Characteristics of a propagating, self-pulsing, constricted ‘<i>γ</i>-mode-like’ discharge

Schröder, Daniel; Burhenn, Sebastian; Arcos, Teresa de los; Gathen, Volker Schulz-von der

doi:10.1088/0022-3727/48/5/055206

Cited by 8 publications

(9 citation statements)

References 27 publications

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“…9,12,15,[19][20][21][22][23] The main factor, which distinguishes the two discharge modes, is the sustaining current supplied from the power source through the R B . 15,24) If the sustaining current is not satisfied Townsend breakdown criteria; γ(exp αd − 1) = 1; where α and γ are the first and secondary electron coefficient, respectively, plasma jet will be discharged in the self-pulsing discharge mode. It should be noted that in the self-pulsing discharge mode, the V s is just above the V BR slightly.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, the self-pulsing discharge mode is constricted in the γ-mode-like discharge. 24) The oscillation of the discharge current and voltage are due to a stray capacitance existing in the circuit and a large ballast resistance (RC oscillation). The stray capacitance inevitably not only comes from the wiring arrangement but also from the contact between the gas jet and the dielectric electrode holder or even from the antennas.…”

Section: Discussionmentioning

confidence: 99%

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DC non-thermal atmospheric-pressure plasma jet generated using a syringe needle electrode

Matra¹

2016

Jpn. J. Appl. Phys.

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Non-thermal plasma jet was generated by applying a dc source voltage between the syringe needle anode with flowing Argon gas and a planar or a hollow copper cathode in an atmospheric-pressure environment. The two operating discharge modes, which were self-pulsing and a continuous discharge mode, these were mainly controlled by the limitations of the current flowing in the discharge circuit. A ballast resistor was an important factor in affecting the limitations of the operating discharge mode. The gas breakdown was initially generated in the self-pulsing discharge mode at the source voltage of 1.2 kV. This was slightly higher than the breakdown voltage at the experimental condition of 1 lpm of Argon and a 1 mm electrode gap distance. The peak self-pulsing discharge currents were up to 15–20 A with a self-pulsing frequency in the range of 10–20 kHz. The continuous discharge mode could be observed at the higher source voltage with the continuous discharge current within the range of a few milliamperes.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

DC non-thermal atmospheric-pressure plasma jet generated using a syringe needle electrode

Matra¹

2016

Jpn. J. Appl. Phys.

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“…the flow of the gas is perpendicular to the electric field [17], as its predecessor, namely the micro-scaled atmospheric pressure plasma jet (µ-APPJ) [18][19][20]. The µ-APPJ, which is an extensively investigated jet, both experimentally and computationally, comes in a number of designs: (a) with quartz panes covering the whole discharge channel length [19,20], (b) with smaller quartz panes, leaving 3 mm of the discharge channel uncovered [18,21], (c) with larger quartz panes, allowing for an extended flow channel (50 mm) after the electrodes [22,23], (d) with an extended discharge channel (40 mm) [22,23], and (e) with an inter-electrode distance from 0.25 to 3 mm [23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…These modes of operation have been studied both experimentally and computationally in the µ-APPJ and the COST jet, as they are crucial not only for biomedicine applications but also for the operation of the device itself [2,26,27,44,45]. For the case of the µ-APPJ, the experimental studies on the modes included measurements of (a) phase resolved emission profiles of pure He for low-and medium-power regimes [46] and for low-and high-power regimes [25,41], (b) PV characteristics of He/O 2 and He/N 2 mixtures [20], (c) currentvoltage characteristics of pure He [25] and (d) time-averaged sheath width [25]. For the case of the COST jet, there are studies with measurements of (a) phase resolved emission profiles of pure He for low-, medium-, and high-power regimes [33], of He/O 2 for low-power [47], and of He/N 2 mixture for low-and medium-power regimes [36], (b) PV characteristics of He/O 2 mixtures [2,15,32,39,48] and pure He [33], and (c) timeaveraged sheath width in pure He discharges [32].…”

