Encontrados 35 documentos, a visualizar página 1 de 4
Electron-scale shear instabilities: magnetic field generation and particle acce...
Alves, E. P.; Grismayer, T.; Fonseca, R. A.; Silva, L. O.WOS:000333714500001 (Nº de Acesso Web of Science) ; Strong shear flow regions found in astrophysical jets are shown to be important dissipation regions, where the shear flow kinetic energy flow is converted into electric and magnetic field energy via shear instabilities. The emergence of these self-consistent fields makes shear flows significant sites for radiation emission and particle acceleration. We focus ...
Exploring the nature of collisionless shocks under laboratory conditions
Stockem, A.; Fiuza, F.; Bret, A.; Fonseca, R. A.; Silva, L. O.WOS:000331215400005 (Nº de Acesso Web of Science) ; Collisionless shocks are pervasive in astrophysics and they are critical to understand cosmic ray acceleration. Laboratory experiments with intense lasers are now opening the way to explore and characterise the underlying microphysics, which determine the acceleration process of collisionless shocks. We determine the shock character – electrostatic or electro...
dc-Magnetic-Field Generation in Unmagnetized Shear Flows
Grismayer, T.; Alves, E. P.; Fonseca, R. A.; Silva, L. O.WOS:000321278300010 (Nº de Acesso Web of Science) ; The generation of dc magnetic fields in unmagnetized electron-ion shear flows is shown to be associated to either initial thermal effects or the onset of electron-scale shear instabilities, in particular the cold Kelvin-Helmholtz instability. This mechanism, intrinsic to shear gradients on the electron scale, is described through a kinetic model that predicts...
Ion acceleration from laser-driven electrostatic shocks
Fiuza, F.; Stockem, A.; Boella, E.; Fonseca, R. A.; Silva, L. O.; Haberberger, D.; Tochitsky, S.; Mori, W. B.; Joshi, C.WOS:000320000000092 (Nº de Acesso Web of Science) ; Multi-dimensional particle-in-cell simulations are used to study the generation of electrostatic shocks in plasma and the reflection of background ions to produce high-quality and high-energy ion beams. Electrostatic shocks are driven by the interaction of two plasmas with different density and/or relative drift velocity. The energy and number of ions reflect...
Magnetically assisted self-injection and radiation generation for plasma-based ...
Vieira, J.; Martins, J. L.; Pathak, V. B.; Fonseca, R. A.; Mori, W. B.; Silva, L. O.WOS:000312579500047 (Nº de Acesso Web of Science) ; “Prémio Científico ISCTE-IUL 2013” ; It is shown through analytical modeling and numerical simulations that external magnetic fields can relax the self-trapping thresholds in plasma-based accelerators. In addition, the transverse location where self-trapping occurs can be selected by adequate choice of the spatial profile of the external magnetic field. We a...
Effect of the frequency chirp on laser wakefield acceleration
Pathak, V. B.; Vieira, J.; Fonseca, R. A.; Silva, L. O.WOS:000302310200002 (Nº de Acesso Web of Science) ; “Prémio Científico ISCTE-IUL 2013” ; The role of laser frequency chirps in the laser wakefield accelerator is examined. We show that in the linear regime, the evolution of the laser pulse length is affected by the frequency chirp, and that positive (negative) chirp compresses (stretches) the laser pulse, thereby increasing (decreasing) the peak vector potent...
Large-scale magnetic field generation via the kinetic Kelvin-Helmholtz instabil...
Alves, E.P.; Grismayer, T.; Martins, S. F.; Fiuza, F.; Fonseca, R. A.; Silva, L. O.WOS:000300611100001 (Nº de Acesso Web of Science) ; “Prémio Científico ISCTE-IUL 2013” ; Collisionless plasma instabilities are fundamental in magnetic field generation in astrophysical scenarios, but their role has been addressed in scenarios where velocity shear is absent. In this work we show that velocity shears must be considered when studying realistic astrophysical scenarios, since these trigger the co...
Weibel-Instability-Mediated Collisionless Shocks in the Laboratory with Ultrain...
Fiuza, F.; Fonseca, R. A.; Tonge, J. W.; Mori, W. B.; Silva, L. O.WOS:000305032100015 (Nº de Acesso Web of Science) ; “Prémio Científico ISCTE-IUL 2013” ; The formation of nonrelativistic collisionless shocks in the laboratory with ultrahigh intensity lasers is studied via ab initio multidimensional particle-in-cell simulations. The microphysics behind shock formation and dissipation and the detailed shock structure are analyzed, illustrating that the Weibel instability pla...
Laser-Driven Shock Acceleration of Monoenergetic Ion Beams
Fiuza, F.; Stockem, A.; Boella, E.; Fonseca, R. A.; Silva, L. O.; Haberberger, D.; Tochitsky, S.; Gong, C.; Mori, W. B.; Joshi, C.WOS:000311284200008 (Nº de Acesso Web of Science) ; “Prémio Científico ISCTE-IUL 2013” ; We show that monoenergetic ion beams can be accelerated by moderate Mach number collisionless, electrostatic shocks propagating in a long scale-length exponentially decaying plasma profile. Strong plasma heating and density steepening produced by an intense laser pulse near the critical density can launch such shocks that...
Ion Motion in Self-Modulated Plasma Wakefield Accelerators
Vieira, J.; Fonseca, R. A.; Mori, W. B.; Silva, L. O.WOS:000309589600007 (Nº de Acesso Web of Science) ; “Prémio Científico ISCTE-IUL 2013” ; The effects of plasma ion motion in self-modulated plasma-based accelerators are examined. An analytical model describing ion motion in the narrow beam limit is developed and confirmed through multidimensional particle-in-cell simulations. It is shown that the ion motion can lead to the early saturation of the self-modula...
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