| 1. |
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| 2. |
- Lloyd, B., et al.
(författare)
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Overview of physics results from MAST
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9, s. 094013 (paper no.)-
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Tidskriftsartikel (refereegranskat)abstract
- Major developments on the Mega Amp Spherical Tokamak (MAST) have enabled important advances in support of ITER and the physics basis of a spherical tokamak (ST) based component test facility (CTF), as well as providing new insight into underlying tokamak physics. For example, L-H transition studies benefit from high spatial and temporal resolution measurements of pedestal profile evolution (temperature, density and radial electric field) and in support of pedestal stability studies the edge current density profile has been inferred from motional Stark effect measurements. The influence of the q-profile and E x B flow shear on transport has been studied in MAST and equilibrium flow shear has been included in gyro-kinetic codes, improving comparisons with the experimental data. H-modes exhibit a weaker q and stronger collisionality dependence of heat diffusivity than implied by IPB98(gamma, 2) scaling, which may have important implications for the design of an ST-based CTF. ELM mitigation, an important issue for ITER, has been demonstrated by applying resonant magnetic perturbations (RMPs) using both internal and external coils, but full stabilization of type-I ELMs has not been observed. Modelling shows the importance of including the plasma response to the RMP fields. MAST plasmas with q > 1 and weak central magnetic shear regularly exhibit a long-lived saturated ideal internal mode. Measured plasma braking in the presence of this mode compares well with neo-classical toroidal viscosity theory. In support of basic physics understanding, high resolution Thomson scattering measurements are providing new insight into sawtooth crash dynamics and neo-classical tearing mode critical island widths. Retarding field analyser measurements show elevated ion temperatures in the scrape-off layer of L-mode plasmas and, in the presence of type-I ELMs, ions with energy greater than 500 eV are detected 20 cm outside the separatrix. Disruption mitigation by massive gas injection has reduced divertor heat loads by up to 70%.
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| 3. |
- Sharapov, S.E., et al.
(författare)
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Energetic particle instabilities in fusion plasmas
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104022-
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Tidskriftsartikel (refereegranskat)abstract
- Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfvén instabilities and modelling tools developed world-wide, and discusses progress in interpreting the observed phenomena. A multi-machine comparison is presented giving information on the performance of both diagnostics and modelling tools for different plasma conditions outlining expectations for ITER based on our present knowledge.
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| 4. |
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| 5. |
- Anderson, D., et al.
(författare)
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A variational approach to spherical aberrations in the thermal-wave model for beam dynamics in charged particle accelerators
- 1998
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Ingår i: Physica Scripta. - : Institute of Physics Publishing. - 0031-8949 .- 1402-4896. ; 58:6, s. 608-612
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Tidskriftsartikel (refereegranskat)abstract
- A direct variational approach involving trial functions and Ritz optimization, which has previously been found very useful in nonlinear optics, is applied to analyze the effects of spherical aberrations on the focusing properties of charged particle beams in particle colliders. As compared to conventional perturbation theory, the variational approach provides a simple and physically clear analysis. Explicit expressions are given for the transverse particle beam density, the spot size, and the luminosity reduction factor at the interaction point, in good agreement with the perturbative results.
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| 6. |
- Anderson, D., et al.
(författare)
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Collapse of optical vacuum pulses due to QED nonlinearities
- 2002
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Ingår i: Nonlinear Guided Waves and Their Applications, 1–4 September 2002, Stresa, Italy. - : Optics Info Base, Optical Society of America. - 1557527237
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Due to quantum electrodynamical (QED) effects there are nonlinear corrections to Maxwell's equations in vacuum. We show that stationary two-dimensional light bullets can form, which are unstable and exhibit, the possibility of self-focusing collapse.
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| 7. |
- Dimitrevski, K., et al.
(författare)
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Analysis of stable self-trapping of laser beams in cubic-quintic nonlinear media
- 1998
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Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 248:5-6, s. 369-376
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Tidskriftsartikel (refereegranskat)abstract
- A numerical and analytical analysis of two-dimensional laser beam propagation in cubic-quintic nonlinear optical media demonstrates the existence of stable stationary radially symmetric modes. By means of a variational method, involving super-Gaussian trial functions and Ritz optimization, approximate stationary solutions are obtained, showing very good agreement with numerical results, even in the strongly non-linear, almost saturated, regime. The stability of the stationary modes are verified by analytical analysis and by direct numerical simulations.
