

    A new hybrid reduced model for relativistic electron beam transport in solids and dense plasmas is presented. It is based on the two first angular moments of the relativistic kinetic equation completed with the Minerbo maximum angular entropy closure. It takes into account collective effects with the self-generated electromagnetic fields as well as collisional effects with the slowing down of the electrons in collisions with plasmons, bound and free electrons and their angular scattering on both ions and electrons. This model allows for fast computations of relativistic electron beam transport while describing the kinetic distribution function evolution. Despite the loss of information concerning the angular distribution of the electron beam, the model reproduces analytical estimates in the academic case of a collimated and monoenergetic electron beam propagating through a warm and dense Hydrogen plasma and hybrid PIC simulation results in a realistic laser-generated electron beam transport in a solid target. The model is applied to the study of the emission of Kα photons in laser-solid experiments and to the generation of shock waves. (author) [fr

  20. Linear and nonlinear electrostatic modes in a nonuniform magnetized electron plasma

    International Nuclear Information System (INIS)

    Vranjes, J.; Shukla, P.K.; Kono, M.; Poedts, S.

    2001-01-01

    Linear and nonlinear low-frequency modes in a magnetized electron plasma are studied, taking into account a proper description of the equilibrium plasma state that is inhomogeneous. Assuming a homogeneous magnetic field and sheared plasma flows, flute-like perturbations are studied in the presence of density and potential gradients. Linear analysis reveals the presence of a streaming instability and depicts conditions for global linear spiral mode. In the nonlinear domain, a tripolar vortex, which is driven and carried by the flow, is found. Also investigated are the consequences of a magnetic shear as well as nonuniformities along the magnetic field lines, which are shown to be responsible for the possible annulment of the magnetic shear effects. Streaming along the lines of the sheared magnetic field is also studied. A variety of nonlinear structures (viz. global multipolar vortices, local vortex chains, and tripolar vortices) is shown to be the consequence of the simultaneous action of the parallel and perpendicular flows

  1. A theoretical study of structural, opto-electronic and nonlinear properties of arylboroxine derivatives

    Science.gov (United States)

    Islam, Nasarul; Pandith, Altaf Hussain

    2018-01-01

    Density functional theory at CAM-B3LYP/6-311G++ (2d, 2p) level was employed to study the Triphenylboroxine derivatives ( TB) containing electron donating and electron substituents, for their charge transfer and nonlinear optical properties. The results reveal that electron donating groups facilitate the rapid electron injection as compared to unsubstituted TB. It was observed that upon substitution with electron donating groups, the TB derivatives show an increased double bond character in the B3-C18 bond indicating an increase in the degree of conjugation. The Frontier molecular orbital studies indicate that highest occupied molecular orbitals of the neutral molecules delocalize primarily over the three phenyl rings and bridging oxygen atoms, whereas the lowest unoccupied molecular orbitals localize largely on the two phenyl rings and the boron atoms. Further, the TD-DFT studies indicate that the maximum absorption band results from the electron transitions from the initial states that are contributed by the HOMO and HOMO-1 to the final states that are mainly contributed by the LUMOs. In addition, we have observed that the introduction of electron donating group to the TB-7 leads to more active nonlinear performance.

  2. LOO: a low-order nonlinear transport scheme for acceleration of method of characteristics

    International Nuclear Information System (INIS)

    Li, Lulu; Smith, Kord; Forget, Benoit; Ferrer, Rodolfo

    2015-01-01

    This paper presents a new physics-based multi-grid nonlinear acceleration method: the low-order operator method, or LOO. LOO uses a coarse space-angle multi-group method of characteristics (MOC) neutron transport calculation to accelerate the fine space-angle MOC calculation. LOO is designed to capture more angular effects than diffusion-based acceleration methods through a transport-based low-order solver. LOO differs from existing transport-based acceleration schemes in that it emphasizes simplified coarse space-angle characteristics and preserves physics in quadrant phase-space. The details of the method, including the restriction step, the low-order iterative solver and the prolongation step are discussed in this work. LOO shows comparable convergence behavior to coarse mesh finite difference on several two-dimensional benchmark problems while not requiring any under-relaxation, making it a robust acceleration scheme. (author)

  3. Existence regimes for the formation of nonlinear dissipative structures in inhomogeneous magnetoplasmas with non-Maxwellian electrons

    Science.gov (United States)

    Masood, W.; Zahoor, Sara; Gul-e-Ali, Ahmad, Ali

    2016-09-01

    Nonlinear dissipative structures are studied in one and two dimensions in nonuniform magnetized plasmas with non-Maxwellian electrons. The dissipation is incorporated in the system through ion-neutral collisions. Employing the drift approximation, nonlinear drift waves are derived in 1D, whereas coupled drift-ion acoustic waves are derived in 2D in the weak nonlinearity limit. It is found that the ratio of the diamagnetic drift velocity to the velocity of nonlinear structure determines the nature (compressive or rarefactive) of the shock structure. The upper and lower bounds for velocity of the nonlinear shock structures are also found. It is noticed that the existence regimes for the drift shock waves in one and two dimensions for Cairns distributed electrons are very distinct from those with kappa distributed electrons. Interestingly, it is found that both compressive and rarefactive shock structures could be obtained for the one dimensional drift waves with kappa distributed electrons.

  4. Existence regimes for the formation of nonlinear dissipative structures in inhomogeneous magnetoplasmas with non-Maxwellian electrons

    Energy Technology Data Exchange (ETDEWEB)

    Masood, W. [COMSATS Institute of Information Technology, Park Road, Chak Shahzad, Islamabad (Pakistan); National Centre for Physics, Shahdara Valley Road, Islamabad (Pakistan); Zahoor, Sara [COMSATS Institute of Information Technology, Park Road, Chak Shahzad, Islamabad (Pakistan); Gul-e-Ali [Theoretical Plasma Physics Group, Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ahmad, Ali, E-mail: aliahmad79@hotmail.com [National Centre for Physics, Shahdara Valley Road, Islamabad (Pakistan)

    2016-09-15

    Nonlinear dissipative structures are studied in one and two dimensions in nonuniform magnetized plasmas with non-Maxwellian electrons. The dissipation is incorporated in the system through ion-neutral collisions. Employing the drift approximation, nonlinear drift waves are derived in 1D, whereas coupled drift-ion acoustic waves are derived in 2D in the weak nonlinearity limit. It is found that the ratio of the diamagnetic drift velocity to the velocity of nonlinear structure determines the nature (compressive or rarefactive) of the shock structure. The upper and lower bounds for velocity of the nonlinear shock structures are also found. It is noticed that the existence regimes for the drift shock waves in one and two dimensions for Cairns distributed electrons are very distinct from those with kappa distributed electrons. Interestingly, it is found that both compressive and rarefactive shock structures could be obtained for the one dimensional drift waves with kappa distributed electrons.

  5. Investigation of electronic transport properties of some liquid transition metals

    Science.gov (United States)

    Patel, H. P.; Sonvane, Y. A.; Thakor, P. B.

    2018-04-01

    We investigated electronic transport properties of some liquid transition metals (V, Cr, Mn, Fe, Co and Pt) using Ziman formalism. Our parameter free model potential which is realized on ionic and atomic radius has been incorporated with the Hard Sphere Yukawa (HSY) reference system to study the electronic transport properties like electrical resistivity (ρ), thermal conductivity (σ) and thermo electrical power (Q). The screening effect on aforesaid properties has been studied by using different screening functions. The correlations of our results and others data with in addition experimental values are profoundly promising to the researchers working in this field. Also, we conclude that our newly constructed parameter free model potential is capable to explain the aforesaid electronic transport properties.

  6. Role of electron-electron scattering on spin transport in single layer graphene

    Directory of Open Access Journals (Sweden)

    Bahniman Ghosh

    2014-01-01

    Full Text Available In this work, the effect of electron-electron scattering on spin transport in single layer graphene is studied using semi-classical Monte Carlo simulation. The D’yakonov-P’erel mechanism is considered for spin relaxation. It is found that electron-electron scattering causes spin relaxation length to decrease by 35% at 300 K. The reason for this decrease in spin relaxation length is that the ensemble spin is modified upon an e-e collision and also e-e scattering rate is greater than phonon scattering rate at room temperature, which causes change in spin relaxation profile due to electron-electron scattering.

  7. Electron and impurity transport studies in the TCV Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, D.

    2013-05-15

    In this thesis electron and impurity transport are studied in the Tokamak à Configuration Variable (TCV) located at CRPP-EPFL in Lausanne. Understanding particle transport is primordial for future nuclear fusion power plants. Modeling of experiments in many specific plasma scenarios can help to understand the common elements of the physics at play and to interpret apparently contradictory experiments on the same machine and across different machines. The first part of this thesis deals with electron transport in TCV high confinement mode plasmas. It was observed that the electron density profile in these plasmas flatten when intense electron heating is applied, in contrast to observations on other machines where the increase of the profile peakedness was reported. It is shown with quasi-linear gyrokinetic simulations that this effect, usually interpreted as collisionality dependence, stems from the combined effect of many plasma parameters. The influence of the collisionality, electron to ion temperature ratio, the ratio of temperature gradients, and the Ware-pinch are studied with detailed parameter scans. It is shown that the complex interdependence of the various plasma parameters is greatly simplified when the simulation results are interpreted as a function of the average frequency of the main modes contributing to radial transport. In this way the model is able to explain the experimental results. It was also shown that the same basic understanding is at play in L-modes, H-modes and electron internal transport barriers. The second part of the thesis is devoted to impurity transport. A multi-purpose gas injection system is developed, commissioned and calibrated. It is shown that the system is capable of massive gas injections to provoke disruptions and delivering small puffs of gaseous impurities for perturbative transport experiments. This flexible tool is exploited in a series of impurity transport measurements with argon and neon injections. The impurities

  8. Electron and impurity transport studies in the TCV Tokamak

    International Nuclear Information System (INIS)

    Wagner, D.

    2013-05-01

    In this thesis electron and impurity transport are studied in the Tokamak à Configuration Variable (TCV) located at CRPP-EPFL in Lausanne. Understanding particle transport is primordial for future nuclear fusion power plants. Modeling of experiments in many specific plasma scenarios can help to understand the common elements of the physics at play and to interpret apparently contradictory experiments on the same machine and across different machines. The first part of this thesis deals with electron transport in TCV high confinement mode plasmas. It was observed that the electron density profile in these plasmas flatten when intense electron heating is applied, in contrast to observations on other machines where the increase of the profile peakedness was reported. It is shown with quasi-linear gyrokinetic simulations that this effect, usually interpreted as collisionality dependence, stems from the combined effect of many plasma parameters. The influence of the collisionality, electron to ion temperature ratio, the ratio of temperature gradients, and the Ware-pinch are studied with detailed parameter scans. It is shown that the complex interdependence of the various plasma parameters is greatly simplified when the simulation results are interpreted as a function of the average frequency of the main modes contributing to radial transport. In this way the model is able to explain the experimental results. It was also shown that the same basic understanding is at play in L-modes, H-modes and electron internal transport barriers. The second part of the thesis is devoted to impurity transport. A multi-purpose gas injection system is developed, commissioned and calibrated. It is shown that the system is capable of massive gas injections to provoke disruptions and delivering small puffs of gaseous impurities for perturbative transport experiments. This flexible tool is exploited in a series of impurity transport measurements with argon and neon injections. The impurities

  9. Increased expression of electron transport chain genes in uterine leiomyoma.

    Science.gov (United States)

    Tuncal, Akile; Aydin, Hikmet Hakan; Askar, Niyazi; Ozkaya, Ali Burak; Ergenoglu, Ahmet Mete; Yeniel, Ahmet Ozgur; Akdemir, Ali; Ak, Handan

    2014-01-01

    The etiology and pathophysiology of uterine leiomyomas, benign smooth muscle tumors of the uterus, are not well understood. To evaluate the role of mitochondria in uterine leiomyoma, we compared electron transport gene expressions of uterine leiomyoma tissue with myometrium tissue in six uterine leiomyoma patients by RT-PCR array. Our results showed an average of 1.562 (±0.445) fold increase in nuclear-encoded electron transport genes. These results might suggest an increase in size, number, or activity of mitochondria in uterine leiomyoma that, to our knowledge, has not been previously reported. © 2014 by the Association of Clinical Scientists, Inc.

  10. Nonlinear electrostatic emittance compensation in kA, fs electron bunches

    International Nuclear Information System (INIS)

    Geer, S.B. van der; Loos, M.J. de; Botman, J.I.M.; Luiten, O.J.; Wiel, M.J. van der

    2002-01-01

    Nonlinear space-charge effects play an important role in emittance growth in the production of kA electron bunches with a bunch length much smaller than the bunch diameter. We propose a scheme employing the radial third-order component of an electrostatic acceleration field, to fully compensate the nonlinear space-charge effects. This results in minimal transverse root-mean-square emittance. The principle is demonstrated using our design simulations of a device for the production of high-quality, high-current, subpicosecond electron bunches using electrostatic acceleration in a 1 GV/m field. Simulations using the GPT code produce a bunch of 100 pC and 73 fs full width at half maximum pulse width, resulting in a peak current of about 1.2 kA at an energy of 2 MeV. The compensation scheme reduces the root-mean-square emittance by 34% to 0.4π mm mrad

  11. Coupled electron/photon transport in static external magnetic fields

    International Nuclear Information System (INIS)

    Halbleib, J.A. Sr.; Vandevender, W.H.

    A model is presented which describes coupled electron/photon transport in the presence of static magnetic fields of arbitrary spatial dependence. The method combines state-of-the-art condensed-history electron collisional Monte Carlo and single-scattering photon Monte Carlo, including electron energy-loss straggling and the production and transport of all generations of secondaries, with numerical field integration via the best available variable-step-size Runge-Kutta-Fehlberg or variable-order/variable-step-size Adams PECE differential equation solvers. A three-dimensional cartesian system is employed in the description of particle trajectories. Although the present model is limited to multilayer material configurations, extension to more complex material geometries should not be difficult. Among the more important options are (1) a feature which permits the neglect of field effects in regions where transport is collision dominated and (2) a method for describing the transport in variable-density media where electron energies and material densities are sufficiently low that the density effect on electronic stopping powers may be neglected. (U.S.)

  12. Analytic approach to auroral electron transport and energy degradation

    International Nuclear Information System (INIS)

    Stamnes, K.

    1980-01-01

    The interaction of a beam of auroral electrons with the atmosphere is described by the linear transport equation, encompassing discrete energy loss, multiple scattering, and secondary electrons. A solution to the transport equation provides the electron intensity as a function of altitude, pitch angle (with respect to the geomagnetic field) and energy. A multi-stream (discrete ordinate) approximation to the transport equation is developed. An analytic solution is obtained in this approximation. The computational scheme obtained by combining the present transport code with the energy degradation method of Swartz (1979) conserves energy identically. The theory provides a framework within which angular distributions can be easily calculated and interpreted. Thus, a detailed study of the angular distributions of 'non-absorbed' electrons (i.e., electrons that have lost just a small fraction of their incident energy) reveals a systematic variation with incident angle and energy, and with penetration depth. The present approach also gives simple yet accurate solutions in low order multi-stream approximations. The accuracy of the four-stream approximation is generally within a few per cent, whereas two-stream results for backscattered mean intensities and fluxes are accurate to within 10-15%. (author)

  13. NMR studies of transmembrane electron transport in human erythrocytes

    International Nuclear Information System (INIS)

    Kennett, E.C.; Bubb, W.A.; Kuchel, P.W.

    2002-01-01

    Full text: Electron transport systems exist in the plasma membranes of all cells. These systems appear to play a role in cell growth and proliferation, intracellular signalling, hormone responses, apoptotic events, cell defence and perhaps most importantly they enable the cell to respond to changes in the redox state of both the intra- and extracellular environments. Previously, 13 C NMR has been used to study transmembrane electron transport in human erythrocytes, specifically the reduction of extracellular 13 C-ferricyanide. NMR is a particularly useful tool for studying such systems as changes in the metabolic state of the cell can be observed concomitantly with extracellular reductase activity. We investigated the oxidation of extracellular NADH by human erythrocytes using 1 H and 31 P NMR spectroscopy. Recent results for glucose-starved human erythrocytes indicate that, under these conditions, extracellular NADH can be oxidised at the plasma membrane with the electron transfer across the membrane resulting in reduction of intracellular NAD + . The activity is inhibited by known trans-plasma membrane electron transport inhibitors (capsaicin and atebrin) and is unaffected by inhibition of the erythrocyte Band 3 anion transporter. These results suggest that electron import from extracellular NADH allows the cell to re-establish a reducing environment after the normal redox balance is disturbed

  14. Electron cyclotron waves, transport and instabilities in hot plasmas

    International Nuclear Information System (INIS)

    Westerhof, E.

    1987-01-01

    A number of topics relevant to the magnetic confinement approach to the thermonuclear fusion is addressed. The absorption and emission of electron cyclotron waves in a thermal plasma with a small population of supra-thermal, streaming electrons is examined and the properties of electron cyclotron waves in a plasma with a pure loss-cone distribution are studied. A report is given on the 1-D transport code simulations that were performed to assist the interpretation of the electron cyclotron heating experiments on the TFR tokamak. Transport code simulations of sawteeth discharges in the T-10 tokamak are discussed in order to compare the predictions of different models for the sawtooth oscillations with the experimental findings. 149 refs.; 69 figs.; 7 tabs

  15. Nonequilibrium statistical operator in hot-electron transport theory

    International Nuclear Information System (INIS)

    Xing, D.Y.; Liu, M.

    1991-09-01

    The Nonequilibrium Statistical Operator method developed by Zubarev is generalized and applied to the study of hot-electron transport in semiconductors. The steady-state balance equations for momentum and energy are derived to the lowest order in the electron-lattice coupling. We show that the derived balance equations are exactly the same as those obtained by Lei and Ting. This equivalence stems from the fact that to the linear order in the electron-lattice coupling, two statistical density matrices have identical effect when they are used to calculate the average value of a dynamical operator. The application to the steady-state and transient hot-electron transport in multivalley semiconductors is also discussed. (author). 28 refs, 1 fig

  16. Electron transport in magnetic multilayers: effect of disorder

    Czech Academy of Sciences Publication Activity Database

    Drchal, Václav; Kudrnovský, Josef; Bruno, P.; Dederichs, P. H.; Turek, Ilja; Weinberger, P.

    2002-01-01

    Roč. 65, - (2002), s. 214414-1-214414-8 ISSN 0163-1829 R&D Projects: GA MŠk OC P5.30; GA ČR GA202/00/0122; GA AV ČR IAA1010829; GA AV ČR IBS2041105 Institutional research plan: CEZ:AV0Z1010914 Keywords : electron transport * magnetic multilayers * ballistic transport * diffusive transport * disorder Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.327, year: 2002

  17. Electronic transport properties of nanostructured MnSi-films

    Science.gov (United States)

    Schroeter, D.; Steinki, N.; Scarioni, A. Fernández; Schumacher, H. W.; Süllow, S.; Menzel, D.

    2018-05-01

    MnSi, which crystallizes in the cubic B20 structure, shows intriguing magnetic properties involving the existence of skyrmions in the magnetic phase diagram. Bulk MnSi has been intensively investigated and thoroughly characterized, in contrast to MnSi thin film, which exhibits widely varying properties in particular with respect to electronic transport. In this situation, we have set out to reinvestigate the transport properties in MnSi thin films by means of studying nanostructure samples. In particular, Hall geometry nanostructures were produced to determine the intrinsic transport properties.

  18. Electron transport in EBT in the low collision frequency limit

    International Nuclear Information System (INIS)

    Hastings, D.E.

    1983-01-01

    A variational principle formulation is used to calculate the electron neoclassical transport coefficients in a bumpy torus for the low collisionality regime. The electron radial drift is calculated as a function of the plasma position and the poloidal electric field which is determined self-consistently. A bounce-averaged differential collision operator is used and the results are compared to previous treatments using a BGK operator

  19. Power electronics applied to industrial systems and transports

    CERN Document Server

    Patin, Nicolas

    2015-01-01

    If the operation of electronic components switching scheme to reduce congestion and losses (in power converters in general and switching power supplies in particular), it also generates electromagnetic type of pollution in its immediate environment. Power Electronics for Industry and Transport, Volume 4 is devoted to electromagnetic compatibility. It presents the sources of disturbance and the square wave signal, spectral modeling generic perturbation. Disturbances propagation mechanisms called ""lumped"" by couplings such as a common impedance, a parasitic capacitance or a mutual and ""dis

  20. Enhanced energy deposition symmetry by hot electron transport

    International Nuclear Information System (INIS)

    Wilson, D.; Mack, J.; Stover, E.; VanHulsteyn, D.; McCall, G.; Hauer, A.

    1981-01-01

    High energy electrons produced by resonance absorption carry the CO 2 laser energy absorbed in a laser fusion pellet. The symmetrization that can be achieved by lateral transport of the hot electrons as they deposit their energy is discussed. A K/sub α/ experiment shows a surprising symmetrization of energy deposition achieved by adding a thin layer of plastic to a copper sphere. Efforts to numerically model this effect are described

  1. A non-Linear transport model for determining shale rock characteristics

    Science.gov (United States)

    Ali, Iftikhar; Malik, Nadeem

    2016-04-01

    Unconventional hydrocarbon reservoirs consist of tight porous rocks which are characterised by nano-scale size porous networks with ultra-low permeability [1,2]. Transport of gas through them is not well understood at the present time, and realistic transport models are needed in order to determine rock properties and for estimating future gas pressure distribution in the reservoirs. Here, we consider a recently developed non-linear gas transport equation [3], ∂p-+ U ∂p- = D ∂2p-, t > 0, (1) ∂t ∂x ∂x2 complimented with suitable initial and boundary conditions, in order to determine shale rock properties such as the permeability K, the porosity φ and the tortuosity, τ. In our new model, the apparent convection velocity, U = U(p,px), and the apparent diffusivity D = D(p), are both highly non-linear functions of the pressure. The model incorporate various flow regimes (slip, surface diffusion, transition, continuum) based upon the Knudsen number Kn, and also includes Forchchiemers turbulence correction terms. In application, the model parameters and associated compressibility factors are fully pressure dependent, giving the model more realism than previous models. See [4]. Rock properties are determined by solving an inverse problem, with model parameters adjustment to minimise the error between the model simulation and available data. It is has been found that the proposed model performs better than previous models. Results and details of the model will be presented at the conference. Corresponding author: namalik@kfupm.edu.sa and nadeem_malik@cantab.net References [1] Cui, X., Bustin, A.M. and Bustin, R., "Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications", Geofluids 9, 208-223 (2009). [2] Chiba R., Fomin S., Chugunov V., Niibori Y. and Hashida T., "Numerical Simulation of Non Fickian Diffusion and Advection in a Fractured Porous Aquifer", AIP Conference Proceedings 898, 75 (2007

  2. Electron heat transport in shaped TCV L-mode plasmas

    International Nuclear Information System (INIS)

    Camenen, Y; Pochelon, A; Bottino, A; Coda, S; Ryter, F; Sauter, O; Behn, R; Goodman, T P; Henderson, M A; Karpushov, A; Porte, L; Zhuang, G

    2005-01-01

    Electron heat transport experiments are performed in L-mode discharges at various plasma triangularities, using radially localized electron cyclotron heating to vary independently both the electron temperature T e and the normalized electron temperature gradient R/L T e over a large range. Local gyro-fluid (GLF23) and global collisionless gyro-kinetic (LORB5) linear simulations show that, in the present experiments, trapped electron mode (TEM) is the most unstable mode. Experimentally, the electron heat diffusivity χ e is shown to decrease with increasing collisionality, and no dependence of χ e on R/L T e is observed at high R/L T e values. These two observations are consistent with the predictions of TEM simulations, which supports the fact that TEM plays a crucial role in electron heat transport. In addition, over the broad range of positive and negative triangularities investigated, the electron heat diffusivity is observed to decrease with decreasing plasma triangularity, leading to a strong increase of plasma confinement at negative triangularity

  3. Self-consistent electron transport in collisional plasmas

    International Nuclear Information System (INIS)

    Mason, R.J.

    1982-01-01

    A self-consistent scheme has been developed to model electron transport in evolving plasmas of arbitrary classical collisionality. The electrons and ions are treated as either multiple donor-cell fluids, or collisional particles-in-cell. Particle suprathermal electrons scatter off ions, and drag against fluid background thermal electrons. The background electrons undergo ion friction, thermal coupling, and bremsstrahlung. The components move in self-consistent advanced E-fields, obtained by the Implicit Moment Method, which permits Δt >> ω/sub p/ -1 and Δx >> lambda/sub D/ - offering a 10 2 - 10 3 -fold speed-up over older explicit techniques. The fluid description for the background plasma components permits the modeling of transport in systems spanning more than a 10 7 -fold change in density, and encompassing contiguous collisional and collisionless regions. Results are presented from application of the scheme to the modeling of CO 2 laser-generated suprathermal electron transport in expanding thin foils, and in multi-foil target configurations

  4. Nonlinear State of Sausage-like Instability of Electron Current Channels in Fast Ignition Concept of Inertial Fusion

    International Nuclear Information System (INIS)

    Jain, Neeraj; Das, Amita; Kaw, Predhiman; Sengupta, Sudip

    2003-01-01

    This paper deals with a detailed fluid simulation study of linear and nonlinear aspects of the velocity shear modes in electron current channels in a two dimensional geometry. Simulation results clearly show the flattening of flow profile and the development of sausage like structures (kink structures, which are intrinsically three dimensional excitations, are ruled out in the present simulations) which grow linearly and eventually saturate by nonlinear effects. An analytic understanding of the nonlinear saturation mechanism is also provided

  5. Interesting features of nonlinear shock equations in dissipative pair-ion-electron plasmas

    International Nuclear Information System (INIS)

    Masood, W.; Rizvi, H.

    2011-01-01

    Two dimensional nonlinear electrostatic waves are studied in unmagnetized, dissipative pair-ion-electron plasmas in the presence of weak transverse perturbation. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions. In the linear case, a biquadratic dispersion relation is obtained, which yields the fast and slow modes in a pair-ion-electron plasma. It is shown that the limiting cases of electron-ion and pair-ion can be retrieved from the general biquadratic dispersion relation, and the differences in the characters of the waves propagating in both the cases are also highlighted. Using the small amplitude approximation method, the nonlinear Kadomtsev Petviashvili Burgers as well as Burgers-Kadomtsev Petviashvili equations are derived and their applicability for pair-ion-electron plasma is explained in detail. The present study may have relevance to understand the formation of two dimensional electrostatic shocks in laboratory produced pair-ion-electron plasmas.

  6. Electron-vibron coupling effects on electron transport via a single-molecule magnet

    NARCIS (Netherlands)

    McCaskey, A.; Yamamoto, Y.; Warnock, M.; Burzuri, E.; Van der Zant, H.S.J.; Park, K.

    2015-01-01

    We investigate how the electron-vibron coupling influences electron transport via an anisotropic magnetic molecule, such as a single-molecule magnet (SMM) Fe4, by using a model Hamiltonian with parameter values obtained from density-functional theory (DFT). The magnetic anisotropy parameters,

  7. Nonlinear simulation of magnetic reconnection with a drift kinetic electron model

    International Nuclear Information System (INIS)

    Zwingmann, W.; Ottaviani, M.

    2004-01-01

    The process of reconnection allows for a change of magnetic topology inside a plasma. It is an important process for eruptive phenomena in astrophysical plasma, and the sawtooth relaxation in laboratory plasma close to thermonuclear conditions. The sawtooth relaxation is associated with the collisionless electron tearing instability, caused by the electron inertia. A thorough treatment therefore requires a kinetic model for the electron dynamics. In this contribution, we report on the numerical simulation of the electron tearing instability by solving the Vlasov equation directly. The results confirm results of an early paper on the same subject, and extends them to smaller values of the collision skin depth d e = 0.25. Our results suggest a faster than exponential growth in the early nonlinear phase of the instability. We observe as well an asymmetry of the resulting fields. It seems, however, that the field structure becomes closer to the fluid case for small values of d e

  8. Nonequilibrium Electron Transport Through a Quantum Dot from Kubo Formula

    International Nuclear Information System (INIS)

    Lue Rong; Zhang Guangming

    2005-01-01

    Based on the Kubo formula for an electron tunneling junction, we revisit the nonequilibrium transport properties through a quantum dot. Since the Fermi level of the quantum dot is set by the conduction electrons of the leads, we calculate the electron current from the left side by assuming the quantum dot coupled to the right lead as another side of the tunneling junction, and the other way round is used to calculate the current from the right side. By symmetrizing these two currents, an effective local density states on the dot can be obtained, and is discussed at high and low temperatures, respectively.

