Experimental investigation of streamer radius and length in SF<sub>6</sub>

Bujotzek, M.; Seeger, Martin; Schmidt, Frank; Koch, M.; Franck, Christian M.

doi:10.1088/0022-3727/48/24/245201

Cited by 29 publications

(19 citation statements)

References 33 publications

(125 reference statements)

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“…The discharge channels have the typical signature of leader channels [35], which confirms the interpretation from leader breakdown predictions, i.e., the breakdown is determined by leader propagation. The negative leader channels (Figure 9c) are thicker and less structured than positive leader channels (Figure 9b); this observation is in agreement with the expectation from [49].…”

Section: Protrusions With Sfsupporting

confidence: 89%

Breakdown at Multiple Protrusions in SF6 and CO2

Feet¹,

Seeger²,

Over³

et al. 2020

Energies

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The electric breakdown at single and multiple protrusions in SF6 and CO2 is investigated at 0.4 and 0.6 MPa, respectively. Additionally, the breakdown fields at rough surfaces of two different areas were determined. From the measurements, breakdown probability distributions for single protrusions were determined and fitted by Weibull distributions. This allowed the determination of statistical enlargement laws for the 50% breakdown probability fields E50. Such enlargement laws describe, for example, the scaling of breakdown field with electrode area or number of protrusions. The predictions were compared to the experimental data, and both agreement and discrepancies were observed depending on polarity and number of protrusions and gas. Discharge predictions including first electron, streamer inception and crossing, as well as leader propagation, gave further insight to this. It was found that predictions from enlargement laws based on statistical processes may not describe the measured breakdown fields well and that relevant physical breakdown criteria must also be considered.

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Section: Protrusions With Sfsupporting

confidence: 89%

Breakdown at Multiple Protrusions in SF6 and CO2

Feet¹,

Seeger²,

Over³

et al. 2020

Energies

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“…At room temperature, k 8 ¼ 2.26 Â 10 À30 cm 6 s À1 and k 9 ¼ 1.24 Â 10 À31 cm 6 s À1 . 36,39 At atmospheric pressure air conditions, it is about 20 ns. After forming O 2 À , if the repetition frequency is high enough, before O 2 À disappear through two and three-body ion-ion recombination or diffusion, these species can produce seed electrons through detachment when the next voltage pulse is applied.…”

Section: Photoionization For Plasma Bulletmentioning

confidence: 99%

Guided ionization waves: The physics of repeatability

Lü

Ostrikov

2018

Applied Physics Reviews

160

136

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Guided ionization waves, or plasma streamers, are increasingly important for many applications in spanning materials processing and biomedicine. The highly reproducible, repeatable behavior of the most puzzling kind of the streamers-plasma bullets is highly attractive as it promises a high degree of control in many applications. However, despite a dozen years since the discovery of this phenomenon, the exact reasons for such behavior still remain essentially unclear. To understand the dynamics of the guided ionization wave (plasma bullet), a large number of works have been carried out and many interesting results have been reported. Here, we critically examine the available results and generalize the physical mechanisms of the guided ionization waves, which are of particular interest to practical applications of atmospheric-pressure plasma discharges, in general. The critical examination of the fundamental principles will show that, in order to propagate in a repeatable-mode, the plasma bullet must propagate in a channel with a high seed electron density (HSED), which is on the order of 10 9 cm À3 . This review concludes that to distinguish guided ionization waves from traditional positive streamer discharges, it is most appropriate to describe an atmospheric-pressure discharge featuring a plasma bullet behavior as an HSED discharge. When the HSED condition is met, the dynamics of a plasma plume appears to be repeatable. On the contrary, it propagates in an unrepeatable mode and emerges more like a positive streamer discharge when the HSED condition is not satisfied. According to this theory, the transition of the propagation mode of the plasma bullet between the repeatable mode and the stochastic mode can be well explained. Besides by controlling the seed electron density around the transition region between the HSED discharge and the traditional positive streamer, this knowledge will help in better understanding of the positive streamer discharges in air, in cases relevant to practical applications of such plasma discharges in materials processing technologies, industrial chemistry, nanotechnology, and health care.

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“…Attachment reactions are prevalent, in particular, in gases such as sulphur hexafluoride (SF 6 ), which are used in high voltage equipment such as circuit breakers [19,20]. In air, the attachment processes involve dissociative and three-body reactions with oxygen molecules.…”

Section: Introductionmentioning

confidence: 99%

Electrically isolated propagating streamer heads formed by strong electron attachment

Francisco

Bagheri

Ebert

2021

Plasma Sources Sci. Technol.

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Streamer discharges occur in the early stages of electric breakdown of gases in lightning, as well as in plasma and high voltage technology. They are growing filaments characterized by a curved charge layer at their tip that enhances the electric field ahead of them. In this study, we analyze the effect of strong electron attachment on the propagation of positive streamers. Strong attachment occurs in insulating gases like sulphur hexafluoride (SF 6 ) or in air at increased density. We use the classical fluid approximation with photo-ionization for streamers in ambient air, and we artificially increase the electron attachment rate where the field is below the breakdown value. This modification approximates air pressures above 1 bar at room temperature. We find that the streamer head can keep propagating even though the ionized channel loses its conductivity closely behind the head; hence, even if it is electrically isolated. We describe how, depending on the attachment rate, the streamer propagation in a constant electric field can be accelerating, uniformly translating, or stagnating.

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Experimental investigation of streamer radius and length in SF₆

Cited by 29 publications

References 33 publications

Breakdown at Multiple Protrusions in SF6 and CO2

Breakdown at Multiple Protrusions in SF6 and CO2

Guided ionization waves: The physics of repeatability

Electrically isolated propagating streamer heads formed by strong electron attachment

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Experimental investigation of streamer radius and length in SF6

Cited by 29 publications

References 33 publications

Breakdown at Multiple Protrusions in SF6 and CO2

Breakdown at Multiple Protrusions in SF6 and CO2

Guided ionization waves: The physics of repeatability

Electrically isolated propagating streamer heads formed by strong electron attachment

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Product

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Experimental investigation of streamer radius and length in SF₆