arXiv subjects

M. Shahmansouri

Publications and source records attributed to M. Shahmansouri.

8 recordsLinked to original sources

arXiv2026

Resonant RF Wakefield Coupling for Radiation-Reaction Control of 3D Betatron Dynamics in Hybrid Laser Plasma Accelerators

Hybrid laser plasma radiofrequency (RF) acceleration architectures signify a promising advancement in addressing the stability challenges associated with traditional laser wakefield accelerators. A thorough theoretical and numerical analysis of the three-dimensional dynamics of ultra-relativistic electron bunches in these hybrid systems is presented, clearly explaining how transverse beam stability, betatron oscillation polarisation, and radiative cooling work. By combining analytical models of spatiotemporal plasma wakefield modulation and phase dependent RF-driven oscillations with fully self-consistent 3D particle in cell (PIC) simulations, incorporating classical radiation reaction (RR) via the Landau Lifshitz model (with quantum parameter to account for synchrotron like losses during betatron oscillations. The findings indicate that the external RF fields operate as a tunable lattice, allowing for exact adjustment of amplitude, frequency, and carrier-envelope phase, which facilitates deterministic regulation of transverse focussing gradients and betatron amplitudes. A regime of resonant alignment between RF fields and natural betatron frequencies is established; this resonance enhances controlled transverse excursions while concurrently diminishing parasitic oscillations via increased radiative damping, resulting in substantial emittance reduction and the alleviation of synchrotron-like energy losses. Also, the detailed stability maps and 3D force landscapes show that the gamma factor growth rates change over time depending on the interaction between longitudinal field gradients and initial injection conditions. The paper's results give a clear picture of the nonlinear, resonant, and damping events that happen in hybrid accelerators. They also make it possible to get ultra stable, high-quality electron beams with the right polarisation states.

physics.acc-ph↗

arXiv2025

Tailored Three Dimensional Betatron Dynamics in UltraStable Hybrid Laser Plasma RF Accelerators

The detailed theoretical and numerical investigation of hybrid laser plasma RF accelerators, elucidating the mechanisms governing transverse beam dynamics, betatron polarization, and radiation reaction in ultra-relativistic electron bunches is presented. This framework combines analytical models of spatiotemporal plasma wakefield modulation, phase-dependent RF-driven oscillations, and quantum-corrected Landau Lifshitz radiation reaction with fully self-consistent 3D particle in cell simulations using EPOCH. The results demonstrate that RF amplitude, frequency, and phase enable precise control over transverse focusing strengths, betatron oscillation amplitudes, and polarization states. Resonant alignment between RF fields and natural betatron frequencies amplifies transverse excursions while damping parasitic oscillations through enhanced focusing gradients and radiation reaction, yielding reductions in emittance and mitigation of synchrotron-like energy losses. Stability maps and 3D force landscapes reveal strong phase sensitivity, where initial conditions and RF component ratios govern the temporal evolution of betatron amplitudes, and longitudinal field gradients modulate {\gamma} growth rates. These findings provide a comprehensive picture of nonlinear, resonant, and damping phenomena in hybrid laser plasma RF systems, highlighting the full spectrum of controllable transverse, longitudinal, and polarization dynamics in ultra relativistic electron beams.

physics.plasm-ph↗

arXiv2025

3D PIC simulation and theoretical modeling of RF Laser pulse in magnetized plasma for the generation of multidimensional relativistic Wakefields

The present study, investigates the modulation of plasma wakefields in dense magnetized plasma driven by relativistic electron beams under transverse RF excitation. A self consistent theoretical framework, comprising the RF vector potential, Maxwells equations, and relativistic electron motion, is extended through full 3D electromagnetic particle in cell simulations. The results reveal systematic amplification and reshaping of wakefields under the combined action of external magnetic fields and RF drivers. Variations in the cyclotron to plasma frequency ratio dictate the radial positioning and gyromotion of plasma electrons, sharpening transverse confinement and stabilizing blowout structures. The RF amplitude introduces progressive modulation of radial excursions and transverse forces, enhancing wakefield symmetry and depth. Current density distributions confirm the nonlinear scaling with RF strength, evolving from weak perturbations into sharply structured ion channels. Scalar potentials and longitudinal fields exhibit pronounced sensitivity to pulse shape, polarization angle, frequency ratio, and driver density, each parameter producing distinct oscillatory features and confinement regimes. Plasma density sets the field strength and radial localization, while the modulation parameter governs the emergence of fine scale oscillatory bands, producing smooth to multiband transitions in longitudinal electric fields. Across all conditions, simulations confirm the reinforcement of ponderomotive force, resulting in controlled narrowing of electron sheaths, sharper scalar potential gradients, and extended acceleration zones.

physics.plasm-ph↗

arXiv2024

Mechanisms of THz Radiation Generation in Multi-Color Laser-Plasma Interactions: A Review Across Diverse Media

