3D simulation studies of tokamak plasmas using MHD and extended-MHD models

International Nuclear Information System (INIS)

Park, W.; Chang, Z.; Fredrickson, E.; Fu, G.Y.; Pomphrey, N.; Sugiyama, L.E.

1997-01-01

The M3D (Multi-level 3D) tokamak simulation project aims at the simulation of tokamak plasmas using a multi-level tokamak code package. Several current applications using MHD and Extended-MHD models are presented; high-β disruption studies in reversed shear plasmas using the MHD level MH3D code, ω *i stabilization and nonlinear island rotation studies using the two-fluid level MH3D-T code, studies of nonlinear saturation of TAE modes using the hybrid particle/MHD level MH3D-K code, and unstructured mesh MH3D ++ code studies. In particular, three internal mode disruption mechanisms are identified from simulation results which agree well with experimental data

Pseudo-MHD ballooning modes in tokamak plasmas

International Nuclear Information System (INIS)

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

1996-08-01

The MHD description of a plasma is extended to allow electrons to have both fluid-like and adiabatic-regime responses within an instability eigenmode. In the resultant open-quotes pseudo-MHDclose quotes model, magnetic field line bending is reduced in the adiabatic electron regime. This makes possible a new class of ballooning-type, long parallel extent, MHD-like instabilities in tokamak plasmas for α > s 2 (2 7/3 /9) (r p /R 0 ) or-d√Β/dr > (2 1/6 /3)(s/ R 0q ), which is well below the ideal-MHD stability boundary. The marginally stable pressure profile is similar in both magnitude and shape to that observed in ohmically heated tokamak plasmas

Collisionless plasmas in astrophysics

CERN Document Server

Belmont, Gerard; Mottez, Fabrice; Pantellini, Filippo; Pelletier, Guy

2013-01-01

Collisionless Plasmas in Astrophysics examines the unique properties of media without collisions in plasma physics. Experts in this field, the authors present the first book to concentrate on collisionless conditions in plasmas, whether close or not to thermal equilibrium. Filling a void in scientific literature, Collisionless Plasmas in Astrophysics explains the possibilities of modeling such plasmas, using a fluid or a kinetic framework. It also addresses common misconceptions that even professionals may possess, on phenomena such as "collisionless (Landau) damping". Abundant illustrations

MHD instabilities and their effects on plasma confinement in the large helical device plasmas

International Nuclear Information System (INIS)

Toi, K.

2002-01-01

MHD stability of NBI heated plasmas and impacts of MHD modes on plasma confinement are intensively studied in the Large Helical Device (LHD). Three characteristic MHD instabilities were observed, that is, (1) pressure driven modes excited in the plasma edge, (2) pressure driven mode in the plasma core, and (3) Alfven eigenmodes (AEs) driven by energetic ions. MHD mode excited in the edge region accompanies multiple satellites, and is called Edge Harmonic Modes (EHMs). EHM sometimes has a bursting character. The bursting EHM transiently decreases the stored energy by about 15 percent. In the plasma core region, m=2/n=1 pressure driven mode is typically destabilized. The mode often induces internal collapse in the higher beta regime more than 1 percent. The internal collapse appreciably affects the global confinement. Energetic ion driven AEs are often detected in NBI-heated LHD plasmas. Particular AE with the frequency 8-10 times larger than TAE-frequency was detected in high beta plasmas more than 2 percent. The AE may be related to helicity-induced AE. Excitation of these three types of MHD instabilities and their impacts on plasma confinement are discussed. (author)

MHD Ballooning Instability in the Plasma Sheet

International Nuclear Information System (INIS)

Cheng, C.Z.; Zaharia, S.

2003-01-01

Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum

Studies of MHD stability using data mining technique in helical plasmas

International Nuclear Information System (INIS)

Yamamoto, Satoshi; Pretty, David; Blackwell, Boyd

2010-01-01

Data mining techniques, which automatically extract useful knowledge from large datasets, are applied to multichannel magnetic probe signals of several helical plasmas in order to identify and classify MHD instabilities in helical plasmas. This method is useful to find new MHD instabilities as well as previously identified ones. Moreover, registering the results obtained from data mining in a database allows us to investigate the characteristics of MHD instabilities with parameter studies. We introduce the data mining technique consisted of pre-processing, clustering and visualizations using results from helical plasmas in H-1 and Heliotron J. We were successfully able to classify the MHD instabilities using the criterion of phase differences of each magnetic probe and identify them as energetic-ion-driven MHD instabilities using parameter study in Heliotron J plasmas. (author)

Modeling the astrophysical dynamical process with laser-plasmas

International Nuclear Information System (INIS)

Xia Jiangfan; Zhang Jun; Zhang Jie

2001-01-01

The use of the state-of-the-art laser facility makes it possible to create conditions of the same or similar to those in the astrophysical processes. The introduction of the astrophysics-relevant ideas in laser-plasma experiments is propitious to the understanding of the astrophysical phenomena. However, the great difference between the laser-produced plasmas and the astrophysical processes makes it awkward to model the latter by laser-plasma experiments. The author addresses the physical backgrounds for modeling the astrophysical plasmas by laser plasmas, connecting these two kinds of plasmas by scaling laws. Thus, allowing the creation of experimental test beds where observations and models can be quantitatively compared with laser-plasma data. Special attentions are paid on the possibilities of using home-made laser facilities to model astrophysical phenomena

Gravitational instability in isotropic MHD plasma waves

Science.gov (United States)

Cherkos, Alemayehu Mengesha

2018-04-01

The effect of compressive viscosity, thermal conductivity and radiative heat-loss functions on the gravitational instability of infinitely extended homogeneous MHD plasma has been investigated. By taking in account these parameters we developed the six-order dispersion relation for magnetohydrodynamic (MHD) waves propagating in a homogeneous and isotropic plasma. The general dispersion relation has been developed from set of linearized basic equations and solved analytically to analyse the conditions of instability and instability of self-gravitating plasma embedded in a constant magnetic field. Our result shows that the presence of viscosity and thermal conductivity in a strong magnetic field substantially modifies the fundamental Jeans criterion of gravitational instability.

Linear and Nonlinear MHD Wave Processes in Plasmas. Final Report

International Nuclear Information System (INIS)

Tataronis, J. A.

2004-01-01

This program treats theoretically low frequency linear and nonlinear wave processes in magnetized plasmas. A primary objective has been to evaluate the effectiveness of MHD waves to heat plasma and drive current in toroidal configurations. The research covers the following topics: (1) the existence and properties of the MHD continua in plasma equilibria without spatial symmetry; (2) low frequency nonresonant current drive and nonlinear Alfven wave effects; and (3) nonlinear electron acceleration by rf and random plasma waves. Results have contributed to the fundamental knowledge base of MHD activity in symmetric and asymmetric toroidal plasmas. Among the accomplishments of this research effort, the following are highlighted: Identification of the MHD continuum mode singularities in toroidal geometry. Derivation of a third order ordinary differential equation that governs nonlinear current drive in the singular layers of the Alfven continuum modes in axisymmetric toroidal geometry. Bounded solutions of this ODE implies a net average current parallel to the toroidal equilibrium magnetic field. Discovery of a new unstable continuum of the linearized MHD equation in axially periodic circular plasma cylinders with shear and incompressibility. This continuum, which we named ''accumulation continuum'' and which is related to ballooning modes, arises as discrete unstable eigenfrequency accumulate on the imaginary frequency axis in the limit of large mode numbers. Development of techniques to control nonlinear electron acceleration through the action of multiple coherent and random plasmas waves. Two important elements of this program aye student participation and student training in plasma theory

Study of aluminum emission spectra in astrophysical plasmas

International Nuclear Information System (INIS)

Jin Zhan; Zhang Jie

2001-01-01

High temperature, high density and strong magnetic fields in plasmas produced by ultra-high intensity and ultrashort laser pulses are similar to the main characteristics of astrophysical plasmas. This makes it possible to simulate come astrophysical processes at laboratories. The author presents the theoretic simulation of aluminum emission spectra in astrophysical plasmas. It can be concluded that using laser produced plasmas, the authors can obtain rich information on astrophysical spectroscopy, which is unobservable for astronomer

Linear MHD stability analysis of post-disruption plasmas in ITER

Energy Technology Data Exchange (ETDEWEB)

Aleynikova, K., E-mail: ksenia.aleynikova@gmail.com [EURATOM Association, Max-Planck-Institut für Plasmaphysik (Germany); Huijsmans, G. T. A. [ITER Organization (France); Aleynikov, P. [EURATOM Association, Max-Planck-Institut für Plasmaphysik (Germany)

2016-05-15

Most of the plasma current can be replaced by a runaway electron (RE) current during plasma disruptions in ITER. In this case the post-disruption plasma current profile is likely to be more peaked than the pre-disruption profile. The MHD activity of such plasma will affect the runaway electron generation and confinement and the dynamics of the plasma position evolution (Vertical Displacement Event), limiting the timeframe for runaway electrons and disruption mitigation. In the present paper, we evaluate the influence of the possible RE seed current parameters on the onset of the MHD instabilities. By varying the RE seed current profile, we search for subsequent plasma evolutions with the highest and the lowest MHD activity. This information can be applied to a development of desirable ITER disruption scenario.

A weakened cascade model for turbulence in astrophysical plasmas

International Nuclear Information System (INIS)

Howes, G. G.; TenBarge, J. M.; Dorland, W.

2011-01-01

A refined cascade model for kinetic turbulence in weakly collisional astrophysical plasmas is presented that includes both the transition between weak and strong turbulence and the effect of nonlocal interactions on the nonlinear transfer of energy. The model describes the transition between weak and strong MHD turbulence and the complementary transition from strong kinetic Alfven wave (KAW) turbulence to weak dissipating KAW turbulence, a new regime of weak turbulence in which the effects of shearing by large scale motions and kinetic dissipation play an important role. The inclusion of the effect of nonlocal motions on the nonlinear energy cascade rate in the dissipation range, specifically the shearing by large-scale motions, is proposed to explain the nearly power-law energy spectra observed in the dissipation range of both kinetic numerical simulations and solar wind observations.

Neoclassical MHD descriptions of tokamak plasmas

International Nuclear Information System (INIS)

Callen, J.D.; Kim, Y.B.; Sundaram, A.K.

1988-01-01

Considerable progress has been made in extending neoclassical MHD theory and in exploring the linear instabilities, nonlinear behavior and turbulence models it implies for tokamak plasmas. The areas highlighted in this paper include: extension of the neoclassical MHD equations to include temperature-gradient and heat flow effects; the free energy and entropy evolution implied by this more complete description; a proper ballooning mode formalism analysis of the linear instabilities; a new rippling mode type instability; numerical simulation of the linear instabilities which exhibit a smooth transition from resistive ballooning modes at high collisionality to neoclassical MHD modes at low collisionality; numerical simulation of the nonlinear growth of a single helicity tearing mode; and a Direct-Interaction-Approximation model of neoclassical MHD turbulence and the anomalous transport it induces which substantially improves upon previous mixing length model estimates. 34 refs., 2 figs

MHD description of plasma: handbook of plasma physics

International Nuclear Information System (INIS)

Kulsrud, R.M.

1980-10-01

The basic sets of MHD equations for the description of a plasma in various limits are derived and their usefulness and limits of validity are discussed. These limits are: the one fluid collisional plasma, the two fluid collisional plasma, the Chew-Goldberger Low formulation of the guiding center limit of a collisionless plasma and the double-adiabatic limit. Conservation relations are derived from these sets and the mathematics of the concept of flux freezing is given. An example is given illustrating the differences between guiding center theory and double adiabatic theory

Characterizing electrostatic turbulence in tokamak plasmas with high MHD activity

Energy Technology Data Exchange (ETDEWEB)

Guimaraes-Filho, Z O; Santos Lima, G Z dos; Caldas, I L; Nascimento, I C; Kuznetsov, Yu K [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66316, 05315-970, Sao Paulo, SP (Brazil); Viana, R L, E-mail: viana@fisica.ufpr.b [Departamento de Fisica, Universidade Federal do Parana, Caixa Postal 19044, 81531-990, Curitiba, PR (Brazil)

2010-09-01

One of the challenges in obtaining long lasting magnetic confinement of fusion plasmas in tokamaks is to control electrostatic turbulence near the vessel wall. A necessary step towards achieving this goal is to characterize the turbulence level and so as to quantify its effect on the transport of energy and particles of the plasma. In this paper we present experimental results on the characterization of electrostatic turbulence in Tokamak Chauffage Alfven Bresilien (TCABR), operating in the Institute of Physics of University of Sao Paulo, Brazil. In particular, we investigate the effect of certain magnetic field fluctuations, due to magnetohydrodynamical (MHD) instabilities activity, on the spectral properties of electrostatic turbulence at plasma edge. In some TCABR discharges we observe that this MHD activity may increase spontaneously, following changes in the edge safety factor, or after changes in the radial electric field achieved by electrode biasing. During the high MHD activity, the magnetic oscillations and the plasma edge electrostatic turbulence present several common linear spectral features with a noticeable dominant peak in the same frequency. In this article, dynamical analyses were applied to find other alterations on turbulence characteristics due to the MHD activity and turbulence enhancement. A recurrence quantification analysis shows that the turbulence determinism radial profile is substantially changed, becoming more radially uniform, during the high MHD activity. Moreover, the bicoherence spectra of these two kinds of fluctuations are similar and present high bicoherence levels associated with the MHD frequency. In contrast with the bicoherence spectral changes, that are radially localized at the plasma edge, the turbulence recurrence is broadly altered at the plasma edge and the scrape-off layer.

Laser-Plasma Modeling Using PERSEUS Extended-MHD Simulation Code for HED Plasmas

Science.gov (United States)

Hamlin, Nathaniel; Seyler, Charles

2017-10-01

We discuss the use of the PERSEUS extended-MHD simulation code for high-energy-density (HED) plasmas in modeling the influence of Hall and electron inertial physics on laser-plasma interactions. By formulating the extended-MHD equations as a relaxation system in which the current is semi-implicitly time-advanced using the Generalized Ohm's Law, PERSEUS enables modeling of extended-MHD phenomena (Hall and electron inertial physics) without the need to resolve the smallest electron time scales, which would otherwise be computationally prohibitive in HED plasma simulations. We first consider a laser-produced plasma plume pinched by an applied magnetic field parallel to the laser axis in axisymmetric cylindrical geometry, forming a conical shock structure and a jet above the flow convergence. The Hall term produces low-density outer plasma, a helical field structure, flow rotation, and field-aligned current, rendering the shock structure dispersive. We then model a laser-foil interaction by explicitly driving the oscillating laser fields, and examine the essential physics governing the interaction. This work is supported by the National Nuclear Security Administration stewardship sciences academic program under Department of Energy cooperative agreements DE-FOA-0001153 and DE-NA0001836.

On MHD waves, fire-hose and mirror instabilities in anisotropic plasmas

Directory of Open Access Journals (Sweden)

L.-N. Hau

2007-09-01

Full Text Available Temperature or pressure anisotropies are characteristic of space plasmas, standard magnetohydrodynamic (MHD model for describing large-scale plasma phenomena however usually assumes isotropic pressure. In this paper we examine the characteristics of MHD waves, fire-hose and mirror instabilities in anisotropic homogeneous magnetized plasmas. The model equations are a set of gyrotropic MHD equations closed by the generalized Chew-Goldberger-Low (CGL laws with two polytropic exponents representing various thermodynamic conditions. Both ions and electrons are allowed to have separate plasma beta, pressure anisotropy and energy equations. The properties of linear MHD waves and instability criteria are examined and numerical examples for the nonlinear evolutions of slow waves, fire-hose and mirror instabilities are shown. One significant result is that slow waves may develop not only mirror instability but also a new type of compressible fire-hose instability. Their corresponding nonlinear structures thus may exhibit anticorrelated density and magnetic field perturbations, a property used for identifying slow and mirror mode structures in the space plasma environment. The conditions for nonlinear saturation of both fire-hose and mirror instabilities are examined.

MHD equilibrium of heliotron J plasmas

International Nuclear Information System (INIS)

Suzuki, Yasuhiro; Nakamura, Yuji; Kondo, Katsumi; Nakajima, Noriyoshi; Hayashi, Takaya

2004-01-01

MHD equilibria of Heliotron J plasma are investigated by using HINT code. By assuming some profiles of the current density, effects of the net toroidal currents on the magnetohydrodynamics (MHD) equilibrium are investigated. If the rotational transform can be controlled by the currents, the generation of good flux surfaces is expected. In order to study equilibria with self-consistent bootstrap current, the boozer coordinates are constructed by converged HINT equilibrium as a preliminary study. Obtained spectra are compared with ones of VMEC code and both results are consistent. (author)

MHD mode evolutions prior to minor and major disruptions in SST-1 plasma

Energy Technology Data Exchange (ETDEWEB)

Dhongde, Jasraj; Pradhan, Subrata, E-mail: pradhan@ipr.res.in; Bhandarkar, Manisha

2017-01-15

Highlights: • Observation of different regimes of MHD phenomena in SST-1 plasma. • MHD mode (m/n = 1/1, m/n = 2/1) evolutions prior to minor and major disruptions in SST-1 plasma. • MHD mode characteristics such as mode frequency, mode number, island width etc. in different regimes. - Abstract: Steady State Superconducting Tokamak (SST-1) is a medium size Tokamak (R{sub 0} = 1.1 m, a = 0.2 m, B{sub T} = 1.5T, Ip ∼ 110 kA) in operation at the Institute for Plasma Research, India. SST-1 uniquely experiments large aspect ratio (∼5.5) plasma in different operation regimes. In these experiments, repeatable characteristic MHD phenomena have been consistently observed. As the large aspect ratio plasma pulse progresses, these MHD phenomena display minor-major disruptions ably indicated in Mirnov oscillations, Mirnov oscillations with saw teeth and locked modes etc. Even though somewhat similar observations have been found in some other machines, these observations are found for the first time in large aspect ratio plasma of SST-1. This paper elaborates the magnetic field perturbations and mode evolutions due to MHD activities from Mirnov coils (poloidal and toroidal), Soft X-ray diagnostics, ECE diagnostics etc. This work further, for the first time reports quantitatively different regimes of MHD phenomena observed in SST-1 plasma, their details of mode evolutions characteristics as well as the subsequently observed minor, major disruptions supported with the physical explanations. This study will help developing disruption mitigation and avoidance scenarios for having better confinement plasma experiments.

On nonlinear MHD-stability of toroidal magnetized plasma

International Nuclear Information System (INIS)

Ilgisonis, V.I.; Pastukhov, V.P.

1994-01-01

The variational approach to analyze the nonlinear MHD stability of ideal plasma in toroidal magnetic field is proposed. The potential energy functional to be used is expressed in terms of complete set of independent Lagrangian invariants, that allows to take strictly into account all the restrictions inherent in the varied functions due to MHD dynamic equations. (author). 3 refs

Plasma Astrophysics, part II Reconnection and Flares

CERN Document Server

Somov, Boris V

2007-01-01

This well-illustrated monograph is devoted to classic fundamentals, current practice, and perspectives of modern plasma astrophysics. The first part is unique in covering all the basic principles and practical tools required for understanding and working in plasma astrophysics. The second part presents the physics of magnetic reconnection and flares of electromagnetic origin in space plasmas within the solar system; single and double stars, relativistic objects, accretion disks, and their coronae are also covered. This book is designed mainly for professional researchers in astrophysics. However, it will also be interesting and useful to graduate students in space sciences, geophysics, as well as advanced students in applied physics and mathematics seeking a unified view of plasma physics and fluid mechanics.

Plasma Astrophysics, Part I Fundamentals and Practice

CERN Document Server

Somov, Boris V

2006-01-01

This well-illustrated monograph is devoted to classic fundamentals, current practice, and perspectives of modern plasma astrophysics. The first part is unique in covering all the basic principles and practical tools required for understanding and working in plasma astrophysics. The second part presents the physics of magnetic reconnection and flares of electromagnetic origin in space plasmas within the solar system; single and double stars, relativistic objects, accretion disks, and their coronae are also covered. This book is designed mainly for professional researchers in astrophysics. However, it will also be interesting and useful to graduate students in space sciences, geophysics, as well as advanced students in applied physics and mathematics seeking a unified view of plasma physics and fluid mechanics.

Sawtooth oscillations as MHD relaxation process in a plasma

International Nuclear Information System (INIS)

Yoshida, Zensho; Inoue, Nobuyuki; Ogawa, Yuichi

1992-01-01

The sawtooth oscillation in a tokamak plasma is a spontaneous relaxation process accompanying global instabilities which behave to reduce the internal magnetic energy. This phenomenon has a similarity to the MHD relaxation processes in Reversed Field Pinch (RFP) and Ultra Low Q (ULQ) plasmas. The self-stabilizing effect of instabilities with m (poloidal mode number) = 1 results in an increase in the central safety factor q(0). Nonlinear dynamics of m = 1 instabilities has been discussed both for global and local modes. The latter appears when a pitch minimum exists in the plasma, and is relevant to the compound sawtooth oscillation. The MHD relaxation is a restructuring process of the plasma current profile that is competitive with the resistive diffusion. (author)

Cosmic-ray shock acceleration in oblique MHD shocks

Science.gov (United States)

Webb, G. M.; Drury, L. OC.; Volk, H. J.

1986-01-01

A one-dimensional, steady-state hydrodynamical model of cosmic-ray acceleration at oblique MHD shocks is presented. Upstream of the shock the incoming thermal plasma is subject to the adverse pressure gradient of the accelerated particles, the J x B force, as well as the thermal gas pressure gradient. The efficiency of the acceleration of cosmic-rays at the shock as a function of the upstream magnetic field obliquity and upstream plasma beta is investigated. Astrophysical applications of the results are briefly discussed.

Experiments and models of MHD jets and their relevance to astrophysics and solar physics

Science.gov (United States)

Bellan, Paul M.

2018-05-01

Magnetohydrodynamic (MHD)-driven jets involve poloidal and toroidal magnetic fields, finite pressure gradients, and unbalanced forces. The mechanism driving these jets is first discussed qualitatively by decomposing the magnetic force into a curvature and a gradient component. The mechanism is then considered quantitatively by consideration of all terms in the three components of the MHD equation of motion and in addition, the implications of Ampere's law, Faraday's law, the ideal Ohm's law, and the equation of continuity. The analysis shows that jets are self-collimating with the tip of the jet moving more slowly than the main column of the jet so there is a continuous stagnation near the tip in the jet frame. Experiments supporting these conclusions are discussed and it is shown how this mechanism relates to jets in astrophysical and solar corona contexts.

MHD stability analyses of a tokamak plasma by time-dependent codes

International Nuclear Information System (INIS)

Kurita, Gen-ichi

1982-07-01

The MHD properties of a tokamak plasma are investigated by using time evolutional codes. As for the ideal MHD modes we have analyzed the external modes including the positional instability. Linear and nonlinear ideal MHD codes have been developed. Effects of the toroidicity and conducting shell on the external kink mode are studied minutely by the linear code. A new rezoning algorithm is devised and it is successfully applied to express numerically the axisymmetric plasma perturbation in a cylindrical geometry. As for the resistive MHD modes we have developed nonlinear codes on the basis of the reduced set of the resistive MHD equations. By using the codes we have studied the major disruption processes and properties of the low n resistive modes. We have found that the effects of toroidicity and finite poloidal beta are very important. Considering the above conclusion we propose a new scenario of the initiation of the major disruption. (author)

An analysis of plasma ion toroidal rotation during large amplitude MHD activity in JET

International Nuclear Information System (INIS)

Snipes, J.A.; Esch, H.P.L. de; Lazzaro, E.; Stork, D.; Hellermann, M. von; Galvao, R.; Hender, T.C.; Zasche, D.

1989-01-01

A detailed study of plasma ion toroidal rotation in JET during large amplitude MHD activity has revealed a strong viscous force that couples plasma ions to MHD modes. Depending on the MHD modes present, this force can couple across all of the plasma cross section, across only the central region, roughly within the q=1 surface, or across only the outer region outside the q=1.5 surface. The force acts to flatten the ion toroidal rotation frequency profile, measured by the JET active charge exchange spectroscopy diagnostic, across the coupled region of plasma. The frequency of rotation in this region agrees with the MHD oscillation frequency measured by magnetic pick-up coils at the wall. The strength of the force between the ions and modes becomes evident during high power NBI when the mode locks and drags the ion toroidal rotation frequency to zero, within the errors of the measurements. The present theories of plasma rotation either ignore MHD effects entirely, consider only moderate n toroidal field ripple, or low n ripple effects. (author) 7 refs., 3 figs

Study of MHD events initiated by pellet injection into T-10 plasmas

International Nuclear Information System (INIS)

Kuteev, B.; Khimchenko, L.; Krylov, S.; Pavlov, Y.; Pustovitov, V.; Sarychev, D.; Sergeev, V.; Skokov, V.; Timokhin, V.

2005-01-01

There are several events which might be responsible for ultra fast transport of heat and particles during pellet ablation stage in a tokamak. Those are jumps of transport coefficients, plasma drifts in the pellet vicinity and MHD events with time scale significantly shorter than the pellet ablation time. The role of the latter is still not very well understood due to a lack of studies. This paper is devoted to detailed study of the effects during the pellet ablation phase (∼ one millisecond) with main objective to determine the relation between pellet (material Li, C., KCl, size and velocity) and plasma parameters ( q-value a the pellet position, plasma density and temperature) which initiate microsecond MHD events in plasma. The pellets were injected into both into Ohmic and ECE heated plasmas (up to 3 MW) in the T-10 tokamak at various stages of the plasma discharge, in a wide range from the very beginning up to the post-disruption stage. It is observed that at some conditions a pellet ablates in the plasma without accompanying MHD events. This occurs at the highest plasma densities even if a pellet penetrates through q=1 magnetic surface. The ablation rate corresponds to NGSM in this case. Small scale events may occur near rational magnetic surfaces and the ablation rate fluctuations may be explained by reconnection. Both increase of the longitudinal heat flow due to plasma conventional from higher temperature region and growth of the electric field generation supra-thermal electrons may be responsible for the enhanced ablation. Large scale MHD events envelop a region inside q<3. It is observed that the MHD-cooled area is not poloidally symmetric. Mechanisms of the phenomena observed and their consequences on tokamak operation are discussed. (Author)

3D nonlinear MHD simulations of ultra-low q plasmas

International Nuclear Information System (INIS)

Bonfiglio, D.; Cappello, S.; Piovan, R.; Zanotto, L.; Zuin, M.

2008-01-01

Magnetohydrodynamic (MHD) phenomena occurring in the ultra-low safety factor (ULq) configuration are investigated by means of 3D nonlinear MHD simulations. The ULq configuration, a screw pinch characterized by the edge safety factor q edge in the interval 0 edge edge values which are about the major rational numbers, suggesting plasma self-organization. Similar behaviour is observed in experimental ULq discharges, like those recently obtained exploiting the flexibility of the RFX-mod device. The transition of q edge from a major rational number to the next one occurs together with the development of a kink deformation of the plasma column, whose stabilization yields a nearly axisymmetric state with a rather flat q profile. Numerical simulations also show that it is possible to sustain either of the two conditions, namely, the saturated kink helical configuration and the axisymmetric one, by forcing q edge at a suitable value. Finally, the effects of this MHD phenomenology on the confinement properties of ULq plasmas are discussed.

Magnetic evaluation of hydrogen pressures changes on MHD fluctuations in IR-T1 tokamak plasma

Science.gov (United States)

Alipour, Ramin; Ghanbari, Mohamad R.

2018-04-01

Identification of tokamak plasma parameters and investigation on the effects of each parameter on the plasma characteristics is important for the better understanding of magnetohydrodynamic (MHD) activities in the tokamak plasma. The effect of different hydrogen pressures of 1.9, 2.5 and 2.9 Torr on MHD fluctuations of the IR-T1 tokamak plasma was investigated by using of 12 Mirnov coils, singular value decomposition and wavelet analysis. The parameters such as plasma current, loop voltage, power spectrum density, energy percent of poloidal modes, dominant spatial structures and temporal structures of poloidal modes at different plasma pressures are plotted. The results indicate that the MHD activities at the pressure of 2.5 Torr are less than them at other pressures. It also has been shown that in the stable area of plasma and at the pressure of 2.5 Torr, the magnetic force and the force of plasma pressure are in balance with each other and the MHD activities are at their lowest level.

Kinetic Modifications to MHD Phenomena in Toroidal Plasmas

International Nuclear Information System (INIS)

Cheng, C.Z.; Gorelenkov, N.N.; Kramer, G.J.; Fredrickson, E.

2004-01-01

Particle kinetic effects involving small spatial and fast temporal scales can strongly affect MHD phenomena and the long time behavior of plasmas. In particular, kinetic effects such as finite ion gyroradii, trapped particle dynamics, and wave-particle resonances have been shown to greatly modify the stability of MHD modes. Here, the kinetic effects of trapped electron dynamics and finite ion gyroradii are shown to have a large stabilizing effect on kinetic ballooning modes in low aspect ratio toroidal plasmas such as NSTX [National Spherical Torus Experiment]. We also present the analysis of Toroidicity-induced Alfven Eigenmodes (TAEs) destabilized by fast neutral-beam injected ions in NSTX experiments and TAE stability in ITER due to alpha-particles and MeV negatively charged neutral beam injected ions

Weakly Collisional and Collisionless Astrophysical Plasmas

DEFF Research Database (Denmark)

Berlok, Thomas

are used to study weakly collisional, stratified atmospheres which offer a useful model of the intracluster medium of galaxy clusters. Using linear theory and computer simulations, we study instabilities that feed off thermal and compositional gradients. We find that these instabilities lead to vigorous...... investigate helium mixing in the weakly collisional intracluster medium of galaxy clusters using Braginskii MHD. Secondly, we present a newly developed Vlasov-fluid code which can be used for studying fully collisionless plasmas such as the solar wind and hot accretions flows. The equations of Braginskii MHD...... associated with the ions and is thus well suited for studying collisionless plasmas. We have developed a new 2D-3V Vlasov-fluid code which works by evolving the phase-space density distribution of the ions while treating the electrons as an inertialess fluid. The code uses the particle-incell (PIC) method...

Characteristics of MHD stability of high beta plasmas in LHD

International Nuclear Information System (INIS)

Sato, M.; Nakajima, N.; Watanabe, K.Y.; Todo, Y.; Suzuki, Y.

2012-11-01

In order to understand characteristics of the MHD stability of high beta plasmas obtained in the LHD experiments, full MHD simulations have been performed for the first time. Since there is a magnetic hill in a plasma peripheral region, the ballooning modes extending into the plasma peripheral region with a chaotic magnetic field are destabilized. However, in the nonlinear phase, the core region comes under the in influence of the instabilities and the central pressure decreases. There is a tendency that modes are suppressed as the beta value and/or magnetic Reynolds number increase, which is consistent with a result that high beta plasmas enter the second stable region of the ideal ballooning modes as beta increases and remaining destabilized ballooning modes are considered to be resistive type. (author)

Magnetic stresses in ideal MHD plasmas

DEFF Research Database (Denmark)

Jensen, V.O.

1995-01-01

The concept of magnetic stresses in ideal MHD plasma theory is reviewed and revisited with the aim of demonstrating its advantages as a basis for calculating and understanding plasma equilibria. Expressions are derived for the various stresses that transmit forces in a magnetized plasma...... and it is shown that the resulting magnetic forces on a finite volume element can be obtained by integrating the magnetic stresses over the surface of the element. The concept is used to rederive and discuss the equilibrium conditions for axisymmetric toroidal plasmas, including the virial theorem...... and the Shafranov shift. The method had pedagogical merits as it simplifies the calculations, improves the physical understanding and facilitates an assessment of the approximations made in the calculations....

Critical ionisation velocity effects in astrophysical plasmas

International Nuclear Information System (INIS)

Raadu, M.A.

1979-08-01

Critical ionisation velocity effects are relevant to astrophysical situations where neutral gas moves through a magnetised plasma. The experimental significance of the critical velocity is well established and the physical basis is now becoming clear. The underlying mechanism depends on the combined effects of electron impact ionisation and electron energisation by collective plasma interactions. For low density plasmas a theory based on a circular process involving electron heating through a modified two stream instability has been developed. Several applications of critical velocity effects to astrophysical plasmas have been discussed in the literature. The importance of the effect in any particular case may be determined from a detailed consideration of energy and momentum balance, using appropriate atomic rate coefficients and taking full account of collective plasma processes. (Auth.)

Evolution of the MHD sheet pinch

International Nuclear Information System (INIS)

Matthaeus, W.H.; Montgomery, D.

1979-01-01

A magnetohydrodynamic (MHD) problem of recurrent interest for both astrophysical and laboratory plasmas is the evolution of the unstable sheet pinch, a current sheet across which a dc magnetic field reverses sign. The evolution of such a sheet pinch is followed with a spectral-method, incompressible, two-dimensional, MHD turbulence code. Spectral diagnostics are employed, as are contour plots of vector potential (magnetic field lines), electric current density, and velocity stream function (velocity streamlines). The nonlinear effect which seems most important is seen to be current filamentation: the concentration of the current density onto sets of small measure near a mgnetic X point. A great deal of turbulence is apparent in the current distribution, which, for high Reynolds numbers, requires large spatial grids (greater than or equal to (64) 2 ). 11 figures, 1 table

Doppler tomography in fusion plasmas and astrophysics

DEFF Research Database (Denmark)

Salewski, Mirko; Geiger, B.; Heidbrink, W. W.

2015-01-01

Doppler tomography is a well-known method in astrophysics to image the accretion flow, often in the shape of thin discs, in compact binary stars. As accretion discs rotate, all emitted line radiation is Doppler-shifted. In fast-ion Dα (FIDA) spectroscopy measurements in magnetically confined plasma......, the Dα-photons are likewise Doppler-shifted ultimately due to gyration of the fast ions. In either case, spectra of Doppler-shifted line emission are sensitive to the velocity distribution of the emitters. Astrophysical Doppler tomography has lead to images of accretion discs of binaries revealing bright...... and limits, analogies and differences in astrophysical and fusion plasma Doppler tomography and what can be learned by comparison of these applications....

A Riccati solution for the ideal MHD plasma response with applications to real-time stability control

Science.gov (United States)

Glasser, Alexander; Kolemen, Egemen; Glasser, A. H.

2018-03-01

Active feedback control of ideal MHD stability in a tokamak requires rapid plasma stability analysis. Toward this end, we reformulate the δW stability method with a Hamilton-Jacobi theory, elucidating analytical and numerical features of the generic tokamak ideal MHD stability problem. The plasma response matrix is demonstrated to be the solution of an ideal MHD matrix Riccati differential equation. Since Riccati equations are prevalent in the control theory literature, such a shift in perspective brings to bear a range of numerical methods that are well-suited to the robust, fast solution of control problems. We discuss the usefulness of Riccati techniques in solving the stiff ordinary differential equations often encountered in ideal MHD stability analyses—for example, in tokamak edge and stellarator physics. We demonstrate the applicability of such methods to an existing 2D ideal MHD stability code—DCON [A. H. Glasser, Phys. Plasmas 23, 072505 (2016)]—enabling its parallel operation in near real-time, with wall-clock time ≪1 s . Such speed may help enable active feedback ideal MHD stability control, especially in tokamak plasmas whose ideal MHD equilibria evolve with inductive timescale τ≳ 1s—as in ITER.

Multi-scale Dynamical Processes in Space and Astrophysical Plasmas

CERN Document Server

Vörös, Zoltán; IAFA 2011 - International Astrophysics Forum 2011 : Frontiers in Space Environment Research

2012-01-01

Magnetized plasmas in the universe exhibit complex dynamical behavior over a huge range of scales. The fundamental mechanisms of energy transport, redistribution and conversion occur at multiple scales. The driving mechanisms often include energy accumulation, free-energy-excited relaxation processes, dissipation and self-organization. The plasma processes associated with energy conversion, transport and self-organization, such as magnetic reconnection, instabilities, linear and nonlinear waves, wave-particle interactions, dynamo processes, turbulence, heating, diffusion and convection represent fundamental physical effects. They demonstrate similar dynamical behavior in near-Earth space, on the Sun, in the heliosphere and in astrophysical environments. 'Multi-scale Dynamical Processes in Space and Astrophysical Plasmas' presents the proceedings of the International Astrophysics Forum Alpbach 2011. The contributions discuss the latest advances in the exploration of dynamical behavior in space plasmas environm...

Computing in plasma physics

International Nuclear Information System (INIS)

Nuehrenberg, J.

1986-01-01

These proceedings contain the articles presented at the named conference. These concern numerical methods for astrophysical plasmas, the numerical simulation of reversed-field pinch dynamics, methods for numerical simulation of ideal MHD stability of axisymmetric plasmas, calculations of the resistive internal m=1 mode in tokamaks, parallel computing and multitasking, particle simulation methods in plasma physics, 2-D Lagrangian studies of symmetry and stability of laser fusion targets, computing of rf heating and current drive in tokamaks, three-dimensional free boundary calculations using a spectral Green's function method, as well as the calculation of three-dimensional MHD equilibria with islands and stochastic regions. See hints under the relevant topics. (HSI)

MHD stability of the ITER pedestal and SOL plasma and its influence on the heat flux width

NARCIS (Netherlands)

Loarte, A.; Liu, F.; Huijsmans, G.T.A.; Kukushkin, A.S.; Pitts, R.A.

2015-01-01

Proceedings of the 21st International Conference on Plasma-Surface Interactions in Controlled Fusion Devices Kanazawa, Japan May 26-30, 2014 MHD stability of ITER plasmas has been analyzed for QDT = 10 edge and SOL plasma conditions, showing that the SOL plasma is MHD stable down to pressure

CASTOR: Normal-mode analysis of resistive MHD plasmas

NARCIS (Netherlands)

Kerner, W.; Goedbloed, J. P.; Huysmans, G. T. A.; Poedts, S.; Schwarz, E.

1998-01-01

The CASTOR (complex Alfven spectrum of toroidal plasmas) code computes the entire spectrum of normal-modes in resistive MHD for general tokamak configurations. The applied Galerkin method, in conjunction with a Fourier finite-element discretisation, leads to a large scale eigenvalue problem A (x)

Density profile effects on confinement and MHD stability of currentless NBI plasmas in Heliotron E

International Nuclear Information System (INIS)

Sudo, Shigeru; Zushi, Hideki; Kondo, Katsumi

1993-01-01

Density profile effects on confinement and MHD stability of currentless NBI plasmas in Heliotron E are studied. The peaked density profile produced by pellet injection increases the stored energy by 20-30% compared to the gas puffed plasmas which obey the empirical stellarator/heliotron scaling in a moderate density range. In contrast to confinement, the peaked pressure profile tends to destabilize the plasma. By limiter insertion, MHD instability occurs (seems to locate near ι/2π=1) even in case of low β (β 0 ≤1%, where β 0 is the central β value) plasmas. On the other hand, the mode of m/n=3/2 at ι/2π=2/3, seems to be a key parameter to the major MHD instability in case of high β (β 0 ≥2%) plasmas. (author)

Challenges and opportunities in laboratory plasma astrophysics

Science.gov (United States)

Drake, R. Paul

2017-06-01

We are in a period of explosive success and opportunity in the laboratory study of plasma phenomena that are relevant to astrophysics. In this talk I will share with you several areas in which recent work, often foreshadowed 20 or 30 years ago, has produced dramatic initial success with prospects for much more. To begin, the talk will provide a brief look at the types of devices used and the regimes they access, showing how they span many orders of magnitude in parameters of interest. It will then illustrate the types of work one can do with laboratory plasmas that are relevant to astrophysics, which range from direct measurement of material properties to the production of scaled models of certain dynamics to the pursuit of complementary understanding. Examples will be drawn from the flow of energy and momentum in astrophysics, the formation and structure of astrophysical systems, and magnetization and its consequences. I hope to include some discussion of collisionless shocks, very dense plasmas, work relevant to the end of the Dark Ages, reconnection, and dynamos. The talk will conclude by highlighting some topics where it seems that we may be on the verge of exciting new progress.The originators of work discussed, and collaborators and funding sources when appropriate, will be included in the talk.

A plasma deflagration accelerator as a platform for laboratory astrophysics

Science.gov (United States)

Underwood, Thomas C.; Loebner, Keith T. K.; Cappelli, Mark A.

2017-06-01

The replication of astrophysical flows in the laboratory is critical for isolating particular phenomena and dynamics that appear in complex, highly-coupled natural systems. In particular, plasma jets are observed in astrophysical contexts at a variety of scales, typically at high magnetic Reynolds number and driven by internal currents. In this paper, we present detailed measurements of the plasma parameters within deflagration-produced plasma jets, the scaling of these parameters against both machine operating conditions and the corresponding astrophysical phenomena. Using optical and spectroscopic diagnostics, including Schlieren cinematography, we demonstrate the production of current-driven plasma jets of ∼100 km/s and magnetic Reynolds numbers of ∼100, and discuss the dynamics of their acceleration into vacuum. The results of this study will contribute to the reproduction of various types of astrophysical jets in the laboratory and indicate the ability to further probe active research areas such as jet collimation, stability, and interaction.

MHD simulation of a beat frequency heated plasma

International Nuclear Information System (INIS)

Milroy, R.D.; Capjack, C.E.; James, C.R.; McMullin, J.N.

1976-01-01

The heating of a plasma in a solenoid, with a beat frequency harmonic which is excited at a frequency near to that of a Langmuir mode in a plasma, is examined. It is shown that at high temperatures the heating rate is very insensitive to changes in plasma density. The amount of energy that can be coupled to a plasma in a solenoid with this heating scheme is investigated by using a one-dimensional computer code which incorporates an exact solution of the relevant MHD equations. The absorption of energy from a high powered laser is shown to be significantly enhanced with this process. (author)

Magnetic Reconnection in Extreme Astrophysical Environments

Science.gov (United States)

Uzdensky, Dmitri

Magnetic reconnection is a fundamental plasma physics process of breaking ideal-MHD's frozen-in constraints on magnetic field connectivity and of dramatic rearranging of the magnetic topol-ogy, which often leads to a violent release of the free magnetic energy. Reconnection has long been acknowledged to be of great importance in laboratory plasma physics (magnetic fusion) and in space and solar physics (responsible for solar flares and magnetospheric substorms). In addition, its importance in Astrophysics has been increasingly recognized in recent years. However, due to a great diversity of astrophysical environments, the fundamental physics of astrophysical magnetic reconnection can be quite different from that of the traditional recon-nection encountered in the solar system. In particular, environments like the solar corona and the magnetosphere are characterized by relatively low energy densities, where the plasma is ad-equately described as a mixture of electrons and ions whose numbers are conserved and where the dissipated magnetic energy basically stays with the plasma. In contrast, in many high-energy astrophysical phenomena the energy density is so large that photons play as important a role as electrons and ions and, in particular, radiation pressure and radiative cooling become dominant. In this talk I focus on the most extreme case of high-energy-density astrophysical reconnec-tion — reconnection of magnetar-strength (1014 - 1015 Gauss) magnetic fields, important for giant flares in soft-gamma repeaters (SGRs), and for rapid magnetic energy release in either the central engines or in the relativistic jets of Gamma Ray Bursts (GRBs). I outline the key relevant physical processes and present a new theoretical picture of magnetic reconnection in these environments. The corresponding magnetic energy density is so enormous that, when suddenly released, it inevitably heats the plasma to relativistic temperatures, resulting in co-pious production of electron

Plasma phenomenology in astrophysical systems: Radio-sources and jets

International Nuclear Information System (INIS)

Montani, Giovanni; Petitta, Jacopo

2014-01-01

We review the plasma phenomenology in the astrophysical sources which show appreciable radio emissions, namely Radio-Jets from Pulsars, Microquasars, Quasars, and Radio-Active Galaxies. A description of their basic features is presented, then we discuss in some details the links between their morphology and the mechanisms that lead to the different radio-emissions, investigating especially the role played by the plasma configurations surrounding compact objects (Neutron Stars, Black Holes). For the sake of completeness, we briefly mention observational techniques and detectors, whose structure set them apart from other astrophysical instruments. The fundamental ideas concerning angular momentum transport across plasma accretion disks—together with the disk-source-jet coupling problem—are discussed, by stressing their successes and their shortcomings. An alternative scenario is then inferred, based on a parallelism between astrophysical and laboratory plasma configurations, where small-scale structures can be found. We will focus our attention on the morphology of the radio-jets, on their coupling with the accretion disks and on the possible triggering phenomena, viewed as profiles of plasma instabilities

Mini-conference and Related Sessions on Laboratory Plasma Astrophysics

International Nuclear Information System (INIS)

Hantao Ji

2004-01-01

This paper provides a summary of some major physics issues and future perspectives discussed in the Mini-Conference on Laboratory Plasma Astrophysics. This Mini-conference, sponsored by the Topical Group on Plasma Astrophysics, was held as part of the American Physical Society's Division of Plasma Physics 2003 Annual Meeting (October 27-31, 2003). Also included are brief summaries of selected talks on the same topic presented at two invited paper sessions (including a tutorial) and two contributed focus oral sessions, which were organized in coordination with the Mini-Conference by the same organizers

Mini-conference and Related Sessions on Laboratory Plasma Astrophysics

Energy Technology Data Exchange (ETDEWEB)

Hantao Ji

2004-02-27

This paper provides a summary of some major physics issues and future perspectives discussed in the Mini-Conference on Laboratory Plasma Astrophysics. This Mini-conference, sponsored by the Topical Group on Plasma Astrophysics, was held as part of the American Physical Society's Division of Plasma Physics 2003 Annual Meeting (October 27-31, 2003). Also included are brief summaries of selected talks on the same topic presented at two invited paper sessions (including a tutorial) and two contributed focus oral sessions, which were organized in coordination with the Mini-Conference by the same organizers.

Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics - Revisiting Perturbative Hybrid Kinetic-MHD Theory.

Science.gov (United States)

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

2016-05-10

It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle's Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas.

MHD studies in FTU plasmas with low and negative magnetic shear

International Nuclear Information System (INIS)

Buratti, P.; Alladio, F.; Bracco, G.

1999-01-01

Fast current ramps with central ECRH and pellet injection in ohmic plasmas allowed to study several kinds of MHD instabilities in plasmas with peaked pressure profile and low or negative magnetic shear. Double tearing modes were systematically observed when the minimum q value crossed the q min =2 value; such modes either ended into full core reconnection, or saturated at a large amplitude, with a displacement involving more than one third of the plasma radius. Macroscopic fluctuations clamp the peak temperature during central ECRH; the cause of such fluctuations is attributed to MHD modes that are excited when q min is close to a low order rational value; gaps in the distribution of such values can explain the effective transport barriers observed near integer q min values. When q min ∼1 either sawteeth or saturated internal kink modes are observed. (author)

MHD marking using the MSE polarimeter optics in ILW JET plasmas

CERN Document Server

Reyes Cortes, S.; Alves, D.; Baruzzo, M.; Bernardo, J.; Buratti, P.; Coelho, R.; Challis, C.; Chapman, I.; Hawkes, N.; Hender, T.C.; Hobirk, J.; Joffrin, E.

2016-01-01

In this communication we propose a novel diagnostic technique, which uses the collection optics of the JET Motional Stark Effect (MSE) diagnostic, to perform polarimetry marking of observed MHD in high temperature plasma regimes. To introduce the technique, first we will present measurements of the coherence between MSE polarimeter, electron cyclotron emission, and Mirnov coil signals aiming to show the feasibility of the method. The next step consists of measuring the amplitude fluctuation of the raw MSE polarimeter signals, for each MSE channel, following carefully the MHD frequency on Mirnov coil data spectrograms. A variety of experimental examples in JET ITER-Like Wall (ILW) plasmas are presented, providing an adequate picture and interpretation for the MSE optics polarimeter technique.

PARTICLE-IN-CELL SIMULATIONS OF CONTINUOUSLY DRIVEN MIRROR AND ION CYCLOTRON INSTABILITIES IN HIGH BETA ASTROPHYSICAL AND HELIOSPHERIC PLASMAS

International Nuclear Information System (INIS)

Riquelme, Mario A.; Quataert, Eliot; Verscharen, Daniel

2015-01-01

We use particle-in-cell simulations to study the nonlinear evolution of ion velocity space instabilities in an idealized problem in which a background velocity shear continuously amplifies the magnetic field. We simulate the astrophysically relevant regime where the shear timescale is long compared to the ion cyclotron period, and the plasma beta is β ∼ 1-100. The background field amplification in our calculation is meant to mimic processes such as turbulent fluctuations or MHD-scale instabilities. The field amplification continuously drives a pressure anisotropy with p > p ∥ and the plasma becomes unstable to the mirror and ion cyclotron instabilities. In all cases, the nonlinear state is dominated by the mirror instability, not the ion cyclotron instability, and the plasma pressure anisotropy saturates near the threshold for the linear mirror instability. The magnetic field fluctuations initially undergo exponential growth but saturate in a secular phase in which the fluctuations grow on the same timescale as the background magnetic field (with δB ∼ 0.3 (B) in the secular phase). At early times, the ion magnetic moment is well-conserved but once the fluctuation amplitudes exceed δB ∼ 0.1 (B), the magnetic moment is no longer conserved but instead changes on a timescale comparable to that of the mean magnetic field. We discuss the implications of our results for low-collisionality astrophysical plasmas, including the near-Earth solar wind and low-luminosity accretion disks around black holes

The usage of numerical code FLASH in plasma astrophysics

OpenAIRE

BROŽ, Jaroslav

2013-01-01

My diploma thesis is focused on the use of numerical computer codes for simulation in plasma astrophysics. They will learn the basic characteristics of the Sun, a closer focus on the solar corona and the solar corona heating problem. The following section is devoted to simulation software in plasma astrophysics, their installing and displaying the results using the visualization software. In the conclusion is demonstrated using this software on a model example and a simulation that performs s...

Solving free-plasma-boundary problems with the SIESTA MHD code

Science.gov (United States)

Sanchez, R.; Peraza-Rodriguez, H.; Reynolds-Barredo, J. M.; Tribaldos, V.; Geiger, J.; Hirshman, S. P.; Cianciosa, M.

2017-10-01

SIESTA is a recently developed MHD equilibrium code designed to perform fast and accurate calculations of ideal MHD equilibria for 3D magnetic configurations. It is an iterative code that uses the solution obtained by the VMEC code to provide a background coordinate system and an initial guess of the solution. The final solution that SIESTA finds can exhibit magnetic islands and stochastic regions. In its original implementation, SIESTA addressed only fixed-boundary problems. This fixed boundary condition somewhat restricts its possible applications. In this contribution we describe a recent extension of SIESTA that enables it to address free-plasma-boundary situations, opening up the possibility of investigating problems with SIESTA in which the plasma boundary is perturbed either externally or internally. As an illustration, the extended version of SIESTA is applied to a configuration of the W7-X stellarator.

ZAPP: The Z Astrophysical Plasma Properties collaboration

International Nuclear Information System (INIS)

Rochau, G. A.; Bailey, J. E.; Falcon, R. E.; Loisel, G. P.; Nagayama, T.; Mancini, R. C.; Hall, I.; Winget, D. E.; Montgomery, M. H.; Liedahl, D. A.

