arXiv subjects

Marija Vranic

Publications and source records attributed to Marija Vranic.

At least 19 recordsLinked to original sources

arXiv2026

Single-laser scheme for reaching strong field QED regime via direct laser acceleration

We investigate a single-laser scheme for reaching the strong-field QED regime based on direct laser acceleration (DLA) of electrons followed by their head-on collision with the same laser pulse reflected from an overdense foil. In this configuration, electrons are first accelerated inside an underdense plasma by a relativistic laser pulse and subsequently interact with the reflected laser field, emitting high-energy photons via nonlinear Compton scattering which decay into electron-positron pairs through the nonlinear Breit-Wheeler process. Using analytical scalings supported by quasi-3D particle-in-cell simulations including QED effects, we demonstrate that a laser pulse with power as low as 2 PW is sufficient to reach the quantum regime characterized by $\chi_e> 1$ . For higher powers, we observe a rapid nonlinear increase in the number of generated positrons, reaching more than 2 nC for a 10 PW laser pulse with energy of approximately 1.1 kJ. A semi-analytical model is employed to estimate the positron yield, showing good agreement with simulation results. We further study the influence of laser depletion and the positioning of the reflecting foil on the efficiency of pair production. The presented scheme provides an experimentally feasible platform for probing strong-field QED effects using currently available multi-petawatt laser systems.

physics.plasm-ph↗

arXiv2025

Betatron radiation emitted during the direct laser acceleration of electrons in underdense plasmas

Relativistic laser pulses can accelerate electrons up to energies of several GeV during the interaction with gaseous targets through the direct laser acceleration (DLA) mechanism. While the electrons are accelerated to high energies, they oscillate transversely to the laser propagation direction, emitting radiation. We demonstrate using particle-in-cell (PIC) simulations that the high accelerated electron charge enables DLA sources to emit $\sim 10^{10}~\rm{photons}/0.1\%\rm{BW}$ at energies of hundreds MeV when interacting with multi-petawatt laser pulses. We provide an analytical estimate of the expected critical frequency for the DLA betatron spectrum which is in strong agreement with PIC simulations. We also show that using gas jets of low density ($\sim 10^{19}~\rm{cm^{-3}}$) is beneficial for the brightness of the source, since low plasma density produces collimated radiation. If the laser pulse is focused to an optimal spot size that results in the highest cut-off energies, conversion efficiency from laser to radiation can reach up to a few percent, which makes the DLA a promising high-brilliance source of gamma-ray radiation.

physics.plasm-ph↗

arXiv2024

Variational Quantum Simulation of the Fokker-Planck Equation applied to Quantum Radiation Reaction

Near-future experiments with Petawatt class lasers are expected to produce a high flux of gamma-ray photons and electron-positron pairs through Strong Field Quantum Electrodynamical processes. Simulations of the expected regime of laser-matter interaction are computationally intensive due to the disparity of the spatial and temporal scales and because quantum and classical descriptions need to be accounted for simultaneously (classical for collective effects and quantum for nearly-instantaneous events of hard photon emission and pair creation). A typical configuration for experiments is a scattering of an electron and a laser beam which can be mapped to an equivalent problem with constant magnetic field. We study the stochastic cooling of an electron beam in a strong constant uniform magnetic field, both its particle distribution functions and their energy momenta. We start by obtaining approximate closed-form analytical solutions to the relevant observables. Then, we apply the quantum-hybrid Variational Quantum Imaginary Time Evolution to the Fokker-Planck equation describing this process, and compare against theory and results from Particle-In-Cell simulations and classical Partial Differential Equation solvers, showing good agreement. This work will be useful as a first step towards quantum simulation of plasma physics scenarios where diffusion processes are important, in particular in strong electromagnetic fields.

