Ionisation waves in low pressure SF<sub>6</sub>gas

Ishikawa, Itsuo; Matsumoto, Michio; Suganomata, Shinji

doi:10.1088/0022-3727/17/1/013

Cited by 14 publications

(8 citation statements)

References 11 publications

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“…Ionisation instability can be observed in a gas discharge with negative ions [19,20]. In DC discharge in electro-negative gases such as CO 2 , CO and O 2 , the attachment-induced ionisation instability was observed by the authors of papers [21][22][23].…”

Section: Introductionmentioning

confidence: 98%

Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Lisovskiy

Yegorenkov

2004

Vacuum

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We report the recorded current-voltage characteristics of a RF capacitive discharge in oxygen. Low-frequency oscillations of the plasma potential in a kilohertz frequency range are observed to accompany the transition of the discharge from a weak-(a-) to a strong-current (g-) regime in the low-pressure range. The weak-current regime of the RF capacitive discharge is observed within the pressure range limited not only from the medium pressure side but also from the lower-pressure one. Electron temperature and plasma density are registered with a probe technique. r

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Section: Introductionmentioning

confidence: 98%

Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Lisovskiy

Yegorenkov

2004

Vacuum

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“…For many years they have already been studied in the positive column of low pressure oxygen glow discharges, e.g. [2][3][4][5] or, for example, in SF 6 [6]. Recent measurements focused on the quantitative diagnostics of O − ions, mainly realized by photo-detachment and probe measurements [7,8].…”

Section: Introductionmentioning

confidence: 99%

Investigations on the stability of the low pressure positive column in oxygen

Testrich

Pasedag

Navrátil

et al. 2009

J. Phys. D: Appl. Phys.

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The stability of the low pressure positive column in oxygen was investigated in a pressure range from 0.5 to 0.9 Torr within a discharge current interval from 0.5 to 90 mA. The transition between the well-known T-and H-modes has been studied. The H-to T-mode transition showed a marked hysteresis in the E(I) characteristic which is affected by wall processes. For the first time temporally resolved electric field measurements were realized. At small discharge current the electric field showed a significant modulation, characterized by incoherent fluctuations with a broadband Fourier spectrum. With increasing current the discharge operates in the T-mode, where a mode selection with high modulation degree occurred, resulting in a periodic oscillation of the electric field at a discrete frequency spectrum. The dynamic state in the T-mode is expressed by T-waves moving from the cathode to the anode. It seems that they were excited by oscillations in the cathode region. The waves were damped in the direction of the anode and show no dispersion. The discharge stability was studied using a hydrodynamic model considering electrons, positive and negative ions as well as metastable O 2 (a 1 g) molecules. Here the negative O −-ions play a crucial role. In good agreement with the experiments the transition between the Hand T-modes was explained as a linear unstable equilibrium state where the energy dependence of the corresponding rate coefficients is the driving mechanism (attachment-induced instability).

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“…In these system the appearance of striations is explained by theories based on the electron kinetics. Little is known, however, about the nature of striations in electronegative plasmas where the ion kinetics may play the dominant role: observations have been limited to DC plasmas [27,28], and striations have never been observed in electronegative capacitively-coupled RF (CCRF) plasmas, to our best knowledge. Here we report the observation of striations, that form in the bulk of electronegative CCRF plasmas.…”

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confidence: 99%

Experimental Observation and Computational Analysis of Striations in Electronegative Capacitively Coupled Radio-Frequency Plasmas

et al. 2016

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Self-organized spatial structures in the light emission from the ion-ion capacitive RF plasma of a strongly electronegative gas (CF4) are observed experimentally for the first time. Their formation is analyzed and understood based on particle-based kinetic simulations. These "striations" are found to be generated by the resonance between the driving radio-frequency and the eigenfrequency of the ion-ion plasma (derived from an analytical model) that establishes a modulation of the electric field, the ion densities, as well as the energy gain and loss processes of electrons in the plasma. The growth of the instability is followed by the numerical simulations.Plasmas in electronegative gases exhibit complex physical and chemical kinetics [1][2][3][4][5][6][7][8][9][10][11]. Their main constituents are typically positive and negative ions, and electrons are only present as a minor species. Such a composition leads to unique effects, e.g., the dominant mechanism of electron energy gain is typically due to the ambipolar and drift electric fields within the ion-ion plasma bulk [12][13][14][15][16][17][18], in sharp contrast with the mechanisms in (more common) electropositive (electron-ion) plasmas where the dynamics of the boundary sheaths conveys energy to the electrons.Being complex dynamical systems, plasmas are susceptible to various instabilities. Strong modulations of the plasma density and light emission -termed as "striations" -have extensively been studied in electropositive DC discharges [19][20][21][22], wherein ion-acoustic or ionization waves form the basics of these features. Striations also occur in electropositive inductively coupled plasmas [23], plasma display panels [24], and in plasma clouds in the ionosphere [25,26]. In these system the appearance of striations is explained by theories based on the electron kinetics. Little is known, however, about the nature of striations in electronegative plasmas where the ion kinetics may play the dominant role: observations have been limited to DC plasmas [27,28], and striations have never been observed in electronegative capacitively-coupled RF (CCRF) plasmas, to our best knowledge. Here we report the observation of striations, that form in the bulk of electronegative CCRF plasmas. The experimental observations are compared with simulation data, which allow a detailed investigation of the underlying physics.In the experiment (described in detail in [18]) the plasma is produced in CF 4 between two parallel electrodes made of stainless steel with a diameter of 10 cm. The gap between the electrodes is L=1.5 cm. The bottom electrode and the chamber walls are grounded. A sinusoidal voltage of a function generator is amplified and applied to the top electrode via a matching network. The generator is also connected to a pulse delay generator that triggers in a synchronized manner an intensified charge-coupled device (ICCD) camera for Phase Resolved Optical Emission Spectroscopy (PROES) measurements. The ICCD camera is equipped with an objective lens and an interfer...

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Ionisation waves in low pressure SF₆gas

Cited by 14 publications

References 11 publications

Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Investigations on the stability of the low pressure positive column in oxygen

Experimental Observation and Computational Analysis of Striations in Electronegative Capacitively Coupled Radio-Frequency Plasmas

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Ionisation waves in low pressure SF6gas

Cited by 14 publications

References 11 publications

Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Alpha–gamma transition in RF capacitive discharge in low-pressure oxygen

Investigations on the stability of the low pressure positive column in oxygen

Experimental Observation and Computational Analysis of Striations in Electronegative Capacitively Coupled Radio-Frequency Plasmas

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Product

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Ionisation waves in low pressure SF₆gas