arXiv subjects

Jian-Xing Li

Publications and source records attributed to Jian-Xing Li.

At least 19 recordsLinked to original sources

arXiv2026

High-charge, highly polarized positron beams generated from a laser-driven nanowire-array target

The generation of high-charge, highly polarized positron beams in the interaction of a linearly polarized laser pulse with a nanowire-array target is investigated. Here, laser-driven electrons emit high-energy photons through nonlinear Compton scattering (NCS), which subsequently produce electron--positron pairs through the nonlinear Breit--Wheeler (NBW) process. We model this interaction using two-dimensional spin-resolved quantum electrodynamics particle-in-cell (QED-PIC)} simulations. At positron birth, the sign of $S_z$ is statistically correlated with that of the local $B_z$. The spatiotemporal field structure arising from the laser--nanowire interaction strengthens the correlation between the birth spin sign and the direction of the subsequent transverse Lorentz impulse, thereby limiting cancellation between opposite-spin contributions at a given angle. The results show that the average polarization degree reaches $|\bar S_z|\approx0.46$, and the positron charge satisfying $|\bar S_z|>0.3$ is approximately $308\,\mathrm{nC}$. Parameter scans reveal that the high-polarization positron charge is maximized at intermediate target densities and nanowire periods. Such a source could enable polarization-sensitive studies of strong-field QED and spin-dependent phenomena in high-energy and materials physics.

physics.plasm-ph↗

arXiv2026

Revealing the Nonlinear Amplification of Radiation Reaction Effects via Vortex Radiation

Radiation reaction (RR), the back-action of emitted radiation on an accelerated charge, dominates the dynamics of ultrarelativistic electrons in an intense electromagnetic field. By solving the Landau-Lifshitz (LL) equation for an electron in an intense circularly polarized plane wave, we find that once the cumulative RR effect on the oscillation radius becomes non-negligible over hundreds of laser cycles, the laser intensity nonlinearly amplifies RR through the modified longitudinal drift velocity, reshaping the vortex $γ$-ray emission in nonlinear inverse Thomson scattering. The energy spectrum acquires MeV-scale central-frequency red shifts, spectral broadening, and harmonic overlap, while the ellipticity of higher-order harmonics becomes non-smooth and overlapping in frequency--angle space, so that the superposed total ellipticity deviates progressively from the RR-free case. These harmonic-resolved spectral and polarization fingerprints constitute a self-referenced multidimensional diagnostic of RR effects that complements energy-spectrum measurements, with direct implications for bright high-energy $γ$-ray sources and the modeling of extreme astrophysical environments such as neutron-star magnetospheres.

physics.plasm-ph↗

arXiv2026

Polarization-resolved attosecond gamma-ray emission from few-cycle laser interactions with cone targets

Linearly polarized attosecond $γ$-ray pulses in the MeV range are generated from a cone target irradiated by a single few-cycle laser pulse. Electron layers are periodically extracted from the cone walls and subsequently accelerated. Their interaction with the counter-propagating reflected attosecond field produces high-energy photons through nonlinear Compton scattering (NCS), forming attosecond $γ$-ray pulses. We model this interaction using two-dimensional quantum electrodynamics particle-in-cell (QED-PIC) simulations that resolve electron spin and photon polarization during emission. The results show a shortest equivalent duration of $300\,\mathrm{as}$, with a corresponding linear polarization degree of 0.78. The photon spectrum extends to $6\,\mathrm{MeV}$, and the linear polarization degree in the high-energy range reaches 0.88. The linear polarization degree remains high when photons from both emission directions are collected over wide momentum-angle ranges. Scans over the cone opening angle and the coupled laser-plasma parameters reveal tradeoffs among photon number, mean photon energy, and polarization. Such highly polarized attosecond $γ$-ray pulses could be used to investigate ultrafast nuclear dynamics and polarization-dependent processes in strong-field quantum electrodynamics.

physics.plasm-ph↗

arXiv2026

Generation of dense relativistic electron beams via vortex laser-driven self-generated magnetic pinching

