Axionlike-particle generation by laser-plasma interaction

Axion, a hypothetical particle that is crucial to quantum chromodynamics and dark matter theory, has not yet been found in any experiment. With the improvement of laser technique, much stronger quasi-static electric and magnetic fields can be created in laboratory using laser-plasma interaction. In this article, we discuss the feasibility of axion or axionlike-particle's exploring experiments using planar and cylindrically symmetric laser-plasma fields as backgrounds while probing with an ultrafast superstrong optical laser or x-ray free-electron laser with high photon number. Compared to classical magnet design, the axion source in laser-plasma interaction trades the accumulating length for the source's interacting strength. Besides, a structured field in the plasma creates a tunable transverse profile of the interaction and improves the signal-noise ratio via the mechanisms such as phase-matching. The mass of axion discussed in this article ranges from 1 \textmu eV to 1 eV. Some simple schemes and estimations of axion production and probe's polarization rotation are given, which reveals the possibility of future laser-plasma axion source in laboratory.Comment: 24 pages, 5 figure

Transfer of spin to orbital angular momentum in the Bethe-Heitler process

According to the conservation of angular momentum, when a plane-wave polarized photon splits into a pair of electron-positron under the influence of the Coulomb field, the spin angular momentum (SAM) of the photon is converted into the angular momentum of the leptons. We investigate this process (the Bethe-Heitler process) by describing the final electron and positron with twisted states and find that the SAM of the incident photon is not only converted into SAM of the produced pair, but also into their orbital angular momentum (OAM), which has not been considered previously. The average OAM gained by the leptons surpasses the average SAM, while their orientations coincide. Both properties depend on the energy and open angle of the emitted leptons. The demonstrated spin-orbit transfer shown in the Bethe-Heitler process may exist in a large group of QED scattering processes

Research on Lidar Network Observation of Aerosol and Pollution in Beijing 2022 Winter Olympics

During the Beijing Winter Olympics, three sets of aerosol lidar in different regions were used to conduct continuous observations to study the optical properties and vertical distribution characteristics of atmospheric aerosol. Based on the lidar data and sun photometer data, the accurate lidar ratio was determined to improve the inversion accuracy of the aerosol backscattering coefficient. The influence of meteorological conditions such as temperature, relative humidity, wind speed, and wind direction on the optical properties of aerosol were analyzed, and the type of aerosol was classified by the depolarization ratio of aerosol particles and CALIPSO data. Furthermore, the backward trajectory analysis, potential source contribution function (PSCF), and concentration weighted trajectories (CWT) were employed to explore the sources and transport mechanisms of pollutants. The analysis found that the extinction coefficient under the atmospheric boundary layer during the Winter Olympics had a spatial distribution pattern of high value in the southeast and low value in the northwest. The occurrence of aerosol pollution events is not only caused by local emissions, but is also related to regional transmission

Dynamic Reconstruction Strategy of Distribution Network Based on Uncertainty Modeling and Impact Analysis of Wind and Photovoltaic Power

The distribution network with high penetration of renewable energy such as wind and photovoltaic power has higher flexibility and power supply efficiency, but it also faces more faults and uncertainties. Traditional dynamic reconfiguration under fault conditions are still limited by problems such as low load recovery rate and strong decision conservatism. To overcome these challenges, this article proposes a dynamic reconstruction strategy for distribution network under fault conditions that takes into account multivariate uncertainty. Firstly, in response to the uncertainty of distributed power generation output and load demand in the distribution network, an interval prediction method is adopted to construct a uncertainty model for source and load side. Then, the Latin hypercube sampling method is used to generate multiple operation scenarios, and computational efficiency is improved by reducing scenario samples using Cholesky sorting principle and synchronous backpropagation reduction method. Finally, a robust dynamic reconstruction model based on mixed-integer second-order cone programming (MISOCP) is constructed, and the feasibility and robustness of the proposed dynamic strategy are verified using the improved IEEE-33 node system. Through analysis, the proposed method effectively addresses the risk factors in the operation, thus improving the safety and reliability of the distribution network

Vortex beam of tilted orbital angular momentum generated from grating

Diffracted vortex beams carrying stable tilted total orbital angular momentum (OAM) vector with respect to the propagation direction are generated, when a linearly polarized Laguerre-Gaussian laser pulse impinges on a solid plasma grating target as shown in the particle-in-cell simulation. The diffracted beams are space-separated in the corresponding diffraction directions. It is found that the transverse OAM results from the rotation of the transverse momentum of the vortex harmonics, and can be modulated by the grating period. The stable average transverse OAM provides us deeper insight to the vortex property of light and may provide an additional controllable parameter for potential applications