Laser-plasma interactions in magnetized environment

NASA Astrophysics Data System (ADS)

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2018-05-01

Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes strongly magnetized. With mega-Gauss magnetic fields, scattering of optical lasers already becomes manifestly anisotropic. Special angles exist where coherent laser scattering is either enhanced or suppressed, as we demonstrate using a cold-fluid model. Consequently, by aiming laser beams at special angles, one may be able to optimize laser-plasma coupling in magnetized implosion experiments. In addition, magnetized scattering can be exploited to improve the performance of plasma-based laser pulse amplifiers. Using the magnetic field as an extra control variable, it is possible to produce optical pulses of higher intensity, as well as compress UV and soft x-ray pulses beyond the reach of other methods. In even stronger giga-Gauss magnetic fields, laser-plasma interaction enters a relativistic-quantum regime. Using quantum electrodynamics, we compute a modified wave dispersion relation, which enables correct interpretation of Faraday rotation measurements of strong magnetic fields.

Magnetic confinement of weakly ionized plasma with superconducting bulk magnets

NASA Astrophysics Data System (ADS)

Matsuzawa, Hidenori; Ohishi, Kazuya; Ishikawa, Kazuhito; Morita, Tomonori; Yoshikawa, Masaaki; Ikuta, Hiroshi; Mizutani, Uichiro

2003-04-01

This letter describes the application of single-domain superconducting bulk magnets as a plasma confinement. A through-hole was drilled at the center of a Sm123 bulk superconductor of 39 mm diameter and 17 mm thickness. When the sample was field cooled to 77 K, the resulting bulk magnet trapped a magnetic field of ˜0.65 T called a magnetic mirror, in the bore of the hole. The magnet was applied to a weakly ionized neon plasma column. Both the magnet and discharge glass tube were immersed in liquid nitrogen. The spatial distribution in the tube of red fluorescence of the plasma showed that the magnet certainly confined the plasma. These results would provide a clue to applications of the compact magnet of strong magnetic field.

Nonlinear magnetic electron tripolar vortices in streaming plasmas.

PubMed

Vranjes, J; Marić, G; Shukla, P K

2000-06-01

Magnetic electron modes in nonuniform magnetized and unmagnetized streaming plasmas, with characteristic frequencies between the ion and electron plasma frequencies and at spatial scales of the order of the collisionless skin depth, are studied. Two coupled equations, for the perturbed (in the case of magnetized plasma) or self-generated (for the unmagnetized plasma case) magnetic field, and the temperature, are solved in the strongly nonlinear regime and stationary traveling solutions in the form of tripolar vortices are found.

Collective dynamics and transport in extremely magnetized dusty plasmas

NASA Astrophysics Data System (ADS)

Hartmann, Peter

2016-09-01

We have built an experimental setup to realize and observe rotating dusty plasmas in a co-rotating frame. Based on the Larmor theorem, the ``RotoDust'' setup is able to create effective magnetizations, mimicked by the Coriolis inertial force, in strongly coupled dusty plasmas that are impossible to approach with superconducting magnets. At the highest rotation speed, we have achieved effective magnetic fields of 3200 T. The effective magnetization β =ωc /ωp (ratio of cyclotron to plasma frequency) reaches 0.76 which is typical for many strongly magnetized and strongly correlated plasmas in compact astrophysical objects. The analysis of the wave spectra as observed in the rotating frame clearly shows the equivalence of the rotating dust cloud and a magnetized plasma. Further, the analysis of the mean square displacement (MSD) and the velocity autocorrelation function (VAC) revealed the transport parameters diffusion and viscosity, which are in reasonable agreement with numerical predictions for magnetized 2D Yukawa systems. Small degree of super-diffusion is observed. This research was supported by grant NKFIH K-115805 and the Janos Bolyai Research Scholarship of the HAS.

Laser-Plasma Interactions in Magnetized Environment

NASA Astrophysics Data System (ADS)

Shi, Yuan

2017-10-01

Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes magnetized. Starting from mega-Gauss magnetic fields, laser scattering becomes manifestly anisotropic [arXiv 1705.09758]. By arranging beams at special angles, one may be able to optimize laser-plasma coupling in magnetized environment. In stronger giga-Gauss magnetic field, laser propagation becomes modified by relativistic quantum effects [PRA 94.012124]. The modified wave dispersion relation enables correct interpretation of Faraday rotation measurements of strong magnetic fields, as well as correct extraction of plasma parameters from the X-ray spectra of pulsars. In addition, magnetized plasmas can be utilized to mediate laser pulse compression [PRE 95.023211]. Using magnetic resonances, it is not only possible to produce optic pulses of higher intensity, but also possible to amplify UV and soft X-ray pulses that cannot be compressed using existing technology. This research is supported by NNSA Grant No. DE-NA0002948 and DOE Research Grant No. DEAC02- 09CH11466.

Magnetic field in expanding quark-gluon plasma

NASA Astrophysics Data System (ADS)

Stewart, Evan; Tuchin, Kirill

2018-04-01

Intense electromagnetic fields are created in the quark-gluon plasma by the external ultrarelativistic valence charges. The time evolution and the strength of this field are strongly affected by the electrical conductivity of the plasma. Yet, it has recently been observed that the effect of the magnetic field on the plasma flow is small. We compute the effect of plasma flow on magnetic field and demonstrate that it is less than 10%. These observations indicate that the plasma hydrodynamics and the dynamics of electromagnetic field decouple. Thus, it is a very good approximation, on the one hand, to study QGP in the background electromagnetic field generated by external sources and, on the other hand, to investigate the dynamics of magnetic field in the background plasma. We also argue that the wake induced by the magnetic field in plasma is negligible.

Heat flux viscosity in collisional magnetized plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C., E-mail: cliu@pppl.gov; Fox, W.; Bhattacharjee, A.

2015-05-15

Momentum transport in collisional magnetized plasmas due to gradients in the heat flux, a “heat flux viscosity,” is demonstrated. Even though no net particle flux is associated with a heat flux, in a plasma there can still be momentum transport owing to the velocity dependence of the Coulomb collision frequency, analogous to the thermal force. This heat-flux viscosity may play an important role in numerous plasma environments, in particular, in strongly driven high-energy-density plasma, where strong heat flux can dominate over ordinary plasma flows. The heat flux viscosity can influence the dynamics of the magnetic field in plasmas through themore » generalized Ohm's law and may therefore play an important role as a dissipation mechanism allowing magnetic field line reconnection. The heat flux viscosity is calculated directly using the finite-difference method of Epperlein and Haines [Phys. Fluids 29, 1029 (1986)], which is shown to be more accurate than Braginskii's method [S. I. Braginskii, Rev. Plasma Phys. 1, 205 (1965)], and confirmed with one-dimensional collisional particle-in-cell simulations. The resulting transport coefficients are tabulated for ease of application.« less

Strong terahertz emission by optical rectification of shaped laser pulse in transversely magnetized plasma

NASA Astrophysics Data System (ADS)

Singh, Ram Kishor; Singh, Monika; Rajouria, Satish Kumar; Sharma, R. P.

2017-07-01

This communication presents a theoretical model for efficient terahertz (THz) radiation generation by the optical rectification of shaped laser pulse in transversely magnetised ripple density plasma. The laser beam imparts a nonlinear ponderomotive force to the electron and this force exerts a nonlinear velocity component in both transverse and axial directions which have spectral components in the THz range. These velocity components couple with the pre-existing density ripple and give rise to a strong nonlinear current density which drives the THz wave in the plasma. The THz yield increases with the increasing strength of the background magnetic field and the sensitivity depends on the ripple wave number. The emitted power is directly proportional to the square of the amplitude of the density ripple. For exact phase matching condition, the normalised power of the generated THz wave can be achieved of the order of 10-4.

Magnetic Field Effects on Plasma Plumes

NASA Technical Reports Server (NTRS)

Ebersohn, F.; Shebalin, J.; Girimaji, S.; Staack, D.

2012-01-01

Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results

Heavy quark complex potential in a strongly magnetized hot QGP medium

NASA Astrophysics Data System (ADS)

Singh, Balbeer; Thakur, Lata; Mishra, Hiranmaya

2018-05-01

We study the effect of a strong constant magnetic field, generated in relativistic heavy ion collisions, on the heavy quark complex potential. We work in the strong magnetic field limit with the lowest Landau level approximation. We find that the screening of the real part of the potential increases with the increase in the magnetic field. Therefore, we expect less binding of the Q Q ¯ pair in the presence of a strong magnetic field. The imaginary part of the potential increases in magnitude with the increase in magnetic field, leading to an increase of the width of the quarkonium state with the magnetic field. All of these effects result in the early dissociation of Q Q ¯ states in a magnetized hot quark-gluon plasma medium.

COMPRESSIBLE RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE IN MAGNETICALLY DOMINATED PLASMAS AND IMPLICATIONS FOR A STRONG-COUPLING REGIME

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takamoto, Makoto; Lazarian, Alexandre, E-mail: mtakamoto@eps.s.u-tokyo.ac.jp, E-mail: alazarian@facstaff.wisc.edu

2016-11-10

In this Letter, we report compressible mode effects on relativistic magnetohydrodynamic (RMHD) turbulence in Poynting-dominated plasmas using three-dimensional numerical simulations. We decomposed fluctuations in the turbulence into 3 MHD modes (fast, slow, and Alfvén) following the procedure of mode decomposition in Cho and Lazarian, and analyzed their energy spectra and structure functions separately. We also analyzed the ratio of compressible mode to Alfvén mode energy with respect to its Mach number. We found the ratio of compressible mode increases not only with the Alfvén Mach number, but also with the background magnetization, which indicates a strong coupling between the fastmore » and Alfvén modes. It also signifies the appearance of a new regime of RMHD turbulence in Poynting-dominated plasmas where the fast and Alfvén modes are strongly coupled and, unlike the non-relativistic MHD regime, cannot be treated separately. This finding will affect particle acceleration efficiency obtained by assuming Alfvénic critical-balance turbulence and can change the resulting photon spectra emitted by non-thermal electrons.« less

Laser-pulse compression using magnetized plasmas

DOE PAGES

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2017-02-28

Proposals to reach the next generation of laser intensities through Raman or Brillouin backscattering have centered on optical frequencies. Higher frequencies are beyond the range of such methods mainly due to the wave damping that accompanies the higher-density plasmas necessary for compressing higher frequency lasers. However, we find that an external magnetic field transverse to the direction of laser propagation can reduce the required plasma density. Using parametric interactions in magnetized plasmas to mediate pulse compression, both reduces the wave damping and alleviates instabilities, thereby enabling higher frequency or lower intensity pumps to produce pulses at higher intensities and longermore » durations. Finally, in addition to these theoretical advantages, our method in which strong uniform magnetic fields lessen the need for high-density uniform plasmas also lessens key engineering challenges or at least exchanges them for different challenges.« less

Simulations of plasmas pentrating magnetic barriers

NASA Astrophysics Data System (ADS)

Gunell, Herbert; Hurtig, Tomas; Koepke, Mark; Brenning, Nils; Nilsson, Hans

2007-11-01

Perturbed currents perpendicular to the magnetic are generated by plasma motions in which the equilibrium magnetic field (and the corresponding equilibrium currents) are compressed, stretched, and deformed. One example of this is the Earth's magnetopause with its ever-present equilibrium transverse currents and its strong perturbations. Experiments have recently been performed using a plasma gun to shoot a plasma at a magnetic barrier (Brenning, et al., PoP, 2005). It was found that, at a critical drift that is about 2-3 times the ion thermal speed, non-linear oscillations in the lower hybrid range give rise to a resistivity which is at least 200-300 times the Spitzer resistivity. We present simulations of the above scenario for different values of the plasma kinetic energy density. We find waves with frequencies on the order of the plasma frequency. These waves contribute to the electron heating that has been observed both in the experiments and in previous simulations (Hurtig, et al., PoP, 2003).

Radiative decay of keV-mass sterile neutrino in magnetized electron plasma

NASA Astrophysics Data System (ADS)

Dobrynina, Alexandra; Mikheev, Nicolay; Raffelt, Georg

2017-10-01

The radiative decay of sterile neutrinos with typical masses of 10 keV is investigated in the presence of an external magnetic field and degenerate electron plasma. Full account is taken of the modified photon dispersion relation relative to vacuum. The limiting cases of relativistic and nonrelativistic plasma are analyzed. The decay rate calculated in a strongly magnetized plasma, as a function of the electron number density, is compared with the unmagnetized plasma limit. It is found that the presence of the strong magnetic field in the electron plasma suppresses the catalyzing influence of the plasma by itself on the sterile-neutrino decay rate.

Scaling laws in magnetized plasma turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boldyrev, Stanislav

2015-06-28

Interactions of plasma motion with magnetic fields occur in nature and in the laboratory in an impressively broad range of scales, from megaparsecs in astrophysical systems to centimeters in fusion devices. The fact that such an enormous array of phenomena can be effectively studied lies in the existence of fundamental scaling laws in plasma turbulence, which allow one to scale the results of analytic and numerical modeling to the sized of galaxies, velocities of supernovae explosions, or magnetic fields in fusion devices. Magnetohydrodynamics (MHD) provides the simplest framework for describing magnetic plasma turbulence. Recently, a number of new features ofmore » MHD turbulence have been discovered and an impressive array of thought-provoking phenomenological theories have been put forward. However, these theories have conflicting predictions, and the currently available numerical simulations are not able to resolve the contradictions. MHD turbulence exhibits a variety of regimes unusual in regular hydrodynamic turbulence. Depending on the strength of the guide magnetic field it can be dominated by weakly interacting Alfv\\'en waves or strongly interacting wave packets. At small scales such turbulence is locally anisotropic and imbalanced (cross-helical). In a stark contrast with hydrodynamic turbulence, which tends to ``forget'' global constrains and become uniform and isotropic at small scales, MHD turbulence becomes progressively more anisotropic and unbalanced at small scales. Magnetic field plays a fundamental role in turbulent dynamics. Even when such a field is not imposed by external sources, it is self-consistently generated by the magnetic dynamo action. This project aims at a comprehensive study of universal regimes of magnetic plasma turbulence, combining the modern analytic approaches with the state of the art numerical simulations. The proposed study focuses on the three topics: weak MHD turbulence, which is relevant for laboratory devices, the

MMS Observations of Ion-Scale Magnetic Island in the Magnetosheath Turbulent Plasma

NASA Technical Reports Server (NTRS)

Huang, S. Y.; Sahraoui, F.; Retino, A.; Contel, O. Le; Yuan, Z. G.; Chasapis, A.; Aunai, N.; Breuillard, H.; Deng, X. H.; Zhou, M.;

First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

DOE PAGES

Rosenberg, M. J.; Li, C. K.; Fox, W.; ...

2015-04-08

Novel experiments to study the strongly-driven collision of parallel magnetic fields in β~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compressionmore » and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.« less

Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas

NASA Astrophysics Data System (ADS)

Wang, Zhehui; Ticoş, Cǎtǎlin M.; Wurden, Glen A.

2007-10-01

Plasma interaction with dust is of growing interest for a number of reasons. On the one hand, dusty plasma research has become one of the most vibrant branches of plasma science. On the other hand, substantially less is known about dust dynamics outside the laboratory strongly coupled dusty-plasma regime, which typically corresponds to 1015m-3 electron density with ions at room temperature. Dust dynamics is also important to magnetic fusion because of concerns about safety and potential dust contamination of the fusion core. Dust trajectories are measured under two plasma conditions, both of which have larger densities and hotter ions than in typical dusty plasmas. Plasma-flow drag force, dominating over other forces in flowing plasmas, can explain the dust motion. In addition, quantitative understanding of dust trajectories is the basis for diagnostic applications using dust. Observation of hypervelocity dust in laboratory enables dust as diagnostic tool (hypervelocity dust injection) in magnetic fusion. In colder plasmas (˜10eV or less), dust with known physical and chemical properties can be used as microparticle tracers to measure both the magnitude and directions of flows in plasmas with good spatial resolution as the microparticle tracer velocimetry.

Magnetic curvature effects on plasma interchange turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, B., E-mail: bli@pku.edu.cn; Liao, X.; Sun, C. K.

2016-06-15

The magnetic curvature effects on plasma interchange turbulence and transport in the Z-pinch and dipole-like systems are explored with two-fluid global simulations. By comparing the transport levels in the systems with a different magnetic curvature, we show that the interchange-mode driven transport strongly depends on the magnetic geometry. For the system with large magnetic curvature, the pressure and density profiles are strongly peaked in a marginally stable state and the nonlinear evolution of interchange modes produces the global convective cells in the azimuthal direction, which lead to the low level of turbulent convective transport.

Magnetic-flutter-induced pedestal plasma transport

NASA Astrophysics Data System (ADS)

Callen, J. D.; Hegna, C. C.; Cole, A. J.

2013-11-01

Plasma toroidal rotation can limit reconnection of externally applied resonant magnetic perturbation (RMP) fields δB on rational magnetic flux surfaces. Hence it causes the induced radial perturbations δBρ to be small there, thereby inhibiting magnetic island formation and stochasticity at the top of pedestals in high (H-mode) confinement tokamak plasmas. However, the δBρs induced by RMPs increase away from rational surfaces and are shown to induce significant sinusoidal radial motion (flutter) of magnetic field lines with a radial extent that varies linearly with δBρ and inversely with distance from the rational surface because of the magnetic shear. This produces a radial electron thermal diffusivity that is (1/2)(δBρ/B0)2 times a kinetically derived, electron-collision-induced, magnetic-shear-reduced, effective parallel electron thermal diffusivity in the absence of magnetic stochasticity. These low collisionality flutter-induced transport processes and thin magnetic island effects are shown to be highly peaked in the vicinity of rational surfaces at the top of low collisionality pedestals. However, the smaller but finite level of magnetic-flutter-induced electron heat transport midway between rational surfaces is the primary factor that determines the electron temperature difference between rational surfaces at the pedestal top. The magnetic-flutter-induced non-ambipolar electron density transport can be large enough to push the plasma toward an electron density transport root. Requiring ambipolar density transport is shown to determine the radial electric field, the plasma toroidal rotation (via radial force balance), a reduced electron thermal diffusivity and increased ambipolar density transport in the pedestal. At high collisionality the various flutter effects are less strongly peaked at rational surfaces and generally less significant. They are thus less likely to exhibit flutter-induced resonant behaviour and transition toward an electron

Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

DOE PAGES

Kim, Kimin; Ahn, J. -W.; Scotti, F.; ...

2015-09-03

Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifiesmore » the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.« less

Initial Results from the Magnetized Dusty Plasma Experiment (MDPX)

NASA Astrophysics Data System (ADS)

Thomas, Edward; Konopka, Uwe; Lynch, Brian; Adams, Stephen; Leblanc, Spencer; Artis, Darrick; Dubois, Ami; Merlino, Robert; Rosenberg, Marlene

2014-10-01

The MDPX device is envisioned as a flexible, multi-user, research instrument that can perform a wide range of studies in fundamental and applied plasma physics. The MDPX device consists of two main components. The first is a four-coil, open bore, superconducting magnet system that is designed to produce uniform magnetic fields of up to 4 Tesla and non-uniform magnetic fields with gradients up to up to 2 T/m configurations. Within the warm bore of the magnet is placed an octagonal vacuum chamber that has a 46 cm outer diameter and is 22 cm tall. The primary missions of the MDPX device are to: (1) investigate the structural, thermal, charging, and collective properties of a plasma as the electrons, ions, and finally charged microparticles become magnetized; (2) study the evolution of a dusty plasma containing magnetic particles (paramagnetic, super-paramagnetic, or ferromagnetic particles) in the presence of uniform and non-uniform magnetic fields; and, (3) explore the fundamental properties of strongly magnetized plasmas (``i.e., dust-free'' plasmas). This presentation will summarize the initial characterization of the magnetic field structure, initial plasma parameter measurements, and the development of in-situ and optical diagnostics. This work is supported by funding from the NSF and the DOE.

Confinement of plasma along shaped open magnetic fields from the centrifugal force of supersonic plasma rotation.

PubMed

Teodorescu, C; Young, W C; Swan, G W S; Ellis, R F; Hassam, A B; Romero-Talamas, C A

2010-08-20

Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic E × B rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.

On the stability of self-gravitating magnetized dusty plasmas

NASA Astrophysics Data System (ADS)

Salimullah, M.; Shukla, P. K.

1999-03-01

The effects of a homogeneous magnetic field and the plasma nonuniformity on the dispersion relations of various electrostatic waves in self-gravitating magnetized dusty plasmas have been investigated. For this purpose, the kinetic dielectric response functions for the electrons and ions distributions have been used and the dielectric response function for the magnetized dust grains has been derived from the hydrodynamic equations that include the self-gravitational potential. Thus, extremely massive charged dust grains are subjected to both the electromagnetic and gravitational forces. Analytical studies of the dispersion relations in various frequency and wave number regimes reveal that both the magnetic fields and plasma inhomogeneities contribute to the stability of a self-gravitating dusty plasma system. The results of this investigation should be useful in understanding the stability of dusty proto-stars and dusty dark molecular clouds, which are held in strong magnetic fields and equilibrium density gradients.

ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, Nicholas A.; Lukin, Vyacheslav S., E-mail: namurphy@cfa.harvard.edu

2015-06-01

Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection,more » the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase.« less

Turbulent inward pinch of plasma confined by a levitated dipole magnet

NASA Astrophysics Data System (ADS)

Boxer, A. C.; Bergmann, R.; Ellsworth, J. L.; Garnier, D. T.; Kesner, J.; Mauel, M. E.; Woskov, P.

2010-03-01

The rearrangement of plasma as a result of turbulence is among the most important processes that occur in planetary magnetospheres and in experiments used for fusion energy research. Remarkably, fluctuations that occur in active magnetospheres drive particles inward and create centrally peaked profiles. Until now, the strong peaking seen in space has been undetectable in the laboratory because the loss of particles along the magnetic field is faster than the net driven flow across the magnetic field. Here, we report the first laboratory measurements in which a strong superconducting magnet is levitated and used to confine high-temperature plasma in a configuration that resembles planetary magnetospheres. Levitation eliminates field-aligned particle loss, and the central plasma density increases markedly. The build-up of density characterizes a sustained turbulent pinch and is equal to the rate predicted from measured electric-field fluctuations. Our observations show that dynamic principles describing magnetospheric plasma are relevant to plasma confined by a levitated dipole.

Filamentation instability in a quantum magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bret, A.; and Instituto de Investigaciones Energeticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real

2008-02-15

The filamentation instability occurring when a nonrelativistic electron beam passes through a quantum magnetized plasma is investigated by means of a cold quantum magnetohydrodynamic model. It is proved that the instability can be completely suppressed by quantum effects if and only if a finite magnetic field is present. A dimensionless parameter is identified that measures the strength of quantum effects. Strong quantum effects allow for a much smaller magnetic field to suppress the instability than in the classical regime.

Interaction of laser radiation with plasma under the MG external magnetic field

NASA Astrophysics Data System (ADS)

Ivanov, V. V.; Maximov, A. V.; Betti, R.; Sawada, H.; Sentoku, Y.

2016-10-01

Strong magnetic fields play an important role in many physical processes relevant to astrophysical events and fusion research. Laser produced plasma in the MG external magnetic field was studied at the 1 MA pulsed power generator coupled with the laser operated in ns and ps regimes. Rod loads and coils under 1 MA current were used to produce a magnetic field of 2-3 MG. In one type of experiments, a 0.8 ns laser pulse was focused on the load surface with intensity of 3x1015 W/cm2. Laser diagnostics showed that the laser produced plasma expands in the transversal magnetic field and forms a thin plasma disc with a typical diameter of 3-7 mm and thickness of 0.2-0.4 mm. A magnetosonic-type wave was observed in the plasma disc and on the surface of the rod load. The plasma disc expands radially across the magnetic field with a velocity of the order of the magnetosonic velocity. Physical mechanisms involved in the formation of the plasma disc may be relevant to the generation of plasma loops in sun flares. Other experiments, with a 0.4 ps laser pulse were carried for investigation of the isochoric heating of plasma with fast electrons confined by the strong magnetic field. The laser beam was focused by the parabola mirror on a solid target in the magnetic field of the coil. Work was supported by the DOE Grant DE-SC0008824 and DOE/NNSA UNR Grant DE-FC52-06NA27616.

Magnetic Field Design for a Strongly Improved PHALL Thruster

NASA Astrophysics Data System (ADS)

Martins, Alexandre A.; Rodrigo, Miranda; Ferreira, José Leonardo

2017-10-01

In this article, we are going to go through some steps that we took in the refining of engineering work related to the development of a permanent magnet Hall thruster. The use of permanent magnets in these thrusters is mainly related to the decrease of used power for propulsion, especially important for low power thrusters as for micro-satellites. The advantage of our chosen configuration is that the magnetic field can be used either perpendicular or parallel to the thruster channel walls, whereas in the last case the generated erosion forces are strongly reduced by at least three orders of magnitude. We are going to show how each magnetic field configuration affects the generated plasma and consequently the generated propulsion force and efficiency.

Ion heating and magnetic flux pile-up in a magnetic reconnection experiment with super-Alfvénic plasma inflows

NASA Astrophysics Data System (ADS)

Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; Ciardi, A.; Loureiro, N. F.; Burdiak, G. C.; Chittenden, J. P.; Clayson, T.; Halliday, J. W. D.; Niasse, N.; Russell, D.; Suzuki-Vidal, F.; Tubman, E.; Lane, T.; Ma, J.; Robinson, T.; Smith, R. A.; Stuart, N.

2018-04-01

This work presents a magnetic reconnection experiment in which the kinetic, magnetic, and thermal properties of the plasma each play an important role in the overall energy balance and structure of the generated reconnection layer. Magnetic reconnection occurs during the interaction of continuous and steady flows of super-Alfvénic, magnetized, aluminum plasma, which collide in a geometry with two-dimensional symmetry, producing a stable and long-lasting reconnection layer. Optical Thomson scattering measurements show that when the layer forms, ions inside the layer are more strongly heated than electrons, reaching temperatures of Ti˜Z ¯ Te≳300 eV—much greater than can be expected from strong shock and viscous heating alone. Later in time, as the plasma density in the layer increases, the electron and ion temperatures are found to equilibrate, and a constant plasma temperature is achieved through a balance of the heating mechanisms and radiative losses of the plasma. Measurements from Faraday rotation polarimetry also indicate the presence of significant magnetic field pile-up occurring at the boundary of the reconnection region, which is consistent with the super-Alfvénic velocity of the inflows.

Inward transport of a toroidally confined plasma subject to strong radial electric fields

NASA Technical Reports Server (NTRS)

Roth, J. R.; Krawczonek, W. M.; Powers, E. J.; Hong, J.; Kim, Y.

1977-01-01

The paper aims at showing that the density and confinement time of a toroidal plasma can be enhanced by radial electric fields far stronger than the ambipolar values, and that, if such electric fields point into the plasma, radially inward transport can result. The investigation deals with low-frequency fluctuation-induced transport using digitally implemented spectral analysis techniques and with the role of strong applied radial electric fields and weak vertical magnetic fields on plasma density and particle confinement times in a Bumpy Torus geometry. Results indicate that application of sufficiently strong radially inward electric fields results in radially inward fluctuation-induced transport into the toroidal electrostatic potential well; this inward transport gives rise to higher average electron densities and longer particle confinement times in the toroidal plasma.

Magnetic field line draping in the plasma depletion layer

NASA Technical Reports Server (NTRS)

Sibeck, D. G.; Lepping, R. P.; Lazarus, A. J.

1990-01-01

Simultaneous IMP 8 solar wind and ISEE 1/2 observations for a northern dawn ISEE 1/2 magnetopause crossing on November 6, 1977. During this crossing, ISEE 1/2 observed quasi-periodic pulses of magnetosheathlike plasma on northward magnetic field lines. The ISEE 1/2 observations were originally interpreted as evidence for strong diffusion of magnetosheath plasma across the magnetopause and the Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer. An alternate explanation, in terms of magnetic field merging and flux transfer events, has also been advocated. In this paper, a third interpretation is proposed in terms of quasi-periodic magnetopause motion which causes the satellites to repeatedly exit the magnetosphere and observe draped northward magnetosheath magnetic field lines in the plasma depletion layer.

Non-Maxwellian and magnetic field effects in complex plasma wakes★

NASA Astrophysics Data System (ADS)

Ludwig, Patrick; Jung, Hendrik; Kählert, Hanno; Joost, Jan-Philip; Greiner, Franko; Moldabekov, Zhandos; Carstensen, Jan; Sundar, Sita; Bonitz, Michael; Piel, Alexander

2018-05-01

In a streaming plasma, negatively charged dust particles create complex charge distributions on the downstream side of the particle, which are responsible for attractive forces between the like-charged particles. This wake phenomenon is studied by means of refined linear response theory and molecular dynamics simulations as well as in experiments. Particular attention is paid to non-Maxwellian velocity distributions that are found in the plasma sheath and to situations with strong magnetic fields, which are becoming increasingly important. Non-Maxwellian distributions and strong magnetic fields result in a substantial damping of the oscillatory wake potential. The interaction force in particle pairs is explored with the phase-resolved resonance method, which demonstrates the non-reciprocity of the interparticle forces in unmagnetized and magnetized systems.

Pressure profiles of plasmas confined in the field of a dipole magnet

NASA Astrophysics Data System (ADS)

Davis, Matthew Stiles

Understanding the maintenance and stability of plasma pressure confined by a strong magnetic field is a fundamental challenge in both laboratory and space plasma physics. Using magnetic and X-ray measurements on the Levitated Dipole Experiment (LDX), the equilibrium plasma pressure has been reconstructed, and variations of the plasma pressure for different plasma conditions have been examined. The relationship of these profiles to the magnetohydrodynamic (MHD) stability limit, and to the enhanced stability limit that results from a fraction of energetic trapped electrons, has been analyzed. In each case, the measured pressure profiles and the estimated fractional densities of energetic electrons were qualitatively consistent with expectations of plasma stability. LDX confines high temperature and high pressure plasma in the field of a superconducting dipole magnet. The strong dipole magnet can be either mechanically supported or magnetically levitated. When the dipole was mechanically supported, the plasma density profile was generally uniform while the plasma pressure was highly peaked. The uniform density was attributed to the thermal plasma being rapidly lost along the field to the mechanical supports. In contrast, the strongly peaked plasma pressure resulted from a fraction of energetic, mirror trapped electrons created by microwave heating at the electron cyclotron resonance (ECRH). These hot electrons are known to be gyrokinetically stabilized by the background plasma and can adopt pressure profiles steeper than the MHD limit. X-ray measurements indicated that this hot electron population could be described by an energy distribution in the range 50-100 keV. Combining information from the magnetic reconstruction of the pressure profile, multi-chord interferometer measurements of the electron density profile, and X-ray measurements of the hot electron energy distribution, the fraction of energetic electrons at the pressure peak was estimated to be ˜ 35% of the

Operating a magnetic nozzle helicon thruster with strong magnetic field

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Komuro, Atsushi; Ando, Akira

2016-03-01

A pulsed axial magnetic field up to ˜2.8 kG is applied to a 26-mm-inner-diameter helicon plasma thruster immersed in a vacuum chamber, and the thrust is measured using a pendulum target. The pendulum is located 30-cm-downstream of the thruster, and the thruster rf power and argon flow rate are fixed at 1 kW and 70 sccm (which gives a chamber pressure of 0.7 mTorr). The imparted thrust increases as the applied magnetic field is increased and saturates at a maximum value of ˜9.5 mN for magnetic field above ˜2 kG. At the maximum magnetic field, it is demonstrated that the normalized plasma density, and the ion flow energy in the magnetic nozzle, agree within ˜50% and of 10%, respectively, with a one-dimensional model that ignores radial losses from the nozzle. This magnetic nozzle model is combined with a simple global model of the thruster source that incorporates an artificially controlled factor α, to account for radial plasma losses to the walls, where α = 0 and 1 correspond to zero losses and no magnetic field, respectively. Comparison between the experiments and the model implies that the radial losses in the thruster source are experimentally reduced by the applied magnetic field to about 10% of that obtained from the no magnetic field model.

Localized Electron Heating by Strong Guide-Field Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Guo, Xuehan; Sugawara, Takumichi; Inomoto, Michiaki; Yamasaki, Kotaro; Ono, Yasushi; UTST Team

2015-11-01

Localized electron heating of magnetic reconnection was studied under strong guide-field (typically Bt 15Bp) using two merging spherical tokamak plasmas in Univ. Tokyo Spherical Tokamak (UTST) experiment. Our new slide-type two-dimensional Thomson scattering system documented for the first time the electron heating localized around the X-point. The region of high electron temperature, which is perpendicular to the magnetic field, was found to have a round shape with radius of 2 [cm]. Also, it was localized around the X-point and does not agree with that of energy dissipation term Et .jt . When we include a guide-field effect term Bt / (Bp + αBt) for Et .jt where α =√{ (vin2 +vout2) /v∥2 } , the energy dissipation area becomes localized around the X-point, suggesting that the electrons are accelerated by the reconnection electric field parallel to the magnetic field and thermalized around the X-point. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus,'' a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.

Transverse conductivity of a relativistic plasma in oblique electric and magnetic fields

NASA Technical Reports Server (NTRS)

Melia, Fulvio; Fatuzzo, Marco

1991-01-01

Resistive tearing in a primary candidate for flares occurring in stressed magnetic fields. Its possible application to the strongly magnetized environments (Hz about 10 to the 12th G) near the surface of neutron stars, particularly as a mechanism for generating the plasma heating and particle acceleration leading to gamma-ray bursts, has motivated a quantum treatment of this process, which requires knowledge of the electrical conductivity sigma of a relativistic gas in a new domain (i.e., that of a low-density n/e/) plasma in oblique electric and magnetic fields. This paper discusses the mathematical formalism for calculating sigma and present numerical results for a wide range of parameter values. The results indicate that sigma depends very strongly on both the applied electric and magnetic fields.

Raman Scattering in the Magnetized Semiconductor Plasma

NASA Astrophysics Data System (ADS)

Jankauskas, Zigmantas; Kvedaras, Vygaudas; Balevičius, Saulius

2005-04-01

Radio frequency (RF) magnetoplasmic waves known as helicons will propagate in solid-state plasmas when a strong magnetic field is applied. In our device the helicons were excited by RFs (the range 100-2000 MHz) much higher than the helicon generation frequency (the main peak at 20 MHz). The excitation of helicons in this case may be described by the effect similar to the Combination Scattering (Raman effect) when a part of the high RF wave energy that passes through the active material is absorbed and re-emitted by the magnetized solid-state plasma. It is expedient to call this experimental device a Helicon Maser (HRM) and the higher frequency e/m field - a pumping field. In full analogy with the usual Raman maser (or laser) the magnetized semiconductor sample plays the role of active material and the connecting cable - the role of high quality external resonator.

Raman Scattering in the Magnetized Semiconductor Plasma

NASA Astrophysics Data System (ADS)

Jankauskas, Zigmantas; Kvedaras, Vygaudas; Balevičius, Saulius

Radio frequency (RF) magnetoplasmic waves known as helicons will propagate in solid-state plasmas when a strong magnetic field is applied. In our device the helicons were excited by RFs (the range 100-2000 MHz) much higher than the helicon generation frequency (the main peak at 20 MHz). The excitation of helicons in this case may be described by the effect similar to the Combination Scattering (Raman effect) when a part of the high RF wave energy that passes through the active material is absorbed and re-emitted by the magnetized solid-state plasma. It is expedient to call this experimental device a Helicon Maser (HRM) and the higher frequency e/m field - a pumping field. In full analogy with the usual Raman maser (or laser) the magnetized semiconductor sample plays the role of active material and the connecting cable - the role of high quality external resonator.

Strong Little Magnets

ERIC Educational Resources Information Center

Moloney, Michael J.

2007-01-01

Did you know that some strong little cylindrical magnets available in local hardware stores can have an effective circumferential current of 2500 A? This intriguing information can be obtained by hanging a pair of magnets at the center of a coil, as shown in Fig. 1, and measuring the oscillation frequency as a function of coil current.

Interaction of laser beams with magnetized substance in a strong magnetic field

NASA Astrophysics Data System (ADS)

Kuzenov, V. V.

2018-03-01

Laser-driven magneto-inertial fusion assumed plasma and magnetic flux compression by quasisymmetric laser-driven implosion of magnetized target. We develop a 2D radiation magnetohydrodynamic code and a formulation for the one-fluid two-temperature equations for simulating compressible non-equilibrium magnetized target plasma. Laser system with pulse radiation with 10 ns duration is considered for numerical experiments. A numerical study of a scheme of magnetized laser-driven implosion in the external magnetic field is carried out.

Operating a magnetic nozzle helicon thruster with strong magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takahashi, Kazunori, E-mail: kazunori@ecei.tohoku.ac.jp; Komuro, Atsushi; Ando, Akira

A pulsed axial magnetic field up to ∼2.8 kG is applied to a 26-mm-inner-diameter helicon plasma thruster immersed in a vacuum chamber, and the thrust is measured using a pendulum target. The pendulum is located 30-cm-downstream of the thruster, and the thruster rf power and argon flow rate are fixed at 1 kW and 70 sccm (which gives a chamber pressure of 0.7 mTorr). The imparted thrust increases as the applied magnetic field is increased and saturates at a maximum value of ∼9.5 mN for magnetic field above ∼2 kG. At the maximum magnetic field, it is demonstrated that the normalized plasma density, and the ionmore » flow energy in the magnetic nozzle, agree within ∼50% and of 10%, respectively, with a one-dimensional model that ignores radial losses from the nozzle. This magnetic nozzle model is combined with a simple global model of the thruster source that incorporates an artificially controlled factor α, to account for radial plasma losses to the walls, where α = 0 and 1 correspond to zero losses and no magnetic field, respectively. Comparison between the experiments and the model implies that the radial losses in the thruster source are experimentally reduced by the applied magnetic field to about 10% of that obtained from the no magnetic field model.« less

Diffusion of Magnetized Binary Ionic Mixtures at Ultracold Plasma Conditions

NASA Astrophysics Data System (ADS)

Vidal, Keith R.; Baalrud, Scott D.

2017-10-01

Ultracold plasma experiments offer an accessible means to test transport theories for strongly coupled systems. Application of an external magnetic field might further increase their utility by inhibiting heating mechanisms of ions and electrons and increasing the temperature at which strong coupling effects are observed. We present results focused on developing and validating a transport theory to describe binary ionic mixtures across a wide range of coupling and magnetization strengths relevant to ultracold plasma experiments. The transport theory is an extension of the Effective Potential Theory (EPT), which has been shown to accurately model correlation effects at these conditions, to include magnetization. We focus on diffusion as it can be measured in ultracold plasma experiments. Using EPT within the framework of the Chapman-Enskog expansion, the parallel and perpendicular self and interdiffusion coefficients for binary ionic mixtures with varying mass ratios are calculated and are compared to molecular dynamics simulations. The theory is found to accurately extend Braginskii-like transport to stronger coupling, but to break down when the magnetization strength becomes large enough that the typical gyroradius is smaller than the interaction scale length. This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-16-1-0221.

Strongly coupled colloidal plasmas

NASA Astrophysics Data System (ADS)

Thomas, Hubertus M.; Morfill, Gregor E.; Konopka, Uwe; Rothermel, Hermann; Zuzic, Milenko

1998-11-01

The research of strongly coupled effects in colloidal plasmas started a few years ago with the discovery of the Coulomb crystallization of micron-sized particles in a plasma. The particles are charged negatively to a few thousands of electron charges due to the flux of electrons and ions from the plasma and then react via their Coulomb-potentials. The Coulomb coupling parameter Γ - which is the ratio of the Coulomb energy between two neighboring particles to their thermal energy - could be much larger than the critical value of 172 (calculated for an one-component-plasma). That means that Coulomb-crystallization can be achieved easily. Such systems, which reach equilibrium very rapidly and can be easily tuned between their ordered and disordered states, are ideally suited for investigating the processes underlying the solid-to-liquid phase transition. Furthermore, the strongly coupled collidal plasma can be excited externally and the response can be studied in great detail dynamically. Gravity plays an important role for the production and stability of plasma crystals. In laboratory plasmas gravity has to be balanced out by the electrostatic field in the sheath of the electrodes of the experimental apparatus. Thus, in the vertical direction only monolayer crystals or crystals with a few lattice layers can be formed. This restricts the analysis to processes in 2-dimensional or ``2 1/2-dimensional'' crystals (e.g. the physics of monolayers, nano-crystals or grain boundaries). Under zero gravity larger (volume) systems are possible and the field of plasma crystal research can be extended to include the physics of 3-dimensional systems. We performed the worldwide first experiments under zero-g conditions on parabolic flights and two sounding rockets. During these experiments the behaviour of dust particles in a rf-discharge under zero-g conditions was investigated. Very interesting experiments were performed, which are possible only under low gravity conditions.

High-power broadband plasma maser with magnetic self-insulation

NASA Astrophysics Data System (ADS)

Litvin, Vitaliy O.; Loza, Oleg T.

2018-01-01

Presented in this paper are the results of a particle-in-cell modelling of a novel high-power microwave (HPM) source which combines the properties of two devices. The first prototype is a magnetically insulated transmission line oscillator (MILO), an HPM self-oscillator which does not need an external magnetic field and irradiates a narrow spectrum depending on its iris-loaded slow-wave structure. The second prototype is a plasma maser, a Cherenkov HPM amplifier driven by a high-current relativistic electron beam propagating in a strong external magnetic field in plasma which acts as a slow-wave structure. The radiation frequency of plasma masers mainly depends on an easily variable plasma concentration; hence, their spectrum may overlap a few octaves. The plasma-based HPM device described in this paper operates without an external magnetic field: it looks like an MILO in which the iris-loaded slow-wave structure is substituted by a hollow plasma tube. The small pulse duration of ˜1.5 ns prevents a feedback rise in the 20-cm long generation section so that the device operates as a noise amplifier. Unlike conventional ultra wideband generators, the spectrum depends not only on the pulse duration but mainly on plasma, so the operation frequency of the device ranges within 12 GHz. For irradiated frequencies above 2 GHz, the total pulse energy efficiency of 7% is demonstrated at the HPM power level ˜1 GW.

Dynamics of Magnetized Plasma Jets and Bubbles Launched into a Background Magnetized Plasma

NASA Astrophysics Data System (ADS)

Wallace, B.; Zhang, Y.; Fisher, D. M.; Gilmore, M.

