Bai-Song Xie

Effect of adiabatic variation of dust charges on dust-acoustic solitary waves

Abstract The effect of dust charging and the influence of its adiabatic variation on dust-acoustic solitary waves is further studied. A more reasonable normalization for the dust velocity by the dust-acoustic speed is adopted, which varies self-consistently with the system parameters. By employing the reductive perturbation technique we derive small-amplitude dust-acoustic solitons with varying dust charges. The Sagdeev potential shows that only the rarefactive solitary waves exist when the Mach number lies within an appropriate regime depending on the system parameters. An approximate similarity law is obtained and discussed in this dust-charge-fluctuation system.

Dust-acoustic solitary waves and double layers in dusty plasma with variable dust charge and two-temperature ions

With two-temperature ions in dusty plasma, the effects of variable dust charge on small-amplitude dust-acoustic solitons and large-amplitude dust-acoustic solitary waves are investigated. It is found that both compressive and rarefactive solitons (and solitary waves), as well as double layers, exist. The introduced small, but finite, number density of the lower temperature ions provides the possibility of the coexistence of large-amplitude rarefactive with compressive dust-density solitary waves. The amplitudes of those dust-density solitary waves become smaller and the regime of Mach number is extended wider for the variable dust charge situation compared to the constant dust charge situation.

Attractive potential in weak ion flow coupling with dust-acoustic waves

Abstract For a weak ion flow coupling with collective dusty-acoustic waves, it is demonstrated that there exists an attractive potential necessary for the formation of dusty plasma crystals with the characteristic spacing of potential minima less than plasma Debye length, which agrees with the experimental results in some conditions.

Solitary waves of laser pulse in a plasma channel

The propagation of a Gaussian laser pulse in a preformed plasma channel is investigated. The conditions for the existence of electromagnetic solitary waves are obtained theoretically by analyzing the differential equation of the pulse spot size including the effects of relativistic self-focusing, ponderomotive self-channeling, and preformed channel focusing. Some solitarylike wave solutions are presented numerically and their possible implications on laser-plasma acceleration are discussed briefly.

Analysis of the electromagnetic fields and electron acceleration in the bubble regime of the laser-plasma interaction

An analytical model for the electromagnetic fields in the bubble regime of the interaction of ultrahigh-intensity laser with plasma is given. The two-dimensional model is based on the results of particle-in-cell simulation and includes the bubble front region. It is used to consider the generation of dense ultrashort quasimonoenergetic high-energy electron bunches. The resulting bunch parameters agree fairly well with those from the simulation.

Dust-acoustic waves in strongly coupled plasmas with variable dust charge

A generalized theory of dust-acoustic waves in strongly coupled dusty plasmas containing variable-charge dusts or impurities is given. Relaxation processes associated with the strong coupling, as well as dust-charge variation, are taken into account. It is shown that the dispersion and damping properties of the waves are strongly affected by dust-dust correlation, dust charging and viscoelastic relaxations, and dust-neutral collisions. Multiple transitions between positive to negative dispersions are also found and discussed.

QED cascade induced by a high-energy γ photon in a strong laser field

The QED cascade induced by the two counter-propagating lasers is studied. It is demonstrated that the probability of a seed-photon to create a pair is much larger than that of a seed-electron. By analyzing the dynamic characteristics of the electron and positron created by the seed-photon, it is found that the created particles are more probable to emit photons than the seed-electron. With these result, further more, we also demonstrate that the QED cascade can be easier to be triggered by the seed-photon than by the seed-electron with the same incident energy and the same laser.

High quality ion acceleration from a double-layer target dominated by the radiation pressure of a transversely Gaussian laser pulse

The ion acceleration from a double-layer target irradiated by a transversely Gaussian laser pulse is investigated by theoretical analysis and particle-in-cell simulations. The main idea of the double-layer target is to match the transverse areal mass density of the target with the laser intensity profile by single ion specie with two densities or by two ion species. Two-dimensional particle-in-cell simulations show that the target deformation and the transverse instability are efficiently suppressed in the double-layer scheme, ions within the laser spot are uniformly accelerated and are well collimated in the forward direction, GeV/u monoenergetic ion beams with very low divergency are observed.

Dust shielding and correlation function for dusty plasmas

Dust shielding and correlation function are investigated using a viscoelastic fluid theory, which allows for internal energy relaxation. The corresponding dispersion relation for dust-acoustic waves is derived. The dust static structure factor is calculated using the fluctuation-dissipation theorem. It is found that when the shear viscosity and relaxation time satisfy a certain condition the static structure factor of the strongly coupled system retains the Debye–Huckel form. In general, the characteristic shielding of the dust is found to be determined by a combination of the dust and plasma Debye lengths.

Energetic protons from an ultraintense laser interacting with a symmetric parabolic concave target

A scheme of a symmetric parabolic concave target irradiated by an ultraintense laser for efficient proton acceleration is proposed and involved problem is studied by using two-dimensional particle-in-cell (PIC) simulations. Results indicate that on one hand, the laser field is focused by the front parabolic concave surface of target and, on the other hand, more energetic hot electrons will traverse to the rear surface of target due to concave shape. The space-charge-separation field, induced by those hot electrons escaping form parabolic concave rear surface of target, can accelerate protons to relatively high energy with narrow energy spread. The dependence of the efficiency of proton acceleration on the target parameters is examined, and the optimal target parameters are obtained. Particle-in-cell simulations show that the proton peak energy and energy spread are greatly enhanced when the target parameters are chosen optimal, for example, a proton bunch with the maximum energy ∼27.5 MeV and energy sprea...