| 1. |
- Aaltonen, T., et al.
(författare)
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Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode
- 2010
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:6, s. 061802-
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Tidskriftsartikel (refereegranskat)abstract
- We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W+W-. The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(-1) of p (p) over bar collisions at root s = 1.96 TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162-166 GeV at the 95% C.L.
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| 2. |
- Buyanova, M., et al.
(författare)
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Influence of secondary emission yield on the saturation properties of multipactor discharges between two parallel metal plates
- 2010
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 17:4, s. 043504 -
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Tidskriftsartikel (refereegranskat)abstract
- A detailed numerical simulation analysis is made of the saturation stage of multipactor discharges between two infinite parallel metal plates in vacuum exposed to a rf voltage. The main physical effect causing saturation of the multipactor discharge is increased space charge, as the electron density becomes large. It is found that the properties of the saturation stage depend crucially on the value of the secondary emission yield of the metal surfaces. Below a certain threshold value, the discharge has a two-sided character, but at this threshold the discharge makes an abrupt transition into two decoupled single-sided multipactor discharges containing significantly increased electron densities. The result of the numerical simulations gives a good picture of the saturation properties of the multipactor discharge and is also supplemented by an approximate analytical investigation that highlights and explains the characteristic properties of the observed saturation behavior.
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| 3. |
- Kossyi, I.A., et al.
(författare)
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Electrical breakdown in space-borne microwave equipment
- 2010
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Ingår i: Europhysics News. - 1432-1092 .- 0531-7479. ; 41:6
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Tidskriftsartikel (refereegranskat)abstract
- An experimental and numerical investigation is made of multipactor discharges in a coaxial waveguide. Particular attention is given to the determination of the multipactor threshold and the distribution of the impact energy of the electrons. Simulations are carried out for different parameters of the secondary emission coefficient of the electrode surfaces. This makes it possible to determine these parameters through a comparison between the numerical and experimental results. The comparison also shows that the observed multipactor is mainly of polyphase (non-resonant) nature and represents a mixture of single- and double-surface multipactor discharges.
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| 4. |
- Kossyi, I.A., et al.
(författare)
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Experimental and numerical investigation of multipactor discharges in a coaxial waveguide
- 2010
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 43:34
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Tidskriftsartikel (refereegranskat)abstract
- An experimental and numerical investigation is made of multipactor discharges in a coaxial waveguide. Particular attention is given to the determination of the multipactor threshold and the distribution of the impact energy of the electrons. Simulations are carried out for different parameters of the secondary emission coefficient of the electrode surfaces. This makes it possible to determine these parameters through a comparison between the numerical and experimental results. The comparison also shows that the observed multipactor is mainly of polyphase (non-resonant) nature and represents a mixture of single- and double-surface multipactor discharges.
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| 5. |
- Rasch, Joel, 1982, et al.
(författare)
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Microwave multipactor breakdown between two cylinders
- 2010
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 38:8, s. 1997 - 2005
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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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| 6. |
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| 7. |
- Rasch, Joel, 1982, et al.
(författare)
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On the microwave breakdown stability of a spherical hot spot in air
- 2010
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 43:32
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Tidskriftsartikel (refereegranskat)abstract
- An analysis is made of the basic physical conditions under which a small local microwave-induced breakdown region in a gas may develop to extended 'global' breakdown. The analysis describes the different nonlinear stages of the microwave breakdown process. In the first stage, the increasing breakdown plasma density suppresses the electric field in the breakdown region to reach a quasi-stationary state with constant electron density. The subsequent heating of the gas due to absorption of microwave power in the breakdown plasma is then analysed and the corresponding steady state for the thermal evolution is found including the temperature dependence of the breakdown electric field. The stability properties of the stationary state are examined and it is found that there exists a critical (unstable) radius of the initial breakdown plasma region such that initial regions smaller than this critical dimension will shrink to ultimately vanish whereas plasma regions larger than the critical dimension will grow indefinitely and transform the local breakdown region into full scale 'global' breakdown. The practical implication of this model is to give an order of magnitude estimate for the critical size of hot spots, regions of enhanced field and intensified heating in rf systems.
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| 8. |
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| 9. |
- Semenov, V. E., et al.
(författare)
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Simulations of multipactor in circular waveguides
- 2010
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 17:12
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Tidskriftsartikel (refereegranskat)abstract
- Detailed numerical simulations have been done to investigate the properties of multipactorbreakdown in circular waveguides operating in the propagating fundamental TE11 mode. Mainattention has been given to a comparison between the two fundamental cases corresponding to linearand circular polarizations, respectively, of the propagating electromagnetic wave. It is found thatcircular polarization is considerably more susceptible to multipactor than linear polarization. Thereason for this difference is clarified by a comprehensive study of the electron motion in thewaveguide.
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