  9. Role of hot electron transport in scintillators: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Huihui [SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology, Key Lab. of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen Univ. (China); Li, Qi [Physical Sciences Division, IBM TJ Watson Research Center, Yorktown Heights, NY (United States); Department of Computer Science, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Lu, Xinfu; Williams, R.T. [Department of Physics, Wake Forest University, Winston Salem, NC (United States); Qian, Yiyang [College of Engineering and Applied Science, Nanjing University (China); Wu, Yuntao [Scintillation Materials Research Center, University of Tennessee, Knoxville, TN (United States)

    2016-10-15

    Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab-initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte-Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Anticancer Drugs Targeting the Mitochondrial Electron Transport Chain

    Czech Academy of Sciences Publication Activity Database

    Rohlena, Jakub; Dong, L.-F.; Ralph, S.J.; Neužil, Jiří

    2011-01-01

    Roč. 15, č. 12 (2011), s. 2951-2974 ISSN 1523-0864 R&D Projects: GA AV ČR(CZ) KAN200520703 Institutional research plan: CEZ:AV0Z50520701 Keywords : Targets for anticancer drugs * mitochondrial electron transport chain * mitocans Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 8.456, year: 2011

  11. Electron transport and coherence in semiconductor quantum dots and rings

    NARCIS (Netherlands)

    Van der Wiel, W.G.

    2002-01-01

    A number of experiments on electron transport and coherence in semiconductor vertical and lateral quantum dots and semiconductor rings is described. Quantum dots are often referred to as "artificial atoms", because of their similarities with real atoms. Examples of such atom-like properties that

  12. Electron spin transport in graphene and carbon nanotubes

    NARCIS (Netherlands)

    Tombros, Nikolaos

    2008-01-01

    Electron spin transport in grafeen en in koolstof nanobuisjes Grafeen, is een kristaal laag van koolstof atomen die slechts één atoomlaag dik is. Een koolstof nanobuisje is te verkrijgen door een grafeen laag op te rollen. In dit proefschrift laten we zien, met behulp van experimenten, dat deze

  13. Defect engineering of the electronic transport through cuprous oxide interlayers

    KAUST Repository

    Fadlallah, Mohamed M.; Eckern, Ulrich; Schwingenschlö gl, Udo

    2016-01-01

    The electronic transport through Au–(Cu2O)n–Au junctions is investigated using first-principles calculations and the nonequilibrium Green’s function method. The effect of varying the thickness (i.e., n) is studied as well as that of point defects

  14. Discrete and continuum links to a nonlinear coupled transport problem of interacting populations

    Science.gov (United States)

    Duong, M. H.; Muntean, A.; Richardson, O. M.

    2017-07-01

    We are interested in exploring interacting particle systems that can be seen as microscopic models for a particular structure of coupled transport flux arising when different populations are jointly evolving. The scenarios we have in mind are inspired by the dynamics of pedestrian flows in open spaces and are intimately connected to cross-diffusion and thermo-diffusion problems holding a variational structure. The tools we use include a suitable structure of the relative entropy controlling TV-norms, the construction of Lyapunov functionals and particular closed-form solutions to nonlinear transport equations, a hydrodynamics limiting procedure due to Philipowski, as well as the construction of numerical approximates to both the continuum limit problem in 2D and to the original interacting particle systems.

  15. Molecular electronics: insight from first-principles transport simulations.

    Science.gov (United States)

    Paulsson, Magnus; Frederiksen, Thomas; Brandbyge, Mads

    2010-01-01

    Conduction properties of nanoscale contacts can be studied using first-principles simulations. Such calculations give insight into details behind the conductance that is not readily available in experiments. For example, we may learn how the bonding conditions of a molecule to the electrodes affect the electronic transport. Here we describe key computational ingredients and discuss these in relation to simulations for scanning tunneling microscopy (STM) experiments with C60 molecules where the experimental geometry is well characterized. We then show how molecular dynamics simulations may be combined with transport calculations to study more irregular situations, such as the evolution of a nanoscale contact with the mechanically controllable break-junction technique. Finally we discuss calculations of inelastic electron tunnelling spectroscopy as a characterization technique that reveals information about the atomic arrangement and transport channels.

  16. Flux and reactive contributions to electron transport in methane

    International Nuclear Information System (INIS)

    Ness, K.F.; Nolan, A.M.

    2000-01-01

    A previously developed theoretical analysis (Nolan et al. 1997) is applied to the study of electron transport in methane for reduced electric fields in the range 1 to 1000 Td. The technique of analysis identifies the flux and reactive components of the measurable transport, without resort to the two-term approximation. A comparison of the results of the Monte Carlo method with those of a multiterm Boltzmann equation analysis (Ness and Robson 1986) shows good agreement. The sensitivity of the modelled electron transport to post-ionisation energy partitioning is studied by comparison of three ionisation energy partitioning regimes at moderate (300 Td) and high (1000 Td) values of the reduced electric field. Copyright (2000) CSIRO Australia

  17. Linear versus non-linear structural information limit in high-resolution transmission electron microscopy

    International Nuclear Information System (INIS)

    Van Aert, S.; Chen, J.H.; Van Dyck, D.

    2010-01-01

    A widely used performance criterion in high-resolution transmission electron microscopy (HRTEM) is the information limit. It corresponds to the inverse of the maximum spatial object frequency that is linearly transmitted with sufficient intensity from the exit plane of the object to the image plane and is limited due to partial temporal coherence. In practice, the information limit is often measured from a diffractogram or from Young's fringes assuming a weak phase object scattering beyond the inverse of the information limit. However, for an aberration corrected electron microscope, with an information limit in the sub-angstrom range, weak phase objects are no longer applicable since they do not scatter sufficiently in this range. Therefore, one relies on more strongly scattering objects such as crystals of heavy atoms observed along a low index zone axis. In that case, dynamical scattering becomes important such that the non-linear and linear interaction may be equally important. The non-linear interaction may then set the experimental cut-off frequency observed in a diffractogram. The goal of this paper is to quantify both the linear and the non-linear information transfer in terms of closed form analytical expressions. Whereas the cut-off frequency set by the linear transfer can be directly related with the attainable resolution, information from the non-linear transfer can only be extracted using quantitative, model-based methods. In contrast to the historic definition of the information limit depending on microscope parameters only, the expressions derived in this paper explicitly incorporate their dependence on the structure parameters as well. In order to emphasize this dependence and to distinguish from the usual information limit, the expressions derived for the inverse cut-off frequencies will be referred to as the linear and non-linear structural information limit. The present findings confirm the well-known result that partial temporal coherence has

  18. Electronic repository and standardization of processes and electronic documents in transport

    Directory of Open Access Journals (Sweden)

    Tomasz DĘBICKI

    2007-01-01

    Full Text Available The article refers to the idea of the use of electronic repository to store standardised scheme of processes between a Logistics Service Provider and its business partners. Application of repository for automatic or semi-automatic configuration of interoperability in electronic data interchange between information systems of differentcompanies based on transport (road, rail, sea and combined related processes. Standardisation includes processes, scheme of cooperation and related to them, electronic messages.

  19. Electron collision cross sections and transport parameters in Cl2

    International Nuclear Information System (INIS)

    Pinhao, N.; Chouki, A.

    1995-01-01

    Molecular chlorine, Cl 2 , is a widely used gas with important application in gas discharge physics, namely in plasma etching, UV lasers and gas-filled particle detectors. However, due to experimental difficulties and to a complicated electronic spectrum, only some of the electron collision cross section have been measured and only recently the electronic structure has been resolved. This situation hampered the theoretical analysis of chlorine mixtures by a lack of relevant transport parameters. To our best knowledge there is only one published measurement of electron drift velocity and characteristic energy. Regrettably these data are considered of doubtful quality. There is also only one measurement of attachment and ionisation coefficients and one published set of cross sections. However those authors used the transport data from a He-Cl 2 mixture (80/20) where chlorine's effect can be hidden by the other component. Consequently that set is not completely consistent with the measurements in pure chlorine. This paper presents a new proposal of a consistent set of electron collision cross sections and the corresponding transport parameters and collision frequencies

  20. Power electronics for renewable energy systems, transportation and industrial applications

    CERN Document Server

    Malinowski, Mariusz; Al-Haddad, Kamal

    2014-01-01

    Power Electronics for Renewable Energy, Transportation, and Industrial Applications combines state-of-the-art global expertise to present the latest research on power electronics and its application in transportation, renewable energy, and different industrial applications. This timely book aims to facilitate the implementation of cutting-edge techniques to design problems offering innovative solutions to the growing power demands in small- and large-size industries. Application areas in the book range from smart homes and electric and plug-in hybrid electrical vehicles (PHEVs), to smart distribution and intelligence operation centers where significant energy efficiency improvements can be achieved through the appropriate use and design of power electronics and energy storage devices.

  1. Ion-acoustic nonlinear periodic waves in electron-positron-ion plasma

    International Nuclear Information System (INIS)

    Chawla, J. K.; Mishra, M. K.

    2010-01-01

    Ion-acoustic nonlinear periodic waves, namely, ion-acoustic cnoidal waves have been studied in electron-positron-ion plasma. Using reductive perturbation method and appropriate boundary condition for nonlinear periodic waves, the Korteweg-de Vries (KdV) equation is derived for the system. The cnoidal wave solution of the KdV equation is discussed in detail. It is found that the frequency of the cnoidal wave is a function of its amplitude. It is also found that the positron concentration modifies the properties of the ion-acoustic cnoidal waves. The existence regions for ion-acoustic cnoidal wave in the parameters space (p,σ), where p and σ are the positron concentration and temperature ratio of electron to positron, are discussed in detail. In the limiting case these ion-acoustic cnoidal waves reduce to the ion-acoustic soliton solutions. The effect of other parameters on the characteristics of the nonlinear periodic waves is also discussed.

  2. Nonlinear bound on unstable field energy in relativistic electron beams and plasmas

    International Nuclear Information System (INIS)

    Davidson, R.C.; Yoon, P.H.

    1989-01-01

    This paper makes use of Fowler's method [J. Math Phys. 4, 559 (1963)] to determine the nonlinear thermodynamic bound on field energy in unstable plasmas or electron beams in which the electrons are relativistic. Treating the electrons as the only active plasma component, the nonlinear Vlasov--Maxwell equations and the associated global conservation constraints are used to calculate the lowest upper bound on the field energy [ΔE-script/sub F/]/sub max/ that can evolve for the general initial electron distribution function f/sub b//sub / 0 equivalentf/sub b/(x,p,0). The results are applied to three choices of the initial distribution function f/sub b//sub / 0 . Two of the distribution functions have an inverted population in momentum p/sub perpendicular/ perpendicular to the magnetic field B 0 e/sub z/, and the third distribution function reduces to a bi-Maxwellian in the nonrelativistic limit. The lowest upper bound on the efficiency of radiation generation, eta/sub max/ = [ΔE-script/sub F/]/sub max//[V -1 ∫ d 3 x∫ d 3 p(γ-1)mc 2 f/sub b//sub / 0 ], is calculated numerically over a wide range of system parameters for varying degrees of initial anisotropy

  3. Nonlinear electrostatic excitations in magnetized dense plasmas with nonrelativistic and ultra-relativistic degenerate electrons

    International Nuclear Information System (INIS)

    Mahmood, S.; Sadiq, Safeer; Haque, Q.

    2013-01-01

    Linear and nonlinear electrostatic waves in magnetized dense electron-ion plasmas are studied with nonrelativistic and ultra-relativistic degenerate and singly, doubly charged helium (He + , He ++ ) and hydrogen (H + ) ions, respectively. The dispersion relation of electrostatic waves in magnetized dense plasmas is obtained under both the energy limits of degenerate electrons. Using reductive perturbation method, the Zakharov-Kuznetsov equation for nonlinear propagation of electrostatic solitons in magnetized dense plasmas is derived for both nonrelativistic and ultra-relativistic degenerate electrons. It is found that variations in plasma density, magnetic field intensity, different mass, and charge number of ions play significant role in the formation of electrostatic solitons in magnetized dense plasmas. The numerical plots are also presented for illustration using the parameters of dense astrophysical plasma situations such as white dwarfs and neutron stars exist in the literature. The present investigation is important for understanding the electrostatic waves propagation in the outer periphery of compact stars which mostly consists of hydrogen and helium ions with degenerate electrons in dense magnetized plasmas

  4. Electron heat transport analysis of low-collisionality plasmas in the neoclassical-transport-optimized configuration of LHD

    International Nuclear Information System (INIS)

    Murakami, Sadayoshi; Yamada, Hiroshi; Wakasa, Arimitsu

    2002-01-01

    Electron heat transport in low-collisionality LHD plasma is investigated in order to study the neoclassical transport optimization effect on thermal plasma transport with an optimization level typical of so-called ''advanced stellarators''. In the central region, a higher electron temperature is obtained in the optimized configuration, and transport analysis suggests the considerable effect of neoclassical transport on the electron heat transport assuming the ion-root level of radial electric field. The obtained experimental results support future reactor design in which the neoclassical and/or anomalous transports are reduced by magnetic field optimization in a non-axisymmetric configuration. (author)

  5. Nonlinear ionization of many-electron systems over a broad photon-energy range

    International Nuclear Information System (INIS)

    Karamatskou, Antonia

    2015-11-01

    Rapid developments in laser technology and, in particular, the advances in the realm of free-electron lasers have initiated tremendous progress in both theoretical and experimental atomic, molecular and optical physics. Owing to high intensities in combination with short pulse durations we can enter the utterly nonlinear regime of light-matter interaction and study the dynamics and features of matter under extreme conditions. The capabilities of X-ray free-electron laser sources have promoted the importance of nonlinear optics also in the X-ray regime. I show in my thesis how we can exploit the nonlinear response regime to reveal hidden information about resonance structures that are not resolved in the weak-field regime. This prospect points to many applications for future investigations of various complex systems with free-electron lasers. In the present thesis the interaction of atomic closed-shell systems with ultrashort and strong laser pulses is investigated. Over a broad photon-energy range the characteristics of the atomic shell are studied with a particular focus on the nonlinear response regime and on electron correlation effects. Several computational extensions of the XCID package for multi-electron dynamics are presented and their applications in various studies are demonstrated; a completely new capability of the numerical method is realized by implementing the calculation of photoelectron spectra and by calculating eigenstates of the many-electron Hamiltonian. The field of study within the present work encompasses (1) the strong-field regime, where the question of the adiabatic character in tunneling ionization is discussed and analyzed, especially for the case of few-cycle pulses; (2) the XUV regime, in which we show for the first time that the collectivity in resonant excitation reveals new information; and (3) the (hard) x-ray regime, which is highly relevant for x-ray free-electron laser experiments, and where we show how important two

  6. Experimental study on nonlinear vibrating of aluminum foam using electronic speckle pattern interferometry

    Science.gov (United States)

    Yang, Fujun; Ma, Yinhang; Tao, Nan; He, Xiaoyuan

    2017-06-01

    Due to its multi properties, including excellent stiffness-to-weight and strength-to-weight ratios, closed-cell aluminum and its alloy foams become candidate materials for use in many high-technology industries, such as the automotive and aerospace industries. For the efficient use of closed-cell foams in structural applications, it is necessary and important to detailly understand their mechanical characteristics. In this paper, the nonlinear vibration responses of the cantilever beams of closed-cell aluminum foams were investigated by use of electronic speckle pattern interferometry (ESPI). The nonlinear resonant mode shapes of testing specimens under harmonic excitation were measured. It is first time to obtain from the experimental results that there exist super-harmonic responses when the cantilever beams of closed-cell aluminum foam were forced to vibrate, which was caused by its specific cellular structures.

  7. Hybrid transport and diffusion modeling using electron thermal transport Monte Carlo SNB in DRACO

    Science.gov (United States)

    Chenhall, Jeffrey; Moses, Gregory

    2017-10-01

    The iSNB (implicit Schurtz Nicolai Busquet) multigroup diffusion electron thermal transport method is adapted into an Electron Thermal Transport Monte Carlo (ETTMC) transport method to better model angular and long mean free path non-local effects. Previously, the ETTMC model had been implemented in the 2D DRACO multiphysics code and found to produce consistent results with the iSNB method. Current work is focused on a hybridization of the computationally slower but higher fidelity ETTMC transport method with the computationally faster iSNB diffusion method in order to maximize computational efficiency. Furthermore, effects on the energy distribution of the heat flux divergence are studied. Work to date on the hybrid method will be presented. This work was supported by Sandia National Laboratories and the Univ. of Rochester Laboratory for Laser Energetics.

  8. Modelling of electron transport and of sawtooth activity in tokamaks

    International Nuclear Information System (INIS)

    Angioni, C.

    2001-10-01

    Transport phenomena in tokamak plasmas strongly limit the particle and energy confinement and represent a crucial obstacle to controlled thermonuclear fusion. Within the vast framework of transport studies, three topics have been tackled in the present thesis: first, the computation of neoclassical transport coefficients for general axisymmetric equilibria and arbitrary collisionality regime; second, the analysis of the electron temperature behaviour and transport modelling of plasma discharges in the Tokamak a configuration Variable (TCV); third, the modelling and simulation of the sawtooth activity with different plasma heating conditions. The work dedicated to neoclassical theory has been undertaken in order to first analytically identify a set of equations suited for implementation in existing Fokker-Planck codes. Modifications of these codes enabled us to compute the neoclassical transport coefficients considering different realistic magnetic equilibrium configurations and covering a large range of variation of three key parameters: aspect ratio, collisionality, and effective charge number. A comparison of the numerical results with an analytical limit has permitted the identification of two expressions for the trapped particle fraction, capable of encapsulating the geometrical effects and thus enabling each transport coefficient to be fitted with a single analytical function. This has allowed us to provide simple analytical formulae for all the neoclassical transport coefficients valid for arbitrary aspect ratio and collisionality in general realistic geometry. This work is particularly useful for a correct evaluation of the neoclassical contribution in tokamak scenarios with large bootstrap cur- rent fraction, or improved confinement regimes with low anomalous transport and for the determination of the plasma current density profile, since the plasma conductivity is usually assumed neoclassical. These results have been included in the plasma transport code

  9. Chord-based versus voxel-based methods of electron transport in the skeletal tissues

    International Nuclear Information System (INIS)

    Shah, Amish P.; Jokisch, Derek W.; Rajon, Didier A.; Watchman, Christopher J.; Patton, Phillip W.; Bolch, Wesley E.

    2005-01-01

    Anatomic models needed for internal dose assessment have traditionally been developed using mathematical surface equations to define organ boundaries, shapes, and their positions within the body. Many researchers, however, are now advocating the use of tomographic models created from segmented patient computed tomography (CT) or magnetic resonance (MR) scans. In the skeleton, however, the tissue structures of the bone trabeculae, marrow cavities, and endosteal layer are exceedingly small and of complex shape, and thus do not lend themselves easily to either stylistic representations or in-vivo CT imaging. Historically, the problem of modeling the skeletal tissues has been addressed through the development of chord-based methods of radiation particle transport, as given by studies at the University of Leeds (Leeds, UK) using a 44-year male subject. We have proposed an alternative approach to skeletal dosimetry in which excised sections of marrow-intact cadaver spongiosa are imaged directly via microCT scanning. The cadaver selected for initial investigation of this technique was a 66-year male subject of nominal body mass index (22.7 kg m -2 ). The objectives of the present study were to compare chord-based versus voxel-based methods of skeletal dosimetry using data from the UF 66-year male subject. Good agreement between chord-based and voxel-based transport was noted for marrow irradiation by either bone surface or bone volume sources up to 500-1000 keV (depending upon the skeletal site). In contrast, chord-based models of electron transport yielded consistently lower values of the self-absorbed fraction to marrow tissues than seen under voxel-based transport at energies above 100 keV, a feature directly attributed to the inability of chord-based models to account for nonlinear electron trajectories. Significant differences were also noted in the dosimetry of the endosteal layer (for all source tissues), with chord-based transport predicting a higher fraction of

  10. Symmetries in Hall-like systems: microwave and nonlinear transport effects

    International Nuclear Information System (INIS)

    Torres, Manuel; Kunold, Alejandro

    2008-01-01

    In this work, we present a model to describe the nonlinear response to a dc electrical current of a two-dimensional electron system subjected to magnetic and microwave fields. Considering the separation of the electron coordinates into the non-commuting relative and guiding center coordinates, we obtain a unitary transformation that exactly solves the time-dependent Schroedinger equation in the presence of arbitrarily strong electric, magnetic and microwave fields. Based on this formalism, we provide a Kubo-like formula that takes into account the oscillatory Floquet structure of the problem. We discuss results related to the recently discovered zero-resistance states and to the microwave-induced resistivity oscillations and the Hall-induced resistivity oscillations

  11. Electron and ion beam transport to fusion targets

    International Nuclear Information System (INIS)

    Freeman, J.R.; Baker, L.; Miller, P.A.; Mix, L.P.; Olsen, J.N.; Poukey, J.W.; Wright, T.P.

    1979-01-01

    ICF reactors have been proposed which incorporate a gas-filled chamber to reduce x-ray and debris loading of the first wall. Focused beams of either electrons or ions must be transported efficiently for 2-4 m to a centrally located fusion target. Laser-initiated current-carrying plasma discharge channels provide the guiding magnetic field and the charge- and current-neutralizing medium required for beam propagation. Computational studies of plasma channel formation in air using a 1-D MHD model with multigroup radiation diffusion have provided a good comparison with the expansions velocity and time dependent refractivity profile determined by holographic interferometry. Trajectory calculations have identified a beam expansion mechanism which combines with the usual ohmic dissipation to reduce somewhat the transported beam fluence for electrons. Additional trajectory calculations have been performed for both electrons and light ions to predict the limits on the particle current density which can be delivered to a central target by overlapping the many independently-generated beams. Critical features of the use of plasma channels for transport and overlap of charged particle beams are being tested experimentally with up to twelve electron beams from the Proto II accelerator

  12. Vibronic coupling effect on the electron transport through molecules

    Science.gov (United States)

    Tsukada, Masaru; Mitsutake, Kunihiro

    2007-03-01

    Electron transport through molecular bridges or molecular layers connected to nano-electrodes is determined by the combination of coherent and dissipative processes, controlled by the electron-vibron coupling, transfer integrals between the molecular orbitals, applied electric field and temperature. We propose a novel theoretical approach, which combines ab initio molecular orbital method with analytical many-boson model. As a case study, the long chain model of the thiophene oligomer is solved by a variation approach. Mixed states of moderately extended molecular orbital states mediated and localised by dress of vibron cloud are found as eigen-states. All the excited states accompanied by multiple quanta of vibration can be solved, and the overall carrier transport properties including the conductance, mobility, dissipation spectra are analyzed by solving the master equation with the transition rates estimated by the golden rule. We clarify obtained in a uniform systematic way, how the transport mode changes from a dominantly coherent transport to the dissipative hopping transport.

  13. Nonlinear interaction of photons and phonons in electron-positron plasmas

    International Nuclear Information System (INIS)

    Tajima, T.; Taniuti, T.

    1990-03-01

    Nonlinear interaction of electromagnetic waves and acoustic modes in an electron-positron plasma is investigated. The plasma of electrons and positrons is quite plastic so that the imposition of electromagnetic (EM) waves causes depression of the plasma and other structural imprints on it through either the nonresonant or resonant interaction. Our theory shows that the nonresonant interaction can lead to the coalescence of photons and collapse of plasma cavity in higher (≥ 2) dimensions. The resonant interaction, in which the group velocity of EM waves is equal to the phase velocity of acoustic waves, is analyzed and a set of basic equations of the system is derived via the reductive perturbation theory. We find new solutions of solitary types: bright solitons, kink solitons, and dark solitons as the solutions to these equations. Our computation hints their stability. An impact of the present theory on astrophysical plasma settings is expected, including the cosmological relativistically hot electron-positron plasma. 20 refs., 9 figs

  14. Electron thermal effect on linear and nonlinear coupled Shukla-Varma and convective cell modes in dust-contaminated magnetoplasma

    Science.gov (United States)

    Masood, W.; Mirza, Arshad M.

    2010-11-01

    Linear and nonlinear properties of coupled Shukla-Varma (SV) and convective cell modes in the presence of electron thermal effects are studied in a nonuniform magnetoplasma composed of electrons, ions, and extremely massive and negatively charged immobile dust grains. In the linear case, the modified dispersion relation is given and, in the nonlinear case, stationary solutions of the nonlinear equations that govern the dynamics of coupled SV and convective cell modes are obtained. It is found that electrostatic dipolar and vortex street type solutions can appear in such a plasma. The relevance of the present investigation with regard to the Earth's mesosphere as well as in ionospheric plasmas is also pointed out.

  15. Electron thermal effect on linear and nonlinear coupled Shukla-Varma and convective cell modes in dust-contaminated magnetoplasma

    International Nuclear Information System (INIS)

    Masood, W.; Mirza, Arshad M.

    2010-01-01

    Linear and nonlinear properties of coupled Shukla-Varma (SV) and convective cell modes in the presence of electron thermal effects are studied in a nonuniform magnetoplasma composed of electrons, ions, and extremely massive and negatively charged immobile dust grains. In the linear case, the modified dispersion relation is given and, in the nonlinear case, stationary solutions of the nonlinear equations that govern the dynamics of coupled SV and convective cell modes are obtained. It is found that electrostatic dipolar and vortex street type solutions can appear in such a plasma. The relevance of the present investigation with regard to the Earth's mesosphere as well as in ionospheric plasmas is also pointed out.

  16. Comparison of the effect of annular and solid electron beams on linear and nonlinear traveling wave tube

    Directory of Open Access Journals (Sweden)

    F. Sheykhe

    Full Text Available The present paper, compares the effect of the annular and solid electron beam on the efficiency of linear and nonlinear TWTs. To do this, first we introduce four different geometric structure of the beam-helix. Then, we calculate the output power of each structure, in linear and nonlinear modes, at different frequencies using the numerical solution of the mathematical equations of the multi-frequency Eulerian model. Now, plot the output power in terms of distance for each structure at different frequencies and compare them. In a linear tube, the effect of annular beams on the output power is better than the solid beam, while this affects the frequency in nonlinear tubes. It is shown that in linear regime the power increase linearly with frequency but for nonlinear regimes is nonlinear. Keywords: Annular beam, Solid beam, Circuit power, Nonlinear, Traveling wave tube, Helix

  17. The nonlinear theory of slow-wave electron cyclotron masers with inclusion of the beam velocity spread

    International Nuclear Information System (INIS)

    Kong, Ling-Bao; Wang, Hong-Yu; Hou, Zhi-Ling; Jin, Hai-Bo; Du, Chao-Hai

    2013-01-01

    The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency. -- Highlights: •The theory of slow-wave electron cyclotron masers is considered. •The calculation of efficiency under the resonance condition is presented. •The efficiency under Gaussian velocity spreads has been obtained

  18. The nonlinear theory of slow-wave electron cyclotron masers with inclusion of the beam velocity spread

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Ling-Bao, E-mail: konglingbao@gmail.com [School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Key Laboratory of Environmentally Harmful Chemicals Assessment, Beijing University of Chemical Technology, Beijing 100029 (China); Wang, Hong-Yu [School of Physics, Anshan Normal University, Anshan 114005 (China); Hou, Zhi-Ling, E-mail: houzl@mail.buct.edu.cn [School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Key Laboratory of Environmentally Harmful Chemicals Assessment, Beijing University of Chemical Technology, Beijing 100029 (China); Jin, Hai-Bo [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Du, Chao-Hai [Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

    2013-12-15

    The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency. -- Highlights: •The theory of slow-wave electron cyclotron masers is considered. •The calculation of efficiency under the resonance condition is presented. •The efficiency under Gaussian velocity spreads has been obtained.

