Experimental Observations of the Virtual Anode Motion and Streamer Breakdown Mechanisms in a Pseudospark Discharge

Zambra, Marcelo; Moreno, José; Inostroza, Jacqueline; Araneda, J.C.

doi:10.1109/tps.2004.823995

Cited by 15 publications

(12 citation statements)

References 8 publications

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“…As shown in Fig. 4, The virtual anode speed was observed to decrease as the virtual anode approaches the hollow cathode cavity, which is consistent with the analytical model of virtual anode formation first proposed by Lucas's experimental observations [13,14] to explain the rapid discharge formation at low pressure. However, at this time α ionization process will continue.…”

Section: Simulation Results and Analysissupporting

confidence: 88%

The Numerical Simulation Study of Pseudospark Hollow Cathode Discharge

Meng

Yan

et al. 2009

J Infrared Milli Terahz Waves

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Pseudospark discharges are sources of intense electron beams. Reported in this paper are theoretical studies of the Pseudospark discharges. A theoretical and computational model has been adopted to study the initiation phase of Pseudospark discharges via a twodimensional electrostatic particle-in-cell plus Monte Carlo (PIC-MCC) collision method. From the numerical results, a sequence of physical events has been identified. It has been found that the ionization processes determined by local electric field and hollow cathode effect. The growth phenomena is dependent of α ionization multiplication due to local space charge from initial ionization growth to onset of the hollow cathode effect, and then hollow cathode effect become leading factor.

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Section: Simulation Results and Analysissupporting

confidence: 88%

The Numerical Simulation Study of Pseudospark Hollow Cathode Discharge

Meng

Yan

et al. 2009

J Infrared Milli Terahz Waves

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“…2 and 7). This bright front propagation occurs > 1.5 µs after the breakdown process has ended, demonstrating that it is different from streamer fronts [22] associated with breakdown mechanisms. The time scale rules out ion acoustic velocities (8 km/s) from consideration and the flow direction rules out electrostatic acceleration.…”

mentioning

confidence: 74%

Dynamic and Stagnating Plasma Flow Leading to Magnetic-Flux-Tube Collimation

2005

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Highly collimated, plasma-filled magnetic flux tubes are frequently observed on galactic, stellar and laboratory scales. We propose that a single, universal magnetohydrodynamic pumping process explains why such collimated, plasma-filled magnetic flux tubes are ubiquitous. Experimental evidence from carefully diagnosed laboratory simulations of astrophysical jets confirms this assertion and is reported here. The magnetohydrodynamic process pumps plasma into a magnetic flux tube and the stagnation of the resulting flow causes this flux tube to become collimated.The extreme collimation of astrophysical jets [1,2,3] and the solar corona heating mechanism [4] are two seemingly unrelated astrophysical mysteries, yet both involve collimation of magnetic flux tubes. Astrophysical observations [2,3] and simulations [1,5] indicate that bipolar plasma outflows (jets) are natural [1,6] features of young stellar objects, black holes, active galactic nuclei and even aspherical planetary nebula [7]. Although it has long been presumed [8,9] that astrophysical jets are magnetohydrodynamically driven, the standard models do not agree on a single collimation process. A similar issue exists in solar physics: solar spicules [10], prominences [11,12] and coronal loops [13] are considered to be plasma-filled filamentary magnetic flux tubes; coronal heating models [14,15] then invoke magnetic reconnection and plasma flow within such filamentary loops. However, the models explain neither the origin of the observed flows nor the extreme collimation (filamentary nature) of the observed structures.We propose that the collimation of any, initially flared, current-carrying magnetic flux tube is due to the following process [16]: a magnetohydrodynamic (MHD) force resulting from the flared current profile drives axial plasma flows along the flux tube; the flows convect frozen-in magnetic flux from strong magnetic field regions to weak magnetic field regions; flow stagnation then piles up this embedded magnetic flux, increasing the local magnetic field and collimating the flux tube via the pinch effect. Thus, the flux tube fills with ingested plasma and simultaneously becomes collimated. This paper presents direct experimental evidence for this process. We use ultra-high-speed imaging and Doppler measurements of the fast plasma flows, combined with direct density measurements before and after the filling of the flux tube.Our experimental setup [17] simulates magneticallydriven astrophysical jets at the laboratory scale by imposing boundary conditions analogous to astrophysical jet boundary conditions (Fig. 1): a disk (cathode) representing a central object such as a star, is coaxial and co-planar with an annulus (anode) representing an accretion disk. A vacuum poloidal magnetic field produced by an external coil links these two electrodes, mimicking a poloidal magnetic field threading the accretion disk. A radial electric field applied across the gap between the FIG. 1: (log color) Typical plasma discharge sequence (#6577, 2 million fps, 40 ns/...

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“…Zambra et al [19] have examined the movement characteristics of a virtual anode in single-gap pseudospark discharge under pulsed voltages for seven different gas pressures. The mean velocity increases monotonically with pressure from a range of 21.73-49.75 cm/µs at 10 Pa to a range of 77.02-112.82 cm/µs at 70 Pa. Based on the results, we can calculate that the mean time of virtual anode through the anode-cathode gap of 1 cm equality to each gap distance is about 10ns at 80 Pa. As the cathode-anode gap distance is 8 cm, the delay should be about 80 ns.…”

Section: Resultsmentioning

confidence: 99%

Fast Electron Ionization Effect in Multigap Pseudospark Discharge Under Nanosecond Pulsed Voltages

Jia

Zhao

Zhang

2015

IEEE Trans. Plasma Sci.

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In this paper, research studies on the breakdown progresses of multigap pseudospark discharge under nanosecond pulsed voltages are reported. The experimental results show great differences from dc voltages. The discharge mechanism of the pseudospark under nanosecond pulsed voltages has been successfully explained by the fast electron ionization effect. In each gap, collision ionizations caused by the fast electron start step by step, and development progresses are almost the same and approximately simultaneous until the main gap breaks down.Index Terms-Fast electron ionization, multigap pseudospark, nanosecond pulsed voltages.

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Experimental Observations of the Virtual Anode Motion and Streamer Breakdown Mechanisms in a Pseudospark Discharge

Cited by 15 publications

References 8 publications

The Numerical Simulation Study of Pseudospark Hollow Cathode Discharge

The Numerical Simulation Study of Pseudospark Hollow Cathode Discharge

Dynamic and Stagnating Plasma Flow Leading to Magnetic-Flux-Tube Collimation

Fast Electron Ionization Effect in Multigap Pseudospark Discharge Under Nanosecond Pulsed Voltages

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