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Free electron model
About: Free electron model is a research topic. Over the lifetime, 4678 publications have been published within this topic receiving 103535 citations.
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TL;DR: In this paper, the authors show that a large number of modes with random phases can coexist in practice at any excess of the current over threshold; the energy distribution in the mode spectrum can be described by the quasi-linear theory.
Abstract: According to the general concept of the modern theory of self-oscillatory systems with many degrees of freedom, in free-electron lasers (FELs) with multimode resonators and high-quality (low-emittance) electron beams the increase of the electron current results in a sequence of bifurcations. If the excess of the current over self-excitation threshold is moderate, then the electron beam organizes the ‘cold’ resonator modes into strictly periodic wave structures (supermodes). At a large excess over threshold the self-oscillations become stochastic with a quasi-continuous frequency spectrum. In FELs with broad dispersion of the initial electron velocities (high emittance) a large number of modes with random phases can coexist in practice at any excess of the current over threshold; the energy distribution in the mode spectrum can be described by the quasi-linear theory. If the electrodynamic methods ensure suppression of ali the modes except for the operating one, then in the case of low-quality electron bea...
33 citations
TL;DR: In this article, a lattice model for strongly interacting electrons with the potential to explain the main phenomenology of the strange metal phase in the cuprate high temperature superconductors was proposed.
Abstract: We propose a lattice model for strongly interacting electrons with the potential to explain the main phenomenology of the strange metal phase in the cuprate high temperature superconductors. Our model is motivated by the recently developed "tetrahedron" rank-3 tensor model that mimics much of the physics of the better-known Sachdev-Ye-Kitaev (SYK) model. Our electron model has the following advantageous properties: (1) it only needs one orbital per site on the square lattice; (2) it does not require any quenched random interaction; (3) it has local interactions and respects all the symmetries of the system; (4) the soluble limit of this model has a longitudinal DC resistivity that scales linearly with temperature within a finite temperature window; (5) again the soluble limit of this model has a fermion pairing instability in the infrared, which can lead to either superconductivity or a "pseudogap" phase. The linear$-T$ longitudinal resistivity and the pairing instability originate from the generic scaling feature of the SYK model and the tetrahedron tensor model.
33 citations
TL;DR: In this article, it is shown that by proper stepping up of the ripple magnetic field strength prior to electrostatic wave saturation, the efficiency can be substantially increased along with some bandwidth improvement and shortening of the device length.
Abstract: The electronic conversion efficiency of a free-electron laser using an intense relativistic electron beam in a rippled magnetic field as its active medium is limited mainly by the destruction of the coherent slow space-charge wave through particle trapping and the depletion of the available beam energy. It is shown that by proper stepping up of the ripple magnetic field strength prior to electrostatic wave saturation, the efficiency can be substantially increased along with some bandwidth improvement and shortening of the device length.
33 citations
21 Dec 2001-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this paper, the authors present an analysis of a Smith-Purcell system in which a thin current sheet of electrons moves above a grating surface in the direction perpendicular to the grating grooves.
Abstract: We present an analysis of a Smith–Purcell system in which a thin current sheet of electrons moves above a grating surface in the direction perpendicular to the grating grooves. We develop a consistent theory for evolution of the electromagnetic field and electron distribution in the exponential growth regime starting from the initial electron noise and the incoming amplitude. The dispersion relation for the complex growth rate for this system is a quadratic equation.
33 citations
TL;DR: In this paper, the development of trapped structures in decaying and saturated drift wave turbulence is studied via computer simulation using a two-dimensional electrostatic fluid model, which takes into account the effects of broadening and shifting of the frequency spectrum.
Abstract: The development of trapped structures in decaying and saturated drift wave turbulence is studied via computer simulation. A two‐dimensional electrostatic fluid model is used. The turbulence that evolves in the pure decay runs (i.e., no nonadiabatic electrons) is characterized by tightly bound monopole vortices and a very narrow frequency spectrum. For the studies of saturated turbulence, a new nonadiabatic electron model is introduced, which gives the qualitatively correct response to a coherent trapped structure. This model takes into account the effects of broadening and shifting of the frequency spectrum. These effects are found to be quite important. Trapped structures are observed in many of the saturated simulations, even in the presence of moderately broad frequency spectra. The extent of the trapping varies dramatically, becoming a much stronger effect as the average electric field increases.
33 citations