  19. Semiclassical electronic transport in MnAs thin films

    International Nuclear Information System (INIS)

    Helman, C.; Milano, J.; Steren, L.; Llois, A.M.

    2008-01-01

    Magneto-transport experiments have been recently performed on MnAs thin films. Hall effect and transverse magnetoresistance measurements have shown interesting and, until now, unknown results. For instance, the transverse magnetoresistance shows no saturation in the presence of very high magnetic fields. In order to understand the contribution of the electronic band structure to the non-saturating magnetoresistance, we perform ab initio calculations, using the Wien2K code and analyze the magneto-transport properties within the semiclassical approximation. We show that non-saturation may be due to the presence of open orbits on the majority Fermi surface

  20. Semiclassical electronic transport in MnAs thin films

    Energy Technology Data Exchange (ETDEWEB)

    Helman, C. [Dpto de Fisica, ' Juan Jose Giambiagi' , Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Unidad de Actividad Fisica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Buenos Aires (Argentina)], E-mail: helman@tandar.cnea.gov.ar; Milano, J.; Steren, L. [Departamento de Fisica, Centro Atomico Bariloche, Comision Nacional de Energia Atomica, S.C. Bariloche (Argentina); Llois, A.M. [Dpto de Fisica, ' Juan Jose Giambiagi' , Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Unidad de Actividad Fisica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica, Buenos Aires (Argentina)

    2008-07-15

    Magneto-transport experiments have been recently performed on MnAs thin films. Hall effect and transverse magnetoresistance measurements have shown interesting and, until now, unknown results. For instance, the transverse magnetoresistance shows no saturation in the presence of very high magnetic fields. In order to understand the contribution of the electronic band structure to the non-saturating magnetoresistance, we perform ab initio calculations, using the Wien2K code and analyze the magneto-transport properties within the semiclassical approximation. We show that non-saturation may be due to the presence of open orbits on the majority Fermi surface.

  1. Discrete Diffusion Monte Carlo for Electron Thermal Transport

    Science.gov (United States)

    Chenhall, Jeffrey; Cao, Duc; Wollaeger, Ryan; Moses, Gregory

    2014-10-01

    The iSNB (implicit Schurtz Nicolai Busquet electron thermal transport method of Cao et al. is adapted to a Discrete Diffusion Monte Carlo (DDMC) solution method for eventual inclusion in a hybrid IMC-DDMC (Implicit Monte Carlo) method. The hybrid method will combine the efficiency of a diffusion method in short mean free path regions with the accuracy of a transport method in long mean free path regions. The Monte Carlo nature of the approach allows the algorithm to be massively parallelized. Work to date on the iSNB-DDMC method will be presented. This work was supported by Sandia National Laboratory - Albuquerque.

  2. Electronic transport behavior of diameter-graded Ag nanowires

    International Nuclear Information System (INIS)

    Wang Xuewei; Yuan Zhihao

    2010-01-01

    Ag nanowires with a graded diameter in anodic aluminum oxide (AAO) membranes were fabricated by the direct-current electrodeposition. The Ag nanowires have a graded-change in diameter from 8 to 32 nm, which is matched with the graded-change of the AAO pore diameter. Electronic transport measurements show that there is a transport behavior similar to that of a metal-semiconductor junction along the axial direction in the diameter-graded Ag nanowires. Such a novel homogeneous nanojunction will be of great fundamental and practical significance.

  3. Electronic transport behavior of diameter-graded Ag nanowires

    Science.gov (United States)

    Wang, Xue Wei; Yuan, Zhi Hao

    2010-05-01

    Ag nanowires with a graded diameter in anodic aluminum oxide (AAO) membranes were fabricated by the direct-current electrodeposition. The Ag nanowires have a graded-change in diameter from 8 to 32 nm, which is matched with the graded-change of the AAO pore diameter. Electronic transport measurements show that there is a transport behavior similar to that of a metal-semiconductor junction along the axial direction in the diameter-graded Ag nanowires. Such a novel homogeneous nanojunction will be of great fundamental and practical significance.

  4. Anomalous plasma transport due to electron temperature gradient instability

    International Nuclear Information System (INIS)

    Tokuda, Sinji; Ito, Hiroshi; Kamimura, Tetsuo.

    1979-01-01

    The collisionless drift wave instability driven by an electron temperature inhomogeneity (electron temperature gradient instability) and the enhanced transport processes associated with it are studied using a two-and-a-half dimensional particle simulation code. The simulation results show that quasilinear diffusion in phase space is an important mechanism for the saturation of the electron temperature gradient instability. Also, the instability yields particle fluxes toward the hot plasma regions. The heat conductivity of the electron temperature perpendicular to the magnetic field, T sub(e'), is not reduced by magnetic shear but remains high, whereas the heat conductivity of the parallel temperature, T sub(e''), is effectively reduced, and the instability stabilized. (author)

  5. Transition phenomena and thermal transport property in LHD plasmas with an electron internal transport barrier

    International Nuclear Information System (INIS)

    Shimozuma, T.; Kubo, S.; Idei, H.

    2005-01-01

    Two kinds of improved core confinement were observed during centrally focused Electron Cyclotron Heating (ECH) into plasmas sustained by Counter (CNTR) and Co Neutral Beam Injections (NBI) in the Large Helical Device (LHD). One shows transition phenomena to the high-electron-temperature state and has a clear electron Internal Transport Barrier (eITB) in CNTR NBI plasma. Another has no clear transition and no ECH power threshold, but shows a broad high temperature profiles with moderate temperature gradient, which indicates the improved core confinement with additional ECH in Co NBI plasma. The electron heat transport characteristics of these plasmas were directly investigated by using the heat pulse propagation excited by Modulated ECH (MECH). The difference of the features could be caused by the existence of the m/n=2/1 rational surface or island determined by the direction of NBI beam-driven current. (author)

  6. Transition phenomena and thermal transport properties in LHD plasmas with an electron internal transport barrier

    International Nuclear Information System (INIS)

    Shimozuma, T.; Kubo, S.; Idei, H.; Inagaki, S.; Tamura, N.; Tokuzawa, T.; Morisaki, T.; Watanabe, K.Y.; Ida, K.; Yamada, I.; Narihara, K.; Muto, S.; Yokoyama, M.; Yoshimura, Y.; Notake, T.; Ohkubo, K.; Seki, T.; Saito, K.; Kumazawa, R.; Mutoh, T.; Watari, T.; Komori, A.

    2005-01-01

    Two types of improved core confinement were observed during centrally focused electron cyclotron heating (ECH) into plasmas sustained by counter (CNTR) and Co neutral beam injections (NBI) in the Large Helical Device. The CNTR NBI plasma displayed transition phenomena to the high-electron-temperature state and had a clear electron internal transport barrier, while the Co NBI plasma did not show a clear transition or an ECH power threshold but showed broad high temperature profiles with moderate temperature gradient. This indicated that the Co NBI plasma with additional ECH also had an improved core confinement. The electron heat transport characteristics of these plasmas were directly investigated using heat pulse propagation excited by modulated ECH. These effects appear to be related to the m/n = 2/1 rational surface or the island induced by NBI beam-driven current

  7. Electron density measurements during ion beam transport on Gamble II

    International Nuclear Information System (INIS)

    Weber, B.V.; Hinshelwood, D.D.; Neri, J.M.; Ottinger, P.F.; Rose, D.V.; Stephanakis, S.J.; Young, F.C.

    1999-01-01

    High-sensitivity laser interferometry was used to measure the electron density created when an intense proton beam (100 kA, 1 MeV, 50 ns) from the Gamble II generator was transported through low-pressure gas as part of a project investigating Self-Pinched Transport (SPT) of intense ion beams. This measurement is non-perturbing and sufficiently quantitative to allow benchmarking of codes (particularly IPROP) used to model beam-gas interaction and ion-beam transport. Very high phase sensitivity is required for this measurement. For example, a 100-kA, 1-MeV, 10-cm-radius proton beam with uniform current density has a line-integrated proton density equal to n b L = 3 x 10 13 cm -2 . An equal electron line-density, n e L = n b L, (expected for transport in vacuum) will be detected as a phase shift of the 1.064 microm laser beam of only 0.05degree, or an optical path change of 1.4 x 10 -4 waves (about the size of a hydrogen atom). The time-history of the line-integrated electron density, measured across a diameter of the transport chamber at 43 cm from the input aperture, starts with the proton arrival time and decays differently depending on the gas pressure. The gas conditions included vacuum (10 -4 Torr air), 30 to 220 mTorr He, and 1 Torr air. The measured densities vary by three orders of magnitude, from 10 13 to 10 16 cm -2 for the range of gas pressures investigated. In vacuum, the measured electron densities indicate only co-moving electrons (n e L approximately n b L). In He, when the gas pressure is sufficient for ionization by beam particles and SPT is observed, n e L increases to about 10 n b L. At even higher pressures where electrons contribute to ionization, even higher electron densities are observed with an ionization fraction of about 2%. The diagnostic technique as used on the SPT experiment will be described and a summary of the results will be given. The measurements are in reasonable agreement with theoretical predictions from the IPROP code

  8. Fabrication and electronic transport studies of single nanocrystal systems

    Energy Technology Data Exchange (ETDEWEB)

    Klein, David Louis [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01

    Semiconductor and metallic nanocrystals exhibit interesting electronic transport behavior as a result of electrostatic and quantum mechanical confinement effects. These effects can be studied to learn about the nature of electronic states in these systems. This thesis describes several techniques for the electronic study of nanocrystals. The primary focus is the development of novel methods to attach leads to prefabricated nanocrystals. This is because, while nanocrystals can be readily synthesized from a variety of materials with excellent size control, means to make electrical contact to these nanocrystals are limited. The first approach that will be described uses scanning probe microscopy to first image and then electrically probe surfaces. It is found that electronic investigations of nanocrystals by this technique are complicated by tip-sample interactions and environmental factors such as salvation and capillary forces. Next, an atomic force microscope technique for the catalytic patterning of the surface of a self assembled monolayer is described. In principle, this nano-fabrication technique can be used to create electronic devices which are based upon complex arrangements of nanocrystals. Finally, the fabrication and electrical characterization of a nanocrystal-based single electron transistor is presented. This device is fabricated using a hybrid scheme which combines electron beam lithography and wet chemistry to bind single nanocrystals in tunneling contact between closely spaced metallic leads. In these devices, both Au and CdSe nanocrystals show Coulomb blockade effects with characteristic energies of several tens of meV. Additional structure is seen the transport behavior of CdSe nanocrystals as a result of its electronic structure.

  9. Transport of a nonneutral electron plasma due to electron collisions with neutral atoms

    International Nuclear Information System (INIS)

    Douglas, M.H.; O'Neil, T.M.

    1978-01-01

    Transport of a nonneutral electron plasma across a magnetic field is caused by electron scattering from ambient neutral atoms. A theoretical model of such transport is presented, assuming the plasma is quiescent and the scattering is elastic scattering from infinite mass scattering centers of constant momentum transfer cross section. This model is motivated by recent experiments. A reduced transport equation is obtained by expanding the Boltzmann equation for the electron distribution in inverse powers of the magnetic field. The equation together with Poisson's equation for the radial electric field, which must exist in a nonneutral column, determine the evolution of the system. When these two equations are properly scaled, they contain only a single parameter: the ratio of initial Debye length to initial column radius. For cases where this parameter is either large or small, analytical solutions, or at least partial solutions, are obtained. For intermediate values of the parameter, numerical solutions are obtained

  10. Experimental study of fast electron transport in dense plasmas

    International Nuclear Information System (INIS)

    Vaisseau, Xavier

    2014-01-01

    The framework of this PhD thesis is the inertial confinement fusion for energy production, in the context of the electron fast ignition scheme. The work consists in a characterization of the transport mechanisms of fast electrons, driven by intense laser pulses (10 19 - 10 20 W/cm 2 ) in both cold-solid and warm-dense matter. The first goal was to study the propagation of a fast electron beam, characterized by a current density ≥ 10 11 A/cm 2 , in aluminum targets initially heated close to the Fermi temperature by a counter-propagative planar shock. The planar compression geometry allowed us to discriminate the energy losses due to the resistive mechanisms from collisional ones by comparing solid and compressed targets of the same initial areal densities. We observed for the first time a significant increase of resistive energy losses in heated aluminum samples. The confrontation of the experimental data with the simulations, including a complete characterization of the electron source, of the target compression and of the fast electron transport, allowed us to study the time-evolution of the material resistivity. The estimated resistive electron stopping power in a warm-compressed target is of the same order as the collisional one. We studied the transport of the fast electrons generated in the interaction of a high-contrast laser pulse with a hollow copper cone, buried into a carbon layer, compressed by a counter-propagative planar shock. A X-ray imaging system allowed us to visualize the coupling of the laser pulse with the cone at different moments of the compression. This diagnostic, giving access to the fast electron spatial distribution, showed a fast electron generation in the entire volume of the cone for late times of compression, after shock breakout from the inner cone tip. For earlier times, the interaction at a high-contrast ensured that the source was contained within the cone tip, and the fast electron beam was collimated into the target depth by

  11. Effect of nonlinear wave-particle interaction on electron-cyclotron absorption

    Energy Technology Data Exchange (ETDEWEB)

    Tsironis, C; Vlahos, L [Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2006-09-15

    We perform a self-consistent analysis of the nonlinear interaction of magnetized plasmas with electron-cyclotron (EC) waves. A closed set of equations is derived, which consists of the relativistic equations of motion under the wave field and the wave equation for the vector potential. The plasma is described in terms of ensembles of electrons which collectively determine the evolution of the wave amplitude and frequency through the current response. This description allows for effects of the electron motions on the efficiency of the wave absorption, for example, the asynchrony between the wave phase and the gyroperiod. As an application, we study the absorption of an EC wave beam in a simplified tokamak geometry, for plasma parameters relevant to current and future fusion experiments. We conclude that, within the limits of our model, there are cases where the linear theory for the absorption of EC waves, used widely in the current literature, may overestimate the energy deposition. In such cases, nonlinear effects are essential for the accurate estimation of the plasma-wave coupling and their inclusion should be considered, especially when the wave power is dramatically increased as in the case of ITER.

  12. Effect of nonlinear wave-particle interaction on electron-cyclotron absorption

    International Nuclear Information System (INIS)

    Tsironis, C; Vlahos, L

    2006-01-01

    We perform a self-consistent analysis of the nonlinear interaction of magnetized plasmas with electron-cyclotron (EC) waves. A closed set of equations is derived, which consists of the relativistic equations of motion under the wave field and the wave equation for the vector potential. The plasma is described in terms of ensembles of electrons which collectively determine the evolution of the wave amplitude and frequency through the current response. This description allows for effects of the electron motions on the efficiency of the wave absorption, for example, the asynchrony between the wave phase and the gyroperiod. As an application, we study the absorption of an EC wave beam in a simplified tokamak geometry, for plasma parameters relevant to current and future fusion experiments. We conclude that, within the limits of our model, there are cases where the linear theory for the absorption of EC waves, used widely in the current literature, may overestimate the energy deposition. In such cases, nonlinear effects are essential for the accurate estimation of the plasma-wave coupling and their inclusion should be considered, especially when the wave power is dramatically increased as in the case of ITER

  13. A self-consistent nonlinear theory of resistive-wall instability in a relativistic electron beam

    International Nuclear Information System (INIS)

    Uhm, H.S.

    1994-01-01

    A self-consistent nonlinear theory of resistive-wall instability is developed for a relativistic electron beam propagating through a grounded cylindrical resistive tube. The theory is based on the assumption that the frequency of the resistive-wall instability is lower than the cutoff frequency of the waveguide. The theory is concentrated on study of the beam current modulation directly related to the resistive-wall klystron, in which a relativistic electron beam is modulated at the first cavity and propagates downstream through the resistive wall. Because of the self-excitation of the space charge waves by the resistive-wall instability, a highly nonlinear current modulation of the electron beam is accomplished as the beam propagates downstream. A partial integrodifferential equation is obtained in terms of the initial energy modulation (ε), the self-field effects (h), and the resistive-wall effects (κ). Analytically investigating the partial integrodifferential equation, a scaling law of the propagation distance z m at which the maximum current modulation occurs is obtained. It is found in general that the self-field effects dominate over the resistive-wall effects at the beginning of the propagation. As the beam propagates farther downstream, the resistive-wall effects dominate. Because of a relatively large growth rate of the instability, the required tube length of the klystron is short for most applications

  14. Does menaquinone participate in brain astrocyte electron transport?

    Science.gov (United States)

    Lovern, Douglas; Marbois, Beth

    2013-10-01

    Quinone compounds act as membrane resident carriers of electrons between components of the electron transport chain in the periplasmic space of prokaryotes and in the mitochondria of eukaryotes. Vitamin K is a quinone compound in the human body in a storage form as menaquinone (MK); distribution includes regulated amounts in mitochondrial membranes. The human brain, which has low amounts of typical vitamin K dependent function (e.g., gamma carboxylase) has relatively high levels of MK, and different regions of brain have different amounts. Coenzyme Q (Q), is a quinone synthesized de novo, and the levels of synthesis decline with age. The levels of MK are dependent on dietary intake and generally increase with age. MK has a characterized role in the transfer of electrons to fumarate in prokaryotes. A newly recognized fumarate cycle has been identified in brain astrocytes. The MK precursor menadione has been shown to donate electrons directly to mitochondrial complex III. Vitamin K compounds function in the electron transport chain of human brain astrocytes. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Power electronics applied to industrial systems and transports

    CERN Document Server

    Patin, Nicolas

    2015-01-01

    This book provides a comprehensive overview of power electronic converters (DC / DC, DC / AC, AC / DC and AC / AC) conventionally used in industrial and transportation applications, specifically for the supply of electric machines with variable speed drop off window. From the perspective of design and sizing, this book presents the different functions encountered in a modular way for power electronics.Power Converters and Their Control details less traditional topics such as matrix converters and multilevel converters. This book also features a case study design of an industrial controller, wh

  16. Electron transport in ethanol & methanol absorbed defected graphene

    Science.gov (United States)

    Dandeliya, Sushmita; Srivastava, Anurag

    2018-05-01

    In the present paper, the sensitivity of ethanol and methanol molecules on surface of single vacancy defected graphene has been investigated using density functional theory (DFT). The changes in structural and electronic properties before and after adsorption of ethanol and methanol were analyzed and the obtained results show high adsorption energy and charge transfer. High adsorption happens at the active site with monovacancy defect on graphene surface. Present work confirms that the defected graphene increases the surface reactivity towards ethanol and methanol molecules. The presence of molecules near the active site affects the electronic and transport properties of defected graphene which makes it a promising choice for designing methanol and ethanol sensor.

  17. Power electronics applied to industrial systems and transports

    CERN Document Server

    Patin, Nicolas

    2015-01-01

    Some power electronic converters are specifically designed to power equipment under a smoothed DC voltage. Therefore, the filtering part necessarily involves the use of auxiliary passive components (inductors and capacitors). This book deals with technical aspects such as classical separation between isolated and non-isolated power supplies, and soft switching through a special converter. It addresses the problem of regulating the output voltage of the switching power supplies in terms of modeling and obtaining transfer of SMPS functions.Power Electronics for Industry and Transport, Volume 3,

  18. Electronic transport for armchair graphene nanoribbons with a potential barrier

    International Nuclear Information System (INIS)

    Ben-Hu, Zhou; Ben-Liang, Zhou; Guang-Hui, Zhou; Zi-Gang, Duan

    2010-01-01

    This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon (AGNR). Using the Dirac equation with the continuity condition for wave functions at the interfaces between regions with and without a barrier, we calculate the mode-dependent transmission probability for both semiconducting and metallic AGNRs, respectively. It is shown that, by some numerical examples, the transmission probability is generally an oscillating function of the height and range of the barrier for both types of AGNRs. The main difference between the two types of systems is that the magnitude of oscillation for the semiconducting AGNR is larger than that for the metallic one. This fact implies that the electronic transport property for AGNRs depends sensitively on their widths and edge details due to the Dirac nature of fermions in the system

  19. Electron effects in the Neutralized Transport Experiment (NTX)

    Energy Technology Data Exchange (ETDEWEB)

    Eylon, S. [Lawrence Berkeley National Laboratory (LBNL), MS47R 0112, 1 Cyclotron Road, Berkeley, CA 94720 (United States) and Heavy Ion Fusion Virtual National Laboratory, Cyclotron Road, CA 94720 (United States)]. E-mail: S_Eylon@lbl.gov; Henestroza, E. [Lawrence Berkeley National Laboratory (LBNL), MS47R 0112, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Heavy Ion Fusion Virtual National Laboratory, Cyclotron Road, CA 94720 (United States); Roy, P.K. [Lawrence Berkeley National Laboratory (LBNL), MS47R 0112, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Heavy Ion Fusion Virtual National Laboratory, Cyclotron Road, CA 94720 (United States); Yu, S.S. [Lawrence Berkeley National Laboratory (LBNL), MS47R 0112, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Heavy Ion Fusion Virtual National Laboratory, Cyclotron Road, CA 94720 (United States)

    2005-05-21

    The Neutralized Transport Experiment (NTX) at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high-perveance heavy ion beams. To focus a high-intensity beam to a small spot requires a high-brightness beam. In the NTX experiment, a potassium ion beam of up to 400 keV and 80 mA is generated in a Pierce-type diode. At the diode exit, an aperture with variable opening provides the capability to vary the beam perveance. The beam is transported through four quadrupole magnets to a distance of 2.5 m. The beam can be neutralized and focused using a MEVVA plasma plug and a RF plasma source. We shall report on the measurement of the electron effects and the ways to mitigate the effects. Furthermore, we shall present the results of EGUN calculations consistent with the measurements effects of the electrons.

  20. Electron effects in the Neutralized Transport Experiment (NTX)

    International Nuclear Information System (INIS)

    Eylon, S.; Henestroza, E.; Roy, P.K.; Yu, S.S.

    2005-01-01

    The Neutralized Transport Experiment (NTX) at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high-perveance heavy ion beams. To focus a high-intensity beam to a small spot requires a high-brightness beam. In the NTX experiment, a potassium ion beam of up to 400 keV and 80 mA is generated in a Pierce-type diode. At the diode exit, an aperture with variable opening provides the capability to vary the beam perveance. The beam is transported through four quadrupole magnets to a distance of 2.5 m. The beam can be neutralized and focused using a MEVVA plasma plug and a RF plasma source. We shall report on the measurement of the electron effects and the ways to mitigate the effects. Furthermore, we shall present the results of EGUN calculations consistent with the measurements effects of the electrons

  1. Electron effects in the Neutralized Transport Experiment (NTX)

    Science.gov (United States)

    Eylon, S.; Henestroza, E.; Roy, P. K.; Yu, S. S.

    2005-05-01

    The Neutralized Transport Experiment (NTX) at the Heavy Ion Fusion Virtual National Laboratory is exploring the performance of neutralized final focus systems for high-perveance heavy ion beams. To focus a high-intensity beam to a small spot requires a high-brightness beam. In the NTX experiment, a potassium ion beam of up to 400 keV and 80 mA is generated in a Pierce-type diode. At the diode exit, an aperture with variable opening provides the capability to vary the beam perveance. The beam is transported through four quadrupole magnets to a distance of 2.5 m. The beam can be neutralized and focused using a MEVVA plasma plug and a RF plasma source. We shall report on the measurement of the electron effects and the ways to mitigate the effects. Furthermore, we shall present the results of EGUN calculations consistent with the measurements effects of the electrons.

  2. Nanoscale electron transport at the surface of a topological insulator

    Science.gov (United States)

    Bauer, Sebastian; Bobisch, Christian A.

    2016-04-01

    The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless transport of electrons at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the electronic transport. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role.

  3. Two-point model for electron transport in EBT

    International Nuclear Information System (INIS)

    Chiu, S.C.; Guest, G.E.

    1980-01-01

    The electron transport in EBT is simulated by a two-point model corresponding to the central plasma and the edge. The central plasma is assumed to obey neoclassical collisionless transport. The edge plasma is assumed turbulent and modeled by Bohm diffusion. The steady-state temperatures and densities in both regions are obtained as functions of neutral influx and microwave power. It is found that as the neutral influx decreases and power increases, the edge density decreases while the core density increases. We conclude that if ring instability is responsible for the T-M mode transition, and if stability is correlated with cold electron density at the edge, it will depend sensitively on ambient gas pressure and microwave power

  4. Temperature dependence of electronic transport property in ferroelectric polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, X.L.; Wang, J.L., E-mail: jlwang@mail.sitp.ac.cn; Tian, B.B.; Liu, B.L.; Zou, Y.H.; Wang, X.D.; Sun, S.; Sun, J.L., E-mail: jlsun@mail.sitp.ac.cn; Meng, X.J.; Chu, J.H.

    2014-10-15

    Highlights: • The ferroelectric polymer was fabricated by Langmuir–Blodgett method. • The electrons as the dominant injected carrier were conformed in the ferroelectric polymer films. • The leakage current conduction mechanisms in ferroelectric polymer were investigated. - Abstract: The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir–Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel–Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.

  5. Acceleration of relativistic electrons in plasma reactors and non-linear spectra of cosmic radio sources

    International Nuclear Information System (INIS)

    Kaplan, S.A.; Lomadze, R.D.

    1978-01-01

    A second approximation to the theory of turbulent plasma reactors in connection with the problem of interpretation of the non-linear spectra of cosmic radio sources has been investigated by the authors (Kaplan and Lomadze, 1977; Lomadze, 1977). The present paper discusses the basic results received for a Compton reactor with plasma waves of phase velocities smaller than the velocity of light, as well as for the synchrotron reactor. The distortion of the distribution function of relativistic electrons caused by their diffusion from the reactor is also presented as an example. (Auth.)

  6. Self-consistent nonlinear simulations of high-power free-electron lasers

    International Nuclear Information System (INIS)

    Freund, H.P.; Jackson, R.H.

    1993-01-01

    Two 3-D nonlinear formulations of FEL amplifiers are described which treat both planar and helical wiggler geometries. For convenience, the authors refer to the planar (helical) formulation and simulation code as WIGGLIN (ARACHNE). These formulations are slow-time-scale models for FEL amplifiers in which the electron dynamics are treated using the complete 3-D Lorentz force equations without recourse to a wiggler period average. The application of these codes to the description of a collective reversed-field FEL experiment and to random wiggler field errors is described

  7. Weakly nonlinear electromagnetic waves in an electron-ion positron plasma

    International Nuclear Information System (INIS)

    Rizzato, F.B.; Schneider, R.S.; Dillenburg, D.

    1987-01-01

    The modulation of a high-frequency electromagnetic wave which is circulary polarized and propagates in a plasma made up of electrons, ions and positrons is investigated. The coefficient of the cubic nonlinear term in the Schroedinger equation may change sign as the relative particle concentrations vary, and consequently a marginal state of modulation instability may exist. To described the system in the neighbourhood of this state an appropriate equation is derived. Particular stationary solutions of this equation are envelope solitary waves, envelope Kinks and envelope hole solitary waves. The dependence of the amplitude of the solutions on the propagation velocity and the particle concentrations is discussed. (author) [pt

  8. Nonlinear Ion-Acoustic Waves in a Plasma Consisting of Warm Ions and Isothermal Distributed Electrons

    International Nuclear Information System (INIS)

    Abourabia, A.M.; Hassan, K.M.; Shahein, R.A.

    2008-01-01

    The formation of (1+1) dimensional ion-acoustic waves (IAWs) in an unmagnetized collisionless plasma consisting of warm ions and isothermal distributed electrons is investigated. The electrodynamics system of equations are solved analytically in terms of a new variable ξκ χ -φ τ, where k=k(ω) is a complex function, at a fixed position. The analytical calculations gives that the critical value σ = τ/τ ∼ 0.25 distinguishes between the linear and nonlinear characters of IAW within the nanosecond time scale. The flow velocity, pressure, number density, electric potential, electric field, mobility and the total energy in the system are estimated and illustrated

  9. Internal crisis in a second-order non-linear non-autonomous electronic oscillator

    International Nuclear Information System (INIS)

    Stavrinides, S.G.; Deliolanis, N.C.; Miliou, A.N.; Laopoulos, Th.; Anagnostopoulos, A.N.

