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)
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).
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
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.
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
Garland, N. A.; Boyle, G. J.; Cocks, D. G.; White, R. D.
2018-02-01
This study reviews the neutral density dependence of electron transport in gases and liquids and develops a method to determine the nonlinear medium density dependence of electron transport coefficients and scattering rates required for modeling transport in the vicinity of gas-liquid interfaces. The method has its foundations in Blanc’s law for gas-mixtures and adapts the theory of Garland et al (2017 Plasma Sources Sci. Technol. 26) to extract electron transport data across the gas-liquid transition region using known data from the gas and liquid phases only. The method is systematically benchmarked against multi-term Boltzmann equation solutions for Percus-Yevick model liquids. Application to atomic liquids highlights the utility and accuracy of the derived method.
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.
Electron-phonon interaction and nonlinear transport phenomena in solid Hg point-contacts
Energy Technology Data Exchange (ETDEWEB)
Khotkevych, V V [Department of Physics, University of Bath, Claverton Down, BA2 7AY Bath (United Kingdom); Khotkevych, N V [Department of Physics, Karazin National University, 61077 Kharkiv (Ukraine); Morlok, S V [National Technical University, 61002, Kharkiv (Ukraine); Konopatskyi, B L; Khotkevych, A V [B.Verkin Institute for Low Temperature Physics and Engineering, 61103 Kharkiv (Ukraine)], E-mail: V.Khotkevych@bath.ac.uk
2009-02-01
At cryogenic temperatures the conductivity of Hg point-contacts was studied in both the superconducting and normal state. An original method of fabricating the Hg-based point-contacts directly in liquid {sup 4}He was proposed, which guaranteed creation of small-size high-purity ballistic contacts. The resistance of the contacts as well as the current-voltage characteristics along with the voltage dependence of their first and second derivatives were experimentally investigated at 1.5 K. We analyze such characteristics of the contacts as Josephson critical current, excess current, energy gap and the nonlinear part of conductivity caused by electron-phonon interaction (EPI). The point-contact EPI function g{sub pc}({omega}) for Hg was reconstructed and integral parameters of EPI were calculated. The g{sub pc}({omega}) was then used as an approximation to the phonon density of states for estimations of the thermodynamic characteristics in Hg. Finally we discuss the results of our calculations of non-linear conductivity caused by manifestation of the frequency dependence of the energy gap function in the elastic current component through the contact.
Nonlinear chiral transport phenomena
Chen, Jiunn-Wei; Ishii, Takeaki; Pu, Shi; Yamamoto, Naoki
2016-06-01
We study the nonlinear responses of relativistic chiral matter to the external fields such as the electric field E , gradients of temperature and chemical potential, ∇T and ∇μ . Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to ∇μ ×E due to the interplay between the effects of the Berry curvature and collisions. We also derive an analog of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.
Nonlinear heat and particle transport due to collisional drift waves
Energy Technology Data Exchange (ETDEWEB)
Nishi-kawa, K.I.; Hatori, T.; Terashima, Y.
1977-03-01
The nonlinear evolution of unstable modes which govern transport processes in magnetically confined plasmas were investigated. A nonlinear theory of unstable collisional drift wave, and the consequent nonlinear transport were extended to include electron and ion temperature gradients. Thermal transport properties are discussed and basic equations are given.
Nonlinear dynamics and plasma transport
Energy Technology Data Exchange (ETDEWEB)
Antonsen, T.M. Jr.; Drake, J.F.; Finn, J.M.; Guzdar, P.N.; Hassam, A.B.; Sageev, R.Z.
1993-01-01
This progress report details work done on a program in nonlinear dynamical aspects of plasma turbulence and transport funded by DOE since 1989. This program has been in cooperation with laboratories in theUSSR [now Russia and the Confederation of Independent States (CIS)]. The purpose of this program has been: To promote the utilization of recent pathbreaking developments in nonlinear science in plasma turbulence and transport. To promote cooperative scientific investigations between the US and CIS in the related areas of nonlinear science and plasma turbulence and transport. 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. This allows for a deeper analysis and understanding of the system both analytically and numerically.
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)
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...
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...
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)
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)
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)
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.
Minimum Dissipation Principle in Nonlinear Transport
Directory of Open Access Journals (Sweden)
Giorgio Sonnino
2015-10-01
Full Text Available We extend Onsager’s minimum dissipation principle to stationary states that are only subject to local equilibrium constraints, even when the transport coefficients depend on the thermodynamic forces. Crucial to this generalization is a decomposition of the thermodynamic forces into those that are held fixed by the boundary conditions and the subspace that is orthogonal with respect to the metric defined by the transport coefficients. We are then able to apply Onsager and Machlup’s proof to the second set of forces. As an example, we consider two-dimensional nonlinear diffusion coupled to two reservoirs at different temperatures. Our extension differs from that of Bertini et al. in that we assume microscopic irreversibility, and we allow a nonlinear dependence of the fluxes on the forces.
International Nuclear Information System (INIS)
Rudjak, Yu.V.; Vladyko, V.B.
1993-01-01
The electron beam transport in ion channel has been investigated. The influence of the external longitudinal magnetic field and self beam magnetic field on the charge neutralization process was defined. Beam head erosion under channel is curved or the availability of transverse external magnetic field was numerically simulated. The numerical investigation of the ion-hose instability was performed. The conditions, when as a result of ion-hose instability development may be coming out of the channel by beam tail, were founded. It was shown, that supplementary creation of plasma by electron beam and ions did not lead to the reduction of ion-hose instability. Sufficient slowing down of ion-hose instability development could be achieved if betatron length increased to impulse tail. In the case of a weak initial nonsymmetrical perturbation, sausage instability was investigated. Numerical simulation showed that this instability could lead to beam radius increasing in order. The electron beam guiding by low conductive plasma channel was considered. The attractive force of beam to this channel under nonsymmetrical injection was defined analytically
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
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
Nonlinear acceleration of Sn 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)
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 focuses on mechanism, structure/function relations, regimes and mechanisms of transport, some molecular regularities, and some substantial challenges facing the field. Because there are many regimes and mechanisms in transport junctions, we will discuss time scales, geometries, and inelastic scattering...
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...
Electron transport in molecular junctions
DEFF Research Database (Denmark)
Jin, Chengjun
This thesis addresses the electron transport in molecular junctions, focusing on the energy level alignment and correlation effects. Various levels of theory have been applied to study the structural and electronic effects in different molecular junctions, starting from the single particle density...
Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zheng, Huinan; Shen, Chao; Wang, Yuming; Wang, Shui
2013-06-01
Electromagnetic ion cyclotron (EMIC) waves are long suggested to account for the rapid loss of radiation belt relativistic electrons. Here we perform both theoretical analysis and numerical simulation to comprehensively investigate the nonlinear interaction between EMIC wave and relativistic electrons. In particular, we emphasize the dependence of nonlinear processes on the electron initial latitude. The nonlinear phase trapping yields negative equatorial pitch angle transport, with efficiency varying over the electron initial latitude, implying that it can increase the loss rate predicted by quasilinear theory. The nonlinear channel effect phase bunching produces positive equatorial pitch angle transport, less dependent on the electron initial latitude, suggesting that it can decrease the loss rate predicted by quasilinear theory. The nonlinear cluster effect phase bunching alternately causes positive and negative equatorial pitch angle transport, quasi-periodically dependent on the electron initial latitude, suggesting that it can either decrease or increase the loss rate predicted by the quasilinear theory. Such latitudinal dependence of nonlinear processes should be taken into account in the evaluation of radiation belt electron loss rate driven by EMIC waves.
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
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.
Nonlinear evolution of the auroral electron beam
Maggs, James E.
1989-01-01
The nonlinear spatial evolution, from the source to the atmosphere, of the auroral electron beam and the beam-generated electrostatic whistler noise was studied, calculating changes in beam parameters from equations for the conservation of total particle and wave energy and momentum flux density. Wave power fluxes were calculated by numerically integrating the wave kinetic equations, and the levels of beam-generated noise were determined by using thermal levels of Cerenkov radiation as a source. It was found that beam parameters evolve on ionospheric scale lengths, and their positive slope feature in velocity space is maintained over altitudes measured in thousands of kilometers of altitude, even though they can generate wave energy density fluxes sufficient to modify the ionospheric density profile.
Nonlinear electromagnetic gyrokinetic particle simulations with the electron hybrid model
Nishimura, Y.; Lin, Z.; Chen, L.; Hahm, T.; Wang, W.; Lee, W.
2006-10-01
The electromagnetic model with fluid electrons is successfully implemented into the global gyrokinetic code GTC. In the ideal MHD limit, shear Alfven wave oscillation and continuum damping is demonstrated. Nonlinear electromagnetic simulation is further pursued in the presence of finite ηi. Turbulence transport in the AITG unstable β regime is studied. This work is supported by Department of Energy (DOE) Grant DE-FG02-03ER54724, Cooperative Agreement No. DE-FC02-04ER54796 (UCI), DOE Contract No. DE-AC02-76CH03073 (PPPL), and in part by SciDAC Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas. Z. Lin, et al., Science 281, 1835 (1998). F. Zonca and L. Chen, Plasma Phys. Controlled Fusion 30, 2240 (1998); G. Zhao and L. Chen, Phys. Plasmas 9, 861 (2002).
XXIII International Conference on Nonlinear Dynamics of Electronic Systems
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.
Nonlinear fiber optics formerly quantum electronics
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
Ballistic transport and electronic structure
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
Electron Transport in Si Nanowires
Energy Technology Data Exchange (ETDEWEB)
Ramayya, E [Arizona State University, Tempe, AZ (United States); Vasileska, D [Arizona State University, Tempe, AZ (United States); Goodnick, S M [Arizona State University, Tempe, AZ (United States); Knezevic, I [University of Wisconsin, Madison, WI (United States)
2006-05-15
We investigate electron transport in silicon nanowires taking into account acoustic, non-polar optical phonons and surface/interface roughness scattering. We find that at very high transverse fields the reduced density of final states to which the carriers can scatter into gives rise to a reduced influence of interface-roughness scattering, which is promising result from a fabrication point of view.
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
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
Excess electron transport in cryoobjects
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...
Mesoscopic electronics beyond DC transport
di Carlo, Leonardo
Since the inception of mesoscopic electronics in the 1980's, direct current (dc) measurements have underpinned experiments in quantum transport. Novel techniques complementing dc transport are becoming paramount to new developments in mesoscopic electronics, particularly as the road is paved toward quantum information processing. This thesis describes seven experiments on GaAs/AlGaAs and graphene nanostructures unified by experimental techniques going beyond traditional dc transport. Firstly, dc current induced by microwave radiation applied to an open chaotic quantum dot is investigated. Asymmetry of mesoscopic fluctuations of induced current in perpendicular magnetic field is established as a tool for separating the quantum photovoltaic effect from classical rectification. A differential charge sensing technique is next developed using integrated quantum point contacts to resolve the spatial distribution of charge inside a double quantum clot. An accurate method for determining interdot tunnel coupling and electron temperature using charge sensing is demonstrated. A two-channel system for detecting current noise in mesoscopic conductors is developed, enabling four experiments where shot noise probes transmission properties not available in dc transport and Johnson noise serves as an electron thermometer. Suppressed shot noise is observed in quantum point contacts at zero parallel magnetic field, associated with the 0.7 structure in conductance. This suppression evolves with increasing field into the shot-noise signature of spin-lifted mode degeneracy. Quantitative agreement is found with a phenomenological model for density-dependent mode splitting. Shot noise measurements of multi-lead quantum-dot structures in the Coulomb blockade regime distill the mechanisms by which Coulomb interaction and quantum indistinguishability correlate electron flow. Gate-controlled sign reversal of noise cross correlation in two capacitively-coupled dots is observed, and shown to
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)
Electron dynamics and transport in a mirror field
International Nuclear Information System (INIS)
Irie, Haruyuki; Hatori, Tadatsugu.
1985-01-01
The nonlinear dynamics and the radial transport of an electron in a magnetic mirror field are considered in the presence of an electrostatic monochromatic wave. It is found that a stochastic heating and a stochastic radial diffusion of electrons can simultaneously occur due to the nonlinear interaction between two motions, one is the bounce motion in the mirror and the other is the motion by the monochromatic wave. Three types of dependence of the diffusion coefficient on the wave amplitude are obtained which are different from that derived by the quasilinear theory. (author)
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
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)
Electron transport in quantum dots
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...
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.
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 )
Nonlinear heat and particle transport due to collisional drift waves
Energy Technology Data Exchange (ETDEWEB)
Nishi-Kawa, K.I.; Hatori, T.; Terashima, Y.
1978-07-01
A nonlinear analysis of collisional drift instability is developed in a slab model based on the two fluid equations, where inhomogeneities in electron and ion temperatures and unperturbed current are included in addition to ion inertia, finite ion gyroradius, and viscosity. A systematic expansion is introduced by taking epsilon=vertical-barkappavertical-barl as a smallness parameter, where kappa is the degree of density gradient and l is the linear scale of the slab along the density gradient. The nonlinear development of the drift wave near marginal stability is studied on the basis of the model equations. A new feature, hard excitation, has been found, which is due to the effects of the nonlinear frequency shift and the electron temperature gradient. The saturation amplitude is calculated, and the expressions for wave-associated particle and heat fluxes are obtained. A comparison of the expressions with the experimental results of a stellerator device is also made.
Phonon limited electronic transport in Pb
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 \
Nonlinear electron cloud modification of satellite modes
International Nuclear Information System (INIS)
Stettner, R.; Sveum, M.D.
1984-01-01
A one-dimensional circuit analog of the modes of a triaxial satellite is derived. Self consistent one-dimensional particle calculations utilizing this model are presented. The results suggest that electrons arriving at the satellite from tank walls and damper in an SGEMP experiment, can under some circumstances, materially affect the response of the satellite
Electron and Phonon Transport in Molecular Junctions
DEFF Research Database (Denmark)
Li, Qian
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......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...
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)
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)
Nonlinearly-enhanced energy transport in many dimensional quantum chaos
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.
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
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
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.
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...
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)
Electron transport in wurtzite InN
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 79; Issue 1 ... InN transport; mobility; energy and momentum relaxation; impurity scattering. ... the transport properties of InN such as the drift velocity, the drift mobility, the average electron, energy relaxation times and momentum relaxation times at high electric ﬁeld.
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)
The Electron Transport Chain: An Interactive Simulation
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…
Electronic Ticketing in Public Transport
Dekkers, J.E.C.; Rietveld, P.
2007-01-01
The NoordNed Mobile Ticketing service (in this article referred to as M-Ticketing) is an early example of electronic ticketing in the Netherlands. Using this service, customers no longer need to buy a ticket at a ticket office or ticket machine. Instead, people can order M-Tickets through the
Transport experiments with Dirac electrons
Checkelsky, Joseph George
This thesis presents transport experiments performed on solid state systems in which the behavior of the charge carriers can be described by the Dirac equation. Unlike the massive carriers in a typical material, in these systems the carriers behave like massless fermions with a photon-like dispersion predicted to greatly modify their spin and charge transport properties. The first system studied is graphene, a crystalline monolayer of carbon arranged in a hexagonal lattice. The band structure calculated from the hexagonal lattice has the form of the massless Dirac Hamiltonian. At the charge neutral Dirac point, we find that application of a magnetic field drives a transition to an insulating state. We also study the thermoelectric properties of graphene and find that the states near the Dirac point have a unique response compared to those at higher charge density. The second system is the 3D topological insulator Bi2Se3, where a Dirac-like dispersion for states on the 2D surface of the insulating 3D crystal arises as a result of the topology of the 3D bands and time reversal symmetry. To access the transport properties of the 2D states, we suppress the remnant bulk conduction channel by chemical doping and electrostatic gating. In bulk crystals we find strong quantum corrections to transport at low temperature when the bulk conduction channel is maximally suppressed. In microscopic crystals we are able better to isolate the surface conduction channel properties. We identify in-gap conducting states that have relatively high mobility compared to the bulk and exhibit weak anti-localization, consistent with predictions for protected 2D surface states with strong spin-orbit coupling.
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
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
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)
Taking an electron-magnon duality shortcut from electron to magnon transport
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.
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.
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
Electron transport through monovalent atomic wires
DEFF Research Database (Denmark)
Lee, Y. J.; Brandbyge, Mads; Puska, M. J.
2004-01-01
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...... 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...
A deterministic model of electron transport for electron probe microanalysis
Bünger, J.; Richter, S.; Torrilhon, M.
2018-01-01
Within the last decades significant improvements in the spatial resolution of electron probe microanalysis (EPMA) were obtained by instrumental enhancements. In contrast, the quantification procedures essentially remained unchanged. As the classical procedures assume either homogeneity or a multi-layered structure of the material, they limit the spatial resolution of EPMA. The possibilities of improving the spatial resolution through more sophisticated quantification procedures are therefore almost untouched. We investigate a new analytical model (M 1-model) for the quantification procedure based on fast and accurate modelling of electron-X-ray-matter interactions in complex materials using a deterministic approach to solve the electron transport equations. We outline the derivation of the model from the Boltzmann equation for electron transport using the method of moments with a minimum entropy closure and present first numerical results for three different test cases (homogeneous, thin film and interface). Taking Monte Carlo as a reference, the results for the three test cases show that the M 1-model is able to reproduce the electron dynamics in EPMA applications very well. Compared to classical analytical models like XPP and PAP, the M 1-model is more accurate and far more flexible, which indicates the potential of deterministic models of electron transport to further increase the spatial resolution of EPMA.
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.
Epitaxial graphene electronic structure and transport
Energy Technology Data Exchange (ETDEWEB)
De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N [School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Stroscio, Joseph A [Center for Nanoscale Science and Technology, NIST, Gaithersburg, MD 20899 (United States); Haddon, Robert [Center for Nanoscale Science and Engineering, Departments of Chemistry and Chemical and Environmental Engineering, University of California, Riverside, CA 92521 (United States); Piot, Benjamin; Faugeras, Clement; Potemski, Marek [LNCMI -CNRS, Grenoble, 38042 Cedex 9 (France); Moon, Jeong-Sun, E-mail: walt.deheer@physics.gateh.ed [HRL Laboratories LLC, Malibu, CA 90265 (United States)
2010-09-22
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.
High current nonlinear transmission line based electron beam driver
Directory of Open Access Journals (Sweden)
B. W. Hoff
2017-10-01
Full Text Available A gigawatt-class nonlinear transmission line based electron beam driver is experimentally demonstrated. Four experimental series, each with a different Marx bank charge voltage (15, 20, 25, and 30 kV, were completed. Within each experimental series, shots at peak frequencies ranging from 950 MHz to 1.45 GHz were performed. Peak amplitude modulations of the NLTL output voltage signal were found to range between 18% and 35% for the lowest frequency shots and between 5% and 20% for the highest frequency shots (higher modulation at higher Marx charge voltage. Peak amplitude modulations of the electron beam current were found to range between 10% and 20% for the lowest frequency shots and between 2% and 7% for the highest frequency shots (higher modulation at higher Marx charge voltage.
High current nonlinear transmission line based electron beam driver
Hoff, B. W.; French, D. M.; Simon, D. S.; Lepell, P. D.; Montoya, T.; Heidger, S. L.
2017-10-01
A gigawatt-class nonlinear transmission line based electron beam driver is experimentally demonstrated. Four experimental series, each with a different Marx bank charge voltage (15, 20, 25, and 30 kV), were completed. Within each experimental series, shots at peak frequencies ranging from 950 MHz to 1.45 GHz were performed. Peak amplitude modulations of the NLTL output voltage signal were found to range between 18% and 35% for the lowest frequency shots and between 5% and 20% for the highest frequency shots (higher modulation at higher Marx charge voltage). Peak amplitude modulations of the electron beam current were found to range between 10% and 20% for the lowest frequency shots and between 2% and 7% for the highest frequency shots (higher modulation at higher Marx charge voltage).
Punchets: nonlinear transport in Hamiltonian pump-ratchet hybrids
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.
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
Enhanced transport of relativistic electrons through nanochannels
Directory of Open Access Journals (Sweden)
Prashant Kumar Singh
2013-06-01
Full Text Available Efficient transport of fast electrons driven by intense laser solid interaction depends crucially on optimal target design. We demonstrate a hybrid target design that incorporates two important features—efficient generation of relativistic electrons and their unimpeded transport in dense media. The target was fabricated on a porous alumina base consisting of an array of sublambda cylindrical holes partially filled with Cu nanorods, such that light field propagates in the hollow channels, located ahead of the metallic fillings. The hollow array acts as an efficient source of hot electrons when driven by relativistically intense, femtosecond laser pulses and shows a 60-fold enhancement in electron flux compared to a solid target. This enhancement is ascribed to an increased penetration of laser through subwavelength pores and enhanced local electric fields. The metal doped part facilitates efficient transport of the generated electrons, due to its large background conductivity. A 4-fold enhancement in target rear side electron flux is observed compared with unfilled porous alumina.
Kinetic theory of nonlinear transport phenomena in complex plasmas
Energy Technology Data Exchange (ETDEWEB)
Mishra, S. K. [Institute for Plasma Research (IPR), Gandhinagar 382428 (India); Sodha, M. S. [Centre for Energy Studies (CES), Indian Institute of Technology Delhi (IITD), New Delhi 110016 (India)
2013-03-15
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.
Electronic and transport properties of kinked graphene
Directory of Open Access Journals (Sweden)
Jesper Toft Rasmussen
2013-02-01
Full Text Available 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 into a transport gap for electronic transport across the kink lines. We finally consider pseudo-ribbon-based heterostructures and propose that such structures present a novel approach for band gap engineering in nanostructured graphene.
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...
Electron transport in wurtzite InN
Indian Academy of Sciences (India)
E-mail: fadlaeg@yahoo.com. MS received 4 July 2011; revised 7 January 2012; accepted 8 February 2012. Abstract. Using ensemble Monte Carlo simulation technique, we have calculated the transport properties of InN such as the drift velocity, the drift mobility, the average electron, energy relaxation times and momentum ...
Electronic transport in partially ionized water plasmas
French, Martin; Redmer, Ronald
2017-09-01
We use ab initio simulations based on density functional theory to calculate the electrical and thermal conductivities of electrons in partially ionized water plasmas at densities above 0.1 g/cm3. The resulting conductivity data are then fitted to analytic expressions for convenient application. For low densities, we develop a simple and fully analytic model for electronic transport in low-density plasmas in the chemical picture using the relaxation-time approximation. In doing so, we derive a useful analytic expression for electronic transport cross sections with neutral particles, based on a model potential. In the regime of thermal ionization, electrical conductivities from the analytic model agree with the ab initio data within a factor of 2. Larger deviations are observed for the thermal conductivity, and their origin is discussed. Our results are relevant for modeling the interior and evolution of water-rich planets as well as for technical plasma applications.
Electronic and transport properties of kinked graphene
DEFF Research Database (Denmark)
Rasmussen, Jesper Toft; Gunst, Tue; Bøggild, Peter
2013-01-01
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......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......, 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...
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.
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)
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......, the linewidth and the relaxation time τ. We obtain a state-dependent τ and show its necessity to reproduce the increased thermopower for temperatures below the Debye temperature, without accounting for the phonon-drag effect. Despite the detailed investigations of various k- and q-dependencies, the presented...
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.
Nonlinear transport in semiconducting polymers at high carrier densities.
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'.
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
Fused electron deficient semiconducting polymers for air stable electron transport
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.
Quantum electron transport in toroidal carbon nanotubes
Jack, Mark; Encinosa, Mario
2008-03-01
Electron transport under bias is treated in tight-binding approximation using a non-equilibrium Green's function approach. Density-of-states D(E), transmissivity T(E), and current ISD are calculated through a (3,3) armchair nanotorus with laterally attached metallic leads and a magnetic field penetrating the toroidal plane. Plateaus in T(E) through the torus are observed as a function of both the relative angle between leads and magnetic flux. Initial computational studies performed with 1800 atoms and attached leads show substantial computational slowdown when increasing the system size by a factor of two. Results are generated by inverting the device Hamiltonian with a standard recursion method extended to account for unit cell toroidal closure. Significant computational speed-up is expected for a parallelized code on a multiprocessor computer cluster. The dependence of electronic features on torus size and torus curvature is tested for three tori with 900, 1800 and 3600 carbon atoms, respectively. References: 1. M. Jack and M. Encinosa, Quantum electron transport in toroidal carbon nanotubes with metallic leads. ArXiv: quant-ph/0709.0760. 2. M. Encinosa and M. Jack, Dipole and solenoidal magnetic moments of electronic surface currents on toroidal nanostructures. J. Comp.-Aided Mat. Design (Springer), 14 (1) (2007) 65 -- 71.
Electronic transport in graphene-based heterostructures
Energy Technology Data Exchange (ETDEWEB)
Tan, J. Y.; Avsar, A.; Balakrishnan, J.; Taychatanapat, T.; O' Farrell, E. C. T.; Eda, G.; Castro Neto, A. H. [Graphene Research Center, National University of Singapore, Singapore 117542 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Koon, G. K. W.; Özyilmaz, B., E-mail: barbaros@nus.edu.sg [Graphene Research Center, National University of Singapore, Singapore 117542 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); NanoCore, National University of Singapore, Singapore 117576 (Singapore); Watanabe, K.; Taniguchi, T. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)
2014-05-05
While boron nitride (BN) substrates have been utilized to achieve high electronic mobilities in graphene field effect transistors, it is unclear how other layered two dimensional (2D) crystals influence the electronic performance of graphene. In this Letter, we study the surface morphology of 2D BN, gallium selenide (GaSe), and transition metal dichalcogenides (tungsten disulfide (WS{sub 2}) and molybdenum disulfide (MoS{sub 2})) crystals and their influence on graphene's electronic quality. Atomic force microscopy analysis shows that these crystals have improved surface roughness (root mean square value of only ∼0.1 nm) compared to conventional SiO{sub 2} substrate. While our results confirm that graphene devices exhibit very high electronic mobility (μ) on BN substrates, graphene devices on WS{sub 2} substrates (G/WS{sub 2}) are equally promising for high quality electronic transport (μ ∼ 38 000 cm{sup 2}/V s at room temperature), followed by G/MoS{sub 2} (μ ∼ 10 000 cm{sup 2}/V s) and G/GaSe (μ ∼ 2200 cm{sup 2}/V s). However, we observe a significant asymmetry in electron and hole conduction in G/WS{sub 2} and G/MoS{sub 2} heterostructures, most likely due to the presence of sulphur vacancies in the substrate crystals. GaSe crystals are observed to degrade over time even under ambient conditions, leading to a large hysteresis in graphene transport making it a less suitable substrate.
Replacing Electron Transport Cofactors with Hydrogenases
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.
Mitochondrial Electron Transport and Plant Stress
DEFF Research Database (Denmark)
Rasmusson, Allan G; Møller, Ian Max
2011-01-01
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...... conservation in the ETC. The alternative oxidase provides a non-energy-conserving alternative to electron transport through complexes III and IV. There also appears to be a special coupling between specific NAD(P)H dehydrogenases and specific members of the alternative oxidase family. These additional enzymes...
Electron transport in doped fullerene molecular junctions
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.
Electronic transport properties of (fluorinated) metal phthalocyanine
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.
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...
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.
Electron Transport through Porphyrin Molecular Junctions
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
Theory of electronic transport through molecular nanostructures
International Nuclear Information System (INIS)
Koentopp, M.B.
2005-05-01
The main issue of this work is to describe electronic transport through single molecule junctions. We implemented the ''standard'' approach to molecular conductance, namely transport calculations in a Landauer-Buettiker framework based on Kohn-Sham orbitals extracted from density functional theory (DFT). Our particular implementation ensures, that apart from approximations inherent in the exchange-correlation functional in DFT no further approximations are made. Comparison of our numerical calculations with available experimental data shows, that, while in some cases qualitative information on transport can be gained, the experimental conductance is two to three orders of magnitude below the theoretical estimate. Changes in bond geometry can not account for this discrepancy. We are led to the conclusion that approximations in the exchange-correlation functional may be the major underlying reason for the discrepancy. To this end, we formulated the condition under which the ''standard'' approach would be exact. Furthermore, we investigated three situations where despite these shortcomings quantitative results can be obtained. Thereby we, for first time, calculated the step positions in the I-V characteristics of a ''diode-type'' molecule quantitatively. (orig.)
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).
A nonlinear multiobjective approach for the supplier selection, integrating transportation policies
Aguezzoul, Aicha; Ladet, Pierre
2007-01-01
13 pages; International audience; Purpose - The impact of transportation on the supplier selection has received a very scant attention in the literature. This is a great limitation because splitting orders across multiple suppliers will lead to smaller transportation quantities which will likely imply larger transportation cost. Moreover, transportation and inventory elements are highly interrelated and contribute most to the total logistics costs. This paper seeks to present a nonlinear mult...
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.
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
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)].
Ion age transport: developing devices beyond electronics
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
Karabulut, Ibrahim
2017-11-01
We investigate theoretically the saturation problem of the nonlinear intersubband response in a symmetric quantum well. We first obtain the analytical expressions for the absorption/dispersion spectra from the steady-state solutions of the nonlinear density matrix equations. This expressions include the depolarization effect that results from the electron-electron interactions and also depends on the population difference between the first two subbands. We calculate the line shape of the dispersion spectrum and show that the dispersion spectrum becomes non-antisymetric as the intensity of the radiation increases. For larger values of the electron sheet density, this distortion becomes more apparent. We also find that the optical bistability can be obtained for appropriate values of the electron sheet density and the intensity of the optical radiation. Our results also show that the electron redistribution among the subbands by additional external factor has a dramatic effect on the nonlinear intersubband response.
Magnetoelectronic transport of the two-dimensional electron gas in ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 72; Issue 2 ... CdSe quantum wells; 2D electron gas; magneto-electronic transport. Abstract. Hall mobility and magnetoresistance coefficient for the two-dimensional (2D) electron transport parallel to the heterojunction interfaces in a single quantum well of CdSe are ...
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...
Yao, Bo; Li, Xiaoping; Shi, Lei; Liu, Yanming; Lei, Fan; Zhu, Congying
2017-10-01
An experiment on the propagation of electromagnetic (EM) signals in continuous time-varying plasma is designed to establish the nonlinear mirror between electron density and transmission coefficient. The nonlinearity is confirmed from the theoretical and experimental results. The amplitude and phase can be considered nonlinear functions of electron density when the complex interaction between plasma and EM waves is ignored. Results show that amplitude and phase distributions are asymmetrical when electron density follows symmetric distribution. The skewness of amplitude is positive, whereas the skewness of phase is negative. The nonlinear degree is closely related to the ratio of plasma frequency to the incident wave frequency and the range of electron density. The conclusions are crucial to the modeling of plasma sheath channels and understanding the blackout problem.
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.
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.)
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
Electronic absorption spectra and nonlinear optical properties of CO ...
Indian Academy of Sciences (India)
We have investigated the structural aspects of several carbon dioxide molecular aggregates and their spectroscopic and nonlinear optical properties within the quantum chemical theory framework. We find that, although the single carbon dioxide molecule prefers to be in a linear geometry, the puckering of angles occur in ...
Problems of linear electron (polaron) transport theory in semiconductors
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
Melatonin and the electron transport chain.
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.
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..
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
Nonlinear dynamics and plasma transport. Progress report, September 15, 1992--September 14, 1993
Energy Technology Data Exchange (ETDEWEB)
Antonsen, T.M. Jr.; Drake, J.F.; Finn, J.M.; Guzdar, P.N.; Hassam, A.B.; Sageev, R.Z.
1993-05-01
This progress report details work done on a program in nonlinear dynamical aspects of plasma turbulence and transport funded by DOE since 1989. This program has been in cooperation with laboratories in theUSSR [now Russia and the Confederation of Independent States (CIS)]. The purpose of this program has been: To promote the utilization of recent pathbreaking developments in nonlinear science in plasma turbulence and transport. To promote cooperative scientific investigations between the US and CIS in the related areas of nonlinear science and plasma turbulence and transport. 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. This allows for a deeper analysis and understanding of the system both analytically and numerically.
Energy Technology Data Exchange (ETDEWEB)
Ngai, J.H.; Segal, Y.; Su, D.; Zhu, Y.; Walker, F.J.; Ismail-Beigi, S.; Le Hur, K.; Ahn, C.H.
2010-06-21
Electron gases created by modulating the charge density near interfaces and surfaces of insulating SrTiO{sub 3} offer a wide range of tunable behavior. Here, we utilize the nonlinear dielectric response of SrTiO{sub 3} to electrostatically manipulate the spatial confinement of an electron gas relative to an interface, where scattering is enhanced. Magnetotransport measurements reveal that the electron gas can be tuned from weakly localized to classical transport regimes. This crossover in transport demonstrates that elastic scattering can be electrostatically controlled, providing another degree of tunability for electron gases in SrTiO{sub 3}.
Electron transport through a diatomic molecule
Energy Technology Data Exchange (ETDEWEB)
Imran, Muhammad, E-mail: imran1gee@gmail.com
2014-08-01
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.
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.
Electron transport in bulk GaN under ultrashort high-electric field transient
Korotyeyev, V. V.; Kochelap, V. A.; Kim, K. W.
2011-10-01
We have investigated nonlinear electron transport in GaN induced by high-electric field transients by analyzing the temporal dependence of the electron drift velocity and temperature. For picosecond transients, our calculations have established that the electron dynamics retain almost all the features of the steady-state velocity-field characteristics including the portion with negative differential conductivity. It was also found that transient currents in GaN samples give rise to the THz re-emission effect—radiation of electromagnetic field, temporal and spectral properties of which directly relate to the velocity-field characteristics of the sample. The results clearly indicate that existing methods for the generation of high-electric field transients and subpicosecond signal measurements can be applied to the characterization of hot electron transport at ultrahigh fields while avoiding Joule self-heating, hot phonon accumulation and other undesirable effects.