2014-01-01

The Z Facility at Sandia National Laboratories [Matzen et al., Phys. Plasmas 12, 055503 (2005)] provides MJ-class x-ray sources that can emit powers >0.3 PW. This capability enables benchmark experiments of fundamental material properties in radiation-heated matter at conditions previously unattainable in the laboratory. Experiments on Z can produce uniform, long-lived, and large plasmas with volumes up to 20 cc, temperatures from 1–200 eV, and electron densities from 10 17–23  cc −1 . These unique characteristics and the ability to radiatively heat multiple experiments in a single shot have led to a new effort called the Z Astrophysical Plasma Properties (ZAPP) collaboration. The focus of the ZAPP collaboration is to reproduce the radiation and material characteristics of astrophysical plasmas as closely as possible in the laboratory and use detailed spectral measurements to strengthen models for atoms in plasmas. Specific issues under investigation include the LTE opacity of iron at stellar-interior conditions, photoionization around active galactic nuclei, the efficiency of resonant Auger destruction in black-hole accretion disks, and H-Balmer line shapes in white dwarf photospheres

Plasma state. The universe's fire

International Nuclear Information System (INIS)

Lehner, Th.

2004-01-01

The plasma is the fourth state of matter, obtained at a very high temperature by the separation of the electrons from their nuclei. Plasma represents 99% of the visible mass of our present day universe and was the unique state of matter at its very beginning. Plasmas are present in the core of stars and in the interstellar environment. More closer to us, they are responsible of spectacular phenomena, like aurora borealis, lightning, comet queues etc.. This book makes a review of the different types of plasmas (electromagnetic, Earth's plasmas, spatial plasmas, solar plasmas, astrophysical plasmas). One chapter presents the thermonuclear fusion as future energy source. Another one treats of the chaos and turbulence inside plasmas. Some applications of plasmas are reviewed: MHD and ionic propulsion systems, MHD energy conversion and MHD generators, thermo-ionic converters, solid-state plasmas, particle accelerators, coherent radiation sources, 'Zeta' machines, X-ray lasers, isotopic separation, non-neutral plasmas and charged beams, free-electrons lasers, electrons and positrons plasmas, industrial applications (etching and cleaning, manufacturing of solar cells, flat screens, industrial reactors, waste treatment, cold plasma-assisted sterilization, effluents decontamination etc.). A last chapter makes an overview of the modern research in plasma physics. (J.S.)

Surface currents on the plasma-vacuum interface in MHD equilibria

Science.gov (United States)

Hanson, James

2017-10-01

The VMEC non-axisymmetric MHD equilibrium code can compute free-boundary equilibria. Since VMEC assumes that magnetic fields within the plasma form closed and nested flux surfaces, the plasma-vacuum interface is a flux surface, and the total magnetic field there has no normal component. VMEC imposes this condition of zero normal field using the potential formulation of Merkel, and solves a Neumann problem for the magnetic potential in the exterior region. This boundary condition necessarily admits the possibility of a surface current on the interface. While this surface current may be small in MHD equilibrium, it is readily computed in terms of the magnetic potentials in both the interior and exterior regions, evaluated on the surface. If only the external magnetic potential is known (as in VMEC), then the surface current can be computed from the discontinuity of the tangential field across the interface. Examples of the surface current for VMEC equilibria will be shown for a zero-pressure stellarator equilibrium. Field-line following of the vacuum magnetic field shows magnetic islands within the plasma region.

MHD waveguides in space plasma

International Nuclear Information System (INIS)

Mazur, N. G.; Fedorov, E. N.; Pilipenko, V. A.

2010-01-01

The waveguide properties of two characteristic formations in the Earth's magnetotail-the plasma sheet and the current (neutral) sheet-are considered. The question of how the domains of existence of different types of MHD waveguide modes (fast and slow, body and surface) in the (k, ω) plane and their dispersion properties depend on the waveguide parameters is studied. Investigation of the dispersion relation in a number of particular (limiting) cases makes it possible to obtain a fairly complete qualitative pattern of all the branches of the dispersion curve. Accounting for the finite size of perturbations across the wave propagation direction reveals new additional effects such as a change in the critical waveguide frequencies, the excitation of longitudinal current at the boundaries of the sheets, and a change in the symmetry of the fundamental mode. Knowledge of the waveguide properties of the plasma and current sheets can explain the occurrence of preferred frequencies in the low-frequency fluctuation spectra in the magnetotail. In satellite observations, the type of waveguide mode can be determined from the spectral properties, as well as from the phase relationships between plasma oscillations and magnetic field oscillations that are presented in this paper.

FIRST KODAI-TRIESTE WORKSHOP ON PLASMA ASTROPHYSICS

CERN Document Server

Hasan, S. S; Krishan, V; TURBULENCE, DYNAMOS, ACCRETION DISKS, PULSARS AND COLLECTIVE PLASMA PROCESSES

2008-01-01

It is well established and appreciated by now that more than 99% of the baryonic matter in the universe is in the plasma state. Most astrophysical systems could be approximated as conducting fluids in a gravitational field. It is the combined effect of these two that gives rise to the mind boggling variety of configurations in the form of filaments, loops , jets and arches. The plasma structures that cannot last for more than a second or less in a laboratory remain intact for astronomical time and spatial scales in an astrophysical setting. The case in point is the well known extragalactic jets whose collimation and stability has remained an enigma inspite of the efforts of many for many long years. The high energy radiation sources such as the active galactic nuclei again summon the coherent plasma radiation processes for their exceptionally large output from regions of relatively small physical sizes. The generation of magnetic field, anomalous transport of angular momentum with decisive bearing on star for...

EMAPS: An Efficient Multiscale Approach to Plasma Systems with Non-MHD Scale Effects

Energy Technology Data Exchange (ETDEWEB)

Omelchenko, Yuri A. [Trinum Research, Inc., San Diego, CA (United States)

2016-08-08

Global interactions of energetic ions with magnetoplasmas and neutral gases lie at the core of many space and laboratory plasma phenomena ranging from solar wind entry into and transport within planetary magnetospheres and exospheres to fast-ion driven instabilities in fusion devices to astrophysics-in-lab experiments. The ability of computational models to properly account for physical effects that underlie such interactions, namely ion kinetic, ion cyclotron, Hall, collisional and ionization processes is important for the success and planning of experimental research in plasma physics. Understanding the physics of energetic ions, in particular their nonlinear resonance interactions with Alfvén waves, is central to improving the heating performance of magnetically confined plasmas for future energy generation. Fluid models are not adequate for high-beta plasmas as they cannot fully capture ion kinetic and cyclotron physics (e.g., ion behavior in the presence of magnetic nulls, shock structures, plasma interpenetration, etc.). Recent results from global reconnection simulations show that even in a MHD-like regime there may be significant differences between kinetic and MHD simulations. Therefore, kinetic modeling becomes essential for meeting modern day challenges in plasma physics. The hybrid approximation is an intermediate approximation between the fluid and fully kinetic approximations. It eliminates light waves, removes the electron inertial temporal and spatial scales from the problem and enables full-orbit ion kinetics. As a result, hybrid codes have become effective tools for exploring ion-scale driven phenomena associated with ion beams, shocks, reconnection and turbulence that control the large-scale behavior of laboratory and space magnetoplasmas. A number of numerical issues, however, make three-dimensional (3D) large-scale hybrid simulations of inhomogeneous magnetized plasmas prohibitively expensive or even impossible. To resolve these difficulties

3D MHD simulations of pellet injection and disruptions in tokamak plasmas

International Nuclear Information System (INIS)

Strauss, H.R.; Park, W.; Belova, E.; Fu, G.Y.; Sugiyama, L.E.

2001-01-01

Nonlinear MHD simulation results of pellet injection show that MHD forces can accelerate large pellets, injected on the high field side of a tokamak, to the plasma center. Magnetic reconnection can produce a reverse shear q profile. Ballooning instability caused by pellets is also reduced by high field side injection. Studies are also reported of the current quench phase of disruptions, which can cause 3D halo currents and runaway electrons. (author)

3D MHD simulations of pellet injection and disruptions in tokamak plasmas

International Nuclear Information System (INIS)

Strauss, H.R.; Park, W.; Belova, E.; Fu, G.Y.; Sugiyama, L.E.

1999-01-01

Nonlinear MHD simulation results of pellet injection show that MHD forces can accelerate large pellets, injected on the high field side of a tokamak, to the plasma center. Magnetic reconnection can produce a reverse shear q profile. Ballooning instability caused by pellets is also reduced by high field side injection. Studies are also reported of the current quench phase of disruptions, which can cause 3D halo currents and runaway electrons. (author)

Generalized MHD for numerical stability analysis of high-performance plasmas in tokamaks

International Nuclear Information System (INIS)

Mikhailovskii, A.B.

1998-01-01

A set of generalized magnetohydrodynamic (MHD) equations is formulated to accommodate the effects associated with high ion and electron temperatures in high-performance plasmas in tokamaks. The effects of neoclassical bootstrap current, neoclassical ion viscosity, the ion finite Larmor radius effect and electron and ion drift effects are taken into account in two-fluid MHD equations together with gyroviscosity, parallel viscosity, electron parallel inertia and collisionless ion heat flux. The ion velocity is identified as the plasma velocity, while the electron velocity is expressed in terms of the plasma velocity and electric current. Ion and electron momentum equations are combined to give the plasma momentum equation. The perpendicular (with respect to the equilibrium magnetic field) ion momentum equation is used as perpendicular Ohm's law and the parallel electron momentum equation - as parallel Ohm's law. Perpendicular Ohm's law allows for the Hall and ion drift effects. Parallel Ohm's law includes the electron drift effect, collisionless skin effect and bootstrap current. In addition, both perpendicular and parallel Ohm's laws contain the resistivity. Due to the quasineutrality condition, the ions and electrons are characterized by the same number density which is described by the ion continuity equation. On the other hand, the ion and electron temperatures are allowed to be different. The ion temperature is described by the ion energy equation allowing for the oblique heat flux, in addition to the perpendicular ion heat flux. The electron temperature is determined by the condition of high parallel electron heat conductivity. The ion and electron parallel viscosities are represented in a form valid for all the collisionality regimes (Pfirsch-Schluter, plateau, and banana). An optimized form of the generalized MHD equations is then represented in terms of the toroidal coordinate system used in the JET equilibrium and stability codes. The derived equations

A plasma formulary for physics, technology, and astrophysics

CERN Document Server

Diver, Declan

2011-01-01

Plasma physics has matured rapidly as a discipline, and now touches on many different research areas, including manufacturing processes. This collection of fundamental formulae and definitions in plasma physics is vital to anyone with an interest in plasmas or ionized gases, whether in physics, astronomy or engineering.Both theorists and experimentalists will find this book useful, as it incorporates the latest results and findings.The text treats astrophysical plasmas, fusion plasmas, industrial plasmas and low temperature plasmas as aspects of the same discipline - a unique approach made pos

Physical phenomena in a low-temperature non-equilibrium plasma and in MHD generators with non-equilibrium conductivity

International Nuclear Information System (INIS)

Velikhov, E.P.; Golubev, V.S.; Dykhne, A.M.

1976-01-01

The paper assesses the position in 1975 of theoretical and experimental work on the physics of a magnetohydrodynamic generator with non-equilibrium plasma conductivity. This research started at the beginning of the 1960s; as work on the properties of thermally non-equilibrium plasma in magnetic fields and also in MHD generator ducts progressed, a number of phenomena were discovered and investigated that had either been unknown in plasma physics or had remained uninvestigated until that time: ionization instability and ionization turbulence of plasma in a magnetic field, acoustic instability of a plasma with anisotropic conductivity, the non-equilibrium ionization wave and the energy balance of a non-equilibrium plasma. At the same time, it was discovered what physical requirements an MHD generator with non-equilibrium conductivity must satisfy to achieve high efficiency in converting the thermal or kinetic energy of the gas flow into electric energy. The experiments on MHD power generation with thermally non-equilibrium plasma carried out up to 1975 indicated that it should be possible to achieve conversion efficiencies of up to 20-30%. (author)

Analyses of MHD instabilities

International Nuclear Information System (INIS)

Takeda, Tatsuoki

1985-01-01

In this article analyses of the MHD stabilities which govern the global behavior of a fusion plasma are described from the viewpoint of the numerical computation. First, we describe the high accuracy calculation of the MHD equilibrium and then the analysis of the linear MHD instability. The former is the basis of the stability analysis and the latter is closely related to the limiting beta value which is a very important theoretical issue of the tokamak research. To attain a stable tokamak plasma with good confinement property it is necessary to control or suppress disruptive instabilities. We, next, describe the nonlinear MHD instabilities which relate with the disruption phenomena. Lastly, we describe vectorization of the MHD codes. The above MHD codes for fusion plasma analyses are relatively simple though very time-consuming and parts of the codes which need a lot of CPU time concentrate on a small portion of the codes, moreover, the codes are usually used by the developers of the codes themselves, which make it comparatively easy to attain a high performance ratio on the vector processor. (author)

X-ray measurements of MHD activity in shaped TCV plasmas

International Nuclear Information System (INIS)

Furno, I.; Weisen, H.; Moret, J.M.; Blanchard, P.; Anton, M.

1997-01-01

The ability of TCV to produce a wide variety of plasma shapes has allowed an investigation of MHD behaviour in a large number of limited ohmic L-mode discharges in which the elongation κ and the triangularity δ have been varied over a wide range: κ = 1.1 → 2.5, δ = -0.3 → 0.7. A 200 channel soft X-ray tomography system in conjunction with toroidal spaced soft X-ray diodes has been used to study the structure of internal disruptions and MHD modes. A strong reduction of sawtooth amplitude is observed as the plasma triangularity is decreased together with an increase in mode activity. The reduced sawtooth amplitudes are not correlated with any significant changes of the inversion radius and hence are not simply due to changes in current profiles; the inversion radius however is strongly correlated with the Spitzer conductivity profile and with the edge safety factor. (author) 5 figs., 4 refs

Physics and astrophysics of quark-gluon plasma

Energy Technology Data Exchange (ETDEWEB)

Anon.

1993-06-15

The quark gluon plasma - matter too hot or dense for quarks to crystallize into particles - played a vital role in the formation of the Universe. Efforts to recreate and understand this type of matter are forefront physics and astrophysics, and progress was highlighted in the Second International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPA-QGP 93), held in Calcutta from 19-23 January. (The first conference in the series was held in Bombay in February 1988). Although primarily motivated towards enlightening the Indian physics community in this new and rapidly evolving area, in which India now plays an important role, the conference also catered for an international audience. Particular emphasis was placed on the role of quark gluon plasma in astrophysics and cosmology. While Charles Alcock of Lawrence Livermore looked at a less conventional picture giving inhomogeneous ('clumpy') nucleosynthesis, David Schramm (Chicago) covered standard big bang nucleosynthesis. The abundances of very light elements do not differ appreciably for these contrasting scenarios; the crucial difference between them shows up for heavier elements like lithium-7 and -8 and boron-11. Richard Boyd (Ohio State) highlighted the importance of accurate measurements of the primordial abundances of these elements for clues to the cosmic quark hadron phase transition. B. Banerjee (Bombay) argued, on the basis of lattice calculations, for only slight supercooling in the cosmic quark phase transition - an assertion which runs counter to the inhomogeneous nucleosynthesis scenario.

Physics and astrophysics of quark-gluon plasma

International Nuclear Information System (INIS)

Anon.

1993-01-01

The quark gluon plasma - matter too hot or dense for quarks to crystallize into particles - played a vital role in the formation of the Universe. Efforts to recreate and understand this type of matter are forefront physics and astrophysics, and progress was highlighted in the Second International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPA-QGP 93), held in Calcutta from 19-23 January. (The first conference in the series was held in Bombay in February 1988). Although primarily motivated towards enlightening the Indian physics community in this new and rapidly evolving area, in which India now plays an important role, the conference also catered for an international audience. Particular emphasis was placed on the role of quark gluon plasma in astrophysics and cosmology. While Charles Alcock of Lawrence Livermore looked at a less conventional picture giving inhomogeneous ('clumpy') nucleosynthesis, David Schramm (Chicago) covered standard big bang nucleosynthesis. The abundances of very light elements do not differ appreciably for these contrasting scenarios; the crucial difference between them shows up for heavier elements like lithium-7 and -8 and boron-11. Richard Boyd (Ohio State) highlighted the importance of accurate measurements of the primordial abundances of these elements for clues to the cosmic quark hadron phase transition. B. Banerjee (Bombay) argued, on the basis of lattice calculations, for only slight supercooling in the cosmic quark phase transition - an assertion which runs counter to the inhomogeneous nucleosynthesis scenario

A toroidal plasma MHD equilibrium code 'EQUCIR version 1'

International Nuclear Information System (INIS)

Ninomiya, Hiromasa; Shinya, Kichiro; Kameari, Akihisa.

1980-10-01

A new free-boundary toroidal MHD equilibrium code ''EQUCIR version 1'' has been developed. The central problems approached by this code is as follows: 1) The magnetic flux distribution of a plasma at equilibrium is determined in the given external field. 2) A set of circuit equations between the plasma and the external conductors are constructed. These circuit equations and the Grad-Shafranov equation are solved self-consistently and the time evolutions of plasma equilibria and currents in external conductors are determined at the same time. 3) The currents in the external conductors are determined so that the plasma cross-section and plasma parameters are to be maintained with desired ones. It is shown that this code is very useful for study of the tokamak plasma equilibria, for design of the poloidal coil system and for investigation of experimental results. (author)

Goya - an MHD equilibrium code for toroidal plasmas

International Nuclear Information System (INIS)

Scheffel, J.

1984-09-01

A description of the GOYA free-boundary equilibrium code is given. The non-linear Grad-Shafranov equation of ideal MHD is solved in a toroidal geometry for plasmas with purely poloidal magnetic fields. The code is based on a field line-tracing procedure, making storage of a large amount of information on a grid unnecessary. Usage of the code is demonstrated by computations of equi/libria for the EXTRAP-T1 device. (Author)

A Fast MHD Code for Gravitationally Stratified Media using Graphical Processing Units: SMAUG

Science.gov (United States)

Griffiths, M. K.; Fedun, V.; Erdélyi, R.

2015-03-01

Parallelization techniques have been exploited most successfully by the gaming/graphics industry with the adoption of graphical processing units (GPUs), possessing hundreds of processor cores. The opportunity has been recognized by the computational sciences and engineering communities, who have recently harnessed successfully the numerical performance of GPUs. For example, parallel magnetohydrodynamic (MHD) algorithms are important for numerical modelling of highly inhomogeneous solar, astrophysical and geophysical plasmas. Here, we describe the implementation of SMAUG, the Sheffield Magnetohydrodynamics Algorithm Using GPUs. SMAUG is a 1-3D MHD code capable of modelling magnetized and gravitationally stratified plasma. The objective of this paper is to present the numerical methods and techniques used for porting the code to this novel and highly parallel compute architecture. The methods employed are justified by the performance benchmarks and validation results demonstrating that the code successfully simulates the physics for a range of test scenarios including a full 3D realistic model of wave propagation in the solar atmosphere.

MHD stability properties of a system of reduced toroidal MHD equations

International Nuclear Information System (INIS)

Maschke, E.K.; Morros Tosas, J.; Urquijo, G.

1993-01-01

A system of reduced toroidal magneto-hydrodynamic (MHD) equations is derived from a general scalar representation of the complete MHD system, using an ordering in terms of the inverse aspect ratio ε of a toroidal plasma. It is shown that the energy principle for the reduced equations is identical with the usual energy principle of the complete MHD system, to the appropriate order in ε. Thus, the reduced equations have the same ideal MHD stability limits as the full MHD equations. (authors). 6 refs

Laboratory studies of photoionized plasma related to astrophysics

International Nuclear Information System (INIS)

Yang Peiqiang; Wang Feilu; Zhao Gang

2011-01-01

Photoionized plasma is universal in astronomy and has great importance on account of its close relation to compact astrophysical objects such as black holes. Recently, with the development of high energy density lasers and Z-pinch facilities, it has become possible to simulate astronomical photoionized plasma in the laboratory. These experiments help us to benchmark and modify the photoionization models, and to understand the photoionization processes to diagnose related astronomical plasma environments. (authors)

HIDENEK: an implicit particle simulation of kinetic-MHD phenomena in three-dimensional plasmas

International Nuclear Information System (INIS)

Tanaka, Motohiko.

1993-05-01

An advanced 'kinetic-MHD' simulation method and its applications to plasma physics are given in this lecture. This method is quite suitable for studying strong nonlinear, kinetic processes associated with large space-scale, low-frequency electromagnetic phenomena of plasmas. A full set of the Maxwell equations, and the Newton-Lorentz equations of motion for particle ions and guiding-center electrons are adopted. In order to retain only the low-frequency waves and instabilities, implicit particle-field equations are derived. The present implicit-particle method is proved to reproduce the MHD eigenmodes such as Alfven, magnetosonic and kinetic Alfven waves in a thermally near-equilibrium plasma. In the second part of the lecture, several physics applications are shown. These include not only the growth of the instabilities of beam ions against the background plasmas and helical kink of the current, but they also demonstrate nonlinear results such as pitch-angle scattering of the ions. Recent progress in the simulation of the Kelvin-Helmholtz instability is also presented with a special emphasis on the mixing of plasma particles. (author)

MHD pilot industrial applications

International Nuclear Information System (INIS)

Freeman, M.; Riviere-Wekstein, G.

1994-01-01

MHD industrial applications (and their historical developments) are sketched in the fields of nuclear fission, nuclear fusion and marine vehicles propelling. Nuclear fission projects resulted in promising prototypes between 1972 and 1980, especially for liquid-metal MHD generators. All of them have been stopped by the scientific policies of the governments. Nuclear fusion projects used mainly the equilibrium plasma of tokamak type reactors; some military projects used pulsed plasma to perform pulsed MHD generators. Marine vehicle propelling is the most advanced field. By june 1992, the japanese sea-going boat 'Yamato 1' was sailing with two MHD propellers. A few months later, the building of 'Yamato 2' has begun

The temporal behaviour of MHD waves in a partially ionized prominence-like plasma: Effect of heating and cooling

Science.gov (United States)

Ballester, J. L.; Carbonell, M.; Soler, R.; Terradas, J.

2018-01-01

Context. During heating or cooling processes in prominences, the plasma microscopic parameters are modified due to the change of temperature and ionization degree. Furthermore, if waves are excited on this non-stationary plasma, the changing physical conditions of the plasma also affect wave dynamics. Aims: Our aim is to study how temporal variation of temperature and microscopic plasma parameters modify the behaviour of magnetohydrodynamic (MHD) waves excited in a prominence-like hydrogen plasma. Methods: Assuming optically thin radiation, a constant external heating, the full expression of specific internal energy, and a suitable energy equation, we have derived the profiles for the temporal variation of the background temperature. We have computed the variation of the ionization degree using a Saha equation, and have linearized the single-fluid MHD equations to study the temporal behaviour of MHD waves. Results: For all the MHD waves considered, the period and damping time become time dependent. In the case of Alfvén waves, the cut-off wavenumbers also become time dependent and the attenuation rate is completely different in a cooling or heating process. In the case of slow waves, while it is difficult to distinguish the slow wave properties in a cooling partially ionized plasma from those in an almost fully ionized plasma, the period and damping time of these waves in both plasmas are completely different when the plasma is heated. The temporal behaviour of the Alfvén and fast wave is very similar in the cooling case, but in the heating case, an important difference appears that is related with the time damping. Conclusions: Our results point out important differences in the behaviour of MHD waves when the plasma is heated or cooled, and show that a correct interpretation of the observed prominence oscillations is very important in order to put accurate constraints on the physical situation of the prominence plasma under study, that is, to perform prominence

Astrophysical fluid dynamics

Science.gov (United States)

Ogilvie, Gordon I.

2016-06-01

> These lecture notes and example problems are based on a course given at the University of Cambridge in Part III of the Mathematical Tripos. Fluid dynamics is involved in a very wide range of astrophysical phenomena, such as the formation and internal dynamics of stars and giant planets, the workings of jets and accretion discs around stars and black holes and the dynamics of the expanding Universe. Effects that can be important in astrophysical fluids include compressibility, self-gravitation and the dynamical influence of the magnetic field that is `frozen in' to a highly conducting plasma. The basic models introduced and applied in this course are Newtonian gas dynamics and magnetohydrodynamics (MHD) for an ideal compressible fluid. The mathematical structure of the governing equations and the associated conservation laws are explored in some detail because of their importance for both analytical and numerical methods of solution, as well as for physical interpretation. Linear and nonlinear waves, including shocks and other discontinuities, are discussed. The spherical blast wave resulting from a supernova, and involving a strong shock, is a classic problem that can be solved analytically. Steady solutions with spherical or axial symmetry reveal the physics of winds and jets from stars and discs. The linearized equations determine the oscillation modes of astrophysical bodies, as well as their stability and their response to tidal forcing.

Measurements of radiative material properties for astrophysical plasmas

International Nuclear Information System (INIS)

Bailey, James E.

2010-01-01

The new generation of z-pinch, laser, and XFEL facilities opens the possibility to produce astrophysically-relevant laboratory plasmas with energy densities beyond what was previously possible. Furthermore, macroscopic plasmas with uniform conditions can now be created, enabling more accurate determination of the material properties. This presentation will provide an overview of our research at the Z facility investigating stellar interior opacities, AGN warm-absorber photoionized plasmas, and white dwarf photospheres. Atomic physics in plasmas heavily influence these topics. Stellar opacities are an essential ingredient of stellar models and they affect what we know about the structure and evolution of stars. Opacity models have become highly sophisticated, but laboratory tests have not been done at the conditions existing inside stars. Our research is presently focused on measuring Fe at conditions relevant to the base of the solar convection zone, where the electron temperature and density are believed to be 190 eV and 9 x 10 22 e/cc, respectively. The second project is aimed at testing atomic kinetics models for photoionized plasmas. Photoionization is an important process in many astrophysical plasmas and the spectral signatures are routinely used to infer astrophysical object's characteristics. However, the spectral synthesis models at the heart of these interpretations have been the subject of very limited experimental tests. Our current research examines photoionization of neon plasma subjected to radiation flux similar to the warm absorber that surrounds active galactic nuclei. The third project is a recent initiative aimed at producing a white dwarf photosphere in the laboratory. Emergent spectra from the photosphere are used to infer the star's effective temperature and surface gravity. The results depend on knowledge of H, He, and C spectral line profiles under conditions where complex physics such as quasi-molecule formation may be important. These

Extended MHD modeling of nonlinear instabilities in fusion and space plasmas

Energy Technology Data Exchange (ETDEWEB)

Germaschewski, Kai [Univ. of New Hampshire, Durham, NH (United States)

2017-11-15

A number of different sub-projects where pursued within this DOE early career project. The primary focus was on using fully nonlinear, curvilinear, extended MHD simulations of instabilities with applications to fusion and space plasmas. In particular, we performed comprehensive studies of the dynamics of the double tearing mode in different regimes and confi gurations, using Cartesian and cyclindrical geometry and investigating both linear and non-linear dynamics. In addition to traditional extended MHD involving Hall term and electron pressure gradient, we also employed a new multi-fluid moment model, which shows great promise to incorporate kinetic effects, in particular off-diagonal elements of the pressure tensor, in a fluid model, which is naturally computationally much cheaper than fully kinetic particle or Vlasov simulations. We used our Vlasov code for detailed studies of how weak collisions effect plasma echos. In addition, we have played an important supporting role working with the PPPL theory group around Will Fox and Amitava Bhattacharjee on providing simulation support for HED plasma experiments performed at high-powered laser facilities like OMEGA-EP in Rochester, NY. This project has support a great number of computational advances in our fluid and kinetic plasma models, and has been crucial to winning multiple INCITE computer time awards that supported our computational modeling.

Magnetohydrodynamic Particle Acceleration Processes: SSX Experiments, Theory and Astrophysical Applications

International Nuclear Information System (INIS)

Matthaeus, W.; Brown, M.

2006-01-01

This is the final technical report for a funded program to provide theoretical support to the Swarthmore Spheromak Experiment. We examined mhd relaxation, reconnecton between two spheromaks, particle acceleration by these processes, and collisonless effects, e.g., Hall effect near the reconnection zone,. Throughout the project, applications to space plasma physics and astrophysics were included. Towards the end of the project we were examining a more fully turbulent relaxation associated with unconstrained dynamics in SSX. We employed experimental, spacecraft observations, analytical and numerical methods.

MHD stability, operational limits and disruptions

International Nuclear Information System (INIS)

1999-01-01

The present physics understandings of magnetohydrodynamic (MHD) stability of tokamak plasmas, the threshold conditions for onset of MHD instability, and the resulting operational limits on attainable plasma pressure (beta limit) and density (density limit), and the consequences of plasma disruption and disruption related effects are reviewed and assessed in the context of their application to a future DT burning reactor prototype tokamak experiment such as ITER. The principal considerations covered within the MHD stability and beta limit assessments are (i) magnetostatic equilibrium, ideal MHD stability and the resulting ideal MHD beta limit; (ii) sawtooth oscillations and the coupling of sawtooth activity to other types of MHD instability; (iii) neoclassical island resistive tearing modes and the corresponding limits on beta and energy confinement; (iv) wall stabilization of ideal MHD instabilities and resistive wall instabilities; (v) mode locking effects of non-axisymmetric error fields; (vi) edge localized MHD instabilities (ELMs, etc.); and (vii) MHD instabilities and beta/pressure gradient limits in plasmas with actively modified current and magnetic shear profiles. The principal considerations covered within the density limit assessments are (i) empirical density limits; (ii) edge power balance/radiative density limits in ohmic and L-mode plasmas; and (iii) edge parameter related density limits in H-mode plasmas. The principal considerations covered in the disruption assessments are (i) disruption causes, frequency and MHD instability onset; (ii) disruption thermal and current quench characteristics; (iii) vertical instabilities (VDEs), both before and after disruption, and plasma and in-vessel halo currents; (iv) after disruption runaway electron formation, confinement and loss; (v) fast plasma shutdown (rapid externally initiated dissipation of plasma thermal and magnetic energies); (vi) means for disruption avoidance and disruption effect mitigation; and

Plasma rotation evolution near the peripheral transport barrier in the presence of low-frequency MHD bursts in TUMAN-3M tokamak

International Nuclear Information System (INIS)

Bulanin, V V; Askinazi, L G; Lebedev, S V; Gorohov, M V; Kornev, V A; Petrov, A V; Tukachinsky, A S; Vildjunas, M I

2006-01-01

The experiments described in the paper are aimed at investigating the possible influence of the low frequency magnetohydrodynamic (MHD) activity burst on the Ohmic H-mode in the TUMAN-3M tokamak. During the MHD burst a transient deterioration of improved confinement was observed. The study has been focused on the measurements of plasma fluctuation poloidal velocity performed by microwave Doppler reflectometry. The plasma fluctuation rotation observed before the MHD burst in the vicinity of the edge transport barrier was in the direction of plasma drift in the negative radial electric field. During the MHD activity the measured poloidal velocity was drastically decreased and even changed its sign. Radial profiles of the poloidal velocity measured in a set of reproducible tokamak shots exhibited the plasma fluctuation rotation in the ion diamagnetic drift direction at the location of the peripheral transport barrier. The possible reasons for this phenomenon are discussed

MHD stability of JET high performance discharges. Comparison of MHD calculations with experimental observations

International Nuclear Information System (INIS)

Huysmans, G.

1998-03-01

One of the aims of the JET, the Joint European Torus, project is to optimise the maximum fusion performance as measured by the neutron rate. At present, two different scenarios are developed at JET to achieve the high performance the so-called Hot-Ion H-mode scenario and the more recent development of the Optimised Shear scenario. Both scenarios have reached similar values of the neutron rate in Deuterium plasmas, up to 5 10 17 neutrons/second. Both scenarios are characterised by a transport barrier, i.e., a region in the plasma where the confinement is improved. The Hot-Ion H-mode has a transport barrier at the plasma boundary just inside the separatrix, an Optimised Shear plasma exhibits a transport barrier at about mid radius. Associated with the improved confinement of the transport barriers are locally large pressure gradients. It is these pressure gradients which, either directly or indirectly, can drive MHD instabilities. The instabilities limit the maximum performance. In the optimised shear scenario a global MHD instability leads to a disruptive end of the discharge. In the Hot-Ion H-mode plasmas, so-called Outer Modes can occur which are localised at the plasma boundary and lead to a saturation of the plasma performance. In this paper, two examples of the MHD instabilities are discussed and identified by comparing the experimentally observed modes with theoretical calculations from the ideal MHD code MISHKA-1. Also, the MHD stability boundaries of the two scenarios are presented. Section 3 contains a discussion of the mode observed just before the disruption

Boundary effects on the MHD dynamo in laboratory plasmas

International Nuclear Information System (INIS)

Ho, Y.L.; Prager, S.C.

1989-07-01

In recent laboratory experiments, a dynamo-like mechanism has been demonstrated in which a portion of the axisymmetric component of the magnetic field is believed to be sustained by 3D spatial fluctuations in the field and flow. With a conducting shell at the plasma surface, past MHD computation shows that sustainment arises from fluctuations which cause magnetic reconnection. If the conducting wall is retracted from the plasma surface, the fluctuations are amplified and the dynamo sustainment is still active for the times studied, but an increased energy input to the plasma is required through the applied electric field. The retraction of the conducting wall enhances the helicity dissipation rate by the intersection of the fields with the resistive surface which bounds the plasma. This enhanced helicity dissipation is balanced by the helicity injection that accompanies the increased applied electric field. 17 refs., 7 figs., 1 tab

Simulating solar MHD

Directory of Open Access Journals (Sweden)

M. Schüssler

Full Text Available Two aspects of solar MHD are discussed in relation to the work of the MHD simulation group at KIS. Photospheric magneto-convection, the nonlinear interaction of magnetic field and convection in a strongly stratified, radiating fluid, is a key process of general astrophysical relevance. Comprehensive numerical simulations including radiative transfer have significantly improved our understanding of the processes and have become an important tool for the interpretation of observational data. Examples of field intensification in the solar photosphere ('convective collapse' are shown. The second line of research is concerned with the dynamics of flux tubes in the convection zone, which has far-reaching implications for our understanding of the solar dynamo. Simulations indicate that the field strength in the region where the flux is stored before erupting to form sunspot groups is of the order of 10⁵ G, an order of magnitude larger than previous estimates based on equipartition with the kinetic energy of convective flows.

Key words. Solar physics · astrophysics and astronomy (photosphere and chromosphere; stellar interiors and dynamo theory; numerical simulation studies.

Two dimensional MHD flows between porous boundaries

International Nuclear Information System (INIS)

Gratton, F.T.

1994-01-01

Similarity solutions of dissipative MHD equations representing conducting fluids injected through porous walls and flowing out in both directions from the center of the channel, are studied as a function of four non dimensional parameters, Reynolds number R e , magnetic Reynolds number R m , Alfvenic Mach number, M A , and pressure gradient coefficient, C. The effluence is restrained by an external magnetic field normal to the walls. When R m m >>1, the solution may model a collision of plasmas of astrophysical interest. In this case the magnetic field lines help to drive the outflow acting jointly with the pressure gradient. The law for C as a function of the other parameters is given for several asymptotic limits. (author). 3 refs, 6 figs

Study on MHD instabilities in the CECI plasma device using Fourier probes

International Nuclear Information System (INIS)

Rosal, A.C.; Aso, Y.; Ueda, M.

1991-01-01

A magnetic diagnostics called Fourier analyser aiming to study MHD instabilities by Fourier series expansion of poloidal magnetic field for m ≤ 3 modes was developed and tested. The diagnostics will be used in the RFP (reversed field pinch) type toroidal plasma device. (M.C.K.)

Convective plasma stability consistent with MHD equilibrium in magnetic confinement systems with a decreasing field

International Nuclear Information System (INIS)

Tsventoukh, M. M.

2010-01-01

A study is made of the convective (interchange, or flute) plasma stability consistent with equilibrium in magnetic confinement systems with a magnetic field decreasing outward and large curvature of magnetic field lines. Algorithms are developed which calculate convective plasma stability from the Kruskal-Oberman kinetic criterion and in which the convective stability is iteratively consistent with MHD equilibrium for a given pressure and a given type of anisotropy in actual magnetic geometry. Vacuum and equilibrium convectively stable configurations in systems with a decreasing, highly curved magnetic field are calculated. It is shown that, in convectively stable equilibrium, the possibility of achieving high plasma pressures in the central region is restricted either by the expansion of the separatrix (when there are large regions of a weak magnetic field) or by the filamentation of the gradient plasma current (when there are small regions of a weak magnetic field, in which case the pressure drops mainly near the separatrix). It is found that, from the standpoint of equilibrium and of the onset of nonpotential ballooning modes, a kinetic description of convective stability yields better plasma confinement parameters in systems with a decreasing, highly curved magnetic field than a simpler MHD model and makes it possible to substantially improve the confinement parameters for a given type of anisotropy. For the Magnetor experimental compact device, the maximum central pressure consistent with equilibrium and stability is calculated to be as high as β ∼ 30%. It is shown that, for the anisotropy of the distribution function that is typical of a background ECR plasma, the limiting pressure gradient is about two times steeper than that for an isotropic plasma. From a practical point of view, the possibility is demonstrated of achieving better confinement parameters of a hot collisionless plasma in systems with a decreasing, highly curved magnetic field than those

The energy associated with MHD waves generation in the solar wind plasma

Science.gov (United States)

delaTorre, A.

1995-01-01

Gyrotropic symmetry is usually assumed in measurements of electron distribution functions in the heliosphere. This prevents the calculation of a net current perpendicular to the magnetic field lines. Previous theoretical results derived by one of the authors for a collisionless plasma with isotropic electrons in a strong magnetic field have shown that the excitation of MHD modes becomes possible when the external perpendicular current is non-zero. We consider then that any anisotropic electron population can be thought of as 'external', interacting with the remaining plasma through the self-consistent electromagnetic field. From this point of view any perpendicular current may be due to the anisotropic electrons, or to an external source like a stream, or to both. As perpendicular currents cannot be derived from the measured distribution functions, we resort to Ampere's law and experimental data of magnetic field fluctuations. The transfer of energy between MHD modes and external currents is then discussed.

Proceedings of the workshop on nonlinear MHD and extended MHD

International Nuclear Information System (INIS)

1998-01-01

Nonlinear MHD simulations have proven their value in interpreting experimental results over the years. As magnetic fusion experiments reach higher performance regimes, more sophisticated experimental diagnostics coupled with ever expanding computer capabilities have increased both the need for and the feasibility of nonlinear global simulations using models more realistic than regular ideal and resistive MHD. Such extended-MHD nonlinear simulations have already begun to produce useful results. These studies are expected to lead to ever more comprehensive simulation models in the future and to play a vital role in fully understanding fusion plasmas. Topics include the following: (1) current state of nonlinear MHD and extended-MHD simulations; (2) comparisons to experimental data; (3) discussions between experimentalists and theorists; (4) /equations for extended-MHD models, kinetic-based closures; and (5) paths toward more comprehensive simulation models, etc. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database

Proceedings of the workshop on nonlinear MHD and extended MHD

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-12-01

Nonlinear MHD simulations have proven their value in interpreting experimental results over the years. As magnetic fusion experiments reach higher performance regimes, more sophisticated experimental diagnostics coupled with ever expanding computer capabilities have increased both the need for and the feasibility of nonlinear global simulations using models more realistic than regular ideal and resistive MHD. Such extended-MHD nonlinear simulations have already begun to produce useful results. These studies are expected to lead to ever more comprehensive simulation models in the future and to play a vital role in fully understanding fusion plasmas. Topics include the following: (1) current state of nonlinear MHD and extended-MHD simulations; (2) comparisons to experimental data; (3) discussions between experimentalists and theorists; (4) /equations for extended-MHD models, kinetic-based closures; and (5) paths toward more comprehensive simulation models, etc. Selected papers have been indexed separately for inclusion in the Energy Science and Technology Database.

Plasma Jet Simulations Using a Generalized Ohm's Law

Science.gov (United States)

Ebersohn, Frans; Shebalin, John V.; Girimaji, Sharath S.

2012-01-01

Plasma jets are important physical phenomena in astrophysics and plasma propulsion devices. A currently proposed dual jet plasma propulsion device to be used for ISS experiments strongly resembles a coronal loop and further draws a parallel between these physical systems [1]. To study plasma jets we use numerical methods that solve the compressible MHD equations using the generalized Ohm s law [2]. Here, we will discuss the crucial underlying physics of these systems along with the numerical procedures we utilize to study them. Recent results from our numerical experiments will be presented and discussed.

Losses of runaway electrons in MHD-active plasmas of the COMPASS tokamak.

Czech Academy of Sciences Publication Activity Database

Ficker, Ondřej; Mlynář, Jan; Vlainic, Milos; Čeřovský, Jaroslav; Urban, Jakub; Vondráček, Petr; Weinzettl, Vladimír; Macúšová, Eva; Decker, J.; Gospodarczyk, M.; Martin, P.; Nardon, E.; Papp, G.; Plyusnin, V.V.; Reux, C.; Saint-Laurent, F.; Sommariva, C.; Cavalier, Jordan; Havlíček, Josef; Havránek, Aleš; Hronová-Bilyková, Olena; Imríšek, Martin; Markovič, Tomáš; Varju, Jozef; Papřok, Richard; Pánek, Radomír; Hron, Martin

2017-01-01

Roč. 57, č. 7 (2017), č. článku 076002. ISSN 0029-5515 R&D Projects: GA MŠk LG14002; GA MŠk(CZ) LM2015045; GA MŠk(CZ) 8D15001 EU Projects: European Commission(XE) 633053 - EUROfusion Institutional support: RVO:61389021 Keywords : tokamaks * runaway electrons * MHD instabilities * disruptions Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 3.307, year: 2016

3-D resistive MHD calculations for tokamak plasmas: beyond the simple reduced set of equations

International Nuclear Information System (INIS)

Carreras, B.A.; Garcia, L.; Hender, T.C.; Hicks, H.R.; Holmes, J.A.; Lynch, V.E.; Masden, B.F.

1983-01-01

Numerical studies of the resistive stability of tokamak plasmas in cylindrical geometry have been performed using: (1) the full set of resistive Magnetohydrodynamic (MHD) equations and (2) an extended version of the reduced set of resistive MHD equations including diamagnetic and electron temperature effects. In particular, the nonlinear interaction of tearing modes of many helicities has been investigated. The numerical results confirm many of the features uncovered previously using the simple reduced equations. (author)

Magnetohydrodynamics: Parallel computation of the dynamics of thermonuclear and astrophysical plasmas. 1. Annual report of massively parallel computing pilot project 93MPR05

International Nuclear Information System (INIS)

1994-08-01

This is the first annual report of the MPP pilot project 93MPR05. In this pilot project four research groups with different, complementary backgrounds collaborate with the aim to develop new algorithms and codes to simulate the magnetohydrodynamics of thermonuclear and astrophysical plasmas on massively parallel machines. The expected speed-up is required to simulate the dynamics of the hot plasmas of interest which are characterized by very large magnetic Reynolds numbers and, hence, require high spatial and temporal resolutions (for details see section 1). The four research groups that collaborated to produce the results reported here are: The MHD group of Prof. Dr. J.P. Goedbloed at the FOM-Institute for Plasma Physics 'Rijnhuizen' in Nieuwegein, the group of Prof. Dr. H. van der Vorst at the Mathematics Institute of Utrecht University, the group of Prof. Dr. A.G. Hearn at the Astronomical Institute of Utrecht University, and the group of Dr. Ir. H.J.J. te Riele at the CWI in Amsterdam. The full project team met frequently during this first project year to discuss progress reports, current problems, etc. (see section 2). The main results of the first project year are: - Proof of the scalability of typical linear and nonlinear MHD codes - development and testing of a parallel version of the Arnoldi algorithm - development and testing of alternative methods for solving large non-Hermitian eigenvalue problems - porting of the 3D nonlinear semi-implicit time evolution code HERA to an MPP system. The steps that were scheduled to reach these intended results are given in section 3. (orig./WL)

Magnetohydrodynamics: Parallel computation of the dynamics of thermonuclear and astrophysical plasmas. 1. Annual report of massively parallel computing pilot project 93MPR05

Energy Technology Data Exchange (ETDEWEB)

NONE

1994-08-01

This is the first annual report of the MPP pilot project 93MPR05. In this pilot project four research groups with different, complementary backgrounds collaborate with the aim to develop new algorithms and codes to simulate the magnetohydrodynamics of thermonuclear and astrophysical plasmas on massively parallel machines. The expected speed-up is required to simulate the dynamics of the hot plasmas of interest which are characterized by very large magnetic Reynolds numbers and, hence, require high spatial and temporal resolutions (for details see section 1). The four research groups that collaborated to produce the results reported here are: The MHD group of Prof. Dr. J.P. Goedbloed at the FOM-Institute for Plasma Physics `Rijnhuizen` in Nieuwegein, the group of Prof. Dr. H. van der Vorst at the Mathematics Institute of Utrecht University, the group of Prof. Dr. A.G. Hearn at the Astronomical Institute of Utrecht University, and the group of Dr. Ir. H.J.J. te Riele at the CWI in Amsterdam. The full project team met frequently during this first project year to discuss progress reports, current problems, etc. (see section 2). The main results of the first project year are: - Proof of the scalability of typical linear and nonlinear MHD codes - development and testing of a parallel version of the Arnoldi algorithm - development and testing of alternative methods for solving large non-Hermitian eigenvalue problems - porting of the 3D nonlinear semi-implicit time evolution code HERA to an MPP system. The steps that were scheduled to reach these intended results are given in section 3. (orig./WL).

Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades In Magentized Weakly Collisional Plasmas

Energy Technology Data Exchange (ETDEWEB)

Schekochihin, A. A.; Cowley, S. C.; Dorland, W.; Hammett, G. W.; Howes, G. G.; Quataert, E.; Tatsuno, T.

2009-04-23

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulentmotions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the "inertial range" above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-fieldstrength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations

Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades In Magnetized Weakly Collisional Plasmas

International Nuclear Information System (INIS)

Schekochihin, A.A.; Cowley, S.C.; Dorland, W.; Hammett, G.W.; Howes, G.G.; Quataert, E.; Tatsuno, T.

2009-01-01

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulent motions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the 'inertial range' above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-field strength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations

Plasma tubes becoming collimated as a result of magnetohydrodynamic pumping

International Nuclear Information System (INIS)

Yun, Gunsu S.; Bellan, Paul M.

2010-01-01

Collimated magnetized plasma structures are commonly observed on galactic, stellar, and laboratory scales. The Caltech plasma gun produces magnetically driven plasma jets bearing a striking resemblance to astrophysical jets and solar coronal loops by imposing boundary conditions analogous to those plasmas. This paper presents experimental observations of gun-produced plasma jets that support a previously proposed magnetohydrodynamic (MHD) pumping model [P. M. Bellan, Phys. Plasmas 10, 1999 (2003)] as a universal collimation mechanism. For any initially flared, magnetized plasma tube with a finite axial current, the model predicts (i) magnetic pumping of plasma particles from a constricted region into a bulged region and (ii) tube collimation if the flow slows down at the bulged region leading to accumulation of mass and thus concentrating the azimuthal magnetic flux frozen in the mass flow (i.e., increasing the pinch force). Time- and space-resolved spectroscopic measurements of gun-produced plasmas have confirmed the highly dynamic nature of the process leading to a collimated state, namely, (i) suprathermal Alfvenic flow (30-50 km/s), (ii) large density amplification from ∼10 17 to ∼10 22 m -3 in an Alfvenic time scale (5-10 μs), and (iii) flow slowing down and mass accumulation at the flow front, the place where the tube collimation occurs according to high-speed camera imaging. These observations are consistent with the predictions of the MHD pumping model, and offer valuable insight into the formation mechanism of laboratory, solar, and astrophysical plasma structures.

Heating and ionization in MHD shock waves propagating into partially ionized plasma

International Nuclear Information System (INIS)

Bighel, L.; Collins, A.R.; Cramer, N.F.; Watson-Munro, C.N.

1975-09-01

A model of the structure of MHD switch-on shocks propagating in a partially ionized plasma, in which the primary dissipation mechanism is friction between ions and neutrals, is here compared favourably with experimental results. Four degrees of upstream ionization were studied, ranging from almost complete to very small ionization. (author)

Heating and ionization in MHD shock wave propagating into partially ionized plasma

International Nuclear Information System (INIS)

Bighel, L.; Collins, A.R.; Cramer, N.F.; Watson-Munro, C.N.

1975-09-01

A model of the structure of MHD switch-on shocks propagating in a partially ionized plasma, in which the primary dissipation mechanism is friction between ions and neutrals, is here compared favourably with experimental results. Four degrees of upstream ionization were studied, ranging from almost complete to very small ionization. (author)

Nonideal plasmas - experimental research

International Nuclear Information System (INIS)

Guenther, K.; Hess, H.; Radtke, R.

1986-01-01

The investigation of nonideal, strongly coupled, or non-Debye plasmas is a new field of the well-known arc plasma physics. The increased pressure and density cause different behaviour of the dense plasma. The paper surveys the main differences between the nonideal and the usual arc plasmas. The electrical conductivity, continuum radiation absorption coefficient, shift and broadening of spectral lines, and plasma phase transition are discussed. The problems of generation and diagnostics of nonideal plasmas are also described. Finally, the importance of the topic is underlined: possible applications in astrophysics and in different fields of technology: light sources, MHD generators, circuit breakers, laser mirrors and shutters, high temperature gas-phase fission reactors, material treatment and laser fusion are mentioned. (D.Gy.)

Astrophysics of magnetically collimated jets generated from laser-produced plasmas.

Science.gov (United States)

Ciardi, A; Vinci, T; Fuchs, J; Albertazzi, B; Riconda, C; Pépin, H; Portugall, O

2013-01-11

The generation of astrophysically relevant jets, from magnetically collimated, laser-produced plasmas, is investigated through three-dimensional, magnetohydrodynamic simulations. We show that for laser intensities I∼10(12)-10(14) W cm(-2), a magnetic field in excess of ∼0.1  MG, can collimate the plasma plume into a prolate cavity bounded by a shock envelope with a standing conical shock at its tip, which recollimates the flow into a supermagnetosonic jet beam. This mechanism is equivalent to astrophysical models of hydrodynamic inertial collimation, where an isotropic wind is focused into a jet by a confining circumstellar toruslike envelope. The results suggest an alternative mechanism for a large-scale magnetic field to produce jets from wide-angle winds.

Numerical Methods for Radiation Magnetohydrodynamics in Astrophysics

Energy Technology Data Exchange (ETDEWEB)

Klein, R I; Stone, J M

2007-11-20

We describe numerical methods for solving the equations of radiation magnetohydrodynamics (MHD) for astrophysical fluid flow. Such methods are essential for the investigation of the time-dependent and multidimensional dynamics of a variety of astrophysical systems, although our particular interest is motivated by problems in star formation. Over the past few years, the authors have been members of two parallel code development efforts, and this review reflects that organization. In particular, we discuss numerical methods for MHD as implemented in the Athena code, and numerical methods for radiation hydrodynamics as implemented in the Orion code. We discuss the challenges introduced by the use of adaptive mesh refinement in both codes, as well as the most promising directions for future developments.

Numerical Methods for Radiation Magnetohydrodynamics in Astrophysics

International Nuclear Information System (INIS)

Klein, R I; Stone, J M

2007-01-01

We describe numerical methods for solving the equations of radiation magnetohydrodynamics (MHD) for astrophysical fluid flow. Such methods are essential for the investigation of the time-dependent and multidimensional dynamics of a variety of astrophysical systems, although our particular interest is motivated by problems in star formation. Over the past few years, the authors have been members of two parallel code development efforts, and this review reflects that organization. In particular, we discuss numerical methods for MHD as implemented in the Athena code, and numerical methods for radiation hydrodynamics as implemented in the Orion code. We discuss the challenges introduced by the use of adaptive mesh refinement in both codes, as well as the most promising directions for future developments

Ideal-MHD beta limits: scaling laws and comparison with Doublet III high-beta plasmas

International Nuclear Information System (INIS)

Bernard, L.C.; Bhadra, D.K.; Helton, F.J.; Lao, L.L.; Todd, T.N.

