Stability and excitation dynamics of an argon micro-scaled atmospheric pressure plasma jet
Stability and excitation dynamics of an argon micro-scaled atmospheric pressure plasma jet
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DOI：
10.1088/0963-0252/24/6/065018
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发表时间：
2015-12-01
影响因子：
3.8
通讯作者：
Weltmann, K-D
中科院分区：
文献类型：
--
作者：
Duennbier, M.;Becker, M. M.;Weltmann, K-D
兆赫驱动的等离子体射流在大气压下-所谓的微尺度大气压等离子体射流（μ APPJ）-在纯氩气中工作进行了实验研究和数值模拟。为了在射流几何形状内点燃氩气放电，设计了自制的等离子体调谐单元，该单元还能够测量等离子体本身的耗散功率。实验研究了不同频率下α-模式放电到γ-模式的过渡。发现在α-γ跃迁处的电压表现为与所施加的频率f成反比，并且对应的功率与f（3/2）定律成比例。这两个发现都同意与时间相关的，空间一维流体建模的放电行为，其中的f（3/2）缩放的α-γ过渡功率的结果，另外验证了鞘击穿的临界等离子体密度的既定概念。此外，相位分辨光谱的光发射在750.39 nm以及在810.37 nm和811.53 nm的应用，以分析在27 MHz的放电的激发动力学为不同的应用功率。功率的增加导致在α-γ转变点处750.39 nm线发射的激发结构中的额外最大值，而在811 nm附近的发射结构不发生质的变化。根据流体模拟结果，这种不同的行为源于氩的相应能级的不同布居机制。
A megahertz-driven plasma jet at atmospheric pressure-the so-called micro-scaled atmospheric pressure plasma jet (mu APPJ)-operating in pure argon has been investigated experimentally and by numerical modelling. To ignite the discharge in argon within the jet geometry, a self-made plasma tuning unit was designed, which additionally enables measurements of the dissipated power in the plasma itself. Discharges in the alpha-mode up to their transition to the gamma-mode were studied experimentally for varying frequencies. It was found that the voltage at the alpha-gamma transition behaves inversely proportional to the applied frequency f and that the corresponding power scales with an f(3/2)law. Both these findings agree well with the results of time-dependent, spatially one-dimensional fluid modelling of the discharge behaviour, where the f(3/2) scaling of the alpha-gamma transition power is additionally verified by the established concept of a critical plasma density for sheath breakdown. Furthermore, phase resolved spectroscopy of the optical emission at 750.39 nm as well as at 810.37 nm and 811.53 nm was applied to analyse the excitation dynamics of the discharge at 27 MHz for different applied powers. The increase of the power leads to an additional maximum in the excitation structure of the 750.39 nm line emission at the alpha-gamma transition point, whereas the emission structure around 811 nm does not change qualitatively. According to the fluid modelling results, this differing behaviour originates from the different population mechanisms of the corresponding energy levels of argon.