physics.plasm-ph↗

arXiv2024

Direct laser acceleration in varying plasma density profiles

Direct laser acceleration has proven to be an efficient source of high-charge electron bunches and high brilliance X-rays. However, an analytical description of the acceleration in the interaction with varying plasma density targets is still missing. Here, we provide an analytical estimate of the maximum energies that electrons can achieve in such a case. We demonstrate that the maximum energy depends on the local electron properties at the moment when the electron fulfills the resonant condition at the beginning of the acceleration. This knowledge enables density shaping for various purposes. One application is to decrease the required acceleration distance which has important implications for multi-petawatt laser experiments, where strong laser depletion could play a crucial role. Another use for density tailoring is to achieve acceleration beyond the radiation reaction limit. We derive the energy scaling law that is valid for arbitrary density profile that varies slowly compared with the betatron period. Our results can be applied to electron heating in exponential preplasma of thin foils, ablating plasma plumes, or gas jets with long-scale ramp-up.

physics.plasm-ph↗

arXiv2024

Direct Laser Acceleration of Bethe-Heitler positrons in laser-channel interactions

Positron creation and acceleration is one of the major challenges for constructing future lepton colliders. On the one hand, conventional technology can provide a solution, but at a prohibitive cost and scale. On the other hand, alternative, reduced-scale ideas for positron beam generation could bring this dream closer to reality. Here we propose a novel plasma-based positron acceleration method using a powerful laser propagating through a dense and narrow plasma channel. A large amount of electrons is injected within the channel during laser propagation. This electron loading creates static fields in the plasma, enabling positrons to be guided transversely while they directly gain energy from the laser field itself. Within this context, we present a theoretical model to describe how the laser injects the electrons and estimate the beam-loaded effective electron density. We validate our theoretical predictions through Quasi-3D PIC simulations and demonstrate the robustness of this guiding and direct laser acceleration process for positrons. Our approach could pave the way for testing this new positron acceleration scheme at ELI-Beamlines, showcasing unprecedentedly high average energy gain rate of a few TeV/m. The fireball jet produced contains GeV-level electrons, positrons, and x-rays, opening the path towards potential laboratory astrophysics experiments using these beams.

physics.plasm-ph↗

arXiv2023

Parametric study of the polarization dependence of nonlinear Breit-Wheeler pair creation process using two laser pulses

With the rapid development of high-power petawatt class lasers worldwide, exploring physics in the strong field QED regime will become one of the frontiers for laser-plasma interactions research. Particle-in-cell codes, including quantum emission processes, are powerful tools for predicting and analyzing future experiments where the physics of relativistic plasma is strongly affected by strong-field QED processes. The spin/polarization dependence of these quantum processes has been of recent interest. In this article, we perform a parametric study of the interaction of two laser pulses with an ultrarelativistic electron beam. The first pulse is optimized to generate high-energy photons by nonlinear Compton scattering and efficiently decelerate the electron beam through quantum radiation reaction. The second pulse is optimized to generate electron-positron pairs by nonlinear Breit-Wheeler decay of the photons with the maximum polarization dependence. This may be experimentally realized as a verification of the strong field QED framework, including the spin/polarization rates.

hep-ph↗

arXiv2023

Magnetic field generation in laser-solid interactions at strong-field QED relevant intensities

Magnetic field generation in ultra-intense laser-solid interactions is studied over a range of laser intensities relevant to next-generation laser facilities ($a_0 = 50-500$) using 2D particle-in-cell simulations. It is found that fields on the order of 0.1 MT (1 GigaGauss) may be generated by relativistic electrons traveling along the surface of the target. However a significant fraction of the energy budget is converted to high-energy photons, ~38% at $a_0=500$, greatly reducing the available energy for field generation. A model for the evolution of the target-surface fields and their scaling with $a_0$ is developed using laser parameters and assumed values for the average radial electron velocity and reflectivity. The model and empirical scaling allow for the estimation of field strengths on the next generation of laser facilities, a necessary component to the proposal of any future magnetized experiment.

physics.plasm-ph↗

arXiv2023

Radiation-dominated injection of positrons generated by the nonlinear Breit-Wheeler process into a plasma channel