2016-10-01

The propagation of dense magnetized plasma, either collimated with mainly azimuthal B-field (jet) or toroidal with closed B-field (bubble), in a background plasma occurs in a number of solar and astrophysical cases. Such cases include coronal mass ejections moving in the background solar wind and extragalactic radio lobes expanding into the extragalactic medium. Understanding the detailed MHD behavior is crucial for correctly modeling these events. In order to further the understanding of such systems, we are investigating the injection of dense magnetized jets and bubbles into a lower density background magnetized plasma using a coaxial plasma gun and a background helicon or cathode plasma. In both jet and bubble cases, the MHD dynamics are found to be very different when launched into background plasma or magnetic field, as compared to vacuum. In the jet case, it is found that the inherent kink instability is stabilized by velocity shear developed due to added magnetic tension from the background field. In the bubble case, rather than directly relaxing to a minimum energy Taylor state (spheromak) as in vacuum, there is an expansion asymmetry and the bubble becomes Rayleigh-Taylor unstable on one side. Recent results will be presented. Work supported by the Army Research Office Award No. W911NF1510480.

Plasma separation from magnetic field lines in a magnetic nozzle

NASA Technical Reports Server (NTRS)

Kaufman, D. A.; Goodwin, D. G.; Sercel, J. C.

1993-01-01

This paper discusses conditions for separation of a plasma from the magnetic field of a magnetic nozzle. The analysis assumes a collisionless, quasineutral plasma, and therefore the results represent a lower bound on the amount of detachment possible for a given set of plasma conditions. We show that collisionless separation can occur because finite electron mass inhibits the flow of azimuthal currents in the nozzle. Separation conditions are governed by a parameter G which depends on plasma and nozzle conditions. Several methods of improving plasma detachment are presented, including moving the plasma generation zone downstream from the region of strongest magnetic field and using dual magnets to focus the plasma beam. Plasma detachment can be enhanced by manipulation of the nozzle configuration.

Magnetic Field Measurements In Magnetized Plasmas Using Zeeman Broadening Diagnostics

NASA Astrophysics Data System (ADS)

Haque, Showera; Wallace, Matthew; Presura, Radu; Neill, Paul

2017-10-01

The Zeeman effect has been used to measure the magnetic field in high energy density plasmas. This method is limited when plasma conditions are such that the line broadening due to the high plasma density and temperature surpasses the Zeeman splitting. We have measured magnetic fields in magnetized laser plasmas under conditions where the Zeeman splitting was not spectrally resolved. The magnetic field strength was determined from the difference in widths of two doublet components, using an idea proposed by Tessarin et al. (2011). Time-gated spectra with one-dimensional space-resolution were obtained at the Nevada Terawatt Facility for laser plasmas created by 20 J, 1 ns Leopard laser pulses, and expanding in the azimuthal magnetic field produced by the 0.6 MA Zebra pulsed power generator. We explore the response of the Al III 4s 2S1/2 - 4p 2P1 / 2 , 3 / 2 doublet components to the external magnetic field spatially along the plasma. Radial magnetic field and electron density profiles were measured within the plasma plume. This work was supported by the DOE/OFES Grant DE-SC0008829 and DOE/NNSA contract DE-FC52-06NA27616.

Perpendicular relativistic shocks in magnetized pair plasma

NASA Astrophysics Data System (ADS)

Plotnikov, Illya; Grassi, Anna; Grech, Mickael

2018-07-01

Perpendicular relativistic (γ0= 10) shocks in magnetized pair plasmas are investigated using two-dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 < σ < 10-2 at which a strong perpendicular net current is observed in the precursor, driving the so-called current-filamentation instability. The global structure of the shock and shock formation time are discussed. The magnetohydrodynamics shock jump conditions are found in good agreement with the numerical results, except for 10-4 < σ < 10-2 where a deviation up to 10 per cent is observed. The particle precursor length converges towards the Larmor radius of particles injected in the upstream magnetic field at intermediate magnetizations. For σ > 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive shock acceleration is observed only in weakly magnetized shocks, while a dominant contribution of shock drift acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of active galactic nucleus jets and in the termination shocks of pulsar wind nebulae.

Perpendicular relativistic shocks in magnetized pair plasma

NASA Astrophysics Data System (ADS)

Plotnikov, Illya; Grassi, Anna; Grech, Mickael

2018-04-01

Perpendicular relativistic (γ0 = 10) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately capturing the transition from Weibel-mediated to magnetic-reflection-shaped shocks. This transition is found to occur for upstream flow magnetizations 10-3 < σ < 10-2 at which a strong perpendicular net current is observed in the precursor, driving the so-called current-filamentation instability. The global structure of the shock and shock formation time are discussed. The MHD shock jump conditions are found in good agreement with the numerical results, except for 10-4 < σ < 10-2 where a deviation up to 10% is observed. The particle precursor length converges toward the Larmor radius of particles injected in the upstream magnetic field at intermediate magnetizations. For σ > 10-2, it leaves place to a purely electromagnetic precursor following from the strong emission of electromagnetic waves at the shock front. Particle acceleration is found to be efficient in weakly magnetized perpendicular shocks in agreement with previous works, and is fully suppressed for σ > 10-2. Diffusive Shock Acceleration is observed only in weakly magnetized shocks, while a dominant contribution of Shock Drift Acceleration is evidenced at intermediate magnetizations. The spatial diffusion coefficients are extracted from the simulations allowing for a deeper insight into the self-consistent particle kinematics and scale with the square of the particle energy in weakly magnetized shocks. These results have implications for particle acceleration in the internal shocks of AGN jets and in the termination shocks of Pulsar Wind Nebulae.

Plasma Equilibrium in a Magnetic Field with Stochastic Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

J.A. Krommes and Allan H. Reiman

The nature of plasma equilibrium in a magnetic field with stochastic regions is examined. It is shown that the magnetic differential equation that determines the equilibrium Pfirsch-Schluter currents can be cast in a form similar to various nonlinear equations for a turbulent plasma, allowing application of the mathematical methods of statistical turbulence theory. An analytically tractable model, previously studied in the context of resonance-broadening theory, is applied with particular attention paid to the periodicity constraints required in toroidal configurations. It is shown that even a very weak radial diffusion of the magnetic field lines can have a significant effect onmore » the equilibrium in the neighborhood of the rational surfaces, strongly modifying the near-resonant Pfirsch-Schluter currents. Implications for the numerical calculation of 3D equilibria are discussed« less

Spectroscopic Measurements of Collision-less Coupling Between Explosive Debris Plasmas and Ambient, Magnetized Background Plasmas

NASA Astrophysics Data System (ADS)

Bondarenko, Anton; Schaeffer, Derek; Everson, Erik; Vincena, Stephen; van Compernolle, Bart; Constantin, Carmen; Clark, Eric; Niemann, Christoph

2013-10-01

Emission spectroscopy is currently being utilized in order to assess collision-less momentum and energy coupling between explosive debris plasmas and ambient, magnetized background plasmas of astrophysical relevance. In recent campaigns on the Large Plasma Device (LAPD) (nelec =1012 -1013 cm-3, Telec ~ 5 eV, B0 = 200 - 400 G) utilizing the new Raptor laser facility (1053 nm, 100 J per pulse, 25 ns FWHM), laser-ablated carbon debris plasmas were generated within ambient, magnetized helium background plasmas and prominent spectral lines of carbon and helium ions were studied in high spectral (0 . 01 nm) and temporal (50 ns) resolution. Time-resolved velocity components extracted from Doppler shift measurements of the C+4 227 . 1 nm spectral line along two perpendicular axes reveal significant deceleration as the ions stream and gyrate within the helium background plasma, indicating collision-less momentum coupling. The He+1 320 . 3 nm and 468 . 6 nm spectral lines of the helium background plasma are observed to broaden and intensify in response to the carbon debris plasma, indicative of strong electric fields (Stark broadening) and energetic electrons. The experimental results are compared to 2D hybrid code simulations.

Collisional relaxation of an isotopic, strongly magnetized pure ion plasma and topics in resonant wave-particle interaction of plasmas

NASA Astrophysics Data System (ADS)

Chim, Chi Yung

First in Chapter 2, we discuss the collisional relaxation of a strongly magnetized pure ion plasma that is composed of two species with slightly different masses, but both with singly-ionized atoms. In a limit of high cyclotron frequencies O j, the total cyclotron action Ij for the two species are adiabatic invariants. In a few collisions, maximizing entropy yields a modified Gibbs distribution of the form exp[-H/T ∥-alpha1 I 1-alpha2I2]. Here, H is the total Hamiltonian and alphaj's are related to parallel and perpendicular temperatures through T ⊥j=(1/T∥ +alphaj/Oj) -1. On a longer timescale, the two species share action so that alpha 1 and alpha2 relax to a common value alpha. On an even longer timescale, the total action ceases to be a constant of the motion and alpha relaxes to zero. Next, weak transport produces a low density halo of electrons moving radially outward from the pure electron plasma core, and the m = 1 mode begins to damp algebraically when the halo reaches the wall. The damping rate is proportional to the particle flux through the resonant layer at the wall. Chapter 3 explains analytically the new algebraic damping due to both mobility and diffusion transport. Electrons swept around the resonant "cat's eye" orbits form a dipole (m = 1) density distribution, setting up a field that produces ExB-drift of the core back to the axis, that is, damps the mode. Finally, Chapter 4 provides a simple mechanistic interpretation of the resonant wave-particle interaction of Landau. For the simple case of a Vlasov plasma oscillation, the non-resonant electrons are driven resonantly by the bare electric field from the resonant electrons, and this complex driver field is of a phase to reduce the oscillation amplitude. The wave-particle resonant interaction also occurs in 2D ExB-drift waves, such as a diocotron wave. In this case, the bare electric field from the resonant electrons causes ExB-drift motion back in the core plasma, thus damping the wave.

Polarized x-ray emission from magnetized neutron stars: signature of strong-field vacuum polarization.

PubMed

Lai, Dong; Ho, Wynn C G

2003-08-15

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.

Polarized X-Ray Emission from Magnetized Neutron Stars: Signature of Strong-Field Vacuum Polarization

NASA Astrophysics Data System (ADS)

Lai, Dong; Ho, Wynn C.

2003-08-01

In the atmospheric plasma of a strongly magnetized neutron star, vacuum polarization can induce a Mikheyev-Smirnov-Wolfenstein type resonance across which an x-ray photon may (depending on its energy) convert from one mode into the other, with significant changes in opacities and polarizations. We show that this vacuum resonance effect gives rise to a unique energy-dependent polarization signature in the surface emission from neutron stars. The detection of polarized x rays from neutron stars can provide a direct probe of strong-field quantum electrodynamics and constrain the neutron star magnetic field and geometry.

The thermo magnetic instability in hot viscose plasmas

NASA Astrophysics Data System (ADS)

Haghani, A.; Khosravi, A.; Khesali, A.

2017-10-01

Magnetic Rotational Instability (MRI) can not performed well in accretion disks with strong magnetic field. Studies have indicated a new type of instability called thermomagnetic instability (TMI) in systems where Nernst coefficient and gradient temperature were considered. Nernst coefficient would appear if Boltzman equation could be expanded through ω_{Be} (cyclotron frequency). However, the growth rate of this instability was two magnitude orders below MRI growth (Ωk), which could not act the same as MRI. Therefor, a higher growth rate of unstable modes was needed. In this paper, rotating viscid hot plasma with strong magnetic filed was studied. Firstly, a constant alpha viscosity was studied and then a temperature sensitive viscosity. The results showed that the temperature sensitive viscosity would be able to increase the growth rate of TMI modes significantly, hence capable of acting similar to MRI.

Onset of magnetic reconnection in a weakly collisional, high- β plasma

NASA Astrophysics Data System (ADS)

Alt, Andrew; Kunz, Matthew

2017-10-01

In a magnetized, weakly collisional plasma, the magnetic moment of the constituent particles is an adiabatic invariant. An increase of the magnetic-field strength in such a plasma thus leads to an increase in the thermal pressure perpendicular to the field lines. Above a β-dependent threshold, this pressure anisotropy drives the mirror instability, which produces strong distortions in the field lines and traps particles on ion-Larmor scales. The impact of this instability on magnetic reconnection is investigated using simple analytical and numerical models for the formation of a current sheet and the associated production of pressure anisotropy. The difficulty in maintaining an isotropic, Maxwellian particle distribution during the formation and subsequent thinning of a current sheet in a weakly collisional plasma, coupled with the low threshold for the mirror instability in a high- β plasma, imply that the topology of reconnecting magnetic fields can radically differ from the standard Harris-sheet profile often used in kinetic simulations of collisionless reconnection. Depending on the rate of current-sheet formation, this mirror-induced disruption may occur before standard tearing modes are able to develop. This work was supported by U.S. DOE contract DE-AC02-09CH11466.

A table top experiment to study plasma confined by a dipole magnet

NASA Astrophysics Data System (ADS)

Bhattacharjee, Sudeep; Baitha, Anuj Ram

2016-10-01

There has been a long quest to understand charged particle generation, confinement and underlying complex processes in a plasma confined by a dipole magnet. Our earth's magnetosphere is an example of such a naturally occurring system. A few laboratory experiments have been designed for such investigations, such as the Levitated Dipole Experiment (LDX) at MIT, the Terella experiment at Columbia university, and the Ring Trap-1 (RT-1) experiment at the University of Tokyo. However, these are large scale experiments, where the dipole magnetic field is created with superconducting coils, thereby, necessitating power supplies and stringent cryogenic requirements. We report a table top experiment to investigate important physical processes in a dipole plasma. A strong cylindrical permanent magnet, is employed to create the dipole field inside a vacuum chamber. The magnet is suspended and cooled by circulating chilled water. The plasma is heated by electromagnetic waves of 2.45 GHz and a second frequency in the range 6 - 11 GHz. Some of the initial results of measurements and numerical simulation of magnetic field, visual observations of the first plasma, and spatial measurements of plasma parameters will be presented.

Magnetic flux pile-up and ion heating in a current sheet formed by colliding magnetized plasma flows

NASA Astrophysics Data System (ADS)

Suttle, L.; Hare, J.; Lebedev, S.; Ciardi, A.; Loureiro, N.; Niasse, N.; Burdiak, G.; Clayson, T.; Lane, T.; Robinson, T.; Smith, R.; Stuart, N.; Suzuki-Vidal, F.

2017-10-01

We present data from experiments carried out at the Magpie pulsed power facility, which show the detailed structure of the interaction of counter-streaming magnetized plasma flows. In our quasi-2D setup, continuous supersonic flows are produced with strong embedded magnetic fields of opposing directions. Their interaction leads to the formation of a dense and long-lasting current sheet, where we observe the pile-up of the magnetic flux at the sheet boundary, as well as the annihilation of field inside, accompanied by an increase in plasma temperature. Spatially resolved measurements with Faraday rotation polarimetry, B-dot probes, XUV imaging, Thomson scattering and laser interferometry diagnostics show the detailed distribution of the magnetic field and other plasma parameters throughout the system. This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) Grant No. EP/G001324/1, and by the U.S. Department of Energy (DOE) Awards No. DE-F03-02NA00057 and No. DE-SC-0001063.

A Novel Experimental Setup to Investigate Magnetized Dusty Plasmas

NASA Astrophysics Data System (ADS)

Romero-Talamas, C. A.; Larocque, P.; Alvarez, J.; Sardin, J.

2013-10-01

Progress on the design and construction of a novel experimental setup to investigate dusty plasmas at the University of Maryland, Baltimore County (UMBC) is presented. The setup includes separation adjustability of discharge electrodes and their orientation with respect to gravity without breaking vacuum, and a pair of water-cooled coils to produce magnetic fields with strengths of up to several Tesla. The coils' orientation is also designed to be adjustable with respect to gravity. A pulse-forming network to power the coils with flattop times of several seconds is under design. The setup is mounted inside a large glass bell jar to provide wide optical access to the dusty plasmas, and to minimize interference of chamber walls and mounts with imposed electric or magnetic fields. Planned experiments include crystallization and wave propagation under strong magnetic fields.

Modeling Laser-Plasma Interactions in a Magnetized Plasma

NASA Astrophysics Data System (ADS)

Los, Eva; Strozzi, D. J.; Chapman, T.; Farmer, W. A.; Cohen, B. I.

2017-10-01

We consider how laser-plasma interactions, namely stimulated Raman and Brillouin scattering, develop in the presence of a background magnetic field. Externally-launched waves in magnetized plasma have been studied in magnetic fusion devices for several decades, with relatively little work on their parametric decay. The topic has received scant attention in the laser-plasma and high-energy-density fields, but is becoming timely. The MagLIF pulsed-power scheme relies on an imposed axial field and laser-preheat [S. Slutz et al., Phys. Rev. Lett. 2012]. Imposing a field on a hohlraum to reduce hotspot losses has also been proposed [L. J. Perkins et al., Phys. Plasmas 2013]. We consider how the field affects the linear light waves in a plasma, e.g. by decoupling the left- and right- circular polarizations (Faraday rotation). Parametric instability growth rates are presented, as functions of plasma conditions, field strength, and geometry. The scattered-light spectrum, which is routinely measured, is also found. Work performed under auspices of US DoE by LLNL under Contract DE-AC52-07NA27344.

De-Excitation of High-Rydberg Antihydrogen in a Strongly Magnetized Pure Positron Plasma

NASA Astrophysics Data System (ADS)

Bass, E. M.

2005-10-01

The rate at which highly excited atoms relax to deeper binding is found with classical theories and simulations. This rate relates to antihydrogen formation experiments where such atoms are formed in pure-positron, Penning trap plasmas.ootnotetextG.Gabrielse, N.S. Bowden, P. Oxley, et al., Phys. Rev. Lett. 89, 213401 (2002); M. Amoretti, C. Amsler, G. Bonomi, et al., Nature (London) 419, 456 (2002). The analysis concerns atoms that have passed the kinetic bottleneck at binding energy ɛ 4kT.ootnotetextM.E. Glinsky and T.M. O'Neil, Phys. Fluids B 3, 1279 (1991). Energy loss caused by collisions between atoms and plasma positrons is calculated in two ways: For close collisions, a molecular dynamics simulation gives the energy loss; for large-impact parameter collisions, theoretical expressions based on Fokker-Planck theory are employed.ootnotetextEric M. Bass and Daniel H.E. Dubin, Phys. Plasmas 11, 1240 (2004). For a finite magnetic field, the energy loss rate scales as 1/ɛ, just as for infinite field,^2 but with a larger coefficient. A statistical description of energy loss by radiation and Stark mixing will also be discussed.

Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma.

PubMed

Tzeferacos, P; Rigby, A; Bott, A F A; Bell, A R; Bingham, R; Casner, A; Cattaneo, F; Churazov, E M; Emig, J; Fiuza, F; Forest, C B; Foster, J; Graziani, C; Katz, J; Koenig, M; Li, C-K; Meinecke, J; Petrasso, R; Park, H-S; Remington, B A; Ross, J S; Ryu, D; Ryutov, D; White, T G; Reville, B; Miniati, F; Schekochihin, A A; Lamb, D Q; Froula, D H; Gregori, G

2018-02-09

Magnetic fields are ubiquitous in the Universe. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. The standard theoretical model for the origin of these strong magnetic fields is through the amplification of tiny seed fields via turbulent dynamo to the level consistent with current observations. However, experimental demonstration of the turbulent dynamo mechanism has remained elusive, since it requires plasma conditions that are extremely hard to re-create in terrestrial laboratories. Here we demonstrate, using laser-produced colliding plasma flows, that turbulence is indeed capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. These results support the notion that turbulent dynamo is a viable mechanism responsible for the observed present-day magnetization.

Wave propagation in strongly coupled classical plasmas in an external magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genga, R.O.

When a small perturbation is applied to the plasma dispersion, a small shift of frequency due to correlation occurs. This is justified even for strong coupling, since the effect is proportional to k/sup 2/ (k is the wave vector) and it is sufficient to consider the k ..-->.. 0 limit. Then by solving the dispersion relations for delta omega, the shift of frequency due to correlation, at different angles of propagation, we obtain all information needed. The plasma modes in which we are primarily interested are the whistler and the extraordinary modes. In this work the STLS (Singwi, Tosi, Land,more » and Sjolander) approximation scheme is used. It is seen that the correlational effects enter only through terms of order k/sup 6/ for the whistler mode and terms of order k/sup 2/ for the nonresonant situation of the extraordinary mode.« less

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

DOEpatents

Doughty, Frank C.; Spencer, John E.

2000-12-19

In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

Magnetic Nozzle and Plasma Detachment Experiment

NASA Technical Reports Server (NTRS)

Chavers, Gregory; Dobson, Chris; Jones, Jonathan; Martin, Adam; Bengtson, Roger D.; Briezman, Boris; Arefiev, Alexey; Cassibry, Jason; Shuttpelz, Branwen; Deline, Christopher

2006-01-01

High power plasma propulsion can move large payloads for orbit transfer (such as the ISS), lunar missions, and beyond with large savings in fuel consumption owing to the high specific impulse. At high power, lifetime of the thruster becomes an issue. Electrodeless devices with magnetically guided plasma offer the advantage of long life since magnetic fields confine the plasma radially and keep it from impacting the material surfaces. For decades, concerns have been raised about the plasma remaining attached to the magnetic field and returning to the vehicle along the closed magnetic field lines. Recent analysis suggests that this may not be an issue of the magnetic field is properly shaped in the nozzle region and the plasma has sufficient energy density to stretch the magnetic field downstream. An experiment was performed to test the theory regarding the Magneto-hydrodynamic (MHD) detachment scenario. Data from this experiment will be presented. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) being developed by the Ad Astra Rocket Company uses a magnetic nozzle as described above. The VASIMR is also a leading candidate for exploiting an electric propulsion test platform being considered for the ISS.

Studies on probe measurements in presence of magnetic field in dust containing hydrogen plasma

NASA Astrophysics Data System (ADS)

Kalita, Deiji; Kakati, Bharat; Kausik, Siddhartha Sankar; Saikia, Bipul Kumar; Bandyopadhyay, Mainak

2018-04-01

The accuracy of plasma parameters measured by Langmuir probe in presence of magnetic field is studied in our present work. It is observed that the ratio of electron to ion saturation current shows almost identical behavior with that of unmagnetized hydrogen plasma when r L > 10 r p (here r L : Larmor radius and r p : probe radius). At magnetic field strength, B = 594 gauss, the electron temperature ( T e ) shows an overestimated value up to 35-40%, whereas at B ≤ 37 gauss, T e shows around ≤10% overestimated value w.r.t. unmagnetized case. A bi-Maxwellian electron energy probability function is observed for entire magnetic field range for both pristine and dust containing hydrogen plasma. The bulk (cold) electron collection by the Langmuir probe is strongly suppressed whereas the higher energetic electron collection remains unaffected in presence of magnetic field. In presence of dust grains, it is found that the low energy electron population decreases even more than the magnetized plasma and the high-energy tail slightly increases compared to the pristine plasma.

Collisional Thermalization in Strongly Coupled Ultracold Neutral Plasmas

DTIC Science & Technology

2017-01-25

Beaumont, TX (4/16). “Studying Strongly Coupled Systems with Ultracold Plasmas," Department of Physics and Astronomy Colloquium, University of South...Alabama, Mobile, AL (11/15). “Collective Modes and Correlations in Strongly Coupled Ultracold Plasmas," Department of Physics and Astronomy

Energy loss of ions by electric-field fluctuations in a magnetized plasma.

PubMed

Nersisyan, Hrachya B; Deutsch, Claude

2011-06-01

The results of a theoretical investigation of the energy loss of charged particles in a magnetized classical plasma due to the electric-field fluctuations are reported. The energy loss for a test particle is calculated through the linear-response theory. At vanishing magnetic field, the electric-field fluctuations lead to an energy gain of the charged particle for all velocities. It has been shown that in the presence of strong magnetic field, this effect occurs only at low velocities. In the case of high velocities, the test particle systematically loses its energy due to the interaction with a stochastic electric field. The net effect of the fluctuations is the systematic reduction of the total energy loss (i.e., the sum of the polarization and stochastic energy losses) at vanishing magnetic field and reduction or enhancement at strong field, depending on the velocity of the particle. It is found that the energy loss of the slow heavy ion contains an anomalous term that depends logarithmically on the projectile mass. The physical origin of this anomalous term is the coupling between the cyclotron motion of the plasma electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion. This effect may strongly enhance the stochastic energy gain of the particle.

A table top experiment to investigate production and properties of a plasma confined by a dipole magnet

NASA Astrophysics Data System (ADS)

Baitha, Anuj Ram; Kumar, Ashwani; Bhattacharjee, Sudeep

2018-02-01

We report a table top experiment to investigate production and properties of a plasma confined by a dipole magnet. A water cooled, strong, cylindrical permanent magnet (NdFeB) magnetized along the axial direction and having a surface magnetic field of ˜0.5 T is employed to create a dipole magnetic field. The plasma is created by electron cyclotron resonance heating. Visual observations of the plasma indicate that radiation belts appear due to trapped particles, similar to the earth's magnetosphere. The electron temperature lies in the range 2-13 eV and is hotter near the magnets and in a downstream region. It is found that the plasma (ion) density reaches a value close to 2 × 1011 cm-3 and peaks at a radial distance about 3 cm from the magnet. The plasma beta β (β = plasma pressure/magnetic pressure) increases radially outward, and the maximum β for the present experimental system is ˜2%. It is also found that the singly charged ions are dominant in the discharge.

Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma

DOE PAGES

Tzeferacos, P.; Rigby, A.; Bott, A. F. A.; ...

2018-02-09

Magnetic fields are ubiquitous in the Universe. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. The standard theoretical model for the origin of these strong magnetic fields is through the amplification of tiny seed fields via turbulent dynamo to the level consistent with current observations. However, experimental demonstration of the turbulent dynamo mechanism has remained elusive, since it requires plasma conditions that are extremely hard to re-create in terrestrial laboratories. Heremore » in this paper, we demonstrate, using laser-produced colliding plasma flows, that turbulence is indeed capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. These results support the notion that turbulent dynamo is a viable mechanism responsible for the observed present-day magnetization.« less

Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tzeferacos, P.; Rigby, A.; Bott, A. F. A.

Magnetic fields are ubiquitous in the Universe. The energy density of these fields is typically comparable to the energy density of the fluid motions of the plasma in which they are embedded, making magnetic fields essential players in the dynamics of the luminous matter. The standard theoretical model for the origin of these strong magnetic fields is through the amplification of tiny seed fields via turbulent dynamo to the level consistent with current observations. However, experimental demonstration of the turbulent dynamo mechanism has remained elusive, since it requires plasma conditions that are extremely hard to re-create in terrestrial laboratories. Heremore » in this paper, we demonstrate, using laser-produced colliding plasma flows, that turbulence is indeed capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. These results support the notion that turbulent dynamo is a viable mechanism responsible for the observed present-day magnetization.« less

Stopping power of ions in a magnetized two-temperature plasma.

PubMed

Nersisyan, H B; Walter, M; Zwicknagel, G

2000-06-01

Using the dielectric theory for a weakly coupled plasma, we investigate the stopping power of an ion in an anisotropic two-temperature electron plasma in the presence of a magnetic field. The analysis is based on the assumption that the energy variation of the ion is much less than its kinetic energy. A general expression for the stopping power is analyzed for weak and strong magnetic fields (i.e., for the electron cyclotron frequency less than and greater than the plasma frequency), and for low and high ion velocities. It is found that the usually velocity independent friction coefficient contains an anomalous term which diverges logarithmically as the projectile velocity approaches zero. The physical origin of this anomalous term is the coupling between the cyclotron motion of the electrons and the long-wavelength, low-frequency fluctuations produced by the projectile ion.

A model for particle confinement in a toroidal plasma subject to strong radial electric fields

NASA Technical Reports Server (NTRS)

Roth, J. R.

1977-01-01

The approach adopted in the NASA Lewis Bumpy Torus experiment is to confine and heat a toroidal plasma by the simultaneous application of strong dc magnetic fields and electric fields. Strong radial electric fields (about 1 kV/cm) are imposed by biasing the plasma with up to 12 negative electrode rings which surround its minor circumference. The plasma containment is consistent with a balance of two processes: a radial infusion of ions in those sectors not containing electrode rings, resulting from the radially inward electric fields; and ion losses to the electrode rings, each of which acts as a sink and draws ions out the plasma in the manner of a Langmuir probe in the ion saturation regime. The highest density on axis which has been observed so far in this steady-state plasma is 6.2 trillion particles per cu cm, for which the particle containment time is 2.5 msec. The deuterium ion kinetic temperature for these conditions was in the range of 360 to 520 eV.

Observation of magnetic fluctuations and rapid density decay of magnetospheric plasma in Ring Trap 1

NASA Astrophysics Data System (ADS)

Saitoh, H.; Yoshida, Z.; Morikawa, J.; Yano, Y.; Mikami, H.; Kasaoka, N.; Sakamoto, W.

2012-06-01

The Ring Trap 1 device, a magnetospheric configuration generated by a levitated dipole field magnet, has created high-β (local β ˜ 70%) plasma by using electron cyclotron resonance heating (ECH). When a large population of energetic electrons is generated at low neutral gas pressure operation, high frequency magnetic fluctuations are observed. When the fluctuations are strongly excited, rapid loss of plasma was simultaneously observed especially in a quiet decay phase after the ECH microwave power is turned off. Although the plasma is confined in a strongly inhomogeneous dipole field configuration, the frequency spectra of the fluctuations have sharp frequency peaks, implying spatially localized sources of the fluctuations. The fluctuations are stabilized by decreasing the hot electron component below approximately 40%, realizing stable high-β confinement.

Pair production rates in mildly relativistic, magnetized plasmas

NASA Technical Reports Server (NTRS)

Burns, M. L.; Harding, A. K.

1984-01-01

Electron-positron pairs may be produced by either one or two photons in the presence of a strong magnetic field. In magnetized plasmas with temperatures kT approximately sq mc, both of these processes may be important and could be competitive. The rates of one-photon and two-photon pair production by photons with Maxwellian, thermal bremsstrahlung, thermal synchrotron and power law spectra are calculated as a function of temperature or power law index and field strength. This allows a comparison of the two rates and a determination of the conditions under which each process may be a significant source of pairs in astrophysical plasmas. It is found that for photon densities n(gamma) or = 10 to the 25th power/cu cm and magnetic field strengths B or = 10 to the 12th power G, one-photon pair production dominates at kT approximately sq mc for a Maxwellian, at kT approximately 2 sq mc for a thermal bremsstrahlung spectrum, at all temperatures for a thermal synchrotron spectrum, and for power law spectra with indices s approximately 4.

Two-Dimensional Turbulence in Magnetized Plasmas

ERIC Educational Resources Information Center

Kendl, A.

2008-01-01

In an inhomogeneous magnetized plasma the transport of energy and particles perpendicular to the magnetic field is in general mainly caused by quasi two-dimensional turbulent fluid mixing. The physics of turbulence and structure formation is of ubiquitous importance to every magnetically confined laboratory plasma for experimental or industrial…

A practical nonlocal model for heat transport in magnetized laser plasmas

NASA Astrophysics Data System (ADS)

Nicolaï, Ph. D.; Feugeas, J.-L. A.; Schurtz, G. P.

2006-03-01

A model of nonlocal transport for multidimensional radiation magnetohydrodynamics codes is presented. In laser produced plasmas, it is now believed that the heat transport can be strongly modified by the nonlocal nature of the electron conduction. Other mechanisms, such as self-generated magnetic fields, may also affect the heat transport. The model described in this work, based on simplified Fokker-Planck equations aims at extending the model of G. Schurtz, Ph. Nicolaï, and M. Busquet [Phys. Plasmas 7, 4238 (2000)] to magnetized plasmas. A complete system of nonlocal equations is derived from kinetic equations with self-consistent electric and magnetic fields. These equations are analyzed and simplified in order to be implemented into large laser fusion codes and coupled to other relevant physics. The model is applied to two laser configurations that demonstrate the main features of the model and point out the nonlocal Righi-Leduc effect in a multidimensional case.

Dust Particle Dynamics in The Presence of Highly Magnetized Plasmas

NASA Astrophysics Data System (ADS)

Lynch, Brian; Konopka, Uwe; Thomas, Edward; Merlino, Robert; Rosenberg, Marlene

2016-10-01

Complex plasmas are four component plasmas that contain, in addition to the usual electrons, ions, and neutral atoms, macroscopic electrically charged (nanometer to micrometer) sized ``dust'' particles. These macroscopic particles typically obtain a net negative charge due to the higher mobility of electrons compared to that of ions. Because the electrons, ions, and dust particles are charged, their dynamics may be significantly modified by the presence of electric and magnetic fields. Possible consequences of this modification may be the charging rate and the equilibrium charge. For example, in the presence of a strong horizontal magnetic field (B >1 Tesla), it may be possible to observe dust particle gx B deflection and, from that deflection, determine the dust grain charge. In this poster, we present recent data from performing multiple particle dropping experiments to characterize the g x B deflection in the Magnetized Dusty Plasma Experiment (MDPX). This work is supported by funding from the U. S. Department of Energy Grant Number DE - SC0010485 and the NASA/Jet Propulsion Laboratory, JPL-1543114.

Dynamics of Exploding Plasma Within a Magnetized Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dimonte, G; Dipeso, G; Hewett, D

2002-02-01

This memo describes several possible laboratory experiments on the dynamics of an exploding plasma in a background magnetized plasma. These are interesting scientifically and the results are applicable to energetic explosions in the earth's ionosphere (DOE Campaign 7 at LLNL). These proposed experiments are difficult and can only be performed in the new LAPD device at UCLA. The purpose of these experiments would be to test numerical simulations, theory and reduced models for systems performance codes. The experiments are designed to investigate the affect of the background plasma on (1) the maximum diamagnetic bubble radius given by Eq. 9; andmore » (2) the Alfven wave radiation efficiency produced by the induced current J{sub A} (Eqs. 10-12) These experiments involve measuring the bubble radius using a fast gated optical imager as in Ref [1] and the Alfven wave profile and intensity as in Ref [2] for different values of the exploding plasma energy, background plasma density and temperature, and background magnetic field. These experiments extend the previously successful experiments [2] on Alfven wave coupling. We anticipate that the proposed experiments would require 1-2 weeks of time on the LAPD. We would perform PIC simulations in support of these experiments in order to validate the codes. Once validated, the PIC simulations would then be able to be extended to realistic ionospheric conditions with various size explosions and altitudes. In addition to the Alfven wave coupling, we are interested in the magnetic containment and transport of the exploding ''debris'' plasma to see if the shorting of the radial electric field in the magnetic bubble would allow the ions to propagate further. This has important implications in an ionospheric explosion because it defines the satellite damage region. In these experiments, we would field fast gated optical cameras to obtain images of the plasma expansion, which could then be correlated with magnetic probe measurements

Production and Study of High-Beta Plasma Confined by a Superconducting Dipole Magnet

NASA Astrophysics Data System (ADS)

Garnier, Darren

2005-10-01

The Levitated Dipole Experiment (LDX)http://psfcwww2.psfc.mit.edu/ldx/ is a new research facility that is exploring the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. Unlike other configurations in which stability depends on curvature and magnetic shear, MHD stability of a dipole derives from plasma compressibility. Theoretically, the dipole magnetic geometry can stabilize a centrally-peaked plasma pressure that exceeds the local magnetic pressure (β> 1), and the absence of magnetic shear allows particle and energy confinement to decouple. In this presentation, the first experiments using the LDX facility are reported. Long-pulse, quasi-steady state microwave discharges lasting up to 12 seconds have been produced that are consistent with equilibria having peak beta values of 10%. Detailed measurements have been made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. In these initial experiments, the high-field superconducting floating coil was supported by three thin supports and later the coil will be magnetically levitated. The plasma was created by multi- frequency electron cyclotron resonance heating at 2.45 and 6.4 GHz, and a population of energetic electrons, with mean energies above 50 keV, dominated the plasma pressure. Creation of high-pressure, high-beta plasma is only possible when intense hot electron interchange instabilities are stabilized sufficiently by a high background plasma density. A dramatic transition from a low-density, low-beta regime to a more quiescent, high-beta regime is observed when the plasma-fueling rate and confinement times are sufficiently long. External shaping coils are seen to modify the outer plasma boundary and affect the transition.

Correlation Between the Magnetic Field and Plasma Parameters at 1 AU

NASA Astrophysics Data System (ADS)

Yang, Zicai; Shen, Fang; Zhang, Jie; Yang, Yi; Feng, Xueshang; Richardson, Ian G.

2018-02-01

The physical parameters of the solar wind observed in-situ near 1 AU have been studied for several decades, and relationships between them, such as the positive correlation between the solar wind plasma temperature, T, and velocity, V, and the negative correlation between density, N, and velocity, V, are well known. However, the magnetic field intensity, B, does not appear to be well correlated with any individual plasma parameter. In this article, we discuss previously under-reported correlations between B and the combined plasma parameters √{N V2} as well as between B and √{NT}. These two correlations are strong during periods of corotating interaction regions and high-speed streams, and moderate during intervals of slow solar wind. The results indicate that the magnetic pressure in the solar wind is well correlated both with the plasma dynamic pressure and the thermal pressure.

Enhancement of Quasistationary Shocks and Heating via Temporal Staging in a Magnetized Laser-Plasma Jet

DOE PAGES

Higginson, D. P.; Khiar, B.; Revet, G.; ...

2017-12-22

Here, we investigate the formation of a laser-produced magnetized jet under conditions of a varying mass ejection rate and a varying divergence of the ejected plasma flow. This is done by irradiating a solid target placed in a 20 T magnetic field with, first, a collinear precursor laser pulse (10 12 W/cm 2) and, then, a main pulse (10 13 W/cm 2) arriving 9–19 ns later. Varying the time delay between the two pulses is found to control the divergence of the expanding plasma, which is shown to increase the strength of and heating in the conical shock that ismore » responsible for jet collimation. These results show that plasma collimation due to shocks against a strong magnetic field can lead to stable, astrophysically relevant jets that are sustained over time scales 100 times the laser pulse duration (i.e., >70 ns), even in the case of strong variability at the source.« less

On Floating Potential of Emissive Probes in a Partially-Magnetized Plasma

NASA Astrophysics Data System (ADS)

Raitses, Yevgeny; Kraus, Brian

2016-10-01

We compare measurements of plasma potential in a cross-field Penning discharge from two probes: swept biased Langmuir probe and floating emissive probe. The plasma potential was deduced from the first derivative of the Langmuir probe characteristic. In previous studies, the emissive and swept biased probes were placed at the channel exit of a Hall thruster (HT). Measurements showed that the emissive probe floats below the plasma potential, in agreement with conventional theories. However, recent measurements in the Penning discharge indicate a floating potential of a strongly-emitting hot probe above the plasma potential. In both probe applications, xenon plasmas have magnetized electrons and non-magnetized ions with similar plasma densities (1010 - 1011 cm-3) . Though their electron temperatures differ by an order of magnitude (Penning 5 eV, HT 50 eV), this difference cannot explain the difference in measurement values of the hot floating potential because both temperatures are much higher than the emitting wire. In this work, we investigate how the ion velocity and other plasma parameters affect this discrepancy between probe measurements of the plasma potential. This work was supported by DOE contract DE-AC02-09CH11466.

Initial design for an experimental investigation of strongly coupled plasma behavior in the Atlas facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munson, C.P.; Benage, J.F. Jr.; Taylor, A.J.

Atlas is a high current ({approximately} 30 MA peak, with a current risetime {approximately} 4.5 {micro}sec), high energy (E{sub stored} = 24 MJ, E{sub load} = 3--6 MJ), pulsed power facility which is being constructed at Los Alamos National Laboratory with a scheduled completion date in the year 2000. When operational, this facility will provide a platform for experiments in high pressure shocks (> 20 Mbar), adiabatic compression ({rho}/{rho}{sub 0} > 5, P > 10 Mbar), high magnetic fields ({approximately} 2,000 T), high strain and strain rates ({var_epsilon} > 200%, d{var_epsilon}/dt {approximately} 10{sup 4} to 10{sup 6} s{sup {minus}1}), hydrodynamicmore » instabilities of materials in turbulent regimes, magnetized target fusion, equation of state, and strongly coupled plasmas. For the strongly coupled plasma experiments, an auxiliary capacitor bank will be used to generate a moderate density (< 0.1 solid), relatively cold ({approximately} 1 eV) plasma by ohmic heating of a conducting material of interest such as titanium. This stargate plasma will be compressed against a central column containing diagnostic instrumentation by a cylindrical conducting liner that is driven radially inward by current from the main Atlas capacitor bank. The plasma is predicted to reach densities of {approximately} 1.1 times solid, achieve ion and electron temperatures of {approximately} 10 eV, and pressures of {approximately} 4--5 Mbar. This is a density/temperature regime which is expected to experience strong coupling, but only partial degeneracy. X-ray radiography is planned for measurements of the material density at discrete times during the experiments; diamond Raman measurements are anticipated for determination of the pressure. In addition, a neutron resonance spectroscopic technique is being evaluated for possible determination of the temperature (through low percentage doping of the titanium with a suitable resonant material). Initial target plasma formation experiments

Nonthermally dominated electron acceleration during magnetic reconnection in a low- β plasma

DOE PAGES

Li, Xiaocan; Guo, Fan; Li, Hui; ...

2015-09-24

By means of fully kinetic simulations, we investigate electron acceleration during magnetic reconnection in a nonrelativistic proton–electron plasma with conditions similar to solar corona and flares. We demonstrate that reconnection leads to a nonthermally dominated electron acceleration with a power-law energy distribution in the nonrelativistic low-β regime but not in the high-β regime, where β is the ratio of the plasma thermal pressure and the magnetic pressure. The accelerated electrons contain most of the dissipated magnetic energy in the low-β regime. A guiding-center current description is used to reveal the role of electron drift motions during the bulk nonthermal energization.more » We find that the main acceleration mechanism is a Fermi-type acceleration accomplished by the particle curvature drift motion along the electric field induced by the reconnection outflows. Although the acceleration mechanism is similar for different plasma β, low-β reconnection drives fast acceleration on Alfvénic timescales and develops power laws out of thermal distribution. Thus, the nonthermally dominated acceleration resulting from magnetic reconnection in low-β plasma may have strong implications for the highly efficient electron acceleration in solar flares and other astrophysical systems.« less

Magnetic bucket for rotating unmagnetized plasma.

PubMed

Katz, Noam; Collins, Cami; Wallace, John; Clark, Mike; Weisberg, David; Jara-Almonte, Jon; Reese, Ingrid; Wahl, Carl; Forest, Cary

2012-06-01

A new experiment is described which generates flow in unmagnetized plasma. Confinement is provided by a cage of permanent magnets, arranged to form an axisymmetric, high-order, multipolar magnetic field. This field configuration-sometimes called a "magnetic bucket"-has a vanishingly small field in the core of the experiment. Toroidal rotation is driven by J × B forces applied in the magnetized edge. The cross-field current that is required for this forcing flows from anodes to thermionic cathodes, which are inserted between the magnet rings. The rotation at the edge reaches 3 km/s and is viscously coupled to the unmagnetized core plasma. We describe the conditions necessary for rotation, as well as a 0-dimensional power balance used to understand plasma confinement in the experiment.

