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

A. Sobota, O. Guaitella, G.B. Sretenović, I.B. Krstić, V.V. Kovačević, A. Obrusník, Y.N. Nguyen, L. Zajíčková, B.M. Obradović, M.M. Kuraica

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Abstract

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.

LanguageEnglish
Article number065026
Pages1-9
Number of pages9
JournalPlasma Sources Science and Technology
Volume25
Issue number6
DOIs
StatePublished - 18 Nov 2016

Fingerprint

gas flow
electric fields
effluents
air
profiles
causes
gas composition
electric field strength
plasma jets
travel
contraction
rooms
plumes
alternating current
indication
flow velocity
vortices
polarization
geometry
configurations

Keywords

  • atmospheric pressure
  • discharge
  • electric field
  • helium
  • ionization front
  • plasma bullet
  • plasma jet

Cite this

Sobota, A., Guaitella, O., Sretenović, G. B., Krstić, I. B., Kovačević, V. V., Obrusník, A., ... Kuraica, M. M. (2016). Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed. Plasma Sources Science and Technology, 25(6), 1-9. [065026]. DOI: 10.1088/0963-0252/25/6/065026
Sobota, A. ; Guaitella, O. ; Sretenović, G.B. ; Krstić, I.B. ; Kovačević, V.V. ; Obrusník, A. ; Nguyen, Y.N. ; Zajíčková, L. ; Obradović, B.M. ; Kuraica, M.M./ Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed. In: Plasma Sources Science and Technology. 2016 ; Vol. 25, No. 6. pp. 1-9
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abstract = "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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Sobota, A, Guaitella, O, Sretenović, GB, Krstić, IB, Kovačević, VV, Obrusník, A, Nguyen, YN, Zajíčková, L, Obradović, BM & Kuraica, MM 2016, 'Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed' Plasma Sources Science and Technology, vol. 25, no. 6, 065026, pp. 1-9. DOI: 10.1088/0963-0252/25/6/065026

Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed. / Sobota, A.; Guaitella, O.; Sretenović, G.B.; Krstić, I.B.; Kovačević, V.V.; Obrusník, A.; Nguyen, Y.N.; Zajíčková, L.; Obradović, B.M.; Kuraica, M.M.

In: Plasma Sources Science and Technology, Vol. 25, No. 6, 065026, 18.11.2016, p. 1-9.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed

AU - Sobota,A.

AU - Guaitella,O.

AU - Sretenović,G.B.

AU - Krstić,I.B.

AU - Kovačević,V.V.

AU - Obrusník,A.

AU - Nguyen,Y.N.

AU - Zajíčková,L.

AU - Obradović,B.M.

AU - Kuraica,M.M.

PY - 2016/11/18

Y1 - 2016/11/18

N2 - 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.

AB - 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.

KW - atmospheric pressure

KW - discharge

KW - electric field

KW - helium

KW - ionization front

KW - plasma bullet

KW - plasma jet

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U2 - 10.1088/0963-0252/25/6/065026

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JO - Plasma Sources Science and Technology

T2 - Plasma Sources Science and Technology

JF - Plasma Sources Science and Technology

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Sobota A, Guaitella O, Sretenović GB, Krstić IB, Kovačević VV, Obrusník A et al. Electric field measurements in a kHz-driven He jet - The influence of the gas flow speed. Plasma Sources Science and Technology. 2016 Nov 18;25(6):1-9. 065026. Available from, DOI: 10.1088/0963-0252/25/6/065026