Characteristic Parameters of the Anode Spot

Lefort, A.; Andanson, P

doi:10.1109/tps.1985.4316424

Cited by 10 publications

(5 citation statements)

References 5 publications

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“…In absence of the FB electrode the grounded chamber wall would be the main anode but as soon as a high positive potential is applied to the grid this may change and the gridded cube becomes the primary anode, collecting most of the electron current. This distinct overshoot was also observed in front of FB anodes by Lefort and Andanson [16] and modelled by Ecker [17]. These authors explained the occurrence of such a potential overshoot by a loss of kinetic energy by the electrons due to radiation or collision with other particles which might also lead to additional ionisation processes.…”

Section: Resultssupporting

confidence: 56%

Basic plasma parameters and physical properties of inverted He fireballs

Gruenwald¹,

Reynvaan

Geistlinger

2018

Plasma Sources Sci. Technol.

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In this paper, we present systematic measurements of the basic plasma parameters of inverted fireballs (FBs) in a helium plasma for the first time. Inverted FBs in helium with a diameter of 10 cm are generated in a highly transparent hollow electrode via impact ionisation of accelerated electrons from an existing background plasma. The measured quantities are the plasma potential, the electron density and the electron temperature. The dependence of the plasma parameters on the discharge current was studied experimentally inside as well as outside the inverted FB. Furthermore, estimations of the neutral gas temperature inside the inverted FBs are made and possible explanations of the creation of macroscopic gas flows from the inverted FBs are given. It is shown in this paper that due to efficient thermalisation of electrons with neutrals the gas temperature inside the inverted FB can reach several thousand Kelvin, which also leads to a thermal equilibrium of ions and electrons inside this plasma structure.

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Section: Resultssupporting

confidence: 56%

Basic plasma parameters and physical properties of inverted He fireballs

Gruenwald¹,

Reynvaan

Geistlinger

2018

Plasma Sources Sci. Technol.

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“…It remained a common belief for quite some time that the electric field in the boundary layer must increase significantly to maintain the current continuity. However, subsequent detailed modelling [2,3,7,8,33] of the anode boundary layer revealed that the electric field close to the anode might be zero or even negative depending on the current passing through it. Functionally, the anode layer may be divided into four different zones: starting from the anode wall, they are the Langmuir sheath zone (∼Debye length), the ambipolar diffusion zone (∼0.01 mm), the non-LTE plasma zone (∼1 mm) and the LTE plasma zone (∼1 mm).…”

Section: A Technique For Estimation Of Electric Field In the Anode Bo...mentioning

confidence: 99%

Current transfer in dc non-transferred arc plasma torches

Ghorui¹,

Sahasrabudhe²,

Das³

2010

J. Phys. D: Appl. Phys.

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Fundamentals of current transfer to the anodes in dc non-transferred arc plasma torches are investigated. Specially designed anodes made of three mutually isolated sections and external dc axial magnetic fields of various strengths are utilized to explore the conditions for different diffused and constricted attachments of the arc with the anode. A number of new facts are revealed in the exercise. Under constricted attachment, formation of arc root takes place. Spontaneous and magnetically induced movements of the arc root, their dependence on the arc current and the strength of the external magnetic field, most probable arc root velocity, variation of the root velocity with strength of the applied magnetic field, the effect of swirl on the rotational speed of the arc root are some of the important features investigated. Two new techniques are introduced: one for measurement of the arc root diameter and the other for determination of the negative electric field in the boundary layer over the anode. While the first one exploits the rigid column behaviour of the arcs, the second one utilizes the shooting back of the residual electrons over an arc spot. Sample calculations are provided.

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“…Anode spot existence theories have been presented in [8]- [11], and [12]. The mathematical description includes a system of equations based on the anode energy balance and equation for the total current [8].…”

Section: Introductionmentioning

confidence: 99%

“…The mathematical description includes a system of equations based on the anode energy balance and equation for the total current [8]. Because the system of equation is not closed, the different authors assumed some free parameters such as anode radius [9], electron temperature [10], [12], or arbitrary conditions such as Steenbeck's minimum principle [10], self-magnetic pressure is equal the vapor pressure in the spot [11], [12]. These theories did not consider the plasma energy balance, and therefore the main questions about the mechanism of the plasma electron heating and the degree of the anode vapor ionization remained unsolved.…”

Section: Introductionmentioning

confidence: 99%

“…In the case when these processes was considered the plasma velocity in spot was arbitrarily assumed to be equal to the sonic speed [10]. In some cases, the erosion rate was calculated using the Dushman relationship [11], [12]. However, the application of the Dushman formula [13] as well as the assumption that the vapor flows with sonic speed are correct only in vacuum [14], while in the arc the vapor pressure in the anode region is very high [8]- [12].…”

Section: Introductionmentioning

confidence: 99%

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Anode spot vacuum arc model: graphite anode

Beilis

2000

IEEE Trans. Comp. Packag. Technol.

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A model of near anode processes in vacuum arc anode spots on graphite electrode is developed. The physical model is based on a kinetic treatment of anode evaporation and plasma production. The system of equations formulated in the paper includes description of plasma flow in the kinetic and in the plasma acceleration regions in a self-consistent manner. Spot parameters, such as, anode surface temperature, current density, plasma density and temperature, plasma velocity in the near-electrode region and in region of plasma expansion are calculated numerically. The calculation includes the dependence of spot parameters on anode erosion rate, initial anode surface temperature and spot life time. The calculations indicate that Joule energy in the anode body is significant, and in some cases may exceed the anode surface energy source (difference between the electron energy flux and energy flux related to the anode mass loss). The anode erosion rate in vacuum arc can sufficiently differ from the anode material evaporation rate in vacuum obtained by Dushman formula.Index Terms-Anode plasma, anode spot, current density, erosion rate, graphite, plasma density and degree of atom ionization, vacuum arc.

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Characteristic Parameters of the Anode Spot

Cited by 10 publications

References 5 publications

Basic plasma parameters and physical properties of inverted He fireballs

Basic plasma parameters and physical properties of inverted He fireballs

Current transfer in dc non-transferred arc plasma torches

Anode spot vacuum arc model: graphite anode

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