arXiv subjects

Brandon K. Russell

Publications and source records attributed to Brandon K. Russell.

12 recordsLinked to original sources

arXiv2026

Helical jets driven by a ring of laser irradiation

Plasma jets are formed in various astrophysical systems as plasma is rapidly ejected from a source, with a subset of these jets being magnetized and having a helical structure. Here, we demonstrate that helical jets may be formed using a ring of laser pulses that arrive on planar foils sequentially with increasing energy. The formation of the jets and their properties, including kinetic helicity, are studied through a set of three-dimensional magneto-hydrodynamics simulations with conditions informed by the parameters of the OMEGA laser facility. We find that jets with a higher degree of helicity may be generated under realistic experimental conditions when compared to a uniform jet. Synthetic x-ray and Thomson scattering diagnostics computed from simulated data demonstrate that the helical jet provides a unique fingerprint in both its morphology and plasma parameters. This laboratory helical jet platform may allow for controlled experimental study of the dynamics of helical plasma structures and, through interaction with other jets or targets, can allow for studies of shear-driven turbulence and mixing relevant to interactions between astrophysical jets and ambient clouds or crosswind.

physics.plasm-ph↗

arXiv2026

Energy-optimized scaling laws for self-guided laser wakefield accelerators

Laser wakefield acceleration promises compact electron accelerators for applications in medicine, industry, and fundamental science. Yet, despite rapid progress, accurately predicting the electron energy attainable in a given experimental configuration and the acceleration length required to reach it remains an open challenge. Here we use Bayesian optimization combined with advanced particle-in-cell simulation techniques to determine the maximum electron energy that a self-guided laser wakefield accelerator driven by a laser of a given energy and wavelength can produce. By systematically optimizing the accelerator performance across a range of laser energies and wavelengths, we derive energy-optimized scaling laws. These scaling laws yield the highest electron energy over the shortest acceleration length possible, are expressed solely in terms of laser energy and wavelength, and are accompanied by the complete set of laser and plasma parameters required to enable the scaling. The resulting scaling laws provide practical guidance for designing state-of-the-art laser wakefield acceleration experiments operating at their fundamental performance limits.

physics.plasm-ph↗

arXiv2026

Photon Acceleration in Magnetized Plasma: A Mechanism for Fast Radio Bursts

We propose a mechanism for fast radio bursts based on photon acceleration by relativistic shocks propagating through highly magnetized electron--positron plasmas, as expected in magnetar magnetospheres. Density modulations at the shock front create relativistically moving refractive-index perturbations that transform low-frequency electromagnetic precursors into amplified high-frequency radiation. We show that the predicted frequencies, durations, and energetics of the resulting fast radio bursts are consistent with the magnetic-field strengths, shock Lorentz factors, and characteristic spatial scales expected in magnetar magnetospheres.

physics.space-ph↗

arXiv2026

Plasma Flow Generation and Particle Acceleration from Expanding Magnetic Bubbles

Impulsive plasma dynamics in the laboratory are often driven by rising electric currents, yet their quantitative plasma response has not been well established. By means of fully kinetic particle-in-cell simulations and laser-driven capacitor-coil experiments, we show that a rising current expels plasma, forming an expanding magnetic bubble and accelerating particles. The expansion front velocity scales with the Alfv\'en speed determined by the magnetic field at its inner edge and the plasma density at its outer edge. This mechanism establishes impulsive current drive as a fundamental way that generates plasma flows and accelerates particles in laboratory plasmas, with potential relevance to astrophysics.

physics.plasm-ph↗

arXiv2026

Interaction of Strong Electromagnetic Waves with Unmagnetized Pair Plasmas

We investigate analytically and numerically the interaction of strong electromagnetic waves with unmagnetized pair plasmas. We show that the interaction is governed by a single nonlinearity parameter, $\varepsilon_{\rm p}$, defined as the ratio of the wave strength parameter to the wave frequency in units of the plasma frequency (with both frequencies measured in the plasma rest frame prior to the interaction). When $\varepsilon_{\rm p}<1$, the number of wavelengths that propagate through the plasma without attenuation from induced Compton scattering is approximately $\varepsilon_{\rm p}^{-2/3}$. This attenuation can imprint sub-structures as narrow as a few wavelengths on the pulse profile. When $\varepsilon_{\rm p}>1$, the electromagnetic pulse acts as a relativistic piston and drives a shock into the plasma. Our results establish a framework for the interaction of strong electromagnetic waves with pair plasmas, a process relevant for intense radio pulses from neutron stars and for next-generation pair plasma experiments at multi-petawatt laser facilities.

physics.plasm-ph↗

arXiv2026

Pair-loaded electron-only magnetic reconnection using laser-driven capacitor coils

We propose and simulate a laboratory platform to study the effects of positrons in magnetic reconnection using laser-driven capacitor coils. Using particle-in-cell simulations, we show that externally injected MeV electron-positron pairs are trapped in the coil current sheet, significantly modifying the reconnection dynamics and particle acceleration. These pairs increase the reconnection rate by a factor of approximately 8, which Ohm's law decomposition reveals to be driven by the divergence of the generalized pressure tensor. Based on their high energy and magnetization, the pairs also substantially broaden the diffusion region. Particle tracking simulations in realistic coil magnetic fields further demonstrate that injected pairs can remain confined for several picoseconds, providing conditions for sustained interaction with the reconnection region. These results establish a near-term pathway to laboratory studies of positron-influenced reconnection, bridging high-energy-density experiments with pair-dominated astrophysical environments.

