Transit time instabilities in an inverted fireball. I. Basic properties

Stenzel, R. L.; Gruenwald, J.; Fonda, B.; Ioniţă, C.; Schrittwieser, R.

doi:10.1063/1.3533437

Cited by 39 publications

(25 citation statements)

References 23 publications

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“…A positive bias leads to discharge phenomena and transit time instabilities which have been studied earlier. 20 In the present experiments, the grid is biased negatively. Ions are accelerated toward the grid, partly collected on the wire, but mainly injected through the mesh openings into the bubble.…”

Section: Resultsmentioning

confidence: 99%

Oscillating plasma bubbles. II. Pulsed experiments

Stenzel

Urrutia

2012

Physics of Plasmas

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Time-dependent phenomena have been investigated in plasma bubbles which are created by inserting spherical grids into an ambient plasma and letting electrons and ions form a plasma of different parameters than the ambient one. There are no plasma sources inside the bubble. The grid bias controls the particle flux. There are sheaths on both sides of the grid, each of which passes particle flows in both directions. The inner sheath or plasma potential develops self consistently to establish charge neutrality and divergence free charge and mass flows. When the electron supply is restricted, the inner sheath exhibits oscillations near the ion plasma frequency. When all electrons are excluded, a virtual anode forms on the inside sheath, reflects all ions such that the bubble is empty. By pulsing the ambient plasma, the lifetime of the bubble plasma has been measured. In an afterglow, plasma electrons are trapped inside the bubble and the bubble decays as slow as the ambient plasma. Pulsing the grid voltage yields the time scale for filling and emptying the bubble. Probes have been shown to modify the plasma potential. Using pulsed probes, transient ringing on the time scale of ion transit times through the bubble has been observed. The start of sheath oscillations has been investigated. The instability mechanism has been qualitatively explained. The dependence of the oscillation frequency on electrons in the sheath has been clarified. V C 2012 American Institute of Physics. [http://dx.

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Section: Resultsmentioning

confidence: 99%

Oscillating plasma bubbles. II. Pulsed experiments

Stenzel

Urrutia

2012

Physics of Plasmas

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“…Stenzel et al [236,237] have also investigated an "inverted fireball" configuration where a spherical high density plasma is generated inside of a wire grid formed into a sphere. This has some similar properties to fireballs on the surface of electrodes, such as being produced by increased ionization due to energetic electrons and having a double layer electric field, but it is also particular to the transparent anode grid geometry.…”

Section: Multiple Fireballsmentioning

confidence: 99%

“…This instability is associated with a variety of nonlinear behaviors such as amplitude clipping of the collected electron current and bursty transient behavior as indicated by the fluctuations in electrode current. A high frequency transit time instability has also been extensively studied in inverted fireballs which are present on the interior of large gridded spherical electrodes [236,237,276]. The instability frequency in such cases is related to the electron transit time across the fireball.…”

Section: 52mentioning

confidence: 99%

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

Baalrud

Scheiner

Yee

et al. 2020

Plasma Sources Sci. Technol.

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Biased electrodes are common components of plasma sources and diagnostics. The plasma-electrode interaction is mediated by an intervening sheath structure that influences properties of the electrons and ions contacting the electrode surface, as well as how the electrode influences properties of the bulk plasma. A rich variety of sheath structures have been observed, including ion sheaths, electron sheaths, double sheaths, double layers, anode glow, and fireballs. These represent complex self-organized responses of the plasma that depend not only on the local influence of the electrode, but also on the global properties of the plasma and the other boundaries that it is in contact with. This review summarizes recent advances in understanding the conditions under which each type of sheath forms, what the basic stability criteria and steady-state properties of each are, and the ways in which each can influence plasma-boundary interactions and bulk plasma properties. These results may be of interest to a number of application areas where biased electrodes are used, including diagnostics, plasma modification of materials, plasma sources, electric propulsion, and the interaction of plasmas with objects in space.

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“…A fireball (a plasma of a ball shape) is often generated near a positively biased electrode in a (usually) low pressure gas. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The generation of the fireball is believed to be associated with an excitation of a double layer around the fireball, across which part of the discharge voltage drops and in which electrons acquire the energy for ionizing the gas. 1 One would expect the momentum of the particle flow outward of the ball to equal the momentum that the ions acquire while they are accelerated in the double layer.…”

Section: Introductionmentioning

confidence: 99%

The force exerted by a fireball

Makrinich

Fruchtman

2014

Physics of Plasmas

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The force exerted by a fireball was deduced both from the change of the equilibrium position of a pendulum and from the change in the pendulum oscillation period. That measured force was found to be several times larger than the force exerted by the ions accelerated across the double layer that is assumed to surround the fireball. The force enhancement that is expected by ion-neutral collisions in the fireball is evaluated to be too small to explain the measured enhanced force. Gas pressure increase, due to gas heating through electron-neutral collisions, as recently suggested [Stenzel et al., J. Appl. Phys. 109, 113305 (2011)], is examined as the source for the force enhancement. V C 2014 AIP Publishing LLC. [http://dx.

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Transit time instabilities in an inverted fireball. I. Basic properties

Cited by 39 publications

References 23 publications

Oscillating plasma bubbles. II. Pulsed experiments

Oscillating plasma bubbles. II. Pulsed experiments

Interaction of biased electrodes and plasmas: sheaths, double layers, and fireballs

The force exerted by a fireball

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