arXiv subjects

A. V. Arefiev

Publications and source records attributed to A. V. Arefiev.

At least 19 recordsLinked to original sources

arXiv2026

Ion-motion-driven enhancement of energy coupling and stability in relativistic laser-microchannel interaction

For sufficiently short relativistic-intensity laser pulses, the disparity in time scales for electron and ion motion causes ions to behave as a fixed, neutralizing background. As the pulse duration or intensity is increased, ion motion becomes important, leading to instability in uniform plasmas but more complex, and potentially desirable behavior in structured targets. In this work, we introduce a new self-organized regime in laser-driven microchannels wherein ion motion facilitates stronger peak fields and high charge and photon conversion efficiency. 3-D particle-in-cell simulations demonstrate that the qualitative laser-microchannel interaction regime is governed by similarity parameters relating the pulse duration, spot size, and intensity to channel scales. The observed similarity suggests that lower-intensity experiments can inform designs for next-generation facilities, where the high-field, highly-radiative properties of the self-organized regime are especially desirable.

physics.plasm-ph↗

arXiv2025

Progress in relativistic laser-plasma interaction with kilotesla-level applied magnetic fields

We report on progress in the understanding of the effects of kilotesla-level applied magnetic fields on relativistic laser-plasma interactions. Ongoing advances in magnetic-field-generation techniques enable new and highly desirable phenomena, including magnetic-field-amplification platforms with reversible sign, focusing ion acceleration, and bulk-relativistic plasma heating. Building on recent advancements in laser-plasma interactions with applied magnetic fields, we introduce simple models for evaluating the effects of applied magnetic fields in magnetic-field amplification, sheath-based ion acceleration, and direct laser acceleration. These models indicate the feasibility of observing beneficial magnetic-field effects under experimentally relevant conditions and offer a starting point for future experimental design.

physics.plasm-ph↗

arXiv2024

The Influence of Laser Focusing Conditions on the Direct Laser Acceleration of Electrons

Direct Laser Acceleration (DLA) of electrons during a high-energy, picosecond laser interaction with an underdense plasma has been demonstrated to be substantially enhanced by controlling the laser focusing geometry. Experiments using the OMEGA EP facility measured electrons accelerated to maximum energies exceeding 120 times the ponderomotive energy under certain laser focusing, pulse energy, and plasma density conditions. Two-dimensional particle-in-cell simulations show that the laser focusing conditions alter the laser field evolution, channel fields generation, and electron oscillation, all of which contribute to the final electron energies. The optimal laser focusing condition occurs when the transverse oscillation amplitude of the accelerated electron in the channel fields matches the laser beam width, resulting in efficient energy gain. Through this observation, a simple model was developed to calculate the optimal laser focal spot size in more general conditions and is validated by experimental data.

physics.plasm-ph↗

arXiv2023

Space-time structured plasma waves

Electrostatic waves play a critical role in nearly every branch of plasma physics from fusion to advanced accelerators, to astro, solar, and ionospheric physics. The properties of planar electrostatic waves are fully determined by the plasma conditions, such as density, temperature, ionization state, or details of the distribution functions. Here we demonstrate that electrostatic wavepackets structured with space-time correlations can have properties that are independent of the plasma conditions. For instance, an appropriately structured electrostatic wavepacket can travel at any group velocity, even backward with respect to its phase fronts, while maintaining a localized energy density. These linear, propagation-invariant wavepackets can be constructed with or without orbital angular momentum by superposing natural modes of the plasma and can be ponderomotively excited by space-time structured laser pulses like the flying focus.

physics.plasm-ph↗

arXiv2022

Twisted plasma waves driven by twisted ponderomotive force

We present results of twisted plasma waves driven by twisted ponderomotive force. With beating of two, co-propagating, Laguerre-Gaussian (LG) orbital angular momentum (OAM) laser pulses with different frequencies and also different twist indices, we can get twisted ponderomotive force. Three-dimensional particle-in-cell simulations are used to demonstrate the twisted plasma waves driven by lasers. The twisted plasma waves have an electron density perturbation with a helical rotating structure. Different from the predictions of the linear fluid theory, the simulation results show a nonlinear rotating current and a static axial magnetic field. Along with the rotating current is the axial OAM carried by particles in the twisted plasma waves. Detailed theoretical analysis of twisted plasma waves is given too.

