| 51. |
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| 52. |
- Rasch, Joel, 1982, et al.
(författare)
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Simulations of Multipactor Breakdown Between Two Cylinders
- 2011
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Ingår i: IEEE Transactions on Plasma Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0093-3813 .- 1939-9375. ; 39:9, s. 1786-1794
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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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| 53. |
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| 54. |
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| 55. |
- 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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| 56. |
- Semenov, V. E., et al.
(författare)
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General Study of Multipactor Between Curved Metal Surfaces
- 2014
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 42:3, s. 721-728
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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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| 57. |
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| 58. |
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| 59. |
- 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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| 60. |
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