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
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
Thermal Transport in Diamond Films for Electronics Thermal Management
2018-03-01
Advanced Research Projects Agency EBSD Electron Backscatter Diffraction EELS Electron Energy Loss Spectroscopy EOM electro-optic modulator ERT...AFRL-RY-WP-TR-2017-0219 THERMAL TRANSPORT IN DIAMOND FILMS FOR ELECTRONICS THERMAL MANAGEMENT Samuel Graham Georgia Institute of Technology MARCH...TYPE 3. DATES COVERED (From - To) March 2018 Final 5 December 2014 – 30 September 2017 4. TITLE AND SUBTITLE THERMAL TRANSPORT IN DIAMOND FILMS FOR
Nonlinear transport in beta-Na0.33V2O5
Sirbu, S; Yamauchi, T; Ueda, Y; van Loosdrecht, PHM
2005-01-01
The transport properties of the charge ordering compound beta-Na0.33V2O5 are studied in the temperature range from 65 K to 300 K using current driven DC conductivity experiments. Below the metal-insulator transition temperature (T-MI = 136 K) this material shows a typical non-linear charge density
Non-linear effects on neutral gas transport in divertors
International Nuclear Information System (INIS)
Reiter, D.; May, C.; Baelmans, M.; Boerner, P.
1997-01-01
The effects of neutral particles on the condition of the plasma edge play a key role in divertor and limiter physics. In computational models they are usually treated in the linear test particle approximation. However, in some divertor concepts a large neutral gas pressure is required in the divertor chamber to provide sufficient neutral-plasma interaction in the plasma fan (momentum removal and energy dissipation) and to permit adequate pumping performance. In such regimes viscous effects in the neutral gas may become relevant. We have extended the EIRENE code to solve the Boltzmann equation with a non-linear BGK-model collision term added to its standard linear collision integrals. The linear in-elastic collision integrals are reconsidered with respect to volume recombination and momentum removal efficiency from the plasma. The numerical procedure in the EIRENE Monte Carlo code is outlined. A simple test application (Couette flow) shows that the procedure works properly. First numerical studies have been carried out and the results are discussed. (orig.)
Electron transport in wurtzite InN
Indian Academy of Sciences (India)
It is found that the maximum peak velocity only occurs when the electric field is increased to a value above a certain critical field. This critical field is strongly dependent on InN parameters. The steady-state transport parameters are in fair agreement with other recent calculations. Keywords. InN transport; mobility; energy and ...
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.
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.
Nonlinear features of electrostatic waves in a plasma with nonthermal-Tsallis distributed electrons
Energy Technology Data Exchange (ETDEWEB)
Dutta, Debjit [Department of Mathematics, National Institute of Technology, Agartala, Jiraniya 799046 (India); Sahu, Biswajit, E-mail: biswajit-sahu@yahoo.co.in [Department of Mathematics, West Bengal State University, Barasat, Kolkata 700126 (India)
2016-06-15
Linear and nonlinear properties of electrostatic waves are investigated in an unmagnetized multicomponent plasma system consisting of cold and hot electrons obeying nonthermal-Tsallis distribution and warm ions using the Sagdeev pseudopotential technique. It is found that such a plasma supports soliton, supersoliton, and double layer structures. Also, the present plasma system supports the coexistence of arbitrary amplitude compressive and rarefactive solitons in a certain region of parameter space. Furthermore, numerical results reveal that the nonthermal-Tsallis distribution of electrons may affect the spatial profiles as well as the nature of the electrostatic nonlinear structures.
Behavior of electronic interferometers in the nonlinear regime.
Neder, I; Ginossar, E
2008-05-16
We investigate theoretically the behavior of the current oscillations in an electronic Mach-Zehnder interferometer (MZI) as a function of its source bias. Recently, the MZI visibility data showed an unexplained lobe pattern with a peculiar phase rigidity. Moreover, the effect did not depend on the MZI path length difference. We argue that these effects may be a new many-body manifestation of particle-wave duality in quantum mechanics. When biasing the interferometer sources so much that multiple electrons are on each arm at any instant in time, quantum shot noise (a particle phenomena) must affect the interference pattern of the electrons that create it. A solution to the interaction Hamiltonian presented here shows that the interference visibility has a lobe pattern with applied bias that has a period proportional to the average path length and independent of the path length difference, together with a phase rigidity.
Photosynthetic, respiratory and extracellular electron transport pathways in cyanobacteria.
Lea-Smith, David J; Bombelli, Paolo; Vasudevan, Ravendran; Howe, Christopher J
2016-03-01
Cyanobacteria have evolved elaborate electron transport pathways to carry out photosynthesis and respiration, and to dissipate excess energy in order to limit cellular damage. Our understanding of the complexity of these systems and their role in allowing cyanobacteria to cope with varying environmental conditions is rapidly improving, but many questions remain. We summarize current knowledge of cyanobacterial electron transport pathways, including the possible roles of alternative pathways in photoprotection. We describe extracellular electron transport, which is as yet poorly understood. Biological photovoltaic devices, which measure electron output from cells, and which have been proposed as possible means of renewable energy generation, may be valuable tools in understanding cyanobacterial electron transfer pathways, and enhanced understanding of electron transfer may allow improvements in the efficiency of power output. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Conrad Mullineaux. Copyright © 2015. Published by Elsevier B.V.
Electron Transport in Quantum Dots and Heat Transport in Molecules
DEFF Research Database (Denmark)
Kirsanskas, Gediminas
to make a device in order to get fundamentally new properties?” [1], or more concretely, when do the quantum effects become important. During the last 30 years, the innovations in fabrication and cooling techniques allowed to produce nanometer scale solid-state or single molecule-based devices......, electrically confined electrons in semiconductor nanowires, two dimensional electron gases, carbon nanotubes, or just small metallic particles, nanoscale pieces of semiconductor....
Oleschko, K.; Khrennikov, A.
2017-10-01
This paper is about a novel mathematical framework to model transport (of, e.g., fluid or gas) through networks of capillaries. This framework takes into account the tree structure of the networks of capillaries. (Roughly speaking, we use the tree-like system of coordinates.) As is well known, tree-geometry can be topologically described as the geometry of an ultrametric space, i.e., a metric space in which the metric satisfies the strong triangle inequality: in each triangle, the third side is less than or equal to the maximum of two other sides. Thus transport (e.g., of oil or emulsion of oil and water in porous media, or blood and air in biological organisms) through networks of capillaries can be mathematically modelled as ultrametric diffusion. Such modelling was performed in a series of recently published papers of the authors. However, the process of transport through capillaries can be only approximately described by the linear diffusion, because the concentration of, e.g., oil droplets, in a capillary can essentially modify the dynamics. Therefore nonlinear dynamical equations provide a more adequate model of transport in a network of capillaries. We consider a nonlinear ultrametric diffusion equation with quadratic nonlinearity - to model transport in such a network. Here, as in the linear case, we apply the theory of ultrametric wavelets. The paper also contains a simple introduction to theory of ultrametric spaces and analysis on them.
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)
Electronic absorption spectra and nonlinear optical properties of ...
Indian Academy of Sciences (India)
Administrator
These materials find numerous device applications, from lasers to optical switches and electronics. 1. So far, the organic π-conjugated molecules have been considered mostly for this pur- pose because of their easy functionalization to fine tune the desired properties and the ease of fabrica- tion and integration into devices.
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
Fast electron generation and transport in a turbulent, magnetized plasma
Energy Technology Data Exchange (ETDEWEB)
Stoneking, Matthew Randall [Univ. of Wisconsin, Madison, WI (United States)
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.
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
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
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
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 the ...
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)
Trust-region based solver for nonlinear transport in heterogeneous porous media
Wang, Xiaochen; Tchelepi, Hamdi A.
2013-11-01
We describe a new nonlinear solver for immiscible two-phase transport in porous media, where viscous, buoyancy, and capillary forces are significant. The flux (fractional flow) function, F, is a nonlinear function of saturation and typically has inflection points and can be non-monotonic. The non-convexity and non-monotonicity of F are major sources of difficulty for nonlinear solvers of coupled multiphase flow and transport in natural porous media. We describe a modified Newton algorithm that employs trust regions of the flux function to guide the Newton iterations. The flux function is divided into saturation trust regions delineated by the inflection, unit-flux, and end points. The updates are performed such that two successive iterations cannot cross any trust-region boundary. If a crossing is detected, the saturation value is chopped back to the appropriate trust-region boundary. The proposed trust-region Newton solver, which is demonstrated across the parameter space of viscous, buoyancy and capillary effects, is a significant extension of the inflection-point strategy of Jenny et al. (JCP, 2009) [5] for viscous dominated flows. We analyze the discrete nonlinear transport equation obtained using finite-volume discretization with phase-based upstream weighting. Then, we prove convergence of the trust-region Newton method irrespective of the timestep size for single-cell problems. Numerical results across the full range of the parameter space of viscous, gravity and capillary forces indicate that our trust-region scheme is unconditionally convergent for 1D transport. That is, for a given choice of timestep size, the unique discrete solution is found independently of the initial guess. For problems dominated by buoyancy and capillarity, the trust-region Newton solver overcomes the often severe limits on timestep size associated with existing methods. To validate the effectiveness of the new nonlinear solver for large reservoir models with strong heterogeneity
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
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...... equation for electrons in Wannier-Stark states. We find good quantitative agreement of the approximations (ii) and (iii) with (i) in their respective ranges of validity. (C) 1999 Elsevier Science B.V. All rights reserved....
Energy Technology Data Exchange (ETDEWEB)
El-Taibany, W. F., E-mail: eltaibany@du.edu.eg, E-mail: eltaibany@hotmail.com; Selim, M. M.; Al-Abbasy, O. M. [Department of Physics, Faculty of Science, Damietta University, New Damietta P. O. 34517 (Egypt); El-Bedwehy, N. A., E-mail: nab-elbedwehy@yahoo.com [Department of Mathematics, Faculty of Science, Damietta University, New Damietta P. O. 34517 (Egypt)
2014-07-15
The propagation of both linear and nonlinear dust acoustic waves (DAWs) in an inhomogeneous magnetized collisional and warm dusty plasma (DP) consisting of Boltzmann ions, nonextensive electrons, and inertial dust particles is investigated. The number density gradients of all DP components besides the inhomogeneities of electrostatic potential and the initial dust fluid velocity are taken into account. The linear dispersion relation and a nonlinear modified Zakharov-Kusnetsov (MZK) equation governing the propagation of the three-dimensional DAWs are derived. The analytical solution of the MZK reveals the creation of both compressive and rarefactive DAW solitons in the proposed model. It is found that the inhomogeneity dimension parameter and the electron nonextensive parameter affect significantly the nonlinear DAW's amplitude, width, and Mach number. The relations of our findings with some astrophysical situations have been given.
Nano-structured electron transporting materials for perovskite solar cells
Liu, Hefei; Huang, Ziru; Wei, Shiyuan; Zheng, Lingling; Xiao, Lixin; Gong, Qihuang
2016-03-01
Organic-inorganic hybrid perovskite solar cells have been developing rapidly in the past several years, and their power conversion efficiency has reached over 20%, nearing that of polycrystalline silicon solar cells. Because the diffusion length of the hole in perovskites is longer than that of the electron, the performance of the device can be improved by using an electron transporting layer, e.g., TiO2, ZnO and TiO2/Al2O3. Nano-structured electron transporting materials facilitate not only electron collection but also morphology control of the perovskites. The properties, morphology and preparation methods of perovskites are reviewed in the present article. A comprehensive understanding of the relationship between the structure and property will benefit the precise control of the electron transporting process and thus further improve the performance of perovskite solar cells.
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
Electronic transport in disordered bilayer and trilayer graphene
Yuan, Shengjun; De Raedt, Hans; Katsnelson, Mikhail I.
2010-01-01
We present a detailed numerical study of the electronic transport properties of bilayer and trilayer graphene within a framework of single-electron tight-binding model. Various types of disorder are considered, such as resonant (hydrogen) impurities, vacancies, short-or long-range Gaussian random
Nonlinear resonant interaction between acoustic impulse and electrons in superconductors
International Nuclear Information System (INIS)
Bratus, E.N.; Shumeiko, V.S.
1985-01-01
The problem of inelastic electron interaction in a perfectly pure superconductor with a longitudinal sound impulse is considered. It is shown that the problem reduces to the equivalent one of elastic scattering by the static potential, and the sound absorption is expressed in terms of the reflection coefficient of this scattering. The classical and quantum properties of the scattering are studied and the phase region in which new excitations are created is indicated. A formula is derived that expresses the density matrix of the excitations created in terms of the exact scattering matrix of an impulse. The quasiclassical creation of excitations by a smooth-shaped impulse is investigated with regard to both overbarrier and underbarrier processes
Transport of secondary electrons and reactive species in ion tracks
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.
Molecular Electronics: Insight from First-Principles Transport Simulations
DEFF Research Database (Denmark)
Paulsson, Magnus; Frederiksen, Thomas; Brandbyge, Mads
2010-01-01
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 electronic transport. Here we describe key computational ingredients and discuss these in relation to simulations for scanning tunneling microscopy (STM) experiments with C-60 molecules where the experimental geometry is well characterized. We then show how molecular dynamics simulations may be combined...... the atomic arrangement and transport channels....
Extracellular Electron Transport Coupling Biogeochemical Processes Centimeters
DEFF Research Database (Denmark)
Risgaard-Petersen, Nils; Fossing, Henrik; Christensen, Peter Bondo
2010-01-01
Recent observations in marine sediment have revealed conductive networks transmitting electrons from oxidation processes in the anoxic zone to oxygen reduction in the oxiczone [1]. The electrochemical processes and conductors seem to be biologically controlled and may account for more than half...
Correction of non-linear thickness effects in HAADF STEM electron tomography
Energy Technology Data Exchange (ETDEWEB)
Van den Broek, W., E-mail: wouter.vandenbroek@uni-ulm.de [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Rosenauer, A. [Institut fuer Festkoerperphysik (IFP), Universitaet Bremen, Otto-Hahn-Allee 1, 28359 Bremen (Germany); Goris, B.; Martinez, G.T.; Bals, S.; Van Aert, S.; Van Dyck, D. [Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium)
2012-05-15
In materials science, high angle annular dark field scanning transmission electron microscopy is often used for tomography at the nanometer scale. In this work, it is shown that a thickness dependent, non-linear damping of the recorded intensities occurs. This results in an underestimated intensity in the interior of reconstructions of homogeneous particles, which is known as the cupping artifact. In this paper, this non-linear effect is demonstrated in experimental images taken under common conditions and is reproduced with a numerical simulation. Furthermore, an analytical derivation shows that these non-linearities can be inverted if the imaging is done quantitatively, thus preventing cupping in the reconstruction. -- Highlights: Black-Right-Pointing-Pointer In HAADF STEM, a thickness dependent, non-linear damping of the projected intensities occurs. Black-Right-Pointing-Pointer In tomography, this leads to underestimated intensities in the interior of homogeneous particles, the cupping artifact. Black-Right-Pointing-Pointer The non-linear damping is demonstrated in experimental images and reproduced with numerical simulations. Black-Right-Pointing-Pointer The non-linear damping can be undone if the imaging is done quantitatively. Black-Right-Pointing-Pointer Experimental proof is provided showing that cupping can be prevented.
Structural disorder and electron transport in graphene at low temperatures
Bobenko, N. G.; Egorushkin, V. E.; Melnikova, N. V.; Ponomarev, A. N.; Belosludtseva, A. A.; Barkalov, L. D.
2017-12-01
A theoretical study of electron transport characteristics of metalized epitaxial graphene with impurities and structural inhomogeneous of the short-range order type was performed. The electron relaxation time, mean free path, and diffusion coefficient were calculated and shown to be of the same order of magnitude as the corresponding values for phonon characteristics. It means that electron scattering on the short-range ordered domains has to be taken into account, especially at low temperatures when it may dominate phonon scattering.
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
Kinetic Theory of Electronic Transport in Random Magnetic Fields
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 .
Electronic transport in Si:P δ-doped wires
DEFF Research Database (Denmark)
Smith, J. S.; Drumm, D. W.; Budi, Akin
2015-01-01
Despite the importance of Si:P δ-doped wires for modern nanoelectronics, there are currently no computational models of electron transport in these devices. In this paper we present a nonequilibrium Green’s function model for electronic transport in a δ-doped wire, which is described by a tight......-binding Hamiltonian matrix within a single-band effective-mass approximation. We use this transport model to calculate the current-voltage characteristics of a number of δ-doped wires, achieving good agreement with experiment. To motivate our transport model we have performed density-functional calculations...... for a variety of δ-doped wires, each with different donor configurations. These calculations also allow us to accurately define the electronic extent of a δ-doped wire, which we find to be at least 4.6 nm....
A ballistic transport model for electronic excitation following particle impact
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.
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
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)
Nonlinear electron-magnetohydrodynamic simulations of three dimensional current shear instability
International Nuclear Information System (INIS)
Jain, Neeraj; Das, Amita; Sengupta, Sudip; Kaw, Predhiman
2012-01-01
This paper deals with detailed nonlinear electron-magnetohydrodynamic simulations of a three dimensional current shear driven instability in slab geometry. The simulations show the development of the instability in the current shear layer in the linear regime leading to the generation of electromagnetic turbulence in the nonlinear regime. The electromagnetic turbulence is first generated in the unstable shear layer and then spreads into the stable regions. The turbulence spectrum shows a new kind of anisotropy in which power transfer towards shorter scales occurs preferentially in the direction perpendicular to the electron flow. Results of the present three dimensional simulations of the current shear instability are compared with those of our earlier two dimensional simulations of sausage instability. It is found that the flattening of the mean velocity profile and thus reduction in the electron current due to generation of electromagnetic turbulence in the three dimensional case is more effective as compared to that in the two dimensional case.
Nonlinear electron-magnetohydrodynamic simulations of three dimensional current shear instability
Jain, Neeraj; Das, Amita; Sengupta, Sudip; Kaw, Predhiman
2012-09-01
This paper deals with detailed nonlinear electron-magnetohydrodynamic simulations of a three dimensional current shear driven instability in slab geometry. The simulations show the development of the instability in the current shear layer in the linear regime leading to the generation of electromagnetic turbulence in the nonlinear regime. The electromagnetic turbulence is first generated in the unstable shear layer and then spreads into the stable regions. The turbulence spectrum shows a new kind of anisotropy in which power transfer towards shorter scales occurs preferentially in the direction perpendicular to the electron flow. Results of the present three dimensional simulations of the current shear instability are compared with those of our earlier two dimensional simulations of sausage instability. It is found that the flattening of the mean velocity profile and thus reduction in the electron current due to generation of electromagnetic turbulence in the three dimensional case is more effective as compared to that in the two dimensional case.
Nonlinear Dynamics of Fast-electron Driven Beta-induced Alfven eigenmode
Cheng, Junyi; Zhang, Wenlu; Lin, Zhihong; Li, Ding
2017-10-01
The fast-electron driven beta-induced Alfven eigenmode (e-BAE) has been routinely observed in HL-2A tokamak. We study e-BAE for the first time using global gyrokinetic GTC simulations, where the fast electrons are described by the drift kinetic model. Frequency chirping is observed in nonlinear simulations in the absence of sources and sinks, which provides a new nonlinear paradigm beyond the standard ``bump-on-tail'' model. Analysis of nonlinear wave-particle interactions shows that the frequency chirping is induced by the nonlinear evolution of the coherent structures in the fast electron phase space, where the dynamics of the coherent structure is controlled by the formation and destruction of phase space islands in the canonical variables. Furthermore, we put forward a new theory frame to demonstrate that the evolution of chirping phenomenon is essentially induced by balance and destruction of net shear flow in the toroidal direction combined by the background shear flow and perturbed shear flow, which provides a novel and clear physical image.
Nonlinear structures: Explosive, soliton, and shock in a quantum electron-positron-ion magnetoplasma
Sabry, R.; Moslem, W. M.; Haas, F.; Ali, S.; Shukla, P. K.
2008-12-01
Theoretical and numerical studies are performed for the nonlinear structures (explosive, solitons, and shock) in quantum electron-positron-ion magnetoplasmas. For this purpose, the reductive perturbation method is employed to the quantum hydrodynamical equations and the Poisson equation, obtaining extended quantum Zakharov-Kuznetsov equation. The latter has been solved using the generalized expansion method to obtain a set of analytical solutions, which reflects the possibility of the propagation of various nonlinear structures. The relevance of the present investigation to the white dwarfs is highlighted.
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
Evidence for global electron transportation into the jovian inner magnetosphere.
Yoshioka, K; Murakami, G; Yamazaki, A; Tsuchiya, F; Kimura, T; Kagitani, M; Sakanoi, T; Uemizu, K; Kasaba, Y; Yoshikawa, I; Fujimoto, M
2014-09-26
Jupiter's magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electron transportation in the inner magnetosphere is not well understood. By analyzing the extreme ultraviolet line emission from the inner magnetosphere, we show evidence for global inward transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot electron fraction. It gradually decreases with decreasing radial distance, despite the short collisional time scale that should thermalize them rapidly. This indicates a fast and continuous resupply of hot electrons responsible for exciting the whistler-mode waves. Copyright © 2014, American Association for the Advancement of Science.
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
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.
Three-dimensional nonlinear Schrödinger equation in electron-positron-ion magnetoplasmas
Sabry, R.; Moslem, W. M.; El-Shamy, E. F.; Shukla, P. K.
2011-03-01
Three-dimensional ion-acoustic envelope soliton excitations in electron-positron-ion magnetoplasmas are interpreted. This is accomplished through the derivation of three-dimensional nonlinear Schrödinger equation, where the nonlinearity is balancing with the dispersive terms. The latter contains both an external magnetic field besides the usual plasma parameter effects. Based on the balance between the nonlinearity and the dispersion terms, the regions for possible envelope solitons are investigated indicating that new regimes for modulational instability of envelope ion-acoustic waves could be obtained, which cannot exist in the unmagnetized case. This will allow us to establish additional new regimes, different from the usual unmagnetized plasma, for envelope ion-acoustic waves to propagate in multicomponent plasma that may be observed in space or astrophysics.
Osmane, Adnane; Wilson, Lynn B., III; Blum, Lauren; Pulkkinen, Tuija I.
2016-01-01
Using a dynamical-system approach, we have investigated the efficiency of large-amplitude whistler waves for causing microburst precipitation in planetary radiation belts by modeling the microburst energy and particle fluxes produced as a result of nonlinear wave-particle interactions. We show that wave parameters, consistent with large amplitude oblique whistlers, can commonly generate microbursts of electrons with hundreds of keV-energies as a result of Landau trapping. Relativistic microbursts (greater than 1 MeV) can also be generated by a similar mechanism, but require waves with large propagation angles Theta (sub k)B greater than 50 degrees and phase-speeds v(sub phi) greater than or equal to c/9. Using our result for precipitating density and energy fluxes, we argue that holes in the distribution function of electrons near the magnetic mirror point can result in the generation of double layers and electron solitary holes consistent in scales (of the order of Debye lengths) to nonlinear structures observed in the radiation belts by the Van Allen Probes. Our results indicate a relationship between nonlinear electrostatic and electromagnetic structures in the dynamics of planetary radiation belts and their role in the cyclical production of energetic electrons (E greater than or equal to 100 keV) on kinetic timescales, which is much faster than previously inferred.
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)
Investigation of electronic transport properties of some liquid transition metals
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.
Electron thermal transport in RTP: filaments, barriers and bifurcations
International Nuclear Information System (INIS)
Lopes Cardozo, N.J.; Hogeweij, G.M.D.; Baar, M. de; Barth, C.J.; Beurskens, M.N.A.; Donne, A.J.H.; Gelder, J.F.M. van; Groot, B. de; Karelse, F.A.; Kloe, J. de; Kruijt, O.G.; Lok, J.; Meiden, H.J. van der; Oomens, A.A.M.; Oyevaar, Th.; Pijper, R.J.; Polman, R.W.; Salzedas, F.; Schueller, F.C.; Westerhof, E.; De Luca, F.; Galli, P.; Gorini, G.; Jacchia, A.; Mantica, P.
1997-01-01
Experiments with strong localized electron cyclotron heating (ECH) in the RTP tokamak show that electron heat transport is governed by alternating layers of good and bad thermal conduction. For central deposition hot T e filaments are observed inside the q = 1 radius. Moving the ECH resonance from the centre to the edge of the plasma results in discrete steps of the central electron temperature. The transitions occur when the minimum q value crosses q = 1,2,5/2 or 3, and correspond to the loss of a transport barrier situated close to the rational q value. Close to the transitions a new type of sawtooth activity is observed, characterized by the formation of sharp off-axis maxima on the T e profile, which collapse abruptly. The formation of the off-axis maxima is attributed to heat deposition precisely 'on top of' a transport barrier. (author)
Effect of dephasing on DNA sequencing via transverse electronic transport
Energy Technology Data Exchange (ETDEWEB)
Zwolak, Michael [Los Alamos National Laboratory; Krems, Matt [NON LANL; Pershin, Yuriy V [NON LANL; Di Ventra, Massimiliano [NON LANL
2009-01-01
We study theoretically the effects of dephasing on DNA sequencing in a nanopore via transverse electronic transport. To do this, we couple classical molecular dynamics simulations with transport calculations using scattering theory. Previous studies, which did not include dephasing, have shown that by measuring the transverse current of a particular base multiple times, one can get distributions of currents for each base that are distinguishable. We introduce a dephasing parameter into transport calculations to simulate the effects of the ions and other fluctuations. These effects lower the overall magnitude of the current, but have little effect on the current distributions themselves. The results of this work further implicate that distinguishing DNA bases via transverse electronic transport has potential as a sequencing tool.
Chaotic electron transport in semiconductor devices
Scannell, William Christian
The field of quantum chaos investigates the quantum mechanical behavior of classically chaotic systems. This dissertation begins by describing an experiment conducted on an apparatus constructed to represent a three dimensional analog of a classically chaotic system. Patterns of reflected light are shown to produce fractals, and the behavior of the fractal dimension D F is shown to depend on the light's ability to escape the apparatus. The classically chaotic system is then used to investigate the conductance properties of semiconductor heterostructures engineered to produce a conducting plane relatively free of impurities and defects. Introducing walls that inhibit conduction to partition off sections considerably smaller than the mean distance between impurities defines devices called 'billiards'. Cooling to low temperatures enables the electrons traveling through the billiard to maintain quantum mechanical phase. Exposure to a changing electric or magnetic field alters the electron's phase, leading to fluctuations in the conductance through the billiard. Magnetoconductance fluctuations in billiards have previously been shown to be fractal. This behavior has been charted using an empirical parameter, Q, that is a measure of the resolution of the energy levels within the billiard. The relationship with Q is shown to extend beyond the ballistic regime into the 'quasi-ballistic' and 'diffusive' regimes, characterized by having defects within the conduction plane. A model analogous to the classically chaotic system is proposed as the origin of the fractal conductance fluctuations. This model is shown to be consistent with experiment and to account for changes of fine scale features in MCF known to occur when a billiard is brought to room temperature between low temperature measurements. An experiment is conducted in which fractal conductance fluctuations (FCF) are produced by exposing a billiard to a changing electric field. Comparison of DF values of FCF produced by
Spin-Dependent Quasiparticle Transport in Aluminum Single Electron Transistors
Ferguson, A. J.; Andresen, S. E.; Brenner, R.; Clark, R. G.
2006-01-01
We investigate the effect of Zeeman-splitting on quasiparticle transport in normal-superconducting-normal (NSN) aluminum single electron transistors (SETs). In the above-gap transport the interplay of Coulomb blockade and Zeeman-splitting leads to spin-dependence of the sequential tunneling. This creates regimes where either one or both spin species can tunnel onto or off the island. At lower biases, spin-dependence of the single quasiparticle state is studied and operation of the device as a...
Advances in Monte Carlo electron transport
International Nuclear Information System (INIS)
Bielajew, Alex F.
1995-01-01
Notwithstanding the success of Monte Carlo (MC) calculations for determining ion chamber correction factors for air-kerma standards and radiotherapy applications, a great challenge remains. MC is unable to calculate ion chamber response to better than 1% for low-Z and 3% for high-Z wall materials. Moreover, the two major MC code systems employed in radiation dosimetry, the EGS and ITS codes, differ in opposite directions from ion chamber experiments. The discrepancy with experiment is due to inadequacies in the underlying e - condensed-history algorithms. As modeled by MC calculations, the e - step-lengths in the chamber walls and the ionisation cavity differ in terms of material traversed by about three orders of magnitude. This demands that the underlying e - transport algorithms be very stable over a great dynamic range. Otherwise a spurious e - disequilibrium may be generated. The multiple-scattering (MS) algorithms, Moliere in the case of EGS and Goudsmit-Saunderson (GS) in the case of ITS, are either mathematically or numerically unstable in the plural-scattering environment of the ionisation cavity. Recently, a new MS theory has been developed that is an exact solution of the Wentzel small-angle formalism using a screened Rutherford cross section. This new MS theory is mathematically, physically and numerically stable from the no-scattering to the MS regimes. This theory is the small-angle equivalent of the GS equation for a Rutherford cross section. Large-angle corrections connecting this theory to GS theory have been derived by Bethe. The Moliere theory is the large-pathlength limit of this theory. The strategy for employing this new theory for ion chamber and radiotherapy calculations is described
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
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
Nonlinear spectroscopy of photon-dressed Dirac electrons in a quantum dot
Roslyak, O.; Gumbs, Godfrey; Mukamel, S.
2013-01-01
We study the localization of dressed Dirac electrons in a cylindrical quantum dot (QD) formed on monolayer and bilayer graphene by spatially different potential profiles. Short-lived excitonic states which are too broad to be resolved in linear spectroscopy are revealed by cross-peaks in the photon-echo nonlinear technique. Signatures of the dynamic gap in the two-dimensional photon-echo spectra are discussed.
Power electronics applied to industrial systems and transports
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
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
Electron-vibron coupling effects on electron transport via a single-molecule magnet
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,
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
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)
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.
Investigation of electron beam transport in a helical undulator
Energy Technology Data Exchange (ETDEWEB)
Jeong, Y.U.; Lee, B.C.; Kim, S.K. [Korea Atomic Energy Research Institute, Taejon (Korea, Democratic People`s Republic of)] [and others
1995-12-31
Lossless transport of electrons through the undulator is essential for CW operation of the FELs driven by recirculating electrostatic accelerators. We calculate the transport ratio of an electron beam in a helical undulator by using a 3-D simulation code and compare the results with the experimental results. The energy and the current of the electron beam are 400 keV and 2 A, respectively. The 3-D distribution of the magnetic field of a practical permanent-magnet helical undulator is measured and is used in the calculations. The major parameters of the undutlator are : period = 32 mm, number of periods = 20, number of periods in adiabatic region = 3.5, magnetic field strength = 1.3 kG. The transport ratio is very sensitive to the injection condition of the electron beam such as the emittance, the diameter, the divergence, etc.. The injection motion is varied in the experiments by changing the e-gun voltage or the field strength of the focusing magnet located at the entrance of the undulator. It is confirmed experimentally and with simulations that most of the beam loss occurs at the adiabatic region of the undulator regardless of the length of the adiabatic region The effect of axial guiding magnetic field on the beam finish is investigated. According to the simulations, the increase of the strength of axial magnetic field from 0 to 1 kG results in the increase of the transport ratio from 15 % to 95%.
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
Magnetoelectronic transport of the two-dimensional electron gas in ...
Indian Academy of Sciences (India)
Abstract. Hall mobility and magnetoresistance coefficient for the two-dimensional (2D) electron transport parallel to the heterojunction interfaces in a single quantum well of. CdSe are calculated with a numerical iterative technique in the framework of Fermi–Dirac statistics. Lattice scatterings due to polar-mode longitudinal ...
Electron transport and coherence in semiconductor quantum dots and rings
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
International Nuclear Information System (INIS)
Yin, L.; Daughton, W.; Albright, B. J.; Bowers, K. J.; Montgomery, D. S.; Kline, J. L.; Fernandez, J. C.; Roper, Q.
2006-01-01
The backward stimulated Raman scattering (BSRS) of a laser from electron beam acoustic modes (BAM) in the presence of self-consistent non-Maxwellian velocity distributions is examined by linear theory and particle-in-cell (PIC) simulations in one and two dimensions (1D and 2D). The BAM evolve from Langmuir waves (LW) as electron trapping modifies the distribution to a non-Maxwellian form that exhibits a beam component. Linear dispersion relations using the nonlinearly modified distribution from simulations are solved for the electrostatic modes involved in the parametric coupling. Results from linear analysis agree well with electrostatic spectra from simulations. It is shown that the intersection of the Stokes root with BAM (instead of LW) determines the matching conditions for BSRS at a nonlinear stage. As the frequency of the unstable Stokes mode decreases with increasing wave number, the damping rate and the phase velocity of BAM decreases with the phase velocity of the Stokes mode, providing a self-consistently evolving plasma linear response that favors continuation of the nonlinear frequency shift. Coincident with the emergence of BAM is a rapid increase in BSRS reflectivity. The details of the wave-particle interaction region in the electron velocity distribution determine the growth/damping rate of these electrostatic modes and the nonlinear frequency shift; in modeling this behavior, the use of sufficiently large numbers of particles in the simulations is crucial. Both the reflectivity scaling with laser intensity and the spectral features from simulations are discussed and are consistent with recent Trident experiments
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
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
Relativistic electron transport and bremsstrahlung production in solar flares
Miller, James A.; Ramaty, Reuven
1989-01-01
A Monte Carlo simulation of ultrarelativistic electron transport in solar flare magnetic loops has been developed. It includes Coulomb, synchrotron, and bremsstrahlung energy losses; pitch-angle scattering by Alfven and whistler turbulence in the coronal region of the loop; and magnetic mirroring in the converging magnetic flux tubes beneath the transition region. Depth distributions, time profiles, energy spectra, and angular distributions of the resulting bremsstrahlung emission are calculated. It is found that both the preferential detection of solar flares with greater than 10 MeV emission near the limb of the sun and the observation of ultrarelativistic electron bremsstrahlung from flares on the disk are consequences of the loop transport model. The declining portions of the observed time profiles of greater than 10 MeV emission from solar flares can also be accounted for, and it is proposed that these portions are determined by transport and not acceleration.
