Direct measurement of the ionization source rate and closure of the particle balance in a helicon plasma using laser induced fluorescence
Direct measurement of the ionization source rate and closure of the particle balance in a helicon plasma using laser induced fluorescence
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DOI：
10.1063/1.5129232
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发表时间：
2020-04-01
影响因子：
2.2
通讯作者：
Zepp, Michael
中科院分区：
文献类型：
--
作者：
Green, Jonathan;Schmitz, Oliver;Zepp, Michael
对螺旋等离子体中离子和中性氩粒子的流动进行了详细的研究。了解中性燃料的离子汇和离子源的原理，对于了解螺旋波加热产生高密度等离子体的能力至关重要。这种加热机制和中性燃料所需的维持它，也许操纵长圆柱形等离子体的轴向密度分布是一个积极的研究课题先进的等离子体韦克菲尔德加速器的概念。利用离子和中性氩的激光诱导荧光（LIF）技术，测量了螺旋等离子体核心的离子流，其峰值电子密度为4.0 × 1018 m（-3），离子流高达2.5 × 1021 m（-2）s（-1）。采用轴向离子通量分布的发散度得到的最小电离率估计值为2 x 10 21 m（-3）s（-1），包括径向发散度后，估计的电离率增加到约10（22）m（-3）s（-1）。使用LIF测量的中性流速度揭示了具有径向或轴向源和汇占主导地位的不同区域的循环加燃料和损失机制。
A detailed study of the flows of ion and neutral argon populations in a helicon plasma was carried out. Understanding the principle ion sinks and sources of neutral fueling is essential to understanding the ability of helicon wave heating to create high density plasmas. This heating mechanism and the neutral fueling required to sustain it and perhaps manipulate the axial density profile in long cylindrical plasmas are an active research topic for advanced plasma wakefield accelerator concepts. Using laser induced fluorescence (LIF) of ion and neutral argon species, an ion flux of up to 2.5 x 10 21 m(-2) s(-1) was measured leaving the core of a helicon plasma with a peak electron density of 4.0 x 10 18 m(-3). Taking the divergence of the axial ion flux profile yields a minimum ionization rate estimate of 2 x 10 21 m(-3) s(-1), and including the radial divergence increases the estimated ionization rate to approximately 10(22) m(-3) s(-1). Neutral flow velocities measured using LIF reveal a circulatory fueling and loss mechanism with distinct zones where radial or axial sources and sinks dominate.