Generation of runaway electrons in plasma after a breakdown of a gap with a sharply non-uniform electric field strength distribution

Белоплотов, Д. В.; Тарасенко, В. Ф.; Shklyaev, V. A.; Сорокин, Д. А.

doi:10.1088/1361-6463/abfddc

Cited by 20 publications

(26 citation statements)

References 46 publications

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“…DDC caused by the redistribution of the electric filed during the streamer formation was measured with a collector placed downstream of the grounded electrode. To exclude the influence of sub-nanosecond current pulses of runaway electrons (REs) generated during a pre-breakdown stage [22], printer paper with a thickness of ≈0.1 mm was placed on the back of the grounded grid close to it. The paper absorbed the REs, and they did not give a signal.…”

Section: Resultsmentioning

confidence: 99%

“…The use of electrodes with a small radius of curvature ensures the enhancement of the electric field near its surface up to several MV/cm at a voltage of tens of kilovolts [22]. However, the average electric field strength can remain below the breakdown threshold.…”

Section: Resultsmentioning

confidence: 99%

“…The polarity of DDC shows that the electric field near the grounded electrode increases as the streamer develops in the vicinity of the pointed electrode (Figure 4d), and the electric field is 'squeezed out' from there by dense plasma. The electric field strength near the surface of the grounded electrode was calculated using the DDC signal according to the method described in [22]. The appearance of DDC correlates with the moment when voltage drops and current arises and corresponds the moment of the streamer start.…”

Section: Resultsmentioning

confidence: 99%

“…The appearance of DDC correlates with the moment when voltage drops and current arises and corresponds the moment of the streamer start. The use of electrodes with a small radius of curvature ensures the enhancement of the electric field near its surface up to several MV/cm at a voltage of tens of kilovolts [22]. However, the average electric field strength can remain below the breakdown threshold.…”

Section: Resultsmentioning

confidence: 99%

“…Knowing the incident wave, U 0 , we could easily calculate the reflected wave, U ref , from U CVD (signal from CVD).The current of discharge, I d , can also be easily defined from the incident and reflected waves:I d = (U 0 − U ref )/Z.DDC caused by the redistribution of the electric filed during the streamer formation was measured with a collector placed downstream of the grounded electrode. To exclude the influence of sub-nanosecond current pulses of runaway electrons (REs) generated during a pre-breakdown stage[22], printer paper with a thickness of ≈0.1 mm was placed on the back of the grounded grid close to it. The paper absorbed the REs, and they did not give a signal.…”

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confidence: 99%

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High-Voltage Nanosecond Discharge as a Means of Fast Energy Switching

2021

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The formation of a nanosecond discharge with the use of a Hamamatsu streak-camera and with simultaneously wideband (10 GHz) measurement of voltage and displacement current caused by a streamer in one pulse has been studied. Nanosecond voltage pulses of various amplitudes (16, 20, and 27 kV) were applied across a point-to-plane gap (8.5 mm) filled with air at various pressures (13, 25, 50, 100, and 200 kPa). It was found that the voltage across the gap drops as soon as a streamer appears in the vicinity of the pointed electrode. At the same time, a pre-breakdown current begins to flow. The magnitude of the pre-breakdown current, as well as the voltage drop, is determined by the rate of formation of dense plasma and, accordingly, by the rate of redistribution of the electric field in the gap. The streamer velocity determines the rise time and amplitude of the current. The higher the streamer velocity, the shorter the rise time and the higher the amplitude of the pre-breakdown current. The propagation of a backward and third ionization waves was observed both with the streak camera and by measuring the displacement current. As they propagate, the discharge current increases to its amplitude value.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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High-Voltage Nanosecond Discharge as a Means of Fast Energy Switching

2021

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Investigation of the microsecond-pulse acoustic wave generated by a single nanosecond-pulse discharge

Wang

et al. 2022

Physics of Plasmas

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A single nanosecond-pulse discharge can produce a high-intensity pulsed acoustic wave. The pulse width of the acoustic wave is much wider than that of the current, more than 20 μs at 30 cm from the source, which is the basis of synthesizing low-frequency sound by repetitively nanosecond-pulse discharges. The investigations of electroacoustic characteristics and the sound formation process of the single nanosecond-pulse discharge are vital to advance this technology. In this paper, an experimental platform for the single nanosecond-pulse discharge was built, and time-domain waveforms of the voltage, the current, and the sound pressure were measured. The effects of electrode shape, current limiting resistors, and current pulse width on the acoustic wave were discussed. To analyze the formation process of the acoustic wave, the gas densities near the electrodes at different moments after the discharge were diagnosed by laser Schlieren photography. The result shows that the formation of the acoustic wave is much slower than the discharge. A two-stage model was developed to qualitatively describe the formation process of the acoustic wave, and numerical calculations were carried out using thermodynamic and hydrodynamic equations. At the end of the discharge, a huge pressure difference is formed inside and outside the gas channel due to the Joule heating, which can be considered as a shock wave. During the outward propagation, the wave tail is elongated by the difference in sound velocity at each point, and the thickness of the shock wave increases due to the dissipation. This eventually leads to the half-duration of more than 20 μs.

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Backward fast electrons supported by ionization wave passing through the grid cathode

Babaeva,

Naidis,

Tereshonok

et al. 2023

Physics of Plasmas

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In this paper, the effect of appearance of fast electrons behind the grid cathode in the direction reverse to the anode is studied computationally. Fast electrons are observed within 0.5 ns after application of a short voltage pulse. The results obtained confirm the possibility of generation of backward fast electrons (some of them are in a runaway mode) and explain the main trends of this process. It is shown that backward fast electrons are supported by the ionization wave (IW). The IW evolution proceeds via two phases. During the first phase, first fast electrons are observed moving toward the anode. Then, multiple individual IWs starting from each individual cathode wire are formed in the anode–cathode gap. The duration of this stage is 0.3 ns and corresponds to the pulse rise time. At the second phase, the separate individual IWs merge in a single flat ionization wave. The IW penetrates through the cathode wires and propagates in the direction reverse to the anode. The preferred direction of fast electrons propagation also reverses. Now, the trajectories of fast electrons are mainly directed away from the anode. The duration of the recorded flux of fast electrons is of the order of a few picoseconds. This time interval correlates with the available experimental data.

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Generation of runaway electrons in plasma after a breakdown of a gap with a sharply non-uniform electric field strength distribution

Cited by 20 publications

References 46 publications

High-Voltage Nanosecond Discharge as a Means of Fast Energy Switching

High-Voltage Nanosecond Discharge as a Means of Fast Energy Switching

Investigation of the microsecond-pulse acoustic wave generated by a single nanosecond-pulse discharge

Backward fast electrons supported by ionization wave passing through the grid cathode

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