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Träfflista för sökning "WFRF:(Rakova E.) "

Sökning: WFRF:(Rakova E.)

  • Resultat 1-34 av 34
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1.
  • Mader, P., et al. (författare)
  • Experimental validation of fringing field effects for the multipactor phenomenon
  • 2012
  • Ingår i: 15th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2012, Toulouse, 25-28 June 2012. - 9781467302913
  • Konferensbidrag (refereegranskat)abstract
    • The multipactor effect is a constraining phenomenon in the design of RF components. Due to an increasing number of channels and power levels for multicarrier signals, specific requirements of design must be taken into account in order to prevent the multipactor effect. The current methods of analysis are based on the Hatch and Williams diagrams, which provide the multipaction threshold voltage for a parallel plate geometry as a function of the frequency gap product. However, whereas experimental results have shown good correlation with the theoretical charts for the parallel plate geometry, discrepancies have been found for complex geometries such as irises.
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  • Puech, J., et al. (författare)
  • CNES-Chalmers-IAP-ONERA-XLIM activities in the domain of high RF power breakdown phenomena
  • 2017
  • Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 157
  • Konferensbidrag (refereegranskat)abstract
    • Multipactor breakdown is an important potential failure mechanism in many different microwave devices working under close to vacuum conditions. Applications range from space borne RF equipment to high-power microwave generators. The basic physics involved in the multipactor phenomenon is well known for the case of two infinite pallel plates made of metal. However, most realistic RF device geometries involve inhomogeneous RF electric fields and curved field lines and sometimes also dielectric material. The purpose of this paper is to set up methodologies to determine the Multipactor threshold in such situations.
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  • Semenov, V. E., et al. (författare)
  • Preliminary results on the Multipactor effect prediction in RF components with ferrites
  • 2013
  • Ingår i: 14th IEEE International Vacuum Electronics Conference, IVEC 2013 - Proceedings. - 9781467359757 ; , s. Art. no. 6571019-
  • Konferensbidrag (refereegranskat)abstract
    • This paper deals with the analysis of the Multipactor effect in RF components with ferrites performed through the preliminary measurements of ferrites secondary emission coefficient and the simulations of the effect of a continuous magnetic field on the electron bunch spread. The impact of this effect on the Multipactor threshold was quantified. © 2013 IEEE.
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  • Kossyi, I.A., et al. (författare)
  • Polyphase (non-resonant) multipactor in rectangular waveguides
  • 2008
  • Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 41:6, s. 065203 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • The polyphase multipactor, i.e. the non-resonant form of secondary electron emission rf discharges in vacuum, has been analysed and studied experimentally. The multipactor discharge was observed in an evacuated standard rectangular waveguide through which pulsed high-power microwave radiation in the decimeter wavelength range was transmitted. The power interval in which the two-sided (between the wide walls of the waveguide) multipactor appeared has been determined. It is found that there is a characteristic delay time for the onset of the multipactor breakdown as compared with the time at which the microwave power is applied. The dependence of this delay time on the microwave power has been established. The experimental results are compared with results of numerical simulations which make it possible to estimate the secondary emission properties of the waveguide walls. Reasons for some observed discrepancies between numerical results and experimental data are discussed as well as the nature of the observed multipactor delay.
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  • Rasch, Joel, 1982, et al. (författare)
  • Microwave multipactor breakdown between two cylinders
  • 2010
  • Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 38:8, s. 1997 - 2005
  • Tidskriftsartikel (refereegranskat)abstract
    • An analysis has been made of the microwave breakdownthreshold for multipactor in an open structure comprisingtwo parallel cylinders, approximating, e.g., parts of a helix antenna. The electron motion in the corresponding electromagnetic field is analyzed by separating the motion into a slowly varying drift velocity (driven by the ponderomotive force due to the electric field inhomogeneity) and a rapidly oscillating part (driven bythe oscillating electric field). Furthermore, the curvature of the cylindrical surfaces of emission is shown to give rise to a new effect that implies a loss of electrons. This leads to a more stringent multipactor breakdown condition for the two-wire structure thanfor the classical situation corresponding to the case of two plane parallel infinite plates. The importance of this effect is determined by the ratio of the cylinder radii and the distance between the cylinders, and it is shown that when this ratio is small, multipactor can only occur for surfaces having very large secondary emissioncoefficients. A detailed analysis is also made to determine the lowest voltage between the cylinders at which multipactor becomes possible.
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  • Rasch, Joel, 1982, et al. (författare)
  • Simulations of Multipactor Breakdown Between Two Cylinders
  • 2011
  • Ingår i: IEEE Transactions on Plasma Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0093-3813 .- 1939-9375. ; 39:9, s. 1786-1794
  • Tidskriftsartikel (refereegranskat)abstract
    • Simulations have been performed to determine the multipactor breakdown threshold in a microwave structure composed of two parallel cylinders, chosen to be an approximate model of an open helix microwave antenna system. The electromagnetic field between the cylinders is available in closed analytical form, and a Monte Carlo software has been developed to calculate the 2-D electron trajectories and to simulate the multipactor avalanche in this inhomogeneous electric field for different ratios of cylinder radius and distance of separation between the cylinders. The results are compared with those of a recently published analytical theory and show a qualitatively good agreement. In particular, it is confirmed that, for a given distance between cylinders, there exists a smallest cylinder radius below which no two-sided multipactor breakdown can occur. The basic physical explanation is a loss mechanism for secondary emitted electrons that is caused by the curvature of the cylinder surfaces together with the strong electric field at the surfaces. The results imply that the breakdown threshold in realistic open helix antennas is significantly higher than those predicted using extrapolations based on resonance theory and the classical two parallel plate model.
