Investigations on pulsed, dielectric barrier discharges in multi-filament arrangements

介质阻挡放电（DBD）是产生非热大气压等离子体的常用方法，其用于例如化学处理。分子气体混合物（例如氮氧混合物）中的DBD是连续的，即它们形成单独的和瞬态的放电通道。各种研究表明，脉冲操作比经典正弦驱动操作更有效地产生反应物质。申请人关于单灯丝布置中的脉冲驱动DBD的初步研究已经证明，击穿和放电发展可以直接由HV脉冲宽度（预电离）控制。特别是，新的，到目前为止未知的DBD击穿regimes首次被报道。记住，等离子体化学反应是由单灯丝内的物理过程触发的，有可能影响等离子体参数，以启动更有选择性和更有效的等离子体化学过程。在实践中使用的DBD布置中，出现许多丝，但不知道对于单丝获得的结果是否可以转移到多丝布置。因此，开放的问题不仅涉及在差距的电击穿，而且在多丝安排的体积和表面过程的相互影响。本项目的目标是解决这些问题，因此，将逐步实现从单灯丝到多灯丝的过渡。为此，将利用我们关于DBD配置设计的专业知识开发新颖且特殊的空间固定和自由的多丝布置。将有一个系统的研究在N2-O2气体混合物在大气压下的多丝排列中的单丝的行为。单和多丝操作的比较将允许关于控制DBD的击穿和动态的一般机制的存在的声明。此外，单放电通道的体积和介电表面上的相互作用将被调查。其目的是澄清如果单灯丝安排的体积预电离的主导作用也发生在多灯丝安排。对于这些研究，将使用快速成像和光谱诊断，这是在申请人的初步工作中建立的，可在INP Greifswald获得。同时，时间分辨气体分析方法将被应用于研究等离子体化学过程的动力学。结合介质阻挡放电特性，将得出放电物理和等离子体化学之间的关系。实验研究将伴随着等离子体建模，其中包括时空放电发展，等离子体参数和等离子体化学的模拟。

Dielectric barrier discharges (DBDs) are a common method to generate non-thermal atmospheric pressure plasmas, which are used e.g. for chemical processing. The DBDs in molecular gas mixtures, such as nitrogen oxygen mixtures, are filamentary, i.e. they form individual and transient discharge channels. It was shown in various studies that the generation of reactive species is more efficient for pulsed operation than for classical sine-driven operation. Preliminary investigations of the applicant concerning pulsed-driven DBDs in a single-filament arrangement have demonstrated that the breakdown and the discharge development can be directly controlled by the HV pulse width (pre-ionisation). In particular, new, up to now unknown DBD breakdown regimes were reported for the first time.Having in mind that the plasma-chemical reactions are triggered by the physical processes within single filaments, there is the possibility to influence the plasma parameters in a way to initiate more selective and effective plasma chemical processes. In DBD arrangements which are used in practice, many filaments occur, but it is not known if the results obtained for a single filament can be transferred to multi-filament arrangements. Therefore, open questions not only concern the electrical breakdown in the gap, but also the interacting impact of volume and surface processes in multi-filament arrangements. The goal of this project is to address and resolve these issues.Therefore, the stepwise transition from a single-filament to a multi-filament arrangement will be performed. For this purpose, novel and special, spatially fixed and free multi-filament arrangements will be developed using our expertise concerning the design of DBD configurations. There will be a systematic study on the behaviour of a single filament in multi-filament arrangements in N2-O2 gas mixtures at atmospheric pressure. The comparison of both single- and multi-filament operation will allow statements concerning the existence of general mechanisms to control the breakdown and the dynamics of DBDs. Furthermore, the interaction of single discharge channels in the volume and on the dielectric surface will be investigated. The aim is to clarify if the dominating effect of volume pre-ionisation for single-filament arrangements occurs also in multi-filament arrangements. For these investigations, fast imaging and spectroscopical diagnostics will be used, which were established during the applicant’s preliminary work and are available at the INP Greifswald. Simultaneously, temporally resolved gas analysis methods will be applied to study the dynamics of plasma-chemical processes. In combination with the DBD characterisation, a correlation of discharge physics and plasma chemistry will be worked out. The experimental investigations will be accompanied by plasma modelling, which includes the simulation of the spatio-temporal discharge development, plasma parameters and plasma chemistry.