arXiv subjects

Srimanta Maity

Publications and source records attributed to Srimanta Maity.

At least 19 recordsLinked to original sources

arXiv2026

Terahertz Generation through Photon Deceleration of Long-Wavelength Infrared Laser Pulses in Plasma

Efficient terahertz (THz) generation with high field amplitude and pulse energy is studied through the interaction of a single-color long-wavelength infrared (LWIR) laser pulse with gaseous targets. Particle-In-Cell (PIC) simulations are performed to investigate the underlying mechanism and analyze the properties of the emitted THz radiation. The results reveal that THz pulses are generated via photon deceleration of the LWIR laser, driven by enhanced electron density accumulation at the pulse front in the self-modulated wakefield regime. The influence of key parameters, including target density, laser intensity, and propagation length, on nonlinear laser modulation and the resulting THz generation efficiency is analyzed. Important scalings governing the laser-to-THz energy conversion efficiency are identified from PIC simulations and validated through theoretical analysis. The study demonstrates a laser-to-THz energy conversion efficiency of approximately $4\%$, significantly exceeding previously reported values. The field amplitude of the emitted THz pulses is found to be on the order of 100 GV/m, with a pulse energy of approximately 50 mJ for the laser parameters considered in this work. The findings of this study provide valuable insights for the development of next-generation high-energy THz sources.

physics.plasm-ph↗

arXiv2025

Laser Wakefield Acceleration in a Capillary Gas Cell Producing GeV-Scale High-Quality Electron Beams

Laser Wakefield Acceleration (LWFA) is a promising approach for producing high-brightness electron beams in the GeV energy range, offering significant potential for compact next-generation accelerator facilities. In this work, we present a computational study of LWFA in a specially designed single-stage capillary gas-cell target aimed at producing high-quality, GeV-class electron beams. The capillary cell includes a short ($\sim 2$ mm) injection region at the entrance filled with a helium (He) and nitrogen (N$_2$) gas mixture. This is followed by a longer ($\sim 14$ mm) pure He section, which provides the required acceleration length and limits continuous ionization injection, thereby significantly reducing the energy spread of the accelerated beam. Hydrodynamic simulations are performed to optimize the capillary geometry and generate the required two-section gas-pressure profile. The resulting gas-density distributions for various cases are then directly incorporated in Particle-In-Cell (PIC) simulations to study LWFA. In particular, our hydrodynamic simulations demonstrate how tailored density profiles with longitudinal density tapering in the acceleration section can be realized in a capillary gas cell, while the corresponding PIC simulations reveal how these profiles influence the acceleration process and the resulting beam quality. Using a 100~TW-class laser system with parameters relevant to the L2-DUHA laser at the ELI Beamlines Facility, the PIC results demonstrate electron acceleration to mean energies exceeding $1.0$~GeV with high-quality beam properties. Self-injected He electrons are also observed, and their impact on the main beam quality is evaluated. The findings of this study provide valuable insights for upcoming LWFA experiments planned within the EuPRAXIA Project at the ELI Beamlines Facility.

physics.acc-ph↗

arXiv2025

Coupling and Acceleration of Externally Injected Electron Beams in Laser-Driven Plasma Wakefields

The multi-stage method of laser wakefield acceleration (LWFA) presents a promising approach for developing stable, full-optical, high-energy electron accelerators. By segmenting the acceleration process into several booster stages, each powered by independent laser drivers, this technique effectively mitigates challenges such as electron dephasing, pump depletion, and laser diffraction. A critical aspect of multi-stage LWFA is the nonlinear interaction between the injected electron beam and the laser-driven wakefields in the booster stage. This study investigates the injection and acceleration of external electron beams within wakefields in the booster stage using multi-dimensional Particle-In-Cell (PIC) simulations. We provide both qualitative and quantitative descriptions of the observed physical processes. Key parameters influencing charge coupling process and the resultant beam quality have been identified. Furthermore, we have examined how off-axis injection relative to the driver laser influences the acceleration process and beam quality. Our findings provide valuable insights for advancing and optimizing multi-stage plasma-based accelerators.