physics.plasm-ph↗

arXiv2026

Time-Resolved Interferometric Measurements of Plasma Density Evolution in Laser-Driven Capacitor-Coil Targets

Laser-driven capacitor-coil targets provide a compact platform for generating strong magnetic fields and are widely used in magnetized high-energy-density plasma experiments. In addition to magnetic-field generation, these targets also produce plasma in the coil region, which can influence the subject physical processes, interact with secondary targets or external plasmas in their applications. However, direct, time-resolved measurements of the plasma density surrounding the coil remain limited. Here, we report interferometric measurements of the plasma density evolution in laser-driven capacitor-coil targets irradiated by the University of Osaka LFEX laser. Two-dimensional electron density maps reveal two distinct plasma sources loading the coil region: plasma generated in the coil itself and plasma produced by laser ablation of the target plates. These results provide quantitative information on plasma loading and evolution in capacitor-coil targets and are directly relevant to the design and modeling of magnetized high-energy-density plasma experiments.

physics.plasm-ph↗

arXiv2025

Reaching extreme fields in laser-electron beam collisions with XUV laser light

Plasma-based particle accelerators promise to extend the revolutionary work performed with conventional particle accelerators to studies with smaller footprints, lower costs, and higher energies. Here, we propose a new approach to access an unexplored regime of strong-field quantum electrodynamics by plasma wakefield acceleration of both charged particles and photons. Instead of using increasingly powerful accelerators and lasers, we show that photon acceleration of optical pulses into the extreme ultraviolet allows multi-GeV electrons to reach quantum nonlinearity parameters $\chi_e \gg 10$ with a high probability due to the reduced radiative losses. A significant fraction of photons produced in high-$\chi_e$ regions will propagate to detectors without generating pairs because of the reduction in the quantum rates. The photon spectra obtained may be used to characterize the predicted breakdown of strong-field quantum electrodynamics theory as it enters the fully non-perturbative regime.

physics.plasm-ph↗

arXiv2025

Record Magnetic Field Generation by Short-Pulse Laser-Driven Capacitor-Coil Targets

Magnetic fields generated by capacitor-coil targets driven by intense short-pulse lasers have been characterized using ultrafast proton radiography. A 1-kJ, 15-ps laser at a center wavelength of 1053 nm irradiated the back plate of the capacitor with an intensity of $\sim$8.3 $\times$ 10$^{18}$ W$/$cm$^{2}$, creating ultra large currents in the connecting coils. High-quality proton data obtained in the axial probing geometry show definitive signatures of magnetic field generation allowing precision measurement of the field distribution and strength. The data show a coil current of 120 $\pm$ 10 kA producing 200 $\pm$ 20 Tesla magnetic fields at the coil center at 1.127 ns afer the laser drive. This sets a record for magnetic field generation by the short-pulse-powered capacitor-coil targets.

physics.plasm-ph↗

arXiv2025

Diagnosing electric and magnetic fields in laser-driven coil targets

Laser-driven capacitor coils are widely used to generate intense magnetic fields for various applications in high-energy-density physics research. Accurate measurement of the magnetic fields is essential but challenging, due to the overlapping contributions from magnetic and electric fields in proton radiography, which is the primary tool diagnosing the field generation around the coils. In this study, we systematically analyze proton radiographs obtained from laser-driven capacitor-coil targets along two orthogonal axes under various electromagnetic field conditions, including magnetic field only, electric field only, and combined electromagnetic fields. By analyzing key features in the radiographs, we distinguish and characterize the respective contributions from magnetic and electric fields. Using detailed simulations validated by experimental benchmarks, methods to isolate and quantify the magnetic field and electric field are given. The methods are successfully applied to determine the electric current and charge distribution in a double coil configuration. Our findings provide insights into improving the diagnostic capability of proton radiography, potentially leading to more accurate measurements of electromagnetic fields and enhancing the utility of laser-driven capacitor coils in high-energy-density experiments.

physics.plasm-ph↗

arXiv2024

Photon acceleration of high-intensity vector vortex beams into the extreme ultraviolet

Extreme ultraviolet (XUV) light sources allow for the probing of bound electron dynamics on attosecond scales, interrogation of high-energy-density matter, and access to novel regimes of strong-field quantum electrodynamics. Despite the importance of these applications, coherent XUV sources remain relatively rare, and those that do exist are limited in their peak intensity and spatio-polarization structure. Here, we demonstrate that photon acceleration of an optical vector vortex pulse in the moving density gradient of an electron beam-driven plasma wave can produce a high-intensity, tunable-wavelength XUV pulse with the same vector vortex structure as the original pulse. Quasi-3D, boosted-frame particle-in-cell simulations show the transition of optical vector vortex pulses with 800-nm wavelengths and intensities below $10^{18}$ W/cm$^2$ to XUV vector vortex pulses with 36-nm wavelengths and intensities exceeding $10^{20}$ W/cm$^2$ over a distance of 1.2 cm. The XUV pulses have sub-femtosecond durations and nearly flat phase fronts. The production of such high-quality, high-intensity XUV vector vortex pulses could expand the utility of XUV light as a diagnostic and driver of novel light-matter interactions.

physics.optics↗

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↗