Analyses of spatiotemporal dynamic behavior of microplasmas based on three-dimensional diagnostics

在整个项目中，我们小组的主要工作是开发气相诊断方法，用于各种类型微等离子体的等离子体参数和活性物质，并具有足够的时空分辨率。作为研究对象，我们首先选择了等离子体显示面板（PDP）的单个放电单元，采用特殊设计的结构结合二极管激光吸收光谱技术对单元内的激发原子进行了三维测量。我们还将类似的方法应用于大面积大气压等离子体源的微等离子体阵列的诊断。对于电子密度n_e，我们开发了一种利用频率在10 ~ 100 GHz范围内的微波进行诊断的方法，得到了平面微等离子体阵列的电子密度n_e在空间上的平均值，具有较好的时间分辨率。作为补充，我们利用波长10.6 μm的CO_2激光器构建了外差干涉仪。它的空间分辨率优于0.1毫米，尽管时间分辨率被仪器限制在几十微秒内。我们还开发了一种太赫兹时域光谱（TDS）方法，通过微等离子体阵列的有效复介电函数同时测量n_e和碰撞频率v_e。另一方面，我们的目标是利用微等离子体的固有特性创造新的功能。作为这样的例子，我们开发了几种类型的等离子体光子晶体，用于控制毫米到亚毫米范围的微波。另一个方向是在非均匀介质中产生微等离子体，如水下气泡微放电。我们将织物电极结构浸入水中，通过电解在表面产生气泡，并对含有H_2或O_2的气泡进行点火放电。

The major roll of our group in the whole project was to develop diagnostic methods in the gas phase for plasma parameters and active species in various types of microplasmas with sufficient spatiotemporal resolutions. As the targets, firstly, we selected a single discharge cell of a plasma display panel (PDP) and performed a three-dimensional measurement of excited atoms in the unit cell by using a specially designed structure combined with a diode-laser absorption spectroscopy technique. We applied also a similar method to the diagnostics in an array of microplasmas for a large area atmospheric pressure plasma source. For the electron density n_e, we developed a diagnostic method using microwaves in the frequency range of 10 to 100 GHz, and obtained average values of n_e in space for planar microplasma arrays with a good temporal resolution. As a complementary method, we constructed a heterodyne interferometer using a CO_2 laser of 10.6 μm wavelength. It has a spatial resolution better than 0.1 mm although the temporal resolution is instrumentally limited up to a few tens of microseconds. We also developed also a THz time-domain spectroscopy (TDS) method for the simultaneous measurement of n_e and the collision frequency v_e through the effective complex dielectric function of microplasma arrays.On the other hand, we directed our objective toward the creation of new functions with microplasmas utilizing their inherent properties. As such examples, we developed several types of plasma photonic crystals for controlling microwaves of mm to sub-mm ranges. Another direction is the generation of microplasmas in heterogeneous media such as microdischarge in bubbles under water. We tested a fabric electrode structure immersed in water to generate bubbles on the surface by electrolysis, and ignited discharge in those bubbles containing H_2 or O_2.