Effect of the reference electrode size on the ionization instability in the plasma sheath of a small positively biased electrode

Bliokh, Yu. P.; Brodsky, Y U L; Chashka, K H B; Felsteiner, J.; Slutsker, Y A Z

doi:10.1063/1.3587179

Cited by 4 publications

(8 citation statements)

References 18 publications

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“…14 Note, the electron saturation current for positive probe potentials higher than about 40 V demonstrated unstable behavior appeared as sudden increase of electron saturation current, which may be explained by additional ionization in the probe vicinity. 26 Visual observation of arcing [see inset diagram in Fig. 3(a)] and post-discharge evaluation of arc electrodes indicated that arc was supported by erosion of the cathode material from the cathode spots, while anode ablation was not observed.…”

Section: Resultsmentioning

confidence: 99%

“…6(c)], that may be due to gas atoms ionization in vicinity of positively biased probe. 26 It may be also argued that these current spikes are caused by the fact that positively biased probe becomes acting as discharge electrode and additional path for the discharge current is created (namely, cathodeprobe), since the current spikes were mainly observed at the moments of time when the cathode spot run far onto the side surface of the cathode being closely faced the probe surface.…”

Section: Cs Modementioning

confidence: 99%

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Application of electrostatic Langmuir probe to atmospheric arc plasmas producing nanostructures

Shashurin

Zhuang

et al. 2011

Physics of Plasmas

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The temporal evolution of a high pressure He arc producing nanotubes was considered and the Langmuir probe technique was applied for plasma parameter measurements. Two modes of arc were observed: cathodic arc where discharge is supported by erosion of cathode material and anodic arc which is supported by ablation of the anode packed with carbon and metallic catalysts in which carbon nanotubes are synthesized. Voltage-current (V-I) characteristics of single probes were measured and unusually low ratio of saturation current on positively biased probe to that on negatively biased of about 1-4 was observed. This effect was explained by increase of measured current at the negatively biased probe above the level of ion saturation current due to secondary electron emission from the probe surface. Since utilization of standard collisionless approach to determine plasma parameters from the measured V-I characteristic is not correct, the electron saturation current was used to estimate the plasma density. V

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Section: Resultsmentioning

confidence: 99%

Section: Cs Modementioning

confidence: 99%

Application of electrostatic Langmuir probe to atmospheric arc plasmas producing nanostructures

Shashurin

Zhuang

et al. 2011

Physics of Plasmas

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“…With this FIC source the plasma density increased a few hundred times (at the same pressure) and the ionization rate could reach a value of (20 -30) %. It has been shown recently that in this case there is no ionization instability in the probe vicinity [6]. Also the electron temperature T e was found to be (2 -4) eV [5].…”

Section: Methodsmentioning

confidence: 58%

“…To prevent the additional ionization in the probe vicinity we increased drastically the plasma density at the same pressure, i.e. the level of ionization of the gas [6]. As it was mentioned above, we used a pulsed (2 ms) FIC plasma source [5] (Fig.…”

Section: Resultsmentioning

confidence: 99%

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X-band microwave generation caused by plasma-sheath instability

Bliokh

Felsteiner

Slutsker

2012

Journal of Applied Physics

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It is well known that oscillations at the electron plasma frequency may appear due to instability of the plasma sheath near a positively biased electrode immersed in plasma. This instability is caused by transit-time effects when electrons, collected by this electrode, pass through the sheath. Such oscillations appear as low-power short spikes due to additional ionization of a neutral gas in the electrode vicinity. Herein we present first results obtained when the additional ionization was eliminated. We succeeded to prolong the oscillations during the whole time a positive bias was applied to the electrode. These oscillations could be obtained at much higher frequency than previously reported (tens of GHz compared to few hundreds of MHz) and power of tens of mW. These results in combination with presented theoretical estimations may be useful, e.g., for plasma diagnostics. IntroductionInstability of the plasma sheath around a positively-biased plasma-immersed electrode has been a known phenomenon during the last few decades [1]. This instability appears due to transit-time effects, when the collected electrons pass through the sheath. As a consequence, this instability causes oscillations in the electrode circuit with a frequency close to the electron plasma frequency f p . These oscillations were of low power and could be detected either with the heterodyne method [1] or with a 30 dB amplifier before the detector [2]. All these experiments were performed in low dense (~ 10 9 cm -3 ) weakly ionized (~ 3•10 -2 %) plasma of a hot-cathode discharge. Values of f p typically did not exceed a few hundred megahertz, with maximum at ~ 1 GHz [1]. Also it should be pointed out that these oscillations appeared as periodic narrow spikes, of certainly less than 1 µs. These spikes were always correlated with strong low frequency (~ 100 kHz) oscillations of the electron current collected by this electrode (probe). These low frequency oscillations were caused by additional ionization of the neutral gas in the probe vicinity with "fireball" creation [2,3]. The microwave (UHF) spikes at f p existed just together with the low frequency current oscillations. This is reasonable because the transit-time effects and the additional ionization appeared approximately at the same potential fall ~ 50 V between plasma and probe [1,3]. The fireball effectively increased the electron-collecting area to achieve the current balance through the plasma [4]

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Physical limitations in ferromagnetic inductively coupled plasma sources

Bliokh

Felsteiner

Slutsker

2013

Journal of Applied Physics

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The Ferromagnetic Inductively Coupled Plasma (FICP) source, which is a version of the common inductively coupled plasma sources, has a number of well known advantages such as high efficiency, high level of ionization, low minimal gas pressure, very low required driver frequency, and even a possibility to be driven by single current pulses. We present an experimental study of such an FICP source which showed that above a certain value of the driving pulse power the properties of this device changed rather drastically. Namely, the plasma became non-stationary and non-uniform contrary to the stationary and uniform plasmas typical for this kind of plasma sources. In this case the plasma appeared as a narrow dense spike which was short compared to the driving pulse. The local plasma density could exceed the neutral atoms density by a few orders of magnitude. When that happened, the afterglow plasma decay time after the end of the pulse was long compared to an ordinary case with no plasma spike. Experiments were performed with various gases and in a wide range of pressures which enabled us to understand the physical mechanism and derive the parameters responsible for such plasma behavior. A qualitative model of this phenomenon is discussed.

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Effect of the reference electrode size on the ionization instability in the plasma sheath of a small positively biased electrode

Cited by 4 publications

References 18 publications

Application of electrostatic Langmuir probe to atmospheric arc plasmas producing nanostructures

Application of electrostatic Langmuir probe to atmospheric arc plasmas producing nanostructures

X-band microwave generation caused by plasma-sheath instability

Physical limitations in ferromagnetic inductively coupled plasma sources

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