Power electronics for renewable energy systems, transportation and industrial applications
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.
International Nuclear Information System (INIS)
Sanchez, Richard; Rabiti, Cristian; Wang, Yaqi
2013-01-01
Nonlinear acceleration of a continuous finite element (CFE) discretization of the transport equation requires a modification of the transport solution in order to achieve local conservation, a condition used in nonlinear acceleration to define the stopping criterion. In this work we implement a coarse-mesh finite difference acceleration for a CFE discretization of the second-order self-adjoint angular flux (SAAF) form of the transport equation and use a postprocessing to enforce local conservation. Numerical results are given for one-group source calculations of one-dimensional slabs. We also give a novel formal derivation of the boundary conditions for the SAAF. (authors)
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
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
Gorelick, Steven M.; Voss, Clifford I.; Gill, Philip E.; Murray, Walter; Saunders, Michael A.; Wright, Margaret H.
1984-01-01
A simulation-management methodology is demonstrated for the rehabilitation of aquifers that have been subjected to chemical contamination. Finite element groundwater flow and contaminant transport simulation are combined with nonlinear optimization. The model is capable of determining well locations plus pumping and injection rates for groundwater quality control. Examples demonstrate linear or nonlinear objective functions subject to linear and nonlinear simulation and water management constraints. Restrictions can be placed on hydraulic heads, stresses, and gradients, in addition to contaminant concentrations and fluxes. These restrictions can be distributed over space and time. Three design strategies are demonstrated for an aquifer that is polluted by a constant contaminant source: they are pumping for contaminant removal, water injection for in-ground dilution, and a pumping, treatment, and injection cycle. A transient model designs either contaminant plume interception or in-ground dilution so that water quality standards are met. The method is not limited to these cases. It is generally applicable to the optimization of many types of distributed parameter systems.
Quantitative Assessment of MeV Electron Acceleration in Non-Linear Interactions with VLF Chorus
Foster, J. C.; Erickson, P. J.; Omura, Y.; Baker, D. N.
2016-12-01
For occurrences of apparent rapid acceleration of radiation belt electrons to MeV energies at L 4, we examine the energy gained by seed electrons in non-linear (NL) interactions with VLF chorus rising tones. For the 17-18 March 2013 storm, observations of outer zone radiation belt electron populations were made with the magEIS and REPT instruments on Van Allen Probes A & B. These reveal that MeV electron fluxes at L=4.2 increased 10-fold in 30 min at the times of 30 - 100 keV electron injections during "substorm" dipolarizations. Simultaneous enhancements of VLF chorus were observed with the EMFISIS wave instruments. Three-axis burst mode observations of wave electric and magnetic fields have been used to investigate electron interactions with individual chorus rising tones on a sub millisecond time scale. Wave amplitudes at 2500 Hz were 1 nT (|B|) and 30 mV/m (|E|). Frequency - time characteristics of the observed chorus elements closely match those predicted by NL electron-chorus interaction modeling [Omura et al., 2015, J. Geophys. Res. Space Phys., 120, doi:10.1002/2015JA021563]. For seed electrons with initial energies 50 keV to 8 MeV, subpacket wave analysis was used to quantify resonant electron energy gain both by relativistic turning acceleration and by ultrarelativistic acceleration through nonlinear trapping by the chorus waves. Electrons with 1-2 MeV initial energy can experience a 300 keV total energy gain in NL interactions with a single 200 msec rising tone. Maximum energy gain from interaction with a single 10 msec subpacket was 100 keV for a 2 MeV seed electron. Examining a number of chorus elements at different locations during the rapid local acceleration of the radiation belt during this event, we conclude that seed electrons (100s keV - 5 MeV) can be accelerated by 50 keV - 500 keV in resonant NL interactions with a single VLF rising tone on a time scale of 10-100 msec.
Electron transport for spectrum analysis and experiment design
International Nuclear Information System (INIS)
Werner, Wolfgang S.M.
2010-01-01
A survey is presented on modeling the effects of electron transport on the energy and angular spectra of electrons emitted or reflected from non-crystalline solid surfaces and nanostructures. This is intended to aid in the quantitative interpretation of such spectra and should also provide a useful guideline for experiment design. A brief review of the most significant characteristics of the electron-solid interaction is given and the theory describing the energy dissipation and momentum relaxation of electrons in solids is outlined, which is based on the so-called Landau-Goudsmit-Saunderson (LGS) loss function. It is shown that the basis for true quantitative spectrum interpretation is provided by the collision statistics, i.e. the number of electrons arriving at the detector after participating in a given number of inelastic collisions, being equal to the partial intensities. By introducing an appropriate stochastic process for multiple scattering, the validity of the partial intensity approach (PIA) can be extended to the true slowing down regime making it possible, in a very simple way, to fully account for energy fluctuations in the limit of large energy losses. The LGS loss function thus provides a unified theoretical basis for electron spectroscopy and microscopy. The usefulness of the concept of the collision statistics, or partial intensities, for quantitative spectrum interpretation is illustrated by considering various examples of practical significance, including elastic peak electron spectroscopy (EPES), reflection electron energy loss spectroscopy (REELS), (hard) X-ray photoelectron emission ((HA)XPS), electron coincidence spectroscopy, the Auger electron backscattering factor and the ionization depth distribution. Finally, the relationship between the partial intensities and the emission depth is discussed, which allows one to combine the unique features of electron spectroscopy for investigation of chemical, electronic and magnetic properties of
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.
A particle simulation code for analysis of nonlinear electron oscillations in a plasma waveguide
International Nuclear Information System (INIS)
Turikov, V.A.
1978-08-01
A description is given of a computer code for simulation of electron oscillations in a magnetized plasma in a cylindrical waveguide. The one-dimensional particle-in-cell method with the reverse linear interpolation of charge density is used. The program has options for treating nonlinear processes in a plasma with periodical and reflecting boundary conditions. For periodical conditions, Poisson's equation is solved by means of the Fourier method. For reflecting conditions, the double recursive procedure is used. The values of the potential derivatives at the space grid points are calculated by means of the parabolic interpolation. The main purpose of the program is to investigate nonlinear phenomena in a plasma column after applying a short localized impulse of an external electric field. (Auth.)
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)
Modelling of electron transport and of sawtooth activity in tokamaks
Energy Technology Data Exchange (ETDEWEB)
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
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
Magnetism and electronic transport in irradiated organic conductors
International Nuclear Information System (INIS)
Sanquer, M.
1986-01-01
Quasi-one-dimensional conductors are metallic in a large temperature range. The electronic gas instability can drive a phase transition at low temperature. In one-dimensional conditions, precursor fluctuations grow in the high temperature regime and can give a collective current transport. Under irradiation the quasi-one-dimensional electrons are localized and the conductivity becomes typical of a phonon assisted tunneling between metallic particles. In this study we describe the magnetism of this localized electrons. This disorder reduces the interaction between electronic spins and phonons and favours the interaction between localized spins. But if the electronic gas is less one-dimensional, irradiation disorder can not localize electrons. Our conductivity measurements prove that the disorder first reduces the electronic relaxation before induces the above mentioned localization. Moreover the fluctuative conductivity is revealed by irradiation thanks to a discrepancy with respect to one-electron model. TTF-TCNQ and (TMTSF) 2 ClO 4 are investigated in that way [fr
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)
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.
Strain modification on electronic transport of the phosphorene nanoribbon
Yuan, Yawen; Cheng, Fang
2017-07-01
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.
LDRD project 151362 : low energy electron-photon transport.
Energy Technology Data Exchange (ETDEWEB)
Kensek, Ronald Patrick; Hjalmarson, Harold Paul; Magyar, Rudolph J.; Bondi, Robert James; Crawford, Martin James
2013-09-01
At sufficiently high energies, the wavelengths of electrons and photons are short enough to only interact with one atom at time, leading to the popular %E2%80%9Cindependent-atom approximation%E2%80%9D. We attempted to incorporate atomic structure in the generation of cross sections (which embody the modeled physics) to improve transport at lower energies. We document our successes and failures. This was a three-year LDRD project. The core team consisted of a radiation-transport expert, a solid-state physicist, and two DFT experts.
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
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
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
Energy Technology Data Exchange (ETDEWEB)
Ahmad, Ali [National Centre for Physics, Shahdara Valley Road, Islamabad (Pakistan); Masood, W. [National Centre for Physics, Shahdara Valley Road, Islamabad (Pakistan); COMSATS Institute of Information Technology, Park Road, Chak Shahzad, Islamabad (Pakistan)
2016-05-15
Linear and nonlinear electrostatic ion acoustic waves in a weakly relativistic magnetorotating plasma in the presence of non-Maxwellian electrons and warm ions have been examined. The system under consideration has yielded two solutions, namely, the fast and slow acoustic modes which have been observed to depend on the streaming velocity, ion to electron temperature ratio, and the nonthermality parameter of the non-Maxwellian electrons. Using the multiple time scale analysis, we have derived the three dimensional nonlinear Zakharov–Kuznetsov equation and also presented its solution. Both compressive and rarefactive solitary structures have been found in consonance with the satellite observations. It has been observed that although the linear dispersion relation gives both fast and slow ion acoustic waves, the solitary structures form only for the fast acoustic mode. The dependence of the characteristics of the solitary structures on several plasma parameters has also been explored. The present investigation may be beneficial to understanding the rotating plasma environments such as those found in the planetary magnetospheres of Saturn and Jupiter.
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
Foster, J. C.; Erickson, P. J.; Omura, Y.; Baker, D. N.; Kletzing, C. A.; Claudepierre, S. G.
2017-01-01
Prompt recovery of MeV (millions of electron Volts) electron populations in the poststorm core of the outer terrestrial radiation belt involves local acceleration of a seed population of energetic electrons in interactions with VLF chorus waves. Electron interactions during the generation of VLF rising tones are strongly nonlinear, such that a fraction of the relativistic electrons at resonant energies are trapped by waves, leading to significant nonadiabatic energy exchange. Through detailed examination of VLF chorus and electron fluxes observed by Van Allen Probes, we investigate the efficiency of nonlinear processes for acceleration of electrons to MeV energies. We find through subpacket analysis of chorus waveforms that electrons with initial energy of hundreds of keV to 3 MeV can be accelerated by 50 keV-200 keV in resonant interactions with a single VLF rising tone on a time scale of 10-100 ms.
Electron transport properties of ordered networks using carbon nanotubes
International Nuclear Information System (INIS)
Romo-Herrera, J M; Terrones, M; Terrones, H; Meunier, Vincent
2008-01-01
The electronic transport properties of ordered networks using carbon nanotubes as building blocks (ON-CNTs) are investigated within the framework of a multiterminal Landauer-Buttiker formalism using an s,p x ,p y ,p z parameterization of the tight-binding Hamiltonian for carbon. The networks exhibit electron pathway selectiveness, which is shown to depend on the atomic structure of the network nodes imposed by the specific architecture of the network and the distribution of its defects (non-hexagonal rings). This work represents the first understandings towards leading current through well-defined trajectories along an organic nanocircuit
Power electronics applied to industrial systems and transports
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
Power electronics applied to industrial systems and transports
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,
Electronic structure and transport properties of intermetallics. Final report
Energy Technology Data Exchange (ETDEWEB)
Freeman, A.J.; Ellis, D.E.; Welsh, L.B.
1975-12-01
The electronic interactions responsible for the unusual properties of several important classes of materials (including the highly anisotropic layered dichalcogenides, and network and cage structure materials and pseudobinary alloys) have been investigated experimentally and theoretically. The unique ability of NMR to probe the local electronic properties of the various constituents of an intermetallic compound or alloy has provided important new information including correlations with observed changes in superconducting transition temperatures. Novel theoretical models (including relativistic effects) are found to yield energy band structures, Fermi surfaces, transport properties, charge and spin densities, generalized magnetic susceptibilities, and optical properties in very good agreement with experimental determinations of these observable phenomena. (Author) (GRA)
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
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.
Electronic and transport properties of BCN alloy nanoribbons
Darvishi Gilan, Mahdi; Chegel, Raad
2018-03-01
The dependence of the carbon (C) concentration on the electronic and transport properties of boron carbonitride (BCN) alloy nanoribbons have been investigated using surface Green's functions technique and random Hamiltonian model by considering random hopping parameters including first and second nearest neighbors. Our calculations indicate that substituting boron (nitrogen) sites with carbon atoms induces a new band close to conduction (valence) band and carbon atoms behave like a donor (acceptor) dopants. Also, while both nitrogen and boron sites are substituted randomly by carbon atoms, new bands are induced close to both valence and conduction bands. The band gap decreases with C substituting and the number of charge carriers increases in low bias voltage. Far from Fermi level in the higher range of energy, transmission coefficient and current of the system are reduced by increasing the C concentration. Based on our results, tuning the electronic and transport properties of BCN alloy nanoribbons by random carbon dopants could be applicable to design nanoelectronics devices.
On a nonlinear degenerate parabolic transport-diffusion equation with a discontinuous coefficient
Directory of Open Access Journals (Sweden)
John D. Towers
2002-10-01
Full Text Available We study the Cauchy problem for the nonlinear (possibly strongly degenerate parabolic transport-diffusion equation $$ partial_t u + partial_x (gamma(xf(u=partial_x^2 A(u, quad A'(cdotge 0, $$ where the coefficient $gamma(x$ is possibly discontinuous and $f(u$ is genuinely nonlinear, but not necessarily convex or concave. Existence of a weak solution is proved by passing to the limit as $varepsilondownarrow 0$ in a suitable sequence ${u_{varepsilon}}_{varepsilon>0}$ of smooth approximations solving the problem above with the transport flux $gamma(xf(cdot$ replaced by $gamma_{varepsilon}(xf(cdot$ and the diffusion function $A(cdot$ replaced by $A_{varepsilon}(cdot$, where $gamma_{varepsilon}(cdot$ is smooth and $A_{varepsilon}'(cdot>0$. The main technical challenge is to deal with the fact that the total variation $|u_{varepsilon}|_{BV}$ cannot be bounded uniformly in $varepsilon$, and hence one cannot derive directly strong convergence of ${u_{varepsilon}}_{varepsilon>0}$. In the purely hyperbolic case ($A'equiv 0$, where existence has already been established by a number of authors, all existence results to date have used a singular maolinebreak{}pping to overcome the lack of a variation bound. Here we derive instead strong convergence via a series of a priori (energy estimates that allow us to deduce convergence of the diffusion function and use the compensated compactness method to deal with the transport term. Submitted April 29, 2002. Published October 27, 2002. Math Subject Classifications: 35K65, 35D05, 35R05, 35L80 Key Words: Degenerate parabolic equation; nonconvex flux; weak solution; discontinuous coefficient; viscosity method; a priori estimates; compensated compactness
Redox-gated electron transport in electrically wired ferrocene molecules
Energy Technology Data Exchange (ETDEWEB)
Xiao Xiaoyin [Department of Electrical Engineering and Center for Solid State Electronic Research, Arizona State University, Tempe, AZ 85287 (United States); Brune, Daniel [Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287 (United States); He Jin [Center for Single Molecule Biophysics, Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Lindsay, Stuart [Center for Single Molecule Biophysics, Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Gorman, Christopher B. [Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204 (United States); Tao Nongjian [Department of Electrical Engineering and Center for Solid State Electronic Research, Arizona State University, Tempe, AZ 85287 (United States)], E-mail: nongjian.tao@asu.edu
2006-07-11
We have synthesized cysteamine-terminated ferrocene molecules and determined the dependence of the electron transport properties of the molecules on their redox states by measuring the current through the molecules as a function of the electrode potential. The current fluctuates over a large range, but its average value increases with the potential. We attribute the current fluctuation and its increase with the potential to the switching of the molecules from low-conductance reduced state to high-conductance oxidized state.
Redox-gated electron transport in electrically wired ferrocene molecules
International Nuclear Information System (INIS)
Xiao Xiaoyin; Brune, Daniel; He Jin; Lindsay, Stuart; Gorman, Christopher B.; Tao Nongjian
2006-01-01
We have synthesized cysteamine-terminated ferrocene molecules and determined the dependence of the electron transport properties of the molecules on their redox states by measuring the current through the molecules as a function of the electrode potential. The current fluctuates over a large range, but its average value increases with the potential. We attribute the current fluctuation and its increase with the potential to the switching of the molecules from low-conductance reduced state to high-conductance oxidized state
Electronic, adsorption, and transport properties of diamondoid-based complexes
Adhikari, Bibek
2017-01-01
Quantum simulation is an invaluable tool to researchers from various fields of scientific research. It allows the investigation of various complex condensed matter in the regimes of physics, chemistry, and biology. In this work, we focused our attention in unraveling the physical, chemical, electronic, transport, and optical properties of diamondoids and their complexes through quantum simulations. We have implemented a bottom-up approach where we move from the doping and functionalization of...
Electron and hole transport in poly(fluorene-benzothiadiazole)
Zhang, Yuan; Blom, Paul W. M.
2011-01-01
We investigate the electron and hole transport in poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT). An Ohmic hole contact on F8BT is achieved by using the high work function anode MoO(3) as hole injection contact, enabling the occurrence of space-charge limited
Transmembrane electron transport and the neutral theory of evolution.
Scherer, S
1984-01-01
Based on the concept of "pairs of basic functional states" the evolution of the first chemiosmotic mechanism of energy conversion is discussed in terms of point mutations, gene duplications and of the neutral theory of evolution. A model for estimating the overall probability of the evolutionary step in question is presented, both for the "selectionist" and "neutralist" position. It is concluded that, concerning the present stage of knowledge, the evolution of transmembrane electron transport is an unsolved problem in evolutionary biology.
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.
Kinetic theory of transport for inhomogeneous electron fluids
Lucas, Andrew; Hartnoll, Sean A.
2018-01-01
The interplay between electronic interactions and disorder is neglected in the conventional Boltzmann theory of transport, yet can play an essential role in determining the resistivity of unconventional metals. When quasiparticles are long lived, one can account for these intertwined effects by solving spatially inhomogeneous Boltzmann equations. Assuming smooth disorder and neglecting umklapp scattering, we solve these inhomogeneous kinetic equations and compute the electrical resistivity across the ballistic-to-hydrodynamic transition. An important consequence of electron-electron interactions is the modification of the momentum-relaxation time; this effect is ignored in the homogeneous theory. We characterize precisely when interactions enhance the momentum scattering rate, and when they decrease it. Our approach unifies existing semiclassical theories of transport, and explains how the resistivity can be proportional to the rate of momentum-conserving collisions without Baber scattering. We compare this result with existing transport mysteries, including the disorder-independent T2 resistivity of many Fermi liquids, and the linear-in-T "Planckian-limited" resistivity of many strange metals.
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.
Electron transport in gold colloidal nanoparticle-based strain gauges
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.
Electron transport in gold colloidal nanoparticle-based strain gauges
International Nuclear Information System (INIS)
Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen Ke; Viau, Guillaume; Ressier, Laurence
2013-01-01
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 E C . 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 E C values of these 14 nm NPs cannot be neglected in determining the β values. (paper)
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
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
Nenov, Artur; Giussani, Angelo; Segarra-Martí, Javier; Jaiswal, Vishal K.; Rivalta, Ivan; Cerullo, Giulio; Mukamel, Shaul; Garavelli, Marco
2015-06-01
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
Nonlinear resonances in a multi-stage free-electron laser amplifier
Energy Technology Data Exchange (ETDEWEB)
Hashimoto, S. [Graduate Univ. for Advanced Studies, Ibaraki-ken (Japan); Takayama, K. [National Lab. for High Energy Physics, Ibaraki-ken (Japan)
1995-12-31
A two-beam accelerator (TBA) is a possible candidate of future linear colliders, in which the demanded rf power is provided by a multi-stage free-electron laser (MFEL). After if amplification in each stage, a driving beam is re-accelerated by an induction unit and propagates into the next stage. Recently it has been recognized that the multi-stage character of the MFEL causes resonances between its periodicity and the synchrotron motion in an rf bucket. Since the synchrotron oscillation is strongly modulated by the resonance and at the worst a large fraction of particles is trapped in the resonance islands, the nonlinear resonances in the FEL longitudinal beam dynamics can lead to notable degradation of the MFEL performance, such as output fluctuation and phase modulation which have been big concerns in the accelerator society. The overall efficiency of the MFEL and the quality of the amplified microwave power are key issues for realizing the TBA/FEL Particularly the rf phase and amplitude errors must be maintained within tolerance. One of significant obstacles is an amplification of undesired modes. If a small-size waveguide is employed, the FEL resonance energies for undesired higher order modes shift very far from that for a fundamental mode; so it is possible to prevent higher order modes from evolving. Such a small-size waveguide, however, gives a high power density in the FEL. Simulation results have demonstrated that the nonlinear resonances occur in die FEL longitudinal motion when the power density exceeds some threshold. An analytical method for studying the nonlinear resonance in the TBA/FEL is developed based on the macroparticle model which can describe analytically the drastic behaviors in the evolutions of the phase and amplitude. In the theory the basic 1D-FEL equations are reduced to a nonlinear pendulum equation with respect to the ponderomotive phase.
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
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
Electron-vibron coupling effects on electron transport via a single-molecule magnet
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.
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.)
Fast-electron transport in cylindrically laser-compressed matter
Perez, F.; Koenig, M.; Batani, D.; Baton, S. D.; Beg, F. N.; Benedetti, C.; Brambrink, E.; Chawla, S.; Dorchies, F.; Fourment, C.; Galimberti, M.; Gizzi, L. A.; Heathcote, R.; Higginson, D. P.; Hulin, S.; Jafer, R.; Koester, P.; Labate, L.; Lancaster, K.; Mac Kinnon, A. J.; McPhee, A. G.; Nazarov, W.; Nicolai, P.; Pasley, J.; Ravasio, A.; Richetta, M.; Santos, J. J.; Sgattoni, A.; Spindloe, C.; Vauzour, B.; Volpe, L.
2009-12-01
Experimental and theoretical results of relativistic electron transport in cylindrically compressed matter are presented. This experiment, which is a part of the HiPER roadmap, was achieved on the VULCAN laser facility (UK) using four long pulses beams (~4 × 50 J, 1 ns, at 0.53 µm) to compress a hollow plastic cylinder filled with plastic foam of three different densities (0.1, 0.3 and 1 g cm-3). 2D simulations predict a density of 2-5 g cm-3 and a plasma temperature up to 100 eV at maximum compression. A short pulse (10 ps, 160 J) beam generated fast electrons that propagate through the compressed matter by irradiating a nickel foil at an intensity of 5 × 1018 W cm-2. X-ray spectrometer and imagers were implemented in order to estimate the compressed plasma conditions and to infer the hot electron characteristics. Results are discussed and compared with simulations.
Density-functional method for nonequilibrium electron transport
DEFF Research Database (Denmark)
Brandbyge, Mads; Mozos, J.L.; Ordejon, P.
2002-01-01
We describe an ab initio method for calculating the electronic structure, electronic transport, and forces acting on the atoms, for atomic scale systems connected to semi-infinite electrodes and with an applied voltage bias. Our method is based on the density-functional theory (DFT) as implemented...... in the well tested SIESTA approach (which uses nonlocal norm-conserving pseudopotentials to describe the effect of the core electrons, and linear combination of finite-range numerical atomic orbitals to describe the valence states). We fully deal with the atomistic structure of the whole system, treating both...... the contact and the electrodes on the same footing. The effect of the finite bias (including self-consistency and the solution of the electrostatic problem) is taken into account using nonequilibrium Green's functions. We relate the nonequilibrium Green's function expressions to the more transparent scheme...
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.
International Nuclear Information System (INIS)
Miraglia, J. E.
2003-01-01
We introduce a distorted wave method to calculate the nonlinear excitation effects occurring when a fast bare ion penetrates a free-electron gas. The central scheme of this work is to replace the undistorted plane waves leading to the Lindhard dielectric response function (or random phase approximation) by Coulomb waves with an effective charge. This impulse-type approximation is valid for velocities larger than the Fermi velocity. Stopping and mean free path are presented for impact of bare multicharged ions on aluminum free-electron gas. The Barkas effect is theoretically found, i.e., negative heavy particles lose energy at the lower rate than positive particles of the same velocity do. As the projectile charge increases, the single differential cross section per unit energy presents two effects: the plasmon peak sharpens and the binary peak starts to be increasingly noticeable
Energy Technology Data Exchange (ETDEWEB)
Stancari, G. [Fermilab; Carlson, K. [Fermilab; McGee, M. W. [Fermilab; Nobrega, L. E. [Fermilab; Romanov, A. L. [Fermilab; Ruan, J. [Fermilab; Valishev, A. [Fermilab; Noll, D. [Frankfurt U.
2015-06-01
Recent developments in the study of integrable Hamiltonian systems have led to nonlinear accelerator lattice designs with two transverse invariants. These lattices may drastically improve the performance of high-power machines, providing wide tune spreads and Landau damping to protect the beam from instabilities, while preserving dynamic aperture. To test the feasibility of these concepts, the Integrable Optics Test Accelerator (IOTA) is being designed and built at Fermilab. One way to obtain a nonlinear integrable lattice is by using the fields generated by a magnetically confined electron beam (electron lens) overlapping with the circulating beam. The parameters of the required device are similar to the ones of existing electron lenses. We present theory, numerical simulations, and first design studies of electron lenses for nonlinear integrable optics.
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)
International Nuclear Information System (INIS)
Gao, Q. D.; Budny, R. V.
2015-01-01
By using gyro-Landau fluid transport model (GLF23), time-dependent integrated modeling is carried out using TRANSP to explore the dynamic process of internal transport barrier (ITB) formation in the neutral beam heating discharges. When the current profile is controlled by LHCD (lower hybrid current drive), with appropriate neutral beam injection, the nonlinear interplay between the transport determined gradients in the plasma temperature (T i,e ) and toroidal velocity (V ϕ ) and the E×B flow shear (including q-profile) produces transport bifurcations, generating spontaneously a stepwise growing ITB. In the discharge, the constraints imposed by the wave propagation condition causes interplay of the LH driven current distribution with the plasma configuration modification, which constitutes non-linearity in the LH wave deposition. The non-linear effects cause bifurcation in LHCD, generating two distinct quasi-stationary reversed magnetic shear configurations. The change of current profile during the transition period between the two quasi-stationary states results in increase of the E×B shearing flow arising from toroidal rotation. The turbulence transport suppression by sheared E×B flow during the ITB development is analysed, and the temporal evolution of some parameters characterized the plasma confinement is examined. Ample evidence shows that onset of the ITB development is correlated with the enhancement of E×B shearing rate caused by the bifurcation in LHCD. It is suggested that the ITB triggering is associated with the non-linear effects of the LH power deposition
Effect of nonlinear energy transport on neoclassical tearing mode stability in tokamak plasmas
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.
Schneider, P. A.; Bustos, A.; Hennequin, P.; Ryter, F.; Bernert, M.; Cavedon, M.; Dunne, M. G.; Fischer, R.; Görler, T.; Happel, T.; Igochine, V.; Kurzan, B.; Lebschy, A.; McDermott, R. M.; Morel, P.; Willensdorfer, M.; the ASDEX Upgrade Team; The EUROfusion MST1 Team
2017-06-01
In ASDEX Upgrade (AUG), the normalised gyroradius {ρ\\star} was varied via a hydrogen isotope scan while keeping other dimensionless parameters constant. This was done in L-mode, to minimise the impact of pedestal stability on confinement. Power balance and perturbative transport analyses reveal that the electron heat transport is unaffected by the differences in isotope mass. Nonlinear simulations with the Gene code suggest that these L-mode discharges are ion temperature gradient (ITG) dominated. The different gyroradii due to the isotope mass do not necessarily result in a change of the predicted heat fluxes. This result is used in simulations with the Astra transport code to match the experimental profiles. In these simulations the experimental profiles and confinement times are reproduced with the same transport coefficients for hydrogen and deuterium plasmas. The mass only enters in the energy exchange term between electrons and ions. These numerical observations are supported by additional experiments which show a lower ion energy confinement compared to that of the electrons. Additionally, hydrogen and deuterium plasmas have a similar confinement when the energy exchange time between electrons and ions is matched. This strongly suggests that the observed isotope dependence in L-mode is not dominated by a gyroradius effect, but a consequence of the mass dependence in the collisional energy exchange between electrons and ions.
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
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
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
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)
Schunert, Sebastian; Wang, Yaqi; Gleicher, Frederick; Ortensi, Javier; Baker, Benjamin; Laboure, Vincent; Wang, Congjian; DeHart, Mark; Martineau, Richard
2017-06-01
This work presents a flexible nonlinear diffusion acceleration (NDA) method that discretizes both the SN transport equation and the diffusion equation using the discontinuous finite element method (DFEM). The method is flexible in that the diffusion equation can be discretized on a coarser mesh with the only restriction that it is nested within the transport mesh and the FEM shape function orders of the two equations can be different. The consistency of the transport and diffusion solutions at convergence is defined by using a projection operator mapping the transport into the diffusion FEM space. The diffusion weak form is based on the modified incomplete interior penalty (MIP) diffusion DFEM discretization that is extended by volumetric drift, interior face, and boundary closure terms. In contrast to commonly used coarse mesh finite difference (CMFD) methods, the presented NDA method uses a full FEM discretized diffusion equation for acceleration. Suitable projection and prolongation operators arise naturally from the FEM framework. Via Fourier analysis and numerical experiments for a one-group, fixed source problem the following properties of the NDA method are established for structured quadrilateral meshes: (1) the presented method is unconditionally stable and effective in the presence of mild material heterogeneities if the same mesh and identical shape functions either of the bilinear or biquadratic type are used, (2) the NDA method remains unconditionally stable in the presence of strong heterogeneities, (3) the NDA method with bilinear elements extends the range of effectiveness and stability by a factor of two when compared to CMFD if a coarser diffusion mesh is selected. In addition, the method is tested for solving the C5G7 multigroup, eigenvalue problem using coarse and fine mesh acceleration. While NDA does not offer an advantage over CMFD for fine mesh acceleration, it reduces the iteration count required for convergence by almost a factor of two in
Nanoscale Electron Transport Measurements of Immobilized Cytochrome P450 Proteins
Bostick, Christopher D.; Flora, Darcy R.; Gannett, Peter M.; Tracy, Timothy S.; Lederman, David
2015-01-01
Gold nanopillars, functionalized with an organic self-assembled monolayer, can be used to measure the electrical conductance properties of immobilized proteins without aggregation. Measurements of the conductance of nanopillars with cytochrome P450 2C9 (CYP2C9) proteins using conducting probe atomic force microscopy demonstrate that a correlation exists between the energy barrier height between hopping sites and CYP2C9 metabolic activity. Measurements performed as a function of tip force indicate that, when subjected to a large force, the protein is more stable in the presence of a substrate. This agrees with the hypothesis that substrate entry into the active site helps to stabilize the enzyme. The relative distance between hopping sites also increases with increasing force, possibly because protein functional groups responsible for electron transport depend on the structure of the protein. The inhibitor sulfaphenazole, in addition to the previously studied aniline, increased the barrier height for electron transfer and thereby makes CYP2C9 reduction more difficult and inhibits metabolism. This suggests that P450 Type II binders may decrease the ease of electron transport processes in the enzyme, in addition to occupying the active site. PMID:25804257
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.
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.
Helium, Iron and Electron Particle Transport and Energy Transport Studies on the TFTR Tokamak
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.
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
Helium, iron and electron particle transport and energy transport studies on the TFTR tokamak
Energy Technology Data Exchange (ETDEWEB)
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.
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
International Nuclear Information System (INIS)
Ayten, B.; Westerhof, E.
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 previously by Harvey et al (1989 Phys. Rev. Lett. 62 426). We study the non-linear electron cyclotron current drive (ECCD) efficiency through bounce-averaged, quasi-linear Fokker–Planck calculations in the magnetic geometry as created by the islands. The calculations are performed for the parameters of a typical NTM stabilization experiment on ASDEX Upgrade. A particular feature of these experiments is that the rays of the EC wave beam propagate tangential to the flux surfaces in the power deposition region. The calculations show significant non-linear effects on the ECCD efficiency, when the ECCD power is increased from its experimental value of 1 MW to a larger value of 4 MW. The nonlinear effects are largest in the case of locked islands or when the magnetic island rotation period is longer than the collisional time scale. The non-linear effects result in an overall reduction of the current drive efficiency for this case with absorption of the EC power on the low-field side of the electron cyclotron resonance layer. As a consequence of the non-linear effects, also the stabilizing effect of the ECCD on the island is reduced from linear expectations. (paper)
Contacting nanowires and nanotubes with atomic precision for electronic transport
Qin, Shengyong
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.
Transport of ions and electrons in nanostructured liquid crystals
Kato, Takashi; Yoshio, Masafumi; Ichikawa, Takahiro; Soberats, Bartolome; Ohno, Hiroyuki; Funahashi, Masahiro
2017-03-01
The nanosegregated structures of columnar, smectic and bicontinuous cubic liquid crystals can provide well-organized, nano- and sub-nanosized 1D, 2D and 3D channels capable of ion and electron transport. The molecular shape, intermolecular interactions and nanosegregation of the molecular structures can influence their self-assembly into a range of functional liquid-crystalline nanostructures. The formation of stable and soft liquid-crystalline materials leads to their application as electrolytes for batteries and photovoltaics, semiconductors, electroluminescence and electrochemical devices. In addition, electrochemical devices are obtained by using redox-active liquid crystals. In this Review, we focus on the design of liquid-crystalline phases, the resultant self-assembled structures, the transport mechanisms, and the fabrication, function and future development of devices incorporating nanostructured liquid crystals.
