Yan-Xia Xu

Particle-in-cell simulation of the head-on collision between two ion acoustic solitary waves in plasmas

The head-on collision of two ion acoustic solitary waves in plasmas composed of hot electrons and cold ions has been studied by using the Poincare-Lighthill-Kuo (PLK) perturbation method and one-dimensional Particle-in-Cell (PIC) simulation. Then the phase lags of ion acoustic solitary waves (IASWs) obtained from the two approaches have been compared and discussed. It has been found that: if the amplitudes of both the colliding IASWs are small enough, the phase lags obtained from PLK method are in good agreement with those obtained from PIC simulation. As the amplitudes of IASWs increase, the phase lags from PIC simulation become smaller than the analytical ones from PLK method. Besides, the PIC simulation shows the phase lag of an IASW involved in collision depends not only on the characteristics of the wave it collides with but also on itself, which disagrees with the prediction of the PLK method. Finally, the application scopes of the PLK method in studying both the single IASW and the head-on collisio...

Improving the quality of proton beams via double targets driven by an intense circularly polarized laser pulse

A new scheme is proposed to improve the quality of proton beams via ultra-intense laser pulse interacting with double plasma targets, which consist of a pre-target with relatively low density and a main target with high density. Both one- and two-dimensional Particle-in-Cell simulations show that, the using of an appropriate pre-target can help to obtain a much stronger longitudinal charge separation field in contrast to using only the main target. And proton beam with lower momentum divergence, better monochromaticity and collimation, as well as higher current density is generated. Moreover, due to the strengthened coupling between the laser pulse and targets, the energy conversion from laser pulse to protons is also increased.

The application scope of the reductive perturbation method and the upper limit of the dust acoustic solitary waves in a dusty plasma

The dust acoustic solitary waves have been numerically investigated by using one dimensional electrostatic particle-in-cell method. By comparing the numerical results with those obtained from the traditional reductive perturbation method, it is found that there exist the maximum dimensionless amplitude and propagation speed of the dust acoustic solitary wave. And these limitations of the solitary wave are explained by using the Sagdeev potential technique. Furthermore, it is noticed that although ϵ ≪ 1 is required in the reductive perturbation method generally, the reductive perturbation method is also valid for ϵ < 1 in a dusty plasma, which may be extended to branches where the reductive perturbation method is used.

The effect of dust size distribution on the damping of the solitary waves in a dusty plasma

The effect of the dust size distribution on the damping rate of the solitary wave in a dusty plasma is investigated in the present paper. It is found that the damping rate increases as either the mean radius of dust grains increases or as the total number density of the dust grains increases. The damping rate is less for usual dusty plasma (about which the number density of the smaller dust grains is larger than that of the larger dust grains) than that of the unusual dusty plasma (about which the number density of the larger dust grains is larger than that of the smaller dust grains).

Plasma block acceleration via double targets driven by an ultraintense circularly polarized laser pulse

By using two-dimensional particle-in-cell simulations, plasma block acceleration via radiation pressure from an ultraintense circularly polarized laser pulse with intensity I ≈ 10 22 W / cm 2 is investigated based on a double-target scheme, in which the targets are composed of a pre-target with a relatively low plasma density and a main target with a high plasma density. It has been demonstrated that an appropriately selected pre-target can help to greatly enhance the charge separation field in the main target, which then leads to generation of a strongly accelerated and well directed plasma block with proton energy in GeV magnitude. This result can have potential applications in the plasma block ignition of proton-born fusion.

Study of plasma pressure evolution driven by strong picosecond laser pulse

Through one dimensional relativistic particle-in-cell simulation of strong laser interaction with the solid-density plasma, the evolution of the plasma impact pressure behind a thin foil has been investigated in details. An energy-compression mechanism has been proposed to help optimizing the laser and plasma parameters. It has been found that by using a picosecond laser with intensity 1015 W cm–2, an impact pressure as high as several hundreds of GPa order of magnitude can be obtained. The numerical analysis demonstrates that the peak pressure is mainly resulted from the ion contribution. These results are of potential application to the laser loading upon solids in order to study the material properties under extra-high dynamic pressure.