1983-06-01

Doublet III (DIII) recently has achieved a value for #betta#, the ratio of volume averaged plasma to magnetic pressure, of 4.5%. This #betta# value is in the range required for an economically attractive tokamak reactor, and also close to the relevant limit predicted by ideal-MHD theory. It is therefore of great interest to assess the validity of the theory by comparison with experiment and thus to have a basis for the prediction of future reactor performance. A large variety of plasma shapes have been obtained in DIII. These shapes can be divided into two classes: (1) limiter discharges, and (2) diverted discharges, which are of great interest because of their good confinement in the H-mode operation. We derive simple scaling laws from the variation of optimized ideal-MHD beta limits (#betta#/sub c/) with plasma shape parameters. The current profile is optimized for fixed plasma shapes, separately for the high-n (ballooning) and the low-n (kink) modes. Results are presented in the form of suitability normalized curves of #betta# versus poloidal beta, #betta#/sub p/, for both ballooning and kink modes in order to simultaneously compare all the DIII experimental data

Measurements of Prompt and MHD-Induced Fast Ion Loss from National Spherical Torus Experiment Plasmas

Energy Technology Data Exchange (ETDEWEB)

D.S. Darrow; S.S. Medley; A.L. Roquemore; W.W. Heidbrink; A. Alekseyev; F.E. Cecil; J. Egedal; V.Ya. Goloborod' ko; N.N. Gorelenkov; M. Isobe; S. Kaye; M. Miah; F. Paoletti; M.H. Redi; S.N. Reznik; A. Rosenberg; R. White; D. Wyatt; V.A. Yavorskij

2002-10-15

A range of effects may make fast ion confinement in spherical tokamaks worse than in conventional aspect ratio tokamaks. Data from neutron detectors, a neutral particle analyzer, and a fast ion loss diagnostic on the National Spherical Torus Experiment (NSTX) indicate that neutral beam ion confinement is consistent with classical expectations in quiescent plasmas, within the {approx}25% errors of measurement. However, fast ion confinement in NSTX is frequently affected by magnetohydrodynamic (MHD) activity, and the effect of MHD can be quite strong.

Simulation study of MHD relaxation and reconnection processes in RFP plasma

International Nuclear Information System (INIS)

Kusano, Kanya; Kunimoto, Kaito; Suzuki, Yoshio; Tamano, Teruo; Sato, Tetsuya

1991-01-01

The authors have studied several nonlinear processes in RFP plasma through the use of 3D MHD simulations. In particular, they have shed light on: (1) dynamo and self-sustainment in reversed-field pinch (RFP), (2) phase locking process in MHD relaxation, and (3) the heating and acceleration in magnetic reconnection process. First, the contributions of the kink (m = 1) mode (linearly unstable) and of the m = 0 mode (driven by nonlinear coupling) to the dynamo are qualitatively evaluated using a high accuracy simulation. It is found that, if the free energy to drive kink instabilities is as small as that in the actual experimental plasma, the m = 0 modes, driven nonlinearly, play a more important role for the flux generation than the kink modes. Secondly, numerical simulations of the self-sustainment process in a RFP are performed. It is confirmed that the self-sustainment process is a coherent oscillating process composed of the MHD relaxation and the resistive diffusion processes. Toroidal phase locking process of kink modes is numerically observed in simulations of self-reversal and self-sustainment processes. It has characteristics similar to the slinky mode observed in the OHTE experiment. A detailed investigation reveals that nonlinear coupling between the most unstable two kink modes governs the entire dynamics in all kink modes and leads to the phase locking process. They find that reconnection can accelerate plasma over a local Alfven speed. This is a result of the fact that the magnetic field in the downstream area plays a similar role to de Laval nozzle. They also investigate the heating mechanisms in reconnection process. It is revealed that the viscous heating rate is as large as the joule heating rate in the reconnection process. This result implies that the viscous heating in the reconnection process is an important candidate for the mechanism to explain the RFP experiments where the ion temperatures is higher than the electron temperature

Reduced MHD in Astrophysical Applications: Two-dimensional or Three-dimensional?

Energy Technology Data Exchange (ETDEWEB)

Oughton, S. [Department of Mathematics and Statistics, University of Waikato, Hamilton (New Zealand); Matthaeus, W. H. [Department of Physics and Astronomy, University of Delaware, DE 19716 (United States); Dmitruk, P. [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires-Conicet (Argentina)

2017-04-10

Originally proposed as an efficient approach to computation of nonlinear dynamics in tokamak fusion research devices, reduced magnetohydrodynamics (RMHD) has subsequently found application in studies of coronal heating, flux tube dynamics, charged particle transport, and, in general, as an approximation to describe plasma turbulence in space physics and astrophysics. Given the diverse set of derivations available in the literature, there has emerged some level of discussion and a lack of consensus regarding the completeness of RMHD as a turbulence model, and its applicability in contexts such as the solar wind. Some of the key issues in this discussion are examined here, emphasizing that RMHD is properly neither 2D nor fully 3D, being rather an incomplete representation that enforces at least one family of extraneous conservation laws.

MAIA, Eigenvalues for MHD Equation of Tokamak Plasma Stability Problems

International Nuclear Information System (INIS)

Tanaka, Y.; Azumi, M.; Kurita, G.; Tsunematsu, T.; Takeda, T.

1986-01-01

1 - Description of program or function: This program solves an eigenvalue problem zBx=Ax where A and B are real block tri-diagonal matrices. This eigenvalue problem is derived from a reduced set of linear resistive MHD equations which is often employed to study tokamak plasma stability problem. 2 - Method of solution: Both the determinant and inverse iteration methods are employed. 3 - Restrictions on the complexity of the problem: The eigenvalue z must be real

Transverse MHD shock waves in a partly ionized plasma

International Nuclear Information System (INIS)

Mathers, C.D.

1980-01-01

The structure of transverse MHD shock waves in a partly ionized hydrogen plasma is studied using a three-fluid model with collisional transport coefficients. The morphology of the various sublayers in the shock front is analyzed in detail and it is shown that strong shock waves have a characteristic viscous structure. Weak to moderate strength shock waves display a resistive structure in which the enhanced transverse resistivity due to ion-slip plays a significant role, leading to a pronounced peak in the ion temperature profile. Calculated shock structure profiles are also compared with experimental temperature data. Results in the form of tables and figures are presented for shock waves with fast Mach number ranging from 1-10 in hydrogen plasma with initial degree of ionization ranging from 5-100%. (author)

Simulation of some nonstationary astrophysical processes in laser-produced-plasma experiments

International Nuclear Information System (INIS)

Antonov, V.M.; Zakharov, Yu.P.; Orishich, A.M.; Ponomarenko, A.G.; Posukh, V.G.

1985-01-01

Preliminary results and calibration are reported on the astrophysical plasma dynamics simulator. This apparatus creates a spherical plasma cloud by the irradiation of a perlon filament target from two radial opposite directions by pulses of highly ionized background plasma in a high-vacuum chamber with diameter of 1.2 m and length of 5 m. The spherical plasma cloud simulates the exploding peripheric part of a supernova, expanding into the interstellar medium. (author)

Scaling law in laboratory astrophysics

International Nuclear Information System (INIS)

Xia Jiangfan; Zhang Jie

2001-01-01

The use of state-of-the-art lasers makes it possible to produce, in the laboratory, the extreme conditions similar to those in astrophysical processes. The introduction of astrophysics-relevant ideas in laser-plasma interaction experiments is propitious to the understanding of astrophysical phenomena. However, the great difference between laser-produced plasma and astrophysical objects makes it awkward to model the latter by laser-plasma experiments. The author presents the physical reasons for modeling astrophysical plasmas by laser plasmas, connecting these two kinds of plasmas by scaling laws. This allows the creation of experimental test beds where observation and models can be quantitatively compared with laboratory data

Experimental rigs for MHD studies

International Nuclear Information System (INIS)

Venkataramani, N.; Jayakumar, R.; Iyer, D.R.; Dixit, N.S.

1976-01-01

An MHD experimental rig is a miniature MHD installation consisting of basic equipments necessary for specific investigations. Some of the experimental rigs used in the investigations being carried out at the Bhabha Atomic Research Centre, Bombay (India) are dealt with. The experiments included diagnostics and evaluation of materials in seeded combustion plasmas and argon plasmas. The design specifications, schematics and some of the results of the investigations are also mentioned. (author)

Exploring extreme plasma physics in the laboratory and in astrophysics

Science.gov (United States)

Silva, L. O.; Grismayer, T.; Fonseca, R. A.; Cruz, F.; Gaudio, F. D.; Martins, J. L.; Vieira, J.; Vranic, M.

2017-10-01

The interaction of ultra intense fields with plasmas is at the confluence of several sub-fields ranging from QED, and nuclear physics to high energy astrophysics, and fundamental plasma processes. It requires novel theoretical tools, highly optimised numerical codes and algorithms tailored to these complex scenarios, where physical mechanisms at very disparate temporal and spatial scales are self-consistently coupled in multidimensional geometries. The key developments implemented in Osiris will be presented along with some examples of problems, relevant for laboratory or astrophysical scenarios, that are being addressed resorting to the combination of massively parallel simulations with theoretical models. The relevance for near future experimental facilities such as ELI will also be presented. Work supported by the European Research Council (ERC-AdG-2015 InPairs Grant No. 695088).

Magnetic Field Effects on Plasma Plumes

Science.gov (United States)

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

Free-boundary perturbed MHD equilibria

International Nuclear Information System (INIS)

Nührenberg, C

2012-01-01

The concept of perturbed ideal MHD equilibria [Boozer A H and Nuhrenberg C 2006 Phys. Plasmas 13 102501] is employed to study the influence of external error-fields and of small plasma-pressure changes on toroidal plasma equilibria. In tokamak and stellarator free-boundary calculations, benchmarks were successful of the perturbed-equilibrium version of the CAS3D stability code [Nührenberg C et al. 2009 Phys. Rev. Lett. 102 235001] with the ideal MHD equilibrium code NEMEC [Hirshman S P et al. 1986 Comput. Phys. Commun. 43 143].

Nonlinear 2D convection and enhanced cross-field plasma transport near the MHD instability threshold

International Nuclear Information System (INIS)

Pastukhov, V.P.; Chudin, N.V.

2003-01-01

Results of theoretical study and computer simulations of nonlinear 2D convection induced by a convective MHD instability near its threshold in FRC-like non-paraxial magnetic confinement system are presented. An appropriate closed set of weakly nonideal reduced MHD equations is derived to describe the self-consistent plasma dynamics. It is shown that the convection forms nonlinear large scale stochastic vortices (convective cells), which tend to restore and to maintain the marginally stable pressure pro e and result in an essentially nonlocal enhanced heat transport. A large amount of data on the structure of the nascent convective flows is obtained and analyzed. The computer simulations of long time plasma evolutions demonstrate such features of the resulting anomalous transport as pro e consistency, L-H transition, external transport barrier, pinch of impurities, etc. (author)

Nonlinear MHD analysis for LHD plasmas

International Nuclear Information System (INIS)

Ichiguchi, K.; Nakajima, N.; Wakatani, M.; Carreras, B.A.

2003-01-01

The nonlinear behavior of the interchange modes with multi-helicity in the Large Helical Device is analyzed based on the reduced MHD equations. In the equilibrium at sufficiently low beta value, the saturation of a single mode and the following excitation of other single mode whose resonant surface is close to that of the saturated mode are slowly repeated. This sequence leads to the local deformation of the pressure profile. Increasing the beta value with the pressure profile fixed, a bursting phenomenon due to the overlap of multiple modes is observed in the kinetic energy, which results in the global reduction of the pressure profile. Increasing the beta value using the pressure profile saturated at the lower beta value suppresses the bursting behavior. This result indicates the possibility that the pressure profile is self-organized so that the LHD plasma should attain the high beta regime through a stable path. (author)

Kinetic-MHD simulations of gyroresonance instability driven by CR pressure anisotropy

Science.gov (United States)

Lebiga, O.; Santos-Lima, R.; Yan, H.

2018-05-01

The transport of cosmic rays (CRs) is crucial for the understanding of almost all high-energy phenomena. Both pre-existing large-scale magnetohydrodynamic (MHD) turbulence and locally generated turbulence through plasma instabilities are important for the CR propagation in astrophysical media. The potential role of the resonant instability triggered by CR pressure anisotropy to regulate the parallel spatial diffusion of low-energy CRs (≲100 GeV) in the interstellar and intracluster medium of galaxies has been shown in previous theoretical works. This work aims to study the gyroresonance instability via direct numerical simulations, in order to access quantitatively the wave-particle scattering rates. For this, we employ a 1D PIC-MHD code to follow the growth and saturation of the gyroresonance instability. We extract from the simulations the pitch-angle diffusion coefficient Dμμ produced by the instability during the linear and saturation phases, and a very good agreement (within a factor of 3) is found with the values predicted by the quasi-linear theory (QLT). Our results support the applicability of the QLT for modelling the scattering of low-energy CRs by the gyroresonance instability in the complex interplay between this instability and the large-scale MHD turbulence.

Closed cycle MHD specialist meeting. Progress report, 1971--1972

International Nuclear Information System (INIS)

Rietjens, L.H.

1972-04-01

Abstracts of the conference papers on closed cycle MHD research are presented. The general areas of discussion are the following: results on closed cycle experiments; plasma properties, and instabilities and stabilization in nonequilibrium plasmas; loss mechanisms, current distributions, electrode effects, boundary layers, and gas dynamic effects; and design concepts of large MHD generators, and nuclear MHD power plants. (GRA)

Investigation of the Hall MHD channel operating with the ionized instable plasma of inert gases

International Nuclear Information System (INIS)

Vasi'leva, R.V.; D'yakova, E.A.; Erofeev, A.V.; Zuev, A.D.; Lapushkina, T.A.; Markhotok, A.A.

1997-01-01

Possibility of applying ionization-instable plasma of pure inert gases as perspective working substance for closed-cycle MHD generators is studied. The experiment was produced in the model of the disk Hall MHD channel. The ionized gas flux was produced in a shock tube. Xenon was used as a working substance. Gas pressure, flux velocity, electron concentration and temperature, azimuthal current density, potential distribution in the channel and near-electrode voltage drop values were measured in the experiment. Volt-ampere characteristics were taken by various indices of magnetic field and load resistance

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

Science.gov (United States)

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.

Journal of Astrophysics and Astronomy

Indian Academy of Sciences (India)

65

Northern IMF as simulated by PIC code in parallel with MHD model-Journal of Astrophysics ... The global structure of the collisionless bow shock was inves- tigated by ..... international research community, access to modern space science simulations. ...... LaTeX Font Info: Redeclaring math alphabet \\mathbf on input line 29.

MHD equilibrium of toroidal fusion plasma with stationary flows; Rownowaga MHD toroidalnej plazmy termojadrowej z przeplywami

Energy Technology Data Exchange (ETDEWEB)

Galkowski, A. [Institute of Atomic Energy, Otwock-Swierk (Poland)

1994-12-31

Non-linear ideal MHD equilibria in axisymmetric system with flows are examined, both in 1st and 2nd ellipticity regions. Evidence of the bifurcation of solutions is provided and numerical solutions of several problems in a tokamak geometry are given, exhibiting bifurcation phenomena. Relaxation of plasma in the presence of zero-order flows is studied in a realistic toroidal geometry. The field aligned flow allows equilibria with finite pressure gradient but with homogeneous temperature distribution. Numerical calculations have been performed for the 1st and 2nd ellipticity regimes of the extended Grad-Shafranov-Schlueter equation. Numerical technique, alternative to the well-known Grad`s ADM methods has been proposed to deal with slow adiabatic evolution of toroidal plasma with flows. The equilibrium problem with prescribed adiabatic constraints may be solved by simultaneous calculations of flux surface geometry and original profile functions. (author). 178 refs, 37 figs, 5 tabs.

Pedestal characteristics and MHD stability of H-mode plasmas in TCV

International Nuclear Information System (INIS)

Pitzschke, A.

2011-01-01

temperature profile during the ELM cycle, the low repetition rate of the lasers used for Thomson scattering is a limiting. Although the system on TCV comprises 3 laser units that may be triggered in sequence with time separations down to 1 ms, time evolution over longer periods can only be reconstructed from repetitive events. In this context, an adjustment of the laser trigger to improve the synchronization with the ELM event is an advantage. A method was developed and implemented to generate a synchronizing trigger sequence, by a real-time monitoring of the D-alpha emission, which provides a marker for the ELM event. Recently, a ‘snowflake’ (SF) divertor configuration, proposed as a possible solution to reduce the plasma-wall interaction by changing the divertor’s poloidal magnetic field topology, was generated, for the first time, in TCV. A numerical code (KINX), based on a magnetohydrodynamic model (ideal MHD), was used to investigate the stability limits of this configuration under H-mode conditions and compare them with a similar standard single-null equilibrium. In a series of experiments, improved energy confinement was found and explained by improved stability of the edge region in the SF configuration. The influence of the pedestal structure in ELMy H-mode plasmas on the energy confinement and on ELM energy losses was investigated. The different ELM regimes found in TCV were analyzed, in particular the transition between type-III to type-I ELMs. The operational boundary of each ELM regime was characterized and verified by ideal MHD stability simulations for the ETB region. Recent studies on the scaling of the pedestal width with normalized poloidal pressure were confirmed. Using the capabilities of TCV, the influence of plasma shaping on pedestal parameters and MHD stability limits was investigated. In the past, models were developed to describe the onset of type-I ELMs, which are associated with modes in the ETB region arising from a coupling of pressure- and

MHD equilibrium of toroidal fusion plasma with stationary flows

International Nuclear Information System (INIS)

Galkowski, A.

1994-01-01

Non-linear ideal MHD equilibria in axisymmetric system with flows are examined, both in 1st and 2nd ellipticity regions. Evidence of the bifurcation of solutions is provided and numerical solutions of several problems in a tokamak geometry are given, exhibiting bifurcation phenomena. Relaxation of plasma in the presence of zero-order flows is studied in a realistic toroidal geometry. The field aligned flow allows equilibria with finite pressure gradient but with homogeneous temperature distribution. Numerical calculations have been performed for the 1st and 2nd ellipticity regimes of the extended Grad-Shafranov-Schlueter equation. Numerical technique, alternative to the well-known Grad's ADM methods has been proposed to deal with slow adiabatic evolution of toroidal plasma with flows. The equilibrium problem with prescribed adiabatic constraints may be solved by simultaneous calculations of flux surface geometry and original profile functions. (author). 178 refs, 37 figs, 5 tabs

A review on application of MHD theory to plasma boundary problems in tokamaks

International Nuclear Information System (INIS)

Itoh, Kimitaka.

1992-08-01

A survey is made on the problems of the edge plasmas, to which the analyses based on the MHD theory have been successfully applied. Also discussed are the efforts to extend the model equation to more general (and important as well) problems such as H-mode physics. An overview is first made on the advantages of the MHD picture, and the necessary supplementary physics are examined. Next, one- and two-dimensional models of the spatial structure of the edge plasma is discussed. The results on the stationary structure, both analytical and numerical, are reviewed: Typical example as well as the scaling law are shown. The instabilities associated with edge plasma is next reviewed. The surface kink mode, ballooning mode, interchange mode, resistive interchange mode and thermal instability are discussed. Role of the geometry such as the location of the X-point is studied. Influences of the atomic processes, and those of the radial electric field are also discussed. The analysis of the H-mode transition physics is finally discussed. The boundary plasma is a nonlinear media which possesses the possibility for bifurcation in which the radial electric field plays a key role. The model of the ion viscosity is also studied. Transition physics is developed. Analysis on the self-generating oscillation is shown and the relation with ELMs is discussed. After reviewing these problems, several comments are made to what directions the study can be deepened. (author) 53 refs

Global MHD modes excited by energetic ions in heliotron/torsatron plasmas

International Nuclear Information System (INIS)

Toi, K.; Takechi, M.; Takagi, S.

1999-01-01

In the CHS heliotron/torsatron, fishbone instabilities (FBs) and toroidal Alfven eigenmodes(TAEs) are observed for the first time, in NBI heated plasmas where small beam driven current is induced. Pulsed increase in energetic ion loss flux is detected by an escaping ion probe during the m=3/n=2 FBs(m,n:poloidal and toroidal mode numbers). The sawtooth crash is often induced by the m=2/n=1 FBs. The current driven internal kink mode and pressure driven interchange modes are thought to be relevant MHD instabilities to FBs. TAEs with n=1 and n=2 are identified, and localized near the plasma core region where fairly low magnetic shear would be realized by the small net plasma current. So far, the observed TAEs do not lead to enhanced loss of energetic ions because of low magnetic fluctuation level. (author)

Global MHD modes excited by energetic ions in heliotron/torsatron plasmas

International Nuclear Information System (INIS)

Toi, K.; Takechi, M.; Takagi, S.

2001-01-01

In the CHS heliotron/torsatron, fishbone instabilities (FBs) and toroidal Alfven eigenmodes (TAEs) are observed for the first time, in NBI heated plasmas where small beam driven current is induced. Pulsed increase in energetic ion loss flux is detected by an escaping ion probe during the m=3/n=2 FBs (m,n: poloidal and toroidal mode numbers). The sawtooth crash is often induced by the m=2/n=1 FBs. The current driven internal kink mode and pressure driven interchange modes are thought to be relevant MHD instabilities to FBs. TAEs with n=1 and n=2 are identified, and localized near the plasma core region where fairly low magnetic shear would be realized by the small net plasma current. So far, the observed TAEs do not lead to enhanced loss of energetic ions because of low magnetic fluctuation level. (author)

Thought analysis on self-organization theories of MHD plasma

International Nuclear Information System (INIS)

Kondoh, Yoshiomi; Sato, Tetsuya.

1992-08-01

A thought analysis on the self-organization theories of dissipative MHD plasma is presented to lead to three groups of theories that lead to the same relaxed state of ∇ x B = λB, in order to find an essential physical picture embedded in the self-organization phenomena due to nonlinear and dissipative processes. The self-organized relaxed state due to the dissipation by the Ohm loss is shown to be formulated generally as the state such that yields the minimum dissipation rate of global auto-and/or cross-correlations between two quantities in j, B, and A for their own instantaneous values of the global correlations. (author)

Four-dimensional integral equations for the MHD diffraction waves in plasma

International Nuclear Information System (INIS)

Alexandrova, A.A.; Khizhnyak, N.A.

2000-01-01

The superficial analysis of the boundary-value nonstationary problem for Alfven wave has shown the principal possibility of using the method of evolutionary integral equations of non-stationary macroscopic electrodynamical in a case of MHD description of waves in plasma. With the importance of strict mathematical solutions obtained for simple model problems that is the diffraction of one separately taken Alfven wave is that it can be the basis for construction of the approximate solutions of more complex boundary-value problems

Incompressible LFR MHD. A fluid model for stability analysis of a fusion plasma

International Nuclear Information System (INIS)

Scheffel, J.; Faghihi, M.

1986-10-01

A fluid model including FLR effects, named Incompressible Finite Larmor Radius MagnetoHydroDynamics, is presented and derived in this paper. It is an extension of ordinary, incompressible MHD to include the Larmor radius effects due to ion gyroviscosity, Hall current and electron diamagnetism. It is intended to use the model for stability analysis, on the Alfven wave time scale, of a fusion plasma and it is consequently based on transport coefficients in the collisionless limit. It will be demonstrated that for a fairly dense and cool plasma, such as for the EXTRAP z-pinch, all three Larmor radius effects may become important, that for a JET-type plasma no FLR effect is pronounced, and that in a reactor plasma the Hall and electron diamagnetism term may play a role. For scaling lengths signigicantly smaller than the plasma radius the effect of the FLR terms becomes enhanced. To study the importance of the choice of equations of state for the model the m=1 and k 2 r 2 towards infinity instability in cylindrical geometry is given special attention for zero Larmor radius. The full stability criterion of the double adiabatic model, including pressure anisotropy, is presented for what we believe to be the first time. It is found that when perpendicular p > parallel p stability can be reached for very high plasma perpendicular β-values. We demonstrate that no less complicated energy conserving fluid model, which takes into account pressure anisotropy, other than the double adiabativ model can be obtained. Since pressure anisotropy generally only weakly affects stability, we can assume isotropy in the Incompressible FLR MHD model. Also, the energy equation is replaced by the incompressibility condition, making FLR terms appearing in the energy equation irrelevant. (authors)

Plasma Diagnostics by Microwave Interferometry in MHD Channels with the Aid of an Open Waveguide

Energy Technology Data Exchange (ETDEWEB)

Muenkel, J. [Rheinische-Westfalische Technische Hochschule Aachen, Federal Republic of Germany (Germany)

1966-10-15

Plasma diagnostics of a novel kind, using microwave interferometry, is described. Use is made of an open non-conventional waveguide in the test path of the microwave bridge. Guiding the microwave has several advantages over free transmission of the test h.f. beam between two horn antennas if there are small plasma streams bounded by ceramics and metals as in the case of MHD channels. There are less unknown and uncontrolled disturbances of the electromagnetic waves introduced by the boundaries. On the other hand most guiding structures disturb the homogeneity of the streaming plasma (cf. arrangements with Lecher wires, dielectric rods, etc.); the waveguide used here does not do so. This waveguide, a so-called groove guide, consists of two parallel metal plates or bands with a shallow axially-directed groove in each. The plasma stream to be tested flows between these plates in a direction perpendicular to the direction of propagation of the microwaves. The groove guide has properties similar to the ideal parallel-plate guide with infinite side wards extension, but the energy flow is concentrated in the middle region by the grooves. An approximate analysis, the transverse resonance analysis, has been used to calculate the field distribution and propagation characteristics of the guide. Because of the cross-sectional dimensions of the MHD channel in question (height 16 mm) and the wavelength (4 mm) chosen, considering the expected electron density, the groove guide had to be built for use in an oversized quasi-optical technique. The transition from rectangular (hollow pipe) guide to the open guide is done in two steps. With a good knowledge of the groove guide data and an appropriate theory of propagation of electromagnetic waves in ionized media, measuring phase shift and additional damping of the microwaves by introduction of the ionized gas allows the electron density and collision frequency, two of the most important plasma parameters, to be evaluated. The system

Introduction to plasma physics with space, laboratory and astrophysical applications

CERN Document Server

Gurnett, Donald A

2017-01-01

Introducing basic principles of plasma physics and their applications to space, laboratory and astrophysical plasmas, this new edition provides updated material throughout. Topics covered include single-particle motions, kinetic theory, magnetohydrodynamics, small amplitude waves in hot and cold plasmas, and collisional effects. New additions include the ponderomotive force, tearing instabilities in resistive plasmas and the magnetorotational instability in accretion disks, charged particle acceleration by shocks, and a more in-depth look at nonlinear phenomena. A broad range of applications are explored: planetary magnetospheres and radiation belts, the confinement and stability of plasmas in fusion devices, the propagation of discontinuities and shock waves in the solar wind, and analysis of various types of plasma waves and instabilities that can occur in planetary magnetospheres and laboratory plasma devices. With step-by-step derivations and self-contained introductions to mathematical methods, this book...

MHD model including small-scale perturbations in a plasma with temperature variations

International Nuclear Information System (INIS)

Kuvshinov, B.N.; Mikhailovskii, A.B.

1996-01-01

The possibility is studied of using a hydrodynamic model to describe a magnetized plasma with density and temperature variations on scales that are arbitrary with respect to the ion Larmor radius. It is shown that the inertial component of the transverse ion thermal flux should be taken into account. This component is found from the collisionless kinetic equation. It can also be obtained from the equations of the Grad type. A set of two-dimensional hydrodynamic equations for ions is obtained with this component taken into account. These equations are used to derive model hydrodynamic expressions for the density and temperature variations. It is shown that, for large-scale perturbations (when the wavelengths are longer than the ion Larmor radius), the expressions derived coincide with the corresponding kinetic expressions and, for perturbations on sub-Larmor scales (when the wavelengths are shorter than the Larmor radius), they agree qualitatively. Hydrodynamic dispersion relations are derived for several types of drift waves with arbitrary wavenumbers. The range of applicability of the MHD model is determined from a comparison of these dispersion relations with the kinetic ones. It is noted that, on the basis of results obtained, drift effects can be included in numerical MHD codes for studying plasma instabilities in high-temperature regimes in tokamaks

MHD instabilities leading to disruption in JT-60U reversed shear plasmas

International Nuclear Information System (INIS)

Takechi, M.; Fujita, T.; Ishii, Y.; Ozeki, T.; Suzuki, T.; Isayama, A.

2005-01-01

High performance reversed shear discharges with strong internal transport barrier (ITB) and flat pressure profile in the plasma core region disrupt frequently even with low beta. We analyzed MHD instabilities leading to low beta disruption with measuring fluctuations and current profile with MSE measurement. We mainly observed two type of disruptions. One is the disruption without precursor at q surf ∼integer. The other is the disruption with n=1 precursor of γ>10 ms. The poloidal mode number of the n=1 mode is equal to outermost integer of q. The n=1 mode exist from peripheral region to ITB layer or peripheral region and ITB and the phase is 180 degree different between them. To explain these characteristics of disruption, we introduce the simple model such as, disruption occurs when the both MHD instabilities at plasma surface and at safety factor being equal to surface mode are unstable. This simple model can explain almost all observed disruption by two process. One is the surface mode triggered disruption, which occurs when q surf change, corresponding q surface at ITB layer change discretely. The other is the internal mode triggered disruption, which occurs when corresponding q surface become unstable gradually. (author)

Three-dimensional distortions of the tokamak plasma boundary: boundary displacements in the presence of saturated MHD instabilities

International Nuclear Information System (INIS)

Chapman, I.T.; Harrison, J.R.; Holgate, J.; Brunetti, D.; Cooper, W.A.; Graves, J.P.; Buratti, P.; Jardin, S.; Sabbagh, S.A.; Tritz, K.

2014-01-01

The three-dimensional plasma boundary displacement induced by long-lasting core magnetohydrodynamic (MHD) instabilities has been measured in JET, MAST and NSTX. Only saturated instabilities are considered here since transient rapidly growing modes which degrade confinement and act as potential triggers for disruptions bring more fundamental concerns than boundary displacements. The measured displacements are usually small, although in extreme cases in MAST when the rotation braking is strong, a significant global displacement can be observed. The instability most likely to saturate and exist for many energy confinement times whilst distorting the boundary of ITER is the saturated internal kink, or helical core, which can be found in plasmas with a wide region of low magnetic shear such as the hybrid scenario. This mode can lead to non-negligible boundary displacements. Nonetheless, the boundary displacement resultant from core MHD instabilities in ITER is predicted to be less than ±1.5% of the minor radius, well within tolerable limits for heat loads to plasma-facing components. (paper)

A kinetic-MHD model for low frequency phenomena

International Nuclear Information System (INIS)

Cheng, C.Z.

1991-07-01

A hybrid kinetic-MHD model for describing low-frequency phenomena in high beta anisotropic plasmas that consist of two components: a low energy core component and an energetic component with low density. The kinetic-MHD model treats the low energy core component by magnetohydrodynamic (MHD) description, the energetic component by kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic-MHD model optimizes both the physics contents and the theoretical efforts in studying low frequency MHD waves and transport phenomena in general magnetic field geometries, and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit two coupled eigenmode equations for describing the coupling between the transverse Alfven type and the compressional Alfven type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low frequency limit and were previously analyzed both analytically nd numerically to obtain the eigenmode structure of the drift mirror instability which explains successfully the multi-satellite observation of antisymmetric field-aligned structure of the compressional magnetic field of Pc 5 waves in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low-frequency transverse and compressional Alfven type instabilities in terms of the pressure anisotropy parameter τ and the magnetic field curvature-pressure gradient parameter. A procedure for determining the stability of a marginally stable MHD wave due to wave-particle resonances is also presented

Magnetic analysis of tokamak plasma with approximate MHD equilibrium solution

International Nuclear Information System (INIS)

Moriyama, Shin-ichi; Hiraki, Naoji

1993-01-01

A magnetic analysis method for determining equilibrium configuration parameters (plasma shape, poloidal beta and internal inductance) on a non-circular tokamak is described. The feature is to utilize an approximate MHD equilibrium solution which explicitly relates the configuration parameters with the magnetic fields picked up by magnetic sensors. So this method is suitable for the real-time analysis performed during a tokamak discharge. A least-squares fitting procedure is added to the analytical algorithm in order to reduce the errors in the magnetic analysis. The validity is investigated through the numerical calculation for a tokamak equilibrium model. (author)

A study on the fusion reactor - Numerical analyses of MHD equilibrium and= edge plasma transport in tokamak fusion reactor with divertor configurations

Energy Technology Data Exchange (ETDEWEB)

Hong, Sang Hee; Kang, Kyung Doo; Ryu, Ji Myung; Kim, Deok Kyu; Chung, TaeKyun; Chung, Mo Se [Seoul National University, Seoul (Korea, Republic of); Cho, Su Won [Kyungki University, Suwon (Korea, Republic of)

1995-08-01

In the present project for developing the numerical codes of 2-D MHD equilibrium, edge plasma transport and neutral particle transport for the tokamak plasmas, we computed the MHD equilibria of single and double null configurations and determined the external coil currents and the plasma parameters used for operation and control data. Also we numerically acquired the distributions of edge plasma parameters in poloidal and radial directions= and the design-related values according to the various operating conditions using the developed plasma transport code. Furthermore, a neutral particle transport code for the edge region is developed and them used for the analysis of the neutral particle behavior yielding the source terms in the fluid transport equations, and expected to supply the input parameters for the edge plasma transport code. 53 refs., 12 tabs., 44 figs. (author)

Heat transfer characteristics of rectangular coolant channels with various aspect ratios in the plasma-facing components under fully developed MHD laminar flow

International Nuclear Information System (INIS)

Takase, K.; Hasan, M.Z.

1995-01-01

Convective heat transfer in MHD laminar flow through rectangular channels in the plasma-facing components of a fusion reactor has been analyzed numerically to investigate the effects of channel aspect ratio, defined as the ratio of the lengths of the plasma-facing side to the other side. The adverse effect of the nonuniformity of surface heat flus on Nusselt number (Nu) at the plasma-facing side can be alleviated by increasing the aspect ratio of a rectangular duct. At the center and corner of the plasma-facing side of a square duct, the Nu of non-MHD flow are 6.8 and 2.2, respectively, for uniform surface heat flux. In the presence of a strong magnetic field, Nu at the center and corner increases to 22 and 3.6, respectively. However, when the heat flux is highly nonuniform, as in the plasma-facing components, Nu decreases from 22 to 3.1 at the center and from 3.6 to 3.1 at the corner. When the aspect ratio is increased to 4, Nu at the center and corner increase to 5 and 4.7. Along the circumference of a rectangular channel, there are locations where the wall temperature is equal to or less than the bulk coolant temperature, thus making the Nu with conventional definition infinity or negative. The ratio between Nu of MHD flow and Nu of non-MHD flow for various aspect ratios is constant in the region of Hartmann number of more than 200 at least. On the other hand, its ratio increases monotonously with increasing the aspect ratio

Alpha-Driven MHD and MHD-Induced Alpha Loss in TFTR DT Experiments

Science.gov (United States)

Chang, Zuoyang

1996-11-01

Theoretical calculation and numerical simulation indicate that there can be interesting interactions between alpha particles and MHD activity which can adversely affect the performance of a tokamak reactor (e.g., ITER). These interactions include alpha-driven MHD, like the toroidicity-induced-Alfven-eigenmode (TAE) and MHD induced alpha particle losses or redistribution. Both phenomena have been observed in recent TFTR DT experiments. Weak alpha-driven TAE activity was observed in a NBI-heated DT experiment characterized by high q0 ( >= 2) and low core magnetic shear. The TAE mode appears at ~30-100 ms after the neutral beam turning off approximately as predicted by theory. The mode has an amplitude measured by magnetic coils at the edge tildeB_p ~1 mG, frequency ~150-190 kHz and toroidal mode number ~2-3. It lasts only ~ 30-70 ms and has been seen only in DT discharges with fusion power level about 1.5-2.0 MW. Numerical calculation using NOVA-K code shows that this type of plasma has a big TAE gap. The calculated TAE frequency and mode number are close to the observation. (2) KBM-induced alpha particle loss^1. In some high-β, high fusion power DT experiments, enhanced alpha particle losses were observed to be correlated to the high frequency MHD modes with f ~100-200 kHz (the TAE frequency would be two-times higher) and n ~5-10. These modes are localized around the peak plasma pressure gradient and have ballooning characteristics. Alpha loss increases by 30-100% during the modes. Particle orbit simulations show the added loss results from wave-particle resonance. Linear instability analysis indicates that the plasma is unstable to the kinetic MHD ballooning modes (KBM) driven primarily by strong local pressure gradients. ----------------- ^1Z. Chang, et al, Phys. Rev. Lett. 76 (1996) 1071. In collaberation with R. Nazikian, G.-Y. Fu, S. Batha, R. Budny, L. Chen, D. Darrow, E. Fredrickson, R. Majeski, D. Mansfield, K. McGuire, G. Rewoldt, G. Taylor, R. White, K

MHD equilibrium and pressure driven instability in L=1 heliotron plasmas

International Nuclear Information System (INIS)

Nakamura, Y.; Suzuki, Y.; Yamagishi, O.; Kondo, K.; Nakajima, N.; Hayashi, T.; Monticello, D.A.; Reiman, A.H.

2003-01-01

Free boundary MHD equilibrium properties of Heliotron J are investigated by VMEC, HINT and PIES codes, and ideal MHD stability properties are studied by the Mercier criterion, the ballooning mode equation and the CAS3D global stability code. It is shown by the equilibrium calculations that the change of the plasma boundary shape is substantial in a low shear helical system even if the beta is relatively low. Preliminary comparison between PIES results and HINT results shows that the beta value at which the magnetic island begin to be perceptible is almost the same in both codes, but the island width seems to be different. From the stability analysis, good correlation is found between local and global analyses for the three dimensional(3D) or helical ballooning mode whose mode structure shows strong poloidal and toroidal mode (helical mode) coupling. In the helical ballooning mode, the Eigenmode is localized within a flux tube. It is also found that the positive shear of the rotational transform is favorable for the 3D ballooning mode stability in a low shear helical system. (author)

Dusty plasmas in application to astrophysics

International Nuclear Information System (INIS)

Verheest, F.

1999-01-01

Highly charged and massive dust grains have much smaller characteristic frequencies than electrons and ions and lead to interesting modifications of existing modes and to exciting new possibilities for modes and instabilities at the lower frequency end of the spectrum. Space observations of planets and comets have shown wave-like behaviour which can only be explained by the presence of charged dust grains. Two typical solar system applications are spokes and braids in the rings of Saturn and the influence of charged dust on the pickup process of ions of cometary origin by the solar wind. As dust is ubiquitous in the universe, the Jeans instability in astrophysics is modified by incorporating plasma and charged dust and treating electromagnetic and self-gravitational aspects together. Besides the usual mechanism based upon thermal agitation, other ways of countering gravitational contraction are via excitation of electrostatic dust-acoustic modes or via Alfven-Jeans instabilities for perpendicular magnetosonic waves. The unstable wavelengths tend to be much larger, due to the dominance of plasma and magnetic pressures in inhibiting gravitational collapse. (author)

MHD stabilization of high β mirror plasma partially enclosed by conducting wall

International Nuclear Information System (INIS)

Li, X.Z.; Kesner, J.; Lane, B.

1985-04-01

An MHD formulation is used to study a wall stabilized high β mirror plasma with isotropic pressure. The stabilizing wall extends axially only a part of the distance between the mirror midplane and throat. We model this arrangement using a wall that approaches the plasma surface in the bad curvature region and is distant from the plasma in the good curvature region. A variational method is used to solve the equation in the distant wall region and an iterative method is used to solve the equation when the wall is close to the plasma. A jump condition is used to connect the regions of close and distant plasma-wall proximity. A simple trial function is used to perform the variational calculation (the choice of trial function is substantiated by an exact numerical solution). The results show that for a low mirror ratio case more conducting wall surface is needed for stability than in the high mirror ratio case. This agrees with the physical mechanism of the wall stabilization

Maxwell Prize Talk: Scaling Laws for the Dynamical Plasma Phenomena

Science.gov (United States)

Ryutov, Livermore, Ca 94550, Usa, D. D.

2017-10-01

The scaling and similarity technique is a powerful tool for developing and testing reduced models of complex phenomena, including plasma phenomena. The technique has been successfully used in identifying appropriate simplified models of transport in quasistationary plasmas. In this talk, the similarity and scaling arguments will be applied to highly dynamical systems, in which temporal evolution of the plasma leads to a significant change of plasma dimensions, shapes, densities, and other parameters with respect to initial state. The scaling and similarity techniques for dynamical plasma systems will be presented as a set of case studies of problems from various domains of the plasma physics, beginning with collisonless plasmas, through intermediate collisionalities, to highly collisional plasmas describable by the single-fluid MHD. Basic concepts of the similarity theory will be introduced along the way. Among the results discussed are: self-similarity of Langmuir turbulence driven by a hot electron cloud expanding into a cold background plasma; generation of particle beams in disrupting pinches; interference between collisionless and collisional phenomena in the shock physics; similarity for liner-imploded plasmas; MHD similarities with an emphasis on the effect of small-scale (turbulent) structures on global dynamics. Relations between astrophysical phenomena and scaled laboratory experiments will be discussed.

A simplified MHD model of capillary Z-Pinch compared with experiments

Energy Technology Data Exchange (ETDEWEB)

Shapolov, A.A.; Kiss, M.; Kukhlevsky, S.V. [Institute of Physics, University of Pecs (Hungary)

2016-11-15

The most accurate models of the capillary Z-pinches used for excitation of soft X-ray lasers and photolithography XUV sources currently are based on the magnetohydrodynamics theory (MHD). The output of MHD-based models greatly depends on details in the mathematical description, such as initial and boundary conditions, approximations of plasma parameters, etc. Small experimental groups who develop soft X-ray/XUV sources often use the simplest Z-pinch models for analysis of their experimental results, despite of these models are inconsistent with the MHD equations. In the present study, keeping only the essential terms in the MHD equations, we obtained a simplified MHD model of cylindrically symmetric capillary Z-pinch. The model gives accurate results compared to experiments with argon plasmas, and provides simple analysis of temporal evolution of main plasma parameters. The results clarify the influence of viscosity, heat flux and approximations of plasma conductivity on the dynamics of capillary Z-pinch plasmas. The model can be useful for researchers, especially experimentalists, who develop the soft X-ray/XUV sources. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Complex astrophysical experiments relating to jets, solar loops, and water ice dusty plasma

Science.gov (United States)

Bellan, P. M.; Zhai, X.; Chai, K. B.; Ha, B. N.

2015-10-01

> Recent results of three astrophysically relevant experiments at Caltech are summarized. In the first experiment magnetohydrodynamically driven plasma jets simulate astrophysical jets that undergo a kink instability. Lateral acceleration of the kinking jet spawns a Rayleigh-Taylor instability, which in turn spawns a magnetic reconnection. Particle heating and a burst of waves are observed in association with the reconnection. The second experiment uses a slightly different setup to produce an expanding arched plasma loop which is similar to a solar corona loop. It is shown that the plasma in this loop results from jets originating from the electrodes. The possibility of a transition from slow to fast expansion as a result of the expanding loop breaking free of an externally imposed strapping magnetic field is investigated. The third and completely different experiment creates a weakly ionized plasma with liquid nitrogen cooled electrodes. Water vapour injected into this plasma forms water ice grains that in general are ellipsoidal and not spheroidal. The water ice grains can become quite long (up to several hundred microns) and self-organize so that they are evenly spaced and vertically aligned.

Ideal MHD equilibrium of a weakly toroidal plasma column with elongated cross-section

International Nuclear Information System (INIS)

Heesch, E.J.M. van; Schuurman, W.

1980-07-01

Solutions are obtained of the ideal MHD equations describing the equilibrium of a weakly toroidal plasma with an elliptic cross-section surrounded by a force-free magnetic field with constant ratio between current density and magnetic field strength. The force-free field parameter causes the stagnation points to recede along the major axis of the ellipse. Above a certain value of the force-free field parameter, stagnation points do not exist, so that the compression ratio of the plasma column is no longer limited. The analysis was carried out to first order in the force-free field parameter as well as to second order for an estimate of the error

MHD instabilities in heliotron/torsatron

International Nuclear Information System (INIS)

Wakatani, Masahiro; Nakamura, Yuji; Ichiguchi, Katsuji

1992-01-01

Recent theoretical results on MHD instabilities in heliotron/torsatron are reviewed. By comparing the results with experimental data in Heliotron E, Heliotron DR and ATF, it is pointed out that resistive interchange modes are the most crucial instabilities, since the magnetic hill occupies a substantial region of the plasma column. Development of three-dimensional MHD equilibrium codes has made significant progress. By applying the local stability criteria shown by D 1 (ideal MHD mode) and D R (resistive MHD mode) to the equilibria given by the three-dimensional codes such as BETA and VMEC, stability thresholds for the low n ideal modes or the low n resistive modes may be estimated with resonable accuracy, where n is a toroidal mode number. (orig.)

Magnetic processes in astrophysics theory, simulations, experiments

CERN Document Server

Rüdiger, Günther; Hollerbach, Rainer

2013-01-01

In this work the authors draw upon their expertise in geophysical and astrophysical MHD to explore the motion of electrically conducting fluids, the so-called dynamo effect, and describe the similarities and differences between different magnetized objects. They also explain why magnetic fields are crucial to the formation of the stars, and discuss promising experiments currently being designed to investigate some of the relevant physics in the laboratory. This interdisciplinary approach will appeal to a wide audience in physics, astrophysics and geophysics. This second edition covers such add

Relativistic modeling capabilities in PERSEUS extended MHD simulation code for HED plasmas

Energy Technology Data Exchange (ETDEWEB)

Hamlin, Nathaniel D., E-mail: nh322@cornell.edu [438 Rhodes Hall, Cornell University, Ithaca, NY, 14853 (United States); Seyler, Charles E., E-mail: ces7@cornell.edu [Cornell University, Ithaca, NY, 14853 (United States)

2014-12-15

We discuss the incorporation of relativistic modeling capabilities into the PERSEUS extended MHD simulation code for high-energy-density (HED) plasmas, and present the latest hybrid X-pinch simulation results. The use of fully relativistic equations enables the model to remain self-consistent in simulations of such relativistic phenomena as X-pinches and laser-plasma interactions. By suitable formulation of the relativistic generalized Ohm’s law as an evolution equation, we have reduced the recovery of primitive variables, a major technical challenge in relativistic codes, to a straightforward algebraic computation. Our code recovers expected results in the non-relativistic limit, and reveals new physics in the modeling of electron beam acceleration following an X-pinch. Through the use of a relaxation scheme, relativistic PERSEUS is able to handle nine orders of magnitude in density variation, making it the first fluid code, to our knowledge, that can simulate relativistic HED plasmas.

Modeling and analysis of the disk MHD generator component of a gas core reactor/MHD Rankine cycle space power system

International Nuclear Information System (INIS)

Welch, G.E.; Dugan, E.T.; Lear, W.E. Jr.; Appelbaum, J.G.

1990-01-01

A gas core nuclear reactor (GCR)/disk magnetohydrodynamic (MHD) generator direct closed Rankine space power system concept is described. The GCR/disk MHD generator marriage facilitates efficient high electric power density system performance at relatively high operating temperatures. The system concept promises high specific power levels, on the order of 1 kW e /kg. An overview of the disk MHD generator component magnetofluiddynamic and plasma physics theoretical modeling is provided. Results from a parametric design analysis of the disk MHD generator are presented and discussed

PIXIE3D: An efficient, fully implicit, parallel, 3D extended MHD code for fusion plasma modeling

International Nuclear Information System (INIS)

Chacon, L.

2007-01-01

PIXIE3D is a modern, parallel, state-of-the-art extended MHD code that employs fully implicit methods for efficiency and accuracy. It features a general geometry formulation, and is therefore suitable for the study of many magnetic fusion configurations of interest. PIXIE3D advances the state of the art in extended MHD modeling in two fundamental ways. Firstly, it employs a novel conservative finite volume scheme which is remarkably robust and stable, and demands very small physical and/or numerical dissipation. This is a fundamental requirement when one wants to study fusion plasmas with realistic conductivities. Secondly, PIXIE3D features fully-implicit time stepping, employing Newton-Krylov methods for inverting the associated nonlinear systems. These methods have been shown to be scalable and efficient when preconditioned properly. Novel preconditioned ideas (so-called physics based), which were prototypes in the context of reduced MHD, have been adapted for 3D primitive-variable resistive MHD in PIXIE3D, and are currently being extended to Hall MHD. PIXIE3D is fully parallel, employing PETSc for parallelism. PIXIE3D has been thoroughly benchmarked against linear theory and against other available extended MHD codes on nonlinear test problems (such as the GEM reconnection challenge). We are currently in the process of extending such comparisons to fusion-relevant problems in realistic geometries. In this talk, we will describe both the spatial discretization approach and the preconditioning strategy employed for extended MHD in PIXIE3D. We will report on recent benchmarking studies between PIXIE3D and other 3D extended MHD codes, and will demonstrate its usefulness in a variety of fusion-relevant configurations such as Tokamaks and Reversed Field Pinches. (Author)

EDITORIAL: 15th Workshop on MHD Stability Control: 3D Magnetic Field Effects in MHD Control 15th Workshop on MHD Stability Control: 3D Magnetic Field Effects in MHD Control

Science.gov (United States)

Buttery, Richard

2011-08-01

This annual workshop on MHD Stability Control has been held since 1996 with a focus on understanding and developing control of MHD instabilities for future fusion reactors. The workshop generally covers a wide range of stability topics: from disruptions, to tearing modes, error fields, ELMs, resistive wall modes (RWMs) and ideal MHD. It spans many device types, particularly tokamaks, stellarators and reversed field pinches, to pull out commonalities in the physics and improve understanding. In 2010 the workshop was held on 15-17 November at the University of Wisconsin in Madison and was combined with the annual US-Japan MHD Workshop. The theme was `3D Magnetic Field Effects in MHD Control', with a focus on multidisciplinary sessions exploring issues of plasma response to 3D fields, the manifestation of such fields in the plasma, and how they influence stability. This has been a topic of renewed interest, with utilisation of 3D fields for ELM control now planned in ITER, and a focus on the application of such fields for error field correction, disruption avoidance, and RWM control. Key issues included the physics of the interaction, types of coils and harmonic spectra needed to control instabilities, and subsidiary effects such as braking (or rotating) the plasma. More generally, a wider range of issues were discussed including RWM physics, tearing mode physics, disruption mitigation, ballooning stability, the snowflake divertor concept, and the line tied pinch! A novel innovation to the meeting was a panel discussion session, this year on Neoclassical Toroidal Viscosity, which ran well; more will be tried next year. In this special section of Plasma Physics and Controlled Fusion we present several of the invited and contributed papers from the 2010 workshop, which have been subject to the normal refereeing procedures of the journal. These papers give a sense of the exceptional quality of the presentations at this workshop, all of which may be found at http://fusion.gat.com/conferences/mhd

Astrophysical Aspects of Neutrino Dynamics in Ultradegenerate Quark Gluon Plasma

Directory of Open Access Journals (Sweden)

Souvik Priyam Adhya

2017-01-01

Full Text Available The cardinal focus of the present review is to explore the role of neutrinos originating from the ultradense core of neutron stars composed of quark gluon plasma in the astrophysical scenario. The collective excitations of the quarks involving the neutrinos through the different kinematical processes have been studied. The cooling of the neutron stars as well as pulsar kicks due to asymmetric neutrino emission has been discussed in detail. Results involving calculation of relevant physical quantities like neutrino mean free path and emissivity have been presented in the framework of non-Fermi liquid behavior as applicable to ultradegenerate plasma.

