arXiv subjects

Lingang Zhang

Publications and source records attributed to Lingang Zhang.

15 recordsLinked to original sources

arXiv2026

Wakefield-Dressed Relativistic Vortex Electrons in Plasma Accelerators

Plasma wakefield acceleration is usually regarded as a classical mechanism for producing high- energy charged-particle beams. Here we show that an axisymmetric plasma wakefield can also act as a moving quantum structure that supports relativistic vortex electron states. Starting from the Dirac equation, we derive the electron spinor eigenstates with definite total angular momentum in an ideal bubble-regime wakefield. The transverse focusing field confines and quantizes the electron transverse motion into Laguerre-Gaussian vortex modes, while the longitudinal electric field acceler- ates the electron without destroying the symmetry-protected angular momenta. We further analyze the localized and off-axis vortex electron wave-packets, and non-ideal wakefield perturbations, and identify the conditions for preserving electron-vortex-state purity. These results suggest plasma wakefield as a route toward high-energy vortex electrons and extend plasma-based acceleration from classical beam dynamics to quantum-state control of relativistic particles.

physics.acc-ph↗

arXiv2026

$\lambda$PIC: A callback-centric particle-in-cell framework

We present $\lambda$PIC, a Python-based electromagnetic particle-in-cell framework built around a callback-centric architecture. Existing PIC codes typically tie high performance to static, pre-compiled timestep loops, hindering implementation of custom physics, diagnostics, or output logic. $\lambda$PIC breaks this coupling by exposing every stage of the loop as a named stage (hook), permitting attaching arbitrary Python functions that operate on the full simulation state, enabling custom algorithms and in-situ analysis without modifying the core algorithms. Under this flexible framework, performance-critical kernels are written in C extensions and Numba, fields and particles are stored in NumPy arrays, and MPI parallelism is paired with graph partitioning to support dynamic load balancing and non-rectangular domains. Although $\lambda$PIC is designed as general-purpose, it has special focus on intense laser-plasma interactions. Future work will extend the framework to GPU acceleration and additional physics modules including implicit solvers and nuclear physics.

physics.comp-ph↗

arXiv2025

Super light-by-light scattering in vacuum induced by intense vortex lasers

Collision of ultra-intense optical laser and X-ray free electron laser (XFEL) pulses is a promising approach to detecting nonlinear vacuum polarization (VP), a long-standing prediction of quantum electrodynamics remaining to be tested. Identifying the signals induced by polarized vacuum relies on purifying the X-ray polarization and poses significant challenges due to strongly reduced signal and low signal-to-noise ratio (SNR). Here we propose an approach that allows one to directly detect VP signals without the need for an X-ray polarizer. We identify a new VP effect in collision of an X-ray probe with an intense laser in a vortex mode, which we call the super light-by-light scattering (super-LBL), through which signal photons are kicked out of the X-ray background with large tangential momentum. Super-LBL originates from the gradient force of the vortical vacuum current in azimuthal direction and induces momentum exchange beyond the transverse momentum of laser-photon. This effect efficiently sets the scattered signal photons apart from the X-ray background, producing observable signals with both the strength and SNR more than two orders of magnitude higher than those from the known VP effects. This finding paves the way for single-shot detection of nonlinear VP phenomena with current ultra-intense laser and XFEL technologies.

physics.optics↗

arXiv2020

Driving positron beam acceleration with coherent transition radiation

Positron acceleration in plasma wakefield faces significant challenges since the positron beam must be pre-generated and precisely coupled into the wakefield, and most critically, suffers from defocusing issues. Here we propose a scheme that utilizes laser-driven electrons to produce, inject and accelerate positrons in a single set-up. The high-charge electron beam from wakefield acceleration creates copious electron-positron pairs via the Bethe-Heitler process, followed by enormous coherent transition radiation due to the electrons' exiting from the metallic foil. Simulation results show that the coherent transition radiation field reaches up to 10's GV m-1, which captures and accelerates the positrons to cut-off energy of 1.5 GeV with energy peak of 500 MeV and energy spread is about 24.3%. An external longitudinal magnetic field of 30 T is also applied to guide the electrons and positrons during the acceleration process. This proposed method offers a promising way to obtain GeV fast positron sources.