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.
Nonlocal collisionless and collisional electron transport in low temperature plasmas
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
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.
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.
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
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.
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.
Electronic transport in disordered graphene antidot lattice devices
DEFF Research Database (Denmark)
Power, Stephen; Jauho, Antti-Pekka
2014-01-01
Nanostructuring of graphene is in part motivated by the requirement to open a gap in the electronic band structure. In particular, a periodically perforated graphene sheet in the form of an antidot lattice may have such a gap. Such systems have been investigated with a view towards application...... in transistor or waveguiding devices. The desired properties have been predicted for atomically precise systems, but fabrication methods will introduce significant levels of disorder in the shape, position and edge configurations of individual antidots. We calculate the electronic transport properties of a wide...... range of finite graphene antidot devices to determine the effect of such disorders on their performance. Modest geometric disorder is seen to have a detrimental effect on devices containing small, tightly packed antidots, which have optimal performance in pristine lattices. Larger antidots display...
Electronic transport properties of the armchair silicon carbide nanotube
Energy Technology Data Exchange (ETDEWEB)
Song Jiuxu; Yang Yintang; Liu Hongxia [Key Laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi' an 710071 (China); Guo Lixin [School of Science, Xidian University, Xi' an 710071 (China); Zhang Zhiyong, E-mail: songjiuxu@126.com [Information Science and Technology Institution, Northwest University, Xi' an 710069 (China)
2010-11-15
The electronic transport properties of the armchair silicon carbide nanotube (SiCNT) are investigated by using the combined nonequilibrium Green's function method with density functional theory. In the equilibrium transmission spectrum of the nanotube, a transmission valley of about 2.12 eV is discovered around Fermi energy, which means that the nanotube is a wide band gap semiconductor and consistent with results of first principle calculations. More important, negative differential resistance is found in its current voltage characteristic. This phenomenon originates from the variation of density of states caused by applied bias voltage. These investigations are meaningful to modeling and simulation in silicon carbide nanotube electronic devices.
Electron transport in InAs/AlSb quantum wells
International Nuclear Information System (INIS)
Tuttle, G.; Kroemer, H.; English, J.H.
1989-01-01
The authors present data on electron transport in AlSb/InAs/AlSb quantum wells grown by molecular beam epitaxy. Because both anion and cation change across an InAs/Alsb interface, it is possible to grow such wells with two different types of interfaces, one with an InSb-like bond configuration, the other AlAs-like. Electron mobility and concentration were found to depend very strongly on the manner in which the quantum well's interfaces were grown, with high mobilities seen only if the bottom interface is InSb-like. An As-on-Al sites antisite defect model is postulated for bottom AlAs-like interfaces
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.
Short Wavelength Fluctuations and Electron Transport in TFTR
Energy Technology Data Exchange (ETDEWEB)
K.L. Wong; K. Itoh; S.-I. Itoh; A. Fukuyama; M. Yagi
2000-09-08
Correlation between electron heat diffusivity and short wavelength (kri {approximately} 5) fluctuation amplitude was observed in the Tokamak Fusion Test Reactor (TFTR) tokamak in the core of enhanced reversed shear (ERS) plasmas [1]. These fluctuations propagate in the ion diamagnetic drift direction with wave number comparable to wpe/c. Further analysis of these data yields the ratios ce/ci and ce/De, and their values are consistent with the picture that the electron transport is mainly induced by the short wavelength fluctuations in the plasma core where the long wavelength (kri {approximately} 1) fluctuations are absent. Although there is not enough information to identify these short wavelength modes, the values of ce is found to be comparable to theoretical predictions based on the current diffusive ballooning mode theory [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
Electron transport in heavily doped GdN
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.
High efficiency blue phosphorescent organic light-emitting diodes without electron transport layer
Energy Technology Data Exchange (ETDEWEB)
Jeon, Soon Ok [Department of Polymer Science and Engineering, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of); Lee, Jun Yeob, E-mail: leej17@dankook.ac.kr [Department of Polymer Science and Engineering, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of)
2011-08-15
High efficiency blue phosphorescent organic light-emitting diodes were fabricated without an electron transport layer using a spirobifluorene based blue triplet host material. The simple blue PHOLEDs without the electron transport layer showed a high external quantum efficiency and current efficiency of 16.1% and 30.2 cd/A, respectively. The high device performances of the electron transport layer free blue PHOLEDs were comparable to those of blue PHOLEDs with the electron transport layer. - Highlights: > Simple device structure without electron transport layer. > High efficiency blue phosphorescent organic light-emitting diode. > Spirobifluorene based high triplet energy host material.
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.
International Nuclear Information System (INIS)
Koterov, V.N.; Shcheprov, A.V.
1991-01-01
The study of the electron distribution function in weakly ionized gases is necessary for a detailed treatment of the processes in gas discharges which are presently used in a variety of industrial applications. Here, approximate equations are derived for the electron energy spectrum in a gas-discharge plasma. These are applicable both in the case of a nearly isotropic elect distribution function, when the Lorentz approximation is valid, and when the distribution is highly anisotropic. The practical applicability of the proposed technique is verified by solving the problem of the spatially nonequilibrium transport of electrons in the cathode sheath of a glow discharge in helium, assuming that the electric field profile is given
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.
Gaur, Gurudatt; Das, Amita
2012-07-01
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.
Nonlinear electromagnetic perturbations in a degenerate ultrarelativistic electron-positron plasma.
El-Taibany, W F; Mamun, A A
2012-02-01
Nonlinear propagation of fast and slow magnetosonic perturbation modes in an ultrarelativistic, ultracold, degenerate (extremely dense) electron positron (EP) plasma (containing ultrarelativistic, ultracold, degenerate electron and positron fluids) has been investigated by the reductive perturbation method. The Alfvén wave velocity is modified due to the presence of the enthalpy correction in the fluid equations of motion. The degenerate EP plasma system (under consideration) supports the Korteweg-de Vries (KdV) solitons, which are associated with either fast or slow magnetosonic perturbation modes. It is found that the ultrarelativistic model leads to compressive (rarefactive) electromagnetic solitons corresponding to the fast (slow) wave mode. There are certain critical angles, θ(c), at which no soliton solution is found corresponding to the fast wave mode. For the slow mode, the magnetic-field intensity affects both the soliton amplitude and width. It is also illustrated that the basic features of the electromagnetic solitary structures, which are found to exist in such a degenerate EP plasma, are significantly modified by the effects of enthalpy correction, electron and positron degeneracy, magnetic-field strength, and the relativistic effect. The applications of the results in a pair-plasma medium, which occurs in many astrophysical objects (e.g., pulsars, white dwarfs, and neutron stars) are briefly discussed.
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
Sim, K S; Norhisham, S
2016-11-01
A new method based on nonlinear least squares regression (NLLSR) is formulated to estimate signal-to-noise ratio (SNR) of scanning electron microscope (SEM) images. The estimation of SNR value based on NLLSR method is compared with the three existing methods of nearest neighbourhood, first-order interpolation and the combination of both nearest neighbourhood and first-order interpolation. Samples of SEM images with different textures, contrasts and edges were used to test the performance of NLLSR method in estimating the SNR values of the SEM images. It is shown that the NLLSR method is able to produce better estimation accuracy as compared to the other three existing methods. According to the SNR results obtained from the experiment, the NLLSR method is able to produce approximately less than 1% of SNR error difference as compared to the other three existing methods. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.
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
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
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.
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.)
One-Dimensional Electron Transport Layers for Perovskite Solar Cells
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
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.
One-Dimensional Electron Transport Layers for Perovskite Solar Cells.
Thakur, Ujwal K; Kisslinger, Ryan; Shankar, Karthik
2017-04-29
The electron diffusion length ( L n ) is smaller than the hole diffusion length ( L p ) 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.
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.
Lorin, E.; Lytova, M.; Memarian, A.; Bandrauk, A. D.
2015-03-01
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.
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.
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.
Fast-electron transport in cylindrically laser-compressed matter
Energy Technology Data Exchange (ETDEWEB)
Perez, F; Koenig, M; Baton, S D; Brambrink, E [Laboratoire pour l' Utilisation des Lasers Intenses, Palaiseau (France); Batani, D; Jafer, R [Dipartimento di Fisica, Universito di Milano-Bicocca (Italy); Beg, F N; Chawla, S; Higginson, D P [University of California, San Diego, La Jolla (United States); Benedetti, C [Dipartimento di Fisica, Universita di Bologna (Italy); Dorchies, F; Fourment, C; Hulin, S [Universite de Bordeaux - CNRS - CEA, Centre Lasers Intenses et Applications, Talence, F-33405 (France); Galimberti, M; Heathcote, R; Lancaster, K [Central Laser Facility, Rutherford Appleton Laboratory, Didcot (United Kingdom); Gizzi, L A; Koester, P; Labate, L [LIL-IPCF, Consiglio Nazionale delle Ricerche, PISA (Italy); MacKinnon, A J [Lawrence Livermore National Laboratory (United States)
2009-12-15
Experimental and theoretical results of relativistic electron transport in cylindrically compressed matter are presented. This experiment, which is a part of the HiPER roadmap, was achieved on the VULCAN laser facility (UK) using four long pulses beams ({approx}4 x 50 J, 1 ns, at 0.53{mu}m) to compress a hollow plastic cylinder filled with plastic foam of three different densities (0.1, 0.3 and 1 g cm{sup -3}). 2D simulations predict a density of 2-5 g cm{sup -3} and a plasma temperature up to 100 eV at maximum compression. A short pulse (10 ps, 160 J) beam generated fast electrons that propagate through the compressed matter by irradiating a nickel foil at an intensity of 5 x 10{sup 18} W cm{sup -2}. X-ray spectrometer and imagers were implemented in order to estimate the compressed plasma conditions and to infer the hot electron characteristics. Results are discussed and compared with simulations.
Energy Technology Data Exchange (ETDEWEB)
Long, Mingsheng; Gong, Youpin; Wei, Xiangfei; Zhu, Chao; Xu, Jianbao; Liu, Ping; Guo, Yufen; Li, Weiwei; Liu, Liwei, E-mail: lwliu2007@sinano.ac.cn [Key Laboratory of Nanodevices and Applications-CAS and Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); Liu, Guangtong [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)
2014-04-14
We fabricated a vertical structure device, in which graphene is sandwiched between two asymmetric ferromagnetic electrodes. The measurements of electron and spin transport were performed across the combined channels containing the vertical and horizontal components. The presence of electron-electron interaction (EEI) was found not only at low temperatures but also at moderate temperatures up to ∼120 K, and EEI dominates over weak localization (WL) with and without applying magnetic fields perpendicular to the sample plane. Moreover, spin valve effect was observed when magnetic filed is swept at the direction parallel to the sample surface. We attribute the EEI and WL surviving at a relatively high temperature to the effective suppress of phonon scattering in the vertical device structure. The findings open a way for studying quantum correlation at relatively high temperature.
Pompano, Rebecca R; Chiang, Andrew H; Kastrup, Christian J; Ismagilov, Rustem F
2017-06-20
Many biochemical systems are spatially heterogeneous and exhibit nonlinear behaviors, such as state switching in response to small changes in the local concentration of diffusible molecules. Systems as varied as blood clotting, intracellular calcium signaling, and tissue inflammation are all heavily influenced by the balance of rates of reaction and mass transport phenomena including flow and diffusion. Transport of signaling molecules is also affected by geometry and chemoselective confinement via matrix binding. In this review, we use a phenomenon referred to as patchy switching to illustrate the interplay of nonlinearities, transport phenomena, and spatial effects. Patchy switching describes a change in the state of a network when the local concentration of a diffusible molecule surpasses a critical threshold. Using patchy switching as an example, we describe conceptual tools from nonlinear dynamics and chemical engineering that make testable predictions and provide a unifying description of the myriad possible experimental observations. We describe experimental microfluidic and biochemical tools emerging to test conceptual predictions by controlling transport phenomena and spatial distribution of diffusible signals, and we highlight the unmet need for in vivo tools.
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)
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
Bias-dependent oscillatory electron transport of monatomic sulfur chains
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.
Electron transport in Bi2Se3 ultra thin films
Bauer, Sebastian; Bernhart, Alexander M.; Bobisch, Christian A.
2018-02-01
We studied the electronic transport properties of a 4 QL thin Bi2Se3 film in the hybridized phase on Si(111) by scanning tunneling potentiometry. When a transverse voltage is applied, the film exhibits a homogeneous electric field on the nm scale. In addition, thermovoltage signals with lateral nm variations are found which result from sample heating by the transverse current. The thermovoltage signals are directly correlated to morphological structures on the surface, i.e. step edges, and indicate a lateral variation of the local density of states at the Bi2Se3 surface. No discernible voltage drops appear at the surface so that the whole film serves as a current carrying medium and scattering at surface defects is less important.
Tuning electronic transport in a self-assembled nanocomposite.
Chang, Wei Sea; Liu, Heng-Jui; Tra, Vu Thanh; Chen, Jhih-Wei; Wei, Tzu-Chiao; Tzeng, W Y; Zhu, Yuanmin; Kuo, Ho-Hung; Hsieh, Ying-Hui; Lin, Jheng-Cyuan; Zhan, Qian; Luo, Chih Wei; Lin, Jiunn-Yuan; He, Jr-Hau; Wu, Chung Lin; Chu, Ying-Hao
2014-06-24
Self-assembled nanocomposites with a high interface-to-volume ratio offer an opportunity to overcome limitations in current technology, where intriguing transport behaviors can be tailored by the choice of proper interactions of constituents. Here we integrated metallic perovskite oxide SrRuO3-wurzite semiconductor ZnO nanocomposites to investigate the room-temperature metal-insulator transition and its effect on photoresponse. We demonstrate that the band structure at the interface can be tuned by controlling the interface-to-volume ratio of the nanocomposites. Photoinduced carrier injection driven by visible light was detected across the nanocomposites. This work shows the charge interaction of the vertically integrated multiheterostructures by incorporating a controllable interface-to-volume ratio, which is essential for optimization of the design and functionality of electronic devices.
Modeling Blazar Spectra by Solving an Electron Transport Equation
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.
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.
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
A comparison of Eulerian and Lagrangian transport and non-linear reaction algorithms
Benson, David A.; Aquino, Tomás; Bolster, Diogo; Engdahl, Nicholas; Henri, Christopher V.; Fernàndez-Garcia, Daniel
2017-01-01
When laboratory-measured chemical reaction rates are used in simulations at the field-scale, the models typically overpredict the apparent reaction rates. The discrepancy is primarily due to poorer mixing of chemically distinct waters at the larger scale. As a result, realistic field-scale predictions require accurate simulation of the degree of mixing between fluids. The Lagrangian particle-tracking (PT) method is a now-standard way to simulate the transport of conservative or sorbing solutes. The method's main advantage is the absence of numerical dispersion (and its artificial mixing) when simulating advection. New algorithms allow particles of different species to interact in nonlinear (e.g., bimolecular) reactions. Therefore, the PT methods hold a promise of more accurate field-scale simulation of reactive transport because they eliminate the masking effects of spurious mixing due to advection errors inherent in grid-based methods. A hypothetical field-scale reaction scenario is constructed and run in PT and Eulerian (finite-volume/finite-difference) simulators. Grid-based advection schemes considered here include 1st- to 3rd-order spatially accurate total-variation-diminishing flux-limiting schemes, both of which are widely used in current transport/reaction codes. A homogeneous velocity field in which the Courant number is everywhere unity, so that the chosen Eulerian methods incur no error when simulating advection, shows that both the Eulerian and PT methods can achieve convergence in the L1 (integrated concentration) norm, but neither shows stricter pointwise convergence. In this specific case with a constant dispersion coefficient and bimolecular reaction A + B → P , the correct total amount of product is 0.221MA0, where MA0 is the original mass of reactant A. When the Courant number drops, the grid-based simulations can show remarkable errors due to spurious over- and under-mixing. In a heterogeneous velocity field (keeping the same constant and
Electron transport through ac driven graphene p-n junctions
Zhang, Zhi-Qiang; Kang, Yan-Zhuo; Ding, Kai-He
2018-02-01
We study the electronic transport through ac driven graphene p-n junctions under a perpendicular magnetic field. It is found that subject to the transversely or longitudinally polarized ac field, in the p-n region, the conductance versus the on-site energy of the right electrode exhibits a characteristic structure with a zero value plateau and the followed oscillation peaks, whose widths are greatly suppressed by the ac field. In the n-n region, the conductance plateaus at G = (n + 1 / 2) (4e2 / h) (n is an integer) shrink for the transversely polarized ac field, whereas accompanied with the addition of the new quantized plateaus at G = n (4e2 / h) for the longitudinally polarized ac field. The combined influence of the ac field with the disorder can trigger a change in the mixing of the hole and electron states at the p-n interface, which leads to a destruction of the plateaus structure in the conductance versus the disorder strength with the emergence of new ones. The influence of the elliptically and circularly polarized ac field on the conductance is also shown.
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
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
Nonlinear ion-acoustic solitary waves with warm ions and non-Maxwellian electrons in space plasmas
Hussain Shah, Khalid; Qureshi, Nouman
2017-04-01
Electrons velocity distributions are often observed with non-Maxwellian features such flat tops at low energies and/or superthermal tails at high energies from different regions of near Earth plasmas such as Earth's bow shock, auroral zone and magnetosphere by numerous satellites. Such non-Maxwellian distributions are well modelled by generalized (r,q) distribution or Cairns distribution. Solitons are nonlinear solitary structures and are integral part of space plasmas. In this paper, we present a fluid model containing Cairns (r,q) distributed non-Maxwellian electrons and derive the Sagdeev potential for fully nonlinear fluid equations. We found that compressive solitons can be developed in such a plasma. The results from our model can be used to interpret solitary structures in space plasmas when electrons are obeying the non-Maxwellian flat tops along with the high energy tails.
Ibrahima, Fayadhoi; Meyer, Daniel; Tchelepi, Hamdi
2016-04-01
Because geophysical data are inexorably sparse and incomplete, stochastic treatments of simulated responses are crucial to explore possible scenarios and assess risks in subsurface problems. In particular, nonlinear two-phase flows in porous media are essential, yet challenging, in reservoir simulation and hydrology. Adding highly heterogeneous and uncertain input, such as the permeability and porosity fields, transforms the estimation of the flow response into a tough stochastic problem for which computationally expensive Monte Carlo (MC) simulations remain the preferred option.We propose an alternative approach to evaluate the probability distribution of the (water) saturation for the stochastic Buckley-Leverett problem when the probability distributions of the permeability and porosity fields are available. We give a computationally efficient and numerically accurate method to estimate the one-point probability density (PDF) and cumulative distribution functions (CDF) of the (water) saturation. The distribution method draws inspiration from a Lagrangian approach of the stochastic transport problem and expresses the saturation PDF and CDF essentially in terms of a deterministic mapping and the distribution and statistics of scalar random fields. In a large class of applications these random fields can be estimated at low computational costs (few MC runs), thus making the distribution method attractive. Even though the method relies on a key assumption of fixed streamlines, we show that it performs well for high input variances, which is the case of interest. Once the saturation distribution is determined, any one-point statistics thereof can be obtained, especially the saturation average and standard deviation. Moreover, the probability of rare events and saturation quantiles (e.g. P10, P50 and P90) can be efficiently derived from the distribution method. These statistics can then be used for risk assessment, as well as data assimilation and uncertainty reduction
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
Winjum, B. J.; Tableman, A.; Tsung, F. S.; Mori, W. B.
2017-10-01
Nonlinear wave-particle interactions can significantly affect the evolution of stimulated Raman scattering (SRS) for ICF-relevant parameters. An imposed magnetic field can alter the dynamics of these interactions and thereby the dynamics of SRS, altering the instability threshold and saturation. Particles resonant with an SRS-generated electron plasma wave can be rotated in velocity space, disrupting the nonlinear damping of electron plasma waves and changing the kinetically inflated SRS threshold. Resonant particles can also be rotated in physical space, changing the transverse kinetic dissipation of electron plasma waves and restricting trapped particle motion both within a single laser speckle as well as between neighboring laser speckles. We show PIC simulations of driven multi-dimensional electron plasma waves in the presence of an external field and illustrate how their nonlinear evolution is altered, particularly with regard to the dynamical behavior that can impact SRS. Work was supported by the DOE under Grant Nos. DE-NA0001833 and DE-FC02-04ER54789.
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
Defect engineering of the electronic transport through cuprous oxide interlayers
Fadlallah, Mohamed M.
2016-06-03
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 and anion substitution. For all Cu2O thicknesses the conductance is more enhanced by bulk-like (in contrast to near-interface) defects, with the exception of O vacancies and Cl substitutional defects. A similar transmission behavior results from Cu deficiency and N substitution, as well as from Cl substitution and N interstitials for thick Cu2O junctions. In agreement with recent experimental observations, it is found that N and Cl doping enhances the conductance. A Frenkel defect, i.e., a superposition of an O interstitial and O substitutional defect, leads to a remarkably high conductance. From the analysis of the defect formation energies, Cu vacancies are found to be particularly stable, in agreement with earlier experimental and theoretical work.
The electronic transport properties of porous zigzag graphene clusters
Simchi, Hamidreza; Esmaeilzadeh, Mahdi; Mazidabadi, Hossein
2013-12-01
By omitting some carbon atoms from middle of a zigzag graphene cluster, and Hydrogen termination of sp2 orbital, we make the different porous zigzag graphene clusters, and investigate the electron transport properties of the structures by the non-equilibrium Green function method at zero bias regime. It is shown that, the conductance of porous clusters depends on the final symmetry of porous cluster and the local imbalance number (nA-nB), in which nA and nB are the number of omitted atoms from A-sublattice and B-sublattice respectively. Also it is shown that, if three carbon atoms (one type-A and two type-B sites) are omitted the conductance for |E-Ef|≥5 eV is significantly higher than the conductance of original zigzag graphene cluster due to the increment in less affected conducting channels. We show that, spin flipping occurs under Rashba spin orbit interaction at E=Ef, when three atoms are omitted from the original cluster. Therefore the local imbalance number and final symmetry of porous graphene cluster can be used as a rule for designing porous graphene devices and the device can be used in spintronic applications.
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
Comparative investigation of electronic transport across three-dimensional nanojunctions
Wang, Yun-Peng; Zhang, X.-G.; Fry, J. N.; Cheng, Hai-Ping
2017-02-01
We show the thickness-dependent transition from metallic conduction to tunneling in three-dimensional (3D) Ag/Si/Ag nanojunctions through layer-by-layer electronic structure and quantum transport calculations. The transmission coefficients are calculated quantum mechanically within the framework of density functional theory in conjunction with nonequilibrium Green's function techniques. Thin junctions show nearly metallic character with no energy gap opening in Si layers due to the metal-induced interface states, and the transmission is independent of the stacking order of Si layers. An energy gap reemerges for Si layers deeply buried within thick junction, and the decay rate of transmission in this insulating region depends on the stacking order. Complex band analysis indicates that the decay of transmission is not determined by a single exponential constant but also depends on the available number of evanescent states. Calculating the electric resistance from the transmission coefficient requires a 3D generalization of the Landauer formula, which is not unique. We examine two approaches, the Landauer-Büttiker formula, with and without subtraction of the Sharvin resistance, and a semiclassical Boltzmann equation with boundary conditions defined by the transmission coefficients at the junction. We identify an empirical upper limit of ˜0.05 per channel in the transmission coefficient, below which the Landauer-Büttiker formula without the Sharvin resistance correction remains a good approximation. In the high transmission limit, the Landauer-Büttiker formula with Sharvin correction and the semiclassical Boltzmann method reach fair agreement.
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.
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...
International Nuclear Information System (INIS)
Kernbichler, W.; Heyn, M.F.; Kasilov, S.V.
2003-01-01
Convective transport of supra-thermal electrons can play a significant role in the energy balance of stellarators in case of high power electron cyclotron heating. Here, together with neoclassical thermal particle fluxes also the supra-thermal electron flux should be taken into account in the flux ambipolarity condition, which defines the self-consistent radial electric field. Since neoclassical particle fluxes are non-linear functions of the radial electric field, one needs an iterative procedure to solve the ambipolarity condition, where the supra-thermal electron flux has to be calculated for each iteration. A conventional Monte-Carlo method used earlier for evaluation of supra-thermal electron fluxes is rather slow for performing the iterations in reasonable computer time. In the present report, the Stochastic Mapping Technique (SMT), which is more effective than the conventional Monte Carlo method, is used instead. Here, the problem with a local monoenergetic supra-thermal particle source is considered and the effect of supra-thermal electron fluxes on both, the self-consistent radial electric field and the formation of different roots of the ambipolarity condition are studied
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
Mehlenbacher, Randy D.
Carbon nanotubes are an interesting class of materials with many exceptional properties that make them appealing for optoelectronic devices. Their optical properties, particularly when cast in thin films, are not well understood. In this thesis, I describe the development of spectroscopic techniques for measuring energy and charge transport processes in thin films of semiconducting carbon nanotubes. Using transient absorption spectroscopy, I observe energy transport on two time scales in these films, with 20% of nanotubes transferring energy to smaller bandgap nanotubes within 300 fs. After 3 ps, 70% of the photoexcitation resides on small bandgap nanotubes. To study the complete landscape of energy transport in thin films of carbon nanotubes, I developed two dimensional white light spectroscopy (2D-WL). In 2D-WL spectroscopy, a broadband, white light supercontinuum is used to both excite and probe the sample. This technique has a bandwidth spanning > 500-1500 nm, a far broader bandwidth than previously reported in 2D electronic spectra. I take advantage of this large bandwidth to study the interactions and evolution of S1 and S2 excitons in a thin film of carbon nanotubes. I find that energy transfers between S1 excitons on a 2 ps time scale and occurs by a non-Forster energy transfer mechanism. In contrast, the energy in the S2 states redistributes on an ultrafast time scale, films of bare, semiconducting carbon nanotubes. In these films, energy transfer occurs in <100 fs between bare carbon nanotubes and this energy transfer is between parallel nanotubes. By taking advantage of the laser pulse polarization for each interaction, I resolve otherwise difficult to observe couplings between electronic states. To facilitate data interpretation, the orientational response for isotropic two dimensional samples to polarized electric fields is developed. Using polarization control 2D-WL spectroscopy, I measure the coupling between nanotube S1 transitions and radial
Electron transport chains of lactic acid bacteria - walking on crutches is part of their lifestyle
Brooijmans, Rob; Hugenholtz, Jeroen
2009-01-01
A variety of lactic acid bacteria contain rudimentary electron transport chains that can be reconstituted by the addition of heme and menaquinone to the growth medium. These activated electron transport chains lead to higher biomass production and increased robustness, which is beneficial for industrial applications, but a major concern when dealing with pathogenic lactic acid bacteria. PMID:20948651
Photosynthetic electron transport in purple bacteria: An in vivo spectroscopic study
BÍNA, David
2009-01-01
Electron transport in purple bacteria was studied using combination of absorption spectroscopy and induced bacteriochlorophyll fluorescence in whole cells in vivo. Focus is placed on relations between fluorescence yield, the state of the electron transport chain and the membrane potential. A laboratory-built absorption spectrophotometer-fluorimeter is described.
Using Adobe Flash Animations of Electron Transport Chain to Teach and Learn Biochemistry
Teplá, Milada; Klímová, Helena
2015-01-01
Teaching the subject of the electron transport chain is one of the most challenging aspects of the chemistry curriculum at the high school level. This article presents an educational program called "Electron Transport Chain" which consists of 14 visual animations including a biochemistry quiz. The program was created in the Adobe Flash…
Peeters, A.G.; Westerhof, E.
1996-01-01
Numerical simulations using a three-dimensional Fokker-Planck code show that for small tokamaks the transport of electrons across the magnetic surfaces at a level consistent with anomalous transport has a large influence on the formation of the quasilinear plateau during electron cyclotron resonant
Directory of Open Access Journals (Sweden)
Ahmad Irfan
2018-01-01
Full Text Available The oxazole compounds are being used for multifunctional purposes ranging from organic light emitting diodes, organic thin film transistors, and photovoltaic to the nonlinear optical materials. In this study, several structural, electro-optical, charge transport and nonlinear optical properties of (4Z-4-Benzylidene-2-(4-methylphenyl-1,3-oxazol-5(4H-one (BMPO have been investigated. Density functional theory (DFT and time dependent DFT are very accurate and reasonable approaches to optimize the ground and excited state geometries, respectively. Thus, in the present study DFT and TDDFT methods with the B3LYP/6-31G∗∗ levels of theory have been applied to shed some light on the structure-property relationship, frontier molecular orbitals (FMOs, optical properties. A clear intra-molecular charge transfer (ICT from the highest occupied molecular orbitals (HOMOs to the lowest unoccupied molecular orbitals (LUMOs has been observed. The ionization potentials (IP, electron affinities (EA, total and partial densities of states have been discussed intensively. The electron reorganization energy of oxazole compound (BMPO is smaller than the hole reorganization energy revealing that it might be good electron transport contender in OLED. The electron reorganization energy of BMPO is calculated to be 0.223 eV that is smaller than the perfluoropentacene (value is 0.250 eV, which is famous n-type semiconductor material. The first pathway of BMPO has almost comparable hole and electron transfer integral values whereas the calculated electron reorganization energy (0.223 eV is considerably lower than the hole reorganization energy (0.381 eV which leads to superior electron intrinsic mobility of the studied oxazole derivative as compared to the hole one. It is expected that BMPO might be excellent electron transport material.
Multi-scale modelling and numerical simulation of electronic kinetic transport
International Nuclear Information System (INIS)
Duclous, R.
2009-11-01
This research thesis which is at the interface between numerical analysis, plasma physics and applied mathematics, deals with the kinetic modelling and numerical simulations of the electron energy transport and deposition in laser-produced plasmas, having in view the processes of fuel assembly to temperature and density conditions necessary to ignite fusion reactions. After a brief review of the processes at play in the collisional kinetic theory of plasmas, with a focus on basic models and methods to implement, couple and validate them, the author focuses on the collective aspect related to the free-streaming electron transport equation in the non-relativistic limit as well as in the relativistic regime. He discusses the numerical development and analysis of the scheme for the Vlasov-Maxwell system, and the selection of a validation procedure and numerical tests. Then, he investigates more specific aspects of the collective transport: the multi-specie transport, submitted to phase-space discontinuities. Dealing with the multi-scale physics of electron transport with collision source terms, he validates the accuracy of a fast Monte Carlo multi-grid solver for the Fokker-Planck-Landau electron-electron collision operator. He reports realistic simulations for the kinetic electron transport in the frame of the shock ignition scheme, the development and validation of a reduced electron transport angular model. He finally explores the relative importance of the processes involving electron-electron collisions at high energy by means a multi-scale reduced model with relativistic Boltzmann terms
41 CFR 102-118.65 - Can my agency receive electronic billing for payment of transportation services?
2010-07-01
... electronic billing for payment of transportation services? 102-118.65 Section 102-118.65 Public Contracts and... Transportation Services § 102-118.65 Can my agency receive electronic billing for payment of transportation... to use electronic billing for the procurement and billing of transportation services. ...
International Nuclear Information System (INIS)
Kontorovich, V.M.; Kochanov, A.E.
1980-01-01
It is demonstrated that in the case of hard injection of relativistic electrons accompanied by the joint action of synchrotron (Compton) losses and energy-dependent spatial diffusion, a spectrum with 'breaks' is formed containing universal (with index γ = 2) and diffusion regions, both independent of the injection spectrum. The effect from non-linearity of the electron spectrum is considered in averaged electromagnetic spectra for various geometries of sources (sphere, disk, arm). It is shown that an universal region (with index α = 0.5) can occur in the radiation spectrum. (orig.)
Modeling electron transport in the presence of electric and magnetic fields.
Energy Technology Data Exchange (ETDEWEB)
Fan, Wesley C.; Drumm, Clifton Russell; Pautz, Shawn D.; Turner, C. David
2013-09-01
This report describes the theoretical background on modeling electron transport in the presence of electric and magnetic fields by incorporating the effects of the Lorentz force on electron motion into the Boltzmann transport equation. Electromagnetic fields alter the electron energy and trajectory continuously, and these effects can be characterized mathematically by differential operators in terms of electron energy and direction. Numerical solution techniques, based on the discrete-ordinates and finite-element methods, are developed and implemented in an existing radiation transport code, SCEPTRE.
Energy Technology Data Exchange (ETDEWEB)
Stancari, Giulio
2014-09-11
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Hollow electron beam collimation and halo control were studied as an option to complement the collimation system for the upgrades of the Large Hadron Collider (LHC) at CERN; a conceptual design was recently completed. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles. At Fermilab, we are planning to install an electron lens in the Integrable Optics Test Accelerator (IOTA, a 40-m ring for 150-MeV electrons) as one of the proof-of-principle implementations of nonlinear integrable optics to achieve large tune spreads and more stable beams without loss of dynamic aperture.
Sabry, R.; Moslem, W. M.; Shukla, P. K.
2009-03-01
Properties of fully nonlinear ion-acoustic solitary waves in a plasma with positive-negative ions and nonthermal electrons are investigated. For this purpose, the hydrodynamic equations for the positive-negative ions, nonthermal electron density distribution, and the Poisson equation are used to derive the energy integral equation with a new Sagdeev potential. The latter is analyzed to examine the existence regions of the solitary pulses. It is found that the solitary excitations strongly depend on the mass and density ratios of the positive and negative ions as well as the nonthermal electron parameter. Numerical solution of the energy integral equation clears that both positive and negative potentials exist together. It is found that faster solitary pulses are taller and narrower. Furthermore, increasing the electron nonthermality parameter (negative-to-positive ions density ratio) decreases (increases) the localized excitation amplitude but increases (decreases) the pulse width. The present model is used to investigate the solitary excitations in the (H+,O2-) and (H+,H-) plasmas, where they are presented in the D- and F-regions of the Earth's ionosphere. This investigation should be helpful in understanding the salient features of the fully nonlinear ion-acoustic solitary waves in space and in laboratory plasmas where two distinct groups of ions and non-Boltzmann distributed electrons are present.