Coronal seismology waves and oscillations in stellar coronae

CERN Document Server

Stepanov, Alexander; Nakariakov, Valery M

2012-01-01

This concise and systematic account of the current state of this new branch of astrophysics presents the theoretical foundations of plasma astrophysics, magneto-hydrodynamics and coronal magnetic structures, taking into account the full range of available observation techniques -- from radio to gamma. The book discusses stellar loops during flare energy releases, MHD waves and oscillations, plasma instabilities and heating and charged particle acceleration. Current trends and developments in MHD seismology of solar and stellar coronal plasma systems are also covered, while recent p

Influence of ions on relativistic double layers radiation in astrophysical plasmas

Directory of Open Access Journals (Sweden)

AM Ahadi

2009-12-01

Full Text Available As double layers (DLs are one of the most important acceleration mechanisms in space as well as in laboratory plasmas, they are studied from different points of view. In this paper, the emitted power and energy radiated from charged particles, accelerated in relativistic cosmic DLs are investigated. The effect of the presence of additional ions in a multi-species plasma, as a real example of astrophysical plasma, is also investigated. Considering the acceleration role of DLs, radiations from accelerated charged particles could be seen as a loss mechanism. These radiations are influenced directly by the additional ion species as well as their relative densities.

Extended MHD Effects in High Energy Density Experiments

Science.gov (United States)

Seyler, Charles

2016-10-01

The MHD model is the workhorse for computational modeling of HEDP experiments. Plasma models are inheritably limited in scope, but MHD is expected to be a very good model for studying plasmas at the high densities attained in HEDP experiments. There are, however, important ways in which MHD fails to adequately describe the results, most notably due to the omission of the Hall term in the Ohm's law (a form of extended MHD or XMHD). This talk will discuss these failings by directly comparing simulations of MHD and XMHD for particularly relevant cases. The methodology is to simulate HEDP experiments using a Hall-MHD (HMHD) code based on a highly accurate and robust Discontinuous Galerkin method, and by comparison of HMHD to MHD draw conclusions about the impact of the Hall term. We focus on simulating two experimental pulsed power machines under various scenarios. We examine the MagLIF experiment on the Z-machine at Sandia National Laboratories and liner experiments on the COBRA machine at Cornell. For the MagLIF experiment we find that power flow in the feed leads to low density plasma ablation into the region surrounding the liner. The inflow of this plasma compresses axial magnetic flux onto the liner. In MHD this axial flux tends to resistively decay, whereas in HMHD a force-free current layer sustains the axial flux on the liner leading to a larger ratio of axial to azimuthal flux. During the liner compression the magneto-Rayleigh-Taylor instability leads to helical perturbations due to minimization of field line bending. Simulations of a cylindrical liner using the COBRA machine parameters can under certain conditions exhibit amplification of an axial field due to a force-free low-density current layer separated by some distance from the liner. This results in a configuration in which there is predominately axial field on the liner inside the current layer and azimuthal field outside the layer. We are currently attempting to experimentally verify the simulation

MHD Effects of a Ferritic Wall on Tokamak Plasmas

Science.gov (United States)

Hughes, Paul E.

It has been recognized for some time that the very high fluence of fast (14.1MeV) neutrons produced by deuterium-tritium fusion will represent a major materials challenge for the development of next-generation fusion energy projects such as a fusion component test facility and demonstration fusion power reactor. The best-understood and most promising solutions presently available are a family of low-activation steels originally developed for use in fission reactors, but the ferromagnetic properties of these steels represent a danger to plasma confinement through enhancement of magnetohydrodynamic instabilities and increased susceptibility to error fields. At present, experimental research into the effects of ferromagnetic materials on MHD stability in toroidal geometry has been confined to demonstrating that it is still possible to operate an advanced tokamak in the presence of ferromagnetic components. In order to better quantify the effects of ferromagnetic materials on tokamak plasma stability, a new ferritic wall has been installated in the High Beta Tokamak---Extended Pulse (HBT-EP) device. The development, assembly, installation, and testing of this wall as a modular upgrade is described, and the effect of the wall on machine performance is characterized. Comparative studies of plasma dynamics with the ferritic wall close-fitting against similar plasmas with the ferritic wall retracted demonstrate substantial effects on plasma stability. Resonant magnetic perturbations (RMPs) are applied, demonstrating a 50% increase in n = 1 plasma response amplitude when the ferritic wall is near the plasma. Susceptibility of plasmas to disruption events increases by a factor of 2 or more with the ferritic wall inserted, as disruptions are observed earlier with greater frequency. Growth rates of external kink instabilities are observed to be twice as large in the presence of a close-fitting ferritic wall. Initial studies are made of the influence of mode rotation frequency

Effects of MHD slow shocks propagating along magnetic flux tubes in a dipole magnetic field

Directory of Open Access Journals (Sweden)

N. V. Erkaev

2002-01-01

Full Text Available Variations of the plasma pressure in a magnetic flux tube can produce MHD waves evolving into shocks. In the case of a low plasma beta, plasma pressure pulses in the magnetic flux tube generate MHD slow shocks propagating along the tube. For converging magnetic field lines, such as in a dipole magnetic field, the cross section of the magnetic flux tube decreases enormously with increasing magnetic field strength. In such a case, the propagation of MHD waves along magnetic flux tubes is rather different from that in the case of uniform magnetic fields. In this paper, the propagation of MHD slow shocks is studied numerically using the ideal MHD equations in an approximation suitable for a thin magnetic flux tube with a low plasma beta. The results obtained in the numerical study show that the jumps in the plasma parameters at the MHD slow shock increase greatly while the shock is propagating in the narrowing magnetic flux tube. The results are applied to the case of the interaction between Jupiter and its satellite Io, the latter being considered as a source of plasma pressure pulses.

Experimental study on dynamic stabilization of the MHD instability in pinch plasmas surrounded by a conducting shell

International Nuclear Information System (INIS)

Yamamoto, Shunji; Ishii, Shozo; Kawamoto, Shigeshi; Hayashi, Izumi

1981-01-01

Experimental study on the dynamic stabilization of MHD instability with a pinch plasma generator was done, and the results were compared with the theoretical works. The previous results of theoretical analysis showed that a conducting shell worked effectively for the dynamic stabilization of MHD instability. The present experiment was carried out with a linear plasma generator which consisted of a discharge tube, a coil and a conducting shell. The macroscopic behavior of plasma was observed with an image converter camera, and the phenomena due to the instability was measured by a magnetic probe. A sine-cosine coil was employed for the observation of the growth of instability. The following results were obtained. When the frequency of RF current for dynamic stabilization was larger than the growth rate of instability, the experimental results were in agreement with the theoretical ones. The effect of a conducting shell was clearly seen. For the helical instability of short wave length, the dynamic stabilization was easily obtained even without a conducting shell. The self-reversal phenomena due to the helical instability of short wave length was suppressed by the RF current along the axis of a discharge tube. (Kato, T.)

RX emission of thin astrophysical plasma: interstellar medium and intra-cluster medium

International Nuclear Information System (INIS)

Arnaud, Monique

1984-01-01

As previous publications presented an important discrepancy of ionisation rates in astrophysical plasmas, this research thesis first reports a systematic study (by isoelectric sequence) of ionisation cross sections, based on measurements performed by mono-energetic beams, and on quantum assessments. The author proposes simple analytic fits for ionisation rates, for direct ionisation and for excitation-self-ionisation of ions of interest in astrophysics. He reports a critical review of recombination rates published in the literature, and the calculation of radiative recombination rates for different ions (hydrogen-like, helium-like, and lithium-like). Software have then been developed to determine the ionisation rate at the equilibrium and out of it for thin plasma, and to obtain ion fraction tables for different ions (H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni). Then, a software integrating recent data on collisional excitation rates has been used to calculate the emission spectrum of a thin plasma with respect to temperature. These results are then used for the study of the interstellar medium and of supernovae remnants, and finally for the study of the intra-cluster medium [fr

Velocity shear generated Alfven waves in electron-positron plasmas

International Nuclear Information System (INIS)

Rogava, A.D.; Berezhiani, V.I.; Mahajan, S.M.

1996-01-01

Linear MHD modes in cold, nonrelativistic electron-positron plasma shear flow are considered. The general set of differential equations, describing the evolution of perturbations in the framework of the nonmodal approach is derived. It is found, that under certain circumstances, the compressional and shear Alfven perturbations may exhibit large transient growth fuelled by the mean kinetic energy of the shear flow. The velocity shear also induces mode coupling allowing the exchange of energy as well as the possibility of a strong mutual transformation of these modes into each other. The compressional Alfven mode may extract the energy of the mean flow and transfer it to the shear Alfven mode via this coupling. The relevance of these new physical effects to provide a better understanding of the laboratory e + e - plasma is emphasized. It is speculated that the shear-induced effects in the electron-positron plasmas could also help solve some astrophysical puzzles (e.g., the generation of pulsar radio emission). Since most astrophysical plasma are relativistic, it is shown that the major results of the study remain valid for weakly sheared relativistic plasmas. (author). 21 refs, 4 figs

Diagnostics for the Plasma Liner Experiment

International Nuclear Information System (INIS)

Lynn, A. G.; Merritt, E.; Gilmore, M.; Hsu, S. C.; Witherspoon, F. D.; Cassibry, J. T.

2010-01-01

The goal of the Plasma Liner Experiment (PLX) is to explore and demonstrate the feasibility of forming imploding spherical ''plasma liners'' via merging high Mach number plasma jets to reach peak liner pressures of ∼0.1 Mbar using ∼1.5 MJ of initial stored energy. Such a system would provide HED plasmas for a variety of fundamental HEDLP, laboratory astrophysics, and materials science studies, as well as a platform for experimental validation of rad-hydro and rad-MHD simulations. It could also prove attractive as a potential standoff driver for magnetoinertial fusion. Predicted parameters from jet formation to liner stagnation cover a large range of plasma density and temperature, varying from n i ∼10 16 cm -3 , T e ≅T i ∼1 eV at the plasma gun mouth to n i >10 19 cm -3 , T e ≅T i ∼0.5 keV at stagnation. This presents a challenging problem for the plasma diagnostics suite which will be discussed.

Dependence of ideal MHD kink and ballooning modes on plasma shape and profiles in tokamaks

International Nuclear Information System (INIS)

Todd, A.M.M.; Manickam, J.; Okabayashi, M.; Chance, M.S.; Grimm, R.C.; Greene, J.M.; Johnson, J.L.

1978-08-01

Extensive numerical studies of ideal MHD instabilities have been carried out to gain insight into the parametric dependence of critical β's in tokamaks. The large number of interrelated equilibrium quantities involved in establishing a critical β has demanded a careful, systematic survey in order to isolate this dependence. The results of this survey establish the scaling with geometrical quantities including aspect ratio, elongation, and triangularity in the parameter regimes appropriate for both current and reactor-sized plasmas. A moderate dependence on the pressure profile and a strong variation with the current profile is found. The principal result is that for aspect ratio R/a approximately equal to 3, critical β's are of the order of 2% for circular cross sections and 5% for plasmas with elongation K approximately equal to 2; somewhat higher values could be achieved with more optimal shaping. Finally, sequences of equilibria have been analyzed to compare critical β as a function of toroidal mode number n. We conclude that the infinite-n analytic ballooning theory provides a sufficient condition for ideal MHD internal mode stability. Low-n free boundary modes appear to set a lower limit

MHD simulation of Columbia HBT

International Nuclear Information System (INIS)

Li, X.L.

1987-01-01

The plasma of Columbia High Beta Tokamak (HBT) is studied numerically by using the two dimensional resistive MHD model. The main object of this work is to understand the high beta formation process of HBT plasma and to compare the simulation with the experiments. 21 refs., 48 figs., 2 tabs

Route analysis for MHD equilibria

International Nuclear Information System (INIS)

Kikuchi, Fumio; Aizawa, Tatsuhiko

1982-01-01

In Tokamak facilities which are promising in nuclear fusion reactor development, the plasma in the core is often described by MHD approximation. Specifically, since an axisymmetric torus is approximately assumed as the first wall (shell) shape in actual Tokamak facilities, the Grad-Shafranov equation to be satisfied by an axisymmetric equilibrium solution for ideal MHD fluid must be solved, and the characteristics of its solution must be clarified. This paper shows the outline of the numerical calculation which employs both the incremental method taking the particular incremental nodal point values as the control parameters and the interaction method in accordance with Newton method at the same time, the analysis objective being a non-linear eigenvalue problem dealing the boundary of plasma region with surrounding vacuum region as the free boundary. Next, the detailed route analysis of the equilibrium solution is performed, utilizing the above numerical calculation technique, to clarify the effect of shell shape on the behaviour of the equilibrium solution. As the shape of the shell, a rectangular section torus, which have a notch depression at a part of the shell inner boundary, is considered. In the paper, the fundamental MHD equation and its approximate solution by the finite element method, the behaviour of plasma equilibrium solution in a shell having a notch, and the effect of notch shapes on plasma behaviour are described. This analysis verifies the effectiveness of the calculation method. (Wakatsuki, Y.)

Numerical study for determining PF coil system parameters in MHD equilibrium of KT-2 tokamak plasma

International Nuclear Information System (INIS)

Ryu, J.; Hong, S.H.; Lee, K.W.; Hong, B.G.; In, S.R.; Kim, S.K.

1995-01-01

The KT-2 is a large-aspect-ratio medium-sized divertor tokamak in the conceptual design phase and planned to be operational in 1998 at the Korea Atomic Energy Research Institute (KAERI). Plasma equilibrium in tokamak can be acquired by controlling the current of poloidal field (PF) coils in appropriate geometries and positions. In this study, the authors have performed numerical calculations to achieve the various equilibrium conditions fitting given plasma shapes and satisfying PF current limitations. Usually an ideal magnetohydrodynamic (MHD) equation is used to obtain the equilibrium solution of tokamak plasma, and it is practical to take advantage of a numerical method in solving the MHD equation because it has nonlinear source terms. Two equilibrium codes have been applied to find a double-null configuration of free-boundary tokamak plasma in KT-2: one is of the authors' own developing and the other is a free-boundary tokamak equilibrium code (FBT) that has been used mainly for the verification of developed code's results. PF coil system parameters including their positions and currents are determined for the optimization of input power required when the specifications of KT-2 tokamak are met. Then, several sets of equilibrium conditions during the tokamak operation are found to observe the changes of poloidal field currents with the passing of operation time step, and the basic stability problems related with the magnetic field structure is also considered

Coherent emission mechanisms in astrophysical plasmas

Science.gov (United States)

Melrose, D. B.

2017-12-01

Three known examples of coherent emission in radio astronomical sources are reviewed: plasma emission, electron cyclotron maser emission (ECME) and pulsar radio emission. Plasma emission is a multi-stage mechanism with the first stage being generation of Langmuir waves through a streaming instability, and subsequent stages involving partial conversion of the Langmuir turbulence into escaping radiation at the fundamental (F) and second harmonic (H) of the plasma frequency. The early development and subsequent refinements of the theory, motivated by application to solar radio bursts, are reviewed. The driver of the instability is faster electrons outpacing slower electrons, resulting in a positive gradient ({d}f(v_allel )/{d}v_allel >0) at the front of the beam. Despite many successes of the theory, there is no widely accepted explanation for type I bursts and various radio continua. The earliest models for ECME were purely theoretical, and the theory was later adapted and applied to Jupiter (DAM), the Earth (AKR), solar spike bursts and flare stars. ECME strongly favors the x mode, whereas plasma emission favors the o mode. Two drivers for ECME are a ring feature (implying {d}f(v)/{d}v>0) and a loss-cone feature. Loss-cone-driven ECME was initially favored for all applications. The now favored driver for AKR is the ring-feature in a horseshoe distribution, which results from acceleration by a parallel electric on converging magnetic field lines. The driver in DAM and solar and stellar applications is uncertain. The pulsar radio emission mechanism remains an enigma. Ingredients needed in discussing possible mechanisms are reviewed: general properties of pulsars, pulsar electrodynamics, the properties of pulsar plasma and wave dispersion in such plasma. Four specific emission mechanisms (curvature emission, linear acceleration emission, relativistic plasma emission and anomalous Doppler emission) are discussed and it is argued that all encounter difficulties. Coherent

Stability of a two-volume MRxMHD model in slab geometry

Science.gov (United States)

Tuen, Li Huey

Ideal MHD models are known to be inadequate to describe various physical attributes of a toroidal field with non-continuous symmetry, such as magnetic islands and stochastic regions. Motivated by this omission, a new variational principle MRXMHD was developed; rather than include an infinity of magnetic flux surfaces, MRxMHD has a finite number of flux surfaces, and thus supports partial plasma relaxation. The model comprises of relaxed plasma regions which are separated by nested ideal MHD interfaces (flux surfaces), and can be encased in a perfectly conducting wall. In each region the pressure is constant, but can jump across interfaces. The field and field pitch, or rotational transform, can also jump across the interfaces. Unlike ideal MHD, MRxMHD plasmas can support toroidally non-axisymmetric confined magnetic fields, magnetic islands and stochastic regions. In toroidally non-axisymmetric plasma, the existence of interfaces in MRxMHD is contingent on the irrationality of the rotational transform of flux surfaces. That is, the KAM theorem shows that invariant tori (flux surfaces) continue to exist for sufficiently small perturbations to an integrable system (which describes flux surfaces), provided that the rotational transform is sufficiently irrational. Building upon the MRxMHD stability model, we study the effects of irrationality of the rotational transform at interfaces in MRxMHD on plasma stability. We present an MRxMHD equilibrium model to investigate the effects of magnetic field pitch within the plasma and across the aforementioned flux surfaces within a chosen geometry. In this model, it is found that the 2D system stability conditions are dependent on the interface and resonant surface magnetic field pitch at minimised energy states, and the stability of a system as a function of magnetic field pitch destabilises at particular values of magnetic field pitch. We benchmark the treatment of a two-volume system, along with the calculations for

A simulation package for soft X-ray and EUV spectroscopy of astrophysical and laboratory plasmas in different environments

International Nuclear Information System (INIS)

Liang, G Y; Li, F; Wang, F L; Zhong, J Y; Zhao, G; Wu, Y

2014-01-01

Spectroscopic researches in astronomy are significantly dependent on theoretical modelling methods, such as Chianti, Xstar, Cloudy etc. Recently, a different research community - Laboratory Astrophysics tries to benchmark these theoretical models or simulate the astrophysical phenomenon directly in conditions accessed in ground laboratory. Those unavoidable differences between the astrophysical objects and laboratory provide a need for a self-consistent model to make a bridge for the two cases. So we setup a visualized simulation package for soft X-ray and EUV spectroscopy in astrophysical and laboratory plasmas.

Numerical study of the axisymmetric ideal MHD stability of Extrap

International Nuclear Information System (INIS)

Benda, M.

1993-04-01

A numerical study of the free-boundary axisymmetric (n=0) ideal magnetohydrodynamical (MHD) motions of the Extrap device is presented. The dependence of stability on current profiles in the plasma and currents in the external conductors is investigated. Results are shown for linear growth-rates and nonlinear saturation amplitudes and their dependence on plasma radius as well as on the conducting shell radius. A method combined of two different algorithms has been developed and tested. The interior region of the plasma is simulated by means of a Lagrangian Finite Element Method (FEM) for ideal magnetohydrodynamics, The method is based on a nonlinear radiation principle for the Lagrangian description of ideal MHD. The Boundary Element Method (BEM) is used together with the Lagrangian FEM to simulate nonlinear motion of an ideal MHD plasma behaviour in a vacuum region under the influence of external magnetic fields. 31 refs

Two-Fluid 2.5D MHD-Code for Simulations in the Solar Atmosphere

Czech Academy of Sciences Publication Activity Database

Piantschitsch, I.; Amerstorfer, U.; Thalmann, J.; Utz, D.; Hanslmeier, A.; Bárta, Miroslav; Thonhofer, S.; Lemmerer, B.

2014-01-01

Roč. 38, č. 1 (2014), s. 59-66 ISSN 1845-8319 R&D Projects: GA MŠk(CZ) 7AMB14AT022 Institutional support: RVO:67985815 Keywords : MHD simulation * chromosphere * reconnection Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Fully nonlinear heavy ion-acoustic solitary waves in astrophysical degenerate relativistic quantum plasmas

Science.gov (United States)

Sultana, S.; Schlickeiser, R.

2018-05-01

Fully nonlinear features of heavy ion-acoustic solitary waves (HIASWs) have been investigated in an astrophysical degenerate relativistic quantum plasma (ADRQP) containing relativistically degenerate electrons and non-relativistically degenerate light ion species, and non-degenerate heavy ion species. The pseudo-energy balance equation is derived from the fluid dynamical equations by adopting the well-known Sagdeev-potential approach, and the properties of arbitrary amplitude HIASWs are examined. The small amplitude limit for the propagation of HIASWs is also recovered. The basic features (width, amplitude, polarity, critical Mach number, speed, etc.) of HIASWs are found to be significantly modified by the relativistic effect of the electron species, and also by the variation of the number density of electron, light ion, and heavy ion species. The basic properties of HIASWs, that may propagated in some realistic astrophysical plasma systems (e.g., in white dwarfs), are briefly discussed.

Problems in nonlinear resistive MHD

International Nuclear Information System (INIS)

Turnbull, A.D.; Strait, E.J.; La Haye, R.J.; Chu, M.S.; Miller, R.L.

1998-01-01

Two experimentally relevant problems can relatively easily be tackled by nonlinear MHD codes. Both problems require plasma rotation in addition to the nonlinear mode coupling and full geometry already incorporated into the codes, but no additional physics seems to be crucial. These problems discussed here are: (1) nonlinear coupling and interaction of multiple MHD modes near the B limit and (2) nonlinear coupling of the m/n = 1/1 sawtooth mode with higher n gongs and development of seed islands outside q = 1

Merging of coronal and heliospheric numerical two dimensional MHD models

Czech Academy of Sciences Publication Activity Database

Odstrčil, Dušan; Linker, J. A.; Lionello, R.; Mikic, Z.; Riley, P.; Pizzo, J. V.; Luhmann, J. G.

2002-01-01

Roč. 107, A12 (2002), s. SSH14-1 - SSH14-11 ISSN 0148-0227 R&D Projects: GA AV ČR IAA3003003 Institutional research plan: CEZ:AV0Z1003909 Keywords : coronal mass ejection * interplanetary shock * numerical MHD simulation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.245, year: 2002

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

Science.gov (United States)

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.

Report of results of contract research. 'Research on magneto hydrodynamic (MHD) generation'; MHD hatsuden system no kenkyu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1980-03-01

Examination was conducted in detail on an MHD generation system by coal combustion, with the results reported. Concerning a gas table calculation program in coal combustion, it was prepared assuming 100% slag removal ratio in the combustor as the primary approximation. A combustor for MHD generation needs to efficiently burn fuel using high temperature pre-heated air as the oxidant, to fully dissociate/electrolytically dissociate seed, and to supply to the generation channel a high speed combustion gas plasma having a high electrical conductivity which is required for MHD generation. This year, an examination was conducted on technological problems in burning coal in an MHD combustor. As for the NOx elimination system in an MHD generation plant, an examination was made if the method studied so far in MHD generation using heavy oil as the fuel is applicable to coal. Also investigated and reviewed were various characteristics, change in physical properties, recovery method, etc., in a mixed state of seed and slag in the case of coal combustion MHD. (NEDO)

Spectrum of resistive MHD modes in cylindrical plasmas

International Nuclear Information System (INIS)

Ryu, C.M.; Grimm, R.C.

1983-07-01

A numerical study of the normal modes of a compressible resistive MHD fluid in cylindrical geometry is presented. Resistivity resolves the shear Alfven and slow magnetosonic continua of ideal MHD into discrete spectra and gives rise to heavily damped modes whose frequencies lie on specific lines in the complex plane. Fast magnetosonic waves are less affected but are also damped. Overstable modes arise from the shear Alfven spectrum. The stabilizing effect of favorable average curvature is shown. Eigenfunctions illustrating the nature of typical normal modes are displayed

Axisymmetric MHD simulation of ITB crash and following disruption dynamics of Tokamak plasmas with high bootstrap current

International Nuclear Information System (INIS)

Takei, Nahoko; Tsutsui, Hiroaki; Tsuji-Iio, Shunji; Shimada, Ryuichi; Nakamura, Yukiharu; Kawano, Yasunori; Ozeki, Takahisa; Tobita, Kenji; Sugihara, Masayoshi

2004-01-01

Axisymmetric MHD simulation using the Tokamak Simulation Code demonstrated detailed disruption dynamics triggered by a crash of internal transport barrier in high bootstrap current, high β, reversed shear plasmas. Self-consistent time-evolutions of ohmic current bootstrap current and induced loop voltage profiles inside the disrupting plasma were shown from a view point of disruption characterization and mitigation. In contrast with positive shear plasmas, a particular feature of high bootstrap current reversed shear plasma disruption was computed to be a significant change of plasma current profile, which is normally caused due to resistive diffusion of the electric field induced by the crash of internal transport barrier in a region wider than the internal transport barrier. Discussion based on the simulation results was made on the fastest record of the plasma current quench observed in JT-60U reversed shear plasma disruptions. (author)

R-matrix calculations for electron impact excitation and their application in astrophysical plasmas

International Nuclear Information System (INIS)

Liang, G Y; Badnell, N R; Zhao, G; Del Zanna, G; Mason, H E; Storey, P J

2012-01-01

The large number of high-resolution spectra routinely recorded in the astrophysical and fusion communities leads to the need for an extensive set of accurate baseline atomic data. The advantages of the intermediate-coupling frame transformation (ICFT) R-matrix method make it feasible to provide excitation data along iso-electronic sequences (Z ≤ 36) at the high level of accuracy afforded by the R-matrix method. The resultant data helps to overcome the longstanding shortcomings in X-ray and EUV astronomy. This is one of the key goals of the UK Atomic Processes for Astrophysical Plasmas (APAP) network.

Achieving fast reconnection in resistive MHD models via turbulent means

Directory of Open Access Journals (Sweden)

G. Lapenta

2012-04-01

Full Text Available Astrophysical fluids are generally turbulent and this preexisting turbulence must be taken into account for models of magnetic reconnection in astrophysical, solar or heliospheric environments. In addition, reconnection itself induces turbulence which provides an important feedback on the reconnection process. In this paper we discuss both the theoretical model and numerical evidence that magnetic reconnection becomes fast in the approximation of resistive MHD. We consider the relation between the Lazarian and Vishniac turbulent reconnection theory and Lapenta's numerical experiments testifying of the spontaneous onset of turbulent reconnection in systems which are initially laminar.

Visible-light imaging MHD studies of the edge plasma in the JIPP-T-IIU tokamak

International Nuclear Information System (INIS)

Yamazaki, K.; Haba, K.; Hirokura, S.

1984-06-01

MHD activity and turbulence near the plasma edge are studied on the JIPP-T-IIU tokamak using a new high-speed visible-light image-converter video-camera system. Different from conventional cinefilm and photo-diode array systems, this system is convenient for the instantaneous display of the high-speed optical plasma images after plasma discharges. The effectiveness of this instrument for the research of the plasma wall interaction is demonstrated in this experiment. The observed characteristics on the edge-plasma behavior are as follows: (1) The helical mode structure of the luminous plasma boundary suggesting plasma-surface interaction is identified in the case of OH or ICRF-heated discharge. (2) In the LH-current drive case, no clear large-scale coherent modes are identified, however, on the initial stage a medium-scale turbulence (lambda-- a few cm, f -- ten kHz) is found. (3) Before current disruptions, an m=2 or m=3 helical mode is found and up-down asymmetric light emissions are often observed during disruptions. (author)

Production of radiatively cooled hypersonic plasma jets and links to astrophysical jets

International Nuclear Information System (INIS)

Lebedev, S V; Ciardi, A; Ampleford, D J; Bland, S N; Bott, S C; Chittenden, J P; Hall, G N; Rapley, J; Jennings, C; Sherlock, M; Frank, A; Blackman, E G

2005-01-01

We present results of high energy density laboratory experiments on the production of supersonic radiatively cooled plasma jets with dimensionless parameters (Mach number ∼30, cooling parameter ∼1 and density contrast ρ j /ρ a ∼ 10) similar to those in young stellar objects jets. The jets are produced using two modifications of wire array Z-pinch driven by 1 MA, 250 ns current pulse of MAGPIE facility at Imperial College, London. In the first set of experiments the produced jets are purely hydrodynamic and are used to study deflection of the jets by the plasma cross-wind, including the structure of internal oblique shocks in the jets. In the second configuration the jets are driven by the pressure of the toroidal magnetic field and this configuration is relevant to the astrophysical models of jet launching mechanisms. Modifications of the experimental configuration allowing the addition of the poloidal magnetic field and angular momentum to the jets are also discussed. We also present three-dimensional resistive magneto-hydrodynamic simulations of the experiments and discuss the scaling of the experiments to the astrophysical systems

Preliminary Study of Ideal Operational MHD Beta Limit in HL-2A Tokamak Plasmas

International Nuclear Information System (INIS)

Shen Yong; Dong Jiaqi; He Hongda; Turnbull, A. D.

2009-01-01

Magnetohydrodynamic (MHD) n = 1 kink mode with n the toroidal mode number is studied and the operational beta limit, constrained by the mode, is calculated for the equilibrium of HL-2A by using the GATO code. Approximately the same beta limit is obtained for configurations with a value of the axial safety factor q 0 both larger and less than 1. Without the stabilization of the conducting wall, the beta limit is found to be 0.821% corresponding to a normalized beta value of β c N = 2.56 for a typical HL-2A discharge with a plasma current I p = 0.245 MA, and the scaling of β c N ∼constant is confirmed. (magnetically confined plasma)

Boundary modulation effects on MHD instabilities in Heliotrons

International Nuclear Information System (INIS)

Nakajima, N.; Hudson, S.R.; Hegna, C.C.; Nakamura, Y.

2005-01-01

In three-dimensional configurations, the confinement region is surrounded by the stochastic magnetic field lines related to magnetic islands or separatrix, leading to the fact that the plasma-vacuum boundary is not so definite compared with tokamaks that the various modulations of the plasma-vacuum boundary will be induced around the stochastic region by a large Shafranov shift of the whole plasma, in especially high-β operations. To examine such the modulation effects of the plasma boundary on MHD instabilities, high-β plasmas allowing a large Shafranov shift are considered in the inward-shifted LHD configurations with the vacuum magnetic axis R ax of 3.6m, for which previous theoretical analyses indicate that pressure-driven modes are significantly more unstable compared with experimental observations. It is shown that the boundary modulation due to a free motion of the equilibrium plasma has not only significant stabilizing effects on ideal MHD instabilities, but also characteristics consistent to experimental observations. (author)

Diagnostics for the plasma liner experiment.

Science.gov (United States)

Lynn, A G; Merritt, E; Gilmore, M; Hsu, S C; Witherspoon, F D; Cassibry, J T

2010-10-01

The goal of the Plasma Liner Experiment (PLX) is to explore and demonstrate the feasibility of forming imploding spherical "plasma liners" via merging high Mach number plasma jets to reach peak liner pressures of ∼0.1 Mbar using ∼1.5 MJ of initial stored energy. Such a system would provide HED plasmas for a variety of fundamental HEDLP, laboratory astrophysics, and materials science studies, as well as a platform for experimental validation of rad-hydro and rad-MHD simulations. It could also prove attractive as a potential standoff driver for magnetoinertial fusion. Predicted parameters from jet formation to liner stagnation cover a large range of plasma density and temperature, varying from n(i)∼10(16) cm(-3), T(e)≈T(i)∼1 eV at the plasma gun mouth to n(i)>10(19) cm(-3), T(e)≈T(i)∼0.5 keV at stagnation. This presents a challenging problem for the plasma diagnostics suite which will be discussed.

Characteristics of Plasma Probes in an MHD Working Fluid

Energy Technology Data Exchange (ETDEWEB)

Whitman, A. M.; Hsuan, Yeh [Towne School of Civil and Mechanical Engineering, University of Pennsylvania (United States)

1966-10-15

In this paper an attempt is made to formulate a theory of electrostatic probes in a high-pressure plasma in which an external electrical field may be imposed. Such a situation exists in high-pressure arc discharges and in MHD channels. First, it is shown that an adequate theory must include the ionization and recombination phenomena which were ignored in almost all previous theories. Secondly, due to the preferred direction induced by the presence of the electric field, the probe problem is no longer a symmetrical one. The analysis is based on the assumption that the three-body recombination and ionization is the dominant process. In a typical MHD working fluid, say an argon gas seeded with caesium at 2000 Degree-Sign K and one atmosphere of pressure, the penetration length I of ions and electrons, i.e. the distance that an ion or electron diffuses before recombination, is of the order of 10{sup -3} cm. (It is to be noted that ambipolar diffusion prevents the electrons from travelling much faster than the ions. ) We thus have a situation where Script-Small-L /L << 1, d/ Script-Small-L << 1, {lambda}/L <<1, and {lambda}/d >> 1, where L is the characteristic dimension of the probe {lambda} is the mean free path and d the Debye length. Because of the last condition, i. e, d << {lambda}, the space charge region is contained wholly in a ''free-falling'' zone in the immediate neighbourhood of the probe. Since, also, (d/ Script-Small-L ) << 1, the region outside of the ''free-falling'' zone is in a state of ''quasi-neutrality'', i.e. the number densities of electrons and ions are approximately equal. In this latter region, the mechanisms of diffusion and recombination are both important. The two regions must of course be matched at their connecting boundaries. Furthermore, the external boundary of the ''quasi-neutrality'' region must be matched to the discharge field. Using the approximations of the classical boundary layer theory, analytic solutions are obtained in

Preliminary results of MHD stability in HL-1 tokamak

International Nuclear Information System (INIS)

Zheng Yongzhen; Ma Tengcai; Xiao Zhenggui Cai Renfang

1987-01-01

In this paper, MHD activities of HL-1 tokamak plasma are studied with Fourier transform and correlatio analysis. The poloidal modes m = 1, 2, 3,4 and toroidal modes n of MHD magnetic fluctuation signals are detected. Methods for suppressing MHD instabilities are suggested and tested, after MHD instabilities are studied in HL-1. The effects of MHD characteristics in the beginning stage of discharge on the whole process of discharge are analyzed. The disruption, in HL-1 device could be divided into three kinds: internal disruption, minor disruption and major disruption. The result shows that HL-1 will have a better operation condition if internal disruption appears. In is end, the stable operation region of HL-1 tokamak is also given

Two dimensional Hall MHD modeling of a plasma opening switch with density inhomogeneities

Energy Technology Data Exchange (ETDEWEB)

Zabaidullin, O [Kurchatov Institute, Moscow (Russian Federation); Chuvatin, A; Etlicher, B [Ecole Polytechnique, Palaiseau (France). Laboratoire de Physique des Milieux Ionises

1997-12-31

The results of two-dimensional numerical modeling of the Plasma Opening Switch in the MHD framework with Hall effect are presented. An enhanced Hall diffusion coefficient was used in the simulations. Recent experiments justify the application of this approach. The result of the modeling also correlates better with the experiment than in the case of the classical diffusion coefficient. Numerically generated pictures propose a switching scenario in which the translation between the conduction and opening phases can be explained by an abrupt `switching on` and further domination of the Hall effect at the end of the conduction phase. (author). 3 figs., 6 refs.

Report of results of contract research. 'Research on magneto hydrodynamic (MHD) generation'; MHD hatsuden system no kenkyu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

1980-03-01

Examination was conducted in detail on an MHD generation system by coal combustion, with the results reported. Concerning a gas table calculation program in coal combustion, it was prepared assuming 100% slag removal ratio in the combustor as the primary approximation. A combustor for MHD generation needs to efficiently burn fuel using high temperature pre-heated air as the oxidant, to fully dissociate/electrolytically dissociate seed, and to supply to the generation channel a high speed combustion gas plasma having a high electrical conductivity which is required for MHD generation. This year, an examination was conducted on technological problems in burning coal in an MHD combustor. As for the NOx elimination system in an MHD generation plant, an examination was made if the method studied so far in MHD generation using heavy oil as the fuel is applicable to coal. Also investigated and reviewed were various characteristics, change in physical properties, recovery method, etc., in a mixed state of seed and slag in the case of coal combustion MHD. (NEDO)

Interferometric characterization of laboratory plasma astrophysical jets produced by a 1-μs pulsed power driver

International Nuclear Information System (INIS)

Plouhinec, Damien; Zucchini, Frederic; Loyen, Arnaud; Sol, David; Combes, Philippe; Grunenwald, Julien; Hammer, David A.

2014-01-01

A high current driver based on microsecond LTD technology has been used to perform laboratory plasma astrophysics studies using a conical wire array load coupled a 950 kA, 1.2-μs pulsed power generator. A plasma jet is generated as a result of the on-axis shock formed by the ablation streams from the wires of a conical tungsten wire-array load together with conservation of the axial momentum. The aim of this paper is to produce a scaled-down laboratory simulation of astrophysical Herbig-Haro plasma jets occurring during star formation along with some of their interactions with the interstellar medium, such as a cross wind. Due to the relatively long duration of the current pulse delivered by the driver, the jet develops on a 2-μs timescale and grows up to 100 mm. A time-resolved laser interferometer has been fielded to measure the plasma areal electron density as a function of time in and around the plasma jets. The setup consists of a continuous diode-pumped solid state laser (5 W-532 nm), a Mach-Zehnder interferometer and fast gated visible multi frame camera. (authors)

Calculation code NIRVANA for free boundary MHD equilibrium

International Nuclear Information System (INIS)

Ninomiya, Hiromasa; Suzuki, Yasuo; Kameari, Akihisa

1975-03-01

The calculation method and code of solving the free boundary problem for MHD equilibrium has been developed. Usage of the code ''NIRVANA'' is described. The toroidal plasma current density determined as a function of the flux function PSI is substituted by a group of the ring currents, whereby the equation of MHD equilibrium is transformed into an integral equation. Either of the two iterative methods is chosen to solve the integral equation, depending on the assumptions made of the plasma surface points. Calculation of the magnetic field configurations is possible when the plasma surface coincides self-consistently with the magnetic flux including the separatrix points. The code is usable in calculation of the circular or non-circular shell-less Tokamak equilibrium. (auth.)

Analytical and numerical study of MHD instabilities development in magnetized accretion-ejection structures

International Nuclear Information System (INIS)

Kersale, Evy

2000-01-01

The first part of this work proposes a new version of the mathematical formalism used to describe pressure-driven instabilities in magnetized accretion-ejection structures. Such processes, occurring in magnetically confined plasmas, pose very stringent limits to thermonuclear fusion devices but their influence in astrophysical objects has rarely been considered. In a framework which eliminates fast magnetosonic waves one develops a system of equations allowing us to follow both ballooning and interchange modes. An application of this result to a cylindrical jet being subject to solid rotation shows that the inner parts of such structures are destabilized by magnetic shear. Furthermore, while clarifying somewhat previous studies, one finds that jets confined by a dominant toroidal magnetic field are generically unstable with respect to interchange modes. Moreover, one has written a numerical code to solve the MHD partial differential equations. Starting with a basic algorithm, one has assessed the effects of the geometry, boundary conditions and artificial dissipation on numerical computation. The code has been tested by solving classical hydrodynamic and MHD Riemann problems. A new mechanism of ultra high energy cosmic ray production in gamma-ray bursts composes the last part of this work. In these objects, particles are accelerated up to energies of the order of 10 21 eV, by means of relativistic Alfven perturbations crossings. A stream instability involving a highly relativistic shell of plasma, the fireball, and baryons going through it produces such Alfven fronts. Then, Brillouin-like backscattering processes redistribute the available energy between the forward and backward Alfven waves and the magnetosonic ones. (author) [fr

MHD stability of tandem mirrors

International Nuclear Information System (INIS)

Poulsen, P.; Molvik, A.; Shearer, J.

1982-01-01

The TMX-Upgrade experiment was described, and the manner in which various plasma parameters could be affected was discussed. The initial analysis of the MHD stability of the tandem mirror was also discussed, with emphasis on the negative tandem configuration

Studies of energetic-ion-driven MHD instabilities in helical plasmas with low magnetic shear

International Nuclear Information System (INIS)

Yamamoto, S.; Ascasibar, E.; Jimenez-Gomez, R.

2012-11-01

We discuss the features of energetic-ion-driven MHD instabilities such as Alfvén eigenmodes (AEs) in three-dimensional magnetic configuration with low magnetic shear and low toroidal field period number (N p ) that are characteristic of advanced helical plasmas. Comparison of experimental and numerical studies in Heliotron J with those in TJ-II indicates that the most unstable AE is global AE (GAE) in low magnetic shear configuration in spite of the iota and the helicity-induced AE (HAE) is also the most unstable AE in the high iota configuration. (author)

Sub-grid-scale effects on short-wave instability in magnetized hall-MHD plasma

International Nuclear Information System (INIS)

Miura, H.; Nakajima, N.

2010-11-01

Aiming to clarify effects of short-wave modes on nonlinear evolution/saturation of the ballooning instability in the Large Helical Device, fully three-dimensional simulations of the single-fluid MHD and the Hall MHD equations are carried out. A moderate parallel heat conductivity plays an important role both in the two kinds of simulations. In the single-fluid MHD simulations, the parallel heat conduction effectively suppresses short-wave ballooning modes but it turns out that the suppression is insufficient in comparison to an experimental result. In the Hall MHD simulations, the parallel heat conduction triggers a rapid growth of the parallel flow and enhance nonlinear couplings. A comparison between single-fluid and the Hall MHD simulations reveals that the Hall MHD model does not necessarily improve the saturated pressure profile, and that we may need a further extension of the model. We also find by a comparison between two Hall MHD simulations with different numerical resolutions that sub-grid-scales of the Hall term should be modeled to mimic an inverse energy transfer in the wave number space. (author)

Simulations of Dynamo and Magnetorotational Instability in Madison Plasma Experiments and Astrophysical Disks

Energy Technology Data Exchange (ETDEWEB)

Ebrahimi, Fatima [Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences

2018-02-22

Magnetic fields are observed to exist on all scales in many astrophysical sources such as stars, galaxies, and accretion discs. Understanding the origin of large scale magnetic fields, whereby the field emerges on spatial scales large compared to the fluctuations, has been a particularly long standing challenge. Our physics objective are: 1) what are the minimum ingredients for large-scale dynamo growth? 2) could a large-scale magnetic field grow out of turbulence and sustained despite the presence of dissipation? These questions are fundamental for understanding the large-scale dynamo in both laboratory and astrophysical plasmas. Here, we report major new findings in the area of Large-Scale Dynamo (magnetic field generation).

Feedback stabilization of MHD instabilities. Report on the Workshop held at Princeton Plasma Physics Lab., Princeton Univ., Princeton, New Jersey, United States of America, 11-13 December 1996

International Nuclear Information System (INIS)

McGuire, K.M.; Kugel, H.W.; La Haye, R.J.; Mauel, M.E.; Nevins, W.M.; Prager, S.C.

1997-01-01

The transient operating performance of magnetic confinement devices is often limited by one or two unstable MHD modes. The feedback stabilization of MHD instabilities is an area of research that is critical for improving the steady state performance and economic attractiveness of magnetic confinement devices. This growing realization motivated a Workshop dedicated to feedback stabilization of MHD instabilities, which was held from 11 to 13 December 1996 at Princeton Plasma Physics Laboratory. The resulting presentations, conclusions and recommendations are summarized. (author)

MHD equilibrium and stability in heliotron plasmas

Energy Technology Data Exchange (ETDEWEB)

Ichiguchi, Katsuji [National Inst. for Fusion Science, Toki, Gifu (Japan)

1999-09-01

Recent topics in the theoretical magnetohydrodynamic (MHD) analysis in the heliotron configuration are overviewed. Particularly, properties of three-dimensional equilibria, stability boundary of the interchange mode, effects of the net toroidal current including the bootstrap current and the ballooning mode stability are focused. (author)

Effect of bootstrap current on MHD equilibrium beta limit in heliotron plasmas

International Nuclear Information System (INIS)

Watanabe, K.Y.

2001-01-01

The effect of bootstrap current on the beta limit of MHD equilibria is studied systematically by an iterative calculation of MHD equilibrium and the consistent bootstrap current in high beta heliotron plasmas. The LHD machine is treated as a standard configuration heliotron with an L=2 planar axis. The effects of vacuum magnetic configurations, pressure profiles and the vertical field control method are studied. The equilibrium beta limit with consistent bootstrap current is quite sensitive to the magnetic axis location for finite beta, compared with the currentless cases. For a vacuum configuration with the magnetic axis shifted inwards in the torus, even in the high beta regimes, the bootstrap current flows to increase the rotational transform, leading to an increase in the equilibrium beta limit. On the contrary, for a vacuum configuration with the magnetic axis shifted outwards in the torus, even in the low beta regimes, the bootstrap current flows so as to reduce the rotational transform; therefore, there is an acceleration of the Shafranov shift increase as beta increases, leading to a decrease in the equilibrium beta limit. The pressure profiles and vertical field control methods influence the equilibrium beta limit through the location of the magnetic axis for finite beta. These characteristics are independent of both device parameters, such as magnetic field strength, and device size in the low collisional regime. (author)

Neoclassical MHD equations for tokamaks

International Nuclear Information System (INIS)

Callen, J.D.; Shaing, K.C.

1986-03-01

The moment equation approach to neoclassical-type processes is used to derive the flows, currents and resistive MHD-like equations for studying equilibria and instabilities in axisymmetric tokamak plasmas operating in the banana-plateau collisionality regime (ν* approx. 1). The resultant ''neoclassical MHD'' equations differ from the usual reduced equations of resistive MHD primarily by the addition of the important viscous relaxation effects within a magnetic flux surface. The primary effects of the parallel (poloidal) viscous relaxation are: (1) Rapid (approx. ν/sub i/) damping of the poloidal ion flow so the residual flow is only toroidal; (2) addition of the bootstrap current contribution to Ohm's laws; and (3) an enhanced (by B 2 /B/sub theta/ 2 ) polarization drift type term and consequent enhancement of the perpendicular dielectric constant due to parallel flow inertia, which causes the equations to depend only on the poloidal magnetic field B/sub theta/. Gyroviscosity (or diamagnetic vfiscosity) effects are included to properly treat the diamagnetic flow effects. The nonlinear form of the neoclassical MHD equations is derived and shown to satisfy an energy conservation equation with dissipation arising from Joule and poloidal viscous heating, and transport due to classical and neoclassical diffusion

Temperature oscillating regimes in Tore Supra diagnosed by MHD activity

International Nuclear Information System (INIS)

Maget, P.; Imbeaux, F.; Giruzzi, G.; Udintsev, V.S.; Huysmans, G.T.A.; Segui, J.-L.; Goniche, M.; Moreau, Ph.; Sabot, R.; Garbet, X.

2006-01-01

This paper describes what we can learn on the regimes of spontaneous electron temperature oscillations discovered in Tore Supra from the analysis of MHD activity. Since the first observations of this oscillating behaviour of plasma equilibrium, and its interpretation as a predator-prey system involving lower hybrid waves power deposition and electron confinement, analysis of MHD modes has confirmed the reality of safety factor profile oscillations. This points towards the importance of rational values of the safety factor in the transition to transport barriers in reversed magnetic shear plasmas

MHD limits in non-inductive tokamak plasmas: simulations and comparison to experiments on Tore Supra

International Nuclear Information System (INIS)

Maget, P.; Huysmans, G.; Ottaviani, M.; Garbet, X.; Moreau, Ph.; Segui, J.-L.; Luetjens, H.

2008-01-01

Non-inductive tokamak discharges with a flat or hollow current profile are prone to the triggering of large tearing modes when the minimum of the safety factor is just below a low order rational. This issue is of particular importance for discussing the optimal safety factor for MHD modes avoidance in Steady-State reactor plasmas. Different non-linear regimes of such magnetic configurations in Tore Supra are studied using the full MHD code XTOR. Numerical simulations show that the non-linear stage of the Double-Tearing Mode (DTM) is governed by the full reconnection model, but a single tearing mode in a low magnetic shear configuration can have a similar impact on the confinement. The different regimes observed experimentally are recovered in the simulations: a small amplitude (2,1) DTM for close resonant surfaces as seen in Tore Supra, a sawtooth-like behaviour of the (2,1) Double-Tearing Mode as first seen in TFTR, or a large amplitude (2,1) tearing mode that severely degrades the energy confinement, as reported in Tore Supra, JET or DIII-D. Situations where q min ≅1.5 with a stable n = 1 mode, as seen in Tore Supra longest discharges, seem to put specific constraints on the MHD model that is used. Indeed, curvature stabilisation without transport terms as could explain linear stability, but such effect vanishes in presence of heat transport. Electron diamagnetic rotation effect is investigated as a possible mechanism for n = 1 mode stabilization.

MHD waves, reconnection, and plasma transport at the dayside magnetopause

International Nuclear Information System (INIS)

Johnson, J.R.; Cheng, C.Z.

1996-01-01

The magnetic field of the Earth creates a huge cavity in the solar wind known as the magnetosphere. The transition region between the solar wind plasma and magnetosphere plasma is of substantial interest because many magnetospheric processes are governed by the transport of particles, momentum and energy across that boundary. At this boundary, the magnetopause, there is an abrupt decrease in plasma bulk flow, density and pressure, and large increase in temperature and magnetic field. Throughout this region the plasmas is large. Large amplitude compressional waves are nearly always found in the region just outside of the magnetopause. These waves are either intrinsic solar wind fluctuations or they may be global mirror modes which are generated in a localized region of large pressure anisotropy just outside the magnetopause. The substantial background gradients observed at the magnetopause strongly couple the compressional waves with kinetic Alfven waves near the Alfven resonance location, leading to substantial particle transport. Moreover, for a sheared background magnetic field, as is found at times of southward interplanetary magnetic field, the mode converted kinetic Alfven waves can propagate to the location where k parallel = 0 and generate islands in phase space. We present a solution of the kinetic-MHD wave equations for the magnetic field structure based on a realistic steady state profile which includes: a sheared magnetic field; magnetic curvature; and gradients in the background density, pressure and magnetic field. We incorporate wave-particle resonance interactions for electrons and ions to obtain the dissipation. The background magnetic Keld curvature and gradient give rise to drifts which alter the resonance condition for the various particle species (ω - k circ V d - k parallel v parallel ) and reduces the Landau damping of the kinetic Alfven wave, allowing it to propagate to the k parallel = 0 location

The 3D MHD code GOEMHD3 for astrophysical plasmas with large Reynolds numbers Code description, verification, and computational performance

Czech Academy of Sciences Publication Activity Database

Skála, Jan; Baruffa, F.; Rampp, M.

2015-01-01

Roč. 580, August (2015), A48-A48 ISSN 0004-6361 R&D Projects: GA ČR GA13-24782S Institutional support: RVO:67985815 Keywords : magnetohydrodynamics * corona * magnetic fields Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

Suppression and excitation of MHD activity with an electrically polarized electrode at the TCABR tokamak plasma edge

International Nuclear Information System (INIS)

Nascimento, I.C.; Kuznetsov, Yu.K.; Guimaraes-Filho, Z.O.; Chamaa-Neto, I. El; Usuriaga, O.; Fonseca, A.M.M.; Galvao, R.M.O.; Caldas, I.L.; Severo, J.H.F.; Semenov, I.B.; Ribeiro, C.; Heller, M.V.P.; Bellintani, V.; Elizondo, J.I.; Sanada, E.