physics.plasm-ph↗

arXiv2020

A spin-filter for polarized electron acceleration in plasma wakefields

We propose a filter method to generate electron beams of high polarization from bubble and blow-out wakefield accelerators. The mechanism is based on the idea to identify all electron-beam subsets with low-polarization and to filter them out by an X-shaped slit placed right behind the plasma accelerator. To find these subsets we investigate the dependence between the initial azimuthal angle and the spin of single electrons during the trapping process. This dependence shows that transverse electron spins preserve their orientation during injection if they are initially aligned parallel or anti-parallel to the local magnetic field. We derive a precise correlation of the local beam polarization as a function of the coordinate and the electron phase angle. Three-dimensional particle-in-cell simulations, incorporating classical spin dynamics, show that the beam polarization can be increased from 35% to about 80% after spin filtering. The injected flux is strongly restricted to preserve the beam polarization, e.g. <1kA in Ref.[27]. This limitation is removed by employing the proposed filter mechanism. The robust of the method is discussed that contains drive beam fluctuations, jitters, the thickness of the filter and initial temperature. This idea marks an efficient and simple strategy to generate energetic polarized electron beams based on wakefield acceleration

physics.plasm-ph↗

arXiv2019

Polarized electron-beam acceleration driven by vortex laser pulses

We propose a new approach based on an all-optical set-up for generating relativistic polarized electron beams via vortex Laguerre-Gaussian (LG) laser-driven wakefield acceleration. Using a pre-polarized gas target, we find that the topology of the vortex wakefield resolves the depolarization issue of the injected electrons. In full three-dimensional particle-in-cell simulations, incorporating the spin dynamics via the Thomas-Bargmann Michel Telegdi equation, the LG laser preserves the electron spin polarization by more than 80% at high beam charge and flux. The method releases the limit on beam flux for polarized electron acceleration and promises more than an order of magnitude boost in peak flux, as compared to Gaussian beams. These results suggest a promising table-top method to produce energetic polarized electron beams.

physics.plasm-ph↗

arXiv2019

Polarization sensitive laser intensity inside femtosecond filament in air

Polarization dependence on clamping intensity inside femtosecond filament was experimentally measured in air. By tuning the laser pulse ellipse from linear polarization to circular polarization, the measured clamping intensity inside laser filament is gradually increased up to 1.7 times. The experimental results are in good agreement with the simulation results by solving the extended nonlinear Schrodinger equation (NLSE). The polarization sensitive clamping intensity inside filaments offers an important factor towards fully understanding the polarization related phenomenon observed so far.

physics.optics↗

arXiv2016

Generation of Gamma-ray Beam with Orbital Angular Momentum in the QED Regime

We propose a scheme to generate gamma-ray photons with an orbital angular momentum (OAM) and high energy simultaneously from laser-plasma interactions by irradiating a circularly polarized Laguerre-Gaussian laser on a thin plasma target. The spin angular momentum and OAM are first transferred to electrons from the driving laser photons, and then the OAM is transferred to the gamma-ray photons from the electrons through quantum radiation. This scheme has been demonstrated using three-dimensional quantum electrodynamics particle-in-cell simulation. The topological charge, chirality and carrier-envelope phase of the short ultra-intense vortex laser can be revealed according to the pattern feature of the energy density of radiated photons.

physics.plasm-ph↗

arXiv2015

Generation of Ultra-intense Gamma-ray Train by QED Harmonics

When laser intensity exceeds 10^22W/cm^2, photons with energy above MeV can be generated from high-order harmonics process in the laser-plasma interaction. We find that under such laser intensity, QED effect plays a dominating role in the radiation pattern. Contrast to the gas and relativistic HHG processes, both the occurrence and energy of gamma-ray emission produced by QED harmonics are random and QED harmonics are usually not coherent, while the property of high intensity and ultra-short duration is conserved. Our simulation shows that the period of gamma-ray train is half of the laser period and the peak intensity is 1.4e22W/cm^2. This new harmonic production with QED effects are crucial to light-matter interaction in strong field and can be verified in experiments by 10PW laser facilities in the near future.

