Numerical and experimental study on the dynamics of a $\mu$s helium plasma gun with various amounts of O$_2$ or N$_2$ admixtures
Résumé
Recently to tailor the generation of reactive species in plasma jets for biomedical applications, several research groups [1-5] have studied the use of admixtures (mostly O2 and N2) to the helium buffer. Furthermore, there exists also a recent interest for the consideration of electric field associated with the plasma plume delivery over tissues in comparison with the previously reported potent effects of the pulsed electric fields [6].
So far, most experiments have been dedicated to the study of the plasma plume. For endoscopic treatments, it is also important to better understand and optimize the propagation of discharges in long dielectric tubes as catheters. In this work, we present an experimental and numerical study on the dynamics of a s helium plasma discharge with N2 or O2 admixture in a long dielectric tube. In a previous work [5] we have compared experiments and simulations for different amounts of nitrogen admixture added to the buffer gas at the inlet of the plasma gun. In this work, in experiments, we first compare with results obtained previously in N2 with results obtained with O2 admixture added in the helium buffer at the inlet of the plasma gun hollowed electrode but also alternatively downstream along the helium plasma propagation inside long dielectric capillaries to change the plasma jet properties. In simulations, a 2D fluid model is used. For comparison purposes, the geometries of the set-ups used for simulations and experiments are as close as possible and the same applied voltage waveforms are used with a 2 μs rise time and two peak voltages of 10 and 16 kV. In order to study the influence of different amounts of N2 and O2 admixture on the helium discharge dynamics, detailed kinetic schemes have been used. In both He/N2 and He/O2 mixtures, the influence of Penning and charge exchange reactions on the discharge structure and dynamics are studied.
We present results on the comparison of experimental and numerical results obtained on the velocity of the discharge front for various amounts of N2 and O2 and different applied voltages.
Second, we compare time-resolved measurements and simulations of longitudinal and radial electric fields associated with plasma propagation in the dielectric tube and in the plasma plume.
Acknowledgments
P.V. is supported by xxxxx fellowship, and X.D. by INEL/Region Centre-Val de Loire fellowship.
References
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