Material-dependent high-frequency current fluctuations of cathodic vacuum arcs: Evidence for the ecton cutoff of the fractal model

Anders, André; Окс, Е. М.

doi:10.1063/1.2196244

Cited by 12 publications

(6 citation statements)

References 17 publications

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“…It has been pointed out in the literature that the plasma parameters in the highly dynamic cathodic arc plasma are not constant but fluctuate [27], [28]. The fluctuation depends on the cathode material [29]. In the case of Al and Cr single-element cathodes, the larger standard deviation of the Al charge states revealed greater fluctuations than the charge states of Cr.…”

Section: A Discharges In Vacuummentioning

confidence: 95%

Ion Charge State Distributions of Al and Cr in Cathodic Arc Plasmas From Composite Cathodes in Vacuum, Argon, Nitrogen, and Oxygen

Franz

Polcik

Anders

2013

IEEE Trans. Plasma Sci.

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Multielement cathodes are increasingly used for advanced coatings, yet most cathodic arc plasma measurements have been reported for pure element cathodes. In this contribution, we measure the charge state distributions of aluminum and chromium ions from Al-Cr composite cathodes of different Al to Cr ratios. The arc discharges are pulsed, with pulse duration of around 300 µs and currents of 175 A, operated at high vacuum and in gases with a pressure of up to 1.3 Pa of Ar, N 2 , and O 2 . For comparison with literature data, the measurements also included the plasma compositions of discharges using pure Al and Cr cathodes. As expected, the charge distributions are found to be affected by the cathode conditions, the type of gas, and the pressure of the gas into which the arc spot plasma is expanding. Generally, large effects of gas are observed when the pressure exceeded 0.1 Pa, which can be mainly associated with the ions' mean-free path with respect to charge exchange collisions. Differences between ions can be attributed to the energy-and species-dependent charge-exchange cross sections. Considering different cathode compositions, we found that Cr ions tend to have lower charge states from the composite cathodes compared with the pure element cathode, whereas Al ions are relatively unaffected by the cathode composition. Despite the wealth of detailed experimental results, it is difficult to discern trends and rules that could be generalized because measured data involve a convolution of cathode phenomena and gas collisional effects.

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Section: A Discharges In Vacuummentioning

confidence: 95%

Ion Charge State Distributions of Al and Cr in Cathodic Arc Plasmas From Composite Cathodes in Vacuum, Argon, Nitrogen, and Oxygen

Franz

Polcik

Anders

2013

IEEE Trans. Plasma Sci.

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“…Since these frequencies are far above the plasma frequency for these arcs, and because for an arc of 50 microsecond width the initial arc plasma would be much more dense and have a higher plasma frequency than the plasma at later times, it is tempting to discount the plasma as the source of radiation. Other published work on vacuum arc spectra [1,6] use longtimescale arcs and average arc current spectra, and seem to show that on the average, there are arc current fluctuations in the right frequency range, depending on the cathode material, but these are not the narrow RF lines seen here. Although it is certain that the laboratory arcs and the arcs in space have similar RF spectra, the origin of the radiation is still unknown.…”

Section: Laboratory Arcing Vs True Satellite Arcsmentioning

confidence: 58%

“…Thus, arc duration may be different for satellites with different solar array designs and buildup. Following the reasoning in Rosen and Anders [6] and Anders and Oks [1], it is likewise to be expected that the arc spectra of different satellites may differ.…”

Section: Arc Spectra and Arc Widths Of Different Satellitesmentioning

confidence: 96%

Spectral Characteristics of GEO Satellite Arcing – 300 To 350 MHz

Ferguson

Perillat²,

Vayner

2022

J Astronaut Sci

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In a series of previous papers, the detection of arcing on GPS, Van Allen Probe, and GEO satellites with the Arecibo Observatory Wm. E. Gordon 305 m radiotelescope has been reported and elaborated. In this paper, characteristics of the radiofrequency spectra of two true GEO satellites are reported as they were measured with the Arecibo Mock spectrometer every 9.6 microseconds, and are contrasted with spectra of impulsive RFI (RadioFrequency Interference) events. It is shown that the arc spectra in the 300–350 MHz range are not continuous, but consist of a number of narrow spectral lines. These lines are consistent within the duration of single arcs, but change between arcs, so that when averaged over many arcs, the appearance of a continuous spectrum is approximated. This behavior is replicated in the laboratory within charging-induced vacuum arcing on small solar array samples. In contrast, the spectrum of impulsive RFI (including, but not limited to lightning strokes) is essentially random from one 9.6 microsecond sampling interval to the next. Since the spectrum of a true arc changes little throughout many samples, it cannot be due to the risetime of the arc current, which is much less than one sampling interval. Furthermore, in laboratory experiments done at very high time resolution (< 1 ns), there is little correlation between the arc current spectra and the arcing RFI spectra, indicating that even arc current fluctuations within each arc can have little to do with the UHF spectra observed.

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“…Furthermore, the electron density is related to the Debye length λD = (εoTe/(nee)) 1/2 , where εo is the vacuum permittivity and Te the electron temperature in eV [18]. The Debye length of the laser-induced sparks follows to be in the same range as the size of the craters 1- Oscillations are a fingerprint of the different plasma processes and are unique for a given cathodic material [19].…”

Section: A Electron Emission From Laser-induced Ectons and Low-densimentioning

confidence: 99%

Emission of charged particles from laser-induced germanium ecton, vacuum spark, and vacuum arc

Porshyn

2020

Physics of Plasmas

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The highly resolved temporal evolution of laser-induced micro-explosions on a germanium surface is studied in a triode configuration for various gate charge levels and cathode currents. Electron emission from individual spots is directly imaged with a luminescence screen, showing that the opening angle of the source is about 30°. Electron bunches of several nanocoulombs per pulse in a time interval of about 150 ns are directly extracted to the anode without vacuum breakdown in the cathodic gap. When breakdown occurs, a remarkable change in the arc behavior of a threshold gap potential of around 1 kV is observed, which hints at two different evaporation mechanisms that depend on the cathodic fall of an individual spot. Therefore, for voltages well above the threshold, a fast gate discharge is observed within the first 100-200 ns, followed by fundamental plasma oscillations and an electron emission of several µC per pulse from the plasma boundary. Additionally, highly efficient emission of germanium ion clusters occurs, evidencing a stable twofold electron multiplication in the plasma, with a charge of several µC per pulse below the threshold.

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Material-dependent high-frequency current fluctuations of cathodic vacuum arcs: Evidence for the ecton cutoff of the fractal model

Cited by 12 publications

References 17 publications

Ion Charge State Distributions of Al and Cr in Cathodic Arc Plasmas From Composite Cathodes in Vacuum, Argon, Nitrogen, and Oxygen

Ion Charge State Distributions of Al and Cr in Cathodic Arc Plasmas From Composite Cathodes in Vacuum, Argon, Nitrogen, and Oxygen

Spectral Characteristics of GEO Satellite Arcing – 300 To 350 MHz

Emission of charged particles from laser-induced germanium ecton, vacuum spark, and vacuum arc

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