physics.plasm-ph↗

arXiv2022

Energy-chirp compensation of laser-driven ion beams enabled by structured targets

We show using 3D simulations that the challenge of generating dense mono-energetic laser-driven ion beams with low angular divergence can be overcome by utilizing structured targets with a relativistically transparent channel and an overdense wall. In contrast to a uniform target that produces a chirped ion beam, the target structure facilitates formation of a dense electron bunch whose longitudinal electric field reverses the energy chirp. This approach works in conjunction with existing acceleration mechanisms, augmenting the ion spectra. For example, our 3D simulations predict a significant improvement for a 2 PW laser pulse with a peak intensity of $5 \times 10^{22}$ W/cm$^2$. The simulations show a mono-energetic proton peak in a highly desirable energy range of 200 MeV with an unprecedented charge of several nC and relatively low divergence that is below 10$^{\circ}$.

physics.plasm-ph↗

arXiv2022

Underdense relativistically thermal plasma produced by magnetically assisted direct laser acceleration

We introduce the first approach to volumetrically generate relativistically thermal plasma at gas-jet--accessible density. Using fully kinetic simulations and theory, we demonstrate that two stages of direct laser acceleration driven by two laser pulses in an applied magnetic field can heat a significant plasma volume to multi-MeV average energy. The highest-momentum feature is 2D-isotropic, persists after the interaction, and includes the majority of electrons, enabling experimental access to bulk-relativistic, high-energy-density plasma in an optically diagnosable regime for the first time.

physics.plasm-ph↗

arXiv2021

Dominance of $γ$-$γ$ electron-positron pair creation in a plasma driven by high-intensity lasers

Creation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Here we show that it is possible to create ${>}10^8$ positrons by dual laser irradiation of a structured plasma target, at intensities of $2 \times 10^{22} \mathrm{W}\mathrm{cm}^{-2}$. In contrast to previous work, the pair creation is primarily driven by the linear Breit-Wheeler process ($γγ\to e^+ e^-$), not the nonlinear process assumed to be dominant at high intensity, because of the high density of $γ$ rays emitted inside the target. The favorable scaling with laser intensity of the linear process prompts reconsideration of its neglect in simulation studies, but also permits positron jet formation at intensities that are already experimentally feasible. Simulations show that the positrons, confined by a quasistatic plasma magnetic field, may be accelerated by the lasers to energies $> 200$ MeV.

physics.plasm-ph↗

arXiv2021

Towards the Optimisation of Direct Laser Acceleration

Experimental measurements using the OMEGA EP laser facility demonstrated direct laser acceleration (DLA) of electron beams to (505 $\pm$ 75) MeV with (140 $\pm$ 30)~nC of charge from a low-density plasma target using a 400 J, picosecond duration pulse. Similar trends of electron energy with target density are also observed in self-consistent two-dimensional particle-in-cell simulations. The intensity of the laser pulse is sufficiently large that the electrons are rapidly expelled from along the laser pulse propagation axis to form a channel. The dominant acceleration mechanism is confirmed to be DLA and the effect of quasi-static channel fields on energetic electron dynamics is examined. A strong channel magnetic field, self-generated by the accelerated electrons, is found to play a comparable role to the transverse electric channel field in defining the boundary of electron motion.

physics.plasm-ph↗

arXiv2020

Sign reversal in magnetic field amplification by relativistic laser-driven microtube implosions

We demonstrate and explain the surprising phenomenon of sign reversal in magnetic field amplification by the laser-driven implosion of a structured target. Relativistically intense laser pulses incident on the outer surface of a microtube target consisting of thin opaque shell surrounding a $μ$m-scale cylindrical void drive an initial ion implosion and later explosion capable of generating and subsequently amplifying strong magnetic fields. While the magnetic field generation is enhanced and spatially smoothed by the application of a kilotesla-level seed field, the sign of the generated field does not always follow the sign of the seed field. One unexpected consequence of the amplification process is a reversal in the sign of the amplified magnetic field when, for example, the target outer cross section is changed from square to circular. Using 2D particle-in-cell simulations, we demonstrate that sign reversal is linked to the stability of the surface magnetic field of opposite sign from the seed which arises at the target inner surface during laser irradiation. The stability of the surface magnetic field and consequently the sign of the final amplified field depends sensitively on the target, laser, and seed magnetic field conditions, which could be leveraged to make laser-driven microtube implosions an attractive platform for the study of magnetic fields in high energy density plasma in regimes where sign reversal either is or is not desired.