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| 8. |
- Ding, R., et al.
(författare)
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Gold-modified paper as microfluidic substrates with reduced biofouling in potentiometric ion sensing
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 344
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Tidskriftsartikel (refereegranskat)abstract
- Microfluidic sampling media based on paper and its modifications with either gold nanoparticles or sputtered gold were evaluated for potentiometric determination of Na+, K+, and Cl– ions in clinically relevant samples. The measurements were conducted in comparison to other commonly considered microfluidic substrates, i.e. sponge, polyester textile, and polyamide textile. Ion determination was done by using solid-contact ion-selective electrodes based on plasticized PVC membranes for Na+, K+, and Cl– ions and utilizing PEDOT(PSS) or PEDOT(Cl) as the ion-to-electron transducer. The solid-contact ion-selective electrodes and a solid-state reference electrode were placed directly on the substrate into which the sample solution was wicked. Transport of bovine serum albumin (BSA) through the paper substrate was studied by ellipsometry. Modification of the paper substrates by gold nanoparticles (AuNPs) was found to slow down the transport of BSA through the paper, when compared with unmodified paper substrates and when compared with all the other alternative sampling matrices studied. The retention of BSA obtained with AuNP-modified paper substrates significantly improved the accuracy of the potentiometric ion determinations in sweat, saliva, artificial tears, and artificial serum. The potentiometric results were validated by inductively coupled plasma optical emission spectrometry (ICP-OES) and ion chromatography (IC). The study indicates that modification of paper by AuNPs is a feasible approach to reduce biofouling of sensors that are used in the paper-based analysis of clinically relevant samples. © 2021 Elsevier B.V.
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| 9. |
- Helczynski, L., et al.
(författare)
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Cross Phase Modulation Induced Pulse Splitting - The Optical Axe
- 2000
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Ingår i: Physica scripta. T. - 0281-1847. ; 84, s. 81-84
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Tidskriftsartikel (refereegranskat)abstract
- An analytical as well as numerical analysis is made of the dynamics induced on a weak signal wave pulse by a co-propagating strong pump wave pulse in a nonlinear Kerr medium. Emphasis is given to the situation where the group velocity dispersion and the non-linearity of the signal pulse have opposite signs. In this defocusing situation, it is demonstrated that the pump splits the signal pulse into two frequency shifted pulse fragments which separate in time, asymptotically with constant separation velocity. Explicit analytical predictions for the velocity of separation are obtained and corroborated by numerical simulations.
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| 10. |
- Malomed, B. A., et al.
(författare)
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Decay of parametric solitons in a lossy medium with quadratic nonlinearity
- 1996
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Ingår i: Pure and Applied Optics (Print edition) (United Kingdom). - : IOP Publishing. - 0963-9659. ; 5:6, s. 941-946
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Tidskriftsartikel (refereegranskat)abstract
- An investigation is made into the evolution of two-wave solitons in a second-haimonic-generation system under the action of weak dissipation. Using the balance equation for the soliton energy and a previously developed variational approximation for its shape, a general evolutional equation is derived for the soliton parameters. The equation is solved explicitly for the asymptotic stage of the evolution
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| 11. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Compression of optical solitons by conversion of nonlinear modes
- 1995
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 12:6, s. 1110-1116
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Tidskriftsartikel (refereegranskat)abstract
- One can transform an optical pulse containing higher-order soliton modes and/or radiation modes into a compressed almost ideal single-soliton pulse by passing it through an initial adaptive fiber of suitably chosen length and dispersion. Analytical approximations, in good agreement with numerical simulations, are found for the optimal values of the length and the dispersion of the adaptive fiber. The technique is applied to the case of nonadiabatically amplified soliton pulses, for which the transformation is shown to result in efficiently compressed soliton pulses.