Plasma acceleration is considered a prospective technology for building a compact multi-TeV electron-positron collider in the future. The challenge of this endeavor is greater for positrons than for the electrons because usually the self-generated fields from laser-plasma interaction are not well-suited for positron focusing and on-axis guiding. In addition, an external positron source is required, while electrons are naturally available in the plasma. Here, we study electron-positron pair generation by an orthogonal collision of a multi-PW laser pulse and a GeV electron beam by the nonlinear Breit-Wheeler process. We studied conditions favorable for positron deflection in the direction of the laser pulse propagation, which favors injection into the plasma for further acceleration. We demonstrate using the OSIRIS particle-in-cell framework that the radiation reaction triggered by ultra-high laser intensity plays a crucial role in the positron injection. It provides a suppression of the initial transverse momentum gained by the positrons from the Breit-Wheeler process. For the parameters used in this work, the intensity of at least 2.2x1023 W/cm2 is needed in order to inject more than 1% of positrons created. Above this threshold, the percentage of injected positrons rapidly increases with intensity. Moreover, subsequent direct laser acceleration of positrons in a plasma channel, using the same laser pulse that created them, can ensure a boost of the final positron energy by a factor of two. The positron focusing and guiding on the axis is provided by significant electron beam loading that changes the internal structure of the channel fields.

physics.plasm-ph↗

arXiv2023

QScatter: Numerical Framework for Fast Prediction of Particle Distributions in Electron-Laser Scattering

The new generation of multi-PetaWatt laser facilities will allow tests of Strong Field QED, as well as provide an opportunity for novel photon and lepton sources. The first experiments are planned to study the (nearly) head-on scattering of intense, focused laser pulses with either relativistic electron beams or high-energy photon sources. In this work, we present a numerical framework that can provide fast predictions of the asymptotic particle and photon distributions after the scattering. The works presented in this manuscript includes multiple features such as spatial and temporal misalignment between the laser and the scattering beam, broadband electron beams, and beam divergence. The expected mean energy, energy spread, divergence or other observables are calculated by combining an analytical description and numerical integration. This method can provide results within minutes on a personal computer, which would otherwise require full-scale 3D QED-PIC simulations using thousands of cores. The model, which has been compiled into an open-source code QScatter, may be used to support the analysis of large-size data sets from high-repetition rate experiments, leveraging its speed for optimization or reconstruction of experimental parameters.

physics.plasm-ph↗

arXiv2023

Beam Delivery and Beamstrahlung Considerations for Ultra-High Energy Linear Colliders

As part of the Snowmass'21 community planning excercise, the Advanced Accelerator Concepts (AAC) community proposed future linear colliders with center-of-mass energies up to 15 TeV and luminosities up to 50$\times10^{34}$ cm$^{-2}$s$^{-1}$ in a compact footprint. In addition to being compact, these machines must also be energy efficient. We identify two challenges that must be addressed in the design of these machines. First, the Beam Delivery System (BDS) must not add significant length to the accelerator complex. Second, beam parameters must be chosen to mitigate beamstrahlung effects and maximize the luminosity-per-power of the machine. In this paper, we review advances in plasma lens technology that will help to reduce the length of the BDS system and we detail new Particle-in-Cell simulation studies that will provide insight into beamstrahlung mitigation techniques. We apply our analysis to both $e^+e^-$ and $γγ$ colliders.

physics.acc-ph↗

arXiv2023

Charged particle beam transport in a flying focus pulse with orbital angular momentum

