Time-resolved line emission spectroscopy and the electrical currents in the plasma jet generated by dielectric barrier discharge for soft ionization
Time-resolved line emission spectroscopy and the electrical currents in the plasma jet generated by dielectric barrier discharge for soft ionization
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DOI：
10.1016/j.sab.2015.09.017
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发表时间：
2015-11
期刊：
影响因子：
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通讯作者：
V. Horvatić;A. Michels;N. Ahlmann;G. Jestel;C. Vadla;J. Franzke
中科院分区：
文献类型：
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作者：
V. Horvatić;A. Michels;N. Ahlmann;G. Jestel;C. Vadla;J. Franzke
测量了高压方波驱动下氦毛细管介质阻挡放电的时空分辨光发射和正负电压期间的放电电流。在501 nm和391 nm处分别监测He和N2+的发射强度。等离子体射流仅在正电压阶段形成，且在毛细管放电点火之前形成。因此，在正电压和负电压期间毛细管放电电流之间的差异的测量使得通过等离子体射流传输的电荷的量化成为可能。通过对等离子体射流中He发射强度的时空特性分析，得到了氦激发的传播速度和等离子体射流的有效长度。这些测量的结合使等离子体喷射电流的绝对值得以确定。在两个数量级的发射强度范围内，等离子体射流中He发射强度与等离子体射流电流之间存在线性关系。N2+的发射强度也与等离子体喷射电流呈线性关系。产生激发态He原子的快电子大多位于估计的有效等离子体射流长度范围内。在这一区域，激发He原子、N2+和H2O分子的一系列过程建立了等离子体射流作为软电离源的必要条件。反应物质的产生可能与等离子体射流有关，这可以作为软电离效率的衡量标准。
The spatially and temporally resolved optical emission from the helium capillary dielectric barrier discharge driven by a square wave high voltage was measured simultaneously with the discharge currents during the positive and negative voltage periods. The He and N2+emission intensities were monitored at 501 nm and 391 nm, respectively. The plasma jet was found to be formed only during the positive voltage period, and it preceded the discharge ignition in the capillary. Thus, the measurements of the difference between the capillary discharge currents during the positive and negative voltage periods enabled quantification of the charge, which was transported through the plasma jet. The analysis of the spatiotemporal behavior of the He emission intensities in the plasma jet yielded the velocity of the helium excitation propagation and the effective plasma jet length. The combination of these measurements enabled determination of the absolute values of the plasma jet currents. The linear relationship between the He emission intensities in the plasma jet and the plasma jet currents was found to exist over the emission intensity range of two orders of magnitude. The N2+emission intensity was also found to be linearly dependent on the plasma jet current. The fast electrons, producing the excited He atoms, were found to be located mostly within the estimated effective plasma jet length. In this region a cascade of processes involving excited He atoms, N2+and H2O molecules lead to establishment of the conditions necessary for the plasma jet to be used as soft ionization source. The production of reactive species can be related to the plasma jet current, which can serve as a measure of the soft ionization efficiency.