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.

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 subrelativistic 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 manifest 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.

Ultrafast extreme ultraviolet (XUV) sources with tailored spin and orbital angular momentum are expected to achieve higher sensitivity and information dimensionality in exploring material microstructures. However, generating bright sources with simultaneous and flexible control in a compact setup remains a challenge. Here, we numerically demonstrate a laser-plasma scheme to generate bright XUV pulses with controlled spin-orbital angular momentum. In this scheme, a circularly polarized vortex laser pulse is obliquely incident on a plasma mirror, and the reflected radiation contains topological-spectral-correlated XUV pulses. Particle-in-cell simulations reveal a linear topological-spectral relationship: the orbital angular momentum of the nth harmonic scales as nm, where m is the topological charge of the driver, while its spin state is preserved. By synthesizing a selected harmonic band, spatiotemporal optical beams with programmable helical structures (e.g., single- or multiple-armed light springs) can be constructed. This scheme opens a promising route to generate bright attosecond XUV pulses with multidimensional control of photon angular momentum in a straightforward and efficient way.

The continuous development of bright x/gamma-ray sources has opened up new frontiers of science and advanced applications. Currently, there is still a lack of efficient approaches to produce high-energy gamma-rays with peak brilliance comparable to modern free-electron lasers. Here, we report a novel mechanism called beam fast pinching radiation burst to generate such gamma-ray sources. It is achieved by injecting a giga-electron volt electron beam into a submillimeter plasma with an upramp density profile, enabling violent beam pinching to occur rapidly. During this process, a burst of collimated gamma-rays is efficiently produced with photon energies ranging from mega-electron volts to giga-electron volts, electron-to-photon energy conversion efficiency above 20%, and peak brilliance exceeding 1028 photons s−1 mm−2 mrad−2 per 0.1% bandwidth. All of these are several orders of magnitude higher than existing gamma-ray sources. This opens a novel avenue for the development of extremely bright gamma-ray sources for both fundamental research and cutting-edge applications.

Light amplification via Raman scattering in plasma has been severely constrained by stringent phase matching conditions and the need for plasma uniformity. To overcome these limitations, we propose a forward Raman amplification scheme that employs a positively chirped seed pulse co-propagating with a pump pulse in a nonuniform plasma with an upramp density profile. We demonstrate that the phase detuning induced by plasma nonuniformity can be dynamically compensated, enabling broadband amplification across the entire spectral bandwidth of the seed pulse. Concurrently, the chirped pulse duration undergoes continuous compression as a result of the spatially varying dispersion of the plasma. Our theoretical model, incorporating the detuning term and supported by particle-in-cell simulations, elucidates the compensation mechanism. It is shown that a chirped seed pulse with an initial bandwidth 10

We propose a scheme to generate two isolated attosecond pulses at controllable angles through the interaction between relativistic laser pulses and a solid target. Two p-polarized laser pulses with certain frequency chirps are employed to drive oscillating plasma gratings (OPGs) on the target surface, while an s-polarized laser serves as the seed to trigger high-order harmonic generation (HHG) from the OPGs. Unlike HHG from the usual oscillating plasma mirrors, the OPGs not only generate harmonics but also diffract them. The evolution of the emission angles of the diffracted harmonics can be controlled through the laser chirp. At three specific angles, selected harmonics can be synthesized to attosecond pulse trains, and at two of these angles to isolated attosecond pulses. Two-dimensional particle-in-cell simulations are used to demonstrate the feasibility and robustness of the scheme, which shows that isolated attosecond pulse with duration around 30 as and intensity close to 10^{17}W/cm^{2} can be stably generated. The scheme enables applications that require two isolated attosecond pulses with independent controllability.