Three-dimensional modeling of a negative ion source with a magnetic filter: impact of biasing the plasma electrode on the plasma asymmetry

NASA Astrophysics Data System (ADS)

Fubiani, G.; Boeuf, J. P.

2015-10-01

The effect on the plasma characteristics of biasing positively the plasma electrode (PE) in negative ion sources with a magnetic filter is analysed using a 3D particle-in-cell model with Monte-Carlo collisions (PIC-MCC). We specialize to the one driver (i.e. one inductively coupled radio-frequency discharge) BATMAN negative ion source and the 4-drivers (large volume) ELISE device. Both are ITER prototype high power tandem-type negative ion sources developed for the neutral beam injector (NBI) system. The plasma is generated in the driver and diffuses inside the second chamber which is magnetized. Asymmetric plasma profiles originate from the formation of an electric field transverse to the electron current flowing through the magnetic filter (Hall effect). The model shows that the importance of the asymmetry increases with the PE bias potential, i.e. with the electron flow from the driver to the extraction region and depends on the shape of the magnetic filter field. We find that although the plasma density and potential profiles may be more or less asymmetric depending on the filter field configuration, the electron current to the plasma grid is always strongly asymmetric.

Helium-like magnesium embedded in strongly coupled plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharyya, Sukhamoy

2016-05-06

In recent days, with the advent of the x-ray free electron laser (FEL) with Linac coherent light source (LCLS) and the Orion laser, experimental studies on atomic systems within strongly coupled plasma environment with remarkable improvement in accuracy as compared to earlier experiments have become possible. In these kinds of experiments, hydrogen-like and helium-like spectral lines are used for determination of plasma parameters such as temperature, density. Accurate theoretical calculations are, therefore, necessary for such kind of studies within a dense plasma environment. In this work, ab initio calculations are carried out in the framework of the Rayleigh-Ritz variation principlemore » to estimate the ground state energy of helium-like magnesium within strongly coupled plasma environment. Explicitly correlated wave functions in Hylleraas coordinates have been used to incorporate the effect of electron correlation. The ion-sphere model potential that confines the central positive ion in a finite domain filled with plasma electrons has been adopted to mimic the strongly coupled plasma environment. Thermodynamic pressure ’felt’ by the ion in the ground states due to the confinement inside the ion spheres is also estimated.« less

Effective Induction Heating around Strongly Magnetized Stars

NASA Astrophysics Data System (ADS)

Kislyakova, K. G.; Fossati, L.; Johnstone, C. P.; Noack, L.; Lüftinger, T.; Zaitsev, V. V.; Lammer, H.

2018-05-01

Planets that are embedded in the changing magnetic fields of their host stars can experience significant induction heating in their interiors caused by the planet’s orbital motion. For induction heating to be substantial, the planetary orbit has to be inclined with respect to the stellar rotation and dipole axes. Using WX UMa, for which the rotation and magnetic axes are aligned, as an example, we show that for close-in planets on inclined orbits, induction heating can be stronger than the tidal heating occurring inside Jupiter’s satellite Io; namely, it can generate a surface heat flux exceeding 2 W m‑2. An internal heating source of such magnitude can lead to extreme volcanic activity on the planet’s surface, possibly also to internal local magma oceans, and to the formation of a plasma torus around the star aligned with the planetary orbit. A strongly volcanically active planet would eject into space mostly SO2, which would then dissociate into oxygen and sulphur atoms. Young planets would also eject CO2. Oxygen would therefore be the major component of the torus. If the O I column density of the torus exceeds ≈1012 cm‑2, the torus could be revealed by detecting absorption signatures at the position of the strong far-ultraviolet O I triplet at about 1304 Å. We estimate that this condition is satisfied if the O I atoms in the torus escape the system at a velocity smaller than 1–10 km s‑1. These estimates are valid also for a tidally heated planet.

Collisionless Coupling between Explosive Debris Plasma and Magnetized Ambient Plasma

NASA Astrophysics Data System (ADS)

Bondarenko, Anton

2016-10-01

The explosive expansion of a dense debris plasma cloud into relatively tenuous, magnetized, ambient plasma characterizes a wide variety of astrophysical and space phenomena, including supernova remnants, interplanetary coronal mass ejections, and ionospheric explosions. In these rarified environments, collective electromagnetic processes rather than Coulomb collisions typically mediate the transfer of momentum and energy from the debris plasma to the ambient plasma. In an effort to better understand the detailed physics of collisionless coupling mechanisms in a reproducible laboratory setting, the present research jointly utilizes the Large Plasma Device (LAPD) and the Phoenix laser facility at UCLA to study the super-Alfvénic, quasi-perpendicular expansion of laser-produced carbon (C) and hydrogen (H) debris plasma through preformed, magnetized helium (He) ambient plasma via a variety of diagnostics, including emission spectroscopy, wavelength-filtered imaging, and magnetic field induction probes. Large Doppler shifts detected in a He II ion spectral line directly indicate initial ambient ion acceleration transverse to both the debris plasma flow and the background magnetic field, indicative of a fundamental process known as Larmor coupling. Characterization of the laser-produced debris plasma via a radiation-hydrodynamics code permits an explicit calculation of the laminar electric field in the framework of a ``hybrid'' model (kinetic ions, charge-neutralizing massless fluid electrons), thus allowing for a simulation of the initial response of a distribution of He II test ions. A synthetic Doppler-shifted spectrum constructed from the simulated velocity distribution of the accelerated test ions excellently reproduces the spectroscopic measurements, confirming the role of Larmor coupling in the debris-ambient interaction.

The influence of magnetic fields on the wake field and stopping power of an ion-beam pulse in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Xiao-ying; Zhang, Ya-ling; Duan, Wen-shan

2015-09-15

We performed two-dimensional particle-in-cell simulations to investigate how a magnetic field affects the wake field and stopping power of an ion-beam pulse moving in plasmas. The corresponding density of plasma electrons is investigated. At a weak magnetic field, the wakes exhibit typical V-shaped cone structures. As the magnetic field strengthens, the wakes spread and lose their typical V-shaped structures. At a sufficiently strong magnetic field, the wakes exhibit conversed V-shaped structures. Additionally, strengthening the magnetic field reduces the stopping power in regions of low and high beam density. However, the influence of the magnetic field becomes complicated in regions ofmore » moderate beam density. The stopping power increases in a weak magnetic field, but it decreases in a strong magnetic field. At high beam density and moderate magnetic field, two low-density channels of plasma electrons appear on both sides of the incident beam pulse trajectory. This is because electrons near the beam pulses will be attracted and move along with the beam pulses, while other electrons nearby are restricted by the magnetic field and cannot fill the gap.« less

Magnetic Flux Compression Experiments Using Plasma Armatures

NASA Technical Reports Server (NTRS)

Turner, M. W.; Hawk, C. W.; Litchford, R. J.

2003-01-01

Magnetic flux compression reaction chambers offer considerable promise for controlling the plasma flow associated with various micronuclear/chemical pulse propulsion and power schemes, primarily because they avoid thermalization with wall structures and permit multicycle operation modes. The major physical effects of concern are the diffusion of magnetic flux into the rapidly expanding plasma cloud and the development of Rayleigh-Taylor instabilities at the plasma surface, both of which can severely degrade reactor efficiency and lead to plasma-wall impact. A physical parameter of critical importance to these underlying magnetohydrodynamic (MHD) processes is the magnetic Reynolds number (R(sub m), the value of which depends upon the product of plasma electrical conductivity and velocity. Efficient flux compression requires R(sub m) less than 1, and a thorough understanding of MHD phenomena at high magnetic Reynolds numbers is essential to the reliable design and operation of practical reactors. As a means of improving this understanding, a simplified laboratory experiment has been constructed in which the plasma jet ejected from an ablative pulse plasma gun is used to investigate plasma armature interaction with magnetic fields. As a prelude to intensive study, exploratory experiments were carried out to quantify the magnetic Reynolds number characteristics of the plasma jet source. Jet velocity was deduced from time-of-flight measurements using optical probes, and electrical conductivity was measured using an inductive probing technique. Using air at 27-inHg vacuum, measured velocities approached 4.5 km/s and measured conductivities were in the range of 30 to 40 kS/m.

Relativistically strong electromagnetic radiation in a plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bulanov, S. V., E-mail: svbulanov@gmail.com, E-mail: bulanov.sergei@jaea.go.jp; Esirkepov, T. Zh.; Kando, M.

Physical processes in a plasma under the action of relativistically strong electromagnetic waves generated by high-power lasers have been briefly reviewed. These processes are of interest in view of the development of new methods for acceleration of charged particles, creation of sources of bright hard electromagnetic radiation, and investigation of macroscopic quantum-electrodynamical processes. Attention is focused on nonlinear waves in a laser plasma for the creation of compact electron accelerators. The acceleration of plasma bunches by the radiation pressure of light is the most efficient regime of ion acceleration. Coherent hard electromagnetic radiation in the relativistic plasma is generated inmore » the form of higher harmonics and/or electromagnetic pulses, which are compressed and intensified after reflection from relativistic mirrors created by nonlinear waves. In the limit of extremely strong electromagnetic waves, radiation friction, which accompanies the conversion of radiation from the optical range to the gamma range, fundamentally changes the behavior of the plasma. This process is accompanied by the production of electron–positron pairs, which is described within quantum electrodynamics theory.« less

Lithium As Plasma Facing Component for Magnetic Fusion Research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masayuki Ono

The use of lithium in magnetic fusion confinement experiments started in the 1990's in order to improve tokamak plasma performance as a low-recycling plasma-facing component (PFC). Lithium is the lightest alkali metal and it is highly chemically reactive with relevant ion species in fusion plasmas including hydrogen, deuterium, tritium, carbon, and oxygen. Because of the reactive properties, lithium can provide strong pumping for those ions. It was indeed a spectacular success in TFTR where a very small amount (~ 0.02 gram) of lithium coating of the PFCs resulted in the fusion power output to improve by nearly a factor ofmore » two. The plasma confinement also improved by a factor of two. This success was attributed to the reduced recycling of cold gas surrounding the fusion plasma due to highly reactive lithium on the wall. The plasma confinement and performance improvements have since been confirmed in a large number of fusion devices with various magnetic configurations including CDX-U/LTX (US), CPD (Japan), HT-7 (China), EAST (China), FTU (Italy), NSTX (US), T-10, T-11M (Russia), TJ-II (Spain), and RFX (Italy). Additionally, lithium was shown to broaden the plasma pressure profile in NSTX, which is advantageous in achieving high performance H-mode operation for tokamak reactors. It is also noted that even with significant applications (up to 1,000 grams in NSTX) of lithium on PFCs, very little contamination (< 0.1%) of lithium fraction in main fusion plasma core was observed even during high confinement modes. The lithium therefore appears to be a highly desirable material to be used as a plasma PFC material from the magnetic fusion plasma performance and operational point of view. An exciting development in recent years is the growing realization of lithium as a potential solution to solve the exceptionally challenging need to handle the fusion reactor divertor heat flux, which could reach 60 MW/m2 . By placing the liquid lithium (LL) surface in the path of

Generation of strong pulsed magnetic fields using a compact, short pulse generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanuka, D.; Efimov, S.; Nitishinskiy, M.

2016-04-14

The generation of strong magnetic fields (∼50 T) using single- or multi-turn coils immersed in water was studied. A pulse generator with stored energy of ∼3.6 kJ, discharge current amplitude of ∼220 kA, and rise time of ∼1.5 μs was used in these experiments. Using the advantage of water that it has a large Verdet constant, the magnetic field was measured using the non-disturbing method of Faraday rotation of a polarized collimated laser beam. This approach does not require the use of magnetic probes, which are sensitive to electromagnetic noise and damaged in each shot. It also avoids the possible formation of plasma bymore » either a flashover along the conductor or gas breakdown inside the coil caused by an induced electric field. In addition, it was shown that this approach can be used successfully to investigate the interesting phenomenon of magnetic field enhanced diffusion into a conductor.« less

Generation of strong pulsed magnetic fields using a compact, short pulse generator

NASA Astrophysics Data System (ADS)

Yanuka, D.; Efimov, S.; Nitishinskiy, M.; Rososhek, A.; Krasik, Ya. E.

2016-04-01

The generation of strong magnetic fields (˜50 T) using single- or multi-turn coils immersed in water was studied. A pulse generator with stored energy of ˜3.6 kJ, discharge current amplitude of ˜220 kA, and rise time of ˜1.5 μs was used in these experiments. Using the advantage of water that it has a large Verdet constant, the magnetic field was measured using the non-disturbing method of Faraday rotation of a polarized collimated laser beam. This approach does not require the use of magnetic probes, which are sensitive to electromagnetic noise and damaged in each shot. It also avoids the possible formation of plasma by either a flashover along the conductor or gas breakdown inside the coil caused by an induced electric field. In addition, it was shown that this approach can be used successfully to investigate the interesting phenomenon of magnetic field enhanced diffusion into a conductor.

Mass ablation and magnetic flux losses through a magnetized plasma-liner wall interface

NASA Astrophysics Data System (ADS)

García-Rubio, F.; Sanz, J.

2017-07-01

The understanding of energy and magnetic flux losses in a magnetized plasma medium confined by a cold wall is of great interest in the success of magnetized liner inertial fusion (MagLIF). In a MagLIF scheme, the fuel is magnetized and subsonically compressed by a cylindrical liner. Magnetic flux conservation is degraded by the presence of gradient-driven transport processes such as thermoelectric effects (Nernst) and magnetic field diffusion. In previous publications [Velikovich et al., Phys. Plasmas 22, 042702 (2015)], the evolution of a hot magnetized plasma in contact with a cold solid wall (liner) was studied using the classical collisional Braginskii's plasma transport equations in one dimension. The Nernst term degraded the magnetic flux conservation, while both thermal energy and magnetic flux losses were reduced with the electron Hall parameter ωeτe with a power-law asymptotic scaling (ωeτe)-1/2. In the analysis made in the present paper, we consider a similar situation, but with the liner being treated differently. Instead of a cold solid wall acting as a heat sink, we model the liner as a cold dense plasma with low thermal conduction (that could represent the cryogenic fuel layer added on the inner surface of the liner in a high-gain MagLIF configuration). Mass ablation comes into play, which adds notably differences to the previous analysis. The direction of the plasma motion is inverted, but the Nernst term still convects the magnetic field towards the liner. Magnetization suppresses the Nernst velocity and improves the magnetic flux conservation. Thermal energy in the hot plasma is lost in heating the ablated material. When the electron Hall parameter is large, mass ablation scales as (ωeτe)-3/10, while both the energy and magnetic flux losses are reduced with a power-law asymptotic scaling (ωeτe)-7/10.

MAGNETIC NULL POINTS IN KINETIC SIMULATIONS OF SPACE PLASMAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olshevsky, Vyacheslav; Innocenti, Maria Elena; Cazzola, Emanuele

2016-03-01

We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind, and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3–9.more » We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their cross sections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data.« less

Nonthermal Particle Acceleration in 3D Relativistic Magnetic Reconnection in Pair Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Werner, Gregory R.; Uzdensky, Dmitri A., E-mail: Greg.Werner@colorado.edu

As a fundamental process converting magnetic to plasma energy in high-energy astrophysical plasmas, relativistic magnetic reconnection is a leading explanation for the acceleration of particles to the ultrarelativistic energies that are necessary to power nonthermal emission (especially X-rays and gamma-rays) in pulsar magnetospheres and pulsar wind nebulae, coronae and jets of accreting black holes, and gamma-ray bursts. An important objective of plasma astrophysics is therefore the characterization of nonthermal particle acceleration (NTPA) effected by reconnection. Reconnection-powered NTPA has been demonstrated over a wide range of physical conditions using large 2D kinetic simulations. However, its robustness in realistic 3D reconnection—in particular,more » whether the 3D relativistic drift-kink instability (RDKI) disrupts NTPA—has not been systematically investigated, although pioneering 3D simulations have observed NTPA in isolated cases. Here, we present the first comprehensive study of NTPA in 3D relativistic reconnection in collisionless electron–positron plasmas, characterizing NTPA as the strength of 3D effects is varied systematically via the length in the third dimension and the strength of the guide magnetic field. We find that, while the RDKI prominently perturbs 3D reconnecting current sheets, it does not suppress particle acceleration, even for zero guide field; fully 3D reconnection robustly and efficiently produces nonthermal power-law particle spectra closely resembling those obtained in 2D. This finding provides strong support for reconnection as the key mechanism powering high-energy flares in various astrophysical systems. We also show that strong guide fields significantly inhibit NTPA, slowing reconnection and limiting the energy available for plasma energization, yielding steeper and shorter power-law spectra.« less

Simulating the interplay between plasma transport, electric field, and magnetic field in the near-earth nightside magnetosphere

NASA Astrophysics Data System (ADS)

Gkioulidou, Malamati

The convection electric field resulting from the coupling of the Earth's magnetosphere with the solar wind and interplanetary magnetic field (IMF) drives plasma in the tail plasma sheet earthward. This transport and the resulting energy storage in the near Earth plasma sheet are important for setting up the conditions that lead to major space weather disturbances, such as storms and substorms. Penetration of plasma sheet particles into the near-Earth magnetosphere in response to enhanced convection is crucial to the development of the Region 2 field-aligned current system and large-scale magnetosphere-ionosphere (M-I) coupling, which results in the shielding of the convection electric field. In addition to the electric field, plasma transport is also strongly affected by the magnetic field, which is distinctly different from dipole field in the inner plasma sheet and changes with plasma pressure in maintaining force balance. The goal of this dissertation is to investigate how the plasma transport into the inner magnetosphere is affected by the interplay between plasma, electric field and magnetic field. For this purpose, we conduct simulations using the Rice Convection Model (RCM), which self-consistently calculates the electric field resulting from M-I coupling. In order to quantitatively evaluate the interplay, we improved the RCM simulations by establishing realistic plasma sheet particle sources, by incorporating it with a modified Dungey force balance magnetic field solver (RCM-Dungey runs), and by adopting more realistic electron loss rates. We found that plasma sheet particle sources strongly affect the shielding of the convection electric field, with a hotter and more tenuous plasma sheet resulting in less shielding than a colder and denser one and thus in more earthward penetration of the plasma sheet. The Harang reversal, which is closely associated with the shielding of the convection electric field and the earthward penetration of low-energy protons, is

Magnetic field production via the Weibel instability in interpenetrating plasma flows

DOE PAGES

Huntington, C. M.; Manuel, M. J. -E.; Ross, J. S.; ...

2017-04-26

Here, many astrophysical systems are effectively “collisionless,” that is, the mean free path for collisions between particles is much longer than the size of the system. The absence of particle collisions does not preclude shock formation, however, as shocks can be the result of plasma instabilities that generate and amplify electromagnetic fields. The magnetic fields required for shock formation may either be initially present, for example, in supernova remnants or young galaxies, or they may be self-generated in systems such as gamma-ray bursts (GRBs). In the case of GRB outflows, the Weibel instability is a candidate mechanism for the generationmore » of sufficiently strong magnetic fields to produce shocks. In experiments on the OMEGA Laser, we have demonstrated a quasi-collisionless system that is optimized for the study of the non-linear phase of Weibel instability growth. Using a proton probe to directly image electromagnetic fields, we measure Weibel-generated magnetic fields that grow in opposing, initially unmagnetized plasma flows. The collisionality of the system is determined from coherent Thomson scattering measurements, and the data are compared to similar measurements of a fully collisionless system. The strong, persistent Weibel growth observed here serves as a diagnostic for exploring large-scale magnetic field amplification and the microphysics present in the collisional–collisionless transition.« less

Experimental investigation of coaxial-gun-formed plasmas injected into a background transverse magnetic field or plasma

NASA Astrophysics Data System (ADS)

Zhang, Yue; Fisher, Dustin M.; Gilmore, Mark; Hsu, Scott C.; Lynn, Alan G.

2018-05-01

Injection of coaxial-gun-formed magnetized plasmas into a background transverse vacuum magnetic field or into a background magnetized plasma has been studied in the helicon-cathode (HelCat) linear plasma device at the University of New Mexico [M. Gilmore et al., J. Plasma Phys. 81, 345810104 (2015)]. A magnetized plasma jet launched into a background transverse magnetic field shows emergent kink stabilization of the jet due to the formation of a sheared flow in the jet above the kink stabilization threshold 0.1kVA [Y. Zhang et al., Phys. Plasmas 24, 110702 (2017)]. Injection of a spheromak-like plasma into a transverse background magnetic field led to the observation of finger-like structures on the side with a stronger magnetic field null between the spheromak and the background field. The finger-like structures are consistent with magneto-Rayleigh-Taylor instability. Jets or spheromaks launched into a background, low-β magnetized plasma show similar behavior as above, respectively, in both cases.

Plasma Equilibria With Stochastic Magnetic Fields

NASA Astrophysics Data System (ADS)

Krommes, J. A.; Reiman, A. H.

2009-05-01

Plasma equilibria that include regions of stochastic magnetic fields are of interest in a variety of applications, including tokamaks with ergodic limiters and high-pressure stellarators. Such equilibria are examined theoretically, and a numerical algorithm for their construction is described.^2,3 % The balance between stochastic diffusion of magnetic lines and small effects^2 omitted from the simplest MHD description can support pressure and current profiles that need not be flattened in stochastic regions. The diffusion can be described analytically by renormalizing stochastic Langevin equations for pressure and parallel current j, with particular attention being paid to the satisfaction of the periodicity constraints in toroidal configurations with sheared magnetic fields. The equilibrium field configuration can then be constructed by coupling the prediction for j to Amp'ere's law, which is solved numerically. A. Reiman et al., Pressure-induced breaking of equilibrium flux surfaces in the W7AS stellarator, Nucl. Fusion 47, 572--8 (2007). J. A. Krommes and A. H. Reiman, Plasma equilibrium in a magnetic field with stochastic regions, submitted to Phys. Plasmas. J. A. Krommes, Fundamental statistical theories of plasma turbulence in magnetic fields, Phys. Reports 360, 1--351.

Plasma sweeper to control the coupling of RF power to a magnetically confined plasma

DOEpatents

Motley, Robert W.; Glanz, James

1985-01-01

A device for coupling RF power (a plasma sweeper) from a phased waveguide array for introducing RF power to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the phased waveguide array; and a potential source coupled to the electrode for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.

Plasma waves in the magnetic hole

NASA Technical Reports Server (NTRS)

Lin, Naiguo; Kellogg, P. J.; MacDowall, R.; Balogh, A.; Forsyth, R. J.; Phillips, J. L.; Pick, M.

1995-01-01

Magnetic holes in the solar wind, which are characterized by isolated local depressions in the magnetic field magnitude, have been observed previously. The Unified Radio and Plasma Wave (URAP) instrument of Ulysses has found that within such magnetic structures, electrostatic waves at kHz frequency and ultralow frequency electromagnetic waves are often excited and seen as short duration wave bursts. Most of these bursts occur near the ambient electron plasma frequency, which suggests that the waves are Langmuir waves. Such waves are usually excited by electron streams. Some evidence of the streaming of energetic electrons required for exciting Langmuir waves has been observed. These electrons may have originated at sources near the Sun, which would imply that the magnetic structures containing the waves would exist as long channels formed by field and plasma conditions near the Sun. On the other hand, the electrons could be suprathermal 'tails' from wave collapse processes occurring near the spacecraft. In either case, the Langmuir waves excited in the magnetic holes provide a measurement of the plasma density inside the holes. Low frequency electromagnetic waves, having frequencies of a fraction of the local electron cyclotron frequency, sometimes accompany the Langmuir waves observed in magnetic holes. Waves excited in this frequency range are very likely to be whistler-mode waves. They may have been excited by an electron temperature anisotropy which has been observed in the vicinity of the magnetic holes or generated through the decay of Langmuir waves.

Robust GRMHD Evolutions of Merging Black-Hole Binaries in Magnetized Plasma

NASA Astrophysics Data System (ADS)

Kelly, Bernard; Etienne, Zachariah; Giacomazzo, Bruno; Baker, John

2016-03-01

Black-hole binary (BHB) mergers are expected to be powerful sources of gravitational radiation at stellar and galactic scales. A typical astrophysical environment for these mergers will involve magnetized plasmas accreting onto each hole; the strong-field gravitational dynamics of the merger may churn this plasma in ways that produce characteristic electromagnetic radiation visible to high-energy EM detectors on and above the Earth. Here we return to a cutting-edge GRMHD simulation of equal-mass BHBs in a uniform plasma, originally performed with the Whisky code. Our new tool is the recently released IllinoisGRMHD, a compact, highly-optimized ideal GRMHD code that meshes with the Einstein Toolkit. We establish consistency of IllinoisGRMHD results with the older Whisky results, and investigate the robustness of these results to changes in initial configuration of the BHB and the plasma magnetic field, and discuss the interpretation of the ``jet-like'' features seen in the Poynting flux post-merger. Work supported in part by NASA Grant 13-ATP13-0077.

Electric flux tube in a magnetic plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liao Jinfeng; Shuryak, Edward

2008-06-15

In this paper we study a methodical problem related to the magnetic scenario recently suggested and initiated by Liao and Shuryak [Phys. Rev. C 75, 054907 (2007)] to understand the strongly coupled quark-gluon plasma (sQGP): the electric flux tube in a monopole plasma. A macroscopic approach, in which we interpolate between a Bose condensed (dual superconductor) medium and a classical gas medium, is developed first. Then we work out a microscopic approach based on detailed quantum mechanical calculations of the monopole scattering on the electric flux tube, evaluating induced currents for all partial waves. As expected, the flux tube losesmore » its stability when particles can penetrate it: We make this condition precise by calculating the critical value for the product of the flux tube size times the particle momentum, above which the flux tube dissolves. Lattice static potentials indicate that flux tubes seem to dissolve at T>T{sub dissolution}{approx_equal}1.3T{sub c}. Using our criterion one gets an estimate of the magnetic density n{approx_equal}4.4-6.6 fm{sup -3} at this temperature.« less

Anomalous transport of charged dust grains in a magnetized collisional plasma: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Bezbaruah, Pratikshya; Das, Nilakshi

2018-05-01

Anomalous diffusion of charged dust grains immersed in a plasma in the presence of strong ion-neutral collision, flowing ions, and a magnetic field has been observed. Molecular Dynamics simulation confirms the deviation from normal diffusion in an ensemble of dust grains probed in laboratory plasma chambers. Collisional effects are significant in governing the nature of diffusion. In order to have a clear idea on the transport of particles in a real experimental situation, the contribution of streaming ions and the magnetic field along with collision is considered through the relevant interaction potential. The nonlinear evolution of Mean Square Displacement is an indication of the modification in particle trajectories due to several effects as mentioned above. It is found that strong collision and ion flow significantly affect the interparticle interaction potential in the presence of the magnetic field and lead to the appearance of the asymmetric type of Debye Hückel (D H) potential. Due to the combined effect of the magnetic field, ion flow, and collision, dusty plasma exhibits a completely novel behavior. The coupling parameter Γ enhances the asymmetric D H type potential arising due to ion flow, and this may drive the system to a disordered state.

Ion-Flow-Induced Excitation of Electrostatic Cyclotron Mode in Magnetized Dusty Plasma

NASA Astrophysics Data System (ADS)

Bezbaruah, P.; Das, N.

2018-05-01

The stability of electrostatic cyclotron mode is investigated in a flowing magnetized dusty plasma in the presence of strong ion-neutral collisions. In the high magnetic field limit, when the dust magnetization becomes important, it is expected that the collective behavior of magnetized dust grains suspended in the near-sheath region substantially influences the dispersion properties of electrostatic modes. The growth/damping of the collective excitation is significantly controlled by such parameters as the ion-neutral collision frequency, Mach number, and magnetic field strength. In our case, the explicit dependence of the Mach number on the magnetic field and collision frequency has been taken into account and possible implications on the stability of the mode is analyzed. Streaming instability of cyclotron modes may be important to understand issues related to the interaction mechanism between dust grains and other associated phenomena like Coulomb crystallization, phase behavior, transport properties, etc., in the relatively strong magnetic field limit, which is currently accessible in the DPD (Kiel University) and MDPX (PSL, Auburn University) experiments.

Interaction of rotating helical magnetic field with the HIST spherical torus plasmas

NASA Astrophysics Data System (ADS)

Kikuchi, Yusuke; Sugahara, Masato; Yamada, Satoshi; Yoshikawa, Tatsuya; Fukumoto, Naoyuki; Nagata, Masayoshi

2006-10-01

The physical mechanism of current drive by co-axial helicity injection (CHI) has been experimentally investigated on both spheromak and spherical torus (ST) configurations on the HIST device [1]. It has been observed that the n = 1 kink mode rotates toroidally with a frequency of 10-20 kHz in the ExB direction. It seems that the induced toroidal current by CHI strongly relates with the observed rotating kink mode. On the other hand, it is well known that MHD instabilities can be controlled or even suppressed by an externally applied helical magnetic field in tokamak devices. Therefore, we have started to install two sets of external helical coils in order to produce a rotating helical magnetic field on HIST. Mode structures of the generated rotating helical magnetic field and preliminary experimental results of the interaction of the rotating helical magnetic field with the HIST plasmas will be shown in the conference. [1] M. Nagata, et al., Physics of Plasmas 10, 2932 (2003)

Characterization of high flux magnetized helium plasma in SCU-PSI linear device

NASA Astrophysics Data System (ADS)

Xiaochun, MA; Xiaogang, CAO; Lei, HAN; Zhiyan, ZHANG; Jianjun, WEI; Fujun, GOU

2018-02-01

A high-flux linear plasma device in Sichuan University plasma-surface interaction (SCU-PSI) based on a cascaded arc source has been established to simulate the interactions between helium and hydrogen plasma with the plasma-facing components in fusion reactors. In this paper, the helium plasma has been characterized by a double-pin Langmuir probe. The results show that the stable helium plasma beam with a diameter of 26 mm was constrained very well at a magnetic field strength of 0.3 T. The core density and ion flux of helium plasma have a strong dependence on the applied current, magnetic field strength and gas flow rate. It could reach an electron density of 1.2 × 1019 m-3 and helium ion flux of 3.2 × 1022 m-2 s-1, with a gas flow rate of 4 standard liter per minute, magnetic field strength of 0.2 T and input power of 11 kW. With the addition of -80 V applied to the target to increase the helium ion energy and the exposure time of 2 h, the flat top temperature reached about 530 °C. The different sizes of nanostructured fuzz on irradiated tungsten and molybdenum samples surfaces under the bombardment of helium ions were observed by scanning electron microscopy. These results measured in the SCU-PSI linear device provide a reference for International Thermonuclear Experimental Reactor related PSI research.

Radial Distribution Functions of Strongly Coupled Two-Temperature Plasmas

NASA Astrophysics Data System (ADS)

Shaffer, Nathaniel R.; Tiwari, Sanat Kumar; Baalrud, Scott D.

2017-10-01

We present tests of three theoretical models for the radial distribution functions (RDFs) in two-temperature strongly coupled plasmas. RDFs are useful in extending plasma thermodynamics and kinetic theory to strong coupling, but they are usually known only for thermal equilibrium or for approximate one-component model plasmas. Accurate two-component modeling is necessary to understand the impact of strong coupling on inter-species transport, e.g., ambipolar diffusion and electron-ion temperature relaxation. We demonstrate that the Seuferling-Vogel-Toeppfer (SVT) extension of the hypernetted chain equations not only gives accurate RDFs (as compared with classical molecular dynamics simulations), but also has a simple connection with the Yukawa OCP model. This connection gives a practical means to recover the structure of the electron background from knowledge of the ion-ion RDF alone. Using the model RDFs in Effective Potential Theory, we report the first predictions of inter-species transport coefficients of strongly coupled plasmas far from equilibrium. This work is supported by NSF Grant No. PHY-1453736, AFSOR Award No. FA9550-16-1-0221, and used XSEDE computational resources.

Plasma membrane isolation using immobilized concanavalin A magnetic beads.

PubMed

Lee, Yu-Chen; Srajer Gajdosik, Martina; Josic, Djuro; Lin, Sue-Hwa

2012-01-01

Isolation of highly purified plasma membranes is the key step in constructing the plasma membrane proteome. Traditional plasma membrane isolation method takes advantage of the differential density of organelles. While differential centrifugation methods are sufficient to enrich for plasma membranes, the procedure is lengthy and results in low recovery of the membrane fraction. Importantly, there is significant contamination of the plasma membranes with other organelles. The traditional agarose affinity matrix is suitable for isolating proteins but has limitation in separating organelles due to the density of agarose. Immobilization of affinity ligands to magnetic beads allows separation of affinity matrix from organelles through magnets and could be developed for the isolation of organelles. We have developed a simple method for isolating plasma membranes using lectin concanavalin A (ConA) magnetic beads. ConA is immobilized onto magnetic beads by binding biotinylated ConA to streptavidin magnetic beads. The ConA magnetic beads are used to bind glycosylated proteins present in the membranes. The bound membranes are solubilized from the magnetic beads with a detergent containing the competing sugar alpha methyl mannoside. In this study, we describe the procedure of isolating rat liver plasma membranes using sucrose density gradient centrifugation as described by Neville. We then further purify the membrane fraction by using ConA magnetic beads. After this purification step, main liver plasma membrane proteins, especially the highly glycosylated ones and proteins containing transmembrane domains could be identified by LC-ESI-MS/MS. While not described here, the magnetic bead method can also be used to isolate plasma membranes from cell lysates. This membrane purification method should expedite the cataloging of plasma membrane proteome.

Tomography of a simply magnetized toroidal plasma

NASA Astrophysics Data System (ADS)

Ruggero, BARNI; Stefano, CALDIROLA; Luca, FATTORINI; Claudia, RICCARDI

2018-02-01

Optical emission spectroscopy is a passive diagnostic technique, which does not perturb the plasma state. In particular, in a hydrogen plasma, Balmer-alpha (H α ) emission can be easily measured in the visible range along a line of sight from outside the plasma vessel. Other emission lines in the visible spectral range from hydrogen atoms and molecules can be exploited too, in order to gather complementary pieces of information on the plasma state. Tomography allows us to capture bi-dimensional structures. We propose to adopt an emission spectroscopy tomography for studying the transverse profiles of magnetized plasmas when Abel inversion is not exploitable. An experimental campaign was carried out at the Thorello device, a simple magnetized torus. The characteristics of the profile extraction method, which we implemented for this purpose are discussed, together with a few results concerning the plasma profiles in a simply magnetized torus configuration.

Stability properties of a thin relativistic beam propagation in a magnetized plasma

NASA Astrophysics Data System (ADS)

Jovanović, Dušan; Fedele, Renato; Belić, Milivoj; De Nicola, Sergio; Akhter, Tamina

2018-05-01

A self-consistent nonlinear hydrodynamic theory is presented of the propagation of a long and thin relativistic electron beam through a plasma that is relatively strongly magnetized. Such situation is encountered when the gyro-frequency is comparable to the plasma frequency, i.e. |Ω e | ω pe . In addition, it is assumed the plasma density is much bigger than that of the beam. In the regime when the solution propagates in the comoving frame with a velocity that is much smaller than the thermal speed, a nonlinear stationary beam structure is found in which the electron motion in the transverse direction is negligible and whose transverse localization comes from the nonlinearity associated with its 3-D adiabatic expansion. Conversely, when the parallel velocity of the structure is sufficiently large to prevent the heat convection along the magnetic field, a helicoidally shaped stationary solution is found that is governed by the transverse convective nonlinearity. The profile of such beam is determined from a nonlinear dispersion relation and depends on the transverse size of the beam and its pitch angle to the magnetic field.

Penetration of Magnetosheath Plasma into Dayside Magnetosphere. 2. ; Magnetic Field in Plasma Filaments

NASA Technical Reports Server (NTRS)

Lyatsky, Wladislaw; Pollock, Craig; Goldstein, Melvyn L.; Lyatskaya, Sonya Inna; Avanov, Levon Albert

2016-01-01

In this paper, we examined plasma structures (filaments), observed in the dayside magnetosphere but containing magnetosheath plasma. These filaments show the stable antisunward motion (while the ambient magnetospheric plasma moved in the opposite direction) and the existence of a strip of magnetospheric plasma, separating these filaments from the magnetosheath. These results, however, contradict both theoretical studies and simulations by Schindler (1979), Ma et al. (1991), Dai and Woodward (1994, 1998), and other researchers, who reported that the motion of such filaments through the magnetosphere is possible only when their magnetic field is directed very close to the ambient magnetic field, which is not the situation that is observed. In this study, we show that this seeming contradiction may be related to different events as the theoretical studies and simulations are related to the case when the filament magnetic field is about aligned with filament orientation, whereas the observations show that the magnetic field in these filaments may be rotating. In this case, the rotating magnetic field, changing incessantly its direction, drastically affects the penetration of plasma filaments into the magnetosphere. In this case, the filaments with rotating magnetic field, even if in each moment it is significantly inclined to the ambient magnetic field, may propagate through the magnetosphere, if their average (for the rotation period) magnetic field is aligned with the ambient magnetic field. This shows that neglecting the rotation of magnetic field in these filaments may lead to wrong results.

First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

NASA Astrophysics Data System (ADS)

Berdyugina, S. V.; Harrington, D. M.; Kuzmychov, O.; Kuhn, J. R.; Hallinan, G.; Kowalski, A. F.; Hawley, S. L.

2017-09-01

We report the first direct detection of a strong, 5 kG magnetic field on the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting transient radio and optical emission bursts modulated by fast rotation. We have detected the surface magnetic field as circularly polarized signatures in the 819 nm sodium lines when an active emission region faced the Earth. Modeling Stokes profiles of these lines reveals the effective temperature of 2800 K and log gravity acceleration of 4.5. These parameters place LSR J1835+3259 on evolutionary tracks as a young brown dwarf with the mass of 55+/- 4{M}{{J}} and age of 22 ± 4 Myr. Its magnetic field is at least 5.1 kG and covers at least 11% of the visible hemisphere. The active region topology recovered using line profile inversions comprises hot plasma loops with a vertical stratification of optical and radio emission sources. These loops rotate with the dwarf in and out of view causing periodic emission bursts. The magnetic field is detected at the base of the loops. This is the first time that we can quantitatively associate brown dwarf non-thermal bursts with a strong, 5 kG surface magnetic field and solve the puzzle of their driving mechanism. This is also the coolest known dwarf with such a strong surface magnetic field. The young age of LSR J1835+3259 implies that it may still maintain a disk, which may facilitate bursts via magnetospheric accretion, like in higher-mass T Tau-type stars. Our results pave a path toward magnetic studies of brown dwarfs and hot Jupiters.

Magnetic reconnection in plasma under inertial confinement fusion conditions driven by heat flux effects in Ohm's law.

PubMed

Joglekar, A S; Thomas, A G R; Fox, W; Bhattacharjee, A

2014-03-14

In the interaction of high-power laser beams with solid density plasma there are a number of mechanisms that generate strong magnetic fields. Such fields subsequently inhibit or redirect electron flows, but can themselves be advected by heat fluxes, resulting in complex interplay between thermal transport and magnetic fields. We show that for heating by multiple laser spots reconnection of magnetic field lines can occur, mediated by these heat fluxes, using a fully implicit 2D Vlasov-Fokker-Planck code. Under such conditions, the reconnection rate is dictated by heat flows rather than Alfvènic flows. We find that this mechanism is only relevant in a high β plasma. However, the Hall parameter ωcτei can be large so that thermal transport is strongly modified by these magnetic fields, which can impact longer time scale temperature homogeneity and ion dynamics in the system.

Megagauss magnetic fields in ultra-intense laser generated dense plasmas

NASA Astrophysics Data System (ADS)

Shaikh, Moniruzzaman; Lad, Amit D.; Jana, Kamalesh; Sarkar, Deep; Dey, Indranuj; Kumar, G. Ravindra

2017-01-01

Table-top terawatt lasers can create relativistic light intensities and launch megaampere electron pulses in a solid. These pulses induce megagauss (MG) magnetic pulses, which in turn strongly affect the hot electron transport via electromagnetic instabilities. It is therefore crucial to characterize the MG magnetic fields in great detail. Here, we present measurements of the spatio-temporal evolution of MG magnetic fields produced by a high contrast (picosecond intensity contrast 10-9) laser in a dense plasma on a solid target. The MG magnetic field is measured using the magneto-optic Cotton-Mouton effect, with a time delayed second harmonic (400 nm) probe. The magnetic pulse created by the high contrast laser in a glass target peaks much faster and has a more rapid fall than that induced by a low contrast (10-6) laser.

Optimization of the Magnetic Field Structure for Sustained Plasma Gun Helicity Injection for Magnetic Turbulence Studies at the Bryn Mawr Plasma Laboratory

NASA Astrophysics Data System (ADS)

Cartagena-Sanchez, C. A.; Schaffner, D. A.; Johnson, H. K.; Fahim, L. E.

2017-10-01

A long-pulsed magnetic coaxial plasma gun is being implemented and characterized at the Bryn Mawr Plasma Laboratory (BMPL). A cold cathode discharged between the cylindrical electrodes generates and launches plasma into a 24cm diameter, 2m long chamber. Three separately pulsed magnetic coils are carefully positioned to generate radial magnetic field between the electrodes at the gun edge in order to provide stuffing field. Magnetic helicity is continuously injected into the flux-conserving vacuum chamber in a process akin to sustained slow-formation of spheromaks. The aim of this source, however, is to supply long pulses of turbulent magnetized plasma for measurement rather than for sustained spheromak production. The work shown here details the optimization of the magnetic field structure for this sustained helicity injection.

Suppression of runaway electrons with a resonant magnetic perturbation in MST tokamak plasmas

NASA Astrophysics Data System (ADS)

Munaretto, Stefano; Chapman, B. E.; Almagri, A. F.; Cornille, B. S.; Dubois, A. M.; Goetz, J. A.; McCollam, K. J.; Sovinec, C. R.

2016-10-01

Runaway electrons generated in MST tokamak plasmas are now being probed with resonant magnetic perturbations (RMP's). An RMP with m =3 strongly suppresses the runaway electrons. Initial modeling of these plasmas with NIMROD shows the degradation of flux surfaces with an m =3 RMP, which may account for the runaway electron suppression. These MST tokamak plasmas have Bt =0.14 T, Ip =50kA, and q(a) =2.2, with a bulk electron density and temperature of 5x1017 m-3 and 150 eV. Runaway electrons are detected via x-ray emission. The RMP is produced by a poloidal array of 32 saddle coils at the narrow vertical insulated cut in MST's thick conducting shell. Each RMP has a single m but a broad n spectrum. A sufficiently strong m =3 RMP completely suppresses the runaway electrons, while a comparable m =1 RMP has little effect. The impact of the RMP's on the magnetic topology of these plasmas is being studied with the nonlinear MHD code, NIMROD. With an m =3 RMP, stochasticity is introduced in the outer third of the plasma. No such change is observed with the m =1 RMP. NIMROD also predicts regularly occurring sawtooth oscillations with a period comparable to MHD activity observed in the experiment. Work supported by USDOE.

