Study of fast atoms in molecular gas plasma via emission spectroscopy

Fast atoms are generated in reactions of ions with the molecular gas in laboratory and astrophysical plasma. In hydrogen they are observed in the emission spectra via Excessive line broadening. Energetic atoms also occur in astrophysical plasma in hydrogen, nitrogen and oxygen. The proposal here is that low pressure discharges can be used to simulate the phenomena in certain space plasma. In this study, we have used a special configuration of the electrode system, to obtain energetic atoms in plasma of three types of diatomic gases (H₂, O₂, N₂). Emission spectroscopy was used to detect the atoms and measure their velocity. Energy analysis was performed to obtain atoms’ distributions and evaluate the mean energy of atoms. This was compared to the potential energy available from the electric field. The field acceleration model, previously established for hydrogen, was extended to nitrogen and oxygen. We suggest, that the same method of analysis can be applied for astrophysical plasma spectrum.     

面向空间通信的DTN一体化传输性能约束研究

相比于地面网络，空间通信链路具有较长的延迟、频繁的中断、较高的误码率及上下行链路非对称等特性，互联网成熟的网络技术并不适用，对网络可靠传输性能的保障提出了挑战。不同于空间IP协议体系方案，针对空间通信链路特性，采用多种传输机制兼容的DTN（delay tolerant networking）协议架构。重点针对链路非对称、和信道误码率等特性，研究对保障可靠传输的TCP和LTP两种传输机制的性能制约，并给出LTP（Licklider transport protocol）机制的跨层包尺寸优化模型。基于半实物仿真平台，构建静止轨道GEO以下的空间通信场景，进行真实数据流仿真，分析链路因素对协议传输性能的影响。仿真结果表明，在近地端误码率和信道非对称比例较小的空间通信场景中，仍可以采用TCP机制保障可靠传输，但对于误码率和信道非对称比例较高的通信场景，应考虑采用LTP传输机制保障通信的有效性和可靠性。     

Plasma transport simulation under different conditions and optimization analysis of dual-stage grid ion thruster

In order to study the extraction and acceleration mechanism of the dual-stage grid, a three-dimensional model based on the Particle-In-Cell/Monte Carlo Collision(PIC/MCC) method is performed. Dual-stage grid ion thruster is a new type of electrostatic ion thruster, which can break through the limitations of traditional gridded ion thrusters, and greatly improve the specific impulse. The high performance also makes the grid sensitive to operating parameters. In this paper,the influence of grid pa...     

Gas-dynamic approach to the theory of non-linear ion-acoustic waves in plasma with Kaniadakis’ distributed species

The non-linear theory of ion-acoustic waves in two-spesies isotropic collisionless plasma is developed. Both light electron and heavy ion species in the plasma are distributed with Kaniadakis’ statistics. Kaniadakis’ gas law is derived. The exact formula for the Sagdeev pseudopotential in parametric form is derived by the method based on the integration of the inverse function. The pseudopotential is analyzed. It is shown that periodic ion-acoustic waves and solitons are possible in the studied plasma. The differential equation describing the profile of the ion concentration in the wave is derived. The profiles of this concentration in the periodic ion-acoustic wave and soliton are calculated.     

Numerical simulations of a continuously injected relativistic electron beam relaxation into a plasma with large-scale density gradients

In this paper the influence of large-scale decreasing and increasing gradients of the density of magnetized plasma on the relaxation process of a continuously injected relativistic electron beam with an energy of 660 keV ($v_b=0.9c$) and a pitch-angle distribution is studied using particle-in-cell numerical simulations. It is found that for the selected parameters in the case of a smoothly decreasing gradient and in a homogeneous plasma the formation of spatially limited plasma oscillations of large amplitude occurs. In such cases, modulation instability develops and a long-wave longitudinal modulation of the ion density is formed. In addition, the large amplitude of plasma waves accelerates plasma electrons to energies on the order of the beam energy. In the case of increasing and sharply decreasing gradients, a significant decrease in the amplitude of plasma oscillations and the formation of a turbulent ion density spectrum are observed. The possibility of acceleration of beam electrons to energies more than 2 times higher than the initial energy of the beam particles is also demonstrated. This process takes place not only during beam propagation in growing plasma density, but also in homogeneous plasma due to interaction of beam particles with plasma oscillations of large amplitude.     