physics.plasm-ph↗

arXiv2024

Enhanced Terahertz Emission from the Wakefield of CO2 Laser-Created Plasma

High-field terahertz (THz) pulse generation is investigated through the interaction of an intense single-color CO2 laser pulse with helium (He) gas targets. Employing multi-dimensional Particle-In-Cell (PIC) simulations, this study reveals a substantial enhancement in THz generation efficiency, even with a single-color laser pulse interacting with gas targets in the self-modulated-laser-wakefield (SMLWF) regime. Our study demonstrates that in the presence of photoionization, a synergistic interplay of laser self-modulation, self-focusing, and local pump depletion leads to the generation of robust THz pulses polarized parallel to the laser electric field. The dependence of THz generation efficiency on target density and laser pulse duration has been investigated. Our study identifies a favourable parametric regime for producing THz fields with amplitudes reaching hundreds of GV/m, surpassing those reported in previous studies.

physics.plasm-ph↗

arXiv2024

Parametric analysis of electron beam quality in laser wakefield acceleration based on the truncated ionization injection mechanism

Laser wakefield acceleration (LWFA) in a gas cell target separating injection and acceleration section has been investigated to produce high-quality electron beams. A detailed study has been performed on controlling the quality of accelerated electron beams using a combination of truncated ionization and density downramp injection mechanisms. For this purpose, extensive two-dimensional Particle-In-Cell (PIC) simulations have been carried out considering a gas cell target consisting of a hydrogen and nitrogen mixture in the first part and pure hydrogen in the second part. Such a configuration can be realized experimentally using a specially designed capillary setup. Using the parameters already available in the existing experimental setups, we show the generation of an electron beam with a peak energy of 500-600 MeV, relative energy spread less than 5%, normalized beam emittance around 1.5 mm-mrad, and beam charge of 2-5 pC/micrometer. Our study reveals that the quality of the accelerated electron beam can be independently controlled and manipulated through the beam loading effect by tuning the parameters, e.g., laser focusing position, nitrogen concentration, and gas target profile. These simulation results will be useful for future experimental campaigns on LWFA, particularly at ELI Beamlines.

physics.plasm-ph↗

arXiv2023

Self-excited converging shock structure in a complex plasma medium

We report the study of a self-excited converging shock structure observed in a complex plasma medium for the first time. A high-density dust cloud of melamine formaldehyde particles is created and horizontally confined by a circular ring in a DC glow discharge plasma at a particular discharge voltage and pressure. Later on, as the discharge voltage is increased, a circular density crest is spontaneously generated around the outer boundary of the dust cloud. This nonlinear density structure is seen to propagate inward towards the center of the dust cloud. The properties of the excited structure are analyzed and found to follow the characteristics of a converging shock structure. A three dimension molecular dynamics (MD) simulation has also been performed in which a stable dust cloud is formed and levitated by the balance of forces due to gravity and an external electric field mimicking the cathode sheath electric field in the experiment. Particles are also horizontally confined by an external electric field, representing the sheath electric field of the circular ring present in the experiment. A circular shock structure has been excited by applying an external perturbation in the horizontal electric field around the outer boundary of the dust cloud. The characteristic properties of the shock are analyzed in the simulation and qualitatively compared with the experimental findings. This study is not only of fundamental interest but has many implications concerning the study of converging shock waves excited in other media for various potential applications.

