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首页> 外文期刊>Plasma Sources Science & Technology >Nanosecond pulsed discharges in distilled water-Part II: line emission and plasma propagation
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Nanosecond pulsed discharges in distilled water-Part II: line emission and plasma propagation

机译：蒸馏水中的纳秒脉冲放电 - 第二部分：线排放和等离子体繁殖

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摘要

Nanosecond plasmas in liquids can initiate chemical processes that are exploited in the fields of water treatment, electrolysis or biomedical applications. The understanding of these chemical processes relies on unraveling the dynamics of the variation of pressures, temperatures and species densities during the different stages of plasma ignition and plasma propagation as well as the conversion of the liquid into the plasma state and the gas phase. This is analyzed by monitoring the emission of nanosecond pulsed plasmas that are generated by high voltages of 20 kV and pulse lengths of 10 ns applied to a tungsten tip with 50 μm diameter immersed in water. The spectra are acquired with a temporal resolution of 2 ns and the emission pattern is modelled by a combination of black body radiation from the hot tungsten tip and the pronounced emission lines of the hydrogen Balmer series. The data indicate two contributions of the hydrogen line radiation that differ with respect to the degree of self-absorption. It is postulated that one contribution originates from a recombination region showing strong self absorption and one contribution from an ionization region showing very little self-absorption. The emission lines from the ionization region are evaluated assuming Stark broadening, that yielded electron densities up to 5 ×10~(25) m~(-3). The electron density evolution follows the same trend as the temporal evolution of the voltage applied to the tungsten tip. The propagation mechanism of the plasma is similar to that of a positive streamer in the gas phase, although in the liquid phase field effects such as electron transport by tunneling should play an important role.
机译：液体中的纳秒等离子体可以启动化学过程，这些化学过程被用于水处理、电解或生物医学应用领域。对这些化学过程的理解有赖于揭示等离子体点火和等离子体传播的不同阶段以及液体转化为等离子体状态和气相期间压力、温度和物种密度变化的动力学。这是通过监测纳秒脉冲等离子体的发射来分析的，该等离子体是由20 kV的高压和10 ns的脉冲长度施加在浸入水中的直径为50μm的钨尖上产生的。光谱以2 ns的时间分辨率获得，发射模式由来自热钨尖端的黑体辐射和氢巴尔默系列的显著发射线的组合建模。数据表明，氢线辐射的两种贡献在自吸收程度上有所不同。假设一个贡献来自显示出强自吸收的复合区，另一个贡献来自显示出很少自吸收的电离区。假设斯塔克展宽，计算了电离区的发射线，产生了高达5×10~（25）m-3的电子密度。电子密度的变化趋势与施加在钨尖上的电压的时间变化趋势相同。等离子体的传播机制类似于气相中正流光的传播机制，尽管在液相场中，电子隧穿传输等效应应起重要作用。

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