Xie Bai-Song

Enhanced Electron-Positron Pair Production of a Vacuum in a Strong Laser Pulse Field by Frequency Variation

Effects of frequency variation on vacuum electron-positron pair production in strong pulsed laser fields are investigated in the framework of a quantum kinetic method. It is found that the slowly varying frequency can influence the pair production to some extent, while rapid varying frequency can increase the pair creation rate a few orders if the time lies within a narrow time window, in which frequency jump occurs. The possible physical mechanism behind the pair enhancement phenomenon is discussed briefly.

Effects of Ions Charge-Mass Ratio on Energy and Energy Spread of Accelerated Ions in Laser Driven Plasma

Effects of ions charge-mass ratio on energy and energy spread of accelerated ions in laser driven plasma are investigated in detail by proposing a simple double-layer model for a foil target driven by an ultrastrong laser. The radiation pressure acceleration mechanism plays an important role on the studied problem. For the ions near the plasma mirror, i.e. electrons layer, the dependence of ions energy on their charge-mass ratio is derived theoretically. It is found that the larger the charge-mass ratio is, the higher the accelerated ions energy gets. For those ions far away from the layer, the dependence of energy and energy spread on ions charge-mass ratio are also obtained by numerical performance. It exhibits that, as ions charge-mass ratio increases, not only the accelerated ions energy but also the energy spread will become large.

FLOQUET EIGENSTATE, PHASE SPACE DISTRIBUTION AND ENTROPY IN THE ATOMIC STABILIZATION DYNAMICS

A simple numerical method is developed to calculate the Floquet eigenstate and the quasienergy; the quantum Wigner function and the Husimi function in phase space in the atomic stabilization dynamics have also been studied within the Kramers-Henneberger reference frame. The characteristic Wehrl entropy is introduced and used to measure the spreading and ionization of those obtained Floquet eigenstate wave packets.

Electron-Positron Pair Creation from Vacuum by using Negative Frequency Chirping Laser Pulses

The influences of laser pulses with negative frequency chirp and different pulse cycles on pair production are studied. By solving the quantum Vlasov equation, the momentum distribution and the number density of the created pairs are obtained numerically. It is found that the chirp rate can enhance the pair production rate in both supercycle and subcycle pulses. Moreover, there is an optimal cycle parameter corresponding to the maximum number density under the same chirp rate. The pair number density is sensitive to the cycle parameter when it is less than the optimal one. Compared to the positive frequency chirp, in the case of the negative frequency chirp, the optimal cycle parameter is increased.

Levitation and Oscillation of Dust Grains in Plasma Sheath with Wake Potential

We investigate the equilibrium and levitation of dust grains in a plasma sheath with various forces, in particular the wake potential force. The vertical oscillation frequency of dust chains is also obtained by including the wake potential term. It is found that the wake potential has a significant role for the levitation and oscillation of dust grains.

Classical Description of Intense Field Stabilization Dynamics of 1D Model Atom

In this paper classical nonlinear dynamics approaches are used to study the intense field stabilization (IFS) for ID model atom according to differential equation (DE) and map approximation (MA). The exact stability boundary and region of 1-period fixed points in the parameter space of field strength and frequency are obtained, and the results of MA are in excellent agreement with those of DE. The electrons dynamical behavior in phase space is investigated and the IFS mainly occurring in high frequency regime is confirmed. The stabilization phenomenon connected with the stable fixed points is also examined. In particular it is shown that this phenomenon depends on tightly the KAM tori. It can be predicted that the stabilization probability is just the fraction of initial electrons confined by the KAM tori.