Vector beams with spatially structured polarization and intertwined spin-orbital angular momentum (SAM-OAM) provide powerful degrees of freedom for tailoring light-matter interactions. While such structured beams are well established in the visible and infrared regimes, extending them to the extreme-ultraviolet (EUV) and soft X-ray (SXR) domains at relativistic intensities remains a major challenge. Here, we investigate the generation of higher-order harmonic vector beams driven by relativistic laser-plasma interactions. Combining theoretical analysis with three-dimensional particle-in-cell simulations, we elucidate the underlying physical mechanisms governing the transfer and conversion of polarization and orbital angular momentum during harmonic generation. We demonstrate that both the polarization topology and OAM of the emitted harmonics can be deterministically controlled by the topological charges of the driving field. Owing to the intrinsic properties of vector beams, either few-cycle driving pulses or vector polarization gating applied to multi-cycle pulses enable the production of intense isolated attosecond pulses featuring spiral wavefronts and spatially tailored polarization states. These results establish a pathway toward high-intensity structured light sources in the EUV and SXR regimes and open new opportunities for ultrafast and strong-field light-matter interaction studies with engineered angular momentum.

Moir & eacute; lattices are photonic lattices characterized by moir & eacute; patterns. Quasiperiodic photonic moir & eacute; lattices possess flat energy bands, enabling the localization of the beam and long-distance optical guiding. However, intense lasers can change the induced refractive index of photorefractive crystals, limiting milliwatt-level guiding in quasiperiodic moir & eacute; lattices based on such materials. To achieve efficient optical guiding with long-distance and low-dispersion propagation, in this study, we introduce the concept of moir & eacute; lattices into plasmas, leveraging the high damage threshold of plasmas, and propose a plasma moir & eacute; lattice. Theoretical calculations are performed by approximating quasiperiodic moir & eacute; lattices with periodic ones constructed using specific adjacent angles and employing the finite difference method. It is demonstrated that plasma moir & eacute; lattices also exhibit flat energy bands where the propagation constant is independent of the transverse wavenumber, providing a theoretical foundation for long-distance guiding. Three-dimensional particle-in-cell simulations are conducted to investigate the guiding characteristics of relativistic intense laser pulses (a(0) = 1, corresponding to E-z = 4 x 10(12) V/m) in plasma moir & eacute; lattices. Under the given parameters, the lattice can effectively confine laser pulses of different initial spot sizes to a similar channel depth, enabling stable long-distance propagation over d = 1000 lambda(0). When the initial spot size exceeds the channel depth, part of the beam energy converges toward the center, resulting in a doubling of peak intensity, while the remaining part is scattered, thereby reducing the total energy. Under conditions of matched average density, compared with traditional preformed parabolic plasma density channels, the plasma moir & eacute; lattice significantly suppresses laser redshift usually caused by wakefield excitation. For example, for a high-energy short pulse ( W = 25.4 mJ, tau(0) = 15 lambda(0)) or a low-energy long pulse ( W = 2 mJ, tau(0) = 30 lambda(0)), the redshift in the moir & eacute; lattice is markedly less than that in the parabolic channel after propagating a distance d = 800 lambda(0), as stronger wakefield is excited in the latter. By scaling the moir & eacute; lattice up 75 times, the plasma moir & eacute; lattice can effectively guide intense terahertz pulses (center frequency f(0) = 5 THz, lambda(0) = 60 mu m, a(0) = 0.45, W = 24.7 mJ). During long-distance propagation up to 5Z(R) maintain their original central frequency, and achieve low-dispersion transmission. The plasma moir & eacute; lattice provides a new approach for efficient and low-dispersion transmission of intense lasers and terahertz pulses. Potential experimental implementations could include generating such lattices through two-beam interference with masks or dielectric barrier discharge methods, enabling tunable lattice constants for optimized guidance of various electromagnetic pulses. (Rayleigh length) in the moir & eacute; lattice, intense terahertz pulses experience negligible photon deceleration,

Laser wakefield acceleration (LWFA) is a promising way for producing GeV-scale electron beams within a tabletop size. Increasing acceleration energy and reducing energy spread are extremely important for many applications. Here, we experimentally demonstrate that using a plasma channel with a longitudinally up-ramp density profile can simultaneously boost the accelerated electron energy and lower the final beam energy spread. In a plasma channel with uniform plasma density, electron beams with a peak energy of 250 MeV and a large energy spread (similar to 40%) were obtained. In contrast, within a plasma channel of the same length with an up-ramp density profile, stable electron beams with energies up to 1 GeV and a small energy spread (similar to 20%) were observed. Particle-in-cell simulations show that the plasma channel not only suppresses laser diffraction, but also affects the self-injection and acceleration of the electron beam. In the up-ramp plasma channel, the continual electron injection is suppressed and electrons can be locked in the acceleration phase for a longer duration, which leads to the reduction of energy spread and the increase of electron energy. This method provides a relatively simple and reliable way toward compact, high-performance tabletop electron accelerators.

