RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field
RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field
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DOI：
10.3389/fphy.2017.00002
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发表时间：
2017-01-26
影响因子：
3.1
通讯作者：
Fredriksen, Ashild
中科院分区：
文献类型：
--
作者：
Gulbrandsen, Njal;Fredriksen, Ashild
在感应耦合等离子体的Njord helicon设备，我们有，对于相同的参数，对于其中的离子束存在，测量的下游人口的高能电子出现的源。高能尾电子的单独测量进行了减速场能量分析仪（RFEA）与接地入口网格，在电子收集模式下操作。在一个径向扫描与RFEA指向源，我们发现了一个显着的人口的高能电子就在磁场线映射到源的边缘。高能电子密度的第二个峰值在对应于源半径的径向位置处观察到。此外，在整个主柱中观察到高能电子的小贡献。在一个径向扫描与RFEA偏置收集离子的磁场线附近的等离子体离子密度的局部增加出现在源的壁附近的等离子体。这被解释为高能电子电离中性气体的特征。此外，在朗缪尔探针的浮动电位的下降是明显的，在该区域中观察到高能电子。
In the inductively coupled plasma of the Njord helicon device we have, for the same parameters as for which an ion beam exists, measured a downstream population of high-energy electrons emerging from the source. Separated measurements of energetic tail electrons was carried out by Retarding Field Energy Analyzer (RFEA) with a grounded entrance grid, operated in an electron collection mode. In a radial scan with the RFEA pointed toward the source, we found a significant population of high-energy electrons just inside the magnetic field line mapping to the edge of the source. A second peak in high-energy electrons density was observed in a radial position corresponding to the radius of the source. Also, throughout the main column a small contribution of high-energy electrons was observed. In a radial scan with a RFEA biased to collect ions a localized increase in the plasma ion density near the magnetic field line emerging from the plasma near the wall of the source was observed. This is interpreted as a signature of high-energy electrons ionizing the neutral gas. Also, a dip in the floating potential of a Langmuir probe is evident in this region where high-energy electrons is observed.