Role of sheath dynamics in multiple double layer formations in expanding RF plasma

Paul, Manash Kumar; Chakraborty, Shamik; Bose, Subhojit

doi:10.1063/1.5050584

Cited by 13 publications

(14 citation statements)

References 28 publications

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“…When the electron sheath between the fireball and electrode reaches the ionization potential of the neutral gas, a second fireball would be predicted to form by the same mechanism as described in section 6.2. Indeed, such multiple fireball formation has been observed [261,262,263,264,265,266,267,268,269,270,271,272,273]. These usually take the form of concentric spheres or hemispheres, as shown in figure 35 [261,263,264].…”

Section: Multiple Fireballsmentioning

confidence: 98%

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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Section: Multiple Fireballsmentioning

confidence: 98%

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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“…The effective area of the anode rod is much smaller than the semi‐transparent mesh source, the asymmetric plasma source generates diverging electric field. [ 17–19 ] In the present case, pd = 0.375 Torr. cm., where p is the gas pressure and d is the diameter of the gridded cylindrical cathode.…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 62%

“…However, charge particles oscillate at an ion‐acoustic frequency (∼100 kHz) after the sheath and pre‐sheath formations. [ 19,29 ] The reduction of a layer with rising anode potential indicates a local shift in the phase space trajectory observed in Figure 7b. The charged layers re‐organise through SOC phenomena leading to phase change occurring through layer reduction resulting in the gradual re‐organisation of multiple charged layers in front of mesh opening into a single layer, as shown in Figure 3c.…”

Section: Resultsmentioning

confidence: 96%

“…The electrons trapped by the ion sheath formations essentially oscillate inside the plasma source at the ion oscillation frequency (∼100 kHz). [ 19,29 ] The electrostatic force between two adjacent layers maintains the localised sheath structures. However, the motion of the trapped electrons away from the ion‐rich sheath results in the generation of the higher frequency peak (∼200 kHz) when the electrons move axially out of the cylindrical cathode plasma source.…”

Section: Resultsmentioning

confidence: 99%

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Study of self‐organised criticality in a coaxial plasma source with gridded cathode

Bose

Paul

2022

Contributions to Plasma Physics

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Multiple luminous sheath structures develop in the localised plasma formation inside a cylindrical gridded cathode plasma source. These structures gradually expand into the whole vessel and undergo a critical state through self‐organised criticality (SOC) along with pronounced sheath oscillations during the variation of anode potential. The present investigation emphasises the stability properties associated with the oscillations of the sheath potential structures in the cylindrical‐gridded cathode in glow discharge regime through SOC phenomena through non‐linear time series analysis. The non‐linear temporal and spatial analysis of potential structure and dynamics of charged particles are correlated with SOC in cylindrical‐gridded cathode in glow discharge regime through the dynamics of multiple sheath structure formations. The existence of flicker noise and long‐range correlation in the time series suggests the existence of SOC behaviour in the system, the multiple sheath structures evolve through reduction and addition of layers. Cylindrical‐gridded cathode discharge initiation during formations of multiple sheath structures, switching of discharge regimes with anode potential, layer reduction and addition inside the sheath structures through SOC behaviour, renders uniqueness to the present regime of investigation. Self‐organised pattern formations and self‐organised criticality behaviour investigated in the present glow discharge regime using the cylindrical‐gridded cathode source are of prime importance to understand the complex behaviour of plasmas in the field of hollow cathode discharges.

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“…The appearance of multiple charged layered structures is quite common during various laboratory experiments under different experimental conditions such as, by limiting current in a uniform cross‐section plasma, applying potential difference, and immerging a biased electrode inside an ambient plasma inside a vacuum vessel. [ 1–5 ] However, in almost all of these cases, an ambient cathode plasma was produced by filament within a certain gas pressure range, in the absence of a magnetic field as well as in the presence of a magnetic field. [ 6 – 9 ] Self‐organized criticality (SOC) behaviour was investigated earlier during Double Layer (DL) formations in various confinement devices, mostly near the electrodes, [ 8,10,12 ] owing to its vital importance in the investigation and understanding of complexities in space plasma and fusion plasmas.…”

Section: Introductionmentioning

confidence: 99%

Formation of multiple anodic fire spots inside an electrostatic cavity

Bose

Debnath

Paul

2022

Contributions to Plasma Physics

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Charged particles exhibit self‐organized behaviour during the discharge state transitions inside an electrostatic cavity, along with the energy redistribution in different coherent modes with progressive anode potential. Multiple sheath formations around the spherical metallic ball anode placed inside the cavity transit to intensely glowing multiple anode spot formations (fireballs) on the anode surface with progressive anode potential. The intensely glowing anode spots reorganize over the anode surface and multiply quickly on increasing the anode potential. The nonlinear analysis of the fluctuating discharge current reveals the presence of self‐organized criticality (SOC) during different states of discharge along with a strong memory effect within (10–104) time lags in every state of discharge. The multiple anode spots exhibit long‐range correlation in the absence of a magnetic field, indicating SOC behaviour. The present study investigates energy distribution among the coherent modes of discharge through the application of the Empirical Mode Decomposition technique. The analysis indicates that the introduction of a magnetic field results in the interchange of coherent modes carrying most of the energy during multiple spot formations. The present experimental configuration produces stable multiple coherent modes along with the evolution of anodic sheath layers in the absence and then in the presence of the magnetic field. Relating SOC with such discharge transitions may help to understand the relation between complex structure formations in plasma with nonlinear aspects of glow discharge, which is of vital importance in the investigation of complexities in space plasma.

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Role of sheath dynamics in multiple double layer formations in expanding RF plasma

Cited by 13 publications

References 28 publications

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

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

Study of self‐organised criticality in a coaxial plasma source with gridded cathode

Formation of multiple anodic fire spots inside an electrostatic cavity

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