Characteristics of a Sheath with Secondary Electron Emission in the Double Walls of a Hall Thruster

In order to investigate the effects of secondary electrons,which are emitted from the wall,on the performance of a thruster,a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath.The effects of secondary electron emission (SEE) coefficients and trapping coefficients,as well as magnetic field,on the structure of the plasma sheath are investigated.The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness.In addition,magnetic field strength will influence the sheath potential distributions.     

Vicinage Effects for a Nitrogen Molecular Cluster in Plasmas

The vicinage effects are studied for a fast nitrogen diatomic molecular cluster in a high-density plasma target.A variety of plasma parameters are discussed with regard to stopping power ratio,molecular axis deflection and Coulomb explosion.Emphasis is placed on the vicinage effects on Coulomb explosion and stopping power for a nitrogen cluster in plasmas.The results indicate that vicinage effects influence the correlation between ions in the cluster,and the Coulomb explosion will proceed faster with higher projectile speed,lower plasma density and higher plasma temperature.Comparing hydrogen and nitrogen molecular ions for Coulomb explosion and deflection angle under the same set of parameters,one can find that the nitrogen ion has faster Coulomb explosion and stronger deflection of molecular axis due to the contribution of charge.In the initial stage of the Coulomb explosion the stopping power ratio has a higher value due to enhanced vicinage effects while in the later stage the stopping power ratio approaches one,indicating that the vicinage effects disappear and the ions in the cluster simply behave as independent atomic ions in the plasma.     

稳态等离子体发动机磁场设计的发展及其展望

论述了稳态等离子体发动机对于我国空间发展战略的重要意义和作用，指出磁场设计是提高稳态等离子体发动机性能的关键技术之一；分析了稳态等离子体发动机通道内磁场设计的发展过程，在此基础上提出了用于稳态等离子发动机磁场设计的体系化构想，并且指出了其中存在的一些关键问题和拟采取的解决措施以及磁场体系化设计对稳态等离子体发动机带来的预期效益和影响；最后展望了稳态等离子体发动机磁场设计体系的进一步发展和应用。     

SPERF环向场线圈脉冲电流源设计

空间等离子体环境模拟与研究装置SPERF （Space Plasma Environment Research Facility）中,环向场TF （toroidal field）线圈用于磁重联实验,物理上要求该线圈的脉冲电流在80 μs的时刻大于200 kA,这对脉冲电流源的整体设计、放电开关和放电测试等提出了较高的技术要求。研究TF线圈脉冲电流源的设计、关键技术和测试,以实现这种100 μs量级的脉冲大电流。首先,介绍了脉冲电源的结构,计算了脉冲电源的参数,设计了脉冲电源的模块化结构;其次,研究了放电开关组件的设计和测试;最后,介绍了脉冲电流源的测试,测试结果表明脉冲电流源能可靠地工作。所研究的脉冲电源对SPERF磁重联实验的开展具有重要意义,同时对脉冲强磁场、脉冲功率和电磁兼容等领域也具有参考价值。