Development of a Rotating Magnetized Plasma Device

NASA Astrophysics Data System (ADS)

Cooke, David; Patton, James; Reid, Remington; Stiles, Ashley; Morrison, Patrik; Koch, Andrei

2017-10-01

Momentum coupling in plasma is a mechanism that is central to a wide range of interesting and important phenomena, magnetosphere-ionosphere coupling, solar eruptions, the interaction of an electro-dynamic tether system in the Earth's ionosphere, and the Critical Ionization Velocity (CIV) mechanism are a few examples. One result of the Space Shuttle Tethered Satellite experiment, TSS-1R, was that the current-voltage response of the experiment in all orbit conditions fell into a narrow range of curves when parameterized as a plasma probe [Thompson, GRL,1998]. Another striking result was the lack of dependence on the Alfvén velocity or other electro-magnetic parameters. This result has led us to revisit the understanding of the speed with which an electric field propagates along the magnetic field using EM-PIC simulation and experiments in our new magnetized plasma chamber. Our initial experiment is a rotating plasma using a solenoidal magnetic field and a radial electric field, with pulsed differential rotation of the plasma column to study the strength of coupling and propagation speed. Characteristics of our `first light' rotating plasma will be presented. Supported by Air Force Office Scientific Research 16RVCOR264.

Comptonization in Ultra-Strong Magnetic Fields: Numerical Solution to the Radiative Transfer Problem

NASA Technical Reports Server (NTRS)

Ceccobello, C.; Farinelli, R.; Titarchuk, L.

2014-01-01

We consider the radiative transfer problem in a plane-parallel slab of thermal electrons in the presence of an ultra-strong magnetic field (B approximately greater than B(sub c) approx. = 4.4 x 10(exp 13) G). Under these conditions, the magnetic field behaves like a birefringent medium for the propagating photons, and the electromagnetic radiation is split into two polarization modes, ordinary and extraordinary, that have different cross-sections. When the optical depth of the slab is large, the ordinary-mode photons are strongly Comptonized and the photon field is dominated by an isotropic component. Aims. The radiative transfer problem in strong magnetic fields presents many mathematical issues and analytical or numerical solutions can be obtained only under some given approximations. We investigate this problem both from the analytical and numerical point of view, provide a test of the previous analytical estimates, and extend these results with numerical techniques. Methods. We consider here the case of low temperature black-body photons propagating in a sub-relativistic temperature plasma, which allows us to deal with a semi-Fokker-Planck approximation of the radiative transfer equation. The problem can then be treated with the variable separation method, and we use a numerical technique to find solutions to the eigenvalue problem in the case of a singular kernel of the space operator. The singularity of the space kernel is the result of the strong angular dependence of the electron cross-section in the presence of a strong magnetic field. Results. We provide the numerical solution obtained for eigenvalues and eigenfunctions of the space operator, and the emerging Comptonization spectrum of the ordinary-mode photons for any eigenvalue of the space equation and for energies significantly lesser than the cyclotron energy, which is on the order of MeV for the intensity of the magnetic field here considered. Conclusions. We derived the specific intensity of the

Integrity of the Plasma Magnetic Nozzle

NASA Technical Reports Server (NTRS)

Gerwin, Richard A.

2009-01-01

This report examines the physics governing certain aspects of plasma propellant flow through a magnetic nozzle, specifically the integrity of the interface between the plasma and the nozzle s magnetic field. The injection of 100s of eV plasma into a magnetic flux nozzle that converts thermal energy into directed thrust is fundamental to enabling 10 000s of seconds specific impulse and 10s of kW/kg specific power piloted interplanetary propulsion. An expression for the initial thickness of the interface is derived and found to be approx.10(exp -2) m. An algorithm is reviewed and applied to compare classical resistivity to gradient-driven microturbulent (anomalous) resistivity, in terms of the spatial rate and time integral of resistive interface broadening, which can then be related to the geometry of the nozzle. An algorithm characterizing plasma temperature, density, and velocity dependencies is derived and found to be comparable to classical resistivity at local plasma temperatures of approx. 200 eV. Macroscopic flute-mode instabilities in regions of "adverse magnetic curvature" are discussed; a growth rate formula is derived and found to be one to two e-foldings of the most unstable Rayleigh-Taylor (RT) mode. After establishing the necessity of incorporating the Hall effect into Ohm s law (allowing full Hall current to flow and concomitant plasma rotation), a critical nozzle length expression is derived in which the interface thickness is limited to about 1 ion gyroradius.

Dust dynamics and diagnostic applications in quasi-neutral plasmas and magnetic fusion

NASA Astrophysics Data System (ADS)

Wang, Zhehui; Ticos, Catalin M.; Si, Jiahe; Delzanno, Gian Luca; Lapenta, Gianni; Wurden, Glen

2007-11-01

Little is known about dust dynamics in highly ionized quasi-neutral plasmas with ca. 1.0 e+20 per cubic meter density and ion temperature at a few eV and above, including in magnetic fusion. For example, dust motion in fusion, better known as UFO's, has been observed since 1980's but not explained. Solid understanding of dust dynamics is also important to International Thermonuclear Experimental Reactor (ITER) because of concerns about safety and dust contamination of fusion core. Compared with well studied strongly-coupled dusty plasma regime, new physics may arise in the higher density quasi-neutral plasma regime because of at least four orders of magnitude higher density and two orders of magnitude hotter ion temperature. Our recent laboratory experiments showed that plasma-flow drag force dominates over other forces in a quasi-neutral flowing plasma. In contrast, delicate balance among different forces in dusty plasma has led to many unique phenomena, in particular, the formation of dust crystal. Based on our experiments, we argue that 1) dust crystal will not form in the highly ionized plasmas with flows; 2) the UFO's are moving dust dragged by plasma flows; 3) dust can be used to measure plasma flow. Two diagnostic applications using dust for laboratory quasi-neutral plasmas and magnetic fusion will also be presented.

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field.

PubMed

Patel, A D; Sharma, M; Ramasubramanian, N; Ganesh, R; Chattopadhyay, P K

2018-04-01

A new multi-line cusp magnetic field plasma device consisting of electromagnets with core material has been constructed with a capability to experimentally control the relative volume fractions of magnetized to unmagnetized plasma volume as well as accurate control on the gradient length scales of mean density and temperature profiles. Argon plasma has been produced using a hot tungsten cathode over a wide range of pressures 5 × 10 -5 -1 × 10 -3 mbar, achieving plasma densities ranging from 10 9 to 10 11 cm -3 and the electron temperature in the range 1-8 eV. The radial profiles of plasma parameters measured along the non-cusp region (in between two consecutive magnets) show a finite region with uniform and quiescent plasma, where the magnetic field is very low such that the ions are unmagnetized. Beyond that region, both plasma species are magnetized and the profiles show gradients both in temperature and density. The electrostatic fluctuation measured using a Langmuir probe radially along the non-cusp region shows less than 1% (δI isat /I isat < 1%). The plasma thus produced will be used to study new and hitherto unexplored physics parameter space relevant to both laboratory multi-scale plasmas and astrophysical plasmas.

A new multi-line cusp magnetic field plasma device (MPD) with variable magnetic field

NASA Astrophysics Data System (ADS)

Patel, A. D.; Sharma, M.; Ramasubramanian, N.; Ganesh, R.; Chattopadhyay, P. K.

2018-04-01

A new multi-line cusp magnetic field plasma device consisting of electromagnets with core material has been constructed with a capability to experimentally control the relative volume fractions of magnetized to unmagnetized plasma volume as well as accurate control on the gradient length scales of mean density and temperature profiles. Argon plasma has been produced using a hot tungsten cathode over a wide range of pressures 5 × 10-5 -1 × 10-3 mbar, achieving plasma densities ranging from 109 to 1011 cm-3 and the electron temperature in the range 1-8 eV. The radial profiles of plasma parameters measured along the non-cusp region (in between two consecutive magnets) show a finite region with uniform and quiescent plasma, where the magnetic field is very low such that the ions are unmagnetized. Beyond that region, both plasma species are magnetized and the profiles show gradients both in temperature and density. The electrostatic fluctuation measured using a Langmuir probe radially along the non-cusp region shows less than 1% (δIisat/Iisat < 1%). The plasma thus produced will be used to study new and hitherto unexplored physics parameter space relevant to both laboratory multi-scale plasmas and astrophysical plasmas.

Experimental measurement of self-diffusion in a strongly coupled plasma

DOE PAGES

Strickler, Trevor S.; Langin, Thomas K.; McQuillen, Paul; ...

2016-05-17

Here, we present a study of the collisional relaxation of ion velocities in a strongly coupled, ultracold neutral plasma on short time scales compared to the inverse collision rate. The measured average velocity of a tagged population of ions is shown to be equivalent to the ion-velocity autocorrelation function. We thus gain access to fundamental aspects of the single-particle dynamics in strongly coupled plasmas and to the ion self-diffusion constant under conditions where experimental measurements have been lacking. Nonexponential decay towards equilibrium of the average velocity heralds non-Markovian dynamics that are not predicted by traditional descriptions of weakly coupled plasmas.more » This demonstrates the utility of ultracold neutral plasmas for studying the effects of strong coupling on collisional processes, which is of interest for dense laboratory and astrophysical plasmas.« less

Effect of electron reflection on magnetized plasma sheath in an oblique magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ting-Ting; Ma, J. X., E-mail: jxma@ustc.edu.cn; Wei, Zi-An

Magnetized plasma sheaths in an oblique magnetic field were extensively investigated by conventionally assuming Boltzmann relation for electron density. This article presents the study of the magnetized sheath without using the Boltzmann relation but by considering the electron reflection along the magnetic field lines caused by the negative sheath potential. A generalized Bohm criterion is analytically derived, and sheath profiles are numerically obtained, which are compared with the results of the conventional model. The results show that the ion Mach number at the sheath edge normal to the wall has a strong dependence on the wall potential, which differs significantlymore » from the conventional model in which the Mach number is independent of the wall potential. The floating wall potential is lower in the present model than that in the conventional model. Furthermore, the sheath profiles are appreciably narrower in the present model when the wall bias is low, but approach the result of the conventional model when the wall bias is high. The sheath thickness decreases with the increase of ion-to-electron temperature ratio and magnetic field strength but has a complex relationship with the angle of the magnetic field.« less

Experimental investigation of plasma relaxation using a compact coaxial magnetized plasma gun in a background plasma

NASA Astrophysics Data System (ADS)

Zhang, Yue; Lynn, Alan; Gilmore, Mark; Hsu, Scott; University of New Mexico Collaboration; Los Alamos National Laboratory Collaboration

2013-10-01

A compact coaxial plasma gun is employed for experimental studies of plasma relaxation in a low density background plasma. Experiments are being conducted in the linear HelCat device at UNM. These studies will advance the knowledge of basic plasma physics in the areas of magnetic relaxation and space and astrophysical plasmas, including the evolution of active galactic jets/radio lobes within the intergalactic medium. The gun is powered by a 120pF ignitron-switched capacitor bank which is operated in a range of 5-10 kV and ~100 kA. Multiple diagnostics are employed to investigate plasma relaxation process. Magnetized Argon plasma bubbles with velocities ~1.2Cs and densities ~1020 m-3 have been achieved. Different distinct regimes of operation with qualitatively different dynamics are identified by fast CCD camera images, with the parameter determining the operation regime. Additionally, a B-dot probe array is employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify detached plasma bubble configurations. Experimental data and analysis will be presented.

Strong Static Magnetic Fields Increase the Gel Signal in Partially Hydrated DPPC/DMPC Membranes.

PubMed

Tang, Jennifer; Alsop, Richard J; Schmalzl, Karin; Epand, Richard M; Rheinstädter, Maikel C

2015-09-29

NIt was recently reported that static magnetic fields increase lipid order in the hydrophobic membrane core of dehydrated native plant plasma membranes [Poinapen, Soft Matter 9:6804-6813, 2013]. As plasma membranes are multicomponent, highly complex structures, in order to elucidate the origin of this effect, we prepared model membranes consisting of a lipid species with low and high melting temperature. By controlling the temperature, bilayers coexisting of small gel and fluid domains were prepared as a basic model for the plasma membrane core. We studied molecular order in mixed lipid membranes made of dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) using neutron diffraction in the presence of strong static magnetic fields up to 3.5 T. The contribution of the hydrophobic membrane core was highlighted through deuterium labeling the lipid acyl chains. There was no observable effect on lipid organization in fluid or gel domains at high hydration of the membranes. However, lipid order was found to be enhanced at a reduced relative humidity of 43%: a magnetic field of 3.5 T led to an increase of the gel signal in the diffraction patterns of 5%. While all biological materials have weak diamagnetic properties, the corresponding energy is too small to compete against thermal disorder or viscous effects in the case of lipid molecules. We tentatively propose that the interaction between the fatty acid chains' electric moment and the external magnetic field is driving the lipid tails in the hydrophobic membrane core into a better ordered state.

A plasma generator utilizing the high intensity ASTROMAG magnets

NASA Technical Reports Server (NTRS)

Sullivan, James D.; Post, R. S.; Lane, B. G.; Tarrh, J. M.

1986-01-01

The magnet configuration for the proposed particle astrophysics magnet facility (ASTROMAG) on the space station includes a cusp magnetic field with an intensity of a few tesla. With these large magnets (or others) located in the outer ionosphere, many quite interesting and unique plasma physics experiments become possible. First there are studies utilizing the magnet alone to examine the supersonic, sub-Alfvenic interaction with the ambient medium; the scale length for the magnet perturbation is approx. 20 m. The magnetic field geometry when combined with the Earth's and their relative motion will give rise to a host of plasma phenomena: ring nulls, x-points, ion-acoustic and lower-hybrid shocks, electron heating (possible shuttle glow without a surface) launching of Alfvenwaves, etc. Second, active experiments are possible for a controlled study of fundamental plasma phenomena. A controlled variable species plasma can be made by using an RF ion source; use of two soft iron rings placed about the line cusp would give an adequate resonance zone (ECH or ICH) and a confining volume suitable for gas efficiency. The emanating plasma can be used to study free expansion of plasma along and across field lines (polar wind), plasma flows around the space platform, turbulent mixing in the wake region, long wavelength spectrum of convecting modes, plasma-dust interactions, etc.

Kinetic treatment of nonlinear magnetized plasma motions - General geometry and parallel waves

NASA Technical Reports Server (NTRS)

Khabibrakhmanov, I. KH.; Galinskii, V. L.; Verheest, F.

1992-01-01

The expansion of kinetic equations in the limit of a strong magnetic field is presented. This gives a natural description of the motions of magnetized plasmas, which are slow compared to the particle gyroperiods and gyroradii. Although the approach is 3D, this very general result is used only to focus on the parallel propagation of nonlinear Alfven waves. The derivative nonlinear Schroedinger-like equation is obtained. Two new terms occur compared to earlier treatments, a nonlinear term proportional to the heat flux along the magnetic field line and a higher-order dispersive term. It is shown that kinetic description avoids the singularities occurring in magnetohydrodynamic or multifluid approaches, which correspond to the degenerate case of sound speeds equal to the Alfven speed, and that parallel heat fluxes cannot be neglected, not even in the case of low parallel plasma beta. A truly stationary soliton solution is derived.

Effect of self-consistent magnetic field on plasma sheet penetration to the inner magnetosphere under enhanced convection: RCM simulations combined with force-balance magnetic field solver

NASA Astrophysics Data System (ADS)

Gkioulidou, M.; Wang, C.; Lyons, L. R.; Wolf, R. A.

2010-12-01

Transport of plasma sheet particles into the inner magnetosphere is strongly affected by the penetration of the convection electric field, which is the result of the large-scale magnetosphere-ionosphere electromagnetic coupling. This transport, on the other hand, results in plasma heating and magnetic field stretching, which become very significant in the inner plasma sheet (inside 20 RE). We have previously run simulations with the Rice Convection Model (RCM) to investigate how the earthward penetration of convection electric field, and therefore plasma sheet population, depends on plasma sheet boundary conditions. Outer boundary conditions at r ~20 RE are a function of MLT and interplanetary conditions based on 11 years of Geotail data. In the previous simulations, Tsyganenko 96 magnetic field model (T96) was used so force balance between plasma pressure and magnetic fields was not maintained. We have now integrated the RCM with a magnetic field solver (Liu et al., 2006) to obtain the required force balance in the equatorial plane. We have run the self-consistent simulations under enhanced convection with different boundary conditions in which we kept different parameters (flux tube particle content, plasma pressure, plasma beta, or magnetic fields) at the outer boundary to be MLT-dependent but time independent. Different boundary conditions result in qualitatively similar plasma sheet profiles. The results show that magnetic field has a dawn dusk asymmetry with field lines being more stretched in the pre-midnight sector, due to relatively higher plasma pressure there. The asymmetry in the magnetic fields in turn affects the radial distance and MLT of plasma sheet penetration into the inner magnetosphere. In comparison with results using the T96, plasma transport under self-consistent magnetic field results in proton and electron plasma sheet inner edges that are located in higher latitudes, weaker pressure gradients, and more efficient shielding of the near

Magnetic field generation, Weibel-mediated collisionless shocks, and magnetic reconnection in colliding laser-produced plasmas

NASA Astrophysics Data System (ADS)

Fox, W.; Bhattacharjee, A.; Fiksel, G.

2016-10-01

Colliding plasmas are ubiquitous in astrophysical environments and allow conversion of kinetic energy into heat and, most importantly, the acceleration of particles to extremely high energies to form the cosmic ray spectrum. In collisionless astrophysical plasmas, kinetic plasma processes govern the interaction and particle acceleration processes, including shock formation, self-generation of magnetic fields by kinetic plasma instabilities, and magnetic field compression and reconnection. How each of these contribute to the observed spectra of cosmic rays is not fully understood, in particular both shock acceleration processes and magnetic reconnection have been proposed. We will review recent results of laboratory astrophysics experiments conducted at high-power, inertial-fusion-class laser facilities, which have uncovered significant results relevant to these processes. Recent experiments have now observed the long-sought Weibel instability between two interpenetrating high temperature plasma plumes, which has been proposed to generate the magnetic field necessary for shock formation in unmagnetized regimes. Secondly, magnetic reconnection has been studied in systems of colliding plasmas using either self-generated magnetic fields or externally applied magnetic fields, and show extremely fast reconnection rates, indicating fast destruction of magnetic energy and further possibilities to accelerate particles. Finally, we highlight kinetic plasma simulations, which have proven to be essential tools in the design and interpretation of these experiments.

Magnetic pressure effects in a plasma-liner interface

NASA Astrophysics Data System (ADS)

García-Rubio, F.; Sanz, J.

2018-04-01

A theoretical analysis of magnetic pressure effects in a magnetized liner inertial fusion-like plasma is presented. In previous publications [F. García-Rubio and J. Sanz, Phys. Plasmas 24, 072710 (2017)], the evolution of a hot magnetized plasma in contact with a cold unmagnetized plasma, aiming to represent the hot spot and liner, respectively, was investigated in planar geometry. The analysis was made in a double limit low Mach and high thermal to magnetic pressure ratio β. In this paper, the analysis is extended to an arbitrary pressure ratio. Nernst, Ettingshausen, and Joule effects come into play in the energy balance. The region close to the liner is governed by thermal conduction, while the Joule dissipation becomes predominant far from it when the pressure ratio is low. Mass ablation, thermal energy, and magnetic flux losses are reduced with plasma magnetization, characterized by the electron Hall parameter ω e τ e , until β values of order unity are reached. From this point forward, increasing the electron Hall parameter no longer improves the magnetic flux conservation, and mass ablation is enhanced due to the magnetic pressure gradients. A thoughtful simplification of the problem that allows to reduce the order of the system of governing equations while still retaining the finite β effects is presented and compared to the exact case.

Studies of Magnetic Reconnection in Colliding Laser-Produced Plasmas

NASA Astrophysics Data System (ADS)

Rosenberg, Michael

2013-10-01

Novel images of magnetic fields and measurements of electron and ion temperatures have been obtained in the magnetic reconnection region of high- β, laser-produced plasmas. Experiments using laser-irradiated foils produce expanding, hemispherical plasma plumes carrying MG Biermann-battery magnetic fields, which can be driven to interact and reconnect. Thomson-scattering measurements of electron and ion temperatures in the interaction region of two colliding, magnetized plasmas show no thermal enhancement due to reconnection, as expected for β ~ 8 plasmas. Two different proton radiography techniques used to image the magnetic field structures show deformation, pileup, and annihilation of magnetic flux. High-resolution images reveal unambiguously reconnection-induced jets emerging from the interaction region and show instabilities in the expanding plasma plumes and supersonic, hydrodynamic jets due to the plasma collision. Quantitative magnetic flux data show that reconnection in experiments with asymmetry in the scale size, density, temperature, and plasma flow across the reconnection region occurs less efficiently than in similar, symmetric experiments. This result is attributed to disruption of the Hall mechanism mediating collisionless reconnection. The collision of plasmas carrying parallel magnetic fields has also been probed, illustrating the deformation of magnetic field structures in high-energy-density plasmas in the absence of reconnection. These experiments are particularly relevant to high- β reconnection environments, such as the magnetopause. This work was performed in collaboration with C. Li, F. Séguin, A. Zylstra, H. Rinderknecht, H. Sio, J. Frenje, and R. Petrasso (MIT), I. Igumenshchev, V. Glebov, C. Stoeckl, and D. Froula (LLE), J. Ross and R. Town (LLNL), W. Fox (UNH), and A. Nikroo (GA), and was supported in part by the NLUF, FSC/UR, U.S. DOE, LLNL, and LLE.

Equilibrium and magnetic properties of a rotating plasma annulus

NASA Astrophysics Data System (ADS)

Wang, Zhehui; Si, Jiahe; Liu, Wei; Li, Hui

2008-10-01

Local linear analysis shows that magneto-rotational instability can be excited in laboratory rotating plasmas with a density of 1019m-3, a temperature on the order of 10eV, and a magnetic field on the order of 100G. A laboratory plasma annulus experiment with a dimension of ˜1m, and rotation at ˜0.5 sound speed is described. Correspondingly, magnetic Reynolds number of these plasmas is ˜1000, and magnetic Prandtl number ranges from about one to a few hundred. A radial equilibrium, ρUθ2/r =d(p+Bz2/2μ0)/dr=K0, with K0 being a nonzero constant, is proposed for the experimental data. Plasma rotation is observed to drive a quasisteady diamagnetic electrical current (rotational current drive) in a high-β plasma annulus. The rotational energy depends on the direction and the magnitude of the externally applied magnetic field. Radial current (Jr) is produced through biasing the center rod at a negative electric potential relative to the outer wall. Jr×Bz torque generates and sustains the plasma rotation. Rotational current drive can reverse the direction of vacuum magnetic field, satisfying a necessary condition for self-generated closed magnetic flux surfaces inside plasmas. The Hall term is found to be substantial and therefore needs to be included in the Ohm's law for the plasmas. Azimuthal magnetic field (Bθ) is found to be comparable with the externally applied vacuum magnetic field Bz, and mainly caused by the electric current flowing in the center cylinder; thus, Bθ∝r-1. Magnetic fluctuations are anisotropic, radial-dependent, and contain many Fourier modes below the ion cyclotron frequency. Further theoretical analysis reflecting these observations is needed to interpret the magnetic fluctuations.

Shear viscosities of photons in strongly coupled plasmas

DOE PAGES

Yang, Di-Lun; Müller, Berndt

2016-07-18

We investigate the shear viscosity of thermalized photons in the quark gluon plasma (QGP) at weak coupling and N=4 super Yang–Mills plasma (SYMP) at both strong and weak couplings. We find that the shear viscosity due to the photon–parton scattering up to the leading order of electromagnetic coupling is suppressed when the coupling of the QGP/SYMP is increased, which stems from the blue-shift of the thermal-photon spectrum at strong coupling. In addition, the shear viscosity rapidly increases near the deconfinement transition in a phenomenological model analogous to the QGP.

A model for the nonlocal transport and the associated distribution function deformation in magnetized laser-plasmas

NASA Astrophysics Data System (ADS)

Nicolaï, Ph.; Feugeas, J.-L.; Schurtz, G.

2006-06-01

We present a model of nonlocal transport for multidimensional radiation magneto hydrodynamic codes. In laser produced plasmas, it is now believed that the heat transfert can be strongly modified by the nonlocal nature of the electron conduction. Nevertheless other mechanisms as self generated magnetic fields may affect heat transport too. The model described in this work aims at extending the formula of G. Schurtz, Ph. Nicolaï and M. Busquet [1] to magnetized plasmas. A system of nonlocal equations is derived from kinetic equations with self-consistent electric and magnetic fields. These equations are analyzed and applied to a physical problem in order to demonstrate the main features of the model.

Strong Turbulence in Alkali Halide Negative Ion Plasmas

NASA Astrophysics Data System (ADS)

Sheehan, Daniel

1999-11-01

Negative ion plasmas (NIPs) are charge-neutral plasmas in which the negative charge is dominated by negative ions rather than electrons. They are found in laser discharges, combustion products, semiconductor manufacturing processes, stellar atmospheres, pulsar magnetospheres, and the Earth's ionosphere, both naturally and man-made. They often display signatures of strong turbulence^1. Development of a novel, compact, unmagnetized alkali halide (MX) NIP source will be discussed, it incorporating a ohmically-heated incandescent (2500K) tantulum solenoid (3cm dia, 15 cm long) with heat shields. The solenoid ionizes the MX vapor and confines contaminant electrons, allowing a very dry (electron-free) source. Plasma densities of 10^10 cm-3 and positive to negative ion mass ratios of 1 <= fracm_+m- <= 20 are achievable. The source will allow tests of strong turbulence theory^2. 1 Sheehan, D.P., et al., Phys. Fluids B5, 1593 (1993). 2 Tsytovich, V. and Wharton, C.W., Comm. Plasma Phys. Cont. Fusion 4, 91 (1978).

Two density peaks in low magnetic field helicon plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Y.; Zhao, G.; Ouyang, J. T., E-mail: jtouyang@bit.edu.cn, E-mail: lppmchenqiang@hotmail.com

2015-09-15

In this paper, we report two density peaks in argon helicon plasma under an axial magnetic field from 0 G to 250 G with Boswell-type antenna driven by radio frequency (RF) power of 13.56 MHz. The first peak locates at 40–55 G and the second one at 110–165 G, as the RF power is sustainably increased from 100 W to 250 W at Ar pressure of 0.35 Pa. The absorbed power of two peaks shows a linear relationship with the magnetic field. End views of the discharge taken by intensified charge coupled device reveal that, when the first peak appeared, the discharge luminance moves to the edge ofmore » the tube as the magnetic field increases. For the second peak, the strong discharge area is centered at the two antenna legs after the magnetic field reaches a threshold value. Comparing with the simulation, we suggest that the efficient power absorption of two peaks at which the efficient power absorption mainly appears in the near-antenna region is due to the mode conversion in bounded non-uniform helicon plasma. The two low-field peaks are caused, to some extent, by the excitation of Trivelpiece-Gould wave through non-resonance conversion.« less

Low frequency electromagnetic fluctuations in Kappa magnetized plasmas

NASA Astrophysics Data System (ADS)

Kim, Sunjung; Lazar, M.; Schlickeiser, R.; López, R. A.; Yoon, P. H.

2018-07-01

The present paper provides a theoretical approach for the evaluation of the low frequency spontaneously emitted electromagnetic (EM) fluctuations in Kappa magnetized plasmas, which include the kinetic Alfvén, fast magnetosonic/whistler, kinetic slow mode, ion Bernstein cyclotron modes, and higher-order modes. The model predictions are consistent with particle-in-cell simulations. Effects of suprathermal particles on low frequency fluctuations are studied by varying the power index, either for ions (κ i) or for electrons (κ e). Computations for an arbitrary wave vector orientation and wave polarization provide the intensity of spontaneous emissions to be enhanced in the presence of suprathermal populations. These results strongly suggest that spontaneous fluctuations may significantly contribute to the EM fluctuations observed in space plasmas, where suprathermal Kappa distributed particles are ubiquitous.

Toroidal magnetized plasma device with sheared magnetic field lines using an internal ring conductor.

PubMed

Pierre, Th

2013-01-01

In a new toroidal laboratory plasma device including a poloidal magnetic field created by an internal circular conductor, the confinement efficiency of the magnetized plasma and the turbulence level are studied in different situations. The plasma density is greatly enhanced when a sufficiently large poloidal magnetic field is established. Moreover, the instabilities and the turbulence usually found in toroidal devices without sheared magnetic field lines are suppressed by the finite rotational transform. The particle confinement time is estimated from the measurement of the plasma decay time. It is compared to the Bohm diffusion time and to the value predicted by different diffusion models, in particular neoclassical diffusion involving trapped particles.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Formation of a plasma jet of multiply charged ions in the interaction of a laser plasma with an external pulsed magnetic field

NASA Astrophysics Data System (ADS)

Dyakin, V. M.; Pikuz, T. A.; Skobelev, I. Yu; Faenov, A. Ya; Wolowski, J.; Karpinski, L.; Kasperczuk, A.; Pisarczyk, T.

1994-12-01

A dense jet of a plasma consisting of multiply charged ions was generated in the interaction of a laser plasma with a strong external axial magnetic field. Images were formed by spectral lines and the soft x-ray spectrum range of the plasma jet was obtained with a large-aperture spectrograph containing a mica crystal bent to form a spherical surface with a radius of R = 10 cm. A tenfold increase in the density of the He-like Mg XI plasma, compared with a freely expanding plasma, was observed at a distance of 5 mm from the target.

Injection of a coaxial-gun-produced magnetized plasma into a background helicon plasma

NASA Astrophysics Data System (ADS)

Zhang, Yue; Lynn, Alan; Gilmore, Mark; Hsu, Scott

2014-10-01

A compact coaxial plasma gun is employed for experimental investigation of plasma bubble relaxation into a lower density background plasma. Experiments are being conducted in the linear device HelCat at UNM. The gun is powered by a 120-uF ignitron-switched capacitor bank, which is operated in a range of 5 to 10 kV and 100 kA. Multiple diagnostics are employed to investigate the plasma relaxation process. Magnetized argon plasma bubbles with velocities 1.2Cs, densities 1020 m-3 and electron temperature 13eV have been achieved. The background helicon plasma has density 1013 m-3, magnetic field from 200 to 500 Gauss and electron temperature 1eV. Several distinct operational regimes with qualitatively different dynamics are identified by fast CCD camera images. Additionally a B-dot probe array has been employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify plasma bubble configurations. Experimental data and analysis will be presented.

The development of magnetic field line wander in gyrokinetic plasma turbulence: dependence on amplitude of turbulence

NASA Astrophysics Data System (ADS)

Bourouaine, Sofiane; Howes, Gregory G.

2017-06-01

The dynamics of a turbulent plasma not only manifests the transport of energy from large to small scales, but also can lead to a tangling of the magnetic field that threads through the plasma. The resulting magnetic field line wander can have a large impact on a number of other important processes, such as the propagation of energetic particles through the turbulent plasma. Here we explore the saturation of the turbulent cascade, the development of stochasticity due to turbulent tangling of the magnetic field lines and the separation of field lines through the turbulent dynamics using nonlinear gyrokinetic simulations of weakly collisional plasma turbulence, relevant to many turbulent space and astrophysical plasma environments. We determine the characteristic time 2$ for the saturation of the turbulent perpendicular magnetic energy spectrum. We find that the turbulent magnetic field becomes completely stochastic at time 2$ for strong turbulence, and at 2$ for weak turbulence. However, when the nonlinearity parameter of the turbulence, a dimensionless measure of the amplitude of the turbulence, reaches a threshold value (within the regime of weak turbulence) the magnetic field stochasticity does not fully develop, at least within the evolution time interval 22$ . Finally, we quantify the mean square displacement of magnetic field lines in the turbulent magnetic field with a functional form 2\\rangle =A(z/L\\Vert )p$ ( \\Vert $ is the correlation length parallel to the magnetic background field \\mathbf{0}$ , is the distance along \\mathbf{0}$ direction), providing functional forms of the amplitude coefficient and power-law exponent as a function of the nonlinearity parameter.

Sheared-flow induced confinement transition in a linear magnetized plasma

NASA Astrophysics Data System (ADS)

Zhou, S.; Heidbrink, W. W.; Boehmer, H.; McWilliams, R.; Carter, T. A.; Vincena, S.; Friedman, B.; Schaffner, D.

2012-01-01

A magnetized plasma cylinder (12 cm in diameter) is induced by an annular shape obstacle at the Large Plasma Device [W. Gekelman, H. Pfister, Z. Lucky, J. Bamber, D. Leneman, and J. Maggs, Rev. Sci. Instrum. 62, 2875 (1991)]. Sheared azimuthal flow is driven at the edge of the plasma cylinder through edge biasing. Strong fluctuations of density and potential (δn /n~eδφ/kTe~0.5) are observed at the plasma edge, accompanied by a large density gradient (Ln=|∇lnn |-1~2cm) and shearing rate (γ ~300kHz). Edge turbulence and cross-field transport are modified by changing the bias voltage (Vbias) on the obstacle and the axial magnetic field (Bz) strength. In cases with low Vbias and large Bz, improved plasma confinement is observed, along with steeper edge density gradients. The radially sheared flow induced by E ×B drift dramatically changes the cross-phase between density and potential fluctuations, which causes the wave-induced particle flux to reverse its direction across the shear layer. In cases with higher bias voltage or smaller Bz, large radial transport and rapid depletion of the central plasma density are observed. Two-dimensional cross-correlation measurement shows that a mode with azimuthal mode number m =1 and large radial correlation length dominates the outward transport in these cases. Linear analysis based on a two-fluid Braginskii model suggests that the fluctuations are driven by both density gradient (drift wave like) and flow shear (Kelvin-Helmholtz like) at the plasma edge.

Design and Fabrication of a Magnetic System to Investigate Magnetized Dusty Plasmas

NASA Astrophysics Data System (ADS)

Bates, Evan M.; Romero-Talamas, Carlos A.

2013-10-01

The interest in researching the dynamics and equilibrium of magnetized dusty plasma crystallization has led to the design and fabrication of a novel experimental setup at UMBC. The proposed magnets will be an important subsystem of this setup, and will produce a uniform magnetic field of several tesla for a duration of several seconds. The magnets will be arranged in the Helmholtz configuration and will have a cooling system for temperature compensation of the coils, as well as the ability to adjust the orientation of the magnetic field with respect to gravity. Planned experiments include propagation of magnetized waves in dusty plasma crystals under various boundary conditions.

Electrostatic acceleration of helicon plasma using a cusped magnetic field

NASA Astrophysics Data System (ADS)

Harada, S.; Baba, T.; Uchigashima, A.; Yokota, S.; Iwakawa, A.; Sasoh, A.; Yamazaki, T.; Shimizu, H.

2014-11-01

The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in the field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.

High density plasma etching of magnetic devices

NASA Astrophysics Data System (ADS)

Jung, Kee Bum

Magnetic materials such as NiFe (permalloy) or NiFeCo are widely used in the data storage industry. Techniques for submicron patterning are required to develop next generation magnetic devices. The relative chemical inertness of most magnetic materials means they are hard to etch using conventional RIE (Reactive Ion Etching). Therefore ion milling has generally been used across the industry, but this has limitations for magnetic structures with submicron dimensions. In this dissertation, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma) for the etching of magnetic materials (NiFe, NiFeCo, CoFeB, CoSm, CoZr) and other related materials (TaN, CrSi, FeMn), which are employed for magnetic devices like magnetoresistive random access memories (MRAM), magnetic read/write heads, magnetic sensors and microactuators. This research examined the fundamental etch mechanisms occurring in high density plasma processing of magnetic materials by measuring etch rate, surface morphology and surface stoichiometry. However, one concern with using Cl2-based plasma chemistry is the effect of residual chlorine or chlorinated etch residues remaining on the sidewalls of etched features, leading to a degradation of the magnetic properties. To avoid this problem, we employed two different processing methods. The first one is applying several different cleaning procedures, including de-ionized water rinsing or in-situ exposure to H2, O2 or SF6 plasmas. Very stable magnetic properties were achieved over a period of ˜6 months except O2 plasma treated structures, with no evidence of corrosion, provided chlorinated etch residues were removed by post-etch cleaning. The second method is using non-corrosive gas chemistries such as CO/NH3 or CO2/NH3. There is a small chemical contribution to the etch mechanism (i.e. formation of metal carbonyls) as determined by a comparison with Ar and N2 physical sputtering. The discharge should be NH3

Physics in strong magnetic fields near neutron stars

NASA Technical Reports Server (NTRS)

Harding, Alice K.

1991-01-01

Electromagnetic phenomena occurring in the strong magnetic fields of neutron stars are currently of great interest in high-energy astrophysics. Observations of rotation rate changes and cyclotron lines in pulsars and gamma-ray bursts indicate that surface magnetic fields of neutron stars often exceed a trillion gauss. In fields this strong, where electrons behave much as if they were in bound atomic states, familiar processes undergo profound changes, and exotic processes become important. Strong magnetic fields affect the physics in several fundamental ways: energies perpendicular to the field are quantized, transverse momentum is not conserved, and electron-positron spin is important. Neutron stars therefore provide a unique laboratory for the study of physics in extremely high fields that cannot be generated on earth.

Plasma-induced magnetic responses during nonlinear dynamics of magnetic islands due to resonant magnetic perturbations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishimura, Seiya, E-mail: n-seiya@kobe-kosen.ac.jp

Resonant magnetic perturbations (RMPs) produce magnetic islands in toroidal plasmas. Self-healing (annihilation) of RMP-induced magnetic islands has been observed in helical systems, where a possible mechanism of the self-healing is shielding of RMP penetration by plasma flows, which is well known in tokamaks. Thus, fundamental physics of RMP shielding is commonly investigated in both tokamaks and helical systems. In order to check this mechanism, detailed informations of magnetic island phases are necessary. In experiments, measurement of radial magnetic responses is relatively easy. In this study, based on a theoretical model of rotating magnetic islands, behavior of radial magnetic fields duringmore » the self-healing is investigated. It is confirmed that flips of radial magnetic fields are typically observed during the self-healing. Such behavior of radial magnetic responses is also observed in LHD experiments.« less

Electromagnetic fluctuations in magnetized plasmas. I. The rigorous relativistic kinetic theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlickeiser, R., E-mail: rsch@tp4.rub.de, E-mail: yoonp@umd.edu; Yoon, P. H., E-mail: rsch@tp4.rub.de, E-mail: yoonp@umd.edu; School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701

2015-07-15

Using the system of the Klimontovich and Maxwell equations, the general linear fluctuation theory for magnetized plasmas is developed. General expressions for the electromagnetic fluctuation spectra (electric and magnetic fields) from uncorrelated plasma particles in plasmas with a uniform magnetic field are derived, which are covariantly correct within the theory of special relativity. The general fluctuation spectra hold for plasmas of arbitrary composition, arbitrary momentum dependences of the plasma particle distribution functions, and arbitrary orientations of the wave vector with respect to the uniform magnetic field. Moreover, no restrictions on the values of the real and the imaginary parts ofmore » the frequency are made. The derived fluctuation spectra apply to both non-collective fluctuations and collective plasma eigenmodes in magnetized plasmas. In the latter case, kinetic equations for the components of fluctuating electric and magnetic fields in magnetized plasmas are derived that include the effect of spontaneous emission and absorption. In the limiting case of an unmagnetized plasmas, the general fluctuation spectra correctly reduce to the unmagnetized fluctuation spectra derived before.« less

Emergent kink stability of a magnetized plasma jet injected into a transverse background magnetic field

NASA Astrophysics Data System (ADS)

Zhang, Yue; Gilmore, Mark; Hsu, Scott C.; Fisher, Dustin M.; Lynn, Alan G.

2017-11-01

We report experimental results on the injection of a magnetized plasma jet into a transverse background magnetic field in the HelCat linear plasma device at the University of New Mexico [M. Gilmore et al., J. Plasma Phys. 81(1), 345810104 (2015)]. After the plasma jet leaves the plasma-gun muzzle, a tension force arising from an increasing curvature of the background magnetic field induces in the jet a sheared axial-flow gradient above the theoretical kink-stabilization threshold. We observe that this emergent sheared axial flow stabilizes the n = 1 kink mode in the jet, whereas a kink instability is observed in the jet when there is no background magnetic field present.

Chirality-induced negative refraction in magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, B.

2013-09-15

Characteristic equations in magnetized plasma with chirality are derived in simple formulations and the dispersion relations for propagation parallel and perpendicular to the external magnetic field are studied in detail. With the help of the dispersion relations of each eigenwave, the author explores chirality-induced negative refraction in magnetized plasma and investigates the effects of parameters (i.e., chirality degree, external magnetic field, etc.) on the negative refraction. The results show that the chirality is the necessary and only one factor which leads to negative refraction without manipulating electrical permittivity and magnetic permeability. Both increasing the degree of chirality and reducing themore » external magnetic field can result in greater range negative refraction. Parameter dependence of the effects is calculated and discussed.« less

Influence of Magnetic Field Ripple on the Intrinsic Rotation of Tokamak Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nave, M. F. F.; Johnson, T.; Eriksson, L.-G.

Using the unique capability of JET to monotonically change the amplitude of the magnetic field ripple, without modifying other relevant equilibrium conditions, the effect of the ripple on the angular rotation frequency of the plasma column was investigated under the conditions of no external momentum input. The ripple amplitude was varied from 0.08% to 1.5% in Ohmic and ion-cyclotron radio-frequency (ICRF) heated plasmas. In both cases the ripple causes counterrotation, indicating a strong torque due to nonambipolar transport of thermal ions and in the case of ICRF also fast ions.

Progress In Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Francis Y. C.; Kirkpatrick, Ronald C.; Knapp, Charles E.; Cassibry, Jason; Eskridge, Richard; Lee, Michael; Smith, James; Martin, Adam; Wu, S. T.; Schmidt, George;

Relativistic nonlinear plasma waves in a magnetic field

NASA Technical Reports Server (NTRS)

Kennel, C. F.; Pellat, R.

1975-01-01

Five relativistic plane nonlinear waves were investigated: circularly polarized waves and electrostatic plasma oscillations propagating parallel to the magnetic field, relativistic Alfven waves, linearly polarized transverse waves propagating in zero magnetic field, and the relativistic analog of the extraordinary mode propagating at an arbitrary angle to the magnetic field. When the ions are driven relativistic, they behave like electrons, and the assumption of an 'electron-positron' plasma leads to equations which have the form of a one-dimensional potential well. The solutions indicate that a large-amplitude superluminous wave determines the average plasma properties.

