会切磁场多极离子源中磁场对等离子体特性的影响

本文提出了会切磁场多极离子源中,磁场对等离子体参数以及可引出离子束流和放电室阳极收集的离子电流影响的实验研究结果,并对该结果进行了分析讨论。     

会切磁场中大回旋电子束产生的研究

研究了会切磁场产生的机理。通过对Moster-Molnar 模型的探讨, 建立了会切磁场的物理模型。在会切磁场理论分析和数值模拟基础上, 探讨了影响会切磁场设计的因数; 利用拉格朗日公式求解了会切磁场中电子运动轨迹。探讨了会切磁场与大回旋空心会切电子枪的关系, 得到了改进会切电子枪性能的一些一般性结论。     

脉冲等离子体推力器等离子体羽流的光谱研究

脉冲等离子体推力器(pulsed plasma thruster, PPT)具有体积小、重量轻、比冲高等优点,特别适合作为执行微小卫星轨道转移、阻力补偿和姿态控制等任务的推进系统。为了深入理解PPT推力产生的机理,本文对采用具有张角的舌型极板的尾部馈送式PPT等离子体羽流开展了时空分辨光谱诊断研究。通过对光谱数据的分析发现： 等离子体羽流的主要成分为C,F,C+,F+,C2+,还含有少量的由于极板烧蚀产生的Cu+和Cu2+;等离子体在放电通道内的分布不均匀,通道中心的等离子体浓度最大,靠近阳极板的等离子浓度要明显大于靠近阴极板的等离子体浓度;在不同位置处等离子体成分也具有较大差别,F+和中性粒子主要分布在靠近阳极侧的区域;通过对各个分立谱线进行多普勒线性拟合,得到了放电通道内等离子体温度信息;以中轴线靠近工质的观测点为例,对该点在整个放电过程中不同时刻的谱线进行分析,得到了该点等离子体的具体演化过程,发现在放电的不同阶段羽流成分及各组分所占比例差别较大。     

30 cm口径离子推力器磁场设计

为了对30 cm口径离子推力器的磁场设计提出合理建议,研究了四极磁场结构下,不同尺寸的磁极宽度和磁极间距对磁极表面磁场强度和放电室电子约束长度的影响,并利用Maxwell-3D磁场分析软件得到柱段和锥段永磁体分别呈30,60和90夹角时的放电室磁场强度分布,根据不同磁场强度计算了电子温度、离子密度以及电离率等推力器放电参数。结果表明,当推力器放电电压为30 V时,磁极长度设计为0.008 m且磁极间距取为0.12 m,电子约束路径大约为50 m;柱段和锥段永磁体分别呈30,60和90夹角时,放电室磁场等势线基本在0.002~0.005 T之间;永磁体夹角为60时磁场分布和磁空区相比30和90夹角更为合理,此时的电子温度约在2~6 eV,等离子体密度约在41017~81017 m-3,电子碰撞频率比率约在0.2~1.8范围内。     

30cm口径离子推力器磁场设计

为了对30cm口径离子推力器的磁场设计提出合理建议,研究了四极磁场结构下,不同尺寸的磁极宽度和磁极间距对磁极表面磁场强度和放电室电子约束长度的影响,并利用Maxwell-3D磁场分析软件得到柱段和锥段永磁体分别呈30°,60°和90°夹角时的放电室磁场强度分布,根据不同磁场强度计算了电子温度、离子密度以及电离率等推力器放电参数。结果表明,当推力器放电电压为30V时,磁极长度设计为0.008m且磁极间距取为0.12m,电子约束路径大约为50m;柱段和锥段永磁体分别呈30°,60°和90°夹角时,放电室磁场等势线基本在0.002~0.005T之间;永磁体夹角为60°时磁场分布和磁空区相比30°和90°夹角更为合理,此时的电子温度约在2~6eV,等离子体密度约在4×1017~8×1017 m-3,电子碰撞频率比率约在0.2~1.8范围内。     