physics.plasm-ph↗

arXiv2023

Amplitude modulation and surface wave generation in a complex plasma monolayer

The response of a two-dimensional plasma crystal to an externally imposed initial perturbation has been explored using molecular dynamics (MD) simulations. A two-dimensional (2D) monolayer of micron-sized charged particles (dust) is formed in the plasma environment under certain conditions. The particles interacting via Yukawa pair potential are confined in the vertical ($\hat z$) direction by an external parabolic confinement potential, which mimics the combined effect of gravity and the sheath electric field typically present in laboratory dusty plasma experiments. An external perturbation is introduced in the medium by displacing a small central region of particles in the vertical direction. The displaced particles start to oscillate in the vertical direction, and their dynamics get modulated through a parametric decay process. Consequently, beats generate in the vertical motion of the particles. It has also been shown that the same motion is excited in the dynamics of unperturbed particles as they are coupled via pair interactions. A simple theoretical model is provided to understand the origin of the beat motions of particles. Additionally, in our simulations, concentric circular wavefronts propagating radially outward are observed on the surface of the monolayer. The physical mechanism and parametric dependence of the observed phenomena are discussed in detail. It has been shown that the generated surface wave follows the dispersion relation of a transverse shear wave. This research provides insight into complex plasma crystals from the perspective of soft matter.

physics.plasm-ph↗

arXiv2023

Ion heating in Laser interacting with magnetized plasma

The ion heating mechanism in the context of laser interacting with plasma immersed in a strong magnetic field is studied. The magnetic field is chosen to be strong for laser electromagnetic field propagation inside the plasma to be governed by the magnetized dispersion relation. Both X and RL mode configurations have been studied in detail using Particle - In - Cell (PIC) simulations. It is shown that the energy absorption process is governed by a resonant mechanism wherein the laser frequency matches with an underlying mode in the plasma. For X and RL mode configurations, these correspond to lower hybrid and ion cyclotron resonance, respectively. The absorption, however, is found to be most efficient at frequencies close to but not exactly matching with the resonance frequency. An understanding of the same has been provided. The role of laser polarization has been studied in detail.

physics.plasm-ph↗

arXiv2023

Harmonic generation in magnetized plasma for Electromagnetic wave propagating parallel to external magnetic field

The harmonic generation has always been of fundamental interest in studying the nonlinear nature of any physical system. In the present study, Particle - In - Cell (PIC) simulations have been carried out to explore the harmonic generation of Electromagnetic waves in a magnetized plasma. The EM wave propagation is chosen to be parallel to the applied external magnetic field. The simulations show the excitation of odd higher harmonics of RCP (Right circularly polarized) and LCP (Left circularly polarized) when the incident wave is linearly polarised. The harmonic generation is maximum when the incident EM wave frequency matches the electron cyclotron frequency. When the incident EM wave has a circular polarization, no harmonics get excited. A theoretical understanding of these observations has also been provided. The studies thus show that by appropriately tailoring of plasma parameters EM waves of higher frequencies and desired nature of circular polarization can be generated.

physics.plasm-ph↗

arXiv2022

Structure formation by electrostatic interactions in strongly coupled medium

The formation of correlated structures is of importance in many diverse contexts such as strongly coupled plasmas, soft matter, and even biological mediums. In all these contexts the dynamics are mainly governed by electrostatic interactions and result in the formation of a variety of structures. In this study, the process of formation of structures is investigated with the help of Molecular (MD) simulations in 2 and 3 dimensions. The overall medium has been modelled with an equal number of positive and negatively charged particles interacting via long-range pair Coulomb potential. A repulsive short-range Lennard-Jones (LJ) potential is added to take care of the blowing up of attractive Coulomb interaction between unlike charges. In the strongly coupled regime, a variety of classical bound states form. However, complete crystallization of the system, as typically observed in the context of one component strongly coupled plasmas, does not occur. The influence of localized perturbation in the system has also been studied. The formation of a crystalline pattern of shielding clouds around this disturbance is observed. The spatial properties of the shielding structure have been analyzed using the radial distribution function and Voronoi diagram. The process of accumulation of oppositely charged particles around the disturbance triggers a lot of dynamical activity in the bulk of the medium, wherein close encounters between widely separated particles occur. This leads to the formation of a larger number of bigger clusters. There are, however, also instances when bound pairs break up to provide the appropriate signed charge to the shielding cloud. A detailed discussion of these features has been provided in the manuscript.