2007-01-01

Two reproducible regimes of tokamak operation, with excitation or suppression of MHD activity can be obtained using a voltage-biased electrode inside the edge of the TCABR tokamak. The experiment was carried out adjusting the tokamak parameters to obtain two types of discharges: with strong or weak MHD activity, without biasing in both cases. The plasma current was adjusted to cover a range of safety factor from 2.9 up to 3.5, so that when biasing was applied the magnetic island (3,1) could interact with the edge barrier. The application of biasing in subsequent discharges of each type resulted in excitation or suppression of the MHD activity. The results show that the dominant modes are m = 2, n = 1 and m = 3, n = 1 for excitation and partial suppression, respectively. In both regimes a strong decrease in the radial electric field is detected with destruction of the transport barrier and of the improved confinement caused by different mechanisms. The measurements include temporal behaviour of edge transport, turbulence, poloidal electric and magnetic fields, edge density, radial electric fields and radial profile of H α line intensity. The explanation of the excitation and suppression processes is discussed in the paper

Modeling of flow-dominated MHD instabilities at WiPPAL using NIMROD

Science.gov (United States)

Flanagan, K.; McCollam, K. J.; Milhone, J.; Mirnov, V. V.; Nornberg, M. D.; Peterson, E. E.; Siller, R.; Forest, C. B.

2017-10-01

Using the NIMROD (non-ideal MHD with rotation - open discussion) code developed at UW-Madison, we model two different flow scenarios to study the onset of MHD instabilities in flow-dominated plasmas in the Big Red Ball (BRB) and the Plasma Couette Experiment (PCX). Both flows rely on volumetric current drive, where a large current is drawn through the plasma across a weak magnetic field, injecting J × B torque across the whole volume. The first scenario uses a vertical applied magnetic field and a mostly radial injected current to create Couette-like flows which may excite the magnetorotational instability (MRI). In the other scenario, a quadrupolar field is applied to create counter-rotating von Karman-like flow that demonstrates a dynamo-like instability. For both scenarios, the differences between Hall and MHD Ohm's laws are explored. The implementation of BRB geometry in NIMROD, details of the observed flows, and instability results are shown. This work was funded by DoE and NSF.

MHD stability calculations of high-β quasi-axisymmetric stellarators

International Nuclear Information System (INIS)

Fu, G.Y.; Ku, L.P.; Pomphrey, N.; Redi, M.; Kessel, C.; Monticello, D.; Reiman, A.; Hughes, M.; Cooper, W.A.; Nuehrenberg, C.

2001-01-01

The MHD stability of quasi-axisymmetric compact stellarators is investigated. It is shown that bootstrap current driven external kink modes can be stabilized by a combination of edge magnetic shear and appropriate 3D plasma boundary shaping while maintaining good quasi-axisymmetry. The results demonstrate that there exists a new class of stellarators with quasi-axisymmetry, large bootstrap current, high MHD beta limit, and compact size. (author)

MHD stability calculations of high-β quasi-axisymmetric stellarators

International Nuclear Information System (INIS)

Fu, G.Y.; Ku, L.P.; Pomphrey, N.; Redi, M.H.; Kessel, C.; Monticello, D.A.; Reiman, A.; Hughes, M.; Cooper, W.A.; Nuehrenberg, C.

1999-01-01

The MHD stability of quasi-axisymmetric compact stellarators is investigated. It is shown that bootstrap current driven external kink modes can be stabilized by a combination of edge magnetic shear and appropriate 3D plasma boundary shaping while maintaining good quasi-axisymmetry. The results demonstrate that there exists a new class of stellarators with quasi-axisymmetry, large bootstrap current, high MHD beta limit, and compact size. (author)

MHD Stability Calculations of High-Beta Quasi-Axisymmetric Stellarators

International Nuclear Information System (INIS)

Kessel, C.; Fu, G.Y.; Ku, L.P.; Redi, M.H.; Pomphrey, N.

1999-01-01

The MHD stability of quasi-axisymmetric compact stellarators is investigated. It is shown that bootstrap current driven external kink modes can be stabilized by a combination of edge magnetic shear and appropriate 3D plasma boundary shaping while maintaining good quasi-axisymmetry. The results demonstrate that there exists a new class of stellarators with quasi-axisymmetry, large bootstrap current, high MHD beta limit, and compact size

Ideal MHD stability analysis of KSTAR target AT mode

International Nuclear Information System (INIS)

Yi, S.M.; Kim, J.H.; You, K.I.; Kim, J.Y.

2009-01-01

Full text: A main research objective of KSTAR (Korea Superconducting Tokamak Advanced Research) device is to demonstrate the steady-state operation capability of high-performance AT (Advanced Tokamak) mode. To meet this goal, it is critical for KSTAR to have a good MHD stability boundary, particularly against the high-beta ideal instabilities such as the external kink and the ballooning modes. To support this MHD stability KSTAR has been designed to have a strong plasma shape and a close interval between plasma and passive- plate wall. During the conceptual design phase of KSTAR, a preliminary study was performed to estimate the high beta MHD stability limit of KSTAR target AT mode using PEST and VACUUM codes and it was shown that the target AT mode can be stable up to β N ∼ 5 with a well-defined plasma pressure and current profiles. Recently, a new calculation has been performed to estimate the ideal stability limit in various KSTAR operating conditions using DCON code, and it has been observed that there is some difference between the new and old calculation results, particularly in the dependence of the maximum β N value on the toroidal mode number. Here, we thus present a more detailed analysis of the ideal MHD stability limit of KSTAR target AT mode using various codes, which include GATO as well as PEST and DCON, in the comparison of calculation results among the three codes. (author)

Observation of finite-β MHD phenomena in Tokamaks

International Nuclear Information System (INIS)

McGuire, K.M.

1985-01-01

Stable high beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n > 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1 internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of qsub(o) and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded

New insights into MHD dynamics of magnetically confined plasmas from experiments in RFX

International Nuclear Information System (INIS)

Martin, P.; Martini, S.; Antoni, V.

2001-01-01

The experimental and theoretical activity performed in the RFX experiment has allowed a deeper insight into the MHD properties of the RFP configuration. A set of successful experiments has demonstrated the possibility of influencing both the amplitude and the spectrum of the magnetic fluctuations which characterise the RFP configuration. A new regime (QSH states) where the dynamo mechanism works in a nearly laminar way and a helical core plasma is produced has been investigated. With these studies a reduction of the magnetic chaos has been obtained. The continuos rotation of wall locked resistive tearing modes has been obtained by an m=0 rotating perturbation. This perturbation induces rotation of m=1 non-linearly coupled modes. (author)

MHD simulation study of compact toroid injection into magnetized plasmas

International Nuclear Information System (INIS)

Suzuki, Yoshio; Kishimoto, Yasuaki

2000-01-01

To understand the fuelling process in a fusion device by a compact toroid (CT) plasmoid injection method, we have carried out MHD numerical simulations where a spheromak-like CT (SCT) is injected into a magnetized target plasma region. So far, we revealed that the penetration depth of the SCT plasma becomes shorter than that estimated from the conducting sphere (CS) model, because in the simulation the Lorentz force of the target magnetic field sequentially decelerates the injected SCT while in the CS model only the magnetic pressure force acts as the deceleration mechanism. In this study, we represent the new theoretical model where the injected SCT is decelerated by both the magnetic pressure force and the magnetic tension force (we call it the non-slipping sphere (NS) model) and investigate in detail the deceleration mechanism of the SCT by comparison with simulation results. As a result, it is found that the decrease of the SCT kinetic energy in the simulation coincides with that in the NS model more than in the CS model. It means that not only the magnetic pressure force but also the magnetic tension force acts as the deceleration mechanism of the SCT. Furthermore, it is revealed that magnetic reconnection between the SCT magnetic field and the target magnetic field plays a role to relax the SCT deceleration. (author)

MHD stability limits in the TCV Tokamak

International Nuclear Information System (INIS)

Reimerdes, H.

2001-07-01

Magnetohydrodynamic (MHD) instabilities can limit the performance and degrade the confinement of tokamak plasmas. The Tokamak a Configuration Variable (TCV), unique for its capability to produce a variety of poloidal plasma shapes, has been used to analyse various instabilities and compare their behaviour with theoretical predictions. These instabilities are perturbations of the magnetic field, which usually extend to the plasma edge where they can be detected with magnetic pick-up coils as magnetic fluctuations. A spatially dense set of magnetic probes, installed inside the TCV vacuum vessel, allows for a fast observation of these fluctuations. The structure and temporal evolution of coherent modes is extracted using several numerical methods. In addition to the setup of the magnetic diagnostic and the implementation of analysis methods, the subject matter of this thesis focuses on four instabilities, which impose local and global stability limits. All of these instabilities are relevant for the operation of a fusion reactor and a profound understanding of their behaviour is required in order to optimise the performance of such a reactor. Sawteeth, which are central relaxation oscillations common to most standard tokamak scenarios, have a significant effect on central plasma parameters. In TCV, systematic scans of the plasma shape have revealed a strong dependence of their behaviour on elongation κ and triangularity δ, with high κ, and low δ leading to shorter sawteeth with smaller crashes. This shape dependence is increased by applying central electron cyclotron heating. The response to additional heating power is determined by the role of ideal or resistive MHD in triggering the sawtooth crash. For plasma shapes where additional heating and consequently, a faster increase of the central pressure shortens the sawteeth, the low experimental limit of the pressure gradient within the q = 1 surface is consistent with ideal MHD predictions. The observed decrease

Order out of Randomness: Self-Organization Processes in Astrophysics

Science.gov (United States)

Aschwanden, Markus J.; Scholkmann, Felix; Béthune, William; Schmutz, Werner; Abramenko, Valentina; Cheung, Mark C. M.; Müller, Daniel; Benz, Arnold; Chernov, Guennadi; Kritsuk, Alexei G.; Scargle, Jeffrey D.; Melatos, Andrew; Wagoner, Robert V.; Trimble, Virginia; Green, William H.

2018-03-01

Self-organization is a property of dissipative nonlinear processes that are governed by a global driving force and a local positive feedback mechanism, which creates regular geometric and/or temporal patterns, and decreases the entropy locally, in contrast to random processes. Here we investigate for the first time a comprehensive number of (17) self-organization processes that operate in planetary physics, solar physics, stellar physics, galactic physics, and cosmology. Self-organizing systems create spontaneous " order out of randomness", during the evolution from an initially disordered system to an ordered quasi-stationary system, mostly by quasi-periodic limit-cycle dynamics, but also by harmonic (mechanical or gyromagnetic) resonances. The global driving force can be due to gravity, electromagnetic forces, mechanical forces (e.g., rotation or differential rotation), thermal pressure, or acceleration of nonthermal particles, while the positive feedback mechanism is often an instability, such as the magneto-rotational (Balbus-Hawley) instability, the convective (Rayleigh-Bénard) instability, turbulence, vortex attraction, magnetic reconnection, plasma condensation, or a loss-cone instability. Physical models of astrophysical self-organization processes require hydrodynamic, magneto-hydrodynamic (MHD), plasma, or N-body simulations. Analytical formulations of self-organizing systems generally involve coupled differential equations with limit-cycle solutions of the Lotka-Volterra or Hopf-bifurcation type.

Relativistic MHD modeling of magnetized neutron stars, pulsar winds, and their nebulae

Science.gov (United States)

Del Zanna, L.; Pili, A. G.; Olmi, B.; Bucciantini, N.; Amato, E.

2018-01-01

Neutron stars are among the most fascinating astrophysical sources, being characterized by strong gravity, densities about the nuclear one or even above, and huge magnetic fields. Their observational signatures can be extremely diverse across the electromagnetic spectrum, ranging from the periodic and low-frequency signals of radio pulsars, up to the abrupt high-energy gamma-ray flares of magnetars, where energies of ∼ {10}46 {erg} are released in a few seconds. Fast-rotating and highly magnetized neutron stars are expected to launch powerful relativistic winds, whose interaction with the supernova remnants gives rise to the non-thermal emission of pulsar wind nebulae, which are known cosmic accelerators of electrons and positrons up to PeV energies. In the extreme cases of proto-magnetars (magnetic fields of ∼ {10}15 G and millisecond periods), a similar mechanism is likely to provide a viable engine for the still mysterious gamma-ray bursts. The key ingredient in all these spectacular manifestations of neutron stars is the presence of strong magnetic fields in their constituent plasma. Here we will present recent updates of a couple of state-of-the-art numerical investigations by the high-energy astrophysics group in Arcetri: a comprehensive modeling of the steady-state axisymmetric structure of rotating magnetized neutron stars in general relativity, and dynamical 3D MHD simulations of relativistic pulsar winds and their associated nebulae.

Abstracts of 4. IAEA technical meeting on the theory of plasma instabilities

International Nuclear Information System (INIS)

2009-05-01

The Fourth IAEA-TM on Theory of Plasma Instabilities provided a forum for open discussion on theoretical and computational physics issues relevant to burning plasma. The meeting covered linear and non-linear theory and simulation of plasma instabilities, including core/edge turbulence, magneto-hydrodynamic (MHD) process, high energy particle driven dynamics and their effects on plasma confinement. Special attention was paid to the multi-scale interaction dynamics in better understanding the burning plasma and also to the modeling of such complex physical processes. The meeting also organized a panel session to discuss the prospect of plasma theory and simulation for future fusion research for the ITER ERA. Young scientists were enthusiastically encouraged to enjoy this session which may stimulate the research for the future. The meeting covered the following topics: (1) Overview: State of the art and importance of multi-scale physics for understanding burning plasmas; (2) Linear and nonlinear instabilities and their theoretical/computational methodologies including critical gradient problem and comparison with experiments; (3) Core/edge turbulent transport including momentum transport, turbulence-profile interaction and barrier formation, etc and their theoretical/ computational understandings; (4) Magneto-hydrodynamic (MHD) instability including energetic particle physics and their impact on confinement in burning plasmas; (5) Physics and modeling of multi-scale interactions and their impact on the plasma performance and control. Those topics were discussed with close relevance to key experimental results. A panel session 'Theoretical Plasma Physics for the ITER ERA' was organized under interdisciplinary aspects with other fields such as astrophysics and fluid dynamics. Each of the abstracts available has been indexed separately

Ideal MHD stability and performance of ITER steady-state scenarios with ITBs

Science.gov (United States)

Poli, F. M.; Kessel, C. E.; Chance, M. S.; Jardin, S. C.; Manickam, J.

2012-06-01

Non-inductive steady-state scenarios on ITER will need to operate with internal transport barriers (ITBs) in order to reach adequate fusion gain at typical currents of 9 MA. The large pressure gradients at the location of the internal barrier are conducive to the development of ideal MHD instabilities that may limit the plasma performance and may lead to plasma disruptions. Fully non-inductive scenario simulations with five combinations of heating and current drive sources are presented in this work, with plasma currents in the range 7-10 MA. For each configuration the linear, ideal MHD stability is analysed for variations of the Greenwald fraction and of the pressure peaking factor around the operating point, aiming at defining an operational space for stable, steady-state operations at optimized performance. It is shown that plasmas with lower hybrid heating and current drive maintain the minimum safety factor above 1.5, which is desirable in steady-state operations to avoid neoclassical tearing modes. Operating with moderate ITBs at 2/3 of the minor radius, these plasmas have a minimum safety factor above 2, are ideal MHD stable and reach Q ≳ 5 operating above the ideal no-wall limit.

Ideal MHD Stability Characteristics of Advanced Operating Regimes in Spherical Torus Plasmas and the Role of High Harmonic Fast Waves

International Nuclear Information System (INIS)

Kessel, C.E.; Manickam, J.; Menard, J.E.; Jardin, S.C.; Kaye, S.M.

1999-01-01

The ARIES reactor study group has found an economically attractive ST-based reactor configuration with: A = 1.6, κ = 3.4, delta = 0.65, β = 50%, β N = 7.3, f BS = 0.95, R 0 = 3.2 meters, B t0 = 2.08 Tesla, and I P = 28.5 MA which yields a cost of electricity of approximately 80mils/kWh. MHD stability analysis finds that a broad pressure profile is optimal for wall-stabilizing the pressure driven kink modes typical of such configurations, and that wall stabilization is crucial to achieving the high β needed for an economical power plant. The 6MW high-harmonic fast wave system presently being installed on NSTX should allow real-time control of the plasma β, and in combination with NBI may permit experimental investigations of the effect of pressure profile peaking on MHD stability in the near-term. In the longer term, ejection of ions through resonant interaction with HHFW might be used to induce a controllable edge radial electric field with potentially interesting effects on edge MHD and confinement

High density plasmas formation in Inertial Confinement Fusion and Astrophysics

International Nuclear Information System (INIS)

Martinez-Val, J. M.; Minguez, E.; Velarde, P.; Perlado, J. M.; Velarde, G.; Bravo, E.; Eliezer, S.; Florido, R.; Garcia Rubiano, J.; Garcia-Senz, D.; Gil de la Fe, J. M.; Leon, P. T.; Martel, P.; Ogando, F.; Piera, M.; Relano, A.; Rodriguez, R.; Garcia, C.; Gonzalez, E.; Lachaise, M.; Oliva, E.

2005-01-01

In inertially confined fusion (ICF), high densities are required to obtain high gains. In Fast Ignition, a high density, low temperature plasma can be obtained during the compression. If the final temperature reached is low enough, the electrons of the plasma can be degenerate. In degenerate plasmas. Bremsstrahlung emission is strongly suppressed an ignition temperature becomes lower than in classical plasmas, which offers a new design window for ICF. The main difficulty of degenerate plasmas in the compression energy needed for high densities. Besides that, the low specific heat of degenerate electrons (as compared to classical values) is also a problem because of the rapid heating of the plasma. Fluid dynamic evolution of supernovae remnants is a very interesting problem in order to predict the thermodynamical conditions achieved in their collision regions. Those conditions have a strong influence in the emission of light and therefore the detection of such events. A laboratory scale system has been designed reproducing the fluid dynamic field in high energy experiments. The evolution of the laboratory system has been calculated with ARWEN code, 2D Radiation CFD that works with Adaptive Mesh Refinement. Results are compared with simulations on the original system obtained with a 3D SPH astrophysical code. New phenomena at the collision plane and scaling of the laboratory magnitudes will be described. Atomic physics for high density plasmas has been studied with participation in experiments to obtain laser produced high density plasmas under NLTE conditions, carried out at LULI. A code, ATOM3R, has been developed which solves rate equations for optically thin plasmas as well as for homogeneous optically thick plasmas making use of escape factors. New improvements in ATOM3R are been done to calculate level populations and opacities for non homogeneous thick plasmas in NLTE, with emphasis in He and H lines for high density plasma diagnosis. Analytical expression

Final Report. Hydrodynamics by high-energy-density plasma flow and hydrodynamics and radiative hydrodynamics with astrophysical application

International Nuclear Information System (INIS)

R Paul Drake

2004-01-01

OAK-B135 This is the final report from the project Hydrodynamics by High-Energy-Density Plasma Flow and Hydrodynamics and Radiation Hydrodynamics with Astrophysical Applications. This project supported a group at the University of Michigan in the invention, design, performance, and analysis of experiments using high-energy-density research facilities. The experiments explored compressible nonlinear hydrodynamics, in particular at decelerating interfaces, and the radiation hydrodynamics of strong shock waves. It has application to supernovae, astrophysical jets, shock-cloud interactions, and radiative shock waves

Shukla-Spatschek diffusion effects on surface plasma waves in astrophysical turbulent plasmas

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-02-01

The effects of Shukla-Spatschek turbulent diffusion on a temporal mode of surface waves propagating at the interface of an astrophysical turbulent plasma are investigated. The damping rates for high and low modes of surface wave are kinetically derived by employing the Vlasov-Poisson equation and the specular reflection boundary condition. We found that the diffusion caused by the fluctuating electric fields leads to damping for both high and low modes of surface waves. The high-mode damping is enhanced with an increase of the wavenumber and the diffusion coefficient, but suppressed by an increase of electron thermal energy. By contrast, the low-mode damping is suppressed as the wavenumber and the thermal energy increase although it is enhanced as the diffusion increases. The variation of the damping rate due to the Shukla-Spatschek turbulent diffusion is also discussed.

Role of MHD activity in LH-assisted discharges in the PBX-M tokamak

International Nuclear Information System (INIS)

Talvard, M.; Bell, R.E.; Bernabei, S.; Kaye, S.; Okabayashi, M.; Sesnic, S.; von Goeler, S.

1995-01-01

A data base for the 1993 run period of PBX-M has been documented (i) to investigate whether it was possible to forecast the development of MHD instabilities often observed in LH assisted discharges and (ii) to detail the origin, the nature and the effects of those instabilities. The deposition radius of the RF current, the plasma internal inductance and the LH power are used to separate MHD active and quiescent regimes prior the MHD onset. 1/1, 2/1, 3/1 global modes driven by the m = 2, n = 1 component are observed in discharges with LHCD. The destabilization is attributed to an increase of the current density gradient within the q = 2 surface. MHD fluctuations reduce the soft x-ray and hard x-ray intensities mainly around the RF current deposition radius. Minor disruptions with large inversion radii and mode locking are analyzed. Pi possible precursor to the MHD is evidenced on the hard x-ray horizontal profiles. A resonance between fast trapped electrons and turbulent waves present in the background plasma is proposed to support the observations

Numerical Simulation of 3D Viscous MHD Flows

National Research Council Canada - National Science Library

Golovachov, Yurii P; Kurakin, Yurii A; Schmidt, Alexander A; Van Wie, David M

2003-01-01

.... Flows in hypersonic intakes are considered. Preliminary results showed that local MHD interaction in the inlet part of the intake model was the most effective for control over plasma flow field...

Transport processes in space physics and astrophysics

CERN Document Server

Zank, Gary P

2014-01-01

Transport Processes in Space Physics and Astrophysics' is aimed at graduate level students to provide the necessary mathematical and physics background to understand the transport of gases, charged particle gases, energetic charged particles, turbulence, and radiation in an astrophysical and space physics context. Subjects emphasized in the work include collisional and collisionless processes in gases (neutral or plasma), analogous processes in turbulence fields and radiation fields, and allows for a simplified treatment of the statistical description of the system. A systematic study that addresses the common tools at a graduate level allows students to progress to a point where they can begin their research in a variety of fields within space physics and astrophysics. This book is for graduate students who expect to complete their research in an area of plasma space physics or plasma astrophysics. By providing a broad synthesis in several areas of transport theory and modeling, the work also benefits resear...

Collision excitation studies useful for plasma diagnostics in astrophysics and fusion research

International Nuclear Information System (INIS)

Man Mohan; Aggarwal, Sunny

2015-01-01

The urgent research for energy sources has led many countries to collaborate on demonstrating the scientific and technological feasibility of magnetic fusion through the construction of International Thermonuclear Experimental Reactor in France. Data on highly charged ions with high Z will be important in this quest. Atomic data such as energy levels, radiative rates and collision excitation plays an important role in fusion research and extensive knowledge of atomic parameters is needed for plasma diagnostics. There is a very limited knowledge so far about the heavy atoms due to involvement of strong relativistic effects. For heavy atoms, electron correlation effects and relativistic effects are strongly coupled making it necessary to use a relativistic theory which also incorporates 'electron correlations effects on the same footing. For treating heavy atoms there have been new developments and many codes in the relativistic domain have been developed by various authors. Among them, multi-configuration Hartree (Dirac) Fock (MCDF) model based codes have been found very useful in ab-initio investigations. We have calculated the energy levels, radiative rates and lifetimes for heavy charged F, Na and Mg like tungsten ions using MCDF and FAC and compared our results with the other available theoretical and experimental results. Also, we have performed collision excitation calculations for F, Na and Mg like tungsten ions which will be useful for astrophysical and fusion, plasma. Also, we have compared our collision excitation results with distorted wave calculations and they are found to be in good agreement. The main goal of this paper is to provide useful atomic physics data for use in fusion research and in astrophysical and industrial plasmas. (author)

Prospects for observing the magnetorotational instability in the plasma Couette experiment

Science.gov (United States)

Flanagan, K.; Clark, M.; Collins, C.; Cooper, C. M.; Khalzov, I. V.; Wallace, J.; Forest, C. B.

2015-08-01

Many astrophysical disks, such as protoplanetary disks, are in a regime where non-ideal, plasma-specific magnetohydrodynamic (MHD) effects can significantly influence the behaviour of the magnetorotational instability (MRI). The possibility of studying these effects in the plasma Couette experiment (PCX) is discussed. An incompressible, dissipative global stability analysis is developed to include plasma-specific two-fluid effects and neutral collisions, which are inherently absent in analyses of Taylor-Couette flows (TCFs) in liquid metal experiments. It is shown that with boundary driven flows, a ion-neutral collision drag body force significantly affects the azimuthal velocity profile, thus limiting the flows to regime where the MRI is not present. Electrically driven flow (EDF) is proposed as an alternative body force flow drive in which the MRI can destabilize at more easily achievable plasma parameters. Scenarios for reaching MRI relevant parameter space and necessary hardware upgrades are described.

Modeling X-ray Spectra of Astrophysical Plasmas: Current Status and Future Needs

Science.gov (United States)

Smith, Randall

Existing high-resolution astrophysical X-ray spectra has exposed the need for high-quality atomic data of all stripes: wavelengths, collisional and absorption cross sections, and radiative rates. The Astro-H soft X-ray spectrometer (2015 launch) will vastly increase the number and type of high-resolution X-ray spectra available and likely expose a number of shortcomings in our models. I will describe recent advances in theoretical calculations and laboratory measurements, as well as a number of existing needs in the field. These include accurate soft X-ray wavelengths for L-shell ions, diagnostic emission line ratios with estimated error bars, and high-resolution absorption cross sections for abundant ions and molecules. Finally, new models of emission from non-equilibrium ionization plasmas and astrophysical charge exchange will be discussed. This latter emission arises due to the interaction of highly charged ions with neutral atoms, forming a diffuse background in the case of solar wind ions and possibly also arising in more distant environments.

Neoclassical MHD equilibria with ohmic current

International Nuclear Information System (INIS)

Tokuda, Shinji; Takeda, Tatsuoki; Okamoto, Masao.

1989-01-01

MHD equilibria of tokamak plasmas with neoclassical current effects (neoclassical conductivity and bootstrap current) were calculated self-consistently. Neoclassical effects on JFT-2M tokamak plasmas, sustained by ohmic currents, were studied. Bootstrap currents flow little for L-mode type equilibria because of low attainable values of poloidal beta, β J . H-mode type equilibria give bootstrap currents of 30% ohmic currents for β J attained by JFT-2M and 100% for β J ≥ 1.5, both of which are sufficient to change the current profiles and the resultant MHD equilibria. Neoclassical conductivity which has roughly half value of the classical Spitzer conductivity brings peaked ohmic current profiles to yield low safety factor at the magnetic axis. Neoclassical conductivity reduces the value of effective Z(Z eff ) which is necessary to give the observed one-turn voltage but it needs impurities accumulating at the center when such peaked current profiles are not observed. (author)

Numerical resolution of a bi-temperature MHD model with a general Ohm's law: Roe solver - Front-tracking - Nonlinear transport equations with discontinuous coefficients. Simulation of a Plasma Opening Switch

International Nuclear Information System (INIS)

Brassier, Stephane

1998-01-01

The Magnetohydrodynamic (MHD) equations represent the coupling between fluid dynamics equations and Maxwell's equations. We consider here a new MHD model with two temperatures. A Roe scheme is first constructed in the one dimensional case, for a multi-species model and a general equation of state. The multidimensional case is treated thanks to the Powell approach. The notion of Roe-Powell matrix, generalization of the notion of Roe matrix for multidimensional MHD, allows us to develop an original scheme on a curvilinear grid. We focus on a second part on the modelling of a Plasma Opening Switch (POS). A front-tracking method is first set up, in order to correctly handle the deformation of the front between the vacuum and the plasma. Besides, by taking into account a general Ohm's law, we have to deal with the Hall effect, which leads to nonlinear transport equations with discontinuous coefficients. Several numerical schemes are proposed and tested on a variety of test cases. This work has allowed us to construct an industrial MHD code, intended to handle complex flows and in particular to correctly simulate the behaviour of the POS. (author) [fr

Theoretical studies of MHD plasma molecules. I. Potential energy curves and dipole moments of linear KOH

International Nuclear Information System (INIS)

England, W.B.

1978-01-01

Uncorrelated and correlated potential energy curves and dipole moments are reported for linear KOH. The compound is found to be ionic, K + OH - . Minimum energy bond lengths are R/sub KO/=4.2913 au and R/sub OH/=1.7688 au, with an estimated accuracy of 2%. The corresponding dipole moment is 3.3 au (8.46 D) with a similar accuracy estimate. This is to our knowledge the first value ever reported for the KOH dipole moment, and the large value suggests that KOH will be an effective electron scatterer in MHD plasmas

Reminimization of energy integral and stability limit for non-ideal MHD (magnetohydrodynamic) plasma

International Nuclear Information System (INIS)

Kondoh, Y.

1988-03-01

The stability condition of relaxed states is derived from the energy principle for the non-ideal MHD plasma. An Euler equation for the reminimization of energy integral is derived and shown to give the marginal stable, non-singular perturbations for the stability condition. An extended stability limit for the β = 0 relaxed states is derived from the stability condition, with use of the eigenvalue analysis for the Euler equation. By using the perturbation method, the extended stability limit is solved in the 1st order approximation to explain the deviation of the experimental stability limit from the idealized stability limit by Taylor. A procedure to get overall stability limit against both the non-singular and the singular perturbations is discussed. 25 refs

High Energy Density Laboratory Astrophysics

CERN Document Server

Lebedev, Sergey V

2007-01-01

During the past decade, research teams around the world have developed astrophysics-relevant research utilizing high energy-density facilities such as intense lasers and z-pinches. Every two years, at the International conference on High Energy Density Laboratory Astrophysics, scientists interested in this emerging field discuss the progress in topics covering: - Stellar evolution, stellar envelopes, opacities, radiation transport - Planetary Interiors, high-pressure EOS, dense plasma atomic physics - Supernovae, gamma-ray bursts, exploding systems, strong shocks, turbulent mixing - Supernova remnants, shock processing, radiative shocks - Astrophysical jets, high-Mach-number flows, magnetized radiative jets, magnetic reconnection - Compact object accretion disks, x-ray photoionized plasmas - Ultrastrong fields, particle acceleration, collisionless shocks. These proceedings cover many of the invited and contributed papers presented at the 6th International Conference on High Energy Density Laboratory Astrophys...

Exploring Astrophysical Magnetohydrodynamics in the Laboratory

Science.gov (United States)

Manuel, Mario

2014-10-01

Plasma evolution in many astrophysical systems is dominated by magnetohydrodynamics. Specifically of interest to this talk are collimated outflows from accretion systems. Away from the central object, the Euler equations can represent the plasma dynamics well and may be scaled to a laboratory system. We have performed experiments to investigate the effects of a background magnetic field on an otherwise hydrodynamically collimated plasma. Laser-irradiated, cone targets produce hydrodynamically collimated plasma jets and a pulse-powered solenoid provides a constant background magnetic field. The application of this field is shown to completely disrupt the original flow and a new magnetically-collimated, hollow envelope is produced. Results from these experiments and potential implications for their astrophysical analogs will be discussed.

MPI-AMRVAC 2.0 for Solar and Astrophysical Applications

Science.gov (United States)

Xia, C.; Teunissen, J.; El Mellah, I.; Chané, E.; Keppens, R.

2018-02-01

We report on the development of MPI-AMRVAC version 2.0, which is an open-source framework for parallel, grid-adaptive simulations of hydrodynamic and magnetohydrodynamic (MHD) astrophysical applications. The framework now supports radial grid stretching in combination with adaptive mesh refinement (AMR). The advantages of this combined approach are demonstrated with one-dimensional, two-dimensional, and three-dimensional examples of spherically symmetric Bondi accretion, steady planar Bondi–Hoyle–Lyttleton flows, and wind accretion in supergiant X-ray binaries. Another improvement is support for the generic splitting of any background magnetic field. We present several tests relevant for solar physics applications to demonstrate the advantages of field splitting on accuracy and robustness in extremely low-plasma β environments: a static magnetic flux rope, a magnetic null-point, and magnetic reconnection in a current sheet with either uniform or anomalous resistivity. Our implementation for treating anisotropic thermal conduction in multi-dimensional MHD applications is also described, which generalizes the original slope-limited symmetric scheme from two to three dimensions. We perform ring diffusion tests that demonstrate its accuracy and robustness, and show that it prevents the unphysical thermal flux present in traditional schemes. The improved parallel scaling of the code is demonstrated with three-dimensional AMR simulations of solar coronal rain, which show satisfactory strong scaling up to 2000 cores. Other framework improvements are also reported: the modernization and reorganization into a library, the handling of automatic regression tests, the use of inline/online Doxygen documentation, and a new future-proof data format for input/output.

Model of magnetic reconnection in space and astrophysical plasmas

Energy Technology Data Exchange (ETDEWEB)

Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2013-03-15

Maxwell's equations imply that exponentially smaller non-ideal effects than commonly assumed can give rapid magnetic reconnection in space and astrophysical plasmas. In an ideal evolution, magnetic field lines act as stretchable strings, which can become ever more entangled but cannot be cut. High entanglement makes the lines exponentially sensitive to small non-ideal changes in the magnetic field. The cause is well known in popular culture as the butterfly effect and in the theory of deterministic dynamical systems as a sensitive dependence on initial conditions, but the importance to magnetic reconnection is not generally recognized. Two-coordinate models are too constrained geometrically for the required entanglement, but otherwise the effect is general and can be studied in simple models. A simple model is introduced, which is periodic in the x and y Cartesian coordinates and bounded by perfectly conducting planes in z. Starting from a constant magnetic field in the z direction, reconnection is driven by a spatially smooth, bounded force. The model is complete and could be used to study the impulsive transfer of energy between the magnetic field and the ions and electrons using a kinetic plasma model.

Model of magnetic reconnection in space and astrophysical plasmas

International Nuclear Information System (INIS)

Boozer, Allen H.

2013-01-01

Maxwell's equations imply that exponentially smaller non-ideal effects than commonly assumed can give rapid magnetic reconnection in space and astrophysical plasmas. In an ideal evolution, magnetic field lines act as stretchable strings, which can become ever more entangled but cannot be cut. High entanglement makes the lines exponentially sensitive to small non-ideal changes in the magnetic field. The cause is well known in popular culture as the butterfly effect and in the theory of deterministic dynamical systems as a sensitive dependence on initial conditions, but the importance to magnetic reconnection is not generally recognized. Two-coordinate models are too constrained geometrically for the required entanglement, but otherwise the effect is general and can be studied in simple models. A simple model is introduced, which is periodic in the x and y Cartesian coordinates and bounded by perfectly conducting planes in z. Starting from a constant magnetic field in the z direction, reconnection is driven by a spatially smooth, bounded force. The model is complete and could be used to study the impulsive transfer of energy between the magnetic field and the ions and electrons using a kinetic plasma model.

Dynamics of nonlinear resonant slow MHD waves in twisted flux tubes

Directory of Open Access Journals (Sweden)

R. Erdélyi

2002-01-01

Full Text Available Nonlinear resonant magnetohydrodynamic (MHD waves are studied in weakly dissipative isotropic plasmas in cylindrical geometry. This geometry is suitable and is needed when one intends to study resonant MHD waves in magnetic flux tubes (e.g. for sunspots, coronal loops, solar plumes, solar wind, the magnetosphere, etc. The resonant behaviour of slow MHD waves is confined in a narrow dissipative layer. Using the method of simplified matched asymptotic expansions inside and outside of the narrow dissipative layer, we generalise the so-called connection formulae obtained in linear MHD for the Eulerian perturbation of the total pressure and for the normal component of the velocity. These connection formulae for resonant MHD waves across the dissipative layer play a similar role as the well-known Rankine-Hugoniot relations connecting solutions at both sides of MHD shock waves. The key results are the nonlinear connection formulae found in dissipative cylindrical MHD which are an important extension of their counterparts obtained in linear ideal MHD (Sakurai et al., 1991, linear dissipative MHD (Goossens et al., 1995; Erdélyi, 1997 and in nonlinear dissipative MHD derived in slab geometry (Ruderman et al., 1997. These generalised connection formulae enable us to connect solutions obtained at both sides of the dissipative layer without solving the MHD equations in the dissipative layer possibly saving a considerable amount of CPU-time when solving the full nonlinear resonant MHD problem.

Ideal MHD Stability Prediction and Required Power for EAST Advanced Scenario

International Nuclear Information System (INIS)

Chen Junjie; Li Guoqiang; Qian Jinping; Liu Zixi

2012-01-01

The Experimental Advanced Superconducting Tokamak (EAST) is the first fully superconducting tokamak with a D-shaped cross-sectional plasma presently in operation. The ideal magnetohydrodynamic (MHD) stability and required power for the EAST advanced tokamak (AT) scenario with negative central shear and double transport barrier (DTB) are investigated. With the equilibrium code TOQ and stability code GATO, the ideal MHD stability is analyzed. It is shown that a moderate ratio of edge transport barriers' (ETB) height to internal transport barriers' (ITBs) height is beneficial to ideal MHD stability. The normalized beta β N limit is about 2.20 (without wall) and 3.70 (with ideal wall). With the scaling law of energy confinement time, the required heating power for EAST AT scenario is calculated. The total heating power P t increases as the toroidal magnetic field B T or the normalized beta β N is increased. (magnetically confined plasma)

High pressure MHD coal combustors investigation, phase 2

Science.gov (United States)

Iwata, H.; Hamberg, R.

1981-05-01

A high pressure MHD coal combustor was investigated. The purpose was to acquire basic design and support engineering data through systematic combustion experiments at the 10 and 20 thermal megawatt size and to design a 50 MW/sub t/ combustor. This combustor is to produce an electrically conductive plasma generated by the direct combustion of pulverized coal with hot oxygen enriched vitiated air that is seeded with potassium carbonate. Vitiated air and oxygen are used as the oxidizer, however, preheated air will ultimately be used as the oxidizer in coal fired MHD combustors.

A civil engineering approach to ideal MHD

International Nuclear Information System (INIS)

Jensen, V.O.

1992-01-01

It is well known that a magnetic field can be conceived as a medium where an isotropic compressive stress, B 2 /2μ 0 , is superimposed on a tensile stress, B 2 /μ 0 , parallel to the lines of force. When a stationary ideal MHD plasma is present in the magnetic field, the particle pressure adds to the magnetic stresses to form a combined stress tensor. Calculations of plasma equilibria based on this concept are very similar to calculations in civil engineering of static structures based on compressive, tensile, and shear stresses. Therefore the very simple physical pictures known from civil engineering when used in plasma physics provide simple physical understanding and facilitate the physical interpretation of the results. In an earlier paper the concept was used to derive and discuss the equilibrium equations for θ-, Z-, and screw pinches and the Grad-Shafranov shift in a tokamak plasma with circular cross sections of the flux surfaces. Here the concept is used to discuss the virial theorem and to obtain a simple physical interpretation of this theorem. We also reconsider the Grad-Shafranov shift in a tokamak plasma and show that a situation where all flux surfaces have circular cross sections cannot be an exact solution to the ideal MHD equations. (author) 3 refs., 3 figs

Differential neutrino rates and emissivities from the plasma process in astrophysical systems

International Nuclear Information System (INIS)

Ratkovic, Sasa; Iyer Dutta, Sharada; Prakash, Madappa

2003-01-01

The differential rates and emissivities of neutrino pairs from an equilibrium plasma are calculated for the wide range of density and temperature encountered in astrophysical systems. New analytical expressions are derived for the differential emissivities which yield total emissivities in full agreement with those previously calculated. The photon and plasmon pair production and absorption kernels in the source term of the Boltzmann equation for neutrino transport are provided. The appropriate Legendre coefficients of these kernels, in forms suitable for multi-group flux-limited diffusion schemes are also computed

Two-dimensional simulation of the MHD stability, (2)

International Nuclear Information System (INIS)

Kurita, Gen-ichi; Amano, Tsuneo.

1977-09-01

Growth rate and eigen-function of the MHD instability of a toroidal plasma were calculated numerically as an initial-boundary value problem. When a conducting shell is away from the plasma, toroidicity hardly influences growth rate of the external kink modes in a slender tokamak, but it stabilizes the modes in a fat tokamak. On the other hand, when the shell is near to the plasma, the unstable external modes are stabilized by both toroidicity and shell effect. (auth.)

Introduction to magnetohydrodynamics

CERN Document Server

Thompson, Ian

2016-01-01

Magnetohydrodynamics (MHD) plays a crucial role in astrophysics, planetary magnetism, engineering and controlled nuclear fusion. This comprehensive textbook emphasizes physical ideas, rather than mathematical detail, making it accessible to a broad audience. Starting from elementary chapters on fluid mechanics and electromagnetism, it takes the reader all the way through to the latest ideas in more advanced topics, including planetary dynamos, stellar magnetism, fusion plasmas and engineering applications. With the new edition, readers will benefit from additional material on MHD instabilities, planetary dynamos and applications in astrophysics, as well as a whole new chapter on fusion plasma MHD. The development of the material from first principles and its pedagogical style makes this an ideal companion for both undergraduate students and postgraduate students in physics, applied mathematics and engineering. Elementary knowledge of vector calculus is the only prerequisite.

Numerical simulation in plasma physics

International Nuclear Information System (INIS)

Samarskii, A.A.

1980-01-01

Plasma physics is not only a field for development of physical theories and mathematical models but also an object of application of the computational experiment comprising analytical and numerical methods adapted for computers. The author considers only MHD plasma physics problems. Examples treated are dissipative structures in plasma; MHD model of solar dynamo; supernova explosion simulation; and plasma compression by a liner. (Auth.)

Axisymmetric MHD stability of sharp-boundary Tokamaks

International Nuclear Information System (INIS)

Rebhan, E.; Salat, A.

1976-09-01

For a sharp-boundary, constant pressure plasma model of axisymmetric equilibria the MHD stability problem of axisymmetric perturbations is solved by analytic reduction to a one-dimensional problem on the boundary and subsequent numerical treatment, using the energy principle. The stability boundaries are determined for arbitrary aspect ratio, arbitrary βsub(p) and elliptical, triangular and rectangular plasma cross-sections, wall stabilization not being taken into account. It is found that the axisymmetric stability strongly depends on the plasma shape and is almost independent of the safety factor q. (orig.) [de

Comparison of MHD-induced rotation damping with NTV predictions on MAST

International Nuclear Information System (INIS)

Hua, M-D; Chapman, I T; Field, A R; Hastie, R J; Pinches, S D

2010-01-01

Plasma rotation in tokamaks is of special interest for its potential stabilizing effect on micro- and macro-instabilities, leading to increased confinement. In MAST, the torque from neutral beam injection can spin the plasma to a core velocity ∼300 km s -1 (Alfven Mach number ∼0.3). Low density plasmas often exhibit a weakly non-monotonic safety factor profile just above unity. Theory predicts that such equilibria are prone to magneto-hydro-dynamic (MHD) instabilities, which was confirmed by recent observations. The appearance of the mode is accompanied by strong damping of core rotation on a timescale much faster than the momentum confinement time. The mode's saturated structure is estimated using the CASTOR code together with soft x-ray measurements, enabling the calculation of the plasma braking by the MHD mode according to neoclassical toroidal viscosity (NTV) theory. The latter exhibits strong similarities with the torque measured experimentally.

Ion temperature increase during MHD events on the TST-2 spherical tokamak

International Nuclear Information System (INIS)

Ejiri, A.; Shiraiwa, S.; Takase, Y.; Yamada, T.; Nagashima, Y.; Kasahara, H.; Iijima, D.; Kobori, Y.; Nishi, T.; Taniguchi, T.; Aramasu, M.; Ohara, S.; Ushigome, M.; Yamagishi, K.

2003-01-01

Various types of MHD events including internal reconnection events are studied on the TST-2 spherical tokamak. In weak MHD events no positive current spike was observed, but in strong MHD events with positive current spikes, a rapid and significant impurity ion temperature increase was observed. The decrease in the poloidal magnetic energy is the most probable energy source for ion heating. The plasma current shows a stepwise change. The magnitude of this step correlates with the temperature increase and is found to be a good indicator of the strength of each event. (author)

Proceedings of the eighth international colloquium on ultraviolet and x-ray spectroscopy of astrophysical and laboratory plasmas (IAU colloquium 86)

International Nuclear Information System (INIS)

1984-01-01

This volume represents the Proceedings of the Eighth International Colloquium on Ultraviolet and X-Ray Spectroscopy of Astrophysical and Laboratory Plasmas. The aim of this series of colloquia has been to bring together workers in the fields of astrophysical spectroscopy, laboratory spectroscopy and atomic physics in order to exchange ideas and results on problems which are common to these different disciplines. In addition to the presented papers there was a poster paper session

Proceedings of the eighth international colloquium on ultraviolet and x-ray spectroscopy of astrophysical and laboratory plasmas (IAU colloquium 86)

Energy Technology Data Exchange (ETDEWEB)

1984-01-01

This volume represents the Proceedings of the Eighth International Colloquium on Ultraviolet and X-Ray Spectroscopy of Astrophysical and Laboratory Plasmas. The aim of this series of colloquia has been to bring together workers in the fields of astrophysical spectroscopy, laboratory spectroscopy and atomic physics in order to exchange ideas and results on problems which are common to these different disciplines. In addition to the presented papers there was a poster paper session. (WRF)

Compact torus theory: MHD equilibrium and stability

International Nuclear Information System (INIS)

Barnes, D.C.; Seyler, C.E.; Anderson, D.V.

1979-01-01

Field reversed theta pinches have demonstrated the production and confinement of compact toroidal configurations with surprisingly good MHD stability. In these observations, the plasma is either lost by diffusion or by the loss of the applied field or is disrupted by an n = 2 (where n is the toroidal mode number) rotating instability only after 30 to 100 MHD times, when the configuration begins to rotate rigidly above a critical speed. These experiments have led one to investigate the equilibrium, stability, and rotation of a very elongated, toroidally axisymmetric configuration with no toroidal field. Many of the above observations are explained by recent results of these investigations which are summarized

From the Telescope to the Laboratory and Back Again: The Center for Astrophysical Plasma Properties

Science.gov (United States)

Houston Montgomery, Michael; Winget, Don; Schaeuble, Marc; Hawkins, Keith; Wheeler, Craig

2018-01-01

The Center for Astrophysical Plasma Properties (CAPP) is a new center focusing on the spectroscopic properties of stars and accretion disks using “at-parameter” experiments. Currently, these experiments use the X-ray output of the Z machine at Sandia National Laboratories—the largest X-ray source in the world—to heat plasmas to the same conditions (temperature, density, and radiation environment) as those observed in astronomical objects. Current experiments include measuring (1) density-dependent opacities of iron-peak elements at solar interior conditions, (2) spectral lines of low-Z elements at white dwarf photospheric conditions, (3) atomic population kinetics of neon in a radiation-dominated environment, and (4) resonant Auger destruction (RAD) of silicon at accretion disk conditions around supermassive black holes. We will be moving to new astrophysical environments and additional experimental facilities, such as the National Ignition Facility (NIF) and the OMEGA facility at the Laboratory for Laser Energetics (LLE). We seek students and collaborators to work on these experiments as well as the calculations that complement them. CAPP has funding for 5 years and can support up to six graduate students and three post-docs.

Hydrodynamic Instability, Integrated Code, Laboratory Astrophysics, and Astrophysics

Science.gov (United States)

Takabe, Hideaki

2016-10-01

This is an article for the memorial lecture of Edward Teller Medal and is presented as memorial lecture at the IFSA03 conference held on September 12th, 2003, at Monterey, CA. The author focuses on his main contributions to fusion science and its extension to astrophysics in the field of theory and computation by picking up five topics. The first one is the anomalous resisitivity to hot electrons penetrating over-dense region through the ion wave turbulence driven by the return current compensating the current flow by the hot electrons. It is concluded that almost the same value of potential as the average kinetic energy of the hot electrons is realized to prevent the penetration of the hot electrons. The second is the ablative stabilization of Rayleigh-Taylor instability at ablation front and its dispersion relation so-called Takabe formula. This formula gave a principal guideline for stable target design. The author has developed an integrated code ILESTA (ID & 2D) for analyses and design of laser produced plasma including implosion dynamics. It is also applied to design high gain targets. The third is the development of the integrated code ILESTA. The forth is on Laboratory Astrophysics with intense lasers. This consists of two parts; one is review on its historical background and the other is on how we relate laser plasma to wide-ranging astrophysics and the purposes for promoting such research. In relation to one purpose, I gave a comment on anomalous transport of relativistic electrons in Fast Ignition laser fusion scheme. Finally, I briefly summarize recent activity in relation to application of the author's experience to the development of an integrated code for studying extreme phenomena in astrophysics.

Tenth International Colloquium on UV and X-Ray Spectroscopy of Astrophysical and Laboratory Plasmas

Science.gov (United States)

Silver, Eric H.; Kahn, Steven M.

UV and X-ray spectroscopy of astrophysical and laboratory plasmas draws interest from many disciplines. Contributions from international specialists are collected together in this book from a timely recent conference. In astrophysics, the Hubble Space Telescope, Astro 1 and ROSAT observatories are now providing UV and X-ray spectra and images of cosmic sources in unprecedented detail, while the Yohkoh mission recently collected superb data on the solar corona. In the laboratory, the development of ion-trap facilities and novel laser experiments are providing vital new data on high temperature plasmas. Recent innovations in the technology of spectroscopic instrumentation are discussed. These papers constitute an excellent up-to-date review of developments in short-wavelength spectroscopy and offer a solid introduction to its theoretical and experimental foundations. These proceedings give an up-to-date review of developments in short-wavelength spectroscopy and offer a solid introduction to its theoretical and experimental foundations. Various speakers presented some of the first results from the high resolution spectrograph on the Hubble Space Telescope, the high sensitivity far ultraviolet and X-ray spectrometers of the ASTRO 1 Observatory, the imaging X-ray spectrometer on the ROSAT Observatory, and the high resolution solar X-ray spectrometer on Yohkoh. The development of ion trap devices had brought about a revolution in laboratory investigations of atomic processes in highly charged atoms. X-ray laser experiments had not only yielded considerable insight into electron ion interactions in hot dense plasmas, but also demonstrated the versatility of laser plasmas as laboratory X-ray sources. Such measurements also motivated and led to refinements in the development of large-scale atomic and molecular codes. On the instrumental side, the design and development of the next series of very powerful short wavelength observatories had generated a large number of

General Physical Problems Related to MHD. Shock Tubes. Introduction to Papers in Section 1-b

Energy Technology Data Exchange (ETDEWEB)

NONE

1966-10-15

The papers which will be considered here are Nos. SM-74/26, 134, 172, 182 and 219. Each of the five papers will be discussed in turn, but before beginning this discussion, some general comments concerning shock tube studies of MHD generator plasmas seem in order. There is little doubt that the shock tube is an excellent facility-for the study of the basic processes which occur in the bulk of the plasma. It provides a large flow of uniform plasma with well-controlled properties. Because of the very short operating times, the materials problems, which plague continuously operating facilities, are eliminated. Depending upon the mode of operation of the shock tube, the gas dynamic conditions of an MHD generator may also be simulated more or less well. Three different modes have been used by the authors of the present papers. Abbas and Howatson have carried out their measurements in the driver plasma of an electrical shock tube. Both Zauderer and Mori, Kawada, Yamamoto and Imani have used the more conventional technique of experimenting in the plasma produced by the incident shock. Louis uses the plasma produced by reflection of the shock wave from the tube-end as a plasma source for the MHD channel.

