Magnetic Field and Geometry Effects on Finding Plasma Potential with a Cylindrical Impedance Probe

2012 ◽  
Author(s):  
David N. Walker ◽  
R. F. Fernsler ◽  
D. D. Blackwell ◽  
W. E. Amatucci
Keyword(s):  
Magnetic Field ◽  
Plasma Potential ◽  
Impedance Probe ◽  
Geometry Effects

scholarly journals Effect of permanent magnets on plasma confinement and ion beam properties in a double layer helicon plasma source

2019 ◽  
Vol 85 (3) ◽  
Author(s):  
Erik Varberg ◽  
Åshild Fredriksen
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
Ion Beam ◽  
Plasma Source ◽  
Diffusion Chamber ◽  
Plasma Potential ◽  
Field Energy ◽  
Plasma Confinement ◽  
Plasma Device ◽  
Field Lines

The work described in this article was carried out to investigate how permanent magnets (PM) affect the plasma confinement and ion beam properties in an inductively coupled plasma which expands from a helicon source. The cylindrical plasma device Njord has a 13 cm long and 20 cm wide stainless steel port connecting the source chamber and the diffusion chamber. The source chamber has an axial magnetic field produced by two coils, with magnetic field lines expanding into the diffusion chamber. Simulations have shown that the field lines leaving the edge of the source hit the port wall, causing a loss of electrons in this section. In the experiments performed in this work, PMs were added around the port walls near the exit of a plasma source and the effect was investigated experimentally by means of a retarding field energy analyser probe. The plasma potential, ion density and ion beam parameters were estimated, and the results with and without the PMs were compared. The results showed that the plasma density in the centre can in some cases be doubled, and the density at the edges of the plasma increased significantly with PMs in place. Although the plasma potential was slightly affected, and the beam velocity dropped by ${\sim}$ 10 %, the ion beam flux increased by a factor of 1.5.

Plasma Potential Formation and Particle Acceleration Due to ECRH in Diverging Magnetic-Field Lines

1999 ◽  
Vol 35 (1T) ◽  
pp. 325-329 ◽  
Author(s):  
Rikizo Hatakeyama ◽  
Toshiro Kaneko ◽  
Noriyoshi Sato
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Plasma Potential ◽  
Potential Formation ◽  
Field Lines

Using rf impedance probe measurements to determine plasma potential and the electron energy distribution

2010 ◽  
Vol 17 (11) ◽  
pp. 113503 ◽  
Author(s):  
D. N. Walker ◽  
R. F. Fernsler ◽  
D. D. Blackwell ◽  
W. E. Amatucci
Keyword(s):  
Energy Distribution ◽  
Electron Energy ◽  
Plasma Potential ◽  
Electron Energy Distribution ◽  
Impedance Probe ◽  
Probe Measurements

scholarly journals Disturbance of plasma environment in the vicinity of the Astrid-2 microsatellite

2001 ◽  
Vol 19 (6) ◽  
pp. 655-666 ◽  
Author(s):  
N. Ivchenko ◽  
L. Facciolo ◽  
P. A. Lindqvist ◽  
P. Kekkonen ◽  
B. Holback
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Space Plasma ◽  
Plasma Potential ◽  
Space Plasma Physics ◽  
Plasma Environment ◽  
Density Enhancement ◽  
Instruments And Techniques ◽  
Field Lines ◽  
Plasma Depletion

Abstract. The presence of a satellite disturbs the ambient plasma. The charging of the spacecraft creates a sheath around it, and the motion of the satellite creates a wake disturbance. This modification of the plasma environment introduces difficulties in measuring electric fields and plasma densities using the probe technique. We present a study of the structure of the sheath and wake around the Astrid-2 microsatellite, as observed by the probes of the EMMA and LINDA instruments. Measurements with biased LINDA probes, as well as current sweeps on the EMMA probes, show a density enhancement upstream of the satellite and a plasma depletion behind the satellite. The electric field probes detect disturbances in the plasma potential on magnetic field lines connected to the satellite.Key words. Space plasma physics (spacecraft sheaths, wakes, charging; instruments and techniques)

scholarly journals Direct measurement of potentials in a reactive ion-plasma etching system

2021 ◽  
pp. 26-32
Author(s):  
Alexander Abramov
Keyword(s):  
Magnetic Field ◽  
Direct Measurement ◽  
Plasma Etching ◽  
Charged Particles ◽  
Plasma Potential ◽  
The Body ◽  
Local Magnetic Field ◽  
Floating Potential ◽  
Ion Plasma ◽  
Etching System

Devices for direct measurement of the plasma potential and floating potential in a gas dis-charge in a reactive ion-plasma etching system are presented. The action of the devices devel-oped for this purpose is based on the creation of a local magnetic field that allows purposeful-ly changing the conditions of ambipolar diffusion of charged particles. This makes it possible to contact the probe with the body of a positive plasma column without the appearance of a floating potential on it. The results of measuring the plasma potential by the proposed and al-ternative methods are compared

Trade-off in perpendicular electric field control using negatively biased emissive end-electrodes

2022 ◽  
Author(s):  
Baptiste Trotabas ◽  
Renaud Gueroult
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Thermionic Emission ◽  
Potential Drop ◽  
Plasma Potential ◽  
Magnetized Plasma ◽  
Trade Off ◽  
Sheath Edge ◽  
Field Control ◽  
Field Lines

Abstract The benefits of thermionic emission from negatively biased electrodes for perpendicular electric field control in a magnetized plasma are examined through its combined effects on the sheath and on the plasma potential variation along magnetic field lines. By increasing the radial current flowing through the plasma thermionic emission is confirmed to improve control over the plasma potential at the sheath edge compared to the case of a cold electrode. Conversely, thermionic emission is shown to be responsible for an increase of the plasma potential drop along magnetic field lines in the quasi-neutral plasma. These results suggest that there exists a trade-off between electric field longitudinal uniformity and amplitude when using negatively biased emissive electrodes to control the perpendicular electric field in a magnetized plasma.