Plasma flow in peripheral region of detached plasma in linear plasma device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayashi, Y., E-mail: hayashi-yuki13@ees.nagoya-u.ac.jp; Ohno, N.; Kajita, S.

2016-01-15

A plasma flow structure is investigated using a Mach probe under detached plasma condition in a linear plasma device NAGDIS-II. A reverse flow along the magnetic field is observed in a steady-state at far-peripheral region of the plasma column in the upstream side from the recombination front. These experimental results indicate that plasma near the recombination front should strongly diffuse across the magnetic field, and it should be transported along the magnetic field in the reverse flow direction. Furthermore, bursty plasma density fluctuations associated with intermittent convective plasma transport are observed in the far-peripheral region of the plasma column inmore » both upstream and downstream sides from the recombination front. Such a nondiffusive transport can contribute to the intermittent reverse plasma flow, and the experimental results indicate that intermittent transports are frequently produced near the recombination front.« less

Effects of intergranular phase on the coercivity for MnBi magnets prepared by spark plasma sintering

NASA Astrophysics Data System (ADS)

Cao, J.; Huang, Y. L.; Hou, Y. H.; Zhang, G. Q.; Shi, Z. Q.; Zhong, Z. C.; Liu, Z. W.

2018-05-01

MnBi magnets with a high content of low temperature phase (LTP) and excellent magnetic properties were prepared by spark plasma sintering (SPS) using ball milling powders as precursors without magnetic purification. A complicated intergranular phase, which contains Mn phase, Bi phase, MnO phase, and even amorphous phase in MnBi magnets, was characterized and reported systematically. It was found that the formation of intergranular phase which was contributed by ball milling precursors and sintering mechanism, jointly, had important influence on the magnetic properties. The appropriate content of intergranular phase was beneficial in improving the coercivity due to the strong magnetic isolation effects. The optimum magnetic properties with Mr=26.0 emu/g, Hci= 7.11 kOe and (BH)max=1.53 MGOe at room temperature, and a maximum value Hci= 25.37 kOe at 550 K can be obtained. Strongly favorable magnetic properties make SPSed MnBi magnets an attractive candidate material for small permanent magnets used in high-temperature applications.

Observability of atomic line features in strong magnetic fields

NASA Technical Reports Server (NTRS)

Wunner, G.; Ruder, H.; Herold, H.; Truemper, J.

1981-01-01

The physical properties of atoms in superstrong magnetic fields, characteristic of neutron stars, and the possibility of detecting magnetically strongly shifted atomic lines in the spectra of magnetized X-ray pulsars are discussed. It is suggested that it is recommendable to look for magnetically strongly shifted Fe 26 Lyman lines in rotating neutron stars of not too high luminosity using spectrometers working in the energy range 10 - 20 keV, with sensitivities to minus 4 power photons per sq cm and second, and resolution E/delta E approx. 10-100.

Periodical plasma structures controlled by external magnetic field

NASA Astrophysics Data System (ADS)

Schweigert, I. V.; Keidar, M.

2017-11-01

The plasma of Hall thruster type in external magnetic field is studied in 2D3V kinetic simulations using PIC MCC method. The periodical structure with maxima of electron and ion densities is formed and becomes more pronounced with increase of magnetic field incidence angle in the plasma. These ridges of electron and ion densities are aligned with the magnetic field vector and shifted relative each other. This leads to formation of two-dimensional double-layers structure in cylindrical plasma chamber. Depending on Larmor radius and Debye length up to nineteen potential steps appear across the oblique magnetic field. The electrical current gathered on the wall is associated with the electron and ion density ridges.

Disruption of current filaments and isotropization of magnetic field in counter-streaming plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fiuza, Frederico

We study the stability of current filaments produced by the Weibel, or current filamentation, instability in weakly magnetized counter-streaming plasmas. It is shown that a resonance exists between the current-carrying ions and a longitudinal drift-kink mode that strongly deforms and eventually breaks the current filaments. Analytical estimates of the wavelength, growth rate and saturation level of the resonant mode are derived and validated by three-dimensional particle-in-cell simulations. Furthermore, self-consistent simulations of counter-streaming plasmas indicate that this drift-kink mode is dominant in the slow down of the flows and in the isotropization of the magnetic field, playing an important role inmore » the formation of collision less shocks.« less

Production of a large, quiescent, magnetized plasma

NASA Technical Reports Server (NTRS)

Landt, D. L.; Ajmera, R. C.

1976-01-01

An experimental device is described which produces a large homogeneous quiescent magnetized plasma. In this device, the plasma is created in an evacuated brass cylinder by ionizing collisions between electrons emitted from a large-diameter electron gun and argon atoms in the chamber. Typical experimentally measured values of the electron temperature and density are presented which were obtained with a glass-insulated planar Langmuir probe. It is noted that the present device facilitates the study of phenomena such as waves and diffusion in magnetized plasmas.

Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

DOEpatents

Coppi, B.; Montgomery, D.B.

1973-12-11

A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

Magnetic moment of solar plasma and the Kelvin force: -The driving force of plasma up-flow -

NASA Astrophysics Data System (ADS)

Shibasaki, Kiyoto

2017-04-01

Thermal plasma in the solar atmosphere is magnetized (diamagnetic). The magnetic moment does not disappear by collisions because complete gyration is not a necessary condition to have magnetic moment. Magnetized fluid is subjected to Kelvin force in non-uniform magnetic field. Generally, magnetic field strength decreases upwards in the solar atmosphere, hence the Kelvin force is directed upwards along the field. This force is not included in the fluid treatment of MHD. By adding the Kelvin force to the MHD equation of motion, we can expect temperature dependent plasma flows along the field which are reported by many observations. The temperature dependence of the flow speed is explained by temperature dependence of magnetic moment. From the observed parameters, we can infer physical parameters in the solar atmosphere such as scale length of the magnetic field strength and the friction force acting on the flowing plasma. In case of closed magnetic field lines, loop-top concentration of hot plasma is expected which is frequently observed.

Observations of the magnetic field and plasma flow in Jupiter's magnetosheath

NASA Technical Reports Server (NTRS)

Lepping, R. P.; Burlaga, L. F.; Klein, L. W.; Jessen, J. M.; Goodrich, G. C.

1980-01-01

Large scale (many minutes to 10 hours) magnetic field structures consisting predominantly of nearly north-south field direction were discovered in Jupiter's magnetosheath from the data of Voyagers 1 and 2 and Pioneer 10 during their outbound encounter trajectories. The Voyager 2 data, and that of Voyager 1 to a lesser extent, show evidence of a quasi-period of 10 hours (and occasionally 5 hours) for these structures. The north-south components of the field and plasma velocity were strongly correlated in the outbound magnetosheath as observed by Voyagers 1 and 2, and the components orthogonal to the north-south direction showed weak correlations. For both Voyager encounters the sense (positive and negative) of the north-south correlations were directly related to the direction of the ecliptic plane component of the interplanetary magnetic field using the field and plasma measurements of the non-encountering spacecraft.

Termination of a Magnetized Plasma on a Neutral Gas: The End of the Plasma

NASA Astrophysics Data System (ADS)

Cooper, C. M.; Gekelman, W.

2013-06-01

Experiments are performed at the Enormous Toroidal Plasma Device at UCLA to study the neutral boundary layer (NBL) between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. This is the first experiment to measure plasma termination within a neutral gas without the presence of a wall or obstacle. A magnetized, current-free helium plasma created by a lanthanum hexaboride (LaB6) cathode terminates entirely within a neutral helium gas. The plasma is weakly ionized (ne/nn˜1%) and collisional λn≪Lplasma. The NBL occurs where the plasma pressure equilibrates with the neutral gas pressure, consistent with a pressure balance model. It is characterized by a field-aligned ambipolar electric field, developing self-consistently to maintain a current-free termination of the plasma on the neutral gas. Probes are inserted into the plasma to measure the plasma density, flow, temperature, current, and potential. These measurements confirm the presence of the ambipolar field and the pressure equilibration model of the NBL.

Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

NASA Astrophysics Data System (ADS)

Darian, D.; Marholm, S.; Paulsson, J. J. P.; Miyake, Y.; Usui, H.; Mortensen, M.; Miloch, W. J.

2017-09-01

The charging of a sounding rocket in subsonic and supersonic plasma flows with external magnetic field is studied with numerical particle-in-cell (PIC) simulations. A weakly magnetized plasma regime is considered that corresponds to the ionospheric F2 layer, with electrons being strongly magnetized, while the magnetization of ions is weak. It is demonstrated that the magnetic field orientation influences the floating potential of the rocket and that with increasing angle between the rocket axis and the magnetic field direction the rocket potential becomes less negative. External magnetic field gives rise to asymmetric wake downstream of the rocket. The simulated wake in the potential and density may extend as far as 30 electron Debye lengths; thus, it is important to account for these plasma perturbations when analyzing in situ measurements. A qualitative agreement between simulation results and the actual measurements with a sounding rocket is also shown.

Magnetic monopole plasma oscillations and the survival of Galactic magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, E.N.

This paper explores the general nature of magnetic-monopole plasma oscillations as a theoretical possibility for the observed Galactic magnetic field in the presence of a high abundance of magnetic monopoles. The modification of the hydromagnetic induction equation by the monopole oscillations produces the half-velocity effect, in which the magnetic field is transported bodily with a velocity midway between the motion of the conducting fluid and the monopole plasma. Observational studies of the magnetic field in the Galaxy, and in other galaxies, exclude the half-velocity effect, indicating that the magnetic fields is not associated with monopole oscillations. In any case themore » phase mixing would destroy the oscillations in less than 100 Myr. The conclusion is that magnetic monopole oscillations do not play a significant role in the galactic magnetic fields. Hence the existence of galactic magnetic fields places a low limit on the monopole flux, so that their detection - if they exist at all - requires a collecting area at least as large as a football field. 47 references.« less

Observation of Dust Particle Gyromotion in a Magnetized Dusty Plasma

NASA Astrophysics Data System (ADS)

Compton, C. S.; Amatucci, W. E.; Gatling, G.; Tejero, E.

2008-11-01

In dusty plasma research, gyromotion of the dust has been difficult to observe experimentally. Previous experiments by Amatucci et al. have shown gyromotion of a single dust particle [1]. This early work was performed with alumina dust that had a size distribution and non-uniformly shaped particles. In the current experiment, evidence of spherical, monodispersed, dust particles exhibiting gyromotion has been observed. Silica particles 0.97 micrometers in diameter are suspended in a DC glow discharge argon plasma. The experiment is performed in the Naval Research Laboratory's DUsty PLasma EXperiment (DUPLEX Jr.). DUPLEX is a 61-cm tall by 46-cm diameter acrylic chamber allowing full 360 degree optical access for diagnostics. The neutral pressure for the experiment is 230 mTorr with a 275 V bias between the circular electrodes. The electrodes have a separation of 4 cm. A strong magnetic field is created by 2 pairs of neodymium iron boride magnets placed above and below the anode and cathode respectively. The resulting field is 1.4 kG. The dust particles are illuminated with a 25 mW, 672 nm laser. Images are captured using an intensified CCD camera and a consumer digital video cassette recorder. Recent evidence of gyromotion of spherical, monodispersed, dust particles will be presented. [1] Amatucci, W.E., et al., Phys. Plasmas, 11, 2097 (2004)

Magnetic flux conservation in an imploding plasma.

PubMed

García-Rubio, F; Sanz, J; Betti, R

2018-01-01

The theory of magnetic flux conservation is developed for a subsonic plasma implosion and used to describe the magnetic flux degradation in the MagLIF concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010)10.1063/1.3333505]. Depending on the initial magnetic Lewis and Péclet numbers and the electron Hall parameter, the implosion falls into either a superdiffusive regime in which the magnetization decreases or a magnetized regime in which the magnetization increases. Scaling laws for magnetic field, temperature, and magnetic flux losses in the hot spot of radius R are obtained for both regimes. The Nernst velocity convects the magnetic field outwards, pushing it against the liner and enhancing the magnetic field diffusion, thereby reducing the magnetic field compression and degrading the implosion performance. However, in the magnetized regime, the core of the hot spot becomes magnetically insulated and undergoes an ideal adiabatic compression (T∼R^{-4/3} compared to T∼R^{-2/3} without magnetic field), while the detrimental Nernst term is confined to the outer part of the hot spot. Its effect is drastically reduced, improving the magnetic flux conservation.

Magnetic flux conservation in an imploding plasma

NASA Astrophysics Data System (ADS)

García-Rubio, F.; Sanz, J.; Betti, R.

2018-01-01

The theory of magnetic flux conservation is developed for a subsonic plasma implosion and used to describe the magnetic flux degradation in the MagLIF concept [S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010), 10.1063/1.3333505]. Depending on the initial magnetic Lewis and Péclet numbers and the electron Hall parameter, the implosion falls into either a superdiffusive regime in which the magnetization decreases or a magnetized regime in which the magnetization increases. Scaling laws for magnetic field, temperature, and magnetic flux losses in the hot spot of radius R are obtained for both regimes. The Nernst velocity convects the magnetic field outwards, pushing it against the liner and enhancing the magnetic field diffusion, thereby reducing the magnetic field compression and degrading the implosion performance. However, in the magnetized regime, the core of the hot spot becomes magnetically insulated and undergoes an ideal adiabatic compression (T ˜R-4 /3 compared to T ˜R-2 /3 without magnetic field), while the detrimental Nernst term is confined to the outer part of the hot spot. Its effect is drastically reduced, improving the magnetic flux conservation.

Quasi-discrete particle motion in an externally imposed, ordered structure in a dusty plasma at high magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Edward, E-mail: etjr@auburn.edu; Konopka, Uwe; Lynch, Brian

Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas at magnetic fields up to 2.5 T where the electrons and ions are strongly magnetized. Plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper electrode supports a dual mesh consisting of #24 brass and #30 aluminum wire cloth. In this experiment, we study the formation of imposed ordered structures and particle dynamics as a function of magnetic field. Through observations of trapped particles and the quasi-discrete (i.e., “hopping”) motion of particles between the trapping locations, it is possible tomore » make a preliminary estimate of the potential structure that confines the particles to a grid structure in the plasma. This information is used to gain insight into the formation of the imposed grid pattern of the dust particles in the plasma.« less

Experimental Characterization of Plasma Detachment from Magnetic Nozzles

NASA Astrophysics Data System (ADS)

Olsen, Christopher Scott

Magnetic nozzles, like Laval nozzles, are observed in several natural systems and have application in areas such as electric propulsion and plasma processing. Plasma flowing through these nozzles is inherently tied to the field lines and must separate for momentum redirection or particle transport to occur. Plasma detachment and associated mechanisms from a magnetic nozzle are investigated. Experimental results are presented from the plume of the VASIMRRTM VX-200 device flowing along an axisymmetric magnetic nozzle and operated at two ion energies to explore momentum dependent detachment. The argon plume expanded into a 150m3 vacuum chamber where the background pressure was low enough that charge-exchange mean-free-paths were longer than experiment scale lengths. This magnetic nozzle system is demonstrated to hydrodynamically scale up to astrophysical plasmas, particularly the solar chromosphere, implying general relevance to many systems. Plasma parameters were mapped over a large spatial range using measurements from multiple plasma diagnostics. The data show that the plume does not follow the magnetic field lines. A mapped integration of the ion flux shows the plume may be divided into three regions where 1) the plume briefly follows the magnetic flux, 2) diverges quadratically before 3) expanding with linear trajectories. Transitioning from region 1→2, the ion flux departs from the magnetic flux suggesting ion detachment. An instability forms in region 2 driving an oscillating electric field that causes ions to expand before enhancing electron cross-field transport through anomalous resistivity. Transitioning from region 2→3 the electric field dissipates, the trajectories linearize, and the plume effectively detaches. A delineation of sub-to-super Alfvenic flow aligns well with the inflection points of the linearization without a change in magnetic topology. The detachment process is best described as a two part process: First, ions detach by a breakdown of

Response to “Comment on ‘Propagation of surface waves on a semi-bounded quantum magnetized collisional plasma’” [Phys. Plasmas 23, 044701 (2016)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niknam, A. R., E-mail: a-niknam@sbu.ac.ir; Taheri Boroujeni, S.; Khorashadizadeh, S. M., E-mail: smkhorashadi@birjand.ac.ir

2016-04-15

We reply to the Comment of Moradi [Phys. Plasmas 23, 044701 (2016)] on our paper [Phys. Plasmas 20, 122106 (2013)]. It is shown that TM surface waves can propagate on the surface of a semi-bounded quantum magnetized collisional plasma in the Faraday configuration in the electrostatic limit. In addition, in the Faraday configuration, one can neglect the coupling of TM and TE modes in the two limiting cases of weak magnetic field (low cyclotron frequency) and strong magnetic field (high cyclotron frequency).

Langmuir probe study of a magnetically enhanced RF plasma source at pressures below 0.1 Pa

NASA Astrophysics Data System (ADS)

Kousal, Jaroslav; Tichý, Milan; Šebek, Ondřej; Čechvala, Juraj; Biederman, Hynek

2011-08-01

The majority of plasma polymerization sources operate at pressures higher than 1 Pa. At these pressures most common deposition methods do not show significant directionality. One way of enhancing the directional effects is to decrease the working pressure to increase the mean free path of the reactive molecules. The plasma source used in this work was designed to study the plasma polymerization process at pressures below 0.1 Pa. The source consists of the classical radio frequency (RF) (13.56 MHz, capacitive coupled) tubular reactor enhanced by an external magnetic circuit. The working gas is introduced into the discharge by a capillary. This forms a relatively localized zone of higher pressure where the monomer is activated. Due to the magnetic field, the plasma is constricted near the axis of the reactor with nearly collisionless gas flow. The plasma parameters were obtained using a double Langmuir probe. Plasma density in the range ni = 1013-1016 m-3 was obtained in various parts of the discharge under typical conditions. The presence of the magnetic field led to the presence of relatively strong electric fields (103 V m-1) and relatively high electron energies up to several tens of eV in the plasma.

Electrostatic acceleration of helicon plasma using a cusped magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harada, S.; Mitsubishi Heavy Industry ltd., 16-5 Konan 2-chome, Minato-ku, Tokyo 108-8215; Baba, T.

2014-11-10

The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in themore » field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.« less

Effect of magnetic field configuration on the multiply charged ion and plume characteristics in Hall thruster plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Holak; Lim, Youbong; Choe, Wonho, E-mail: wchoe@kaist.ac.kr

2015-04-13

Multiply charged ions and plume characteristics in Hall thruster plasmas are investigated with regard to magnetic field configuration. Differences in the plume shape and the fraction of ions with different charge states are demonstrated by the counter-current and co-current magnetic field configurations, respectively. The significantly larger number of multiply charged and higher charge state ions including Xe{sup 4+} are observed in the co-current configuration than in the counter-current configuration. The large fraction of multiply charged ions and high ion currents in this experiment may be related to the strong electron confinement, which is due to the strong magnetic mirror effectmore » in the co-current magnetic field configuration.« less

Particle acceleration and plasma dynamics during magnetic reconnection in the magnetically dominated regime

DOE PAGES

Guo, Fan; Liu, Yi -Hsin; Daughton, William; ...

2015-06-17

Magnetic reconnection is thought to be the driver for many explosive phenomena in the universe. The energy release and particle acceleration during reconnection have been proposed as a mechanism for producing high-energy emissions and cosmic rays. We carry out two- and three-dimensional (3D) kinetic simulations to investigate relativistic magnetic reconnection and the associated particle acceleration. The simulations focus on electron–positron plasmas starting with a magnetically dominated, force-free current sheet (σ ≡ B 2 / (4πn em ec 2) >> 1). For this limit, we demonstrate that relativistic reconnection is highly efficient at accelerating particles through a first-order Fermi process accomplishedmore » by the curvature drift of particles along the electric field induced by the relativistic flows. This mechanism gives rise to the formation of hard power-law spectra f α (γ - 1) -p and approaches p = 1 for sufficiently large σ and system size. Eventually most of the available magnetic free energy is converted into nonthermal particle kinetic energy. An analytic model is presented to explain the key results and predict a general condition for the formation of power-law distributions. The development of reconnection in these regimes leads to relativistic inflow and outflow speeds and enhanced reconnection rates relative to nonrelativistic regimes. In the 3D simulation, the interplay between secondary kink and tearing instabilities leads to strong magnetic turbulence, but does not significantly change the energy conversion, reconnection rate, or particle acceleration. This paper suggests that relativistic reconnection sites are strong sources of nonthermal particles, which may have important implications for a variety of high-energy astrophysical problems.« less

Application of reflectometry power flow for magnetic field pitch angle measurements in tokamak plasmas (invited).

PubMed

Gourdain, P-A; Peebles, W A

2008-10-01

Reflectometry has successfully demonstrated measurements of many important parameters in high temperature tokamak fusion plasmas. However, implementing such capabilities in a high-field, large plasma, such as ITER, will be a significant challenge. In ITER, the ratio of plasma size (meters) to the required reflectometry source wavelength (millimeters) is significantly larger than in existing fusion experiments. This suggests that the flow of the launched reflectometer millimeter-wave power can be realistically analyzed using three-dimensional ray tracing techniques. The analytical and numerical studies presented will highlight the fact that the group velocity (or power flow) of the launched microwaves is dependent on the direction of wave propagation relative to the internal magnetic field. It is shown that this dependence strongly modifies power flow near the cutoff layer in a manner that embeds the local magnetic field direction in the "footprint" of the power returned toward the launch antenna. It will be shown that this can potentially be utilized to locally determine the magnetic field pitch angle at the cutoff location. The resultant beam drift and distortion due to magnetic field and relativistic effects also have significant consequences on the design of reflectometry systems for large, high-field fusion experiments. These effects are discussed in the context of the upcoming ITER burning plasma experiment.

Magnetized Plasma Compression for Fusion Energy

NASA Astrophysics Data System (ADS)

Degnan, James; Grabowski, Christopher; Domonkos, Matthew; Amdahl, David

2013-10-01

Magnetized Plasma Compression (MPC) uses magnetic inhibition of thermal conduction and enhancement of charge particle product capture to greatly reduce the temporal and spatial compression required relative to un-magnetized inertial fusion (IFE)--to microseconds, centimeters vs nanoseconds, sub-millimeter. MPC greatly reduces the required confinement time relative to MFE--to microseconds vs minutes. Proof of principle can be demonstrated or refuted using high current pulsed power driven compression of magnetized plasmas using magnetic pressure driven implosions of metal shells, known as imploding liners. This can be done at a cost of a few tens of millions of dollars. If demonstrated, it becomes worthwhile to develop repetitive implosion drivers. One approach is to use arrays of heavy ion beams for energy production, though with much less temporal and spatial compression than that envisioned for un-magnetized IFE, with larger compression targets, and with much less ambitious compression ratios. A less expensive, repetitive pulsed power driver, if feasible, would require engineering development for transient, rapidly replaceable transmission lines such as envisioned by Sandia National Laboratories. Supported by DOE-OFES.

Conversion of magnetic energy in the magnetic reconnection layer of a laboratory plasma

DOE PAGES

Yamada, Masaaki; Yoo, Jongsoo; Jara-Almonte, Jonathan; ...

2014-09-10

Magnetic reconnection, in which magnetic field lines break and reconnect to change their topology, occurs throughout the universe. The essential feature of reconnection is that it energizes plasma particles by converting magnetic energy. Despite the long history of reconnection research, how this energy conversion occurs remains a major unresolved problem in plasma physics. Here we report that the energy conversion in a laboratory reconnection layer occurs in a much larger region than previously considered. The mechanisms for energizing plasma particles in the reconnection layer are identified, and a quantitative inventory of the converted energy is presented for the first timemore » in a well defined reconnection layer; 50% of the magnetic energy is converted to particle energy, 2/3 of which transferred to ions and 1/3 to electrons. Our results are compared with simulations and space measurements, for a key step toward resolving one of the most important problems in plasma physics.« less

Correlation of Magnetic Fields with Solar Wind Plasma Parameters at 1AU

NASA Astrophysics Data System (ADS)

Shen, F.

2017-12-01

The physical parameters of the solar wind observed in-situ near 1AU have been studied for several decades, and relationships between them, such as the positive correlation between the solar wind plasma temperature T and velocity V, and the negative correlation between density N and velocity V, are well known. However, the magnetic field intensity does not appear to be well correlated with any individual plasma parameter. In this paper, we discuss previously under-reported correlations between B and the combined plasma parameters √NV2 as well as between B and √NT. These two correlations are strong during the periods of corotating interaction regions and high speed streams, moderate during intervals of slow solar wind, and rather poor during the passage of interplanetary coronal mass ejections. The results indicate that the magnetic pressure in the solar wind is well correlated both with the plasma dynamic pressure and the thermal pressure. Then, we employ a 3D MHD model to simulate the formation of the relationships between the magnetic strength B and √NV2 as well as √NT observed at 1AU. The inner boundary condition is derived by empirical models, with the magnetic field and density are optional. Five kinds of boundary conditions at the inner boundary of heliosphere are tested. In the cases that the magnetic field is related to speed at the inner boundary, the correlation coefficients between B and √NV2 as well as between B and √NT are even higher than that in the observational results. At 1AU the simulated radial magnetic field shows little latitude dependence, which matches the observation of Ulysses. Most of the modeled characters in these cases are closer to observation than others. This inner boundary condition may more accurately characterize Sun's magnetic influence on the heliosphere. The new input may be able to improve the simulation of CME propagation in the inner heliosphere and the space weather forecasting.

Computational modeling of fully-ionized, magnetized plasmas using the fluid approximation

NASA Astrophysics Data System (ADS)

Schnack, Dalton

2005-10-01

Strongly magnetized plasmas are rich in spatial and temporal scales, making a computational approach useful for studying these systems. The most accurate model of a magnetized plasma is based on a kinetic equation that describes the evolution of the distribution function for each species in six-dimensional phase space. However, the high dimensionality renders this approach impractical for computations for long time scales in relevant geometry. Fluid models, derived by taking velocity moments of the kinetic equation [1] and truncating (closing) the hierarchy at some level, are an approximation to the kinetic model. The reduced dimensionality allows a wider range of spatial and/or temporal scales to be explored. Several approximations have been used [2-5]. Successful computational modeling requires understanding the ordering and closure approximations, the fundamental waves supported by the equations, and the numerical properties of the discretization scheme. We review and discuss several ordering schemes, their normal modes, and several algorithms that can be applied to obtain a numerical solution. The implementation of kinetic parallel closures is also discussed [6].[1] S. Chapman and T.G. Cowling, ``The Mathematical Theory of Non-Uniform Gases'', Cambridge University Press, Cambridge, UK (1939).[2] R.D. Hazeltine and J.D. Meiss, ``Plasma Confinement'', Addison-Wesley Publishing Company, Redwood City, CA (1992).[3] L.E. Sugiyama and W. Park, Physics of Plasmas 7, 4644 (2000).[4] J.J. Ramos, Physics of Plasmas, 10, 3601 (2003).[5] P.J. Catto and A.N. Simakov, Physics of Plasmas, 11, 90 (2004).[6] E.D. Held et al., Phys. Plasmas 11, 2419 (2004)

Hydrogen atom in a quantum plasma environment under the influence of Aharonov-Bohm flux and electric and magnetic fields.

PubMed

Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai

2016-05-01

This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics.

Physics in Strong Magnetic Fields Near Neutron Stars.

ERIC Educational Resources Information Center

Harding, Alice K.

1991-01-01

Discussed are the behaviors of particles and energies in the magnetic fields of neutron stars. Different types of possible research using neutron stars as a laboratory for the study of strong magnetic fields are proposed. (CW)

Acceleration of electrons in strong beam-plasma interactions

NASA Technical Reports Server (NTRS)

Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

1984-01-01

The effects of strong beam-plasma interactions on the electron population of the upper atmosphere have been investigated in an electron acceleration experiment performed with a sounding rocket. The rocket carried the Several Complex Experiments (SCEX) payload which included an electron accelerator, three disposable 'throwaway' detectors (TADs), and a stepped electron energy analyzer. The payload was launched in an auroral arc over the rocket at altitudes of 157 and 178 km, respectively. The performance characteristics of the instruments are discussed in detail. The data are combined with the results of laboratory measurements and show that electrons with energies of at least two and probably four times the injection energy of 2 keV were observed during strong beam-plasma interaction events. The interaction events occurred at pitch angles of 54 and 126 degrees. On the basis of the data it is proposed that the superenergization of the electrons is correlated with the length of the beam-plasma interaction region.

Propagation of Plasma Bunches through a Transverse Magnetic Barrier

NASA Astrophysics Data System (ADS)

Bishaev, A. M.; Gavrikov, M. B.; Kozintseva, M. V.; Savel'ev, V. V.

2018-01-01

The injection of a plasma bunch into a multipolar trap can be applied to fill the trap with a plasma. The injection of the bunch into a tokamak-like trap can be considered an additional means for controlling the processes of plasma heating and fuel delivery to the central zone of a thermonuclear reactor. In both cases, the bunch is injected normally to the magnetic field of the trap. It has been shown theoretically, experimentally, and by numerical simulation that the depth of plasma bunch penetration into the magnetic field varies in direct proportion to the bunch energy and in inverse proportion to the magnetic pressure and the cross-sectional area of the plasma bunch. The data of this work allow researchers to estimate the values of plasma bunch parameters at which the bunch will be trapped. As a result, the process of plasma bunch trapping has been optimized.

Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Smith, James; Lee, Michael; Richeson, Jeff; Schmidt, George; Knapp, Charles E.; Kirkpatrick, Ronald C.; Turchi, Peter J.; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). For the successful implementation of the scheme, plasma jets of the requisite momentum flux density need to be produced. Their transport over sufficiently large distances (a few meters) needs to be assured. When they collide and merge into a liner, relative differences in velocity, density and temperature of the jets could give rise to instabilities in the development of the liner. Variation in the jet properties must be controlled to ensure that the growth rate of the instabilities are not significant over the time scale of the liner formation before engaging with the target plasma. On impact with the target plasma, some plasma interpenetration might occur between the liner and the target. The operating parameter space needs to be identified to ensure that a reasonably robust and conducting contact surface is formed between the liner and the target. A mismatch in the "impedance" between the liner and the target plasma could give rise to undesirable shock heating of the liner leading to increased entropy (thermal losses) in the liner. Any irregularities in the liner will accentuate the Rayleigh-Taylor instabilities during the compression of the target plasma by the liner.

3-D MHD modeling and stability analysis of jet and spheromak plasmas launched into a magnetized plasma

NASA Astrophysics Data System (ADS)

Fisher, Dustin; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward; Arge, C. Nick

2016-10-01

The Plasma Bubble Expansion Experiment (PBEX) at the University of New Mexico uses a coaxial plasma gun to launch jet and spheromak magnetic plasma configurations into the Helicon-Cathode (HelCat) plasma device. Plasma structures launched from the gun drag frozen-in magnetic flux into the background magnetic field of the chamber providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, and shocks. Preliminary modeling is presented using the highly-developed 3-D, MHD, BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid that enables the capture and resolution of shock structures and current sheets, and is particularly suited to model the parameter regime under investigation. CCD images and magnetic field data from the experiment suggest the stabilization of an m =1 kink mode trailing a plasma jet launched into a background magnetic field. Results from a linear stability code investigating the effect of shear-flow as a cause of this stabilization from magnetic tension forces on the jet will be presented. Initial analyses of a possible magnetic Rayleigh Taylor instability seen at the interface between launched spheromaks and their entraining background magnetic field will also be presented. Work supported by the Army Research Office Award No. W911NF1510480.

Fluid theory and simulations of instabilities, turbulent transport and coherent structures in partially-magnetized plasmas of \\mathbf{E}\\times \\mathbf{B} discharges

NASA Astrophysics Data System (ADS)

Smolyakov, A. I.; Chapurin, O.; Frias, W.; Koshkarov, O.; Romadanov, I.; Tang, T.; Umansky, M.; Raitses, Y.; Kaganovich, I. D.; Lakhin, V. P.

2017-01-01

Partially-magnetized plasmas with magnetized electrons and non-magnetized ions are common in Hall thrusters for electric propulsion and magnetron material processing devices. These plasmas are usually in strongly non-equilibrium state due to presence of crossed electric and magnetic fields, inhomogeneities of plasma density, temperature, magnetic field and beams of accelerated ions. Free energy from these sources make such plasmas prone to various instabilities resulting in turbulence, anomalous transport, and appearance of coherent structures as found in experiments. This paper provides an overview of instabilities that exist in such plasmas. A nonlinear fluid model has been developed for description of the Simon-Hoh, lower-hybrid and ion-sound instabilities. The model also incorporates electron gyroviscosity describing the effects of finite electron temperature. The nonlinear fluid model has been implemented in the BOUT++ framework. The results of nonlinear simulations are presented demonstrating turbulence, anomalous current and tendency toward the formation of coherent structures.

A self-consistent two-fluid model of a magnetized plasma-wall transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyergyek, T.; Jožef Stefan Institute, Jamova 39, P.O. Box 100, 1000 Ljubljana; Kovačič, J.

A self-consistent one-dimensional two-fluid model of the magnetized plasma-wall transition is presented. The model includes magnetic field, elastic collisions between ions and electrons, and creation/annihilation of charged particles. Two systems of differential equations are derived. The first system describes the whole magnetized plasma-wall transition region, which consists of the pre-sheath, the magnetized pre-sheath (Chodura layer), and the sheath, which is not neutral, but contains a positive space charge. The second system of equations describes only the neutral part of the plasma-wall transition region—this means only the pre-sheath and the Chodura layer, but not also the sheath. Both systems are solvedmore » numerically. The first system of equations has two singularities. The first occurs when ion velocity in the direction perpendicularly to the wall drops below the ion thermal velocity. The second occurs when the electron velocity in the direction perpendicularly to the wall exceeds the electron thermal velocity. The second system of differential equations only has one singularity, which has also been derived analytically. For finite electron to ion mass ratio, the integration of the second system always breaks down before the Bohm criterion is fulfilled. Some properties of the first system of equations are examined. It is shown that the increased collision frequency demagnetizes the plasma. On the other hand, if the magnetic field is so strong that the ion Larmor radius and the Debye length are comparable, the electron velocity in the direction perpendicularly to the wall reaches the electron thermal velocity before the ion velocity in the direction perpendicularly to the wall reaches the ion sound velocity. In this case, the integration of the model equations breaks down before the Bohm criterion is fulfilled and the sheath is formed.« less

Magnetic field diffusion and dissipation in reversed-field plasmas

NASA Technical Reports Server (NTRS)

Drake, J. F.; Gladd, N. T.; Huba, J. D.

1981-01-01

A diffusion equation is derived which describes the evolution of a magnetic field in a plasma of arbitrary beta and resistivity. The equation is valid for a one-dimensional slab geometry, assumes the plasma remains in quasi-equilibrium throughout its evolution and does not include thermal transport. Scaling laws governing the rate of change of the magnetic energy, particle drift energy, and magnetic flux are calculated. It is found that the magnetic free energy can be substantially larger than the particle drift energy and can be an important energy reservoir in driving plasma instabilities (e.g., the lower-hybrid-drift instability). In addition, the effect of a spatially varying resistivity on the evolution of a reversed-field plasma is studied. The resistivity model used is based upon the anomalous transport properties associated with the nonlocal mode structure of the lower-hybrid-drift instability. The relevance of this research to laboratory plasmas (e.g., theta pinches, reversed-field theta pinches) and space plasmas (e.g., the earth's magnetotail) is discussed.

Observations of dusty plasmas with magnetized dust grains

NASA Astrophysics Data System (ADS)

Luo, Q.-Z.; D'Angelo, N.

2000-11-01

We report a newly observed phenomenon in a dusty plasma device of the \\mbox{Q-machine} type. At low plasma densities the time required by the plasma to return to its no-dust conditions, after the dust dispenser is turned off, can be as long as many tens of seconds or longer. A tentative interpretation of this observation in terms of magnetized dust grains is advanced. It appears that an important loss mechanism of fine dust grains is by ion drag along the magnetic field lines. The effect of ion drag is somewhat counteracted by the -µ∇B force present when the magnetic field has a mirror geometry.

Apparatus for magnetic and electrostatic confinement of plasma

DOEpatents

Rostoker, Norman; Binderbauer, Michl

2013-06-11

An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

Apparatus for magnetic and electrostatic confinement of plasma

DOEpatents

Rostoker, Norman; Binderbauer, Michl

2016-07-05

An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

Apparatus for magnetic and electrostatic confinement of plasma

DOEpatents

Rostoker, Norman; Binderbauer, Michl

2006-10-31

An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

Apparatus for magnetic and electrostatic confinement of plasma

DOEpatents

Rostoker, Norman; Binderbauer, Michl

2006-04-11

An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

Apparatus for magnetic and electrostatic confinement of plasma

DOEpatents

Rostoker, Norman [Irvine, CA; Binderbauer, Michl [Irvine, CA

2009-08-04

An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

Mirror-field confined compact plasma source using permanent magnet for plasma processings.

PubMed

Goto, Tetsuya; Sato, Kei-Ichiro; Yabuta, Yuki; Sugawa, Shigetoshi

2016-12-01

A mirror-field confined compact electron cyclotron resonance (ECR) plasma source using permanent magnets was developed, aiming for the realization of high-quality plasma processings where high-density reactive species are supplied to a substrate with minimizing the ion bombardment damages. The ECR position was located between a microwave transmissive window and a quartz limiter, and plasmas were transported from the ECR position to a midplane of the magnetic mirror field through the quartz limiter. Thus, a radius of core plasma could be determined by the limiter, which was 15 mm in this study. Plasma parameters were investigated by the Langmuir probe measurement. High-density plasma larger than 10 11 cm -3 could be produced by applying 5.85-GHz microwave power of 10 W or more. For the outside region of the core plasma where a wafer for plasma processings will be set at, the ion current density was decreased dramatically with distance from the core plasma and became smaller by approximately two orders of magnitude that in the core plasma region for the radial position of 40 mm, suggesting the realization of reduction in ion bombardment damages.

Jeans self gravitational instability of strongly coupled quantum plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Prerana, E-mail: preranaiitd@rediffmail.com; Chhajlani, R. K.

2014-07-15

The Jeans self-gravitational instability is studied for quantum plasma composed of weakly coupled degenerate electron fluid and non-degenerate strongly coupled ion fluid. The formulation for such system is done on the basis of two fluid theory. The dynamics of weakly coupled degenerate electron fluid is governed by inertialess momentum equation. The quantum forces associated with the quantum diffraction effects and the quantum statistical effects act on the degenerate electron fluid. The strong correlation effects of ion are embedded in generalized viscoelastic momentum equation including the viscoelasticity and shear viscosities of ion fluid. The general dispersion relation is obtained using themore » normal mode analysis technique for the two regimes of propagation, i.e., hydrodynamic and kinetic regimes. The Jeans condition of self-gravitational instability is also obtained for both regimes, in the hydrodynamic regime it is observed to be affected by the ion plasma oscillations and quantum parameter while in the kinetic regime in addition to ion plasma oscillations and quantum parameter, it is also affected by the ion velocity which is modified by the viscosity generated compressional effects. The Jeans critical wave number and corresponding critical mass are also obtained for strongly coupled quantum plasma for both regimes.« less

Characterization of >100 T magnetic fields associated with relativistic Weibel instability in laser-produced plasmas

NASA Astrophysics Data System (ADS)

Mishra, Rohini; Ruyer, Charles; Goede, Sebastian; Roedel, Christian; Gauthier, Maxence; Zeil, Karl; Schramm, Ulrich; Glenzer, Siegfried; Fiuza, Frederico

2016-10-01

Weibel-type instabilities can occur in weakly magnetized and anisotropic plasmas of relevance to a wide range of astrophysical and laboratory scenarios. It leads to the conversion of a significant fraction of the kinetic energy of the plasma into magnetic energy. We will present a detailed numerical study, using 2D and 3D PIC simulations of the Weibel instability in relativistic laser-solid interactions. In this case, the instability develops due to the counter-streaming of laser-heated electrons and the background return current. We show that the growth rate of the instability is maximized near the critical density region on the rear side of the expanded plasma, producing up to 400 MG magnetic fields for Hydrogen plasmas. We have found that this strong field can be directly probed by energetic protons accelerated in rear side of the plasma by Target Normal Sheath Acceleration (TNSA). This allows the experimental characterization of the instability from the analysis of the spatial modulation of the detected protons. Our numerical results are compared with recent laser experiments with Hydrogen jets and show good agreement with the proton modulations observed experimentally. This work was supported by the DOE Office of Science, Fusion Energy Science (FWP 100182).

Suppression of cooling by strong magnetic fields in white dwarf stars.

PubMed

Valyavin, G; Shulyak, D; Wade, G A; Antonyuk, K; Zharikov, S V; Galazutdinov, G A; Plachinda, S; Bagnulo, S; Machado, L Fox; Alvarez, M; Clark, D M; Lopez, J M; Hiriart, D; Han, Inwoo; Jeon, Young-Beom; Zurita, C; Mujica, R; Burlakova, T; Szeifert, T; Burenkov, A

2014-11-06

Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.

Confinement properties of tokamak plasmas with extended regions of low magnetic shear

NASA Astrophysics Data System (ADS)

Graves, J. P.; Cooper, W. A.; Kleiner, A.; Raghunathan, M.; Neto, E.; Nicolas, T.; Lanthaler, S.; Patten, H.; Pfefferle, D.; Brunetti, D.; Lutjens, H.

2017-10-01

Extended regions of low magnetic shear can be advantageous to tokamak plasmas. But the core and edge can be susceptible to non-resonant ideal fluctuations due to the weakened restoring force associated with magnetic field line bending. This contribution shows how saturated non-linear phenomenology, such as 1 / 1 Long Lived Modes, and Edge Harmonic Oscillations associated with QH-modes, can be modelled accurately using the non-linear stability code XTOR, the free boundary 3D equilibrium code VMEC, and non-linear analytic theory. That the equilibrium approach is valid is particularly valuable because it enables advanced particle confinement studies to be undertaken in the ordinarily difficult environment of strongly 3D magnetic fields. The VENUS-LEVIS code exploits the Fourier description of the VMEC equilibrium fields, such that full Lorenzian and guiding centre approximated differential operators in curvilinear angular coordinates can be evaluated analytically. Consequently, the confinement properties of minority ions such as energetic particles and high Z impurities can be calculated accurately over slowing down timescales in experimentally relevant 3D plasmas.

Gyrokinetic simulations with external resonant magnetic perturbations: Island torque and nonambipolar transport with plasma rotation

NASA Astrophysics Data System (ADS)

Waltz, R. E.; Waelbroeck, F. L.