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| 12. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Compression of optical solitons by conversion of nonlinear modes
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- One can transform an optical pulse containing higher-order soliton modes and/or radiation modes into a compressed almost ideal single-soliton pulse by passing it through an initial adaptive fiber of suitably chosen length and dispersion. Analytical approximations, in good agreement with numerical simulations, are found for the optimal values of the length and the dispersion of the adaptive fiber. The technique is applied to the case of nonadiabatically amplified soliton pulses, for which the transformation is shown to result in efficiently compressed soliton pulses.
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| 13. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Efficient soliton compression by fast adiabatic amplification
- 1996
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Soc of America. - 0740-3224 .- 1520-8540. ; 13:4, s. 687-692
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Tidskriftsartikel (refereegranskat)abstract
- This paper shows the possibility of obtaining fast, but still adiabatic, amplification of soliton pulses by using a rapidly increasing distributed amplification with scale lengths comparable with the characteristic dispersion length. Explicit expressions for the required distribution of this gain and the variation of the pulse width are given, and theoretical predictions have been verified by numerical simulations. The practical implementation of the compression scheme should be possible by using an active fiber with a doping proportional to the required gain distribution. A study was also made of how efficient compression of solitons can be obtained.
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| 14. |
- Quiroga-Teixeiro, M. L., et al.
(författare)
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Efficient soliton compression by fast adiabatic amplification
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- It is shown that a properly tailored, rapidly increasing gain along the distance of propagation in a monomode fiber can provide fast but still adiabatic soliton amplification and therefore high-quality one-soliton compression for fiber lengths even shorter than the characteristic dispersive length. With the variational approach an explicit expression is given for the required variation of the inhomogeneous gain, and its validity is demonstrated by comparison with direct numerical simulations that include the calculation of the pure soliton component. It is also shown by analytical and numerical perturbation analysis that the compression scheme is stable with respect to small deviations from the ideal soliton form and gain variation. Finally, it is demonstrated that efficient soliton compression can also be obtained by cascading of instantaneous optical amplifiers in an intermediate fiber with higher dispersion, where nonlinear mode conversion preserves the soliton character of the amplified pulse. The practical implementation of these compressor schemes is discussed.
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| 15. |
- Anders, Berntson, et al.
(författare)
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Analysis of coherent and incoherent interactions of amplitude shifted solitons in optical fibres
- 1995
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 52:5, s. 544-553
-
Tidskriftsartikel (refereegranskat)abstract
- Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consequtive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak.
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| 16. |
- Anders, Berntson, et al.
(författare)
-
Analysis of coherent and incoherent interactions of amplitude shifted solitons in optical fibres
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Nonlinear interaction between pulses can severely reduce the bit-rate of an optical communication system. One way of reducing this interaction is amplitude shifting of consecutive pulses. In the present work a detailed analytical and numerical investigation is made of the coherent and incoherent interactions between two soliton pulses of unequal amplitudes. For the case of coherent interaction the obtained expressions for the pulse parameters in terms of initial phase and amplitude differences give a clear and explicit prediction of the reduction of the interaction strength for unequal soliton amplitudes. A comparison with numerical simulation results shows good agreement. For the case of incoherent soliton interaction it is found that the dependence of the interaction strength on the amplitude difference is weak.
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| 17. |
- Anders, Berntson, et al.
(författare)
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Self-phase modulation in dispersion compensated optical fibre transmission systems
- 1996
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Ingår i: Optics Communications. - : Elsevier. - 0030-4018 .- 1873-0310. ; 130:1-3, s. 153-162
-
Tidskriftsartikel (refereegranskat)abstract
- An analysis is made of the influence of self-phase modulation on optical fibre communication systems where the chromatic dispersion is compensated for by a dispersion compensation fibre. In particular we derive a simple and useful expression for the optimal fibre length in the presence of nonlinearities.
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| 18. |
- Anderson, D., et al.