In multi-petawatt laser plasma accelerators, achieving high-density relativistic electron beams is typically accompanied by large transverse divergence, limiting the attainable effective electron density needed for high-flux interaction regimes relevant to laboratory astrophysics. Here we report experimental demonstration of self-generated magnetic pinching (SMP), a collective mechanism that actively regulates transverse beam dynamics using a Laguerre-Gaussian laser at strong relativistic intensity (~8 x 10^19 W/cm^2) interacting with an underdense plasma. The electron beam evolves from a two-lobe high-charge injection structure into a compressed, high-density profile, yielding a threefold reduction in divergence and nearly an order-of-magnitude enhancement in effective beam density compared with a Gaussian driver. Particle-in-cell simulations agree with the experimental observations and reveal that a self-generated azimuthal magnetic field governs the electron dynamics within the SMP regime, which is defined by the forming condition S = 0.717 l a0 [ne(10^18 cm^-3)]^-3/4 = 1, where l, a0, and ne are topological charge, laser amplitude, and plasma density, respectively. A transient kick from a dense inner sheath electron population drives collective magnetic pinching, transforming an initially separated electron distribution into a compressed and well-collimated beam. For higher-power laser systems, the forming condition can be extended to higher plasma densities and larger orbital angular momentum modes, potentially enabling electron beams with charges exceeding several nC and effective densities above 10^19 cm^-3. This mechanism provides a route to overcoming transverse expansion and enhancing rare interaction processes relevant to high-flux particle sources.

physics.plasm-ph↗

arXiv2026

Generation-Resolved Signatures in QED Cascades: Diagnostics for Ultraintense Laser Parameters

We present a generation-resolved analysis of shower-type, spin- and polarization-dependent quantum electrodynamics (QED) cascades initiated by head-on collisions of ultraintense laser pulses ($a_0 = 200$--$1000$) with $10$~GeV electron bunches. Using a Monte Carlo model that tracks cascade evolution across distinct generations, we shows that radiation reaction strongly suppresses high-generation yields. The positron energy spectrum exhibits a systematic softening with increasing $a_0$, and the average photon polarization $\overlineξ_3$ increases with pulse duration $τ$ due to polarization-selective depletion in nonlinear Breit--Wheeler pair production. We identify a scaling relation $a_0^2τ$ that governs both the maximum cascade generation $G_{\max}$ and the fraction of backward-emitted photons $F_r$, thereby establishing experimentally accessible diagnostics for laser intensity and pulse duration using two observables: $F_r$ and the positron peak energy $\varepsilon_+^{\rm peak}$. These generation-dependent signatures suggest a potential shot-resolved, post-interaction approach for characterization of ultraintense laser parameters in the strong-field QED regime.

physics.plasm-ph↗

arXiv2026

Generation of Ultrabrilliant Positron Beam via Superponderomotive Injection in Laser Wakefield Acceleration

Plasma-based acceleration of positrons attracts extensive interest owing to the ultrahigh accelerating gradient and ultrashort duration, while generating wakefield positron beam by the inherent injection is still a great challenge. Here, we put forward a superponderomotive injection method of positrons in the blowout regime of laser wakefield acceleration. The dephasing-rate integral equation reveals a twofold mechanism: the longitudinal laser field delays phase-locking, guiding positrons into the paraxial focusing region, while the transverse laser Lorentz force suppresses the dephasing rate below unity, trapping them into the laser-modulated wakefield. Particle-in-cell (PIC) simulations demonstrate this via a donut-wake--pair-jet collision, generating low-emittance ($\sim$0.05~mm~mrad) multicycle positron beams. Start-to-end simulations for post-acceleration in the second-stage donut wakefield confirm high-throughput injection-to-acceleration coupling, yielding quasi-monoenergetic beam with six-dimensional brightness $\sim 10^{15}~\rm{A/m^2}/0.1\%$. This plasma-based injection-acceleration scheme opens a novel compact route to ultrabrilliant positron sources for ultrafast material diagnostics, laboratory astrophysics, and next-generation electron--positron colliders.

physics.plasm-ph↗

arXiv2026

Generation of Polarized Overdense Pair-photon Fireball via Laser-Driven Nonlinear-linear QED Cascade

