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 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 Beltrami fields in a hot electron–positron–ion plasma

2012 ◽  
Vol 78 (3) ◽  
pp. 207-210 ◽  
Author(s):  
M. IQBAL ◽  
P. K. SHUKLA
Keyword(s):  
Magnetic Field ◽  
Plasma Flow ◽  
Strong Interaction ◽  
Field Configuration ◽  
Hot Electron ◽  
Magnetic Field Configuration ◽  
Beltrami Fields ◽  
Ion Plasma ◽  
Electron Positron ◽  
Laboratory Plasmas

AbstractA possibility of relaxation of relativistically hot electron and positron (e − p) plasma with a small fraction of hot or cold ions has been investigated analytically. It is observed that a strong interaction of plasma flow and field leads to a non-force-free relaxed magnetic field configuration governed by the triple curl Beltrami (TCB) equation. The triple curl Beltrami (TCB) field composed of three different Beltrami fields gives rise to three multiscale relaxed structures. The results may have the strong relevance to some astrophysical and laboratory plasmas.

scholarly journals Generation of focusing ion beams by magnetized electron sheath acceleration

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
K. Weichman ◽  
J. J. Santos ◽  
S. Fujioka ◽  
T. Toncian ◽  
A. V. Arefiev
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Ion Source ◽  
High Energy Density ◽  
Ion Acceleration ◽  
Acceleration Process ◽  
Hot Electron ◽  
Magnetic Field Effects ◽  
Multiple Species ◽  
2D And 3D

Abstract We present the first 3D fully kinetic simulations of laser driven sheath-based ion acceleration with a kilotesla-level applied magnetic field. The application of a strong magnetic field significantly and beneficially alters sheath based ion acceleration and creates two distinct stages in the acceleration process associated with the time-evolving magnetization of the hot electron sheath. The first stage delivers dramatically enhanced acceleration, and the second reverses the typical outward-directed topology of the sheath electric field into a focusing configuration. The net result is a focusing, magnetic field-directed ion source of multiple species with strongly enhanced energy and number. The predicted improvements in ion source characteristics are desirable for applications and suggest a route to experimentally confirm magnetization-related effects in the high energy density regime. We additionally perform a comparison between 2D and 3D simulation geometry, on which basis we predict the feasibility of observing magnetic field effects under experimentally relevant conditions.

scholarly journals Spatiotemporal evolution of a thin plasma foil with Kappa distribution

2014 ◽  
Vol 32 (4) ◽  
pp. 523-529 ◽  
Author(s):  
H. Mehdian ◽  
A. Kargarian ◽  
K. Hajisharifi
Keyword(s):  
Electron Distribution ◽  
Electron Distribution Function ◽  
High Energy ◽  
Spatiotemporal Evolution ◽  
Particle In Cell ◽  
High Energy Electrons ◽  
High Energy Tail ◽  
Kinetic Effects ◽  
The One ◽  
Thin Plasma

AbstractThe one-dimensional behavior of a thin plasma foil heated by laser is studied, emphasizing on the fully kinetic effects associated with initial energetic electrons using a relativistic kinetic 1D3V Particle-In-Cell code. For this purpose, the generalized Lorentzian (Kappa) function inclusive the high energy tail is employed for initial electron distribution. The presence of the initially high-energy electrons leads to a different ion energy spectrum than the initially Maxwellian distribution. It is shown for the smaller Kappa parameter k where the high energy tail of the electron distribution function becomes more significant, the electron cooling rate increases. Moreover, the spatiotemporal evolution of electric field is strongly affected by the initial super-thermal electrons.

scholarly journals High-resolution spectral imaging of SNR W44 and IC443 at 22 GHz with the Sardinia Radio Telescope

