Miniature DBD has been obtaining more and more attention. A recently developed miniature flexible micro-tube plasma (FμTP) has proved to be an excellent soft ionization source for mass spectrometry and ion mobility spectrometry. In this paper, the optical characterization of the novel FμTP ionization source was carried out, aiming to cast light on the plasma propagation mechanism in one discharge cycle. To provide a clean environment for investigating the plasma propagation, the plasma was totally sustained in a capillary tube. It was found that in one discharge cycle, three discharge developments, namely two dielectric guided discharges in both positive and negative half cycle, and a negative glow discharge in the negative half cycle. Compared with the conventional dielectric barrier discharge, there is no formation of a dissociative plasma, which improves the soft ionization capacity of the present source. In addition to the whole light emission from 200 nm to 1100 nm, the lines related to the reactive species including He 706 nm, N₂⁺ 391 nm, and O 777 nm were investigated spatially and temporally. Due to the effect of the attached charges, the plasma of the negative half cycle propagates faster than that of the positive half cycle. It was also found that the plasma in the positive half cycle propagates more discretely than that of the negative one, while the negative one has a larger emission intensity due to the overlap of the signal in both temporal and spatial scales. Further on, the electric field distribution was proved to be in Gaussian shape along the diameter of the capillary, while the negative one has a flat shape. By changing the concentration of N₂ in He, the electron collision and penning ionization for generating N₂⁺ were experimentally proved and identified. This study identifies the typical discharge process of the FμTP in one discharge cycle, indicating the plasma is indeed a dielectric guided discharge.

微型DBD越来越受到关注。最近开发的微型柔性微管等离子体 (FμTP) 已被证明是用于质谱和离子迁移谱的极好的软电离源。在本文中，对新型 FμTP 电离源进行了光学表征，旨在在一个放电周期内将光投射到等离子体传播机制上。为了为研究等离子体传播提供一个干净的环境，等离子体完全保持在毛细管中。发现在一个放电循环中，三个放电发展，即在正半周和负半周中的两次介电引导放电，以及在负半周中的负辉光放电。与传统的介质阻挡放电相比，没有形成解离等离子体，这提高了本源的软电离能力。除了从 200 nm 到 1100 nm 的整个光发射外，与活性物种相关的谱线包括 He 706 nm、N在空间和时间上研究了₂ ⁺ 391 nm 和 O 777 nm。由于附着电荷的影响，负半周的等离子体比正半周的等离子体传播得更快。还发现正半周的等离子体比负半周的等离子体传播更离散，而负半周由于信号在时间和空间尺度上的重叠而具有更大的发射强度。进一步证明电场分布沿毛细管直径呈高斯分布，而负分布呈扁平状。通过改变He中 N ₂的浓度，电子碰撞和 Penning 电离产生 N ₂ ⁺经过实验证明和确定。这项研究确定了 FμTP 在一个放电循环中的典型放电过程，表明等离子体确实是一种介电引导放电。