Transport Theory for Kinetic Emission of Secondary Electrons from Solids
DEFF Research Database (Denmark)
Schou, Jørgen
1980-01-01
Kinetic secondary electron emission from a solid target resulting from incidence of keV electrons or keV and MeV ions is treated theoretically on the basis of ionization cascade theory. The energy and angular distribution and the yield of secondary electrons are calculated for a random target...... a spectrum which shows good agreement with experimental data. The electron- and proton-induced yields from aluminum are evaluated on the basis of existing low-energy-electron stopping-power data. The agreement with existing experimental data is good. Also, experimental yields from electrons, protons...
International Nuclear Information System (INIS)
Merton, S. R.; Smedley-Stevenson, R. P.; Pain, C. C.; Buchan, A. G.; Eaton, M. D.
2009-01-01
This paper describes a new Non-Linear Discontinuous Petrov-Galerkin (NDPG) method and application to the one-speed Boltzmann Transport Equation (BTE) for space-time problems. The purpose of the method is to remove unwanted oscillations in the transport solution which occur in the vicinity of sharp flux gradients, while improving computational efficiency and numerical accuracy. This is achieved by applying artificial dissipation in the solution gradient direction, internal to an element using a novel finite element (FE) Riemann approach. The amount of dissipation added acts internal to each element. This is done using a gradient-informed scaling of the advection velocities in the stabilisation term. This makes the method in its most general form non-linear. The method is designed to be independent of angular expansion framework. This is demonstrated for the both discrete ordinates (S N ) and spherical harmonics (P N ) descriptions of the angular variable. Results show the scheme performs consistently well in demanding time dependent and multi-dimensional radiation transport problems. (authors)
Zhang, Xiaohang
The exploration of new paradigms for micro- and nanoelectronics has engendered several exciting new research fields including molecular electronics and spintronics. Two essential ingredients of the device structures are materials and interfaces. The overarching theme of this dissertation is the study of the (spin-dependent) electronic states and transport in novel magnetic materials and through molecular interfaces. These experiments are necessary first steps in ascertaining potential utilities in molecular electronic and spintronics applications. More importantly for this thesis, the materials and hybrid device structures provide a fertile ground for studying basic physics of magnetism, magnetotransport, and spin transport. In this dissertation, various techniques of superconducting spectroscopy have been used to investigate the spin-dependent electronic density of states of the thiol/Au molecular interface and the ferromagnetic semimetal EuB6. In addition, a fresh analysis of the electronic transport properties of EuB6 reveals a new type of nonlinear Hall effect intimately related to its magnetic state and culminates in a model that offers excellent quantitative understanding of the data and appears applicable to a wide varieties of magnetic materials. In order to directly probe possible induced magnetism at the thiol-gold interface, spin polarized tunneling measurements were performed on planar tunnel junctions incorporating a molecular monolayer of mercaptohexadecanoic acid [HS(CH2)15COOH] (MHA) between aluminum and gold electrodes. The Zeeman resolved tunneling spectra yield no measurable spin polarization at the thiol-gold interface, contrary to the expectations from the reported induced giant magnetic moments at the interface. On the other hand, variations in the resistance of the fabricated tunnel junctions with changing environmental conditions were consistently observed. A systematic investigation revealed that the effect is directly linked to the
Li, Jing-hui
2006-07-01
Chaotic noisy transport of electron pairs in a superconducting junction device (thermal-inertia ratchets) is investigated. The study shows that when the temperature is low enough, the transport of the electron pairs can be mainly chaotic; when the temperature is high enough, it can be mainly stochastic. By controlling the temperature and the amplitude of the input ac signal, the current of electron pairs can be reversed.
International Nuclear Information System (INIS)
Holland, C.; Kim, E.J.; Champeaux, S.; Gurcan, O.; Rosenbluth, M.N.; Diamond, P.H.; Tynan, G.R.; Nevins, W.; Candy, J.
2003-01-01
Understanding the physics of shear flow and structure formation in plasmas is a central problem for the advancement of magnetic fusion because of the roles such flows are believed to play in regulating turbulence and transport levels. In this paper, we report on integrated experimental, computational, and theoretical studies of sheared zonal flows and radially extended convective cells, with the aim of assessing the results of theory experiment and theory-simulation comparisons. In particular, simulations are used as test beds for verifying analytical predictions and demonstrating the suitability of techniques such as bispectral analysis for isolating nonlinear couplings in data. Based on intriguing initial results suggesting increased levels of nonlinear coupling occur during L-H transitions, we have undertaken a comprehensive study of bispectral quantities in fluid and gyrokinetic simulations, and compared these results with theoretical expectations. Topics of study include locality and directionality of energy transfer, amplitude scaling, and parameter dependences. Techniques for inferring nonlinear coupling coefficients from data are discussed, and initial results from experimental data are presented. Future experimental studies are motivated. We also present work investigating the role of structures in transport. Analysis of simulation data indicates that the turbulent heat flux can be represented as an ensemble of 'heat pulses' of varying sizes, with a power law distribution. The slope of the power law is shown to determine global transport scaling (i.e. Bohm or gyro-Bohm). Theoretical work studying the dynamics of the largest cells (termed 'streamers') is presented, as well as results from ongoing analysis studying connections between heat pulse distribution and bispectral quantities. (author)
Colloquium : Electronic transport in single-crystal organic transistors
Gershenson, M.E.; Podzorov, V.; Morpurgo, A.F.
2006-01-01
Small-molecule organic semiconductors, together with polymers, form the basis for the emerging field of organic electronics. Despite the rapid technological progress in this area, our understanding of fundamental electronic properties of these materials remains limited. Recently developed organic
Weerd, van de H.; Leijnse, A.; Riemsdijk, van W.H.
1998-01-01
Transport of reactive colloids in groundwater may enhance the transport of contaminants in groundwater. Often, the interpretation of results of transport experiments is not a simple task as both reactions of colloids with the solid matrix and reactions of contaminants with the solid matrix and
Luo, Zhaochu; Xiong, Chengyue; Zhang, Xu; Guo, Zhen-Gang; Cai, Jianwang; Zhang, Xiaozhong
2016-04-13
The anomalous Hall effect of a magnetic material is coupled to the nonlinear transport effect of a semiconductor material in a simple structure to achieve a large geometric magnetoresistance (MR) based on a diode-assisted mechanism. An extremely large MR (>10(4) %) at low magnetic fields (1 mT) is observed at room temperature. This MR device shows potential for use as a logic gate for the four basic Boolean logic operations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Monte-Carlo treatment of nonlinear collisional effects in charged-particle transport
International Nuclear Information System (INIS)
Weiss, D.L.; Witte, K.H.; Sheppard, M.G.; Oliphant, T.A.
1985-01-01
The effects of two-body coulomb collisions of the simulation particles against a background material are often treated by a Monte-Carlo collisional process in which the collision probability is determined by a Fokker-Planck treatment. This procedure is nonlinear if the properties of the background material are allowed to change as a result of the scattering of the simulation particles. A more completely, nonlinear problem is obtained if the simulation particles themselves form all or part of the background distribution. A new method is presented here for doing this, and examples will be discussed that illustrate the power of the technique
Electronic spin transport and spin precession in single graphene layers at room temperature
Tombros, Nikolaos; Jozsa, Csaba; Popinciuc, Mihaita; Jonkman, Harry T.; van Wees, Bart J.
2007-01-01
Electronic transport in single or a few layers of graphene is the subject of intense interest at present. The specific band structure of graphene, with its unique valley structure and Dirac neutrality point separating hole states from electron states, has led to the observation of new electronic
76 FR 17470 - Notice of Transportation Services' Transition From Paper to Electronic Fare Media
2011-03-29
...] Notice of Transportation Services' Transition From Paper to Electronic Fare Media AGENCY: Office of the... planning to shift to electronic fare media in particular areas, beginning in New York and parts of the... to electronic fare media; thus, compelling the shift from a paper based system (vouchers) to an...
Energy Technology Data Exchange (ETDEWEB)
Reshak, A.H. [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Khan, Wilayat, E-mail: walayat76@gmail.com [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic)
2014-04-01
Highlights: • FP-LAPW technique is used for calculating the electronic structure. • The band structure shows that the calculated compound is semiconductor. • The complex dielectric function has been calculated. • Nonlinear optical properties has also been calculated. • This compound can be used for molecular engineering of the crystals. - Abstract: Self-consistent calculations is performed using the full potential linear augmented plane wave (FP-LAPW) technique based on density functional theory (DFT) to investigate the electronic band structure, density of states, electronic charge density, linear and non-linear optical properties of α-LiAlTe{sub 2} compound having tetragonal symmetry with space group I4{sup ¯}2d. The electronic structure are calculated using the Ceperley Alder local density approach (CA-LDA), Perdew Burke and Ernzerhof generalize gradient approach (PBE-GGA), Engel–Vosko generalize gradient approach (EVGGA) and modified Becke Johnson approach (mBJ). Band structure calculations of (α-LiAlTe{sub 2}) depict semiconducting nature with direct band gap of 2.35 eV (LDA), 2.48 eV (GGA), 3.05 eV (EVGGA) and 3.13 eV (mBJ), which is comparable to experimental value. The calculated electronic charge density show ionic interaction between Te and Li atoms and polar covalent interaction between Al and Te atoms. Some optical susceptibilities like dielectric constants, refractive index, extension co-efficient, reflectivity and energy loss function have been calculated and analyzed on the basis of electronic structure. The compound α-LiAlTe{sub 2} provides a considerable negative value of birefringence of −0.01. Any anisotropy observed in the linear optical properties which are in favor to enhance the nonlinear optical properties. The symbol χ{sub abc}{sup (2)}(ω) represents the second order nonlinear optical susceptibilities, possess six non-zero components in this symmetry (tetragonal), called: 1 2 3, 2 1 3, 2 3 1, 1 3 2, 3 1 2 and 3 2 1
Osherovich, V. A.; Fainberg, J.
2018-01-01
We consider simultaneous oscillations of electrons moving both along the axis of symmetry and also in the direction perpendicular to the axis. We derive a system of three nonlinear ordinary differential equations which describe self-similar oscillations of cold electrons in a constant proton density background (np = n0 = constant). These three equations represent an exact class of solutions. For weak nonlinear conditions, the frequency spectra of electric field oscillations exhibit split frequency behavior at the Langmuir frequency ωp0 and its harmonics, as well as presence of difference frequencies at low spectral values. For strong nonlinear conditions, the spectra contain peaks at frequencies with values ωp0(n +m √{2 }) , where n and m are integer numbers (positive and negative). We predict that both spectral types (weak and strong) should be observed in plasmas where axial symmetry may exist. To illustrate possible applications of our theory, we present a spectrum of electric field oscillations observed in situ in the solar wind by the WAVES experiment on the Wind spacecraft during the passage of a type III solar radio burst.
International Nuclear Information System (INIS)
Shokair, I.R.
1991-01-01
Phase mixing of transverse oscillations changes the nature of the ion hose instability from an absolute to a convective instability. The stronger the phase mixing, the faster an electron beam reaches equilibrium with the guiding ion channel. This is important for long distance propagation of relativistic electron beams where it is desired that transverse oscillations phase mix within a few betatron wavelengths of injection and subsequently an equilibrium is reached with no further beam emittance growth. In the linear regime phase mixing is well understood and results in asymptotic decay of transverse oscillations as 1/Z 2 for a Gaussian beam and channel system, Z being the axial distance measured in betatron wavelengths. In the nonlinear regime (which is likely mode of propagation for long pulse beams) results of the spread mass model indicate that phase mixing is considerably weaker than in the regime. In this paper we consider this problem of phase mixing in the nonlinear regime. Results of the spread mass model will be shown along with a simple analysis of phase mixing for multiple oscillator models. Particle simulations also indicate that phase mixing is weaker in nonlinear regime than in the linear regime. These results will also be shown. 3 refs., 4 figs
Rauf Abdullah, Nzar; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar
2016-09-21
We investigate theoretically the balance of the static magnetic and the dynamical photon forces in the electron transport through a quantum dot in a photon cavity with a single photon mode. The quantum dot system is connected to external leads and the total system is exposed to a static perpendicular magnetic field. We explore the transport characteristics through the system by tuning the ratio, [Formula: see text], between the photon energy, [Formula: see text], and the cyclotron energy, [Formula: see text]. Enhancement in the electron transport with increasing electron-photon coupling is observed when [Formula: see text]. In this case the photon field dominates and stretches the electron charge distribution in the quantum dot, extending it towards the contact area for the leads. Suppression in the electron transport is found when [Formula: see text], as the external magnetic field causes circular confinement of the charge density around the dot.
Directory of Open Access Journals (Sweden)
Daniel Guyomar
2011-06-01
Full Text Available This paper aims at providing an up-to-date review of nonlinear electronic interfaces for energy harvesting from mechanical vibrations using piezoelectric coupling. The basic principles and the direct application to energy harvesting of nonlinear treatment of the output voltage of the transducers for conversion enhancement will be recalled, and extensions of this approach presented. Latest advances in this field will be exposed, such as the use of intermediate energy tanks for decoupling or initial energy injection for conversion magnification. A comparative analysis of each of these techniques will be performed, highlighting the advantages and drawbacks of the methods, in terms of efficiency, performance under several excitation conditions, complexity of implementation and so on. Finally, a special focus of their implementation in the case of low voltage output transducers (as in the case of microsystems will be presented.
Nishiguchi, Norihiko; Wybourne, Martin N
2010-02-17
We investigate theoretically the transport characteristics of a single-electron transistor affected by the dynamic deformation of the device configuration due to phonons. By considering changes in capacitances and tunnel resistances caused by the breathing and oblong vibrations of the island that forms part of the transistor, we formulate the electron-phonon interaction peculiar to the device and derive its transport properties by means of the master equation. For a single electron transistor with a gold nanoparticle island of radius 1 nm, we demonstrate the contribution to the transport properties that originates from tunneling channels associated with THz phonon emission and absorption.
Electronic transport properties of 4f shell elements of liquid metal using hard sphere Yukawa system
Patel, H. P.; Sonvane, Y. A.; Thakor, P. B.
2018-04-01
The electronic transport properties are analyzed for 4f shell elements of liquid metals. To examine the electronic transport properties like electrical resistivity (ρ), thermal conductivity (σ) and thermo electrical power (Q), we used our own parameter free model potential with the Hard Sphere Yukawa (HSY) reference system. The screening effect on aforesaid properties has been examined by using different screening functions like Hartree (H), Taylor (T) and Sarkar (S). The correlations of our resultsand other data with available experimental values are intensely promising. Also, we conclude that our newly constructed parameter free model potential is capable of explaining the above mentioned electronic transport properties.
Electronic transport in amorphous phase-change materials
International Nuclear Information System (INIS)
Luckas, Jennifer Maria
2012-01-01
Phase change materials combine a pronounced contrast in resistivity and reflectivity between their disordered amorphous and ordered crystalline state with very fast crystallization kinetics. Due to this exceptional combination of properties phase-change materials find broad application in non-volatile optical memories such as CD, DVD or Bluray Disc. Furthermore, this class of materials demonstrates remarkable electrical transport phenomena in their disordered state, which have shown to be crucial for their application in electronic storage devices. The threshold switching phenomenon denotes the sudden decrease in resistivity beyond a critical electrical threshold field. The threshold switching phenomenon facilitates the phase transitions at practical small voltages. Below this threshold the amorphous state resistivity is thermally activated and is observed to increase with time. This effect known as resistance drift seriously hampers the development of multi-level storage devices. Hence, understanding the physical origins of threshold switching and resistance drift phenomena is crucial to improve non-volatile phase-change memories. Even though both phenomena are often attributed to localized defect states in the band gap, the defect state density in amorphous phase-change materials has remained poorly studied. Starting from a brief introduction of the physics of phase-change materials this thesis summarizes the most important models behind electrical switching and resistance drift with the aim to discuss the role of localized defect states. The centerpiece of this thesis is the investigation of defects state densities in different amorphous phase-change materials and electrical switching chalcogenides. On the basis of Modulated Photo Current (MPC) Experiments and Photothermal Deflection Spectroscopy, a sophisticated band model for the disordered phase of the binary phase-change alloy GeTe has been developed. By this direct experimental approach the band-model for a
Electronic transport in amorphous phase-change materials
Energy Technology Data Exchange (ETDEWEB)
Luckas, Jennifer Maria
2012-09-14
Phase change materials combine a pronounced contrast in resistivity and reflectivity between their disordered amorphous and ordered crystalline state with very fast crystallization kinetics. Due to this exceptional combination of properties phase-change materials find broad application in non-volatile optical memories such as CD, DVD or Bluray Disc. Furthermore, this class of materials demonstrates remarkable electrical transport phenomena in their disordered state, which have shown to be crucial for their application in electronic storage devices. The threshold switching phenomenon denotes the sudden decrease in resistivity beyond a critical electrical threshold field. The threshold switching phenomenon facilitates the phase transitions at practical small voltages. Below this threshold the amorphous state resistivity is thermally activated and is observed to increase with time. This effect known as resistance drift seriously hampers the development of multi-level storage devices. Hence, understanding the physical origins of threshold switching and resistance drift phenomena is crucial to improve non-volatile phase-change memories. Even though both phenomena are often attributed to localized defect states in the band gap, the defect state density in amorphous phase-change materials has remained poorly studied. Starting from a brief introduction of the physics of phase-change materials this thesis summarizes the most important models behind electrical switching and resistance drift with the aim to discuss the role of localized defect states. The centerpiece of this thesis is the investigation of defects state densities in different amorphous phase-change materials and electrical switching chalcogenides. On the basis of Modulated Photo Current (MPC) Experiments and Photothermal Deflection Spectroscopy, a sophisticated band model for the disordered phase of the binary phase-change alloy GeTe has been developed. By this direct experimental approach the band-model for a
Nonlinear theory of a free electron laser with a helical wiggler and an axial guide magnetic field
Directory of Open Access Journals (Sweden)
N. S. Ginzburg
2013-09-01
Full Text Available A 1D nonlinear theory of a free electron laser (FEL with a helical wiggler and an axial guide magnetic field is developed based on averaged equations of the electron motion. By averaging we separated two different cases of the e-beam/rf-wave interaction. The first one corresponds to the traditional wiggler synchronism (resonance of rf wave with the electrons moving along stationary helical trajectories. The second one corresponds to combination resonances distinguishing by excitation of oscillation of the electrons near the stationary helical trajectory. Comparative analysis of the FEL operation in different regimes has been studied under the traditional wiggler synchronism condition. It was shown that FELs operated far from cyclotron resonance (including a reversed guide field orientation possess low sensitivity to the initial velocity spread in the driving beam resulting in high electron efficiency. In contrast, under the weak guide field (the gyrofrequency is less than the bounce frequency of a conventional orientation, the FEL efficiency is restricted by a significant increase in the transverse velocity of the electrons during the interaction with the rf wave that results in violation of the synchronism conditions and is accompanied by electron current losses. An additional mechanism of FEL efficiency enhancement under the conventional guide field orientation in the conditions when the gyrofrequency is higher than the bounce frequency, based on the dependence of the effective mass of the oscillating electrons on their energy, was demonstrated. Results of the theoretical analysis are compared with the results of experimental studies of FEL oscillators. The specific features of energy extraction from the electron beam under condition of an abnormal Doppler effect in the case of the combination resonance are described. This regime is beneficial to increase radiation frequency keeping wiggler period and electron energies.
ITS - The integrated TIGER series of coupled electron/photon Monte Carlo transport codes
International Nuclear Information System (INIS)
Halbleib, J.A.; Mehlhorn, T.A.
1985-01-01
The TIGER series of time-independent coupled electron/photon Monte Carlo transport codes is a group of multimaterial, multidimensional codes designed to provide a state-of-the-art description of the production and transport of the electron/photon cascade. The codes follow both electrons and photons from 1.0 GeV down to 1.0 keV, and the user has the option of combining the collisional transport with transport in macroscopic electric and magnetic fields of arbitrary spatial dependence. Source particles can be either electrons or photons. The most important output data are (a) charge and energy deposition profiles, (b) integral and differential escape coefficients for both electrons and photons, (c) differential electron and photon flux, and (d) pulse-height distributions for selected regions of the problem geometry. The base codes of the series differ from one another primarily in their dimensionality and geometric modeling. They include (a) a one-dimensional multilayer code, (b) a code that describes the transport in two-dimensional axisymmetric cylindrical material geometries with a fully three-dimensional description of particle trajectories, and (c) a general three-dimensional transport code which employs a combinatorial geometry scheme. These base codes were designed primarily for describing radiation transport for those situations in which the detailed atomic structure of the transport medium is not important. For some applications, it is desirable to have a more detailed model of the low energy transport. The system includes three additional codes that contain a more elaborate ionization/relaxation model than the base codes. Finally, the system includes two codes that combine the collisional transport of the multidimensional base codes with transport in macroscopic electric and magnetic fields of arbitrary spatial dependence
El-Labany, S. K.; Sabry, R.; El-Shamy, E. F.; Khedr, D. M.; Khedr
2013-10-01
Investigation of arbitrary amplitude nonlinear ion-acoustic solitary waves which accompany collisionless positive-negative ion plasmas with high-energy electrons (represented by kappa distribution) is presented. Arbitrary amplitude solitary waves are investigated by deriving an energy-integral equation involving a Sagdeev-like pseudopotential. The existence regions of solitary pulses are, defined precisely, modified by the superthermality of energetic electrons. Furthermore, numerical calculations reveal that both compressive and rarefactive pulses may exist for negative ion mass groups in Titan's atmosphere. The superthermality of energetic electrons are found to modify the existence domains of large amplitude ion-acoustic waves in Titan's atmosphere. The dependence of solitary excitation characteristics on the superthermal parameter, the negative ion concentration, the positive-to-negative ions mass ratio, and the Mach number have been investigated. The present study might be helpful to understand the excitation of fully nonlinear ion-acoustic solitary pulses that may appear in the interplanetary medium and/or in the astrophysical plasmas in general.
Zamani, K.; Bombardelli, F. A.
2014-12-01
Verification of geophysics codes is imperative to avoid serious academic as well as practical consequences. In case that access to any given source code is not possible, the Method of Manufactured Solution (MMS) cannot be employed in code verification. In contrast, employing the Method of Exact Solution (MES) has several practical advantages. In this research, we first provide four new one-dimensional analytical solutions designed for code verification; these solutions are able to uncover the particular imperfections of the Advection-diffusion-reaction equation, such as nonlinear advection, diffusion or source terms, as well as non-constant coefficient equations. After that, we provide a solution of Burgers' equation in a novel setup. Proposed solutions satisfy the continuity of mass for the ambient flow, which is a crucial factor for coupled hydrodynamics-transport solvers. Then, we use the derived analytical solutions for code verification. To clarify gray-literature issues in the verification of transport codes, we designed a comprehensive test suite to uncover any imperfection in transport solvers via a hierarchical increase in the level of tests' complexity. The test suite includes hundreds of unit tests and system tests to check vis-a-vis the portions of the code. Examples for checking the suite start by testing a simple case of unidirectional advection; then, bidirectional advection and tidal flow and build up to nonlinear cases. We design tests to check nonlinearity in velocity, dispersivity and reactions. The concealing effect of scales (Peclet and Damkohler numbers) on the mesh-convergence study and appropriate remedies are also discussed. For the cases in which the appropriate benchmarks for mesh convergence study are not available, we utilize symmetry. Auxiliary subroutines for automation of the test suite and report generation are designed. All in all, the test package is not only a robust tool for code verification but it also provides comprehensive
Coupled electron-phonon transport from molecular dynamics with quantum baths
DEFF Research Database (Denmark)
Lu, Jing Tao; Wang, J. S.
2009-01-01
Based on generalized quantum Langevin equations for the tight-binding wavefunction amplitudes and lattice displacements, electron and phonon quantum transport are obtained exactly using molecular dynamics (MD) in the ballistic regime. The electron-phonon interactions can be handled with a quasi......-classical approximation. Both charge and energy transport and their interplay can be studied. We compare the MD results with those of a fully quantum mechanical nonequilibrium Green's function (NEGF) approach for the electron currents. We find a ballistic to diffusive transition of the electron conduction in one...
Energy Technology Data Exchange (ETDEWEB)
Borowik, Piotr, E-mail: pborow@poczta.onet.pl [Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa (Poland); Thobel, Jean-Luc, E-mail: jean-luc.thobel@iemn.univ-lille1.fr [Institut d' Electronique, de Microélectronique et de Nanotechnologies, UMR CNRS 8520, Université Lille 1, Avenue Poincaré, CS 60069, 59652 Villeneuve d' Ascq Cédex (France); Adamowicz, Leszek, E-mail: adamo@if.pw.edu.pl [Warsaw University of Technology, Faculty of Physics, ul. Koszykowa 75, 00-662 Warszawa (Poland)
2017-07-15
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.
International Nuclear Information System (INIS)
Brenner, D.J.; Miller, J.H.; Ritchie, R.H.; Bichsel, H.
1985-01-01
An insulator model with four experimental energy bands was used to fit the optical properties of liquid water and to extend these data to non-zero momentum transfer. Inelastic mean free paths derived from this dielectric response function provided the basic information necessary to degrade high energy electrons to the subexcitation energy domain. Two approaches for the transport of subexcitation electrons were investigated. (i) Gas phase cross sections were used to degrade subexcitation electrons to thermal energy and the thermalization lengths were scaled to unit density. (ii) Thermalization lengths were estimated by age-diffusion theory with a stopping power deduced from the data on liquid water and transport cross sections derived from elastic scattering in water vapor. Theoretical ranges were compared to recent experimental results. A stochastic model was used to calculate the rapid diffusion and reaction of hydrated electrons with other radiolysis products. The sensitivity of the calculated yields to the model assumptions and comparison with experimental data are discussed
Radial transport of radiation belt electrons due to stormtime Pc5 waves
Directory of Open Access Journals (Sweden)
A. Y. Ukhorskiy
2009-05-01
Full Text Available During geomagnetic storms relativistic electron fluxes in the outer radiation belt exhibit dynamic variability over multiple orders of magnitude. This requires radial transport of electrons across their drift shells and implies violation of their third adiabatic invariant. Radial transport is induced by the interaction of the electron drift motion with electric and magnetic field fluctuations in the ULF frequency range. It was previously shown that solar-wind driven ULF waves have long azimuthal wave lengths and thus can violate the third invariant of trapped electrons in the process of resonant interaction with their gradient-curvature motion. However, the amplitude of solar-wind driven ULF waves rapidly decreases with decreasing L. It is therefore not clear what mechanisms are responsible for fast transport rates observed inside the geosynchronous orbit. In this paper we investigate wether stormtime Pc5 waves can contribute to this process. Stormtime Pc5s have short azimuthal wave lengths and therefore cannot exhibit resonance with the the electron drift motion. However we show that stormtime Pc5s can cause localized random scattering of electron drift motion that violates the third invariant. According to our results electron interaction with stormtime Pc5s can produce rapid radial transport even as low as L≃4. Numerical simulations show that electron transport can exhibit large deviations from radial diffusion. The diffusion approximation is not valid for individual storms but only applies to the statistically averaged response of the outer belt to stormtime Pc5 waves.
Electronic transport in graphene nanoribbons with sublattice-asymmetric doping
DEFF Research Database (Denmark)
Aktor, Thomas; Jauho, Antti-Pekka; Power, Stephen
2016-01-01
Recent experimental findings and theoretical predictions suggest that nitrogen-doped CVD-grown graphene may give rise to electronic band gaps due to impurity distributions which favor segregation on a single sublattice. Here, we demonstrate theoretically that such distributions lead to more complex...... behavior in the presence of edges, where geometry determines whether electrons in the sample view the impurities as a gap-opening average potential or as scatterers. Zigzag edges give rise to the latter case, and remove the electronic band gaps predicted in extended graphene samples.We predict...
2010-07-01
... keeping my agency's electronic commerce transportation billing records? 102-118.80 Section 102-118.80... Transportation and Transportation Services § 102-118.80 Who is responsible for keeping my agency's electronic commerce transportation billing records? Your agency's internal financial regulations will identify...
Numerical design of electron guns and space charge limited transport systems
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.
1980-10-01
This paper describes the capabilities and limitations of computer programs used to design electron guns and similarly space-charge limited transport systems. Examples of computer generated plots from several different types of gun problems are included
Electron transport system activity of microfouling material: Relationships with biomass parameters
Digital Repository Service at National Institute of Oceanography (India)
Bhosle, N.B.; Tulaskar, A.; Wagh, A.B.
Microfouling material developed on aluminium panels immersed in surface waters of the Dona Paula Bay, Goa India was analysed for biomass (measured as dry weight, organic crabon, protein and chlorophyll @ia@@) and electron transport system actitity...
CSIR Research Space (South Africa)
Adekunle, AS
2010-06-01
Full Text Available This work describes the electron transport and electrocatalytic properties of chemically-synthesized nickel (Ni) and nickel oxide (NiO) nanoparticles supported on multi-walled carbon nanotubes (MWCNT) platforms. Successful modification...
Energy Technology Data Exchange (ETDEWEB)
Wook Kim, Jin; Yoo, Seung Il; Sung Kang, Jin [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Eun Lee, Song; Kwan Kim, Young [Department of Information Display, Hongik University, Seoul 121-791 (Korea, Republic of); Hwa Yu, Hyeong; Turak, Ayse [Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada); Young Kim, Woo, E-mail: wykim@hoseo.edu [Department of Green Energy & Semiconductor Engineering, Hoseo University, Asan 336-795 (Korea, Republic of); Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)
2015-06-28
We analyzed the performance of multi-emissive white phosphorescent organic light-emitting diodes (PHOLEDs) in relation to various red emitting sites of hole and electron transport layers (HTL and ETL). The shift of the recombination zone producing stable white emission in PHOLEDs was utilized as luminance was increased with red emission in its electron transport layer. Multi-emissive white PHOLEDs including the red light emitting electron transport layer yielded maximum external quantum efficiency of 17.4% with CIE color coordinates (−0.030, +0.001) shifting only from 1000 to 10 000 cd/m{sup 2}. Additionally, we observed a reduction of energy loss in the white PHOLED via Ir(piq){sub 3} as phosphorescent red dopant in electron transport layer.
Energy Technology Data Exchange (ETDEWEB)
Jeon, Soon Ok [Department of Polymer Science and Engineering, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of); Lee, Jun Yeob, E-mail: leej17@dankook.ac.kr [Department of Polymer Science and Engineering, Dankook University, Jukjeon-dong, Suji-gu, Yongin-si, Gyeonggi-do 448-701 (Korea, Republic of)
2011-05-16
Research highlights: {yields} Pyridine based host material for red phosphorescent organic light emitting diode. {yields} Device optimization at low doping concentration of 2%. {yields} Simplified red phosphorescent organic light emitting diodes. - Abstract: Pyridine based electron transport type host materials were developed and their device performances were investigated according to doping concentration. The pyridine substituent was combined with a spirofluorenebenzofluorene core unit and a high quantum efficiency of 13.3% was achieved in red phosphorescent organic light-emitting diodes at a low doping concentration of 2%. A simple red device without any electron transport layer could be fabricated and a simple device without any electron transport layer showed better power efficiency than the standard device with an electron transport layer.
Surface electronic transport measurements: A micro multi-point probe approach
DEFF Research Database (Denmark)
Barreto, Lucas
2014-01-01
This work is mostly focused on the study of electronic transport properties of two-dimensional materials, in particular graphene and topological insulators. To study these, we have improved a unique micro multi-point probe instrument used to perform transport measurements. Not only the experimental...... quantities are extracted, such as conductivity, carrier density and carrier mobility. • A method to insulate electrically epitaxial graphene grown on metals, based on a stepwise intercalation methodology, is developed and transport measurements are performed in order to test the insulation. • We show...... a direct measurement of the surface electronic transport on a bulk topological insulator. The surface state conductivity and mobility are obtained. Apart from transport properties, we also investigate the atomic structure of the Bi2Se3(111) surface via surface x-ray diraction and low-energy electron...
International Nuclear Information System (INIS)
Bliokh, Yu.P.
