Arc erosion characteristics of pseudospark discharge in multiaperture geometry

Naweed, A.; Kiefer, J.; Gavrilescu, C.; Neff, W.

doi:10.1063/1.1491022

Cited by 3 publications

(3 citation statements)

References 32 publications

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“…In ref. [38], a criterion for the glow-to-arc transition (from the SGD phase to the high current phase with cathode spots) was derived based on the relationship between the amount of transferred charge and the electric field of the cathode sheath. The relationship between the critical field strength E cr and the electron density n e can be described by Equation (3), where β is the field enhancement coefficient, U c is the voltage applied on the cathode sheath, and ε 0 is the vacuum permittivity.…”

Section: Transition From the Sgd Phase To The High Current Phase With...mentioning

confidence: 99%

Revealing phase transitions and instabilities in pseudospark discharges

et al. 2022

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Pseudospark discharge is a low‐pressure high‐voltage pulsed discharge with hollow electrodes, and the overall discharge experiences several distinctive sub‐phases. The instability phenomena, characterised by the sudden oscillations or distortions of discharge voltage and current, restrict the applications of pseudospark discharge. This study presents an investigation into phase transitions and instabilities in pseudospark discharge by combining the evidences from multiple discharge waveforms, time‐resolved images, electron beam current profiles, 2D kinetic simulation results, and the spectral line emission of cathode material. The process of a normal pseudospark discharge is firstly discussed, and the threshold conditions of the transition from the superdense glow discharge (SGD) phase to the high current phase with arc cathode spots are addressed. According to temporal profiles and voltage‐current characteristics, two types and four occurrences of instabilities are distinguished: type I—in the pre‐breakdown phase; type II‐1—in the SGD phase; type II‐2—in the transition of cathode spots propagating from cathode hole edge to cathode plane; type II‐3—in the re‐initiation of spots near current reversal. It is found that the instability of type I is caused by the stepwise penetration of virtual anode plasma, and type II is closely related to the cyclic nature and finite lifetime of cathode spots. It is induced by the fact that the decay of cathode spots is faster than the formation under certain conditions, and the existing spots are not able to provide the current required by the external circuit. Important features and the suppression methods of the instabilities are discussed based on the proposed mechanisms.

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Section: Transition From the Sgd Phase To The High Current Phase With...mentioning

confidence: 99%

Revealing phase transitions and instabilities in pseudospark discharges

et al. 2022

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“…Meanwhile, the anode voltage reaches a similar value before the second collapse, which means the potential falling on the cathode sheath is also similar. According to [35], equation (10) shows the relationship between the transferred charge and the critical field strength that the discharge turns from glow to arc, where β is the field enhancement coefficient, U c is the voltage applied on the cathode sheath, ε 0 is the permittivity of vacuum, µ e is the electron mobility, a c is the area of cathode surface participating into discharge, and k is the coefficient. As shown in figure 7(d), the transferred charge remains constant with different numbers of cores.…”

Section: Influence Of the Number Of Magnetic Coresmentioning

confidence: 99%

Investigations on enhanced plasma expansion in pseudospark discharge assisted by a magnetic switch

Yan¹,

Shen²,

Sun³

et al. 2022

J. Phys. D: Appl. Phys.

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Electrode erosion caused by dense plasma in constrictive discharge channel is one of the fundamentally detrimental effects existing in pulsed discharge switches. An enhanced plasma expansion in pseudospark discharge assisted by a magnetic switch is observed from ICCD images in this paper, accompanied by reduced commutation loss, and the mechanisms are revealed by experiments and simulations. The characteristics of the discharge waveforms and channel images of the pseudospark discharge with and without a series-connected magnetic switch are compared, and the influence of the number of magnetic cores is studied. As the loop current increases, the discharge channel expands radically and reaches the maximum as the current rising rate reaches the maximum. As the number of magnetic cores increases from 0 to 8, the maximum diameter of the discharge channel increases from 16 mm to about 38 mm, and the commutation loss is reduced from 30 mJ to 11 mJ. The electrode erosion rate of the case with a magnetic switch is lower than that without a magnetic switch. A Particle in Cell/Monte Carlo Collision model coupling to nonlinear external circuit elements is established. The simulation results fit well with the experiment phenomena, including the discharge waveforms and the profiles of the discharge channel. The distribution of ions shows more diffused features than that of electrons, while the distribution of electrons is more similar to the discharge channel observed in experiments. The enhanced plasma expansion is mainly caused by the higher radial acceleration component of the charged particles during the magnetically delayed time.

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“…1 to point up the position of the hollow cathode and the horizontally lying bores. One of the most interesting problems concerning the discharge in a pseudospark switch is the electrode erosion [4], [5] which prevents the industrial use of pseudospark switches in full production runs. Because of selfmagnetic fields, the horizontal plasma channels of a radial pseudospark switch move downwards in the perpendicular electrode gap until they reach the bottom of the device.…”

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confidence: 99%

The Influence of an External Permanent Magnetic Field on the Dynamics of Plasma Channels in a Radial Pseudospark Switch

Rainer

Bischoff

Frank

et al. 2004

IEEE Trans. Plasma Sci.

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High-current gas discharges can reach current densities of 10 8 A/cm 2 in order of magnitude and, therefore, damage the electrodes of nearly all types of low-pressure gas discharge switches. In pseudospark switches with radial geometry, the total current is divided by the number of radial channels and so the current per channel is strongly reduced. However, because of electromagnetic forces the plasma channels attract themselves and pinch together already in the first maximum of the switching current. Therefore, the main advantage of the radial pseudospark switch, the division of the total current, is lost. In this paper, a basic idea of how this movement of the plasma channels can be suppressed, will be introduced. Strong permanent magnets of different types (polarization of type A: 0.48 T; type B: 1.31 T; and type C: 1.88 T) are attached to the pseudospark switch near the bores of the hollow cathode. The most effective way to apply the magnets was to put them face to face with the bores of the hollow cathode with the center line of the bores and the cylindric magnets coinciding. In this case, the magnetic field looks like a magnetic bottle viewed along the charge carriers path. The magnetic fields capture the plasma channels for a short time and so the pinch effect is delayed until the first maximum of current is over. The investigated pseudospark switch was a radial switch with three channels. The charging voltage was 10 kV and the discharge capacity was 2.2 F, resulting in a total discharge current of 40 kA, respectively, 13.3 kA per channel. In the switch under consideration, the pinching is fulfilled after 800 ns when no magnets are applied. The smallest possible distance between the front of the magnet and the end of the discharge channel was 2 mm. The strength of the magnetic field in this distance with magnets of type A, B, and C was 390, 1065, and 1525 mT, respectively, and the pinching was delayed for 400, 2000, and 1600 ns, accordingly.Index Terms-Electrode erosion, external magnetic field, pinch effect, pseudospark switch.

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Arc erosion characteristics of pseudospark discharge in multiaperture geometry

Cited by 3 publications

References 32 publications

Revealing phase transitions and instabilities in pseudospark discharges

Revealing phase transitions and instabilities in pseudospark discharges

Investigations on enhanced plasma expansion in pseudospark discharge assisted by a magnetic switch

The Influence of an External Permanent Magnetic Field on the Dynamics of Plasma Channels in a Radial Pseudospark Switch

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