Application of Particle-in-Cell Simulation to the Description of Ion Acoustic Solitary Waves

1-D particle-in-cell simulations are used to investigate the propagation and decomposition of the ion acoustic solitary waves (IASWs) in plasmas. Our results show that for small-amplitude conditions, IASWs are stable and the simulation results are consistent with the theoretical predictions of the reductive perturbation method. As the amplitudes of IASWs increase, the waves become unstable and trains of oscillating waves are emitted behind the main waves. When the amplitude is large enough, the wave cannot exist and will decay into a series of waves with a small amplitude. By comparing our simulations with the theoretical solutions of Kortewag-de Vries soliton, the upper limitation of the amplitude of IASWs in plasmas is found. Moreover, our results show that although the reductive perturbation method is valid only for small perturbations, the application scope of the reductive perturbation method can be expanded to describe the potential profiles of IASWs with any amplitude. Meanwhile, the application scope for the density profiles is still limited in the perturbation cases.

The study of the Poincare-Lighthill-Kuo method by using the particle-in-cell simulation method in a dusty plasma

The application scope of the Poincare-Lighthill-Kuo (PLK) method is suggested by using the Particle-in-cell (PIC) numerical method to study head-on collision of two solitary waves. Comparisons between the numerical results from PIC simulations and the analytical ones from the PLK method indicate that the both are in good agreement with each other. The dependence of the phase shifts after the head-on collision on both amplitudes of two solitary waves is given from our PIC method. It is found that the phase shifts depended on the amplitude of both waves. The maximum amplitude during the colliding process is approximately equal to the sum of both amplitudes for the small amplitude solitary waves.

Plasma block acceleration based upon the interaction between double targets and an ultra-intense linearly polarized laser pulse

A new scheme of plasma block acceleration based upon the interaction between double targets and an ultra-intense linearly polarized laser pulse with intensity I ∼ 1022 W/cm2 is investigated via two-dimensional particle-in-cell simulations. The targets are composed of a pre-target of low-density aluminium plasma and an overdense main-target of hydrogen plasma. Through intensive parameter optimization, we have observed highly efficient plasma block accelerations with a monochromatic proton beam peaked at GeVs. The underlying mechanism is attributed to the enhancement of the charge separation field due to the properly selected pre-target.

Road map to clean energy using laser beam ignition of boron-hydrogen fusion

With the aim to overcome the problems of climatic changes and rising ocean levels, one option is to produce large-scale sustainable energy by nuclear fusion of hydrogen and other very light nuclei similar to the energy source of the sun. Sixty years of worldwide research for the ignition of the heavy hydrogen isotopes deuterium (D) and tritium (T) have come close to a breakthrough for ignition. The problem with the DT fusion is that generated neutrons are producing radioactive waste. One exception as the ideal clean fusion process – without neutron production – is the fusion of hydrogen (H) with the boron isotope 11 B11 (B11). In this paper, we have mapped out our research based on recent experiments and simulations for a new energy source. We suggest how HB11 fusion for a reactor can be used instead of the DT option. We have mapped out our HB11 fusion in the following way: (i) The acceleration of a plasma block with a laser beam with the power and time duration of the order of 10 petawatts and one picosecond accordingly. (ii) A plasma confinement by a magnetic field of the order of a few kiloteslas created by a second laser beam with a pulse duration of a few nanoseconds (ns). (iii) The highly increased fusion of HB11 relative to present DT fusion is possible due to the alphas avalanche created in this process. (iv) The conversion of the output charged alpha particles directly to electricity. (v) To prove the above ideas, our simulations show for example that 14 milligram HB11 can produce 300 kWh energy if all achieved results are combined for the design of an absolutely clean power reactor producing low-cost energy.