利用空气芯电磁铁产生周期会切磁场

给出了一种利用薄金属带构造的、能够产生周期会切磁场的空气芯电磁铁的设计方案,研究了该类型电磁铁产生周期会切磁场的规律。结果表明,通过增加电磁铁的周期长度,减小电子束通道的高度,或在金属带自身的电阻性发热所能承受的范围内增大金属带上传输电流的线密度,都可以提高电磁铁的励磁强度。增加电磁铁的周期长度,还可以提高周期磁场轴向分布的均匀性。     

利用空气芯电磁铁产生周期会切磁场

给出了一种利用薄金属带构造的、能够产生周期会切磁场的空气芯电磁铁的设计方案,研究了该类型电磁铁产生周期会切磁场的规律。结果表明,通过增加电磁铁的周期长度,减小电子束通道的高度,或在金属带自身的电阻性发热所能承受的范围内增大金属带上传输电流的线密度,都可以提高电磁铁的励磁强度。增加电磁铁的周期长度,还可以提高周期磁场轴向分布的均匀性。     

磁场梯度对Hall推力器放电特性影响的实验研究

为进一步探索Hall推力器通道内磁场优化设计理论,通过实验分析了强场区磁场梯度对推进剂的电离与加速等放电过程的影响. 研究发现,在本实验设计的磁场梯度范围内,磁场梯度大小对推进剂的电离过程影响较小,但是对离子流的加速特性会产生较为明显的影响.随着磁场梯度的增加,离子束的能量分布会趋于集中,推力器效率提高. 最后,对磁场轴向梯度进一步变大可能会引起的一系列物理问题如有限Larmor半径效应、电子传导机理转变规律和梯度漂移效应等进行了分析和思考.     

Cusped Solitons and Loop-Solitons of Reduced Ostrovsky Equation

The qualitative theory of differential equations is applied to the Ostrovsky equation. The cusped soliton and loop-soliton solutions of the Ostrovsky equation are obtained. Asymptotic behavior of cusped soliton solutions is given. Numerical simulations are provided for cusped solitons and so-calledloop-solitons of the Ostrovsky equation.     

Particle‐in‐cell simulation of an optimized high‐efficiency multistage plasma thruster

Electric propulsion attracts increasing attention in contemporary space missions as an interesting alternative to chemical propulsion because of the high efficiency it offers. The High‐Efficiency Multistage Plasma thruster, a class of cusped field thruster, is able to operate at different anode voltages and operation points and thereby generate different levels of thrust in a stable and efficient way. Since experiments of such thrusters are inherently expensive, multi‐objective design optimization (MDO) is of great interest. Several optimized thruster designs have resulted from a MDO model based on a zero‐dimensional (0D) power balance model. However, the MDO solutions do not warrant self‐consistency due to their dependency on estimation from empirical modelling based on former experimental studies. In this study, one of the optimized thruster designs is investigated by means of particle‐in‐cell (PIC) analysis to examine the predicted performance characteristics with self‐consistent simulations. The 0D power balance model is used to develop additional diagnostics for the PIC simulations to improve the physics analysis. Using input parameters for the 0D power balance model from the PIC simulations allows further improvement for the design optimization.     

20 cm离子推力器放电室流场计算模拟

为了优化20 cm离子推力器放电室内部推进剂供气方式,研究了在不发生气体放电时,推力器阳极和主阴极供气接口处的流体速度和压强,并以此开展推力器放电室内部的流场计算。结果表明：采用单阳极供气管方式,阳极出口处压强为4~158 Pa,气流出口速度为0.1~47 m/s;阴极小孔出口处的压强约为33.1 Pa,出口速度约为12 m/s;考虑真空系统的返流作用时,单阳极供气管方式下放电室内部压强为0.001~0.4 Pa,大部分区域Xe原子数密度为(0.2~3)1018/m3,在靠近栅极的部分区域数密度达到91019/m3左右;在增加阳极组件的供气管数量后,阳极的气体出口速度为18~40 m/s,放电室压强为0.03~0.1 Pa,大部分区域Xe原子数密度为(0.72~2.4)1019/m3,靠近阳极与主阴极进气端的小部分区域原子数密度约21017/m3,且放电室内部原子密度整体分布较为均匀。     

