Electric field measurements in a kHz-driven He jet-the influence of the gas flow speed

被引:48
作者
Sobota, A. [1 ]
Guaitella, O. [2 ]
Sretenovic, G. B. [3 ]
Krstic, I. B. [3 ]
Kovacevic, V. V. [3 ]
Obrusnik, A. [4 ]
Nguyen, Y. N. [1 ]
Zajickova, L. [4 ,5 ]
Obradovic, B. M. [3 ]
Kuraica, M. M. [3 ]
机构
[1] Eindhoven Univ Technol, EPG, Postbus 513, NL-5600 MB Eindhoven, Netherlands
[2] Ecole Polytech, LPP, Route Saclay, F-91128 Palaiseau, France
[3] Univ Belgrade, Fac Phys, POB 44, Belgrade 11001, Serbia
[4] Masaryk Univ, Fac Sci, Dept Phys Elect, Kotlarska 2, CS-61137 Brno, Czech Republic
[5] Masaryk Univ, Plasma Technol CEITEC, Kotlarska 2, CS-61137 Brno, Czech Republic
关键词
discharge; plasma jet; atmospheric pressure; helium; ionization front; plasma bullet; electric field; BIOMEDICAL APPLICATIONS; PLASMA-JET; HELIUM; DISCHARGE; CELLS;
D O I
10.1088/0963-0252/25/6/065026
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
This report focuses on the dependence of electric field strength in the effluent of a vertically downwards-operated plasma jet freely expanding into room air as a function of the gas flow speed. A 30 kHz AC-driven He jet was used in a coaxial geometry, with an amplitude of 2 kV and gas flow between 700 sccm and 2000 SCCM. The electric field was measured by means of Stark polarization spectroscopy of the He line at 492.19 nm. While the minimum and the maximum measured electric fields remained unchanged, the effect of the gas flow speed is to cause stretching of the measured profile in space-the higher the flow, the longer and less steep the electric field profile. The portion of the effluent in which the electric field was measured showed an increase of electric field with increasing distance from the capillary, for which the probable cause is the contraction of the plasma bullet as it travels through space away from the capillary. There are strong indications that the stretching of the electric field profile with increase in the flow speed is caused by differences in gas mixing as a function of the gas flow speed. The simulated gas composition shows that the amount of air entrained into the gas flow behaves in a similar way to the observed behaviour of the electric field. In addition we have shown that the visible length of the plasma plume is associated with a 0.027 molar fraction of air in the He flow in this configuration, while the maximum electric field measured was associated with a 0.014 molar fraction of air at gas flow rates up to 1500 SCCM (4.9 m s(-1)). At higher flows vortices occur in the effluent of the jet, as seen in Schlieren visualization of the gas flow with and without the discharge.
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页数:9
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