We propose a seeded axion-photon conversion scheme to enhance the sensitivity of light-shining-through-a-wall (LSW) experiments for axion detection, where the axions are generated from short pulse lasers and the usual resonant cavity is not applicable. By injecting a weak, coherent seed electromagnetic (EM) field into the axion-photon conversion region, the axion-induced EM field can constructively interfere with the seed field, amplifying the number of regenerated photons to a level exceeding that of the unseeded scenario. We evaluate the expected signal enhancement, statistical limits from Poisson counting with seed fluctuations and background, and the potential improvement in coupling sensitivity. Compared to a standard LSW setup, the seeded scheme can achieve orders-of-magnitude higher photon yield per axion, potentially surpassing resonance-enhanced experiments in certain parameter regimes. This approach presents a promising pathway to extend the reach of laboratory axion searches, particularly in scenarios where the resonant cavities are impractical.

Paired superradiance (PSR) is a macro-coherent two-photon process capable of very large gain, making it promising for detecting ultra-weak signals induced by neutrinos or dark matter. A major goal has been to increase the system volume V and density n, since the signal intensity scales as (nV)^2. We recast finite PSR as a parametric amplifier driven by the electromagnetic vacuum. The usual zero-field semiclassical initial condition is replaced by vacuum inputs fixed by the quantum two-point function. Combining this formulation with Maxwell–Bloch evolution and finite-length stability analysis, we find that PSR produces an irreducible vacuum background that can develop into macroscopic bursts once the gain-length product exceeds ΓL=π/2 for a sufficient coherence time. These results, together with a closed-form formula for estimating the vacuum-seeded photon yield, establish a previously overlooked constraint for high-gain PSR, with direct implications for proposed neutrino and dark-matter studies.

Extremely high axial magnetic fields above the gigagauss (GG) level are supposed to exist in neutron stars, which may be a one of the critical parameters for their internal structures and be responsible for the X and gamma-ray emission from these stars. Here we show that such ultrahigh magnetic fields can be produced by multiple petawatt-class lasers interacting with a cuboid solid target with a cylindrical microtube in the middle. It is found that the obliquely incident intense lasers at the target surfaces enable the produced hot electrons to form an azimuthal current and subsequently induce a seed magnetic field along the cylindrical axis inside the microtube as the hot electrons transport into it. This current-field configuration is similar to a theta-pinch device. When the hot electrons and energetic ions produced via target normal sheath acceleration converge towards the microtube axis, the seed magnetic field is dramatically amplified. This process continues until the magnetic pressure near the axis becomes comparable to the thermal pressure contributed both by hot electrons and energetic ions. Later on, as the plasma in the center start to be expelled outward by the magnetic pressure, an electron current ring with extremely high densities is formed, leading to a further boost of the magnetic fields to well above the GG-level. A scaling of the magnetic field strength with laser intensities, pulse durations, incident angles, and target sizes is presented and verified by numerical simulations, which demonstrates the robustness of our scheme. Our scheme is well suited for experimental realization on 100 terawatt-class to petawatt-class femtosecond or picosecond laser facilities with multiple linearly polarized laser beams.

Two extreme events in the Universe, fast radio bursts (FRBs) and cosmic rays (CRs), could be correlated, where FRBs with extreme field strength near their sources may contribute to CRs. This study investigates localized particle acceleration driven by FRB-like ultra-relativistic electromagnetic pulses in an electron-positron-ion plasma system. It is found that ultrahigh energy neutral plasma sheets form constantly via the front erosion of an FRB pulse. There are two regimes of ion acceleration depending upon the field strength and the plasma density: the piston regime driven by the Lorentz force of the pulse, and the wakefield regime dominated by charge separation field. The predicted energy scalings align well with particle-in-cell simulations. A power-law energy spectrum with an index close to the CRs naturally emerges during FRBs expansion outward. Detecting high-energy particles possibly produced by FRBs enables deeper insights into their origins and promotes the development of multimessenger astronomy.

