Research and Development of Advanced High-Density Helicon Plasma Source for Plasma Rocket Engine

本文研究了一种用于等离子体火箭发动机的无电极等离子体源。几个射频天线进行了检查，以产生无电极放电等离子体。鞍型天线在40-60 MHz附近仅10 W RF输入功率下显示出优越的上级点火特性。对几种工作气体进行了测试，为了便于分析，选择了单原子氩。在内径为2.5 cm的玻璃管内引发等离子体。长80 cm，是世界上最小的螺旋源之一。流速为lmg/s（34 sccm）。当RF输入功率小于50 W时，等离子体似乎是感应耦合的，但超过200 W时，产生超过10 μ cm 2的非常致密的等离子<12><-3>体。此时，<12><-3>在高达200 G的外加磁场下达到2 x 10^ cm^2的密度。从密度突然增加、在没有外加电场的情况下消失以及国外合作者Shamrai分析预测的必要条件来看，这被认为是一次螺旋跃迁。<12><-3>486 cm长，Bmax=2 kG），直径42 cm。4-转向天线，采用最大功率为4千瓦的脉冲射频放大器。提出了通过调整激励天线方向图和外加电场分布来控制径向等离子体密度分布的方法，并在加速机制上提出了两种新的无电极加速方法。一种是通过线圈天线在等离子体内部感应出方位向电流，实现步进脉冲电磁加速。另一种是通过旋转电场的穿透作用来持续加速等离子体。分析发现这两种方法都是可行的。

In this research, we investigated an electrodeless plasma source producing and accelerating high-density plasma for Plasma Rocket Engine. Several RF antennae were examined to produce electrodeless discharge plasmas. A saddle-type antenna showed superior ignition characteristics around 40-60 MHz under only 10 W RF input power. A few working gases were tested and mono-atomic Argon was selected for the sake of easy analysis. The plasma was initiated inside a glass tube with 2.5 cm i.d. and 80 cm length which was one of the world smallest helicon source. The flow rate was 1 mg/s(34 sccm). The plasma seemed to be inductively coupled when the RF input power was less than 50 W, but beyond 200 W very dense plasma over 10^<12> cm^<-3> was produced. At that time, 2 x 10^<12> cm^<-3> density was attained under the applied magnetic field up to 200 G. Judging from its abrupt increase of density, disappearing without applied fields and the necessary conditions analytically predicted by Shamrai, our overseas research collaborator, this was recognized as a helicon jump.The world largest volume helicon plasma over 5 x 10^<12> cm^<-3> density was successfully produced in a large magnetized plasma device (74 cm id.,486 cm length, Bmax=2 kG) with a 42 cm diam. 4-turn antenna, using a maximum power of 4 kW pulsed RF amplifier. The method controling radial plasma density distribution was found by adjusting the excitation antenna pattern and the applied field distribution.On the other hand as for the acceleration mechanisms, we newly proposed 2 kinds of electrodeless methods. One is to induce a azimuth current inside the plasma by coil antenna and make step-by-step pulsed electromagnetic acceleration. The other is to continuously accelerate plasma by the penetration of rotating electric field applied. Both methods were analytically found to be feasible.