Theory of the expanding plasma of vacuum arcs

Hantzsche, E.

doi:10.1088/0022-3727/24/8/017

Cited by 62 publications

(37 citation statements)

References 24 publications

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“…Ref. [9][10][11][12][13][14], which indicate an acceleration zone of less than 1 mm. The assumption will be checked and discussed in section IV of this work.…”

Section: Theorymentioning

confidence: 99%

Ion energy distribution functions of vacuum arc plasmas

Byon

Anders

2003

Journal of Applied Physics

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The velocity distribution function of vacuum arc ions can be measured by a time-of-flight technique similar to a method originally proposed by Yushkov. The measuring principle makes use of the welljustified assumption that the ion drift velocity from the cathode spot region to a collector is approximately constant. It is shown that the negative time derivative of the collector current is directly proportional to the ion distribution function provided that the time-averaged source intensity (i.e., emission of ions from cathode spots) is constant until the arc is rapidly switched off. In the experiment, arc termination took about 700 ns, which is much faster than the decay of the ion current measured at the collector placed in more than 2 meters distance from the cathode. The experimental distribution functions for most cathode materials show one large peak with a tail and one or more small peaks at higher ion velocities. The distribution functions for some other materials exhibit several peaks. No conclusive answer can be given about the nature of these peaks. Arguments are presented that the peaks are not caused by different charge states or plasma contamination but rather due to insufficiently averaged source fluctuations and/or acceleration by plasma instabilties.a Author to whom correspondence should be addressed; electronic mail: aanders@lbl.gov 2

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“…Ref. [9][10][11][12][13][14], which indicate an acceleration zone of less than 1 mm. The assumption will be checked and discussed in section IV of this work.…”

Section: Theorymentioning

confidence: 99%

Ion energy distribution functions of vacuum arc plasmas

Byon

Anders

2003

Journal of Applied Physics

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“…The determination of the IVD from the ion TOF along the first drift section (with length S1) was based on the following assumptions: 1) Ion acceleration takes place very near to the cathode spot, along a distance that is much shorter than S1 [19], [20]; and 2) that the ion velocity is approximately constant along the drift to the ring collector and is given by v = S1/t [11].…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Charge and Velocity Distribution of Ions Emitted From Two Simultaneously Operating and Serially Connected Vacuum Arcs

Shafir

Goldsmith

Cheifetz

2007

IEEE Trans. Plasma Sci.

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Ion velocity distribution (IVD) and ion charge state distribution of silver ions in a plasma beam emitted by two compact, serially connected, and simultaneously operating vacuum arcs were measured using a dynamic time-of-flight diagnostics. The anode and cathode of each arc were made of two strips of silver layers pasted on an alumina wafer and separated by a narrow 100-µm gap. The two arcs were laterally separated by 0.015 m and located on the same horizontal plane, emitting two plasma plums, which merged into a single one and is few centimeters away from the arcs. Each arc was ignited by highvoltage breakdown on the alumina surface gap by 3-µs 100-A current. The IVD of the merged plasma beam was analyzed 0.7 m away from the arcs and compared with that of the ions emitted by a single arc. When only a single arc was active, the plasma beam consisted of more than 90% of Ag ions with an average velocity of v1 = (0.7 − 0.8) · 10 4 m/s and charge state z = 1. About 10% of the beam ion population consisted of oxygen and carbon. When the two arcs operated simultaneously, the form of the IVD was significantly different, containing a second peak with a velocity of v peak = (1.15 − 1.25) · 10 4 m/s, which is significantly higher than that observed with a single arc. However, the integrated ion charge in the merged beam was lower by 30% from the sum of the ion charge obtained from the plasma of each arc. It was found that the observed phenomena were correlated with a formation of conducting channel between the cathode of the first serially connected arc and the anode of the second arc, which is occurring when the plasma plums are expanding from the two arcs merged. When a physical barrier was inserted between the two arcs to prevent a contact between the two expanding plums, the observed plasma shunting did not occur, although the two beams merged in space beyond the barrier, as before. The effect on the IVD due to arc transfer from the first cathode to the second arc anode is currently being investigated.

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“…At increasing distance from the cathode, the plasma expands due to plasma pressure, and the velocity of the plasma increases. The plasma is accelerated by 1) the pressure of the heavy particles near the cathode surface;, 2) plasma electron heating causing ; and 3) the subsequent electron pressure [9], [14], [16]. These are components of the thermal mechanism in which the enthalpy of the particles is transformed into kinetic energy.…”

Section: Modelmentioning

confidence: 99%

Ion acceleration in vacuum arc cathode plasma jets with large rates of current rise

Beilis

2005

IEEE Trans. Plasma Sci.

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A model of plasma acceleration in a high-current short pulse vacuum arc was developed. The mathematical description includes equations for the cathode spot and the plasma jet, which were solved for rates of current rise in the range of 0.01-10 GA/s. The multicharged ions in the cathode spot were taken in account. It was shown that the plasma could be accelerated to the measured energy by a gasdynamic mechanism. The ion energy, cathode erosion rate, and the ratio of the ion flux to the electron flux are linked by the equations. The calculated cathode erosion rate varies from 200 to 10 g C when the ion energy increases from 0.1 to 10 keV. The ion current to the cathode mainly consists of singly-and doubly-charged ions. The singly-charged ion current fraction decreases with spot current decreasing and rate of current rise increasing.

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Theory of the expanding plasma of vacuum arcs

Cited by 62 publications

References 24 publications

Ion energy distribution functions of vacuum arc plasmas

Ion energy distribution functions of vacuum arc plasmas

Charge and Velocity Distribution of Ions Emitted From Two Simultaneously Operating and Serially Connected Vacuum Arcs

Ion acceleration in vacuum arc cathode plasma jets with large rates of current rise

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