(författare)
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A variational approach to nonlinear evolution equations in optics
- 2001
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Ingår i: Pramana (Bangalore). - : Indian Academy of Sciences. - 0304-4289 .- 0973-7111. ; 57:5-6, s. 917-936
-
Tidskriftsartikel (refereegranskat)abstract
- The use of direct variational methods based on Rayleigh-Ritz optimization for finding approximate solutions to various nonlinear evolution equations was presented. The main advantage of the approach is that it provides simple and explicit expressions for physically relevant quantities where exact analytical solutions are not available. It is found that the given method is flexible and can be applied to stationary and dynamical problems.
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| 19. |
- Anderson, D, et al.
(författare)
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Analysis of profile effects on high Q subignited Tokamak fusion plasmas
- 1998
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Ingår i: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; 58:3, s. 256-261
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An analysis is made of the maximum power multiplication factor Q, achievble in subignited Tokamak fusion plasmas where the burn is sustained by feedback controlled auxiliary heating. Using a 1-D model equation for the plasma temperature, simple analytical
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| 20. |
- Anderson, D., et al.
(författare)
-
Exact Schrödinger Solitons in Optical Fibers in the Presence of Space Dependent Damping or Amplification
- 1999
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Ingår i: Physica scripta. T. - 0281-1847. ; 82, s. 42-43
-
Tidskriftsartikel (refereegranskat)abstract
- It is shown that the nonlinear Schrödinger equation describing pulse propagation in optical fibers in the presence of a properly space-tailored damping or amplification is exactly integrable. A simple transformation of variables is given which transforms the inhomogeneous nonlinear Schrödinger equation into the standard form with constant coefficients, thus generating new explicit bright and dark soliton solutions in the cases of anomalous and normal dispersion, respectively.
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| 21. |
- 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-
-
Konferensbidrag (refereegranskat)
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| 22. |
- Anderson, D., et al.
(författare)
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Modulational instabilities within the thermal wave model description of high energy charged particle beam dynamics
- 1999
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Ingår i: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 258:4-6, s. 244-248
-
Tidskriftsartikel (refereegranskat)abstract
- Within the thermal wave model (TWM) description, an investigation was made of the longitudinal instability properties of a coasting high energy charged particle beam, where the interaction between the beam and its surroundings is characterized in terms of a complex impedance. The analysis is shown to correctly reproduce the characteristic features of the coherent instability as obtained previously by conventional techniques based on the Vlasov equation for the beam distribution. The results further validate the TWM approach as a consistent alternative description for analyzing the dynamics of high energy charged particle beams.
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| 23. |
- Anderson, D., et al.
(författare)
-
Self-induced erosion and spectral breaking of high-power microwave pulses
- 2000
-
Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 63:4, s. 329-341
-
Tidskriftsartikel (refereegranskat)abstract
- An analysis is made of the phenomenon of self-induced erosion and spectral breaking of ionizing high-power microwave pulses propagating in a gas. The analysis describes in an analytically explicit and physically clear way the consistent interaction between the microwave pulse and the self-induced breakdown plasma. In particular, it clarifies, both qualitatively and quantitatively, the mechanisms behind the pulse erosion and the spectral breaking phenomenon, i.e. the splitting of the pulse spectrum into a redshifted and a blueshifted peak as observed in numerical simulation results as well as in experiments.
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| 24. |
- Anderson, Dan, 1943, et al.
(författare)
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The optimal journey from A to B
- 2008
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Ingår i: American Journal of Physics. ; 76:9, s. 863-866
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Tidskriftsartikel (refereegranskat)
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| 25. |
- Buyanova, M., et al.
(författare)
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Different saturation regimes of multipactor between parallel metal plates
- 2008
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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 T41, s. 143-
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Konferensbidrag (refereegranskat)
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| 26. |
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| 27. |
- Buyanova, M., et al.
(författare)
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Influence of secondary emission yield on the saturation of two-sided multipactor
- 2008
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Ingår i: MULCOPIM08, 23-26 September 2008, Valencia, Spain, European Space Agency, Nordwijk, The Netherlands, available on CD. ; , s. paper MP5-6
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Konferensbidrag (refereegranskat)
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| 28. |
- 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 -
-
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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| 29. |
- Buyanova, M., et al.
(författare)
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Multi-Phase Regimes of Multipactor Breakdown
- 2005
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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
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Konferensbidrag (refereegranskat)
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| 30. |
- Cattani, F., et al.
