Propagation Dynamics Of A Helium Micro-Tube Plasma: Experiments And Numerical Modeling

Micro-Tube Plasmas (mu TP) have been gaining attention for applications ranging from medicine to material science and analytical chemistry due to their small size, low cost of operation and flexibility. In the present work a specific mu TP, known as the Flexible Micro Tube Plasma (F mu TP) is investigated experimentally and, for the first time, numerically as well. The creation, propagation mechanisms and properties of the ionization waves inside the microtube are investigated during the positive and negative half cycle of a mu s square wave applied voltage. A two-dimensional (2D) axi-symmetric numerical model is developed and compared with optical emission spectroscopy showing good agreement. During the positive half cycle the plasma propagates as an ionization wave (or streamer) depositing charges on the dielectric wall. During the negative half cycle the plasma propagates due to the neutralization of those surface charges on the walls. The different propagation mechanisms affect the accumulation of charges, the induced electric field, and the speed of the ionization waves.