Zhang Xiao-Mei

Processing of earth observation big data: Challenges and countermeasures

Earth observation uses spaceborne sensors to obtain complete and systematic information about the earth. With the help of advances in spatial information technologies, the field of earth observation has entered the era of “big data”. By analyzing the entire process of earth observation data processing and associated algorithms, this paper concludes that the challenges facing earth observation “big data” processing are those of data-intensive computing. We suggest that to solve this problem, there should be research and innovation in the areas of system platforms, processing algorithms, and services models.

Proton Acceleration with Nano-Scale Micro-Structured Target by Circularly Polarized Laser Pulse

Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the target experience the electrostatic fields caused by both the radiation pressure driven shock and the target normal sheath at the rear side of the target. A quasimonoenergetic proton bunch with central energy of about 11 MeV and energy spread of Δe/e about 0.18 is achieved by using a 3.45 × 1019 W/cm2, 66fs laser pulse. A comparison with the case of linearly polarized laser pulse and the same target condition is considered.

The propagation and deposition of fast muons in dense DT mixture

The propagation of the fast muon population mainly due to collisional effect in a dense deuterium-tritium (DT for short) mixture is investigated and analysed within the framework of the relativistic Fokker-Planck equation. Without the approximation that the muons propagate straightly in the DT mixture, the muon penetration length, the straggling length, and the mean transverse dispersion radius are calculated for different initial energies, and especially for different densities of the densely compressed DT mixture in our suggested muon-driven fast ignition (FI). Unlike laser-driven FI requiring super-high temperature, muons can catalyze DT fusion at lower temperatures and may generate an ignition sparkle before the self-heating fusion follows. Our calculation is important for the feasibility and the experimental study of muon-driven FI.

Few-cycle relativistic solitons in plasmas

A set of exact one-dimensional solutions to coupled nonlinear equations describing the propagation of a relativistic ultrashort circularly polarized laser pulse in a cold collisionless and bounded plasma where electrons have an initial velocity in the laser propagating direction is presented. The solutions investigated here are in the form of quickly moving envelop solitons at a propagation velocity comparable to the light speed. The features of solitons in both underdense and overdense plasmas with electrons having different given initial velocities in the laser propagating direction are described. It is found that the amplitude of solitons is larger and soliton width shorter in plasmas where electrons have a larger initial velocity. In overdense plasmas, soliton duration is shorter, the amplitude higher than that in underdense plasmas where electrons have the same initial velocity.