MHD stability limits in the TCV Tokamak

Energy Technology Data Exchange (ETDEWEB)

Reimerdes, H. [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)

2001-07-01

Magnetohydrodynamic (MHD) instabilities can limit the performance and degrade the confinement of tokamak plasmas. The Tokamak a Configuration Variable (TCV), unique for its capability to produce a variety of poloidal plasma shapes, has been used to analyse various instabilities and compare their behaviour with theoretical predictions. These instabilities are perturbations of the magnetic field, which usually extend to the plasma edge where they can be detected with magnetic pick-up coils as magnetic fluctuations. A spatially dense set of magnetic probes, installed inside the TCV vacuum vessel, allows for a fast observation of these fluctuations. The structure and temporal evolution of coherent modes is extracted using several numerical methods. In addition to the setup of the magnetic diagnostic and the implementation of analysis methods, the subject matter of this thesis focuses on four instabilities, which impose local and global stability limits. All of these instabilities are relevant for the operation of a fusion reactor and a profound understanding of their behaviour is required in order to optimise the performance of such a reactor. Sawteeth, which are central relaxation oscillations common to most standard tokamak scenarios, have a significant effect on central plasma parameters. In TCV, systematic scans of the plasma shape have revealed a strong dependence of their behaviour on elongation {kappa} and triangularity {delta}, with high {kappa}, and low {delta} leading to shorter sawteeth with smaller crashes. This shape dependence is increased by applying central electron cyclotron heating. The response to additional heating power is determined by the role of ideal or resistive MHD in triggering the sawtooth crash. For plasma shapes where additional heating and consequently, a faster increase of the central pressure shortens the sawteeth, the low experimental limit of the pressure gradient within the q = 1 surface is consistent with ideal MHD predictions. The

Two-dimensional simulation of the MHD stability, (1)

International Nuclear Information System (INIS)

Kurita, Gen-ichi; Amano, Tsuneo.

1976-03-01

The two-dimensional computer code has been prepared to study MHD stability of an axisymmetric toroidal plasma with and without the surrounding vacuum region. It also includes the effect of magnetic surfaces with non-circular cross sections. The linearized equations of motion are solved as an initial value problem. The results by computer simulation are compared with those by the theory for the cylindrical plasma; they are in good agreement. (auth.)

Wave turbulence in magnetized plasmas

Directory of Open Access Journals (Sweden)

S. Galtier

2009-02-01

Full Text Available The paper reviews the recent progress on wave turbulence for magnetized plasmas (MHD, Hall MHD and electron MHD in the incompressible and compressible cases. The emphasis is made on homogeneous and anisotropic turbulence which usually provides the best theoretical framework to investigate space and laboratory plasmas. The solar wind and the coronal heating problems are presented as two examples of application of anisotropic wave turbulence. The most important results of wave turbulence are reported and discussed in the context of natural and simulated magnetized plasmas. Important issues and possible spurious interpretations are also discussed.

The magnetic universe geophysical and astrophysical dynamo theory

CERN Document Server

Rüdiger, Günther

2004-01-01

Magnetism is one of the most pervasive features of the Universe, with planets, stars and entire galaxies all having associated magnetic fields. All of these fields are generated by the motion of electrically conducting fluids, the so-called dynamo effect. The precise details of what drives the motion, and indeed what the fluid consists of, differ widely though. In this work the authors draw upon their expertise in geophysical and astrophysical MHD to explore some of these phenomena, and describe the similarities and differences between different magnetized objects. They also explain why magn

Conceptual design analysis of an MHD power conversion system for droplet-vapor core reactors. Final report

International Nuclear Information System (INIS)

Anghaie, S.; Saraph, G.

1995-01-01

A nuclear driven magnetohydrodynamic (MHD) generator system is proposed for the space nuclear applications of few hundreds of megawatts. The MHD generator is coupled to a vapor-droplet core reactor that delivers partially ionized fissioning plasma at temperatures in range of 3,000 to 4,000 K. A detailed MHD model is developed to analyze the basic electrodynamics phenomena and to perform the design analysis of the nuclear driven MHD generator. An incompressible quasi one dimensional model is also developed to perform parametric analyses

Experimental identification of nonlinear coupling between (intermediate, small)-scale microturbulence and an MHD mode in the core of a superconducting tokamak

Science.gov (United States)

Sun, P. J.; Li, Y. D.; Ren, Y.; Zhang, X. D.; Wu, G. J.; Xu, L. Q.; Chen, R.; Li, Q.; Zhao, H. L.; Zhang, J. Z.; Shi, T. H.; Wang, Y. M.; Lyu, B.; Hu, L. Q.; Li, J.; The EAST Team

2018-01-01

In this paper, we present clear experimental evidence of core region nonlinear coupling between (intermediate, small)-scale microturbulence and an magnetohydrodynamics (MHD) mode during the current ramp-down phase in a set of L-mode plasma discharges in the experimental advanced superconducting tokamak (EAST, Wan et al (2006 Plasma Sci. Technol. 8 253)). Density fluctuations of broadband microturbulence (k\\perpρi˜2{-}5.2 ) and the MHD mode (toroidal mode number m = -1 , poloidal mode number n = 1 ) are measured simultaneously, using a four-channel tangential CO2 laser collective scattering diagnostic in core plasmas. The nonlinear coupling between the broadband microturbulence and the MHD mode is directly demonstrated by showing a statistically significant bicoherence and modulation of turbulent density fluctuation amplitude by the MHD mode.

Pulsed power sources based on MHD generators (A state-of-art review)

International Nuclear Information System (INIS)

Das, A.K.; Venkatramani, N.; Rohatgi, V.K.

1986-01-01

pulsed Power sources are finding increased applications in powering plasma experiments, CTF devices, investigations of structure of earth's crust or self-contained compact power supplies for military applications. This report reviews the development of magnetohydrodynamic (MHD) power systems for pulsed power applications. The major critical components, which are analysed in detail, include the combustor, high energy fuel development, high field magnet, high power density channel and power conditioning unit. The report concludes that the MHD research has now reached a stage, where it is possible to design and achieve requisite performance from short duration high power compact MHD generators. (author)

Nonlinear MHD dynamics of tokamak plasmas on multiple time scales

International Nuclear Information System (INIS)

Kruger, S.E.; Schnack, D.D.; Brennan, D.P.; Gianakon, T.A.; Sovinec, C.R.

2003-01-01

Two types of numerical, nonlinear simulations using the NIMROD code are presented. In the first simulation, we model the disruption occurring in DIII-D discharge 87009 as an ideal MHD instability driven unstable by neutral-beam heating. The mode grows faster than exponential, but on a time scale that is a hybrid of the heating rate and the ideal MHD growth rate as predicted by analytic theory. The second type of simulations, which occur on a much longer time scale, focus on the seeding of tearing modes by sawteeth. Pressure effects play a role both in the exterior region solutions and in the neoclassical drive terms. The results of both simulations are reviewed and their implications for experimental analysis is discussed. (author)

Lecture and Poster Presentations

International Nuclear Information System (INIS)

2008-01-01

The motivation for this conference is the growing interest of the astrophysical community in the application of kinetic plasma methods to the problems of modern astrophysics. The intent of the meeting is therefore to review the recent progress in this field in wide range of astrophysical applications and to confront the results with observations. The main emphasis of the meeting will be on kinetic plasma methods - numerical (Particle-In-Cell and hybrid simulations) as well as analytical. However, the progress in the MHD modeling of astrophysical plasmas will also be reviewed to enable comparison with kinetic methods and stimulate discussion on what approach is the most appropriate tool to study astrophysical sources. All main topics will also be reviewed from observational perspective

Study of MHD stability beta limit in LHD by hierarchy integrated simulation code

International Nuclear Information System (INIS)

Sato, M.; Watanabe, K.Y.; Nakamura, Y.

2008-10-01

The beta limit by the ideal MHD instabilities (so-called 'MHD stability beta limit') for helical plasmas is studied by a hierarchy integrated simulation code. A numerical model for the effect of the MHD instabilities is introduced such that the pressure profile is flattened around the rational surface due to the MHD instabilities. The width of the flattening of the pressure gradient is determined from the width of the eigenmode structure of the MHD instabilities. It is assumed that there is the upper limit of the mode number of the MHD instabilities which directly affect the pressure gradient. The upper limit of the mode number is determined using a recent high beta experiment in the Large Helical Device (LHD). The flattening of the pressure gradient is calculated by the transport module in a hierarchy integrated code. The achievable volume averaged beta value in the LHD is expected to be beyond 6%. (author)

Astrophysics in a nutshell from the telescope to the sputnik

International Nuclear Information System (INIS)

Alfven, H.; Faelthammar, C.G.

1988-03-01

Progress in astrophysics - as well as in many other sciences - is not only due to new ideas but also to the introduction of new methods of observation. The 'Copernican revolution' was more due to the introduction of the telescope than to the heliocentric model which had been invented 2000 years earlier. Further, the decisive importance of electromagnetic effects in astrophysics originated from Langmuir's invention of the plasma probe and from Birkeland's terrella experiment and his observations of plasma in space (aurora). A similar revolution has now been introduced by space research which has made possible in situ measurements in cosmic plasmas and has opened the X-ray and γ-ray regions to observation. The result is a drastic revision of essential parts of astrophysics (including cosmology) leading to the 'Plasma Universe' model. (authors)

A nonlinear structural subgrid-scale closure for compressible MHD. I. Derivation and energy dissipation properties

Energy Technology Data Exchange (ETDEWEB)

Vlaykov, Dimitar G., E-mail: Dimitar.Vlaykov@ds.mpg.de [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck-Institut für Dynamik und Selbstorganisation, Am Faßberg 17, D-37077 Göttingen (Germany); Grete, Philipp [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Schmidt, Wolfram [Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg (Germany); Schleicher, Dominik R. G. [Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160-C (Chile)

2016-06-15

Compressible magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical phenomena ranging from the intergalactic to the stellar scales. In studying them, numerical simulations are nearly inescapable, due to the large degree of nonlinearity involved. However, the dynamical ranges of these phenomena are much larger than what is computationally accessible. In large eddy simulations (LESs), the resulting limited resolution effects are addressed explicitly by introducing to the equations of motion additional terms associated with the unresolved, subgrid-scale dynamics. This renders the system unclosed. We derive a set of nonlinear structural closures for the ideal MHD LES equations with particular emphasis on the effects of compressibility. The closures are based on a gradient expansion of the finite-resolution operator [W. K. Yeo (CUP, 1993)] and require no assumptions about the nature of the flow or magnetic field. Thus, the scope of their applicability ranges from the sub- to the hyper-sonic and -Alfvénic regimes. The closures support spectral energy cascades both up and down-scale, as well as direct transfer between kinetic and magnetic resolved and unresolved energy budgets. They implicitly take into account the local geometry, and in particular, the anisotropy of the flow. Their properties are a priori validated in Paper II [P. Grete et al., Phys. Plasmas 23, 062317 (2016)] against alternative closures available in the literature with respect to a wide range of simulation data of homogeneous and isotropic turbulence.

Performance of the CNEN MHD Blow-Down Loop Facility

Energy Technology Data Exchange (ETDEWEB)

Bertolini, E.; Brown, R.; Gasparotto, M.; Gay, P.; Toschi, R. [Laboratorio Conversione Diretta, CNEN, Frascati (Italy)

1968-11-15

The CNEN facility has been designed, manufactured and used for alkali-seeded noble gas MHD energy conversion research, as the major experimental effort during the first five-year CNEN Research Programme on MHD. The main specifications and the general arrangement with information on preliminary commissioning tests of some components were given at the Salzburg Symposium. Since then the facility has been successfully commissioned and from March 1967 has been working on MHD experiments. Efforts were made to reduce any adverse effects on the experimental MHD results that were due to inherent limitations of an experimental apparatus (particularly under open-circuit conditions). Great emphasis was placed on problems of caesium vaporization and the mixing with helium, the purity level of the mixture, measurements and the control system. The insulation of the plasma from ground was carefully treated, increasing the ratio between insulator resistance and typical plasma resistance as much as possible. Fluidynamic tests at room and high temperatures have shown that stability in the gas parameters (temperature, pressure and mass flow) can be maintained within few per cent for tens of seconds after a transient, giving a behaviour similar to a continuously running system. The high- temperature, alumina pebble-bed heater has successfully operated, bringing the helium-caesium mixtures up to 2000 Degree-Sign K and up to 4 atm abs pressure, and undergoing seven thermal cycles, for a total of more than 2000 hours operation at top temperature. Preheated generator ducts using alumina as insulator and tantalum for electrodes performed satisfactorily, very much attention having been given in the design to reduction of thermal shocks and to obviating possible paths for caesium leakage and short-circuiting of electrode leads. The pulsed liquid nitrogen precooled magnet has been run for about 50 pulses at high field ( Asymptotically-Equal-To 4.5 tesla) with an operating time of about 10

Plasmafysica - een nieuwe positiebepaling

NARCIS (Netherlands)

Schram, D.C.; Kuperus, M.; Sluijter, F.W.

1982-01-01

Reviews recent developments in plasma physics, with special reference to the prospect of fusion of light atomic nuclei. A table summarises properties of low-temperature plasmas. The Joint European Torus, MHD generators, INTOR and special applications in atomic physics and astrophysics are discussed

Astrophysical opacity library

International Nuclear Information System (INIS)

Huebner, W.F.; Merts, A.L.; Magee, N.H. Jr.; Argo, M.F.

1977-08-01

The astrophysical elements opacity library includes equation of state data, various mean opacities, and 2000 values of the frequency-dependent extinction coefficients in equally spaced intervals u identical with hν/kT from 0 to 20 for 41 degeneracy parameters eta from -28 (nondegenerate) to 500 and 46 temperatures kT from 1 eV to 100 keV. Among available auxiliary quantities are the free electron density, mass density, and plasma cutoff frequency. A library-associated program can produce opacities for mixtures with up to 20 astrophysically abundant constituent elements at 4 levels of utility for the user

Elms: MHD Instabilities at the transport barrier

Energy Technology Data Exchange (ETDEWEB)

Huysmans, G.T.A

2005-07-01

Significant progress has been made in recent years both on the experimental characterisation of ELMs (edge localized modes) and the theory and modelling of ELMs. The observed maximum pressure gradient is in good agreement with the calculated ideal MHD stability limits due to peeling-ballooning modes. The dependence on plasma current and plasma shape are also reproduced by the ideal MHD model. It will be a challenge to verify experimentally the influence of the extensions to the ideal MHD theory such as the possibly incomplete diamagnetic stabilisation, the influence of shear flow, finite resistivity or the stabilizing influence of the separatrix on peeling modes. The observations of the filamentary structures find their explanation in the theory and simulations of the early non-linear phase of the evolution of ballooning modes. One of the remaining open questions is what determines the size of the ELM and its duration. This is related to the loss mechanism of energy and density. Some heuristic descriptions of possible mechanisms have been proposed in literature but none of the models so far makes quantitative predictions on the ELM size. Also the numerical simulations are not yet advanced to the point where the full ELM crash can be modelled. The theory and simulations of the ELMs are necessary to decide between the possible parameters, such as the collisionality or the parallel transport time, that are proposed for the extrapolation of ELM sizes to ITER.

Elms: MHD Instabilities at the transport barrier

International Nuclear Information System (INIS)

Huysmans, G.T.A.

2005-01-01

Significant progress has been made in recent years both on the experimental characterisation of ELMs (edge localized modes) and the theory and modelling of ELMs. The observed maximum pressure gradient is in good agreement with the calculated ideal MHD stability limits due to peeling-ballooning modes. The dependence on plasma current and plasma shape are also reproduced by the ideal MHD model. It will be a challenge to verify experimentally the influence of the extensions to the ideal MHD theory such as the possibly incomplete diamagnetic stabilisation, the influence of shear flow, finite resistivity or the stabilizing influence of the separatrix on peeling modes. The observations of the filamentary structures find their explanation in the theory and simulations of the early non-linear phase of the evolution of ballooning modes. One of the remaining open questions is what determines the size of the ELM and its duration. This is related to the loss mechanism of energy and density. Some heuristic descriptions of possible mechanisms have been proposed in literature but none of the models so far makes quantitative predictions on the ELM size. Also the numerical simulations are not yet advanced to the point where the full ELM crash can be modelled. The theory and simulations of the ELMs are necessary to decide between the possible parameters, such as the collisionality or the parallel transport time, that are proposed for the extrapolation of ELM sizes to ITER

Computational studies of tokamak plasmas

International Nuclear Information System (INIS)

Takizuka, Tomonori; Tsunematsu, Toshihide; Tokuda, Shinji

1981-02-01

Computational studies of tokamak plasmas are extensively advanced. Many computational codes have been developed by using several kinds of models, i.e., the finite element formulation of MHD equations, the time dependent multidimensional fluid model, and the particle model with the Monte-Carlo method. These codes are applied to the analyses of the equilibrium of an axisymmetric toroidal plasma (SELENE), the time evolution of the high-beta tokamak plasma (APOLLO), the low-n MHD stability (ERATO-J) and high-n ballooning mode stability (BOREAS) in the INTOR tokamak, the nonlinear MHD stability, such as the positional instability (AEOLUS-P), resistive internal mode (AEOLUS-I) etc., and the divertor functions. (author)

Measured MHD equilibrium in Alcator C

International Nuclear Information System (INIS)

Pribyl, P.A.

1986-03-01

A method of processing data from a set of partial Rogowski loops is developed to study the MHD equilibrium in Alcator C. Time dependent poloidal fields in the vicinity of the plasma are calculated from measured currents, with field penetration effects being accounted for. Fields from eddy currents induced by the plasma in the tokamak structure are estimated as well. Each of the set of twelve B/sub θ/ measurements can then be separated into a component from the plasma current and a component from currents external to the pickup loops. Harmonic solutions to Maxwell's equations in toroidal coordinates are fit to these measurements in order to infer the fields everywhere in the vacuum region surrounding the plasma. Using this diagnostic, plasma current, position, shape, and the Shafranov term Λ = β/sub p/ + l/sub i//2 - 1 may be computed, and systematic studies of these plasma parameters are undertaken for Alcator C plasmas

Effect of Trapped Energetic Ions on MHD Activity in Spherical Tori

International Nuclear Information System (INIS)

White, R.B.; Kolesnichenko, Ya.I.; Lutsenko, V.V.; Marchenko, V.S.

2002-01-01

It is shown that the increase of beta (the ratio of plasma pressure to the magnetic field pressure) may change the character of the influence of trapped energetic ions on MHD stability in spherical tori. Namely, the energetic ions, which stabilize MHD modes (such as the ideal-kink mode, collisionless tearing mode, and semi-collisional tearing mode) at low beta, have a destabilizing influence at high beta unless the radial distribution of the energetic ions is very peaked

Plasma properties

International Nuclear Information System (INIS)

Weitzner, H.

1990-06-01

This paper discusses the following topics: MHD plasma activity: equilibrium, stability and transport; statistical analysis; transport studies; edge physics studies; wave propagation analysis; basic plasma physics and fluid dynamics; space plasma; and numerical methods

Plasma physics

International Nuclear Information System (INIS)

1979-01-01

This report contains the papers delivered at the AEB - Natal University summer school on plasma physics held in Durban during January 1979. The following topics were discussed: Tokamak devices; MHD stability; trapped particles in tori; Tokamak results and experiments; operating regime of the AEB Tokamak; Tokamak equilibrium; high beta Tokamak equilibria; ideal Tokamak stability; resistive MHD instabilities; Tokamak diagnostics; Tokamak control and data acquisition; feedback control of Tokamaks; heating and refuelling; neutral beam injection; radio frequency heating; nonlinear drift wave induced plasma transport; toroidal plasma boundary layers; microinstabilities and injected beams and quasilinear theory of the ion acoustic instability

Stationary shear flows in CGL anisotropic toroidal plasmas

International Nuclear Information System (INIS)

Pastukhov, V.P.; Ilgisonis, V.I.

1996-01-01

Recently a general structure of stationary shear flows in toroidal plasmas was obtained in the frame of ideal isotropic-pressure MHD model. The structure of the stationary plasma flows was shown to be determined by a hidden symmetry of MHD equations inherent in the toroidal systems with nested magnetic surfaces. However, the characteristic frequencies of the stationary plasma motion can considerably exceed the collisional frequencies in real plasma experiments. In this case the CGL collisionless MHD model seems to be more adequate than the simplified isotropic-pressure MHD model to describe the stationary plasma flows. In this paper we have generalized our approach to analyze the stationary plasma flows in the frame of the collisionless CGL model. We have found again that the hidden symmetry inherent in the toroidal topology results in two integral invariants which depend on two independent surface functions. The structure of stationary flows for CGL model is still the same as for isotropic MHD, however, the pressure tensor components satisfy a appreciably modifies the steady state force-balance equation. These results are applied to analyze the generalized equilibrium in axisymmetric (tokamak-like) magnetic confinement systems

Planar and nonplanar ion acoustic shock waves in relativistic degenerate astrophysical electron-positron-ion plasmas

Energy Technology Data Exchange (ETDEWEB)

Ata-ur-Rahman,; Qamar, A. [Institute of Physics and Electronics, University of Peshawar, Peshawar 25000 (Pakistan); National Centre for Physics, QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, QAU Campus, Shahdrah Valley Road, Islamabad 44000 (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan)

2013-04-15

We have studied the propagation of ion acoustic shock waves involving planar and non-planar geometries in an unmagnetized plasma, whose constituents are non-degenerate ultra-cold ions, relativistically degenerate electrons, and positrons. By using the reductive perturbation technique, Korteweg-deVries Burger and modified Korteweg-deVries Burger equations are derived. It is shown that only compressive shock waves can propagate in such a plasma system. The effects of geometry, the ion kinematic viscosity, and the positron concentration are examined on the ion acoustic shock potential and electric field profiles. It is found that the properties of ion acoustic shock waves in a non-planar geometry significantly differ from those in planar geometry. The present study has relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments) and in dense astrophysical objects.

Recent progress on astrophysical opacity

International Nuclear Information System (INIS)

Rogers, F.J.; Iglesias, C.A.

1992-08-01

Improvements in the calculation of the opacity of astrophysical plasmas has helped to resolve several long-standing puzzles in the modeling of variable stars. The most significant opacity enhancements over the Los Alamos Astrophysical Library (LAOL) are due to improvements in the equation of state and atomic physics. Comparison with experiment has corroborated the predicted large opacity increases due to transitions in M-shell iron. We give a summary of recent developments

MINIMIZING THE MHD POTENTIAL ENERGY FOR THE CURRENT HOLE REGION IN TOKAMAKS

International Nuclear Information System (INIS)

CHU, M.S; PARKS, P.B

2004-01-01

The current hole region in the tokamak has been observed to arise naturally during the development of internal transport barriers. The magnetohydrodynamic (MHD) potential energy in the current hole region is shown to be determined completely in terms of the displacements at the edge of the current hole. For modes with finite toroidal mode number n ≠ 0, the minimized potential energy is the same as if the current hole region were a vacuum region. For modes with toroidal mode number n = 0, the displacement is a superposition of three types of independent displacements: a vertical displacement or displacements that compress only the plasma or the toroidal field uniformly. Thus for ideal MHD perturbations of plasma with a current hole, the plasma behaves as if it were bordered by an extra ''internal vacuum region''. The relevance of the present work to computer simulations of plasma with a current hole region is also discussed

Energetic particle physics with applications in fusion and space plasmas

International Nuclear Information System (INIS)

Cheng, C.Z.

1997-01-01

Energetic particle physics is the study of the effects of energetic particles on collective electromagnetic (EM) instabilities and energetic particle transport in plasmas. Anomalously large energetic particle transport is often caused by low frequency MHD instabilities, which are driven by these energetic particles in the presence of a much denser background of thermal particles. The theory of collective energetic particle phenomena studies complex wave-particle interactions in which particle kinetic physics involving small spatial and fast temporal scales can strongly affect the MHD structure and long-time behavior of plasmas. The difficulty of modeling kinetic-MHD multiscale coupling processes stems from the disparate scales which are traditionally analyzed separately: the macroscale MHD phenomena are studied using the fluid MHD framework, while microscale kinetic phenomena are best described by complicated kinetic theories. The authors have developed a kinetic-MHD model that properly incorporates major particle kinetic effects into the MHD fluid description. For tokamak plasmas a nonvariational kinetic-MHD stability code, the NOVA-K code, has been successfully developed and applied to study problems such as the excitation of fishbone and Toroidal Alfven Eigenmodes (TAE) and the sawtooth stabilization by energetic ions in tokamaks. In space plasmas the authors have employed the kinetic-MHD model to study the energetic particle effects on the ballooning-mirror instability which explains the multisatellite observation of the stability and field-aligned structure of compressional Pc 5 waves in the magnetospheric ring current plasma

Equilibrium and linear analysis of rotating plasmas: fluid and guiding center results

International Nuclear Information System (INIS)

Iacono, R.

1990-06-01

This work is devoted to the equilibrium and stability of rotating plasmas. Apart from its theoretical interest, this subject has become of practical importance in fusion research, due to the use in recent tokamak experiments of auxiliary heating methods such as neutral-beam injection, which can produce large plasma flows. Flow velocities up to the ion sound speed have been measured on different machines and new phenomena associated with the flow, such as distorsions of the plasma equilibrium profiles, have been observed. As a consequence, flows must be included in the macroscopic description of plasma equilibrium, which is the basis for the analysis and the design of magnetic confinement machines, and the stability properties of equilibria with flows need to be investigated. Here, attention is centered on toroidal confinement machines and in particular on tokamaks. However, some of the results to be presented may be of interest also for other domains (strong mass flows also occur in astrophysical and geophysical contexts such as in the Jovian magnetosphere or in the Earth's magnetopause and plasmapause. It should be noted that equilibrium and, in particular, stability with flows are poorly understood at present. Therefore, many of the questions we will consider are of quite a general nature. We are not yet at the point where quantitative comparisons with specific experiments can be made. Even the choice of a convenient model to study plasma flow is far from being evident. So far most of the theoretical investigations have used the magnetohydrodynamic (MHD) model, which is one of the simplest descriptions of a plasma. In this work, however, it will be shown that, for rotating plasmas, the 'simple' MHD model can give very complicated and physically meaningless results, while more 'complicated' models can provide a simpler and more realistic description of the plasma behaviour. 65 refs., 8 figs., 3 tabs

MHD instability studies in ISX-B

International Nuclear Information System (INIS)

Pare, V.K.; Dunlap, J.L.; Navarro, A.P.; Burris, R.D.

1979-01-01

MHD instabilities in Ohmically and beam heated ISX-B plasmas have been studied using collimated x-ray and Mirnov loop diagnostics. The diagnostic systems will be described and the instability signals will be illustrated for a variety of discharges. The latter will include those observed in connection with low and high β operation, density clamping, pellet injection, and deliberate introduction of toroidal field ripple

Simulation of the MHD stabilities of the experiment on HL-2A tokamak by GATO code

International Nuclear Information System (INIS)

Pan Wei; Chen Liaoyuan; Dong Jiaqi; Shen Yong; Zhang Jinhua

2009-01-01

The ideal two-dimensional MHD stabilities code, GATO, has been successfully immigrated to the high-performance computing system of HL-2A and used to the simulation study of the ideal MHD stabilities of the plasmas produced by one of the pellets injection experiments on HL-2A tokamak. The EFIT code was used to reconstruct the equilibrium configures firstly and the GATO was used to compute their MHD stabilities secondly whose source data were obtained by the NO.4050 discharge of the experiments on HL-2A, and finally by analyzing these results the preliminary conclusion was devised that the confinement performance of the plasma was improved because of the stabilization effect of the anti-sheared configures created by the pellets injection. (authors)

Three-dimensional MHD simulation of a loop-like magnetic cloud in the solar wind

Czech Academy of Sciences Publication Activity Database

Vandas, Marek; Odstrčil, Dušan; Watari, S.

2002-01-01

Roč. 107, A9 (2002), s. SSH2-1 - SSH2-11 ISSN 0148-0227 R&D Projects: GA AV ČR KSK3012103; GA ČR GA205/99/1712; GA AV ČR IAA3003003; GA AV ČR IBS1003006 Institutional research plan: CEZ:AV0Z1003909 Keywords : magnetic cloud s * MHD simulations * interplanetary magnetic fields Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.245, year: 2002

EMAPS: An Efficient Multiscale Approach to Plasma Systems with Non-MHD Scale Effects

Energy Technology Data Exchange (ETDEWEB)

Omelchenko, Yuri A. [SciberQuest, Inc., Del Mar, CA (United States); Karimabadi, Homa [SciberQuest, Inc., Del Mar, CA (United States)

2014-10-14

Using Discrete-Event Simulation (DES) as a novel paradigm for time integration of large-scale physics-driven systems, we have achieved significant breakthroughs in simulations of multi-dimensional magnetized plasmas where ion kinetic and finite Larmor radius (FLR) and Hall effects play a crucial role. For these purposes we apply a unique asynchronous simulation tool: a parallel, electromagnetic Particle-in-Cell (PIC) code, HYPERS (Hybrid Particle Event-Resolved Simulator), which treats plasma electrons as a charge neutralizing fluid and solves a self-consistent set of non-radiative Maxwell, electron fluid equations and ion particle equations on a structured computational grid. HYPERS enables adaptive local time steps for particles, fluid elements and electromagnetic fields. This ensures robustness (stability) and efficiency (speed) of highly dynamic and nonlinear simulations of compact plasma systems such spheromaks, FRCs, ion beams and edge plasmas. HYPERS is a unique asynchronous code that has been designed to serve as a test bed for developing multi-physics applications not only for laboratory plasma devices but generally across a number of plasma physics fields, including astrophysics, space physics and electronic devices. We have made significant improvements to the HYPERS core: (1) implemented a new asynchronous magnetic field integration scheme that preserves local divB=0 to within round-off errors; (2) Improved staggered-grid discretizations of electric and magnetic fields. These modifications have significantly enhanced the accuracy and robustness of 3D simulations. We have conducted first-ever end-to-end 3D simulations of merging spheromak plasmas. The preliminary results show: (1) tilt-driven relaxation of a freely expanding spheromak to an m=1 Taylor helix configuration and (2) possibility of formation of a tilt-stable field-reversed configuration via merging and magnetic reconnection of two double-sided spheromaks with opposite helicities.

Stability analysis of resistive MHD modes via a new numerical matching technique

International Nuclear Information System (INIS)

Furukawa, M.; Tokuda, S.; Zheng, L.-J.

2009-01-01

Full text: Asymptotic matching technique is one of the principal methods for calculating linear stability of resistive magnetohydrodynamics (MHD) modes such as tearing modes. In applying the asymptotic method, the plasma region is divided into two regions: a thin inner layer around the mode-resonant surface and ideal MHD regions except for the layer. If we try to solve this asymptotic matching problem numerically, we meet practical difficulties. Firstly, the inertia-less ideal MHD equation or the Newcomb equation has a regular singular point at the mode-resonant surface, leading to the so-called big and small solutions. Since the big solution is not square-integrable, it needs sophisticated treatment. Even if such a treatment is applied, the matching data or the ratio of small solution to the big one, has been revealed to be sensitive to local MHD equilibrium accuracy and grid structure at the mode-resonant surface by numerical experiments. Secondly, one of the independent solutions in the inner layer, which should be matched onto the ideal MHD solution, is not square-integrable. The response formalism has been adopted to resolve this problem. In the present paper, we propose a new method for computing the linear stability of resistive MHD modes via matching technique, where the plasma region is divided into ideal MHD regions and an inner region with finite width. The matching technique using an inner region with finite width was recently developed for ideal MHD modes in cylindrical geometry, and good performance was shown. Our method extends this idea to resistive MHD modes. In the inner region, the low-beta reduced MHD equations are solved, and the solution is matched onto the solution of the Newcomb equation by using boundary conditions such that the parallel electric field vanishes properly as approaching the computational boundaries. If we use the inner region with finite width, the practical difficulties raised above can be avoided from the beginning. Figure

Weakly Ionized Plasmas in Hypersonics: Fundamental Kinetics and Flight Applications

International Nuclear Information System (INIS)

Macheret, Sergey

2005-01-01

The paper reviews some of the recent studies of applications of weakly ionized plasmas to supersonic/hypersonic flight. Plasmas can be used simply as means of delivering energy (heating) to the flow, and also for electromagnetic flow control and magnetohydrodynamic (MHD) power generation. Plasma and MHD control can be especially effective in transient off-design flight regimes. In cold air flow, nonequilibrium plasmas must be created, and the ionization power budget determines design, performance envelope, and the very practicality of plasma/MHD devices. The minimum power budget is provided by electron beams and repetitive high-voltage nanosecond pulses, and the paper describes theoretical and computational modeling of plasmas created by the beams and repetitive pulses. The models include coupled equations for non-local and unsteady electron energy distribution function (modeled in forward-back approximation), plasma kinetics, and electric field. Recent experimental studies at Princeton University have successfully demonstrated stable diffuse plasmas sustained by repetitive nanosecond pulses in supersonic air flow, and for the first time have demonstrated the existence of MHD effects in such plasmas. Cold-air hypersonic MHD devices are shown to permit optimization of scramjet inlets at Mach numbers higher than the design value, while operating in self-powered regime. Plasma energy addition upstream of the inlet throat can increase the thrust by capturing more air (Virtual Cowl), or it can reduce the flow Mach number and thus eliminate the need for an isolator duct. In the latter two cases, the power that needs to be supplied to the plasma would be generated by an MHD generator downstream of the combustor, thus forming the 'reverse energy bypass' scheme. MHD power generation on board reentry vehicles is also discussed

Simulation of MHD instability effects on burning plasma transport with ITB in tokamak and helical reactors

International Nuclear Information System (INIS)

Yamazaki, K.; Yamada, I.; Taniguchi, S.; Oishi, T.

2009-01-01

Full text: The high performance plasma behavior is required to realize economic and environmental-friendly fusion reactors compatible with conventional power plant systems. To improve plasma confinement, the formation of internal transport barrier (ITB) is anticipated, and its behavior is analyzed by the simulation code TOTAL (Toroidal Transport Linkage Analysis). This TOTAL code comprises a 2- or 3-dimensional equilibrium and 1-dimensional predictive transport code for both tokamak and helical systems. In the tokamak code TOTAL-T, the external current drive, bootstrap current, sawtooth oscillation, ballooning mode and neoclassical tearing mode (NTM) analyses are included. The steady-state burning plasma operation is achieved by the feedback control of pellet injection fuelling and external heating power control. The impurity dynamics of iron and tungsten is also included in this code. The NTM effects are evaluated using the modified Rutherford Model with the stabilization of the ECCD current drive. The excitation of m=2/n=1 NTM leads to the 20 % reduction in the central temperature in ITER-like reactors. Recently, the external non-resonant helical field application is analyzed and its stabilization properties are evaluated. The pellet injection effects on ITB formation is also clarified in tokamak and helical plasmas. Relationship between sawtooth oscillation and impurity ejection is recently simulated in comparison with experimental data. In this conference, we will show above-stated new results on MHD instability effects on burning plasma transport. (author)

Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

Science.gov (United States)

Chaplin, Vernon H.

This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel

Study of density fluctuations during MHD activity, soft landing discharges and major disruptions in TEXTOR using CO2 laser collective scattering

International Nuclear Information System (INIS)

Boileau, A.; Van Andel, H.W.H.; Hellermann, M. von; Rogister, A.

1987-01-01

A modulation of microturbulence is observed in TEXTOR during low mode number MHD activity using CO 2 laser collective scattering. This is accomplished by a strong enhancement of density fluctuations near ka s approx. = 3 at the end of soft landing discharges and a displacement of the frequency spectrum towards lower frequencies. The increase is most significant for rapid rampdown of the plasma current accompanied by strong MHD activity but also occurs when the latter is not detected. The evolution of microturbulence is also studied during major plasma disruptions. It was found that disruptions without MHD precursor oscillations are characterized by a rapid increase in the density fluctuations starting approx. 100 ms before plasma disruption. (author)

MHD stability regimes for steady state and pulsed reactors

International Nuclear Information System (INIS)

Jardin, S.C.; Kessel, C.E.; Pomphrey, N.

1994-02-01

A tokamak reactor will operate at the maximum value of β≡2μ 0 /B 2 that is compatible with MHD stability. This value depends upon the plasma current and pressure profiles, the plasma shape and aspect ratio, and the location of nearby conducting structures. In addition, a steady state reactor will minimize its external current drive requirements and thus achieve its maximum economic benefit with a bootstrap fraction near one, I bs /I p ∼ 1, which constrains the product of the inverse aspect ratio and the plasma poloidal beta to be near unity, ε β p ∼ 1. An inductively driven pulsed reactor has different constraints set by the steady-state Ohm's law which relates the plasma temperature and density profiles to the parallel current density. We present the results obtained during the ARIES I, II/IV, and III and the PULSAR reactor studies where these quantities were optimized subject to different design philosophies. The ARIES-II/IV and ARIES-III designs are both in the second stability regime, but differ in requirements on the form of the profiles at the plasma edge, and in the location of the conducting wall. The relation between these, as well as new attractive MHD regimes not utilized in the ARIES or PULSAR studies is also discussed

Quantum chaos theory and the spectrum of ideal-MHD instabilities in toroidal plasmas

International Nuclear Information System (INIS)

Dewar, Robert L.; Carolin, Nuehrenberg; Tatsuno, Tomoya

2004-01-01

In a fully 3-D system such as a stellarator, the toroidal mode number n ceases to be a good quantum number - all ns within a given mode family being coupled. It is found that the discrete spectrum of unstable ideal MHD (magnetohydrodynamic) instabilities ceases to exist unless MHD is modified (regularized) by introducing a short-perpendicular-wavelength cutoff. Attempts to use ray tracing to estimate the regularized MHD spectrum fail due to the occurrence of chaotic ray trajectories. In quantum chaos theory, strong chaos in the semiclassical limit leads to eigenvalue statistics the same as those of a suitable ensemble of random matrices. For instance, the probability distribution function for the separation between neighboring eigenvalues is as derived from random matrix theory and goes to zero at zero separation. This contrasts with the Poissonian distribution found in separable systems, showing that a signature of quantum chaos is level repulsion. In order to determine whether eigenvalues of the regularized MHD problem obey the same statistics as those of the Schroedinger equation in both the separable 1-D case and the chaotic 3-D cases, we have assembled data sets of ideal MHD eigenvalues for a Suydam-unstable cylindrical (1-D) equilibrium using Mathematica and a Mercier-unstable (3-D) equilibrium using the CAS3D code. In the 1-D case, we find that the unregularized Suydam-approximation spectrum has an anomalous peak at zero eigenvalue separation. On the other hand, regularization by restricting the domain of κsub(perpendicular) recovers the expected Poissonian distribution. In the 3-D case we find strong evidence of level repulsion within mode families, but mixing mode families produces Poissonian statistics. (author)

Fast Soft X-ray Images of MHD Phenomena in NSTX

International Nuclear Information System (INIS)

Bush, C.E.; Stratton, B.C.; Robinson, J.; Zakharov, L.E.; Fredrickson, E.D.; Stutman, D.; Tritz, K.

2008-01-01

A variety of magnetohydrodynamic (MHD) phenomena have been observed on the National Spherical Torus Experiment (NSTX). Many of these affect fast particle losses, which are of major concern for future burning plasma experiments. Usual diagnostics for studying these phenomena are arrays of Mirnov coils for magnetic oscillations and PIN diode arrays for soft x-ray emission from the plasma core. Data reported here are from an unique fast soft x-ray imaging camera (FSXIC) with a wide-angle (pinhole) tangential view of the entire plasma minor cross section. The camera provides a 64x64 pixel image, on a CCD chip, of light resulting from conversion of soft x-rays incident on a phosphor to the visible. We have acquired plasma images at frame rates of 1-500 kHz (300 frames/shot), and have observed a variety of MHD phenomena: disruptions, sawteeth, fishbones, tearing modes, and ELMs. New data including modes with frequency > 90 kHz are also presented. Data analysis and modeling techniques used to interpret the FSXIC data are described and compared, and FSXIC results are compared to Mirnov and PIN diode array results.

An introduction to astrophysical hydrodynamics

CERN Document Server

Shore, Steven N

1992-01-01

This book is an introduction to astrophysical hydrodynamics for both astronomy and physics students. It provides a comprehensive and unified view of the general problems associated with fluids in a cosmic context, with a discussion of fluid dynamics and plasma physics. It is the only book on hydrodynamics that addresses the astrophysical context. Researchers and students will find this work to be an exceptional reference. Contents include chapters on irrotational and rotational flows, turbulence, magnetohydrodynamics, and instabilities.

Intermittency in MHD turbulence and coronal nanoflares modelling

Directory of Open Access Journals (Sweden)

P. Veltri

2005-01-01

Full Text Available High resolution numerical simulations, solar wind data analysis, and measurements at the edges of laboratory plasma devices have allowed for a huge progress in our understanding of MHD turbulence. The high resolution of solar wind measurements has allowed to characterize the intermittency observed at small scales. We are now able to set up a consistent and convincing view of the main properties of MHD turbulence, which in turn constitutes an extremely efficient tool in understanding the behaviour of turbulent plasmas, like those in solar corona, where in situ observations are not available. Using this knowledge a model to describe injection, due to foot-point motions, storage and dissipation of MHD turbulence in coronal loops, is built where we assume strong longitudinal magnetic field, low beta and high aspect ratio, which allows us to use the set of reduced MHD equations (RMHD. The model is based on a shell technique in the wave vector space orthogonal to the strong magnetic field, while the dependence on the longitudinal coordinate is preserved. Numerical simulations show that injected energy is efficiently stored in the loop where a significant level of magnetic and velocity fluctuations is obtained. Nonlinear interactions give rise to an energy cascade towards smaller scales where energy is dissipated in an intermittent fashion. Due to the strong longitudinal magnetic field, dissipative structures propagate along the loop, with the typical speed of the Alfvén waves. The statistical analysis on the intermittent dissipative events compares well with all observed properties of nanoflare emission statistics. Moreover the recent observations of non thermal velocity measurements during flare occurrence are well described by the numerical results of the simulation model. All these results naturally emerge from the model dynamical evolution without any need of an ad-hoc hypothesis.

Numerical study of spherical Torus MHD equilibrium configuration

International Nuclear Information System (INIS)

Cheng Faying; Dong Jiaqi; Wang Aike

2003-01-01

Tokamak equilibrium code SWEQU has been modified so that it can be used for the MHD equilibrium study of low aspect ratio device. Evolution of plasma configuration in start-up phase and double-null divertor configuration in steady-state phase has been simulated using the modified code. Results show that the new code can be used not only to obtain the equilibrium configuration of spherical Torus in steady-state phase, but also to simulate the evolution of plasma in the start-up phase

Ultrahigh temperature vapor core reactor-MHD system for space nuclear electric power

Science.gov (United States)

Maya, Isaac; Anghaie, Samim; Diaz, Nils J.; Dugan, Edward T.

1991-01-01

The conceptual design of a nuclear space power system based on the ultrahigh temperature vapor core reactor with MHD energy conversion is presented. This UF4 fueled gas core cavity reactor operates at 4000 K maximum core temperature and 40 atm. Materials experiments, conducted with UF4 up to 2200 K, demonstrate acceptable compatibility with tungsten-molybdenum-, and carbon-based materials. The supporting nuclear, heat transfer, fluid flow and MHD analysis, and fissioning plasma physics experiments are also discussed.

MHD activity in the ISX-B tokamak: experimental results and theoretical interpretation

Energy Technology Data Exchange (ETDEWEB)

Carreras, B.A.; Dunlap, J.L.; Bell, J.D.; Charlton, L.A.; Cooper, W.A.; Dory, R.A.; Hender, T.C.; Hicks, H.R.; Holmes, J.A.; Lynch, V.E.

1982-01-01

The observed spectrum of MHD fluctuations in the ISX-B tokamak is clearly dominated by the n=1 mode when the q=1 surface is in the plasma. This fact agrees well with theoretical predictions based on 3-D resistive MHD calculations. They show that the (m=1; n=1) mode is then the dominant instability. It drives other n=1 modes through toroidal coupling and n>1 modes through nonlinear couplings. These theoretically predicted mode structures have been compared in detail with the experimentally measured wave forms (using arrays of soft x-ray detectors). The agreement is excellent. More detailed comparisons between theory and experiment have required careful reconstructions of the ISX-B equilibria. The equilibria so constructed have permitted a precise evaluation of the ideal MHD stability properties of ISX-B. The present results indicate that the high ..beta.. ISX-B equilibria are marginally stable to finite eta ideal MHD modes. The resistive MHD calculations also show that at finite ..beta.. there are unstable resistive pressure driven modes.

A hybrid LLR-MHD model of kink perturbations in EXTRAP

International Nuclear Information System (INIS)

Lehnert, B.

1987-07-01

In high-beta systems, such as Extrap and other Z-pinch configurations, kinetic large Larmor radius (LLR) phenomena introduce strong phase-mixing and dispersive effects and a corresponding 'kinetic damping' which cannot be treated in terms of MHD theory. In this paper a first attempt is made to include these effects by proposing a hybrid LLR-MHD model in which the kinetic phenomena enter as constraints on the possible forms of the plasma perturbations. The latter then become restricted to a limited class which can be treated in terms of MHD theory. The present model does not claim to produce stability conditions which are exact in all details, but should merely provide a picture of the general relationship between the basic plasma parameters in a state of marginal stability. For kink perturbations in Extrap stability relations have thus been obtained between the pinch and conductor currents, the pinch radius and the axial conductor distance, and the number of contained ion Larmor radii. These relations appear to be consistent with so far obtained experimental data. A short discussion on the effects of a superimposed axial magnetic field has been included. At this stage only experiments can verify whether or not the present simple model becomes relevant to Extrap stability. (author)

Resistive Magnetohydrodynamics Simulation of Fusion Plasmas

International Nuclear Information System (INIS)

Tang, X.Z.; Fu, G.Y.; Jardin, S.C.; Lowe, L.L.; Park, W.; Strauss, H.R.

2001-01-01

Although high-temperature plasmas in laboratory magnetic fusion confinements are sufficiently collisionless that formal fluid closures are difficult to attain, the resistive MHD model has proven, by comparison with experimental data, to be useful for describing the large scale dynamics of magnetized plasmas. Resistive MHD model consists of Faraday's law for the evolution of the magnetic field and Navier-Stokes equation for the plasma flow. These equations are closed by the Ohm's law and an equation of state for the plasma

Macroscopic plasma properties and stability theory

International Nuclear Information System (INIS)

Sakanaka, P.H.

1981-01-01

1. Two-fluid equations: (a) Boltzmann equation: complete set of equations; collision models - Vlasov, BGK, Fokker-Planck-Landau, Boltzmann. (b) Moments of the Boltzmann equation: problem of closure. (c) Two-fluid equations. 2. One-fluid equation: (a) One-fluid variables. (b) One-fluid equations: quasi-neutrality. (c) Resistive MHD equations. (d) Ideal MHD equations: one-adiabatic approximation; double-adiabatic approximation - CGL. 3. MHD stability problem - energy principle: (a) Linearized ideal MHD equations: force-operator equation. (b) Boundary conditions. (c) Self-adjointness of force operator. (d) The energy principle. 4. Stability problems: application of the energy principle; stability of sharp-boundary plasmas. 5. Thermodynamic approach for stability of plasmas: Newcomb and Rosenbluth's stability criteria. (author)

Introduction to Nuclear Astrophysics

International Nuclear Information System (INIS)

Iliadis, Christian

2010-01-01

In the first lecture of this volume, we will present the basic fundamental ideas regarding nuclear processes occurring in stars. We start from stellar observations, will then elaborate on some important quantum-mechanical phenomena governing nuclear reactions, continue with how nuclear reactions proceed in a hot stellar plasma and, finally, we will provide an overview of stellar burning stages. At the end, the current knowledge regarding the origin of the elements is briefly summarized. This lecture is directed towards the student of nuclear astrophysics. Our intention is to present seemingly unrelated phenomena of nuclear physics and astrophysics in a coherent framework.

Present state of research and development of MHD power generation

International Nuclear Information System (INIS)

Ikeda, Shigeru

1978-01-01

MHD power generation can obtain electric energy directly from the heat energy of high speed plasma flow, and the power generating plant of 1 million kW can be realized by this method. When the MHD power generation method is combined before conventional thermal power generation method, the thermal efficiency can be raised to about 60% as compared with 38% in thermal power generation plants. The research and development of MHD power generation are in progress in USA and USSR. The research and development in Japan are in the second stage now after the first stage project for 10 years, and the Mark 7 generator with 100 kW electric output for 200 hr continuous operation is under construction. The MHD power generation is divided into three types according to the conductive fluids used, namely combustion type for thermal power generation, unequilibrated type and liquid metal type for nuclear power generation. The principle of MHD power generation and the constitution of the plant are explained. In Japan, the Mark 2 generator generated 1,180 kW for 1 min in 1971, and the Mark 3 generator generated 1.9 kW continuously for 110 hr in 1967. The MHD generator with superconducting magnet succeeded in 1969 to generate 25 kW for 6 min. The second stage project aimes at collecting design data and obtaining operational experience for the construction of 10 MW class pilot plant, and the Mark 7 and 8 generators are planned. (Kako, I.)

Electricity from MHD, 1968. Vol. IV. Open-Cycle MHD. Proceedings of a Symposium on Magnetohydrodynamic Electrical Power Generation

International Nuclear Information System (INIS)

1968-01-01

Proceedings of a Symposium on Magnetohydrodynamic Electrical Power Generation held by the IAEA at Warsaw, 24-30 July 1968. The meeting was attended by some 300 participants from 21 countries and three international organizations. In contrast to the Symposium held two years ago, much more emphasis was placed on the economic aspects of using MHD generators in large-scale power generation. Among closed- cycle systems, the prospects of linking an ultra-high-temperature reactor with an MHD generator were explored, and the advantages gained by having a liquid-metal generator as a 'topper' in a conventional steam generating plant were presented. Comments were made about the disproportionate effect of end and boundary conditions in experimental MHD generators on the main plasma parameters, and estimates were made of the interrelationship to be expected in real generators. The estimates will have to await confirmation until results are obtained on large-scale prototype MHD systems. Progress in materials research, in design and construction of auxiliary equipment such as heat exchangers, supercooled magnets (which are- now commercially available), etc., is accompanied by sophisticated ideas of plant design. The Proceedings are complemented by three Round Table Discussions in which chosen experts from various countries discuss the outlook for closed-cycle gas, closed-cycle liquid-metal and open-cycle MHD, and give their views as to the most fruitful course to follow to achieve economic full-scale power generation. Contents: (Vol. I) 1. Closed-Cycle MHD with Gaseous Working Fluids: (a) Diagnostics (3 papers); (b) Steady-state non-equilibrium ionization (8 papers); (c) Transient non-equilibrium ionization (7 papers); (d) Pre-ionization and gas discharge (4 papers); (e) Fields and flow in MHD channels (10 papers); (0 Instabilities (8 papers); (g) Generator design and performance studies (6 papers); (Vol. II) (h) Shock waves (6 papers); (i) Power generation experiments (13 papers

Engineering design and development of lead lithium loop for thermo-fluid MHD studies

International Nuclear Information System (INIS)

Kumar, M.; Patel, Anita; Jaiswal, A.; Ranjan, A.; Mohanta, D.; Sahu, S.; Saraswat, A.; Rao, T.S.; Mehta, V.; Bhattacharyay, R.; Rajendra Kumar, E.

