Theories of Cathode Spots

Hantzsche, E.

doi:10.1016/b978-081551375-9.50007-2

Cited by 22 publications

(28 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this work, C a and n e have been estimated assuming T s = 4 × 10 3 K and the plasma pressure was set equal to 20 bar or 100 bar, which are values of the pressure of saturated copper vapor evaluated with the use of [16] for temperatures of 3.8 × 10 3 K and 4.6 ×10 3 K, respectively. Values of the temperature of plasma electrons given by different authors vary from about one to several electronvolts; for example, values of 4 −6 eV; 0.9 eV and 3.5 eV; 1 −6 eV are cited in, respectively, [17], p. 194; [15], p. 231; [12], p. 260. Since variations in T e strongly affect the ionization rate constant, the estimates of this work have been performed for T e varying between 1 and 6 eV.…”

Section: Discussionmentioning

confidence: 99%

Space-charge sheath with ions accelerated into the plasma

Benilov¹

2010

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

To cite this version:M S Benilov. Space-charge sheath with ions accelerated into the plasma. Journal of Physics D: Applied Physics, IOP Publishing, 2010, 43 (17) The conventional model of near-cathode space-charge sheath with ions entering the sheath from the quasi-neutral plasma may be not applicable to discharges burning in cathode vapor, e.g., vacuum arcs, where ionization of emitted atoms may occur inside the sheath with some of the produced ions returning to the cathode and others moving into the plasma. In this connection, a simple model is considered of a sheath formed by electrons and positive ions injected into the sheath with a very low velocity and moving from the sheath into the plasma. It is shown that such sheath is possible provided that the sheath voltage is equal to or exceeds approximately 1.256kT e /e. This limitation is due to the space charge in the sheath and is in this sense analogous to the limitation of ion current in a vacuum diode expressed by the Child-Langmuir law. The ions leave a sheath and enter the plasma with a velocity equal to or exceeding approximately 1.585u B .

show abstract

Section: Discussionmentioning

confidence: 99%

Space-charge sheath with ions accelerated into the plasma

Benilov¹

2010

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

show abstract

“…Computation where performed for a copper cathode with the following parameters: (U c ϭ15 V and U c ϭ20 V, T e ϭ1-3 eV, 4,5,13) U i ϭ18 V, 4) aϭ1, z i ϭ2…”

Section: Resultsmentioning

confidence: 99%

“…The arc cathode region has been studied with a stationary models by numerous authors (as an example Hantzsche,4) Coulombe, 5) Ecker, 6) Zhou, 7) Bolotov,8) Rethfeld,9) Mitterauer 10) and He. 11) In this paper, we will present a stationary model for the arc cathode spot based on the antecedent works and including some recent experimental findings and the "majority" of phenomena studied separately by different authors.…”

Section: Model Of the Arc Cathode Regionmentioning

confidence: 99%

“…12) The current density (J i ) of positive ions which are created in the ionization zone after the metallic vapor have been ionized by electron impact is 4) : Where, a is the backflow coefficient of vapor towards the cathode and b is the ionization degree of the plasma (bϷ1 i.e., all the metal vapor is ionized. 4) The velocity distribution of the electrons at the sheath edge is assumed Maxwellian one, thus some electrons whose velocities are higher than (√ෆ 2eU c /m e ) can overcome the cathode voltage drop and reach the cathode surface. Thus, current density of the back-diffused electrons from the plasma to the cathode surface (J er ) is given by 4,11) :…”

Section: Current Densitiesmentioning

confidence: 99%

“…4) The velocity distribution of the electrons at the sheath edge is assumed Maxwellian one, thus some electrons whose velocities are higher than (√ෆ 2eU c /m e ) can overcome the cathode voltage drop and reach the cathode surface. Thus, current density of the back-diffused electrons from the plasma to the cathode surface (J er ) is given by 4,11) :…”

Section: Current Densitiesmentioning

confidence: 99%

See 2 more Smart Citations

Numerical Model on the Interaction of a Vacuum Arc with a Copper Cathode

et al. 2006

View full text Add to dashboard Cite

Experimental and theoretical studies of arc cathode region have been made during several decades and the task is not yet completed, in spite of many efforts and progress. In this work, a numerical model describing the arc cathode region is developed. The arc is treated as a steady state phenomenon. The model is then applied to a vacuum arc discharge interacting with a Cu cathode at low current (4-50 A). The model yields the temperature and electric field strength at the cathode surface, electrons emitted and total current density, cathode spot radius, different kinds of power densities heating and cooling the cathode, and the plasma electron density. The comparison with experimental results shows good agreements.KEY WORDS: vacuum arc; cathode spot; cathode evaporation; cathode region; current density; power density heating the cathode; arc cathode spot radius.ISIJ International, Vol. 46 (2006), No. 11, pp. 1618-1625 sponsible of accelerating the emitted electrons from the cathode surface towards the ionization zone and the positive ions formed in the ionization zone towards the cathode. A net positive space charge of local density forms in the space charge zone as a result of the imbalance between the ion and electron density. The electrons extracted from the cathode travel mostly without collision in the space charge zone. When entering in the ionization zone, the emitted electrons have sufficient energy to ionize the copper atoms of vapor released from the cathode material. The resultant positive ions in the ionization zone are also accelerated in the space charge zone towards the cathode surface. The high electric field existing at the cathode surface which is necessary for electron emission from the cathode is created by these positive ions accumulated in front of the cathode surface. The ionization zone is the region in which the ion flux to the cathode surface is formed. The space charge sheath is the region in which ions going to the cathode and electrons emitted from the cathode are accelerated. In the next, we present a model for the vacuum arc cathode region in the case of copper cathode. This model can be applied for other metals. Electric FieldThe electric field strength at the cathode surface is created by the positive ions and it is evaluated using a simplified equation of Mackeown. Where m i is the positive ion mass, U c is the cathode fall, e 0 is permittivity of free space, Z i is the mean ion charge, J i is the positive ions current density and e is the elementary charge. Metallic Vapor PressureThe high temperature at the cathode surface causes evaporation of Cu atoms and significant local erosion of the cathode material is observed. During the process of arc operation, the flux density of copper G ev (in kg/m 2 · s) atoms leaving the cathode is described by the Hertz-Knudsen formula Here, T s is the local cathode surface temperature, P vap is the equilibrium vapor of the cathode material that correspond to local temperature, m cu is the atom mass of cathode material (m cu ϭ63 546 uma for Cu) a...

show abstract

Vacuum Arc Discharges with Carbon Cathodes

Schultrich

2018

Tetrahedrally Bonded Amorphous Carbon Films I

View full text Add to dashboard Cite

Theories of Cathode Spots

Cited by 22 publications

References 0 publications

Space-charge sheath with ions accelerated into the plasma

Space-charge sheath with ions accelerated into the plasma

Numerical Model on the Interaction of a Vacuum Arc with a Copper Cathode

Vacuum Arc Discharges with Carbon Cathodes

Contact Info

Product

Resources

About