| 1. |
- Anderson, Dan, 1943, et al.
(författare)
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Microwave breakdown in RF devices
- 2006
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Ingår i: 33rd European Physical Society Conference on Plasma Physics, Rome, June 19-23, 2006. ; , s. 429-
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Konferensbidrag (refereegranskat)
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| 2. |
- Semenov, V.E., et al.
(författare)
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Conformal mapping analysis of multipactor breakdown in waveguide irises
- 2008
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 15:3, s. 033501 1-8
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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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| 3. |
- Semenov, V. E., et al.
(författare)
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Multipactor breakdown in waveguide irises
- 2009
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Ingår i: 2009 IEEE International Vacuum Electronics Conference, IVEC 2009; Rome; Italy; 28 April 2009 through 30 April 2009. - 9781424434992 ; , s. 321-322
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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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| 4. |
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| 5. |
- Semenov, V., et al.
(författare)
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Multipactor in Microwave Transmission Systems Using Quadrature Phase-Shift Keying
- 2010
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 38:4, s. 915-922
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Tidskriftsartikel (refereegranskat)abstract
- A numerical simulation analysis is made of the effect of signal transmission using the quadrature phase-shift keying of a constant-amplitude RF carrier wave on the initiation of multipactor breakdown in RF devices operating under close-to-vacuum conditions. It is found that this form of signal modulation has a suppressing effect on the growth of the multipactor electron avalanche that depends on the parameters of the system. However, for technically realistic values of signal and phase-shift frequencies, the effect is found to be small.
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| 6. |
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| 7. |
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| 8. |
- Udiljak, Richard, 1968, et al.
(författare)
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Multipactor in a Waveguide Iris
- 2007
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Ingår i: IEEE Transactions on Plasma Science. ; 35:2, s. 388-395
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Tidskriftsartikel (refereegranskat)
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| 9. |
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| 10. |
- Udiljak, Richard, 1968
(författare)
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Multipactor in low pressure gas and in nonuniform rf field structures
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Resonant electron multiplication in vacuum, multipactor, is analysed for several geometries where the RF electric field is nonuniform. In particular, it is shown that the multipactor behaviour in a coaxial line is both qualitatively and quantitatively different from that observed with the conventionally used simple parallel-plate model. Analytical estimates based on an approximate solution of the non-linear differential equation of motion for the multipacting electrons are supported by extensive particle-in-cell simulations. Furthermore, in a microwave iris the electrons tend to perform a random walk in the axial direction of the waveguide due to the initial velocity distribution. The effects of this phenomenon on the breakdown threshold are analysed. The study shows that the threshold is a function of the height-to-length ratio of the iris and for a fixed value of this ratio, the multipactor susceptibility charts can be generated in the classical engineering units. Using the parallelplate concept, the multipactor threshold in low pressure gases has been analysed using a model for the electron motion that takes into account three important effects of electron-neutral collisions, viz. the friction force, electron thermalisation, and impact ionisation. It is found thatall three effects play important roles, but the degree of influence depends on parameters such as order of resonance and secondary emission properties. In addition, a new method for detection of multipactor is presented. By applying a weak amplitude modulation to the input signal and performing a fast Fourier transform on the detected signal, accurateand unambiguous measurement results can be obtained. It is demonstrated how the method can be used in both single and multicarrier operation.
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