2001-01-01
During more than 50 years of Plasma Electronics development a great number of experimental and theoretical results have been achieved. These results allow understanding of physical processes which originate under charged particles beams interaction with a plasma. However, one essential aspect of such interaction remains insufficiently studied. The question is about a correlation between conditions of microwave excitation by a beam in plasma and plasma parameters. Each of these effects, namely the influence of plasma parameters on conditions of microwave excitation by a beam and plasma parameters variations under the influence of propagating microwave radiation are well known and investigated enough. However their common action under beam-plasma instability (BPI) development were not studied systematically, although the role of such reciprocal influence on character of these processes may be very large. The aim of this report is a review of recent theoretical and experimental investigations of such plasma nonlinearity in plasma-filled trawling-wave tubes. N.M.Zemlyansky and E.A.Kornilov have done experiments in Kharkov Institute of Physics and Technology (KhPhTI). Development of the theoretical model was started in KhPhTI (Yu.P.Bliokh, Ya.B.Fainberg, M.G.Lyubarsky, and V.O.Podobinsky) and continues by author in Technion. The developed theory takes into account two main reasons of the plasma density redistribution: high frequency pressure (HFP) force which ''push out'' plasma from the regions with increased microwave amplitude, or microwave discharge, which appears in the region where amplitude is large enough. Displaced (under HFP action) or additionally originating (under (BPD) development) plasma propagates from the disturbance source in the form of slow plasma waves (for example, ion-sound or magneto-sound waves), and the BPI develops in the nonhomogeneous plasma. It changes both magnitude and longitudinal distribution of excited microwave amplitude. As a result
Electron transport in NH3/NO2 sensed buckled antimonene
Srivastava, Anurag; Khan, Md. Shahzad; Ahuja, Rajeev
2018-04-01
The structural and electronic properties of buckled antimonene have been analysed using density functional theory based ab-initio approach. Geometrical parameters in terms of bond length and bond angle are found close to the single ruffle mono-layer of rhombohedral antimony. Inter-frontier orbital analyses suggest localization of lone pair electrons at each atomic centre. Phonon dispersion along with high symmetry point of Brillouin zone does not signify any soft mode. With an electronic band gap of 1.8eV, the quasi-2D nano-surface has been further explored for NH3/NO2 molecules sensing and qualities of interaction between NH3/NO2 gas and antimonene scrutinized in terms of electronic charges transfer. A current-voltage characteristic has also been analysed, using Non Equilibrium Green's function (NEGF), for antimonene, in presence of incoming NH3/NO2 molecules.
Ultrafast electron transport across nano gaps in nanowire circuits
Energy Technology Data Exchange (ETDEWEB)
Potma, Eric O. [Univ. of California, Irvine, CA (United States)
2015-07-31
In this Program we aim for a closer look at electron transfer through single molecules. To achieve this, we use ultrafast laser pulses to time stamp an electron tunneling event in a molecule that is connected between two metallic electrodes, while reading out the electron current. A key aspect of this project is the use of metallic substrates with plasmonic activity to efficiently manipulate the tunneling probability. The first Phase of this program is concerned with developing highly sensitive tools for the ultrafast optical manipulation of tethered molecules through the evanescent surface field of plasmonic substrates. The second Phase of the program aims to use these tools for exercising control over the electron tunneling probability.
Optical properties and electron transport in low-dimensional nanostructures
Czech Academy of Sciences Publication Activity Database
Král, Karel; Menšík, Miroslav
2011-01-01
Roč. 54, 2-2 (2011), s. 4-13 ISSN 0021-3411 R&D Projects: GA MŠk(CZ) OC10007 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z40500505 Keywords : quantum dots * electron-photon interaction * optical properties * electron relaxation * DNA molecule Subject RIV: BE - Theoretical Physics http:// elibrary .ru/contents.asp?issueid=1010336
5D simulation study of suprathermal electron transport in non-axisymmetric plasmas
International Nuclear Information System (INIS)
Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.
1999-01-01
ECRH-driven transport of suprathermal electrons is studied in non-axisymmetric plasmas using a new Monte Carlo simulation technique in 5D phase space. Two different phases of the ECRH-driven transport of suprathermal electrons can be seen; one is a rapid convective phase due to the direct radial motion of trapped electrons and the other is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile is clarified in W7-AS. The ECRH driven flux is also evaluated and put in relation with the 'electron root' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity and, thus, the observed 'electron root' feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. The possible scenario of this 'ECRH-driven electron root' is considered in the LHD plasma. (author)
Hemschemeier, Anja; Happe, Thomas
2011-08-01
Oxygenic photosynthesis uses light as energy source to generate an oxidant powerful enough to oxidize water into oxygen, electrons and protons. Upon linear electron transport, electrons extracted from water are used to reduce NADP(+) to NADPH. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor during respiratory electron transport and as oxidant and/or "substrate" in a number of biosynthetic pathways. Though photosynthesis of higher plants, algae and cyanobacteria produces oxygen, there are conditions under which this type of photosynthesis operates under hypoxic or anaerobic conditions. In the unicellular green alga Chlamydomonas reinhardtii, this condition is induced by sulfur deficiency, and it results in the production of molecular hydrogen. Research on this biotechnologically relevant phenomenon has contributed largely to new insights into additional pathways of photosynthetic electron transport, which extend the former concept of linear electron flow by far. This review summarizes the recent knowledge about various electron sources and sinks of oxygenic photosynthesis besides water and NADP(+) in the context of their contribution to hydrogen photoproduction by C. reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts. Copyright © 2011 Elsevier B.V. All rights reserved.
Spin dependent transport of hot electrons through ultrathin epitaxial metallic films
Energy Technology Data Exchange (ETDEWEB)
Heindl, Emanuel
2010-06-23
In this work relaxation and transport of hot electrons in thin single crystalline metallic films is investigated by Ballistic Electron Emission Microscopy. The electron mean free paths are determined in an energy interval of 1 to 2 eV above the Fermi level. While fcc Au-films appear to be quite transmissive for hot electrons, the scattering lengths are much shorter for the ferromagnetic alloy FeCo revealing, furthermore, a strong spin asymmetry in hot electron transport. Additional information is gained from temperature dependent studies in combination with golden rule approaches in order to disentangle the impact of several relaxation and transport properties. It is found that bcc Fe-films are much less effective in spin filtering than films made of the FeCo-alloy. (orig.)
Nonlinear Spatio-Temporal Dynamics and Chaos in Semiconductors
Schöll, Eckehard
2005-08-01
Nonlinear transport phenomena are an increasingly important aspect of modern semiconductor research. This volume deals with complex nonlinear dynamics, pattern formation, and chaotic behavior in such systems. It bridges the gap between two well-established fields: the theory of dynamic systems and nonlinear charge transport in semiconductors. This unified approach helps reveal important electronic transport instabilities. The initial chapters lay a general framework for the theoretical description of nonlinear self-organized spatio-temporal patterns, such as current filaments, field domains, fronts, and analysis of their stability. Later chapters consider important model systems in detail: impact ionization induced impurity breakdown, Hall instabilities, superlattices, and low-dimensional structures. State-of-the-art results include chaos control, spatio-temporal chaos, multistability, pattern selection, activator-inhibitor kinetics, and global coupling, linking fundamental issues to electronic device applications. This book will be of great value to semiconductor physicists and nonlinear scientists alike.
Electron-hole collision limited transport in charge-neutral bilayer graphene
Nam, Youngwoo; Ki, Dong-Keun; Soler-Delgado, David; Morpurgo, Alberto F.
2017-12-01
Ballistic transport occurs whenever electrons propagate without collisions deflecting their trajectory. It is normally observed in conductors with a negligible concentration of impurities, at low temperature, to avoid electron-phonon scattering. Here, we use suspended bilayer graphene devices to reveal a new regime, in which ballistic transport is not limited by scattering with phonons or impurities, but by electron-hole collisions. The phenomenon manifests itself in a negative four-terminal resistance that becomes visible when the density of holes (electrons) is suppressed by gate-shifting the Fermi level in the conduction (valence) band, above the thermal energy. For smaller densities, transport is diffusive, and the measured conductivity is reproduced quantitatively, with no fitting parameters, by including electron-hole scattering as the only process causing velocity relaxation. Experiments on a trilayer device show that the phenomenon is robust and that transport at charge neutrality is governed by the same physics. Our results provide a textbook illustration of a transport regime that had not been observed previously and clarify the nature of conduction through charge-neutral graphene under conditions in which carrier density inhomogeneity is immaterial. They also demonstrate that transport can be limited by a fully electronic mechanism, originating from the same microscopic processes that govern the physics of Dirac-like plasmas.
Nonlinear electron acoustic structures generated on the high-potential side of a double layer
Directory of Open Access Journals (Sweden)
R. Pottelette
2009-04-01
Full Text Available High-time resolution measurements of the electron distribution function performed in the auroral upward current region reveals a large asymmetry between the low- and high-potential sides of a double-layer. The latter side is characterized by a large enhancement of a locally trapped electron population which corresponds to a significant part (~up to 30% of the total electron density. As compared to the background hot electron population, this trapped component has a very cold temperature in the direction parallel to the static magnetic field. Accordingly, the differential drift between the trapped and background hot electron populations generates high frequency electron acoustic waves in a direction quasi-parallel to the magnetic field. The density of the trapped electron population can be deduced from the frequency where the electron acoustic spectrum maximizes. In the auroral midcavity region, the electron acoustic waves may be modulated by an additional turbulence generated in the ion acoustic range thanks to the presence of a pre-accelerated ion beam located on the high-potential side of the double layer. Electron holes characterized by bipolar pulses in the electric field are sometimes detected in correlation with these electron acoustic wave packets.
Computer control of the beam transport system of the Chalk River electron test accelerator
International Nuclear Information System (INIS)
McMichael, G.E.; Kidner, S.H.; Fraser, J.S.
1977-05-01
The beam transport system of the Chalk River Electron Test Accelerator comprises steering coils and solenoidal focusing magnets driven by voltage-programmed, current-regulated power supplies. This report describes the beam transport and beam diagnostics systems presently in use. The computer controls all beam transport magnets from a single, allocatable control knob. The system is currently being expanded to two knobs and two readouts. (author)
The effect of magnetic field and disorders on the electronic transport in graphene nanoribbons
Bala Kumar, S.; Jalil, M. B. A.; Tan, S. G.; Liang, Gengchiau
2010-09-01
We developed a unified mesoscopic transport model for graphene nanoribbons, which combines the nonequilibrium Green's function (NEGF) formalism with the real-space π-orbital model. Based on this model, we probe the spatial distribution of electrons under a magnetic field, in order to obtain insights into the various signature Hall effects in disordered armchair graphene nanoribbons (AGNR). In the presence of a uniform perpendicular magnetic field (B^{ \\perp } -field), a perfect AGNR shows three distinct spatial current profiles at equilibrium, depending on its width. Under nonequilibrium conditions (i.e. in the presence of an applied bias), the net electron flow is restricted to the edges and occurs in opposite directions depending on whether the Fermi level lies within the valence or conduction band. For electrons at an energy level below the conduction window, the B^{ \\perp } -field gives rise to local electron flux circulation, although the global flux is zero. Our study also reveals the suppression of electron backscattering as a result of the edge transport which is induced by the B^{ \\perp } -field. This phenomenon can potentially mitigate the undesired effects of disorder, such as bulk and edge vacancies, on the transport properties of AGNR. Lastly, we show that the effect of B^{ \\perp } -field on electronic transport is less significant in the multimode compared to the single-mode electron transport.
Electronic spin transport in graphene field-effect transistors
Popinciuc, M.; Jozsa, C.; Zomer, P. J.; Tombros, N.; Veligura, A.; Jonkman, H. T.; van Wees, B. J.
2009-01-01
Spin transport experiments in graphene, a single layer of carbon atoms ordered in a honeycomb lattice, indicate spin-relaxation times that are significantly shorter than the theoretical predictions. We investigate experimentally whether these short spin-relaxation times are due to extrinsic factors,
Electron transport in edge-disordered graphene nanoribbons
DEFF Research Database (Denmark)
Saloriutta, Karri; Hancock, Y.; Karkkainen, Asta
2011-01-01
Ab initio methods are used to study the spin-resolved transport properties of graphene nanoribbons (GNRs) that have both chemical and structural edge disorder. Oxygen edge adsorbates on ideal and protruded ribbons are chosen as representative examples, with the protrusions forming the smallest...
Transport properties and electronic structure of epitaxial tunnel junctions
Czech Academy of Sciences Publication Activity Database
Freyss, M.; Papanikolaou, N.; Bellini, V.; Zeller, R.; Dederichs, P.; Turek, Ilja
2002-01-01
Roč. 240, 1/3 (2002), s. 117-120 ISSN 0304-8853 R&D Projects: GA ČR GA106/02/0943; GA MŠk ME 374 Institutional research plan: CEZ:AV0Z2041904 Keywords : junctions * transport Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.046, year: 2002
Odell, Anders
2011-10-03
The influence of the electrode\\'s Fermi surface on the transport properties of a photoswitching molecule is investigated with state-of-the-art ab initio transport methods. We report results for the conducting properties of the two forms of dithienylethene attached either to Ag or to nonmagnetic Ni leads. The I-V curves of the Ag/dithienylethene/Ag device are found to be very similar to those reported previously for Au. In contrast, when Ni is used as the electrode material the zero-bias transmission coefficient is profoundly different as a result of the role played by the Ni d bands in the bonding between the molecule and the electrodes. Intriguingly, despite these differences the overall conducting properties depend little on the electrode material. We thus conclude that electron transport in dithienylethene is, for the cases studied, mainly governed by the intrinsic electronic structure of the molecule. © 2011 American Physical Society.
Directory of Open Access Journals (Sweden)
S. C. Buchert
2008-09-01
Full Text Available Observations by the EISCAT Svalbard radar show that electron temperatures Te in the cusp electrojet reach up to about 4000 K. The heat is tapped and converted from plasma convection in the near Earth space by a Pedersen current that is carried by electrons due to the presence of irregularities and their demagnetising effect. The heat is transfered to the neutral gas by collisions. In order to enhance Te to such high temperatures the maximally possible dissipation at 50% demagnetisation must nearly be reached. The effective Pedersen conductances are found to be enhanced by up to 60% compared to classical values. Conductivities and conductances respond significantly to variations of the electric field strength E, and "Ohm's law" for the ionosphere becomes non-linear for large E.
International Nuclear Information System (INIS)
Mirza, Arshad M.; Hasan, Asma; Azeem, M.; Saleem, H.
2003-01-01
It is found that the low-frequency ion acoustic and electrostatic drift waves can become unstable in uniform electron-ion and electron-positron-ion plasmas due to the ion shear flow. In a collisional plasma a drift-dissipative instability can also take place. In the presence of collisions the temporal behavior of nonlinear drift-dissipative mode can be represented in the form of well-known Lorenz and Stenflo type equations that admit chaotic trajectories. On the other hand, a quasi-stationary solution of the mode coupling equations can be represented in the form of monopolar vortex. The results of the present investigation can be helpful in understanding electrostatic turbulence and wave phenomena in laboratory and astrophysical plasmas
Power electronics applied to industrial systems and transports
Patin, Nicolas
2015-01-01
Power electronics is based on the switching operating mode of semiconductor components. On this basis, the concepts of type (voltage or current) and reversibility of interconnected sources make it possible to apply a methodology for the synthesis of various types of converters. This book also focuses on the importance of packaging by reviewing the electrical representation of components’ thermal models and the currently available electronics’ cooling technologies. Modeling is discussed, as well as different technological aspects used in the engineering design of an electronic power converter, useful for obtaining satisfactory performance and reliability.
New electron multiple scattering distributions for Monte Carlo transport simulation
Energy Technology Data Exchange (ETDEWEB)
Chibani, Omar (Haut Commissariat a la Recherche (C.R.S.), 2 Boulevard Franz Fanon, Alger B.P. 1017, Alger-Gare (Algeria)); Patau, Jean Paul (Laboratoire de Biophysique et Biomathematiques, Faculte des Sciences Pharmaceutiques, Universite Paul Sabatier, 35 Chemin des Maraichers, 31062 Toulouse cedex (France))
1994-10-01
New forms of electron (positron) multiple scattering distributions are proposed. The first is intended for use in the conditions of validity of the Moliere theory. The second distribution takes place when the electron path is so short that only few elastic collisions occur. These distributions are adjustable formulas. The introduction of some parameters allows impositions of the correct value of the first moment. Only positive and analytic functions were used in constructing the present expressions. This makes sampling procedures easier. Systematic tests are presented and some Monte Carlo simulations, as benchmarks, are carried out. ((orig.))
Kline, J.; Afeyan, B.; Bertsche, W.; Kurnit, N.; Montgomery, D.; Savchenko, V.; Won, K.
2004-11-01
Vlasov-Poisson simulations using ponderomotively driven excitations have discovered the existence of stable, nonlinear, multimode coherent structures in plasmas named Kinetic Electrostatic Electron Nonlinear (KEEN) waves.^1 For a given wave number drive, they seem to form and persist for any drive frequency in a band around the electron acoustic^2 frequency. An experiment was recently conducted on Trident jointly by Polymath Research Inc. and LANL to verify these findings. The two lasers used had 527 and 600 nm wavelengths which is predicted to drive waves in the proper KEEN wave excitation band.^1 A Raman cell was developed and fielded on the TRIDENT Laser to convert a 527 nm laser beam to 600 or 697 nm as needed via first or second Stokes emission in N2 gas. Using two beams at these wavelengths, KEEN waves were driven and detected with 263 nm Thomson scattering in a Nitrogen plus Hydrogen gas jet plasma. This presentation will cover experimental conditions and diagnostic attributes associated with the detection of KEEN waves. **Supported by DOE Academic Alliance Grant DE-FG03-03NA00059 and LANL ^1Afeyan et al., Optical Mixing Generated KEEN Waves, IFSA Conference Proceedings, 2003; Invited paper at this conference and to be published. ^2Montgomery et al., PRL 87, 155001 (2001)
5D simulation study of suprathermal electron transport in non-axisymmetric plasmas
International Nuclear Information System (INIS)
Murakami, S.; Idei, H.; Kubo, S.; Nakajima, N.; Okamoto, M.; Gasparino, U.; Maassberg, H.; Rome, M.; Marushchenko, N.
2001-01-01
ECRH-driven transport of is studied in using a new Monte Carlo simulation technique in 5D phase space. Two different phases of the ECRH-driven transport of suprathermal electrons can be seen; one is a rapid convective phase due to the direct radial motion of trapped electrons and the other is a slower phase due to the collisional transport. The important role of the radial transport of suprathermal electrons in the broadening of the ECRH deposition profile is clarified in W7-AS. The ECRH driven flux is also evaluated and put in relation with the ''electron root'' feature recently observed in W7-AS. It is found that, at low collisionalities, the ECRH driven flux due to the suprathermal electrons can play a dominant role in the condition of ambipolarity and, thus, the observed ''electron root'' feature in W7-AS is thought to be driven by the radial (convective) flux of ECRH generated suprathermal electrons. The possible scenario of this ''ECRH-driven electron root'' is considered in the LHD plasma. (author)
The role of transition metal interfaces on the electronic transport in lithium–air batteries
DEFF Research Database (Denmark)
Chen, Jingzhe; Hummelshøj, Jens S.; Thygesen, Kristian Sommer
2011-01-01
Low electronic conduction is expected to be a main limiting factor in the performance of reversible lithium–air, Li–O2, batteries. Here, we apply density functional theory and non-equilibrium Green's function calculations to determine the electronic transport through lithium peroxide, Li2O2, form...
Cytochrome C And The Role Of Zinc Ions In Electron Transport In ...
African Journals Online (AJOL)
The inhibition of electron transfer by zinc ions in the electron transport system of the rat liver mitochondria was investigated. There was an increase in the rate at which oxygen was consumed in rat liver mitochondria pre-incubated with cytochrome c. However, the rate of inhibition of oxygen consumption by zinc ions was ...
The multiplicity of dehydrogenases in the electron transport chain of plant mitochondria
DEFF Research Database (Denmark)
Rasmusson, Allan G; Geisler, Daniela A; Møller, Ian Max
2008-01-01
The electron transport chain in mitochondria of different organisms contains a mixture of common and specialised components. The specialised enzymes form branches to the universal electron path, especially at the level of ubiquinone, and allow the chain to adjust to different cellular and metabolic...
Electron transport in n-doped Si/SiGe quantum cascade structures
Lazic, I.; Ikonic, Z.; Milanovic, V.; Kelsall, R.W.; Indjin, D.; Harrison, P.
2007-01-01
An electron transport model in n-Si/SiGe quantum cascade or superlattice structures is described. The model uses the electronic structure calculated within the effective-mass complex-energy framework, separately for perpendicular (Xz) and in-plane (Xxy) valleys, the degeneracy of which is lifted by
Spin-polarized transport in a two-dimensional electron gas with interdigital-ferromagnetic contacts
DEFF Research Database (Denmark)
Hu, C.-M.; Nitta, Junsaku; Jensen, Ane
2001-01-01
Ferromagnetic contacts on a high-mobility, two-dimensional electron gas (2DEG) in a narrow gap semiconductor with strong spin-orbit interaction are used to investigate spin-polarized electron transport. We demonstrate the use of magnetized contacts to preferentially inject and detect specific spi...
First-principles study of electron transport through monatomic Al and Na wires
DEFF Research Database (Denmark)
Kobayashi, Nobuhiko; Brandbyge, Mads; Tsukada, Masaru
2000-01-01
We present first-principles calculations of electron transport, in particular, the conduction channels of monatomic Al and Na atom wires bridged between metallic jellium electrodes. The electronic structures are calculated by the first-principles recursion-transfer matrix method, and the conducti...
Effects of model approximations for electron, hole, and photon transport in swift heavy ion tracks
Czech Academy of Sciences Publication Activity Database
Rymzhanov, R.A.; Medvedev, Nikita; Volkov, A.E.
2016-01-01
Roč. 388, Dec (2016), s. 41-52 ISSN 0168-583X R&D Projects: GA MŠk LG15013 Institutional support: RVO:68378271 Keywords : swift heavy ion * electronic stopping * TREKIS * Monte Carlo * electronic kinetics * photon transport Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.109, year: 2016
Theory of high-field electronic transport in bulk ZnS and ZnSe
Brennan, Kevin
1988-01-01
This paper theoretically investigates the nature of electronic transport and the high-energy tails of the electron distribution functions in bulk ZnSe and ZnS as a function of the applied electric field were investigated using calculations based on an ensemble Monte Carlo model. The calculations include the full details of the first two conduction bands as well as the full-order treatment of the electron-phonon scattering mechanisms. Results of high-field electronic transport calculations show that the electron energy distribution function is significanty cooler in ZnS than in ZnSe at comparable electric field strengths. The cooler distribution in ZnS is due to the much greater electron scattering rate. Consequently, it is more difficult to achieve carrier heating to comparable energies in ZnS than in ZnSe.
Influence of electron transport on the efficiency of polymer-based solar cells
Energy Technology Data Exchange (ETDEWEB)
Kuxhaus, Viktor; Jaiser, Frank; Neher, Dieter [Institute of Physics and Astronomy, University Potsdam (Germany); Voges, Frank [Merck KGaA, Darmstadt (Germany)
2010-07-01
Recently, we showed that the mobility of electrons in polymer-based solar cells has a large influence on the overall performance of such devices. Here, we investigate the correlation between electron mobility and charge generation efficiency in organic bilayer solar cells for a series of electron transporting materials (ETMs) with comparable HOMO and LUMO levels. The electron mobility was measured by transient electroluminescence. Here, a thin M3EH-PPV was used as a sensing layer. The interface between M3EH-PPV and ETM acted as a recombination zone of electrons transported through the ETM layer and holes that are blocked at the interface. Therefore, the electron mobility can easily be determined from the onset of M3EH-PPV emission which is spectrally well separated from the ETM emission. To determine the charge generation efficiency, the different ETMs were combined in bilayer solar cell with PFB as donator.
International Nuclear Information System (INIS)
Dmitriy Y. Anistratov; Adrian Constantinescu; Loren Roberts; William Wieselquist
2007-01-01
This is a project in the field of fundamental research on numerical methods for solving the particle transport equation. Numerous practical problems require to use unstructured meshes, for example, detailed nuclear reactor assembly-level calculations, large-scale reactor core calculations, radiative hydrodynamics problems, where the mesh is determined by hydrodynamic processes, and well-logging problems in which the media structure has very complicated geometry. Currently this is an area of very active research in numerical transport theory. main issues in developing numerical methods for solving the transport equation are the accuracy of the numerical solution and effectiveness of iteration procedure. The problem in case of unstructured grids is that it is very difficult to derive an iteration algorithm that will be unconditionally stable
Non-Linear Beam Transport System for the LENS 7 MeV Proton Beam
Jones, William P; Derenchuk, Vladimir Peter; Rinckel, Thomas; Solberg, Keith
2005-01-01
A beam transport system has been designed to carry a high-intensity low-emittance proton beam from the exit of the RFQ-DTL acceleration system of the Indiana University Low Energy Neutron System (LENS)* to the neutron production target. The goal of the design was to provide a beam of uniform density over a 3cm by 3cm area at the target. Two octupole magnets** are employed in the beam line to provide the necessary beam phase space manipulations to achieve this goal. First order calculations were done using TRANSPORT and second order calculations have been performed using TURTLE. Second order simulations have been done using both a Gaussian beam distribution and a particle set generated by calculations of beam transport through the RFQ-DTL using PARMILA. Comparison of the design characteristics with initial measurements from the LENS commissioning process will be made.
Electronic Monitoring Of Storage And Transport Temperatures Of ...
African Journals Online (AJOL)
change in locations, type of carriage and storage. The data logger was sent back after the vaccination campaign and data were retrieved using a Tinytag Explorer software. The results showed that I-2 vaccine was stored and transported in temperatures within the range of 1.06ºC to 28.77ºC (average17.50ºC). The storage ...
Intermittent transport and relaxation oscillations of nonlinear reduced models for fusion plasmas
International Nuclear Information System (INIS)
Hamaguchi, S.; Takeda, K.; Bierwage, A.; Tsurimaki, S.; Sato, H.; Unemura, T.; Wakatani, M.; Benkadda, S.
2005-01-01
Generation of sheared flows and their effects on turbulent transport are studied for ion temperature gradient (ITG) driven instability and resistive drift instability. With the use of low degree-of-freedom models as well as the full partial differential equation (PDE) models, the minimum mode structures have been identified that are required for the generation of intermittent transport and relaxation oscillations. Generation of turbulence due to magnetohydrodynamic (MHD) instabilities and their roles in the control of stellarator and tokamak plasmas are also discussed. (author)
Goikhman, M. B.; Gromov, A. V.; Kovalev, N. F.; V. Palitsin, A.
2016-12-01
We consider the properties of thin-walled, strongly magnetized electron beams in closed evacuated transportation channels with arbitrary cross sections of the channel and the electron beam. Explicit precise formulas are obtained for the limiting and Fedosov's currents of such electron beams. The found relationships allow one to explain many observed phenomena and can serve as a basis for verification of the results of more complicated calculations.
Diameter-dependent electronic transport properties of Au-catalyst/Ge-nanowire Schottky diodes
Energy Technology Data Exchange (ETDEWEB)
Picraux, S Thomas [Los Alamos National Laboratory; Leonard, Francois [SNL; Swartzentruber, Brian S [SNL; Talin, A Alee [SNL
2008-01-01
We present electronic transport measurements in individual Au-catalyst/Ge-nanowire interfaces demonstrating the presence of a Schottky barrier. Surprisingly, the small-bias conductance density increases with decreasing diameter. Theoretical calculations suggest that this effect arises because electron-hole recombination in the depletion region is the dominant charge transport mechanism, with a diameter dependence of both the depletion width and the electron-hole recombination time. The recombination time is dominated by surface contributions and depends linearly on the nanowire diameter.
Yu, Minghao; Kihara, Hisashi; Abe, Ken-ichi; Takahashi, Yusuke
2015-06-01
A relatively simple method for calculating accurately the third-order electron transport properties of nitrogen and air thermal plasmas is presented. The electron transport properties, such as the electrical conductivity and the electron thermal conductivity, were computed with the best and latest available collision cross-section data in the temperature and pressure ranges of T = 300 - 15000 K and p = 0.01 - 1.0 atm, respectively. The results obtained under the atmospheric pressure condition showed good agreements with the experimental and the high-accuracy theoretical results. The presently-introduced method has good application potential in numerical simulations of nitrogen and air inductively-coupled plasmas.
Manipulating NiFe/AlOx interfacial chemistry for the spin-polarized electrons transport
International Nuclear Information System (INIS)
Zhao, Chong-Jun; Sun, Li; Ding, Lei; Li, Jian-Wei; Zhang, Jing-Yan; Cao, Yi; Yu, Guang-Hua
2013-01-01
Through vacuum annealing, interfacial chemical composition of sputter-deposited AlO x /NiFe/AlO x can be controlled for electron transport manipulation. Chemical status change at the NiFe/AlO x interface was quantified by X-ray photoelectron spectroscopy and correlated to the structure and electron transport properties of the heterostructure. It is found that elemental Al existed in the insulting AlO x after annealing at intermediate temperature can improve the AlO x /NiFe interface and thus favor the electronic transport. Annealing at higher temperature will result in native AlO x formation and degrade transport properties due to the NiFe/AlO x interfaces deterioration caused by significant difference in thermal expansion coefficients of the two materials.
Tuning the electronic transport properties of graphene through functionalisation with fluorine
Directory of Open Access Journals (Sweden)
Dubois Marc
2011-01-01
Full Text Available Abstract We demonstrate the possibility to tune the electronic transport properties of graphene mono-layers and multi-layers by functionalisation with fluorine. For mono-layer samples, with increasing the fluorine content, we observe a transition from electronic transport through Mott variable range hopping (VRH in two dimensions to Efros-Shklovskii VRH. Multi-layer fluorinated graphene with high concentration of fluorine show two-dimensional Mott VRH transport, whereas CF0.28 multi-layer flakes exhibit thermally activated transport through near neighbour hopping. Our experimental findings demonstrate that the ability to control the degree of functionalisation of graphene is instrumental to engineer different electronic properties in graphene materials.
Steepest entropy ascent quantum thermodynamic model of electron and phonon transport
Li, Guanchen; von Spakovsky, Michael R.; Hin, Celine
2018-01-01
An advanced nonequilibrium thermodynamic model for electron and phonon transport is formulated based on the steepest-entropy-ascent quantum thermodynamics framework. This framework, based on the principle of steepest entropy ascent (or the equivalent maximum entropy production principle), inherently satisfies the laws of thermodynamics and mechanics and is applicable at all temporal and spatial scales even in the far-from-equilibrium realm. Specifically, the model is proven to recover the Boltzmann transport equations in the near-equilibrium limit and the two-temperature model of electron-phonon coupling when no dispersion is assumed. The heat and mass transport at a temperature discontinuity across a homogeneous interface where the dispersion and coupling of electron and phonon transport are both considered are then modeled. Local nonequilibrium system evolution and nonquasiequilibrium interactions are predicted and the results discussed.
International Nuclear Information System (INIS)
Gao, Tao; Xu, Ruimin; Kong, Yuechan; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng
2015-01-01
We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr 0.52 Ti 0.48 )-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (g m -V g ) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric
Energy Technology Data Exchange (ETDEWEB)
Gao, Tao [Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu 611731 (China); Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016 (China); Xu, Ruimin [Fundamental Science on EHF Laboratory, University of Electronic Science and Technology of China (UESTC), Chengdu 611731 (China); Kong, Yuechan, E-mail: kycfly@163.com; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng [Science and Technology on Monolithic Integrated Circuits and Modules Laboratory, Nanjing Electronic Devices Institute, Nanjing 210016 (China)
2015-06-15
We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr{sub 0.52}Ti{sub 0.48})-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (g{sub m}-V{sub g}) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.
Gao, Tao; Xu, Ruimin; Kong, Yuechan; Zhou, Jianjun; Kong, Cen; Dong, Xun; Chen, Tangsheng
2015-06-01
We demonstrate highly improved linearity in a nonlinear ferroelectric of Pb(Zr0.52Ti0.48)-gated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT). Distinct double-hump feature in the transconductance-gate voltage (gm-Vg) curve is observed, yielding remarkable enhancement in gate voltage swing as compared to MIS-HEMT with conventional linear gate dielectric. By incorporating the ferroelectric polarization into a self-consistent calculation, it is disclosed that in addition to the common hump corresponding to the onset of electron accumulation, the second hump at high current level is originated from the nonlinear polar nature of ferroelectric, which enhances the gate capacitance by increasing equivalent dielectric constant nonlinearly. This work paves a way for design of high linearity GaN MIS-HEMT by exploiting the nonlinear properties of dielectric.
Tuning electron transport through functionalized C20H10 molecular junctions.
Zoppi, Laura; Ferretti, Andrea; Baldridge, Kim K
2015-10-13
First-principles methodology based on density functional theory (DFT) is used to investigate charge transport phenomena in molecular junctions, with the central active molecular element based on corannulene, C20H10, assembled between two carbon nanotubes (CNT). A number of key factors associated with the design of the molecular nanojunction are shown to have an impact on electron transport to varying degrees, including (I) the composition of the spacer linking the leads to the active element, (II) the composition of the active molecule element, (III) the sensor capabilities of the active element, and (IV) the response of the junction to an external electric field. This study demonstrates the ability to integrate molecular electronic functionality into electronic nanocircuits and provides novel insight into the design of new types of molecular-based devices by revealing the relationship between charge transport mechanisms and the electronic structure of molecular junction components.
Simultaneous Investigation of Hot-electron Transport and Preplasma Formation in Cone-wire Targets
Friesen, H.; Tiedje, H. F.; Singh, S.; Tsui, Y. Y.; Fedosejevs, R.; Ma, T.; Hey, D.; Ping, Y.; Chen, C. D.; Macphee, A.; Key, M. H.; McLean, H. S.; Patel, P.; MacKinnon, A.; Pasley, J.; Akli, K. U.; Stephens, R.; Link, A.; Schumacher, D. W.; Freeman, R. R.; van Woerkom, L. D.; Westover, B.; Wei, M. S.; Beg, F. N.
2010-11-01
The generation and transport of MeV electrons is essential to the realization of Fast Ignition fusion. An important factor in determining the hot electron source is the preplasma distribution that is inevitably formed even in high-contrast short-pulse laser systems. A larger preplasma moves the critical surface further from the region where heating is required, and has a significant effect on the electron source and transport. In this paper we present analysis of results where bremstrahhlung emission from the preplasma region was imaged simultaneously with k-alpha emission from a copper tracer in cone-wire targets using a grazing-incidence x-Kirkpatrick-Baez x-ray microscope. The predicted scalings from simulations and theory will be compared with experimental results to determine unique characteristics of how the hot electron source and transport are affected by the presence of the wire as well as preplasma.