光纤环非互易相位误差尾纤补偿方法研究CSCD

针对光纤环的热致非互易误差的补偿方法进行研究,并通过仿真分析与实验验证,证明了某种光纤环尾纤长度与光纤环热致非互易误差之间的关系。根据等效介质理论和Mohr理论,建立了光纤环热致非互易相位误差仿真分析模型,并利用该模型计算了不同温度环境条件下,某类型光纤环顺逆时针方向光纤长度发生变化时,陀螺仪输出的全温零位漂移的变化量。仿真及实验结果表明,在1℃/min温变速率条件下,总长约800m的光纤环圈顺逆时针方向光纤长度相差约0.5m时,光纤环全温零位漂移量缩小了0.4(°)/h。研究结果得出了针对此类型的光纤环,当光纤环尾纤每减少0.5m,其热致非互易相位误差减小0.4(°)/h的规律。该项研究成果为后续优化光纤环的全温精度奠定了基础。     

基于改进狼群算法的多无人机协同多目标分配CSCD

针对现代空战多无人机协同多目标任务分配问题,结合标准狼群算法,提出了一种改进狼群算法的多目标任务分配方法。根据狼群的不同分工以及搜索属性,建立了基于自主游走机制的头狼产生规则、基于多策略知识库的探狼游走机制和基于自适应步长的猛狼奔袭及围攻方式,从而对传统狼群算法的随机性进行智能化约束与控制,以解决多无人机协同多目标任务分配问题。数值仿真结果表明,该方法能够快速有效获得任务分配方案,避免陷入局部最优。     

Experimental and numerical investigation on opposing plasma synthetic jet for drag reduction

Experimental and numerical studies are carried out to validate the potential of opposing Plasma Synthetic Jet (PSJ) for drag reduction for a hemisphere. Firstly, flow field changes of opposing PSJ are analyzed by comparing the experimental schlieren images and simulation results in a supersonic free stream of Mach number 3. As PSJ is a kind of unsteady pulsed jet, the shock standoff distance increases initially and then decreases under the control of PSJ, which corresponds to the change of the strength of PSJ. Accordingly, the amount of drag reduction of the hemisphere increases initially and then decreases. It is found that there is a short period of “drag rise” during the formation of PSJ before the drag reduction, which is induced by the generation of normal shock waves and the area difference of the cavity wall of PSJ Actuator (PSJA). Secondly, the effects of five parameters, including exit diameter, discharge energy of PSJA, Mach number, static pressure of incoming flow and angle of attack, on drag reduction of opposing PSJ were studied in detail by using numerical method. It is found that the Maximum Pressure Ratio (MPR) has a significant impact on the average drag reduction for a configuration-determined PSJA. For the configuration selected in this study, the flow field of opposing PSJ shows typical Short Penetration Mode (SPM) in a control cycle of PSJ when the MPR is less than 0.89. However, the flow field shows typical Long Penetration Mode (LPM) at some time when the MPR is bigger than 0.89. Relatively better drag reduction is achieved in this case.     

Calculating the simultaneous effect of ion dynamics and oscillating electric fields on Stark profiles

We calculate hydrogen line shapes resulting from the simultaneous Stark effect of the plasma microfield and an oscillating electric field. Like laboratory plasmas, many kinds of space plasmas are affected by oscillating electric fields with a magnitude similar to that of the microfield. Here we focus on conditions where we expect that the effect of ion dynamics and oscillating electric are both significant. The combined effect of their dynamics on the quantum emitter is retained by a computer simulation coupled to a numerical integration of the Schrödinger equation. Our calculations are applied for conditions and transitions where significant changes in the line shape allow for a diagnostic of the plasma and oscillating field.