We demonstrate the capability of Flying Focus (FF) laser pulses with $\ell = 1$ orbital angular momentum (OAM) to transversely confine ultra-relativistic charged particle bunches over macroscopic distances while maintaining a tight bunch radius. A FF pulse with $\ell = 1$ OAM creates a radial ponderomotive barrier that constrains the transverse motion of particles and travels with the bunch over extended distances. As compared to freely propagating bunches, which quickly diverge due to their initial momentum spread, the particles co-traveling with the ponderomotive barrier slowly oscillate around the laser pulse axis within the spot size of the pulse. This can be achieved at FF pulse energies that are orders of magnitude lower than required by Gaussian or Bessel pulses with OAM. The ponderomotive trapping is further enhanced by radiative cooling of the bunch resulting from rapid oscillations of the charged particles in the laser field. This cooling decreases the mean square radius and emittance of the bunch during propagation.

physics.plasm-ph↗

arXiv2021

Optimal laser focusing for positron production in laser-electron scattering

Laser-electron beam collisions that aim to generate electron-positron pairs require laser intensities $I \gtrsim 10^{21} ~\textrm{W/cm}^2$, which can be obtained by focusing a 1-PW optical laser to a spot smaller than 10 $~μ$m. Spatial synchronization is a challenge, because of the Poynting instability that can be a concern both for the interacting electron beam (if laser-generated) and the scattering laser. One strategy to overcome this problem is to use an electron beam coming from an accelerator (e.g. the planned E-320 experiment at FACET-II). Even using a stable accelerator beam, the plane wave approximation is too simplistic to describe the laser-electron scattering. This work extends analytical scaling laws for pair production, previously derived for the case of a plane wave and a short electron beam. We consider a focused laser beam colliding with electron beams of different shapes and sizes. The results take the spatial and temporal synchronization of the interaction into account, can be extended to arbitrary beam shapes, and prescribe the optimization strategies for near-future experiments.

physics.plasm-ph↗

arXiv2021

Accurately simulating nine-dimensional phase space of relativistic particles in strong fields

Next-generation high-power lasers that can be focused to intensities exceeding 10^23 W/cm^2 are enabling new physics and applications. The physics of how these lasers interact with matter is highly nonlinear, relativistic, and can involve lowest-order quantum effects. The current tool of choice for modeling these interactions is the particle-in-cell (PIC) method. In strong fields, the motion of charged particles and their spin is affected by radiation reaction. Standard PIC codes usually use Boris or its variants to advance the particles, which requires very small time steps in the strong-field regime to obtain accurate results. In addition, some problems require tracking the spin of particles, which creates a 9D particle phase space (x, u, s). Therefore, numerical algorithms that enable high-fidelity modeling of the 9D phase space in the strong-field regime are desired. We present a new 9D phase space particle pusher based on analytical solutions to the position, momentum and spin advance from the Lorentz force, together with the semi-classical form of RR in the Landau-Lifshitz equation and spin evolution given by the Bargmann-Michel-Telegdi equation. These analytical solutions are obtained by assuming a locally uniform and constant electromagnetic field during a time step. The solutions provide the 9D phase space advance in terms of a particle's proper time, and a mapping is used to determine the proper time step for each particle from the simulation time step. Due to the analytical integration, the constraint on the time step needed to resolve trajectories in ultra-high fields can be greatly reduced. We present single-particle simulations and full PIC simulations to show that the proposed particle pusher can greatly improve the accuracy of particle trajectories in 9D phase space for given laser fields. A discussion on the numerical efficiency of the proposed pusher is also provided.

physics.comp-ph↗

arXiv2019

Are we ready to transfer optical light to gamma-rays?

Scattering relativistic electrons with optical lasers can result in a significant frequency upshift for the photons, potentially producing $γ$-rays. This is what linear Compton scattering taught us. Ultra-intense lasers offer nowadays a new paradigm where multi-photon absorption effects come into play. These effects can result in higher harmonics, higher yields and also electron-positron pairs. This article intends to discriminate the different laser scenarios that have been proposed over the past years as well as to give scaling laws for future experiments. The energy conversion from laser or particles to high-frequency photons is addressed for both the well-known counter propagating electron beam-laser interaction and for Quantum-electrodynamics cascades triggered by various lasers. Constructing bright and energetic gamma-ray sources in controlled conditions is within an ace of seeing the light of day.