Study on the Electronic Transport Properties of Zigzag GaN Nanotubes
Energy Technology Data Exchange (ETDEWEB)
Li Enling; Wang Xiqiang; Hou Liping; Zhao Danna; Dai Yuanbin [Sciences School, Xi' an University of Technology, Xi' an, China 710054 (China); Wang Xuewen [Electronic Information Science and Technology, Northwest University, Xi' an, China 710068 (China)
2011-02-01
The electronic transport properties of zigzag GaN nanotubes (n, 0) (4 {<=} n {<=} 9) have been calculated using the density functional theory and non-equilibrium Green's functions method. Firstly, the density functional theory (DFT) is used to optimize and calculate the electronic structure of GaNNTs (n, 0) (4{<=}n{<=}9). Secondly, DFT and non-equilibrium Green function (NEGF) method are also used to predict the electronic transport properties of GaNNTs two-probe system. The results showed: there is a corresponding relation between the electronic transport properties and the valley of state density of each GaNNT. In addition, the volt-ampere curve of GaNNT is approximately linear.
High-speed evaluation of track-structure Monte Carlo electron transport simulations.
Pasciak, A S; Ford, J R
2008-10-07
There are many instances where Monte Carlo simulation using the track-structure method for electron transport is necessary for the accurate analytical computation and estimation of dose and other tally data. Because of the large electron interaction cross-sections and highly anisotropic scattering behavior, the track-structure method requires an enormous amount of computation time. For microdosimetry, radiation biology and other applications involving small site and tally sizes, low electron energies or high-Z/low-Z material interfaces where the track-structure method is preferred, a computational device called a field-programmable gate array (FPGA) is capable of executing track-structure Monte Carlo electron-transport simulations as fast as or faster than a standard computer can complete an identical simulation using the condensed history (CH) technique. In this paper, data from FPGA-based track-structure electron-transport computations are presented for five test cases, from simple slab-style geometries to radiation biology applications involving electrons incident on endosteal bone surface cells. For the most complex test case presented, an FPGA is capable of evaluating track-structure electron-transport problems more than 500 times faster than a standard computer can perform the same track-structure simulation and with comparable accuracy.
Energy transport in mirror machine LISA at electron cyclotron resonance
International Nuclear Information System (INIS)
Cunha Rapozo, C. da; Serbeto, A.; Torres-Silva, H.
1993-01-01
It is shown that a classical transport calculation is adequate to predict the steady state temperature of the RF produced plasma in LISA machine for both large and small resonant volumes. Temperature anisotropy ranging from 55 to 305 was found which was larger for small resonant volume, and the temperature relaxation was larger at large resonant one. This agrees with the fact that there is a Coulomb relaxation ν c which is proportional to T e -3/2 . It is also shown that the fitting parameter alpha is larger for large resonant volume than for small resonant one. (L.C.J.A.)
Boyd, Robert W
2013-01-01
Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q
DEFF Research Database (Denmark)
Wustner, D.
2012-01-01
Elucidation of intracellular cholesterol transport is important for understanding the molecular basis of several metabolic and neuronal diseases, like atheroclerosis or lysosomal storage disorders. Progress in this field depends crucially on the development of new technical approaches to follow...... the cellular movement of this essential lipid molecule. In this article, a survey of the various methods being used for analysis of sterol trafficking is given. Various classical biochemical methods are presented and their suitability for analysis of sterol trafficking is assessed. Special emphasis...... analysis like pixel-wise bleach rate fitting and multiphoton image correlation spectroscopy are introduced. Several applications of the new technology including observation of vectorial sterol trafficking in polarized human hepatoma cells for investigation of reverse cholesterol transport are presented....
Electrode Cultivation and Interfacial Electron Transport in Subsurface Microorganisms
Karbelkar, A. A.; Jangir, Y.; Reese, B. K.; Wanger, G.; Anderson, C.; El-Naggar, M.; Amend, J.
2016-12-01
Continental subsurface environments can present significant energetic challenges to the resident microorganisms. While these environments are geologically diverse, potentially allowing energy harvesting by microorganisms that catalyze redox reactions, many of the abundant electron donors and acceptors are insoluble and therefore not directly bioavailable. Microbes can use extracellular electron transfer (EET) as a metabolic strategy to interact with redox active surfaces. This process can be mimicked on electrode surfaces and hence can lead to enrichment and quantification of subsurface microorganisms A primary bioelectrochemical enrichment with different oxidizing and reducing potentials set up in a single bioreactor was applied in situ to subsurface microorganisms residing in iron oxide rich deposits in the Sanford Underground Research Facility. Secondary enrichment revealed a plethora of classified and unclassified subsurface microbiota on both oxidizing and reducing potentials. From this enrichment, we have isolated a Gram-positive Bacillus along with Gram-negative Cupriavidus and Anaerospora strains (as electrode reducers) and Comamonas (as an electrode oxidizer). The Bacillus and Comamonas isolates were subjected to a detailed electrochemical characterization in half-reactors at anodic and cathodic potentials, respectively. An increase in cathodic current upon inoculation and cyclic voltammetry measurements confirm the hypothesis that Comamonas is capable of electron uptake from electrodes. In addition, measurements of Bacillus on anodes hint towards novel mechanisms that allow EET from Gram-positive bacteria. This study suggests that electrochemical approaches are well positioned to dissect such extracellular interactions that may be prevalent in the subsurface, while using physical electrodes to emulate the microhabitats, redox and geochemical gradients, and the spatially dependent interspecies interactions encountered in the subsurface. Electrochemical
International Nuclear Information System (INIS)
Haussaire, Jean-Matthieu
2017-01-01
Data assimilation methods are constantly evolving to adapt to the various application domains. In atmospheric sciences, each new algorithm has first been implemented on numerical weather prediction models before being ported to atmospheric chemistry models. It has been the case for 4D variational methods and ensemble Kalman filters for instance. The new 4D ensemble variational methods (4D EnVar) are no exception. They were developed to take advantage of both variational and ensemble approaches and they are starting to be used in operational weather prediction centers, but have yet to be tested on operational atmospheric chemistry models. The validation of new data assimilation methods on these models is indeed difficult because of the complexity of such models. It is hence necessary to have at our disposal low-order models capable of synthetically reproducing key physical phenomena from operational models while limiting some of their hardships. Such a model, called L95-GRS, has therefore been developed. Il combines the simple meteorology from the Lorenz-95 model to a tropospheric ozone chemistry module with 7 chemical species. Even though it is of low dimension, it reproduces some of the physical and chemical phenomena observable in real situations. A data assimilation method, the iterative ensemble Kalman smoother (IEnKS), has been applied to this model. It is an iterative 4D EnVar method which solves the full non-linear variational problem. This application validates 4D EnVar methods in the context of non-linear atmospheric chemistry, but also raises the first limits of such methods, most noticeably when they are applied to weakly coupled stable models. After this experiment, results have been extended to a realistic atmospheric pollution prediction model. 4D EnVar methods, via the IEnKS, have once again shown their potential to take into account the non-linearity of the chemistry model in a controlled environment, with synthetic observations. However, the
Novel electronic and transport properties of graphene superlattices
Park, Cheol-Hwan
2009-03-01
Charge carriers in graphene show linear and isotropic energy dispersion relation and chiral behavior, like massless neutrinos in particle physics. Because of these novel properties, many interesting and unconventional phenomena occur in graphene. On the other hand, since the 1970's, metallic and semiconducting superlattice structures -- man-made crystals -- have been extensively studied regarding to their fundamental electronic and optical properties as well as many applications. In this talk, I will present calculations on the properties of charge carriers in graphene under an external periodic potential (graphene superlattices) which are found to be greatly different from those of conventional two-dimensional electron gases in similar conditions [1-3]. I will discuss the anisotropies in the group velocity around the Dirac point and in the gap opening at the supercell Brillouin zone boundary [1]. Next, I will focus on the special cases where the group velocity along one direction becomes zero [1,2], emphasizing the phenomena of pseudospin collapse and possible electron beam supercollimation effects in these systems [2]. Finally, I will discuss the properties of a new generation of massless Dirac fermions at the supercell Brillouin zone boundaries and their experimental implications [3]. [4pt] [1] C. -H. Park, L. Yang, Y. -W. Son, M. L. Cohen, and S. G. Louie, Nature Phys. 4, 870 (2008). [0pt] [2] C. -H. Park, Y. -W. Son, L. Yang, M. L. Cohen, and S. G. Louie, Nano Lett. 8, 2920 (2008). [0pt] [3] C. -H. Park, L. Yang, Y. -W. Son, M. L. Cohen, and S. G. Louie, Phys. Rev. Lett. 101, 126804 (2008).
Hoy, Erik P.; Mazziotti, David A.; Seideman, Tamar
2017-11-01
Can an electronic device be constructed using only a single molecule? Since this question was first asked by Aviram and Ratner in the 1970s [Chem. Phys. Lett. 29, 277 (1974)], the field of molecular electronics has exploded with significant experimental advancements in the understanding of the charge transport properties of single molecule devices. Efforts to explain the results of these experiments and identify promising new candidate molecules for molecular devices have led to the development of numerous new theoretical methods including the current standard theoretical approach for studying single molecule charge transport, i.e., the non-equilibrium Green's function formalism (NEGF). By pairing this formalism with density functional theory (DFT), a wide variety of transport problems in molecular junctions have been successfully treated. For some systems though, the conductance and current-voltage curves predicted by common DFT functionals can be several orders of magnitude above experimental results. In addition, since density functional theory relies on approximations to the exact exchange-correlation functional, the predicted transport properties can show significant variation depending on the functional chosen. As a first step to addressing this issue, the authors have replaced density functional theory in the NEGF formalism with a 2-electron reduced density matrix (2-RDM) method, creating a new approach known as the NEGF-RDM method. 2-RDM methods provide a more accurate description of electron correlation compared to density functional theory, and they have lower computational scaling compared to wavefunction based methods of similar accuracy. Additionally, 2-RDM methods are capable of capturing static electron correlation which is untreatable by existing NEGF-DFT methods. When studying dithiol alkane chains and dithiol benzene in model junctions, the authors found that the NEGF-RDM predicts conductances and currents that are 1-2 orders of magnitude below
Tanaka, Kenya; Kaneko, Masahiro; Ishikawa, Masahito; Kato, Souichiro; Ito, Hidehiro; Kamachi, Toshiaki; Kamiya, Kazuhide; Nakanishi, Shuji
2017-04-19
Redox phospholipid polymers added in culture media are known to be capable of extracting electrons from living photosynthetic cells across bacterial cell membranes with high cytocompatibility. In the present study, we identify the intracellular redox species that transfers electrons to the polymers. The open-circuit electrochemical potential of an electrolyte containing the redox polymer and extracted thylakoid membranes shift to positive (or negative) under light irradiation, when an electron transport inhibitor specific to plastoquinone is added upstream (or downstream) in the photosynthetic electron transport chain. The same trend is also observed for a medium containing living photosynthetic cells of Synechococcus elongatus PCC7942. These results clearly indicate that the phospholipid redox polymers extract photosynthetic electrons mainly from plastoquinone. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
International Nuclear Information System (INIS)
Martinolli, E.
2003-04-01
This work is dedicated to the study of the energy deposition of fast electrons in matter. This topic is of prime importance for inertial fusion driven by laser since relativistic electrons are produced in laser-matter interaction for a laser operating in ultra-intense regime. This thesis is made up of: a theoretical chapter dealing with the generation and transport of fast electrons, of 2 chapters reporting experimental data obtained with optical and X-rays diagnostics at the laser facilities of LULI in France and RAL in U.K., and of a chapter dedicated to the simulation of electron transport by using a Monte-Carlo code combined to a hybrid collisional-electromagnetic PIC code. A new spectrometer has been designed: the detection of Kα rays coming from a fluorescent layer embedded in the target has allowed us to assess the size of the electron beam and the level of ionisation. (A.C.)
Computational aspects of electronic transport in nanoscale devices
Sørensen, Hans Henrik Brandenborg; Hansen, Per Christian; Stokbro, Kurt
2008-01-01
This thesis is concerned with the modeling of electronic properties of nano-scale devices. In particular the computational aspects of calculating the transmission and current-voltage characteristics of Landauer-Büttiker two-probe systems are in focus. To begin with, the main existing methods are described in detail and benchmarked. These are the Green’s function method and the wave function matching method. The methods are subsequently combined in a hybrid scheme in order to benefit from a co...
Electron ray tracing programs for gun design and beam transport
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.
1988-05-01
Computer simulation of electron and ion sources is made by using a class of computer codes known as gun design programs. In this paper, we shall first list most of the necessary and some optional capabilities of such programs. Then we will briefly note specific codes and/or authors of codes with attention to specialized applications if any. There may be many more such programs in use than are treated here; we are only trying to cover a range of examples, not perform a comprehensive survey
Study of kinetic models for nonlinear electron transport in semiconductor superlattices
Álvaro Ballesteros, Mariano
2011-01-01
Las superredes de semiconductores son cristales unidimensionales artificiales formados por muchos períodos, cada uno de ellos compuesto por dos semiconductores diferentes pero con constantes similares, por ejemplo GaAs y AlAs. Estas nanoestructuras fueron inventadas por Esaki y Tsu con el propósito de desarrollar dispositivos en los que pudieran ser observadas las oscilaciones de Bloch. Tienen aplicaciones prácticas como osciladores de alta frecuencia, láseres de cascada cuántica o detectores...
Electronic transport properties of one dimensional lithium nanowire using density functional theory
Energy Technology Data Exchange (ETDEWEB)
Thakur, Anil, E-mail: anil-t2001@yahoo.com [Department of Physics, Govt. P.G. College Solan, Himachal Pradesh, India 173212 (India); Kumar, Arun [Department of Physics, Govt. P.G. College Banjar, Himachal Pradesh (India); Chandel, Surjeet [Department of Physics, Govt. P.G. College Bilaspur, Himachal Pradesh (India); Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University Shimla, Himachal Pradesh, India 171005 (India)
2015-05-15
Single nanowire electrode devices are a unique platform for studying as energy storage devices. Lithium nanowire is of much importance in lithium ion batteries and therefore has received a great deal of attention in past few years. In this paper we investigated structural and electronic transport properties of Li nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Li nanowire are investigated theoretically. The calculations are performed in two steps: first an optimized geometry for Li nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations correspondingly. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Agreement of bulk properties of Li with experimental values make the study of electronic and transport properties in lithium nanowires interesting because they are promising candidates as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Li nano wire indicates that Li nanowire can be used as an electrode device.
Electronic Transport in Hydrogen-Terminated Si(001) Nanomembranes
Peng, Weina; Zamiri, Marziyeh; Scott, Shelley A.; Cavallo, Francesca; Endres, James J.; Knezevic, Irena; Eriksson, Mark A.; Lagally, Max G.
2018-02-01
Charge carrier transport in thin hydrogen (H)-terminated Si(001) sheets is explored via a four-probe device fabricated on silicon-on-insulator (SOI) using the bulk host Si as a back gate. The method enables electrical measurements without the need to contact the sample surface proper. Sheet conductance measurements as a function of back-gate voltage demonstrate the presence of acceptor- and donorlike surface states. These states are distributed throughout the gap and can be removed or transformed with low-temperature annealing. The density of donorlike states is just under 1012 cm-2 eV-1 and 3 times higher than that of the acceptorlike states. We discuss the possible origins of these states. The conductance through the surface layer is too small to measure.
International Nuclear Information System (INIS)
Miah, M. Idrish
2008-01-01
High field electron-spin transport in low temperature-grown gallium arsenide is studied. We generate electron spins in the samples by optical pumping. During transport, we observe the Dyakonov-Perel (DP) [M.I. Dyakonov, V.I. Perel, Zh. Eksp. Teor. Fiz. 60 (1971) 1954] spin relaxation of the drifting electrons. The results are discussed and are compared with those obtained in calculations of the DP spin relaxation frequency of the hot electrons. A good agreement is obtained
Energy Technology Data Exchange (ETDEWEB)
Miah, M. Idrish [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Biomolecular and Physical Sciences, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong-4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au
2008-11-17
High field electron-spin transport in low temperature-grown gallium arsenide is studied. We generate electron spins in the samples by optical pumping. During transport, we observe the Dyakonov-Perel (DP) [M.I. Dyakonov, V.I. Perel, Zh. Eksp. Teor. Fiz. 60 (1971) 1954] spin relaxation of the drifting electrons. The results are discussed and are compared with those obtained in calculations of the DP spin relaxation frequency of the hot electrons. A good agreement is obtained.
International Nuclear Information System (INIS)
Cherepanov, K.V.; Kukushkin, A.B.
2005-01-01
Numerical studies of the contribution of suprathermal electrons to electron cyclotron radiation (ECR) transport in hot (Te > 10 keV) plasmas confined by a strong toroidal magnetic field (B > 5 T) are reported. The respective code (Proc. 14th IAEA Conf. PPCF, Wuerzburg, 1992, v.2, p.35) which, for maxwellian electron velocity distribution (EVD) with inhomogeneous temperature/density, has been tested against well-known numerical and semi-analytical codes by S. Tamor, is now applied to solving the following two problems for ITER-like conditions. (1) Spatial profile of the net radiated power density, P EC (r), is found to be strongly sensitive to the presence of suprathermal electrons. This enables us to evaluate allowable limits for local rise of effective temperature/density of suprathermal electrons (in terms of bi-maxwellian EVD). (2) Self-consistent modeling of the ECR transport and the kinetics of suprathermal electrons gives spatial profile of deviations from maxwellian EVD, caused by the transport of plasma's self EC radiation. These kinetic effects work ultimately for the global flattening of the P EC (r) profile: a lowering, in the core, and a rise, in the periphery. For ITER-like conditions, these effects upon P EC (r) appear to be small. The results of treating the above two tasks suggest the necessity of solving self-consistently the problems of (i) ECRH and ECCD optimization and (ii) ECR transport in the entire range of radiation frequency, when strong enough suprathermals may be produced. (author)
Balanced electron-hole transport in spin-orbit semimetal SrIrO3 heterostructures
Manca, Nicola; Groenendijk, Dirk J.; Pallecchi, Ilaria; Autieri, Carmine; Tang, Lucas M. K.; Telesio, Francesca; Mattoni, Giordano; McCollam, Alix; Picozzi, Silvia; Caviglia, Andrea D.
2018-02-01
Relating the band structure of correlated semimetals to their transport properties is a complex and often open issue. The partial occupation of numerous electron and hole bands can result in properties that are seemingly in contrast with one another, complicating the extraction of the transport coefficients of different bands. The 5 d oxide SrIrO3 hosts parabolic bands of heavy holes and light electrons in gapped Dirac cones due to the interplay between electron-electron interactions and spin-orbit coupling. We present a multifold approach relying on different experimental techniques and theoretical calculations to disentangle its complex electronic properties. By combining magnetotransport and thermoelectric measurements in a field-effect geometry with first-principles calculations, we quantitatively determine the transport coefficients of different conduction channels. Despite their different dispersion relationships, electrons and holes are found to have strikingly similar transport coefficients, yielding a holelike response under field-effect and thermoelectric measurements and a linear electronlike Hall effect up to 33 T.
Fu, Boyi
2015-04-01
The electron deficiency and trans planar conformation of bithiazole is potentially beneficial for the electron transport performance of organic semiconductors. However, the incorporation of bithiazole into polymers through a facile synthetic strategy remains a challenge. Herein, 2,2’-bithiazole was synthesized in one step and copolymerized with dithienyldiketopyrrolopyrrole to afford poly(dithienyldiketopyrrolopyrrole-bithiazole), PDBTz. PDBTz exhibited electron mobility reaching 0.3 cm2V-1s-1 in organic field-effect transistor (OFET) configuration; this contrasts with a recently discussed isoelectronic conjugated polymer comprising an electron rich bithiophene and dithienyldiketopyrrolopyrrole, which displays merely hole transport characteristics. This inversion of charge carrier transport characteristics confirms the significant potential for bithiazole in the development of electron transport semiconducting materials. Branched 5-decylheptacyl side chains were incorporated into PDBTz to enhance polymer solubility, particularly in non-halogenated, more environmentally compatible solvents. PDBTz cast from a range of non-halogenated solvents exhibited film morphologies and field-effect electron mobility similar to those cast from halogenated solvents.
Two-dimensional electron transport in AlGaN/GaN heterostructures
International Nuclear Information System (INIS)
Tan Renbing; Xu Wen; Zhou Yu; Zhang Xiaoyu; Qin Hua
2012-01-01
We present a theoretical study of electron transport properties of two-dimensional electron gas in AlGaN/GaN heterostructures. By assuming a drifted Fermi-Dirac distribution and taking into account all major scattering mechanisms, including polar optical and acoustic phonons, background impurities, dislocation and interface roughness, the momentum- and energy-balance equations derived from Boltzmann equation are solved self-consistently. The dependence of the electron drift velocity and electron temperature as a function of the applied electric field are obtained and discussed.
Two-dimensional electron transport in AlGaN/GaN heterostructures
Energy Technology Data Exchange (ETDEWEB)
Tan Renbing [Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Xu Wen, E-mail: wenxu_issp@yahoo.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Zhou Yu; Zhang Xiaoyu [Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Qin Hua, E-mail: hqin2007@sinano.ac.cn [Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215125 (China)
2012-11-01
We present a theoretical study of electron transport properties of two-dimensional electron gas in AlGaN/GaN heterostructures. By assuming a drifted Fermi-Dirac distribution and taking into account all major scattering mechanisms, including polar optical and acoustic phonons, background impurities, dislocation and interface roughness, the momentum- and energy-balance equations derived from Boltzmann equation are solved self-consistently. The dependence of the electron drift velocity and electron temperature as a function of the applied electric field are obtained and discussed.
Electron transport in nanometer GaAs structure under radiation exposure
Demarina, N V
2002-01-01
One investigates into effect of neutron and proton irradiation on electron transport in nanometer GaAs structures. Mathematical model takes account of radiation defects via introduction of additional mechanisms od scattering of carriers at point defects and disordered regions. To investigate experimentally into volt-ampere and volt-farad characteristics one used a structure based on a field-effect transistor with the Schottky gate and a built-in channel. Calculation results of electron mobility, drift rate of electrons, time of energy relaxation and electron pulse are compared with the experimental data
Radial transport of radiation belt electrons due to stormtime Pc5 waves
Directory of Open Access Journals (Sweden)
A. Y. Ukhorskiy
2009-05-01
Full Text Available During geomagnetic storms relativistic electron fluxes in the outer radiation belt exhibit dynamic variability over multiple orders of magnitude. This requires radial transport of electrons across their drift shells and implies violation of their third adiabatic invariant. Radial transport is induced by the interaction of the electron drift motion with electric and magnetic field fluctuations in the ULF frequency range. It was previously shown that solar-wind driven ULF waves have long azimuthal wave lengths and thus can violate the third invariant of trapped electrons in the process of resonant interaction with their gradient-curvature motion. However, the amplitude of solar-wind driven ULF waves rapidly decreases with decreasing L. It is therefore not clear what mechanisms are responsible for fast transport rates observed inside the geosynchronous orbit. In this paper we investigate wether stormtime Pc5 waves can contribute to this process. Stormtime Pc5s have short azimuthal wave lengths and therefore cannot exhibit resonance with the the electron drift motion. However we show that stormtime Pc5s can cause localized random scattering of electron drift motion that violates the third invariant. According to our results electron interaction with stormtime Pc5s can produce rapid radial transport even as low as L≃4. Numerical simulations show that electron transport can exhibit large deviations from radial diffusion. The diffusion approximation is not valid for individual storms but only applies to the statistically averaged response of the outer belt to stormtime Pc5 waves.
Contacts, non-linear transport effects and failure in multi-walled carbon nanotubes
International Nuclear Information System (INIS)
Berger, C; Yi, Y; Gezo, J; Poncharal, P; Heer, W A de
2003-01-01
Pristine arc-produced multi-walled carbon nanotubes are contacted to liquid mercury in situ in a transmission electron microscope. The conductance G(V) for all tubes increases with increasing bias voltage V. This is related to the electronic density of the nanotubes. Similar G(V) behaviour is observed for HOPG-graphite contacted in air with Hg, with dG(V)/dV∼0.3G 0 . Variations observed in the conductance are related to nanotube-Hg contact effects. For tubes barely touching the Hg surface, the conductance is low (typically G(V=0)∼0.1-0.5G 0 ); G(V) may maximize around V=1.5-2 V or continue to increase linearly depending on the MWNT-Hg contact. For good contacts the maximum low-bias conductance is 1G 0 . Non-conducting tubes are observed having a low-bias conductance smaller than 10 -3 G 0 . High-voltage tube failure usually occurs at the contact with Hg for clean tubes, or at tube defects. An important phenomenon is the formation of a Hg bubble near the contact nanotube-Hg surface when the nanotube is negatively biased, under high bias current conditions, indicating the heating effect of hot electrons injected into the mercury
Theoretical study of electron transport throughout some molecular structures
Abbas, Mohammed A. A.; Hanoon, Falah H.; Al-Badry, Lafy F.
2017-11-01
The present work is a theoretical study of the electronic properties of some molecular structures. The system that takes into account in the study is left lead-donor-molecule-acceptor-right lead. The molecule, such as (phenyl, biphenyl, triphenyl, naphthalene, anthracene, and phenanthrene), is threaded by magnetic flux. This work contains two parts. First is computing density of states of the molecular structures as a closed system by density functional theory (DFT). Second is calculating the transmission probability and electric current of such molecular structures as an open system by steady-state theoretical model. Furthermore, the most important effects, taking into consideration are quantum interference, magnetic flux, and interface structure. Our results show that the connection of the molecule to the two leads, the number of rings, the magnetic flux, and the geometrical structure of the molecule play an important role in determining the energy gap of molecular structures.
Computational aspects of electronic transport in nanoscale devices
DEFF Research Database (Denmark)
Sørensen, Hans Henrik Brandenborg
2008-01-01
is for the calculation of the block tridiagonal matrix inverse of a block tridiagonal matrix in O(N) operations. This algorithm also leads to an optimal evaluation of the frequently used Caroli transmission formula. A modified wave function matching scheme is then developed which allows for a significant reduction...... in the cost of the self-energy matrix calculations when combined with an iterative eigensolver. Finally, such an iterative eigensolver is developed and implemented based of a shift-and-invert Krylov subspace approach. The method is applied to a selection of nano-scale systems and speed-ups of up to an order......This thesis is concerned with the modeling of electronic properties of nano-scale devices. In particular the computational aspects of calculating the transmission and current-voltage characteristics of Landauer-Büttiker two-probe systems are in focus. To begin with, the main existing methods...
Electronic transport on the nanoscale: ballistic transmission and Ohm's law.
Homoth, J; Wenderoth, M; Druga, T; Winking, L; Ulbrich, R G; Bobisch, C A; Weyers, B; Bannani, A; Zubkov, E; Bernhart, A M; Kaspers, M R; Möller, R
2009-04-01
If a current of electrons flows through a normal conductor (in contrast to a superconductor), it is impeded by local scattering at defects as well as phonon scattering. Both effects contribute to the voltage drop observed for a macroscopic complex system as described by Ohm's law. Although this concept is well established, it has not yet been measured around individual defects on the atomic scale. We have measured the voltage drop at a monatomic step in real space by restricting the current to a surface layer. For the Si(111)-( [see text]3 x [see text]3)-Ag surface a monotonous transition with a width below 1 nm was found. A numerical analysis of the data maps the current flow through the complex network and the interplay between defect-free terraces and monatomic steps.
DEFF Research Database (Denmark)
Wustner, D.
2012-01-01
analysis like pixel-wise bleach rate fitting and multiphoton image correlation spectroscopy are introduced. Several applications of the new technology including observation of vectorial sterol trafficking in polarized human hepatoma cells for investigation of reverse cholesterol transport are presented....... the cellular movement of this essential lipid molecule. In this article, a survey of the various methods being used for analysis of sterol trafficking is given. Various classical biochemical methods are presented and their suitability for analysis of sterol trafficking is assessed. Special emphasis...
Opto-electronic and quantum transport properties of semiconductor nanostructures
Energy Technology Data Exchange (ETDEWEB)
Sabathil, M.
2005-01-01
In this work a novel and efficient method for the calculation of the ballistic transport properties of open semiconductor nanostructures connected to external reservoirs is presented. It is based on the Green's function formalism and reduces the effort to obtain the transmission and the carrier density to a single solution of a hermitian eigenvalue problem with dimensions proportional to the size of the decoupled device and the multiple inversion of a small matrix with dimensions proportional to the size of the contacts to the leads. Using this method, the 4-band GaAs hole transport through a 2-dimensional three-terminal T-junction device, and the resonant tunneling current through a 3-dimensional InAs quantum dot molecule embedded into an InP heterostructure have been calculated. The further extension of the method into a charge self-consistent scheme enables the efficient prediction of the IV-characteristics of highly doped nanoscale field effect transistors in the ballistic regime, including the influence of quasi bound states and the exchange-correlation interaction. Buettiker probes are used to emulate the effect of inelastic scattering on the current for simple 1D devices, systematically analyzing the dependence of the density of states and the resulting self-consistent potential on the scattering strength. The second major topic of this work is the modeling of the optical response of quantum confined neutral and charged excitons in single and coupled self-assembled InGaAs quantum dots. For this purpose the existing device simulator nextnano{sup 3} has been extended to incorporate particle-particle interactions within the means of density functional theory in local density approximation. In this way the exciton transition energies for neutral and charged excitons as a function of an externally applied electric field have been calculated, revealing a systematic reduction of the intrinsic dipole with the addition of extra holes to the exciton, a finding
Nonlinear Susceptibility of the Heavy Electron Materials, UPt_3, URu_2Si2 and UPd_2Al_3
Shivaram, B. S.; Wang, H.; Hinks, D. G.; de Andrade, M.; Maple, M. B.
1996-03-01
We report measurements of the leading order nonlinear term, X_3, in the zero frequency magnetic susceptibility of the heavy electron compounds UPt_3, URu_2Si2 and UPd_2Al3 both above and below their respective magnetic ordering temperatures as established through neutron scattering experiments. The only similarity amongst the three materials is the unusually large and positive X3 in the paramagnetic state. In the ordered state the observed behavior is apparently different in each case. In agreement with previous measurements URu_2Si2 exhibits a positive discontinuity in X3 at its Neel temperature. No such behavior is observed in the other two compounds. In addition while UPd_2Al_3, a hexagonal system with spins oriented in the basal plane exhibits a clear signature in X3 at the Neel temperature no discernible signature is observed in UPt_3.
Liu, Baoshun; Li, Ziqiang; Zhao, Xiujian
2015-02-21
In this research, Monte-Carlo Continuity Random Walking (MC-RW) model was used to study the relation between electron transport and photocatalysis of nano-crystalline (nc) clusters. The effects of defect energy disorder, spatial disorder of material structure, electron density, and interfacial transfer/recombination on the electron transport and the photocatalysis were studied. Photocatalytic activity is defined as 1/τ from a statistical viewpoint with τ being the electron average lifetime. Based on the MC-RW simulation, a clear physical and chemical "picture" was given for the photocatalytic kinetic analysis of nc-clusters. It is shown that the increase of defect energy disorder and material spatial structural disorder, such as the decrease of defect trap number, the increase of crystallinity, the increase of particle size, and the increase of inter-particle connection, can enhance photocatalytic activity through increasing electron transport ability. The increase of electron density increases the electron Fermi level, which decreases the activation energy for electron de-trapping from traps to extending states, and correspondingly increases electron transport ability and photocatalytic activity. Reducing recombination of electrons and holes can increase electron transport through the increase of electron density and then increases the photocatalytic activity. In addition to the electron transport, the increase of probability for electrons to undergo photocatalysis can increase photocatalytic activity through the increase of the electron interfacial transfer speed.
Temperature dependent transport of two dimensional electrons in the integral quantum Hall regime
International Nuclear Information System (INIS)
Wi, H.P.
1986-01-01
This thesis is concerned with the temperature dependent electronic transport properties of a two dimensional electron gas subject to background potential fluctuations and a perpendicular magnetic field. The author carried out an extensive temperature dependent study of the transport coefficients, in the region of an integral quantum plateau, in an In/sub x/Ga/sub 1-x/As/InP heterostructure for 4.2K 10 cm -2 meV -1 ) even at the middle between two Landau levels, which is unexpected from model calculations based on short ranged randomness. In addition, the different T dependent behavior of rho/sub xx/ between the states in the tails and those near the center of a Landau level, indicates the existence of different electron states in a Landau level. Additionally, the author reports T-dependent transport measurements in the transition region between two quantum plateaus in several different materials
SPHERE: a spherical-geometry multimaterial electron/photon Monte Carlo transport code
International Nuclear Information System (INIS)
Halbleib, J.A. Sr.
1977-06-01
SPHERE provides experimenters and theorists with a method for the routine solution of coupled electron/photon transport through multimaterial configurations possessing spherical symmetry. Emphasis is placed upon operational simplicity without sacrificing the rigor of the model. SPHERE combines condensed-history electron Monte Carlo with conventional single-scattering photon Monte Carlo in order to describe the transport of all generations of particles from several MeV down to 1.0 and 10.0 keV for electrons and photons, respectively. The model is more accurate at the higher energies, with a less rigorous description of the particle cascade at energies where the shell structure of the transport media becomes important. Flexibility of construction permits the user to tailor the model to specific applications and to extend the capabilities of the model to more sophisticated applications through relatively simple update procedures. 8 figs., 3 tables
The electronic and transport properties of borophane with defects: A first principles study
Sun, Jie; Zhang, Yujin; Leng, Jiancai; Ma, Hong
2018-03-01
Recent works well confirm the stability of hydrogenated borophene, known as borophane. Here, first principles studies have performed on the electronic and transport properties of borophane with defects. The calculations indicate that the introduction of defects results in different behavior of charges redistribution along x and y directions. The intrinsic electronic structure of borophane with Dirac cone is destroyed in various degrees by each type of defect. The inducing defect states lead to the occurrence of flat bands, which are not benefit for the electronic transport properties. According to the transmission spectra and I-V characteristics, these defects decrease the transmission intensity and the current value both along two directions. However, the transport anisotropy can be efficiently tuned by defect, which may contribute to the design of functional device.
