螺旋波等离子体放电特性的射频补偿朗缪尔单探针测量研究

Diagnosis of Helicon Plasma by Single Frequency-Compensated Langmuir Probe

采用射频补偿朗缪尔单探针研究了螺旋波放电中功率、气体压强、磁场强度等对等离子体参数的影响。结果表明,随着功率的增大,等离子体密度会出现两次明显的跳跃,分析认为放电模式经历了由容性模式到感性模式和波模式转变过程。实验发现磁场的增大、放电压强的增大都可以使模式转变的功率阈值提前。同时,在天线上端的测量到低场密度峰的存在,并进行了气压和功率的影响的研究,认为低场峰主要是由螺旋波放电模式引起。

The dependence of thedischarge in the helicon plasma on the discharge conditions,including but not limited to the discharge power,pressure and magnetic field,was experimentally evaluated with a single frequencycompensated Langmuir probe. The results show that as the discharge power increased,the electron density increased,rising up abruptly at discharge powers of 300 and 900 W,respectively. The ＂jumps＂of the electron density suggest a transition from the capacitively-coupled discharge mode to a whistle wave discharge mode. We found that the increases of both the pressure and magnetic field reduce the threshold of the discharge power for the transition of the discharge mode. In addition,a high electron density peak in the low magnetic field in the upstream of the antenna was observed,possibly because of the discharge mode of the helicon wave.