    2008-01-01

    The internal crisis of a second-order non-linear non-autonomous chaotic electronic circuit is studied. The phase portraits consist of two interacting sub-attractors, a chaotic and a periodic one. Maximal Lyapunov exponents were calculated, for both the periodic and the chaotic waveforms, in order to confirm their nature. Transitions between the chaotic and the periodic sub-attractors become more frequent by increasing the circuit driving frequency. The frequency distribution of the corresponding laminar lengths and their average values indicate that an internal crisis takes place in this circuit, manifested in the intermittent behaviour of the corresponding orbits

  10. Electron beam induced electronic transport in alkyl amine-intercalated VOx nanotubes

    International Nuclear Information System (INIS)

    O'Dwyer, C.; Lavayen, V.; Clavijo-Cedeno, C.; Torres, C.M.S.

    2008-01-01

    The electron beam induced electronic transport in primary alkyl amine-intercalated V 2 O 5 nanotubes is investigated where the organic amine molecules are employed as molecular conductive wires to an aminosilanized substrate surface and contacted to Au interdigitated electrode contacts. The results demonstrate that the high conductivity of the nanotubes is related to the non-resonant tunnelling through the amine molecules and a reduced polaron hopping conduction through the vanadium oxide itself. Both nanotube networks and individual nanotubes exhibit similarly high conductivities where the minority carrier transport is bias dependent and nanotube diameter invariant. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Stable solutions of nonlocal electron heat transport equations

    International Nuclear Information System (INIS)

    Prasad, M.K.; Kershaw, D.S.

    1991-01-01

    Electron heat transport equations with a nonlocal heat flux are in general ill-posed and intrinsically unstable, as proved by the present authors [Phys. Fluids B 1, 2430 (1989)]. A straightforward numerical solution of these equations will therefore lead to absurd results. It is shown here that by imposing a minimal set of constraints on the problem it is possible to arrive at a globally stable, consistent, and energy conserving numerical solution

  12. Discussion of electron cross sections for transport calculations

    International Nuclear Information System (INIS)

    Berger, M.J.

    1983-01-01

    This paper deals with selected aspects of the cross sections needed as input for transport calculations and for the modeling of radiation effects in biological materials. Attention is centered mainly on the cross sections for inelastic interactions between electrons and water molecules and the use of these cross sections for the calculation of energy degradation spectra and of ionization and excitation yields. 40 references, 3 figures, 1 table

  13. The role of electron-impact vibrational excitation in electron transport through gaseous tetrahydrofuran

    Energy Technology Data Exchange (ETDEWEB)

    Duque, H. V. [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Do, T. P. T. [School of Education, Can Tho University, Campus II, 3/2 Street, Xuan Khanh, Ninh Kieu, Can Tho City (Viet Nam); Lopes, M. C. A. [Departamento de Física, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora, Minas Gerais (Brazil); Konovalov, D. A.; White, R. D. [College of Science, Technology and Engineering, James Cook University, Townsville (Australia); Brunger, M. J., E-mail: michael.brunger@flinders.edu.au, E-mail: darryl.jones@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); Jones, D. B., E-mail: michael.brunger@flinders.edu.au, E-mail: darryl.jones@flinders.edu.au [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia)

    2015-03-28

    In this paper, we report newly derived integral cross sections (ICSs) for electron impact vibrational excitation of tetrahydrofuran (THF) at intermediate impact energies. These cross sections extend the currently available data from 20 to 50 eV. Further, they indicate that the previously recommended THF ICS set [Garland et al., Phys. Rev. A 88, 062712 (2013)] underestimated the strength of the electron-impact vibrational excitation processes. Thus, that recommended vibrational cross section set is revised to address those deficiencies. Electron swarm transport properties were calculated with the amended vibrational cross section set, to quantify the role of electron-driven vibrational excitation in describing the macroscopic swarm phenomena. Here, significant differences of up to 17% in the transport coefficients were observed between the calculations performed using the original and revised cross section sets for vibrational excitation.

  14. Electronic structure and charge transport in nonstoichiometric tantalum oxide

    Science.gov (United States)

    Perevalov, T. V.; Gritsenko, V. A.; Gismatulin, A. A.; Voronkovskii, V. A.; Gerasimova, A. K.; Aliev, V. Sh; Prosvirin, I. A.

    2018-06-01

    The atomic and electronic structure of nonstoichiometric oxygen-deficient tantalum oxide TaO x<2.5 grown by ion beam sputtering deposition was studied. The TaO x film content was analyzed by x-ray photoelectron spectroscopy and by quantum-chemistry simulation. TaO x is composed of Ta2O5, metallic tantalum clusters and tantalum suboxides. A method for evaluating the stoichiometry parameter of TaO x from the comparison of experimental and theoretical photoelectron valence band spectra is proposed. The charge transport properties of TaO x were experimentally studied and the transport mechanism was quantitatively analyzed with four theoretical dielectric conductivity models. It was found that the charge transport in almost stoichiometric and nonstoichiometric tantalum oxide can be consistently described by the phonon-assisted tunneling between traps.

  15. Transport of solar electrons in the turbulent interplanetary magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ablaßmayer, J.; Tautz, R. C., E-mail: robert.c.tautz@gmail.com [Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin (Germany); Dresing, N., E-mail: dresing@physik.uni-kiel.de [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 11, D-24118 Kiel (Germany)

    2016-01-15

    The turbulent transport of solar energetic electrons in the interplanetary magnetic field is investigated by means of a test-particle Monte-Carlo simulation. The magnetic fields are modeled as a combination of the Parker field and a turbulent component. In combination with the direct calculation of diffusion coefficients via the mean-square displacements, this approach allows one to analyze the effect of the initial ballistic transport phase. In that sense, the model complements the main other approach in which a transport equation is solved. The major advancement is that, by recording the flux of particles arriving at virtual detectors, intensity and anisotropy-time profiles can be obtained. Observational indications for a longitudinal asymmetry can thus be explained by tracing the diffusive spread of the particle distribution. The approach may be of future help for the systematic interpretation of observations for instance by the solar terrestrial relations observatory (STEREO) and advanced composition explorer (ACE) spacecrafts.

  16. Landauer-Datta-Lundstrom Generalized Transport Model for Nano electronics

    International Nuclear Information System (INIS)

    Kruglyak, Y.

    2014-01-01

    The Landauer-Datta-Lundstrom electron transport model is briefly summarized. If a band structure is given, the number of conduction modes can be evaluated and if a model for a mean-free-path for backscattering can be established, then the near-equilibrium thermoelectric transport coefficients can be calculated using the final expressions listed below for 1D, 2D, and 3D resistors in ballistic, quasi ballistic, and diffusive linear response regimes when there are differences in both voltage and temperature across the device. The final expressions of thermoelectric transport coefficients through the Fermi-Dirac integrals are collected for 1D, 2D, and 3D semiconductors with parabolic band structure and for 2D graphene linear dispersion in ballistic and diffusive regimes with the power law scattering.

  17. Radial transport of high-energy runaway electrons in ORMAK

    International Nuclear Information System (INIS)

    Zweben, S.J.; Swain, D.W.; Fleischmann, H.H.

    1978-01-01

    The transport of high-energy runaway electrons near the outside of a low-density ORMAK discharge is investigated by measuring the flux of runaways to the outer limiter during and after an inward shift of the plasma column. The experimental results are interpreted through a runaway confinement model which includes both the classical outward displacement of the runaway orbit with increasing energy and an additional runaway spatial diffusion coefficient which simulates an unspecified source of anomalous transport. Diffusion coefficients in the range D approximately equal to 10 2 -10 4 cms -1 are found under various discharge conditions indicating a significant non-collisional runaway transport near the outside of the discharge, particularly in the presence of MHD instability. (author)

  18. Nonlinear Simulations of Trapped Electron Mode Turbulence in Low Magnetic Shear Stellarators

    Science.gov (United States)

    Faber, B. J.; Pueschel, M. J.; Terry, P. W.; Hegna, C. C.

    2017-10-01

    Optimized stellarators, like the Helically Symmetric eXperiment (HSX), often operate with small global magnetic shear to avoid low-order rational surfaces and magnetic islands. Nonlinear, flux-tube gyrokinetic simulations of density-gradient-driven Trapped Electron Mode (TEM) turbulence in HSX shows two distinct spectral fluctuation regions: long-wavelength slab-like TEMs localized by global magnetic shear that extend along field lines and short-wavelength TEMs localized by local magnetic shear to a single helical bad curvature region. The slab-like TEMs require computational domains significantly larger than one poloidal turn and are computationally expensive, making turbulent optimization studies challenging. A computationally more efficient, zero-average-magnetic-shear approximation is shown to sufficiently describe the relevant nonlinear physics and replicate finite-shear computations, and can be exploited in quasilinear models based on linear gyrokinetics as a feasible optimization tool. TEM quasilinear heat fluxes are computed with the zero-shear approximation and compared to experimentally-relevant nonlinear gyrokinetic TEM heat fluxes for HSX. Research supported by U.S. DoE Grants DE-FG02-99ER54546, DE-FG02-93ER54222 and DE-FG02-89ER53291.

  19. Detecting Electron Transport of Amino Acids by Using Conductance Measurement

    Directory of Open Access Journals (Sweden)

    Wei-Qiong Li

    2017-04-01

    Full Text Available The single molecular conductance of amino acids was measured by a scanning tunneling microscope (STM break junction. Conductance measurement of alanine gives out two conductance values at 10−1.85 G0 (1095 nS and 10−3.7 G0 (15.5 nS, while similar conductance values are also observed for aspartic acid and glutamic acid, which have one more carboxylic acid group compared with alanine. This may show that the backbone of NH2–C–COOH is the primary means of electron transport in the molecular junction of aspartic acid and glutamic acid. However, NH2–C–COOH is not the primary means of electron transport in the methionine junction, which may be caused by the strong interaction of the Au–SMe (methyl sulfide bond for the methionine junction. The current work reveals the important role of the anchoring group in the electron transport in different amino acids junctions.

  20. Electron transport in gold colloidal nanoparticle-based strain gauges

    Science.gov (United States)

    Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M.; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

    2013-03-01

    A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the ‘regular island array model’ that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy EC. This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the EC values of these 14 nm NPs cannot be neglected in determining the β values.

  1. Electron heat transport studies using transient phenomena in ASDEX Upgrade

    International Nuclear Information System (INIS)

    Jacchia, A.; Angioni, C.; Manini, A.; Ryter, F.; Apostoliceanu, M.; Conway, G.; Fahrbach, H.-U.; Kirov, K.K.; Leuterer, F.; Reich, M.; Sutttrop, W.; Cirant, S.; Mantica, P.; De Luca, F.; Weiland, J.

    2005-01-01

    Experiments in tokamaks suggest that a critical gradient length may cause the resilient behavior of T e profiles, in the absence of ITBs. This agrees in general with ITG/TEM turbulence physics. Experiments in ASDEX Upgrade using modulation techniques with ECH and/or cold pulses demonstrate the existence of a threshold in R/L Te when T e >T i and T e ≤T i . For T e >T i linear stability analyses indicate that electron heat transport is dominated by TEM modes. They agree in the value of the threshold (both T e and n e ) and for the electron heat transport increase above the threshold. The stabilization of TEM modes by collisions yielded by gyro-kinetic calculations, which suggests a transition from TEM to ITG dominated transport at high collisionality, is experimentally demonstrated by comparing heat pulse and steady-state diffusivities. For the T e ∼T i discharges above the threshold the resilience, normalized by T e 3/2 , is similar to that of the TEM dominated cases, despite very different conditions. The heat pinch predicted by fluid modeling of ITG/TEM turbulence is investigated by perturbative transport in off-axis ECH-heated discharges. (author)

  2. Time dependence of microsecond intense electron beam transport in gases

    International Nuclear Information System (INIS)

    Lucey, R.F. Jr.; Gilgenback, R.M.; Tucker, J.E.; Brake, M.L.; Enloe, C.L.; Repetti, T.E.

    1987-01-01

    The authors present results of long-pulse (0.5 μs) electron beam propagation in the ion focused regime (IFR). Electron beam parameters are 800 kV with several hundred amperes injected current. For injection into air (from 0.7 mTorr to 75 mTorr) and helium (from 14 mTorr to 227 mTorr) the authors observe a ''time-dependent propagation window'' in which efficient (up to 100%) propagation starts at a time comparable to the electron impact ionization time needed to achieve n/sub i/ -- (1/γ/sup 2/)n/sub eb/. The transport goes abruptly to zero about 50-150 ns after this initial propagation. This is followed by erratic propagation often consisting of numerous narrower pulses 10-40 ns wide. In these pulses the transported current can be 100% of the injected current, but is generally lower. As the fill pressure is increased, there are differences in the propagated beam pulse, which can be summarized as follows: 1) the temporal occurrence of the beam propagation window shifts to earlier times, 2) the propagated beam current has much faster risetimes, 3) a larger portion of the injected beam is propagated. Similar results are observed when the electron beam is propagated in helium. However, at a given pressure, the beam transport window occurs at later times and exhibits a slower risetime. These effects are consistent with electron beam-induced ionization. Experiments are being performed to determine if the observed beam instability is due to the ion hose instability or streaming instability

  3. Effect of nonlinear energy transport on neoclassical tearing mode stability in tokamak plasmas

    Science.gov (United States)

    Fitzpatrick, Richard

    2017-05-01

    An investigation is made into the effect of the reduction in anomalous perpendicular electron heat transport inside the separatrix of a magnetic island chain associated with a neoclassical tearing mode in a tokamak plasma, due to the flattening of the electron temperature profile in this region, on the overall stability of the mode. The onset of the neoclassical tearing mode is governed by the ratio of the divergences of the parallel and perpendicular electron heat fluxes in the vicinity of the island chain. By increasing the degree of transport reduction, the onset of the mode, as the divergence ratio is gradually increased, can be made more and more abrupt. Eventually, when the degree of transport reduction passes a certain critical value, the onset of the neoclassical tearing mode becomes discontinuous. In other words, when some critical value of the divergence ratio is reached, there is a sudden bifurcation to a branch of neoclassical tearing mode solutions. Moreover, once this bifurcation has been triggered, the divergence ratio must be reduced by a substantial factor to trigger the inverse bifurcation.

  4. Multidimensional electron-photon transport with standard discrete ordinates codes

    International Nuclear Information System (INIS)

    Drumm, C.R.

    1997-01-01

    A method is described for generating electron cross sections that are comparable with standard discrete ordinates codes without modification. There are many advantages of using an established discrete ordinates solver, e.g. immediately available adjoint capability. Coupled electron-photon transport capability is needed for many applications, including the modeling of the response of electronics components to space and man-made radiation environments. The cross sections have been successfully used in the DORT, TWODANT and TORT discrete ordinates codes. The cross sections are shown to provide accurate and efficient solutions to certain multidimensional electron-photon transport problems. The key to the method is a simultaneous solution of the continuous-slowing-down (CSD) portion and elastic-scattering portion of the scattering source by the Goudsmit-Saunderson theory. The resulting multigroup-Legendre cross sections are much smaller than the true scattering cross sections that they represent. Under certain conditions, the cross sections are guaranteed positive and converge with a low-order Legendre expansion

  5. Multidimensional electron-photon transport with standard discrete ordinates codes

    International Nuclear Information System (INIS)

    Drumm, C.R.

    1997-01-01

    A method is described for generating electron cross sections that are compatible with standard discrete ordinates codes without modification. There are many advantages to using an established discrete ordinates solver, e.g., immediately available adjoint capability. Coupled electron-photon transport capability is needed for many applications, including the modeling of the response of electronics components to space and synthetic radiation environments. The cross sections have been successfully used in the DORT, TWODANT, and TORT discrete ordinates codes. The cross sections are shown to provide accurate and efficient solutions to certain multidimensional electron-photon transport problems. The key to the method is a simultaneous solution of the continuous-slowing-down and elastic-scattering portions of the scattering source by the Goudsmit-Saunderson theory. The resulting multigroup-Legendre cross sections are much smaller than the true scattering cross sections that they represent. Under certain conditions, the cross sections are guaranteed positive and converge with a low-order Legendre expansion

  6. Distribution of tunnelling times for quantum electron transport

    International Nuclear Information System (INIS)

    Rudge, Samuel L.; Kosov, Daniel S.

    2016-01-01

    In electron transport, the tunnelling time is the time taken for an electron to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for electron transport through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an electron jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.

  7. Electronic transport in VO2—Experimentally calibrated Boltzmann transport modeling

    International Nuclear Information System (INIS)

    Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y.; Kado, Motohisa; Ling, Chen; Zhu, Gaohua; Banerjee, Debasish

    2015-01-01

    Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO 2 has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO 2 in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO 2 films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties

  8. Electronic transport in VO{sub 2}—Experimentally calibrated Boltzmann transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Kinaci, Alper; Rosenmann, Daniel; Chan, Maria K. Y., E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kado, Motohisa [Higashifuji Technical Center, Toyota Motor Corporation, Susono, Shizuoka 410-1193 (Japan); Ling, Chen; Zhu, Gaohua; Banerjee, Debasish, E-mail: debasish.banerjee@toyota.com, E-mail: mchan@anl.gov [Materials Research Department, Toyota Motor Engineering and Manufacturing North America, Inc., Ann Arbor, Michigan 48105 (United States)

    2015-12-28

    Materials that undergo metal-insulator transitions (MITs) are under intense study, because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO{sub 2} has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach with Hubbard U correction (DFT + U) to model electronic transport properties in VO{sub 2} in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high quality VO{sub 2} films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties.

  9. Modeling the high-energy electronic state manifold of adenine: Calibration for nonlinear electronic spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nenov, Artur, E-mail: Artur.Nenov@unibo.it; Giussani, Angelo; Segarra-Martí, Javier; Jaiswal, Vishal K. [Dipartimento di Chimica “G. Ciamician,” Università di Bologna, Via Selmi 2, IT-40126 Bologna (Italy); Rivalta, Ivan [Université de Lyon, CNRS, Institut de Chimie de Lyon, École Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07 (France); Cerullo, Giulio [Dipartimento di Fisica, Politecnico di Milano, IFN-CNR, Piazza Leonardo Da Vinci 32, IT-20133 Milano (Italy); Mukamel, Shaul [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States); Garavelli, Marco, E-mail: marco.garavelli@unibo.it, E-mail: marco.garavelli@ens-lyon.fr [Dipartimento di Chimica “G. Ciamician,” Università di Bologna, Via Selmi 2, IT-40126 Bologna (Italy); Université de Lyon, CNRS, Institut de Chimie de Lyon, École Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07 (France)

    2015-06-07

    Pump-probe electronic spectroscopy using femtosecond laser pulses has evolved into a standard tool for tracking ultrafast excited state dynamics. Its two-dimensional (2D) counterpart is becoming an increasingly available and promising technique for resolving many of the limitations of pump-probe caused by spectral congestion. The ability to simulate pump-probe and 2D spectra from ab initio computations would allow one to link mechanistic observables like molecular motions and the making/breaking of chemical bonds to experimental observables like excited state lifetimes and quantum yields. From a theoretical standpoint, the characterization of the electronic transitions in the visible (Vis)/ultraviolet (UV), which are excited via the interaction of a molecular system with the incoming pump/probe pulses, translates into the determination of a computationally challenging number of excited states (going over 100) even for small/medium sized systems. A protocol is therefore required to evaluate the fluctuations of spectral properties like transition energies and dipole moments as a function of the computational parameters and to estimate the effect of these fluctuations on the transient spectral appearance. In the present contribution such a protocol is presented within the framework of complete and restricted active space self-consistent field theory and its second-order perturbation theory extensions. The electronic excited states of adenine have been carefully characterized through a previously presented computational recipe [Nenov et al., Comput. Theor. Chem. 1040–1041, 295-303 (2014)]. A wise reduction of the level of theory has then been performed in order to obtain a computationally less demanding approach that is still able to reproduce the characteristic features of the reference data. Foreseeing the potentiality of 2D electronic spectroscopy to track polynucleotide ground and excited state dynamics, and in particular its expected ability to provide

  10. Theoretical modeling of electronic transport in molecular devices

    Science.gov (United States)

    Piccinin, Simone

    In this thesis a novel approach for simulating electronic transport in nanoscale structures is introduced. We consider an open quantum system (the electrons of structure) accelerated by an external electromotive force and dissipating energy through inelastic scattering with a heat bath (phonons) acting on the electrons. This method can be regarded as a quantum-mechanical extension of the semi-classical Boltzmann transport equation. We use periodic boundary conditions and employ Density Functional Theory to recast the many-particle problem in an effective single-particle mean-field problem. By explicitly treating the dissipation in the electrodes, the behavior of the potential is an outcome of our method, at variance with the scattering approaches based on the Landauer formalism. We study the self-consistent steady-state solution, analyzing the out-of-equilibrium electron distribution, the electrical characteristics, the behavior of the self-consistent potential and the density of states of the system. We apply the method to the study of electronic transport in several molecular devices, consisting of small organic molecules or atomic wires sandwiched between gold surfaces. For gold wires we recover the experimental evidence that transport in short wires is ballistic, independent of the length of the wire and with conductance of one quantum. In benzene-1,4-dithiol we find that the delocalization of the frontier orbitals of the molecule is responsible for the high value of conductance and that, by inserting methylene groups to decouple the sulfur atoms from the carbon ring, the current is reduced, in agreement with the experimental measurements. We study the effect a geometrical distortion in a molecular device, namely the relative rotation of the carbon rings in a biphenyl-4,4'-dithiol molecule. We find that the reduced coupling between pi orbitals of the rings induced by the rotation leads to a reduction of the conductance and that this behavior is captured by a

  11. Transport of a relativistic electron beam through hydrogen gas

    International Nuclear Information System (INIS)

    Haan, P. de.

    1981-01-01

    In this thesis the author describes the transport properties of an electron beam through vacuum and through hydrogen gas with pressure ranging from 25 to 1000 Pa. Maximum beam energy and current are 0.8 MeV and 6 kA, respectively. The pulse length is around 150 ns. A description is given of the experimental device. Also the diagnostics for probing the beam and the plasma, produced by the beam, are discussed, as well as the data acquisition system. The interaction between the beam and hydrogen gas with a pressure around 200 Pa is considered. A plasma with density around 10 19 m -3 is produced within a few nanoseconds. Measurements yield the atomic hydrogen temperature, electron density, beam energy loss, and induced plasma current and these are compared with the results of a model combining gas ionization and dissociation, and turbulent plasma heating. The angular distribution of the beam electrons about the magnetic field axis is discussed. (Auth.)

  12. Numerical shoves and countershoves in electron transport calculations

    International Nuclear Information System (INIS)

    Filippone, W.L.

    1986-01-01

    The justification for applying the relatively complex (compared to S/sub n/) streaming ray (SR) algorithm to electron transport problems is its potential for doing rapid and accurate calculations. Because of the Lagrangian treatment of the cell-uncollided electrons, the only significant sources of error are the numerical treatment of the scattering kernel and the spatial differencing scheme used for the cell-collided electrons. Considerable progress has been made in reducing the former source of error. If one is willing to pay the price, the latter source of error can be reduced to any desired level by refining the mesh size or by using high-order differencing schemes. Here the method of numerical shoves and countershoves is introduced, which reduces spatial differencing errors using relatively little additional computational effort

  13. Scanning Electron Microscope Calibration Using a Multi-Image Non-Linear Minimization Process

    Science.gov (United States)

    Cui, Le; Marchand, Éric

    2015-04-01

    A scanning electron microscope (SEM) calibrating approach based on non-linear minimization procedure is presented in this article. A part of this article has been published in IEEE International Conference on Robotics and Automation (ICRA), 2014. . Both the intrinsic parameters and the extrinsic parameters estimations are achieved simultaneously by minimizing the registration error. The proposed approach considers multi-images of a multi-scale calibration pattern view from different positions and orientations. Since the projection geometry of the scanning electron microscope is different from that of a classical optical sensor, the perspective projection model and the parallel projection model are considered and compared with distortion models. Experiments are realized by varying the position and the orientation of a multi-scale chessboard calibration pattern from 300× to 10,000×. The experimental results show the efficiency and the accuracy of this approach.

  14. Application of nonlinear models to estimate the gain of one-dimensional free-electron lasers

    Science.gov (United States)

    Peter, E.; Rizzato, F. B.; Endler, A.

    2017-06-01

    In the present work, we make use of simplified nonlinear models based on the compressibility factor (Peter et al., Phys. Plasmas, vol. 20 (12), 2013, 123104) to predict the gain of one-dimensional (1-D) free-electron lasers (FELs), considering space-charge and thermal effects. These models proved to be reasonable to estimate some aspects of 1-D FEL theory, such as the position of the onset of mixing, in the case of a initially cold electron beam, and the position of the breakdown of the laminar regime, in the case of an initially warm beam (Peter et al., Phys. Plasmas, vol. 21 (11), 2014, 113104). The results given by the models are compared to wave-particle simulations showing a reasonable agreement.

  15. A computational study on the electronic and nonlinear optical properties of graphyne subunit

    Energy Technology Data Exchange (ETDEWEB)

    Bahat, Mehmet, E-mail: bahat@gazi.edu.tr; Güney, Merve Nurhan, E-mail: merveng87@gmail.com; Özbay, Akif, E-mail: aozbay@gazi.edu.tr [Department of Physics, Gazi University, Ankara, 06500 (Turkey)

    2016-03-25

    After discovery of graphene, it has been considered as basic material for the future nanoelectronic devices. Graphyne is a two- dimensional carbon allotropes as graphene which expected that its electronic properties is potentialy superior to graphene. The compound C{sub 24}H{sub 12} (tribenzocyclyne; TBC) is a substructure of graphyne. The electronic, and nonlinear optical properties of the C{sub 24}H{sub 12} and its some fluoro derivatives were calculated. The calculated properties are electric dipole moment, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies, polarizability and first hyperpolarizability. All calculations were performed at the B3LYP/6-31+G(d,p) level.

  16. Nonlinear waves in electron-positron-ion plasmas including charge separation

    Science.gov (United States)

    Mugemana, A.; Moolla, S.; Lazarus, I. J.

    2017-02-01

    Nonlinear low-frequency electrostatic waves in a magnetized, three-component plasma consisting of hot electrons, hot positrons and warm ions have been investigated. The electrons and positrons are assumed to have Boltzmann density distributions while the motion of the ions are governed by fluid equations. The system is closed with the Poisson equation. This set of equations is numerically solved for the electric field. The effects of the driving electric field, ion temperature, positron density, ion drift, Mach number and propagation angle are investigated. It is shown that depending on the driving electric field, ion temperature, positron density, ion drift, Mach number and propagation angle, the numerical solutions exhibit waveforms that are sinusoidal, sawtooth and spiky. The introduction of the Poisson equation increased the Mach number required to generate the waveforms but the driving electric field E 0 was reduced. The results are compared with satellite observations.

  17. High Power Amplifiers Chain nonlinearity influence on the accelerating beam stability in free electron laser (FLASH)

    CERN Document Server

    Cichalewski, w

    2010-01-01

    The high power amplifiers transfer characteristics nonlinearities can have a negative influence on the overall system performance. This is also true for the TESLA superconducting cavities accelerating field parameters control systems. This Low Level Radio Frequency control systems uses microwave high power amplifiers (like 10 MW klystrons) as actuators in the mentioned feedback loops. The amplitude compression and phase deviations phenomena introduced to the control signals can reduce the feedback performance and cause electron beam energy instabilities. The transfer characteristics deviations in the Free Electron Laser in Hamburg experiment have been investigated. The outcome of this study together with the description of the developed linearization method based on the digital predistortion approach have been described in this paper. Additionally, the results from the linearization tool performance tests in the FLASH's RF systems have been placed.

  18. Application of the Green's function method to some nonlinear problems of an electron storage ring

    International Nuclear Information System (INIS)

    Kheifets, S.