2017 ◽  
Vol 12 (S331) ◽  
pp. 190-193
Author(s):  
S. Loru ◽  
A. Pellizzoni ◽  
E. Egron ◽  
N. Iacolina ◽  
S. Righini ◽  
...  
Keyword(s):  
High Resolution ◽  
Radio Telescope ◽  
High Frequency ◽  
Electron Distribution ◽  
Ad Hoc ◽  
Imaging Techniques ◽  
High Energy ◽  
Spatially Resolved ◽  
High Energy Tail ◽  
Science Activities

AbstractIn the framework of the Astronomical Validation and Early Science activities of the Sardinia Radio Telescope (SRT, www.srt.inaf.it), we performed 22 GHz imaging observations of SNR W44 and IC443. Thanks to the single-dish imaging performances of SRT and innovative ad hoc imaging techniques, we obtained maps that provide a detailed view of the structure of the remnants. We are planning to exploit the high-frequency radio data of SNRs to better characterize the spatially-resolved spectra and search for possible spectral steepening or breaks in selected SNR regions, assessing the high-energy tail of the region-dependent electron distribution.

scholarly journals Fast magnetic energy dissipation in relativistic plasma induced by high order laser modes

2016 ◽  
Vol 4 ◽  
Author(s):  
Y. J. Gu ◽  
Q. Yu ◽  
O. Klimo ◽  
T. Zh. Esirkepov ◽  
S. V. Bulanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Energy ◽  
Collisionless Plasma ◽  
High Energy ◽  
Field Energy ◽  
Displacement Current ◽  
Particle In Cell ◽  
Magnetic Field Energy ◽  
High Energy Electrons

Fast magnetic field annihilation in a collisionless plasma is induced by using TEM(1,0) laser pulse. The magnetic quadrupole structure formation, expansion and annihilation stages are demonstrated with 2.5-dimensional particle-in-cell simulations. The magnetic field energy is converted to the electric field and accelerate the particles inside the annihilation plane. A bunch of high energy electrons moving backwards is detected in the current sheet. The strong displacement current is the dominant contribution which induces the longitudinal inductive electric field.

Solitons and freak waves in a mixed nonextensive high energy-tail electron distribution

2014 ◽  
Vol 21 (6) ◽  
pp. 062101 ◽  
Author(s):  
Omar Bouzit ◽  
Leila Ait Gougam ◽  
Mouloud Tribeche
Keyword(s):  
Electron Distribution ◽  
High Energy ◽  
Freak Waves ◽  
High Energy Tail

scholarly journals RADIATION HAZARD ON EARTH AND IN NEAR-EARTH SPACE DURING MAGNETIC FIELD INVERSION

2019 ◽  
Vol 47 (1) ◽  
pp. 129-131
Author(s):  
O.O. Tsareva ◽  
V.Yu. Popov ◽  
H.V. Malova ◽  
E.P. Popova ◽  
M.V. Podzolko ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Field Configuration ◽  
Radiation Hazard ◽  
Dynamo Model ◽  
Earth Space ◽  
Near Earth Space ◽  
The Earth ◽  
The Magnetic Field ◽  
Field Inversion

Recent observations, such as the magnetic field strength decrease, a magnetic poles shifts and the South Atlantic anomaly increase, may indicate the beginning of the Earth’s magnetic field inversion. According to the geomagnetic dynamo model, the dipole component of the magnetic field is zeroed at the inversion time, and the quadrupole one becomes dominant. To assess the occurrence of radiation hazards on the Earth’s surface and in near-Earth space at the time of magnetic field inversion, a numerical model was developed that made it possible to compare the GCR and SCR fluxes (at minima and maxima of solar activity) penetrating the Earth (taking into account the atmosphere) and the ISS in periods of the dipole and quadrupole fields dominance. It was found that during the period of inversion the flow of GCR (high-energy particles) can increase no more than three times over the entire surface of the Earth and the radiation dose will not exceed permissible one for man. Also, a change of the magnetic field configuration will redistribute areas of increased radiation on the Earth’s surface (today these are the poles of the Earth), which can adversely affect people’s health in these areas.

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.

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