The exploration of Terahertz (THz) waves has captivated researchers across diverse scientific disciplines such as physics, spectroscopy, chemistry, biology, and engineering, driven by the myriad applications these waves offer. Within this expansive landscape, the development of efficient and reliable THz sources stands as a paramount objective. In the pursuit of this goal, a multitude of approaches have been undertaken, with a notable contender emerging in the form of laser-induced plasma. Harnessing the advancements in ultrafast pulses, laser-induced plasma has proven to be a promising tool for generating THz waves. Its appeal lies in the robust attributes of a high power threshold, intense THz signal, and an broadband THz spectrum. This paper delves into a comprehensive review of the physics and progress underlying THz generation from laser-induced plasmas, exploring scenarios where plasmas are induced in gases, liquids, and solids. The interactions between lasers and plasmas involve complex physical processes, resulting in a variety of laser plasma scenarios for THz generation. In this review, the focus is specifically placed on classifying THz generation based on different physical mechanisms and also examines the characteristics of the emitted THz waves. By categorizing the processes, a deeper understanding of the underlying principles can be attained.

physics.plasm-ph↗

arXiv2020

Optical surface plasmons at a metal-crystal interface with the Drude-Lorentz model for material permittivity

The theory of surface electromagnetic waves (SEMWs) propagating at optical frequencies along the interface of an isotropic noble metal [e.g., gold (Au)] and a uniaxial crystal [e.g., Rutile (TiO$_2$)] is revisited with the Drude-Lorentz (DL) model for the complex dielectric material permittivity $(ε_p)$. The latter accounts for the contributions of both the \textit{intraband} transitions of the free electrons and the multiple \textit{interband} transitions of the bound electrons in metals. The propagation characteristics of the wave vectors and wave frequency of SEMWs, the hybridization factors, i.e., the amplitude ratios between the transverse-electric (TE) and transverse-magnetic (TM) modes in the isotropic metal, and between the ordinary and extraordinary modes in the uniaxial substrate are studied numerically. It is found that the results are significantly modified from those with the Drude model for $ε_p$, especially in the short-wavelength spectra ($λ\lesssim500$ nm) and with a small deviation of the orientation of the optical axis. The excitation of such SEMWs can have novel applications in transportation of EM signals in a specified direction at optical frequencies ($\sim $ PHz).

physics.app-ph↗

arXiv2018

Surface plasmons in a semi-bounded massless Dirac plasma

The collective excitation of surface plasmons in a massless Dirac plasma (e.g., graphene) half-space (bounded by air) is investigated using a relativistic quantum fluid model. The unique features of such surface waves are discussed and compared with those in a Fermi plasma. It is found that in contrast to Fermi plasmas, the long-wavelength surface plasmon frequency $(ω)$ in massless Dirac plasmas is explicitly nonclassical, i.e., $ω\propto1/\sqrt{\hbar}$, where $h=2π\hbar$ is the Planck's constant. Besides some apparent similarities between the surface plasmon frequencies in massless Dirac plasmas and Fermi plasmas, several notable differences are also found and discussed. Our findings elucidate the properties of surface plasmons that may propagate in degenerate plasmas where the relativistic and quantum effects play a vital role.

physics.plasm-ph↗

arXiv2016

Modulation and nonlinear evolution of multi-dimensional Langmuir wave envelopes in a relativistic plasma

The modulational instability (MI) and the evolution of weakly nonlinear two-dimensional (2D) Langmuir wave (LW) packets are studied in an unmagnetized collisionless plasma with weakly relativistic electron flow. By using a 2D self-consistent relativistic fluid model and employing the standard multiple-scale technique, a coupled set of Davey-Stewartson (DS)-like equations is derived which governs the slow modulation and the evolution of LW packets in relativistic plasmas. It is found that the relativistic effects favor the instability of LW envelopes in the kθ plane, where k is the wave number and θ the angle of modulation. It is also found that as the electron thermal velocity or θ increases, the growth rate of MI increases with cutoffs at higher wave numbers of modulation. Furthermore, in the nonlinear evolution of the DS-like equations, it is seen that with an effect of the relativistic flow, a Gaussian wave beam collapses in a finite time, and the collapse can be arrested when the effect of the thermal pressure or the relativistic flow is slightly relaxed. The present results may be useful to the MI and the formation of localized LW envelopes in cosmic plasmas with a relativistic flow of electrons.

physics.plasm-ph↗

arXiv2016

Elliptically polarized electromagnetic waves in a magnetized quantum electron-positron plasma with effects of exchange-correlation

The dispersion properties of elliptically polarized electromagnetic (EM) waves in a magnetized electron-positron-pair (EP-pair) plasma are studied with the effects of particle dispersion associated with the Bohm potential, the Fermi degenerate pressure, and the exchange-correlation force. Two possible modes of the extraordinary or X wave, modified by these quantum effects, are identified and their propagation characteristics are investigated numerically. It is shown that the upper-hybrid frequency, and the cutoff and resonance frequencies are no longer constants but are dispersive due to these quantum effects. It is found that the particle dispersion and the exchange-correlation force can have different dominating roles on each other depending on whether the X waves are of short or long wavelengths (in comparison with the Fermi Debye length). The present investigation should be useful for understanding the collective behaviors of EP plasma oscillations and the propagation of extraordinary waves in magnetized dense EP-pair plasmas.

physics.plasm-ph↗