    1984-01-01

    One of the most important characteristics of an electron storage ring is the size of the beam. However analytical calculations of beam size are beset with problems and the computational methods and programs which are used to overcome these are inadequate for all problems in which stochastic noise is an essential part. Two examples are, for an electron storage ring, beam-size evaluation including beam-beam interactions, and finding the beam size for a nonlinear machine. The method described should overcome some of the problems. It uses the Green's function method applied to the Fokker-Planck equation governing the distribution function in the phase space of particle motion. The new step is to consider the particle motion in two degrees of freedom rather than in one dimension. The technique is described fully and is then applied to a strong-focusing machine. (U.K.)

  19. Anomalous transport of magnetized electrons interacting with EC waves

    Energy Technology Data Exchange (ETDEWEB)

    Tsironis, C; Vlahos, L [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

    2005-01-01

    We consider the nonlinear interaction of magnetized electrons with an oblique narrow-band electromagnetic wave-packet. The interaction is analysed over and near the local threshold to chaos. The statistical character of the forcing that controls the trajectories of the particles is also studied. We focus our analysis on issues related to energy and spatial diffusion across the magnetic field by following the evolution of the ensemble mean squares (({gamma} - {gamma}{sub 0}){sup 2}) and ((r{sub perpendicular}-r{sub perpendicular0}){sup 2}) for various values of the wave amplitude and angle of wave propagation. We study, in particular, the interaction of magnetized electrons with waves having strong and moderate amplitudes, near the transition to chaos, where the dynamics is complex and a mixture of periodic and stochastic orbits coexist. The electron diffusions in real and energy spaces are found to obey simple power laws in time, and the scaling exponents are indicative of sub-diffusion. This is a direct consequence of the effect of the resonant phase-space islands in the particle motion.

  20. Electron-vibron coupling effects on electron transport via a single-molecule magnet

    Science.gov (United States)

    McCaskey, Alexander; Yamamoto, Yoh; Warnock, Michael; Burzurí, Enrique; van der Zant, Herre S. J.; Park, Kyungwha

    2015-03-01

    We investigate how the electron-vibron coupling influences electron transport via an anisotropic magnetic molecule, such as a single-molecule magnet (SMM) Fe4, by using a model Hamiltonian with parameter values obtained from density-functional theory (DFT). The magnetic anisotropy parameters, vibrational energies, and electron-vibron coupling strengths of the Fe4 are computed using DFT. A giant spin model is applied to the Fe4 with only two charge states, specifically a neutral state with a total spin S =5 and a singly charged state with S =9 /2 , which is consistent with our DFT result and experiments on Fe4 single-molecule transistors. In sequential electron tunneling, we find that the magnetic anisotropy gives rise to new features in the conductance peaks arising from vibrational excitations. In particular, the peak height shows a strong, unusual dependence on the direction as well as magnitude of applied B field. The magnetic anisotropy also introduces vibrational satellite peaks whose position and height are modified with the direction and magnitude of applied B field. Furthermore, when multiple vibrational modes with considerable electron-vibron coupling have energies close to one another, a low-bias current is suppressed, independently of gate voltage and applied B field, although that is not the case for a single mode with a similar electron-vibron coupling. In the former case, the conductance peaks reveal a stronger B -field dependence than in the latter case. The new features appear because the magnetic anisotropy barrier is of the same order of magnitude as the energies of vibrational modes with significant electron-vibron coupling. Our findings clearly show the interesting interplay between magnetic anisotropy and electron-vibron coupling in electron transport via the Fe4. Similar behavior can be observed in transport via other anisotropic magnetic molecules.

  1. Theoretical prediction of the electronic transport properties of the Al-Cu alloys based on the first-principle calculation and Boltzmann transport equation

    Science.gov (United States)

    Choi, Garam; Lee, Won Bo

    Metal alloys, especially Al-based, are commonly-used materials for various industrial applications. In this paper, the Al-Cu alloys with varying the Al-Cu ratio were investigated based on the first-principle calculation using density functional theory. And the electronic transport properties of the Al-Cu alloys were carried out using Boltzmann transport theory. From the results, the transport properties decrease with Cu-containing ratio at the temperature from moderate to high, but with non-linearity. It is inferred by various scattering effects from the calculation results with relaxation time approximation. For the Al-Cu alloy system, where it is hard to find the reliable experimental data for various alloys, it supports understanding and expectation for the thermal electrical properties from the theoretical prediction. Theoretical and computational soft matters laboratory.

  2. Structural, electronic, linear, and nonlinear optical properties of ZnCdTe{sub 2} chalcopyrite

    Energy Technology Data Exchange (ETDEWEB)

    Ouahrani, Tarik [Laboratoire de Physique Theorique, Universite de Tlemcen, B.P. 230, Tlemcen 13000 (Algeria); Reshak, Ali H. [Institute of Physical Biology, South Bohemia University, Nove Hrady 37333 (Czech Republic); School of Microelectronic Engineering, University of Malaysia Perlis (UniMAP), Block A, Kompleks Pusat Pengajian, 02600 Arau Jejawi, Perlis (Malaysia); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Baltache, H.; Amrani, B. [Laboratoire de Physique Quantique et de Modelisation Mathematique, Universite de Mascara, Mascara 29000 (Algeria); Bouhemadou, A. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Faculty of Sciences, Department of Physics, University of Setif, Setif 19000 (Algeria)

    2011-03-15

    We report results of first-principles density functional calculations using the full-potential linearized augmented plane wave method. The generalized gradient approximation (GGA) and the Engel-Vosko-GGA (EV-GGA) formalism were used for the exchange-correlation energy to calculate the structural, electronic, linear, and nonlinear optical properties of the chalcopyrite ZnCdTe{sub 2} compound. The valence band maximum and the conduction band minimum are located at the {gamma}-point, resulting in a direct band gap of about 0.71 eV for GGA and 1.29 eV for EV-GGA. The results of bulk properties, such as lattice parameters (a, c, and u), bulk modulus B, and its pressure derivative B' are evaluated. The optical properties of this compound, namely the real and the imaginary parts of the dielectric function, reflectivity, and refractive index, show a considerable anisotropy as a consequence ZnCdTe{sub 2} posseses a strong birefringence. In addition, the extinction coefficient, the electron energy loss function, and the nonlinear susceptibility are calculated and their spectra are analyzed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Nonlinear electron-density distribution around point defects in simple metals. I. Formulation

    International Nuclear Information System (INIS)

    Gupta, A.K.; Jena, P.; Singwi, K.S.

    1978-01-01

    Modification, which is exact in the limit of long wavelength, of the nonlinear theory of Sjoelander and Stott of electron distribution around point defects is given. This modification consists in writing a nonlinear integral equations for the Fourier transform γ 12 (q) of the induced charge density surrounding the point defect, which includes a term involving the density derivative of γ 12 (q). A generalization of the Pauli-Feynman coupling-constant-integration method, together with the Kohn-Sham formalism, is used to exactly determine the coefficient of this derivative term in the long-wavelength limit. The theory is then used to calculate electron-density profiles around a vacancy, an eight-atom void, and a point ion. The results are compared with those of (i) a linear theory, (ii) Sjoelander-Stott theory, and (iii) a fully self-consistent calculation based on the density-functional formalism of Kohn and Sham. It is found that in the case of a vacancy, the results of the present theory are in very good agreement with those based on Kohn-Sham formalism, whereas in the case of a singular attractive potential of a proton, the results are quite poor in the vicinity of the proton, but much better for larger distances. A critical discussion of the theory vis a vis the Kohn-Sham formalism is also given. Some applications of the theory are pointed out

  4. Atomistic simulations of divacancy defects in armchair graphene nanoribbons: Stability, electronic structure, and electron transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jun [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China); Zeng, Hui, E-mail: zenghui@yangtzeu.edu.cn [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China); Wei, Jianwei [College of Optoelectronic Information, Chongqing University of Technology, Chongqing 400054 (China); Li, Biao; Xu, Dahai [College of Physical Science and Technology, Yangtze University, Jingzhou, Hubei 434023 (China)

    2014-01-17

    Using the first principles calculations associated with nonequilibrium Green's function, we have studied the electronic structures and quantum transport properties of defective armchair graphene nanoribbon (AGNR) in the presence of divacancy defects. The triple pentagon–triple heptagon (555–777) defect in the defective AGNR is energetically more favorable than the pentagon–octagon–pentagon (5–8–5) defect. Our calculated results reveal that both 5–8–5-like defect and 555–777-like defect in AGNR could improve the electron transport. It is anticipated that defective AGNRs can exhibit large range variations in transport behaviors, which are strongly dependent on the distributions of the divacancy defect.

  5. Computationally efficient description of relativistic electron beam transport in dense plasma

    Science.gov (United States)

    Polomarov, Oleg; Sefkov, Adam; Kaganovich, Igor; Shvets, Gennady

    2006-10-01

    A reduced model of the Weibel instability and electron beam transport in dense plasma is developed. Beam electrons are modeled by macro-particles and the background plasma is represented by electron fluid. Conservation of generalized vorticity and quasineutrality of the plasma-beam system are used to simplify the governing equations. Our approach is motivated by the conditions of the FI scenario, where the beam density is likely to be much smaller than the plasma density and the beam energy is likely to be very high. For this case the growth rate of the Weibel instability is small, making the modeling of it by conventional PICs exceedingly time consuming. The present approach does not require resolving the plasma period and only resolves a plasma collisionless skin depth and is suitable for modeling a long-time behavior of beam-plasma interaction. An efficient code based on this reduced description is developed and benchmarked against the LSP PIC code. The dynamics of low and high current electron beams in dense plasma is simulated. Special emphasis is on peculiarities of its non-linear stages, such as filament formation and merger, saturation and post-saturation field and energy oscillations. *Supported by DOE Fusion Science through grant DE-FG02-05ER54840.

  6. Nonlinear excitation of electron cyclotron waves by a monochromatic strong microwave: computer simulation analysis of the MINIX results

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, H.; Kimura, T.

    1986-01-01

    Triggered by the experimental results of the MINIX, a computer simulation study was initiated on the nonlinear excitation of electrostatic electron cyclotron waves by a monochromatic electromagnetic wave such as the transmitted microwave in the MINIX. The model used assumes that both of the excited waves and exciting (pumping) electromagnetic wave as well as the idler electromagnetic wave propagate in the direction perpendicular to the external magnetic field. The simulation code used for this study was the one-and-two-half dimensional electromagnetic particle code named KEMPO. The simulation result shows the high power electromagnetic wave produces both the backscattered electromagnetic wave and electrostatic electron cyclotron waves as a result of nonlinear parametric instability. Detailed nonlinear microphysics related to the wave excitation is discussed in terms of the nonlinear wave-wave couplings and associated ponderomotive force produced by the high power electromagnetic waves. 2 references, 4 figures.

  7. Nonlinear excitation of electron cyclotron waves by a monochromatic strong microwave: computer simulation analysis of the MINIX results

    International Nuclear Information System (INIS)

    Matsumoto, H.; Kimura, T.

    1986-01-01

    Triggered by the experimental results of the MINIX, a computer simulation study was initiated on the nonlinear excitation of electrostatic electron cyclotron waves by a monochromatic electromagnetic wave such as the transmitted microwave in the MINIX. The model used assumes that both of the excited waves and exciting (pumping) electromagnetic wave as well as the idler electromagnetic wave propagate in the direction perpendicular to the external magnetic field. The simulation code used for this study was the one-and-two-half dimensional electromagnetic particle code named KEMPO. The simulation result shows the high power electromagnetic wave produces both the backscattered electromagnetic wave and electrostatic electron cyclotron waves as a result of nonlinear parametric instability. Detailed nonlinear microphysics related to the wave excitation is discussed in terms of the nonlinear wave-wave couplings and associated ponderomotive force produced by the high power electromagnetic waves. 2 references, 4 figures

  8. The Nature of Grand Minima and Maxima from Fully Nonlinear Flux Transport Dynamos

    Energy Technology Data Exchange (ETDEWEB)

    Inceoglu, Fadil; Arlt, Rainer [Leibniz-Institute for Astrophysics Potsdam, An der Sternwarte 16, D-14482, Potsdam (Germany); Rempel, Matthias, E-mail: finceoglu@aip.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

    2017-10-20

    We aim to investigate the nature and occurrence characteristics of grand solar minimum and maximum periods, which are observed in the solar proxy records such as {sup 10}Be and {sup 14}C, using a fully nonlinear Babcock–Leighton type flux transport dynamo including momentum and entropy equations. The differential rotation and meridional circulation are generated from the effect of turbulent Reynolds stress and are subjected to back-reaction from the magnetic field. To generate grand minimum- and maximum-like periods in our simulations, we used random fluctuations in the angular momentum transport process, namely the Λ-mechanism, and in the Babcock–Leighton mechanism. To characterize the nature and occurrences of the identified grand minima and maxima in our simulations, we used the waiting time distribution analyses, which reflect whether the underlying distribution arises from a random or a memory-bearing process. The results show that, in the majority of the cases, the distributions of grand minima and maxima reveal that the nature of these events originates from memoryless processes. We also found that in our simulations the meridional circulation speed tends to be smaller during grand maximum, while it is faster during grand minimum periods. The radial differential rotation tends to be larger during grand maxima, while it is smaller during grand minima. The latitudinal differential rotation, on the other hand, is found to be larger during grand minima.

  9. Electronic transport in narrow-gap semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Bloemers, Christian

    2012-10-19

    Throughout this work the electronic transport properties of InAs, InN, and GaAs/InAs core/shell nanowires have been analyzed. This includes the analysis of specific resistivity at room temperature and low temperatures as well as the breakdown of resistivity by a contribution of mobility and carrier concentration using gate measurements. While the InN nanowires showed homogeneous transport properties, there was a large statistical spread in the properties of InAs nanowires. Differing crystal structures and the surface conditions are identified to be the main reasons for the statistical spread. Both quantities of influence have been pointed out by comparing the transport parameters before and after a surface treatment (electron irradiation and long time ambient air exposure), and by comparing the transport parameters of wires grown by different growth methods which exhibit different kinds of crystal structure. In particular, the temperature dependence of the conductivity revealed different activation energies in nanowires with differing crystal structures. An explanation has been suggested in terms of stacking fault induced potential barriers. A field-effect measurement setup has been utilized to determine the nanowire mobility and carrier concentration. Even though this method is widely used for nanowires, it is subject to a serious disadvantage concerning the influence of surface and interface states on the measurements. As an alternative method which does not suffer from this drawback, Hall measurements have been successfully performed on InAs nanowires for the first time. These measurements became possible because of the utilization of a new electron beam lithographic procedure with an alignment accuracy in the 5 nm range. Carrier concentration values could be determined and compared to the ones obtained from conventional field-effect measurements. The results of the Hall measurements revealed a methodical overestimation of the carrier concentrations obtained

  10. Electronic transport in narrow-gap semiconductor nanowires

    International Nuclear Information System (INIS)

    Bloemers, Christian

    2012-01-01

    Throughout this work the electronic transport properties of InAs, InN, and GaAs/InAs core/shell nanowires have been analyzed. This includes the analysis of specific resistivity at room temperature and low temperatures as well as the breakdown of resistivity by a contribution of mobility and carrier concentration using gate measurements. While the InN nanowires showed homogeneous transport properties, there was a large statistical spread in the properties of InAs nanowires. Differing crystal structures and the surface conditions are identified to be the main reasons for the statistical spread. Both quantities of influence have been pointed out by comparing the transport parameters before and after a surface treatment (electron irradiation and long time ambient air exposure), and by comparing the transport parameters of wires grown by different growth methods which exhibit different kinds of crystal structure. In particular, the temperature dependence of the conductivity revealed different activation energies in nanowires with differing crystal structures. An explanation has been suggested in terms of stacking fault induced potential barriers. A field-effect measurement setup has been utilized to determine the nanowire mobility and carrier concentration. Even though this method is widely used for nanowires, it is subject to a serious disadvantage concerning the influence of surface and interface states on the measurements. As an alternative method which does not suffer from this drawback, Hall measurements have been successfully performed on InAs nanowires for the first time. These measurements became possible because of the utilization of a new electron beam lithographic procedure with an alignment accuracy in the 5 nm range. Carrier concentration values could be determined and compared to the ones obtained from conventional field-effect measurements. The results of the Hall measurements revealed a methodical overestimation of the carrier concentrations obtained

  11. Electronic Structure and Transport in Solids from First Principles

    Science.gov (United States)

    Mustafa, Jamal Ibrahim

    The focus of this dissertation is the determination of the electronic structure and trans- port properties of solids. We first review some of the theory and computational methodology used in the calculation of electronic structure and materials properties. Throughout the dissertation, we make extensive use of state-of-the-art software packages that implement density functional theory, density functional perturbation theory, and the GW approximation, in addition to specialized methods for interpolating matrix elements for extremely accurate results. The first application of the computational framework introduced is the determination of band offsets in semiconductor heterojunctions using a theory of quantum dipoles at the interface. This method is applied to the case of heterojunction formed between a new metastable phase of silicon, with a rhombohedral structure, and cubic silicon. Next, we introduce a novel method for the construction of localized Wannier functions, which we have named the optimized projection functions method (OPFM). We illustrate the method on a variety of systems and find that it can reliably construct localized Wannier functions with minimal user intervention. We further develop the OPFM to investigate a class of materials called topological insulators, which are insulating in the bulk but have conductive surface states. These properties are a result of a nontrivial topology in their band structure, which has interesting effects on the character of the Wannier functions. In the last sections of the main text, the noble metals are studied in great detail, including their electronic properties and carrier dynamics. In particular, we investigate, the Fermi surface properties of the noble metals, specifically electron-phonon scattering lifetimes, and subsequently the transport properties determined by carriers on the Fermi surface. To achieve this, a novel sampling technique is developed, with wide applicability to transport calculations

  12. Monte Carlo transport of electrons and positrons through thin foils

    International Nuclear Information System (INIS)

    Legarda, F.; Idoeta, R.

    2000-01-01

    In the different measurements made with electrons traversing matter it becomes useful the knowledge of its transmission through that medium, their paths and their angular distribution through matter so as to process and get information about the traversed medium and to improve and innovate the techniques that employ electrons, as medical applications or materials irradiation. This work presents a simulation of the transport of beams of electrons and positrons through thin foils using an analog Monte Carlo code that simulates in a detailed way every electron movement or interaction in matter. As those particles penetrate thin absorbers it has been assumed that they interact with matter only through elastic scattering, with negligible energy loss. This type of interaction has been described quite precisely because its angular form influences very much the angular distribution of electrons and positrons in matter. With this code it has been calculated the number of particles, with energies between 100 and 3000 keV, that are transmitted through different media of various thicknesses as well as its angular distribution, showing a good agreement with experimental data. The discrepancies are less than 5% for thicknesses lower than about 30% of the corresponding range in the tested material. As elastic scattering is very anisotropic, angular distributions resemble a collimated incident beam for very thin foils becoming slowly more isotropic when absorber thickness is increased. (author)

  13. Electron and hole transport in ambipolar, thin film pentacene transistors

    International Nuclear Information System (INIS)

    Saudari, Sangameshwar R.; Kagan, Cherie R.

    2015-01-01

    Solution-processed, ambipolar, thin-film pentacene field-effect transistors were employed to study both electron and hole transport simultaneously in a single, organic solid-state device. Electron and hole mobilities were extracted from the respective unipolar saturation regimes and show thermally activated behavior and gate voltage dependence. We fit the gate voltage dependent saturation mobility to a power law to extract the characteristic Meyer-Neldel (MN) energy, a measure of the width of the exponential distribution of localized states extending into the energy gap of the organic semiconductor. The MN energy is ∼78 and ∼28 meV for electrons and holes, respectively, which reflects a greater density of localized tail states for electrons than holes. This is consistent with the lower measured electron than hole mobility. For holes, the well-behaved linear regime allows for four-point probe measurement of the contact resistance independent mobility and separate characterization of the width of the localized density of states, yielding a consistent MN energy of 28 meV

  14. Electron and hole transport in ambipolar, thin film pentacene transistors

    Energy Technology Data Exchange (ETDEWEB)

    Saudari, Sangameshwar R. [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Kagan, Cherie R. [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

    2015-01-21

    Solution-processed, ambipolar, thin-film pentacene field-effect transistors were employed to study both electron and hole transport simultaneously in a single, organic solid-state device. Electron and hole mobilities were extracted from the respective unipolar saturation regimes and show thermally activated behavior and gate voltage dependence. We fit the gate voltage dependent saturation mobility to a power law to extract the characteristic Meyer-Neldel (MN) energy, a measure of the width of the exponential distribution of localized states extending into the energy gap of the organic semiconductor. The MN energy is ∼78 and ∼28 meV for electrons and holes, respectively, which reflects a greater density of localized tail states for electrons than holes. This is consistent with the lower measured electron than hole mobility. For holes, the well-behaved linear regime allows for four-point probe measurement of the contact resistance independent mobility and separate characterization of the width of the localized density of states, yielding a consistent MN energy of 28 meV.

  15. Electronic transport and dielectric properties of low-dimensional structures of layered transition metal dichalcogenides

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ashok, E-mail: ashok.1777@yahoo.com; Ahluwalia, P.K., E-mail: pk_ahluwalia7@yahoo.com

    2014-02-25

    Graphical abstract: We present electronic transport and dielectric response of layered transition metal dichalcogenides nanowires and nanoribbons. Illustration 1: Conductance (G) and corresponding local density of states(LDOS) for LTMDs wires at applied bias. I–V characterstics are shown in lowermost panels. Highlights: • The studied configurations show metallic/semiconducting nature. • States around the Fermi energy are mainly contributed by the d orbitals of metal atoms. • The studied configurations show non-linear current–voltage (I–V) characteristics. • Additional plasmonic features at low energy have been observed for both wires and ribbons. • Dielectric functions for both wires and ribbons are anisotropic (isotropic) at low (high) energy range. -- Abstract: We present first principle study of the electronic transport and dielectric properties of nanowires and nanoribbons of layered transition metal dichalcogenides (LTMDs), MX{sub 2} (M = Mo, W; X = S, Se, Te). The studied configuration shows metallic/semiconducting nature and the states around the Fermi energy are mainly contributed by the d orbitals of metal atoms. Zero-bias transmission show 1G{sub 0} conductance for the ribbons of MoS{sub 2} and WS{sub 2}; 2G{sub 0} conductance for MoS{sub 2}, WS{sub 2}, WSe{sub 2} wires, and ribbons of MoTe{sub 2} and WTe{sub 2}; and 3G{sub 0} conductance for WSe{sub 2} ribbon. The studied configurations show non-linear current–voltage (I–V) characteristics. Negative differential conductance (NDC) has also been observed for the nanoribbons of the selenides and tellurides of both Mo and W. Furthermore, additional plasmonic features below 5 eV energy have been observed for both wires and ribbons as compared to the corresponding monolayers, which is found to be red-shifted on going from nanowires to nanoribbons.

  16. Helium, iron and electron particle transport and energy transport studies on the TFTR tokamak

    International Nuclear Information System (INIS)

    Synakowski, E.J.; Efthimion, P.C.; Rewoldt, G.; Stratton, B.C.; Tang, W.M.; Grek, B.; Hill, K.W.; Hulse, R.A.; Johnson, D.W.; Mansfield, D.K.; McCune, D.; Mikkelsen, D.R.; Park, H.K.; Ramsey, A.T.; Redi, M.H.; Scott, S.D.; Taylor, G.; Timberlake, J.; Zarnstorff, M.C.

    1993-03-01

    Results from helium, iron, and electron transport on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor

  17. Helium, Iron and Electron Particle Transport and Energy Transport Studies on the TFTR Tokamak

    Science.gov (United States)

    Synakowski, E. J.; Efthimion, P. C.; Rewoldt, G.; Stratton, B. C.; Tang, W. M.; Grek, B.; Hill, K. W.; Hulse, R. A.; Johnson, D .W.; Mansfield, D. K.; McCune, D.; Mikkelsen, D. R.; Park, H. K.; Ramsey, A. T.; Redi, M. H.; Scott, S. D.; Taylor, G.; Timberlake, J.; Zarnstorff, M. C. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Kissick, M. W. (Wisconsin Univ., Madison, WI (United States))

    1993-03-01

    Results from helium, iron, and electron transport on TFTR in L-mode and Supershot deuterium plasmas with the same toroidal field, plasma current, and neutral beam heating power are presented. They are compared to results from thermal transport analysis based on power balance. Particle diffusivities and thermal conductivities are radially hollow and larger than neoclassical values, except possibly near the magnetic axis. The ion channel dominates over the electron channel in both particle and thermal diffusion. A peaked helium profile, supported by inward convection that is stronger than predicted by neoclassical theory, is measured in the Supershot The helium profile shape is consistent with predictions from quasilinear electrostatic drift-wave theory. While the perturbative particle diffusion coefficients of all three species are similar in the Supershot, differences are found in the L-Mode. Quasilinear theory calculations of the ratios of impurity diffusivities are in good accord with measurements. Theory estimates indicate that the ion heat flux should be larger than the electron heat flux, consistent with power balance analysis. However, theoretical values of the ratio of the ion to electron heat flux can be more than a factor of three larger than experimental values. A correlation between helium diffusion and ion thermal transport is observed and has favorable implications for sustained ignition of a tokamak fusion reactor.

  18. Artemisinin inhibits chloroplast electron transport activity: mode of action.

    Directory of Open Access Journals (Sweden)

    Adyasha Bharati

    Full Text Available Artemisinin, a secondary metabolite produced in Artemisia plant species, besides having antimalarial properties is also phytotoxic. Although, the phytotoxic activity of the compound has been long recognized, no information is available on the mechanism of action of the compound on photosynthetic activity of the plant. In this report, we have evaluated the effect of artemisinin on photoelectron transport activity of chloroplast thylakoid membrane. The inhibitory effect of the compound, under in vitro condition, was pronounced in loosely and fully coupled thylakoids; being strong in the former. The extent of inhibition was drastically reduced in the presence of uncouplers like ammonium chloride or gramicidin; a characteristic feature described for energy transfer inhibitors. The compound, on the other hand, when applied to plants (in vivo, behaved as a potent inhibitor of photosynthetic electron transport. The major site of its action was identified to be the Q(B; the secondary quinone moiety of photosystemII complex. Analysis of photoreduction kinetics of para-benzoquinone and duroquinone suggest that the inhibition leads to formation of low pool of plastoquinol, which becomes limiting for electron flow through photosystemI. Further it was ascertained that the in vivo inhibitory effect appeared as a consequence of the formation of an unidentified artemisinin-metabolite rather than by the interaction of the compound per se. The putative metabolite of artemisinin is highly reactive in instituting the inhibition of photosynthetic electron flow eventually reducing the plant growth.

  19. Nonlinear Right-Hand Polarized Wave in Plasma in the Electron Cyclotron Resonance Region

    Science.gov (United States)

    Krasovitskiy, V. B.; Turikov, V. A.

    2018-05-01

    The propagation of a nonlinear right-hand polarized wave along an external magnetic field in subcritical plasma in the electron cyclotron resonance region is studied using numerical simulations. It is shown that a small-amplitude plasma wave excited in low-density plasma is unstable against modulation instability with a modulation period equal to the wavelength of the excited wave. The modulation amplitude in this case increases with decreasing detuning from the resonance frequency. The simulations have shown that, for large-amplitude waves of the laser frequency range propagating in plasma in a superstrong magnetic field, the maximum amplitude of the excited longitudinal electric field increases with the increasing external magnetic field and can reach 30% of the initial amplitude of the electric field in the laser wave. In this case, the energy of plasma electrons begins to substantially increase already at magnetic fields significantly lower than the resonance value. The laser energy transferred to plasma electrons in a strong external magnetic field is found to increase severalfold compared to that in isotropic plasma. It is shown that this mechanism of laser radiation absorption depends only slightly on the electron temperature.