Radial distribution of the plasma potential in a cylindrical plasma column with a longitudinal magnetic field

2021 ◽  
Vol 87 (4) ◽  
Author(s):  
G. Liziakin ◽  
A. Oiler ◽  
A. Gavrikov ◽  
N. Antonov ◽  
V. Smirnov
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Radial Distribution ◽  
Plasma Column ◽  
Radial Profile ◽  
Plasma Potential ◽  
Symmetric System ◽  
Axially Symmetric ◽  
Cylindrical Plasma ◽  
Cylindrical Plasma Column

The possibility of controlling the electrostatic field distribution in plasma has yielded wide prospects for modern technologies. As a magnetic field primarily allows for creating electric fields in plasma, it serves as an additional obstacle for the current flow through a medium. In the present paper, an axially symmetric system is considered in which the magnetic field is directed along the axis and concentric electrodes are located at the ends. The electrodes are negatively biased. A model which solves the problem of the radial distribution of the plasma potential inside the cylindrical plasma column supported by the end electrodes is proposed. The most commonly encountered configurations of the electrical connection for the end electrodes are considered, and the particular solutions to the problem of the radial distribution are presented. The contribution of ions and electrons to the transverse conductivity is evaluated in detail. The influence of a thermionic element on the radial profile of the plasma potential is considered. To verify the proposed model, an experimental study of the reflex discharge is carried out with both cold electrodes and a thermionic element on the axis. A comparison of the computational model results with experimental data is given. The presented model makes it possible to solve the problem concerning the plasma potential distribution in the case of an arbitrary number of end electrodes, and also to take into account the inhomogeneity of the distribution of plasma density, neutral gas pressure and electron temperature along the radius.

Helicon Plasma Discharge for Processing Wall Material

2014 ◽  
Vol 513-517 ◽  
pp. 28-32
Author(s):  
T.Y. Huang ◽  
C.G. Jin ◽  
M.Z. Wu ◽  
L.J. Zhuge ◽  
X.M. Wu
Keyword(s):  
Magnetic Field ◽  
Electron Density ◽  
Langmuir Probe ◽  
Plasma Processing ◽  
Plasma Potential ◽  
Graphite Surface ◽  
Wall Material ◽  
Helicon Plasma ◽  
Helicon Wave ◽  
Ar Gas

A helicon wave plasma (HWP) discharge with strong magnetic field was investigated. The HWP was produced with an internal Nagoya III antenna that is perpendicular to the magnetic field and driven by a 13.56 MHz radio-frequency (RF) source. HWP was characterized in terms of electron density, electron temperature and plasma potential using a single Langmuir probe in Ar gas. The result of Langmuir probe shows that the electron density increases with RF power, but saturate above 700 W at a density of 2×1019m-3. Scanning electron microscopy (SEM) was extensively used to characterize the quality of the graphite surface. The result of SEM shows the surface of graphite that exposed to plasma processing has exhibited smoother and compacter surface topography. Meanwhile, the concentration of impurity on the graphite surface decreases with plasma processing.

scholarly journals Drift-Alfvén fluctuations and transport in multiple interacting magnetized electron temperature filaments

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
R. D. Sydora ◽  
S. Karbashewski ◽  
B. Van Compernolle ◽  
M. J. Poulos ◽  
J. Loughran
Keyword(s):  
Magnetic Field ◽  
Electron Temperature ◽  
Current Model ◽  
Outer Region ◽  
Wave Pattern ◽  
Plasma Potential ◽  
Magnetized Plasma ◽  
Low Energy Electrons ◽  
Convective Pattern ◽  
Set Up

The results of a basic electron heat transport experiment using multiple localized heat sources in close proximity and embedded in a large magnetized plasma are presented. The set-up consists of three biased probe-mounted crystal cathodes, arranged in a triangular spatial pattern, that inject low energy electrons along a strong magnetic field into a pre-existing, cold afterglow plasma, forming electron temperature filaments. When the three sources are activated and placed within a few collisionless electron skin depths of each other, a non-azimuthally symmetric wave pattern emerges due to interference of the drift-Alfvén modes that form on each filament’s temperature gradient. Enhanced cross-field transport from chaotic ( $\boldsymbol{E}\times \boldsymbol{B}$ , where $\boldsymbol{E}$ is the electric field and $\boldsymbol{B}$ the magnetic field) mixing rapidly relaxes the gradients in the inner triangular region of the filaments and leads to growth of a global nonlinear drift-Alfvén mode that is driven by the thermal gradient in the outer region of the triangle. Azimuthal flow shear arising from the emissive cathode sources modifies the linear eigenmode stability and convective pattern. A steady-current model with emissive sheath boundary predicts the plasma potential and shear flow contribution from the sources.

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