2012-03-01

Static external resonant magnetic field perturbations (RMPs) have been added to the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comp. Phys. 186, 545 (2003)]. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow jr, and the corresponding j→×B→ plasma torque (density) R[jrBp/c], induced by magnetic islands that break the toroidal symmetry of a tokamak. This extends the previous GYRO formulation for the transport of toroidal angular momentum (TAM) [R. E. Waltz, G. M. Staebler, J. Candy, and F. L. Hinton, Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)]. The focus is on electrostatic full torus radial slice simulations of externally induced q =m/n=6/3 islands with widths 5% of the minor radius or about 20 ion gyroradii. Up to moderately strong E ×B rotation, the island torque scales with the radial electric field at the resonant surface Er, the island width w, and the intensity I of the high-n micro-turbulence, as Erw√I . The radial current inside the island is carried (entirely in the n =3 component) and almost entirely by the ion E ×B flux, since the electron E ×B and magnetic flutter particle fluxes are cancelled. The net island torque is null at zero Er rather than at zero toroidal rotation. This means that while the expected magnetic braking of the toroidal plasma rotation occurs at strong co- and counter-current rotation, at null toroidal rotation, there is a small co-directed magnetic acceleration up to the small diamagnetic (ion pressure gradient driven) co-rotation corresponding to the zero Er and null torque. This could be called the residual stress from an externally induced island. At zero Er, the only effect is the expected partial flattening of the electron temperature gradient within the island. Finite-beta GYRO simulations demonstrate almost complete RMP field screening and n =3 mode unlocking at strong Er.

Shock structures in a strongly coupled self-gravitating opposite-polarity dust plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mamun, A. A.; Schlickeiser, R.

2016-03-15

A strongly coupled, self-gravitating, opposite-polarity dust plasma (containing strongly coupled inertial positive and negative dust fluids, and inertialess weakly coupled ions) is considered. The generalized hydrodynamic model and the reductive perturbation method are employed to examine the possibility for the formation of the dust-acoustic (DA) shock structures in such an opposite-polarity dust plasma. It has been shown that the strong correlation among charged dust is a source of dissipation and is responsible for the formation of the DA shock structures in such the opposite-polarity dust plasma medium. The parametric regimes for the existence of the DA shock structures (associated withmore » electrostatic and gravitational potentials) and their basic properties (viz., polarity, amplitude, width, and speed) are found to be significantly modified by the combined effects of positively charged dust component, self-gravitational field, and strong correlation among charged dust. The implications of our results in different space plasma environments and laboratory plasma devices are briefly discussed.« less

Measurement of magnetic field fluctuations and diamagnetic currents within a laser ablation plasma interacting with an axial magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ikeda, S.; Horioka, K.; Okamura, M.

Here, the guiding of laser ablation plasmas with axial magnetic fields has been used for many applications, since its effectiveness has been proven empirically. For more sophisticated and complicated manipulations of the plasma flow, the behavior of the magnetic field during the interaction and the induced diamagnetic current in the plasma plume needs to be clearly understood. To achieve the first milestone for establishing magnetic plasma manipulation, we measured the spatial and temporal fluctuations of the magnetic field caused by the diamagnetic current. We showed that the small fluctuations of the magnetic field can be detected by using a simplemore » magnetic probe. We observed that the field penetrates to the core of the plasma plume. The diamagnetic current estimated from the magnetic field had temporal and spatial distributions which were confirmed to be correlated with the transformation of the plasma plume. Our results show that the measurement by the magnetic probe is an effective method to observe the temporal and spatial distributions of the magnetic field and diamagnetic current. The systematic measurement of the magnetic field variations is a valuable method to establish the magnetic field manipulation of the laser ablation plasma.« less

Measurement of magnetic field fluctuations and diamagnetic currents within a laser ablation plasma interacting with an axial magnetic field

DOE PAGES

Ikeda, S.; Horioka, K.; Okamura, M.

2017-10-10

Here, the guiding of laser ablation plasmas with axial magnetic fields has been used for many applications, since its effectiveness has been proven empirically. For more sophisticated and complicated manipulations of the plasma flow, the behavior of the magnetic field during the interaction and the induced diamagnetic current in the plasma plume needs to be clearly understood. To achieve the first milestone for establishing magnetic plasma manipulation, we measured the spatial and temporal fluctuations of the magnetic field caused by the diamagnetic current. We showed that the small fluctuations of the magnetic field can be detected by using a simplemore » magnetic probe. We observed that the field penetrates to the core of the plasma plume. The diamagnetic current estimated from the magnetic field had temporal and spatial distributions which were confirmed to be correlated with the transformation of the plasma plume. Our results show that the measurement by the magnetic probe is an effective method to observe the temporal and spatial distributions of the magnetic field and diamagnetic current. The systematic measurement of the magnetic field variations is a valuable method to establish the magnetic field manipulation of the laser ablation plasma.« less

Influence of the interplanetary magnetic field on the occurrence and thickness of the plasma mantle

NASA Technical Reports Server (NTRS)

Sckopke, N.; Paschmann, G.; Rosenbauer, H.; Fairfield, D. H.

1976-01-01

The response of the plasma mantle to the orientation of the interplanetary magnetic field (IMF) has been studied by correlating Heos 2 plasma and Imp 6 magnetic field data. The mantle is nearly always present when the IMF has a southward component and often also when the field has a weak northward component. In addition, the mantle appears increasingly thicker with greater southward components. On the other hand, the mantle is thin or missing (from the region where it is normally found) when the average IMF has a strong northward component. This result supports the idea that polar cap convection plays a dominant role in the formation of the plasma mantle: mantle plasma originates in the magnetosheath, enters the magnetosphere through the day side polar cusps, and is transported across the cusp to the night side by means of a convection electric field whose magnitude is controlled by the orientation of the IMF.

Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Kirkpatrick, Ronald C.; Knapp, Charles E.; Rodgers, Stephen L. (Technical Monitor)

2002-01-01

Magnetized target fusion is an emerging, relatively unexplored approach to fusion for electrical power and propulsion application. The physical principles of the concept are founded upon both inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). It attempts to combine the favorable attributes of both these orthogonal approaches to fusion, but at the same time, avoiding the extreme technical challenges of both by exploiting a fusion regime intermediate between them. It uses a material liner to compress, heat and contain the fusion reacting plasma (the target plasma) mentally. By doing so, the fusion burn could be made to occur at plasma densities as high as six orders of magnitude higher than conventional MCF such as tokamak, thus leading to an approximately three orders of magnitude reduction in the plasma energy required for ignition. It also uses a transient magnetic field, compressed to extremely high intensity (100's T to 1000T) in the target plasma, to slow down the heat transport to the liner and to increase the energy deposition of charged-particle fusion products. This has several compounding beneficial effects. It leads to longer energy confinement time compared with conventional ICF without magnetized target, and thus permits the use of much lower plasma density to produce reasonable burn-up fraction. The compounding effects of lower plasma density and the magneto-insulation of the target lead to greatly reduced compressional heating power on the target. The increased energy deposition rate of charged-particle fusion products also helps to lower the energy threshold required for ignition and increasing the burn-up fraction. The reduction in ignition energy and the compressional power compound to lead to reduced system size, mass and R&D cost. It is a fusion approach that has an affordable R&D pathway, and appears attractive for propulsion application in the nearer term.

Effect of anode-cathode geometry on performance of the HIP-1 hot ion plasma. [magnetic mirrors

NASA Technical Reports Server (NTRS)

Lauver, M. R.

1978-01-01

Hot-ion hydrogen plasma experiments were conducted in the NASA Lewis HIP-1 magnetic mirror facility to determine how the ion temperature was influenced by the axial position of the cathode tips relative to the anodes. A steady-state EXB plasma was formed by applying a strong radially inward dc electric field near the throats of the magnetic mirrors. The dc electric field was created between hollow cathode rods inside hollow anode cylinders, both concentric with the magnetic axis. The highest ion temperatures, 900 eV, were attained when the tip of each cathode was in the same plane as the end of its anode. These temperatures were reached with 22 kV applied to the electrodes in a field of 1.1 tesla. Scaling relations were empirically determined for ion temperature and the product of ion density and neutral particle density as a function of cathode voltage, discharge current, and electrode positions. Plasma discharge current vs voltage (I-V) characteristics were determined.

Numerical Investigation of Plasma Detachment in Magnetic Nozzle Experiments

NASA Technical Reports Server (NTRS)

Sankaran, Kamesh; Polzin, Kurt A.

2008-01-01

At present there exists no generally accepted theoretical model that provides a consistent physical explanation of plasma detachment from an externally-imposed magnetic nozzle. To make progress towards that end, simulation of plasma flow in the magnetic nozzle of an arcjet experiment is performed using a multidimensional numerical simulation tool that includes theoretical models of the various dispersive and dissipative processes present in the plasma. This is an extension of the simulation tool employed in previous work by Sankaran et al. The aim is to compare the computational results with various proposed magnetic nozzle detachment theories to develop an understanding of the physical mechanisms that cause detachment. An applied magnetic field topology is obtained using a magnetostatic field solver (see Fig. I), and this field is superimposed on the time-dependent magnetic field induced in the plasma to provide a self-consistent field description. The applied magnetic field and model geometry match those found in experiments by Kuriki and Okada. This geometry is modeled because there is a substantial amount of experimental data that can be compared to the computational results, allowing for validation of the model. In addition, comparison of the simulation results with the experimentally obtained plasma parameters will provide insight into the mechanisms that lead to plasma detachment, revealing how they scale with different input parameters. Further studies will focus on modeling literature experiments both for the purpose of additional code validation and to extract physical insight regarding the mechanisms driving detachment.

Oscillating two-stream instability of beat waves in a hot magnetized plasma

NASA Astrophysics Data System (ADS)

Ferdous, T.; Amin, M. R.; Salimullah, M.

1997-02-01

It is shown that an electrostatic electron plasma beat wave is efficiently unstable for a low-frequency and short-wave-length purely growing perturbation (ω, k), i.e. an oscillating two-stream instability in a transversely magnetized hot plasma. The nonlinear response of electrons and ions with strong finite Larmor radius effects has been obtained by solving the Vlasov equation expressed in the guiding-center coordinates. The effect of ion dynamics has been found to play a vital role around ω ∼ ωci, where ωci is the ion-cyclotron frequency. For typical plasma parameters, it is found that the maximum growth rate of the instability is about two orders higher when ion motion is taken into account in addition to the electron dynamics.

High-time resolution measurements of upstream magnetic field and plasma conditions during flux transfer events at the Earth's dayside magnetopause

NASA Technical Reports Server (NTRS)

Jacob, Jamey D.; Carrell, Cynthia

1993-01-01

We present preliminary results of a study of upstream magnetic field and plasma conditions measured by IRM during flux transfer events observed at the Earth's magnetopause by CCE. This study was designed to determine the importance of various upstream factors in the formation of bipolar magnetic field signatures called flux transfer events (FTEs). Six FTE encounters were examined. In three cases, the two satellites were on similar magnetic field lines. Preliminary investigation showed that fluctuations occurred in the Bz component of the interplanetary magnetic field (IMF) resulting in a southward field preceding the FTE in all three of these cases. In two of these cases, the changes were characterized by a distinct rotation from a strong southward to a strong northward field. There were also accompanying changes in the dynamic and thermal pressure in the solar wind immediately before the FTE was encountered. Examination of the 3D plasma distributions showed that these pulses were due to the addition of energetic upstreaming foreshock particles. There were no consistent changes in either Bz or the plasma pressure at IRM for the three events when the satellites were not connected by the IMF.

Effect of rotation on Jeans instability of magnetized radiative quantum plasma

NASA Astrophysics Data System (ADS)

Joshi, H.; Pensia, R. K.

2017-03-01

The influence of rotation on the Jeans instability of homogeneous magnetized radiative quantum plasma is investigated. The basic equations of the problem are constructed and linearized by using the Quantum Magnetohydrodynamics (QMHD) model. The general dispersion relation is obtained by using the normal mode analysis technique, which is reduced for both the transverse and the longitudinal mode of propagations and further it is reduced for the axis of rotation parallel and perpendicular to the magnetic field. We found that the stabilizing effects of rotation are decreases for a strong magnetic field which is shown in the graphical representation. We also found that the quantum correction modified the condition of Jeans instability in both modes of propagation. The stabilizing effect of rotation is more increased in the presence of quantum correction.

Final Technical Report: Magnetic Reconnection in High-Energy Laser-Produced Plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Germaschewski, Kai; Fox, William; Bhattacharjee, Amitava

This report describes the final results from the DOE Grant DE-SC0007168, “Fast Magnetic Reconnection in HED Laser-Produced Plasmas.” The recent generation of laboratory high-energy-density physics facilities has opened significant physics opportunities for experimentally modeling astrophysical plasmas. The goal of this proposal is to use these new tools to study fundamental problems in plasma physics and plasma astrophysics. Fundamental topics in this area involve study of the generation, amplification, and fate of magnetic fields, which are observed to pervade the plasma universe and govern its evolution. This project combined experiments at DOE laser facilities with kinetic plasma simulation to study thesemore » processes. The primary original goal of the project was to study magnetic reconnection using a new experimental platform, colliding magnetized laser-produced plasmas. However through a series of fortuitous discoveries, the work broadened out to allow significant advancement on multiple topics in laboratory astrophysics, including magnetic reconnection, Weibel instability, and collisionless shocks.« less

A new class of strongly coupled plasmas inspired by sonoluminescence

NASA Astrophysics Data System (ADS)

Bataller, Alexander; Plateau, Guillaume; Kappus, Brian; Putterman, Seth

2014-10-01

Sonoluminescence originates in a strongly coupled plasma with a near liquid density and a temperature of ~10,000 K. This plasma is in LTE and therefore, it should be a general thermodynamic state. To test the universality of sonoluminescence, similar plasma conditions were generated using femtosecond laser breakdown in high pressure gases. Calibrated streak spectroscopy reveals both transport and thermodynamic properties of a strongly coupled plasma. A blackbody spectrum, which persists long after the exciting laser has turned off, indicates the presence of a highly ionized LTE microplasma. In parallel with sonoluminescence, this thermodynamic state is achieved via a considerable reduction in the ionization potential. We gratefully acknowledge support from DARPA MTO for research on microplasmas. We thank Brian Naranjo, Keith Weninger, Carlos Camara, Gary Williams, and John Koulakis for valuable discussions.

Espisodic detachment of Martian crustal magnetic fields leading to bulk atmospheric plasma escape

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brain, D A; Baker, A H; Briggs, J

2009-06-02

We present an analysis of magnetic field and suprathermal electron measurements from the Mars Global Surveyor (MGS) spacecraft that reveals isolated magnetic structures filled with Martian atmospheric plasma located downstream from strong crustal magnetic fields with respect to the flowing solar wind. The structures are characterized by magnetic field enhancements and rotations characteristic of magnetic flux ropes, and characteristic ionospheric electron energy distributions with angular distributions distinct from surrounding regions. These observations indicate that significant amounts of atmosphere are intermittently being carried away from Mars by a bulk removal process: the top portions of crustal field loops are stretched throughmore » interaction with the solar wind and detach via magnetic reconnection. This process occurs frequently and may account for as much as 10% of the total present-day ion escape from Mars.« less

Magnetic moments induce strong phonon renormalization in FeSi.

PubMed

Krannich, S; Sidis, Y; Lamago, D; Heid, R; Mignot, J-M; Löhneysen, H v; Ivanov, A; Steffens, P; Keller, T; Wang, L; Goering, E; Weber, F

2015-11-27

The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths.

Dual-function magnetic structure for toroidal plasma devices

DOEpatents

Brown, Robert L.

1978-01-01

This invention relates to a support system wherein the iron core and yoke of the plasma current system of a tokamak plasma containment device is redesigned to support the forces of the magnet coils. The containment rings, which occupy very valuable space around the magnet coils, are utilized to serve as yokes for the core such that the conventional yoke is eliminated. The overall result is an improved aspect ratio, reduction in structure, smaller overall size, and improved access to the plasma ring.

Orientation of Magnetized MnBi in a Strong Static Magnetic Field

NASA Astrophysics Data System (ADS)

Zheng, Tianxiang; Zhong, Yunbo; Dong, Licheng; Zhou, Bangfei; Ren, Zhongming; Debray, Francois; Beaugnon, Eric

2018-06-01

Solidification of Bi-4.5 wt pct Mn alloy was investigated in the presence and absence of a strong static magnetic field (SSMF). A cooling rate ( R) of 60 K/min caused MnBi to orient with the SSMF, owing to the force moment and attractive force. The attractive force and magnetic gradient force induced formation of multilayered MnBi when R was 5 K/min. The magnetic gradient force was damped when R was 60 K/min. Low cooling rates favored the aggregation process.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

NASA Astrophysics Data System (ADS)

Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S.

2018-05-01

The icy surface of Jupiter's moon, Europa, is thought to lie on top of a global ocean1-4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa's surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5-7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo's closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter's corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa's thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures

NASA Astrophysics Data System (ADS)

Jia, Xianzhe; Kivelson, Margaret G.; Khurana, Krishan K.; Kurth, William S.

2018-06-01

The icy surface of Jupiter's moon, Europa, is thought to lie on top of a global ocean1-4. Signatures in some Hubble Space Telescope images have been associated with putative water plumes rising above Europa's surface5,6, providing support for the ocean theory. However, all telescopic detections reported were made at the limit of sensitivity of the data5-7, thereby calling for a search for plume signatures in in-situ measurements. Here, we report in-situ evidence of a plume on Europa from the magnetic field and plasma wave observations acquired on Galileo's closest encounter with the moon. During this flyby, which dropped below 400 km altitude, the magnetometer8 recorded an approximately 1,000-kilometre-scale field rotation and a decrease of over 200 nT in field magnitude, and the Plasma Wave Spectrometer9 registered intense localized wave emissions indicative of a brief but substantial increase in plasma density. We show that the location, duration and variations of the magnetic field and plasma wave measurements are consistent with the interaction of Jupiter's corotating plasma with Europa if a plume with characteristics inferred from Hubble images were erupting from the region of Europa's thermal anomalies. These results provide strong independent evidence of the presence of plumes at Europa.

Strong plasma turbulence in the earth's electron foreshock

NASA Technical Reports Server (NTRS)

Robinson, P. A.; Newman, D. L.

1991-01-01

A quantitative model is developed to account for the distribution in magnitude and location of the intense plasma waves observed in the earth's electron foreshock given the observed rms levels of waves. In this model, nonlinear strong-turbulence effects cause solitonlike coherent wave packets to form and decouple from incoherent background beam-excited weak turbulence, after which they convect downstream with the solar wind while collapsing to scales as short as 100 m and fields as high as 2 V/m. The existence of waves with energy densities above the strong-turbulence wave-collapse threshold is inferred from observations from IMP 6 and ISEE 1 and quantitative agreement is found between the predicted distribution of fields in an ensemble of such wave packets and the actual field distribution observed in situ by IMP 6. Predictions for the polarization of plasma waves and the bandwidth of ion-sound waves are also consistent with the observations. It is shown that strong-turbulence effects must be incorporated in any comprehensive theory of the propagation and evolution of electron beams in the foreshock. Previous arguments against the existence of strong turbulence in the foreshock are refuted.

Optimal Design of Magnetic ComponentsinPlasma Cutting Power Supply

NASA Astrophysics Data System (ADS)

Jiang, J. F.; Zhu, B. R.; Zhao, W. N.; Yang, X. J.; Tang, H. J.

2017-10-01

Phase-shifted transformer and DC reactor are usually needed in chopper plasma cutting power supply. Because of high power rate, the loss of magnetic components may reach to several kilowatts, which seriously affects the conversion efficiency. Therefore, it is necessary to research and design low loss magnetic components by means of efficient magnetic materials and optimal design methods. The main task in this paper is to compare the core loss of different magnetic material, to analyze the influence of transformer structure, winding arrangement and wire structure on the characteristics of magnetic component. Then another task is to select suitable magnetic material, structure and wire in order to reduce the loss and volume of magnetic components. Based on the above outcome, the optimization design process of transformer and dc reactor are proposed in chopper plasma cutting power supply with a lot of solutions. These solutions are analyzed and compared before the determination of the optimal solution in order to reduce the volume and power loss of the two magnetic components and improve the conversion efficiency of plasma cutting power supply.

Laboratory Study of the Shaping and Evolution of Magnetized Episodic Plasma Jets

NASA Astrophysics Data System (ADS)

Higginson, Drew

2015-11-01

The expansion of hot, dense plasma (100 eV, 1018 cm-3) into vacuum occupied by a strong magnetic field (β =Pkinetic /Pmag ~ 1) along the expansion axis is a seemingly elementary physics problem, yet it is one that has scarcely been investigated. As well as being a fundamental problem in plasma physics, understanding such a situation is important to provide an explanation of large-scale jets observed in the formation of young stellar objects (YSO). Additionally, the ability to manipulate such a situation (e.g. to optimize x-ray emission) may be essential to the feasibility of recently proposed inertial confinement fusion (ICF) schemes with an imposed magnetic field. To investigate these situations, a CF2 foil is irradiated with the ELFIE laser (1013 W/cm2, 0.6 ns) in an external axial magnetic field of 20 T. As the plasma expands radially it is restricted by magnetic pressure that creates a cavity with a shock at the expansion edge. This shock redirects flow back on axis and creates a strong, stationary, conical shock that collimates the flow into a jet traveling over 1000 km/s and extending many centimeters. The effect of episodic heating (e.g. from variable mass ejection in a YSO, or pulse shaping in ICF) was investigated by irradiating the target with a precursor laser (1012 W/cm2, 0.6 ns) at 9 to 19 ns prior to the main pulse. The addition of this relatively small addition of energy (<20% of the main pulse energy) changed the dynamics of the expansion dramatically by increasing the strength of the conical shock, reducing the forward expansion of the cavity and dramatically increasing emission. We also present MHD simulations that reproduce the experimental observables and help to understand dynamics of jet and cavity formation. Prepared by LLNL under Contract DE-AC52-07NA27344. Presently at Lawrence Livermore National Laboratory.

Influence of pinches on magnetic reconnection in turbulent space plasmas

NASA Astrophysics Data System (ADS)

Olshevsky, Vyacheslav; Lapenta, Giovanni; Markidis, Stefano; Divin, Andrey

A generally accepted scenario of magnetic reconnection in space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is widely studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both null-points and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present nitially, and Z-pinches are formed during the simulation. The X-points are relatively stable, and no substantial energy dissipation is associated with them. On contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of approximately 1.5 percent per ion gyro period. Current channels and twisted magnetic fields are ubiquitous in turbulent space plasmas, so pinches can be responsible for the observed high magnetic reconnection rates.

The effects of magnetic nozzle configurations on plasma thrusters

NASA Technical Reports Server (NTRS)

York, Thomas M.

1989-01-01

Plasma thrusters have been operated at power levels from 10kW to 0.1MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations will be studied without applied fields and with applied magnetic nozzle fields. Unique computational studies will utilize existing codes which accurately include transport processes. Unique diagnostic studies will support the experimental studies to generate new data. Both computation and diagnostics will be combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.

Plasma Disks and Rings with ``High'' Magnetic Energy Densities

NASA Astrophysics Data System (ADS)

Coppi, B.; Rousseau, F.

2006-04-01

The nonlinear theory of rotating axisymmetric thin structures in which the magnetic field energy density is comparable with the thermal plasma energy density is formulated. The only flow velocity included in the theory is the velocity of rotation around a central object whose gravity is dominant. The periodic sequence, in the radial direction, of pairs of opposite current channels that can form is shown to lead to relatively large plasma density and pressure modulations, while the relevant magnetic surfaces can acquire a ``crystal structure.'' A new class of equilibria consisting of a series of plasma rings is identified, in the regimes where the plasma pressure is comparable to the magnetic pressure associated with the fields produced by the internal currents. The possible relevance of this result to the formation of dusty plasma rings is pointed out.

One-loop QCD thermodynamics in a strong homogeneous and static magnetic field

NASA Astrophysics Data System (ADS)

Rath, Shubhalaxmi; Patra, Binoy Krishna

2017-12-01

We have studied how the equation of state of thermal QCD with two light flavors is modified in a strong magnetic field. We calculate the thermodynamic observables of hot QCD matter up to one-loop, where the magnetic field affects mainly the quark contribution and the gluon part is largely unaffected except for the softening of the screening mass. We have first calculated the pressure of a thermal QCD medium in a strong magnetic field, where the pressure at fixed temperature increases with the magnetic field faster than the increase with the temperature at constant magnetic field. This can be understood from the dominant scale of thermal medium in the strong magnetic field, being the magnetic field, in the same way that the temperature dominates in a thermal medium in the absence of magnetic field. Thus although the presence of a strong magnetic field makes the pressure of hot QCD medium larger, the dependence of pressure on the temperature becomes less steep. Consistent with the above observations, the entropy density is found to decrease with the temperature in the presence of a strong magnetic field which is again consistent with the fact that the strong magnetic field restricts the dynamics of quarks to two dimensions, hence the phase space becomes squeezed resulting in the reduction of number of microstates. Moreover the energy density is seen to decrease and the speed of sound of thermal QCD medium increases in the presence of a strong magnetic field. These findings could have phenomenological implications in heavy ion collisions because the expansion dynamics of the medium produced in non-central ultra-relativistic heavy ion collisions is effectively controlled by both the energy density and the speed of sound.

Mode conversion in cold low-density plasma with a sheared magnetic field

DOE PAGES

Dodin, I. Y.; Ruiz, D. E.; Kubo, S.

2017-12-19

Here, a theory is proposed that describes mutual conversion of two electromagnetic modes in cold low-density plasma, specifically, in the high-frequency limit where the ion response is negligible. In contrast to the classic (Landau–Zener-type) theory of mode conversion, the region of resonant coupling in low-density plasma is not necessarily narrow, so the coupling matrix cannot be approximated with its first-order Taylor expansion; also, the initial conditions are set up differently. For the case of strong magnetic shear, a simple method is identified for preparing a two-mode wave such that it transforms into a single-mode wave upon entering high-density plasma. Themore » theory can be used for reduced modeling of wave-power input in fusion plasmas. In particular, applications are envisioned in stellarator research, where the mutual conversion of two electromagnetic modes near the plasma edge is a known issue.« less

Mode conversion in cold low-density plasma with a sheared magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dodin, I. Y.; Ruiz, D. E.; Kubo, S.

Here, a theory is proposed that describes mutual conversion of two electromagnetic modes in cold low-density plasma, specifically, in the high-frequency limit where the ion response is negligible. In contrast to the classic (Landau–Zener-type) theory of mode conversion, the region of resonant coupling in low-density plasma is not necessarily narrow, so the coupling matrix cannot be approximated with its first-order Taylor expansion; also, the initial conditions are set up differently. For the case of strong magnetic shear, a simple method is identified for preparing a two-mode wave such that it transforms into a single-mode wave upon entering high-density plasma. Themore » theory can be used for reduced modeling of wave-power input in fusion plasmas. In particular, applications are envisioned in stellarator research, where the mutual conversion of two electromagnetic modes near the plasma edge is a known issue.« less

Observations of strong ion-ion correlations in dense plasmas

DOE PAGES

Ma, T.; Fletcher, L.; Pak, A.; ...

2014-04-24

Using simultaneous spectrally, angularly, and temporally resolved x-ray scattering, we measure the pronounced ion-ion correlation peak in a strongly coupled plasma. Laser-driven shock-compressed aluminum at ~3× solid density is probed with high-energy photons at 17.9 keV created by molybdenum He-α emission in a laser-driven plasma source. The measured elastic scattering feature shows a well-pronounced correlation peak at a wave vector of k=4Å –1. The magnitude of this correlation peak cannot be described by standard plasma theories employing a linear screened Coulomb potential. Advanced models, including a strong short-range repulsion due to the inner structure of the aluminum ions are howevermore » in good agreement with the scattering data. These studies have demonstrated a new highly accurate diagnostic technique to directly measure the state of compression and the ion-ion correlations. Furthermore, we have since applied this new method in single-shot wave-number resolved S(k) measurements to characterize the physical properties of dense plasmas.« less

Laboratory study of collisionless coupling between explosive debris plasma and magnetized ambient plasma

NASA Astrophysics Data System (ADS)

Bondarenko, A. S.; Schaeffer, D. B.; Everson, E. T.; Clark, S. E.; Lee, B. R.; Constantin, C. G.; Vincena, S.; Van Compernolle, B.; Tripathi, S. K. P.; Winske, D.; Niemann, C.

2017-08-01

The explosive expansion of a localized plasma cloud into a relatively tenuous, magnetized, ambient plasma characterizes a variety of astrophysical and space phenomena. In these rarified environments, collisionless electromagnetic processes rather than Coulomb collisions typically mediate the transfer of momentum and energy from the expanding "debris" plasma to the surrounding ambient plasma. In an effort to better understand the detailed physics of collisionless coupling mechanisms, compliment in situ measurements of space phenomena, and provide validation of previous computational and theoretical work, the present research jointly utilizes the Large Plasma Device and the Raptor laser facility at the University of California, Los Angeles to study the super-Alfvénic, quasi-perpendicular expansion of laser-produced carbon (C) and hydrogen (H) debris plasma through preformed, magnetized helium (He) ambient plasma via a variety of diagnostics, including emission spectroscopy, wavelength-filtered imaging, and a magnetic flux probe. Doppler shifts detected in a He1+ ion spectral line indicate that the ambient ions initially accelerate transverse to both the debris plasma flow and the background magnetic field. A qualitative analysis in the framework of a "hybrid" plasma model (kinetic ions and inertia-less fluid electrons) demonstrates that the ambient ion trajectories are consistent with the large-scale laminar electric field expected to develop due to the expanding debris. In particular, the transverse ambient ion motion provides direct evidence of Larmor coupling, a collisionless momentum exchange mechanism that has received extensive theoretical and numerical investigation. In order to quantitatively evaluate the observed Doppler shifts, a custom simulation utilizing a detailed model of the laser-produced debris plasma evolution calculates the laminar electric field and computes the initial response of a distribution of ambient test ions. A synthetic Doppler

Three-dimensional modeling of plasma edge transport and divertor fluxes during application of resonant magnetic perturbations on ITER

NASA Astrophysics Data System (ADS)

Schmitz, O.; Becoulet, M.; Cahyna, P.; Evans, T. E.; Feng, Y.; Frerichs, H.; Loarte, A.; Pitts, R. A.; Reiser, D.; Fenstermacher, M. E.; Harting, D.; Kirschner, A.; Kukushkin, A.; Lunt, T.; Saibene, G.; Reiter, D.; Samm, U.; Wiesen, S.

2016-06-01

Results from three-dimensional modeling of plasma edge transport and plasma-wall interactions during application of resonant magnetic perturbation (RMP) fields for control of edge-localized modes in the ITER standard 15 MA Q  =  10 H-mode are presented. The full 3D plasma fluid and kinetic neutral transport code EMC3-EIRENE is used for the modeling. Four characteristic perturbed magnetic topologies are considered and discussed with reference to the axisymmetric case without RMP fields. Two perturbation field amplitudes at full and half of the ITER ELM control coil current capability using the vacuum approximation are compared to a case including a strongly screening plasma response. In addition, a vacuum field case at high q 95  =  4.2 featuring increased magnetic shear has been modeled. Formation of a three-dimensional plasma boundary is seen for all four perturbed magnetic topologies. The resonant field amplitudes and the effective radial magnetic field at the separatrix define the shape and extension of the 3D plasma boundary. Opening of the magnetic field lines from inside the separatrix establishes scrape-off layer-like channels of direct parallel particle and heat flux towards the divertor yielding a reduction of the main plasma thermal and particle confinement. This impact on confinement is most accentuated at full RMP current and is strongly reduced when screened RMP fields are considered, as well as for the reduced coil current cases. The divertor fluxes are redirected into a three-dimensional pattern of helical magnetic footprints on the divertor target tiles. At maximum perturbation strength, these fingers stretch out as far as 60 cm across the divertor targets, yielding heat flux spreading and the reduction of peak heat fluxes by 30%. However, at the same time substantial and highly localized heat fluxes reach divertor areas well outside of the axisymmetric heat flux decay profile. Reduced RMP amplitudes due to screening or reduced RMP

Dynamics of magnetized plasma sheaths around a trench

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatami, M. M., E-mail: m-hatami@kntu.ac.ir

2016-08-15

Considering a magnetized plasma sheath, the temporal evolution of the ion properties (the incident ion flux, the ion impact angle, and the incident ion dose) around a rectangular trench is studied numerically. Our results show that the ion flux along the bottom surface greatly reduces in the presence of magnetic field and its uniformity improves, but the magnetic field does not considerably affect the ion flux along the sidewall. In addition, the thickness of the plasma sheath increases by increasing the magnetic field while its conformality to the target surface reduces faster. Moreover, it is shown that any increase inmore » the magnitude (inclination angle) of the magnetic field causes a decrease (an increase) in the angle of incidence of ions on the bottom and sidewall surfaces. Furthermore, in the presence of magnetic field, the ions strike nearly normal to the surface of the bottom while they become less oblique along the sidewall surface. In addition, contrary to the corners of the trench, it is found that the magnetic field greatly affects the incident ion dose at the center of the trench surfaces. Also, it is shown that the incident ion dose along the sidewall is the highest near the center of the sidewall in both magnetized and magnetic-free cases. However, uniformity of the incident ion dose along the sidewall is better than that along the bottom in both magnetized and unmagnetized plasma sheath.« less

Highly Resolved Measurements of a Developing Strong Collisional Plasma Shock

NASA Astrophysics Data System (ADS)

Rinderknecht, Hans G.; Park, H.-S.; Ross, J. S.; Amendt, P. A.; Higginson, D. P.; Wilks, S. C.; Haberberger, D.; Katz, J.; Froula, D. H.; Hoffman, N. M.; Kagan, G.; Keenan, B. D.; Vold, E. L.

2018-03-01

The structure of a strong collisional shock front forming in a plasma is directly probed for the first time in laser-driven gas-jet experiments. Thomson scattering of a 526.5 nm probe beam was used to diagnose temperature and ion velocity distribution in a strong shock (M ˜11 ) propagating through a low-density (ρ ˜0.01 mg /cc ) plasma composed of hydrogen. A forward-streaming population of ions traveling in excess of the shock velocity was observed to heat and slow down on an unmoving, unshocked population of cold protons, until ultimately the populations merge and begin to thermalize. Instabilities are observed during the merging, indicating a uniquely plasma-phase process in shock front formation.

Theory of magnetic reconnection in solar and astrophysical plasmas.

PubMed

Pontin, David I

2012-07-13

Magnetic reconnection is a fundamental process in a plasma that facilitates the release of energy stored in the magnetic field by permitting a change in the magnetic topology. In this paper, we present a review of the current state of understanding of magnetic reconnection. We discuss theoretical results regarding the formation of current sheets in complex three-dimensional magnetic fields and describe the fundamental differences between reconnection in two and three dimensions. We go on to outline recent developments in modelling of reconnection with kinetic theory, as well as in the magnetohydrodynamic framework where a number of new three-dimensional reconnection regimes have been identified. We discuss evidence from observations and simulations of Solar System plasmas that support this theory and summarize some prominent locations in which this new reconnection theory is relevant in astrophysical plasmas.

Laser-pulse shape effects on magnetic field generation in underdense plasmas

NASA Astrophysics Data System (ADS)

Gopal, Krishna; Raja, Md. Ali; Gupta, Devki Nandan; Avinash, K.; Sharma, Suresh C.

2018-07-01

Laser pulse shape effect has been considered to estimate the self-generated magnetic field in laser-plasma interaction. A ponderomotive force based physical mechanism has been proposed to investigate the self-generated magnetic field for different spatial profiles of the laser pulse in inhomogeneous plasmas. The spatially inhomogeneous electric field of a laser pulse imparts a stronger ponderomotive force on plasma electrons. Thus, the stronger ponderomotive force associated with the asymmetric laser pulse generates a stronger magnetic field in comparison to the case of a symmetric laser pulse. Scaling laws for magnetic field strength with the laser and plasma parameters for different shape of the pulse have been suggested. Present study might be helpful to understand the plasma dynamics relevant to the particle trapping and injection in laser-plasma accelerators.

Viriato: a Fourier-Hermite spectral code for strongly magnetised fluid-kinetic plasma dynamics

NASA Astrophysics Data System (ADS)

Loureiro, Nuno; Dorland, William; Fazendeiro, Luis; Kanekar, Anjor; Mallet, Alfred; Zocco, Alessandro

2015-11-01

We report on the algorithms and numerical methods used in Viriato, a novel fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic Reduced Electron Heating Model equations [Zocco & Schekochihin, 2011] and (ii) the kinetic reduced MHD (KRMHD) equations [Schekochihin et al., 2009]. Two main applications of these equations are magnetised (Alfvnénic) plasma turbulence and magnetic reconnection. Viriato uses operator splitting to separate the dynamics parallel and perpendicular to the ambient magnetic field (assumed strong). Along the magnetic field, Viriato allows for either a second-order accurate MacCormack method or, for higher accuracy, a spectral-like scheme. Perpendicular to the field Viriato is pseudo-spectral, and the time integration is performed by means of an iterative predictor-corrector scheme. In addition, a distinctive feature of Viriato is its spectral representation of the parallel velocity-space dependence, achieved by means of a Hermite representation of the perturbed distribution function. A series of linear and nonlinear benchmarks and tests are presented, with focus on 3D decaying kinetic turbulence. Work partially supported by Fundação para a Ciência e Tecnologia via Grants UID/FIS/50010/2013 and IF/00530/2013.

METHOD FOR EXCHANGING ENERGY WITH A PLASMA BY MAGNETIC PUMPING

DOEpatents

Hall, L.S.

1963-12-31

A method of heating a plasma confined by a static magnetic field is presented. A time-varying magnetic field having a rise time to a predetermined value substantially less than its fall time is applied to a portion of the plasma. Because of the much shorter rise time, the plasma is reversibly heated. This cycle is repeated until the desired plasma temperature is reached. (AEC)

Interaction dynamics of high Reynolds number magnetized plasma flow on the CTIX plasma accelerator

NASA Astrophysics Data System (ADS)

Howard, Stephen James

The Compact Toroid Injection eXperiment, (CTIX), is a coaxial railgun that forms and accelerates magnetized plasma rings called compact toroids (CT's). CTIX consists of a pair of cylindrical coaxial electrodes with the region between them kept at high vacuum (2 m long, 15 cm outer diameter). Hydrogen is typically the dominant constituent of the CT plasma, however helium can also be used. The railgun effect that accelerates the CT can be accounted for by the Lorentz j x B force density created by the power input from a capacitor bank of roughly a Giga-Watt peak. The final velocity of the CT can be as high as 300 km/s, with an acceleration of about 3 billion times Earth's gravity. The compact toroid is able to withstand these forces because of a large internal magnetic field of about 1 Tesla. Understanding the nature of high speed flow of a magnetized plasma has been the primary challenge of this work. In this dissertation we will explore a sequence of fundamental questions regarding the plasma physics of CTIX. First we will go over some new results about the structure and dynamics of the compact toroid's magnetic field, and its electrical resistivity. Then we will present the results from a sequence of key experiments involving reconnection/compression and thermalization of the plasma during interaction of the CT with target magnetic fields of various geometries. Next, we look at the Doppler shift of a spectral line of the He II ion as a measurement of plasma velocity, and to gain insight into the ionization physics of helium in our plasma. These preliminary experiments provide the background for our primary experimental tool for investigating turbulence, a technique called Gas Puff Imaging (GPI) in which a cloud of helium can be used to enhance plasma brightness, allowing plasma density fluctuations to be imaged. We will conclude with an analysis of the images that show coherent density waves, as well as the transition to turbulence during the interaction with a

Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.; Mayr, H. G.; Curtis, S. A.; Taylor, H. A., Jr.

1983-01-01

A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.

Characteristics of magnetised plasma flow around stationary and expanding magnetic clouds

NASA Astrophysics Data System (ADS)

Dalakishvili, Giorgi

Studies of interplanetary magnetic clouds have shown that the characteristics of the region ahead of these objects, which are moving away from the Sun in the solar wind, play a role in determining their geo-efficiency, i.e. the kind and the degree of their effects on the Earth environment. Therefore, our main goal is to model and study the plasma parameters in the vicinity of interplanetary magnetic clouds. To this end we present a model in which the magnetic clouds are immersed in a magnetised plasma flow with a homogeneous magnetic field. We first calculate the resulting distortion of the external magnetic field and then determine the plasma velocity by employing the frozen-in condition. Subsequently, the plasma density and pressure are expressed as functions of the magnetic field and the velocity field. The plasma flow parameters are determined by solving the time-independent ideal MHD equations for both the stationary regime and for the case of an expand-ing cylindrical magnetic cloud, thus extending previous results that appeared in the literature.

Magnetospheric Multiscale Observations of Electron Vortex Magnetic Hole in the Turbulent Magnetosheath Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, S. Y.; Yuan, Z. G.; Wang, D. D.

We report on the observations of an electron vortex magnetic hole corresponding to a new type of coherent structure in the turbulent magnetosheath plasma using the Magnetospheric Multiscale mission data. The magnetic hole is characterized by a magnetic depression, a density peak, a total electron temperature increase (with a parallel temperature decrease but a perpendicular temperature increase), and strong currents carried by the electrons. The current has a dip in the core region and a peak in the outer region of the magnetic hole. The estimated size of the magnetic hole is about 0.23 ρ {sub i} (∼30 ρ {submore » e}) in the quasi-circular cross-section perpendicular to its axis, where ρ {sub i} and ρ {sub e} are respectively the proton and electron gyroradius. There are no clear enhancements seen in high-energy electron fluxes. However, there is an enhancement in the perpendicular electron fluxes at 90° pitch angle inside the magnetic hole, implying that the electrons are trapped within it. The variations of the electron velocity components V {sub em} and V {sub en} suggest that an electron vortex is formed by trapping electrons inside the magnetic hole in the cross-section in the M – N plane. These observations demonstrate the existence of a new type of coherent structures behaving as an electron vortex magnetic hole in turbulent space plasmas as predicted by recent kinetic simulations.« less

Spectral line intensity irreversibility in circulatory plasma magnetization processes

NASA Astrophysics Data System (ADS)

Qu, Z. Q.; Dun, G. T.

2012-01-01

Spectral line intensity variation is found to be irreversible in circulatory plasma magnetization process by experiments described in this paper, i.e., the curves illustrating spectral line photon fluxes irradiated from a light source immerged in a magnetic field by increasing the magnetic induction cannot be reproduced by decreasing the magnetic induction within the errors. There are two plasma magnetization patterns found. One shows that the intensities are greater at the same magnetic inductions during the magnetic induction decreasing process after the increasing, and the other gives the opposite effect. This reveals that the magneto-induced excitation and de-excitation process is irreversible like ferromagnetic magnetization. But the two irreversible processes are very different in many aspects stated in the text.

Effect of DC magnetic field on atmospheric pressure argon plasma jet

NASA Astrophysics Data System (ADS)

Safari, R.; Sohbatzadeh, F.