  20. Nonperturbative quantum simulation of time-resolved nonlinear spectra: Methodology and application to electron transfer reactions in the condensed phase

    International Nuclear Information System (INIS)

    Wang Haobin; Thoss, Michael

    2008-01-01

    A quantum dynamical method is presented to accurately simulate time-resolved nonlinear spectra for complex molecular systems. The method combines the nonpertubative approach to describe nonlinear optical signals with the multilayer multiconfiguration time-dependent Hartree theory to calculate the laser-induced polarization for the overall field-matter system. A specific nonlinear optical signal is obtained by Fourier decomposition of the overall polarization. The performance of the method is demonstrated by applications to photoinduced ultrafast electron transfer reactions in mixed-valence compounds and at dye-semiconductor interfaces

  1. Elastic properties and electron transport in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Migunov, Vadim

    2013-02-22

    The electron transport and elastic properties of InAs nanowires grown by chemical vapor deposition on InAs (001) substrate were studied experimentally, in-situ in a transmission electron microscope (TEM). A TEM holder allowing the measurement of a nanoforce while simultaneous imaging nanowire bending was used. Diffraction images from local areas of the wire were recorded to correlate elastic properties with the atomic structure of the nanowires. Another TEM holder allowing the application of electrical bias between the nanowire and an apex of a metallic needle while simultaneous imaging the nanowire in TEM or performing electron holography was used to detect mechanical vibrations in mechanical study or holographical observation of the nanowire inner potential in the electron transport studies. The combination of the scanning probe methods with TEM allows to correlate the measured electric and elastic properties of the nanowires with direct identification of their atomic structure. It was found that the nanowires have different atomic structures and different stacking fault defect densities that impacts critically on the elastic properties and electric transport. The unique methods, that were applied in this work, allowed to obtain dependencies of resistivity and Young's modulus of left angle 111 right angle -oriented InAs nanowires on defect density and diameter. It was found that the higher is the defect density the higher are the resistivity and the Young's modulus. Regarding the resistivity, it was deduced that the stacking faults increase the scattering of the electrons in the nanowire. These findings are consistent with the literature, however, the effect described by the other groups is not so pronounced. This difference can be attributed to the significant incompleteness of the physical models used for the data analysis. Regarding the elastic modulus, there are several mechanisms affecting the elasticity of the nanowires discussed in the thesis. It

  2. Electronic transport and magnetization dynamics in magnetic systems

    International Nuclear Information System (INIS)

    Borlenghi, Simone

    2011-01-01

    The aim of this thesis is to understand the mutual influence between electronic transport and magnetization dynamics in magnetic hybrid metallic nano-structures. At first, we have developed a theoretical model, based on random matrix theory, to describe at microscopic level spin dependent transport in a heterogeneous nano-structure. This model, called Continuous Random Matrix Theory (CRMT), has been implemented in a simulation code that allows one to compute local (spin torque, spin accumulation and spin current) and macroscopic (resistance) transport properties of spin valves. To validate this model, we have compared it with a quantum theory of transport based on the non equilibrium Green's functions formalism. Coupling the two models has allowed to perform a multi-scale description of metallic hybrid nano-structures, where ohmic parts are described using CRMT, while purely quantum parts are described using Green's functions. Then, we have coupled CRMT to a micro-magnetic simulation code, in order to describe the complex dynamics of the magnetization induced by spin transfer effect. The originality of this approach consists in modelling a spectroscopic experiment based on a mechanical detection of the ferromagnetic resonance, and performed on a spin torque nano-oscillator. This work has allowed us to obtain the dynamical phase diagram of the magnetization, and to detect the selection rules for spin waves induced by spin torque, as well as the competition between the Eigen-modes of the system when a dc current flows through the multilayer, in partial agreement with experimental data. (author)

  3. Relativistic electron-beam transport in curved channels

    International Nuclear Information System (INIS)

    Vittitoe, C.N.; Morel, J.E.; Wright, T.P.

    1982-01-01

    Collisionless single particle trajectories are modeled for a single plasma channel having one section curved in a circular arc. The magnetic field is developed by superposition of straight and curved channel segments. The plasma density gives charge and beam-current neutralization. High transport efficiencies are found for turning a relativistic electron beam 90 0 under reasonable conditions of plasma current, beam energy, arc radius, channel radius, and injection distributions in velocity and in position at the channel entrance. Channel exit distributions in velocity and position are found consistent with those for a straight plasma channel of equivalent length. Such transport problems are important in any charged particle-beam application constrained by large diode-to-target distance or by requirements of maximum power deposition in a confined area

  4. Contacting nanowires and nanotubes with atomic precision for electronic transport

    KAUST Repository

    Qin, Shengyong; Hellstrom, Sondra; Bao, Zhenan; Boyanov, Boyan; Li, An-Ping

    2012-01-01

    Making contacts to nanostructures with atomic precision is an important process in the bottom-up fabrication and characterization of electronic nanodevices. Existing contacting techniques use top-down lithography and chemical etching, but lack atomic precision and introduce the possibility of contamination. Here, we report that a field-induced emission process can be used to make local contacts onto individual nanowires and nanotubes with atomic spatial precision. The gold nano-islands are deposited onto nanostructures precisely by using a scanning tunneling microscope tip, which provides a clean and controllable method to ensure both electrically conductive and mechanically reliable contacts. To demonstrate the wide applicability of the technique, nano-contacts are fabricated on silicide atomic wires, carbon nanotubes, and copper nanowires. The electrical transport measurements are performed in situ by utilizing the nanocontacts to bridge the nanostructures to the transport probes. © 2012 American Institute of Physics.

  5. Strain modification on electronic transport of the phosphorene nanoribbon

    Directory of Open Access Journals (Sweden)

    Yawen Yuan

    2017-07-01

    Full Text Available We demonstrate theoretically how local strains can be tailored to control quantum transport of carriers on monolayer armchair and zigzag phosphorene nanoribbon. We find that the electron tunneling is forbidden when the in-plane strain exceeds a critical value. The critical strain is different for different crystal orientation of the ribbons, widths, and incident energies. By tuning the Fermi energy and strain, the channels can be transited from opaque to transparent. Moreover, for the zigzag-phosphorene nanoribbon, the two-fold degenerate quasi-flat edge band splits completely under certain strain. These properties provide us an efficient way to control the transport of monolayer phosphorene-based microstructure.

  6. New Computational Approach to Electron Transport in Irregular Graphene Nanostructures

    Science.gov (United States)

    Mason, Douglas; Heller, Eric; Prendergast, David; Neaton, Jeffrey

    2009-03-01

    For novel graphene devices of nanoscale-to-macroscopic scale, many aspects of their transport properties are not easily understood due to difficulties in fabricating devices with regular edges. Here we develop a framework to efficiently calculate and potentially screen electronic transport properties of arbitrary nanoscale graphene device structures. A generalization of the established recursive Green's function method is presented, providing access to arbitrary device and lead geometries with substantial computer-time savings. Using single-orbital nearest-neighbor tight-binding models and the Green's function-Landauer scattering formalism, we will explore the transmission function of irregular two-dimensional graphene-based nanostructures with arbitrary lead orientation. Prepared by LBNL under contract DE-AC02-05CH11231 and supported by the U.S. Dept. of Energy Computer Science Graduate Fellowship under grant DE-FG02-97ER25308.

  7. Discrete-ordinates electron transport calculations using standard neutron transport codes

    International Nuclear Information System (INIS)

    Morel, J.E.

    1979-01-01

    The primary purpose of this work was to develop a method for using standard neutron transport codes to perform electron transport calculations. The method is to develop approximate electron cross sections which are sufficiently well-behaved to be treated with standard S/sub n/ methods, but which nonetheless yield flux solutions which are very similar to the exact solutions. The main advantage of this approach is that, once the approximate cross sections are constructed, their multigroup Legendre expansion coefficients can be calculated and input to any standard S/sub n/ code. Discrete-ordinates calculations were performed to determine the accuracy of the flux solutions for problems corresponding to 1.0-MeV electrons incident upon slabs of aluminum and gold. All S/sub n/ calculations were compared with similar calculations performed with an electron Monte Carlo code, considered to be exact. In all cases, the discrete-ordinates solutions for integral flux quantities (i.e., scalar flux, energy deposition profiles, etc.) are generally in agreement with the Monte Carlo solutions to within approximately 5% or less. The central conclusion is that integral electron flux quantities can be efficiently and accurately calculated using standard S/sub n/ codes in conjunction with approximate cross sections. Furthermore, if group structures and approximate cross section construction are optimized, accurate differential flux energy spectra may also be obtainable without having to use an inordinately large number of energy groups. 1 figure

  8. Nonlocal collisionless and collisional electron transport in low temperature plasmas

    Science.gov (United States)

    Kaganovich, Igor

    2009-10-01

    The purpose of the talk is to describe recent advances in nonlocal electron kinetics in low-pressure plasmas. A distinctive property of partially ionized plasmas is that such plasmas are always in a non-equilibrium state: the electrons are not in thermal equilibrium with the neutral species and ions, and the electrons are also not in thermodynamic equilibrium within their own ensemble, which results in a significant departure of the electron velocity distribution function from a Maxwellian. These non-equilibrium conditions provide considerable freedom to choose optimal plasma parameters for applications, which make gas discharge plasmas remarkable tools for a variety of plasma applications, including plasma processing, discharge lighting, plasma propulsion, particle beam sources, and nanotechnology. Typical phenomena in such discharges include nonlocal electron kinetics, nonlocal electrodynamics with collisionless electron heating, and nonlinear processes in the sheaths and in the bounded plasmas. Significant progress in understanding the interaction of electromagnetic fields with real bounded plasma created by this field and the resulting changes in the structure of the applied electromagnetic field has been one of the major achievements of the last decade in this area of research [1-3]. We show on specific examples that this progress was made possible by synergy between full scale particle-in-cell simulations, analytical models, and experiments. In collaboration with Y. Raitses, A.V. Khrabrov, Princeton Plasma Physics Laboratory, Princeton, NJ, USA; V.I. Demidov, UES, Inc., 4401 Dayton-Xenia Rd., Beavercreek, OH 45322, USA and AFRL, Wright-Patterson AFB, OH 45433, USA; and D. Sydorenko, University of Alberta, Edmonton, Canada. [4pt] [1] D. Sydorenko, A. Smolyakov, I. Kaganovich, and Y. Raitses, IEEE Trans. Plasma Science 34, 895 (2006); Phys. Plasmas 13, 014501 (2006); 14 013508 (2007); 15, 053506 (2008). [0pt] [2] I. D. Kaganovich, Y. Raitses, D. Sydorenko, and

  9. Effect of contact barrier on electron transport in graphene.

    Science.gov (United States)

    Zhou, Yang-Bo; Han, Bing-Hong; Liao, Zhi-Min; Zhao, Qing; Xu, Jun; Yu, Da-Peng

    2010-01-14

    The influence of the barrier between metal electrodes and graphene on the electrical properties was studied on a two-electrode device. A classical barrier model was used to analyze the current-voltage characteristics. Primary parameters including barrier height and effective resistance were achieved. The electron transport properties under magnetic field were further investigated. An abnormal peak-valley-peak shape of voltage-magnetoresistance curve was observed. The underlying mechanisms were discussed under the consideration of the important influence of the contact barrier. Our results indicate electrical properties of graphene based devices are sensitive to the contact interface.

  10. Quantum oscillations and the electronic transport properties in multichain nanorings

    International Nuclear Information System (INIS)

    Racolta, D.

    2009-01-01

    We consider a system of multichain nanorings in static electric and magnetic field. The magnetic field induces characteristic phase changes. These phase shifts produce interference phenomena in the case of nanosystems for which the coherence length is larger than the sample dimension. We obtain energy solutions that are dependent on the number of sites N α characterizing a chain, of phase on the phase φ α and on the applied voltage. We found rich oscillations structures exhibited by the magnetic flux and we established the transmission probability. This proceeds by applying Landauer conductance formulae which opens the way to study electronic transport properties. (authors)

  11. Monte Carlo methods in electron transport problems. Pt. 1

    International Nuclear Information System (INIS)

    Cleri, F.

    1989-01-01

    The condensed-history Monte Carlo method for charged particles transport is reviewed and discussed starting from a general form of the Boltzmann equation (Part I). The physics of the electronic interactions, together with some pedagogic example will be introduced in the part II. The lecture is directed to potential users of the method, for which it can be a useful introduction to the subject matter, and wants to establish the basis of the work on the computer code RECORD, which is at present in a developing stage

  12. Electron transport in silicon nanowires having different cross-sections

    Directory of Open Access Journals (Sweden)

    Muscato Orazio

    2016-06-01

    Full Text Available Transport phenomena in silicon nanowires with different cross-section are investigated using an Extended Hydrodynamic model, coupled to the Schrödinger-Poisson system. The model has been formulated by closing the moment system derived from the Boltzmann equation on the basis of the maximum entropy principle of Extended Thermodynamics, obtaining explicit closure relations for the high-order fluxes and the production terms. Scattering of electrons with acoustic and non polar optical phonons have been taken into account. The bulk mobility is evaluated for square and equilateral triangle cross-sections of the wire.

  13. Electronic transport for armchair graphene nanoribbons with a potential barrier

    International Nuclear Information System (INIS)

    Zhou Benliang; Zhou Benhu; Liao Wenhu; Zhou Guanghui

    2010-01-01

    We theoretically investigate the electronic transport properties through a rectangular potential barrier embedded in armchair-edge graphene nanoribbons (AGNRs) of various widths. Using the Landauer formula and Dirac equation with the continuity conditions for all segments of wave functions at the interfaces between regions inside and outside the barrier, we calculate analytically the conductance and Fano factor for the both metallic and semiconducting AGNRs, respectively. It is shown that, by some numerical examples, at Dirac point the both types of AGNRs own a minimum conductance associated with the maximum Fano factor. The results are discussed and compared with the previous relevant works.

  14. Electronic transport properties in [n]cycloparaphenylenes molecular devices

    Science.gov (United States)

    Hu, Lizhi; Guo, Yandong; Yan, Xiaohong; Zeng, Hongli; Zhou, Jie

    2017-07-01

    The electronic transport of [n]cycloparaphenylenes ([n]CPPs) is investigated based on nonequilibrium Green's function formalism in combination with the density-functional theory. Negative differential resistance (NDR) phenomenon is observed. Further analysis shows that the reduction of the transmission peak induced by the bias changing near Fermi energy results in the NDR effect. Replacing the electrode (from carbon chain to Au electrode), doping with N atom and changing the size of the nanohoop (n = 5, 6, 8, 10) have also been studied and the NDR still exists, suggesting the NDR behavior is the intrinsic feature of such [n]CPPs systems, which would be quite useful in future nanoelectronic devices.

  15. Electronic structure, transport, and collective effects in molecular layered systems

    Directory of Open Access Journals (Sweden)

    Torsten Hahn

    2017-10-01

    Full Text Available The great potential of organic heterostructures for organic device applications is exemplified by the targeted engineering of the electronic properties of phthalocyanine-based systems. The transport properties of two different phthalocyanine systems, a pure copper phthalocyanine (CoPc and a flourinated copper phthalocyanine–manganese phthalocyanine (F16CoPc/MnPc heterostructure, are investigated by means of density functional theory (DFT and the non-equilibrium Green’s function (NEGF approach. Furthermore, a master-equation-based approach is used to include electronic correlations beyond the mean-field-type approximation of DFT. We describe the essential theoretical tools to obtain the parameters needed for the master equation from DFT results. Finally, an interacting molecular monolayer is considered within a master-equation approach.

  16. Transport Characteristics of Mesoscopic Radio-Frequency Single Electron Transistor

    International Nuclear Information System (INIS)

    Phillips, A. H.; Kirah, K.; Aly, N. A. I.; El-Sayes, H. E.

    2008-01-01

    The transport property of a quantum dot under the influence of external time-dependent field is investigated. The mesoscopic device is modelled as semiconductor quantum dot coupled weakly to superconducting leads via asymmetric double tunnel barriers of different heights. An expression for the current is deduced by using the Landauer–Buttiker formula, taking into consideration of both the Coulomb blockade effect and the magnetic field. It is found that the periodic oscillation of the current with the magnetic field is controlled by the ratio of the frequency of the applied ac-field to the electron cyclotron frequency. Our results show that the present device operates as a radio-frequency single electron transistor

  17. Fundamental models of electronic transport in amorphous semiconductors

    International Nuclear Information System (INIS)

    Emin, D.

    1982-01-01

    Significant fundamental questions lie at the heart of our understanding of the electronic and optical properties of semiconducting and insulating glasses. In this article the principal features of the Mott-CFO model and the small-polaron model are described. While the Mott-CFO model seems to apply to the high-mobility electron transport in glassy SiO 2 and Cd 2 As 3 it does not appear applicable to the most frequently studied chalocogenide glasses. Furthermore, the Mott-CFO model does not account for as basic a feature as the sign of the Hall effect. On the other hand, the small-polaron model accounts for the observed d.c. conductivity, Peltier heat and Hall mobility in a very simple and direct manner

  18. Electronic transport properties of carbon nanotube metal-semiconductor-metal

    Directory of Open Access Journals (Sweden)

    F Khoeini

    2008-07-01

    Full Text Available  In this work, we study electronic transport properties of a quasi-one dimensional pure semi-conducting Zigzag Carbon Nanotube (CNT attached to semi-infinite clean metallic Zigzag CNT leads, taking into account the influence of topological defect in junctions. This structure may behave like a field effect transistor. The calculations are based on the tight-binding model and Green’s function method, in which the local density of states(LDOS in the metallic section to semi-conducting section, and muli-channel conductance of the system are calculated in the coherent and linear response regime, numerically. Also we have introduced a circuit model for the system and investigated its current. The theoretical results obtained, can be a base, for developments in designing nano-electronic devices.

  19. Nonlinear dust-acoustic structures in space plasmas with superthermal electrons, positrons, and ions

    Energy Technology Data Exchange (ETDEWEB)

    Saberian, E., E-mail: e.saberian@neyshabur.ac.ir [University of Neyshabur, Department of Physics, Faculty of Basic Sciences (Iran, Islamic Republic of); Esfandyari-Kalejahi, A.; Afsari-Ghazi, M. [Azarbaijan Shahid Madani University, Department of Physics, Faculty of Sciences (Iran, Islamic Republic of)

    2017-01-15

    Some features of nonlinear dust-acoustic (DA) structures are investigated in a space plasma consisting of superthermal electrons, positrons, and positive ions in the presence of negatively charged dust grains with finite-temperature by employing a pseudo-potential technique in a hydrodynamic model. For this purpose, it is assumed that the electrons, positrons, and ions obey a kappa-like (κ) distribution in the background of adiabatic dust population. In the linear analysis, it is found that the dispersion relation yield two positive DA branches, i.e., the slow and fast DA waves. The upper branch (fast DA waves) corresponds to the case in which both (negatively charged) dust particles and (positively charged) ion species oscillate in phase with electrons and positrons. On the other hand, the lower branch (slow DA waves) corresponds to the case in which only dust particles oscillate in phase with electrons and positrons, while ion species are in antiphase with them. On the other hand, the fully nonlinear analysis shows that the existence domain of solitons and their characteristics depend strongly on the dust charge, ion charge, dust temperature, and the spectral index κ. It is found that the minimum/maximum Mach number increases as the spectral index κ increases. Also, it is found that only solitons with negative polarity can propagate and that their amplitudes increase as the parameter κ increases. Furthermore, the domain of Mach number shifts to the lower values, when the value of the dust charge Z{sub d} increases. Moreover, it is found that the Mach number increases with an increase in the dust temperature. Our analysis confirms that, in space plasmas with highly charged dusts, the presence of superthermal particles (electrons, positrons, and ions) may facilitate the formation of DA solitary waves. Particularly, in two cases of hydrogen ions H{sup +} (Z{sub i} = 1) and doubly ionized Helium atoms He{sup 2+} (Z{sub i} = 2), the mentioned results are the same

  20. Control of electron internal transport barriers in TCV

    Energy Technology Data Exchange (ETDEWEB)

    Henderson, M A; Behn, R; Coda, S; Condrea, I; Duval, B P; Goodman, T P; Karpushov, A; Martin, Y; Martynov, An; Moret, J-M; Nikkola, P; Porte, L; Sauter, O; Scarabosio, A; Zhuang, G [Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CRPP-EPFL, 1015 Lausanne (Switzerland)

    2004-05-01

    Current profile tailoring has been performed by application of electron cyclotron heating (ECH) and electron cyclotron current drive, leading to improved energy confinement in the plasma core of the TCV tokamak. The improved confinement is characterized by a substantial enhancement (H-factor) of the global electron energy confinement time relative to the prediction of the RLW scaling law (Rebut P H et al 1989 Proc. 12th Int. Conf. of Plasma Physics and Controlled Fusion Research (Nice, 1988) vol 2 (Vienna: IAEA) p 191), which predicts well Ohmic and standard ECH discharges on TCV. The improved confinement is attributed to a hollow current density profile producing a reversed shear profile creating an electron internal transport barrier. We relate the strength of the barrier to the depth of the hollow current density profile and the volume enclosed by the radial location of the peak current density. The {rho}{sub T}{sup *} (Tresset G et al 2002 Nucl. Fusion 42 520) criterion is used to evaluate the performance of the barrier relative to changes in the ECH parameters or the addition of Ohmic current, which aid in identifying the control parameters available for improving either the strength or volume of the barrier for enhanced performance. A figure of merit for the global scaling factor is used that scales the confinement enhancement as the product of the barrier volume and strength.

  1. Electron transport in heavily doped GdN

    Science.gov (United States)

    Maity, T.; Trodahl, H. J.; Natali, F.; Ruck, B. J.; Vézian, S.

    2018-01-01

    We report measurements of electron transport phenomena in the intrinsic ferromagnetic semiconductor GdN doped with 1.3 ×1021cm-3 electrons. The conductivity, carrier concentration, and thermoelectric power are compared with expectations based on an LSDA+U band structure. In the ferromagnetic state the carriers fill the majority-spin conduction band pockets to the bottom of the minority-spin band. The resistance implies an electron mobility of 18 cm2V-1s-1 at zero temperature, and in turn a mean-free path of 10-30 nm. Spin disorder scattering rapidly reduces the mobility near the 70 K Curie temperature (TC). The thermoelectric power is negative in the paramagnetic phase, as expected for a n -type conductor, with a magnitude that is in agreement with the Fermi energy implied by the band structure. The thermopower reverses sign to be positive in the ferromagnetic phase, which correlates with a strongly temperature-dependent electron diffusion from spin-disorder scattering that increases rapidly as the temperature rises toward TC.

  2. Control of electron internal transport barriers in TCV

    International Nuclear Information System (INIS)

    Henderson, M A; Behn, R; Coda, S; Condrea, I; Duval, B P; Goodman, T P; Karpushov, A; Martin, Y; Martynov, An; Moret, J-M; Nikkola, P; Porte, L; Sauter, O; Scarabosio, A; Zhuang, G

    2004-01-01

    Current profile tailoring has been performed by application of electron cyclotron heating (ECH) and electron cyclotron current drive, leading to improved energy confinement in the plasma core of the TCV tokamak. The improved confinement is characterized by a substantial enhancement (H-factor) of the global electron energy confinement time relative to the prediction of the RLW scaling law (Rebut P H et al 1989 Proc. 12th Int. Conf. of Plasma Physics and Controlled Fusion Research (Nice, 1988) vol 2 (Vienna: IAEA) p 191), which predicts well Ohmic and standard ECH discharges on TCV. The improved confinement is attributed to a hollow current density profile producing a reversed shear profile creating an electron internal transport barrier. We relate the strength of the barrier to the depth of the hollow current density profile and the volume enclosed by the radial location of the peak current density. The ρ T * (Tresset G et al 2002 Nucl. Fusion 42 520) criterion is used to evaluate the performance of the barrier relative to changes in the ECH parameters or the addition of Ohmic current, which aid in identifying the control parameters available for improving either the strength or volume of the barrier for enhanced performance. A figure of merit for the global scaling factor is used that scales the confinement enhancement as the product of the barrier volume and strength

  3. Modified Monte Carlo method for study of electron transport in degenerate electron gas in the presence of electron-electron interactions, application to graphene

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2017-07-01

    Standard computational methods used to take account of the Pauli Exclusion Principle into Monte Carlo (MC) simulations of electron transport in semiconductors may give unphysical results in low field regime, where obtained electron distribution function takes values exceeding unity. Modified algorithms were already proposed and allow to correctly account for electron scattering on phonons or impurities. Present paper extends this approach and proposes improved simulation scheme allowing including Pauli exclusion principle for electron-electron (e-e) scattering into MC simulations. Simulations with significantly reduced computational cost recreate correct values of the electron distribution function. Proposed algorithm is applied to study transport properties of degenerate electrons in graphene with e-e interactions. This required adapting the treatment of e-e scattering in the case of linear band dispersion relation. Hence, this part of the simulation algorithm is described in details.

  4. Unique electron transport in ultrathin black phosphorene: Ab-initio study

    International Nuclear Information System (INIS)

    Srivastava, Anurag; Khan, Md. Shahzad; Gupta, Sanjeev Kumar; Pandey, Ravindra

    2015-01-01

    Graphical abstract: Charge transfer configuration for NH 3 and NO 2 adsorbed 2D black-phospherene. - Highlights: • Ultrathin black phosphorene has been investigated, in terms of its optical and ballistic quantum transport properties. • The device performance subtaintially increases in armchair direction of black phosphorene. • Maximum reflectivity (43%) is observed at 1.85 eV (670 nm) and the reflective spectrum dispersed in visible range. • At low bias semiconducting and higher bias ohmic nature pointing black phospherene a promising material for high perfomrance device applications. • For NO 2 gas, this quasi 2D-black phosphorene surface shows strong affinity followed with substantial charge tranfer. - Abstract: We present first principle structural, electronic, optical and transport analysis of black phosphorene a 2D layered material. The studied configuration shows semiconducting nature and the states around the Fermi energy are mainly contributed by the p-orbitals of atoms. In optical properties, the reflective spectrum is approximately dispersed in visible range suggesting that this 2D-nanostructure can be considered as shielding for visible region. Due to the anisotropy of the electronic structure of black phosphorene, the device performance is subtaintially preferable in armchair direction. Zero-bias transmission shows no conductance channel near Fermi level but in far region prominent spectra for the same is observed for black-phospherene. The studied configurations show non-linear current–voltage (I–V) characteristics. The sensitivity for NH 3 and NO 2 gas molecule is explored using electronic and current–voltage (I–V) characteristics. Investigations show that the black phosphorene has strong affinity for electron seeking NO 2 molecule, thus providing an opportunity for its sensor application.

  5. Unique electron transport in ultrathin black phosphorene: Ab-initio study

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Anurag, E-mail: profanurag@gmail.com [Advanced Materials Research Group, Computational Nanoscience & Technology Lab, ABV-Indian Institute of Information Technology and Management, Gwalior (M.P.) 474010 India (India); Khan, Md. Shahzad [Advanced Materials Research Group, Computational Nanoscience & Technology Lab, ABV-Indian Institute of Information Technology and Management, Gwalior (M.P.) 474010 India (India); Gupta, Sanjeev Kumar [Department of Physics, St. Xavier' s College, Ahmedabad 380009 (India); Pandey, Ravindra [Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States)

    2015-11-30

    Graphical abstract: Charge transfer configuration for NH{sub 3} and NO{sub 2} adsorbed 2D black-phospherene. - Highlights: • Ultrathin black phosphorene has been investigated, in terms of its optical and ballistic quantum transport properties. • The device performance subtaintially increases in armchair direction of black phosphorene. • Maximum reflectivity (43%) is observed at 1.85 eV (670 nm) and the reflective spectrum dispersed in visible range. • At low bias semiconducting and higher bias ohmic nature pointing black phospherene a promising material for high perfomrance device applications. • For NO{sub 2} gas, this quasi 2D-black phosphorene surface shows strong affinity followed with substantial charge tranfer. - Abstract: We present first principle structural, electronic, optical and transport analysis of black phosphorene a 2D layered material. The studied configuration shows semiconducting nature and the states around the Fermi energy are mainly contributed by the p-orbitals of atoms. In optical properties, the reflective spectrum is approximately dispersed in visible range suggesting that this 2D-nanostructure can be considered as shielding for visible region. Due to the anisotropy of the electronic structure of black phosphorene, the device performance is subtaintially preferable in armchair direction. Zero-bias transmission shows no conductance channel near Fermi level but in far region prominent spectra for the same is observed for black-phospherene. The studied configurations show non-linear current–voltage (I–V) characteristics. The sensitivity for NH{sub 3} and NO{sub 2} gas molecule is explored using electronic and current–voltage (I–V) characteristics. Investigations show that the black phosphorene has strong affinity for electron seeking NO{sub 2} molecule, thus providing an opportunity for its sensor application.

