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41.
《等离子体科学和技术》2015,17(12):996-999
Since laser intensity plays an important role in laser plasma interactions,a method of increasing laser intensity- focusing of an intense laser via a parabolic plasma concave surface- is proposed and investigated by three-dimensional particle-in-cell simulations.The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude.Compared with the improvement via laser optics approaches,this scheme is much more economic and appropriate for most femtosecond laser facilities. 相似文献
42.
We use quantum electrodynamics particle-in-cell simulation to study the generation of dense electron–positron plasma and strong γ-ray bursts in counter-propagating laser beam interactions with two different solid targets, i.e. planar(type I) and convex(type II). We find that type II limits fast electron flow most effectively. while the photon density is increased by about an order of magnitude and energy by approx. 10%–20% compared with those in type I target. γ-photon source with an ultrahigh peak brilliance of 2?×?1025 photons/s/mm2/mrad2/0.1% BW is generated by nonlinear Compton scattering process. Furthermore, use of type II target increases the positron density and energy by 3 times and 32% respectively, compared with those in type I target. In addition, the conversion efficiencies of total laser energy to γ-rays and positrons of type II are improved by 13.2% and 9.86% compared with type I. Such improvements in conversion efficiency and positron density are envisaged to have practical applications in experimental field. 相似文献
43.
在气固两相流动的模拟中严格处理颗粒运动和颗粒相互作用时,欧拉?拉格朗日(EL)方法比欧拉?欧拉(EE)方法更具优势。但传统的EL方法仅能处理少量颗粒。将颗粒群作为单个计算颗粒处理可扩大模拟规模,粗粒化离散颗粒法(CG-DPM)和多相物质点法(MP-PIC)是其中两种主要方法,分别更适用于稠密和稀疏的颗粒流体系统。将两种方法耦合建立了更通用、准确和有效的EL方法,比较了不同耦合参数下流型、固相分率分布等定量信息,确定了最佳耦合参数。 相似文献
44.
《等离子体科学和技术》2020,22(6):65001
A relativistic canonical symplectic particle-in-cell(RCSPIC) method for simulating energetic plasma processes is established. By use of the Hamiltonian for the relativistic Vlasov–Maxwell system, we obtain a discrete relativistic canonical Hamiltonian dynamical system, based on which the RCSPIC method is constructed by applying the symplectic temporal discrete method.Through a 10~6-step numerical test, the RCSPIC method is proven to possess long-term energy stability. The ability to calculate energetic plasma processes is shown by simulations of the reflection processes of a high-energy laser(1?×?10~(20) W cm~(-2)) on the plasma edge. 相似文献
45.
Microwave frequency downshift in the time-varying collision plasma has been demonstrated by particle-in-cell simulations.The simulation results are consistent with the theoretical analysis,and the preconditions for microwave frequency downshift are that the collision frequency needs to be greater than the incident wave frequency,and the plasma frequency is two times greater than the incident wave frequency.Finally,the simulation results are compared with the reported experimental results indicating good agreement. 相似文献
46.
The spatially modulated electron distribution of plasma is the basis for obtaining programmable electron density patterns. It has an important influence on plasma technology applications. We propose an efficient scheme to realize controllable electron density patterns in underdense plasma based on the array laser–plasma interaction. Theoretical evidence for the realization of programmable electron density patterns and the corresponding electrostatic field is provided analytically, which is confirmed by particle-in-cell simulations. Results show that the spatial distribution of electron density in the propagation and transverse directions of the laser can be highly modulated to obtain rich programmable electron density patterns by adjusting the array pattern code and pulse width of the array laser beam. 相似文献
47.
48.
Explicit structure-preserving geometric particle-in-cell(PIC) algorithm in curvilinear orthogonal coordinate systems is developed. The work reported represents a further development of the structure-preserving geometric PIC algorithm achieving the goal of practical applications in magnetic fusion research. The algorithm is constructed by discretizing the field theory for the system of charged particles and electromagnetic field using Whitney forms, discrete exterior calculus, and explicit non-canonical symplectic integration. In addition to the truncated infinitely dimensional symplectic structure, the algorithm preserves exactly many important physical symmetries and conservation laws, such as local energy conservation, gauge symmetry and the corresponding local charge conservation. As a result, the algorithm possesses the long-term accuracy and fidelity required for first-principles-based simulations of the multiscale tokamak physics. The algorithm has been implemented in the Sym PIC code, which is designed for highefficiency massively-parallel PIC simulations in modern clusters. The code has been applied to carry out whole-device 6 D kinetic simulation studies of tokamak physics. A self-consistent kinetic steady state for fusion plasma in the tokamak geometry is numerically found with a predominately diagonal and anisotropic pressure tensor. The state also admits a steady-state subsonic ion flow in the range of 10 km s~(-1), agreeing with experimental observations and analytical calculations Kinetic ballooning instability in the self-consistent kinetic steady state is simulated.It is shown that high-n ballooning modes have larger growth rates than low-n global modes, and in the nonlinear phase the modes saturate approximately in 5 ion transit times at the 2% level by the E × B flow generated by the instability. These results are consistent with early and recent electromagnetic gyrokinetic simulations. 相似文献
49.
The use of a novel double-cone funnel target with high density layers (HDL) to collimate and focus electrons is investigated by two-dimensional particle-in-cell simulations. The proposed scheme can guide, collimate and focus electron beams to smaller sizes. The collimation reasons are analyzed by the quasi-static magnetic fields generation inside the beam collimator with HDL. It is found that the energy conversion efficiency is increased by a factor of 2.2 in this new scheme in comparison with the that without HDL. Such a target structure has potential for design flexibility and prevents inefficiencies in important applications such as fast ignition, etc. 相似文献
50.
采用三维PIC模型仿真研究了等离子体浸没离子注入过程中工件高度变化对鞘层扩展动力学和离子注入效果的影响。模拟结果表明,随着工件高度减小,中心水平截面内鞘层扩展速度明显下降,鞘层最终尺寸也明显减小。随着工件高度减小,工件上表面的注入剂量峰幅值明显增大,表面注入剂量均匀性则显著下降。随着工件高度减小,工件上表面的离子垂直入射面积和高能离子注入面积略有减小。这是由于工件高度减小造成鞘层曲率半径减小,弯曲的鞘层增大了离子聚焦现象将更多离子聚焦注入到工件边角附近位置。随着工件高度减小工件侧壁上的注入剂量峰幅值明显增大,而且工件棱线上的剂量数值也显著增大,且均匀性更好。 相似文献