2015-05-01

In this work, external DC magnetic field effect on the atmospheric pressure plasma jet has been investigated, experimentally. The magnetic field has been produced using a Helmholtz coil configuration. It has been applied parallel and transverse to the jet flow. The strength of the DC magnetic field is 0-0.28 and 0-0.57 Tesla between the two coils in parallel and transverse applications, respectively. It has been shown that the plasma gas flow plays the main role in magneto-active collision-dominated plasma. The effect of plasma fluid velocity on the jet emission has been discussed, qualitatively. It has been observed that the external DC magnetic field has different trends in parallel and transverse applications. The measurements reveal that the plasma jet irradiance increases in parallel field, while it decreases in transverse field. The former has been attributed to increasing plasma number density and the latter to loss of plasma species that reduces the magneto-plasma jet irradiance and in turn shrinks plasma jet number density. As a result, the plasma fluid velocity is responsible for such trends though the magneto-active plasma remains isotropic.

Multiple Plasma Ejections and Intermittent Nature of Magnetic Reconnection in Solar Chromospheric Anemone Jets

NASA Astrophysics Data System (ADS)

Singh, K. A. P.; Isobe, H.; Nishizuka, N.; Nishida, K.; Shibata, K.

2012-11-01

The recent discovery of chromospheric anemone jets with the Solar Optical Telescope (SOT) on board Hinode has shown an indirect evidence of magnetic reconnection in the solar chromosphere. However, the basic nature of magnetic reconnection in chromosphere is still unclear. We studied nine chromospheric anemone jets from SOT/Hinode using Ca II H filtergrams, and we found multiple bright, plasma ejections along the jets. In most cases, the major intensity enhancements (larger than 30% relative to the background intensity) of the loop correspond to the timing of the plasma ejections. The typical lifetime and size of the plasma ejecta are about 20-60 s and 0.3-1.5 Mm, respectively. The height-time plot of jet shows many sub-structures (or individual jets) and the typical lifetime of the individual jet is about one to five minutes. Before the onset of the jet activity, a loop appears in Ca II H and gradually increases in size, and after few minutes several jets are launched from the loop. Once the jet activity starts and several individual jets are launched, the loop starts shrinking with a speed of ~4 km s-1. In some events, a downward moving blob with a speed of ~35 km s-1 was observed, associated with the upward moving plasma along one of the legs of the loop hosting the jets. The upward moving plasma gradually developed into jets. Multiple plasma ejections in chromospheric anemone jet show the strongly time-dependent as well as intermittent nature of magnetic reconnection in the solar chromosphere.

Studies on the transmission of sub-THz waves in magnetized inhomogeneous plasma sheath

NASA Astrophysics Data System (ADS)

Yuan, Kai; Shen, Linfang; Yao, Ming; Deng, Xiaohua; Chen, Zhou; Hong, Lujun

2018-01-01

There have been many studies on the sub-terahertz (sub-THz) wave transmission in reentry plasma sheaths. However, only some of them have paid attention to the transmission of sub-THz waves in magnetized plasma sheaths. In this paper, the transmission of sub-THz waves in both unmagnetized and magnetized reentry plasma sheaths was investigated. The impacts of temporal evolution of the plasma sheath on the wave transmission were studied. The transmission of "atmospheric window" frequencies in a magnetized plasma sheath was discussed in detail. According to the study, the power transmission rates (Tp) for the left hand circular (LHC) and the right hand circular modes in the magnetized plasma sheath are obviously higher and lower than those in the unmagnetized plasma sheath, respectively. The Tp of LHC mode increases with both wave frequency and external magnetic field strength. Also, the Tp of LHC mode in both magnetized and unmagnetized plasma sheaths varies with time due to the temporal evolution of the plasma sheath. Moreover, the performance of sub-THz waves in magnetized plasma sheath hints at a new approach to the "blackout" problem. The new approach, which is in the capability of modern technology, is to utilize the communication system operating at 140 GHz with an onboard magnet installed near the antenna.

Formation of collisionless shocks in magnetized plasma interaction with kinetic-scale obstacles

DOE PAGES

Cruz, F.; Alves, E. P.; Bamford, R. A.; ...

2017-02-06

We investigate the formation of collisionless magnetized shocks triggered by the interaction between magnetized plasma flows and miniature-sized (order of plasma kinetic-scales) magnetic obstacles resorting to massively parallel, full particle-in-cell simulations, including the electron kinetics. The critical obstacle size to generate a compressed plasma region ahead of these objects is determined by independently varying the magnitude of the dipolar magnetic moment and the plasma magnetization. Here we find that the effective size of the obstacle depends on the relative orientation between the dipolar and plasma internal magnetic fields, and we show that this may be critical to form a shockmore » in small-scale structures. We also study the microphysics of the magnetopause in different magnetic field configurations in 2D and compare the results with full 3D simulations. Finally, we evaluate the parameter range where such miniature magnetized shocks can be explored in laboratory experiments.« less

Observations of two-dimensional magnetic field evolution in a plasma opening switch

NASA Astrophysics Data System (ADS)

Shpitalnik, R.; Weingarten, A.; Gomberoff, K.; Krasik, Ya.; Maron, Y.

1998-03-01

The time dependent magnetic field distribution was studied in a coaxial 100-ns positive-polarity Plasma Opening Switch (POS) by observing the Zeeman effect in ionic line emission. Measurements local in three dimensions are obtained by doping the plasma using laser evaporation techniques. Fast magnetic field penetration with a relatively sharp magnetic field front (⩽1 cm) is observed at the early stages of the pulse (t≲25). Later in the pulse, the magnetic field is observed at the load-side edge of the plasma, leaving "islands" of low magnetic field at the plasma center that last for about 10 ns. The two-dimensional (2-D) structure of the magnetic field in the r,z plane is compared to the results of an analytical model based on electron-magneto-hydrodynamics, that utilizes the measured 2-D plasma density distribution and assumes fast magnetic field penetration along both POS electrodes. The model results provide quantitative explanation for the magnetic field evolution observed.

External control of photonic bands in a magnetized cold plasma

NASA Astrophysics Data System (ADS)

Kumar, N.; Singh, P. P.; Suthar, B.; Kumar, A.; Thapa, K. B.

2018-05-01

In this analysis, the effect of external rectangle-wave-like periodic magnetic field, on photonic bandgaps (PBGs) exhibited by bulk cold plasma, has been illustrated. It is found that the forbidden gap for normal incidence decreases with a decrease in the thickness ratio for a constant magnetic field. A new gap appears for TM polarization at oblique incidence that is attributed to the Bragg's interference of plasma layers and this new gap width depends on the incident angle as well as the magnitude of the magnetic field. There is also a shifting in gap locations depending on the magnitude of the magnetic field. It is demonstrated that external parameters like magnetic field strength and the ratio of two parts of spatial period along with incident angle can tune the PBGs in a magnetized cold plasma.

Development of superparamagnetic high-magnetization C18-functionalized magnetic silica nanoparticles as sorbents for enrichment and determination of methylprednisolone in rat plasma by high performance liquid chromatography.

PubMed

Yu, Panfeng; Wang, Qi; Zhang, Xifeng; Zhang, Xuesong; Shen, Shun; Wang, Yan

2010-09-23

In this study, a novel extraction and enrichment technique based on superparamagnetic high-magnetization C(18)-functionalized magnetic silica nanoparticles (C(18)-MNPs) as sorbents was successfully developed for the determination of methylprednisolone (MP) in rat plasma by high performance liquid chromatography (HPLC). The synthesized silica-coated magnetite modified with chlorodimethyl-n-octadecylsilane was about 320 nm in diameter with strong magnetism and high surface area. It provided an efficient way for extraction and concentration of MP in the samples through hydrophobic interaction by the interior C(18) groups. Moreover, MP adsorbed with C(18)-MNPs could be simply and rapidly isolated through placing a strong magnet on the bottom of container, and then easily eluted from C(18)-MNPs by n-hexane solution. Extraction conditions such as amounts of C(18)-MNPs added, adsorption time and desorption solvent, were investigated. Method validations including linear range, detection limit, precision, and recovery were also studied. The results showed that the proposed method based on C(18)-MNPs was a simple, accurate and high efficient approach for the analysis of MP in the complex plasma samples. Copyright © 2010 Elsevier B.V. All rights reserved.

Demonstration of Ion Kinetic Effects in Inertial Confinement Fusion Implosions and Investigation of Magnetic Reconnection Using Laser-Produced Plasmas

NASA Astrophysics Data System (ADS)

Rosenberg, M. J.

2016-10-01

Shock-driven laser inertial confinement fusion (ICF) implosions have demonstrated the presence of ion kinetic effects in ICF implosions and also have been used as a proton source to probe the strongly driven reconnection of MG magnetic fields in laser-generated plasmas. Ion kinetic effects arise during the shock-convergence phase of ICF implosions when the mean free path for ion-ion collisions (λii) approaches the size of the hot-fuel region (Rfuel) and may impact hot-spot formation and the possibility of ignition. To isolate and study ion kinetic effects, the ratio of N - K =λii /Rfuel was varied in D3He-filled, shock-driven implosions at the Omega Laser Facility and the National Ignition Facility, from hydrodynamic-like conditions (NK 0.01) to strongly kinetic conditions (NK 10). A strong trend of decreasing fusion yields relative to the predictions of hydrodynamic models is observed as NK increases from 0.1 to 10. Hydrodynamics simulations that include basic models of the kinetic effects that are likely to be present in these experiments-namely, ion diffusion and Knudsen-layer reduction of the fusion reactivity-are better able to capture the experimental results. This type of implosion has also been used as a source of monoenergetic 15-MeV protons to image magnetic fields driven to reconnect in laser-produced plasmas at conditions similar to those encountered at the Earth's magnetopause. These experiments demonstrate that for both symmetric and asymmetric magnetic-reconnection configurations, when plasma flows are much stronger than the nominal Alfvén speed, the rate of magnetic-flux annihilation is determined by the flow velocity and is largely insensitive to initial plasma conditions. This work was supported by the Department of Energy Grant Number DENA0001857.

Self-focusing and defocusing of Gaussian laser beams in collisional underdense magnetized plasmas with considering the nonlinear ohmic heating and ponderomotive force effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ettehadi Abari, Mehdi; Sedaghat, Mahsa; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir

2015-10-15

The propagation characteristics of a Gaussian laser beam in collisional magnetized plasma are investigated by considering the ponderomotive and ohmic heating nonlinearities. Here, by taking into account the effect of the external magnetic field, the second order differential equation of the dimensionless beam width parameter is solved numerically. Furthermore, the nonlinear dielectric permittivity of the mentioned plasma medium in the paraxial approximation and its dependence on the propagation characteristics of the Gaussian laser pulse is obtained, and its variation in terms of the dimensionless plasma length is analyzed at different initial normalized plasma and cyclotron frequencies. The results show thatmore » the dimensionless beam width parameter is strongly affected by the initial plasma frequency, magnetic strength, and laser pulse intensity. Furthermore, it is found that there exists a certain intensity value below which the laser pulse tends to self focus, while the beam diverges above of this value. In addition, the results confirm that, by increasing the plasma and cyclotron frequencies (plasma density and magnetic strength), the self-focusing effect can occur intensively.« less

Theory of plasma confinement in non-axisymmetric magnetic fields.

PubMed

Helander, Per

2014-08-01

The theory of plasma confinement by non-axisymmetric magnetic fields is reviewed. Such fields are used to confine fusion plasmas in stellarators, where in contrast to tokamaks and reversed-field pinches the magnetic field generally does not possess any continuous symmetry. The discussion is focussed on magnetohydrodynamic equilibrium conditions, collisionless particle orbits, and the kinetic theory of equilbrium and transport. Each of these topics is fundamentally affected by the absence of symmetry in the magnetic field: the field lines need not trace out nested flux surfaces, the particle orbits may not be confined, and the cross-field transport can be very large. Nevertheless, by tailoring the magnetic field appropriately, well-behaved equilibria with good confinement can be constructed, potentially offering an attractive route to magnetic fusion. In this article, the mathematical apparatus to describe stellarator plasmas is developed from first principles and basic elements underlying confinement optimization are introduced.

Astrophysical particle acceleration mechanisms in colliding magnetized laser-produced plasmas

DOE PAGES

Fox, W.; Park, J.; Deng, W.; ...

2017-08-11

Significant particle energization is observed to occur in numerous astrophysical environments, and in the standard models, this acceleration occurs alongside energy conversion processes including collisionless shocks or magnetic reconnection. Recent platforms for laboratory experiments using magnetized laser-produced plasmas have opened opportunities to study these particle acceleration processes in the laboratory. Through fully kinetic particle-in-cell simulations, we investigate acceleration mechanisms in experiments with colliding magnetized laser-produced plasmas, with geometry and parameters matched to recent high-Mach number reconnection experiments with externally controlled magnetic fields. 2-D simulations demonstrate significant particle acceleration with three phases of energization: first, a “direct” Fermi acceleration driven bymore » approaching magnetized plumes; second, x-line acceleration during magnetic reconnection of anti-parallel fields; and finally, an additional Fermi energization of particles trapped in contracting and relaxing magnetic islands produced by reconnection. Furthermore, the relative effectiveness of these mechanisms depends on plasma and magnetic field parameters of the experiments.« less

An analytic expression for the sheath criterion in magnetized plasmas with multi-charged ion species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatami, M. M., E-mail: m-hatami@kntu.ac.ir

2015-04-15

The generalized Bohm criterion in magnetized multi-component plasmas consisting of multi-charged positive and negative ion species and electrons is analytically investigated by using the hydrodynamic model. It is assumed that the electrons and negative ion density distributions are the Boltzmann distribution with different temperatures and the positive ions enter into the sheath region obliquely. Our results show that the positive and negative ion temperatures, the orientation of the applied magnetic field and the charge number of positive and negative ions strongly affect the Bohm criterion in these multi-component plasmas. To determine the validity of our derived generalized Bohm criterion, itmore » reduced to some familiar physical condition and it is shown that monotonically reduction of the positive ion density distribution leading to the sheath formation occurs only when entrance velocity of ion into the sheath satisfies the obtained Bohm criterion. Also, as a practical application of the obtained Bohm criterion, effects of the ionic temperature and concentration as well as magnetic field on the behavior of the charged particle density distributions and so the sheath thickness of a magnetized plasma consisting of electrons and singly charged positive and negative ion species are studied numerically.« less

Midlatitude Plasma Bubbles Over China and Adjacent Areas During a Magnetic Storm on 8 September 2017

NASA Astrophysics Data System (ADS)

Aa, Ercha; Huang, Wengeng; Liu, Siqing; Ridley, Aaron; Zou, Shasha; Shi, Liqin; Chen, Yanhong; Shen, Hua; Yuan, Tianjiao; Li, Jianyong; Wang, Tan

2018-03-01

This paper presents observations of postsunset super plasma bubbles over China and adjacent areas during the second main phase of a storm on 8 September 2017. The signatures of the plasma bubbles can be seen or deduced from (1) deep field-aligned total electron content depletions embedded in regional ionospheric maps derived from dense Global Navigation Satellite System networks, (2) significant equatorial and midlatitudinal plasma bite-outs in electron density measurements on board Swarm satellites, and (3) enhancements of ionosonde virtual height and scintillation in local evening associated with strong southward interplanetary magnetic field. The bubbles/depletions covered a broad area mainly within 20°-45°N and 80°-110°E with bifurcated structures and persisted for nearly 5 hr (˜13-18 UT). One prominent feature is that the bubbles extended remarkably along the magnetic field lines in the form of depleted flux tubes, reaching up to midlatitude of around 50°N (magnetic latitude: 45.5°N) that maps to an altitude of 6,600 km over the magnetic equator. The maximum upward drift speed of the bubbles over the magnetic equator was about 700 m/s and gradually decreased with altitude and time. The possible triggering mechanism of the plasma bubbles was estimated to be storm time eastward prompt penetration electric field, while the traveling ionospheric disturbance could play a role in facilitating the latitudinal extension of the depletions.

Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas.

PubMed

Lynn, Alan G; Gilmore, Mark

2014-11-01

Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ∼10(4) T (100 Megagauss) over small volumes (∼10(-10)m(3)) at high plasma densities (∼10(28)m(-3)) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

Karpman-Washimi magnetization with electron-exchange effects in quantum plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Woo-Pyo; Jamil, M.; Rasheed, A.

2015-07-15

The influence of quantum electron-exchange on the Karpman-Washimi ponderomotive magnetization is investigated in quantum plasmas. The ponderomotive magnetization and the total radiation power due to the non-stationary Karpman-Washimi interaction related to the time-varying field intensity are obtained as functions of the de Broglie wave length, Debye length, and electron-exchange parameter. The result shows that the electron-exchange effect enhances the cyclotron frequency due to the ponderomotive interactions in quantum plasmas. It is also shown that the electron-exchange effect on the Karpman-Washimi magnetization increases with increasing wave number. In addition, the Karpman-Washimi magnetization and the total radiation power increase with an increasemore » in the ratio of the Debye length to the de Broglie wave length. In streaming quantum plasmas, it is shown that the electron-exchange effect enhances the ponderomotive magnetization below the resonant wave number and, however, suppresses the ponderomotive magnetization above the resonant wave number. The variation of the Karpman-Washimi magnetization and the radiation power due to the variation of the electron-exchange effect and plasma parameters is also discussed.« less

Phase mixing of Alfvén waves in axisymmetric non-reflective magnetic plasma configurations

NASA Astrophysics Data System (ADS)

Petrukhin, N. S.; Ruderman, M. S.; Shurgalina, E. G.

2018-02-01

We study damping of phase-mixed Alfvén waves propagating in non-reflective axisymmetric magnetic plasma configurations. We derive the general equation describing the attenuation of the Alfvén wave amplitude. Then we applied the general theory to a particular case with the exponentially divergent magnetic field lines. The condition that the configuration is non-reflective determines the variation of the plasma density along the magnetic field lines. The density profiles exponentially decreasing with the height are not among non-reflective density profiles. However, we managed to find non-reflective profiles that fairly well approximate exponentially decreasing density. We calculate the variation of the total wave energy flux with the height for various values of shear viscosity. We found that to have a substantial amount of wave energy dissipated at the lower corona, one needs to increase shear viscosity by seven orders of magnitude in comparison with the value given by the classical plasma theory. An important result that we obtained is that the efficiency of the wave damping strongly depends on the density variation with the height. The stronger the density decrease, the weaker the wave damping is. On the basis of this result, we suggested a physical explanation of the phenomenon of the enhanced wave damping in equilibrium configurations with exponentially diverging magnetic field lines.

Wigner functions for fermions in strong magnetic fields

NASA Astrophysics Data System (ADS)

Sheng, Xin-li; Rischke, Dirk H.; Vasak, David; Wang, Qun

2018-02-01

We compute the covariant Wigner function for spin-(1/2) fermions in an arbitrarily strong magnetic field by exactly solving the Dirac equation at non-zero fermion-number and chiral-charge densities. The Landau energy levels as well as a set of orthonormal eigenfunctions are found as solutions of the Dirac equation. With these orthonormal eigenfunctions we construct the fermion field operators and the corresponding Wigner-function operator. The Wigner function is obtained by taking the ensemble average of the Wigner-function operator in global thermodynamical equilibrium, i.e., at constant temperature T and non-zero fermion-number and chiral-charge chemical potentials μ and μ_5, respectively. Extracting the vector and axial-vector components of the Wigner function, we reproduce the currents of the chiral magnetic and separation effect in an arbitrarily strong magnetic field.

Large-Area Permanent-Magnet ECR Plasma Source

NASA Technical Reports Server (NTRS)

Foster, John E.

2007-01-01

A 40-cm-diameter plasma device has been developed as a source of ions for material-processing and ion-thruster applications. Like the device described in the immediately preceding article, this device utilizes electron cyclotron resonance (ECR) excited by microwave power in a magnetic field to generate a plasma in an electrodeless (noncontact) manner and without need for an electrically insulating, microwave-transmissive window at the source. Hence, this device offers the same advantages of electrodeless, windowless design - low contamination and long operational life. The device generates a uniform, high-density plasma capable of sustaining uniform ion-current densities at its exit plane while operating at low pressure [<10(exp -4) torr (less than about 1.3 10(exp -2) Pa)] and input power <200 W at a frequency of 2.45 GHz. Though the prototype model operates at 2.45 GHz, operation at higher frequencies can be achieved by straightforward modification to the input microwave waveguide. Higher frequency operation may be desirable in those applications that require even higher background plasma densities. In the design of this ECR plasma source, there are no cumbersome, power-hungry electromagnets. The magnetic field in this device is generated by a permanent-magnet circuit that is optimized to generate resonance surfaces. The microwave power is injected on the centerline of the device. The resulting discharge plasma jumps into a "high mode" when the input power rises above 150 W. This mode is associated with elevated plasma density and high uniformity. The large area and uniformity of the plasma and the low operating pressure are well suited for such material-processing applications as etching and deposition on large silicon wafers. The high exit-plane ion-current density makes it possible to attain a high rate of etching or deposition. The plasma potential is <3 V low enough that there is little likelihood of sputtering, which, in plasma processing, is undesired

Negative specific heat of a magnetically self-confined plasma torus

PubMed Central

Kiessling, Michael K.-H.; Neukirch, Thomas

2003-01-01

It is shown that the thermodynamic maximum-entropy principle predicts negative specific heat for a stationary, magnetically self-confined current-carrying plasma torus. Implications for the magnetic self-confinement of fusion plasma are considered. PMID:12576553

Radiative corrections to the Coulomb law and model of dense quantum plasmas: Dispersion of longitudinal waves in magnetized quantum plasmas

NASA Astrophysics Data System (ADS)

Andreev, Pavel A.

2018-04-01

Two kinds of quantum electrodynamic radiative corrections to electromagnetic interactions and their influence on the properties of highly dense quantum plasmas are considered. Linear radiative correction to the Coulomb interaction is considered. Its contribution in the spectrum of the Langmuir waves is presented. The second kind of radiative corrections are related to the nonlinearity of the Maxwell equations for the strong electromagnetic field. Their contribution in the spectrum of transverse waves of magnetized plasmas is briefly discussed. At the consideration of the Langmuir wave spectrum, we included the effect of different distributions of the spin-up and spin-down electrons revealing in the Fermi pressure shift.

Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

NASA Astrophysics Data System (ADS)

Zanáška, M.; Adámek, J.; Peterka, M.; Kudrna, P.; Tichý, M.

2015-03-01

The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents Isat-/Isat+ to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma of a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.

MAGNETIC END CLOSURES FOR PLASMA CONFINING AND HEATING DEVICES

DOEpatents

Post, R.F.

1963-08-20

More effective magnetic closure field regions for various open-ended containment magnetic fields used in fusion reactor devices are provided by several spaced, coaxially-aligned solenoids utilized to produce a series of nodal field regions of uniform or, preferably, of incrementally increasing intensity separated by lower intensity regions outwardly from the ends of said containment zone. Plasma sources may also be provided to inject plasma into said lower intensity areas to increase plasma density therein. Plasma may then be transported, by plasma diffusion mechanisms provided by the nodal fields, into the containment field. With correlated plasma densities and nodal field spacings approximating the mean free partl cle collision path length in the zones between the nodal fields, optimum closure effectiveness is obtained. (AEC)

Magnetic flux and heat losses by diffusive, advective, and Nernst effects in magnetized liner inertial fusion-like plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.

The magnetized liner inertial fusion (MagLIF) approach to inertial confinement fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010); Cuneo et al., IEEE Trans. Plasma Sci. 40, 3222 (2012)] involves subsonic/isobaric compression and heating of a deuterium-tritium plasma with frozen-in magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic field diffusion, and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstratesmore » that the heat loss from the hot compressed magnetized plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of magnetic flux is dominated by advection and the Nernst effect. For a large electron Hall parameter (ω{sub e}τ{sub e}≫1), the effective diffusion coefficients determining the losses of heat and magnetic flux to the liner wall are both shown to decrease with ω{sub e}τ{sub e} as does the Bohm diffusion coefficient cT/(16eB), which is commonly associated with low collisionality and two-dimensional transport. We demonstrate how this family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.« less

Nonlinear mechanism for the generation of electromagnetic fields in a magnetized plasma by the beatings of waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aburjania, G. D.; Machabeli, G. Z.; Kharshiladze, O. A.

2006-07-15

The modulational instability in a plasma in a strong constant external magnetic field is considered. The plasmon condensate is modulated not by conventional low-frequency ion sound but by the beatings of two high-frequency transverse electromagnetic waves propagating along the magnetic field. The instability reduces the spatial scales of Langmuir turbulence along the external magnetic field and generates electromagnetic fields. It is shown that, for a pump wave with a sufficiently large amplitude, the effect described in the present paper can be a dominant nonlinear process.

Periodical plasma structures controlled by external magnetic field

NASA Astrophysics Data System (ADS)

Schweigert, I. V.; Keidar, M.

2017-06-01

The characteristics of two-dimensional periodical structures in a magnetized plasma are studied using kinetic simulations. Ridges (i.e. spikes in electron and ion density) are formed and became more pronounced with an increase of magnetic field incidence angle in the plasma volume in the cylindrical chamber. These ridges are shifted relative to each other, which results in the formation of a two-dimensional double-layer structure. Depending on Larmor radius and Debye length up to 19 potential steps appear across the oblique magnetic field. The electrical current gathered into the channels is associated with the electron and ion density ridges.

Magnetic tearing of plasma discharges due to nonuniform resistivity

NASA Technical Reports Server (NTRS)

Hassam, A. B.

1988-01-01

The rearrangement of current in a plasma discharge in response to resistivity nonuniformities within a magnetic surface is studied. It is shown that macroscopic magnetic islands develop about those surfaces where the nonuniformity is aligned with the magnetic field. If the nonuniformity and the field are not aligned anywhere, there is no current rearrangement; instead, relatively large plasma flows are set up. Such resistivity inhomogeneities can obtain in solar coronal loops and, in some circumstances, in tokamak discharges.

Antiproton powered propulsion with magnetically confined plasma engines

NASA Technical Reports Server (NTRS)

Lapointe, Michael R.

1989-01-01

Matter-antimatter annihilation releases more energy per unit mass than any other method of energy production, making it an attractive energy source for spacecraft propulsion. In the magnetically confined plasma engine, antiproton beams are injected axially into a pulsed magnetic mirror system, where they annihilate with an initially neutral hydrogen gas. The resulting charged annihilation products transfer energy to the hydrogen propellant, which is then exhausted through one end of the pulsed mirror system to provide thrust. The calculated energy transfer efficiencies for a low number density (10(14)/cu cm) hydrogen propellant are insufficient to warrant operating the engine in this mode. Efficiencies are improved using moderate propellant number densities (10(16)/cu cm), but the energy transferred to the plasma in a realistic magnetic mirror system is generally limited to less than 2 percent of the initial proton-antiproton annihilation energy. The energy transfer efficiencies are highest for high number density (10(18)/cu cm) propellants, but plasma temperatures are reduced by excessive radiation losses. Low to moderate thrust over a wide range of specific impulse can be generated with moderate propellant number densities, while higher thrust but lower specific impulse may be generated using high propellant number densities. Significant mass will be required to shield the superconducting magnet coils from the high energy gamma radiation emitted by neutral pion decay. The mass of such a radiation shield may dominate the total engine mass, and could severely diminish the performance of antiproton powered engines which utilize magnetic confinement. The problem is compounded in the antiproton powered plasma engine, where lower energy plasma bremsstrahlung radiation may cause shield surface ablation and degradation.

Measurements of ion species separation in strong plasma shocks

NASA Astrophysics Data System (ADS)

Rinderknecht, Hans

2017-10-01

Shocks are important dynamic phenomena in inertial confinement fusion (ICF) and astrophysical plasmas. While the relationship between upstream and downstream plasmas far from the shock front is fully determined by conservation equations, the structure of shock fronts is determined by dynamic kinetic processes. Kinetic theory and simulations predict that the width of a strong (M >2) collisional plasma shock front is on the order of tens of ion mean-free-paths. The shock front structure plays an important role for overall dynamics when the shock front width approaches plasma scale lengths, as in the spherically converging shock in the DT-vapor in an ICF implosion. However, there has been no experimental data benchmarking shock front structure in the plasma phase. The structure of a shock front in a plasma with multiple ion species has been directly measured for the first time using a combination of Thomson scattering and proton radiography in experiments on the OMEGA laser. Thomson scattering of a 263.25 nm probe beam is used to diagnose electron density, electron and ion temperature, ion species concentration, and flow velocity in strong shocks (M 5) propagating through low-density (ρ 0.1 mg/cc) plasmas composed of H(98%) +Ne(2%). Within the shock front, velocity separation of the ion species is observed for the first time: the light species (H) accelerates to of order the shocked fluid velocity (450 microns/ns) before the heavy species (Ne) begins to move. This velocity-space separation implies that the separation of ion species occurs at the shock front, a predicted feature of shocks in multi-species plasmas but never observed experimentally until now. Comparison of experimental data with PIC, Vlasov-Fokker-Planck, and multi-component hydrodynamic simulations will be presented.

Spatial Transport of Magnetic Flux Surfaces in Strongly Anisotropic Turbulence

NASA Astrophysics Data System (ADS)

Matthaeus, W. H.; Servidio, S.; Wan, M.; Ruffolo, D. J.; Rappazzo, A. F.; Oughton, S.

2013-12-01

Magnetic flux surfaces afford familiar descriptions of spatial structure, dynamics, and connectivity of magnetic fields, with particular relevance in contexts such as solar coronal flux tubes, magnetic field connectivity in the interplanetary and interstellar medium, as well as in laboratory plasmas and dynamo problems [1-4]. Typical models assume that field-lines are orderly, and flux tubes remain identifiable over macroscopic distances; however, a previous study has shown that flux tubes shred in the presence of fluctuations, typically losing identity after several correlation scales [5]. Here, the structure of magnetic flux surfaces is numerically investigated in a reduced magnetohydrodynamic (RMHD) model of homogeneous turbulence. Short and long-wavelength behavior is studied statistically by propagating magnetic surfaces along the mean field. At small scales magnetic surfaces become complex, experiencing an exponential thinning. At large scales, instead, the magnetic flux undergoes a diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established by means of a multiple scale analysis. Both large and small scales limits are controlled by the Kubo number. These results have consequences for understanding and interpreting processes such as magnetic reconnection and field-line diffusion in plasmas [6]. [1] E. N. Parker, Cosmical Magnetic Fields (Oxford Univ. Press, New York, 1979). [2] J. R. Jokipii and E. N. Parker, Phys. Rev. Lett. 21, 44 (1968). [3] R. Bruno et al., Planet. Space Sci. 49, 1201 (2001). [4] M. N. Rosenbluth et al., Nuclear Fusion 6, 297 (1966). [5] W. H. Matthaeus et al., Phys. Rev. Lett. 75, 2136 (1995). [6] S. Servidio et al., submitted (2013).

Investigation of MHD Instabilities in Jets and Bubbles Using a Compact Coaxial Plasma Gun in a Background Magnetized Plasma

NASA Astrophysics Data System (ADS)

Zhang, Y.; Fisher, D. M.; Wallace, B.; Gilmore, M.; Hsu, S. C.

2016-10-01

A compact coaxial plasma gun is employed for experimental investigation of launching plasma into a lower density background magnetized plasma. Experiments are being conducted in the linear device HelCat at UNM. Four distinct operational regimes with qualitatively different dynamics are identified by fast CCD camera images. For regime I plasma jet formation, a global helical magnetic configuration is determined by a B-dot probe array data. Also the m =1 kink instability is observed and verified. Furthermore, when the jet is propagating into background magnetic field, a longer length and lifetime jet is formed. Axial shear flow caused by the background magnetic tension force contributes to the increased stability of the jet body. In regime II, a spheromak-like plasma bubble formation is identified when the gun plasma is injected into vacuum. In contrast, when the bubble propagates into a background magnetic field, the closed magnetic field configuration does not hold anymore and a lateral side, Reilgh-Taylor instability develops. Detailed experimental data and analysis will be presented for these cases.

Highly Resolved Measurements of a Developing Strong Collisional Plasma Shock

DOE PAGES

Rinderknecht, Hans G.; Park, H. -S.; Ross, J. S.; ...

2018-03-02

In this paper, the structure of a strong collisional shock front forming in a plasma is directly probed for the first time in laser-driven gas-jet experiments. Thomson scattering of a 526.5 nm probe beam was used to diagnose temperature and ion velocity distribution in a strong shock (more » $$M{\\sim}11$$) propagating through a low-density ($${\\rho}{\\sim}0.01\\text{ }\\text{ }\\mathrm{mg}/\\mathrm{cc}$$) plasma composed of hydrogen. A forward-streaming population of ions traveling in excess of the shock velocity was observed to heat and slow down on an unmoving, unshocked population of cold protons, until ultimately the populations merge and begin to thermalize. Finally, instabilities are observed during the merging, indicating a uniquely plasma-phase process in shock front formation.« less

Highly Resolved Measurements of a Developing Strong Collisional Plasma Shock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rinderknecht, Hans G.; Park, H. -S.; Ross, J. S.

In this paper, the structure of a strong collisional shock front forming in a plasma is directly probed for the first time in laser-driven gas-jet experiments. Thomson scattering of a 526.5 nm probe beam was used to diagnose temperature and ion velocity distribution in a strong shock (more » $$M{\\sim}11$$) propagating through a low-density ($${\\rho}{\\sim}0.01\\text{ }\\text{ }\\mathrm{mg}/\\mathrm{cc}$$) plasma composed of hydrogen. A forward-streaming population of ions traveling in excess of the shock velocity was observed to heat and slow down on an unmoving, unshocked population of cold protons, until ultimately the populations merge and begin to thermalize. Finally, instabilities are observed during the merging, indicating a uniquely plasma-phase process in shock front formation.« less

Magnetic-Nozzle Studies for Fusion Propulsion Applications: Gigawatt Plasma Source Operation and Magnetic Nozzle Analysis

NASA Technical Reports Server (NTRS)

Gilland, James H.; Mikekkides, Ioannis; Mikellides, Pavlos; Gregorek, Gerald; Marriott, Darin

2004-01-01

This project has been a multiyear effort to assess the feasibility of a key process inherent to virtually all fusion propulsion concepts: the expansion of a fusion-grade plasma through a diverging magnetic field. Current fusion energy research touches on this process only indirectly through studies of plasma divertors designed to remove the fusion products from a reactor. This project was aimed at directly addressing propulsion system issues, without the expense of constructing a fusion reactor. Instead, the program designed, constructed, and operated a facility suitable for simulating fusion reactor grade edge plasmas, and to examine their expansion in an expanding magnetic nozzle. The approach was to create and accelerate a dense (up to l0(exp 20)/m) plasma, stagnate it in a converging magnetic field to convert kinetic energy to thermal energy, and examine the subsequent expansion of the hot (100's eV) plasma in a subsequent magnetic nozzle. Throughout the project, there has been a parallel effort between theoretical and numerical design and modelling of the experiment and the experiment itself. In particular, the MACH2 code was used to design and predict the performance of the magnetoplasmadynamic (MPD) plasma accelerator, and to design and predict the design and expected behavior for the magnetic field coils that could be added later. Progress to date includes the theoretical accelerator design and construction, development of the power and vacuum systems to accommodate the powers and mass flow rates of interest to out research, operation of the accelerator and comparison to theoretical predictions, and computational analysis of future magnetic field coils and the expected performance of an integrated source-nozzle experiment.

Magnetized Target Fusion Propulsion: Plasma Injectors for MTF Guns

NASA Technical Reports Server (NTRS)

Griffin, Steven T.

2003-01-01

To achieve increased payload size and decreased trip time for interplanetary travel, a low mass, high specific impulse, high thrust propulsion system is required. This suggests the need for research into fusion as a source of power and high temperature plasma. The plasma would be deflected by magnetic fields to provide thrust. Magnetized Target Fusion (MTF) research consists of several related investigations into these topics. These include the orientation and timing of the plasma guns and the convergence and interface development of the "pusher" plasma. Computer simulations of the gun as it relates to plasma initiation and repeatability are under investigation. One of the items under development is the plasma injector. This is a surface breakdown driven plasma generator designed to function at very low pressures. The performance, operating conditions and limitations of these injectors need to be determined.

Probing a dusty magnetized plasma with self-excited dust-density waves

NASA Astrophysics Data System (ADS)

Tadsen, Benjamin; Greiner, Franko; Piel, Alexander

2018-03-01

A cloud of nanodust particles is created in a reactive argon-acetylene plasma. It is then transformed into a dusty magnetized argon plasma. Plasma parameters are obtained with the dust-density wave diagnostic introduced by Tadsen et al. [Phys. Plasmas 22, 113701 (2015), 10.1063/1.4934927]. A change from an open to a cylindrically enclosed nanodust cloud, which was observed earlier, can now be explained by a stronger electric confinement if a vertical magnetic field is present. Using two-dimensional extinction measurements and the inverse Abel transform to determine the dust density, a redistribution of the dust with increasing magnetic induction is found. The dust-density profile changes from being peaked around the central void to being peaked at an outer torus ring resulting in a hollow profile. As the plasma parameters cannot explain this behavior, we propose a rotation of the nanodust cloud in the magnetized plasma as the origin of the modified profile.

Practicality of magnetic compression for plasma density control

DOE PAGES

Gueroult, Renaud; Fisch, Nathaniel J.

2016-03-16

Here, plasma densification through magnetic compression has been suggested for time-resolved control of the wave properties in plasma-based accelerators [P. F. Schmit and N. J. Fisch, Phys. Rev. Lett. 109, 255003 (2012)]. Using particle in cell simulations with real mass ratio, the practicality of large magnetic compression on timescales shorter than the ion gyro-period is investigated. For compression times shorter than the transit time of a compressional Alfven wave across the plasma slab, results show the formation of two counter-propagating shock waves, leading to a highly non-uniform plasma density profile. Furthermore, the plasma slab displays large hydromagnetic like oscillations aftermore » the driving field has reached steady state. Peak compression is obtained when the two shocks collide in the mid-plane. At this instant, very large plasma heating is observed, and the plasmaβ is estimated to be about 1. Although these results point out a densification mechanism quite different and more complex than initially envisioned, these features still might be advantageous in particle accelerators.« less

Strongly Magnetized Accretion Disks in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Begelman, Mitchell

Accretion disks likely provide the conduit for fueling active galactic nuclei (AGN), linking the black hole's immediate surroundings to the host galaxy's nuclear star cluster, and possibly beyond. Yet detailed AGN disk models fail to explain several of the most basic observational features of AGN: How do the outer regions of the disk avoid stalling as a result of wholesale gravitational fragmentation? What regulates the amount of star formation that is inferred to accompany accretion in some AGN? Why is the broad emission line region a ubiquitous feature of luminous AGN? What processes create and maintain the so-called "dusty torus"? Analytic work suggests that vertical pressure support of the disk primarily by a toroidal magnetic field, rather than by gas or radiation pressure, can readily resolve these problems. And recent numerical simulations have indicated that such a strong toroidal field is the inevitable consequence of the magnetorotational instability (MRI) when a disk accumulates a modest amount of net magnetic flux, thus providing a sound theoretical basis for strongly magnetized disks. We propose an analytic and computational study of such disks in the AGN context, focusing on: (1) The basic physical properties of strongly magnetized AGN disks. We will focus on the competition between field generation and buoyancy, improving on previous work by considering realistic equations of state, dissipative processes and radiative losses. We will use global simulations to test the limiting magnetic fields that can be produced by MRIdriven accretion disk dynamos and explore the driving mechanisms of disk winds and the resulting levels of mass, angular momentum and energy loss. (2) Gravitational fragmentation and star formation in strongly magnetized disks. We will determine how a strong field reduces and regulates gravitational fragmentation, by both lowering the disk density and creating a stratified structure in which star formation near the equator can co

Plasma Detachment Mechanisms in Propulsive Magnetic Nozzles

DTIC Science & Technology

2013-03-07

distribution is unlimited. 41A. Fruchtman, Phys. Rev. Lett. 96, 065002 (2006). 42M. Merino and E. Ahedo, IEEE Trans. Plasma Sci. 39, 2938 (2011). 43J...Ahedo, E., “Simulation of plasma flows in divergent magnetic nozzles,” IEEE Transactions on Plasma Science, Vol. 39, No. 11, 2011, pp. 2938 –2939...Plasma Science, Vol. 39, No. 11, 2011, pp. 2938 –2939. 14Zucrow, M. and Hoffman, J., Gas dynamics, Wiley, New York, 1976. 15Ahedo, E., “Parametric analysis

Magnetic Fluctuation-Driven Intrinsic Flow in a Toroidal Plasma

NASA Astrophysics Data System (ADS)

Brower, D. L.; Ding, W. X.; Lin, L.; Almagri, A. F.; den Hartog, D. J.; Sarff, J. S.

2012-10-01

Magnetic fluctuations have been long observed in various magnetic confinement configurations. These perturbations may arise naturally from plasma instabilities such as tearing modes and energetic particle driven modes, but they can also be externally imposed by error fields or external magnetic coils. It is commonly observed that large MHD modes lead to plasma locking (no rotation) due to torque produced by eddy currents on the wall, and it is predicted that stochastic field induces flow damping where the radial electric field is reduced. Flow generation is of great importance to fusion plasma research, especially low-torque devices like ITER, as it can act to improve performance. Here we describe new measurements in the MST reversed field pinch (RFP) showing that the coherent interaction of magnetic and particle density fluctuations can produce a turbulent fluctuation-induced kinetic force, which acts to drive intrinsic plasma rotation. Key observations include; (1) the average kinetic force resulting from density fluctuations, ˜ 0.5 N/m^3, is comparable to the intrinsic flow acceleration, and (2) between sawtooth crashes, the spatial distribution of the kinetic force is directed to create a sheared parallel flow profile that is consistent with the measured flow profile in direction and amplitude, suggesting the kinetic force is responsible for intrinsic plasma rotation.

Matched dipole probe for precise electron density measurements in magnetized and non-magnetized plasmas

NASA Astrophysics Data System (ADS)

Rafalskyi, Dmytro; Aanesland, Ane

2015-09-01

We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).

Particle energization in magnetic reconnection in high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Deng, W.; Fox, W.; Bhattacharjee, A.

2014-10-01

Significant particle energization is inferred to occur in many astrophysical environments and magnetic reconnection has been proposed to be the driver in many cases. Recent observation of magnetic reconnection in high-energy-density (HED) plasmas on the Vulcan, Omega and Shenguang laser facilities has opened up a new regime of reconnection study of great interest to laboratory and plasma astrophysics. In these experiments, plasma bubbles, excited by laser shots on solid targets and carrying magnetic fields, expand into one another, squeezing the opposite magnetic fields together to drive reconnection. 2D particle-in-cell (PIC) simulations have been performed to study the particle energization in such experiments. Two energization mechanisms have been identified. The first is a Fermi acceleration process between the expanding plasma bubbles, wherein the electromagnetic fields of the expanding plasma bounce particles, acting as moving walls. Particles can gain significant energy through multiple bounces between the bubbles. The second mechanism is a subsequent direct acceleration by electric field at the reconnection X-line when the bubbles collide into each other and drive reconnection.

