离子推力器放电腔内等离子体流动规律的全粒子模型

为了详细描述等离子体在放电腔内的产生、演化过程,建立了放电腔内部等离子体流动的二维轴对称全粒子数值模型。在考虑壁面二次电子发射影响的前提下,模拟得到了稳态后放电腔内电磁场、电子与离子数密度,电流密度等一系列参数分布,且与相关实验数据进行了比较,吻合较好。模型得到了实验中难以观测到的放电腔内等离子体的产生、演化过程以及稳态下的分布规律,合理解释了放电腔工作的基本原理。     

A Carbon Nano Tube electron impact ionisation source for low-power,compact spacecraft mass spectrometers

A novel ionisation source which uses commercially available Carbon Nano Tube devices is demonstrated as a replacement for a filament based ionisation source in an ion trap mass spectrometer. The carbon nanotube ion source electron emission was characterised and exhibited typical emission of 30 ± 1.7 μA with an applied voltage differential of 300 V between the carbon nanotube tips and the extraction grid. The ion source was tested for longevity and operated under a condition of continuous emission for a period of 44 h; there was an observed reduction in emission current of 26.5% during operation. Spectra were generated by installing the ion source into a Finnigan Mat ITD700 ion trap mass spectrometer; the spectra recorded showed all of the characteristic m/z peaks from m/z 69 to m/z 219. Perfluorotributylamine spectra were collected and averaged contiguously for a period of 48 h with no significant signal loss or peak mass allocation shift. The low power requirements and low mass of this novel ionisation source are considered be of great value to future space missions where mass spectrometric technology will be employed.     

Reconstruction of topside density profile by using the topside sounder model profiler and digisonde data

To improve the accuracy of the real time topside electron density profiles given by the Digisonde software a new model-assisted technique is used. This technique uses the Topside Sounder Model (TSM), which provides the plasma scale height (H_s), O⁺–H⁺ transition height (H_T), and their ratio Rt = H_s/H_T, derived from topside sounder data of Alouette and ISIS satellites. The Topside Sounder Model Profiler (TSMP) incorporates TSM and uses the model quantities as anchor points in construction of topside density (Ne) profiles. For any particular location, TSMP calculates topside Ne profiles by specifying the values of foF2 and hmF2. In the present version, TSMP takes the F2 peak characteristics – foF2, hmF2, and the scale height at hmF2 – from the Digisonde measurements. The paper shows results for the Digisonde stations Athens and Juliusruh. It is found that the topside scale height used in Digisonde reconstruction is less than that extracted from topside sounder profiles. Rough comparison of their bulk distributions showed that they differ by an average factor of 1.25 for locations of Athens and Juliusruh. When the Digisonde scale heights are adjusted by this factor, the reconstructed topside profiles are close to those provided by TSM. Compared with CHAMP reconstruction profiles in two cases, TSMP/Digisonde profiles show lower density between 400 and 2000 km.     

离子推力器高效高可靠性屏栅电源设计

为了进一步提高离子推力器的可靠性和使用寿命,采用6个电源模块串联输出的方法设计了高效高可靠性的屏栅电源试验样机,每个模块采用全桥LLC谐振变换器,并对屏栅电源模块的性能、打火时开关管的瞬态电流应力分别进行了测试研究。结果表明：屏栅电源模块采用全桥LLC谐振变换器,可以实现零电压开通零电流关断（ZVSZCS）,整个电源的转换效率提高到96.9%;单个电源模块输出电压为210V,电源模块内部没有大于250V 的交流电压峰值,简化了高压绝缘设计的难度;变换器初级较大谐振电感的限流作用使得推力器出现打火时,开关器件瞬态电流仅为40A。该设计可以有效提高屏栅电源的效率和可靠性,可以应用于小行星探测等深空探测航天器的电推进系统。     