2017-01-01

In the frame of the design and development of LLCB TBM, number of R and D activities is in progress in the area of Pb-Li technology development. Molten Pb-Li is used as a tritium breeder and also as a coolant for the internals of the TBM structure. In presence of strong plasma confining toroidal magnetic field, motion of electrically conducting Pb-Li leads to Magneto Hydro Dynamic (MHD) phenomena, as a consequence of which the flow profile of Pb-Li is significantly modified inside the Pb-Li channels of TBM. This causes additional pressure drop inside TBM and affects the heat transfer from internal structure. The detail studies of these MHD effects are of prime importance for successful design of LLCB TBM and its performance evaluation. Although, various numerical MHD codes have been developed, validated in simple flow configuration and are being used to study MHD phenomena in LLCB TBM, experimental validation of these codes in TBM relevant complex flow geometry is yet to be performed. A Pb-Li MHD experimental loop is, therefore, being developed at IPR to perform thermo-fluid MHD experiments in various LLCB TBM relevant flow configuration. MHD experiments are planned with different test sections instrumented with potential pins, thermo couples, etc. under a uniform magnetic field of ∼1.4 T. The obtained experimental data will be analyzed to understand the MHD phenomena in TBM like flow configuration and also for validation of MHD codes. This paper describes the detailed process as well as engineering design of the Pb-Li MHD loop and its major components along with the plan of MHD experiments in various test mock ups. (author)

Waveguide and loop coupling to fast MHD toroidal eigenmodes

International Nuclear Information System (INIS)

Paoloni, F.J.

1975-12-01

Heating of plasmas by wave techniques requires an effective method of coupling rf energy to the plasma. In cavities the presence of weakly damped eigenmodes will enhance the loading of antennas when the wave frequency equals an eigenmode frequency. This report considers two methods of coupling to fast MHD eigenmodes in a toroidal cavity: one is by a waveguide mounted perpendicular to the vacuum vessel wall; and the other by a loop placed within the cavity

Magnetohydrodynamic (MHD) power generation

International Nuclear Information System (INIS)

Chandra, Avinash

1980-01-01

The concept of MHD power generation, principles of operation of the MHD generator, its design, types, MHD generator cycles, technological problems to be overcome, the current state of the art in USA and USSR are described. Progress of India's experimental 5 Mw water-gas fired open cycle MHD power generator project is reported in brief. (M.G.B.)

US/USSR cooperative program in open-cycle MHD electrical power gneration. Joint test report No. 2: tests in the U-25B facility; MHD generator test No. 3

International Nuclear Information System (INIS)

Tempelmeyer, K.E.; Sokolov, Y.N.

1979-04-01

The third joint test with a Soviet U-25B MHD generator and a US superconducting magnet system (SCMS) was conducted in the Soviet U-25B Facility. The primary objectives of the 3rd test were: (1) to operate the facility and MHD channel over a wider range of test parameters, and (2) to study the performance of all components and systems of the flow train at increased mass flow rates of combustion products (up to 4 kg/s), at high magnetic-field induction (up to 5 T), and high values of the electrical field in the MHD generator. The third test has demonstrated that all components and systems of the U-25B facility performed reliably. The electric power generated by the MHD generaor reached a maximum of 575 kW during this test. The MHD generator was operated under electrical loading conditions for 9 hours, and the combustor for a total of approximately 14 hours. Very high Hall fields (2.1 kV/m) were produced in the MHD channel, with a total Hall voltage of 4.24 kV. A detailed description is given of (1) performance of all components and systems of the U-25B facility, (2) analysis of the thermal, gasdynamic, and electrical characteristics of the MHD generator, (3) results of plasma diagnostic studies, (4) studies of vibrational characteristics of the flow train, (5) fluctuation of electrodynamic and gasdynamic parameters, (6) interaction of the MHD generator with the superconducting magnet, and (7) an operational problem, which terminated the test

Two-fluid (plasma-neutral) Extended-MHD simulations of spheromak configurations in the HIT-SI experiment with PSI-Tet

Science.gov (United States)

Sutherland, D. A.; Hansen, C. J.; Jarboe, T. R.

2017-10-01

A self-consistent, two-fluid (plasma-neutral) dynamic neutral model has been implemented into the 3-D, Extended-MHD code PSI-Tet. A monatomic, hydrogenic neutral fluid reacts with a plasma fluid through elastic scattering collisions and three inelastic collision reactions: electron-impact ionization, radiative recombination, and resonant charge-exchange. Density, momentum, and energy are evolved for both the plasma and neutral species. The implemented plasma-neutral model in PSI-Tet is being used to simulate decaying spheromak configurations in the HIT-SI experimental geometry, which is being compare to two-photon absorption laser induced fluorescence measurements (TALIF) made on the HIT-SI3 experiment. TALIF is used to measure the absolute density and temperature of monatomic deuterium atoms. Neutral densities on the order of 1015 m-3 and neutral temperatures between 0.6-1.7 eV were measured towards the end of decay of spheromak configurations with initial toroidal currents between 10-12 kA. Validation results between TALIF measurements and PSI-Tet simulations with the implemented dynamic neutral model will be presented. Additionally, preliminary dynamic neutral simulations of the HIT-SI/HIT-SI3 spheromak plasmas sustained with inductive helicity injection will be presented. Lastly, potential benefits of an expansion of the two-fluid model into a multi-fluid model that includes multiple neutral species and tracking of charge states will be discussed.

Journal of Astrophysics and Astronomy | Indian Academy of Sciences

Indian Academy of Sciences (India)

2016-01-27

Jan 27, 2016 ... Home; Journals; Journal of Astrophysics and Astronomy. NAGENDRA KUMAR. Articles written in Journal of Astrophysics and Astronomy. Volume 29 Issue 1-2 March-June 2008 pp 243-248. Damping of Slow Magnetoacoustic Waves in an Inhomogeneous Coronal Plasma · Nagendra Kumar Pradeep ...

Conducting grids to stabilize MHD generator plasmas against ionization instabilities

International Nuclear Information System (INIS)

Veefkind, A.

1972-09-01

Ionization instabilities in MHD generators may be suppressed by the use of grids that short circuit the AC electric field component corresponding to the direction of maximum growth. An analysis of the influence of the corresponding boundary conditions has been performed in order to obtain more quantitative information about the stabilizing effect of this system

Nuclear astrophysics

International Nuclear Information System (INIS)

Arnould, M.; Takahashi, K.

1999-01-01

Nuclear astrophysics is that branch of astrophysics which helps understanding of the Universe, or at least some of its many faces, through the knowledge of the microcosm of the atomic nucleus. It attempts to find as many nuclear physics imprints as possible in the macrocosm, and to decipher what those messages are telling us about the varied constituent objects in the Universe at present and in the past. In the last decades much advance has been made in nuclear astrophysics thanks to the sometimes spectacular progress made in the modelling of the structure and evolution of the stars, in the quality and diversity of the astronomical observations, as well as in the experimental and theoretical understanding of the atomic nucleus and of its spontaneous or induced transformations. Developments in other subfields of physics and chemistry have also contributed to that advance. Notwithstanding the accomplishment, many long-standing problems remain to be solved, and the theoretical understanding of a large variety of observational facts needs to be put on safer grounds. In addition, new questions are continuously emerging, and new facts endangering old ideas. This review shows that astrophysics has been, and still is, highly demanding to nuclear physics in both its experimental and theoretical components. On top of the fact that large varieties of nuclei have to be dealt with, these nuclei are immersed in highly unusual environments which may have a significant impact on their static properties, the diversity of their transmutation modes, and on the probabilities of these modes. In order to have a chance of solving some of the problems nuclear astrophysics is facing, the astrophysicists and nuclear physicists are obviously bound to put their competence in common, and have sometimes to benefit from the help of other fields of physics, like particle physics, plasma physics or solid-state physics. Given the highly varied and complex aspects, we pick here some specific nuclear

MHD simulations of DC helicity injection for current drive in tokamaks

International Nuclear Information System (INIS)

Sovinec, C.R.; Prager, S.C.

1994-12-01

MHD computations of DC helicity injection in tokamak-like configurations show current drive with no ''loop voltage'' in a resistive, pressureless plasma. The self-consistently generated current profiles are unstable to resistive modes that partially relax the profile through the MHD dynamo mechanism. The current driven by the fluctuations leads to closed contours of average poloidal flux. However, the 1% fluctuation level is large enough to produce a region of stochastic magnetic field. A limited Lundquist number (S) scan from 2.5 x 10 3 to 4 x 10 4 indicates that both the fluctuation level and relaxation increase with S

MHD equilibrium with toroidal rotation

International Nuclear Information System (INIS)

Li, J.

1987-03-01

The present work attempts to formulate the equilibrium of axisymmetric plasma with purely toroidal flow within ideal MHD theory. In general, the inertial term Rho(v.Del)v caused by plasma flow is so complicated that the equilibrium equation is completely different from the Grad-Shafranov equation. However, in the case of purely toroidal flow the equilibrium equation can be simplified so that it resembles the Grad-Shafranov equation. Generally one arbitrary two-variable functions and two arbitrary single variable functions, instead of only four single-variable functions, are allowed in the new equilibrium equations. Also, the boundary conditions of the rotating (with purely toroidal fluid flow, static - without any fluid flow) equilibrium are the same as those of the static equilibrium. So numerically one can calculate the rotating equilibrium as a static equilibrium. (author)

Nonlinear MHD waves and discontinuities in the Martian magnetosheath. Observations and 2D bi-ion MHD simulations

Science.gov (United States)

Sauer, K.; Dubinin, E.; Baumgärtel, K.

1998-09-01

The characteristic scale of the Martian magnetosheath is less than the pick-up gyroradius of oxygen ions. This leads to admissible differential motion of protons and heavies and a strong coupling between both ion fluids. 2D bi-ion MHD simulations reveal many new interesting features in such Large Larmour Radius systems. The formation of an ion-composition boundary, which separates both plasmas, and structuring of the transition from proton dominated plasma of the solar wind origin to massive planetary plasma are the main features of the interaction. A comprehensive multi-instrument study of Martian plasma environment and the comparison with theoretical modelling initiated in the framework of the Visiting Science Programme of the International Space Science Institute (ISSI) in Bern (Switzerland) gives confirmation that Mars interacts with the solar wind like a comet which has a outgassing rate near to that of Grigg-Skjellerup. The results may also be relevant for small bodies which are surrounded by a neutral gas atmosphere (icy moons, asteroids, Mercury).

Solar High-energy Astrophysical Plasmas Explorer (SHAPE). Volume 1: Proposed concept, statement of work and cost plan

Science.gov (United States)

Dennis, Brian R.; Martin, Franklin D.; Prince, T.; Lin, R.; Bruner, M.; Culhane, L.; Ramaty, R.; Doschek, G.; Emslie, G.; Lingenfelter, R.

1986-01-01

The concept of the Solar High-Energy Astrophysical Plasmas Explorer (SHAPE) is studied. The primary goal is to understand the impulsive release of energy, efficient acceleration of particles to high energies, and rapid transport of energy. Solar flare studies are the centerpieces of the investigation because in flares these high energy processes can be studied in unmatched detail at most wavelenth regions of the electromagnetic spectrum as well as in energetic charged particles and neutrons.

Measuring the equations of state in a relaxed magnetohydrodynamic plasma

Science.gov (United States)

Kaur, M.; Barbano, L. J.; Suen-Lewis, E. M.; Shrock, J. E.; Light, A. D.; Brown, M. R.; Schaffner, D. A.

2018-01-01

We report measurements of the equations of state of a fully relaxed magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma, called Taylor states, are formed in a coaxial magnetized plasma gun, and are allowed to relax and drift into a closed flux conserving volume. Density, ion temperature, and magnetic field are measured as a function of time as the Taylor states compress and heat. The theoretically predicted MHD and double adiabatic equations of state are compared to experimental measurements. We find that the MHD equation of state is inconsistent with our data.

MHD stability studies in the Proto S-1 A/B device

International Nuclear Information System (INIS)

Munson, C.; Janos, A.; Newhouse, M.; Salberta, E.; Wysocki, F.; Yamada, M.

1982-01-01

An experimental study of the gross MHD stability properties of Spheromak plasmas in the Proto S-1 A/B device is presented. Utilizing the previously demonstrated S-1 slow formation technique, plasmas have been produced which exhibit the predicted tilting instability in a regime of slightly negative field index. A relatively simple passive coil system suggested by numerical stability studies has proven to be effective in stabilizing the observed tilting mode

Localized MHD activity near transport barriers in JT-60U and TFTR

International Nuclear Information System (INIS)

Manickam, J.

2001-01-01

Localized MHD activity observed in JT-60U and TFTR near transport barriers with their associated large pressure gradients is investigated. Stability analysis of equilibria modeling the experiments supports an identification of this MHD as being due to an ideal MHD n=1 instability. The appearance of the instability depends on the local pressure gradient, local shear in the q profile and the proximity of rational surfaces where q∼m/n and m and n are the poloidal and toroidal mode numbers respectively. The mode width is shown to depend on the local value of q, and is larger when q is smaller. In addition the role of the edge current density in coupling the internal mode to the plasma edge and of the energetic particles which can drive fishbone like modes is investigated. (author)

Trigger mechanism for the abrupt loss of energetic ions in magnetically confined plasmas.

Science.gov (United States)

Ida, K; Kobayashi, T; Yoshinuma, M; Akiyama, T; Tokuzawa, T; Tsuchiya, H; Itoh, K; Itoh, S-I

2018-02-12

Interaction between a quasi-stable stationary MHD mode and a tongue-shaped deformation is observed in the toroidal plasma with energetic particle driven MHD bursts. The quasi-stable stationary 1/1 MHD mode with interchange parity appears near the resonant rational surface of q = 1 between MHD bursts. The tongue-shaped deformation rapidly appears at the non-resonant non-rational surface as a localized large plasma displacement and then collapses (tongue event). It curbs the stationary 1/1 MHD mode and then triggers the collapse of energetic particle and magnetic field reconnection. The rotating 1/1 MHD mode with tearing parity at the q = 1 resonant surface, namely, the MHD burst, is excited after the tongue event.

Divergence-free MHD Simulations with the HERACLES Code

Directory of Open Access Journals (Sweden)

Vides J.

2013-12-01

Full Text Available Numerical simulations of the magnetohydrodynamics (MHD equations have played a significant role in plasma research over the years. The need of obtaining physical and stable solutions to these equations has led to the development of several schemes, all requiring to satisfy and preserve the divergence constraint of the magnetic field numerically. In this paper, we aim to show the importance of maintaining this constraint numerically. We investigate in particular the hyperbolic divergence cleaning technique applied to the ideal MHD equations on a collocated grid and compare it to the constrained transport technique that uses a staggered grid to maintain the property. The methods are implemented in the software HERACLES and several numerical tests are presented, where the robustness and accuracy of the different schemes can be directly compared.

Ideal MHD B limits in the BIG DEE tokamak

International Nuclear Information System (INIS)

Helton, F.J.; Bernard, L.C.; Greene, J.M.

1983-01-01

Using D-D reactions, tokamak reactors become economically attractive when B (the ratio of volume averaged pressure to magnetic pressure) exceeds 5 percent. Ideal MID instabilities are of great concern because they have the potential to limit B below this range and so extensive studies have been done to determine ideal MHD B limits. As B increases with inverse aspect ratio, elongation and triangularity, the Doublet III upgrade machine -- BIG DEE -- is particularly suited to study the possibility of very high B. The authors have done computations to determine ideal MHD B limits for various plasma shapes and elongations in BIG DEE. They have determined that for q at the plasma surface greater than 2, B is limited by the ballooning mode if the wall is reasonably close to the plasma surface (d/a < 1.5 where d and a are the wall and plasma radii respectively). On the other hand, for q at the plasma surface less than 2, the n=1 external kink is unstable even with a wall close by. Thus, relevant values of limiting B can be obtained by assuming that the external kink limits the value of q at the limiter to a value greater than 2 and that the ballooning modes limit B. Under this assumption, a relevant B limit for the BIG DEE would be over 18%. For such an equilibrium, the wall position necessary to stabilize the n=1 and n=2 modes is 2a and the equilibrium is stable for n=3

Observation of SOL Current Correlated with MHD Activity in NBI-heated DIII-D Tokamak Discharges

International Nuclear Information System (INIS)

Takahashi, H.; Fredrickson, E.D.; Schaffer, M.J.; Austin, M.E.; Evans, T.E.; Lao, L.L.; Watkins, J.G.

2004-01-01

This work investigates the potential roles played by the scrape-off-layer current (SOLC) in MHD activity of tokamak plasmas, including effects on stability. SOLCs are found during MHD activity that are: (1) slowly growing after a mode-locking-like event, (2) oscillating in the several kHz range and phase-locked with magnetic and electron temperature oscillations, (3) rapidly growing with a sub-ms time scale during a thermal collapse and a current quench, and (4) spiky in temporal behavior and correlated with spiky features in Da signals commonly identified with the edge localized mode (ELM). These SOLCs are found to be an integral part of the MHD activity, with a propensity to flow in a toroidally non-axisymmetric pattern and with magnitude potentially large enough to play a role in the MHD stability. Candidate mechanisms that can drive these SOLCs are identified: (a) toroidally non-axisymmetric thermoelectric potential, (b) electromotive force (EMF) from MHD activity, and (c) flux swing, both toroidal and poloidal, of the plasma column. An effect is found, stemming from the shear in the field line pitch angle, that mitigates the efficacy of a toroidally non-axisymmetric SOLC to generate a toroidally non-axisymmetric error field. Other potential magnetic consequences of the SOLC are identified: (i) its error field can introduce complications in feedback control schemes for stabilizing MHD activity and (ii) its toroidally non-axisymmetric field can be falsely identified as an axisymmetric field by the tokamak control logic and in equilibrium reconstruction. The radial profile of a SOLC observed during a quiescent discharge period is determined, and found to possess polarity reversals as a function of radial distance

MHD Program Plan, FY 1992

International Nuclear Information System (INIS)

1991-10-01

The current MHD program being implemented is a result of a consensus established in public meetings held by the Department of Energy in 1984. Essential elements of the current program include: (1) develop technical and environmental data for the integrated MHD topping cycle system through POC testing (1,000 hours); (2) develop technical and environmental data for the integrated MHD bottoming cycle sub system through POC testing (4,000 hours); (3) design, construct, and operate a seed regeneration POC facility (SRPF) capable of processing spent seed materials from the MHD bottoming cycle; (4) prepare conceptual designs for a site specific MHD retrofit plant; and (5) continue system studies and supporting research necessary for system testing. The current MHD program continues to be directed toward coal fired power plant applications, both stand-alone and retrofit. Development of a plant should enhance the attractiveness of MHD for applications other than electrical power. MHD may find application in electrical energy intensive industries and in the defense sector

The Statistical Mechanics of Ideal MHD Turbulence

Science.gov (United States)

Shebalin, John V.

2003-01-01

Turbulence is a universal, nonlinear phenomenon found in all energetic fluid and plasma motion. In particular. understanding magneto hydrodynamic (MHD) turbulence and incorporating its effects in the computation and prediction of the flow of ionized gases in space, for example, are great challenges that must be met if such computations and predictions are to be meaningful. Although a general solution to the "problem of turbulence" does not exist in closed form, numerical integrations allow us to explore the phase space of solutions for both ideal and dissipative flows. For homogeneous, incompressible turbulence, Fourier methods are appropriate, and phase space is defined by the Fourier coefficients of the physical fields. In the case of ideal MHD flows, a fairly robust statistical mechanics has been developed, in which the symmetry and ergodic properties of phase space is understood. A discussion of these properties will illuminate our principal discovery: Coherent structure and randomness co-exist in ideal MHD turbulence. For dissipative flows, as opposed to ideal flows, progress beyond the dimensional analysis of Kolmogorov has been difficult. Here, some possible future directions that draw on the ideal results will also be discussed. Our conclusion will be that while ideal turbulence is now well understood, real turbulence still presents great challenges.

Coupling to fast MHD eigenmodes in a toroidal cavity

International Nuclear Information System (INIS)

Paoloni, F.J.

1975-05-01

The coupling to fast MHD waves in toroidal-like geometry is calculated when eigenmodes exist in the plasma. The torus is considered to be a resonant cavity into which energy is coupled by a half turn loop. The cavity Q is calculated for the minority heating process, for cyclotron harmonic damping, electron transit-time magnetic pumping, wall loading, and Coulomb collisional damping. The problem of sustaining the eigenmode as the plasma conditions change with time is also discussed. One method that seems to be practical is a feedback scheme that varies the plasma major radius by a small amount as the conditions change. (U.S.)

Impact of the plasma response in three-dimensional edge plasma transport modelling for RMP ELM control scenarios at ITER

Science.gov (United States)

Schmitz, Oliver

2014-10-01

The constrains used in magneto-hydrodynamic (MHD) modeling of the plasma response to external resonant magnetic perturbation (RMP) fields have a profound impact on the three-dimensional (3-D) shape of the plasma boundary induced by RMP fields. In this contribution, the consequences of the plasma response on the actual 3D boundary structure and transport during RMP application at ITER are investigated. The 3D fluid plasma and kinetic neutral transport code EMC3-Eirene is used for edge transport modeling. Plasma response modeling is conducted with the M3D-C1 code using a single fluid, non-linear and a two fluid, linear MHD constrain. These approaches are compared to results with an ideal MHD like plasma response. A 3D plasma boundary is formed for all cases consisting of magnetic finger structures at the X-point intersecting the divertor surface in a helical footprint pattern. The width of the helical footprint pattern is largely reduced compared to vacuum magnetic fields when using the ideal MHD like screening model. This yields increasing peak heat fluxes in contrast to a beneficial heat flux spreading seen with vacuum fields. The particle pump out as well as loss of thermal energy is reduced by a factor of two compared to vacuum fields. In contrast, the impact of the plasma response obtained from both MHD constrains in M3D-C1 is nearly negligible at the plasma boundary and only a small modification of the magnetic footprint topology is detected. Accordingly, heat and particle fluxes on the target plates as well as the edge transport characteristics are comparable to the vacuum solution. This span of modeling results with different plasma response models highlights the importance of thoroughly validating both, plasma response and 3D edge transport models for a robust extrapolation towards ITER. Supported by ITER Grant IO/CT/11/4300000497 and F4E Grant GRT-055 (PMS-PE) and by Start-Up Funds of the University of Wisconsin - Madison.

MHD phenomena in advanced scenarios on ASDEX upgrade and the influence of localised electron heating and current drive

International Nuclear Information System (INIS)

Guenter, S.; Gude, A.; Hobirk, J.; Maraschek, M.; Peeters, A.G.; Pinches, S.D.; Schade, S.; Wolf, R.C.; Saarelma, S.

2001-01-01

MHD instabilities in advanced tokamak scenarios on the one hand are favourable as they can contribute to the stationarity of the current profiles and act as a trigger for the formation of internal transport barriers. In particular fishbone oscillations driven by fast particles arising from neutral beam injection (NBI) are shown to trigger internal transport barriers in low and reversed magnetic shear discharges. During the whistling down period of the fishbone oscillation the transport is reduced around the corresponding rational surface, leading to an increased pressure gradient. This behaviour is explained by the redistribution of the resonant fast particles resulting in a sheared plasma rotation due to the return current in the bulk plasma, which is equivalent to a radial electric field. On the other hand MHD instabilities limit the accessible operating regime. Ideal and resistive MHD modes such as double tearing modes, infernal modes and external kinks degrade the confinement or even lead to disruptions in ASDEX Upgrade reversed shear discharges. Localized electron cyclotron heating and current drive is shown to significantly affect the MHD stability of this type of discharges. (author)

MHD phenomena in advanced scenarios on ASDEX Upgrade and the influence of localized electron heating and current drive

International Nuclear Information System (INIS)

Guenter, S.; Gude, A.; Hobirk, J.; Maraschek, M.; Schade, S.; Wolf, R.C.; Saarelma, S.

2001-01-01

On the one hand, MHD instabilities in advanced tokamak scenarios are favourable as they can contribute to the stationarity of the current profiles and act as a trigger for the formation of internal transport barriers (ITBs). In particular, fishbone oscillations driven by fast particles arising from NBI are shown to trigger ITBs in low and reversed magnetic shear discharges. During the whistling down period of the fishbone oscillation the transport is reduced around the corresponding rational surface, leading to an increased pressure gradient. This behaviour could be explained by the redistribution of the resonant fast particles resulting in a sheared plasma rotation due to the return current in the bulk plasma, which is equivalent to a radial electric field. On the other hand, MHD instabilities limit the accessible operating regime. Ideal and resistive MHD modes such as double tearing modes, infernal modes and external kinks degrade the confinement or even lead to disruptions in ASDEX Upgrade reversed shear discharges. Localized electron cyclotron heating and current drive are shown to significantly affect the MHD stability of this type of discharge. (author)

Current fusion plasma theory grant: Task I, Magnetic confinement fusion plasma theory: Final report, December 1, 1987--November 14, 1988

International Nuclear Information System (INIS)

Callen, J.D.

1988-07-01

The research performed under this grant over the current 11-1/2 month period has concentrated on key tokamak plasma confinement and heating theory issues: extensions of neoclassical MHD; viscosity coefficients and transport; nonlinear resistive MHD simulations of Tokapole II plasmas; ICRF and edge plasma interactions; energy confinement degradation due to macroscopic phenomena; and coordination of a new transport initiative. Progress and publications in these areas are briefly summarized in this report. 21 refs

Two-fluid and parallel compressibility effects in tokamak plasmas

International Nuclear Information System (INIS)

Sugiyama, L.E.; Park, W.

1998-01-01

The MHD, or single fluid, model for a plasma has long been known to provide a surprisingly good description of much of the observed nonlinear dynamics of confined plasmas, considering its simple nature compared to the complexity of the real system. On the other hand, some of the supposed agreement arises from the lack of the detailed measurements that are needed to distinguish MHD from more sophisticated models that incorporate slower time scale processes. At present, a number of factors combine to make models beyond MHD of practical interest. Computational considerations still favor fluid rather than particle models for description of the full plasma, and suggest an approach that starts from a set of fluid-like equations that extends MHD to slower time scales and more accurate parallel dynamics. This paper summarizes a set of two-fluid equations for toroidal (tokamak) geometry that has been developed and tested as the MH3D-T code [1] and some results from the model. The electrons and ions are described as separate fluids. The code and its original MHD version, MH3D [2], are the first numerical, initial value models in toroidal geometry that include the full 3D (fluid) compressibility and electromagnetic effects. Previous nonlinear MHD codes for toroidal geometry have, in practice, neglected the plasma density evolution, on the grounds that MHD plasmas are only weakly compressible and that the background density variation is weaker than the temperature variation. Analytically, the common use of toroidal plasma models based on aspect ratio expansion, such as reduced MHD, has reinforced this impression, since this ordering reduces plasma compressibility effects. For two-fluid plasmas, the density evolution cannot be neglected in principle, since it provides the basic driving energy for the diamagnetic drifts of the electrons and ions perpendicular to the magnetic field. It also strongly influences the parallel dynamics, in combination with the parallel thermal

Ideal MHD Stability Prediction and Required Power for EAST Advanced Scenario

Science.gov (United States)

Chen, Junjie; Li, Guoqiang; Qian, Jinping; Liu, Zixi

2012-11-01

The Experimental Advanced Superconducting Tokamak (EAST) is the first fully superconducting tokamak with a D-shaped cross-sectional plasma presently in operation. The ideal magnetohydrodynamic (MHD) stability and required power for the EAST advanced tokamak (AT) scenario with negative central shear and double transport barrier (DTB) are investigated. With the equilibrium code TOQ and stability code GATO, the ideal MHD stability is analyzed. It is shown that a moderate ratio of edge transport barriers' (ETB) height to internal transport barriers' (ITBs) height is beneficial to ideal MHD stability. The normalized beta βN limit is about 2.20 (without wall) and 3.70 (with ideal wall). With the scaling law of energy confinement time, the required heating power for EAST AT scenario is calculated. The total heating power Pt increases as the toroidal magnetic field BT or the normalized beta βN is increased.

Exact Turbulence Law in Collisionless Plasmas: Hybrid Simulations

Science.gov (United States)

Hellinger, P.; Verdini, A.; Landi, S.; Franci, L.; Matteini, L.

2017-12-01

An exact vectorial law for turbulence in homogeneous incompressible Hall-MHD is derived and tested in two-dimensional hybrid simulations of plasma turbulence. The simulations confirm the validity of the MHD exact law in the kinetic regime, the simulated turbulence exhibits a clear inertial range on large scales where the MHD cascade flux dominates. The simulation results also indicate that in the sub-ion range the cascade continues via the Hall term and that the total cascade rate tends to decrease at around the ion scales, especially in high-beta plasmas. This decrease is like owing to formation of non-thermal features, such as collisionless ion energization, that can not be retained in the Hall MHD approximation.

HPC parallel programming model for gyrokinetic MHD simulation

International Nuclear Information System (INIS)

Naitou, Hiroshi; Yamada, Yusuke; Tokuda, Shinji; Ishii, Yasutomo; Yagi, Masatoshi

2011-01-01

The 3-dimensional gyrokinetic PIC (particle-in-cell) code for MHD simulation, Gpic-MHD, was installed on SR16000 (“Plasma Simulator”), which is a scalar cluster system consisting of 8,192 logical cores. The Gpic-MHD code advances particle and field quantities in time. In order to distribute calculations over large number of logical cores, the total simulation domain in cylindrical geometry was broken up into N DD-r × N DD-z (number of radial decomposition times number of axial decomposition) small domains including approximately the same number of particles. The axial direction was uniformly decomposed, while the radial direction was non-uniformly decomposed. N RP replicas (copies) of each decomposed domain were used (“particle decomposition”). The hybrid parallelization model of multi-threads and multi-processes was employed: threads were parallelized by the auto-parallelization and N DD-r × N DD-z × N RP processes were parallelized by MPI (message-passing interface). The parallelization performance of Gpic-MHD was investigated for the medium size system of N r × N θ × N z = 1025 × 128 × 128 mesh with 4.196 or 8.192 billion particles. The highest speed for the fixed number of logical cores was obtained for two threads, the maximum number of N DD-z , and optimum combination of N DD-r and N RP . The observed optimum speeds demonstrated good scaling up to 8,192 logical cores. (author)

Three-dimensional nonlinear ideal MHD equilibria with field-aligned incompressible and compressible flows

International Nuclear Information System (INIS)

Moawad, S. M.; Ibrahim, D. A.

2016-01-01

The equilibrium properties of three-dimensional ideal magnetohydrodynamics (MHD) are investigated. Incompressible and compressible flows are considered. The governing equations are taken in a steady state such that the magnetic field is parallel to the plasma flow. Equations of stationary equilibrium for both of incompressible and compressible MHD flows are derived and described in a mathematical mode. For incompressible MHD flows, Alfvénic and non-Alfvénic flows with constant and variable magnetofluid density are investigated. For Alfvénic incompressible flows, the general three-dimensional solutions are determined with the aid of two potential functions of the velocity field. For non-Alfvénic incompressible flows, the stationary equilibrium equations are reduced to two differential constraints on the potential functions, flow velocity, magnetofluid density, and the static pressure. Some examples which may be of some relevance to axisymmetric confinement systems are presented. For compressible MHD flows, equations of the stationary equilibrium are derived with the aid of a single potential function of the velocity field. The existence of three-dimensional solutions for these MHD flows is investigated. Several classes of three-dimensional exact solutions for several cases of nonlinear equilibrium equations are presented.

Stability of plasma cylinder with current in a helical plasma flow

Science.gov (United States)

Leonovich, Anatoly S.; Kozlov, Daniil A.; Zong, Qiugang

2018-04-01

Stability of a plasma cylinder with a current wrapped by a helical plasma flow is studied. Unstable surface modes of magnetohydrodynamic (MHD) oscillations develop at the boundary of the cylinder enwrapped by the plasma flow. Unstable eigenmodes can also develop for which the plasma cylinder is a waveguide. The growth rate of the surface modes is much higher than that for the eigenmodes. It is shown that the asymmetric MHD modes in the plasma cylinder are stable if the velocity of the plasma flow is below a certain threshold. Such a plasma flow velocity threshold is absent for the symmetric modes. They are unstable in any arbitrarily slow plasma flows. For all surface modes there is an upper threshold for the flow velocity above which they are stable. The helicity index of the flow around the plasma cylinder significantly affects both the Mach number dependence of the surface wave growth rate and the velocity threshold values. The higher the index, the lower the upper threshold of the velocity jump above which the surface waves become stable. Calculations have been carried out for the growth rates of unstable oscillations in an equilibrium plasma cylinder with current serving as a model of the low-latitude boundary layer (LLBL) of the Earth's magnetic tail. A tangential discontinuity model is used to simulate the geomagnetic tail boundary. It is shown that the magnetopause in the geotail LLBL is unstable to a surface wave (having the highest growth rate) in low- and medium-speed solar wind flows, but becomes stable to this wave in high-speed flows. However, it can remain weakly unstable to the radiative modes of MHD oscillations.

Turbulence in collisionless plasmas: statistical analysis from numerical simulations with pressure anisotropy

Energy Technology Data Exchange (ETDEWEB)

Kowal, G [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, 05508-900, Sao Paulo (Brazil); Falceta-Goncalves, D A; Lazarian, A, E-mail: kowal@astro.iag.usp.br [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States)

2011-05-15

In recent years, we have experienced increasing interest in the understanding of the physical properties of collisionless plasmas, mostly because of the large number of astrophysical environments (e.g. the intracluster medium (ICM)) containing magnetic fields that are strong enough to be coupled with the ionized gas and characterized by densities sufficiently low to prevent the pressure isotropization with respect to the magnetic line direction. Under these conditions, a new class of kinetic instabilities arises, such as firehose and mirror instabilities, which have been studied extensively in the literature. Their role in the turbulence evolution and cascade process in the presence of pressure anisotropy, however, is still unclear. In this work, we present the first statistical analysis of turbulence in collisionless plasmas using three-dimensional numerical simulations and solving double-isothermal magnetohydrodynamic equations with the Chew-Goldberger-Low laws closure (CGL-MHD). We study models with different initial conditions to account for the firehose and mirror instabilities and to obtain different turbulent regimes. We found that the CGL-MHD subsonic and supersonic turbulences show small differences compared to the MHD models in most cases. However, in the regimes of strong kinetic instabilities, the statistics, i.e. the probability distribution functions (PDFs) of density and velocity, are very different. In subsonic models, the instabilities cause an increase in the dispersion of density, while the dispersion of velocity is increased by a large factor in some cases. Moreover, the spectra of density and velocity show increased power at small scales explained by the high growth rate of the instabilities. Finally, we calculated the structure functions of velocity and density fluctuations in the local reference frame defined by the direction of magnetic lines. The results indicate that in some cases the instabilities significantly increase the anisotropy of

Turbulence in collisionless plasmas: statistical analysis from numerical simulations with pressure anisotropy

International Nuclear Information System (INIS)

Kowal, G; Falceta-Goncalves, D A; Lazarian, A

2011-01-01

In recent years, we have experienced increasing interest in the understanding of the physical properties of collisionless plasmas, mostly because of the large number of astrophysical environments (e.g. the intracluster medium (ICM)) containing magnetic fields that are strong enough to be coupled with the ionized gas and characterized by densities sufficiently low to prevent the pressure isotropization with respect to the magnetic line direction. Under these conditions, a new class of kinetic instabilities arises, such as firehose and mirror instabilities, which have been studied extensively in the literature. Their role in the turbulence evolution and cascade process in the presence of pressure anisotropy, however, is still unclear. In this work, we present the first statistical analysis of turbulence in collisionless plasmas using three-dimensional numerical simulations and solving double-isothermal magnetohydrodynamic equations with the Chew-Goldberger-Low laws closure (CGL-MHD). We study models with different initial conditions to account for the firehose and mirror instabilities and to obtain different turbulent regimes. We found that the CGL-MHD subsonic and supersonic turbulences show small differences compared to the MHD models in most cases. However, in the regimes of strong kinetic instabilities, the statistics, i.e. the probability distribution functions (PDFs) of density and velocity, are very different. In subsonic models, the instabilities cause an increase in the dispersion of density, while the dispersion of velocity is increased by a large factor in some cases. Moreover, the spectra of density and velocity show increased power at small scales explained by the high growth rate of the instabilities. Finally, we calculated the structure functions of velocity and density fluctuations in the local reference frame defined by the direction of magnetic lines. The results indicate that in some cases the instabilities significantly increase the anisotropy of

Spectral properties of electromagnetic turbulence in plasmas

Directory of Open Access Journals (Sweden)

D. Shaikh

2009-03-01

Full Text Available We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth. This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfvén time-scales. The turbulent fluctuation associated with kinetic-Alfvén interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.

Resistive MHD studies of high-β-tokamak plasmas

International Nuclear Information System (INIS)

Lynch, V.E.; Carreras, B.A.; Hicks, H.R.; Holmes, J.A.; Garcia, L.

1981-01-01

Numerical calculations have been performed to study the MHD activity in high-β tokamaks such as ISX-B. These initial value calculations built on earlier low β techniques, but the β effects create several new numerical issues. These issues are discussed and resolved. In addition to time-stepping modules, our system of computer codes includes equilibrium solvers (used to provide an initial condition) and output modules, such as a magnetic field line follower and an X-ray diagnostic code. The transition from current driven modes at low β to predominantly pressure driven modes at high β is described. The nonlinear studies yield X-ray emissivity plots which are compared with experiment

11th International Conference on Numerical Modeling of Space Plasma Flows: ASTRONUM-2016

International Nuclear Information System (INIS)

2017-01-01

accretion, numerical methods for ideal and non-ideal, relativistic and nonrelativistic MHD, etc. The proceedings volume is structured so that it covers all of these topics.A distinctive feature of the ASTRONUM conference series is based on the idea that modelers working in seemingly distant fields should have an opportunity to share their scientific achievements with the broad community of computational scientists performing numerical experiments. As in previous ASTRONUM meetings, we were interested in physical systems that are coupled across a multiplicity of spatial and temporal that incorporate diverse physical processes.The contributors to this volume are both young researchers and renowned experts in space physics and astrophysics, applied mathematics, and computational physics. This book describes the application of numerical methods and the algorithms themselves, allowing us to discuss the challenges that theory imposes on numerical schemes for solving partial differential equations describing collisional and collisionless processes in space and astrophysical plasmas.We would like to thank the participants who submitted their papers to Proceedings of ASTRONUM-2016 and especially to those who reviewed manuscripts thus ensuring the high quality of this publication. We also are grateful to Adele Corona (International Conferencing and Networking Solutions) for the excellent management of the conference.The book will be useful to graduate and postgraduate students majoring in space physics, astrophysics, numerical, engineering, and applied mathematics. It is also aimed at specialists in applied mathematics, and various fields of physics that involve flows of partially ionized plasmas at both the collisional and collisionless levels.Nikolai V. Pogorelov, Edouard Audit, and Gary P. ZankApril 21, 2017 (paper)

THE FORMATION OF ROTATIONAL DISCONTINUITIES IN COMPRESSIVE THREE-DIMENSIONAL MHD TURBULENCE

Energy Technology Data Exchange (ETDEWEB)

Yang, Liping; Feng, Xueshang [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, 100190, Beijing (China); Zhang, Lei; He, Jiansen; Tu, Chuanyi; Wang, Linghua; Wang, Xin [School of Earth and Space Sciences, Peking University, 100871 Beijing (China); Marsch, Eckart [Institute for Experimental and Applied Physics, Christian Albrechts University at Kiel, D-24118 Kiel (Germany); Zhang, Shaohua, E-mail: jshept@gmail.com [Center of Spacecraft Assembly Integration and Test, China Academy of Space Technology, Beijing 100094 (China)

2015-08-20

Measurements of solar wind turbulence reveal the ubiquity of discontinuities. In this study we investigate how the discontinuities, especially rotational discontinuities (RDs), are formed in MHD turbulence. In a simulation of the decaying compressive three-dimensional (3D) MHD turbulence with an imposed uniform background magnetic field, we detect RDs with sharp field rotations and little variations of magnetic field intensity, as well as mass density. At the same time, in the de Hoffman–Teller frame, the plasma velocity is nearly in agreement with the Alfvén speed, and is field-aligned on both sides of the discontinuity. We take one of the identified RDs to analyze its 3D structure and temporal evolution in detail. By checking the magnetic field and plasma parameters, we find that the identified RD evolves from the steepening of the Alfvén wave with moderate amplitude, and that steepening is caused by the nonuniformity of the Alfvén speed in the ambient turbulence.

Computational modeling of neoclassical and resistive MHD tearing modes in tokamaks

International Nuclear Information System (INIS)

Gianakon, T.A.; Hegna, C.C.; Callen, J.D.

1996-01-01

Numerical studies of the nonlinear evolution of MHD-type tearing modes in three-dimensional toroidal geometry with neoclassical effects are presented. The inclusion of neoclassical physics introduces an additional free-energy source for the nonlinear formation of magnetic islands through the effects of a bootstrap current in Ohm's law. The neoclassical tearing mode is demonstrated to be destabilized in plasmas which are otherwise Δ' stable, albeit once an island width threshold is exceeded. The plasma pressure dynamics and neoclassical tearing growth is shown to be sensitive to the choice of the ratio of the parallel to perpendicular diffusivity (Χ parallel/Χ perpendicular). The study is completed with a demonstration and theoretical comparison of the threshold for single helicity neoclassical MHD tearing modes, which is described based on parameter scans of the local pressure gradient, the ratio of perpendicular to parallel pressure diffusivities Χ perpendicular/Χ parallel, and the magnitude of an initial seed magnetic perturbation

MHD simulations of molybdenum X-pinches

International Nuclear Information System (INIS)

Ivanenkov, G.V.; Stepnevski, V.

2002-01-01

One investigates into compression of molybdenum X-pinches applying numerical MHD-models with parabolic and conical initial geometry. The second model describing plasma axial motion in greater detail offers a real geometry of a discharge and is applicable to loads characterized by higher masses in contrast to the first one. Both models enabled to describe all basic phases of compression including origination of a minidiode, occurrence of a narrow neck, microexplosion of a hot point and origination of shock waves followed by sausage instability [ru

Non-equilibrium in flowing atmospheric plasmas

International Nuclear Information System (INIS)

Haas, J.C.M. de.

1986-01-01

This thesis deals with the fundamental aspects of two different plasmas applied in technological processes. The first one is the cesium seeded argon plasma in a closed cycle Magnetohydrodynamic (MHD) generator, the second is the thermal argon plasma in a cascade arc with an imposed flow. In Chapter 2 the influence of non-equilibrium on the mass and energy balances of a plasma is worked out. The general theory presented there can be applied to both the plasma in an MHD generator and to the cascade arc with imposed flow. Introductions to these plasmas are given in the Chapters 3 and 6 respectively. These chapters are both followed by two chapters which treat the theoretical and the experimental investigations. The results are summarized in Chapter 9. (Auth.)

Modeling of Low Frequency MHD Induced Beam Ion Transport In NSTX

International Nuclear Information System (INIS)

Gorelenkov, N.N.; Medley, S.S.

2004-01-01

Beam ion transport in the presence of low frequency MHD activity in National Spherical Tokamak Experiment (NSTX) plasma is modeled numerically and analyzed theoretically in order to understand basic underlying physical mechanisms responsible for the observed fast ion redistribution and losses. Numerical modeling of the beam ions flux into the NPA in NSTX shows that after the onset of low frequency MHD activity high energy part of beam ion distribution, E b > 40keV, is redistributed radially due to stochastic diffusion. Such diffusion is caused by high order harmonics of the transit frequency resonance overlap in the phase space. Large drift orbit radial width induces such high order resonances. Characteristic confinement time is deduced from the measured NPA energy spectrum and is typically ∼ 4msec. Considered MHD activity may induce losses on the order of 10% at the internal magnetic field perturbation (delta)B/B = Ο (10 -3 ), which is comparable to the prompt orbit losses

Coaxial plasma thrusters for high specific impulse propulsion

Science.gov (United States)

Schoenberg, Kurt F.; Gerwin, Richard A.; Barnes, Cris W.; Henins, Ivars; Mayo, Robert; Moses, Ronald, Jr.; Scarberry, Richard; Wurden, Glen

1991-01-01

A fundamental basis for coaxial plasma thruster performance is presented and the steady-state, ideal MHD properties of a coaxial thruster using an annular magnetic nozzle are discussed. Formulas for power usage, thrust, mass flow rate, and specific impulse are acquired and employed to assess thruster performance. The performance estimates are compared with the observed properties of an unoptimized coaxial plasma gun. These comparisons support the hypothesis that ideal MHD has an important role in coaxial plasma thruster dynamics.

MHD channel performance for potential early commercial MHD power plants

International Nuclear Information System (INIS)

Swallom, D.W.

1981-01-01

The commercial viability of full and part load early commercial MHD power plants is examined. The load conditions comprise a mass flow of 472 kg/sec in the channel, Rosebud coal, 34% by volume oxygen in the oxidizer preheated to 922 K, and a one percent by mass seeding with K. The full load condition is discussed in terms of a combined cycle plant with optimized electrical output by the MHD channel. Various electrical load parameters, pressure ratios, and magnetic field profiles are considered for a baseload MHD generator, with a finding that a decelerating flow rate yields slightly higher electrical output than a constant flow rate. Nominal and part load conditions are explored, with a reduced gas mass flow rate and an enriched oxygen content. An enthalpy extraction of 24.6% and an isentropic efficiency of 74.2% is predicted for nominal operation of a 526 MWe MHD generator, with higher efficiencies for part load operation

Modelling of diamagnetic stabilization of ideal MHD eigenmodes associated with the transport barrier

International Nuclear Information System (INIS)

Huysmans, G.; Sharapov, S.; Mikhailovskii, A.; Kerner, W.

2001-01-01

A new code, MISHKA-D (Drift MHD), has been developed as an extension of the ideal MHD code MISHKA-1 in order to investigate the finite gyroradius stabilizing effect of ion diamagnetic drift frequency, ω *i , on linear ideal MHD eigenmodes in tokamaks with shaped plasma cross-section. The MISHKA-D code gives a self-consistent computation of both stable and unstable eigenmodes with eigenvalues [γ] ≅ ω *i in plasmas with strong radial variation in the ion diamagnetic frequency. Test results of the MISHKA-D code show good agreement with the analytically obtained ω *i -spectrum and stability limits of the internal kink mode, n/m=1/1, used as a benchmark case. Finite-n ballooning and low-n kink (peeling) modes in the edge transport barrier just inside the separatrix are studied for H-mode plasma with the ω *i -effect included. The ion diamagnetic stabilization of the ballooning modes is found to be most effective for narrow edge pedestals. For low enough plasma density the ω *i - stabilization can lead to a second zone of ballooning stability, in which all the ballooning modes are stable for any value of the pressure gradient. For internal transport barriers typical of JET optimised shear discharges, the stabilizing influence of ion diamagnetic frequency on the n=1 global pressure driven disruptive mode is studied. A strong radial variation of ω *i is found to significantly decrease the stabilizing ω *i - effect on the n=1 mode, in comparison with the case of constant ω *i estimated at the foot of the internal transport barrier. (author)

Contributions to the study of astrophysical plasmas. From accretion-ejection flows to particle acceleration in shocks

International Nuclear Information System (INIS)

Casse, Fabien

2013-01-01

After having outlined that the study of turbulence is a point of convergence between mathematics and physics, and that magnetic turbulence is omnipresent in astrophysical plasmas and also present in the interstellar medium, in stars and in their environment, in accretion disks, at the vicinity of shocks, and so on, the author proposes an overview of his research works which started with a research thesis on magnetised accretion disks and transport of relativistic particles in a magnetic turbulence. So, in this report for an accreditation to supervise research (HDR), he first focuses on physics of systems in accretion, and particularly on magnetised accretion-ejection structures. He evokes his work on a stationary modelling of these structures, on magnetohydrodynamics digital simulation of these systems, and on some instabilities in accretion disks and their interest in astrophysics. In a second part, the author reports his works on numerical assessment of coefficients of spatial diffusion of cosmic rays in a magnetic turbulence, and the description of multi-scale environments such as supernovae debris or different regions of extra-galactic jets.

Self-organizing magnetohydrodynamic plasma

International Nuclear Information System (INIS)

Sato, T.; Horiuchi, R.; Watanabe, K.; Hayashi, T.; Kusano, K.

1990-09-01

In a resistive magnetohydrodynamic (MHD) plasma, both the magnetic energy and the magnetic helicity dissipate with the resistive time scale. When sufficiently large free magnetic energy does exist, however, an ideal current driven instability is excited whereby magnetic reconnection is driven at a converging point of induced plasma flows which does exist in a bounded compressible plasma. At a reconnection point excess free energy (entropy) is rapidly dissipated by ohmic heating and lost by radiation, while magnetic helicity is completely conserved. The magnetic topology is largely changed by reconnection and a new ordered structure with the same helicity is created. It is discussed that magnetic reconnection plays a key role in the MHD self-organization process. (author)

Anisotropic plasma with flows in tokamak: Steady state and stability

International Nuclear Information System (INIS)

Ilgisonis, V.I.

1996-01-01

An adequate description of equilibrium and stability of anisotropic plasma with macroscopic flows in tokamaks is presented. The Chew-Goldberger-Low (CGL) approximation is consistently used to analyze anisotropic plasma dynamics. The admissible structure of a stationary flow is found to be the same as in the ideal magnetohydrodynamics with isotropic pressure (MHD), which means an allowance for the same relabeling symmetry as in ideal MHD systems with toroidally nested magnetic surfaces. A generalization of the Grad-Shafranov equation for the case of anisotropic plasma with flows confined in the axisymmetric magnetic field is derived. A variational principle was obtained, which allows for a stability analysis of anisotropic pressure plasma with flows, and takes into account the conservation laws resulting from the relabeling symmetry. This principle covers the previous stability criteria for static CGL plasma and for ideal MHD flows in isotropic plasma as well. copyright 1996 American Institute of Physics

Global kinetic theory of astrophysical jets

International Nuclear Information System (INIS)

Chang, T.

1989-01-01

We suggest that an astrophysical plasma stream flowing outward from a central object aling an open magnetic field line with decreasing field strength generally will have anisotropic velocity distributions. I particular, the electron distribution function of this type of plasma streams will contain a 'thermally populated' region and a stretche out high energy tail (or 'jet-like') region collimated in the utward direction of the magnetic field line. Our argument is based on a global, collisional, kinetic theory. Because the 'kinetic jets' are always pointed aling the outward direction of the field lines, thy are automatically collimated and will assume whatever the peculiar geometries dictated by the magnetic field. This result should be useful in the understanding of the basic structures of such diverse astrophysical objects as the extragalactic radio jets, stellar winds, the solar wind, planetary polar winds, and galactic jets. (author). 8 refs.; 2 figs

MHD Equilibrium with Reversed Current Density and Magnetic Islands Revisited: the Vacuum Vector Potential Calculus

Science.gov (United States)

L. Braga, F.

2013-10-01

The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic (MHD) equilibrium with reversed current density (RCD) profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

Physical processes in hot cosmic plasmas

International Nuclear Information System (INIS)

Fabian, A.G.; Giovannelli, F.

