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125 results on '"Farokhi B"'

3. Chaotic particle dynamics in free-electron lasers with coaxial wiggler

Author

Farokhi, B. and Mobarakabadi, S.

Subjects
Physics - Plasma Physics
Abstract

The motion of a relativistic test electron in a free electron laser can be altered significantly by an ideal coaxial wiggler field and uniform axial guide field. I have investigated the group I, group II and group III (the new group that, it is found in coaxial wiggler) orbits and finally have found that those groups become chaotic at sufficiently high beam density and at sufficiently high amplitude of wiggler field. The threshold value of the wiggler amplitude for the onset of chaos is estimated analytically and confirmed by computer simulation for spatial case where self-field effects are negligibly small. It is shown that the electron dynamic is nonintegrable. There is evidence for chaos from numerical calculations of Poincare maps and nonzero Lyaponov exponents using different approaches of Benetin's method which are described and compared. Moreover, it is shown that the particle motion becomes chaotic on a time scale comparable with the beam transit time through a few wiggler periods., Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)

Published
2004

17. Propagational characteristics in a warm hybrid plasmonic waveguide.

Author

Moghadam, M. Mahmodi, Shahmansouri, M., and Farokhi, B.

Subjects
WAVEGUIDES, PLASMONICS, ELECTRICAL conductors, MAXWELL equations, POLARITONS, HYDRODYNAMICS
Abstract

We theoretically analyze the properties of guided modes in a warm planar conductor-gap-dielectric (CGD) system. The latter consists of a high index dielectric, separated from a warm metallic plasma with a low index nano-sized dielectric layer (gap) by using the hydrodynamic model coupled to Maxwell's equations. The effects of thermal pressure on the confinement and the propagation losses of Hybrid Plasmon Polariton (HPP) modes are studied. We found that the thermal effect leads to a reduction in the effective refractive index as well as in the propagation losses of the HPP mode. Furthermore, the cutoff thickness in the warm CGD waveguide is found to be smaller than that in a cold CGD waveguide. The results may be useful in understanding the essential physics of active/passive Plasmonic devices and chip-scale systems. [ABSTRACT FROM AUTHOR]

Published
2017
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18. «Particle-wake» взаимодействия в гексагональной двухмерной пылевой решетке

Author

Shahmansouri, M. and Farokhi, B.

Abstract

Вивчаються моди пилової гратки у гексагональній двовимірній пиловій гратці у кристалі плазми, пов'язані з взаємодією типу "пробудження частинок". Відбувається взаємодія поздовжніх і горизонтальних поперечних мод з вертикальною поперечною модою для пилових зерен внаслідок взаємодії типу "пробудження частинок"., Изучаются моды пылевой решетки в гексагональной двумерной пылевой решетке в кристалле плазмы, связанные с взаимодействием типа "пробуждение частиц". Происходит взаимодействие продольных и горизонтальных поперечных мод с вертикальной поперечной модой для пылевых зерен в результате взаимодействия типа "пробуждение частиц"., Dust lattice (DL) modes are studied in a hexagonal two-dimensional dust lattice in plasma crystal, associated with the particle-wake interaction. The longitudinal and horizontal transverse modes are coupled with the vertical transverse mode for dust grains, due to the particle-wake interaction.

Published
2009

22. Investigation of Dielectric Response Function in Strongly Coupled Magnetized Dusty Plasmas.

Author

Khodabakhshi, N., Shahmansouri, M., and Farokhi, B.

Subjects
DIELECTRICS, DUSTY plasmas, MAGNETIC fields, PLASMA-particle interactions, HYDRODYNAMICS
Abstract

Theoretical investigation of dielectric response function of a magnetized dusty plasma has been considered for dust acoustic (DA) modes in the presence of strong interaction between dust grains employing the generalized hydrodynamic (GHD) fluid model. This dielectric response function can be used for analyzing of the behavior of the complex plasma and also wake potential in magnetic field. [ABSTRACT FROM AUTHOR]

Published
2017
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