Relativistic, polarized pair-photon fireballs are central to understand the microscopic energy transfer of high-energy astrophysical outflows, yet generating an overdense fireball in the laboratory, especially via an ultraintense laser, remains a formidable challenge. Here, we propose a novel method of laser-driven nonlinear-linear quantum electrodynamics (NL-QED) plasma, that dramatically lowers the laser intensity threshold for dense pair-photon fireball creation. By coupling polarization-resolved linear Breit-Wheeler and Compton processes with strong-field nonlinear radiation, we find that a self-organized NL-QED cascade is ignited in the laser-driven hole boring at intensities of $\sim 10^{22}~\mathrm{W/cm^2}$, accessible with current 10-PW-class laser facilities. Consequently, we demonstrate the generation of a pair-photon fireball with an overdense gamma-ray bath (maximum average density $\overline{n_γ} \approx 3 \times 10^{22}~\mathrm{cm^{-3}}$) and a pair plasma reaching collective regime (maximum average density $\overline{n_\pm} \approx 3 \times 10^{17}~\mathrm{cm^{-3}}$), which is highly polarized. Our method provides a comprehensive framework for studying laser-driven QED plasma and its application in laboratory astrophysics, probing multi-process QED physics.

physics.plasm-ph↗

arXiv2026

Nuclear excitation via inelastic scattering of low-energy vortex electrons

Vortex particles carrying orbital angular momenta (OAMs) have found important applications in broad fields. However, the experimental verification of OAM transfer at the nuclear scale remains a great challenge. Here, we put forward a novel method to probe such OAM transfer through nuclear excitation via inelastic scattering of low-energy vortex electrons. We develop a Dirac distorted-wave Born approximation framework that incorporates the incident-electron OAM and a nonperturbative treatment of the Coulomb field, and apply it to $^{229}\mathrm{Th}$. We find that the vortex and non-vortex electrons yield opposite angular distributions, attributed to the OAM-modified selection rule and the Coulomb-induced redistribution of partial-wave strengths, providing an angle-resolved signature. Moreover, the vortex electron exhibits topological protection in the nuclear Coulomb field. Our method offers a route to probing nuclear-scale OAM transfer and deepens our understanding of the topological properties of vortex particles.

nucl-th↗

arXiv2026

Manipulation of Superposed Vortex States of $γ$ Photon via Nonlinear Compton Scattering

Vortex $γ$ photons in superposition states have important applications in photonuclear, high-energy, and strong-field physics. However, their controlled generation in the $γ$-ray regime remains a great challenge. Here, we put forward a novel method for the generation of vortex $γ$ photon in superposition states, with controllable orbital angular momentum (OAM) separation $Δ\ell^\prime$ and modal weights, via nonlinear Compton scattering driven by multifrequency circularly polarized laser fields. We develop a strong-field quantum electrodynamics (QED) framework to reveal the underlying mechanism and calculate the radiation probabilities. In our method, the superposition arises from interference between energy-degenerate multiphoton pathways carrying distinct OAM. For two-frequency fields, the OAM separation follows $Δ\ell'=ν\mp1$ (upper/lower sign for equal/opposite helicities), and modal weights are tunable by laser intensities, with $ν$ the frequency ratio. Vortex $γ$ photons in controllable superposition states from our method have significant applications in strong-field QED and nuclear photonics.

quant-ph↗

arXiv2025

Generation of Polarization-Tunable Hybrid Cylindrical Vector gamma Rays

Cylindrical vector (CV) gamma rays can introduce spatially structured polarization as a new degree of freedom for fundamental research and practical applications. However, their generation and control remain largely unexplored. Here, we put forward a novel method to generate CV gamma rays with tunable hybrid polarization via a rotating electron beam interacting with a solid foil. In this process, the beam generates a coherent transition radiation field and subsequently emits gamma rays through nonlinear Compton scattering. By manipulating the initial azimuthal momentum of the beam, the polarization angle of gamma rays relative to the transverse momentum can be controlled, yielding tunable hybrid CV polarization states. Three-dimensional spin-resolved particle-in-cell simulations demonstrate continuous tuning of the polarization angle across (-90°, 90°) with a high polarization degree exceeding 60%. Our work contributes to the development of structured gamma rays, potentially opening new avenues in high-energy physics, nuclear science, and laboratory astrophysics.

physics.plasm-ph↗

arXiv2025

Generating Cylindrical Vector γ Rays via Beam-Target Interactions: Towards Structured Light at High Energies