1990-01-01

The interpretation of many high energy astrophysical phenomena relies on a detailed knowledge of radiation and transport processes in hot plasmas. The understanding of these plasma properties is one of the aims of terrestrial plasma physics. While the microscopic properties of astrophysical plasmas can hardly be determined experimentally, laboratory plasmas are more easily accessible to experimental techniques, but transient phenomena and the interaction of the plasma with boundaries often make the interpretation of measurements cumbersome. This book contains the talks given at the NATO Advanced Research Workshop on astro- and plasma-physics in Vulcano, Sicily, May 29-June 2, 1989. The book focuses on three main areas: radiation transport processes in hot (astrophysical and laboratory) plasmas; magnetic fields; their generation, reconnection and their effects on plasma transport properties; relativistic and ultra-high density plasmas

On the significance of magnetospheric research for progress in astrophysics

International Nuclear Information System (INIS)

Faelthammar, C-G.; Akasofu, S-I.; Alfen, H.

1978-04-01

Recent discoveries by means of in situ measurements have led to a substantial revision of our picture of the magnetosphere and parts of the heliosphere. This concerns such essential aspects as the character and distribution of electric fields and currents, the ways in which charged particles are energized, and the chemical composition of the magnetospheric plasma. This revision reflects the fact that even in fundamental respects, real cosmical plasmas behave in different ways than predicted by the idealized models that have traditionally been used in magnetospheric physics as well as in astrophysics. The new understanding of the general properties of cosmical plasma that has been, and continues to be, provided by in situ measurements gives us a much improved basis on which to interpret astrophysical observations

The SOL width and the MHD interchange instability in tokamaks

Energy Technology Data Exchange (ETDEWEB)

Kerner, W [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Pogutse, O [Kurchatov institute, Moscow (Russian Federation)

1994-07-01

Instabilities in the SOL plasma can strongly influence the SOL plasma behaviour and in particular the SOL width. The SOL stability analysis shows that there exists a critical ratio of the thermal energy and the magnetic energy. If the SOL beta is greater than this critical value, the magnetic field cannot prevent the plasma displacement and a strong MHD instability in the SOL occurs. In the opposite case only slower resistive instabilities can develop. A theoretical investigation of the SOL plasma stability is presented for JET single-null and double-null divertor configurations. The dependence of the stability threshold on the SOL beta and on the sheath resistance is established. Applying a simple mixing length argument gives the scaling of the SOL width. 5 refs., 2 figs.

Investigation of MHD instabilities and control in KSTAR preparing for high beta operation

Science.gov (United States)

Park, Y. S.; Sabbagh, S. A.; Bialek, J. M.; Berkery, J. W.; Lee, S. G.; Ko, W. H.; Bak, J. G.; Jeon, Y. M.; Park, J. K.; Kim, J.; Hahn, S. H.; Ahn, J.-W.; Yoon, S. W.; Lee, K. D.; Choi, M. J.; Yun, G. S.; Park, H. K.; You, K.-I.; Bae, Y. S.; Oh, Y. K.; Kim, W.-C.; Kwak, J. G.

2013-08-01

Initial H-mode operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) is expanded to higher normalized beta and lower plasma internal inductance moving towards design target operation. As a key supporting device for ITER, an important goal for KSTAR is to produce physics understanding of MHD instabilities at long pulse with steady-state profiles, at high normalized beta, and over a wide range of plasma rotation profiles. An advance from initial plasma operation is a significant increase in plasma stored energy and normalized beta, with Wtot = 340 kJ, βN = 1.9, which is 75% of the level required to reach the computed ideal n = 1 no-wall stability limit. The internal inductance was lowered to 0.9 at sustained H-mode duration up to 5 s. In ohmically heated plasmas, the plasma current reached 1 MA with prolonged pulse length up to 12 s. Rotating MHD modes are observed in the device with perturbations having tearing rather than ideal parity. Modes with m/n = 3/2 are triggered during the H-mode phase but are relatively weak and do not substantially reduce Wtot. In contrast, 2/1 modes to date only appear when the plasma rotation profiles are lowered after H-L back-transition. Subsequent 2/1 mode locking creates a repetitive collapse of βN by more than 50%. Onset behaviour suggests the 3/2 mode is close to being neoclassically unstable. A correlation between the 2/1 mode amplitude and local rotation shear from an x-ray imaging crystal spectrometer suggests that the rotation shear at the mode rational surface is stabilizing. As a method to access the ITER-relevant low plasma rotation regime, plasma rotation alteration by n = 1, 2 applied fields and associated neoclassical toroidal viscosity (NTV) induced torque is presently investigated. The net rotation profile change measured by a charge exchange recombination diagnostic with proper compensation of plasma boundary movement shows initial evidence of non-resonant rotation damping by the n = 1, 2 applied

Investigation of MHD instabilities and control in KSTAR preparing for high beta operation

International Nuclear Information System (INIS)

Park, Y.S.; Sabbagh, S.A.; Bialek, J.M.; Berkery, J.W.; Lee, S.G.; Ko, W.H.; Bak, J.G.; Jeon, Y.M.; Kim, J.; Hahn, S.H.; Yoon, S.W.; Lee, K.D.; You, K.-I.; Bae, Y.S.; Oh, Y.K.; Park, J.K.; Ahn, J.-W.; Choi, M.J.; Yun, G.S.; Park, H.K.

2013-01-01

Initial H-mode operation of the Korea Superconducting Tokamak Advanced Research (KSTAR) is expanded to higher normalized beta and lower plasma internal inductance moving towards design target operation. As a key supporting device for ITER, an important goal for KSTAR is to produce physics understanding of MHD instabilities at long pulse with steady-state profiles, at high normalized beta, and over a wide range of plasma rotation profiles. An advance from initial plasma operation is a significant increase in plasma stored energy and normalized beta, with W tot = 340 kJ, β N = 1.9, which is 75% of the level required to reach the computed ideal n = 1 no-wall stability limit. The internal inductance was lowered to 0.9 at sustained H-mode duration up to 5 s. In ohmically heated plasmas, the plasma current reached 1 MA with prolonged pulse length up to 12 s. Rotating MHD modes are observed in the device with perturbations having tearing rather than ideal parity. Modes with m/n = 3/2 are triggered during the H-mode phase but are relatively weak and do not substantially reduce W tot . In contrast, 2/1 modes to date only appear when the plasma rotation profiles are lowered after H–L back-transition. Subsequent 2/1 mode locking creates a repetitive collapse of β N by more than 50%. Onset behaviour suggests the 3/2 mode is close to being neoclassically unstable. A correlation between the 2/1 mode amplitude and local rotation shear from an x-ray imaging crystal spectrometer suggests that the rotation shear at the mode rational surface is stabilizing. As a method to access the ITER-relevant low plasma rotation regime, plasma rotation alteration by n = 1, 2 applied fields and associated neoclassical toroidal viscosity (NTV) induced torque is presently investigated. The net rotation profile change measured by a charge exchange recombination diagnostic with proper compensation of plasma boundary movement shows initial evidence of non-resonant rotation damping by the n = 1, 2

Stability of axisymmetric plasmas in closed line magnetic fields

International Nuclear Information System (INIS)

Simakov, A.N.; Vernon Wong, H.; Berk, H.L.

2003-01-01

The stability of axisymmetric plasmas confined by closed poloidal magnetic field lines is considered. The results are relevant to plasmas in the dipolar fields of stars and planets, as well as the Levitated Dipole Experiment, multipoles, Z pinches and field reversed configurations. The ideal MHD energy principle is employed to study the stability of pressure driven shear Alfven modes. A point dipole is considered in detail to demonstrate that equilibria exist which are MHD stable for arbitrary beta. Effects of sound waves and plasma resistivity are investigated for Z pinch and point dipole equilibria by means of resistive MHD theory. Kinetic theory is used to study drift frequency modes and their interaction with MHD modes near the ideal stability boundary for different collisionality regimes. Effects of collisional dissipation on drift mode stability are explicitly evaluated and applied to a Z pinch. The role of finite Larmor radius effects and drift reversed particles in modifying ideal stability thresholds is examined. (author)

MHD activity and energy loss during beta saturation and collapse at high beta poloidal in PBX

International Nuclear Information System (INIS)

Kugel, H.W.; Sesnic, S.; Bol, K.

1987-10-01

High-β experiments, in medium to high-q tokamak plasmas, exhibit a temporal β saturation and collapse. This behavior has been attributed to ballooning, ideal kink, or tearing modes. In PBX, a unique diagnostic capability allowed studies of the relation between MHD and energy loss for neutral-beam-heated (<6 MW), mildly indented (10 to 15%), nearly steady I/sub p/ discharges that approached the Troyon-Gruber limit. Under these conditions, correlations between MHD activity and energy losses have shown that the latter can be almost fully accounted for by various long wavelength MHD instabilities and that there is no need to invoke high-n ballooning modes in PBX. 6 refs., 4 figs

3-D nonlinear evolution of MHD instabilities

International Nuclear Information System (INIS)

Bateman, G.; Hicks, H.R.; Wooten, J.W.

1977-03-01

The nonlinear evolution of ideal MHD internal instabilities is investigated in straight cylindrical geometry by means of a 3-D initial-value computer code. These instabilities are characterized by pairs of velocity vortex cells rolling off each other and helically twisted down the plasma column. The cells persist until the poloidal velocity saturates at a few tenths of the Alfven velocity. The nonlinear phase is characterized by convection around these essentially fixed vortex cells. For example, the initially centrally peaked temperature profile is convected out and around to form an annulus of high temperature surrounding a small region of lower temperature. Weak, centrally localized instabilities do not alter the edge of the plasma. Strong, large-scale instabilities, resulting from a stronger longitudinal equilibrium current, drive the plasma against the wall. After three examples of instability are analyzed in detail, the numerical methods and their verification are discussed

Influence of the plasma edge on tokamak performance

International Nuclear Information System (INIS)

Wilson, H.R.; Connor, J.W.; Field, A.R.; Fielding, S.J.; Hastie, R.J.; Taylor, J.B.; Miller, R.L.

2000-01-01

A number of edge plasma physics phenomena are considered to determine tokamak performance: transport barrier, edge MHD instabilities and plasma flow. These phenomena are thought to be causally related: a spontaneous increase in the plasma flow (actually, its radial variation) suppresses heat and particle fluxes at the plasma edge to form a transport barrier; the edge pressure gradient steepens until limited by MHD instabilities, resulting in a temperature pedestal at the top of the steep gradient region; a number of core transport models predict enhanced confinement for higher values of the temperature pedestal. The article examines these phenomena and their interaction. (author)

Influence of the plasma edge on tokamak performance

International Nuclear Information System (INIS)

Wilson, H.R.; Connor, J.W.; Field, A.R.; Fielding, S.J.; Hastie, R.J.; Taylor, J.B.; Miller, R.L.

1999-01-01

A number of edge plasma physics phenomena are considered to determine tokamak performance: transport barrier, edge magneto-hydrodynamic (MHD) instabilities, plasma flow. These phenomena are thought to be causally related: a spontaneous increase in the plasma flow (actually, its radial variation) suppresses heat and particle fluxes at the plasma edge, to form a transport barrier; the edge pressure gradient steepens until limited by MHD instabilities, resulting in a temperature pedestal at the top of the steep gradient region; a number of core transport models predict enhanced confinement for higher values of the temperature pedestal. This paper examines these phenomena and their interaction. (author)

Influence of the plasma edge on tokamak performance

International Nuclear Information System (INIS)

Wilson, H.R.; Connor, J.W.; Field, A.R.; Fielding, S.J.; Hastie, R.J.; Taylor, J.B.; Miller, R.L.

2001-01-01

A number of edge plasma physics phenomena are considered to determine tokamak performance: transport barrier, edge magneto-hydrodynamic (MHD) instabilities, plasma flow. These phenomena are thought to be causally related: a spontaneous increase in the plasma flow (actually, its radial variation) suppresses heat and particle fluxes at the plasma edge, to form a transport barrier; the edge pressure gradient steepens until limited by MHD instabilities, resulting in a temperature pedestal at the top of the steep gradient region; a number of core transport models predict enhanced confinement for higher values of the temperature pedestal. This paper examines these phenomena and their interaction. (author)

Battery-powered pulsed high density inductively coupled plasma source for pre-ionization in laboratory astrophysics experiments.

Science.gov (United States)

Chaplin, Vernon H; Bellan, Paul M

2015-07-01

An electrically floating radiofrequency (RF) pre-ionization plasma source has been developed to enable neutral gas breakdown at lower pressures and to access new experimental regimes in the Caltech laboratory astrophysics experiments. The source uses a customized 13.56 MHz class D RF power amplifier that is powered by AA batteries, allowing it to safely float at 3-6 kV with the electrodes of the high voltage pulsed power experiments. The amplifier, which is capable of 3 kW output power in pulsed (<1 ms) operation, couples electrical energy to the plasma through an antenna external to the 1.1 cm radius discharge tube. By comparing the predictions of a global equilibrium discharge model with the measured scalings of plasma density with RF power input and axial magnetic field strength, we demonstrate that inductive coupling (rather than capacitive coupling or wave damping) is the dominant energy transfer mechanism. Peak ion densities exceeding 5 × 10(19) m(-3) in argon gas at 30 mTorr have been achieved with and without a background field. Installation of the pre-ionization source on a magnetohydrodynamically driven jet experiment reduced the breakdown time and jitter and allowed for the creation of hotter, faster argon plasma jets than was previously possible.

Inclusion of pressure and flow in the KITES MHD equilibrium code

International Nuclear Information System (INIS)

Raburn, Daniel; Fukuyama, Atsushi

2013-01-01

One of the simplest self-consistent models of a plasma is single-fluid magnetohydrodynamic (MHD) equilibrium with no bulk fluid flow under axisymmetry. However, both fluid flow and non-axisymmetric effects can significantly impact plasma equilibrium and confinement properties: in particular, fluid flow can produce profile pedestals, and non-axisymmetric effects can produce islands and stochastic regions. There exist a number of computational codes which are capable of calculating equilibria with arbitrary flow or with non-axisymmetric effects. Previously, a concept for a code to calculate MHD equilibria with flow in non-axisymmetric systems was presented, called the KITES (Kyoto ITerative Equilibrium Solver) code. Since then, many of the computational modules for the KITES code have been completed, and the work-in-progress KITES code has been used to calculate non-axisymmetric force-free equilibria. Additional computational modules are required to allow the KITES code to calculate equilibria with pressure and flow. Here, the authors report on the approaches used in developing these modules and provide a sample calculation with pressure. (author)

Low-frequency linear waves and instabilities in uniform and stratified plasmas: the role of kinetic effects

Directory of Open Access Journals (Sweden)

K. M. Ferrière

2004-01-01

Full Text Available We review the basic approximations underlying magnetohydrodynamic (MHD theory, with special emphasis on the closure approximations, i.e. the approximations used in any fluid approach to close the hierarchy of moment equations. We then present the main closure models that have been constructed for collisionless plasmas in the large-scale regime, and we describe our own mixed MHD-kinetic model, which is designed to study low-frequency linear waves and instabilities in collisionless plasmas. We write down the full dispersion relation in a new, general form, which gathers all the specific features of our MHD-kinetic model into four polytropic indices, and which can be applied to standard adiabatic MHD and to double-adiabatic MHD through a simple change in the expressions of the polytropic indices. We study the mode solutions and the stability properties of the full dispersion relation in each of these three theories, first in the case of a uniform plasma, and then in the case of a stratified plasma. In both cases, we show how the results are affected by the collisionless nature of the plasma.

A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

Energy Technology Data Exchange (ETDEWEB)

You, Setthivoine [Univ. of Washington, Seattle, WA (United States)

2017-12-20

Understanding the interaction between plasma flows and magnetic fields remains a fundamental problem in plasma physics, with important applications to astrophysics, fusion energy, and advanced space propulsion. For example, flows are of primary importance in astrophysical jets even if it is not fully understood how jets become so long without becoming unstable. Theories for the origin of magnetic fields in the cosmos rely on flowing charged fluids that should generate magnetic fields, yet this remains to be demonstrated experimentally. Fusion energy reactors can be made smaller with flows that improve stability and confinement. Advanced space propulsion could be more efficient with collimated and stable plasma flows through magnetic nozzles but must eventually detach from the nozzle. In all these cases, there appears to be a spontaneous emergence of flowing and/or magnetic structures, suggesting a form of self-organization in plasmas. Beyond satisfying simple intellectual curiosity, understanding plasma self-organization could enable the development of methods to control plasma structures for fusion energy, space propulsion, and other applications. The research project has therefore built a theory and an experiment to investigate the interaction between magnetic fields and plasma flows. The theory is called canonical field theory for short, and the experiment is called Mochi after a rice cake filled with surprising, yet delicious fillings.

Novel laboratory simulations of astrophysical jets

Science.gov (United States)

Brady, Parrish Clawson

This thesis was motivated by the promise that some physical aspects of astrophysical jets and collimation processes can be scaled to laboratory parameters through hydrodynamic scaling laws. The simulation of astrophysical jet phenomena with laser-produced plasmas was attractive because the laser- target interaction can inject energetic, repeatable plasma into an external environment. Novel laboratory simulations of astrophysical jets involved constructing and using the YOGA laser, giving a 1064 nm, 8 ns pulse laser with energies up to 3.7 + 0.2 J . Laser-produced plasmas were characterized using Schlieren, interferometry and ICCD photography for their use in simulating jet and magnetosphere physics. The evolution of the laser-produced plasma in various conditions was compared with self-similar solutions and HYADES computer simulations. Millimeter-scale magnetized collimated outflows were produced by a centimeter scale cylindrically symmetric electrode configuration triggered by a laser-produced plasma. A cavity with a flared nozzle surrounded the center electrode and the electrode ablation created supersonic uncollimated flows. This flow became collimated when the center electrode changed from an anodeto a cathode. The plasma jets were in axially directed permanent magnetic fields with strengths up to 5000 Gauss. The collimated magnetized jets were 0.1-0. 3 cm wide, up to 2.0 cm long, and had velocities of ~4.0 × 10 6 cm/s. The dynamics of the evolution of the jet were compared qualitatively and quantitatively with fluxtube simulations from Bellan's formulation [6] giving a calculated estimate of ~2.6 × 10 6 cm/s for jet evolution velocity and evidence for jet rotation. The density measured with interferometry was 1.9 ± 0.2 × 10 17 cm -3 compared with 2.1 × 10 16 cm -3 calculated with Bellan's pressure balance formulation. Kinks in the jet column were produced consistent with the Kruskal-Shafranov condition which allowed stable and symmetric jets to form with

A hybrid gyrokinetic ion and isothermal electron fluid code for astrophysical plasma

Science.gov (United States)

Kawazura, Y.; Barnes, M.

2018-05-01

This paper describes a new code for simulating astrophysical plasmas that solves a hybrid model composed of gyrokinetic ions (GKI) and an isothermal electron fluid (ITEF) Schekochihin et al. (2009) [9]. This model captures ion kinetic effects that are important near the ion gyro-radius scale while electron kinetic effects are ordered out by an electron-ion mass ratio expansion. The code is developed by incorporating the ITEF approximation into AstroGK, an Eulerian δf gyrokinetics code specialized to a slab geometry Numata et al. (2010) [41]. The new code treats the linear terms in the ITEF equations implicitly while the nonlinear terms are treated explicitly. We show linear and nonlinear benchmark tests to prove the validity and applicability of the simulation code. Since the fast electron timescale is eliminated by the mass ratio expansion, the Courant-Friedrichs-Lewy condition is much less restrictive than in full gyrokinetic codes; the present hybrid code runs ∼ 2√{mi /me } ∼ 100 times faster than AstroGK with a single ion species and kinetic electrons where mi /me is the ion-electron mass ratio. The improvement of the computational time makes it feasible to execute ion scale gyrokinetic simulations with a high velocity space resolution and to run multiple simulations to determine the dependence of turbulent dynamics on parameters such as electron-ion temperature ratio and plasma beta.

Hydrodynamic instabilities in astrophysics and ICF

International Nuclear Information System (INIS)

Paul Drake, R.

2005-01-01

Inertial fusion systems and astrophysical systems both involve hydrodynamic effects, including sources of pressure, shock waves, rarefactions, and plasma flows. In the evolution of such systems, hydrodynamic instabilities naturally evolve. As a result, a fundamental understanding of hydrodynamic instabilities is necessary to understand their behavior. In addition, high-energy-density facilities designed for ICF purposes can be used to provide and experimental basis for understanding astrophysical processes. In this talk. I will discuss the instabilities that appear in astrophysics and ICF from the common perspective of the basic mechanisms at work. Examples will be taken from experiments aimed at ICF, from astrophysical systems, and from experiments using ICF systems to address issues in astrophysics. The high-energy-density research facilities of today can accelerate small but macroscopic amounts of material to velocities above 100 km/s, can heat such material to temperature above 100 eV, can produce pressures far above a million atmospheres (10''12 dybes/cm''2 or 0.1 TPascal), and can do experiments under these conditions that address basic physics issues. This enables on to devise experiments aimed directly at important process such as the Rayleigh Taylor instability at an ablating surface or at an embedded interface that is accelerating, the Richtmeyer Meshkov evolution of shocked interfaces, and the Kelvin-Helmholtz instability of shear flows. The talk will include examples of such phenomena from the laboratory and from astrophysics, and will discuss experiments to study them. (Author)

Plasma confinement in a magnetic dipole

International Nuclear Information System (INIS)

Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.

1999-01-01

A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)

Plasma confinement in a magnetic dipole

International Nuclear Information System (INIS)

Kesner, J.; Bromberg, L.; Garnier, D.; Mauel, M.

2001-01-01

A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)

MHD Generating system

Science.gov (United States)

Petrick, Michael; Pierson, Edward S.; Schreiner, Felix

1980-01-01

According to the present invention, coal combustion gas is the primary working fluid and copper or a copper alloy is the electrodynamic fluid in the MHD generator, thereby eliminating the heat exchangers between the combustor and the liquid-metal MHD working fluids, allowing the use of a conventional coalfired steam bottoming plant, and making the plant simpler, more efficient and cheaper. In operation, the gas and liquid are combined in a mixer and the resulting two-phase mixture enters the MHD generator. The MHD generator acts as a turbine and electric generator in one unit wherein the gas expands, drives the liquid across the magnetic field and thus generates electrical power. The gas and liquid are separated, and the available energy in the gas is recovered before the gas is exhausted to the atmosphere. Where the combustion gas contains sulfur, oxygen is bubbled through a side loop to remove sulfur therefrom as a concentrated stream of sulfur dioxide. The combustor is operated substoichiometrically to control the oxide level in the copper.

Characteristics of laminar MHD fluid hammer in pipe

International Nuclear Information System (INIS)

Huang, Z.Y.; Liu, Y.J.

2016-01-01

As gradually wide applications of MHD fluid, transportation as well as control with pumps and valves is unavoidable, which induces MHD fluid hammer. The paper attempts to combine MHD effect and fluid hammer effect and to investigate the characteristics of laminar MHD fluid hammer. A non-dimensional fluid hammer model, based on Navier–Stocks equations, coupling with Lorentz force is numerically solved in a reservoir–pipe–valve system with uniform external magnetic field. The MHD effect is represented by the interaction number which associates with the conductivity of the MHD fluid as well as the external magnetic field and can be interpreted as the ratio of Lorentz force to Joukowsky force. The transient numerical results of pressure head, average velocity, wall shear stress, velocity profiles and shear stress profiles are provided. The additional MHD effect hinders fluid motion, weakens wave front and homogenizes velocity profiles, contributing to obvious attenuation of oscillation, strengthened line packing and weakened Richardson annular effect. Studying the characteristics of MHD laminar fluid hammer theoretically supplements the gap of knowledge of rapid-transient MHD flow and technically provides beneficial information for MHD pipeline system designers to better devise MHD systems. - Highlights: • Characteristics of laminar MHD fluid hammer are discussed by simulation. • MHD effect has significant influence on attenuation of wave. • MHD effect strengthens line packing. • MHD effect inhibits Richardson annular effect.

Perturbed solutions of fixed boundary MHD equilibria

International Nuclear Information System (INIS)

Portone, A.

2004-01-01

In this study, the fixed boundary plasma MHD equilibrium problem is solved by the finite element method; then, by perturbing the flux at the plasma boundary nodes, linear formulae are derived linking the variation of several plasma parameters of interest to the variation of the currents flowing in the external circuits. On the basis of these formulae it is shown how it is possible to efficiently solve two central problems in plasma engineering, namely (1) the optimization of the currents in a given set of coils necessary to maintain a specified equilibrium configuration and (2) the derivation of a linear dynamic model describing the plasma axisymmetric displacement (n = 0 mode) about a given magnetic configuration. A case study-based on the ITER reference equilibrium magnetic configuration at burn-is analysed both in terms of equilibrium currents optimality as well as axisymmetric stability features. The results obtained by these formulae are also compared with the predictions of a non-linear free boundary code and of a linear, dynamic model. As shown, the formulae derived here are in good agreement with such predictions, confirming the validity of the present approach. (author)

Theoretical parameters of powerful radio galaxies. II. Generation of MHD turbulence by collisionless shock waves

International Nuclear Information System (INIS)

Baryshev, Yu.V.; Morozov, V.N.

1988-01-01

It is shown that MHD turbulence can be generated by collisionless shock waves due to anisotropy of the pressure behind the front of the reverse sock at the hot spot of a powerful radio galaxy. The energy density of the MHD turbulence generated behind the shock front is estimated. Analysis of the theoretical studies and experimental data on collisionless shock waves in the solar wind indicates that an important part is played by streams of ions reflected by the shock fronts, the streams generating plasma and MHD turbulence in the region ahead of the front. The extension of these ideas to shock waves in powerful radio galaxies must be made with care because of the great difference between the parameters of the shock waves in the two cases

Bootstrap current control studies in the Wendelstein 7-X stellarator using the free-plasma-boundary version of the SIESTA MHD equilibrium code

Science.gov (United States)

Peraza-Rodriguez, H.; Reynolds-Barredo, J. M.; Sanchez, R.; Tribaldos, V.; Geiger, J.

2018-02-01

The recently developed free-plasma-boundary version of the SIESTA MHD equilibrium code (Hirshman et al 2011 Phys. Plasmas 18 062504; Peraza-Rodriguez et al 2017 Phys. Plasmas 24 082516) is used for the first time to study scenarios with considerable bootstrap currents for the Wendelstein 7-X (W7-X) stellarator. Bootstrap currents in the range of tens of kAs can lead to the formation of unwanted magnetic island chains or stochastic regions within the plasma and alter the boundary rotational transform due to the small shear in W7-X. The latter issue is of relevance since the island divertor operation of W7-X relies on a proper positioning of magnetic island chains at the plasma edge to control the particle and energy exhaust towards the divertor plates. Two scenarios are examined with the new free-plasma-boundary capabilities of SIESTA: a freely evolving bootstrap current one that illustrates the difficulties arising from the dislocation of the boundary islands, and a second one in which off-axis electron cyclotron current drive (ECCD) is applied to compensate the effects of the bootstrap current and keep the island divertor configuration intact. SIESTA finds that off-axis ECCD is indeed able to keep the location and phase of the edge magnetic island chain unchanged, but it may also lead to an undesired stochastization of parts of the confined plasma if the EC deposition radial profile becomes too narrow.

Space potential fluctuations during MHD activities in the Compact Helical System (CHS)

International Nuclear Information System (INIS)

Iguchi, H.; Fujisawa, A.; Crowley, T.P.

1998-02-01

Local space potential fluctuations have been measured during MHD activities in a low-beta NBI heated plasma in the Compact Helical System (CHS) by the use of a heavy ion beam probe (HIBP). Two types of MHD modes with accompanying potential oscillations are observed. One appears in periodic bursts with relatively low frequency (< 40 kHz) and large amplitude (20-40 volts), and is localized around the q=2 surface (average minor radius ρ ∼ 0.7). The other appears in continuous and coherent oscillation with higher frequency (105-125 kHz) and smaller amplitude (∼5 volts). This oscillation also has spatial structure. Possible interpretation for the space potential oscillations is presented. (author)

Changes of the electron density distribution during MHD activity in CHS

International Nuclear Information System (INIS)

Soltwisch, H.; Tanaka, K.

2000-09-01

Density oscillations induced by MHD activities were observed in NBI heated plasmas on CHS by using an HCN laser interferometer. The accompanied changes of the density profiles were also observed. The oscillations are composition of m=0 sawteeth like crash and m=2 sinusoidal oscillations as a post courser of the crash. Possible models of the oscillation structure are examined in order to explain experimental data of the interferometer. Rotating plasma core, which is hollow profile and keeps constant elongation of the flux surface can explain amplitude and phase distribution of the sinusoidal oscillation. (author)

MHD Collimation Mechanism in Arched Flux Ropes Characterized Using Volumetric, Time-Dependent B-Vector Measurements

Science.gov (United States)

Haw, Magnus A.; Bellan, Paul M.

2017-10-01

Laboratory measurements of B(x,t) in a volume enclosing portions of two arched flux ropes show flux rope collimation driven by gradients in axial current density. These measurements verify the three predictions of a proposed MHD collimation mechanism: (1) axial magnetic forces exist in current channels with spatially varying minor radius, (2) these forces can drive counterpropagating axial flows, and (3) this process collimates the flux rope. This mechanism may explain the axial uniformity of solar loops and is relevant to other systems with current channels of varying minor radius such as solar prominences and astrophysical jets.

Analysis and measurement of property disturbances in a combustion magnetohydrodynamic plasma

International Nuclear Information System (INIS)

Simons, T.D.; Mitchner, M.; Eustis, R.H.

1984-01-01

Measurements of propagating pressure and temperature (entropy) waves in a combustion magnetohydrodynamic (MHD) generator are presented along with a general model which describes how to produce controlled rapid property disturbances in a combustion MHD plasma. The model identifies the principal mechanisms of wave formation and predicts the qualitative and quantitative wave shapes as a function of average plasma and electrical properties but does not describe wave amplification. The model exhibits quantitatively the coupling between the entropy and acoustic waves and the electric current and magnetic field under conditions applicable to MHD power generation

Analysis of ELM stability with extended MHD models in JET, JT-60U and future JT-60SA tokamak plasmas

Science.gov (United States)

Aiba, N.; Pamela, S.; Honda, M.; Urano, H.; Giroud, C.; Delabie, E.; Frassinetti, L.; Lupelli, I.; Hayashi, N.; Huijsmans, G.; JET Contributors, the; Research Unit, JT-60SA

2018-01-01

The stability with respect to a peeling-ballooning mode (PBM) was investigated numerically with extended MHD simulation codes in JET, JT-60U and future JT-60SA plasmas. The MINERVA-DI code was used to analyze the linear stability, including the effects of rotation and ion diamagnetic drift ({ω }* {{i}}), in JET-ILW and JT-60SA plasmas, and the JOREK code was used to simulate nonlinear dynamics with rotation, viscosity and resistivity in JT-60U plasmas. It was validated quantitatively that the ELM trigger condition in JET-ILW plasmas can be reasonably explained by taking into account both the rotation and {ω }* {{i}} effects in the numerical analysis. When deuterium poloidal rotation is evaluated based on neoclassical theory, an increase in the effective charge of plasma destabilizes the PBM because of an acceleration of rotation and a decrease in {ω }* {{i}}. The difference in the amount of ELM energy loss in JT-60U plasmas rotating in opposite directions was reproduced qualitatively with JOREK. By comparing the ELM affected areas with linear eigenfunctions, it was confirmed that the difference in the linear stability property, due not to the rotation direction but to the plasma density profile, is thought to be responsible for changing the ELM energy loss just after the ELM crash. A predictive study to determine the pedestal profiles in JT-60SA was performed by updating the EPED1 model to include the rotation and {ω }* {{i}} effects in the PBM stability analysis. It was shown that the plasma rotation predicted with the neoclassical toroidal viscosity degrades the pedestal performance by about 10% by destabilizing the PBM, but the pressure pedestal height will be high enough to achieve the target parameters required for the ITER-like shape inductive scenario in JT-60SA.

Non-disruptive MHD dynamics in inward-shifted LHD configurations

International Nuclear Information System (INIS)

Miura, H.; Ichiguchi, K.; Nakajima, N.; Hayashi, T.; Carreras, B.A.

2005-01-01

Two kinds of nonlinear simulations are conducted to study behaviors of the pressure-driven modes in the Large Helical Device (LHD) plasma with the vacuum magnetic axis located at R ax =3.6 m (so called inward-shifted configuration). One is the three-field reduced magnetohydrodynamic (RMHD) simulations. The other is the direct numerical simulations (DNS) of fully three-dimensional (3D) compressible MHD equations. The RMHD results suggest that the plasma behavior depends on the strength of the interaction between the unstable modes with different helicity. Similar plasma behaviors are also obtained in the DNS. In addition to some basic coincidence between RMHD and DNS, substantial toroidal flow generation is observed in the DNS. It is shown that toroidal flow can become stronger than the poloidal flow. (author)

Non-disruptive MHD dynamics in inward-shifted LHD configurations

International Nuclear Information System (INIS)

Miura, H.; Ichiguchi, K.; Nakajima, N.; Hayashi, T.; Carreras, B.A.

2005-01-01

Two kinds of nonlinear simulations are conducted to study behaviors of the pressure-driven modes in the Large Helical Device (LHD) plasma with the vacuum magnetic axis located at R ax = 3.6m (so called inward-shifted configuration). One is the three-field reduced magnetohydrodynamic (RMHD) simulations. The other is the direct numerical simulations (DNS) of fully three-dimensional (3D) compressible MHD equations. The RMHD results suggest that the plasma behavior depends on the strength of the interaction between the unstable modes with different helicity. Similar plasma behaviors are also obtained in the DNS. In addition to some basic coincidence between RMHD and DNS, substantial toroidal flow generation is observed in the DNS. It is shown that toroidal flow can become stronger than the poloidal flow. (author)

Magnetoacoustic waves in current-carrying plasmas

International Nuclear Information System (INIS)

Brennan, M.H.

1980-04-01

The results of theoretical and experimental investigations of the characteristics of magnetoacoustic waves in non-uniform, current-carrying plasmas are reviewed. Dissipative MHD and collisionless theories are considered. Also discussed is the use of magnetoacoustic waves in plasma diagnostics and plasma heating

Analysis of the instability growth rate during the jet– background interaction in a magnetic field

Czech Academy of Sciences Publication Activity Database

Horký, Miroslav; Kulhánek, P.

2013-01-01

Roč. 13, č. 6 (2013), s. 687-694 ISSN 1674-4527 R&D Projects: GA ČR GD205/09/H033 Institutional support: RVO:67985815 Keywords : plasmas * numerical methods * instabilities * turbulence * waves * MHD Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.516, year: 2013

A Model for Straight and Helical Solar Jets: II. Parametric Study of the Plasma Beta

Science.gov (United States)

Pariat, E.; Dalmasse, K.; DeVore, C. R.; Antiochos, S. K.; Karpen, J. T.

2016-01-01

Context. Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Aims. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g. in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. Methods. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma beta on the generation and properties of solar-like jets. Results. The parametric study validates our model of jets for plasma beta ranging from 10(sup 3) to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various beta less than or equal to 1. We show that the plasma beta modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Conclusions. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

Laboratory Astrophysics Using High Energy Density Photon and Electron Beams

CERN Document Server

Bingham, Robert

2005-01-01

The development of intense laser and particle beams has opened up new opportunities to study high energy density astrophysical processes in the Laboratory. With even higher laser intensities possible in the near future vacuum polarization processes such as photon - photon scattering with or without large magnetic fields may also be experimentally observed. In this talk I will review the status of laboratory experiments using intense beans to investigate extreme astrophysical phenomena such as supernovae explosions, gamma x-ray bursts, ultra-high energy cosmic accelerators etc. Just as intense photon or electron beams can excite relativistic electron plasma waves or wakefields used in plasma acceleration, intense neutrino beams from type II supernovae can also excite wakefields or plasma waves. Other instabilities driven by intense beams relevant to perhaps x-ray bursts is the Weibel instability. Simulation results of extreme processes will also be presented.

Outline of fiscal 1970 achievements in research on MHD power generation; 1970 nendo MHD hatsuden kenkyu seika gaiyo

Energy Technology Data Exchange (ETDEWEB)

NONE

1970-07-01

Compiled are the results of studies conducted in fiscal 1970 on MHD (magnetohydrodynamic) power generation. In the operation test and modification of the 1000kW-class MHD power generator, modification is carried out involving the combustion system, seed collecting method, and power generation channel, and reviews through experiments are conducted about the analysis and control of the boundary layer structure. In the operation test of the MHD power generator designed for prolonged operation, a test operation for resistance to heat and seeds continues more than 100 hours using a cold wall type power generation channel constituted of water cooled ceramics, and the ceramics are analyzed for failure and loss. Studies are also conducted involving MHD power generator heat exchangers, seed collecting methods, electrode materials for MHD power generators, heat-resistant materials for MHD power generators, thermal performance rating for MHD power plants, etc. In the research and development of superconductive electromagnets, superconductive electromagnets are developed and tested for 1000kW-class MHD power generators, and studies are conducted on turbine type helium liquefiers, superinsulated superconductive electromagnetic field generators, etc. (NEDO)

Experimental observations of MHD instabilities in the high-beta tokamak Torus-II

International Nuclear Information System (INIS)

Machida, M.

1982-01-01

The CO 2 laser scattering and interferometry diagnostics have been used to study the MHD instabilities in the high-beta tokamak Torus-II. Detailed measurements of the density and density fluctuation profiles have been performed. In order to measure density fluctuations with wavelengths longer than 2 cm, an interferometric like, phase matching technique has been developed. The toroidal and poloidal mode numbers have been measured using a double-beam, two-position technique. Working at high-beta values, average β greater than or equal to 10%, we have found parameters where the growing instabilities are created or suppressed. The plasma lifetime for both cases is seen to be about the same and the loss of the plasma appears to be caused by the decay in the external fields. The growing instability parameters are within the MHD regime, and it only grows at the outer edge of the plasma. This is in agreement with the theoretical Ballooning mode instability. The frequency and mode number measurements also agree with the Kinetic theory description of Ballooning modes. The comparison with possible other modes, such as Tearing and Drift instabilities, is performed and the Ballooning growth rate is shown to be the best fit to the experimental values

Radiation-magnetohydrodynamics of fusion plasmas on parallel supercomputers

International Nuclear Information System (INIS)

Yasar, O.; Moses, G.A.; Tautges, T.J.

1993-01-01

A parallel computational model to simulate fusion plasmas in the radiation-magnetohydrodynamics (R-MHD) framework is presented. Plasmas are often treated in a fluid dynamics context (magnetohydrodynamics, MHD), but when the flow field is coupled with the radiation field it falls into a more complex category, radiation magnetohydrodynamics (R-MHD), where the interaction between the flow field and the radiation field is nonlinear. The solution for the radiation field usually dominates the R-MHD computation. To solve for the radiation field, one usually chooses the S N discrete ordinates method (a deterministic method) rather than the Monte Carlo method if the geometry is not complex. The discrete ordinates method on a massively parallel processor (Intel iPSC/860) is implemented. The speedup is 14 for a run on 16 processors and the performance is 3.7 times better than a single CRAY YMP processor implementation. (orig./DG)

Development in Diagnostics Application to Control Advanced Tokamak Plasma

International Nuclear Information System (INIS)

Koide, Y.

2008-01-01

For continuous operation expected in DEMO, all the plasma current must be non-inductively driven, with self-generated neoclassical bootstrap current being maximized. The control of such steady state high performance tokamak plasma (so-called 'Advanced Tokamak Plasma') is a challenge because of the strong coupling between the current density, the pressure profile and MHD stability. In considering diagnostic needs for the advanced tokamak research, diagnostics for MHD are the most fundamental, since discharges which violate the MHD stability criteria either disrupt or have significantly reduced confinement. This report deals with the development in diagnostic application to control advanced tokamak plasma, with emphasized on recent progress in active feedback control of the current profile and the pressure profile under DEMO-relevant high bootstrap-current fraction. In addition, issues in application of the present-day actuators and diagnostics for the advanced control to DEMO will be briefly addressed, where port space for the advanced control may be limited so as to keep sufficient tritium breeding ratio (TBR)

Direct measurements of damping rates and stability limits for low frequency MHD modes and Alfven Eigenmodes in the JET tokamak

International Nuclear Information System (INIS)

Fasoli, A.F.; Testa, D.; Jaun, A.; Sharapov, S.; Gormezano, C.

2001-01-01

The linear stability properties of global modes that can be driven by resonant energetic particles or by the bulk plasma are studied using an external excitation method based on the JET saddle coil antennas. Low toroidal mode number, stable plasma modes are driven by the saddle coils and detected by magnetic probes to measure their structure, frequency and damping rate, both in the Alfven Eigenmode (AE) frequency range and in the low frequency Magneto-Hydro-Dynamic (MHD) range. For AEs, the dominant damping mechanisms are identified for different plasma conditions of relevance for reactors. Spectra and damping rates of low frequency MHD modes that are localized at the foot of the internal transport barrier and can affect the plasma performance in advanced tokamak scenarios have been directly measured for the first time. This gives the possibility of monitoring in real time the approach to the instability boundary. (author)

MHD activity triggered by monster sawtooth crashes on Tore Supra

International Nuclear Information System (INIS)

Maget, P; Artaud, J-F; Eriksson, L-G; Huysmans, G; Lazaros, A; Moreau, P; Ottaviani, M; Segui, J-L; Zwingmann, W

2005-01-01

The crash of monster sawteeth in Tore Supra ion cyclotron resonance heated plasmas is observed to trigger long-lived magneto hydrodynamic (MHD) activity, dominated by a (m = 3, n = 2) magnetic perturbation at the edge. This phenomenon is reminiscent of the triggering of neoclassical tearing modes, although in Tore Supra the MHD activity decays and eventually vanishes. It can be explained by the linear destabilization of the (3, 2) mode as the current sheet developed in the non-linear stage of the internal kink relaxation gets closer to q = 3/2. However, the lifetime of the (3, 2) island is longer than the period of linear instability. We find that the neoclassical drive is essential for explaining the observed lifetime and width of the island, although the overall dynamics is controlled by the relaxation of the current profile on a resistive time scale

DAMPING OF MAGNETOHYDRODYNAMIC TURBULENCE IN PARTIALLY IONIZED PLASMA: IMPLICATIONS FOR COSMIC RAY PROPAGATION

International Nuclear Information System (INIS)

Xu, Siyao; Yan, Huirong; Lazarian, A.

2016-01-01

We study the damping processes of both incompressible and compressible magnetohydrodynamic (MHD) turbulence in a partially ionized medium. We start from the linear analysis of MHD waves, applying both single-fluid and two-fluid treatments. The damping rates derived from the linear analysis are then used in determining the damping scales of MHD turbulence. The physical connection between the damping scale of MHD turbulence and the cutoff boundary of linear MHD waves is investigated. We find two branches of slow modes propagating in ions and neutrals, respectively, below the damping scale of slow MHD turbulence, and offer a thorough discussion of their propagation and dissipation behavior. Our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ISM) phases and the solar chromosphere. The importance of neutral viscosity in damping the Alfvenic turbulence in the interstellar warm neutral medium and the solar chromosphere is demonstrated. As a significant astrophysical utility, we introduce damping effects to the propagation of cosmic rays in partially ionized ISM. The important role of turbulence damping in both transit-time damping and gyroresonance is identified.

Wind-type flows in astrophysical jets. III. Temporal evolution of perturbations and the formation of shocks

International Nuclear Information System (INIS)

Trussoni, E.; Ferrari, A.; Rosner, R.; Tsinganos, K.

1988-01-01

The temporal evolution of disturbances in a spherically symmetric polytropic wind from a central object is studied. Such disturbances may be due to localized momentum addition/subtraction, as, for example, by MHD waves, heating/cooling mechanisms in the outflow, or localized deviations from spherical symmetric expansion. The evolution of an initial perturbed state to a continuous or discontinuous final equilibrium state, as predicted by previous analytic calculations for stationary flows, is followed. It is shown that some of the predicted discontinuous equilibrium states are not physically accessible, while the attainment of the remaining equilibrium states depends on both the temporal and the spatial parameters characterizing the perturbation. The results are derived for solar conditions, but in fact can be applied to outflows in other astrophysical systems. In particular, applications to the solar wind and flows in astrophysical jets are discussed. 32 references

MHD program plan, FY 1991

Science.gov (United States)

1990-10-01

The current magnetohydrodynamic MHD program being implemented is a result of a consensus established in public meetings held by the Department of Energy in 1984. The public meetings were followed by the formulation of a June 1984 Coal-Fired MHD Preliminary Transition and Program Plan. This plan focused on demonstrating the proof-of-concept (POC) of coal-fired MHD electric power plants by the early 1990s. MHD test data indicate that while there are no fundamental technical barriers impeding the development of MHD power plants, technical risk remains. To reduce the technical risk three key subsystems (topping cycle, bottoming cycle, and seed regeneration) are being assembled and tested separately. The program does not require fabrication of a complete superconducting magnet, but rather the development and testing of superconductor cables. The topping cycle system test objectives can be achieved using a conventional iron core magnet system already in place at a DOE facility. Systems engineering-derived requirements and analytical modeling to support scale-up and component design guide the program. In response to environmental, economic, engineering, and utility acceptance requirements, design choices and operating modes are tested and refined to provide technical specifications for meeting commercial criteria. These engineering activities are supported by comprehensive and continuing systems analyses to establish realistic technical requirements and cost data. Essential elements of the current program are to: develop technical and environmental data for the integrated MHD topping cycle and bottoming cycle systems through POC testing (1000 and 4000 hours, respectively); design, construct, and operate a POC seed regeneration system capable of processing spent seed materials from the MHD bottoming cycle; prepare conceptual designs for a site specific MHD retrofit plant; and continue supporting research necessary for system testing.

Plasma Theory Division

International Nuclear Information System (INIS)

Callen, J.D.; Dory, R.A.; Aghevli, R.

1977-01-01

The progress during the past year is organized by group efforts and divided into five major areas. The basic tokamak areas and the sections in which their work is summarized are: magnetohydrodynamic (MHD) theory, kinetic theory, and transport simulation. The ELMO Bumpy Torus (EBT) theory work has its own research projects on MHD theory, kinetic theory, and transport simulation. In the plasma engineering area, relevant research work is further developed and synthesized into models that are used in the design of advanced fusion systems--The Next Step (TNS), demonstration fusion reactor (Demo), EBT ignition test, etc. Specific plasma engineering projects on providing the TNS physics basis and the development of the EBT reactor study are discussed. The computing support activities during the past year are summarized

Plasma physics and instabilities

International Nuclear Information System (INIS)

Lashmore-Davies, C.N.

1981-01-01

These lectures procide an introduction to the theory of plasmas and their instabilities. Starting from the Bogoliubov, Born, Green, Kirkwood, and Yvon (BBGKY) hierarchy of kinetic equations, the additional concept of self-consistent fields leads to the fundamental Vlasov equation and hence to the warm two-fluid model and the one-fluid MHD, or cold, model. The properties of small-amplitude waves in magnetized (and unmagnetized) plasmas, and the instabilities to which they give rise, are described in some detail, and a complete chapter is devoted to Landau damping. The linear theory of plasma instabilities is illustrated by the current-driven electrostatic kind, with descriptions of the Penrose criterion and the energy principle of ideal MHD. There is a brief account of the application of feedback control. The non-linear theory is represented by three examples: quasi-linear velocity-space instabilities, three-wave instabilities, and the stability of an arbitrarily largeamplitude wave in a plasma. (orig.)

FOREWORD: The 5th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas

Science.gov (United States)

Tchang-Brillet, Wad Lydia; Wyart, Jean-François; Zeippen, Claude

1996-01-01

The 5th International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas was held in Meudon, France, from August 28 to 31 1995. It was the fifth in a series started by the Atomic Spectroscopic Group at the University of Lund, Sweden, in 1983. Then followed the meetings in Toledo, USA, Amsterdam, The Nether- lands and Gaithersburg, USA, with a three year period. The original title of the series ended with "... for Astrophysics and Fusion Research" and became more general with the 4th colloquium in Gaithersburg. The purpose of the present meeting was, in line with tradition, to bring together "producers" and "users" of atomic data so as to ensure optimal coordination. Atomic physicists who study the structure of atoms and their radiative and collisional properties were invited to explain the development of their work, emphasizing the possibilities of producing precise transition wavelengths and relative line intensities. Astrophysicists and laboratory plasma physicists were invited to review their present research interests and the context in which atomic data are needed. The number of participants was about 70 for the first three meetings, then exploded to 170 at Gaithersburg. About 140 participants, coming from 13 countries, attended the colloquium in Meudon. This large gathering was partly due to a number of participants from Eastern Europe larger than in the past, and it certainly showed a steady interest for interdisciplinary exchanges between different communities of scientists. This volume includes all the invited papers given at the conference and, in the appendix, practical information on access to some databases. All invited speakers presented their talks aiming at good communication between scientists from different backgrounds. A separate bound volume containing extended abstracts of the poster papers has been published by the Publications de l'Observatoire de Paris, (Meudon 1996), under the responsibility of

Plasma heating by kinetic Alfven wave

International Nuclear Information System (INIS)

Assis, A.S. de.

1982-01-01

The heating of a nonuniform plasma (electron-ion) due to the resonant excitation of the shear Alfven wave in the low β regime is studied using initially the ideal MHD model and posteriorly using the kinetic model. The Vlasov equation for ions and the drift kinetic equation for electrons have been used. Through the ideal MHD model, it is concluded that the energy absorption is due to the continuous spectrum (phase mixing) which the shear Alfven wave has in a nonuniform plasma. An explicit expression for the energy absorption is derived. Through the kinetic model it is concluded that the energy absorption is due to a resonant mode convertion of the incident wave into the kinetic Alfven wave which propagates away from the resonant region. Its electron Landau damping has been observed. There has been a concordance with the MHD calculations. (Author) [pt

MHD equilibrium identification on ASDEX-Upgrade

International Nuclear Information System (INIS)

McCarthy, P.J.; Schneider, W.; Lakner, K.; Zehrfeld, H.P.; Buechl, K.; Gernhardt, J.; Gruber, O.; Kallenbach, A.; Lieder, G.; Wunderlich, R.

1992-01-01

A central activity accompanying the ASDEX-Upgrade experiment is the analysis of MHD equilibria. There are two different numerical methods available, both using magnetic measurements which reflect equilibrium states of the plasma. The first method proceeds via a function parameterization (FP) technique, which uses in-vessel magnetic measurements to calculate up to 66 equilibrium parameters. The second method applies an interpretative equilibrium code (DIVA) for a best fit to a different set of magnetic measurements. Cross-checks with the measured particle influxes from the inner heat shield and the divertor region and with visible camera images of the scrape-off layer are made. (author) 3 refs., 3 figs

Advanced energy utilization MHD power generation

International Nuclear Information System (INIS)

2008-01-01

The 'Technical Committee on Advanced Energy Utilization MHD Power Generation' was started to establish advanced energy utilization technologies in Japan, and has been working for three years from June 2004 to May 2007. This committee investigated closed cycle MHD, open cycle MHD, and liquid metal MHD power generation as high-efficiency power generation systems on the earth. Then, aero-space application and deep space exploration technologies were investigated as applications of MHD technology. The spin-off from research and development on MHD power generation such as acceleration and deceleration of supersonic flows was expected to solve unstart phenomena in scramjet engine and also to solve abnormal heating of aircrafts by shock wave. In addition, this committee investigated researches on fuel cells, on secondary batteries, on connection of wind power system to power grid, and on direct energy conversion system from nuclear fusion reactor for future. The present technical report described results of investigations by the committee. (author)

Nonlinear evolution of astrophysical Alfven waves

Science.gov (United States)