  6. Nonlinear collisionless electron cyclotron interaction in the pre-ionisation stage

    Science.gov (United States)

    Farina, D.

    2018-06-01

    Electron cyclotron (EC) wave-particle interaction is theoretically investigated in the pre-ionisation phase, much before collisions and other mechanisms can play a role. In the very first phase of a plasma discharge with EC-assisted breakdown, the motion of an electron at room temperature in a static magnetic field under the action of a localised microwave beam is nonlinear, and transition to states of larger energy can occur via wave trapping. Within a Hamiltonian adiabatic formalism, the conditions at which the particles gain energy in single beam crossing are derived in a rigorous way, and the energy variation is characterized quantitatively as a function of the wave frequency, harmonic number, polarisation and EC power and beam width. Estimates of interest for applications to tokamak start-up are obtained for the first, second and third cyclotron harmonic. The investigation confirms that electrons can easily gain energies well above the ionisation energy in most conditions at the first two harmonics, while not at the third harmonic, as observed in experiments.

  7. Non-linear effects and thermoelectric efficiency of quantum dot-based single-electron transistors.

    Science.gov (United States)

    Talbo, Vincent; Saint-Martin, Jérôme; Retailleau, Sylvie; Dollfus, Philippe

    2017-11-01

    By means of advanced numerical simulation, the thermoelectric properties of a Si-quantum dot-based single-electron transistor operating in sequential tunneling regime are investigated in terms of figure of merit, efficiency and power. By taking into account the phonon-induced collisional broadening of energy levels in the quantum dot, both heat and electrical currents are computed in a voltage range beyond the linear response. Using our homemade code consisting in a 3D Poisson-Schrödinger solver and the resolution of the Master equation, the Seebeck coefficient at low bias voltage appears to be material independent and nearly independent on the level broadening, which makes this device promising for metrology applications as a nanoscale standard of Seebeck coefficient. Besides, at higher voltage bias, the non-linear characteristics of the heat current are shown to be related to the multi-level effects. Finally, when considering only the electronic contribution to the thermal conductance, the single-electron transistor operating in generator regime is shown to exhibit very good efficiency at maximum power.

  8. Linear and nonlinear studies of velocity shear driven three dimensional electron-magnetohydrodynamics instability

    International Nuclear Information System (INIS)

    Gaur, Gurudatt; Das, Amita

    2012-01-01

    The study of electron velocity shear driven instability in electron magnetohydrodynamics (EMHD) regime in three dimensions has been carried out. It is well known that the instability is non-local in the plane defined by the flow direction and that of the shear, which is the usual Kelvin-Helmholtz mode, often termed as the sausage mode in the context of EMHD. On the other hand, a local instability with perturbations in the plane defined by the shear and the magnetic field direction exists which is termed as kink mode. The interplay of these two modes for simple sheared flow case as well as that when an external magnetic field exists has been studied extensively in the present manuscript in both linear and nonlinear regimes. Finally, these instability processes have been investigated for the exact 2D dipole solutions of EMHD equations [M. B. Isichenko and A. N. Marnachev, Sov. Phys. JETP 66, 702 (1987)] for which the electron flow velocity is sheared. It has been shown that dipoles are very robust and stable against the sausage mode as the unstable wavelengths are typically longer than the dipole size. However, we observe that they do get destabilized by the local kink mode.

  9. Electron transport in a bilayer graphene/layered superconductor NbSe2 junction: effect of work function difference

    Science.gov (United States)

    Yarimizu, Katsuhide; Tomori, Hikari; Watanabe, Kenji; Taniguchi, Takashi; Kanda, Akinobu

    2018-03-01

    We have experimentally studied electron transport in a bilayer graphene (BLG)/layered superconductor NbSe2 junction encapsulated with hexagonal boron nitride. The junction exhibits nonlinear current-voltage characteristics which strongly depend on the gate voltage around the charge neutrality point (CNP) of the BLG. Besides, we observe that the gate voltage dependence of electron transport in the BLG portion close to the junction interface is different from that of the BLG portion apart from the interface, indicating that the spatial variation of the Dirac point in the charge transfer region due to the difference in work function between superconductor and graphene needs to be considered in the analysis of the superconducting proximity effect.

  10. Electron beam instabilities in unmagnetized plasmas via the Stieltjes transform (linear theory and nonlinear mode coupling)

    International Nuclear Information System (INIS)

    Krishan, S.

    2007-01-01

    The Stieltjes transform has been used in place of a more common Laplace transform to determine the time evolution of the self-consistent field (SCF) of an unmagnetized semi-infinite plasma, where the plasma electrons together with a primary and a low-density secondary electron beam move perpendicular to the boundary surface. The secondary beam is produced when the primary beam strikes the grid. Such a plasma system has been investigated by Griskey and Stanzel [M. C. Grisky and R. L. Stenzel, Phys. Rev. Lett. 82, 556 (1999)]. The physical phenomenon, observed in their experiment, has been named by them as ''secondary beam instability.'' The character of the instability observed in the experiment is not the same as predicted by the conventional treatments--the field amplitude does not grow with time. In the frequency spectrum, the theory predicts peak values in the amplitude of SCF at the plasma frequency of plasma and secondary beam electrons, decreasing above and below it. The Stieltjes transform for functions, growing exponentially in the long time limit, does not exist, while the Laplace transform technique gives only exponentially growing solutions. Therefore, it should be interesting to know the kind of solutions that an otherwise physically unstable plasma will yield. In the high-frequency limit, the plasma has been found to respond to any arbitrary frequency of the initial field differentiated only by the strength of the resulting SCF. The condition required for exponential growth in the conventional treatments, and the condition for maximum amplitude (with respect to frequency) in the present treatment, have been found to be the same. Nonlinear mode coupling between the modes excited by the plasma electrons and the low-density secondary beam gives rise to two frequency-dependent peaks in the field amplitude, symmetrically located about the much stronger peak due to the plasma electrons, as predicted by the experiment

  11. Nonlinear theory of ion-acoustic waves in an ideal plasma with degenerate electrons

    International Nuclear Information System (INIS)

    Dubinov, A. E.; Dubinova, A. A.

    2007-01-01

    A nonlinear theory is constructed that describes steady-state ion-acoustic waves in an ideal plasma in which the electron component is a degenerate Fermi gas and the ion component is a classical gas. The parameter ranges in which such a plasma can exist are determined, and dispersion relations for ion-acoustic waves are obtained that make it possible to find the linear ion-acoustic velocity. Analytic gas-dynamic models of ion sound are developed for a plasma with the ion component as a cold, an isothermal, or an adiabatic gas, and moreover, the solutions to the equations of all the models are brought to a quadrature form. Profiles of a subsonic periodic and a supersonic solitary wave are calculated, and the upper critical Mach numbers of a solitary wave are determined. For a plasma with cold ions, the critical Mach number is expressed by an explicit exact formula

  12. Initial state dependence of nonlinear kinetic equations: The classical electron gas

    International Nuclear Information System (INIS)

    Marchetti, M.C.; Cohen, E.G.D.; Dorfman, J.R.; Kirkpatrick, T.R.

    1985-01-01

    The method of nonequilibrium cluster expansion is used to study the decay to equilibrium of a weakly coupled inhomogeneous electron gas prepared in a local equilibrium state at the initial time, t=0. A nonlinear kinetic equation describing the long time behavior of the one-particle distribution function is obtained. For consistency, initial correlations have to be taken into account. The resulting kinetic equation-differs from that obtained when the initial state of the system is assumed to be factorized in a product of one-particle functions. The question of to what extent correlations in the initial state play an essential role in determining the form of the kinetic equation at long times is discussed. To that end, the present calculations are compared wih results obtained before for hard sphere gases and in general with strong short-range forces. A partial answer is proposed and some open questions are indicated

  13. Identifying the molecular functions of electron transport proteins using radial basis function networks and biochemical properties.

    Science.gov (United States)

    Le, Nguyen-Quoc-Khanh; Nguyen, Trinh-Trung-Duong; Ou, Yu-Yen

    2017-05-01

    The electron transport proteins have an important role in storing and transferring electrons in cellular respiration, which is the most proficient process through which cells gather energy from consumed food. According to the molecular functions, the electron transport chain components could be formed with five complexes with several different electron carriers and functions. Therefore, identifying the molecular functions in the electron transport chain is vital for helping biologists understand the electron transport chain process and energy production in cells. This work includes two phases for discriminating electron transport proteins from transport proteins and classifying categories of five complexes in electron transport proteins. In the first phase, the performances from PSSM with AAIndex feature set were successful in identifying electron transport proteins in transport proteins with achieved sensitivity of 73.2%, specificity of 94.1%, and accuracy of 91.3%, with MCC of 0.64 for independent data set. With the second phase, our method can approach a precise model for identifying of five complexes with different molecular functions in electron transport proteins. The PSSM with AAIndex properties in five complexes achieved MCC of 0.51, 0.47, 0.42, 0.74, and 1.00 for independent data set, respectively. We suggest that our study could be a power model for determining new proteins that belongs into which molecular function of electron transport proteins. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    Magerl, Elisabeth

    2011-01-01

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  15. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  16. Electronic transport properties of copper and gold at atomic scale

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadzadeh, Saeideh

    2010-11-23

    The factors governing electronic transport properties of copper and gold atomic-size contacts are theoretically examined in the present work. A two-terminal conductor using crystalline electrodes is adopted. The non-equilibrium Green's function combined with the density functional tight-binding method is employed via gDFTB simulation tool to calculate the transport at both equilibrium and non-equilibrium conditions. The crystalline orientation, length, and arrangement of electrodes have very weak influence on the electronic characteristics of the considered atomic wires. The wire width is found to be the most effective geometric aspect determining the number of conduction channels. The obtained conductance oscillation and linear current-voltage curves are interpreted. To analyze the conduction mechanism in detail, the transmission channels and their decomposition to the atomic orbitals are calculated in copper and gold single point contacts. The presented results offer a possible explanation for the relation between conduction and geometric structure. Furthermore, the results are in good agreement with available experimental and theoretical studies. (orig.)

  17. One-Dimensional Electron Transport Layers for Perovskite Solar Cells

    Directory of Open Access Journals (Sweden)

    Ujwal K. Thakur

    2017-04-01

    Full Text Available The electron diffusion length (Ln is smaller than the hole diffusion length (Lp in many halide perovskite semiconductors meaning that the use of ordered one-dimensional (1D structures such as nanowires (NWs and nanotubes (NTs as electron transport layers (ETLs is a promising method of achieving high performance halide perovskite solar cells (HPSCs. ETLs consisting of oriented and aligned NWs and NTs offer the potential not merely for improved directional charge transport but also for the enhanced absorption of incoming light and thermodynamically efficient management of photogenerated carrier populations. The ordered architecture of NW/NT arrays affords superior infiltration of a deposited material making them ideal for use in HPSCs. Photoconversion efficiencies (PCEs as high as 18% have been demonstrated for HPSCs using 1D ETLs. Despite the advantages of 1D ETLs, there are still challenges that need to be overcome to achieve even higher PCEs, such as better methods to eliminate or passivate surface traps, improved understanding of the hetero-interface and optimization of the morphology (i.e., length, diameter, and spacing of NWs/NTs. This review introduces the general considerations of ETLs for HPSCs, deposition techniques used, and the current research and challenges in the field of 1D ETLs for perovskite solar cells.

  18. One-Dimensional Electron Transport Layers for Perovskite Solar Cells

    Science.gov (United States)

    Thakur, Ujwal K.; Kisslinger, Ryan; Shankar, Karthik

    2017-01-01

    The electron diffusion length (Ln) is smaller than the hole diffusion length (Lp) in many halide perovskite semiconductors meaning that the use of ordered one-dimensional (1D) structures such as nanowires (NWs) and nanotubes (NTs) as electron transport layers (ETLs) is a promising method of achieving high performance halide perovskite solar cells (HPSCs). ETLs consisting of oriented and aligned NWs and NTs offer the potential not merely for improved directional charge transport but also for the enhanced absorption of incoming light and thermodynamically efficient management of photogenerated carrier populations. The ordered architecture of NW/NT arrays affords superior infiltration of a deposited material making them ideal for use in HPSCs. Photoconversion efficiencies (PCEs) as high as 18% have been demonstrated for HPSCs using 1D ETLs. Despite the advantages of 1D ETLs, there are still challenges that need to be overcome to achieve even higher PCEs, such as better methods to eliminate or passivate surface traps, improved understanding of the hetero-interface and optimization of the morphology (i.e., length, diameter, and spacing of NWs/NTs). This review introduces the general considerations of ETLs for HPSCs, deposition techniques used, and the current research and challenges in the field of 1D ETLs for perovskite solar cells. PMID:28468280

  19. Electronic transport in bismuth selenide in the topological insulator regime

    Science.gov (United States)

    Kim, Dohun

    The 3D topological insulators (TIs) have an insulating bulk but spin-momentum coupled metallic surface states stemming from band inversion due to strong spin-orbit interaction, whose existence is guaranteed by the topology of the band structure of the insulator. While the STI surface state has been studied spectroscopically by e.g. photoemission and scanned probes, transport experiments have failed to demonstrate clear signature of the STI due to high level of bulk conduction. In this thesis, I present experimental results on the transport properties of TI material Bi2Se3 in the absence of bulk conduction (TI regime), achieved by applying novel p-type doping methods. Field effect transistors consisting of thin (thickness: 5-17 nm) Bi2Se3 are fabricated by mechanical exfoliation of single crystals, and a combination of conventional dielectric (300 nm thick SiO2) and electrochemical or chemical gating methods are used to move the Fermi energy through the surface Dirac point inside bulk band gap, revealing the ambipolar gapless nature of transport in the Bi2Se3 surface states. The minimum conductivity of the topological surface state is understood within the self-consistent theory of Dirac electrons in the presence of charged impurities. The intrinsic finite-temperature resistivity of the topological surface state due to electron-acoustic phonon scattering is measured to be 60 times larger than that of graphene largely due to the smaller Fermi and sound velocities in Bi2Se 3, which will have implications for topological electronic devices operating at room temperature. Along with semi-classical Boltzmann transport, I also discuss 2D weak anti-localization (WAL) behavior of the topological surface states. By investigating gate-tuned WAL behavior in thin (5-17 nm) TI films, I show that WAL in the TI regime is extraordinarily sensitive to the hybridization induced quantum mechanical tunneling between top and bottom topological surfaces, and interplay of phase coherence

  20. Self-amplified spontaneous emission free electron laser devices and nonideal electron beam transport

    Directory of Open Access Journals (Sweden)

    L. L. Lazzarino

    2014-11-01

    Full Text Available We have developed, at the SPARC test facility, a procedure for a real time self-amplified spontaneous emission free electron laser (FEL device performance control. We describe an actual FEL, including electron and optical beam transport, through a set of analytical formulas, allowing a fast and reliable on-line “simulation” of the experiment. The system is designed in such a way that the characteristics of the transport elements and the laser intensity are measured and adjusted, via a real time computation, during the experimental run, to obtain an on-line feedback of the laser performances. The detail of the procedure and the relevant experimental results are discussed.

  1. Development of nonperturbative nonlinear optics models including effects of high order nonlinearities and of free electron plasma: Maxwell–Schrödinger equations coupled with evolution equations for polarization effects, and the SFA-like nonlinear optics model

    International Nuclear Information System (INIS)

    Lorin, E; Bandrauk, A D; Lytova, M; Memarian, A

    2015-01-01

    This paper is dedicated to the exploration of non-conventional nonlinear optics models for intense and short electromagnetic fields propagating in a gas. When an intense field interacts with a gas, usual nonlinear optics models, such as cubic nonlinear Maxwell, wave and Schrödinger equations, derived by perturbation theory may become inaccurate or even irrelevant. As a consequence, and to include in particular the effect of free electrons generated by laser–molecule interaction, several heuristic models, such as UPPE, HOKE models, etc, coupled with Drude-like models [1, 2], were derived. The goal of this paper is to present alternative approaches based on non-heuristic principles. This work is in particular motivated by the on-going debate in the filamentation community, about the effect of high order nonlinearities versus plasma effects due to free electrons, in pulse defocusing occurring in laser filaments [3–9]. The motivation of our work goes beyond filamentation modeling, and is more generally related to the interaction of any external intense and (short) pulse with a gas. In this paper, two different strategies are developed. The first one is based on the derivation of an evolution equation on the polarization, in order to determine the response of the medium (polarization) subject to a short and intense electromagnetic field. Then, we derive a combined semi-heuristic model, based on Lewenstein’s strong field approximation model and the usual perturbative modeling in nonlinear optics. The proposed model allows for inclusion of high order nonlinearities as well as free electron plasma effects. (paper)

  2. Generation of Nonlinear Electric Field Bursts in the Outer Radiation Belt through Electrons Trapping by Oblique Whistler Waves

    Science.gov (United States)

    Agapitov, Oleksiy; Drake, James; Mozer, Forrest

    2016-04-01

    Huge numbers of different nonlinear structures (double layers, electron holes, non-linear whistlers, etc. referred to as Time Domain Structures - TDS) have been observed by the electric field experiment on board the Van Allen Probes. A large part of the observed non-linear structures are associated with whistler waves and some of them can be directly driven by whistlers. The parameters favorable for the generation of TDS were studied experimentally as well as making use of 2-D particle-in-cell (PIC) simulations for the system with inhomogeneous magnetic field. It is shown that an outward propagating front of whistlers and hot electrons amplifies oblique whistlers which collapse into regions of intense parallel electric field with properties consistent with recent observations of TDS from the Van Allen Probe satellites. Oblique whistlers seed the parallel electric fields that are driven by the beams. The resulting parallel electric fields trap and heat the precipitating electrons. These electrons drive spikes of intense parallel electric field with characteristics similar to the TDSs seen in the VAP data. The decoupling of the whistler wave and the nonlinear electrostatic component is shown in PIC simulation in the inhomogeneous magnetic field system. These effects are observed by the Van Allen Probes in the radiation belts. The precipitating hot electrons propagate away from the source region in intense bunches rather than as a smooth flux.

  3. Particle-in-cell simulations of electron transport from plasma turbulence: recent progress in gyrokinetic particle simulations of turbulent plasmas

    International Nuclear Information System (INIS)

    Lin, Z; Rewoldt, G; Ethier, S; Hahm, T S; Lee, W W; Lewandowski, J L V; Nishimura, Y; Wang, W X

    2005-01-01

    Recent progress in gyrokinetic particle-in-cell simulations of turbulent plasmas using the gyrokinetic toroidal code (GTC) is surveyed. In particular, recent results for electron temperature gradient (ETG) modes and their resulting transport are presented. Also, turbulence spreading, and the effects of the parallel nonlinearity, are described. The GTC code has also been generalized for non-circular plasma cross-section, and initial results are presented. In addition, two distinct methods of generalizing the GTC code to be electromagnetic are described, along with preliminary results. Finally, a related code, GTC-Neo, for calculating neoclassical fluxes, electric fields, and velocities, are described

  4. Effects of Electrode Distances on Geometric Structure and Electronic Transport Properties of Molecular 4,4'-Bipyridine Junction

    International Nuclear Information System (INIS)

    Li Zongliang; Zou Bin; Wang Chuankui; Luo Yi

    2006-01-01

    Influences of electrode distances on geometric structure of molecule and on electronic transport properties of molecular junctions have been investigated by means of a generalized quantum chemical approach based on the elastic scattering Green's function method. Numerical results show that, for organic molecule 4,4'-bipyridine, the geometric structure of the molecule especially the dihedral angle between the two pyridine rings is sensitive to the distances between the two electrodes. The currents of the molecular junction are taken nonlinearly increase with the increase of the bias. Shortening the distance of the metallic electrodes will result in stronger coupling and larger conductance

  5. Electronic Interactions of n-Doped Perylene Diimide Groups Appended to Polynorbornene Chains: Implications for Electron Transport in Organic Electronics.

    Science.gov (United States)

    Nguyen, Minh T; Biberdorf, Joshua D; Holliday, Bradley J; Jones, Richard A

    2017-11-01

    A polymer consisting of a polynorbornene backbone with perylene diimide (PDI) pendant groups on each monomeric unit is synthesized via ring opening metathesis polymerization. The PDI pendant groups along the polymer backbone, studied by UV-vis absorption, fluorescence emission, and electron paramagnetic resonance spectroscopy in addition to electrochemical methods, show evidence of molecular aggregation and corresponding electronic coupling with neighboring groups, which forms pathways for efficient electron transport from one group to another in a specific reduced form. When n-doped, the title polymer shows redox conductivity of 5.4 × 10 -3 S cm -1 , comparable with crystalline PDI materials, and is therefore a promising material for use in organic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Nonlinear dynamics of circularly polarized laser pulse propagating in a magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons distributions

    Energy Technology Data Exchange (ETDEWEB)

    Etemadpour, R.; Dorranian, D., E-mail: doran@srbiau.ac.ir [Laser Laboratory, Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Sepehri Javan, N. [Department of Physics, University of Mohaghegh Ardabili, P.O. Box 179, Ardabil (Iran, Islamic Republic of)

    2016-05-15

    The nonlinear dynamics of a circularly polarized laser pulse propagating in the magnetized plasmas whose constituents are superthermal ions and mixed nonthermal high-energy tail electrons is studied theoretically. A nonlinear equation which describes the dynamics of the slowly varying amplitude is obtained using a relativistic two-fluid model. Based on this nonlinear equation and taking into account some nonlinear phenomena such as modulational instability, self-focusing and soliton formation are investigated. Effect of the magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons on these phenomena is considered. It is shown that the nonthermality and superthermality of particles can substantially change the nonlinearity of medium.

  7. Nonlinear dynamics of circularly polarized laser pulse propagating in a magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons distributions

    International Nuclear Information System (INIS)

    Etemadpour, R.; Dorranian, D.; Sepehri Javan, N.

    2016-01-01

    The nonlinear dynamics of a circularly polarized laser pulse propagating in the magnetized plasmas whose constituents are superthermal ions and mixed nonthermal high-energy tail electrons is studied theoretically. A nonlinear equation which describes the dynamics of the slowly varying amplitude is obtained using a relativistic two-fluid model. Based on this nonlinear equation and taking into account some nonlinear phenomena such as modulational instability, self-focusing and soliton formation are investigated. Effect of the magnetized plasma with superthermal ions and mixed nonthermal high-energy tail electrons on these phenomena is considered. It is shown that the nonthermality and superthermality of particles can substantially change the nonlinearity of medium.

  8. Transport in a toroidally confined pure electron plasma

    International Nuclear Information System (INIS)

    Crooks, S.M.; ONeil, T.M.

    1996-01-01

    O close-quote Neil and Smith [T.M. O close-quote Neil and R.A. Smith, Phys. Plasmas 1, 8 (1994)] have argued that a pure electron plasma can be confined stably in a toroidal magnetic field configuration. This paper shows that the toroidal curvature of the magnetic field of necessity causes slow cross-field transport. The transport mechanism is similar to magnetic pumping and may be understood by considering a single flux tube of plasma. As the flux tube of plasma undergoes poloidal ExB drift rotation about the center of the plasma, the length of the flux tube and the magnetic field strength within the flux tube oscillate, and this produces corresponding oscillations in T parallel and T perpendicular . The collisional relaxation of T parallel toward T perpendicular produces a slow dissipation of electrostatic energy into heat and a consequent expansion (cross-field transport) of the plasma. In the limit where the cross section of the plasma is nearly circular the radial particle flux is given by Γ r =1/2ν perpendicular,parallel T(r/ρ 0 ) 2 n/(-e∂Φ/∂r), where ν perpendicular,parallel is the collisional equipartition rate, ρ 0 is the major radius at the center of the plasma, and r is the minor radius measured from the center of the plasma. The transport flux is first calculated using this simple physical picture and then is calculated by solving the drift-kinetic Boltzmann equation. This latter calculation is not limited to a plasma with a circular cross section. copyright 1996 American Institute of Physics

  9. Projection-reduction method applied to deriving non-linear optical conductivity for an electron-impurity system

    Directory of Open Access Journals (Sweden)

    Nam Lyong Kang

    2013-07-01

    Full Text Available The projection-reduction method introduced by the present authors is known to give a validated theory for optical transitions in the systems of electrons interacting with phonons. In this work, using this method, we derive the linear and first order nonlinear optical conductivites for an electron-impurity system and examine whether the expressions faithfully satisfy the quantum mechanical philosophy, in the same way as for the electron-phonon systems. The result shows that the Fermi distribution function for electrons, energy denominators, and electron-impurity coupling factors are contained properly in organized manners along with absorption of photons for each electron transition process in the final expressions. Furthermore, the result is shown to be represented properly by schematic diagrams, as in the formulation of electron-phonon interaction. Therefore, in conclusion, we claim that this method can be applied in modeling optical transitions of electrons interacting with both impurities and phonons.

  10. Cross sections for electron and photon processes required by electron-transport calculations

    International Nuclear Information System (INIS)

    Peek, J.M.

    1979-11-01

    Electron-transport calculations rely on a large collection of electron-atom and photon-atom cross-section data to represent the response characteristics of the target medium. These basic atomic-physics quantities, and certain qualities derived from them that are now commonly in use, are critically reviewed. Publications appearing after 1978 are not given consideration. Processes involving electron or photon energies less than 1 keV are ignored, while an attempt is made to exhaustively cover the remaining independent parameters and target possibilities. Cases for which data improvements can be made from existing information are identified. Ranges of parameters for which state-of-the-art data are not available are sought out, and recommendations for explicit measurements and/or calculations with presently available tools are presented. An attempt is made to identify the maturity of the atomic-physics data and to predict the possibilities for rapid changes in the quality of the data. Finally, weaknesses in the state-of-the-art atomic-physics data and in the conceptual usage of these data in the context of electron-transport theory are discussed. Brief attempts are made to weight the various aspects of these questions and to suggest possible remedies

  11. Nonlinear optics

    International Nuclear Information System (INIS)

    Boyd, R.W.

    1992-01-01

    Nonlinear optics is the study of the interaction of intense laser light with matter. This book is a textbook on nonlinear optics at the level of a beginning graduate student. The intent of the book is to provide an introduction to the field of nonlinear optics that stresses fundamental concepts and that enables the student to go on to perform independent research in this field. This book covers the areas of nonlinear optics, quantum optics, quantum electronics, laser physics, electrooptics, and modern optics

  12. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    Energy Technology Data Exchange (ETDEWEB)

    Bajaj, Sanyam, E-mail: bajaj.10@osu.edu; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Reza, Shahed; Chumbes, Eduardo M. [Raytheon Integrated Defense Systems, Andover, Massachusetts 01810 (United States); Khurgin, Jacob [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Material Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2015-10-12

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  13. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    International Nuclear Information System (INIS)

    Bajaj, Sanyam; Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth

    2015-01-01

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10 7  cm/s at a low sheet charge density of 7.8 × 10 11  cm −2 . An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs

  14. Nonlinear interaction of a parallel-flow relativistic electron beam with a plasma

    International Nuclear Information System (INIS)

    Jungwirth, K.; Koerbel, S.; Simon, P.; Vrba, P.

    1975-01-01

    Nonlinear evolution of single-mode high-frequency instabilities (ω approximately ksub(parallel)vsub(b)) excited by a parallel-flow high-current relativistic electron beam in a magnetized plasma is investigated. Fairly general dimensionless equations are derived. They describe both the temporal and the spatial evolution of amplitude and phase of the fundamental wave. Numerically, the special case of excitation of the linearly most unstable mode is solved in detail assuming that the wave energy dissipation is negligible. Then the strength of interaction and the relativistic properties of the beam are fully respected by a single parameter lambda. The value of lambda ensuring the optimum efficiency of the wave excitation as well as the efficiency of the self-acceleration of some beam electrons at higher values of lambda>1 are determined in the case of a fully compensated relativistic beam. Finally, the effect of the return current dissipation is also included (phenomenologically) into the theoretical model, its role for the beam-plasma interaction being checked numerically. (J.U.)

