On the nature of arc cathode spots in vacuum and plasmas

Jüttner, B.

doi:10.1088/0741-3335/26/1a/323

Cited by 17 publications

(4 citation statements)

References 53 publications

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“…7) shows clearly defined sites of partial film erosion and uneroded regions at the cathode periphery against the fully eroded zirconium film. Such nonuniform erosion of compound film cathode is due to the nature of chaotic movement of cascades of vacuum arc cathode spots on its surface [14].…”

Section: Resultsmentioning

confidence: 99%

Mass-to-Charge State of Vacuum Arc Plasma With a Film-Coated Composite Cathode

Savkin

Frolova

Nikolaev

et al. 2015

IEEE Trans. Plasma Sci.

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We describe here our investigation of the mass-to-charge state of the plasma ions produced in a vacuum arc discharge with a composite cathode, which is a flat copper substrate coated with a hydrogen-saturated zirconium film of thickness 25-30 µm. It is shown that during the arc current pulse, the fractions of hydrogen and zirconium ions in the plasma decrease synchronously, while the copper ion fraction increases. The use of a film-coated cathode in a vacuum arc ion source allows generation of multicomponent gas and metal ion beams with a hydrogen ion fraction from several percent to several tens of percent. The lifetime of the cathode in terms of the total ion charge transported in the arc is as high as 1800 C.

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Section: Resultsmentioning

confidence: 99%

Mass-to-Charge State of Vacuum Arc Plasma With a Film-Coated Composite Cathode

Savkin

Frolova

Nikolaev

et al. 2015

IEEE Trans. Plasma Sci.

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“…However, many of the abovementioned measurements and theoretical approaches with modelling are not conclusive related to the question whether or not arc spots have characteristic times (or frequencies) such as a 'spot lifetime' or a 'characteristic time between spot ignitions'. Many papers in vacuum arc research claim that cathode spots have lifetimes of nanoseconds [28,29] or microseconds [30], which is in contrast to a fractal description of vacuum arcs.…”

Section: Introductionmentioning

confidence: 94%

High-resolution observation of cathode spots in a magnetically steered vacuum arc plasma source

Oh¹,

Kalanov²,

Anders³

2021

Plasma Sources Sci. Technol.

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The properties of cathode spots in a magnetically steered vacuum arc plasma source were investigated. The cathode spots were observed with a long-distance microscope coupled to a streak camera, where the entrance slit of the camera was aligned with one of the linear sections of the steered arc source. This is a key feature that allows the observation of spots as they appear along the erosion racetrack. The trends of spot motion and patterns in the emitted light were observed with different sweep times. The streak images were analysed by fast Fourier transformation to check for the presence or absence of characteristic features like characteristic spot lifetimes, since their existence remains a disputed issue. We found that the power spectrum of the arc spot fluctuations does not show any specific frequencies or related times, rather, the spot fluctuations have a broad spectrum following a power law (spectral power density versus frequency), which is indicative for the fractal (self-similar) nature of spot processes. Moreover, we show that-at about 300 MHz under our conditions-we reach the ultimate temporal resolution limit of the method, which is associated with the finite lifetime of excited atomic and ion states. This is a fundamental limit given by the physics of atoms and ions, not a measurement flaw. The temporal resolution limit of about 3 ns also implies a spatial resolution limit of order of a few μm given that radiating species move laterally to the observation direction with at least 10 3 m s −1 .

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“…Improving the spatial and temporal resolution of the available measuring instruments, such as the scanning electron microscope (SEM) [3][4][5], and high-speed image converter and streak camera [6][7][8][9], our understanding of microscopic spot structures has increased rapidly, especially concerning the basic operation mechanisms of cathode spots. Studies have also been aimed at determining the characteristics of cathode spots, including their geometrical properties, dynamics, electrical current density and ions emitted, and electron temperature [10,11]. Thus far, all cathode materials used for these studies have been crystalline materials such as pure Cu, Ti, Mo, Pd and their alloys, while no amorphous materials have been used.…”

Section: Introductionmentioning

confidence: 99%

“…Vacuum arc behaviours, such as arc erosion pattern, chopping current and breakdown voltage, are often affected by grain size, composition segregation and surface contamination of cathode materials [10,12,13]. Amorphous materials are boundary-free and homogeneous, and they possess high resistances to oxidation and erosion.…”

Section: Introductionmentioning

confidence: 99%

A worm-like trace of cathode spots on Cu–Zr–Ti amorphous ribbons

Zhang

Yang

Wang

et al. 2003

J. Phys. D: Appl. Phys.

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On Cu–Zr–Ti amorphous ribbons, a lot of worm-like traces or quasi-continuous traces of cathode spots have been clearly observed using a scanning electron microscope (SEM). This kind of trace is eroded by the motion of a single spot step by step, and could not be observed on cathodes made of crystalline materials. Spot motion direction can be identified from the trace. The arc spreading velocity and spot lifetime can also be evaluated by these traces on SEM photographs, and they are 2.3 m s−1 for arc spreading velocity and (1.10 ± 0.32) µs for spot lifetime. Previously, these could only be measured using high-speed photographs. A linear relationship was found between the length of spot displacement and number of steps, which is quite different from that obtained by high-speed photographs, which fit Gaussian curves and a Rayleigh function. Possible reasons for this discrepancy are discussed.

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On the nature of arc cathode spots in vacuum and plasmas

Cited by 17 publications

References 53 publications

Mass-to-Charge State of Vacuum Arc Plasma With a Film-Coated Composite Cathode

Mass-to-Charge State of Vacuum Arc Plasma With a Film-Coated Composite Cathode

High-resolution observation of cathode spots in a magnetically steered vacuum arc plasma source

A worm-like trace of cathode spots on Cu–Zr–Ti amorphous ribbons

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