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arXiv 2011.03875physics.plasm-ph
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不同长度尺度图案化介质阻挡放电中等离子体传播动力学

Plasma propagation dynamics in a patterned dielectric barrier discharge at different length scales

Zaka-ul-islam Mujahid, Julian Schulze

摘要:

填充床等离子体反应器(PBPR)固有地具有复杂的几何形状,其中电极之间的体积填充有介电/催化颗粒以形成空隙和空腔的阵列。该设计产生多个长度尺度,即等离子体区域的尺寸(厘米量级)、介电/催化颗粒的尺寸(毫米量级)以及可达到微米尺寸的颗粒(或空腔)和/或表面孔之间的空隙的尺寸。等离子体形成为连接或分段的微放电的阵列。在这些不同的长度尺度上的等离子体传播的理解是重要的,在优化和控制这个过程。在这项工作中,我们调查的放电形成和传播在不同的长度尺度作为施加电压的函数在一个简化的设计PBPR,图案化的介质阻挡放电(p-DBD),在大气压下的氦气中操作,使用相位和空间分辨光学发射光谱(PROES)。p-DBD基于面向等离子体的玻璃半球的阵列,该玻璃半球被实现为两个电极中的一个,并且以六边形图案规则地排列。等离子体在最小间隙的位置处作为辅助性微放电被引发,随后在电介质表面上作为表面电离波的电子的径向加速,以最终在颗粒之间的空隙处,即在接触点处形成表面微放电。随着电压幅值的增加,在接触点处产生后续的表面微放电脉冲。每个表面微放电(S-MD)的等离子体发射被发现由微观结构组成,其发射强度作为驱动电压幅值的函数而增加。相邻的微放电相互作用,以产生从阵列的中心到边缘的波状发射强度传播。

英文摘要:

Packed bed plasma reactors (PBPRs) inherently have complex geometries where the volume between the electrodes is filled with dielectric/catalytic pellets to form an array of voids and cavities. This design generates multiple length scales i.e. the dimension of the plasma region (of the order of centimeters), of the dielectric/catalytic pellets (of the order of millimeters) and of the void between the dielectrics (or cavities) and/or surface pores that can reach micrometer dimensions. The plasma is formed as an array of connected or segmented microdischarges. The understanding of plasma propagation on these diverse length scales is important in optimizing and controlling this process. In this work, we investigate the discharge formation and propagation at different length scales as a function of applied voltage in a simplified design of PBPRs, a patterned dielectric barrier discharge (p-DBD), operated in helium at atmospheric pressure, using phase and space resolved optical emission spectroscopy (PROES). The p-DBD is based on an array of plasma facing glass hemispheres implemented into one of two electrodes and regularly arranged in a hexagonal pattern. The plasma is initiated as filamentary microdischarges at the positions of minimum gap followed by radial acceleration of electrons over the dielectric surface as surface ionization waves to finally form surface microdischarges at the voids between the pellets, i.e. at the contact points. With the increase of the voltage amplitude, subsequent pulses of surface microdischarges are generated at the contact points. The plasma emission of each of the surface micro-discharges (S-MD) is found to consist of microscopic structures whose emission intensity increases as a function of the driving voltage amplitude. Adjacent microdischarges interact to generate a wave-like emission intensity propagation from the center of the array to the edges.

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