NASA Researcher Adjusts a Travelling Magnetic Wave Plasma Engine

NASA Image and Video Library

1964-02-21

Raymond Palmer, of the Electromagnetic Propulsion Division’s Plasma Flow Section, adjusts the traveling magnetic wave plasma engine being operated in the Electric Power Conversion at the National Aeronautics and Space Administration (NASA) Lewis Research Center. During the 1960s Lewis researchers were exploring several different methods of creating electric propulsion systems, including the traveling magnetic wave plasma engine. The device operated similarly to alternating-current motors, except that a gas, not a solid, was used to conduct the electricity. A magnetic wave induced a current as it passed through the plasma. The current and magnetic field pushed the plasma in one direction. Palmer and colleague Robert Jones explored a variety of engine configurations in the Electric Propulsion Research Building. The engine is seen here mounted externally on the facility’s 5-foot diameter and 16-foot long vacuum tank. The four magnetic coils are seen on the left end of the engine. The researchers conducted two-minute test runs with varying configurations and used of both argon and xenon as the propellant. The Electric Propulsion Research Building was built in 1942 as the Engine Propeller Research Building, often called the Prop House. It contained four test cells to study large reciprocating engines with their propellers. After World War II, the facility was modified to study turbojet engines. By the 1960s, the facility was modified again for electric propulsion research and given its current name.

Anomalous skin effects in a weakly magnetized degenerate electron plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abbas, G., E-mail: gohar.abbas@gcu.edu.pk; Sarfraz, M.; Shah, H. A.

2014-09-15

Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized degenerate electron plasma is presented and a graphical comparison is made with the results obtained using relativistic Maxwellian distribution function [G. Abbas, M. F. Bashir, and G. Murtaza, Phys. Plasmas 18, 102115 (2011)]. It is found that the penetration depth for R- and L-waves for degenerate case is qualitatively small in comparison with the Maxwellian plasma case. The quantitative reduction due to weak magnetic field in the skin depth in R-wave for degenerate plasma is large as compared to the non-degenerate one. By ignoring themore » ambient magnetic field, previous results for degenerate field free case are salvaged [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Principles of Plasma Electrodynamics (Springer-Verlag, Berlin/Heidelberg, 1984), p. 90].« less

Jets in a strongly coupled anisotropic plasma

NASA Astrophysics Data System (ADS)

Fadafan, Kazem Bitaghsir; Morad, Razieh

2018-01-01

In this paper, we study the dynamics of the light quark jet moving through the static, strongly coupled N=4, anisotropic plasma with and without charge. The light quark is presented by a 2-parameters point-like initial condition falling string in the context of the AdS/CFT. We calculate the stopping distance of the light quark in the anisotropic medium and compare it with its isotropic value. We study the dependency of the stopping distance to the both string initial conditions and background parameters such as anisotropy parameter or chemical potential. Although the typical behavior of the string in the anisotropic medium is similar to the one in the isotropic AdS-Sch background, the string falls faster to the horizon depending on the direction of moving. Particularly, the enhancement of quenching is larger in the beam direction. We find that the suppression of stopping distance is more prominent when the anisotropic plasma have the same temperature as the isotropic plasma.

Strongly Emitting Surfaces Unable to Float below Plasma Potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campanell, M. D.; Umansky, M. V.

2016-02-25

One important unresolved question in plasma physics concerns the effect of strong electron emission on plasma-surface interactions. Previous papers reported solutions with negative and positive floating potentials relative to the plasma edge. For these two models a very different predictions for particle and energy balance is given. Here we show that the positive potential state is the only possible equilibrium in general. Even if a negative floating potential existed at t=0, the ionization collisions near the surface will force a transition to the positive floating potential state. Moreover, this transition is demonstrated with a new simulation code.

Comparative measurements of plasma potential with ball-pen and Langmuir probe in low-temperature magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zanáška, M.; Kudrna, P.; Tichý, M.

The ball-pen probe (BPP) is used for direct plasma potential measurements in magnetized plasma. The probe can adjust the ratio of the electron and ion saturation currents I{sub sat}{sup −}/I{sub sat}{sup +} to be close to one and therefore its I-V characteristic becomes nearly symmetric. If this is achieved, the floating potential of the BPP is close to the plasma potential. Because of its rather simple construction, it offers an attractive probe for measurements in magnetized plasma. Comparative measurements of plasma potential by BPPs of different dimensions as well as one Langmuir probe (LP) in an argon discharge plasma ofmore » a cylindrical magnetron were performed at various experimental conditions. An additional comparison by an emissive probe was also performed. All these types of probes provide similar values of plasma potential in a wide range of plasma parameters. Our results for three different BPP dimensions indicate that the BPP can be operated in a cylindrical magnetron DC argon discharge if the value of the ratio of the magnetic field and neutral gas pressure, B/p, is greater than approximately 10 mT/Pa.« less

Energy and Mass Transport of Magnetospheric Plasmas during the November 2003 Magnetic Storm

NASA Technical Reports Server (NTRS)

Fok, Mei-Chging; Moore, Thomas

2008-01-01

Intensive energy and mass transport from the solar wind across the magnetosphere boundary is a trigger of magnetic storms. The storm on 20-21 November 2003 was elicited by a high-speed solar wind and strong southward component of interplanetary magnetic field. This storm attained a minimum Dst of -422 nT. During the storm, some of the solar wind particles enter the magnetosphere and eventually become part of the ring current. At the same time, the fierce solar wind powers strong outflow of H+ and O+ from the ionosphere, as well as from the plasmasphere. We examine the contribution of plasmas from the solar wind, ionosphere and plasmasphere to the storm-time ring current. Our simulation shows, for this particular storm, ionospheric O+ and solar wind ions are the major sources of the ring current particles. The polar wind and plasmaspheric H+ have only minor impacts. In the storm main phase, the strong penetration of solar wind electric field pushes ions from the geosynchronous orbit to L shells of 2 and below. Ring current is greatly intensified during the earthward transport and produces a large magnetic depression in the surface field. When the convection subsides, the deep penetrating ions experience strong charge exchange loss, causing rapid decay of the ring current and fast initial storm recovery. Our simulation reproduces very well the storm development indicated by the Dst index.

Magnetic island and plasma rotation under external resonant magnetic perturbation in the T-10 tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eliseev, L. G.; Ivanov, N. V., E-mail: ivanov-nv@nrcki.ru; Kakurin, A. M.

2015-05-15

Experimental comparison of the m = 2, n = 1 mode and plasma rotation velocities at q = 2 magnetic surface in a wide range of the mode amplitudes is presented. Phase velocity of the mode rotation is measured with a set of poloidal magnetic field sensors located at the inner side of the vacuum vessel wall. Plasma rotation velocity at the q = 2 magnetic surface in the direction of the mode phase velocity is measured with the heavy ion beam probe diagnostics. In the presence of a static Resonant Magnetic Perturbation (RMP), the rotation is irregular that appears as cyclical variations of the mode and plasmamore » instantaneous velocities. The period of these variations is equal to the period of the mode oscillations. In the case of high mode amplitude, the rotation irregularity of the mode is consistent with the rotation irregularity of the resonant plasma layer. On the contrary, the observed rise of the mode rotation irregularity in the case of low mode amplitude occurs without an increase of the rotation irregularity of the resonant plasma layer. The experimental results are simulated and analyzed with the TEAR code based on the two-fluid MHD approximation. Calculated irregularities of the mode and plasma rotation depend on the mode amplitude similar to the experimental data. For large islands, the rotation irregularity is attributed to oscillations of the electromagnetic torque applied to the resonant plasma layer. For small islands, the deviation of the mode rotation velocity from the plasma velocity occurs due to the effect of finite plasma resistivity.« less

Effects of a vertical magnetic field on particle confinement in a magnetized plasma torus.

PubMed

Müller, S H; Fasoli, A; Labit, B; McGrath, M; Podestà, M; Poli, F M

2004-10-15

The particle confinement in a magnetized plasma torus with superimposed vertical magnetic field is modeled and measured experimentally. The formation of an equilibrium characterized by a parallel plasma current canceling out the grad B and curvature drifts is described using a two-fluid model. Characteristic response frequencies and relaxation rates are calculated. The predictions for the particle confinement time as a function of the vertical magnetic field are verified in a systematic experimental study on the TORPEX device, including the existence of an optimal vertical field and the anticorrelation between confinement time and density.

Investigation of radiative bow-shocks in magnetically accelerated plasma flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bott-Suzuki, S. C., E-mail: sbottsuzuki@ucsd.edu; Caballero Bendixsen, L. S.; Cordaro, S. W.

2015-05-15

We present a study of the formation of bow shocks in radiatively cooled plasma flows. This work uses an inverse wire array to provide a quasi-uniform, large scale hydrodynamic flow accelerated by Lorentz forces to supersonic velocities. This flow impacts a stationary object placed in its path, forming a well-defined Mach cone. Interferogram data are used to determine a Mach number of ∼6, which may increase with radial position suggesting a strongly cooling flow. Self-emission imaging shows the formation of a thin (<60 μm) strongly emitting shock region, where T{sub e} ∼ 40–50 eV, and rapid cooling behind the shock. Emission is observed upstreammore » of the shock position which appears consistent with a radiation driven phenomenon. Data are compared to 2-dimensional simulations using the Gorgon MHD code, which show good agreement with the experiments. The simulations are also used to investigate the effect of magnetic field in the target, demonstrating that the bow-shocks have a high plasma β, and the influence of B-field at the shock is small. This consistent with experimental measurement with micro bdot probes.« less

Irregular-regular mode oscillations inside plasma bubble and its fractal analysis in glow discharge magnetized plasma

NASA Astrophysics Data System (ADS)

Megalingam, Mariammal; Hari Prakash, N.; Solomon, Infant; Sarma, Arun; Sarma, Bornali

2017-04-01

Experimental evidence of different kinds of oscillations in floating potential fluctuations of glow discharge magnetized plasma is being reported. A spherical gridded cage is inserted into the ambient plasma volume for creating plasma bubbles. Plasma is produced between a spherical mesh grid and chamber. The spherical mesh grid of 80% optical transparency is connected to the positive terminal of power supply and considered as anode. Two Langmuir probes are kept in the ambient plasma to measure the floating potential fluctuations in different positions within the system, viz., inside and outside the spherical mesh grid. At certain conditions of discharge voltage (Vd) and magnetic field, irregular to regular mode appears, and it shows chronological changes with respect to magnetic field. Further various nonlinear analyses such as Recurrence Plot, Hurst exponent, and Lyapunov exponent have been carried out to investigate the dynamics of oscillation at a range of discharge voltages and external magnetic fields. Determinism, entropy, and Lmax are important measures of Recurrence Quantification Analysis which indicate an irregular to regular transition in the dynamics of the fluctuations. Furthermore, behavior of the plasma oscillation is characterized by the technique called multifractal detrended fluctuation analysis to explore the nature of the fluctuations. It reveals that it has a multifractal nature and behaves as a long range correlated process.

Plasma Waves and Structures Associated with Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Ergun, R.; Wilder, F. D.; Ahmadi, N.; Goodrich, K.; Holmes, J.; Newman, D. L.; Burch, J.; Torbert, R. B.; Le Contel, O.; Giles, B. L.; Strangeway, R. J.; Lindqvist, P. A.

2017-12-01

Space observations of magnetic reconnection indicate a variety of plasma wave modes and structures in the vicinity of the electron diffusion region including electromagnetic whistler waves, quasi-electrostatic whistler waves, electron phase-space holes, double layers, electron acoustic waves, lower hybrid waves, upper hybrid waves, and electromagnetic drift waves. These waves and plasma structures are seen in magnetotail reconnection and subsolar reconnection. The MMS mission has the unique ability to unequivocally identify the electron diffusion region and distinguish waves in the EDR from those in the extended separatrix. Such a distinction is critical since some of the observed waves may be involved the reconnection process while others may result from subsequent or associated events and do not directly influence the reconnection process. For example, some of the largest amplitude (> 100 mV/m) electrostatic waves have been identified as electron acoustic waves and upper hybrid waves. These waves are likely generated as a result of reconnection and do not appear to strongly influence the reconnection process. On the other hand, large-amplitude electrostatic whistler waves have been observed very near the X-line, are seen in simulations, and may be participating in reconnection physics. Electromagnetic drift waves almost always appear in cases of asymmetric reconnection and may lead to a more turbulent process. We summarize wave observations by MMS and discuss the relative their possible role in magnetic reconnection physics, concentrating on recent magnetotail observations.

Laboratory Experiments on Propagating Plasma Bubbles into Vacuum, Vacuum Magnetic Field, and Background Plasmas

NASA Astrophysics Data System (ADS)

Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott

2014-10-01

We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.

RF magnetized ring-shaped plasma for target utilization obtained with circular magnet monopole arrangement

NASA Astrophysics Data System (ADS)

Amzad Hossain, Md.; Ohtsu, Yasunori

2018-01-01

We proposed a new setup for generating outer ring-shaped radio frequency (RF) magnetized plasma near the chamber wall using monopole magnet setups. Three monopole magnet setups with (a) R = 5 mm, (b) R = 20 mm, and (c) R = 35 mm were investigated, where R is the gap between the magnets in consecutive circles. The distributions of the two dimensional magnetic flux lines, the absolute value of the horizontal magnetic flux density, and the discharge voltage were investigated for the proposed setups to produce outer ring-shaped plasma. A highly luminous ring-shaped plasma was observed for the setup (a), whereas multi-ring discharges were observed for the setups (b) and (c). It was found that the electron temperature decreases with increasing gas pressure for all cases. The electron temperatures were 2.42, 1.71, and 1.15 eV at an Ar gas pressure of 4 Pa for setups (a), (b), and (c), respectively. The plasma density was approximately the same for setups (b) and (c) at all gas pressures. The highest plasma densities were 6.26 × 1015, 1.06 × 1016, and 1.11 × 1016 m-3 at 5 Pa for setups (a), (b), and (c), respectively. It was found that the electron mean free path was 41.4, 63.17, and 84.66 mm at an Ar gas pressure of 5 Pa for setups (a), (b), and (c), respectively. The electron neutral collision frequency for setup (a) was higher than those for setups (b) and (c) at a constant RF power of 40 W and an axial distance of z = 13 mm from the target surface. The radial profile of the ion saturation current for setup (b) was more uniform than those for setups (a) and (c).

Plasma Transport and Magnetic Flux Circulation in Saturn's Magnetosphere

NASA Astrophysics Data System (ADS)

Neupane, B. R.; Delamere, P. A.; Ma, X.; Wilson, R. J.

2017-12-01

Radial transport of plasma in the rapidly rotating magnetospheres is an important dynamical process. Radial transport is due to the centrifugally driven interchange instability and magnetodisc reconnection, allowing net mass to be transported outward while conserving magnetic flux. Using Cassini Plasma Spectrometer instrument (CAPS) data products (e.g., Thomsen et al., [2010]; Wilson et al., [2017]) we estimate plasma mass and magnetic flux transport rates as functions of radial distance and local time. The physical requirement for zero net magnetic flux transport provides a key benchmark for assessing the validity of our mass transport estimate. We also evaluate magnetodisc stability using a two-dimensional axisymmetric equilibrium model [Caudal, 1986]. Observed local properties (e.g., specific entropy and estimates of flux tube mass and entropy content) are compared with modeled equilibrium conditions such that departures from equilibrium can be correlated with radial flows and local magnetic field structure. Finally, observations of specific entropy indicate that plasma is non-adiabatic heated during transport. However, the values of specific entropy are well organized in inner magnetosphere (i.e. L<10), and become widely scattered in the middle magnetosphere, suggesting that the transport dynamics of the inner and middle magnetosphere are different.

Effective potential kinetic theory for strongly coupled plasmas

NASA Astrophysics Data System (ADS)

Baalrud, Scott D.; Daligault, Jérôme

2016-11-01

The effective potential theory (EPT) is a recently proposed method for extending traditional plasma kinetic and transport theory into the strongly coupled regime. Validation from experiments and molecular dynamics simulations have shown it to be accurate up to the onset of liquid-like correlation parameters (corresponding to Γ ≃ 10-50 for the one-component plasma, depending on the process of interest). Here, this theory is briefly reviewed along with comparisons between the theory and molecular dynamics simulations for self-diffusivity and viscosity of the one-component plasma. A number of new results are also provided, including calculations of friction coefficients, energy exchange rates, stopping power, and mobility. The theory is also cast in the Landau and Fokker-Planck kinetic forms, which may prove useful for enabling efficient kinetic computations.

Progress towards experimental realization of extreme-velocity flow-dominated magnetized plasmas

NASA Astrophysics Data System (ADS)

Weber, T. E.; Adams, C. S.; Welch, D. R.; Kagan, G.; Bean, I. A.; Henderson, B. R.; Klim, A. J.

2017-10-01

Interactions of flow-dominated plasmas with other plasmas, neutral gases, magnetic fields, solids etc., take place with sufficient velocity that kinetic energy dominates the dynamics of the interaction (as opposed to magnetic or thermal energy, which dominates in most laboratory plasma experiments). Building upon progress made by the Magnetized Shock Experiment (MSX) at LANL, we are developing the experimental and modeling capability to increase our ultimate attainable plasma velocities well in excess of 1000 km/s. Ongoing work includes designing new pulsed power switches, triggering, and inductive adder topologies; development of novel high-speed optical diagnostics; and exploration of new numerical techniques to specifically model the unique physics of translating/stagnating flow-dominated plasmas. Furthering our understanding of the physical mechanisms of energy conversion from kinetic to other forms, such as thermal energy, non-thermal tails/accelerated populations, enhanced magnetic fields, and radiation (both continuum and line), has wide-ranging significance in basic plasma science, astrophysics, and plasma technology applications such as inertial confinement fusion and intense radiation sources. This work is supported by the U.S. Department of Energy, National Nuclear Security Administration. LA-UR-17-25786.

Performance improvement of magnetized coaxial plasma gun by magnetic circuit on a bias coil

NASA Astrophysics Data System (ADS)

Edo, Takahiro; Matsumoto, Tadafumi; Asai, Tomohiko; Kamino, Yasuhiro; Inomoto, Michiaki; Gota, Hiroshi

2016-10-01

A magnetized coaxial plasmoid accelerator has been utilized for compact torus (CT) injection to refuel into fusion reactor core plasma. Recently, CT injection experiments have been conducted on the C-2/C-2U facility at Tri Alpha Energy. In the series of experiments successful refueling, i.e. increased particle inventory of field-reversed configuration (FRC) plasma, has been observed. In order to improve the performance of CT injector and to refuel in the upgraded FRC device, called C-2W, with higher confinement magnetic field, magnetic circuit consisting of magnetic material onto a bias magnetic coil is currently being tested at Nihon University. Numerical work suggests that the optimized bias magnetic field distribution realizes the increased injection velocity because of higher conversion efficiency of Lorenz self force to kinetic energy. Details of the magnetic circuit design as well as results of the test experiment and field calculations will be presented and discussed.

Diagnosing laser-preheated magnetized plasmas relevant to magnetized liner inertial fusion

DOE PAGES

Harvey-Thompson, Adam James; Sefkow, Adam B.; Nagayama, Taisuke N.; ...

2015-12-22

In this paper, we present a platform on the OMEGA EP Laser Facility that creates and diagnoses the conditions present during the preheat stage of the MAGnetized Liner Inertial Fusion (MagLIF) concept. Experiments were conducted using 9 kJ of 3ω (355 nm) light to heat an underdense deuterium gas (electron density: 2.5 × 10 20 cm -3 = 0.025 of critical density) magnetized with a 10 T axial field. Results show that the deuterium plasma reached a peak electron temperature of 670 ± 140 eV, diagnosed using streaked spectroscopy of an argon dopant. The results demonstrate that plasmas relevant tomore » the preheat stage of MagLIF can be produced at multiple laser facilities, thereby enabling more rapid progress in understanding magnetized preheat. Results are compared with magneto-radiation-hydrodynamics simulations, and plans for future experiments are described.« less

Superconducting applications in propulsion systems. Magnetic insulation for plasma propulsion devices

NASA Technical Reports Server (NTRS)

Gonzalez, Dora E.; Karr, Gerald R.

1990-01-01

The purpose of this paper is to review the status of knowledge of the basic concepts needed to establish design parameters for effective magnetic insulation. The objective is to estimate the effectiveness of the magnetic field in insulating the plasma, to calculate the magnitude of the magnetic field necessary to reduce the heat transfer to the walls sufficiently enough to demonstrate the potential of magnetically driven plasma rockets.

Magnetic Nozzles for Plasma Thrusters: Acceleration, Thrust, and Detachment Mechanisms

DTIC Science & Technology

2011-10-01

Energy Distribution Function M. Merino-Mart́ınez∗ Universidad Politécnica de Madrid, Spain A two-dimensional plasma beam model is used to investigate the...2D model of the supersonic expansion of a collisionless plasma in a divergent magnetic nozzle was de - veloped by Ahedo and Merino.7 An important...Universidad Politecnica de Madrid, Spain A magnetic nozzle model for the supersonic expansion of a collisionless, low-beta plasma characterizes the

Plasma transport in a simulated magnetic-divertor configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strawitch, C. M.

1981-03-01

The transport properties of plasma on magnetic field lines that intersect a conducting plate are studied experimentally in the Wisconsin internal ring D.C. machine. The magnetic geometry is intended to simulate certain aspects of plasma phenomena that may take place in a tokamak divertor. It is found by a variety of measurements that the cross field transport is non-ambipolar; this may have important implications in heat loading considerations in tokamak divertors. The undesirable effects of nonambipolar flow make it preferable to be able to eliminate it. However, we find that though the non-ambipolarity may be reduced, it is difficult tomore » eliminate entirely. The plasma flow velocity parallel to the magnetic field is found to be near the ion acoustic velocity in all cases. The experimental density and electron temperature profiles are compared to the solutions to a one dimensional transport model that is commonly used in divertor theory.« less

Mobility in a strongly coupled dusty plasma with gas.

PubMed

Liu, Bin; Goree, J

2014-04-01

The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force F, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity up. The mobility μp=up/F of the projectile's motion is obtained. Two regimes depending on F are identified. In the high-force regime, μp∝F0.23, and the scattering cross section σs diminishes as up-6/5. Results for σs are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments.

Mobility in a strongly coupled dusty plasma with gas

NASA Astrophysics Data System (ADS)

Liu, Bin; Goree, J.

2014-04-01

The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force F, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity up. The mobility μp=up/F of the projectile's motion is obtained. Two regimes depending on F are identified. In the high-force regime, μp∝F0.23, and the scattering cross section σs diminishes as up-6/5. Results for σs are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments.

Effect of magnetic field on the phase transition in dusty plasma

NASA Astrophysics Data System (ADS)

Jaiswal, Surabhi; Thomas, Edward; Mukherjee, Rupak

2017-10-01

The formation of self-consistent crystalline structure is a well-known phenomenon in complex plasmas. In most experiments the pressure and rf power are the main controlling parameter in determining the phase of the system. We have studied the effect of externally applied magnetic field on the configuration of plasma crystals, suspended in the sheath of a radio-frequency discharge using the Magnetized Dusty Plasma Experiment (MDPX) device. Experiments are performed at a fixed pressure and rf power where a crystalline structure formed within the confining ring, but ramping the magnetic field up to 1.28 T. We report on the breakdown of the crystalline structure with increasing magnetic field. The magnetic field affects the dynamics of the plasma particles and first leads to a rotation of the crystal. At higher magnetic field, there is a radial variation (shear) in the angular velocity of the moving particles which we believe leads to the melting of the crystal. This melting is confirmed by evaluating the variation of the pair correlation function as a function of magnetic field. This work was supported by the US Dept. of Energy, DE - SC0010485.

Magnetic Field and Plasma Diagnostics from Coordinated Prominence Observations

NASA Astrophysics Data System (ADS)

Schmieder, B.; Levens, P.; Dalmasse, K.; Mein, N.; Mein, P.; Lopez-Ariste, A.; Labrosse, N.; Heinzel, P.

2016-04-01

We study the magnetic field in prominences from a statistical point of view, by using THEMIS in the MTR mode, performing spectropolarimetry of the He I D3 line. Combining these measurements with spectroscopic data from IRIS, Hinode/EIS as well as ground-based telescopes, such as the Meudon Solar Tower, we infer the temperature, density, and flow velocities of the plasma. There are a number of open questions that we aim to answer: - What is the general direction of the magnetic field in prominences? Is the model using a single orientation of magnetic field always valid for atypical prominences? %- Does this depend on the location of the filament on the disk (visible in Hα, in He II 304 Å) over an inversion line between weak or strong network ? - Are prominences in a weak environment field dominated by gas pressure? - Measuring the Doppler shifts in Mg II lines (with IRIS) and in Hα can tell us if there are substantial velocities to maintain vertical rotating structures, as has been suggested for tornado-like prominences. We present here some results obtained with different ground-based and space-based instruments in this framework.

The Effects of Magnetic Nozzle Configurations on Plasma Thrusters

NASA Technical Reports Server (NTRS)

Turchi, P. J.

1997-01-01

Over the course of eight years, the Ohio State University has performed research in support of electric propulsion development efforts at the NASA Lewis Research Center, Cleveland, OH. This research has been largely devoted to plasma propulsion systems including MagnetoPlasmaDynamic (MPD) thrusters with externally-applied, solenoidal magnetic fields, hollow cathodes, and Pulsed Plasma Microthrusters (PPT's). Both experimental and theoretical work has been performed, as documented in four master's theses, two doctoral dissertations, and numerous technical papers. The present document is the final report for the grant period 5 December 1987 to 31 December 1995, and summarizes all activities. Detailed discussions of each area of activity are provided in appendices: Appendix 1 - Experimental studies of magnetic nozzle effects on plasma thrusters; Appendix 2 - Numerical modeling of applied-field MPD thrusters; Appendix 3 - Theoretical and experimental studies of hollow cathodes; and Appendix 4 -Theoretical, numerical and experimental studies of pulsed plasma thrusters. Especially notable results include the efficacy of using a solenoidal magnetic field downstream of a plasma thruster to collimate the exhaust flow, the development of a new understanding of applied-field MPD thrusters (based on experimentally-validated results from state-of-the art, numerical simulation) leading to predictions of improved performance, an experimentally-validated, first-principles model for orificed, hollow-cathode behavior, and the first time-dependent, two-dimensional calculations of ablation-fed, pulsed plasma thrusters.

Photonic band structures of two-dimensional magnetized plasma photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qi, L.

By using modified plane wave method, photonic band structures of the transverse electric polarization for two types of two-dimensional magnetized plasma photonic crystals are obtained, and influences of the external magnetic field, plasma density, and dielectric materials on the dispersion curves are studied, respectively. Results show that two areas of flat bands appear in the dispersion curves due to the role of external magnetic field, and the higher frequencies of the up and down flat bands are corresponding to the right-circled and left-circled cutoff frequencies, respectively. Adjusting external magnetic field and plasma density can not only control positions of themore » flat bands, but also can control the location and width of the local gap; increasing relative dielectric constant of the dielectric materials makes omni-direction gaps appear.« less

Experimental research on time-resolved evolution of cathode plasma expansion velocity in a long pulsed magnetically insulated coaxial diode

NASA Astrophysics Data System (ADS)

Zhu, Danni; Zhang, Jun; Zhong, Huihuang; Ge, Xingjun; Gao, Jingming

2018-02-01

Unlike planar diodes, separate research of the axial and radial plasma expansion velocities is difficult for magnetically insulated coaxial diodes. Time-resolved electrical diagnostic which is based on the voltage-ampere characteristics has been employed to study the temporal evolution of the axial and radial cathode plasma expansion velocities in a long pulsed magnetically insulated coaxial diode. Different from a planar diode with a "U" shaped profile of temporal velocity evolution, the temporal evolution trend of the axial expansion velocity is proved to be a "V" shaped profile. Apart from the suppression on the radial expansion velocity, the strong magnetic field is also conducive to slowing down the axial expansion velocity. Compared with the ordinary graphite cathode, the carbon velvet and graphite composite cathode showed superior characteristics as judged by the low plasma expansion velocity and long-term electrical stability as a promising result for applications where long-pulsed and reliable operation at high power is required.

Nonlinear Laser-Plasma Interaction in Magnetized Liner Inertial Fusion

DOE PAGES

Geissel, Matthias; Awe, Thomas James; Bliss, David E.; ...

2016-03-04

Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. Although magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Ultimately, nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Wemore » determine and discuss key LPI processes and mitigation methods. Results with and without improvement measures are presented.« less

Nonlinear Laser-Plasma Interaction in Magnetized Liner Inertial Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geissel, Matthias; Awe, Thomas James; Bliss, David E.

Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. Although magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Ultimately, nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Wemore » determine and discuss key LPI processes and mitigation methods. Results with and without improvement measures are presented.« less

Effect of ECRH and resonant magnetic fields on formation of magnetic islands in the T-10 tokamak plasma

NASA Astrophysics Data System (ADS)

Shestakov, E. A.; Savrukhin, P. V.

2017-10-01

Experiments in the T-10 tokamak demonstrated possibility of controlling the plasma current during disruption instability using the electron cyclotron resonance heating (ECRH) and the controlled operation of the ohmic current-holding system. Quasistable plasma discharge with repeating sawtooth oscillations can be restored after energy quench using auxiliary ECRH power when PEC / POH > 2-5. The external magnetic field generation system consisted of eight saddle coils that were arranged symmetrically relative to the equatorial plane of the torus outside of the vacuum vessel of the T-10 tokamak to study the possible resonant magnetic field effects on the rotation frequency of magnetic islands. The saddle coils power supply system is based on four thyristor converters with a total power of 300 kW. The power supply control system is based on Siemens S7 controllers. As shown by preliminary experiments, the interaction efficiency of external magnetic fields with plasma depends on the plasma magnetic configuration. Optimal conditions for slowing the rotation of magnetic islands were determined. Additionally, the direction of the error magnetic field in the T-10 tokamak was determined, and the threshold value of the external magnetic field was determined.

Dynamics of Plasma Jets and Bubbles Launched into a Transverse Background Magnetic Field

NASA Astrophysics Data System (ADS)

Zhang, Yue

2017-10-01

A coaxial magnetized plasma gun has been utilized to launch both plasma jets (open B-field) and plasma bubbles (closed B-field) into a transverse background magnetic field in the HelCat (Helicon-Cathode) linear device at the University of New Mexico. These situations may have bearing on fusion plasmas (e.g. plasma injection for tokamak fueling, ELM pacing, or disruption mitigation) and astrophysical settings (e.g. astrophysical jet stability, coronal mass ejections, etc.). The magnetic Reynolds number of the gun plasma is 100 , so that magnetic advection dominates over magnetic diffusion. The gun plasma ram pressure, ρjetVjet2 >B02 / 2μ0 , the background magnetic pressure, so that the jet or bubble can easily penetrate the background B-field, B0. When the gun axial B-field is weak compared to the gun azimuthal field, a current-driven jet is formed with a global helical magnetic configuration. Applying the transverse background magnetic field, it is observed that the n = 1 kink mode is stabilized, while magnetic probe measurements show contrarily that the safety factor q(a) drops below unity. At the same time, a sheared axial jet velocity is measured. We conclude that the tension force arising from increasing curvature of the background magnetic field induces the measured sheared flow gradient above the theoretical kink-stabilization threshold, resulting in the emergent kink stabilization of the injected plasma jet. In the case of injected bubbles, spheromak-like plasma formation is verified. However, when the spheromak plasma propagates into the transverse background magnetic field, the typical self-closed global symmetry magnetic configuration does not hold any more. In the region where the bubble toroidal field opposed the background B-field, the magneto-Rayleigh-Taylor (MRT) instability has been observed. Details of the experiment setup, diagnostics, experimental results and theoretical analysis will be presented. Supported by the National Science Foundation

Effect of large magnetic islands on screening of external magnetic perturbation fields at slow plasma flow

NASA Astrophysics Data System (ADS)

Li, L.; Liu, Y. Q.; Huang, X.; Luan, Q.; Zhong, F. C.

2017-02-01

A toroidal resistive magneto-hydrodynamic plasma response model, involving large magnetic islands, is proposed and numerically investigated, based on local flattening of the equilibrium pressure profile near a rational surface. It is assumed that such islands can be generated near the edge of the tokamak plasma, due to the penetration of the resonant magnetic perturbations, used for the purpose of controlling the edge localized mode. Within this model, it is found that the local flattening of the equilibrium pressure helps to mitigate the toroidal curvature induced screening effect [Glasser et al., Phys. Fluids 7, 875 (1975)]—the so called Glasser-Greene-Johnson screening, when the local toroidal flow near the mode rational surface is very slow (for example, as a result of mode locking associated with the field penetration). The saturation level of the plasma response amplitude is computed, as the plasma rotation frequency approaches zero. The local modification of the plasma resistivity inside the magnetic island is found to also affect the saturation level of the plasma response at vanishing flow.

Recent Progress on the magnetic turbulence experiment at the Bryn Mawr Plasma Laboratory

NASA Astrophysics Data System (ADS)

Schaffner, D. A.; Cartagena-Sanchez, C. A.; Johnson, H. K.; Fahim, L. E.; Fiedler-Kawaguchi, C.; Douglas-Mann, E.

2017-10-01

Recent progress is reported on the construction, implementation and testing of the magnetic turbulence experiment at the Bryn Mawr Plasma Laboratory (BMPL). The experiment at the BMPL consists of an ( 300 μs) long coaxial plasma gun discharge that injects magnetic helicity into a flux-conserving chamber in a process akin to sustained slow-formation of spheromaks. A 24cm by 2m cylindrical chamber has been constructed with a high density axial port array to enable detailed simultaneous spatial measurements of magnetic and plasma fluctuations. Careful positioning of the magnetic structure produced by the three separately pulsed coils (one internal, two external) are preformed to optimize for continuous injection of turbulent magnetized plasma. High frequency calibration of magnetic probes is also underway using a power amplifier.

PLASMA DEVICE

DOEpatents

Gow, J.D.; Wilcox, J.M.

1961-12-26

A device is designed for producing and confining highenergy plasma from which neutrons are generated in copious quantities. A rotating sheath of electrons is established in a radial electric field and axial magnetic field produced within the device. The electron sheath serves as a strong ionizing medium to gas introdueed thereto and also functions as an extremely effective heating mechanism to the resulting plasma. In addition, improved confinement of the plasma is obtained by ring magnetic mirror fields produced at the ends of the device. Such ring mirror fields are defined by the magnetic field lines at the ends of the device diverging radially outward from the axis of the device and thereafter converging at spatial annular surfaces disposed concentrically thereabout. (AFC)

Effects of resistivity and rotation on the linear plasma response to non-axisymmetric magnetic perturbations on DIII-D

DOE PAGES

Haskey, Shaun R.; Lanctot, Matthew J.; Liu, Y. Q.; ...

2015-01-05

Parameter scans show the strong dependence of the plasma response on the poloidal structure of the applied field highlighting the importance of being able to control this parameter using non-axisymmetric coil sets. An extensive examination of the linear single fluid plasma response to n = 3 magnetic perturbations in L-mode DIII-D lower single null plasmas is presented. The effects of plasma resistivity, toroidal rotation and applied field structure are calculated using the linear single fluid MHD code, MARS-F. Measures which separate the response into a pitch-resonant and resonant field amplification (RFA) component are used to demonstrate the extent to whichmore » resonant screening and RFA occurs. The ability to control the ratio of pitch-resonant fields to RFA by varying the phasing between upper and lower resonant magnetic perturbations coils sets is shown. The predicted magnetic probe outputs and displacement at the x-point are also calculated for comparison with experiments. Additionally, modelling of the linear plasma response using experimental toroidal rotation profiles and Spitzer like resistivity profiles are compared with results which provide experimental evidence of a direct link between the decay of the resonant screening response and the formation of a 3D boundary. As a result, good agreement is found during the initial application of the MP, however, later in the shot a sudden drop in the poloidal magnetic probe output occurs which is not captured in the linear single fluid modelling.« less

Magnetic circuit for hall effect plasma accelerator

NASA Technical Reports Server (NTRS)

Manzella, David H. (Inventor); Jacobson, David T. (Inventor); Hofer, Richard (Inventor); Peterson, Peter (Inventor); Jankovsky, Robert S. (Inventor)

2009-01-01

A Hall effect plasma accelerator includes inner and outer electromagnets, circumferentially surrounding the inner electromagnet along a thruster centerline axis and separated therefrom, inner and outer magnetic conductors, in physical connection with their respective inner and outer electromagnets, with the inner magnetic conductor having a mostly circular shape and the outer magnetic conductor having a mostly annular shape, a discharge chamber, located between the inner and outer magnetic conductors, a magnetically conducting back plate, in magnetic contact with the inner and outer magnetic conductors, and a combined anode electrode/gaseous propellant distributor, located at a bottom portion of the discharge chamber. The inner and outer electromagnets, the inner and outer magnetic conductors and the magnetically conducting back plate form a magnetic circuit that produces a magnetic field that is largely axial and radially symmetric with respect to the thruster centerline.

Plasma observations at the Earth's magnetic equator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsen, R.C.; Shawhan, S.D.; Gallagher, D.L.

1987-03-01

The magnetic equator provides a unique location for thermal plasma and plasma wave measurements. Plasma populations are found to be confined within a few degrees latitude of the equator, particularly the ions. The equatorially trapped ion population is found to be primarily hydrogen, and the authors find little evidence for preferential heating of heavier ions. Helium is occasionally found to be heated along with the protons, and forms about 10% of the equatorially trapped populations at such times, similar to the percentage of He{sup +} in the cold, core plasma of the plasmasphere. One case of a heated O{sup +}more » component was found; at the 0.1% level it generally comprises in the outer plasmasphere core plasma. The heated H{sup +} ions can be characterized by a bi-Maxwellian with kT{sub {parallel}} = 0.5-1.0 eV, and kT = 5-50 eV, with a density of 10-100 cm{sup {minus}3}. The total plasma density, as inferred from the plasma wave instrument measurements of the upper hybrid measurements of the upper hybrid resonance (UHR), is relatively constant with latitude, occasionally showing a local minimum at the magnetic equator, even though the ion flux has increased substantially. The first measurements of the equatorially trapped plasma and coincident UHR measurements show that the trapped plasma is a feature of the plasmapause region, found at total plasma densities of 20-200 cm{sup {minus}3}. The warm, trapped plasma is found in conjunction with equatorial noise, a plasma wave feature found at frequencies near 100 Hz, with a broad spectrum generally found between the proton gyrofrequency at the low frequency edge and the geometric mean gyrofrequency at the high frequency edge. This latter frequency is generally the lower hybrid resonance (LHR) for a proton-electron plasma. Sharp spatial boundaries are occasionally found with latitude, delimiting the equatorially trapped plasma.« less

The spatial structure of magnetospheric plasma disturbance estimated by using magnetic data obtained by SWARM satellites.

NASA Astrophysics Data System (ADS)

Yokoyama, Y.; Iyemori, T.; Aoyama, T.

2017-12-01

Field-aligned currents with various spatial scales flow into and out from high-latitude ionosphere. The magnetic fluctuations observed by LEO satellites along their orbits having period longer than a few seconds can be regarded as the manifestations of spatial structure of field aligned currents.This has been confirmed by using the initial orbital characteristics of 3 SWARM-satellites. From spectral analysis, we evaluated the spectral indices of these magnetic fluctuations and investigated their dependence on regions, such as magnetic latitude and MLT and so on. We found that the spectral indices take quite different values between the regions lower than the equatorward boundary of the auroral oval (around 63 degrees' in magnetic latitude) and the regions higher than that. On the other hands, we could not find the clear MLT dependence. In general, the FACs are believed to be generated in the magnetiospheric plasma sheet and boundary layer, and they flow along the field lines conserving their currents.The theory of FAC generation [e.g., Hasegawa and Sato ,1978] indicates that the FACs are strongly connected with magnetospheric plasma disturbances. Although the spectral indices above are these of spatial structures of the FACs over the ionosphere, by using the theoretical equation of FAC generation, we evaluate the spectral indices of magnetospheric plasma disturbance in FAC's generation regions. Furthermore, by projecting the area of fluctuations on the equatorial plane of magnetosphere (i.e. plasma sheet), we can estimate the spatial structure of magnetospheric plasma disturbance. In this presentation, we focus on the characteristics of disturbance in midnight region and discuss the relations to the substorm.

Shock waves in strongly coupled plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khlebnikov, Sergei; Kruczenski, Martin; Michalogiorgakis, Georgios

2010-12-15

Shock waves are supersonic disturbances propagating in a fluid and giving rise to dissipation and drag. Weak shocks, i.e., those of small amplitude, can be well described within the hydrodynamic approximation. On the other hand, strong shocks are discontinuous within hydrodynamics and therefore probe the microscopics of the theory. In this paper, we consider the case of the strongly coupled N=4 plasma whose microscopic description, applicable for scales smaller than the inverse temperature, is given in terms of gravity in an asymptotically AdS{sub 5} space. In the gravity approximation, weak and strong shocks should be described by smooth metrics withmore » no discontinuities. For weak shocks, we find the dual metric in a derivative expansion, and for strong shocks we use linearized gravity to find the exponential tail that determines the width of the shock. In particular, we find that, when the velocity of the fluid relative to the shock approaches the speed of light v{yields}1 the penetration depth l scales as l{approx}(1-v{sup 2}){sup 1/4}. We compare the results with second-order hydrodynamics and the Israel-Stewart approximation. Although they all agree in the hydrodynamic regime of weak shocks, we show that there is not even qualitative agreement for strong shocks. For the gravity side, the existence of shock waves implies that there are disturbances of constant shape propagating on the horizon of the dual black holes.« less

Electron diamagnetic effect in a magnetic nozzle on a helicon plasma thruster performance

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Lafleur, Trevor; Charles, Christine; Alexander, Peter; Boswell, Rod

2012-10-01

The axial force, which is called thrust sometimes, imparted from a magnetically expanding helicon plasma thruster is directly measured and the results are compared with a two-dimensional fluid theory. The force component solely transmitted to the expanding field is directly measured and identified as an axial force produced by the azimuthal current due to an electron diamagnetic drift and the radial component of the applied magnetic field. In this type of configuration, plasma diffusion in magnetic field affects a spatial profile of the plasma density and the resultant axial force onto the magnetic field. It is observed that the force component onto the magnetic field increases with an increase in the magnetic field strength, simultaneously with an increase in the plasma density downstream of the source exit, which could be due to suppression of the cross field diffusion in the magnetic nozzle.