Direct measurements of the ionization profile in krypton helicon plasmas
Direct measurements of the ionization profile in krypton helicon plasmas
复制标题
直接测量氪螺旋等离子体中的电离剖面
DOI：
10.1063/1.4772060
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发表时间：
2012
影响因子：
2.2
通讯作者：
E. Scime
中科院分区：
文献类型：
--
作者：
R. Magee;M. Galante;N. Gulbrandsen;D. McCarren;E. Scime
螺旋是高效的等离子体源，只需 100 秒 W 的输入射频功率即可产生 1019 m−3 的等离子体密度。中性密度和等离子体密度通常都存在陡峭的密度梯度，导致几厘米宽的完全电离核心被弱电离等离子体包围。电离分布通常不太清楚，因为中性密度通常是从间接光谱测量或边缘压力计测量中推断出来的。我们开发了一种双光子吸收激光诱导荧光 (TALIF) 诊断仪，能够直接测量中性密度分布。我们将 TALIF 与 Langmuir 探针结合使用，测量电离分数随驱动频率、磁场和输入功率的变化。研究发现，当驱动波频率大于临界频率fc≈3flh（其中flh为天线处的较低混合频率）时，电离分数较小（0.1%），等离子体密度较低（1...
Helicons are efficient plasma sources, capable of producing plasma densities of 1019 m−3 with only 100 s W of input rf power. There are often steep density gradients in both the neutral density and plasma density, resulting in a fully ionized core a few cm wide surrounded by a weakly ionized plasma. The ionization profile is usually not well known because the neutral density is typically inferred from indirect spectroscopic measurements or from edge pressure gauge measurements. We have developed a two photon absorption laser induced fluorescence (TALIF) diagnostic capable of directly measuring the neutral density profile. We use TALIF in conjunction with a Langmuir probe to measure the ionization fraction profile as a function of driving frequency, magnetic field, and input power. It is found that when the frequency of the driving wave is greater than a critical frequency, fc≈3flh, where flh is the lower hybrid frequency at the antenna, the ionization fraction is small (0.1%) and the plasma density low (1...