  15. Enzymology of Electron Transport: Energy Generation with Geochemical Consequences

    Energy Technology Data Exchange (ETDEWEB)

    Dichristina, Thomas J.; Fredrickson, Jim K.; Zachara, John M.

    2005-12-20

    Dissimilatory metal-reducing bacteria (DMRB) are important components of the microbial community residing in redox-stratified freshwater and marine environments. DMRB occupy a central position in the biogeochemical cycles of metals, metalloids and radionuclides, and serve as catalysts for a variety of other environmentally important processes including biomineralization, biocorrosion, bioremediation and mediators of ground water quality. DMRB are presented, however, with a unique physiological challenge: they are required to respire anaerobically on terminal electron acceptors which are either highly insoluble (e.g., Fe(III)- and Mn(IV)-oxides) and reduced to soluble end-products or highly soluble (e.g., U(VI) and Tc(VII)) and reduced to insoluble end-products. To overcome physiological problems associated with metal and radionuclide solubility, DMRB are postulated to employ a variety of novel respiratory strategies not found in other gram-negative bacteria which respire on soluble electron acceptors such as O2, NO3- and SO42-. The novel respiratory strategies include (1) direct enzymatic reduction at the outer membrane, (2) electron shuttling pathways and (3) metal solubilization by exogenous or bacterially-produced organic ligands followed by reduction of soluble organic-metal compounds. The first section of this chapter highlights the latest findings on the enzymatic mechanisms of metal and radionuclide reduction by two of the most extensively studied DMRB (Geobacter and Shewanella), with particular emphasis on electron transport chain enzymology. The second section emphasizes the geochemical consequences of DMRB activity, including the direct and indirect effects on metal solubility, the reductive transformation of Fe- and Mn-containing minerals, and the biogeochemical cycling of metals at redox interfaces in chemically stratified environments.

  16. Enzymology of Electron Transport: Energy Generation with Geochemical Consequences

    International Nuclear Information System (INIS)

    Dichristina, Thomas J.; Fredrickson, Jim K.; Zachara, John M.

    2005-01-01

    Dissimilatory metal-reducing bacteria (DMRB) are important components of the microbial community residing in redox-stratified freshwater and marine environments. DMRB occupy a central position in the biogeochemical cycles of metals, metalloids and radionuclides, and serve as catalysts for a variety of other environmentally important processes including biomineralization, biocorrosion, bioremediation and mediators of ground water quality. DMRB are presented, however, with a unique physiological challenge: they are required to respire anaerobically on terminal electron acceptors which are either highly insoluble (e.g., Fe(III)- and Mn(IV)-oxides) and reduced to soluble end-products or highly soluble (e.g., U(VI) and Tc(VII)) and reduced to insoluble end-products. To overcome physiological problems associated with metal and radionuclide solubility, DMRB are postulated to employ a variety of novel respiratory strategies not found in other gram-negative bacteria which respire on soluble electron acceptors such as O2, NO3- and SO42-. The novel respiratory strategies include (1) direct enzymatic reduction at the outer membrane, (2) electron shuttling pathways and (3) metal solubilization by exogenous or bacterially-produced organic ligands followed by reduction of soluble organic-metal compounds. The first section of this chapter highlights the latest findings on the enzymatic mechanisms of metal and radionuclide reduction by two of the most extensively studied DMRB (Geobacter and Shewanella), with particular emphasis on electron transport chain enzymology. The second section emphasizes the geochemical consequences of DMRB activity, including the direct and indirect effects on metal solubility, the reductive transformation of Fe- and Mn-containing minerals, and the biogeochemical cycling of metals at redox interfaces in chemically stratified environments

  17. Electron cyclotron absorption in Tokamak plasmas in the presence of radial transport of particles

    International Nuclear Information System (INIS)

    Rosa, Paulo R. da S.; Ziebell, Luiz F.

    1998-01-01

    We use quasilinear theory to study effects of particle radial transport on the electron cyclotron absorption coefficient by a current carrying plasma, in a tokamak modelated as a plasma slab. Our numerical results indicate significant modification in the profile of the electron cyclotron absorption coefficient when transport is taken into account relative to the situation without transport. (author)

  18. Non-linear effects in electron cyclotron current drive applied for the stabilization of neoclassical tearing modes

    NARCIS (Netherlands)

    Ayten, B.; Westerhof, E.; ASDEX Upgrade team,

    2014-01-01

    Due to the smallness of the volumes associated with the flux surfaces around the O-point of a magnetic island, the electron cyclotron power density applied inside the island for the stabilization of neoclassical tearing modes (NTMs) can exceed the threshold for non-linear effects as derived

  19. Test of models for electron transport in laser produced plasmas

    International Nuclear Information System (INIS)

    Colombant, D.G.; Manheimer, W.M.; Busquet, M.

    2005-01-01

    This paper examines five different models of electron thermal transport in laser produced spherical implosions. These are classical, classical with a flux limit f, delocalization, beam deposition model, and Fokker-Planck solutions. In small targets, the results are strongly dependent on f for flux limit models, with small f's generating very steep temperature gradients. Delocalization models are characterized by large preheat in the center of the target. The beam deposition model agrees reasonably well with the Fokker-Planck simulation results. For large, high gain fusion targets, the delocalization model shows the gain substantially reduced by the preheat. However, flux limitation models show gain largely independent of f, with the beam deposition model also showing the same high gain

  20. Transport and acceleration of low-emittance electron beams

    International Nuclear Information System (INIS)

    Henke, H.

    1989-01-01

    Linear accelerators for colliders and for free-electron lasers require beams with both high brightness and low emittance. Their transport and acceleration is limited by single-particle effects originating from injection jitter, from the unavoidable position jitter of components, and from chromaticity. Collective phenomena, essentially due to wake fields acting within the bunch, are most severe in the case of high-frequency structures, i.e. a small aperture. Whilst, in the past, the transverse wake-field effects were believed to be most serious, we know that they can even be beneficial when inducing a corresponding spread in betatron oscillation either by an energy spread along the bunch or by an RF focusing system acting on the bunch scale. This paper evaluates the different effects by simple analytical means after making use of the smooth focusing approximation and the two-particle model. Numerical simulation results are used for verification. 14 refs., 6 figs., 2 tabs

  1. Hot Electron Generation and Transport Using Kα Emission

    International Nuclear Information System (INIS)

    Akli, K.U.; Stephens, R.B.; Key, M.H.; Bartal, T.; Beg, F.N.; Chawla, S.; Chen, C.D.; Fedosejevs, R.; Freeman, R.R.; Friesen, H.; Giraldez, E.; Green, J.S.; Hey, D.S.; Higginson, D.P.; Hund, J.; Jarrott, L.C.; Kemp, G.E.; King, J.A.; Kryger, A.; Lancaster, K.; LePape, S.; Link, A.; Ma, T.; Mackinnon, A.J.; MacPhee, A.G.; McLean, H.S.; Murphy, C.; Norreys, P.A.; Ovchinnikov, V.; Patel, P.K.; Ping, Y.; Sawada, H.; Schumacher, D.; Theobald, W.; Tsui, Y.Y.; Van Woerkom, L.D.; Wei, M.S.; Westover, B.; Yabuuchi, T.

    2010-01-01

    We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40(micro)m diameter wire emulating a 40(micro)m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of prepulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.

  2. Bias-dependent oscillatory electron transport of monatomic sulfur chains

    KAUST Repository

    Yu, Jing-Xin; Cheng, Yan; Sanvito, Stefano; Chen, Xiang-Rong

    2012-01-01

    The bias-dependent oscillatory electron transport of monatomic sulfur chains sandwiched between gold electrodes is investigated with density functional theory and non-equilibrium Green's function method. At zero bias, in contrast to the typical odd-even oscillations observed in most metallic chains, we find that the conductance oscillates with a period of four atoms. However, as the bias voltage is increased the current displays a two-atom periodicity. This emerges gradually, first for the longer chains and then, at voltages larger than 0.7 V, for lengths. The oscillatory behaviors are analyzed by the density of states and the energy-dependent and bias-dependent transmission coefficients. © 2012 American Institute of Physics.

  3. Bias-dependent oscillatory electron transport of monatomic sulfur chains

    KAUST Repository

    Yu, Jing-Xin

    2012-01-01

    The bias-dependent oscillatory electron transport of monatomic sulfur chains sandwiched between gold electrodes is investigated with density functional theory and non-equilibrium Green\\'s function method. At zero bias, in contrast to the typical odd-even oscillations observed in most metallic chains, we find that the conductance oscillates with a period of four atoms. However, as the bias voltage is increased the current displays a two-atom periodicity. This emerges gradually, first for the longer chains and then, at voltages larger than 0.7 V, for lengths. The oscillatory behaviors are analyzed by the density of states and the energy-dependent and bias-dependent transmission coefficients. © 2012 American Institute of Physics.

  4. Modeling Blazar Spectra by Solving an Electron Transport Equation

    Science.gov (United States)

    Lewis, Tiffany; Finke, Justin; Becker, Peter A.

    2018-01-01

    Blazars are luminous active galaxies across the entire electromagnetic spectrum, but the spectral formation mechanisms, especially the particle acceleration, in these sources are not well understood. We develop a new theoretical model for simulating blazar spectra using a self-consistent electron number distribution. Specifically, we solve the particle transport equation considering shock acceleration, adiabatic expansion, stochastic acceleration due to MHD waves, Bohm diffusive particle escape, synchrotron radiation, and Compton radiation, where we implement the full Compton cross-section for seed photons from the accretion disk, the dust torus, and 26 individual broad lines. We used a modified Runge-Kutta method to solve the 2nd order equation, including development of a new mathematical method for normalizing stiff steady-state ordinary differential equations. We show that our self-consistent, transport-based blazar model can qualitatively fit the IR through Fermi g-ray data for 3C 279, with a single-zone, leptonic configuration. We use the solution for the electron distribution to calculate multi-wavelength SED spectra for 3C 279. We calculate the particle and magnetic field energy densities, which suggest that the emitting region is not always in equipartition (a common assumption), but sometimes matter dominated. The stratified broad line region (based on ratios in quasar reverberation mapping, and thus adding no free parameters) improves our estimate of the location of the emitting region, increasing it by ~5x. Our model provides a novel view into the physics at play in blazar jets, especially the relative strength of the shock and stochastic acceleration, where our model is well suited to distinguish between these processes, and we find that the latter tends to dominate.

  5. Nonlinear analysis of wiggler-imperfections in free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Freund, H.P. [Naval Research Lab., Washington, DC (United States); Yu, L.H. [Brookhaven National Lab., Upton, NY (United States)

    1995-12-31

    We present an analysis of the effect of wiggler imperfections in FELs using a variety of techniques. Our basic intention is to compare wiggler averaged nonlinear simulations to determine the effect of various approximations on the estimates of gain degradation due to wiggler imperfections. The fundamental assumption in the wiggler-averaged formulations is that the electrons are described by a random walk model, and an analytic representation of the orbits is made. This is fundamentally different from the approach taken for the non-wiggler-averaged formulation in which the wiggler imperfections are specified at the outset, and the orbits are integrated using a field model that is consistent with the Maxwell equations. It has been conjectured on the basis of prior studies using the non-wiggler-averaged formalism that electrons follow a {open_quotes}meander line{close_quotes} through the wiggler governed by the specific imperfections; hence, the electrons behave more as a ball-in-groove than as a random walk. This conjecture is tested by comparison of the wiggler-averaged and non-wiggler-averaged simulations. In addition, two different wiggler models are employed in the non-wiggler-averaged simulation: one based upon a parabolic pole face wiggler which is not curl and divergence free in the presence of wiggler imperfections, and a second model in which the divergence and z-component of the curl vanish identically. This will gauge the effect of inconsistencies in the wiggler model on the estimation of the effect of the imperfections. Preliminary results indicate that the inconsistency introduced by the non-vanishing curl and divergence result in an overestimation of the effect of wiggler imperfections on the orbit. The wiggler-averaged simulation is based upon the TDA code, and the non-wiggler-averaged simulation is a variant of the ARACHNE and WIGGLIN codes called MEDUSA developed to treat short-wavelength Gauss-Hermite modes.

  6. Depolarization of the electron spin in storage rings by nonlinear spin-orbit coupling

    International Nuclear Information System (INIS)

    Kewisch, J.

    1985-10-01

    Electrons and positrons which circulate in the storage ring are polarized at the emission of synchrotron radiation by the so called Sokolov-Ternov effect. This polarization is on the one hand of large interest for the study of the weak interaction, on the other hand it can be used for the accurate measurement of the beam energy and by this of the mass of elementary particles. The transverse and longitudinal particle vibrations simultaneously excited by the synchrotron radiation however can effect that this polarization is destroyed. This effect is called spin-orbit coupling. For the calculation of the spin-orbit coupling the computer program SITROS was written. This program is a tracking program: The motion of some sample particles and their spin vectors are calculated for some thousand circulations. From this the mean depolarization and by extrapolation the degree of polarization of the equilibrium state is determined. Contrarily to the known program SLIM which is based on perturbational calculations in SITROS the nonlinear forces in the storage ring can be regarded. By this the calculation of depolarizing higher order resonances is made possible. In this thesis the equations of motion for the orbital and spin motion of the electrons are derived which form the base for the program SITROS. The functions of the program and the approximations necessary for the saving of calculational time are explained. The comparison of the SITROS results with the measurement results obtained at the PETRA storage ring shows that the SITROS program is a useful means for the planning and calculation of storage rings with polarized electron beams. (orig.) [de

  7. A parallel multi-domain solution methodology applied to nonlinear thermal transport problems in nuclear fuel pins

    Energy Technology Data Exchange (ETDEWEB)

    Philip, Bobby, E-mail: philipb@ornl.gov [Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831 (United States); Berrill, Mark A.; Allu, Srikanth; Hamilton, Steven P.; Sampath, Rahul S.; Clarno, Kevin T. [Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, TN 37831 (United States); Dilts, Gary A. [Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545 (United States)

    2015-04-01

    This paper describes an efficient and nonlinearly consistent parallel solution methodology for solving coupled nonlinear thermal transport problems that occur in nuclear reactor applications over hundreds of individual 3D physical subdomains. Efficiency is obtained by leveraging knowledge of the physical domains, the physics on individual domains, and the couplings between them for preconditioning within a Jacobian Free Newton Krylov method. Details of the computational infrastructure that enabled this work, namely the open source Advanced Multi-Physics (AMP) package developed by the authors is described. Details of verification and validation experiments, and parallel performance analysis in weak and strong scaling studies demonstrating the achieved efficiency of the algorithm are presented. Furthermore, numerical experiments demonstrate that the preconditioner developed is independent of the number of fuel subdomains in a fuel rod, which is particularly important when simulating different types of fuel rods. Finally, we demonstrate the power of the coupling methodology by considering problems with couplings between surface and volume physics and coupling of nonlinear thermal transport in fuel rods to an external radiation transport code.

  8. Simulation of electron beam formation and transport in a gas-filled electron-optical system with a plasma emitter

    Energy Technology Data Exchange (ETDEWEB)

    Grishkov, A. A. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation); Kornilov, S. Yu., E-mail: kornilovsy@gmail.com; Rempe, N. G. [Tomsk State University of Control Systems and Radioelectronics (Russian Federation); Shidlovskiy, S. V. [Tomsk State University (Russian Federation); Shklyaev, V. A. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation)

    2016-07-15

    The results of computer simulations of the electron-optical system of an electron gun with a plasma emitter are presented. The simulations are performed using the KOBRA3-INP, XOOPIC, and ANSYS codes. The results describe the electron beam formation and transport. The electron trajectories are analyzed. The mechanisms of gas influence on the energy inhomogeneity of the beam and its current in the regions of beam primary formation, acceleration, and transport are described. Recommendations for optimizing the electron-optical system with a plasma emitter are presented.

  9. ETRAN, Electron Transport and Gamma Transport with Secondary Radiation in Slab by Monte-Carlo

    International Nuclear Information System (INIS)

    1992-01-01

    A - Nature of physical problem solved: ETRAN computes the transport of electrons and photons through plane-parallel slab targets that have a finite thickness in one dimension and are unbound in the other two-dimensions. The incident radiation can consist of a beam of either electrons or photons with specified spectral and directional distribution. Options are available by which all orders of the electron-photon cascade can be included in the calculation. Thus electrons are allowed to give rise to secondary knock-on electrons, continuous Bremsstrahlung and characteristic x-rays; and photons are allowed to produce photo-electrons, Compton electrons, and electron- positron pairs. Annihilation quanta, fluorescence radiation, and Auger electrons are also taken into account. If desired, the Monte- Carlo histories of all generations of secondary radiations are followed. The information produced by ETRAN includes the following items: 1) reflection and transmission of electrons or photons, differential in energy and direction; 2) the production of continuous Bremsstrahlung and characteristic x-rays by electrons and the emergence of such radiations from the target (differential in photon energy and direction); 3) the spectrum of the amounts of energy left behind in a thick target by an incident electron beam; 4) the deposition of energy and charge by an electron beam as function of the depth in the target; 5) the flux of electrons, differential in energy, as function of the depth in the target. B - Method of solution: A programme called DATAPAC-4 takes data for a particular material from a library tape and further processes them. The function of DATAPAC-4 is to produce single-scattering and multiple-scattering data in the form of tabular arrays (again stored on magnetic tape) which facilitate the rapid sampling of electron and photon Monte Carlo histories in ETRAN. The photon component of the electron-photon cascade is calculated by conventional random sampling that imitates

  10. Nonlinear two-stream interaction between a cold, relativistic electron beam and a collisional plasma-Astron experiment

    International Nuclear Information System (INIS)

    Newberger, B.S.; Thode, L.E.

    1979-05-01

    Experiments on the two-stream instability of a relativistic electron beam propagating through a neutral gas, carried out with the Lawrence Livermore Laboratory Astron beam, have been analyzed using a nonlinear saturation model for a cold beam. The behavior of the observed microwave emission due to the instability is in good agreement with that of the beam energy loss. Collisions on the plasma electrons weaken the nonlinear state of the instability but do not stabilize the mode. The beam essentially acts as if it were cold, a result substantiated by linear theory for waves propagating along the beam. In order to predict the effect of both beam momentum scatter and plasma electron collisions on the stability of the mode in future experiments a full two-dimensional linear theory must be developed

  11. Humidity effects on the electronic transport properties in carbon based nanoscale device

    International Nuclear Information System (INIS)

    He, Jun; Chen, Ke-Qiu

    2012-01-01

    By applying nonequilibrium Green's functions in combination with the density functional theory, we investigate the effect of humidity on the electronic transport properties in carbon based nanoscale device. The results show that different humidity may form varied localized potential barrier, which is a very important factor to affect the stability of electronic transport in the nanoscale system. A mechanism for the humidity effect is suggested. -- Highlights: ► Electronic transport in carbon based nanoscale device. ► Humidity affects the stability of electronic transport. ► Different humidity may form varied localized potential barrier.

  12. Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions.

    Science.gov (United States)

    Krafft, C; Volokitin, A

    2013-05-01

    Horseshoe distributions are shell-like particle distributions that can arise in space and laboratory plasmas when particle beams propagate into increasing magnetic fields. The present paper studies the stability and the dynamics of wave packets interacting resonantly with electrons presenting low-energy horseshoe or shell-type velocity distributions in a magnetized plasma. The linear instability growth rates are determined as a function of the ratio of the plasma to the cyclotron frequencies, of the velocity and the opening angle of the horseshoe, and of the relative thickness of the shell. The nonlinear stage of the instability is investigated numerically using a symplectic code based on a three-dimensional Hamiltonian model. Simulation results show that the dynamics of the system is mainly governed by wave-particle interactions at Landau and normal cyclotron resonances and that the high-order normal cyclotron resonances play an essential role. Specific features of the dynamics of particles interacting simultaneously with two or more waves at resonances of different natures and orders are discussed, showing that such complex processes determine the main characteristics of the wave spectrum's evolution. Simulations with wave packets presenting quasicontinuous spectra provide a full picture of the relaxation of the horseshoe distribution, revealing two main phases of the evolution: an initial stage of wave energy growth, characterized by a fast filling of the shell, and a second phase of slow damping of the wave energy, accompanied by final adjustments of the electron distribution. The influence of the density inhomogeneity along the horseshoe on the wave-particle dynamics is also discussed.

  13. Electron Temperature Fluctuation Measurements and Transport Model Validation at Alcator C-Mod

    Energy Technology Data Exchange (ETDEWEB)

    White, Anne [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

    2017-06-22

    The tokamak is a type of toroidal device used to confine a fusion plasma using large magnetic fields. Tokamaks and stellarators the leading devices for confining plasmas for fusion, and the capability to predict performance in these magnetically confined plasmas is essential for developing a sustainable fusion energy source. The magnetic configuration of tokamaks and stellarators does not exist in Nature, yet, the fundamental processes governing transport in fusion plasmas are universal – turbulence and instabilities, driven by inhomogeneity and asymmetry in the plasma, conspire to transport heat and particles across magnetic field lines and can play critical roles in impurity confinement and generation of intrinsic rotation. Turbulence exists in all plasmas, and in neutral fluids as well. The study of turbulence is essential to developing a fundamental understanding of the nature of the fourth state of matter, plasmas. Experimental studies of turbulence in tokamaks date back to early scattering observations from the late 1970s. Since that time, great advances in turbulence diagnostics have been made, all of which have significantly enhanced our knowledge and understanding of turbulence in tokamaks. Through comparisons with advanced gyrokinetic theory and turbulent-transport models a great deal of evidence exists to implicate turbulent-driven transport as an important mechanism determining transport in all channels: heat, particle and momentum However, prediction and control of turbulent-driven transport remains elusive. Key to development of predictive transport models for magnetically confined fusion plasmas is validation of the nonlinear gyrokinetic transport model, which describes transport due to turbulence. Validation of gyrokinetic codes must include detailed and quantitative comparisons with measured turbulence characteristics, in addition to comparisons with inferred transport levels and equilibrium profiles. For this reason, advanced plasma diagnostics

  14. Nonlinear optics

    CERN Document Server

    Bloembergen, Nicolaas

    1996-01-01

    Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe

  15. Nonlinear systems

    CERN Document Server

    Palmero, Faustino; Lemos, M; Sánchez-Rey, Bernardo; Casado-Pascual, Jesús

    2018-01-01

    This book presents an overview of the most recent advances in nonlinear science. It provides a unified view of nonlinear properties in many different systems and highlights many  new developments. While volume 1 concentrates on mathematical theory and computational techniques and challenges, which are essential for the study of nonlinear science, this second volume deals with nonlinear excitations in several fields. These excitations can be localized and transport energy and matter in the form of breathers, solitons, kinks or quodons with very different characteristics, which are discussed in the book. They can also transport electric charge, in which case they are known as polarobreathers or solectrons. Nonlinear excitations can influence function and structure in biology, as for example, protein folding. In crystals and other condensed matter, they can modify transport properties, reaction kinetics and interact with defects. There are also engineering applications in electric lattices, Josephson junction a...

  16. Monte Carlo Studies of Electron Transport In Semiconductor Nanostructures

    Science.gov (United States)

    Tierney, Brian David

    An Ensemble Monte Carlo (EMC) computer code has been developed to simulate, semi-classically, spin-dependent electron transport in quasi two-dimensional (2D) III-V semiconductors. The code accounts for both three-dimensional (3D) and quasi-2D transport, utilizing either 3D or 2D scattering mechanisms, as appropriate. Phonon, alloy, interface roughness, and impurity scattering mechanisms are included, accounting for the Pauli Exclusion Principle via a rejection algorithm. The 2D carrier states are calculated via a self-consistent 1D Schrodinger-3D-Poisson solution in which the charge distribution of the 2D carriers in the quantization direction is taken as the spatial distribution of the squared envelope functions within the Hartree approximation. The wavefunctions, subband energies, and 2D scattering rates are updated periodically by solving a series of 1D Schrodinger wave equations (SWE) over the real-space domain of the device at fixed time intervals. The electrostatic potential is updated by periodically solving the 3D Poisson equation. Spin-polarized transport is modeled via a spin density-matrix formalism that accounts for D'yakanov-Perel (DP) scattering. Also, the code allows for the easy inclusion of additional scattering mechanisms and structural modifications to devices. As an application of the simulator, the current voltage characteristics of an InGaAs/InAlAs HEMT are simulated, corresponding to nanoscale III-V HEMTs currently being fabricated by Intel Corporation. The comparative effects of various scattering parameters, material properties and structural attributes are investigated and compared with experiments where reasonable agreement is obtained. The spatial evolution of spin-polarized carriers in prototypical Spin Field Effect Transistor (SpinFET) devices is then simulated. Studies of the spin coherence times in quasi-2D structures is first investigated and compared to experimental results. It is found that the simulated spin coherence times for

  17. NON-LINEAR TRANSIENT HEAT CONDUCTION ANALYSIS OF INSULATION WALL OF TANK FOR TRANSPORTATION OF LIQUID ALUMINUM

    Directory of Open Access Journals (Sweden)

    Miroslav M Živković

    2010-01-01

    Full Text Available This paper deals with transient nonlinear heat conduction through the insulation wall of the tank for transportation of liquid aluminum. Tanks designed for this purpose must satisfy certain requirements regarding temperature of loading and unloading, during transport. Basic theoretical equations are presented, which describe the problem of heat conduction finite element (FE analysis, starting from the differential equation of energy balance, taking into account the initial and boundary conditions of the problem. General 3D problem for heat conduction is considered, from which solutions for two- and one-dimensional heat conduction can be obtained, as special cases. Forming of the finite element matrices using Galerkin method is briefly described. The procedure for solving equations of energy balance is discussed, by methods of resolving iterative processes of nonlinear transient heat conduction. Solution of this problem illustrates possibilities of PAK-T software package, such as materials properties, given as tabular data, or analytical functions. Software also offers the possibility to solve nonlinear and transient problems with incremental methods. Obtained results for different thicknesses of the tank wall insulation materials enable its comparison in regards to given conditions

  18. Considerations of beta and electron transport in internal dose calculations

    International Nuclear Information System (INIS)

    Bolch, W.E.; Poston, J.W. Sr.

    1990-12-01

    Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A ampersand M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial transport of electron and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each use, preliminary results are very encouraging and plans for further research are detailed within this document. 22 refs., 13 figs., 1 tab

  19. Changes in mitochondrial electron transport chain activity during insect metamorphosis.

    Science.gov (United States)

    Chamberlin, M E

    2007-02-01

    The midgut of the tobacco hornworm (Manduca sexta) is a highly aerobic tissue that is destroyed by programmed cell death during larval-pupal metamorphosis. The death of the epithelium begins after commitment to pupation, and the oxygen consumption of isolated midgut mitochondria decreases soon after commitment. To assess the role of the electron transport chain in this decline in mitochondrial function, the maximal activities of complexes I-IV of the respiratory chain were measured in isolated midgut mitochondria. Whereas there were no developmental changes in the activity of complex I or III, activities of complexes II and IV [cytochrome c oxidase (COX)] were higher in mitochondria from precommitment than postcommitment larvae. This finding is consistent with a higher rate of succinate oxidation in mitochondria isolated from precommitment larvae and reveals that the metamorphic decline in mitochondrial respiration is due to the targeted destruction or inactivation of specific sites within the mitochondria, rather than the indiscriminate destruction of the organelles. The COX turnover number (e- x s(-1) x cytochrome aa3(-1)) was greater for the enzyme from precommitment than postcommitment larvae, indicating a change in the enzyme structure and/or its lipid environment during the early stages of metamorphosis. The turnover number of COX in the intact mitochondria (in organello COX) was also lower in postcommitment larvae. In addition to changes in the protein or membrane phospholipids, the metamorphic decline in this rate constant may be a result of the observed loss of endogenous cytochrome c.

  20. Considerations of beta and electron transport in internal dose calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bolch, W.E.; Poston, J.W. Sr.

    1990-12-01

    Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial transport of electron and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each case, preliminary results are very encouraging and plans for further research are detailed within this document.