physics.plasm-ph↗

arXiv2015

Hollow screw like drill in plasma using an intense Laguerre Gaussian laser

With the development of ultra intense laser technology, MeV ions from the laser foil interaction have been obtained by different mechanisms, such as target normal sheath acceleration, radiation pressure acceleration, collisionless shock acceleration, breakout afterburner, and a combination of different mechanisms. These energetic ion beams can be applied in fast ignition for inertial confinement fusion, medical therapy, and proton imaging. However, these ions are mainly accelerated in the laser propagation direction, and the ion acceleration in an azimuthal orientation is scarcely mentioned. Here, a doughnut Laguerre Gaussian LG laser is used for the first time to study the laser plasma interaction in the relativistic intensity regime in three dimensional particle in cell simulations. Studies have shown that a novel rotation of the plasma is produced from the hollow screw like drill of a LG mode laser. The angular momentum of the protons in the longitudinal direction produced by the LG laser is remarkably enhanced compared with that produced by the usual laser pulses, such as linearly and circularly polarized gaussian pulses. Moreover, the particles, including electrons and ions, can be trapped and uniformly compressed in the dark central minimum of the doughnut LG pulse. Such hollow structured LG laser may be used to investigate some difficult problems, such as screw like drilling in the inertial confinement fusion, laser driven particle accelerations, and pulsars in the astrophysical environment.

physics.plasm-ph↗

arXiv2014

Generation of Intense High-Order Vortex Harmonics

This paper presents the method for the first time to generate intense high-order optical vortices that carry orbital angular momentum in the extreme ultraviolet region. In three-dimensional particle-in-cell simulation, both the reflected and transmitted light beams include high-order harmonics of the Laguerre-Gaussian (LG) mode when a linearly polarized LG laser pulse impinges on a solid foil. The mode of the generated LG harmonic scales with its order, in good agreement with our theoretical analysis. The intensity of the generated high-order vortex harmonics is close to the relativistic region, and the pulse duration can be in attosecond scale. The obtained intense vortex beam possesses the combined properties of fine transversal structure due to the high-order mode and the fine longitudinal structure due to the short wavelength of the high-order harmonics. Thus, the obtained intense vortex beam may have extraordinarily promising applications for high-capacity quantum information and for high-resolution detection in both spatial and temporal scales because of the addition of a new degree of freedom.

physics.plasm-ph↗

arXiv2014

Proton Acceleration in Underdense Plasma by Ultraintense Laguerre-Gaussian Laser Pulse

Three-dimensional particle-in-cell simulation is used to investigate the witness proton acceleration in underdense plasma with a short intense Laguerre-Gaussian (LG) laser pulse. Driven by the LG10 laser pulse, a special bubble with an electron pillar on the axis is formed, in which protons can be well-confined by the generated transversal focusing field and accelerated by the longitudinal wakefield. The risk of scattering prior to acceleration with a Gaussian laser pulse in underdense plasma is avoided, and protons are accelerated stably to much higher energy. In simulation, a proton beam has been accelerated to 7 GeV from 1 GeV in underdense tritium plasma driven by a 2.14x1022 W/cm2 LG10 laser pulse.

physics.plasm-ph↗

arXiv2014

Light fan driven by relativistic laser pulse

When a relativistic laser pulse with high photon density interacts with a specially tailored thin foil target, a strong torque is exerted on the resulting spiral-shaped foil plasma, or light fan. Because of its structure, the latter can gain significant orbital angular momentum (OAM), and the opposite OAM is imparted to the reflected light, creating a twisted relativistic light pulse. Such an interaction scenario is demonstrated by particle-in-cell simulation as well as analytical modeling, and should be easily verifiable in the laboratory. As important characters, twisted relativistic light pulse has strong torque and ultra-high OAM density.

physics.plasm-ph↗

arXiv2014

Positron acceleration in a hollow plasma channel up to TeV regime

We propose a plasma-based high-energy lepton accelerator, in which a weakly focusing plasma structure is formed near the beam axis. The structure preserves the emittance of the accelerated beam and produces low radiation losses. Moreover, the structure allows for a considerable decrease of the witness energy spread at the driver depletion stage.

physics.plasm-ph↗

arXiv2013

Scheme for proton-driven plasma-wakefield acceleration of positively charged particles in a hollow plasma channel

A new scheme for accelerating positively charged particles in a plasma wakefield accelerator is proposed. If the proton drive beam propagates in a hollow plasma channel, and the beam radius is of order of the channel width, the space charge force of the driver causes charge separation at the channel wall, which helps to focus the positively charged witness bunch propagating along the beam axis. In the channel, the acceleration buckets for positively charged particles are much larger than in the blowout regime of the uniform plasma, and stable acceleration over long distances is possible. In addition, phasing of the witness with respect to the wave can be tuned by changing the radius of the channel to ensure the acceleration is optimal. Two dimensional simulations suggest that, for proton drivers likely available in future, positively charged particles can be stably accelerated over 1 km with the average acceleration gradient of 1.3 GeV/m.

physics.plasm-ph↗