physics.plasm-ph↗

arXiv2020

Generation of megatesla magnetic fields by intense-laser-driven microtube implosions

A microtube implosion driven by ultraintense laser pulses is used to produce ultrahigh magnetic fields. Due to the laser-produced hot electrons with energies of mega-electron volts, cold ions in the inner wall surface implode towards the central axis. By pre-seeding uniform magnetic fields on the kilotesla order, the Lorenz force induces the Larmor gyromotion of the imploding ions and electrons. Due to the resultant collective motion of relativistic charged particles around the central axis, strong spin current densities of ~ peta-ampere/cm2 are produced with a few tens of nm size, generating megatesla-order magnetic fields. The underlying physics and important scaling are revealed by particle simulations and a simple analytical model. The concept holds promise to open new frontiers in many branches of fundamental physics and applications in terms of ultrahigh magnetic fields.

physics.plasm-ph↗

arXiv2020

Relativistic Plasma Physics in Supercritical Fields

Since the invention of chirped pulse amplification, which was recognized by a Nobel prize in physics in 2018, there has been a continuing increase in available laser intensity. Combined with advances in our understanding of the kinetics of relativistic plasma, studies of laser-plasma interactions are entering a new regime where the physics of relativistic plasmas is strongly affected by strong-field quantum electrodynamics (QED) processes, including hard photon emission and electron-positron ($e^+$-$e^-$) pair production. This coupling of quantum emission processes and relativistic collective particle dynamics can result in dramatically new plasma physics phenomena, such as the generation of dense $e^+$-$e^-$ pair plasma from near vacuum, complete laser energy absorption by QED processes or the stopping of an ultrarelativistic electron beam, which could penetrate a cm of lead, by a hair's breadth of laser light. In addition to being of fundamental interest, it is crucial to study this new regime to understand the next generation of ultra-high intensity laser-matter experiments and their resulting applications, such as high energy ion, electron, positron, and photon sources for fundamental physics studies, medical radiotherapy, and next generation radiography for homeland security and industry.

physics.plasm-ph↗

arXiv2020

Quantum anti-quenching of radiation from laser-driven structured plasma channels

We demonstrate that in the interaction of a high-power laser pulse with a structured solid-density plasma-channel, clear quantum signatures of stochastic radiation emission manifest, disclosing a novel avenue to studying the quantized nature of photon emission. In contrast to earlier findings we observe that the total radiated energy for very short interaction times, achieved by studying thin plasma channel targets, is significantly larger in a quantum radiation model as compared to a calculation including classical radiation reaction, i.e., we observe quantum anti-quenching. By means of a detailed analytical analysis and a refined test particle model, corroborated by a full kinetic plasma simulation, we demonstrate that this counter-intuitive behavior is due to the constant supply of energy to the setup through the driving laser. We comment on an experimental realization of the proposed setup, feasible at upcoming high-intensity laser facilities, since the required thin targets can be manufactured and the driving laser pulses provided with existing technology.

physics.plasm-ph↗

arXiv2020

Generation of focusing ion beams by magnetized electron sheath acceleration

We present the first 3D particle-in-cell simulations of laser driven sheath-based ion acceleration in a kilotesla-level applied magnetic field. The applied magnetic field creates two distinct stages in the acceleration process associated with the time-evolving magnetization of the hot electron sheath and results in a focusing, magnetic field-directed ion source of multiple species with strongly enhanced energy and number. The benefits of adding the magnetic field are downplayed in 2D simulations, which strongly suggests the feasibility of observing magnetic field effects under experimentally relevant conditions.

physics.plasm-ph↗

arXiv2020

Magnetic field amplification in a laser-irradiated thin foil by return current electrons carrying orbital angular momentum