Section: Introductionmentioning

confidence: 99%

Predicting power–voltage characteristics and mode transitions in the COST reference microplasma jet

Mouchtouris

Kokkoris²,

Boudouvis³

2022

J. Phys. D: Appl. Phys.

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A 2D cross-field plasma fluid model (CFPM) is applied to He and He/O2 discharges in the COST reference microplasma jet to investigate the operating modes, namely α-, α-γ, and γ-mode. The model not only captures the measured spatiotemporal behavior of He excitation to He metastable but also quantitatively predicts measured power – voltage (PV) characteristics for He/O2 discharges; although not addressed by previous studies, this is a prerequisite for the reliability of the model predictions for the critical-for-applications densities of reactive species. Through a comparison to time-averaged emission profiles and allowed by the dimensionality of the CFPM, the localized, close to the outlet of the discharge channel, onset of γ-mode for He discharges is predicted and justified. Τhe sheath boundary is defined by the maximum of the electron density derivative and the model results compare well to measurements of time-averaged sheath width. Criteria for the transition between the operating modes are formulated. It is considered that when the production rate of He metastable in the sheaths reaches 10% of its total production rate, transition from α- to α-γ mode takes place. When this percentage reaches ~50%, i.e. α- and γ- modes have an almost equal contribution to the discharge, the electron temperature becomes maximum. Finally, the sensitivity of PV characteristics on the secondary electron emission coefficients, condition of the electrode surface, and fabrication or assembly mishits of the COST jet, is investigated.

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“…Previous studies of electron power absorption in atmospheric pressure plasma jets (µAPPJ) uncovered different power absorption mechanisms, viz. the Ωand Penning-mode [25][26][27][28][29] and mode transitions between them [21]. In the Ω-mode, electrons are mainly accelerated at the times of sheath expansion and collapse within the RF period.…”

Section: Introductionmentioning

confidence: 99%

Electron power absorption in micro atmospheric pressure plasma jets driven by tailored voltage waveforms in He/N$_2$

Vass,

Wilczek,

Schulze

et al. 2021

Preprint

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In atmospheric pressure capacitively coupled microplasma jets, Voltage Waveform Tailoring (VWT) was demonstrated to provide ultimate control of the Electron Energy Distribution Function (EEDF), which allows to enhance and adjust the generation of selected neutral species by controlling the electron power absorption dynamics. However, at the fundamental level, the physical origin of these effects of VWT remained unclear. Therefore, in this work, the electron power absorption dynamics is investigated in a He/N 2 jet with a nitrogen concentration of 0.05% driven by a valleys voltage waveform at a base frequency of 13.56 MHz for different numbers of harmonics using a self-consistent Particle in Cell simulation coupled with a spatio-temporally resolved analysis of the electron power absorption based on moments of the Boltzmann equation. Due to the local nature of the transport at atmospheric pressure, ohmic power absorption is dominant. Increasing the number of harmonics, due to the peculiar shape of the excitation waveform the sheath collapse at the grounded electrode is shortened relative to the one at the powered electrode. As a consequence, and in order to ensure flux compensation of electrons and positive ions at this electrode, a high current is driven through the discharge at the time of this short sheath collapse. This current is primarily driven by a high ohmic electric field. Close to the grounded electrode, where the electron density is low and the electric field is, thus, high, electrons are accelerated to high energies and strong ionization as well as the formation of a local electron density maximum are observed. This electron density maximum leads to a local ambipolar electric field that acts as an electric field reversal and accelerates electrons to even higher energies. These effects are understood in detail to fundamentally explain the unique potential of VWT for EEDF control in such plasmas.

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Characteristics of a propagating, self-pulsing, constricted ‘γ-mode-like’ discharge

Cited by 8 publications

References 27 publications

DC non-thermal atmospheric-pressure plasma jet generated using a syringe needle electrode

DC non-thermal atmospheric-pressure plasma jet generated using a syringe needle electrode

Predicting power–voltage characteristics and mode transitions in the COST reference microplasma jet

Electron power absorption in micro atmospheric pressure plasma jets driven by tailored voltage waveforms in He/N$_2$

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