Fluid Simulation of a Cusped Field Thruster

The cusped field thruster is a kind of newly developed electric propulsion device. The electric field at the channel exit and the low frequency oscillation were measured by former experiments. While the formation mechanism of them have not been fully interpreted yet. Through studying two distinguishing typical electron paths in the thrusters, a fluid model is built up along two electron paths, and then the model is completed by synthetically analyzing the effect of two electron paths. Time‐averaged electric potential distribution, anode current oscillation curve and time‐synchronized atom density and ion density distribution are obtained by simulation. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Cusped Solitons and Loop-Solitons of Reduced Ostrovsky Equation

The qualitative theory of differential equations is applied to the Ostrovsky equation. The cusped soliton and loop-soliton solutions of the Ostrovsky equation are obtained. Asymptotic behavior of eusped soliton solutions is given. Numerical simulations are provided for cusped solitons and so-called loop-solitons of the Ostrovsky equation.     

离子推力器放电腔数值模拟

为更好地理解放电腔内等离子体物理机制,对Kaufman型离子推力器放电腔进行了数值研究,其中初始电子采用粒子模拟的方法处理,二次电子和离子采用漂移-扩散流体近似描述。模拟结果与已有实验测量数据进行对比表明：所采用计算方法适用于放电腔内等离子体流动规律的数值研究;模拟得到的稳态下等离子体分布及变化规律与实验测量数据相吻合;磁场的设计对初始电子起到显著的约束作用,有效地提高了其与工质气体的电离碰撞几率;二次电子的精确描述还需在流体方程中耦合磁场效应。     

20 cm氙离子推力器放电室性能优化

束流离子生产成本和推进剂利用率是表征离子推力器放电室性能的重要参数。在考虑不改变放电室几何结构、磁场分布并保持离子推力器比冲和效率的前提下,利用一维经验分析模型对兰州空间技术物理研究所研制的LIPS-200离子推力器放电室性能进行了优化分析,以实现推力器的推力从40 mN提高到60 mN的目标要求。分析结果表明,提高放电室推进剂流率至2.06 mg/s,放电室内放电电流维持在6.9 A,放电室内平均氙离子密度达到2.1671017 m-3时,可以保证引出1.2 A的束流,推力器达到60 mN的推力。与之对应的推进剂利用率为92%,束流离子生产成本约为188.515 W/A,相比推力40 mN时,推进剂利用率为88%、束流离子生产成本为188.29 W/A的情况,放电室性能有所提高。另外,放电室性能优化过程中其鞘层电位始终保持在3.80~6.65 eV范围内。     

Particle‐in‐cell simulation of the effect of curved magnetic field on wall bombardment and erosion in a hall thruster

A curved, convex towards the channel bottom magnetic field is an important feature of an advanced Hall thruster that allows confining the plasma flow in the channel center, reducing the divergence angle of the ejected ion beam, and improving the discharge performance. In this article, the discharge behaviour of a Hall thruster in magnetic fields with different degrees of curvature is simulated with a particle‐in‐cell numerical method, and the effect of curved magnetic field on the ion bombardment and wall erosion and the associated mechanisms are studied and analysed. The results show that, as the curvature of the magnetic field increases, the propellant ionization becomes more confined at the channel center, the potential drop inside the channel decreases, and the acceleration region shifts outside the channel, which lead to the attenuation of the ion energy bombarding the wall and the deviation of the bombardment angle from the optimal sputtering angle. Conversely, the ion flux bombarding the wall near the channel exit increases. Nevertheless, the bombardment energy and angle are the dominant factors for the wall erosion, and the wall erosion rate clearly decreases with the increasing curvature of the magnetic field. These findings are closely related to the behaviour of electron conduction under a curved magnetic field; the relevant mechanisms are clarified in this article.     

肼电弧增强推力器羽流温度光谱诊断

建立了一套光谱温度诊断系统,对以肼催化分解产物为推进剂的电弧增强推力器羽流信号进行了光谱温度诊断,基于谱线的绝对强度法得到对应不同波长的激发温度,由玻尔兹曼图法获得各条谱线的平均激发温度。结果表明:肼电弧增强推力器羽流中心激发温度最高,沿径向方向迅速下降;羽流的热力学非平衡态程度随径向距离增大和电流减小而降低;羽流温度随肼催化分解混合气中氨气比例增加而升高。