physics.plasm-ph↗

arXiv2019

Suitability and robustness of triangular nanostructured targets for proton acceleration

Ion acceleration in the MeV range can be routinely achieved with table-top laser technology. One of the current challenges is to improve the energy coupling from the laser to the proton beam without increasing the laser peak power. Introducing nanostructures at the front target surface was shown to be beneficial for an efficient transfer of energy to the electrons. In this manuscript, we study by using full-scale three-dimensional particle-in-cell simulations and finite laser pulses, the process when a proposed optimal target with triangular nanostructure (previously found to allow 97% laser energy absorption) is used . We demonstrate that the absorbed laser energy does not depend on the dimensionality in the range of parameters presented. We also present an analytical model for laser absorption that includes deviations from the ideal conditions. This is supported by a numerical parameter study that establishes the tolerance with respect to the nanostructure size, use of different ion species, existence of preplasma, etc. We found that altering the target thickness or using different ions does not affect the absorption, but it does affect the energy redistribution among the different plasma species. The optimal configuration ($h = 1~λ,~ w = 0.7~ λ$) is robust with respect to the target fabrication errors. However, high contrast laser pulses are required, because a pre-plasma layer with a thickness on the order of 0.5 lambda is enough to lower the laser absorption by more than a 10% in a non-optimal scenario.

physics.plasm-ph↗

arXiv2019

Extremely intense laser-based electron acceleration in a plasma channel

Laser pulses of extreme intensities ($I>10^{22}~ \mathrm{W/cm^2}$) are about to become available in the laboratory. The prepulse of such a laser can induce a plasma expansion that generates a low-density channel in near-critical gas jets. We present a study of channel formation and subsequent direct laser acceleration of electrons within the pre-formed channel. Radiation reaction affects the acceleration in several ways. It first interferes with the motion of the return current on the channel walls. In addition, it reduces the radial expelling efficiency of the transverse ponderomotive force, leading to the radiative trapping of particles near the channel axis. These particles then interact with the peak laser intensity and can attain multi-GeV energies.

physics.plasm-ph↗

arXiv2017

Multi-GeV electron-positron beam generation from laser-electron scattering

The new generation of laser facilities is expected to deliver short (10 fs - 100 fs) laser pulses with 10 - 100 PW of peak power. This opens an opportunity to study matter at extreme intensities in the laboratory and provides access to new physics. Here we propose to scatter GeV-class electron beams from laser-plasma accelerators with a multi-PW laser at normal incidence. In this configuration, one can both create and accelerate electron-positron pairs. The new particles are generated in the laser focus and gain relativistic momentum in the direction of laser propagation. Short focal length is an advantage, as it allows the particles to be ejected from the focal region with a net energy gain in vacuum. Electron-positron beams obtained in this setup have a low divergence, are quasi-neutral and spatially separated from the initial electron beam. The pairs attain multi-GeV energies which are not limited by the maximum energy of the initial electron beam. We present an analytical model for the expected energy cutoff, supported by 2D and 3D particle-in-cell simulations. The experimental implications, such as the sensitivity to temporal synchronisation and laser duration is assessed to provide guidance for the future experiments.

physics.plasm-ph↗

arXiv2016

Seeded QED cascades in counter propagating laser pulses

The growth rates of seeded QED cascades in counter propagating lasers are calculated with first principles 2D/3D QED-PIC simulations. The dependence of the growth rate on laser polarization and intensity are compared with analytical models that support the findings of the simulations. The models provide an insight regarding the qualitative trend of the cascade growth when the intensity of the laser field is varied. A discussion about the cascade's threshold is included, based on the analytical and numerical results. These results show that relativistic pair plasmas and efficient conversion from laser photons to gamma rays can be observed with the typical intensities planned to operate on future ultra-intense laser facilities such as ELI or VULCAN.

physics.plasm-ph↗