Structured γ rays, particularly cylindrical vector γ rays, offer promising tools for sub-nuclear imaging and polarization-sensitive probes in fundamental research and applications, but conventional optical methods face great challenges at such photon energy. Here, we put forward a novel method generating such γ rays through relativistic beam-target interactions. For instance, radially polarized γ rays can be generated by using a dense electron beam striking a multifoil target. We find that the radial polarization is transferred from the generated coherent transition radiation (CTR) fields to $γ$ photons through nonlinear Compton scattering, with the high polarization preserved by phase matching. Three-dimensional spin-resolved simulations demonstrate radial polarization degrees approaching 60\%. Furthermore, these γ rays can decay into azimuthally spin-polarized positrons via the nonlinear Breit-Wheeler process, with their spins aligning along the CTR magnetic field. Our work extends the concept of structured light into the γ-ray regime, offering new prospects for broad fields such as nuclear structure probing, fundamental symmetries tests, polarization-sensitive studies in extreme conditions, and laboratory astrophysical observations.

physics.optics↗

arXiv2025

Generation of Relativistic Structured Spin-Polarized Lepton Beams

Relativistic structured spin-polarized (SSP) particle beams, characterized by polarization structures, are of critical importance in a wide range of applications, such as material properties investigation, imaging, and information storage. However, generation of relativistic SSP beams faces significant challenges. Here, we put forward a novel method for generating relativistic SSP lepton beams via employing a moderate-intensity terahertz (THz) wave. Building upon our foundational work on velocity-matched spin rotation in dielectric-lined waveguides [Phys. Rev. Lett. 134, 075001 (2025)], we present the first demonstration of spin-polarization mode matching - a novel mechanism that establishes a direct relation between waveguide modes and beam polarization states. This breakthrough enables precise spatial control over spin structures at relativistic energies, generating customizable spin-polarization configurations such as spider-like, azimuthal, and helical structures, etc. Such SSP beams have the potential to generate high-energy structured photon beams and open a new avenue for research on relativistic structured particle beams, especially in nuclear physics, high-energy physics, materials science and atomic physics.

physics.optics↗

arXiv2025

Experimental Evidence of Vortex $γ$ Photons in All-Optical Inverse Compton Scattering

Vortex $γ$ photons carrying orbital angular momenta (OAM) hold great potential for various applications. However, their generation remains a great challenge. Here, we successfully generate sub-MeV vortex $γ$ photons via all-optical inverse Compton scattering of relativistic electrons colliding with a sub-relativistic Laguerre-Gaussian laser. In principle, directly measuring the OAM of $γ$ photons is challenging due to their incoherence and extremely short wavelength. Therein, we put forward a novel method to determine the OAM properties by revealing the quantum opening angle of vortex $γ$ photons, since vortex particles exhibit not only a spiral phase but also transverse momentum according to the quantum electrodynamics theory. Thus,$γ$ photons carrying OAM anifest a much larger angular distribution than those without OAM, which has been clearly observed in our experiments. This angular expansion is considered as an overall effect lying beyond classical theory. Our method provides the first experimental evidence for detecting vortex $γ$ photons and opens a new perspective for investigating OAM-induced quantum phenomena in broad fields.

physics.plasm-ph↗

arXiv2025

Nuclear Excitation and Control Induced by Intense Vortex Laser

The existing intense laser-based approaches for nuclear excitation offer ultrafast temporal resolution and high efficiency compared to traditional accelerator probes. However, controlling nuclear properties such as spin and magnetic moment remains an unprecedented challenge. Here, we put forward a novel method for nuclear excitation and control induced by intense vortex lasers. We develop a theory incorporating the orbital angular momentum (OAM) of vortex laser within the nuclear hyperfine mixing framework. We find that intense vortex laser can effectively excite hydrogen-like thorium-229 nucleus and induce three-dimensional rotation of the nuclear magnetic moment. This rotation arises from the localized electromagnetic field and new transition channels excited by the vortex laser, and can be reconstructed through radiation spectrum analysis. Moreover, the OAM of vortex laser enables the chaotic system to exhibit topologically protected periodic patterns in nuclear excitation and radiation, facilitating precise experimental measurements. Our findings underscore the potential of vortex laser for high-precision nuclear control and imaging, deepening our understanding of nuclear properties and hyperfine structure, and advancing quantum information and nuclear technologies.

nucl-th↗

arXiv2025

Controlling the polarization and vortex charge of $γ$ photons via nonlinear Compton scattering