(författare)
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Effect of self-phase modulation in chirped-pulse-amplification-like schemes
- 1999
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 16:11, s. 1874-1879
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Tidskriftsartikel (refereegranskat)abstract
- A detailed analytical investigation is made of the effect of nonlinear self-phase modulation in chirped-pulse-amplification-like schemes. It is demonstrated that self-phase modulation in the amplifier between the stretcher and the compressor breaks the dispersive sign symmetry of the configuration. This implies that, although self-phase modulation is usually considered a deleterious effect, different situations are possible, depending on the parameter regimes considered. In particular, the influence of self-phase modulation on the low-intensity wings of the compressed pulse may be more or less deleterious, depending on the dispersive sign combination of the stretcher and the compressor; in certain parameter regimes, it may in fact even enhance the pulse compression.
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| 31. |
- Desaix, Mats, et al.
(författare)
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Nonlinear Schrödinger Solitons with non-zero velocities emerging from real symmetric initial conditions
- 2009
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Konferensbidrag (refereegranskat)abstract
- Solutions of the nonlinear Schrodinger equation for initial conditions in the form of two separated sech-shaped in-phase pulsed,; are analyzed. It is found that; this initial condition, with appropriate amplitude, may give rise to, not; only stationary solitons, but also to symmetrically separating solitons, if the initial distance of separation is large enough. The condition for the generation of a separating soliton pair is derived from the Zakharov-Shabat eigenvalue problem using a variational approach.
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| 32. |
- Desaix, M., et al.
(författare)
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Nonlinear Schrödinger solitons with non-zero velocities emerging from real symmetric initial conditions
- 2008
-
Ingår i: in Proceedings of SIAM Conference on Nonlinear Waves and Coherent Structures, July 21-24, 2008, Rome, Italy, Society for Industrial and Applied Mathematics (SIAM), Philadelphia, PA, USA. ; , s. 51-
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Konferensbidrag (refereegranskat)
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| 33. |
- Desaix, M., et al.
(författare)
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Nonlinear Schrödinger Solitons with non-zero velocities emerging from real symmetric initial conditions
- 2008
-
Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; , s. 299-303
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Solutions of the nonlinear Schrodinger equation for initial conditions in the form of two separated sech-shaped in-phase pulses are analyzed. It is found that this initial condition, with appropriate amplitude, may give rise to, not only stationary solitons, but also to symmetrically separating soli- tons, if the initial distance of separation is large enough. The condition for the generation of a separating soliton pair is derived from the Zakharov-Shabat eigenvalue problem using a variational approach.
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| 34. |
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| 35. |
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| 36. |
- Einarsdottir, Sigrun, et al.
(författare)
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Vaccination against tick-borne encephalitis (TBE) after autologous and allogeneic stem cell transplantation
- 2021
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Ingår i: Vaccine. - : Elsevier BV. - 0264-410X .- 1873-2518. ; 39:7, s. 1035-1038
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Our aim was to assess response and side effects of 4 doses of TBE vaccine to patients (pts) after allo- and autologous stem cell transplantation (SCT). PATIENTS: Included were 104 pts with leukaemia, myeloma and lymphoma, median age 61 yrs. METHODS: Vaccine (FSME-Immun (R)) was given at 9, 10, 12, and 21 months post-transplant. Serum samples were obtained before and after vaccinations. Healthy controls (n = 27) received 3 vaccinations. Assessments of TBE specific IgG antibodies were performed by Enzygnost anti-TBE ELISA test (Siemens, Sweden). Results: Antibody levels (>12 U/mL; "seropositivity") were seen in 77% and 80% of pts after allo- and autoSCT; IgG levels; 89 vs 94 U/mL. Ongoing chronic GvHD and immunosuppression (n = 29) was associated with sero-negativity in the last sample (p = 0.007). All controls (n = 27) developed protective antibody levels. Conclusions: TBE vaccination was safe, and 4 doses starting 9 months post-SCT, induced seropositivity in a vast majority of pts. (C) 2021 Elsevier Ltd. All rights reserved.