International Nuclear Information System (INIS)
Casuso, I; Fumagalli, L; Samitier, J; Padros, E; Reggiani, L; Akimov, V; Gomila, G
2007-01-01
We present a reliable methodology to perform electron transport measurements at the nanoscale on supported biomembranes by conductive atomic force microscopy (C-AFM). It allows measurement of both (a) non-destructive conductive maps and (b) force controlled current-voltage characteristics in wide voltage bias range in a reproducible way. Tests experiments were performed on purple membrane monolayers, a two-dimensional (2D) crystal lattice of the transmembrane protein bacteriorhodopsin. Non-destructive conductive images show uniform conductivity of the membrane with isolated nanometric conduction defects. Current-voltage characteristics under different compression conditions show non-resonant tunneling electron transport properties, with two different conduction regimes as a function of the applied bias, in excellent agreement with theoretical predictions. This methodology opens the possibility for a detailed study of electron transport properties of supported biological membranes, and of soft materials in general
Electron transport in InAs nanowires and heterostructure nanowire devices
Thelander, C.; Björk, M. T.; Larsson, M. W.; Hansen, A. E.; Wallenberg, L. R.; Samuelson, L.
2004-09-01
Nanowires in the InAs/InP material system are grown with catalyst-assisted chemical beam epitaxy. Ohmic contacts are then fabricated to selected wires, allowing electron transport measurements to be carried out at room-temperature as well as at low T. InAs nanowires show strong quantum confinement effects, where thin wires (Heterostructure barriers of InP are also incorporated into InAs wires to produce resonant tunneling diodes and single-electron transistors (SETs) with different dot lengths. Wires containing dots with a length of 100 nm function as ideal SETs, whereas the transport in wires with 15 nm long dots is strongly governed by quantum confinement and resonant tunneling. For the smaller dots it is possible to observe electron transport through excited states.
Evans, John R; Morgan, Patrick B; von Caemmerer, Susanne
2017-10-01
Chl fluorescence has been used widely to calculate photosynthetic electron transport rates. Portable photosynthesis instruments allow for combined measurements of gas exchange and Chl fluorescence. We analyzed the influence of spectral quality of actinic light on Chl fluorescence and the calculated electron transport rate, and compared this with photosynthetic rates measured by gas exchange in the absence of photorespiration. In blue actinic light, the electron transport rate calculated from Chl fluorescence overestimated the true rate by nearly a factor of two, whereas there was closer agreement under red light. This was consistent with the prediction made with a multilayer leaf model using profiles of light absorption and photosynthetic capacity. Caution is needed when interpreting combined measurements of Chl fluorescence and gas exchange, such as the calculation of CO2 partial pressure in leaf chloroplasts. © Crown copyright 2017.
Light harvesting and chloroplast electron transport in NADP-malic enzyme type C4 plants.
Nakajima Munekage, Yuri
2016-06-01
The structure of thylakoids in chloroplasts and the organization of the electron transport chain changed dynamically during the evolution of C4 photosynthesis, especially in the nicotinamide adenine dinucleotide phosphate (NADP)-malic enzyme type C4 species. Stacked grana membranes are strongly reduced in the bundle sheath chloroplasts of these plants, where photosystem II activity is diminished and cyclic electron transport around photosystem I mainly occurs. This change optimizes the ATP/NADPH production ratio in bundle sheath chloroplasts to drive the metabolic cycle of C4 photosynthesis. This review summarizes the current model of light harvesting and electron transport in the NADP-malic enzyme type C4 plants and discusses how it changed during the evolution of C4 photosynthesis. Copyright © 2016 Elsevier Ltd. All rights reserved.
Electron transport in nano-scaled piezoelectronic devices
Jiang, Zhengping; Kuroda, Marcelo A.; Tan, Yaohua; Newns, Dennis M.; Povolotskyi, Michael; Boykin, Timothy B.; Kubis, Tillmann; Klimeck, Gerhard; Martyna, Glenn J.
2013-05-01
The Piezoelectronic Transistor (PET) has been proposed as a post-CMOS device for fast, low-power switching. In this device, the piezoresistive channel is metalized via the expansion of a relaxor piezoelectric element to turn the device on. The mixed-valence compound SmSe is a good choice of PET channel material because of its isostructural pressure-induced continuous metal insulator transition, which is well characterized in bulk single crystals. Prediction and optimization of the performance of a realistic, nano-scaled PET based on SmSe requires the understanding of quantum confinement, tunneling, and the effect of metal interface. In this work, a computationally efficient empirical tight binding (ETB) model is developed for SmSe to study quantum transport in these systems and the scaling limit of PET channel lengths. Modulation of the SmSe band gap under pressure is successfully captured by ETB, and ballistic conductance shows orders of magnitude change under hydrostatic strain, supporting operability of the PET device at nanoscale.
Conceptual density functional theory for electron transfer and transport in mesoscopic systems.
Bueno, Paulo R; Miranda, David A
2017-02-22
Molecular and supramolecular systems are essentially mesoscopic in character. The electron self-exchange, in the case of energy fluctuations, or electron transfer/transport, in the case of the presence of an externally driven electrochemical potential, between mesoscopic sites is energetically driven in such a manner where the electrochemical capacitance (C [small mu, Greek, macron] ) is fundamental. Thus, the electron transfer/transport through channels connecting two distinct energetic (ΔE [small mu, Greek, macron] ) and spatially separated mesoscopic sites is capacitively modulated. Remarkably, the relationship between the quantum conductance (G) and the standard electrochemical rate constant (k r ), which is indispensable to understanding the physical and chemical characteristics governing electron exchange in molecular scale systems, was revealed to be related to C [small mu, Greek, macron] , that is, C [small mu, Greek, macron] = G/k r . Accordingly, C [small mu, Greek, macron] is the proportional missing term that controls the electron transfer/transport in mesoscopic systems in a wide-range, and equally it can be understood from first principles density functional quantum mechanical approaches. Indeed the differences in energy between states is calculated (or experimentally accessed) throughout the electrochemical capacitance as ΔE [small mu, Greek, macron] = β/C [small mu, Greek, macron] , and thus constitutes the driving force for G and/or k r , where β is only a proportional constant that includes the square of the unit electron charge times the square of the number of electron particles interchanged.
Kracke, Frauke; Vassilev, Igor; Krömer, Jens O.
2015-01-01
Microbial electrochemical techniques describe a variety of emerging technologies that use electrode–bacteria interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and the production of valuable products. Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism. And here also lies the key challenge. A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth. Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis. We analyze the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production. Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g., cytochromes, ferredoxin, quinones, flavins) are identified and analyzed regarding their possible role in electrode–microbe interactions. This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism. As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bioelectrochemical
Directory of Open Access Journals (Sweden)
Frauke eKracke
2015-06-01
Full Text Available Microbial electrochemical techniques describe a variety of emerging technologies that use electrode-bacteria-interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and production of valuable products. Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism. And here also lies the key challenge. A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth. Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis. We analyse the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production. Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bio-electrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g. cytochromes, ferredoxin, quinones, flavins are identified and analysed regarding their possible role in electrode-microbe-interactions. This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism. As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bio
On the validity of travel-time based nonlinear bioreactive transport models in steady-state flow
Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A.
2015-04-01
conceptualization of nonlinear bioreactive transport in complex multidimensional domains by quasi 1-D travel-time models is valid for steady-state flow fields if the reactants are introduced over a wide cross-section, flow is at quasi steady state, and dispersive mixing is adequately parametrized.
International Nuclear Information System (INIS)
Zhao, P.; Wang, P.J.; Zhang, Z.; Liu, D.S.
2010-01-01
We have studied the electronic transport properties of a new kind of optical molecular switch with two single-walled carbon nanotube (SWCNT) electrodes using first-principles transport calculations. It is shown that the enol form shows an overall higher conductance than the keto form at low-bias voltage, which is independent of the SWCNTs' chirality. Meantime, it is possible to tune the conductance of the molecular switch by changing the chirality of the SWCNTs.
Proton stoichiometry of electron transport in rodent tumor mitoplasts.
Ferreira, J; Reynafarje, B; Costa, L E; Lehninger, A L
1988-02-01
The mechanistic vectorial H+/O translocation ratios characteristic of energy-conserving sites 2 + 3 and site 3 of the respiratory chain of two tumor cell lines were determined using succinate and ferrocytochrome c, respectively, as electron donors. The measurements were carried out on mitoplasts in order to allow ferrocytochrome c free access to its binding site on the inner mitochondrial membrane. The tumor cell lines used were Ehrlich ascites tumor and the AS30-D ascites tumor. K+ was used as charge-compensating cation in the presence of valinomycin. The O2 uptake rate measurements were made with a fast-responding membrane-less electrode whose response time was closely matched with that of a pH electrode. The rates of O2 uptake and H+ ejection during the apparent zero-order rate phase of respiration, analyzed by computer, were extrapolated to zero time. The observed H+/O ratios for succinate oxidation in both tumors exceeded 7 and approached 8 and the H+/O ratios for the cytochrome oxidase reaction closely approached 4.0, in agreement with data or normal mitochondria. However, the rates of H+ back decay in the tumor mitochondria are relatively high and may influence the net efficiency of oxidative phosphorylation under intracellular conditions.
Single-electron transport in graphene-like nanostructures
Energy Technology Data Exchange (ETDEWEB)
Chiu, Kuei-Lin, E-mail: klc43@mit.edu [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Xu, Yang, E-mail: yangxu-isee@zju.edu.cn [Institute of Microelectronics and Optoelectronics, College of Information Science and Electronic Engineering, Zhejiang University, 310027 (China)
2017-01-31
Two-dimensional (2D) materials for their versatile band structures and strictly 2D nature have attracted considerable attention over the past decade. Graphene is a robust material for spintronics owing to its weak spin–orbit and hyperfine interactions, while monolayer transition metal dichalcogenides (TMDs) possess a Zeeman effect-like band splitting in which the spin and valley degrees of freedom are nondegenerate. The surface states of topological insulators (TIs) exhibit a spin–momentum locking that opens up the possibility of controlling the spin degree of freedom in the absence of an external magnetic field. Nanostructures made of these materials are also viable for use in quantum computing applications involving the superposition and entanglement of individual charge and spin quanta. In this article, we review a selection of transport studies addressing the confinement and manipulation of charges in nanostructures fabricated from various 2D materials. We supply the entry-level knowledge for this field by first introducing the fundamental properties of 2D bulk materials followed by the theoretical background relevant to the physics of nanostructures. Subsequently, a historical review of experimental development in this field is presented, from the early demonstration of graphene nanodevices on SiO{sub 2} substrate to more recent progress in utilizing hexagonal boron nitride to reduce substrate disorder. In the second part of this article, we extend our discussion to TMDs and TI nanostructures. We aim to outline the current challenges and suggest how future work will be geared towards developing spin qubits in 2D materials.
Graphene frameworks promoted electron transport in quantum dot-sensitized solar cells.
Zhu, Yanyan; Meng, Xin; Cui, Huijuan; Jia, Suping; Dong, Jianhui; Zheng, Jianfeng; Zhao, Jianghong; Wang, Zhijian; Li, Li; Zhang, Li; Zhu, Zhenping
2014-08-27
Graphene frameworks (GFs) were incorporated into TiO2 photoanode as electron transport medium to improve the photovoltaic performance of quantum dot-sensitized solar cells (QDSSCs) for their excellent conductivity and isotropic framework structure that could permit rapid charge transport. Intensity modulated photocurrent/photovoltage spectroscopy and electrochemical impedance spectroscopy results show that the electron transport time (τ(d)) of 1.5 wt % GFs/TiO2 electrode is one-fifth of that of the TiO2 electrode, and electron lifetime (τ(n)) and diffusion path length (Ln) are thrice those of the TiO2 electrode. Results also revealed that the GFs/TiO2 electrode has a shorter electron transport time (τ(d)), as well as longer electron lifetime (τ(n)) and diffusion path length (Ln), than conventional 2D graphene sheets/TiO2 electrode, thus indicating that GFs could promote rapid electron transfer in TiO2 photoanodes. Photocurrent-voltage curves demonstrated that when incorporating 1.5 wt % GFs into TiO2 photoanode, a maximum power conversion efficiency of 4.2% for QDSSCs could be achieved. This value was higher than that of TiO2 photoanode and 2D graphene sheets/TiO2 electrode. In addition, the reasons behind the sensitivity of photoelectric conversion efficiency to the graphene concentration in the TiO2 were also systematically investigated. Our results provide a basic understanding of how GFs can efficiently promote electron transport in TiO2-based solar cells.
Energy Technology Data Exchange (ETDEWEB)
Croy, Alexander
2010-06-30
In this thesis the time-resolved electron transport in quantum dot systems was studied. For this two different formalisms were presented: The nonequilibrium Green functions and the generalized quantum master equations. For both formalisms a propagation method for the numerical calculation of time-resolved expectation values, like the occupation and the electron current, was developed. For the demonstration of the propagation method two different question formulations were considered. On the one hand the stochastically driven resonant-level model was studied. On the other hand the pulse-induced transport through a double quantum dot was considered.
Parallelizing an electron transport Monte Carlo simulator (MOCASIN 2.0)
International Nuclear Information System (INIS)
Schwetman, H.; Burdick, S.
1988-01-01
Electron transport simulators are tools for studying electrical properties of semiconducting materials and devices. As demands for modeling more complex devices and new materials have emerged, so have demands for more processing power. This paper documents a project to convert an electron transport simulator (MOCASIN 2.0) to a parallel processing environment. In addition to describing the conversion, the paper presents PPL, a parallel programming version of C running on a Sequent multiprocessor system. In timing tests, models that simulated the movement of 2,000 particles for 100 time steps were executed on ten processors, with a parallel efficiency of over 97%
Transport and Non-Invasive Position Detection of Electron Beams from Laser-Plasma Accelerators
International Nuclear Information System (INIS)
Osterhoff, Jens; Sokollik, Thomas; Nakamura, Kei; Bakeman, Michael; Weingartner, R.; Gonsalves, Anthony; Shiraishi, Satomi; Lin, Chen; vanTilborg, Jeroen; Geddes, Cameron; Schroeder, Carl; Esarey, Eric; Toth, Csaba; DeSantis, Stefano; Byrd, John; Gruner, F.; Leemans, Wim
2011-01-01
The controlled imaging and transport of ultra-relativistic electrons from laser-plasma accelerators is of crucial importance to further use of these beams, e.g. in high peak-brightness light sources. We present our plans to realize beam transport with miniature permanent quadrupole magnets from the electron source through our THUNDER undulator. Simulation results demonstrate the importance of beam imaging by investigating the generated XUV-photon flux. In addition, first experimental findings of utilizing cavity-based monitors for non-invasive beam-position measurements in a noisy electromagnetic laser-plasma environment are discussed.
International Nuclear Information System (INIS)
Villegas, D.
2010-01-01
Understanding impurity transport is a key to an optimal regime for a future fusion device. In this thesis, the theoretical and experimental influence of the electron temperature gradient R/L Te on heavy impurity transport is analyzed both in Tore Supra and ASDEX Upgrade. The electron temperature profile is modified locally by heating the plasma with little ECRH power deposited at two different radii. Experimental results have been obtained with the impurity transport code (ITC) which has been completed with a genetic algorithm allowing to determine the transport coefficient profiles with more accuracy. Transport coefficient profiles obtained by a quasilinear gyrokinetic code named QuaLiKiz are consistent with the experimental ones despite experimental uncertainties on gradients. In the core dominated by electron modes, the lower R/L Te the lower the nickel diffusion coefficient. The latter tends linearly to the neoclassical level when the instability threshold is approached. The experimental threshold is in agreement with the one computed by QuaLiKiz. Further out, where the plasma is dominated by ITG, which are independent of R/L Te , both experimental and simulated results show no modification in the diffusion coefficient profile. Furthermore, the convection velocity profile is not modified. This is attributed to a very small contribution of the thermodiffusion (1/Z dependence) in the total convection. On ASDEX, the preliminary results, very different from the Tore Supra ones, show a internal transport barrier for impurities located at the same radius as the strong ECRH power deposit. (author) [fr
Probing the electronic transport on the reconstructed Au/Ge(001 surface
Directory of Open Access Journals (Sweden)
Franciszek Krok
2014-09-01
Full Text Available By using scanning tunnelling potentiometry we characterized the lateral variation of the electrochemical potential µec on the gold-induced Ge(001-c(8 × 2-Au surface reconstruction while a lateral current flows through the sample. On the reconstruction and across domain boundaries we find that µec shows a constant gradient as a function of the position between the contacts. In addition, nanoscale Au clusters on the surface do not show an electronic coupling to the gold-induced surface reconstruction. In combination with high resolution scanning electron microscopy and transmission electron microscopy, we conclude that an additional transport channel buried about 2 nm underneath the surface represents a major transport channel for electrons.
ZZ ENDLIB, Coupled Electron and Photon Transport Library in ENDL Format
International Nuclear Information System (INIS)
2002-01-01
Description of program or function: The LLNL Evaluated Nuclear Data Library has existed since 1958 in a succession of forms and formats. The present form is as a machine-independent character file format and contains data for the evaluated atomic relaxation data library (EADL), the evaluated photon interaction data library (EPDL), and the evaluated electron interaction data library (EEDL). The purpose of these libraries is to furnish data for coupled electron-photon transport calculations. In order to perform coupled photon-electron transport calculations, all three libraries are required. The UCRL-ID-117796 report included in the documentation for this package provides information on the contents and formats for all three libraries, which are included in this package. All of these libraries span atomic numbers, Z, from 1 to 100. Additionally the electron and photon interaction libraries cover the incident particle energy range from 10 eV to 100 GeV
Energy Technology Data Exchange (ETDEWEB)
Martínez-Orozco, J.C. [Unidad Académica de Física. Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060. Zacatecas, Zac. (Mexico); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)
2014-11-01
The conduction band states of GaAs-based vertically coupled double triangular quantum dots in two dimensions are investigated within the effective mass and parabolic approximation, using a diagonalization procedure to solve the corresponding Schrödinger-like equation. The effect of an externally applied static electric field is included in the calculation, and the variation of the lowest confined energy levels as a result of the change of the field strength is reported for different geometrical setups. The linear and nonlinear optical absorptions and the relative change of the refractive index, associated with the energy transition between the ground and the first excited state in the system, are studied as a function of the incident light frequency for distinct configurations of inter-dot distance and electric field intensities. The blueshift of the resonant absorption peaks is detected as a consequence of the increment in the field intensity, whereas the opposite effect is obtained from the increase of inter-dot vertical distance. It is also shown that for large enough values of the electric field there is a quenching of the optical absorption due to field-induced change of symmetry of the first excited state wavefunction, in the case of triangular dots of equal shape and size.
Guasp, J.; Pastor, I.; Álvarez-Estrada, R. F.; Castejón, F.
2015-02-01
Analytical results obtained recently of the ab-initio classical incoherent Thomson Scattering (TS) spectrum from a single-electron (Alvarez-Estrada et al 2012 Phys. Plasmas 19 062302) have been numerically implemented in a paralelized code to efficiently compute the TS emission from a given electron distribution function, irrespective of its characteristics and/or the intensity of the incoming radiation. These analytical results display certain differences, when compared with other authors, in the general case of incoming linearly and circularly polarized radiation and electrons with arbitrary initial directions. We regard such discrepancies and the ubiquitous interest in TS as motivations for this work. Here, we implement some analytical advances (like generalized Bessel functions for incoming linearly polarized radiation) in TS. The bulk of this work reports on the efficient computation of TS spectra (based upon our analytical approach), for an electron population having an essentially arbitrary distribution function and for both incoming linearly and circularly polarized radiation. A detailed comparison between the present approach and a previous Monte Carlo one (Pastor et al 2011 Nuclear Fusion 51 043011), dealing with the ab-initio computation of TS spectra, is reported. Both approaches are shown to fully agree with each other. As key computational improvements, the analytical technique yields a × 30 to × 100 gain in computation time and is a very flexible tool to compute the scattered spectrum and eventually the scattered electromagnetic fields in the time domain. The latter are computed explicitly here for the first time, as far as we know. Scaling laws for the power integrated over frequency versus initial kinetic energy are studied for the case of isotropic and monoenergetic electron distribution functions and their potential application as diagnostic tools for high-energy populations is briefly discussed. Finally, we discuss the application of these
Asymmetric electron and hole transport in a high-mobility n-type conjugated polymer
Wetzelaer, Gert-Jan A. H.; Kuik, Martijn; Olivier, Yoann; Lemaur, Vincent; Cornil, Jerome; Fabiano, Simone; Loi, Maria Antonietta; Blom, Paul W. M.; Cornil, Jérôme
2012-01-01
Electron-and hole-transport properties of the n-type copolymer poly{[N, N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-dithiophene)} [P(NDI2OD-T2), PolyeraActivInk (TM) N2200] are investigated. Electron- and hole-only devices with Ohmic contacts are
Zeeman splitting spin filter in a single quantum dot electron transport with Coulomb blockade effect
Lai, Wenxi
2014-01-01
Electron spin filter induced by Zeeman splitting in a few-electron quantum dot coupled to two normal electrodes is studied considering Coulomb blockade effect. Based on the Anderson model and Liouville-von Neumann equation, equation of motion of the system is derived and analytical solutions are achieved. Transport windows for perfectly polarized current, partially polarized current and non-polarized current induced by the Zeeman splitting energy and Coulomb blockade potential are exploited. ...
Diffusive transport of energetic electrons in the solar corona: X-ray and radio diagnostics
Musset, S.; Kontar, E.; Vilmer, N.
2017-12-01
Solar flares are associated with efficient particule acceleration. Energetic electrons are diagnosed through X-ray and radio emissions produced as they interact in the solar atmosphere. Particle transport from the acceleration region to the emission sites has a crucial impact on the interpretation of particle emissions in the context of acceleration models, and remains one of the challenging topics in the field of high energy solar physics. In order to address the transport of flare accelerated electrons in the low corona, we used the imaging spectroscopy capabilities of the RHESSI spacecraft to analyze X-ray emissions during the 2004 May 21 flare. We show that non-thermal energetic electrons are trapped in the coronal part of the flaring loop. In the hypothesis of turbulent pitch-angle scattering of energetic electrons (Kontar et al, 2014), diffusive transport of energetic electrons can lead to a confinement of accelerated electrons in the coronal part of the loop. We show that this model can explain the X-ray observations with a scattering mean free path of the order of 108 cm, much smaller than the length of the whole loop. Such results are compared to the observation of the gyrosynchrotron emission of the same flare (Kuznetsov et al, 2015). The diffusive transport model can explain the radio observations with a scattering mean free path of the order or 107 cm. The presented combination of X-ray and radio diagnostics during a flare leads to the first estimate of the energy dependence of the scattering mean free path of energetic electrons in the low corona. This result is comparable with studies of the energy dependence of the scattering mean free path of electrons in the interplanetary medium.
Non-steady-state transport of superthermal electrons in the plasmasphere
Energy Technology Data Exchange (ETDEWEB)
Khazanov, G.V.; Liemohn, M.W.; Gombosi, T.I.; Nagy, A.F. (Univ. of Michigan, Ann Arbor, MI (United States))
1993-12-23
Numerical solutions to the time-dependent kinetic equation, which describes the transport of superthermal electrons in the plasmasphere between the two conjugate ionospheres, are presented. The model calculates the distribution function as a function of time, field-aligned distance, energy, and pitch-angle. The processes of refilling, depleting, and establishing steady-state conditions of superthermal electrons in the plasmasphere are discussed. 10 refs., 6 figs.
Hong, Yi-Guo; Gu, Ji-Dong
2010-01-01
Azo dyes are toxic, highly persistent, and ubiquitously distributed in the environments. The large-scale production and application of azo dyes result in serious environmental pollution of water and sediments. Bacterial azo reduction is an important process for removing this group of contaminants. Recent advances in this area of research reveal that azo reduction by Shewanella strains is coupled to the oxidation of electron donors and linked to the electron transport and energy conservation i...
International Nuclear Information System (INIS)
Xia Caijuan; Fang Changfeng; Zhao Peng; Xie Shijie; Liu Desheng
2009-01-01
By applying nonequilibrium Green's function formalism combined with first-principles density functional theory, we investigate effect of torsion angle on electronic transport properties of 4,4 ' -biphenyl molecule connected with different anchoring groups (dithiocarboxylate and thiol group) to Au(111) electrodes. The influence of the HOMO-LUMO gaps and the spatial distributions of molecular orbitals on the quantum transport through the molecular device are discussed. Theoretical results show that the torsion angle plays important role in conducting behavior of molecular devices. By changing the torsion angle between two phenyl rings, namely changing the magnitude of the intermolecular coupling effect, a different transport behavior can be observed in these two systems.
Electromagnetic radiation and nonlinear energy flow in an electron beam-plasma system
Whelan, D. A.; Stenzel, R. L.
1985-01-01
It is shown that the unstable electron-plasma waves of a beam-plasma system can generate electromagnetic radiation in a uniform plasma. The generation mechanism is a scattering of the unstable electron plasma waves off ion-acoustic waves, producing electromagnetic waves whose frequency is near the local plasma frequency. The wave vector and frequency matching conditions of the three-wave mode coupling are experimentally verified. The electromagnetic radiation is observed to be polarized with the electric field parallel to the beam direction, and its source region is shown to be localized to the unstable plasma wave region. The frequency spectrum shows negligible intensity near the second harmonic of the plasma frequency. These results suggest that the observed electromagnetic radiation of type III solar bursts may be generated near the local plasma frequency and observed downstream where the wave frequency is near the harmonic of the plasma frequency.
Relativistic electron transport in wire and foil targets driven by intense short pulse lasers
Mason, R. J.; Stephens, R. B.; Wei, M.; Freeman, R. R.; Hill, J.; van Woerkom, L. D.
2006-10-01
We model intense laser driven electron transport in wires and foils with the new implicit hybrid code e-PLAS. We focus on background plasma heating for Fast Ignitor applications. The model tracks collisional relativistic PIC electrons undergoing scatter and drag in a background plasma of colliding cold electron and ion Eulerian fluids. Application to 10 μm diameter, 250 μm long, fully ionized carbon wires with an attached cone [Kodama et al. Nature 432 1005 (2004)], exposed to 1 ps, 10^19 W/cm^2 pulses in a 30 μm centered spot, directly calculates resistive Joule heating of the background electrons in the wire to 1.7 KeV. 150 MG magnetic fields arise at the wire surfaces corresponding to hot electron flow outside the wire and a return electron flow just within it. Shorter wires (25 μm) exhibit hot electron recycling. Preliminary simulations indicate that reduction of the cone to a 30 μm diameter nail head produces little change in these results. We also report on tapered wires, wires attached to foils, and the modifying effects of pre-plasma on electron transport into the foils.
Non-linear and stimulated effects in laser-free electrons interaction
International Nuclear Information System (INIS)
Kupersztych, Joseph.
1977-11-01
A new method of calculating interaction processes between free particles and the strong field of an arbitrary plane electromagnetic wave is presented. To construct the method, the electron behavior is examined by investigating the most general space-time symmetry properties of the field. The classical evolution operator is shown to describe both the evolution of the electron and the evolution of its spin in the external field. The quantum evolution operator allows one to define a representation well adapted to the calculation of scattering processes that occur in a laser beam. The nonrelativistic and ultra-relativistic limits of that representation are obtained by means of two unitary transformations which enable the Volkov states to be put exactly in two-component forms. The physical meaning of those transformations is shown to be connected to the motion of the electron spin (rigorously described by the Bargmann-Michel-Telegdi equation) and to the motion of its helicity in the wave. The method is used to calculate completely the relativistic cross-sections of the stimulated Bremsstrahlung and multiphoton inverse Bremsstrahlung processes. This last process is also investigated numerically and a saturation effect at high flux is exhibited [fr
Directory of Open Access Journals (Sweden)
H Rabani
2015-07-01
Full Text Available In this paper, we study the electronic conductance of molecular nanowires by considering the electron hopping between the first and second neighbors with the help Green’s function method at the tight-binding approach. We investigate three types of structures including linear uniform and periodic chains as well as poly(p-phenylene molecule which are embedded between two semi-infinite metallic leads. The results show that in the second neighbor approximation, the resonance, anti-resonance and Fano phenomena occur in the conductance spectra of these structures. Moreover, a new gap is observed at edge of the lead energy band wich its width depends on the value of the electron hopping energy between the second neighbors. In the systems including intrinsic gap, this hopping energy shifts the gap in the energy spectra.
Diffusive Transport of Several Hundred keV Electrons in the Earth's Slot Region
Ma, Q.; Li, W.; Thorne, R. M.; Bortnik, J.; Reeves, G. D.; Spence, H. E.; Turner, D. L.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Baker, D. N.
2017-10-01
We investigate the gradual diffusion of energetic electrons from the inner edge of the outer radiation belt into the slot region. The Van Allen Probes observed slow inward diffusion and decay of 200-600 keV electrons following the intense geomagnetic storm that occurred on 17 March 2013. During the 10 day nondisturbed period following the storm, the peak of electron fluxes gradually moved from L 2.7 to L 2.4, and the flux levels decreased by a factor of 2-4 depending on the electron energy. We simulated the radial intrusion and decay of electrons using a three-dimensional diffusion code, which reproduced the energy-dependent transport of electrons from 100 keV to 1 MeV in the slot region. At energies of 100-200 keV, the electrons experience fast transport across the slot region due to the dominance of radial diffusion; at energies of 200-600 keV, the electrons gradually diffuse and decay in the slot region due to the comparable rate of radial diffusion and pitch angle scattering by plasmaspheric hiss; at energies of E > 700 keV, the electrons stopped diffusing near the inner edge of outer radiation belt due to the dominant pitch angle scattering loss. In addition to plasmaspheric hiss, magnetosonic waves and VLF transmitters can cause the loss of high pitch angle electrons, relaxing the sharp "top-hat" shaped pitch angle distributions created by plasmaspheric hiss. Our simulation indicates the importance of balance between radial diffusion and loss through pitch angle scattering in forming the diffusive intrusion of energetic electrons across the slot region.
Diffusive transport of several hundred keV electrons in the Earth's slot region
Ma, Q.; Li, W.; Thorne, R. M.; Bortnik, J.
2017-12-01
We investigate the gradual diffusion of energetic electrons from the inner edge of the outer radiation belt into the slot region. The Van Allen Probes observed slow inward diffusion and decay of 200-600 keV electrons following the intense geomagnetic storm that occurred on 17 March 2013. During the 10-day non-disturbed period following the storm, the peak of electron fluxes gradually moved from L 2.7 to L 2.4, and the flux levels decreased by a factor of 2-4 depending on the electron energy. We simulated the radial intrusion and decay of electrons using a 3-dimentional diffusion code, which reproduced the energy-dependent transport of electrons from 100 keV to 1 MeV in the slot region. At energies of 100-200 keV, the electrons experience fast transport across the slot region due to the dominance of radial diffusion; at energies of 200-600 keV, the electrons gradually diffuse and decay in the slot region due to the comparable radial diffusion rate and pitch angle scattering rate by plasmaspheric hiss; at energies of E > 700 keV, the electrons stopped diffusing near the inner edge of outer radiation belt due to the dominant pitch angle scattering loss. In addition to plasmaspheric hiss, magnetosonic waves and VLF waves can cause the loss of high pitch angle electrons, relaxing the sharp `top-hat' shaped pitch angle distributions created by plasmaspheric hiss. Our simulation indicates the importance of radial diffusion and pitch angle scattering in forming the diffusive intrusion of energetic electrons across the slot region.
Energy Technology Data Exchange (ETDEWEB)
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 {beta} or the normalized Larmor radius, {rho}{sub *}. 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 {beta} and {rho}{sub *}. 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 Possibilities of Installing Electronic CMR Waybill in Road Transport Sector
Directory of Open Access Journals (Sweden)
Arvydas Baublys
2016-02-01
Full Text Available In the article opportunities of changing paper CMR waybill into electronic are analysed, whereas the paper CMR waybill does not guarantee operational information exchange between participants of logistics chain components in road transport. Due to this reason use ofelectronic CMR waybill becomes more and more important. According to researches done by article authors, the article submitted the limitations of paper CMR waybill, benefits of electronic CMR waybill, concept model of implementing electronic CMR waybill and application possibilities of supply chain components.
Effect of increasing length on the electronic transport of an armchair graphene nano-ribbons
Directory of Open Access Journals (Sweden)
Sh Aghamiri Esfahani
2015-12-01
Full Text Available In this research, we have investigated the effect of increasing length on the electronic transport of an armchair graphene nano-ribbons with nitrogen atom impurity and without impurity. The semi-infinite, one-dimensional molecular systems are connected to two electrodes and the electron-electron interaction is ignored. The system is described by a simple tight binding model. All calculations are based on the Green's function and Landauer–Buttiker approach, and the electrodes are described in a wide band approximation.
The effect of non-uniformities on the measured transport parameters of electron swarms in hydrogen
International Nuclear Information System (INIS)
Blevin, H.A.; Fletcher, J.; Hunter, S.R.
1978-01-01
Measurements of transport parameters of pulsed electron swarms moving through a low-pressure gas by observation of the photon flux resulting from electron-molecule collisions have been recently reported by Blevin et al. (J. Phys. D., 9:465, 471 and 1671 (1976)). One of the possible sources of error in this kind of experiment is the variation of mean electron energy through the swarm. This effect is considered here along with the resulting variation of ionisation and excitation frequency through the swarm. The validity of the experimental method is considered in the light of the above factors. (author)