Magnetized high energy density physics offers new opportunities for observing magnetic field-related physics for the first time in the laser-plasma context. We focus on one such phenomenon, which is the ability of a laser-irradiated magnetized plasma to amplify a seed magnetic field. We performed a series of fully kinetic 3D simulations of magnetic field amplification by a picosecond-scale relativistic laser pulse of intensity $4.2\times 10^{18}$ W/cm$^2$ incident on a thin foil. We observe axial magnetic field amplification from an initial 0.1 kT seed to 1.5 kT over a volume of several cubic microns, persisting hundreds of femtoseconds longer than the laser pulse duration. The magnetic field amplification is driven by electrons in the return current gaining favorable orbital angular momentum from the seed magnetic field. This mechanism is robust to laser polarization and delivers order-of-magnitude amplification over a range of simulation parameters.

physics.plasm-ph↗

arXiv2019

Radiation rebound and Quantum Splash in Electron-Laser Collision

The radiation reaction (RR) is expected to play a critical role in light-matter interactions at extreme intensity. Utilizing the theoretical analyses and three-dimensional (3D) numerical simulations, we demonstrate that electron reflection, induced by the RR in a head-on collision with an intense laser pulse, can provide pronounced signatures to discern the classical and quantum RR. In the classical regime, there is a precipitous threshold of laser intensity to achieve the whole electron bunch rebound. However, this threshold becomes a gradual transition in the quantum regime, where the electron bunch is quasi-isotropically scattered by the laser pulse and this process resembles a water splash. Leveraged on the derived dependence of classical radiation rebound on the parameters of laser pulses and electron bunches, a practical detecting method is proposed to distinguish the quantum discrete recoil and classical continuous RR force.

physics.acc-ph↗

arXiv2019

Strong energy enhancement in a laser-driven plasma-based accelerator through stochastic friction

Conventionally, friction is understood as an efficient dissipation mechanism depleting a physical system of energy as an unavoidable feature of any realistic device involving moving parts, e.g., in mechanical brakes. In this work, we demonstrate that this intuitive picture loses validity in nonlinear quantum electrodynamics, exemplified in a scenario where spatially random friction counter-intuitively results in a highly directional energy flow. This peculiar behavior is caused by radiation friction, i.e., the energy loss of an accelerated charge due to the emission of radiation. We demonstrate analytically and numerically how radiation friction can enhance the performance of a specific class of laser-driven particle accelerators. We find the unexpected directional energy boost to be due to the particles' energy being reduced through friction whence the driving laser can accelerate them more efficiently. In a quantitative case we find the energy of the laser-accelerated particles to be enhanced by orders of magnitude.

physics.acc-ph↗

arXiv2019

Impact of ion dynamics on laser-driven electron acceleration and gamma-ray emission in structured targets at ultra-high laser intensities

We examine the impact of the ion dynamics on laser-driven electron acceleration in an initially empty channel irradiated by an ultra-high intensity laser pulse with $I > 10^{22}$ W/cm$^2$. The negative charge of the accelerated electrons inside the channel generates a quasi-static transverse electric field that causes gradual ion expansion into the channel. Once the ions fill the channel, the pinching force from the quasi-static magnetic field generated by the accelerated electrons becomes uncompensated due to the reduction of the quasi-static transverse electric field. As a result there are two distinct populations of accelerated electrons: those that accelerate ahead of the expanding ion front while moving predominantly forward and those that accelerate in the presence of the ions in the channel while performing strong transverse oscillations. The ions diminish the role of the longitudinal laser electric field, making the transverse electric field the dominant contributor to the electron energy. The ion expansion also has a profound impact on the gamma-ray emission, causing it to become volumetrically distributed while reducing the total emitted energy. We formulate a criterion for the laser pulse duration that must be satisfied in order to minimize the undesired effect from the ions and to allow the electrons to remain highly collimated. \textcolor{black}{We demonstrate the predictive capability of this criterion by applying it to assess the impact of a given pre-pulse on ion expansion. Our results provide a} guideline for future experiments at multi-PW laser facilities with ultra-high intensities.

physics.plasm-ph↗