Radiation reaction (RR) is a fundamental yet incompletely validated process in laser-particle interactions, since it lacks quantitatively definitive experimental verifications, especially the transition from classical to quantum regime. Herein, we propose a novel experimental scenario for investigating radiation RR within the classical radiation-dominated regime (CRDR), via the collision of a high-intensity petawatt-class laser with a tens-of-MeV electron beam from a LINAC. This approach enables access to a distinct parameter regime wherein RR dominates electron dynamics while quantum effects remain modest. Numerical simulations demonstrate that three key observables exist for identifying the RR within this CRDR regime: (i) quantitative measurement of energy spectra to validate the quantum correction factor; (ii) control of the collision time delay with charge-counting to map intensity dependence of RR; and (iii) verification of large angle ($90^\circ$) photon emission under the recoil condition $2γ\gtrsim a_0$. These experimental measurements will establish the benchmarks for RR models spanning the classical-to-quantum regime, thereby providing critical insights into fundamental strong-field quantum electrodynamics.

High-power lasers offer ultrahigh intensities for plasma interactions, but they lack advanced techniques to control the properties of the fields, because no optical elements could withstand their high intensities. The vibrant field of metasurfaces has transformed modern optics by enabling unprecedented control over light at subwavelength through deliberate design. However, metasurfaces have traditionally been limited to solid-state materials and low light intensities. Extending the sophisticated capabilities of metasurfaces from solids into the plasma realm would open new horizons for high-field science. Here, we present a proof-of-concept experimental demonstration of plasma-state metasurfaces (PSMs) via the photonic spin Hall effect and the generation of stable-propagating vortex beams under intense laser irradiation. Time-resolved pump-probe measurements reveal that the functionality of PSMs can persist for several picoseconds, making them suitable for controlling ultra-intense femtosecond lasers, even in state-of-the-art multi-petawatt systems. Harnessing the powerful toolkit of metasurfaces, this approach holds the promise to revolutionize our ability to manipulate the amplitude, phase, polarization, and wavefront of high-power lasers during their pulse duration. It also opens new possibilities for innovative applications in laser-plasma interactions such as compact particle acceleration and novel radiation sources.

Proton radiography is an effective technique for diagnosing field distributions in plasmas. However, due to the complexity of electromagnetic field structure, reconstructing electromagnetic field from proton radiographs is extremely challenging and often requires some simplified symmetry assumptions for the field. Here, we present a machine learning method to reconstruct three-dimensional (3D) magnetic field distributions from complex proton radiographs without relying on such assumptions. In order to do this, we construct the target 3D magnetic fields by linearly superposing multiple elementary magnetic structures generated from the Weibel instability. Each element is characterized by eight parameters-structural parameters (a, b, B-0), spatial coordinates (x(0), y(0), z(0)), and rotation angles (theta, phi), -resulting in 80 degrees of freedom in total. The parameters are uniformly sampled within +/- 25% of their baseline values, and a dataset consisting of 50000 magnetic field-proton radiograph pairs is generated through forward simulation using GEANT4. All proton radiographs exist in the caustic regime, exhibiting multiple asymmetric caustics and significant flux concentrations. A lightweight three-layer convolutional neural network (CNN) is designed for the reconstruction task. The network consists of an input layer, three convolutional modules (in which the first two follow a "convolution-batch normalization-max pooling" cascaded structure, and the third is simplified into a single convolutional layer), a flattening layer, a dropout layer, and an output layer. Bayesian optimization is used to determine the optimal hyperparameters. The model is trained on 40000 samples, with 5000 samples used for validation and 5000 for testing. On the test set, the CNN achieves a mean absolute percentage error (MAPE) of 8.5% in predicting the 80 magnetic parameters, which is below the random-guessing threshold of 12.9%. Prediction errors for most parameters follow a near-zero-mean Gaussian distribution, with a relative standard deviation of less than 6%. The reconstructed fields show a high degree of spatial consistency with the reference fields, and the corresponding proton images match the original images with a cosine similarity of 0.89. This study demonstrates that our CNN-based proton radiography reconstruction method can effectively reconstruct complex 3D magnetic fields without the need for symmetry assumptions or manual parameter tuning, providing a novel tool for diagnosing electromagnetic fields in high-intensity laser-plasma interactions. Future work may combine multi-angle proton radiography with transfer learning from experimental data to improve the practicality and robustness of this method.