High-energy vortex $γ$ photons have significant applications in many fields, however, their generation and angular momentum manipulation are still great challenges. Here, we first investigated the generation of vortex $γ$ photons with controllable spin and orbital angular momenta via nonlinear Compton scattering of two-color counter-rotating circularly polarized (CP) laser fields. The radiation probabilities of vortex photons are calculated using the semiclassical approach that resolves angular momenta of emitted photons. We find that the angular momenta transferred to emitted photons are determined by the dominating photon absorption channel, leading to a structured spectrum with alternations in helicity and twist directions. By tuning the relative intensity ratio of the two-color CP laser fields, %the preferred photon absorption channel can be enhanced, providing the polarization and vortex charge of the emitted $γ$ photons can be controlled, enabling the generation of circularly polarized vortex $γ$ photons with a user-defined polarization and topological charge, which may have a plenty of applications in nuclear physics, astrophysics, particle physics, etc.

hep-ph↗

arXiv2024

Ultrafast Spin Rotation of Relativistic Lepton Beams via Terahertz Wave in a Dielectric-Lined Waveguide

Spin rotation is central for the spin-manipulation of lepton beams which, in turn, plays an important role in investigation of the properties of spin-polarized lepton beams and the examination of spin-dependent interactions. However, realization of compact and ultrafast spin rotation of lepton beams, between longitudinal and transverse polarizations, still faces significant challenges. Here, we put forward a novel method for ultrafast (picosecond-timescale) spin rotation of a relativistic lepton beam via employing a moderate-intensity terahertz (THz) wave in a dielectric-lined waveguide (DLW). The lepton beam undergoes spin precession induced by the THz magnetic field. We find that optimizing the lepton velocity and THz phase velocity in the DLW can mitigate the impact of transverse Lorentz forces on the lepton beam and increase the precession frequency, thereby maintaining the beam quality and enhancing the efficiency of transverse-to-longitudinal spin rotation. The final polarization degree of the lepton beam exceeds $98\%$, and the energy spread can be improved significantly. Flexibility in adjusting the electromagnetic modes within the DLW adds further potential for spin-manipulation, and holds promise for advancing the development of spin-polarized particle beams, which have broad applications in materials science and atomic, nuclear, and high-energy physics.

physics.plasm-ph↗

arXiv2024

Dynamics of relativistic vortex electrons in external laser fields

Investigating the interactions of vortex electrons with electromagnetic fields is crucial for advancing particle acceleration techniques, scattering theory in background fields, and developing novel electron beams for material diagnostics. In this work, we systematically study the dynamics of relativistic vortex electrons during their head-on collisions with linearly polarized (LP) and circularly polarized (CP) laser pulses, as well as their superposition. We develop a theoretical framework using Volkov-Bessel wave functions to describe the spatiotemporal characteristics of vortex electrons in these external fields. We show that the beam center of the vortex electron follows the classical trajectory of a point-charge electron while maintaining the transverse structure of both vortex eigenstates and superposition states. Specifically, CP laser pulses cause the beam center to rotate, while LP laser pulses induce a lateral shift. The combined effect of LP and CP laser pulses in a two-mode field results in a twisted spiral pattern. Our findings demonstrate the potential for versatile control of vortex electron beams using various laser modes, providing a foundation for future experimental and theoretical studies. This work serves as a benchmark reference for investigations into the manipulation of vortex electron beams using more realistic laser or other types of external fields.

physics.optics↗

arXiv2024

Generation of Ultrarelativistic Vortex Leptons with Large Orbital Angular Momenta

Ultrarelativistic vortex leptons with intrinsic orbital angular momenta (OAM) have important applications in high energy particle physics, nuclear physics, astrophysics, etc. However, unfortunately, their generation still poses a great challenge. Here, we put forward a novel method for generating ultrarelativistic vortex positrons and electrons through nonlinear Breit-Wheeler (NBW) scattering of vortex $γ$ photons. For the first time, a complete angular momentum-resolved scattering theory has been formulated, introducing the angular momentum of laser photons and vortex particles into the conventional NBW scattering framework. We find that vortex positron (electron) can be produced when the outgoing electron (positron) is generated along the collision axis. By unveiling the angular momentum transfer mechanism, we clarify that OAM of the $γ$ photon and angular momenta of multiple laser photons are entirely transferred to the generated pairs, leading to the production of ultrarelativistic vortex positrons or electrons with large OAM. Furthermore, we find that the cone opening angle and superposition state of the vortex $γ$ photon, distinct characteristics aside from its intrinsic OAM, can be determined via the angular distribution of created pairs in NBW processes. Our method paves the way for investigating strong-field quantum electrodynamics processes concerning the generation and detection of vortex particle beams in intense lasers.

hep-ph↗