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Title: Particle-in-cell simulation of multipactor discharge on a dielectric in a parallel-plate waveguide

Abstract

An original 2D3V (two-dimensional in coordinate space and three-dimensional in velocity space) particle-in-cell code has been developed for simulation of multipactor discharge on a dielectric in a parallelplate metal waveguide with allowance for secondary electron emission (SEE) from the dielectric surface and waveguide walls, finite temperature of secondary electrons, electron space charge, and elastic and inelastic scattering of electrons from the dielectric and metal surfaces. The code allows one to simulate all stages of the multipactor discharge, from the onset of the electron avalanche to saturation. It is shown that the threshold for the excitation of a single-surface multipactor on a dielectric placed in a low-profile waveguide with absorbing walls increases as compared to that in the case of an unbounded dielectric surface due to escape of electrons onto the waveguide walls. It is found that, depending on the microwave field amplitude and the SEE characteristics of the waveguide walls, the multipactor may operate in two modes. In the first mode, which takes place at relatively low microwave amplitudes, a single-surface multipactor develops only on the dielectric, the surface of which acquires a positively potential with respect to the waveguide walls. In the second mode, which occurs at sufficiently highmore » microwave intensities, a single-surface multipactor on the dielectric and a two-surface multipactor between the waveguide walls operate simultaneously. In this case, both the dielectric surface and the interwall space acquire a negative potential. It is shown that electron scattering from the dielectric surface and waveguide walls results in the appearance of high-energy tails in the electron distribution function.« less

Authors:
; ;  [1]
  1. Russian Academy of Sciences, Prokhorov General Physics Institute (Russian Federation)
Publication Date:
OSTI Identifier:
22614114
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plasma Physics Reports; Journal Volume: 42; Journal Issue: 6; Other Information: Copyright (c) 2016 Pleiades Publishing, Ltd.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COORDINATES; DIELECTRIC MATERIALS; DISTRIBUTION FUNCTIONS; ELECTRON EMISSION; ELECTRONS; EXCITATION; INELASTIC SCATTERING; METALS; MICROWAVE RADIATION; PLASMA SIMULATION; SPACE CHARGE; SURFACES; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS; WALLS; WAVEGUIDES

Citation Formats

Sakharov, A. S., E-mail: sakharov-as@mail.ru, Ivanov, V. A., and Konyzhev, M. E. Particle-in-cell simulation of multipactor discharge on a dielectric in a parallel-plate waveguide. United States: N. p., 2016. Web. doi:10.1134/S1063780X16060064.
Sakharov, A. S., E-mail: sakharov-as@mail.ru, Ivanov, V. A., & Konyzhev, M. E. Particle-in-cell simulation of multipactor discharge on a dielectric in a parallel-plate waveguide. United States. doi:10.1134/S1063780X16060064.
Sakharov, A. S., E-mail: sakharov-as@mail.ru, Ivanov, V. A., and Konyzhev, M. E. 2016. "Particle-in-cell simulation of multipactor discharge on a dielectric in a parallel-plate waveguide". United States. doi:10.1134/S1063780X16060064.
@article{osti_22614114,
title = {Particle-in-cell simulation of multipactor discharge on a dielectric in a parallel-plate waveguide},
author = {Sakharov, A. S., E-mail: sakharov-as@mail.ru and Ivanov, V. A. and Konyzhev, M. E.},
abstractNote = {An original 2D3V (two-dimensional in coordinate space and three-dimensional in velocity space) particle-in-cell code has been developed for simulation of multipactor discharge on a dielectric in a parallelplate metal waveguide with allowance for secondary electron emission (SEE) from the dielectric surface and waveguide walls, finite temperature of secondary electrons, electron space charge, and elastic and inelastic scattering of electrons from the dielectric and metal surfaces. The code allows one to simulate all stages of the multipactor discharge, from the onset of the electron avalanche to saturation. It is shown that the threshold for the excitation of a single-surface multipactor on a dielectric placed in a low-profile waveguide with absorbing walls increases as compared to that in the case of an unbounded dielectric surface due to escape of electrons onto the waveguide walls. It is found that, depending on the microwave field amplitude and the SEE characteristics of the waveguide walls, the multipactor may operate in two modes. In the first mode, which takes place at relatively low microwave amplitudes, a single-surface multipactor develops only on the dielectric, the surface of which acquires a positively potential with respect to the waveguide walls. In the second mode, which occurs at sufficiently high microwave intensities, a single-surface multipactor on the dielectric and a two-surface multipactor between the waveguide walls operate simultaneously. In this case, both the dielectric surface and the interwall space acquire a negative potential. It is shown that electron scattering from the dielectric surface and waveguide walls results in the appearance of high-energy tails in the electron distribution function.},
doi = {10.1134/S1063780X16060064},
journal = {Plasma Physics Reports},
number = 6,
volume = 42,
place = {United States},
year = 2016,
month = 6
}
  • This paper presents a novel theory for describing the initial stage of a single-surface multipactor discharge on a dielectric surface in the presence of a dc electric field, which returns secondary emitted electrons to the surface. The calculations employ a statistical method based on an exact analytical solution for the probability density of the arrival times of the secondary electrons. A general integral equation determining the steady-state distribution of the emission phases of the secondary electrons and the threshold of the multipactor growth is formulated. A computer program has been developed to implement this theory for realistic secondary yield curvesmore » and arbitrary, nonuniform, distributions for velocities and angles of emitted electrons. Susceptibility diagrams, applicable to a wide range of materials, are obtained in terms of the rf and dc electric fields and are found to be relatively independent of the emission distribution of the electrons.« less
  • Properties of transition radiation generated by charged particle in dielectric plate in a regular waveguide are considered. It is assumed that the particle crosses a waveguide perpendicular to its axis. The field and energy of particle radiatlon and its spectrum are obtained. It was shown that in a certain part of the spectrum the radiation is locked in the plate. (auth)
  • A dielectric loaded parallel plate waveguide sheet electron beam system can be taken as a reliable model for the practical dielectric loaded rectangular waveguide sheet beam system that has a transverse cross section with a large width to height ratio. By using kinetic theory, the dispersion equations for Cerenkov and cyclotron Cerenkov instabilities in the parallel plate waveguide sheet beam system have been obtained rigorously. The dependences of the growth rate of both instabilities on the electric and structural parameters have also been investigated in detail through numerical calculations. It is worthwhile to point out that adopting an electron beammore » with transverse velocity can evidently improve the growth rate of Cerenkov instability, which seems like the case of cyclotron Cerenkov instability.« less
  • The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. Themore » impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high.« less
  • This paper presents a Monte-Carlo model to explain the multipactor discharge and its high-power absorption in a dielectric-loaded accelerating (DLA) structure reported recently [J. G. Power et al., Phys. Rev. Lett. 92, 164801 (2004)]. Susceptibility diagrams are constructed. Dynamic calculations for beam loading and its power absorption by the multipactor discharge are performed. It is found that the fraction of power absorbed by multipactor discharge at saturation is much larger than the case of a simple rf window, and it is sensitive to the incident power, which confirms the prior experimental results. This enhanced power absorption is due to themore » fact that the length of a DLA structure is much larger than the radius of the structure. A resonant condition of a maximum growth region has also been determined numerically and analytically. The difference between the resonant condition and saturation (due to beam loading) is clarified.« less