激光支持的脉冲等离子体推力器工作过程实验研究

为了加深对激光支持的脉冲等离子体推力器工作过程的认识，本文对有无陶瓷隔离板和不同初始电压下的激光支持的脉冲等离子体推力器进行了实验研究。利用放电伏安特性对比了放电特性参数和性能参数，然后利用结合窄带滤光镜的高速摄影技术揭示了性能差异背后的物理过程变化。结果表明，陶瓷隔离板可以有效避免放电电弧对工质的烧蚀，这可以抑制滞后烧蚀的产生，从而提高推力器的推进性能。对激光烧蚀产生的工质的电离和加速是在多次振荡放电过程中进行，而不像理想电流片模型那样只电离和加速一次。放电通道内工质的电离和加速效果最为显著的时间为放电的第2个半周期。随着初始电压的增加，单位放电能量产生的推进性能先增加后趋于平稳，然后继续增加。单位放电能量产生的推进性能在初始电压高于2050V后得到较大的提高，通过放电等离子体图像推测，这意味着附着等离子体电弧的存在对推力器性能的提高有重要影响。     

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.     

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.     

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.     

Recent developments in thermal characteristics of surface dielectric barrier discharge plasma actuators driven by sinusoidal high-voltage power

Flow control using surface Dielectric Barrier Discharge(DBD) plasma actuators driven by a sinusoidal alternating-current power supply has gained significant attention from the aeronautic industry. The induced flow field of the plasma actuator, with the starting vortex in the wall jet,plays an important role in flow control. However, the energy consumed for producing the induced flow field is only a small fraction of the total energy utilized by the plasma actuator, and most of the total energy i...