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| 37. |
- Jordan, Ulf, 1974, et al.
(författare)
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Microwave breakdown in slots
- 2004
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Ingår i: IEEE Trans. Plasma Science. ; 32, s. 2250-
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Tidskriftsartikel (refereegranskat)
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| 38. |
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| 39. |
- Kossyi, I., et al.
(författare)
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Metal-dielectric interface as a low-threshold microwave discharge initiation in waveguides and in free space
- 2008
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Ingår i: MULCOPIM08, 23-26 September 2008, Valencia, Spain, European Space Agency, Nordwijk, The Netherlands, available on CD. ; , s. paper MP1-3
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Konferensbidrag (refereegranskat)
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| 40. |
- Mader, P., et al.
(författare)
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Experimental validation of fringing field effects for the multipactor phenomenon
- 2012
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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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| 41. |
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| 42. |
- Malomed, B. A., et al.
(författare)
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Spatiotemporal solitons in multidimensional optical media with a quadratic nonlinearity
- 1997
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 56:4, s. 4725-4735
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Tidskriftsartikel (refereegranskat)abstract
- We consider solutions to the second-harmonic generation equations in two- and three-dimensional dispersive media in the form of solitons localized in space and time. As is known, collapse does not take place in these models, which is why the solitons may be stable. The general solution is obtained in an approximate analytical form by means of a variational approach, which also allows the stability of the solutions to be predicted. Then, we directly simulate the two-dimensional case, taking the initial configuration as suggested by the variational approximation. We thus demonstrate that spatiotemporal solitons indeed exist and are stable. Furthermore, they are not, in the general case, equivalent to the previously known cylindrical spatial solitons. Direct simulations generate solitons with some internal oscillations. However, these oscillations neither grow nor do they exhibit any significant radiative damping. Numerical solutions of the stationary version of the equations produce the same solitons in their unperturbed form, i.e., without internal oscillations. Strictly stable solitons exist only if the system has anomalous dispersion at both the fundamental harmonic and second harmonic (SH), including the case of zero dispersion at SH. Quasistationary solitons, decaying extremely slowly into radiation, are found in the presence of weak normal dispersion at the second-harmonic frequency
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| 43. |
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| 44. |
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| 45. |
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| 46. |
- Maslowski, P., et al.
(författare)
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Optical frequency comb spectroscopy for gas metrology and trace gas detection
- 2017
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Ingår i: 2017 Conference on lasers and electro-optics (CLEO). - : IEEE. - 9781943580279 - 9781538620199
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Konferensbidrag (refereegranskat)abstract
- We report recent developments of comb-based broadband absorption spectroscopy. The comb-line resolving approaches and Fourier transform spectroscopy with sub-nominal resolution overcome the frequency resolution limits of conventional techniques. Advantages for various applications will be discussed.
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| 47. |
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| 48. |
- Puech, J., et al.
(författare)
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Summary of Research Activities on Multipactor phenomenon with dielectric materials within INTAS project
- 2005
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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. 161-167
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Konferensbidrag (refereegranskat)
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| 49. |
- Sandquist, P., et al.
(författare)
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Bidirectional tornado modes on the joint european torus
- 2007
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- In discharges on the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] with safety factor q(0)< 1 and high-power ion cyclotron resonance heating (ICRH), monster sawtooth crashes are preceded by frequency sweeping tornado modes in the toroidal Alfven eigenmode frequency range. A suite of equilibrium and spectral magnetohydrodynamical codes is used for explaining the observed evolution of the tornado mode frequency and for identifying temporal evolution of the safety factor inside the q=1 radius just before sawtooth crashes. In some cases, the tornado modes are observed simultaneously with both positive and negative toroidal mode numbers. Hence, a free energy source other than the radial gradient of the energetic ion pressure exciting these modes is sought. The distribution function of the ICRH-accelerated ions is assessed with the SELFO code [J. Hedin , Nucl. Fusion 42, 527 (2002)] and energetic particle drive due to the velocity space anisotropy of ICRH-accelerated ions is considered analytically as the possible source for excitation of bidirectional tornado modes.
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| 50. |
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