Basic plasma parameters and physical properties of inverted He fireballs

Gruenwald, J.; Reynvaan, J.; Geistlinger, P.

doi:10.1088/1361-6595/aaa332

Cited by 9 publications

(3 citation statements)

References 20 publications

(20 reference statements)

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“…The heat transport from plasma to neutrals deserves further investigations for gas flow applications [46]. The research on sheaths, instabilities and global effects should be advanced and extended to applications such as plasma propulsion [42], plasma processing [43] and depositions [44] and plasma medicine [51]. The research on sheaths can also have applications in industry, medicine and defense, for example isotope separation.…”

Section: Discussionmentioning

confidence: 99%

Sheaths and Double Layers with Instabilities

Stenzel

Grünwald²,

Ioniţă³

et al. 2021

J. Technol. Space Plasmas

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The properties of sheaths and associated potential structures and instabilities cover a broad field which even a review cannot cover everything. Thus, the focus will be on about a dozen examples, describe their observations and focus on the basic physical explanations for the effects, while further details are found in the references. Due to familiarity the review focuses mainly on the authors work but compared and referenced related work. The topics start with a high frequency oscillations near the electron plasma frequency. Low frequency instabilities also occur at the ion plasma frequency.The injection of ions into an electron-rich sheath widens the sheath and forms a double layer. Likewise, the injection of electrons into an ion rich sheath widens and establishes a double layer which occurs in free plasma injection into vacuum. The sheath widens and forms a double layer by ionization in an electron rich sheath. When particle fluxes in "fireballs" gets out of balance the double layer performs relaxation instabilities which has been studied extensively. Fireballs inside spherical electrodes create a new instability due to the transit time of trapped electrons. On cylindrical and spherical electrodes the electron rich sheath rotates in magnetized plasmas. Electrons rotate due to $\mathbf E \times \mathbf B_0$ which excites electron drift waves with azimuthal eigenmodes. Conversely a permanent magnetic dipole has been used as a negative electrode. The impact of energetic ions produces secondary electron emission, forming a ring of plasma around the magnetic equator. Such "magnetrons" are subject to various instabilities. Finally, the current to a positively biased electrode in a uniformly magnetized plasma is unstable to relaxation oscillations, which shows an example of global effects. The sheath at the electrode raises the potential in the flux tube of the electrode thereby creating a radial sheath which moves unmagnetized ions radially. The ion motion creates a density perturbation which affects the electrode current. If the electrode draws large currents the current disruptions create large inductive voltages on the electrode, which again produce double layers. This phenomenon has been seen in reconnection currents. Many examples of sheath properties will be explained. Although the focus is on the physics some examples of applications will be suggested such as neutral gas heating and accelerating, sputtering of plasma magnetrons and rf oscillators.

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Section: Discussionmentioning

confidence: 99%

Sheaths and Double Layers with Instabilities

Stenzel

Grünwald²,

Ioniţă³

et al. 2021

J. Technol. Space Plasmas

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“…Since the potential drop in the sheath surrounding the gridded anode is usually in the order of the first ionisation potential φ ion [11,12,7], the potential on the IFB electrode (in Volt) is given by:…”

Section: The Practical Equationmentioning

confidence: 99%

Derivation of a simple engineering equation for the minimum voltage of inverted fireball onset

Gruenwald

2022

J. Technol. Space Plasmas

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This paper describes the derivation of a simple engineering equation to calculate the minimal necessary bias voltage for the onset of an inverted fireball. The calculation uses the electron density in the absence of an inverted fireball as well as the grid constant and the working gas species as input parameters. It will be shown that the interplay between ionsation potential, dissociation potential (for molecular working gases), as well as the electron density in the background plasma, play an important role in the necessary minimum bias on the fireball electrode. Some of the most common working gases and their relevant parameters will also be listed in this paper. This should give experimentalists and engineers a practical equation that can be used to quickly determine the most important electrical properties of the anode that is used to trap the inverted fireball. Thus, the planning and design of experimental setups or technological devices will be made much less time-consuming and, thus, more convenient.

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“…The Langmuir Probe method is highlighted as a prevalent technique for measuring critical plasma parameters, including electron temperature (T e ), electron density (n e ), ion density (n i ), and floating voltage (V f ) [15]. Despite the wealth of research in these areas, it is noteworthy that there appears to be a gap in the literature regarding the study of silica-Al 2 O 3 as a means to increase electron density within plasma.…”

Section: Introductionmentioning

confidence: 99%

Estimation of electron density, temperature and electrical characterization of silica seeded arc plasma at atmospheric pressure

Jha,

Mishra,

Narayan

et al. 2023

EEJET

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Plasma technology stands at the forefront of numerous industrial applications, offering versatile solutions from materials processing to aerospace engineering. This study employs a single Langmuir probe technique operating at atmospheric pressure to scrutinize the transformative impact of silica seeding on low-temperature arc plasma. The investigation unveils a dynamic interplay of electrons and ions within the plasma, unveiling key electrical properties. The I–V electrical properties of the arcs plasma before seeding, having a floating voltage of –39 V, demonstrate electron and ion currents for varied probe voltages. The electrons’ density is calculated to be 2.11×1013 m–3, and the electrons’ temperature is at 6.25 eV. The I–V characteristics show a floating potential of about –35 V and –37 V after seeding an arc plasma using silica in the presence of aluminum oxide (2 % by weight) powder and grain, respectively. After seeding, it is discovered that the electron temperature falls to 1.18 eV for powder while 1.16 eV for grain and electron density rises to 2×1016 m–3 for powder and 1.84×1016 m–3 for grain. In addition, a notable fall in electron temperature and a discernible rise in electron density are seen. This non-equilibrium behavior is related to silica’s catalytic function, which is enhanced by the presence of aluminum oxide. Additionally, increased ionizing activity brought on by inelastic electron collisions causes the electron temperatures in the silica-seeded arcs plasma to rise with discharge voltage. These findings can be essential for enhancing plasma-based technologies in a variety of industrial applications because they provide insightful information on how silica seeding affects arc plasma properties

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Basic plasma parameters and physical properties of inverted He fireballs

Cited by 9 publications

References 20 publications

Sheaths and Double Layers with Instabilities

Sheaths and Double Layers with Instabilities

Derivation of a simple engineering equation for the minimum voltage of inverted fireball onset

Estimation of electron density, temperature and electrical characterization of silica seeded arc plasma at atmospheric pressure

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