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15.
  • Semenov, V.E., et al. (författare)
  • Conformal mapping analysis of multipactor breakdown in waveguide irises
  • 2008
  • Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 15:3, s. 033501 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • Multipactor breakdown in a single waveguide iris is analyzed using the quasistatic approximation for the spatial distribution of the rf field in the iris. Based on the conformal mapping approach, an analytical description is given of the rf field structure in the iris. It is shown that in the central part of any iris with a length to height ratio greater than approximately 0.5, the rf field structure is close to that between two parallel plates. The multipactor threshold for the iris is determined mainly by electron losses from the central part of the iris where the losses are due to the tangential component of the emission velocity of secondary electrons. The effective length of the iris central part is determined and an estimate of the multipactor threshold for the iris is found in terms of the conventional parameters: Applied rf voltage, product of rf frequency and iris height, and iris length to height ratio. Numerical simulations are also carried out using the exact analytical description of the quasistatic rf field and taking into account a spread of electron emission velocities.
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16.
  • Semenov, V. E., et al. (författare)
  • General Study of Multipactor Between Curved Metal Surfaces
  • 2014
  • Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 42:3, s. 721-728
  • Tidskriftsartikel (refereegranskat)abstract
    • An analytical study of the electron trajectories between two opposite electrodes having curved surfaces is undertaken for the case when the electron transit time exceeds the RF period. The analysis is based on a statistical approach, which makes it possible to calculate the width of an electron bunch after a number of electron transits taking into account the spread of electron emission velocity, and the spatial nonuniformity of the RF field using the concept of the ponderomotive force. The results are used to estimate the multipactor threshold in terms of a value of the secondary emission yield, which is necessary to balance electron losses. Based on the model, it is predicted that multipactor is impossible inside the realistic configuration of a helix antenna where four electrodes are placed on the same cylindrical surface
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  • Semenov, V. E., et al. (författare)
  • Multipactor breakdown in waveguide irises
  • 2009
  • Ingår i: 2009 IEEE International Vacuum Electronics Conference, IVEC 2009; Rome; Italy; 28 April 2009 through 30 April 2009. - 9781424434992 ; , s. 321-322
  • Konferensbidrag (refereegranskat)abstract
    • A detailed analysis is made in order to establish the multipactor breakdown threshold in wave guide irises. The analysis involves an analytical investigation based on the conformal mapping technique and also extensive numerical simulations. Comparison with recent experimental results shows good agreement. The main goal of the work is to obtain multipactor charts for the iris, i.e. the breakdown voltage as a function of the frequency - gap product, for different height to width ratios of the iris.
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  • Semenov, V. E., et al. (författare)
  • Simple model of the rf noise generated by multipacting electrons
  • 2014
  • Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 47:5
  • Tidskriftsartikel (refereegranskat)abstract
    • A simplified analytical model is developed to predict the spectrum of electric current induced by the multipacting electrons between two parallel electrodes exposed to an rf voltage of fixed amplitude. The model is based on the resonant multipactor theory and makes it possible to calculate the relative spectral amplitudes of electric current at different harmonics and sub-harmonics of the applied rf frequency. The theoretical predictions are confirmed by numerical simulations of multipactor inside a rectangular waveguide. Specifically it is seen that the relative height of the spectral peaks decreases with increasing gap height.
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  • Buyanova, M., et al. (författare)
  • Multi-Phase Regimes of Multipactor Breakdown
  • 2005
  • Ingår i: Proc. 5th International Workshop on Multipactor, Corona and Passive Intermodulation, September 12 – 14, 2005, ESTEC, Noordwijk, The Netherlands, In: Space RF Hardware (MULCOPIM' 2005). ; , s. 135-142
  • Konferensbidrag (refereegranskat)
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27.
  • Semenov, V., et al. (författare)
  • Analytical description of the multipactor inside narrow waveguide iris
  • 2008
  • Ingår i: Proceedings of the 7th International Workshop “Strong microwaves: Sources and Applications, Nizhny Novgorod, Russia, July 27 – Aug. 2, 2008, Institute of Applied Physics, Russian Academy of Sciences. ; :paper T42, s. 144-
  • Konferensbidrag (refereegranskat)
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  • Semenov, V., et al. (författare)
  • Influence of the wave guide cross section on the multipactor threshold
  • 2008
  • Ingår i: Proceedings of the 7th International Workshop “Strong microwaves: Sources and Applications, Nizhny Novgorod, Russia, July 27 – Aug. 2, 2008, Institute of Applied Physics, Russian Academy of Sciences. ; :paper T38, s. 140-
  • Konferensbidrag (refereegranskat)
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  • Semenov, V., et al. (författare)
  • Simulations of multipactor in micro-strip lines
  • 2008
  • Ingår i: MULCOPIM08, 23-26 September 2008, Valencia, Spain, European Space Agency, Nordwijk, The Netherlands, available on CD. ; , s. paper MP1-2
  • Konferensbidrag (refereegranskat)
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  • Semenov, V., et al. (författare)
  • Study of multipactor in waveguide irises
  • 2008
  • Ingår i: MULCOPIM08, 23-26 September 2008, Valencia, Spain, European Space Agency, Nordwijk, The Netherlands, available on CD. ; , s. paper MP-3-3-
  • Konferensbidrag (refereegranskat)
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  • Resultat 1-34 av 34

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