physics.plasm-ph↗

arXiv2022

Localized absorption of laser energy in X-mode configuration of magnetized plasma

The heating of ions via lower hybrid waves has been observed in several astrophysical as well as laboratory plasmas. We have conducted Particle-In-Cell simulations to demonstrate absorption of the incident laser pulse at a chosen localized point in the target by manipulating the plasma density profile. We show that a part of the incident laser propagates inside plasma target, when its frequency lies below the lower hybrid resonance frequency. Thereafter, as it experiences a negative density gradient, it approaches the resonance point where its group velocity approaches zero. This is where the electromagnetic energy prominently gets converted into electrostatic and eventually into kinetic energy of ions. Thus by tailoring the plasma density profile one can have the absorption of incident electromagnetic wave energy at a designated location inside the plasma. This may have importance in various applications where energy deposition/heating of plasma at a localized region is desirable.

physics.plasm-ph↗

arXiv2022

Particle-In-Cell observations of Brillouin scattering for laser interacting with magnetized overdense plasma

One dimensional Particle-in-cell simulations using OSIRIS-4.0 has been conducted to study the interaction of a laser electromagnetic pulse with an overdense magnetized plasma target. The external magnetic field has been chosen to be directed along the laser propagation direction. This geometry supports the propagation of right (R) and left (L) circularly polarised electromagnetic waves in the plasma. The laser pulse is allowed to propagate inside the plasma when its frequency falls in the pass band of the dispersion curves of L and/or R waves. The strength of the applied external magnetic field is chosen as a parameter to ensure that the laser frequency lies in the appropriate pass band. It is demonstrated that for all possible polarization of the incident laser, parametric process involving a scattered Electromagnetic wave and an electrostatic mode occur. The parametric process has been identified as that due to the Brillouin back scattering process.

physics.plasm-ph↗

arXiv2022

Mode conversion and laser energy absorption by plasma under an inhomogeneous external magnetic field

The interaction of a high-frequency laser with plasma in the presence of an inhomogeneous external magnetic field has been studied here with the help of Particle-In-Cell simulation. It has been shown that laser enters inside the plasma as an extraordinary wave (X-wave), where the electric field of the wave oscillates perpendicular to both external magnetic field and propagation direction, and as it travels through the plasma, its dispersion property changes due to the inhomogeneity of the externally applied magnetic field. Our study shows that the X-wave's electromagnetic energy is converted to an electrostatic mode as it encounters the upper-hybrid (UH) resonance layer. In the later stage of the evolution, this electrostatic wave breaks and converts its energy to electron kinetic energy. Our study reveals two additional processes involved in decaying electrostatic mode at the UH resonance layer. We have shown that the energy of the electrostatic mode also converts to a low-frequency lower-hybrid mode and high-frequency electromagnetic harmonic radiations at the resonance layer. The dependence of energy conversion processes on the gradient of external magnetic field has also been studied and analyzed.

physics.plasm-ph↗

arXiv2021

Chaotic dynamics of small sized charged Yukawa Dust Clusters

In a recent work, [1] the equilibrium of a cluster of charged dust particles mutually interacting with screened Coulomb force and radially confined by an externally applied electric field in a 2-D configuration was studied. It was shown that the particles arranged themselves on discrete radial rings forming a lattice structure. In some cases with the specific number of particles, no static equilibrium was observed; instead, angular rotation of particles positioned at various rings was observed. In a two-ringed structure, it was shown that the direction of rotation was opposite. The direction of rotation was also observed to change apparently at random time intervals. A detailed characterization of the dynamics of small-sized Yukawa clusters has been carried out in the present work. In particular, it has been shown that the dynamical time reversal of angular rotation exhibits chaotic behavior.

physics.plasm-ph↗

arXiv2021

Harmonic generation in the interaction of laser with a magnetized overdense plasma