阳极电流和屏栅电压对5kW离子推力器性能的影响

为了研究5kW离子推力器功率宽范围工作能力,采用试验的方法得到阳极电流和屏栅电压与其性能的影响关系。研究结果表明：离子束流随阳极电流增大呈线性增大。当屏栅电压增加时,推力器离子束流先增加然后趋于稳定,加速栅电流单调减小。推力随功率增大呈线性增长,比冲随功率的增大呈非线性增长,在功率308W~4813W下实现了推力12mN~184mN,比冲1817s~3538s, 效率34%~67%的宽范围调节。同时推力器效率随功率增大逐渐增大,并在2902W时存在明显拐点,在实际在轨应用中要根据任务需求确定最佳工作区间提高推力器性能和效率。     

防原子氧与抗辐射环境薄膜性能研究

金属氧化物薄膜具有良好的光学,电学特性,因此是卫星表面热控材料防静电积累的重要材料之一。实验研究发现这些金属氧化物薄膜还是具有优良的防原子氧和抗空间辐照环境的能力,而且这种能力与成膜方法及工艺过程直接相关。经模拟原子氧环境的氧等离子体作用后,溅射镀氧化锡样品的质损明显小于蒸镀氧化铟锡薄膜的质损,而氧化铟锡薄膜的质损又小于未镀薄膜试样质损。     

离子推力器双阶栅极系统引出性能研究

针对基于最优导流工况设计的双阶四栅栅极系统在多工况下的引出性能,采用浸入式有限元和粒子云算法(IFE-PIC)对其聚焦和引出过程进行了研究.研究结果表明,相较于相同聚焦电压下的传统栅极系统,基于最优导流工况设计的双阶四栅栅极系统由过聚焦进入正常聚焦的拐点右移,栅极系统的引出性能变差.因此建议双阶栅极离子推力器在设计时使...     

Confinement characteristic of primary electrons with the variation of channel width in the discharge chamber of annular ion thruster

In this paper, the confinement characteristic of primary electrons in the non-axisymmetric discharge chamber of annular ion thruster is investigated by a three-dimensional (3D) non-self-consistent particle tracking model with Monte Carlo Collision (MCC) method. The results show that: The density of primary electrons upstream of ion optics on cathode axis is about 5–50 times higher than that of the other side, which means that the density of primary electrons is obviously non-axisymmetric. The channel width has a significant effect on the average density and uniformity of primary electrons. The average density can be increased by nearly 1.5 times under the appropriate channel width, meanwhile, the variance of density distribution can be reduced by more than 2 times. This is because that increasing the channel width can improve the average confinement length of primary electrons greatly. Furthermore, there is an infection point in the increase of primary electron average confinement length with the channel width, which caused by the significant change of magnetic field structure. Under the case after the inflection point, primary electron mainly (more than 50%) moves to the channel center, which makes the average confinement length of primary electrons and their number in the discharge chamber increase largely.     

极区顶部电离层离子上行的太阳活动依赖性研究

利用第23太阳活动周DMSP F12,F13和F15卫星数据,分别对南北半球极区顶部电离层离子上行的太阳活动依赖性进行了研究.结果表明,南北半球上行事件对太阳活动的响应特征基本一致,即高（低）太阳活动时,离子上行通量以及上行数密度较大（小）,但是上行速度及上行发生率较低（高）.以南半球高纬为例,计算得到离子上行通量、数密度、速度及发生率在高低太阳活动条件下的比值分别约为2.26,3.35,0.71,0.51.对离子上行太阳活动依赖性的可能原因进行了分析.不同太阳活动水平下,光致电离及高能粒子沉降的差异会导致电离层离子密度的不同,而电离层离子密度的变化会改变离子elax-elax中性大气之间的碰撞频率,这是影响离子上行发生率的一个重要原因.     

基于各向异性分布的非相干散射雷达谱仿真

基于离子在加热条件下呈现各向异性分布的假设,建立离子声波激发条件下非平衡态的三维离子速度分布函数模型,给出任意视线方向上非相干散射谱的计算方法,分析幅度修正因子、离子声速粒子组分、雷达波束方向与磁场方向夹角及温度各向异性对功率谱的影响.研究结果可以解释离子线谱超过一个量级的幅度增强现象和上行离子线强于下行离子线的不对称现象,对加热强扰动电离层条件下的等离子体参数反演具有重要意义.