In this paper, the negative permittivity of perovskite-type La0.7Ca0.2Sr0.1CrO3 ceramics (LCSCOs) was reported for the first time. The effects of sintering temperature on their conductivity, permittivity, and electromagnetic shielding performance were explored. As the sintering temperature increased, the density of the LCSCOs increased. This enlarged the contact area between the grains and optimized the conductive pathways, consequently improving the electrical conductivity. Due to a certain number of free carriers in the LCSCOs, their collective oscillations resulted in negative permittivity. The elevated sintering temperature promoted the solid solubility of dopant atoms in ceramics, which ultimately resulted in an increase in the absolute values of negative permittivity. The Drude model could explain the negative permittivity. As the sintering temperature increased, the electromagnetic shielding performance of the ceramics improved due to the synergistic effect of increased density and conductivity.

The process e^+e^-→K_S^0K_S^0ψ (3686) is studied by analyzing e+e− collision data samples collected at eight center-of-mass energies ranging from 4.682 to 4.951 GeV with the BESIII detector operating at the BEPCII collider, corresponding to an integrated luminosity of 4.1 fb−1. Observation of the e^+e^-→K_S^0K_S^0ψ (3686) process is found for the first time with a statistical significance of 6.3σ, and the cross sections at each center-of-mass energy are measured. The ratio of cross sections of e^+e^-→K_S^0K_S^0ψ (3686) relative to e+e− → K+K−ψ(3686) is determined to be σ(e^+e^-→K_S^0K_S^0ψ (3686))/σ(e^+e^-→K^+K^-ψ (3686))=0.45± 0.25 , which is consistent with the prediction based on isospin symmetry. The uncertainty includes both statistical and systematic contributions. Additionally, the K_S^0ψ (3686) invariant mass distribution is found to be consistent with three-body phase space. The significance of a contribution beyond three-body phase space is only 0.8σ.

Fractional optical vortices in the terahertz (THz) regime are supposed to have unique applications in various areas, i.e., THz communications, optical manipulations, and THz imaging. However, it is still challenging to generate and manipulate high-power THz vortices. Here, we present a way to generate intense THz vortex beams with a continuously tunable topological charge by injecting a weakly relativistic ultrashort laser pulse into a parabolic plasma channel. By adjusting the injection conditions of the laser pulse, the trajectory of the laser centroid can be twisted into a cylindrical spiral, along which laser wakefields are also excited. Due to the inhomogeneous transverse density profile of the plasma channel and laser wakefield excitation, intense THz radiation carrying orbital angular momentum is produced with field strength reaching sub-GV/m, even though the drive laser energy is at a few tens of mJ. The topological charge of such a radiation is determined by the laser trajectories, which are continuously tunable as demonstrated by theoretical analysis as well as three-dimensional particle-in-cell simulations. Such THz vortices with unique properties may find applications in broad areas.

The axions are compelling candidates for cold dark matter, but their extremely weak interaction with photons makes laboratory searches challenging. We show that the quasi-static electromagnetic fields of a laser-plasma wakefield, which can exceed 10^11 V/m, enable axion generation without an external production magnet and enhance the conversion rate by two orders of magnitude over a conventional magnetic production region. Self-consistent particle-in-cell simulations reveal two complementary routes to detection. In the first route, axions are reconverted into photons within the wakefield and laser fields, eliminating the need for a separate regeneration magnet but requiring to suppress the intense laser-plasma background. The regenerated photons have polarization, harmonic-frequency, and Laguerre-Gaussian transverse-mode signatures that are largely absent from the driving fields, allowing successive filters to isolate the signal. In the second route, axions traverse a wall and undergo reconversion in a downstream magnet, providing a much lower background at the cost of requiring both the magnet and a seed pulse for coherent amplification. For axion masses below 0.1 meV, meter-scale wakefield guiding under our stated assumptions yields a projected coupling sensitivity down to 3.9×10^-12 GeV^-1, surpassing the projected constraint of next-generation laboratory searches. These results establish ultra-strong plasma wakefields as a magnet-free axion source with two experimentally distinct and complementary detection strategies.