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.

scholarly journals Measurement of Plasma Potential, Ion Saturation Current and Mach number using Retarding Field Energy Analyzer

2021 ◽  
Vol 7 (2) ◽  
pp. 76-80
Author(s):  
L. N. Mishra ◽  
Å. Fredriksen
Keyword(s):  
Mach Number ◽  
Plasma Source ◽  
Diffusion Chamber ◽  
Plasma Potential ◽  
Field Energy ◽  
Saturation Current ◽  
Energy Analyzer ◽  
Temperature Plasma ◽  
Helicon Plasma ◽  
Side Walls

This article deals about the experimental measurement of plasma potential, ion saturation current and Mach number obtained with the variation of power, operating gas pressure and radial position using retarding field energy analyzer. We employed a retarding field energy analyzer by rotating with different angles such as 0° (facing toward source), 90° (facing side walls) and 180° (facing opposite the source). The coil current is varied from 0 to 15 A to produce the magnetic field which is used to confine the plasma. The flow of plasma has been characterized which was found to be subsonic. The low-temperature plasma is produced by means of a 13.56 MHz helicon plasma source at 300-1000 kW radio frequency power. The plasma is expanding from 13.8 cm diameter source into a 150 cm long diffusion chamber of 60 cm diameter.

Axial and radial development of the hot electron distribution in a helicon plasma source, measured by a retarding field energy analyzer (RFEA)

2022 ◽  
Author(s):  
Lisa Buschmann ◽  
Ashild Fredriksen
Keyword(s):  
Magnetic Field ◽  
Electron Distribution ◽  
Potential Drop ◽  
Plasma Source ◽  
High Energy ◽  
Plasma Potential ◽  
Field Configuration ◽  
Field Energy ◽  
Hot Electron ◽  
High Energy Tail

Abstract The information about the electron population of a helicon source plasma that expands along a magnetic nozzle is important for understanding the plasma acceleration across the potential drop that forms in the nozzle. The electrons need an energy higher than the potential drop to escape from the source. At these energies the signal of a Langmuir probe is less accurate. An inverted RFEA measures the high-energy tail of the electrons. To reach the probe, they must have energies above the plasma potential VP, which can vary over the region of the measurement. By constructing a full distribution by applying the electron temperature Te obtained from the electron IV-curve and the VP obtained from the ion collecting RFEA or an emissive probe, a density measure of the hot electron distribution independent of VP can be obtained. The variation of the high-energy tail of the EEDF in both radial and axial directions, in the two different cases of 1) a purely expanding magnetic field nozzle, and 2) a more constricted one by applying current in a third, downstream coil was investigated. The electron densities and temperatures from the source are then compared to two analytic models of the downstream development of the electron density. The first model considers the development for a pure Boltzmann distribution while the second model takes an additional magnetic field expansion into account. A good match between the measured densities and the second model was found for both configurations. The RFEA probe also allows for directional measurement of the electron current to the probe. This property is used to compare the densities from the downstream and upstream directions, showing a much lower contribution of downstream electrons into the source for a purely expanding magnetic field in comparison to the confined magnetic field configuration.

scholarly journals Retarded Field Energy Analyzer as a tool to Study the Ion Velocity Distribution Functions on Radio Frequency Argon Plasma in Expanding Magnetic Field at Low Pressures

2016 ◽  
Vol 3 (1) ◽  
pp. 82
Author(s):  
L.N. Mishra
Keyword(s):  
Magnetic Field ◽  
Velocity Distribution ◽  
Argon Plasma ◽  
Distribution Functions ◽  
Field Energy ◽  
Geometrical Shape ◽  
Ion Distribution ◽  
Plasma Flows ◽  
Temperature Plasma ◽  
Plasma Device

<p>Plasma expanding in the space along the magnetic filed is well known phenomenon. This plasma device was constructed to investigate the space plasma in laboratory in connection with plasma flows, electron distribution, ion distribution, instability and turbulence. For this purpose, the low-temperature plasma is produced by means of a 13.56 MHz Helicon plasma source at 300-1000 W rf power. The plasma is expanding from the 13.5 cm diameter source into a 150 cm long chamber of 60 cm diameter. Ion energy and its velocity distribution produced by a current-free double layer at the expansion region have been studied by means of retarding field energy analyzers. Furthermore, the effects due to the geometrical shape of the expanding magnetic field in plasma flows have also been investigated.</p><p>Journal of Nepal Physical Society Vol.3(1) 2015: 82-88</p>

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

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)

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.

Ionospheric Outflow at Jupiter and Saturn

2020 ◽  
Author(s):  
Carley Martin ◽  
Licia Ray ◽  
David Constable ◽  
David Southwood ◽  
Marianna Felici ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Fluid Model ◽  
Plasma Source ◽  
Atmospheric Plasma ◽  
Atmospheric Conditions ◽  
Centrifugal Forces ◽  
Mass Source ◽  
Auroral Emission ◽  
Ionospheric Outflow ◽  
Field Lines

&lt;p&gt;Ionospheric outflow is the outward flow of atmospheric plasma, initiated by a loss of equilibrium along the magnetic field. Terrestrial ionospheric outflow presents as a polar wind triggered by the Dungey cycle, which drives much of Earth&amp;#8217;s magnetospheric dynamics. At Saturn, Felici et al. [2016] observed ionospheric outflow in the lobes at 36 R&lt;sub&gt;S&lt;/sub&gt;. Interestingly, at Jupiter, Valek et al. [2019] reported ionospheric outflow on magnetic field lines with invariant latitudes between Io&amp;#8217;s auroral signatures and the main auroral emission, lower than the polar cap.&lt;/p&gt;&lt;p&gt;At Jupiter and Saturn, the rapid rotation of the planet, coupled with an internal plasma source inside each magnetosphere, results in the Vasyliunas cycle, by which material is circulated throughout the system, eventually being lost down the magnetotail. This constant churning likely results in a system where ionospheric outflow occurs more readily at mid-to-high planetary latitudes that map to the middle magnetosphere, rather than solely at polar latitudes. Furthermore, ionospheric outflow at the Jupiter and Saturn will be affected by strong centrifugal forces and auroral currents, which are near omnipresent in each magnetosphere.&lt;/p&gt;&lt;p&gt;Using a 1-dimensional, hydrodynamic, multi-fluid model, we determine the ionospheric outflow in the jovian and saturnian systems. Our model includes the effect of centrifugal forces and auroral field-aligned currents, both of which act to enhance outflow rates from previous studies. We find that ionospheric outflow may provide a significant contribution to the jovian and saturnian systems, with the mass source rates of 18.7 &amp;#8211; 31.7 kg s&lt;sup&gt;-1&lt;/sup&gt;and 5.5-17.7 kg s&lt;sup&gt;-1&lt;/sup&gt;, respectively, where the range reflects the sensitivity to the assumed initial atmospheric conditions.&lt;/p&gt;

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