The mechanism of harmonic generation in both O and X-mode configurations for a magnetized plasma has been explored here in detail with the help of Particle-In-Cell (PIC) simulations. A detailed characterization of both the reflected and transmitted electromagnetic radiation propagating in the bulk of the plasma has been carried out for this purpose. The efficiency of harmonic generation is shown to increase with the incident laser intensity. Dependency of harmonic efficiency has also been found on magnetic field strength. This work demonstrates that there is an optimum value of the magnetic field at which the efficiency of harmonic generation maximizes. The observations are in agreement with theoretical analysis. For O-mode configuration, this is compelling as the harmonic generation provides for a mechanism by which laser energy can propagate inside an overdense plasma region.

physics.plasm-ph↗

arXiv2021

Ponderomotive force driven mechanism for electrostatic wave excitation and energy absorption of Electromagnetic waves in overdense magnetized plasma

The excitation of electrostatic waves in plasma by laser electromagnetic pulse is important as it provides a scheme by which the power from the laser electromagnetic (EM) field can be transferred into the plasma medium. The paper presents a fundamentally new ponderomotive pressure-driven mechanism of excitation of electrostatic waves in an overdense magnetized plasma by a finite laser pulse. Particle-in-cell (PIC) simulations using the EPOCH-4.17.10 framework have been utilized for the study of a finite laser pulse interacting with a magnetized overdense plasma medium. The external magnetic field is chosen to be aligned parallel to the laser propagation direction. In this geometry, the electromagnetic wave propagation inside the plasma is identified as whistler or R and L waves. The group velocity of these waves being different, a clear spatial separation of the R and L pulses are visible. In addition, excitation of electrostatic perturbation associated with the EM pulses propagating inside the plasma is also observed. These electrostatic perturbations are important as they couple laser energy to the plasma medium. The excitation of electrostatic oscillations are understood here by a fundamentally new mechanism of charge separation created by the difference between the ponderomotive force (of the electromagnetic pulse) felt by the two plasma species, viz., the electrons and the ions in a magnetized plasma.

physics.plasm-ph↗

arXiv2020

Dynamical states in two-dimensional charged dust particle clusters in plasma medium

The formation of novel dynamical states for a collection of dust particles in two dimensions has been shown with the help of Molecular Dynamics (MD) simulation. The charged dust particles interact with each other with Yukawa pair potential mimicking the screening due to plasma. Additionally, an external radial confining force has also been applied to the dust particles to keep them radially confined. When the particle number is low ( say a few), they get arranged on the radial location corresponding to multiple rings/shells. For specific numbers, such an arrangement of particles is stationary. However, for several cases, the cluster of dust particles relaxes to a state for which the dust particles on rings display inter-shell rotation. For a larger number of dust particles ( a few hundred for instance ) a novel equilibrium state with coherent rigid body displaying angular oscillation of the entire cluster is observed. A detailed characterization of the formation of these states in terms of particle number, coupling parameter, etc., has been provided.

physics.plasm-ph↗

arXiv2018

Molecular dynamics study of crystal formation and structural phase transition in Yukawa system for dusty plasma medium

The layered crystal formation in dusty plasma medium depicted by the Yukawa interaction amidst dust has been investigated using Molecular Dynamics simulations. The multilayer structures are shown to form in the presence of a combined gravitational and external electric field force (representing the sheath field in experiments) along the ^ z direction. A detailed study of the dependence of the number of crystal layer formation, their width etc., on various system parameters (viz., the external field profile and the screening length of Yukawa interaction) have been analyzed. The structural properties of crystalline bilayers have been studied in detail identifying their structures with the help of pair correlation function and Voronoi diagrams. It has been shown that the crystalline layers undergo structural phase transition from hexagonal (often also referred as triangular ) to square lattice configurations. A reentrant phase transition from hexagonal to square (and rhombic) structure has been observed in the simulations.

physics.plasm-ph↗